Materials

13 pages, 18141 KiB

Open AccessArticle

The Microstructures and Deformation Mechanism of Hetero-Structured Pure Ti under High Strain Rates

by Shuaizhuo Wang, Haotian Yan, Dongmei Zhang, Jiajun Hu and Yusheng Li

Materials 2023, 16(21), 7059; https://doi.org/10.3390/ma16217059 - 6 Nov 2023

Cited by 2 | Viewed by 1241

This study investigates the microstructures and deformation mechanism of hetero-structured pure Ti under different high strain rates (500 s⁻¹, 1000 s⁻¹, 2000 s⁻¹). It has been observed that, in samples subjected to deformation, the changes in texture [...] Read more.

This study investigates the microstructures and deformation mechanism of hetero-structured pure Ti under different high strain rates (500 s⁻¹, 1000 s⁻¹, 2000 s⁻¹). It has been observed that, in samples subjected to deformation, the changes in texture are minimal and the rise in temperature is relatively low. Therefore, the influence of these two factors on the deformation mechanism can be disregarded. As the strain rate increases, the dominance of dislocation slip decreases while deformation twinning becomes more prominent. Notably, at a strain rate of 2000 s⁻¹, nanoscale twin lamellae are activated within the grain with a size of 500 nm, which is a rarely observed phenomenon in pure Ti. Additionally, martensitic phase transformation has also been identified. In order to establish a correlation between the stress required for twinning and the grain size, a modified Hall–Petch model is proposed, with the obtained value of

K_{t w i n}

serving as an effective metric for this relationship. These findings greatly enhance our understanding of the mechanical responses of Ti and broaden the potential applications of Ti in dynamic deformation scenarios. Full article

(This article belongs to the Special Issue Materials under High Pressure)

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19 pages, 4608 KiB

Open AccessArticle

Synergistic Effects of SAP, Limestone Powder and White Cement on the Aesthetic and Mechanical Properties of Fair-Faced Concrete

by Jun Shi, Zhangbao Wu, Jinping Zhuang, Fan Zhang, Tongran Zhu and Huixia Li

Materials 2023, 16(21), 7058; https://doi.org/10.3390/ma16217058 - 6 Nov 2023

Cited by 3 | Viewed by 1368

Abstract

In this investigation, a comprehensive assessment was conducted on the cooperative effects of Super Absorbent Polymers (SAP), limestone powder, and white cement within the realm of fair-faced concrete. We discerned that while white cement augments the color vibrancy of the concrete, its accelerated [...] Read more.

In this investigation, a comprehensive assessment was conducted on the cooperative effects of Super Absorbent Polymers (SAP), limestone powder, and white cement within the realm of fair-faced concrete. We discerned that while white cement augments the color vibrancy of the concrete, its accelerated hydration rate potentially induced early-stage cracks and compromised performance. To mitigate these challenges, SAP was incorporated to regulate early hydration, and limestone powder was introduced as a fortifying agent to bolster the mechanical robustness of the concrete. Our findings highlighted not only the capability of SAP to enhance concrete workability and longevity but also the pivotal role of limestone powder in amplifying its mechanical attributes. Microscopic evaluations, undertaken via Scanning Electron Microscopy (SEM), unveiled the potential of both SAP and limestone powder in refining the microstructure of the concrete, thereby elevating its performance metrics. Synthesizing the research outcomes, we pinpointed an optimal amalgamation of SAP, limestone powder, and white cement in fair-faced concrete, offering a valuable reference for prospective architectural applications. Full article

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12 pages, 5190 KiB

Open AccessArticle

Enhanced Mechanical Properties of Cast Cu-10 wt%Fe Alloy via Single-Pass Friction Stir Processing

by Xiaobo Yuan, Hui Wang, Ruilin Lai and Yunping Li

Materials 2023, 16(21), 7057; https://doi.org/10.3390/ma16217057 - 6 Nov 2023

Cited by 4 | Viewed by 1205

Abstract

In this study, Cu-10 wt% Fe alloy in as-cast state was modified using friction stir processing (FSP). The microstructure evolution of Cu-10 wt% Fe alloys in different states was characterized in detail using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission [...] Read more.

In this study, Cu-10 wt% Fe alloy in as-cast state was modified using friction stir processing (FSP). The microstructure evolution of Cu-10 wt% Fe alloys in different states was characterized in detail using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results show that due to dynamic recrystallization, the FSPed Cu-10 wt% Fe alloy obtained a uniformly equiaxed ultrafine microstructure with low density of dislocation, high proportion of high-angle grain boundaries (HAGBs), and high degree of recrystallization. Fine equiaxed grains with an average size of 0.6 μm were produced after FSP. Many fine-precipitate Fe-phases with an average size of 20 nm were uniformly distributed in the Cu matrix. The FSPed samples possessed excellent mechanical properties, such as high Vickers hardness (163.5 HV), ultimate tensile strength (538.5 MPa), and good elongation (16%). This single-pass FSP method does not require subsequent aging treatment and provides a simple and efficient way to improve the properties of Cu-Fe alloys. Full article

(This article belongs to the Special Issue State-of-the-Art Functional Materials and Nanomaterials in Asia 2023–2024)

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17 pages, 10743 KiB

Open AccessArticle

Hot Deformation Behavior and Processing Maps of 26CrMo7S Steel Used in Oil Exploration

by Hemiao Jiang, Hongying Li, Dianyuan Huang, Yinghui Zhao, Jiwen Liu, Qing Gao, Hang He and Ximao Liu

Materials 2023, 16(21), 7056; https://doi.org/10.3390/ma16217056 - 6 Nov 2023

Viewed by 1260

Abstract

The hot deformation behavior and flow stress characteristics of experimental 26CrMo7S steel were analyzed using a thermal simulator under a range of conditions, including a strain rate range of 0.01~10 s⁻¹, a temperature range of 850~1250 °C, and a maximum deformation [...] Read more.

