Coatings doi: 10.3390/coatings14030361
Authors: Reem M. Barakat Rahaf A. Almohareb Fahda N. Algahtani Amal A. Altamimi Jenan I. Alfuraih Lena S. Bahlol Ahmed Jamleh
This study compared the fatigue resistance and elemental composition of two blue heat-treated nickel–titanium (NiTi) files used in root canal preparation as follows: Tia Tornado Blue (TTB) and Race Evo (RE) file systems. For cyclic fatigue testing, the two systems were tested where each file was rotated inside an artificial metal canal submerged in either sodium hypochlorite or saline solution until fracture. Time to fracture was recorded. For torsional fatigue testing, the file tip was secured while the file was allowed to rotate at a fixed rate until fracture. Torque at failure was recorded. The two experiments were performed at simulated body temperature and the length of fractured segments was measured. Statistical analysis was carried out with a significance level (p-value) set at 5%. The mean cycles to fracture for RE were superior to that of TTB irrespective of the solution used (p < 0.05). TTB’s cyclic fatigue resistance decreased in NaOCl (p < 0.0001). RE demonstrated lower torque at failure (p = 0.002). All files were fractured at comparable lengths (p = 0.218). Although RE is considered more resistant to cyclic fatigue, it showed inferior torsional resistance compared with TTB. The NaOCl negatively affected the TTB’s cyclic fatigue resistance.
]]>Coatings doi: 10.3390/coatings14030360
Authors: Florian Pape
Dry lubricants used in highly loaded rolling bearings are in the focus of current research. In previous studies, graphene platelets applied as dry lubricants on the surfaces of angular contact ball bearings demonstrated superior properties. These specific bearings, experiencing both rolling and spinning motion, create more severe conditions for dry lubricants. To gain deeper insights into the lubrication effects, micro-tribological studies were carried out on the respective film formation and running behavior effects. In the tests, a fixed steel ball slid against an oscillating counterpart under a defined load. During the measurements, the applied load and tangential forces on the ball were recorded to calculate the friction. Comparative investigations included nano-graphite particles and fullerene as dry lubricants, in addition to graphene platelets of various staple thicknesses. To increase the adhesion of the films to the surfaces, a pre-rolling process was implemented. Afterwards, the friction on the compressed films was measured. The results indicate that the pre-rolling process effectively reduces the friction of the system. After testing, the surfaces underwent analysis using laser scanning microscopy to assess the formed films, wear, and material transfer. It has been demonstrated that the pre-rolling process leads to the formation of a very thin compacted film with surface protective properties. With the ball as a counterpart, the graphene platelets generate a transfer film on the contacting surface.
]]>Coatings doi: 10.3390/coatings14030359
Authors: Young-Ran Yoo Seokyeon Won Young-Sik Kim
A large amount of multi-layer ceramic capacitor (MLCC) is mounted inside a printed circuit board (PCB) constituting electronic components. The use of MLCC in electric vehicles and the latest mobile phones is rapidly increasing with the latest technology. Environments in which electronic components are used are becoming more diverse and conformal coatings are being applied to protect mounted components from these environments. In particular, MLCCs in electronic components mainly have voltage applied. They might be used in environments where humidity exists for various reasons. In a humid environment, electrochemical migration (ECM) will occur, with the cathode and anode on the surface of the MLCC encountering each other. This can result in product damage due to a short circuit. In this study, the effects of voltage, NaCl concentration, and distance between electrodes on a non-mount MLCC, surface mount MLCC, and solder pad pattern were evaluated using a water drop test (WDT). Based on the analysis of the effects of the presence of conformal coating, applied voltage, concentration of NaCl, and the distance between electrodes, a mechanism model for ECM behavior in MLCCs was proposed.
]]>Coatings doi: 10.3390/coatings14030358
Authors: Feng Lyu Xinyue Zhou Zheng Ding Xinglong Qiao Dan Song
This paper presents research on the application of ultrasonic-guided wave technology in corrosion defect identification, expounds the relevant ultrasonic-guided wave theories and the principle of ultrasonic-guided wave non-destructive testing of pipelines, and discusses the Lamb wave and shear horizontal wave mode selection that is commonly used in ultrasonic-guided wave corrosion detection. Furthermore, research progress in the field of ultrasonic-guided wave non-destructive testing (NDT) technology, i.e., regarding transducers, structural health monitoring, convolutional neural networks, machine learning, and other fields, is reviewed. Finally, the future prospects of ultrasonic-guided wave NDT technology are discussed.
]]>Coatings doi: 10.3390/coatings14030357
Authors: Jiping Chen Yu Da Jing Yang Guirong Zhu Haiyan Qin
Craniofacial bone defects are usually secondary to accident trauma, resection of tumor, sever inflammation, and congenital disease. The defects of craniofacial bones impact esthetic appearance and functionality such as mastication, pronunciation, and facial features. During the craniofacial bone regeneration process, different osteogenic cells are introduced, including primary osteoblasts or pluripotent stem cells. However, the defect area is initially avascular, resulting in the death of the introduced cells and failed regeneration. Thus, it is vital to establish vascularization strategies to build a timely and abundant blood vessel supply network. This review paper therefore focuses on the reconstruction of both osteogenesis and vasculogenesis. The current challenges, various strategies, and latest efforts applied to enhance vascularization in craniofacial bone regeneration are discussed. These involve the application of angiogenic growth factors and cell-based vascularization strategies. In addition, surface morphology, porous characters, and the angiogenic release property of scaffolds also have a fundamental effect on vasculogenesis via cell behavior and are further discussed.
]]>Coatings doi: 10.3390/coatings14030356
Authors: Vladimir Bystrov Ekaterina Paramonova Xiangjian Meng Hong Shen Jianlu Wang Tie Lin Vladimir Fridkin
This work is devoted to the study of nanosized polymer polyvinylidene fluoride (PVDF) thin ferroelectric films (two-dimensional ferroelectrics) and their composites with graphene layers, using molecular dynamics methods to (1) study and calculate the polarization switching time depending on the electric field and film thickness, (2) study and calculate the polarization switching time depending on changes of the PVDF in PVDF-TrFE film, and (3) study the polarization switching time in PVDF under the influence of graphene layers. All calculations at each MD run step were carried out using the semi-empirical quantum method PM3. A comparison and analysis of the results of these calculations and the kinetics of polarization switching within the framework of the Landau–Ginzburg–Devonshire theory for homogeneous switching in ferroelectric polymer films is carried out. The study of the composite heterostructures of the “graphene-PVDF” type, and calculations of their polarization switching times, are presented. It is shown that replacing PVDF with PVDF-TrFE significantly changes the polarization switching times in these thin polymer films, and that introducing various graphene layers into the PVDF layered structure leads to both an increase and a decrease in the polarization switching time. It is shown that everything here depends on the position and displacement of the coercive field depending on the damping parameters of the system. These phenomena are very important for various ferroelectric coatings.
]]>Coatings doi: 10.3390/coatings14030355
Authors: Yin Xu Qiang Liu Weiting Zhi Guangqiang Shao Peng Liu
In the context of a main road area with significant traffic flow, posing challenges to constructing the freezing station on the ground, an innovative proposal suggests situating the freezing station at the station. This approach aims to facilitate construction at the same time for the connection aisle, tunneling, and track laying, thereby reducing the construction period; however, this will lead to a corresponding increase in the freezing pipeline distance. The theoretical analysis, numerical analysis, and integration with engineering practices were employed to examine the essential aspects and key technologies in the long-distance freezing design and construction, including the freezing hole construction, thermal insulation method of brine pipelines and tunnel segments, and technique program to retain the brine pressure and flow discharge, as well as the method to reduce the interplay of cross-construction. The validity of the construction program for the long-distance frozen excavation was finally evaluated based on onsite monitoring and theoretical analysis. The results show that the temperature of the brine in both the delivery and return pipelines first decreases linearly and then stabilizes gradually with freezing time, and the temperature difference is between 1 °C and 1.5 °C at the later freezing period. The temperature variation of the frozen wall is similar to that of brine in the delivery and return pipelines, and there is a good correlation between them. After the frozen wall encloses, the internal pressure of the frozen wall increases quickly, which can be effectively reduced to prevent wall cracking and breakage by regulating the pressure relief holes. The above theoretical analysis result shows that the average temperature of the frozen wall should be less than −9.7 °C when the designed thickness of the frozen wall is 2.2 m. The monitoring data indicates that the average temperature of the frozen wall reaches −13.9 °C, which satisfies the design requirement. The design and construction technology of long-distance freezing enhance the construction of the subway connection aisle. The novel method deviates from the conventional practice of establishing freezing stations within tunnels and offers valuable insight and guidance for comparable projects.
]]>Coatings doi: 10.3390/coatings14030354
Authors: Huayang Dang Wenkai Zhang Cuiying Fan Chunsheng Lu Minghao Zhao
The mechanical response of a quasicrystal thin film is strongly affected by an adhesive layer along the interface. In this paper, a theoretical model is proposed to study a thin two-dimensional hexagonal quasicrystal film attached to a half-plane substrate with an adhesive layer, which undergoes a thermally induced deformation. A perfect non-slipping contact condition is assumed at the interface by adopting the membrane assumption. An analytical solution to the problem is obtained by constructing governing integral–differential equations for both single and multiple films in terms of interfacial shear stresses that are reduced to a linear algebraic system via the series expansion of Chebyshev polynomials. The solution is compared to that without adhesive layers, and the effects of the aspect ratio of films, material mismatch, and the adhesive layer, as well as the interaction between films, are discussed in detail. It is found that the adhesive layer can soften the localized stress concentration. This study is instructive to the accurate safety assessment and functional design of a quasicrystal film system.
]]>Coatings doi: 10.3390/coatings14030353
Authors: Shu-Fan Zhou Sheng Lu Wei-Gang Lv Ze-Xin Wang Dubovyy Oleksandr Jun-Jie Gu Jin-Wei Zhang Liang-Yu Chen
This study investigated the impact of NaAlO2 concentration in electrolytic solutions on micro-arc oxidation (MAO) coatings, focusing on their surface quality enhancement and corrosion resistance improvement. The surface morphology and microstructure of these coatings were assessed using scanning electron microscopy. Mechanical properties, such as hardness and wear resistance of MAO coatings, were tested. The hardness of the 6 g/L group was 411.2 HV. X-ray photoelectron spectroscopy examinations showed that MgAl2O4, CaMgP2O7, and MgSiO4 were the phases in the MAO coating. Antibacterial assessments were performed to evaluate the influence of NaAlO2 concentration, and the antibacterial rate of the 6 g/L group reached 97.08%. The hydrophilicity of the coatings was determined using water contact angle measurements, wherein the water contact angle of the 6 g/L was the lowest, at 58.25°. Corrosion resistance was evaluated with an electrochemical workstation. The findings revealed that the MAO coatings prepared with a NaAlO2 concentration of 6 g/L exhibited superior uniformity with fewer defects, enhanced corrosion resistance, and increased adhesive strength compared to other concentration groups. The 6 g/L NaAlO2 concentration MAO coating demonstrated the highest fitting coating resistance R3 (8.14 × 104 Ω∙cm2), signifying better corrosion resistance.
]]>Coatings doi: 10.3390/coatings14030352
Authors: Svilen D. Angelov Christoph Rehbock Vaijayanthi Ramesh Hans E. Heissler Mesbah Alam Stephan Barcikowski Kerstin Schwabe Joachim K. Krauss
The efficacy of electrodes that are chronically implanted and used in the context of deep brain stimulation (DBS) for the treatment of neurological disorders critically depends on stable impedance. Platinum–iridium electrodes were coated with laser-generated platinum nanoparticle colloids (PtNPs) via electrophoretic deposition using pulsed direct currents (DC-EPD). Uncoated electrodes were used as controls. In vitro, electrodes were stimulated for four weeks in a 0.9% NaCl solution. For the in vivo (rats) study, coated electrodes were implanted in the left and uncoated control electrodes in the right subthalamic nucleus (STN). After two weeks of recovery, electrodes were stimulated for four weeks. Impedance measurements were conducted after each week of stimulation, both in vivo and in vitro. NP-coating resulted in a significant and long-lasting reduction in electrode impedance (p < 0.05) over four weeks of in vitro stimulation. Despite an initial increase in impedance after intracranial implantation, the impedance of the NP-coated electrodes was also reduced during in vivo stimulation over four weeks. NP-coated electrodes had a lower fluctuation of impedance during stimulation compared to uncoated electrodes both in vitro and in vivo (p < 0.05). Laser-generated PtNPs applied to electrodes by pulsed DC-EPD lead to lower and more stable electrode impedance during chronic stimulation, with the potential to enhance the performance of DBS systems during chronic use.
]]>Coatings doi: 10.3390/coatings14030351
Authors: Taotao Cheng Yuelu Dong Liang Ma Zhibing Wu Jun Wang Xiang Ma Zhiping Wang Shijie Dai
The failure of premature thermal cycling spalling off is the bottleneck problem currently faced by yttrium oxide partially stabilized zirconia (YSZ) ceramic-based sealing coatings. Studies on the thermal cycling performance of coatings with “brick-mud” structures were carried out by experimental and simulation methods in this paper. The results showed that, as the thickness of “mud” layer increased, the bonding strength of the “brick-mud” structure coatings gradually decreased. When the thickness of the “mud” layer was about 3 μm and 10 μm, the thermal cycling lives of the T1 and T2 coatings were improved by 90.0% and 135.7%, respectively, compared with conventional coating (T0 coating), while that of the T3 coating (containing thick “mud” layers of about 20 μm) was decreased by 81.4%. The stress field of M2 “mud” layers with different thicknesses was subjected to a comprehensive effect by thermal mismatch stress and pores in “brick” layer. Compared with the medium and thick “mud” layers, the thin “mud” layer sustained obvious larger σ22 max and σ12 max, indicating its potential for the preferential initiation of transverse microcracks. In addition, the thin “mud” layer withstood the largest σ11 max and had the strongest potential for longitudinal crack growth. Both transverse and longitudinal cracking could consume energy during thermal cycling and reduce the stress concentration at the top coating/bond coating interface. These were the main reasons for the improvements in the thermal cycling performances of the T1 and T2 coatings. The degree of crack deflection and the capacity of energy dissipation in the “mud” layer increased significantly with its thickness. However, the propagation length of transverse cracks also gradually increased in the meantime. Especially when the “mud” layer was 20 μm, the length of the transverse cracks increased rapidly. Thus, early interlayer delamination failure occurred in the T3 coating during thermal cycling.
]]>Coatings doi: 10.3390/coatings14030350
Authors: Haotian Xing Yunzhi Tang Xinying Fa Hongyun Zhang Zhangzhi Shi Shenglian Yao Luning Wang
Zinc and its alloys have garnered significant attention in the field of biological implantation due to their biodegradable, osteogenic, and mechanical properties. However, the degradation of zinc and its alloys always lead to an increase in local ion concentration, and the bare metal surfaces lack biocompatibility for implantation. To address these issues, a layer of calcium–phosphorus (CaP) coating was prepared on the surface of a Zn-0.5Li alloy. The micro-structure of the coating was observed with scanning electron microscopy (SEM) and a white light interferometry microscope. The phases of the coatings were characterized through X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The bonding strength between the coating and substrate was investigated using a scratch tester with a diamond stylus, and the corrosion properties were assessed using an electrochemical method. For the evaluation of biocompatibility and osteogenic properties, MC3T3-E1 cells were cultured on the coating. Live/dead staining and proliferation tests were performed to assess cell viability and growth. Cell adhesion morphology was observed with SEM, and the level of alkaline phosphatase (ALP) in the MC3T3-E1 cells cultured on the material surface was evaluated by ALP staining and activity measurement. The CaP coating on the zinc alloy surface improved the alloy’s biocompatibility and osteogenic property, and could be a promising surface modification option for a biodegradable zinc alloy.
