Search Results (40)

By integrating cathodic arc evaporation (CAE) with magnetron sputtering (MS) or high-power impulse magnetron sputtering (HiPIMS), hard coatings with diverse multicomponent compositions can be fabricated. Depending on the deposition conditions, the coatings with nano-composite or nano-multilayered microstructures are produced. During the mixing deposition conditions, nano-composite coatings are fabricated, which can be tailored to possess combining properties of super hardness, low friction coefficient, and excellent thermal/chemical stability. For the deposition with larger rotating periods, layer-by-layer deposition was observed. By the nano-multilayered coating design, superior mechanical properties (hardness ≥ 35 GPa), modulated residual stresses, and enhanced high-temperature properties can be obtained. In addition, lubricious elements, low friction (friction coefficient < 0.4), and low wear (<10⁻⁵ mm³/N∙m) both at ambient temperature and high temperature can be realized. Among these coatings, some have been specifically designed to achieve outstanding cutting performance in high-speed cutting applications. Several nitride and oxide hard coatings, such as AlTiN, TiAlN/TiSiN, AlCrN/Cu, and AlCrO, were deposited using a hybrid industrial physical vapor deposition (PVD) coating system. The microstructure, mechanical properties, and cutting performance of these coatings will be discussed. Full article

Electromagnetic wave-absorbing materials (EMAMs) and structures are crucial in aerospace and electronic communications due to their ability to absorb electromagnetic waves. The development of materials that are lightweight, sustainable, and cost-effective, exhibiting high-performance absorption across a broad frequency spectrum, is therefore important. However, homogeneous electromagnetic absorbing materials require assistance to meet all these criteria. Therefore, developing multi-layer absorbing coatings is essential for enhancing performance. The present study uses 21 different composites of varying weight fractions of polypropylene, graphene nanoplatelets, and multiwall carbon nanotubes nanocomposites to develop multi-layer absorbing materials and optimize their performance. These multi-layer carbon polymer nanocomposites were meticulously constructed using evolutionary algorithms like Non-sorted Genetic Algorithm-II and Particle Swarm Optimization to achieve ultra-broadband electromagnetic wave absorption capabilities. Among the designed electromagnetic absorbing materials, a two-layer model, i.e., 1.5 wt% MWCNT/PP/epoxy with a thickness of 1.052 mm and 2.7% GNP/PP/epoxy with a thickness of 4.456 mm totaling 5.506 mm, was identified as optimal using NSGA-II. The structure has exhibited exceptional absorption performance with a minimum reflection loss of −21 dB and a qualified bandwidth extending to 4.2 GHz. PSO validated and optimized this structure, confirming NSGA-II’s efficiency and effectiveness in quickly obtaining optimal solutions. This broadband absorber design combines the structure design and material functioning through additive manufacturing, allowing it to absorb well over a wide frequency range. Full article

This study investigated the moisture absorption and mechanical degradation of epoxy-based polymer systems with Mg-Al/NO₃ layered double hydroxide (LDH) nanoparticles content up to 5 wt%. Such systems are developed for multilayer corrosion protective coatings. A sorption model was developed to calculate the moisture concentration field in the multilayer structures using Fick’s law of diffusion. The finite-difference method was used for the numerical solution. Epoxy/LDH nanocomposites were prepared using various dispersion methods with solvents, wetting agents, and via a three-roll mill. Moisture absorption was measured under different environmental conditions, including temperatures up to 50 °C and salinity levels up to 26.3 wt% salt solution. The results showed that equilibrium moisture content increased by 50% in hot water, while it was reduced by up to two times in salt solution. The diffusion coefficient in hot water increased up to four times compared to room temperature. The numerical algorithm was validated against experimental data, accurately predicting moisture distribution over time in complex polymer systems. Mechanical tests revealed that the elastic modulus did not change after water exposure; however, the ultimate strength decreased by 10–15%, especially in specimens with 5 wt% LDH. Full article