The hot deformation behavior and flow stress characteristics of experimental 26CrMo7S steel were analyzed using a thermal simulator under a range of conditions, including a strain rate range of 0.01~10 s⁻¹, a temperature range of 850~1250 °C, and a maximum deformation amount of 70%. The Arrhenius constitutive model was built for the corresponding conditions, and the model’s accuracy was verified through error analysis. Additionally, hot processing maps were constructed to analyze the processing zone of the steel under different hot deformation conditions. Finally, the microstructure of the processing zones was observed and verified using the electron backscattered diffraction (EBSD). The results indicate that the interaction of work hardening and dynamic softening influences the hot deformation behavior of 26CrMo7S steel. The Arrhenius constitutive equation with a value of the correlation coefficient (r = 0.99523) accurately predicts the flow behavior of 26CrMo7S steel under different strains. The optimal processing zone obtained with the hot processing maps is within a deformation range of 1010~1190 °C and a strain rate range of 0.01~10^−1.5 s⁻¹, and the obtained microstructure is in good agreement with the analysis results. Full article

(This article belongs to the Special Issue Advanced Metal Matrix Functional Composites and Applications)

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16 pages, 10621 KiB

Open AccessArticle

Experimental and Numerical Study on the Perforation Behavior of an Aluminum 6061-T6 Cylindrical Shell

by Seon-Woo Byun, Young-Jung Joo, Soo-Yong Lee and Sang-Woo Kim

Materials 2023, 16(21), 7055; https://doi.org/10.3390/ma16217055 - 6 Nov 2023

Viewed by 1236

Abstract

The modified Johnson–Cook (MJC) material model is widely used in simulation under high-velocity impact. There was a need to estimate a strain rate parameter for the application to the impact analysis, where the method typically used is the Split Hopkinson bar. However, this [...] Read more.

The modified Johnson–Cook (MJC) material model is widely used in simulation under high-velocity impact. There was a need to estimate a strain rate parameter for the application to the impact analysis, where the method typically used is the Split Hopkinson bar. However, this method had a limit to the experiment of strain rate. This study proposed to estimate the strain rate parameter of the MJC model based on the impact energy and obtained a parameter. The proposed method of strain rate parameter calculation uses strain parameters to estimate from the drop weight impact and high-velocity impact experiments. Then, the ballistic experiment and analysis were carried out with the target of the plate and cylindrical shape. These analysis results were then compared with those obtained from the experiment. The penetration velocities of plates could be predicted with an error of a maximum of approximately 3.7%. The penetration shape of the cylindrical target has a similar result shape according to impact velocity and had an error of approximately 6%. Full article

(This article belongs to the Special Issue Fracture Behaviour of Structural Materials)

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33 pages, 12872 KiB

Open AccessReview

Critical Review on Magnetically Impelled Arc Butt Welding: Challenges, Perspectives and Industrial Applications

by Mukti Chaturvedi, Arungalai Vendan Subbiah, George Simion, Carmen Catalina Rusu and Elena Scutelnicu

Materials 2023, 16(21), 7054; https://doi.org/10.3390/ma16217054 - 6 Nov 2023

Cited by 2 | Viewed by 2202

Abstract

Magnetically Impelled Arc Butt (MIAB) welding is a cutting-edge joining method that replaces the conventional welding procedures such as resistance, friction, flash and butt welding. It is a solid-state process that uses a rotating arc to heat up the butt ends of tubes, [...] Read more.

Magnetically Impelled Arc Butt (MIAB) welding is a cutting-edge joining method that replaces the conventional welding procedures such as resistance, friction, flash and butt welding. It is a solid-state process that uses a rotating arc to heat up the butt ends of tubes, being followed by a forging process that completes the joining of the workpieces The magnetic flux density and the current interact to develop the Lorentz force that impels the arc along the faying surfaces. This process is found to produce high tensile strength and defect-free welds in ferrous materials and for this reason, it is predominantly employed in automobile applications for joining metallic tubes. Also, this joining procedure can be applied in the fabrication of boilers, heat exchangers, furnace piping in petrochemical industry and other safety-critical high-pressure machinery parts. The MIAB method has several advantages such as a shorter welding cycle, lower input energy requirement and lower loss of material. Compared to other solid-state welding processes, the MIAB welding has an important advantage in terms of cost-efficient welds with better control and reliability. Moreover, there are researchers who have investigated the joining of non-ferrous dissimilar materials using this welding procedure. The studies have been focused on process parametric analysis that involves optimizing and forecasting the magnetic field and thermal profile distribution. This review article provides competitive insights into various design features, computational methods, tests and material characterization, technical issues and workarounds, as well as automation aspects related to the MIAB-welding process. This work will prove to be a quick reference for researchers, useful to identify the research gaps and conflicting ideas that can be further explored for advancements in joining the similar and dissimilar materials. Full article

(This article belongs to the Special Issue Recent Advances and Perspectives in Welding and Joining Process and Technology)

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13 pages, 9851 KiB

Open AccessArticle

Microstructural Inhomogeneity in the Fusion Zone of Laser Welds

by Libo Wang, Xiuquan Ma, Gaoyang Mi, Lei Su and Zhengwu Zhu

Materials 2023, 16(21), 7053; https://doi.org/10.3390/ma16217053 - 6 Nov 2023

Cited by 1 | Viewed by 1140

Abstract

This paper investigated evolutions of α-Al sub-grains’ morphology and crystalline orientation in the fusion zone during laser welding of 2A12 aluminum alloys. Based on this, a new method for assessing the weldability of materials was proposed. In laser deep-penetration welding, in addition to [...] Read more.

This paper investigated evolutions of α-Al sub-grains’ morphology and crystalline orientation in the fusion zone during laser welding of 2A12 aluminum alloys. Based on this, a new method for assessing the weldability of materials was proposed. In laser deep-penetration welding, in addition to the conventional columnar and equiaxed dendrites, there also exhibited a corrugated structure with several ‘fine-coarse-fine’ transformations. In such regions, an abnormal α-Al coarsening phenomenon was encountered, with a more dispersed crystalline orientation arrangement and a decreased maximum pole density value. Particularly, structural alterations appeared more frequently in the weld bottom than the top. The above results indicated that the laser-induced keyhole presented a continually fluctuating state. Under such a condition, the solid–liquid transformation exhibited an unstable solidification front, a fluctuant undercooling, and a variational solidification rate. Meanwhile, the welding quality of this material is in a critical state to generate pores. Therefore, the appearance and relevant number of corrugated regions can be considered as a new way for judging the weldability, which will help to narrow the processing window with better welding stability. Full article

(This article belongs to the Special Issue Advanced Materials – Microstructure, Manufacturing and Analysis)

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15 pages, 15165 KiB

Open AccessArticle

Grouting Mechanism of Polyurethane Composite Materials in Asphalt Pavement Subsidence

by Maoping Ran, Xinxing Zhou, Yuan Yan, Ruiqie Jiang and Xinglin Zhou

Materials 2023, 16(21), 7052; https://doi.org/10.3390/ma16217052 - 6 Nov 2023

Cited by 5 | Viewed by 1436

Abstract

The mechanical properties of polyurethane grouting materials were significantly improved when cement, sodium meta-silicate, red mud, slag, and fly ash were added. However, the grouting mechanisms of polyurethane composite materials are not clear. The grouting mechanisms of polyurethane composite materials in asphalt pavement [...] Read more.