]]>Coatings doi: 10.3390/coatings14030348
Authors: Jinyong Qiu Xiaoqiang Xu Xu Chen Yaxiong Liu Yanlong Wu
Laser powder bed fusion can fabricate porous structures through lattices, but the preparation of micropores (<50 μm) with a specific pore distribution remains a challenge. Microporous 316L was fabricated by controlling the melting and solidification behavior of the particles using laser energy. The laser energy density was not a determining factor for the porosity and micropore formation, except for the single-factor condition. The high-speed scanning mode required a higher laser power to disorder the pore distribution, whereas low-speed scanning with a low laser impact on the stacking particles formed organized pores. The hatch distance significantly affected the pore distribution and pore size. The pore distribution in the XY plane was organized and homogenous, with channeled pores mainly interconnected along the laser scanning tracks, whereas in the Z direction, it showed a relatively disordered distribution, mainly linked along the layered direction. The microporous 316L displayed a mean pore size and median pore size of 10–50 μm with a high-percentage size distribution in 1–10 μm, a controllable porosity of 17.06%–45.33% and a good yield strength of 79.44–318.42 MPa, superior to the lattice porous 316L with 250.00 MPa at similar porosity.
]]>Coatings doi: 10.3390/coatings14030349
Authors: Di Wang Zhiqiang Xu Na Xu Zengliang Hu Hui Wang Feiting Shi
Steel pipes are commonly used to strengthen the concrete’s load-bearing capacity. However, they are prone to corrosion in salt erosion environments. In this study, the influence of Na2MoO4 and benzotriazole on concrete-filled steel tubes’ corrosion performance is investigated. The steel pipes’ mass loss rates (MRs), ultrasonic velocity, electrical resistance, and the AC impedance spectrum and Tafel curves of concrete-filled steel tubes were used to characterize the degree of corrosion in the steel pipes. Scanning electron microscopy–energy-dispersive spectrometry and X-ray diffraction were used for studying the composition of steel pipe rust. The research results revealed that the NaCl freeze–thaw cycles (F-C) and NaCl dry–wet alternation (D-A) actions had a reducing effect on the mass and ultrasonic velocity of the concrete-filled steel tubes. After 300 NaCl F-C and 30 NaCl D-A, the MRs were 0%~0.00470% and 0%~0.00666%. The corresponding ultrasonic velocities were 0%~21.1% and 0%~23.6%. When a rust inhibitor was added, the results were the opposite. The MRs decreased by 0%~80.3% and 0%~81.6% with the added Na2MoO4 and benzotriazole. Meanwhile, the corresponding ultrasonic velocities were 0%~8.1% and 0%~8.3%. The steel tubes were corroded after 300 NaCl F-C and 30 NaCl D-A. The addition of rust inhibitors improved the corrosion resistance of the concrete-filled steel tubes by increasing the electrical resistance before NaCl erosion. The corrosion area rate decreased by using the rust inhibitors. The corrosion resistance effect of benzotriazole was higher than that of Na2MoO4. The concrete-filled steel tube with an assembly unit comprising 5 kg/m3 of Na2MoO4 and 15 kg/m3 of benzotriazole had the best corrosion resistance under the erosion induced by NaCl F-C and D-A. Rust inhibitors reduced the content of iron-containing crystals and iron elements. The specimens with 5 kg/m3 Na2MoO4 and 15 kg/m3 benzotriazole had the lowest concentration of iron-containing crystals and iron elements.
]]>Coatings doi: 10.3390/coatings14030347
Authors: Mehmet Gürsoy
In recent years, there has been growing interest in pH-responsive polymers. Polymers with ionizable tertiary amine groups, which have the potential to be used in many critical application areas due to their pKa values, have an important place in pH-responsive polymers. In this study, poly(2-Diisopropyl aminoethyl methacrylate) (PDPAEMA) thin films were coated on various substrates such as glass, fabric, and silicon wafer using a one-step environmentally friendly plasma enhanced chemical vapor deposition (PECVD) method. The effects of typical PECVD plasma processing parameters such as substrate temperature, plasma power, and reactor pressure on the deposition rate were studied. The highest deposition rate was obtained at a substrate temperature of 40 °C, a reactor pressure of 300 mtorr, and a plasma power of 60 W. The apparent activation energy was found to be 17.56 kJ/mol. Based on the results of this study, uniform film thickness and surface roughness were observed in a large area. The PDPAEMA thin film was exposed to successive acid/base cycles. The results showed that the pH sensitivity of the thin film produced by the PECVD method is permanent and reversible.
]]>Coatings doi: 10.3390/coatings14030346
Authors: María Belén Almendro-Candel Manuel Miguel Jordán Vidal
For decades, experts have paid considerable scientific and technological attention to the possibility of recycling waste that has reached nature as a result of mining activities related to natural stone, extracting metal or using foreign matter to recover natural environments. Several authors have shown that many of these types of waste can be vitrified or synthesised with an appropriately designed composition, not just to decrease their size but (as is more interesting from a financial point of view) to produce a wide range of glassy and/or ceramic materials that can have uses in industry and, crucially, in the construction sector (building and public works). In this paper, we conduct a comprehensive analysis of the state of the art, defining the different types of materials and their uses in order to decisively contribute to the circular economy and the zero-waste approach. We analyse the achievements accomplished in recent decades to be able to generate novel innovative ideas for collecting new eco-materials.
]]>Coatings doi: 10.3390/coatings14030345
Authors: Coatings Editorial Office Coatings Editorial Office
What is your current research and why did you choose this research field [...]
]]>Coatings doi: 10.3390/coatings14030344
Authors: Chiara Ricci Paola Buscaglia Debora Angelici Anna Piccirillo Enrica Matteucci Daniele Demonte Valentina Tasso Noemi Sanna Francesca Zenucchini Sara Croci Federico Di Iorio Laura Vigo Davide Quadrio Federica Pozzi
Artifacts pertaining to Buddhist culture are often studied in relation to their circulation from India throughout the rest of Asia; however, many traveled to Europe during the last few centuries as trade commodities and pieces for the art market, losing any devotional purpose in favor of a specific aesthetic sensitivity that was typically adapted to Western taste to appeal to collectors. This article presents a technical study of seven polychrome wooden sculptures from the Museo d’Arte Orientale (MAO) in Turin, Italy. Originally from China, these objects are generally attributed to the late Ming–early Qing dynasties (16th–18th centuries) based merely on stylistic and iconographic considerations. Scientific analysis sought to expand the available knowledge on their constituting materials and fabrication techniques, to address questions on their authenticity, to assess their state of preservation, and to trace the history of transformations they have undergone while transitioning from devotional objects to private collection and museum artwork. By delving into the sculptures’ intricate paint stratigraphy, the results were also key to guiding treatment choices. The outcomes of this study were featured in the MAO exhibition “Buddha10. A Fragmented Display on Buddhist Visual Evolution” (October 2022–September 2023).
]]>Coatings doi: 10.3390/coatings14030343
Authors: Gerardo Terán Méndez Selene Irais Capula-Colindres Julio César Velázquez Daniel Angeles-Herrera Noé Eliseo González-Arévalo Esther Torres-Santillan Arturo Cervantes-Tobón
It is well known that the mechanical properties of a steel plate depend on the anisotropy of the material and the rolling directions. This paper presents the results of the Charpy V-Notch (CVN) impact test for the ST, TL, TS, LS, LT, 45°, and SL directions in API 5L X52 pipelines with electric-resistance-welded (ERW) and seamless (SMLS) pipes. Charpy specimens were manufactured and tested according to the ASTM E23 standard in laboratory conditions. All possible directions in the pipe were tested. Three Charpy specimens were tested for each direction, for a total of 21 Charpy tests. Moreover, the microstructures, hardness, ductile and brittle areas, and fracture surfaces of the Charpy specimens are presented in this research. The results show that the Charpy energy values, hardness, and microstructures depend on the direction of the specimens. The Charpy values of the SMLS pipe are higher than those of the ERW pipe because of several metallurgical factors, such as grain size, non-metallic inclusions, delaminations, and microstructures.
]]>Coatings doi: 10.3390/coatings14030342
Authors: Krystyna Radoń-Kobus Monika Madej Joanna Kowalczyk Katarzyna Piotrowska
In this paper, the authors investigated the impact of DLC coatings doped with tungsten (a-C:H:W) coatings obtained using plasma-assisted physical vapor deposition (PVD) on the properties of the 100Cr6 steel. The results of the 100Cr6 steel specimens with and without the coating were compared. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis were used to observe the morphology of the coating surfaces and cross-sections and identify the elements in the coating composition. The contact angle of the investigated surfaces was measured with a tensiometer. Additionally, the effect of the coatings on the tribological properties of lubricated friction pairs was evaluated. Friction tests were performed on a ball-on-disc tribometer under lubrication with cutting fluid. The surface texture of the samples before and after the tribological tests was measured using a confocal profilometer. The results obtained from the tests and analysis allow for the conclusion that the use of DLC coatings a-C:H:W increases the hardness of 100Cr6 steel by three times. The values of the contact angles were indicative of surface hydrophilic characteristics. The tungsten-doped diamond-like coating under friction conditions reduced the coefficient of friction and wear. DLC coatings a-C:H:W lubricated with the cutting fluid improve the mechanical and tribological properties of 100Cr6 steel sliding surfaces under friction.
]]>Coatings doi: 10.3390/coatings14030341
Authors: Changqing Cui Chunyan Yang
Magnesium alloys are the lowest-density structural metals with a wide range of applications, such as aircraft skins, engine casings and automobile hubs. However, its low surface hardness and non-corrosion resistance in natural environments limit its wide range of applications. In this work, Si-DLC coatings (Si: 15 at.%) are fabricated on AZ91 alloy using a hollow cathode discharge combined with a DC bias voltage from 0 to −300 V to increase the deposition rate and modulate the structure and properties of the coatings. The Si interlayer with a thickness of around 0.6 µm is deposited first to enhance the adhesion. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy are used to investigate the effect of DC bias on the microstructure evolution of Si-DLC coatings. Meanwhile, corrosion and wear resistance of the coatings at various bias voltages have been investigated using electrochemical workstations and pin-on-desk wear testers. It is shown that the bias-free coating has a loose structure and is less resistant to corrosion and wear. The bias coating has a compact structure, small carbon cluster size, high chloride ion corrosion resistance, and high wear resistance against Al2O3 spheres. The corrosion potential of the coating bias at −300 V is −0.98 V, the corrosion current density is 1.35 × 10−6 A·cm−2, the friction coefficient is 0.08, and the wear rate is 10−8 orders of magnitude. The formation of SiC nanocrystals and high sp3-C, as well as the formation of transfer films on the surface of their counterparts, are the main reasons for the ultra-high wear resistance of the bias coatings. The wear rate, coefficient of friction, and corrosion rate of the coating are 0.0069 times, 0.2 times, and 0.0088 times that of the AZ91 alloy, respectively. However, the bias coating has only short to medium-term protection against the magnesium alloy and no long-term protection due to cracks caused by its high internal stress.
]]>Coatings doi: 10.3390/coatings14030340
Authors: Subhash Khetre Arunkumar Bongale Satish Kumar B. T. Ramesh
The minimum quantity lubrication (MQL) approach is used for improving tool life at a low cost, and it is environmentally friendly. When compared to traditional flood cooling technology, the flow rate in MQL is thought to be 10,000 times lower. The workpiece’s surface smoothness is enhanced by continuous chip formation during turning, but because the tool is always in touch with the chip, a crater wear zone is formed on the rake face due to high friction and thermal stress. While adding nanoparticles to MQL enhances cutting performance, a high concentration of these nanoparticles causes burr adhesion and decreased chip evacuation capability due to the agglomeration of nanoparticles, which affects the surface finish of the workpiece. A novel “coconut-oil-based SiC–MWCNT nano-cutting fluid for a CBN insert cutting tool” is proposed in this approach to overcome these issues. Silicon carbide (SiC) and multi-walled carbon nanotubes (MWCNTs) are added to coconut oil with an appropriate volume fraction for better lubrication. The thermal properties of the proposed nano-cutting fluid are compared with those of some existing nano MQL cutting fluids, and it was found that the MQL cutting fluid under consideration exhibits an elevated thermal conductivity and convective heat transfer coefficient that efficiently reduce tool temperature and improve tool life. The comparative study between the Finite Element Simulation using computational fluid dynamics (CFD) predicted variation in tool temperature and the corresponding experimental values revealed a remarkable alignment with a marginal error ranging from 1.27% to 3.44%.
]]>Coatings doi: 10.3390/coatings14030339
Authors: Xinbo Wang Shihan Zhang Fei Zhao Zhisheng Wu Zhiwen Xie
A detailed electron microscopy study was performed to clarify the fracture mechanism of WC particles reinforced with FeCoCrNiMn high-entropy alloy coatings at 600 °C. Large-sized fibers and elemental segregation formed in the coating, triggering high local stress in the matrix alloy and resulting in a low tensile strength of 150 MPa. High temperature promoted the homogenization process of elemental segregation, but also facilitated the dissolution of large-sized fibers, resulting in the growth of slim fibers and nanofibers. Both the structural homogenization and multi-scale fiber strengthening led to an enhanced tensile strength of 242 MPa at 600 °C. These current findings provide an understanding of the fracture mechanism of HEA/WC coatings during high-temperature exposure.
]]>Coatings doi: 10.3390/coatings14030338
Authors: Xinrui Yang Shiyuan Fang Yao Xie Jun Mei Jing Xie
In this article, the effect of active coatings of flaxseed gum (FG) and sodium alginate (SA) containing carvacrol (CA) on the quality of turbot (Scophthalmus maximus) after storage at 4 °C for 18 days was evaluated. The experimental results showed that FG/SA-CA could effectively inhibit the growth of microorganisms. At the same time, FG/SA-CA reduced the value of odorous-related compounds including thiobarbituric acid reactive substances (TBARS), total volatile base nitrogen (TVB-N), and K values. The FG/SA-CA significantly delayed the oxidation of myofibrillar protein (MP) through controlling the development of carbonyl groups and maintaining a high content of sulfhydryl groups. Thus, FG/SA-CA inhibits the growth of spoilage microorganisms, maintains the structure of the protein, and extends the refrigerated shelf life of turbot.
]]>Coatings doi: 10.3390/coatings14030337
Authors: Zhendong Zhang Di Wang Guanglei Liu Yiyi Qian Yuquan Xu Dingding Xiang
This work reviews surface modification techniques for improving the wear and corrosion resistance of 42CrMo steel. The advantages and disadvantages of various methods, including thermal spraying, deposition, hardfacing, laser cladding, nitriding, and laser surface treatment, are discussed. The review elaborates on the materials commonly employed in laser cladding technology, including iron-based, cobalt-based, nickel-based, and high-entropy alloys and reinforced composite coatings. Furthermore, the mechanisms and methods of improving the wear and corrosion resistance of 42CrMo steel are summarized. Finally, this review presents research shortcomings and future opportunities of surface modification techniques. This review also provides a theoretical guide for the application of 42CrMo steel.