Single surface texture or coating technology is gradually unable to produce lasting lubrication of a TC4 titanium alloy in a harsh environment. In order to address this problem, a rectangular microstructure is prepared on the surface of a TC4 titanium alloy by laser processing, and then MoS₂/DLC composite interlayer nanocoatings are prepared on the surface by non-equilibrium magnetron sputtering. Friction and wear tests are then carried out on single fabricated, coated and fabricated coatings. The results show that the MoS₂/DLC composite interlayered nanocoating can effectively combine with the texture to achieve better friction reduction compared with the single texture and coating. The textured composite coating has the lowest friction coefficient (reduced from 0.4122 to 0.0978) and wear. Through controlled experiments, the textured coating showed good tribological properties at different temperatures and in different friction cycle tests. This study can effectively improve the tribological properties of metal materials through composite coatings, providing research ideas for enhancing the service life of alloys under long-term friction in high-temperature environments. Full article

TiN/TiAlSiN nanocomposite multilayer coatings were deposited on a titanium alloy by multi-arc ion plating. The investigation of the wear behavior of TiN/TiAlSiN multilayer coatings against Si₃N₄ was conducted at temperatures of 25 °C, 300 °C, and 500 °C using a ball-on-disk tribometer. Additionally, to gain a deeper understanding of medium-temperature oxidation products, an oxidation test was performed at 500 °C for 10 h. The microstructure and chemical composition of the coatings were evaluated by X-ray diffraction and scanning electron microscopy. The primary peak in the XRD pattern of the multilayer coating changed from TiN (111) to Ti₃AlN (111) after the oxidation test. The hardness of the TiN/TiAlSiN multilayer coating was 1540 HV_0.1, representing a notable five times improvement compared to the substrate. The critical load in the scratch test was 52.3 N, indicating robust adhesion performance. The wear rate exhibited a sharp increase from 25 °C to 300 °C, compared to the rise from 300 °C to 500 °C. Furthermore, the friction coefficient of the coated sample was more stable than the substrate, with different scratch track morphologies between the samples before and after the oxidation test. Full article

This paper presents the results of the investigation of a multilayer TiAlSiN/AlSiN coating. A novel coating architecture with a period consisting of nanocomposite sublayers of TiAlSiN and AlSiN was developed. We discovered that the combination of a harder sublayer with a more elastic one allows for obtaining a suitable combination of superhardness and enhanced toughness. The coating was deposited by cathodic arc technology. The EDS, XRD, and XRS analyses revealed that the nanocomposite structure is composed of TiAlSiN and AlSiN nanocrystallites, with sizes of 12–13 nm and 4–5 nm, respectively. The nanograin phase is incorporated in an amorphous Si₃N₄ matrix. The achieved structure causes the presence of four factors contributing to the hardness increase: nanocomposition, solid solution, refinement hardening, and the formation of many interfaces. An instrumented indentation test was used to investigate the mechanical properties. The developed coating possesses a superhardness of 49.5 GPa and a low elastic modulus of 430 GPa, resulting in an improved elastic strain resistance of 0.11, a plastic deformation resistance of 0.58 GPa, and an elastic recovery of 68%. These results imply that the developed coating combines high stability with mechanical degradation under external influence and provides an improved ability to absorb energy at deformation before fracture, and high elastic recovery. The investigation of the effect of the period modulation on the structure, composition, and mechanical properties of the nanocomposite multilayer TiAlSiN/AlSiN coating showed that the superhardness was due to the nanocomposite and solid solution hardening rather than the increased number of interfaces. The demonstrated combination of superhardness with high elasticity and improved toughness determines the developed nanocomposite TiAlSiN/AlSiN coating as very suitable for industrial applications such as high speed and dry machining. Full article

Multiwalled carbon nanotube (MWCNT) nanopaper (NP)-reinforced in-mold coating (IMC) nanocomposites were fabricated by dip soaking without organic solvent. The thermally activated IMC resin was selected to provide electromagnetic interference shielding protection for sheet molding compound (SMC) material as well as other plastic materials due to the proven good adhesion of IMC resin to the substrate. In this work, the technical feasibility of a continuous fabrication process was evaluated for a nanopaper/IMC (NP/IMC) composite. The curing behavior of the candidate IMC resin was studied for a better understanding of the fabrication of NP/IMC nanotape as a prepreg (with 10% polymerization), as well as the final curing once the nanotape was applied to the substrate. The required limiting maximum temperature to prevent curing during infiltration was established. This allows the fabrication of multilayer nanotape or coatings by stacking several layers of tape to improve the EMI shielding protection. To be specific, the average EMI shielding effectiveness for a one-layer composite was 21 dB, while it increased to 48 dB on average for a six-layer composite. Full article