The mechanical properties of polyurethane grouting materials were significantly improved when cement, sodium meta-silicate, red mud, slag, and fly ash were added. However, the grouting mechanisms of polyurethane composite materials are not clear. The grouting mechanisms of polyurethane composite materials in asphalt pavement subsidence were investigated. The results of computed tomography analysis show that polyurethane foam is filled with geopolymer hydration products. The results from ground penetrating radar after grouting show that mapping has no significant fluctuation or dislocation effect, which indicates that the grouting effect is strong. The high-density electrometer can also test the pavement subsidence place and distribution. The grouting mechanisms indicate that polyurethane foam acts as the consolidation structure, and the geopolymer filled with the foam pores of polyurethane and geopolymer forms a stable consolidated body. The seriflux includes under-layer seriflux (red mud, slag, water, and polyurethane composite materials) and upper-layer seriflux (polyurethane seriflux), and there exists a weak phase separation phenomenon, in which the separation phase is mainly polyurethane with little red mud-based geopolymer. Full article

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17 pages, 6839 KiB

Open AccessArticle

AC Electromagnetic Field Controls the Biofilms on the Glass Surface by Escherichia coli & Staphylococcus epidermidis Inhibition Effect

by Natsu Aoyama, Hideyuki Kanematsu, Dana M. Barry, Hidekazu Miura, Akiko Ogawa, Takeshi Kogo, Risa Kawai, Takeshi Hagio, Nobumitsu Hirai, Takehito Kato, Michiko Yoshitake and Ryoichi Ichino

Materials 2023, 16(21), 7051; https://doi.org/10.3390/ma16217051 - 6 Nov 2023

Cited by 1 | Viewed by 1711

Abstract

Biofilms, mainly comprised of bacteria, form on materials’ surfaces due to bacterial activity. They are generally composed of water, extracellular polymeric substances (polysaccharides, proteins, nucleic acids, and lipids), and bacteria. Some bacteria that form biofilms cause periodontal disease, corrosion of the metal materials [...] Read more.

Biofilms, mainly comprised of bacteria, form on materials’ surfaces due to bacterial activity. They are generally composed of water, extracellular polymeric substances (polysaccharides, proteins, nucleic acids, and lipids), and bacteria. Some bacteria that form biofilms cause periodontal disease, corrosion of the metal materials that make up drains, and slippage. Inside of a biofilm is an environment conducive to the growth and propagation of bacteria. Problems with biofilms include the inability of disinfectants and antibiotics to act on them. Therefore, we have investigated the potential application of alternating electromagnetic fields for biofilm control. We obtained exciting results using various materials’ specimens and frequency conditions. Through these studies, we gradually understood that the combination of the type of bacteria, the kind of material, and the application of an electromagnetic field with various low frequencies (4 kHz–12 kHz) changes the circumstances of the onset of the biofilm suppression effect. In this study, relatively high frequencies (20 and 30 kHz) were applied to biofilms caused by Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis), and quantitative evaluation was performed using staining methods. The sample surfaces were analyzed by Raman spectroscopy using a Laser Raman spectrometer to confirm the presence of biofilms on the surface. Full article

(This article belongs to the Special Issue Science and Technology of Advanced Materials Applied to Society: Including Collections from the Latest Papers of KRIS 2023)

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16 pages, 2863 KiB

Open AccessArticle

The Influence of Acid Casein on the Selected Properties of Lime–Metakaolin Mortars

by Przemysław Brzyski and Renata Boris

Materials 2023, 16(21), 7050; https://doi.org/10.3390/ma16217050 - 6 Nov 2023

Viewed by 1312

Abstract

One of the ways to modify selected parameters of lime mortars is the use of biopolymers of animal origin, such as bone glue, skin glue, bovine blood, eggs, and casein. These are protein-based biopolymers. Casein is an example of an organic polymer produced [...] Read more.

One of the ways to modify selected parameters of lime mortars is the use of biopolymers of animal origin, such as bone glue, skin glue, bovine blood, eggs, and casein. These are protein-based biopolymers. Casein is an example of an organic polymer produced from cow’s milk. The aim of the work was to investigate the possibilities of improving selected properties of mortars based on hydrated lime and metakaolin. The mixture was modified with powdered technical casein in amounts of 0.5%, 1.5%, 1%, 1.5%, and 2% as a partial mass replacement for the binding mixture. Additionally, the influence of increasing the amount of water on the properties of the mortar with a casein admixture of 2% was checked. This study examined consistency, shrinkage, water absorption, capillary action, porosity, flexural, compressive strength, and Young’s modulus. The admixture of casein influenced the properties of the mortar, but not in all cases, and it was possible to determine a clear trend related to the variable amount of casein. Strength properties deteriorated as the amount of casein increased. When air bubbles were introduced into the mortar after the casein was dissolved, the porosity increased as the amount of admixture increased. The moisture properties improved; namely, casein led to a reduction in water absorption and water absorption caused by capillary action. No relationship was observed between the amount of casein and the drying shrinkage. Increasing the amount of water in the mixture led to the expected effects, i.e., an increase in porosity, shrinkage, and water absorption, and a decrease in mechanical strength. Full article

(This article belongs to the Special Issue Advances in Natural Building and Construction Materials)

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14 pages, 3250 KiB

Open AccessArticle

Optical Properties of Amorphous Carbon Thin Films Fabricated Using a High-Energy-Impulse Magnetron-Sputtering Technique

by Lukasz Skowronski, Rafal Chodun, Marek Trzcinski and Krzysztof Zdunek

Materials 2023, 16(21), 7049; https://doi.org/10.3390/ma16217049 - 6 Nov 2023

Cited by 3 | Viewed by 1343

Abstract

This paper reports the results of amorphous carbon thin films fabricated by using the gas-impulse-injection magnetron-sputtering method and differing the accelerating voltage (1.0–1.4 kV). The obtained layers were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XRD), and spectroscopic ellipsometry (SE). The analysis of [...] Read more.

This paper reports the results of amorphous carbon thin films fabricated by using the gas-impulse-injection magnetron-sputtering method and differing the accelerating voltage (1.0–1.4 kV). The obtained layers were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XRD), and spectroscopic ellipsometry (SE). The analysis of the Raman and XPS spectra point to the significant content of sp³ hybridization in the synthesized materials (above 54–73%). The refractive index of the films is very high—above 2.45 in the infrared spectral range. The band-gap energy (determined using the inversed-logarithmic-derivative method) depends on the discharging voltage and is in the range from 1.58 eV (785 nm) to 2.45 eV (506 nm). Based on the obtained results, we have elaborated a model explaining the a-C layers’ formation process. Full article

(This article belongs to the Section Carbon Materials)

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7 pages, 1007 KiB

Open AccessCommunication

Ferromagnetic Fluctuations in the Heavily Overdoped Regime of Single-Layer High-T_c Cuprate Superconductors

by Tadashi Adachi, Koshi Kurashima, Takayuki Kawamata, Takashi Noji, Satoru Nakajima and Yoji Koike

Materials 2023, 16(21), 7048; https://doi.org/10.3390/ma16217048 - 6 Nov 2023

Viewed by 1249

Abstract

To investigate proposed ferromagnetic fluctuations in the so-called single-layer Bi-2201 and La-214 high-T_c cuprates, we performed magnetization and electrical resistivity measurements using single-layer Tl-2201 cuprates Tl₂Ba₂CuO_6+δ and La-214 La₂₋_xSr_xCuO₄ in [...] Read more.