]]>Coatings doi: 10.3390/coatings14030336
Authors: Wei Zhang Wenting Xia Zhiwei Chen Guoqing Zhang Sicheng Qian Zhifeng Lin
The cathodic protection provided by epoxy coating/epoxy zinc-rich coatings on defective areas under atmospheric and immersion conditions was studied via a Q235 wire beam electrode (WBE), scanning electron microscopy, X-ray diffraction, and surface morphology analysis. The results showed that the cathodic protection processes under the two test conditions displayed significant differences. The effective protection time of the defective area under the atmospheric condition was 1.7 times that under the immersion condition. Compared with the immersion condition, zinc particles in zinc-rich coatings under the atmospheric condition exhibited higher cathodic protection efficiency. The possible activation mechanism of zinc particles under the two conditions was elucidated.
]]>Coatings doi: 10.3390/coatings14030335
Authors: Žydrūnas Kavaliauskas Arūnas Baltušnikas Mindaugas Milieška Vitas Valinčius
As the industry develops more and more, heat is produced during fabrication processes, resulting in an excess of heat. One of the ways to solve the problem can be the conversion of excess heat into electricity using a thermoelectric generator (TEG). The authors of this paper propose a method of using thin-film TEGs for electricity generation, a procedure that has been given little attention to in the literature. In this study, thin TEGs (about 50–100 nm thick) were obtained from Bi-Ni, using magnetron sputtering technology. This type of TEG can be used not only as a device that generates electricity, but also as a protective layer for various systems, protecting them from environmental influences. In addition, such TEGs can be formed on a complex, uneven surface, with various details changing their geometric shape. As shown from XRD studies, the obtained Bi-Ni layer is polycrystalline. XRD studies help to determine whether the layer obtained is composed of pure layers of Bi and Ni metals or whether metal oxides have formed (metal oxides have a negative effect on electrical conductivity). An increase in the temperature from 80 to 120 K, respectively, increases the voltage generated by the TEG from 0.01 to 0.03 V. Meanwhile, the efficiency of such TEG element changes from 1 to 4.5% when the temperature change increases from 30 to 119 K.
]]>Coatings doi: 10.3390/coatings14030333
Authors: Axaule Mamaeva Aidar Kenzhegulov Aleksander Panichkin Rinat Abdulvaliyev Balzhan Kshibekova Talgat Arynbayev
The development of promising biocompatible composites based on hydroxyapatite with a metallic component is of great interest to researchers. This article describes the synthesis of hydroxyapatite powder by the hydrolytic method and presents the results of mechanical grinding of hydroxyapatite powder. Additionally, in order to study the interaction between titanium and hydroxyapatite powders, the results of their thermal treatment in the temperature range of 600–900 °C are presented. As a result of the hydrolytic method, a powder consisting of Ca5(PO4)3(OH) and CaO phases with a fraction of 400–600 μm was obtained. According to the results of mechanical grinding, it was determined that with an increase in grinding time from 30 to 120 min, the intensive main diffraction lines corresponding to hydroxyapatite decrease. During the thermal treatment of titanium and hydroxyapatite powders, titanium oxidizes forming suboxides and titanium dioxide (TiO2). At higher temperatures, the hydroxyapatite phase disappears from the mixture, and titanium oxide, calcium phosphate compound, and small amounts of calcium titanate and titanium hydrophosphate are present.
]]>Coatings doi: 10.3390/coatings14030334
Authors: Marcelo Broch Cristian Padilha Fontoura Arnaldo Oliveira Lima Michell Felipe Cano Ordoñez Izabel Fernanda Machado Cesar Aguzzoli María Cristina Moré Farias
Low-temperature plasma nitriding is a thermochemical surface treatment that promotes surface hardening and wear resistance enhancement without compromising the corrosion resistance of sintered austenitic stainless steels. Hollow cathode radiofrequency (RF) plasma nitriding was conducted to evaluate the influence of the working pressure and nitriding time on the microstructure and thickness of the nitrided layers. A group of samples of sintered 316L austenitic stainless steel were plasma-nitrided at 400 °C for 4 h, varying the working pressure from 160 to 25 Pa, and the other group was treated at the same temperature, varying the nitriding time (2 h and 4 h) while keeping the pressure at 25 Pa. A higher pressure resulted in a thinner, non-homogeneous nitrided layer with an edge effect. Regardless of the nitriding duration, the lowest pressure (25 Pa) promoted the formation of a homogenously nitrided layer composed of nitrogen-expanded austenite that was free of iron or chromium nitride and harder and more scratching-wear-resistant than the soft steel substrate.
]]>Coatings doi: 10.3390/coatings14030332
Authors: Yan Zhang Ying Zhou Lishou Ban Tian Tang Qian Liu Xijun Liu Jia He
In order to control the production cost of lacquer products, Cu–ethanolamine nanozymes were synthesized to simulate laccase to catalyze the oxidation and polymerization of urushiol. First-principles calculation results indicate that the D-band center of Cu center in the nanozymes was closer to the Fermi level than that of laccase, so Cu–ethanolamine was more conducive to the adsorption of substrate. The activation energy of Cu-ethanolamine catalyzed the oxidation of urushiol was significantly lower than that of laccase. Therefore, we inferred that the synthesized Cu–ethanolamine had a better catalytic effect on urushiol and was more conducive to paint film drying. By comprehensive comparison, the drying characteristics of the Cu–ethanolamine and raw lacquer with a 1:20 ratio are found to be closest to those of the raw lacquer, and the drying time is significantly shortened. The reaction results of the drying process performance test on the sample indicate that the composite lacquer can achieve the market-desired effect and performance requirements of the paint process.
]]>Coatings doi: 10.3390/coatings14030331
Authors: Jing Zhao Tongjun Zhao Yazhou Zhang Zhongtian Zhang Zehao Chen Jinlong Wang Minghui Chen
The 2024 aluminum alloy, a structural material commonly used in aviation aircraft bodies, is susceptible to serious corrosion in marine atmospheric environments. This paper comprehensively studies the corrosion behavior of the 2024 aluminum alloy in the South China Sea atmosphere. Weighing, morphology observation, phase analysis, electrochemical testing, and other methods were used to study the corrosion law and corrosion mechanism of the 2024 aluminum alloy. The main conclusions are as follows: At the initial stage of exposure, pitting corrosion occurred on the surface of the 2024 aluminum alloy. After 3 months of exposure, the self-corrosion current density increased from 0.456 μA·cm−2 to 8.338 μA·cm−2. After 6 months of exposure, the corrosion developed into general corrosion. The main component of the corrosion product was Al2O3·3H2O. The product covered the surface to form a loose corrosion product layer, which had an inhibitory effect on corrosion. The self-corrosion current density was reduced to 2.359 μA·cm−2. After 12 months of exposure, the corrosion product layer fell off and became thinner, and the self-corrosion current density increased to 2.849 μA·cm−2. The corrosion kinetics conformed to the functional equation W = 0.00346t0.73891, indicating that the corrosion products have a certain protective effect on the matrix.
]]>Coatings doi: 10.3390/coatings14030330
Authors: Lijuan An Tenghao Ma Yiran Nie Jing Wang
In this paper, NiMoO4 electrode materials doped with different concentrations of Nd rare earth metals were prepared by sol–gel method. Its morphology, structure, and spectral analysis were characterized by different scanning instruments, and the experimental results show that the NiMoO4 electrode material after adding 0.5% Nd doping showed excellent capacitance performance, with a specific capacity of 2182 F/g at a current density of 1 A/g. The capacitance retention was still 98.5% after 10,000 cycles at a current density of 5 A/g, which has a better electrochemical performance compared with the NiMoO4 material with superior electrochemical performance. In addition, an asymmetric capacitor device was prepared using 0.5% Nd-NiMoO4 material and CNTs as positive and negative electrodes, respectively, and the device showed a high energy density of 73.5 Wh/kg. In addition, the capacitor device still had a capacitance retention of 91.9% after 10,000 cycles. This paper provides an effective reference route for the preparation of rare-earth-doped bimetallic oxide electrode materials.
]]>Coatings doi: 10.3390/coatings14030329
Authors: Gözde Canik Nuran Ulusoy Kaan Orhan
Background: Polymerization shrinkage and microvoid formation has been a significant problem giving way to resin composite failure. The aim of this study was to evaluate the microvoid potential and microleakage of two bulk-fill and a microhybrid resin composite applied with different adhesive materials. Materials and Methods: MOD cavities were prepared in 60 endodontically treated maxillary premolars. The teeth were divided into six different groups (n = 10) according to adhesive systems (Gluma (Kulzer), OptiBond FL (Kerr) and resin composite materials EverX Posterior (GC) and Filtek One Bulk Fill (3M ESPE). An aging procedure with 5000 cycles of thermal cycling was applied. All teeth were individually scanned with micro-computed tomography. A Shapiro–Wilk test, two-way MANOVA, and Bonferroni analysis were used for statistical tests. Results: Self-etch groups showed more microleakage than total-etch groups. Minimum microleakage was observed in Filtek One Bulk Fill groups, whereas G-aenial Posterior groups showed maximum microleakage. Conclusions: Filtek One Bulk Fill (3M ESPE) resin composite was found to be more effective in reducing microvoid formation in MOD cavities when applied with total-etch adhesive systems. However, EverX Posterior (GC) and G-aenial Posterior (GC) showed less microvoid formation with self-etch adhesive systems.
]]>Coatings doi: 10.3390/coatings14030327
Authors: Giulio Casula Marzia Fantauzzi Bernhard Elsener Antonella Rossi
X-ray photoelectron spectroscopy (XPS) and angle-resolved XPS (ARXPS) characterization of surface layers resulting from the functionalization of polymers such as polyvinylchloride (PVC) modified with 3(mercaptopropyl)-trimethoxysilane (MPTMS) and (3-aminopropyl) triethoxysilane (APTES) is challenging due to the overlap in signals, deriving both from the substrate and the functionalized layers. In this work, a freshly cleaved, ideally flat gold surface was used as carbon-free model substrate functionalized with MPTMS and subsequently grafted with APTES. Avoiding the overlap of signals from carbon atoms present in the substrate, the signals in the C1s, O1s, Si2p, S2p and N1s high-resolution spectra could be assigned to the MPTMS/APTES functionalized layer only and the curve-fitting parameters could be determined. Quantitative analysis was in very good agreement with the expected stoichiometry of the functionalized layer, confirming the adopted curve-fitting procedure. In addition, it was found that one molecule of APTES grafted two MPTMS via silane groups. ARXPS allowed for determining the thickness of the functionalized layers: MPTMS thickness was found to be 0.5 (0.2) nm, whereas MPTMS + APTES thickness 1.0 (0.2) nm was in good agreement with Avogadro model calculations. This approach can be considered a powerful tool for characterizing functionalized surfaces of more complex systems by XPS.
]]>Coatings doi: 10.3390/coatings14030328
Authors: Yingna Liang Wei Wang Miaomiao Shen Zhepeng Zhang Hao Xing Cunyuan Wang Dianrong Gao
To explore the friction and wear performance of the valve pair with different wetting combinations under various working conditions in hydraulic oil lubrication, a low surface energy modification method was adopted in this paper to improve the surface wettability of the upper sample composed of SAF2507 and the lower sample composed of CFRPEEK, and to prepare valve plate pairs with different wetting combinations. The MMU-5G friction and wear testing machine was used to investigate its friction and wear characteristics under hydraulic oil lubrication. The results show that the surface free energy of SAF2507 and CFRPEEK decreased significantly after the treatment with a low surface energy solution, and the surface free energy of the upper and lower samples decreased by 41.9% and 42.2%, respectively. The oil contact angle of samples remained lipophilic, but the oil contact angle increased significantly. Under the working condition of low speed (800 r/min), the surface wettability of the valve plate pair has a great influence on its friction and wear characteristics. When operating at high speed (1200 r/min), the surface wettability of the valve plate pair has little influence on its friction and wear characteristics.
]]>Coatings doi: 10.3390/coatings14030326
Authors: Zhihang Xie Qing Liu Xiaopeng Hu Jinwei Guo Wang Zhu
The failure mechanism of the Pt-modified aluminide (Pt-Al) bond coating (β-(Ni, Pt)Al coating) in a simulated service environment has seldom been investigated. Based on a self-developed thermal barrier coating service environment simulator, a thermal shock experiment of single-phase Pt-Al bond coating on DD419 substrate at a temperature of 1170 °C was conducted combined with a real-time monitoring infrared thermal imager. The lifespan and failure mechanism of the coating are analyzed in detail. The results reveal that specimens of the Pt-Al bond coating, subjected to three repeated tests, exhibit failure after 650, 528, and 793 thermal shock cycles at 1170 °C, respectively. After failure, the contents of Pt and Al elements in the peeled region are lower than those in the unpeeled area, and a diffusion zone emerges in the bond coating. The failure mechanism of the Pt-Al bond coating during the thermal shock test can be attributed to three main aspects: (1) the diffusion and consumption of the Pt element reduced the oxidation resistance of the Pt-Al bond coating; (2) the diffusion and depletion of elemental Al causes a phase change in the coating, leading to the failure of the coating; (3) thermal stresses are generated in the Pt-Al bonded coating during the thermal shock test, which ultimately leads to wrinkling.
]]>Coatings doi: 10.3390/coatings14030325
Authors: Fengbo Li Conghui Zhang Yan Li Qingtao Pang
In this study, Cr3C2-Al2O3-NiCr coatings were prepared on INCONEL 600 alloy surfaces using the supersonic flame spraying technique, followed by a laser remelting treatment. In this way, this study further explored what impacts laser remelting has on coating performance. To this end, optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) were employed to carry out microstructural characterization. Energy-dispersive X-ray spectroscopy (EDS) was applied to conduct an analysis of the coatings’ elemental distribution while X-ray diffraction (XRD) was used to determine the coating phases. To measure the microhardness of the coatings, a microhardness tester was applied. In addition, the study investigated the samples’ electrochemical corrosion resistance and friction-wear performance under different surface conditions. According to the results, laser remelting enhanced the coating density, improved metallurgical bonding with the substrate, and optimized the carbide distribution, thereby enhancing corrosion and wear resistance in both air and corrosive media. However, excessive laser power hinders Cr3C2 nucleation, leading to diminished coating hardness and wear resistance in Cr7C3 formation.
]]>Coatings doi: 10.3390/coatings14030324
Authors: Simpy Sanyal SeonJu Park Ramachandran Chelliah Su-Jung Yeon Kaliyan Barathikannan Selvakumar Vijayalakshmi Ye-Jin Jeong Momna Rubab Deog Hawn Oh
Smart self-healing coatings offer a revolutionary approach to mitigating metal corrosion, a problem with significant economic and environmental impacts. Divided into intrinsic and extrinsic types, these coatings autonomously rectify the damage. Intrinsic variants utilize reversible bonds to achieve ongoing repair, while extrinsic ones incorporate micro/nanocontainers that activate upon environmental triggers to mend micro-cracks, their efficacy dictated by the encapsulated healing agents’ volume. This review dissects the rapidly evolving sector of stimuli-responsive self-healing coatings, emphasizing the progress in micro/nano container technology. It discusses the synthesis and encapsulation processes of different micro/nanocontainers and charts the transition from single to multistimulus-responsive systems, which enhances the coatings’ sensitivity and functionality. The addition of multifunctional traits such as self-reporting and anti-microbial actions further broadens their industrial applicability. The review provides a succinct overview of the field’s current state and future potential, envisioning a paradigm shift in corrosion protection through advanced smart coatings.