Thermoelectric (TE) materials have been considered as a promising energy harvesting technology for sustainably providing power to electronic devices. In particular, organic-based TE materials that consist of conducting polymers and carbon nanofillers make a large variety of applications. In this work, we develop organic TE nanocomposites via successive spraying of intrinsically conductive polymers such as polyaniline (PANi) and poly(3,4-ethylenedioxy- thiophene):poly(styrenesulfonate) (PEDOT:PSS) and carbon nanofillers, and single-walled carbon nanotubes (SWNT). It is found that the growth rate of the layer-by-layer (LbL) thin films, which comprise a PANi/SWNT-PEDOT:PSS repeating sequence, made by the spraying method is greater than that of the same ones assembled by traditional dip coating. The surface structure of multilayer thin films constructed by the spraying approach show excellent coverage of highly networked individual and bundled SWNT, which is similarly to what is observed when carbon nanotubes-based LbL assemblies are formed by classic dipping. The multilayer thin films via the spray-assisted LbL process exhibit significantly improved TE performances. A 20-bilayer PANi/SWNT-PEDOT:PSS thin film (~90 nm thick) yields an electrical conductivity of 14.3 S/cm and Seebeck coefficient of 76 μV/K. These two values translate to a power factor of 8.2 μW/m·K², which is 9 times as large as the same films fabricated by a classic immersion process. We believe that this LbL spraying method will open up many opportunities in developing multifunctional thin films for large-scaled industrial use due to rapid processing and the ease with which it is applied. Full article

Food quality is mainly affected by oxygen through oxidative reactions and the proliferation of microorganisms, generating changes in its taste, odor, and color. The work presented here describes the generation and further characterization of films with active oxygen scavenging properties made of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) loaded with cerium oxide nanoparticles (CeO₂NPs) obtained by electrospinning coupled to a subsequent annealing process, which could be used as coating or interlayer in a multilayer concept for food packaging applications. The aim of this work is to explore the capacities of these novel biopolymeric composites in terms of O₂ scavenging capacity, as well as antioxidant, antimicrobial, barrier, thermal, and mechanical properties. To obtain such biopapers, different ratios of CeO₂NPs were incorporated into a PHBV solution with hexadecyltrimethylammonium bromide (CTAB) as a surfactant. The produced films were analyzed in terms of antioxidant, thermal, antioxidant, antimicrobial, optical, morphological and barrier properties, and oxygen scavenging activity. According to the results, the nanofiller showed some reduction of the thermal stability of the biopolyester but exhibited antimicrobial and antioxidant properties. In terms of passive barrier properties, the CeO₂NPs decreased the permeability to water vapor but increased the limonene and oxygen permeability of the biopolymer matrix slightly. Nevertheless, the oxygen scavenging activity of the nanocomposites showed significant results and improved further by incorporating the surfactant CTAB. The PHBV nanocomposite biopapers developed in this study appear as very interesting constituents for the potential design of new active organic recyclable packaging materials. Full article

The properties and oxidation wear patterns in the composite nanostructured coating of Zr-ZrN-(Zr,Mo,Al)N were studied during the turning of Inconel 718 alloy at the cutting speeds of v_c = 125 and 200 m/min. The hardness of the coating, its elastic modulus, and critical fracture load during the scratch testing were determined. The study focused on the tribological properties of the Zr-ZrN-(Zr,Mo,Al)N coating at temperatures of 400–900 °C paired with an insert made of Inconel 718, which exhibited a certain advantage over the reference coatings of Zr-ZrN and Ti-TiN-(Ti,Cr,Al)N of similar thickness. The coating of Zr-ZrN-(Zr,Mo,Al)N provided for the longest tool life at the cutting speed of v_c = 125 m/min (the tool life was four times longer in comparison with that of the uncoated tool and 15% longer in comparison with that of the Ti-TiN-(Ti,Cr,Al)N-coated tool) and at the cutting speed of v_c = 200 m/min (the tool life was 2.5 times longer in comparison with that of the uncoated tool and 75% longer in comparison with that of the Ti-TiN-(Ti,Cr,Al)N-coated tool). While at the cutting speed of v_c = 125 m/min, the surface coating layers exhibit only partial oxidation of the external layers (to a depth not exceeding 250 nm), with mostly preserved cubic nitride phases, and then the cutting speed of v_c = 200 m/min leads to almost complete oxidation (to the depth of at least 500 nm), however, with a partially preserved nanolayered structure of the coating. Full article