To investigate proposed ferromagnetic fluctuations in the so-called single-layer Bi-2201 and La-214 high-T_c cuprates, we performed magnetization and electrical resistivity measurements using single-layer Tl-2201 cuprates Tl₂Ba₂CuO_6+δ and La-214 La₂₋_xSr_xCuO₄ in the heavily overdoped regime. Magnetization of Tl₂Ba₂CuO_6+δ and La₂₋_xSr_xCuO₄ exhibited the tendency to be saturated in high magnetic fields at low temperatures, suggesting the precursor behavior toward the formation of a ferromagnetic order. It was found that the power of temperature n obtained from the temperature dependence of the electrical resistivity is ~4/3 and ~5/3 for Bi-2201 and La₂₋_xSr_xCuO₄, respectively, and is ~4/3 at high temperatures and ~5/3 at low temperatures in Tl₂Ba₂CuO_6+δ. These results suggest that two- and three-dimensional ferromagnetic fluctuations exist in Bi-2201 and La₂₋_xSr_xCuO₄, respectively. In Tl₂Ba₂CuO_6+δ, it is suggested that the dimension of ferromagnetic fluctuations is two at high temperatures and three at low temperatures, respectively. The dimensionality of ferromagnetic fluctuations is understood in terms of the dimensionality of the crystal structure and the bonding of atoms in the blocking layer. Full article

(This article belongs to the Special Issue Structure and Electronic Properties of Emerging Superconductor and Related Materials)

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19 pages, 19869 KiB

Open AccessArticle

Tensile and Tearing Properties of a Geocomposite Mechanically Damaged by Repeated Loading and Abrasion

by José Ricardo Carneiro, Filipe Almeida, Filipa Carvalho and Maria de Lurdes Lopes

Materials 2023, 16(21), 7047; https://doi.org/10.3390/ma16217047 - 5 Nov 2023

Cited by 1 | Viewed by 1349

Abstract

The behaviour of geosynthetics can be affected by many agents, both in the short and long term. Mechanical damage caused by repeated loading or abrasion are examples of agents that may induce undesirable changes in the properties of geosynthetics. The research conducted in [...] Read more.

The behaviour of geosynthetics can be affected by many agents, both in the short and long term. Mechanical damage caused by repeated loading or abrasion are examples of agents that may induce undesirable changes in the properties of geosynthetics. The research conducted in this work complemented previous studies and consisted of submitting a geocomposite, isolated and successively, to two degradation tests: mechanical damage under repeated loading and abrasion. The geocomposite (a nonwoven geotextile reinforced with polyethylene terephthalate filaments) was tested on both sides (with or without filaments) and directions (machine and cross-machine). The impact of the degradation tests on the geocomposite was quantified by monitoring changes in its tensile and tearing behaviour. The results showed that, in most cases, the degradation tests caused the deterioration of the tensile and tearing behaviour of the geocomposite, affecting its reinforcement function. The decline in tensile strength correlated reasonably well with the decline in tearing strength. Changing the side and direction tested influenced, in some cases (those involving abrasion), the degradation experienced by the geocomposite. The reduction factors (referring to tensile and tearing strength) for the combined effect of the degradation agents tended to be lower when determined by using the common method (compared to those resulting directly from the successive exposure to both agents). Full article

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23 pages, 15845 KiB

Open AccessReview

A Review: Design from Beta Titanium Alloys to Medium-Entropy Alloys for Biomedical Applications

by Ka-Kin Wong, Hsueh-Chuan Hsu, Shih-Ching Wu and Wen-Fu Ho

Materials 2023, 16(21), 7046; https://doi.org/10.3390/ma16217046 - 5 Nov 2023

Cited by 11 | Viewed by 4769

Abstract

β-Ti alloys have long been investigated and applied in the biomedical field due to their exceptional mechanical properties, ductility, and corrosion resistance. Metastable β-Ti alloys have garnered interest in the realm of biomaterials owing to their notably low elastic modulus. Nevertheless, the inherent [...] Read more.

β-Ti alloys have long been investigated and applied in the biomedical field due to their exceptional mechanical properties, ductility, and corrosion resistance. Metastable β-Ti alloys have garnered interest in the realm of biomaterials owing to their notably low elastic modulus. Nevertheless, the inherent correlation between a low elastic modulus and relatively reduced strength persists, even in the case of metastable β-Ti alloys. Enhancing the strength of alloys contributes to improving their fatigue resistance, thereby preventing an implant material from failure in clinical usage. Recently, a series of biomedical high-entropy and medium-entropy alloys, composed of biocompatible elements such as Ti, Zr, Nb, Ta, and Mo, have been developed. Leveraging the contributions of the four core effects of high-entropy alloys, both biomedical high-entropy and medium-entropy alloys exhibit excellent mechanical strength, corrosion resistance, and biocompatibility, albeit accompanied by an elevated elastic modulus. To satisfy the demands of biomedical implants, researchers have sought to synthesize the strengths of high-entropy alloys and metastable β-Ti alloys, culminating in the development of metastable high-entropy/medium-entropy alloys that manifest both high strength and a low elastic modulus. Consequently, the design principles for new-generation biomedical medium-entropy alloys and conventional metastable β-Ti alloys can be converged. This review focuses on the design from β-Ti alloys to the novel metastable medium-entropy alloys for biomedical applications. Full article

(This article belongs to the Special Issue Advanced Biomaterials for Dental Implants: Design and Mechanical Properties)

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18 pages, 1894 KiB

Open AccessReview

Controlled-Release Materials for Remediation of Trichloroethylene Contamination in Groundwater

by Shan Zhao, Jianhua Wang and Wenjin Zhu

Materials 2023, 16(21), 7045; https://doi.org/10.3390/ma16217045 - 5 Nov 2023

Cited by 2 | Viewed by 2211

Abstract

Groundwater contamination by trichloroethylene (TCE) presents a pressing environmental challenge with far-reaching consequences. Traditional remediation methods have shown limitations in effectively addressing TCE contamination. This study reviews the limitations of conventional remediation techniques and investigates the application of oxidant-based controlled-release materials, including encapsulated, [...] Read more.