]]>Coatings doi: 10.3390/coatings14030323
Authors: Yong Li Yi Xiong Jinjin Tang Shun Han Fengzhang Ren Chunxu Wang Shubo Wang
High-temperature tensile experiments with tensile rates ranging from 0.01 s−1 to 10 s−1 were carried out at various temperatures ranging from 1000 °C to 1250 °C with a Gleeble-3800 thermal simulation tester to evaluate the physical properties of an as-cast Ni–W–Co–Ta medium–heavy alloy. The microstructure evolution of the alloy during high-temperature stretching was characterized by metallographic microscopy, scanning electron microscopy, and transmission electron microscopy. The results indicated the emergence of multiple slip lines and the parallel arrangement of dislocations in the grain of the alloy after high-temperature stretching, and typical characteristics of plane slipping were observed. The plasticity of the Ni–W–Co–Ta medium–heavy alloy increased, but its strength decreased with an increase in the deformation temperature. In contrast, an increase in the strain rate resulted in a noticeable increase in the strength and plasticity of the medium–heavy alloy. The experiments revealed that the maximum tensile strength of the as-cast Ni–W–Co–Ta medium–heavy alloy was 735 MPa (T = 1000 °C, ε˙ = 10 s−1). Additionally, the maximum reduction in area and elongation was 38.1% and 11.8% (T = 1250 °C, ε˙ = 10 s−1), respectively. The mode of fracture after high-temperature tensile deformation was brittle fracturing.
]]>Coatings doi: 10.3390/coatings14030322
Authors: Antonio Carlos Santos de Arruda Ronaldo Domingues Mansano Nelson Ordonez Ronaldo Ruas Steven Frederick Durrant
TiN-Ag ceramic coatings deposited by magnetron sputtering on silicon wafers and AISI F138 stainless-steel substrates with different Ag concentrations were evaluated for their application as decorative coatings. The results obtained indicated an almost linear increase in the thickness and roughness of the film as a function of the increase in the silver content of the film. For Ag concentrations greater than (8.3 ± 0.5) at %, a matte/satin finish was observed, i.e., a dull surface, produced by the agglomeration of particulates and the increase in roughness, respectively, which was corroborated by SEM and AFM analyses. The EDS analyses indicated particles with a high concentration of silver, but the elements titanium and nitrogen were also observed, indicating the formation of the TiN-Ag coating. The L*a*b* parameters in the CIELab color space were evaluated. No major variations were observed for coatings A and B (Ag concentrations of (4.1 ± 0.4) and (6.3 ± 1.2) at %, respectively). When the Ag content increased substantially, there was a corresponding decrease in L* values, as well as a shift in red reflectance. Furthermore, unwanted changes in the visual appearance and resistance to accelerated corrosion (salt spray) were also analyzed, as these factors compromised the film’s aesthetics in decorative applications.
]]>Coatings doi: 10.3390/coatings14030321
Authors: Izabela Betlej Bogusław Andres Sławomir Borysiak Sławomir Jaworski Marta Kutwin Krzysztof Krajewski Piotr Boruszewski
This work carried out research to determine the possibilities of using graphene oxide to provide wood with new functional features. With the saturation parameters used and working liquid with a concentration of 0.004% graphene oxide, the retention of the nanomaterial in wood was 0.25 kg/m3. The presence of graphene oxide increased the crystallinity of the wood to 64% (compared with 57% for unmodified wood). The TG/DTG spectra of wood impregnated with graphene oxide and the control wood indicated that the initial weight loss of the samples observed at a temperature of 100 °C was similar and amounted to less than 4%. A second mass loss was observed in a temperature range of 270 to 380 °C. The mass loss in this temperature range reached 70% and was similar in the test and control samples. Wood modified with graphene oxide showed increased thermal stability in a temperature range of 360 to 660 °C compared with native wood. Given the results obtained, there were no statistically significant differences in the water absorption of modified or control wood. The presence of low concentrations of graphene oxide in the culture medium did not inhibit the growth of the fungus Trichoderma viride; however, a decrease in the growth activity of mycelial hyphae was observed with an increasing concentration of nanomaterial in the medium. It has been reported that graphene oxide, as a stress factor, initiates changes at the cellular level, characterized by the formation of structures called chlamydospores by the body.
]]>Coatings doi: 10.3390/coatings14030320
Authors: Pritam J. Morankar Rutuja U. Amate Aviraj M. Teli Sonali A. Beknalkar Chan-Wook Jeon
Electrochromic materials allow for precise control of their optical properties by applying an electric field, which has led to recent developments in energy-saving and indoor temperature control systems like smart windows. The selective incorporation of metal dopants is an effective technique for generating highly advanced semiconducting metal oxides with precisely customized physicochemical characteristics. In this report, we employed a one-step electrodeposition process to fabricate nickel-doped tungsten oxide (W–Ni) thin films, systematically probing the impact of nickel (Ni) doping on the collective material characteristics. Comprehensive X-ray diffraction research revealed significant changes in diffraction patterns, suggesting slight modifications in the structure caused by Ni doping. The scanning electron microscopy showed complex differences in the microstructure of the film, such as a dense surface, porosity, and clustering of nanogranules. The WNi-3% thin film doped at 3 wt. % exhibited excellent electrochromic performance by efficiently handling lithium ions and displaying favorable electrochromic properties. The improved electrode, WNi-3%, showed a maximum optical modulation of 81.90%, exceptional reversibility of 99.4%, and a high coloration efficiency of 75.12 cm2/C. These findings underscore the efficacy of Ni-doping in tailoring the electrochromic properties of nickel-doped tungsten oxide thin films, thereby advancing the frontiers of high-performance electrochromic materials for energy-efficient applications.
]]>Coatings doi: 10.3390/coatings14030318
Authors: Henan Bu Zikang Ge Xianpeng Zhu Teng Yang Honggen Zhou
The precise prediction of painting man-hours is significant to ensure the efficient scheduling of shipyard production and maintain a stable production pace, which directly impacts shipbuilding cycles and costs. However, traditional forecasting methods suffer from issues such as low efficiency and poor accuracy. To solve this problem, this paper proposes a selective integrated learning model (ISA-SE) based on an improved simulated annealing algorithm to predict ship painting man-hours. Firstly, the improved particle swarm optimization (MPSO) algorithm and data grouping techniques are employed to achieve the optimal selection and hyperparameter optimization of base learners, constructing a candidate set of base learners. Subsequently, the simulated annealing algorithm is improved by adding random perturbations and using a parallel perturbation search mechanism to enhance the algorithm’s global search capability. Finally, an optimal set of base learners is composed of the candidate set utilizing the ISA-SE model, and a heterogeneous ensemble learning model is constructed with the optimal set of base learners to achieve the precise prediction of ship painting man-hours. The results indicate that the proposed ISA-SE model demonstrates improvements in accuracy, mean absolute error, and root mean square error compared to other models, validating the effectiveness and robustness of ISA-SE in predicting ship painting man-hours.
]]>Coatings doi: 10.3390/coatings14030319
Authors: Anna Kapran Rainer Hippler Harm Wulff Jiri Olejnicek Lenka Volfova Aneta Pisarikova Natalia Nepomniashchaia Martin Cada Zdenek Hubicka
Cobalt nickel oxide films are deposited on Si(111) or fluorine-doped tin-oxide-coated (FTO) glass substrates employing a pulsed hollow-cathode discharge. The hollow cathode is operated with argon gas flowing through the nozzle and with O2 gas admitted to the vacuum chamber. Three different cathode compositions (Co20Ni80, Co50Ni50, and Co80Ni20) are investigated. Deposited and annealed thin films are characterized by X-ray diffraction, infrared (Raman) spectroscopy, and ellipsometry. As-deposited films consist of a single mixed cobalt nickel oxide phase. Upon annealing at 600 °C, the mixed cobalt nickel oxide phase separates into two cystalline sub-phases which consist of cubic NiO and cubic Co3O4. Annealed films are investigated by spectroscopic ellipsometry and the optical bandgaps are determined.
]]>Coatings doi: 10.3390/coatings14030317
Authors: Yihui Cai Zhizhong Dong Lin Zhao Yun Peng Yang Cao
A coating prepared via laser cladding has the advantages of a high-density reinforced layer, a low matrix dilution rate, and combination with matrix metallurgy. In this study, Ni3Al-based alloy cladding layers with Cr7C3 were prepared via laser cladding, and the corresponding microstructures and wear resistance were studied in detail. The results show that the Ni3Al-based cladding layer prepared using laser cladding technology had good metallurgical bonding with the matrix, and there were no pores, cracks, or other defects on the surface. The microstructures of the laser cladding layer were mainly γ′-Ni3Al, β′-NiAl, and in situ C7C3. As the laser power increased, the heat input increased, resulting in an increase in the dilution rate. Simultaneously, the carbide size in the laser cladding layer increased. With the increase in laser power, the hardness of the laser cladding layer of the Ni3Al-based alloy decreased, and the wear resistance of the laser cladding layer first strengthened and then weakened. When the laser power increased to 2.0 kW, the wear rate of the laser cladding layer decreased to 0.480 × 10−5 mm3/N·m. When the laser power increased to 2.4 kW, the wear rate of the laser cladding layer increased to 0.961 × 10−5 mm3/N·m, which was twice the rate at 2.0 kW. This could be attributed to small Cr7C3 particles, which could not effectively separate the wear pairs, resulting in more serious adhesive wear. Large Cr7C3 particles caused the surface of cast iron material with lower hardness to be damaged, which suffered more serious particle wear. The generation of short rod-shaped carbides should be avoided because, in the process of friction and wear, carbides with these shapes are easy to break, thus leading to crack initiation.
]]>Coatings doi: 10.3390/coatings14030316
Authors: Constantin Răzvan Iordache Carmen Bujoreanu Stelian Alaci Florina-Carmen Ciornei Ionut-Cristian Romanu
The roller–shoe mechanism is a classic mechanical assembly with an essential role in motion transmission. Common rail high-pressure pumps are an example of a complex assembly that uses such a mechanism to transform the rotation motion into a translation one. The rolling element of the mechanism is represented by a cylindrical roller. Although it can carry heavy loads due to its design, a proper surface profile could significantly increase the life of the entire mechanism. A better solution can be achieved using a logarithmic profile. The shoe is the second base element of the mechanism. It is a part with an inner cylindrical surface and it is separated from the roller by a thin lubricant film. Considering this, increasing the hardness of the roller–shoe contact surface can be obtained using a suitable coating. The positive results of this coating are highlighted using endurance tests to which high-pressure pumps are subjected. Therefore, the roller profile and the shoe coating represent two directions for improving the contact between the mechanism transmission elements, in terms of wear reduction. The purpose of this paper is to identify a suitable roller profile and to highlight its impact on the shoe coating.
]]>Coatings doi: 10.3390/coatings14030315
Authors: Wenwen Yue Yichuan Zhang Zhengxin Zheng Youbin Lai
Due to the unparalleled benefits of traditional processing techniques, additive manufacturing technology has experienced rapid development and continues to expand its applications. However, as industrial standards advance, the pressing needs for high precision, high performance, and high efficiency in the manufacturing sector have emerged as critical bottlenecks hindering the technology’s progress. Single-laser additive manufacturing methods are insufficient to meet these demands. This review presents a comprehensive exploration of metal hybrid laser additive manufacturing technology, encompassing various aspects, such as multi-process hybrid laser additive manufacturing, additive–subtractive hybrid manufacturing, multi-energy hybrid additive manufacturing, and multi-material hybrid additive manufacturing. Through a thorough examination of the principles of laser additive manufacturing technology and the concept of hybrid manufacturing, this paper investigates in depth the notable advantages of hybrid laser additive manufacturing technology. It provides valuable insights and recommendations to guide the development and research of innovative machining technologies.
]]>Coatings doi: 10.3390/coatings14030314
Authors: Yujie Xu Yong Jiang Jinyang Xie Qingchen Xu Hao Fei Yilan Lu Jianming Gong
Oxygen boost diffusion (OBD) is an effective technology for improving the surface hardness of titanium and its alloys. In this present paper, the effect of temperature, vacuum condition and surface roughness on oxygen boost diffusion of Ti–6Al–4V alloy are studied. Test results show that OBD processing can be achieved at a low temperature and over long times, as well as at a high temperature and over short times. By comparing processing efficiency and mechanical properties, high temperatures and short times are preferred for OBD treatment. The influence of vacuum conditions on oxygen vacuum diffusion is significant. Under low vacuum degree conditions, relatively high oxygen content not only corrodes the OBD layer but also leads to spalling of the outmost surface of the OBD layer and the remaining oxide layer. High surface roughness can induce cracking not only in the oxide layer during the oxidation process but also in the outmost surface of the OBD layer during the vacuum diffusion process.
]]>Coatings doi: 10.3390/coatings14030313
Authors: Wei Sun Fang Duan Jianpeng Zhu Minglai Yang Ying Wang
In processing multilayer thin film materials, scanning electron microscopy (SEM) is commonly employed for observation. In images of SEM, backscattered electron (BSE) images is particularly suitable for distinguishing different components and layers of the films. However, at high magnification levels, BSE images often have blurriness and noise, leading to low edge sharpness. This study proposes a method for improving the integrity and accuracy of the edges. First, we segment the image into different contrast regions using the masking algorithm. Second, we enhance the images in separate regions by the enhancement algorithm. Finally, we combine the regions by logical operations. In instantiation, we implement our approach on SEM-BSE images. It was found that the edges are significantly sharpened through the assessment of the edge evaluation algorithm.
]]>Coatings doi: 10.3390/coatings14030312
Authors: Zhibo Zhang Dongfang Long Qinghao Yang
The adhesion of strain gauges (SGs) onto the underlying spring element plays an important role not only during the fabrication of the SG sensors but also for the final performance of the sensors. A novel and facile method for the evaluation of the adhesion strength of SGs is proposed, tested, and validated in this paper. In comparison with the traditional peel tester method, this method demonstrated both higher reliability and efficiency, especially from an industrial manufacturing point of view. The five-grade adhesion strength, with adhesion strength decreased from Grade 1 (G1) to Grade 5 (G5), results were corroborated by the classical pull-out adhesion testing method with satisfactory consistency and can be employed in the quick evaluation and monitoring of the adhesion strength. The easiness, convenience, and reliability of the method promises a great potential application in the industrial testing and manufacturing of SG sensors.
]]>Coatings doi: 10.3390/coatings14030311
Authors: Naiara P. V. Sebbe Filipe Fernandes Franciso J. G. Silva André F. V. Pedroso Rita C. M. Sales-Contini Marta L. S. Barbosa Luis M. Durão Luis L. Magalhães
The use of coatings on cutting tools offers several advantages from the point of view of wear resistance. A recent technique with great coating deposition potential is PVD HiPIMS. TiAlN-based coatings have good resistance to oxidation due to the oxide layer that is formed on their surface. However, by adding doping elements such as Vanadium, it is expected that the wear resistance will be improved, as well as its adhesion to the substrate surface. INCONEL® 718 is a nickel superalloy with superior mechanical properties, which makes it a difficult-to-machine material. Milling, due to its flexibility, is the most suitable technique for machining this alloy. Based on this, in this work, the influence of milling parameters, such as cutting speed (Vc), feed per tooth (fz), and cutting length (Lcut), on the surface integrity and wear resistance of TiAlVN-coated tools in the milling of INCONEL® 718 was evaluated. The cutting length has a great influence on the process, with the main wear mechanisms being material adhesion, abrasion, and coating delamination. Furthermore, it was noted that delamination occurred due to low adhesion of the film to the substrate, as well as low resistance to crack propagation. It was also observed that using a higher cutting speed resulted in increased wear. Moreover, in general, by increasing the milling parameters, machined surface roughness also increased.