Magnetic nanocomposites (MNCs) combine the features of magnetic nanoparticles and a second material, which provide distinct physical, chemical, and biological properties. The magnetic core for nanocomposite synthesis is extensively used due to its high saturation magnetization, chemical stability, large surface area, and easy functionalization. Moreover, magnetic nanoparticles (MNPs) have great potential for magnetic resonance imaging (MRI), magnetic particle imaging (MPI), hyperthermia, and targeted drug and gene delivery by an external magnetic field. Numerous composing units exist, which leads to the outstanding application of composites. This review focuses on nucleic acid-based bioapplications of MNCs with polymeric, organic, inorganic, biomolecules, and bioinspared surface coating. In addition, different forms, such as core–shell, doping, multilayer, yolk–shell, and Janus-shaped hybrids, are discussed, and their unique properties are highlighted. The unique types of nanocomposites as magnetic molecularly imprinted polymer (MMIP) properties are presented. This review presents only the synthesis of MNCs using ready-made magnetic cores. These restrictions are associated with many materials, the quantitative and qualitative magnetic core composition, and synthesis procedures. This review aims to discuss the features of nucleic acid-based MNC information available to researchers in this field and guide them through some problems in the area, structure variation, and surface functionalization possibilities. The most recent advancements of MNCs and imprinted polymers in nucleic acid-based therapy, diagnostics, theranostics, magnetic separation, biocatalytic, and biosensing are introduced. Full article

Solid particle erosion of gas turbine blades in the aerospace sector results in increased maintenance costs, high pollution, reduced engine efficiency, etc. Gas turbines in aircraft are usually operated at high temperatures. Based on the compressor stage, the temperature varies from 100–600°C, whereas turbine blades, after combustion, experience a very high temperature between 1000–1400 °C. So, a better understanding of temperature-dependent solid particle erosion is required to develop suitable solid particle erosion-resistant coatings for gas turbine blades. In this review, a detailed overview of the effect of temperature on the solid particle erosion process and different types of erosion-resistant coatings developed over the last four decades for compressor blades are discussed in detail. In the initial sections of the paper, solid particle erosion mechanisms, erosion by different erodent media, and the influence of erosion on gas turbine engines are discussed. Then, the erosion rate trend with increasing temperature for ductile and brittle materials, high-temperature erosion tests in a corrosive environment, and the role of oxidation and bonding nature in high-temperature erosion are examined. In most cases, the erosion rate of materials decreased with increasing temperature. After this, the evolution of erosion-resistant coatings over the last four decades that are first-generation (single-phase coatings), second-generation (metal/ceramic multilayer coatings), and third-generation (nanocomposite and nano-multilayer coatings) erosion-resistant coatings are reviewed in detail. The third-generation nano coatings were found to be superior to the first- and second-generation erosion-resistant coatings. Finally, some of the commercial or notable erosion-resistant coatings developed in the last decade are discussed. The paper concluded with the research gaps that need to be addressed to develop efficient erosion-resistant coatings. Full article