Groundwater contamination by trichloroethylene (TCE) presents a pressing environmental challenge with far-reaching consequences. Traditional remediation methods have shown limitations in effectively addressing TCE contamination. This study reviews the limitations of conventional remediation techniques and investigates the application of oxidant-based controlled-release materials, including encapsulated, loaded, and gel-based potassium permanganate since the year 2000. Additionally, it examines reductant controlled-release materials and electron donor-release materials such as tetrabutyl orthosilicate (TBOS) and polyhydroxybutyrate (PHB). The findings suggest that controlled-release materials offer a promising avenue for enhancing TCE degradation and promoting groundwater restoration. This study concludes by highlighting the future research directions and the potential of controlled-release materials in addressing TCE contamination challenges. Full article

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20 pages, 8002 KiB

Open AccessEditor’s ChoiceReview

Recent Progress in Resonant Acoustic Metasurfaces

by Dongan Liu, Limei Hao, Weiren Zhu, Xiao Yang, Xiaole Yan, Chen Guan, You Xie, Shaofang Pang and Zhi Chen

Materials 2023, 16(21), 7044; https://doi.org/10.3390/ma16217044 - 5 Nov 2023

Cited by 5 | Viewed by 2807

Abstract

Acoustic metasurfaces, as two-dimensional acoustic metamaterials, are a current research topic for their sub-wavelength thickness and excellent acoustic wave manipulation. They hold significant promise in noise reduction and isolation, cloaking, camouflage, acoustic imaging, and focusing. Resonant structural units are utilized to construct acoustic [...] Read more.

Acoustic metasurfaces, as two-dimensional acoustic metamaterials, are a current research topic for their sub-wavelength thickness and excellent acoustic wave manipulation. They hold significant promise in noise reduction and isolation, cloaking, camouflage, acoustic imaging, and focusing. Resonant structural units are utilized to construct acoustic metasurfaces with the unique advantage of controlling large wavelengths within a small size. In this paper, the recent research progresses of the resonant metasurfaces are reviewed, covering the design mechanisms and advances of structural units, the classification and application of the resonant metasurfaces, and the tunable metasurfaces. Finally, research interest in this field is predicted in future. Full article

(This article belongs to the Special Issue Metamaterials and Metasurfaces: Fundamentals and Applications)

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21 pages, 2168 KiB

Open AccessReview

Corrosion by Polythionic Acid in the Oil and Gas Sector: A Brief Overview

by Mohammadtaghi Vakili, Petr Koutník and Jan Kohout

Materials 2023, 16(21), 7043; https://doi.org/10.3390/ma16217043 - 5 Nov 2023

Cited by 2 | Viewed by 2716

Abstract

Polythionic acid (PTA) corrosion is a significant challenge in the refinery industry, leading to equipment degradation, safety risks, and costly maintenance. This paper comprehensively investigates the origin, progression, mechanism, and impact of PTA corrosion on various components within refinery operations. Special attention is [...] Read more.

Polythionic acid (PTA) corrosion is a significant challenge in the refinery industry, leading to equipment degradation, safety risks, and costly maintenance. This paper comprehensively investigates the origin, progression, mechanism, and impact of PTA corrosion on various components within refinery operations. Special attention is afforded to the susceptibility of austenitic stainless steels and nickel-based alloys to PTA corrosion and the key factors influencing its occurrence. Practical strategies and methods for mitigating and preventing PTA corrosion are also explored. This paper underscores the importance of understanding PTA corrosion and implementing proactive measures to safeguard the integrity and efficiency of refinery infrastructure. Full article

(This article belongs to the Topic Materials for Corrosion Protection)

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11 pages, 6026 KiB

Open AccessArticle

Size Effect of Graphene Oxide on Graphene-Aerogel-Supported Au Catalysts for Electrochemical CO₂ Reduction

by Shuling Shen, Xuecong Pan, Jin Wang, Tongyu Bao, Xinjuan Liu, Zhihong Tang, Huixin Xiu and Jing Li

Materials 2023, 16(21), 7042; https://doi.org/10.3390/ma16217042 - 5 Nov 2023

Cited by 8 | Viewed by 1375

Abstract

The lateral size of graphene nanosheets plays a critical role in the properties and microstructure of 3D graphene as well as their application as supports of electrocatalysts for CO₂ reduction reactions (CRRs). Here, graphene oxide (GO) nanosheets with different lateral sizes (1.5, [...] Read more.

The lateral size of graphene nanosheets plays a critical role in the properties and microstructure of 3D graphene as well as their application as supports of electrocatalysts for CO₂ reduction reactions (CRRs). Here, graphene oxide (GO) nanosheets with different lateral sizes (1.5, 5, and 14 µm) were utilized as building blocks for 3D graphene aerogel (GA) to research the size effects of GO on the CRR performances of 3D Au/GA catalysts. It was found that GO-L (14 µm) led to the formation of GA with large pores and a low surface area and that GO-S (1.5 µm) induced the formation of GA with a thicker wall and isolated pores, which were not conducive to the mass transfer of CO₂ or its interaction with catalysts. Au/GA constructed with a suitable-sized GO (5 µm) exhibited a hierarchical porous network and the highest surface area and conductivity. As a result, Au/GA-M exhibited the highest Faradaic efficiency (FE) of CO (FE_CO = 81%) and CO/H₂ ratio at −0.82 V (vs. a Reversible Hydrogen Electrode (RHE)). This study indicates that for 3D GA-supported catalysts, there is a balance between the improvement of conductivity, the adsorption capacity of CO₂, and the inhibition of the hydrogen evolution reaction (HER) during the CRR, which is related to the lateral size of GO. Full article

(This article belongs to the Special Issue Preparation and Application of High-Performance Multifunctional Graphene Macroscopic Assemblies and Composites)

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19 pages, 24581 KiB

Open AccessArticle

Study on the Mechanical Properties and Mechanism of a Nickel-Iron Slag Cement-Based Composite under the Action of Sodium Sulfate

by Jingyu Zhang, Yuwan Zhou, Sili Chen, Jinzhu Meng and Junxiang Wang

Materials 2023, 16(21), 7041; https://doi.org/10.3390/ma16217041 - 4 Nov 2023

Viewed by 1225

Abstract

The accumulated amount of nickel–iron slag has increased with the rapid development of the nickel-iron industry. To determine a method for comprehensively utilizing nickel–iron slag, triaxial compression tests of nickel–iron slag cement-based composite materials under the action of sodium sulfate were conducted, and [...] Read more.