]]>Coatings doi: 10.3390/coatings14030309
Authors: Lara Moreno Marta Mohedano Raul Arrabal Endzhe Matykina
Bioactive plasma electrolytic oxidation (PEO) coatings were developed on a wrought Mg0.5Zn0.2Ca alloy using a transparent electrolyte for easy maintenance and waste disposal, compared to a conventional suspension-based solution. Treatment times of 300, 600, and 900 s were evaluated for their effects on coating morphology, composition, and corrosion resistance. A short-time electrochemical impedance spectroscopy (EIS) screening was utilized to identify coatings with optimal corrosion protection. To assess the degradation rate and corrosion mechanisms, hydrogen evolution was monitored under pH-controlled quasi-in vivo conditions over extended immersion periods. Coating thickness increased by only 3% from 300 to 900 s of treatment (13 and 18 µm, respectively), with pore bands formed near the barrier layer at 900 s. The short-term EIS screening revealed that the coatings produced at 600 and 900 s were less protective and consistent than those at 300 s due to the presence of pore bands, which increased permeability. Hydrogen evolution measurements during 5 days of immersion at pH 7.4 indicated a tenfold higher degradation rate of the PEO-coated alloy compared to the bare substrate. Therefore, none of the PEO coatings provided effective corrosion protection after 24 h of immersion, which is attributed to crack formation at the PEO/corrosion products interface. This highlights the importance of crevices in the corrosion of Mg-Zn-Ca alloys. The presence of ZnO exacerbates the corrosion of magnesium in crevice areas.
]]>Coatings doi: 10.3390/coatings14030310
Authors: Karwan Rashid Darbandi Bassam Karem Amin
Additive manufacturing technologies can be used to fabricate 3D-printed dental restorations. In this study, we evaluated the effectiveness of the functionalized loading of zirconium dioxide (ZrO2) nanoparticles and silver-nanoparticles-immobilized halloysite (HNC/Ag) nanotubes into 3D printing resins. We created 3D printing resins by adding different mass fractions of ZrO2 and HNC/Ag. First, six groups of samples containing ZrO2 were prepared, comprising five groups with different mass fractions and one control group of ZrO2 containing 1 to 16 %wt. Different mass fractions of HNC/Ag fillers were combined with the ZrO2 mixture and resin at the ideal ratio from 1 to 7.5 %wt. The mechanical characteristics of 3D resin that we assessed were the flexural strength, flexural modulus, fracture toughness, and the microhardness. Additional rates of ZrO2 4 %wt. and HNC/Ag 5 %wt. significantly increase the flexural strength, flexural modulus, and fracture toughness compared to the control group (p < 0.001). ZrO2 16 %wt. and HNC/Ag 5 %wt. were found to be significantly harder compared to the other groups (p < 0.001). The amounts of NPs that can be added to 3D printing resin modification appears to be 4 %wt., and HNC/Ag 5 %wt. can be advantageous in terms of fracture toughness, flexural strength, and flexural modulus. All additions of nanoparticles raised the resin’s hardness.
]]>Coatings doi: 10.3390/coatings14030308
Authors: Jiapei Yao Zhennan Huo Jie Xu Jingjing Shang Yiping Weng Dongmei Xu Ting Liu Yong Huang Xindie Zhou
Osteoarthritis (OA) is characterized by cartilage degeneration and synovial inflammation, with chondrocytes playing a pivotal role in this disease. However, inflammatory mediators, mechanical stress, and oxidative stress can compromise functionality. The occurrence and progression of OA are intrinsically linked to the immune response. Current research on the treatment of OA mainly concentrates on the synergistic application of drugs and tissue engineering. The surface of engineered hydrogel materials can be immunomodified to affect the function of chondrocytes in drug therapy, gene therapy, and cell therapy. Prior studies have concentrated on the drug-loading function of hydrogels but overlooked the immunomodulatory role of chondrocytes. These modifications can inhibit the proliferation and differentiation of chondrocytes, reduce the inflammatory response, and promote cartilage regeneration. The surface immunomodification of engineered hydrogel materials can significantly enhance their efficacy in the treatment of OA. Thus, immunomodulatory tissue engineering has significant potential for treating osteoarthritis.
]]>Coatings doi: 10.3390/coatings14030307
Authors: Tao Liu Youkun Tao Yanli Wang Mingfeng Wu Jin Zhang Yang Yu Xingfu Wang Jing Shao
As one core component in hydrogen fuel cells and water electrolysis cells, bipolar plates (BPs) perform multiple important functions, such as separating the fuel and oxidant flow, providing mechanical support, conducting electricity and heat, connecting the cell units into a stack, etc. On the path toward commercialization, the manufacturing costs of bipolar plates have to be substantially reduced by adopting low-cost and easy-to-process metallic materials (e.g., stainless steel, aluminum or copper). However, these materials are susceptible to electrochemical corrosion under harsh operating conditions, resulting in long-term performance degradation. By means of advanced thermal spraying technologies, protective coatings can be prepared on bipolar plates so as to inhibit oxidation and corrosion. This paper reviews several typical thermal spraying technologies, including atmospheric plasma spraying (APS), vacuum plasma spraying (VPS) and high-velocity oxygen fuel (HVOF) spraying for preparing coatings of bipolar plates, particularly emphasizing the effect of spraying processes on coating effectiveness. The performance of coatings relies not only on the materials as selected or designed but also on the composition and microstructure practically obtained in the spraying process. The temperature and velocity of in-flight particles have a significant impact on coating quality; therefore, precise control over these factors is demanded.
]]>Coatings doi: 10.3390/coatings14030306
Authors: Haiming Liang Zhihong Duan Weiming Li
Heat exchangers, as essential devices for facilitating heat transfer, have found a variety applications in various industries. However, the occurrence of corrosion-related failures in real-world scenarios remains a prevalent problem that can lead to catastrophic incidents. This paper investigates the problem of corrosion perforation on the outlet flange of a heat exchanger in a sour steam stripper from a petrochemical company. Failure analysis was performed using physical testing and chemical analysis, metallographic examination, microscopic observation, and energy spectrum analysis. Intergranular corrosion experiments and flow calculations were performed to verify the analysis. The results indicate that the main cause of the flange corrosion perforation was the formation of a highly concentrated NH4HS aqueous solution during the cooling process of the NH3, H2S, and water vapor in the fluid passing through the heat exchanger, and the velocity was too high, which triggered alkali-sour water washout corrosion. To prevent the recurrence of similar corrosion perforations, recommendations for material and process optimization are proposed to effectively reduce the safety production risks in refinery units and provide valuable information for the safe long-term operation of a sour steam stripper.
]]>Coatings doi: 10.3390/coatings14030305
Authors: Jixing Sun Chenxi Shao Kun Zhang Jiyong Liu Shengchun Yan Yang Liu Yan Zhang
Circuit breakers, affected by multiple lightning strikes after the breaker has been tripped, can break down again, which will reduce the life of the circuit breaker and threaten the stable operation of the power system. Aiming at this problem, this research obtained the temperature diffusion process of the inrush current process of the circuit breaker’s opening and breaking, using the Schlieren technique combined with existing image recognition technology to obtain the temperature characteristics of the airflow in the air gap of the contact, as well as the characteristics of the flow of air itself. The results of the study show that the circuit breaker breakdown process generates a shock wave with a velocity approximately equal to the speed of sound under the same conditions. The maximum velocity of the airflow boundary diffusion is about one-quarter of the speed of sound under the same condition, and it decays very fast, reducing to the airflow drift velocity within 10 ms after breakdown. The maximum temperature of the thermals is concentrated between 6000 K and 8000 K, and the temperature change is approximately inversely proportional to the square of the time. This research provides the basis for the design of a circuit breaker’s contact structure, opening speed optimization method, interrupter chamber, and insulation design optimization.
]]>Coatings doi: 10.3390/coatings14030304
Authors: Tian-Chiuan Wu Wei-Ming Huang Jenn-Kai Tsai Cheng-En Chang Teen-Hang Meen
Owing to its contribution to carbon emission reduction, green energy has received widespread attention. Among green energy sources, solar energy is regarded as the most important. In solar energy production, dye-sensitized solar cells (DSSCs) have been favored owing to their characteristics of simple manufacturing and high efficiency as a third-generation solar cell technology. DSSCs are prospective candidates for powering indoor Internet of Things (IoT) devices. In this study, to find a method to enhance DSSCs’ efficiency, the advantages and disadvantages of the screen printing method and the mechanical pressing and annealing method were analyzed. Using an improved method, a TiO2 photoanode was processed and annealed, and the DSSCs with the photoanode showed an efficiency increase from 1.10 to 4.78%.
]]>Coatings doi: 10.3390/coatings14030303
Authors: Yifan Wang Yuan You Mufu Yan Yanxiang Zhang Wenping Sheng Yan Wang Shimiao Xu Feng Gu Chaohui Wang Weidong Cheng
This paper investigates the effect of the element La on plasma nitriding of the CoCrCuFeNi high-entropy alloy (HEA) at 440 °C for 8, 16, and 24 h. The phase composition, morphology, and hardness distribution of the nitrided layer are characterized using XRD, optical microscopy, and a microhardness tester. Furthermore, the corrosion resistance is tested using an electrochemical workstation. The study evaluated the friction and wear performance using a testing machine and scanning electron microscope. The thickness of the effective hardening layer after 16 h of treatment with La was similar to that after 24 h of treatment without La. The addition of La significantly increased the growth rate constant of the effective hardening layer from 0.53 × 10−14 m2/s to 0.72 × 10−14 m2/s. In addition, an expanded FCC phase with greater interplanar spacing can be formed on the surface of the sample by introducing La into the plasma nitriding process. This indicates that the expanded FCC phase, with a higher concentration of interstitial nitrogen atoms, can effectively improve the corrosion resistance of the specimen surface. The corrosion rate of the specimen surface was reduced by 27.5% and the wear rate was reduced by 41.7% after 16 h of treatment with the addition of La compared to 24 h of nitriding without the addition of La. It has been shown that the addition of La to the plasma nitriding process results in a higher quality nitrided layer in a shorter time and also demonstrates that La has the potential to optimize the surface properties of plasma nitrided HEAs.
]]>Coatings doi: 10.3390/coatings14030302
Authors: Hai Liu Jihong Liao Chonghua Li Gang Huang
This study investigates the magnetization mechanisms in MnZn ferrites, which are key materials in high-frequency power electronics, to understand their behavior under various sintering conditions. Employing X-ray diffraction and scanning electron microscopy, we analyzed the microstructure and phase purity of ferrites sintered at different temperatures. Our findings confirm consistent spinel structures and highlight significant grain-growth and densification variabilities. Magnetic properties, particularly the saturation magnetization (Ms) and initial permeability (μi), were explored, revealing their direct correlation with the sintering process. The decomposition of magnetic spectra into domain-wall-motion and spin-rotation components offered insights into the dominant magnetization mechanisms, with the domain wall movement becoming increasingly significant at higher sintering temperatures. The samples sintered at 1310 °C showcased superior permeability and the least loss in our investigations. This research underscores the impact of sintering conditions on the magnetic behavior of MnZn ferrites, providing valuable guidelines for optimizing their magnetic performance in advanced electronic applications and contributing to the material science field’s understanding of the interplay between sintering, microstructures, and magnetic properties.
]]>Coatings doi: 10.3390/coatings14030301
Authors: Di Yun Cheng Tang Ulf Sandberg Maoping Ran Xinglin Zhou Jie Gao Liqun Hu
The depth to which the pavement texture is enveloped by the tire tread rubber (d) is an important parameter related to contact performance. This study presents a new method (S-BAC), which relies on the ratio between the real contact area and the nominal tire-pavement contact area (S) and the bearing area curve (BAC), to measure the depth on pavements. The tire-pavement contact was simulated by contact between a non-patterned rubber block and pavement specimens. After analyzing the affecting factors, the new method was compared with previous methods by the d values and the application on the relationship between pavement texture parameters and friction. The results reveal that though there is a linear regression between the d obtained with the S-BAC and previous methods, the d values obtained with different methods differ. Applying the S-BAC method can strengthen the relationship between texture parameters and friction more than other methods.
]]>Coatings doi: 10.3390/coatings14030300
Authors: Sheng Wang Tianle Xu Yingchen Wu Xiguo Chen Xiaohong Yang
Ti-45Al-8Nb alloy is widely utilized in the lightweight design of the aerospace field because of its excellent properties. In order to make full use of this alloy, it is important to carry out relevant research, such as into the joining process of Ti-45Al-8Nb alloy. In this work, Ti-45Al-8Nb alloys were successfully connected by a TiZrCuNi amorphous interlayer, which was fabricated using the rapid solidification method. Ti-45Al-8Nb joints were composed of two zones. The typical microstructure of a Ti-45Al-8Nb joint was Ti-45Al-8Nb/AlCuTi + Ti3Al/(Ti, Zr)(Cu, Ni) + (Ti, Zr)2(Cu, Ni)/Ti3Al + AlCuTi/Ti-45Al-8Nb. The diffusion of elements between the interlayer and the substrate was enhanced by increasing the brazing temperature, which resulted in an increase in the thickness of the interfacial reaction layer. The maximum shear strength was 171.2 MPa, which was obtained at 930 °C. The typical cleavage fracture was found in all of the Ti-45Al-8Nb joints. The mechanical properties of the joint were compromised at high brazing temperature due to the presence of excessive (Ti, Zr)2(Cu, Ni) phase and coarse Ti3Al phase, both of which are inherently brittle and harmful to the shear strength of the obtained joint.
]]>Coatings doi: 10.3390/coatings14030299
Authors: Zhaoyang Kong Zhipeng Wang Yingmin Li Runxia Li
Spark plasma sintering is a process of rapid, low-temperature, and high-density sintering. Moreover, traditional sintering methods can solve the problems of large grain sizes and low densities. The sintering temperature plays a crucial role in influencing the physical properties of high-silicon–aluminum (Si-Al) composites. This work investigated the impact of temperature on the microstructure, interface, and physical properties of high-Si-Al composites by spark plasma sintering. The results demonstrate that when the powder was processed by ball milling at a sintering temperature of 565 °C, the material exhibited the densest microstructure with minimal pore formation. The average size of the silicon phase is the smallest. The material’s thermal conductivity is 134.6 W/m·K, the thermal expansion coefficient is 8.55 × 10−6 K−1, the Brinell hardness is 219 HBW, the density is 2.415 g/cm3, and the density reaches 97.75%. An appropriate sintering temperature facilitates particle rearrangement and dissolution–precipitation processes, enhancing the material structure and performance.