This article discusses the specific application features of end mills with Ti-TiN-(Ti,Cr,Al)N, Zr-ZrN-(Zr,Mo,Al)N, and ZrHf-(Zr,Hf)N-(Zr,Hf,Cr,Mo,Al)N multilayer nanocomposite coatings during the machining of the Inconel 718 nickel–chromium alloy. The hardness, fracture resistance during scratch testing, structure, and phase composition of the coatings were studied. The tribological properties of the samples were compared at temperatures of 400–900 °C. Tests were conducted to study the wear resistance of the coated end mills during the milling of the Inconel 718 alloy. The wear mechanism of the end mills was studied. It was found that in comparison with the other coatings, the Zr-ZrN-(Zr,Mo,Al)N coating had the highest hardness and the lowest value of the adhesion component of the coefficient of friction at high temperatures. However, the Zr-ZrN-(Zr,Mo,Al)N coating exhibited good resistance to cracking and oxidation during the milling of the Inconel 718 alloy. Based on the above, the Zr-ZrN-(Zr,Mo,Al)N coating can be considered a good choice as a wear-resistant coating for the end milling of the Inconel 718 alloy. Full article

Magnetic carbon nanocomposites (α-Fe/Fe₃C@C) synthesized employing fructose and Fe₃O₄ magnetite nanoparticles as the carbon and iron precursors, respectively, are analyzed and applied for the removal of Cr (VI). Initial citric acid-coated magnetite nanoparticles, obtained through the co-precipitation method, were mixed with fructose (weight ratio 1:2) and thermally treated at different annealing temperatures (T_ann = 400, 600, 800, and 1000 °C). The thermal decomposition of the carbon matrix and the Fe₃O₄ reduction was followed by thermogravimetry (TGA) and Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, Raman spectroscopy, SQUID magnetometry, and N₂ adsorption–desorption isotherms. A high annealing temperature (T_ann = 800 °C) leads to optimum magnetic adsorbents (high magnetization enabling the magnetic separation of the adsorbent from the aqueous media and large specific surface area to enhance the pollutant adsorption process). Cr (VI) adsorption tests, performed under weak acid environments (pH = 6) and low pollutant concentrations (1 mg/L), confirm the Cr removal ability and reusability after consecutive adsorption cycles. Physical adsorption (pseudo-first-order kinetics model) and multilayer adsorption (Freundlich isotherm model) characterize the Cr (VI) absorption phenomena and support the enhanced adsorption capability of the synthesized nanostructures. Full article

Tissue-engineered (TE) scaffolds provide an ‘off-the-shelf’ alternative to autograft procedures and can potentially address their associated complications and limitations. The properties of TE scaffolds do not always match the surrounding bone, often sacrificing porosity for improved compressive strength. Previously, the layer-by-layer (LbL) assembly technique was used to deposit nanoclay containing multilayers capable of improving the mechanical properties of open-cell structures without greatly affecting the porosity. However, the previous coatings studied contained poly(ethylenimine) (PEI), which is known to be cytotoxic due to the presence of amine groups, rendering it unsuitable for use in biomedical applications. In this work, poly(diallydimethylammonium chloride) (PDDA)- and chitosan (CHI)-based polyelectrolyte systems were investigated for the purpose of nanoclay addition as an alternative to PEI-based polyelectrolyte systems. Nanocomposite coatings comprising of PEI, poly(acrylic acid) (PAA), Na+ montmorillonite (NC), PDDA, CHI and sodium alginate (ALG) were fabricated. The coatings were deposited in the following manner: (PEI/PAA/PEI/NC), PEI-(PDDA/PAA/PDDA/NC) and (CHI/ALG/CHI/ALG). Results from scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses demonstrated that the nanoclay was successfully incorporated into each polymer bilayer system, creating a nanocomposite coating. Each coating was successful at tailoring the elastic modulus of the open-cell structures, with polyurethane foams exhibiting an increase from 0.15 ± 0.10 MPa when uncoated to 5.51 ± 0.40 MPa, 6.01 ± 0.36 MPa and 2.61 ± 0.41 MPa when coated with (PEI/PAA/PEI/NC), PEI-(PDDA/PAA/PDDA/NC) and (CHI/ALG/CHI/ALG), respectively. Several biological studies were conducted to determine the cytotoxicity of the coatings, including a resazurin reduction assay, scanning electron microscopy and fluorescent staining of the cell-seeded substrates. In this work, the PDDA-based system exhibited equivalent physical and mechanical properties to the PEI-based system and was significantly more biocompatible, making it a much more suitable alternative for biomaterial applications. Full article