The accumulated amount of nickel–iron slag has increased with the rapid development of the nickel-iron industry. To determine a method for comprehensively utilizing nickel–iron slag, triaxial compression tests of nickel–iron slag cement-based composite materials under the action of sodium sulfate were conducted, and the effects of the sodium sulfate concentration on the stress-strain relation, shear strength, cohesion, and internal friction angle of the composite materials were analyzed. In addition, the influence mechanism of the nickel–iron slag content and sodium sulfate concentration on the composite was examined. The results revealed that the stress–strain curve of the nickel–iron slag cement-based composites reflected softening. With the increase in the sodium sulfate concentration, the brittleness increased, while the shear strength, cohesion, and internal friction angle decreased; the addition of nickel–iron slag slowed down the rate at which these parameters decrease. Scanning electron microscopy images revealed that nickel–iron slag can improve the internal structure of the cement composite soil, enhance its compactness, and improve its corrosion resistance. The optimum nickel–iron slag content of 14% can improve the cementitious composites’ resistance to sodium sulfate erosion in terms of solid waste utilization and cementitious soil performance. The results obtained can provide technical parameters for preparing and designing cement-based composite materials as well as certain theoretical significance and engineering reference value. Full article

(This article belongs to the Section Advanced Composites)

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15 pages, 5592 KiB

Open AccessArticle

Innovative Post-Processing for Complex Geometries and Inner Parts of 3D-Printed AlSi10Mg Devices

by Martí Calvet, Anna Domènech, Sergi Vilaró, Toni Meseguer and Lorenzo Bautista

Materials 2023, 16(21), 7040; https://doi.org/10.3390/ma16217040 - 4 Nov 2023

Viewed by 1662

Abstract

A new technology consisting of new and sustainable chemical polishing treatment for aluminum components with complex shapes, such as heat exchangers, manifolds, busbars, aerospace devices, etc., manufactured by Additive Manufacturing (AM) technologies is described in this paper. This technology will contribute to the [...] Read more.

A new technology consisting of new and sustainable chemical polishing treatment for aluminum components with complex shapes, such as heat exchangers, manifolds, busbars, aerospace devices, etc., manufactured by Additive Manufacturing (AM) technologies is described in this paper. This technology will contribute to the development of a more efficient manufacturing process driven by AM, reinforcing the main idea of AM, which is based on reducing the amount of material and achieving cost savings through smart and improved designs. The present study shows a significant reduction in the surface roughness of consolidated AlSi10Mg metal parts manufactured by the SLM technique after carrying out the new chemical polishing post-process investigated in this work. Roughness values have been measured by mechanical and optical profilometry. The results obtained demonstrate the effectiveness of the chemical polishing, decreasing the roughness by up to 40%, being a reproducible and repeatable post-process. The presence of smut as solid residues on such types of chemical treatments has been also analyzed with XRF and ICP-MS techniques. The results obtained show that Si and Mg precipitates are removed from the metal surface at the last step of the investigated post-process. The percentages of the elements decrease from 25.0% to 8.09% Si and from 0.86% to 0.42% Mg, achieving the alloy smut-free composition on the metal surface. Tensile strength measurements have shown that the post-process described not only maintains the mechanical properties of the bulk material but, in comparison with non-post-processed parts, a slight improvement is observed with respect to the initial values, Young modulus (61.1 GPa to final 62.2 GPa), yield strength (from 236.8 to 246.7 MPa), and tensile strength (from 371.9 to 382.5 MPa) is observed, suggesting that the post-process has positive impact on the printed metal part. Full article

(This article belongs to the Topic Advanced Manufacturing and Surface Technology)

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20 pages, 5934 KiB

Open AccessReview

Research and Application Progress of Vegetation Porous Concrete

by Chang Liu, Yangyang Xia, Jianguo Chen, Kai Huang, Jing Wang, Chaojie Wang, Zhuojie Huang, Xunhuai Wang, Cong Rao and Mingsheng Shi

Materials 2023, 16(21), 7039; https://doi.org/10.3390/ma16217039 - 4 Nov 2023

Cited by 4 | Viewed by 2710

Abstract

Vegetation porous concrete is a novel material that integrates concrete technology with plant growth, offering excellent engineering applicability and environmental friendliness. This material is mainly utilized in eco-engineering projects such as riverbank protection, architectural greening, and slope protection along roads. This paper systematically [...] Read more.

Vegetation porous concrete is a novel material that integrates concrete technology with plant growth, offering excellent engineering applicability and environmental friendliness. This material is mainly utilized in eco-engineering projects such as riverbank protection, architectural greening, and slope protection along roads. This paper systematically reviews the current research progress of vegetation porous concrete by collecting and analyzing the relevant literature from both domestic and international sources. It covers several aspects including the material components of vegetation porous concrete, such as aggregates, cementitious materials, chemical admixtures, and plant species, as well as aspects like mix design, workability, porosity, pH value, mechanical strength, and vegetative performance. Furthermore, the application of vegetation porous concrete in riverbank protection, slope protection along highways, and urban architecture is discussed, along with a prospective outlook on future research directions for vegetation porous concrete. Full article

(This article belongs to the Section Construction and Building Materials)

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14 pages, 9389 KiB

Open AccessArticle

Microstructural Characterization of Al_0.5CrFeNiTi High Entropy Alloy Produced by Powder Metallurgy Route

by Laura Elena Geambazu, Dorinel Tălpeanu, Robert Viorel Bololoi, Ciprian Alexandru Manea, Alina Elena Bololoi, Florin Miculescu, Delia Pătroi and Vasile Dănuţ Cojocaru

Materials 2023, 16(21), 7038; https://doi.org/10.3390/ma16217038 - 4 Nov 2023

Cited by 3 | Viewed by 1187

Abstract

Alloys with superior properties represent the main topic of recent studies due to their effectiveness in reducing the cost of equipment maintenance and enhancing usage time, in addition to other benefits in domains such as geothermal, marine, and airspace. Al_0.5CrFeNiTi was [...] Read more.

Alloys with superior properties represent the main topic of recent studies due to their effectiveness in reducing the cost of equipment maintenance and enhancing usage time, in addition to other benefits in domains such as geothermal, marine, and airspace. Al_0.5CrFeNiTi was produced by solid state processing in a planetary ball mill, with the objective of obtaining a high alloying degree and a homogenous composition that could be further processed by pressing and sintering. The metallic powder was technologically characterized, indicating a particle size reduction following mechanical alloying processing when compared to the elemental raw powder materials. The microstructural analysis presented the evolution of the alloying degree during milling but also a compact structure with no major defects in the pressed and sintered bulk samples. The X-ray diffraction results confirmed the presence of face-centered cubic (FCC) and body-centered cubic (BCC) phases, predicted by the theoretical calculations, along with a hexagonal close-packed (HCP) phase, where the Al, Cr, Fe, Ni, and Ti phase was identified in both the alloyed powder material and sintered sample. Full article

(This article belongs to the Special Issue State-of-the-Art Materials Science and Engineering in Romania 2023)

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16 pages, 5090 KiB

Open AccessArticle

Annual Transmittance Behavior of Light-Transmitting Concrete with Optical Fiber Bundles

by Adithya Shenoy, Gopinatha Nayak, Adithya Tantri, Kiran Kumar Shetty and Mangeshkumar R. Shendkar

Materials 2023, 16(21), 7037; https://doi.org/10.3390/ma16217037 - 4 Nov 2023

Cited by 3 | Viewed by 1415

Abstract

This study characterizes the transmittance behavior of structural light-transmitting concrete under natural sunlight. The experimentation involves the use of a novel test setup and a detailed analysis considering the variation and dependence on time of day, month of the year and seasonal variations. [...] Read more.