]]>Coatings doi: 10.3390/coatings14030298
Authors: Musibau Olalekan Ogunlana Mammo Muchie Jan Swanepoel Olukorede Tijani Adenuga Oluseyi Philip Oladijo
Titanium carbide materials are introduced into manufacturing industries for the reinforcement and surface protection of base materials due to their substantial ability to withstand severe environments, which include sliding wear, corrosion, and mechanical failures. A thin film of titanium carbide (TiC) is coated onto brass and copper substrates using the radio frequency magnetron sputtering (RFMS) deposition method. The coating process is carried out at constant processing parameters, which include a sputtering power of 200 W, a temperature of 80 °C, a deposition time of 180 min, and an argon (Ar) gas flow rate at 10 standard cubic centimetres per minute (SCCM). The coating, together with the base materials, is modelled and its behaviours are simulated using ANSYS Workbench R19.2 Academic, supported by Mechanical APDL solver for nonlinear finite element analysis (FEA). The deformation, equivalent stress–strain characteristics, and elastic–plastic properties of the coating are determined at applied loads of 60 N and 25 N and coefficients of friction (CoF) of 0.25 and 0.38 for the thin film deposition on brass and copper substrates. The sliding distance and the speed of the alloy steel ball used during the sliding wear operation are found to be 3 mm and 4 mm/s, respectively. The sliding wear modelling and simulation process are, however, designed for the ball-on-flat (BoF) wear technique with a dry sliding approach. Therefore, BoF wear simulations are also performed on titanium carbide–brass (TiC-Br) and titanium carbide–copper (TiC-Cu) conjugates for the evaluation of surface engineering applications such as cutting tools and in automotive, aerospace, thermomechanical, and biomedical fields. The ball used for the FEA wear simulation is made from alloy steel material (AISI 52100) with a radius of 3.175 mm.
]]>Coatings doi: 10.3390/coatings14030297
Authors: Haiping Zhang Jixing Cui Jiayuan Yang Hui Yan Xinping Zhu Yuanyuan Shao Hui Zhang Jesse Zhu
Environmentally friendly powder coatings which have the advantages of being VOC-free, low-cost, and high-efficiency with a high recovery rate have been attracting increasing research attention. The introduction of antibacterial agents into the powder coatings endows them with a capacity to kill bacteria and viruses on the surface of objects; additionally, this enables them to inhibit the indirect transmission of pathogenic microorganisms. Silver, possessing broad-spectrum, strong, and stable antibacterial properties, is considered to be a promising antibacterial material for use in coating applications. Carrier materials for active silver play an important role in its activity and stability. However, there is a lack of systematic studies on the effects of different types of carriers in such coating systems, especially in green powder coating systems. In this paper, we investigated two types of carriers for active silver agents: zeolite, i.e., Linde type A (LTA) zeolite and Y-type zeolite; clay-based materials, i.e., montmorillonite and vermiculite. All the agents showed high antibacterial activity, with antibacterial rates of over 99% as compared to commercial agents. Among the four agents, the Ag-LTA zeolite antimicrobial agent showed a reduction rate of over 99.99%; additionally, it maintained a reduction rate of 99% after seven washing cycles. Thus, this agent was demonstrated to have the highest effectiveness and high durability; these features can be attributed to the high silver content and small particle size. The LTA zeolite also provides a protective effect for silver ions, protecting them from reduction, due to the restriction of elemental silver formation within the confined interior space of the α-cage structure. The Y-type zeolite antimicrobial agent exhibited a slightly lower antimicrobial performance due to its higher silicon-to-aluminum ratio and its lower cation exchange capacity. Comparatively, antimicrobial agents utilizing clay-based carriers have lower cation exchange capacity, resulting in poorer antimicrobial effectiveness than zeolite carriers. In addition, silver loaded on clay-based materials is prone to detach from the carrier and undergo a reduction reaction, making the coating yellowish in color. This study first provides information on the roles of different types of carriers in powder coating systems; then, this information guides the selection of carriers for active silver for the development of efficient antimicrobial agents and coatings.
]]>Coatings doi: 10.3390/coatings14030296
Authors: Jining He Baoqiang Li Hongjian Zhao Guanya Fu Jiawei Fan Yanfang Qin
In this work, the TiC-reinforced CoNi alloy coatings were prepared by the plasma spraying method. Their microstructure, high-temperature oxidation, and thermal shock resistance at 900 °C were studied. The results showed that the CoNi alloy coating exhibited a single phase (c-Co-Ni-Cr-Mo). After adding Ti-graphite mixed powders, the sprayed coating exhibited TiC and TiO2 phases, besides the c-Co-Ni-Cr-Mo matrix phase. For CoNi alloy coating, the main oxidation products were Cr2O3 and CoCr2O4 (NiCr2O4). For TiC-CoNi alloy coating, the main oxidation products were the TiO2 phase, coupled with Cr2O3 and CoCr2O4 (NiCr2O4) phases. The content of oxides increased with the oxidation time. The oxidation weight gain of the TiC-CoNi composite coating was slightly higher than that of the CoNi alloy coating. The formation of TiC could improve the thermal shock resistance of the CoNi alloy coating.
]]>Coatings doi: 10.3390/coatings14030295
Authors: Lenka Oroszová Karel Saksl Dávid Csík Katarína Nigutová Zuzana Molčanová Beáta Ballóková
X-ray Absorption Fine Structure Spectroscopy (XAFS) has proven instrumental for the study of atomic-scale structures across diverse materials. This study conducts a meticulous comparative analysis between total electron yield (TEY) and absorption coefficients at the K absorption edge of polycrystalline Fe and Zr60Cu20Fe20 alloy. Our findings not only highlight differences between TEY and transmission XAFS measurements but also demonstrate the capabilities and limitations inherent in these measurement modes within the context of XAFS. This article provides an experimental exploration of widely used X-ray absorption spectroscopy methods, shedding light on the nuances of TEY and transmission XAFS. Through presenting experimental results, we aim to offer insights crucial to the material science community, guiding experimentalists in optimizing measurements while raising awareness about potential misinterpretations.
]]>Coatings doi: 10.3390/coatings14030294
Authors: Yang Li Zhongxu Cai Lijuan Huang Ruiquan Liao
The corrosion behavior of P110 casing steel in simulated concrete liquid and simulated annulus fluid was investigated to reveal the corrosion pattern and protective properties of corrosion products in the two environments. Potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), Mott–Schottky tests, and electrochemical noise (EN) tests were used to study the corrosion behavior of P110 casing steel in simulated concrete liquid and simulated annulus fluid saturated with CO2. Scanning electron microscopy (SEM) combined with Energy-Dispersive Spectrometer (EDS) mapping was used to characterize the corrosion morphology and elemental distribution of P110 casing steel. The results show that the corrosion resistance of P110 casing steel deteriorates with the increasing immersion days in the simulated annulus fluid, the impedance decreases gradually, and the corrosion-product film shows a loose and porous structure. In the simulated concrete liquid, under the condition of containing a low concentration of Cl−, the protection of the corrosion products gradually increases with the extension of immersion days. With the increasing concentration of Cl− and the extension of immersion days, the electrochemical noise resistance and charge transfer resistance of P110 steel decrease gradually, and the protective property of the corrosion-product film decreases, which is capable of forming steady pitting corrosion.
]]>Coatings doi: 10.3390/coatings14030293
Authors: Guangchao Hao Aijun Tang Zhenzhong Zhang Hongyu Xing Nan Xu Ran Duan
High cutting temperatures increase tool wear and reduce tool life. To achieve a longer tool life, coated carbide tools have been developed. In this study, the influence of tool coatings on the cutting temperature distribution during the orthogonal cutting of H13-hardened steel is investigated. Firstly, four coating materials, including TiC, TiN, Al2O3, and TiAlN, with the same coating thickness, are selected to evaluate the effects of coating materials on cutting temperature with finite element simulation. The maximum temperatures at the tool rake face and the temperatures at the coating–substrate interface are evaluated. It was found that the maximum temperatures at the tool rake face were the lowest and the highest when TiN and Al2O3 coating materials were applied, respectively. The TiAlN coating material had the best thermal barrier property. Then, the temperature distribution along the direction perpendicular to the tool rake face is investigated for TiAlN-coated tools with different coating thicknesses ranging from 3 μm to 10 μm. It is shown that the temperature gradient increases with the coating thickness. The coating thickness should be kept below 5 μm. Finally, cutting experiments validate the availability of the finite element model.
]]>Coatings doi: 10.3390/coatings14030292
Authors: Tao He Dexin Wang Yu Xu Jing Zhang
Deposited by a reactive atmospheric pressure non-thermal TiCl4/O2/Ar plasma, anatase TiO2 single crystal sheet-connected film exhibits two large exposed {001} facets and a high concentration of oxygen defects. Strong white photoluminescence centered at 542 nm has been observed with naked eyes, whose internal quantum efficiency is 0.62, and whose intensity is comparable to that of commercial fluorescent lamp interior coatings. Based on the simulation results of a hybrid global–analytical model developed on this atmospheric pressure non-equilibrium plasma system, the mechanism of a self-confined growth of single crystal sheets was proposed. A high concentration of oxygen defects is in situ incorporated into the anatase crystal lattice without damaging its crystallographic orientation. This method opens a new way to construct 3D porous metal-oxide single crystal sheet-connected films with two exposing high energy surfaces and a large concentration of oxygen defects.
]]>Coatings doi: 10.3390/coatings14030291
Authors: Felipe Veloso Pascale Chevallier Helton José Wiggers Francesco Copes Bernard Drouin Diego Mantovani
Central venous catheters (CVCs) are largely used to administer chemotherapy, hemodialysis, and other treatments. Mostly made of polydimethylsiloxane (PDMS), these medical devices present an intrinsic risk of infection due to the possible formation of biofilm, thus increasing the risk of complications. Drug-releasing polymer coatings are a well-recognized strategy for combating biofilm formation. However, adhesion of the coating to the substrate over time is a major challenge. Therefore, this work aimed to design a chitosan-based coating designed to have maximum adhesion and stability to guarantee sustained drug release and antibacterial properties for at least 14 days. A coating composed of chitosan (CS) as a drug carrier, caffeic acid (CA) and copper sulphate (Cu) as crosslinkers, and moxifloxacin (Mox) as an antibiotic, was deposited through a controlled casting process onto functionalized PDMS surface. PDMS surface modification was investigated by X-ray photoelectron spectroscopy (XPS), and Fourier-transfer infrared (FTIR). Antibiotic release over time was measured in pseudo-physiological conditions (pH 7.4 and at 37 °C). Indirect cytotoxicity assays were performed on human dermal fibroblasts (HDF). The adhesion of the as-designed coating was evaluated by a specially designed pull-off test, before and after aging for 14 days in PBS. XPS and FTIR analyses confirmed the successful PDMS surface modification. The CS-CA-Cu-Mox coating resulted in being non-cytotoxic towards HDF and exhibited sustained moxifloxacin release for up to 49 days. Furthermore, the CS-CA and CS-CA-Cu coatings presented antibacterial activity for 21 days against E. coli, and for 14 days against S. aureus. Importantly, the coating maintained stable adhesion after 14 days in pseudo-physiological conditions. This study provides new insights into the adhesion behavior of polymeric coatings for medical devices, which is rarely reported in the literature.
]]>Coatings doi: 10.3390/coatings14030290
Authors: Edinei Locks Qianxi He Jose M. DePaiva Monica Guimaraes Abul Fazal Arif Stephen C. Veldhuis Joey R. Kish
This work aimed to ascertain the corresponding influences of several PVD-coated cutting tools on the susceptibility of the machined surface of super duplex stainless steel (SDSS) to stress corrosion cracking. Coatings comprised of AlCrN, AlCrN/TiSiN, and AlTiN were applied to cemented carbide cutting tools using the PVD method; these were then used to turn the outer surface of the SDSS tube section. During the cutting process, the material presents the following combination of features: (i) a tendency for strain hardening, reflected in microstructural modifications and residual stresses of the machined surface and (ii) high temperatures in the cutting region, reducing the tool life. The goal of this work was to evaluate the surface integrity (work hardening and corrosion behaviour) of the SDSS obtained after the machining process (finish turning) with cemented carbide tools coated with three different PVD coatings.
]]>Coatings doi: 10.3390/coatings14030289
Authors: Iasmina-Mădălina Anghel (Petculescu) Diana Uțu Ion Mitelea Albert Titus Constantin Ion-Dragoș Uțu
Fe-based coatings reinforced with TiC particles exhibit outstanding properties and are widely recognized as highly promising coatings or components with superior performance. In the present study, composite materials using a powder mixture of AISI 316 stainless steel and TiC particles were deposited by vacuum plasma spraying onto a S235 low alloyed steel substrate. The coating and the base material were characterized in terms of microstructure and surface properties. The metallographic analysis of the deposited coating revealed the uniform distribution of the TiC into the stainless steel matrix. The results show that the presence of tungsten carbide particles improved the hardness and tribological properties of the composite coating compared with the S235 base material. The wear resistance of the coating was approximately seven times higher than that of the low alloyed steel substrate. The electrochemical corrosion resistance of the coating in chloride media was much higher than that of the base material.
]]>Coatings doi: 10.3390/coatings14030288
Authors: Henan Bu Teng Yang Changzhou Hu Xianpeng Zhu Zikang Ge Honggen Zhou
Affected by the improper operation of the workers, environmental changes during drying and curing or the quality of the paint itself, diverse defects are produced during the process of ship painting. The traditional defect recognition method relies on expert knowledge or experience to detect defects, which is not conducive to ensuring the effectiveness of defect recognition. Therefore, this paper proposes an image generation and recognition model which is suitable for small samples. Based on a deep convolutional neural network (DCNN), the model combines a conditional variational autoencoder (DCCVAE) and auxiliary conditional Wasserstein GAN with gradient penalty (ACWGAN-GP) to gradually expand and generate various coating defect images for solving the overfitting problem due to unbalanced data. The DCNN model is trained based on newly generated image data and original image data so as to build a coating defect image classification model suitable for small samples, which is conducive to improving classification performance. The experimental results showed that our proposed model can achieve up to 92.54% accuracy, an F-score of 88.33%, and a G mean value of 91.93%. Compared with traditional data enhancement methods and classification algorithms, our proposed model can identify various defects in the ship painting process more accurately and consistently, which can provide effective theoretical and technical support for ship painting defect detection and has significant engineering research value and application prospects.
]]>Coatings doi: 10.3390/coatings14030287
Authors: Wei Xiong Jiajun Fu Chao Liu Li Li Huixin Wang Mingjun Zhang Zhiqiang Ge Tairui Zhang Qinghua Wang
Magnesium (Mg) alloy with good biomechanical and biocompatible properties is considered to be a promising biodegradable material for various applications. However, Mg alloy that is chemically active tends to be corroded in a physiological environment. In this work, we proposed a laser–chemical surface treatment to combine laser surface structuring and stearic immersion treatment to enhance the anti-corrosion and antibacterial properties of Mg alloy. The effects of surface structuring, chemistry, and wettability were analyzed, and the performance of the proposed technique was evaluated in terms of corrosion resistance and antibacterial properties. The experiments showed the following: (1) surface structuring by laser-induced dual-scale micro/nanostructures produced superhydrophilicity, with a water contact angle (WCA) of 0° on the surface of the Mg alloy; (2) applying the stearic acid immersion changed the chemistry of the Mg alloy’s surface and thus facilitated the wettability transition to superhydrophobicity, with a WCA of 160.1° ± 0.5°; (3) the proposed laser–chemical surface treatment enhanced corrosion resistance and stabilized the wettability of Mg alloy in a corrosive medium significantly; and (4) the proposed laser–chemical surface treatment enhanced the antibacterial properties of the Mg alloy greatly, with an improved antibacterial rate as high as 82.05%. This work proved that the proposed laser–chemical surface treatment was a simple, effective, and efficient technique to modulate and control the wettability and further improve the anti-corrosion and antibacterial properties of the Mg alloy.