This study characterizes the transmittance behavior of structural light-transmitting concrete under natural sunlight. The experimentation involves the use of a novel test setup and a detailed analysis considering the variation and dependence on time of day, month of the year and seasonal variations. The test set consisted of 28 variations of fiber configurations, with two different diameters, spacing and bundling techniques used to increase the area of fibers while maintaining spacing to aid the placing of concrete without compromising on transmittance. The study provides a real-time observational understanding of the behavior of light-transmitting concrete, a result usually obtained by modelling and simulation. The statistical analysis helps in understanding the impact of various variables as well as their interrelationships, which can help in design optimization. Based on the behavior as well as the stipulations of standards, the applicability of the material to various structural applications has been identified. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior ‖)

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13 pages, 3240 KiB

Open AccessEditor’s ChoiceArticle

Effect of the Solid Solution and Aging Treatment on the Mechanical Properties and Microstructure of a Novel Al-Mg-Si Alloy

by Yan Chen, Wu Wei, Yu Zhao, Wei Shi, Xiaorong Zhou, Li Rong, Shengping Wen, Xiaolan Wu, Kunyuan Gao, Hui Huang and Zuoren Nie

Materials 2023, 16(21), 7036; https://doi.org/10.3390/ma16217036 - 4 Nov 2023

Cited by 5 | Viewed by 1958

Abstract

A novel Al-Mg-Si aluminum alloy with the addition of the micro-alloying element Er and Zr that was promptly quenched after extrusion has been studied. The solid solution and aging treatment of the novel alloy are studied by observing the microstructure, mechanical properties, and [...] Read more.

A novel Al-Mg-Si aluminum alloy with the addition of the micro-alloying element Er and Zr that was promptly quenched after extrusion has been studied. The solid solution and aging treatment of the novel alloy are studied by observing the microstructure, mechanical properties, and strengthening mechanism. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques are employed to examine the changes in the microstructure resulting from various solid solution treatments and aging treatments. The best strengthening effect can be achieved when the solubility of the MgSi phase and precipitate β″ (Mg₂Si phase) is at their maximum. The addition of Er and Zr elements promotes the precipitation of the β″ phase and makes the b″ phase more finely dispersed. The aging strengthening of alloys is a comprehensive effect of the dislocation cutting mechanism and bypass mechanism, the joint effect of diffusion strengthening of Al₃(Er,Zr) particles and the addition of Er and Zr elements promoting the precipitation strengthening of β″ phases. In this paper, by adding Er and Zr elements and exploring the optimal heat treatment system, the yield strength of the alloy reaches 437 MPa and the tensile strength reaches 453 MPa after solid solution treatment at 565 °C/30 min and aging at 175 °C/10 h. Full article

(This article belongs to the Special Issue Metallic Materials: Structure Transition, Processing, Characterization and Applications)

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15 pages, 12763 KiB

Open AccessArticle

Possibilities of Using Geopolymers in Welding Processes and Protection against High Temperatures

by Sławomir Parzych, Maja Paszkowska, Dawid Stanisz, Agnieszka Bąk and Michał Łach

Materials 2023, 16(21), 7035; https://doi.org/10.3390/ma16217035 - 3 Nov 2023

Cited by 1 | Viewed by 978

Abstract

Geopolymer materials have long been known for their competitive properties against traditional construction materials. Their special features include high resistance to elevated temperatures and good fire resistance. They are typically used as insulating materials at temperatures not exceeding 100 °C (because they can [...] Read more.

Geopolymer materials have long been known for their competitive properties against traditional construction materials. Their special features include high resistance to elevated temperatures and good fire resistance. They are typically used as insulating materials at temperatures not exceeding 100 °C (because they can achieve a thermal conductivity coefficient of 0.060 W/m × K or less under these conditions). Still, they can also be used as thermal insulation at temperatures exceeding 1000 °C. One technology that uses very high temperatures is metal welding technology, where temperatures often exceed as many as 3000 °C. Geopolymers, due to their properties, can also be an interesting new alternative in various welding applications. This paper presents the preliminary results of pot-proofing the resistance of geopolymers to temperatures exceeding 3000 °C. Test results of a foamed geopolymer insulating a steel substrate are presented, and a geopolymer mold for thermite rail welding was made and realistically tested. The results confirmed the feasibility of using cast geopolymer molds for thermite welding of railroad rails. The geopolymer material performed well during the test and no cracks or other damage occurred. The following article presents the potential of using geopolymer materials for welding applications. Full article

(This article belongs to the Special Issue Geopolymers and Fiber-Reinforced Concrete Composites)

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29 pages, 13467 KiB

Open AccessReview

Mechanical Properties of Bulk Metallic Glasses Additively Manufactured by Laser Powder Bed Fusion: A Review

by Haojie Luo and Yulei Du

Materials 2023, 16(21), 7034; https://doi.org/10.3390/ma16217034 - 3 Nov 2023

Cited by 8 | Viewed by 1897

Abstract

Bulk metallic glasses (BMGs) display excellent strength, high hardness, exceptional wear resistance and corrosion resistance owing to its amorphous structure. However, the manufacturing of large-sized and complex shaped BMG parts faces significant difficulties, which seriously hinders their applications. Laser powder bed fusion (LPBF) [...] Read more.

Bulk metallic glasses (BMGs) display excellent strength, high hardness, exceptional wear resistance and corrosion resistance owing to its amorphous structure. However, the manufacturing of large-sized and complex shaped BMG parts faces significant difficulties, which seriously hinders their applications. Laser powder bed fusion (LPBF) is a typical additive manufacturing (AM) technique with a cooling rate of up to 10⁸ K/s, which not only allows for the formation of amorphous structures but also solves the forming problem of complex-shaped BMG parts. In recent years, a large amount of work has been carried out on the LPBF processing of BMGs. This review mainly summarizes the latest progress in the field of LPBF additively manufactured BMGs focusing on their mechanical properties. We first briefly review the BMG alloy systems that have been additively manufactured using LPBF, then the mechanical properties of LPBF-fabricated BMGs including the micro- and nano-hardness, micropillar compressive performance, and macro-compressive and tensile performance are clarified. Next, the relationship between the mechanical properties and microstructure of BMGs produced via LPBF are analyzed. Finally, the measures for improving the mechanical properties of LPBF-fabricated BMGs are discussed. This review can provide readers with an essential comprehension of the structural and mechanical properties of LPBF-manufactured BMGs. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Recent Advances and Challenges)

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14 pages, 2457 KiB

Open AccessArticle

Influence Analysis of Polyvinyl Alcohol on the Degradation of Artificial Leather with Cellulose Nitrate Coating Originating from a Suitcase Stored in the Collection of the Auschwitz-Birkenau State Museum in Oświęcim, Poland

by Nel Jastrzębiowska, Anna Wawrzyk and Natalia Uroda

Materials 2023, 16(21), 7033; https://doi.org/10.3390/ma16217033 - 3 Nov 2023

Cited by 1 | Viewed by 1280

Abstract

The aim of this study was to assess the influence of a protective layer of polyvinyl alcohol on the degradation process of artificial leather based on cellulose nitrate. Samples of the artificial leather were obtained from a suitcase dating back to the first [...] Read more.