]]>Coatings doi: 10.3390/coatings14030286
Authors: Yuming Zou Pan Pan Nana Zhang Xiaoxing Yan
To obtain dual functions of antibacterial and self-healing of a coating, nano-silver solution microcapsules coated with urea formaldehyde resin were selected for antibacterial agents, and rosin-modified shellac microcapsules coated with melamine formaldehyde resin were selected for repairing agents. The optical, mechanical, antibacterial, self-healing, and other physicochemical properties of the coatings were analyzed. The method of adding two microcapsules independently did not affect the coating’s hardness. When the primer was prepared by self-healing microcapsules and the topcoats were prepared by antibacterial microcapsules, the hardness of the prepared coatings was maintained at 3 H, with the adhesion up to class 2, the impact strength up to 18 kg·cm, and the roughness as low as 1.144 µm. The elongation at fracture of the coatings prepared by adding microcapsules independently was improved by 2.2%. The self-healing microcapsules release the repair agents to improve the mechanical properties of the coatings. In terms of the antibacterial properties of the coatings, the method that involves adding the microcapsules independently is better than mixed adding. Against Escherichia coli, the antibacterial rate of coatings prepared by adding microcapsules independently reached 82%. Against Staphylococcus aureus, the antibacterial rate of coatings reached 83.3%. At the same time, the self-healing rate was up to 41.1%. The two microcapsules were added to the water-based coating independently to obtain antibacterial and self-healing functions with good comprehensive properties. By modifying coatings on the Andoung wood (Monopetalanthus spp.) with antibacterial microcapsules and self-healing microcapsules, it is possible to obtain good antibacterial properties, further protect the wood substrate, and broaden the application range of functional coatings.
]]>Coatings doi: 10.3390/coatings14030285
Authors: Amanda Suellen de Paula Barbara Mitraud Aroeira Lucas Henrique de Oliveira Souza Alisson Cristian da Cruz Michele Fedel Brunela Pereira da Silva Fernando Cotting
Electrochemical Impedance Spectroscopy (EIS) is a non-destructive and powerful technique for characterizing corrosion systems, allowing for the evaluation of surface reaction mechanisms, mass transport, kinetic evolution, and corrosion levels of materials. This study aims to analyze the progression of corrosion using EIS, with a focus on the influence of organic coating thickness. For this purpose, layers of high-purity epoxy paint were applied to carbon steel plates with thicknesses of 50 µm, 80 µm, and 100 µm. During the research, a direct correlation was observed between coating thickness and corrosion resistance, emphasizing the importance of identifying the optimal thickness for each type of coating. Additionally, it was found that thicker coatings may experience electrode penetration due to the tensions generated during deposition, resulting in cracks between the layers, while thinner coatings allow electrolyte penetration as they do not provide adequate protection to the base steel. Therefore, the 80 µm thickness demonstrated greater resistance to corrosion compared to the other tested thicknesses.
]]>Coatings doi: 10.3390/coatings14030284
Authors: Yi Wu Yicheng Shi Yudie Zhao Yu Yin
New biodegradable paper-based films are a hot research topic in the development of green agriculture. In this study, a black paper-based film coated with cooked tung oil with excellent mechanical properties, a hydrophobic surface, high heat transfer and strong weather resistance was prepared by spraying high-pigment carbon black solution on the surface of base paper. The results showed that the surface-solidified oil film had a rough structure produced via the brush coating process using cooked tung oil. The base film of the black paper had a given hydrophobic structure, and the contact angle reached 98.9°. Cooked tung oil permeates into the inside of the paper base, and after curing, it forms a multi-dimensional network film structure. The maximum tensile stress of the black paper base film is about 123% higher than that of the original paper base film. The coloring of carbon black gives the black paper base film a heat conduction effect, and the average heat transfer rate reaches 15.12 °C/s. Cooked tung oil is combined with the paper-based fiber high-toughness layer to form a stable system. The existence of a cured film improves the basic mechanics and hydrophobicity, and the resistance to ultraviolet radiation and hot air is greatly improved. This study provides a feasible scheme for the application of a black paper base film coated with cooked tung oil.
]]>Coatings doi: 10.3390/coatings14030283
Authors: Daniel Ursu Cristian Casut Daiana Albulescu Melinda Vajda Cristina Mosoarca Marinela Miclau
The rapid spread of the Internet of Things (IoT) along with the development of innovative low-power electronic devices has also driven the development of indoor photovoltaics. In this paper, we propose a simple and economically feasible solution that can improve the efficiency of dye-sensitized solar cells (DSSCs) under indoor light conditions by ~112%, without requiring a complex TiO2 photoanode architecture or the design of new dyes. The ball milling process of the TiO2 paste was optimized for indoor light conditions for the first time, both in terms of efficiency and production costs, by developing a rapid preparation method that can be used industrially for the application of DSSCs. A simple use of 12 mm diameter balls caused beneficial structural modifications, decreasing the size of the crystallites, and leading to a high OH generation on the TiO2 surface responsible for the improvement of energy conversion efficiency.
]]>Coatings doi: 10.3390/coatings14030282
Authors: Xiang Li Xing Chen Niancheng Hong Qianzheng Li Zenghui Xu Ming Sheng Rui Wang
The purpose of this paper is to provide a numerical simulation, taking into account the collisional interactions of droplets in an airless rotary spray coating process. The hydrodynamics of gas and droplets are simulated using the CFD-discrete element method (DEM) with the JKR contact model in an airless rotary spray coating process of a horizontal square duct. The surface energy parameter used in the JKR model is calibrated using a virtual accumulation angle test in the funnel device. Based on the distribution of accumulation angles, a suitable surface energy for wall droplets is proposed. A rational gas RNG k-ε model is suggested in accordance with the comparisons of velocities, standard deviations, and the skewness of droplet number fractions from three turbulence models. The simulations of droplet film thicknesses agree with measurements from the literature regarding the film thickness along a vertical panel. The correlations of the exit gas and droplet velocities of sprayer holes are proposed with a discharge coefficient of 0.85 for gas and 5.87 for droplets. A number index of droplets is introduced in order to measure the uniformity of droplet distributions. A low droplet number index is found at low rotational speeds, representing a more uniform distribution of droplets as the rotation speeds reduce within the square duct. The normal force between the droplet and the wall is approximately an order of magnitude larger than the droplet–wall tangential force of collisions.
]]>Coatings doi: 10.3390/coatings14030281
Authors: Miaoran Liu Afia Kouadri-David Guangyi Ma
The residual stress relaxation behaviour in low-cycle fatigue brings uncertainty to accurately predict fatigue life. Therefore, establishing the residual stress relaxation model for the welded structure is critical. In this paper, the residual stress is simulated through Abaqus finite element software (6.14). The residual stress relaxation model related to the magnitude of cyclic loading and the number of cycles is proposed. Furthermore, the residual stress relaxation model is applied to predict low-cycle fatigue life. Finally, the simulation results are validated by experimental data obtained using the reliable neutron diffraction method, and a good agreement is observed.
]]>Coatings doi: 10.3390/coatings14030280
Authors: Wentao Zhang Fengyin Gao Huiling Zhou Chengtao Li Zhong Liu Haokun Yang Yanxin Qiao
In this work, Fe-20Cr-20Mn-0.75N (wt.%) high-nitrogen stainless steel (HNSS) was studied using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electrochemical testing. The corrosion behaviors of Fe-20Cr-20Mn-0.75N HNSS with different concentrations of NaCl were studied. The composition of a passive film on Fe-20Cr-20Mn-0.75N HNSS was analyzed using X-ray photoelectron spectroscopy (XPS) at an applied potential of 0.2VSCE. The results showed that, with the increase in Cl− concentration, the corrosion tendency and corrosion rate of Fe-20Cr-20Mn-0.75N HNSS get higher. In the solution of a low Cl− concentration, the fraction of Fe and Cr oxides in the passive film is higher, and the passive film is thicker and more stable. By increasing the stability of the passive film and preventing its rupture, the elevated NH4+ concentration can enhance the corrosion resistance of Fe-20Cr-20Mn-0.75N HNSS in a NaCl solution.
]]>Coatings doi: 10.3390/coatings14030279
Authors: Nivin Alktash Stefan Körner Tianhao Liu Andreas Pflug Bernd Szyszka Ruslan Muydinov
The Hollow Cathode Gas Flow Sputtering (GFS) provides special plasma conditions and is of extensive interest as a more affordable alternative to the high vacuum sputtering techniques. In the case of the tubular cathode a circular outlet symmetry stipulates homogeneity issues for both metallic and reactive deposition regimes. Using the results of Direct Simulation Monte Carlo (DSMC), we propose an external coaxial attachment which is manufactured and examined in a nozzle and a diffuser positioning. The impact on the homogeneity of Ti and TiO2 films is examined using profilometry and spectral ellipsometry. Our results demonstrate that the use of the nozzle attachment significantly enhances film homogeneity from about 3 cm2 to more than 12 cm2. It also secures better process control in terms of oxygen stoichiometry and film thickness. Some crucial general issues of the reactive GFS process are discussed.
]]>Coatings doi: 10.3390/coatings14030276
Authors: Mingbo Yang Ruizhe Jiang Jinke Zhu Xuan Zhang Guidong Li Weitao Li Fubin Ma Xueqing Jiang Hong Li
Photocathodic protection (PCP) technology has gained wide attention in the field of corrosion due to its green, environmentally friendly, and sustainable characteristics, and has become a protection technology with broad development prospects in the future marine environment. By investigating recent research results, the mainstream photoanode materials are TiO2, BiVO4, g-C3N4, ZnO, In2O3, SrTiO3 and other materials. Among them, TiO2 is an ideal photoanode material for PCP because of its efficient photochemical corrosion resistance, remarkable reaction stability, and excellent photoelectric properties. However, TiO2 itself has more drawbacks, such as limited utilization of visible light and low photogenerated electron-hole separation efficiency. These defects limit the wide application of TiO2 in PCP. Through modification methods, the reaction efficiency can be substantially improved and the availability of TiO2 can be increased. This paper lists the research progress of modifying TiO2 materials using metal and non-metal doping modification, semiconductor compounding technology, and energy storage materials for application in PCP, and introduces several new types of photoanode materials. This paper suggests new ideas for the design of more efficient photoanodes.
]]>Coatings doi: 10.3390/coatings14030278
Authors: Rubens T. Monteiro Thamyres F. Da Silva Luciana de Souza Guedes Raimundo N. F. Moreira Filho Ana L. B. Soares Niédja F. Vasconcelos Fabia K. Andrade Rodrigo S. Vieira
Alginate is a biocompatible polysaccharide matrix used for bioactive dressings with inherent healing properties. Most alginate dressings are produced as single-layer dressings. This study explores the potential of bilayer membranes to modulate drug release and enhance antimicrobial properties. We used alginate and chitosan loaded with simvastatin, an anti-inflammatory drug. One membrane comprised dense layers of both alginate and chitosan, while the other featured a dense alginate upper layer and a porous chitosan lower layer. The current study introduces a new approach in which a bilayer membrane is modeled instead of creating a polymeric blend between alginate and chitosan. The upper layer of the membrane contains only alginate loaded with simvastatin, while the bottom layer contains only chitosan. Another innovation is the study of the use of a porous lower layer of chitosan. Therefore, the association of these polymers in a bilayer and porous membrane gives advanced therapeutic dressings (with anti-inflammatory and antimicrobial properties intrinsic to the membrane) that are more efficient in the healing of complex wounds. Comprehensive characterization encompassed physicochemical, thermal, morphological, and mechanical properties. Microbiological tests were conducted using chitosan extract, and cytotoxicity evaluations were performed on fibroblast and keratinocyte cells. The results showed interlayer adhesion due to ionic interactions between alginate and chitosan surfaces. The drying process influenced the morphological and physicochemical features of the membranes. Simvastatin release profiles demonstrated sustained release over an extended period (approximately 60%–70% of the drug after 96 h). Storage assessments revealed that after six months, the membranes maintained around 98% of the initial simvastatin content. The antimicrobial activity test underscored the bacteriostatic efficacy of the chitosan porous layer, making it well-suited for infected wounds. Cell viability tests confirmed the non-cytotoxic nature of the films, highlighting their promising characteristics for treating diverse skin lesion types.
]]>Coatings doi: 10.3390/coatings14030277
Authors: Mohammed M. M. Ghisheer Ismail Esen Hayrettin Ahlatci Bengü Akın
There is a scarcity of research on the characterization of the behaviour of titanium and its alloys in highly corrosive environments. These materials are highly recommended for use in various industries such as aviation, maritime, medical, and chemical, due to their perceived superior corrosion resistance. This research examines the mechanical and corrosion characteristics of Ti6Al4V material when exposed to solutions containing 9% NaCl, 25% HCl, and a mixture of 9% NaCl and 25% HCl. Prior to the corrosion process, the prefabricated Ti6Al4V samples underwent microstructure analysis, hardness assessment, and wear evaluation. The microstructure characterization revealed that the microstructure of the Ti6Al4V alloy is composed of α and modified β phases. The Ti6Al4V sample’s hardness value was determined to be 334.23 HB. The Ti6Al4V sample’s wear rate was determined to be 0.0033 g/Nm, while the friction coefficient was determined to be 0.0326. Corrosion testing was conducted at intervals of 24, 48, 72, 168, and 336 h. Based on the corrosion rate measurements, the sample exhibited the minimum corrosion rate of 1.928519 mg/(dm2·day) in a 9% NaCl environment. The sample with a combination of 9% NaCl and 25% HCl had the maximum corrosion rate, measured at 6.493048 mg per square decimetre per day. The formation of a larger oxide layer in the Ti6Al4V corrosion sample immersed in a 9% NaCl solution serves as a protective barrier on the surface and enhances its resistance to corrosion.
]]>Coatings doi: 10.3390/coatings14030275
Authors: David Siniscalco Laurence Pessoni Anne Boussonnière Anne-Sophie Castanet Laurent Billon Guillaume Vignaud Nicolas Delorme
Significant research endeavors have been devoted to developing adhesives with reversible switching capabilities, allowing them to activate adhesion in response to diverse environmental stimuli. Among these, photo-switchable adhesives stand out as particularly promising. The presence of a photo-reversible solid-to-liquid transition, characterized by a transition temperature (TSL), in certain azobenzene-containing polymers offers a compelling avenue for creating such adhesives. The development of a method based on Atomic Force Microscopy to measure both the glass transition temperature (Tg) and TSL provided an opportunity to investigate the impact of various structural parameters on the solid-to-liquid transition of azopolymers. Our findings revealed that increasing the molecular weight (Mn) from 3400 to 8100 g/mol needed to achieve a highly cohesive adhesive resulted in an elevation in TSL (>10 °C), making the solid-to-liquid transition at room temperature more challenging. However, incorporating a highly flexible substituent at the para position of the azobenzene group proved effective in significantly reducing the TSL value (from 42 °C to 0 °C). This approach allows for the creation of photo-switchable adhesives with intriguing properties. We believe that our results establish a pathway toward developing a robust room-temperature photo-switchable adhesive.
]]>Coatings doi: 10.3390/coatings14030274
Authors: Guan Wang Wenlin Chen Xiangyu Shen Xin Ren Jiawei Niu Sihang Pan Yifan Huang Jinliang Wu
This study presents an in-depth investigation into optimizing the mix design of ultra-high-performance concrete (UHPC) for enhanced sulfate erosion resistance, utilizing the modified Andreasen and Andersen (MAA) method. By testing the mechanical properties and slump flow of UHPC, it was determined that the optimal W/B = 0.2, and the best volume content of steel fibers is 2%. Through long-term tests lasting 360 days on three groups of UHPC specimens under different curing conditions, their mass loss, compressive strength corrosion resistance coefficient, surface appearance, and erosion layer thickness were tested. The results indicate that under sulfate attack, the mass and compressive strength corrosion resistance coefficients of UHPC specimens showed a trend of first increasing and then decreasing, due to the formation and expansion of ettringite and gypsum. The thickness of the erosion layer increases over time. By 360 days, the internal damage caused by sulfate attack is about twice as severe as it was after 60 days. However, the addition of steel fibers was found to effectively mitigate these effects, reducing mass loss and preserving the structural integrity of UHPC.
]]>Coatings doi: 10.3390/coatings14030273
Authors: Oana Cătălina Mocioiu Irina Atkinson Ludmila Aricov Veronica Bratan Ana-Maria Mocioiu Ioan Albert Tudor Diana Irinel Băilă
Photovoltaic (PV) solar panels suffer from efficiency losses due to the accumulation of dust on their surface during operation, as well as the loss of transparency in the top glass. The efficiency can be increased when hydrophobic films are deposited on the top glass of the solar cells. The top glass of solar cells must have three characteristics: high transmittance in the 380–750 nm range, a band gap greater than 3.2 eV and a refractive index higher than 1.23. So, the films require the same characteristics. This work presents an increase in the contact angle (related to an increase in the hydrophobic character) when Ta2O5 is partially substituted with ZnO. The studied films, physically deposited on glass by e-gun technology, present a non-crystalline state in the form of the X-ray patterns shown. The films have a transmission of 75%–80% in the visible range. The morphology and roughness of the coatings were evaluated by atomic force microscopy. All films show the values of the Millipore water contact angle higher than 91 degrees, leading to the acquisition of hydrophobic properties on the surface. In comparison, the substrate is hydrophilic, with an average contact angle of 53.81 ± 2.16. The hydrophobic properties and self-cleaning ability make the films recommendable for application. The band gap of the coatings was calculated with the Tauc method, and they have values of 4.5–4.6 eV.
]]>Coatings doi: 10.3390/coatings14030272
Authors: Daniela Pinna
This paper describes and discusses the results of scientific experiences of the physical and mechanical methods used to control and inhibit the growth of lichens and biofilms that grow on indoor and outdoor historical stone artworks. It provides an extensive selection and examination of international papers published in the last two decades on the issue. The great advantage of physical and mechanical methods lies in the lack of potential risks associated with the irreversible application of microbicides. Indeed, they do not introduce any harmful chemicals to humans, to the environment, or to heritage objects. This review focuses on the application of (i) electromagnetic radiation, (ii) high temperatures, (iii) lasers, and (iv) mechanical tools, and includes the main achievements, limitations, and potential applications of the examined studies.
]]>Coatings doi: 10.3390/coatings14030271
Authors: Yuxin Kang Shufang Yan Zhanlin Li Zhigang Wang Ao Yang Wen Ma Weidong Chen Yinhui Qu
Magnesium alloys, notably AZ31B, hold promise for lightweight structural applications in the aerospace, automotive, and biomedical sectors due to their excellent strength-to-weight ratios. The broad adoption of these alloys, however, is hindered by their inherent susceptibility to corrosion, reducing durability and functional integrity in corrosive environments. This study explores anodic oxidation as a viable surface treatment to improve the corrosion resistance of the AZ31B magnesium alloy. Focusing on the impact of oxidation voltage on the oxide film’s structural and electrochemical properties, we aim to optimize these characteristics to enhance the alloy’s utility and lifespan significantly. Through detailed analysis of surface and cross-sectional morphologies, film thickness, phase composition, and corrosion resistance, we identify an optimal oxidation voltage of 17.5 V that notably improves the oxide film’s density and corrosion resistance. Through this research, we contribute to the ongoing efforts to overcome the corrosion vulnerability of magnesium alloys, thereby unlocking their full potential in contributing to more sustainable and efficient technological advancements.
]]>Coatings doi: 10.3390/coatings14030270
Authors: Shifang Wang Lei Song Haijie He Wenjie Zhang
Volatile organic compounds (VOCs), as a primary pollutant in industrial-contaminated sites or polluted soils, cause severe damage to the soil. Therefore, a comprehensive understanding of the transport of VOCs in soil is imperative to develop effective detection means and removal methods. Among them, biochar possesses potential advantages in the adsorption of VOCs, serving as an effective method for removing VOCs from soil. This review provides an overview of the VOCs within soil, their transport mechanisms, monitoring technology, and removal approach. Firstly, the historical development of the VOC migration mechanism within the capping layer is described in detail. Secondly, the in situ monitoring techniques for VOCs are systematically summarized. Subsequently, one of the effective removal technologies, a capping layer for polluted sites, is simply introduced. Following this, the potential application of a biochar-modified capping layer for the removal of VOCs is comprehensively discussed. Finally, the major challenges in the field and present prospects are outlined. The objective of this study is to furnish researchers with a foundational understanding of VOCs, their relevant information, and their removal approach, inspiring environmental protection and soil pollution control.
]]>Coatings doi: 10.3390/coatings14030269
Authors: Guojie Yang Chenbing Han Ying Chen Fangwei Guo Jie Lu Ming Zhou Lirong Luo Xiaofeng Zhao
(La0.2Yb0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 (HEZ) has shown considerable promise as a novel thermal barrier coating material for temperatures exceeding 1300 °C. This study systematically investigates the interfacial stability of (La0.2Yb0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 with yttria-stabilized zirconia (YSZ), which is of paramount importance for its application in double-layer thermal barrier coatings. Our findings highlight that rare earth elements with a smaller radius diffuse more easily into the YSZ lattice, resulting in a broader diffusion zone. Simultaneously, the incorporation of rare earth elements into the YSZ lattice inhibits tetragonal-to-monoclinic phase transformation. Compared to La2Zr2O7/YSZ, HEZ/YSZ demonstrates superior high-temperature stability, which could be attributed to the higher fracture toughness and lower thermal expansion coefficient of HEZ, the absence of t-m transformation and the formation of a continuous gradient diffusion layer that minimizes interface stress. This study offers a practical strategy for designing materials for durable double-layer thermal barrier coating systems.
]]>Coatings doi: 10.3390/coatings14030268
Authors: Stefan Valkov Georgi Kotlarski Stoyan Parshorov Maria Ormanova Borislav Stoyanov Fatme Padikova Ivan Parshorov
In the present work, we present results on the influence of electron beam surface modification on the resistance to plastic deformation and plasticity of Inconel alloy 625. During the treatment procedure, the electron beam currents were 10 and 20 mA, corresponding to beam powers of 600 W and 1200 W. The structures of the modified specimens were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The nanohardness and Young’s modulus were studied through nanoindentation experiments. The plasticity of the treated materials as well as of the untreated ones was studied through an evaluation of H3/E2, which points to resistance to plastic deformation. The results obtained show that the electron beam surface modification procedure leads to a reorientation of microvolumes and the formation of a preferred crystallographic orientation. The surface treatment of the samples using an electron beam with a power of 600 W did not lead to major changes in the structures of the samples. However, the use of a beam with a power of 1200 W led to the formation of a clearly separated modified zone with a thickness in the range of 13 to 15 μm. The Young’s modulus increased from about 100 to 153 GPa in the case of electron beam surface modification using the lower-power electron beam. The application of the higher-power electron beam did not lead to a significant change in the modulus of elasticity as compared to the untreated specimen. Also, it was found that the treatment procedure pointed to a decrease in nanohardness when the maximum power of the electron beam was applied. The resistance to plastic deformation, i.e., the H3/E2 ratio, showed that the ratio decreased significantly in both cases of electron beam surface modification, pointing to an improvement in the plasticity of the surface of the Inconel alloy 625.
]]>Coatings doi: 10.3390/coatings14030267
Authors: Robert Jurczak
For the successful reuse of old asphalt as reclaimed asphalt pavement (RAP) added to new bituminous mixtures, it is necessary to improve some of its properties. This can be attained, for example, by adding an appropriate rejuvenator. The aim of this study was to evaluate the properties of lab-aged 35/50 pen grade bitumen rejuvenated with the addition of two varieties of rapeseed imidazoline. Dynamic shear rheometer (DSR) and ductilometer tests were further conducted to evaluate the properties of bituminous binders at the intermediate operating temperature of road pavements. The obtained results demonstrated a beneficial effect of rapeseed imidazoline on the properties of the tested pen grade bitumen after ageing when added at a rate of 6% or more. This effect was the most pronounced in the case of the fatigue cracking critical temperature (FCCT), where a lower value was obtained for the aged and rejuvenated 35/50 bitumen than for the same bitumen before ageing. The tensile curves developed from the results of the tensile force tests using the ductilometer confirmed the previous conclusions from the measurements using the DSR. However, the original plastic behaviour of the aged pen grade bitumen was restored only through the addition of rapeseed imidazoline at a rate of 8%.
]]>Coatings doi: 10.3390/coatings14030266
Authors: Linas Ardaravičius Oleg Kiprijanovič
A system of two equations based on one of the classical electricity laws was used to determine the sizes and temperatures of ohmic areas formed under action of overcritical nanosecond electrical pulses. Calculations were performed at five points for three experimentally obtained voltage–current (V-I) dependences for samples with the same geometry but different critical current density values. The system included two additional conditions to satisfy the known descriptive model of transition from superconducting (SC) to a normal (N) state—S-N switching—and to obtain physically acceptable solutions over the entire current range of V-I dependence. The solution for each point takes the form of a function, since the initial temperature increase of the primary channel across the film is entered as a parameter. Two modes of concentrated energy release in the channel were disclosed. Their random appearance leads to an unexpected degradation of the sample. As such, the obtained results correspond to the situations occurring during the experiments. The validity of applying additional conditions to the system is discussed. In the discussion, it is also explained at which moments the moving S-N border acquires the velocity of the order of ~106 m/s, comparable to the Fermi velocity. Consideration to describe the moving unstable S-N border as being constantly in a state of Richtmyer–Meshkov instability is presented.
]]>Coatings doi: 10.3390/coatings14030265
Authors: Ao Wei Yiyi Li Lianghai Feng Yongjun Feng Zhiwen Xie
30CrNi2MoVA steel demonstrates excellent performance, meeting the requirements of a crucial material for high-load structural parts. However, after experiencing high loads and thermal cycling, the material undergoes wear on its contact surfaces, resulting in a certain wear depth that determines its service life. Therefore, accurately predicting and evaluating the wear performance and wear depth of this material is of paramount importance. This study employs a combined approach of experimental and simulation methods. Initially, friction and wear tests were conducted to investigate the wear behavior of the 30CrNi2MoVA steel. The experimental results reveal a significant influence of thermal cycling temperature on the material’s wear resistance, with wear mechanisms primarily attributed to adhesive wear and abrasive wear. Subsequently, a ball-on-disc wear model was established. Based on experimental data, the modified Archard model was implemented as a user subroutine in finite element software (ABAQUS version 2020) to assess the material’s wear volume. The simulation results demonstrate a close agreement with the experimental wear depths. Furthermore, a fitting formula was developed to correlate the wear depth of the material with the number of wear cycles, enabling accurate wear depth prediction. This study provides theoretical support for enhancing the performance and extending the service life of 30CrNi2MoVA steel.
]]>Coatings doi: 10.3390/coatings14030264
Authors: Bauyrzhan Rakhadilov Nazerke Muktanova Dauir Kakimzhanov Meruert Adilkanova Sherzod Kurbanbekov Saule Abdulina
This paper presents the results of a metallographic and tribological study of 86WC-10Co-4Cr coatings obtained by the HVOF method on the Termika-3 unit at varying spraying distances. The influence of spraying distance on the coating microstructure, phase composition, as well as mechanical and tribological properties, was studied. According to the results of the study, it was found that the optimum spraying distance for 86WC-10Co-4Cr coatings with improved wear resistance and hardness characteristics and low porosity is 300 mm.
]]>Coatings doi: 10.3390/coatings14030263
Authors: Qi Wang Qian Zhu Lei Cao Lanlan Fan Feng Gu Ying Zhang Chenglin Zheng Shixian Xiong Liang Xu
The two-dimensional layered heterostructure have been demonstrated as an effective method for achieving efficient photocatalytic hydrogen production. In this work, we propose, for the first time, the creation of van der Waals heterostructures from monolayers of SiH and g-C3N4 using first-principle calculations. We also systematically investigated additional properties for the first time, such as the electronic structure and optical behavior of van der Waals heterostructures composed of SiH and g-C3N4 monolayers. The results of this study show that the SiH/g-C3N4 heterostructure is categorized as a type-II heterostructure, which has a bandgap of 2.268 eV. Furthermore, the SiH/g-C3N4 heterostructure interface was observed to efficiently separate and transfer photogenerated charges, resulting in an enhanced photocatalytic redox performance. Moreover, the calculation of HOMO (Highest occupied molecular orbital) and LUMO (Least unoccupied molecular orbital) and charge density difference can further confirm that the SiH/g-C3N4 heterojunction is a type-II heterojunction, which has excellent photocatalytic hydrogen production and water decomposition performance. In addition, the SiH/g-C3N4 heterostructure exhibited excellent HER (Hydrogen evolution reaction) efficiency. This is essential for the process of photocatalytic water splitting. In SiH/g-C3N4 heterojunctions, the redox potential required for water splitting is spanned by the band edge potential. Calculating the absorption spectra, it was discovered that the SiH/g-C3N4 heterostructure possesses outstanding optical properties within the visible-light range, implying its high efficiency in photocatalytic hydrogen production. This research provides a broader research direction for the investigation of novel efficient photocatalysts and offers effective theoretical guidance for future efficient photocatalysts.
]]>Coatings doi: 10.3390/coatings14030262
Authors: Kaixuan Wang Yubin Zhang Jun Chen Qingzhi Li Feng Tang Xin Ye Wanguo Zheng
A femtosecond laser raster-type in situ repetitive direct writing technique was used for the fabrication of anti-reflective microhole structures in Germanium (Ge) in the visible near-infrared range (300–1800 nm). This technique builds a layer of microstructured arrays on the surface of Ge, enabling Ge to exhibit excellent anti-reflective properties. The large-area micro-nanostructures of Ge were fabricated using femtosecond laser raster-type in situ repetitive direct writing. Ge microstructures are characterized by their structural regularity, high processing efficiency, high reproducibility, and excellent anti-reflective properties. Experimental test results showed that the average reflectance of the Ge microporous structure surface in the range of 300–1800 nm was 2.25% (the average reflectance of flat Ge was 41.5%), and the lowest reflectance was ~1.6%. This microstructure fabrication drastically reduced the optical loss of Ge, thus enhancing the photothermal utilization of Ge. The many nanoburrs and voids in the Ge microporous structure provided excellent hydrophobicity, with a hydrophobicity angle of up to 133 ± 2° (the hydrophobicity angle of flat Ge was 70 ± 2°). The high hydrophobicity angle allows for strong and effective self-cleaning performance. The femtosecond laser raster-type in situ repeatable direct writing technology has many desirable properties, including simplicity, high accuracy, flexibility, and repeatability, that make it one of the preferred choices for advanced manufacturing. The Ge micro-nanostructured arrays with excellent optical anti-reflective properties and hydrophobicity have become an attractive alternative to the current photo-thermal absorbers. It is expected to be used in many applications such as solar panels, photovoltaic sensors, and other optoelectronic devices.
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