The aim of this study was to assess the influence of a protective layer of polyvinyl alcohol on the degradation process of artificial leather based on cellulose nitrate. Samples of the artificial leather were obtained from a suitcase dating back to the first half of the 20th century, not considered a historical artifact. The analysis involved Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Artificial aging was employed for the study. The artificial leather sample with a protective coating of polyvinyl alcohol on a cellulose nitrate base exhibited the lowest degree of degradation due to minimal chemical changes in cellulose esters. The obtained FTIR-ATR spectrum indicated significantly higher nitration of cellulose and, consequently, a lower degree of polymer degradation. The sample without the protective polyvinyl alcohol coating and the sample with the coating removed before artificial aging showed similar reactions. Full article

(This article belongs to the Special Issue Advanced Materials & Methods for Heritage & Archaeology)

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21 pages, 9027 KiB

Open AccessArticle

Interaction Mechanism between Slags and Alkali Silicate Activators: An Approach Based on the Al Phases

by Yu Jin, Weipeng Feng, Dapeng Zheng and Zhijun Dong

Materials 2023, 16(21), 7032; https://doi.org/10.3390/ma16217032 - 3 Nov 2023

Viewed by 946

Abstract

In this study, we examined the early-stage interaction of three types of slag and six activators with different chemical compositions. To determine the degree of hydration (DOH) and hydrate assemblage in alkali-activated slag (AAS), we employed EDX, XRD, and NMR analyses. We found [...] Read more.

In this study, we examined the early-stage interaction of three types of slag and six activators with different chemical compositions. To determine the degree of hydration (DOH) and hydrate assemblage in alkali-activated slag (AAS), we employed EDX, XRD, and NMR analyses. We found that with increasing silicate concentration in the activator, the DOH in the AAS varied, whereas the proportion of C-(N)-A-S-H increased and the other Al-containing phase decreased. When examining the impact of the activator on glass dissolution, it is apparent that an index based on the degree of depolymerization of the glass structure correlates with the DOH and the proportion of hydrotalcite in the AAS. Coupled with the activator’s modulus, this index can be utilised to elucidate the dissolution–reprecipitation mechanism that governs the interaction between the activator and slag. Full article

(This article belongs to the Collection Alkali‐Activated Materials for Sustainable Construction)

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11 pages, 1448 KiB

Open AccessArticle

Study of Elastic and Structural Properties of BaFe₂As₂ Ultrathin Film Using Picosecond Ultrasonics

by Di Cheng, Boqun Song, Jong-Hoon Kang, Chris Sundahl, Anthony L. Edgeton, Liang Luo, Joong-Mok Park, Yesusa G. Collantes, Eric E. Hellstrom, Martin Mootz, Ilias E. Perakis, Chang-Beom Eom and Jigang Wang

Materials 2023, 16(21), 7031; https://doi.org/10.3390/ma16217031 - 3 Nov 2023

Viewed by 1252

Abstract

We obtain the through-thickness elastic stiffness coefficient (C₃₃) in nominal 9 nm and 60 nm BaFe₂As₂ (Ba-122) thin films by using picosecond ultrasonics. Particularly, we reveal the increase in elastic stiffness as film thickness decreases from bulk [...] Read more.

We obtain the through-thickness elastic stiffness coefficient (C₃₃) in nominal 9 nm and 60 nm BaFe₂As₂ (Ba-122) thin films by using picosecond ultrasonics. Particularly, we reveal the increase in elastic stiffness as film thickness decreases from bulk value down to 9 nm, which we attribute to the increase in intrinsic strain near the film-substrate interface. Our density functional theory (DFT) calculations reproduce the observed acoustic oscillation frequencies well. In addition, temperature dependence of longitudinal acoustic (LA) phonon mode frequency for 9 nm Ba-122 thin film is reported. The frequency change is attributed to the change in Ba-122 orthorhombicity

(a - b) / (a + b)

. This conclusion can be corroborated by our previous ultrafast ellipticity measurements in 9 nm Ba-122 thin film, which exhibit strong temperature dependence and indicate the structural phase transition temperature T_s. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Materials Physics)

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11 pages, 2234 KiB

Open AccessCommunication

The Role of Carbon in Metal–Organic Chemical Vapor Deposition-Grown MoS₂ Films

by Tianyu Hou, Di Li, Yan Qu, Yufeng Hao and Yun Lai

Materials 2023, 16(21), 7030; https://doi.org/10.3390/ma16217030 - 3 Nov 2023

Viewed by 1484

Abstract

Acquiring homogeneous and reproducible wafer-scale transition metal dichalcogenide (TMDC) films is crucial for modern electronics. Metal–organic chemical vapor deposition (MOCVD) offers a promising approach for scalable production and large-area integration. However, during MOCVD synthesis, extraneous carbon incorporation due to organosulfur precursor pyrolysis is [...] Read more.

Acquiring homogeneous and reproducible wafer-scale transition metal dichalcogenide (TMDC) films is crucial for modern electronics. Metal–organic chemical vapor deposition (MOCVD) offers a promising approach for scalable production and large-area integration. However, during MOCVD synthesis, extraneous carbon incorporation due to organosulfur precursor pyrolysis is a persistent concern, and the role of unintentional carbon incorporation remains elusive. Here, we report the large-scale synthesis of molybdenum disulfide (MoS₂) thin films, accompanied by the formation of amorphous carbon layers. Using Raman, photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM), we confirm how polycrystalline MoS₂ combines with extraneous amorphous carbon layers. Furthermore, by fabricating field-effect transistors (FETs) using the carbon-incorporated MoS₂ films, we find that traditional n-type MoS₂ can transform into p-type semiconductors owing to the incorporation of carbon, a rare occurrence among TMDC materials. This unexpected behavior expands our understanding of TMDC properties and opens up new avenues for exploring novel device applications. Full article

(This article belongs to the Special Issue Advances of Photoelectric Functional Materials and Devices)

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Materials, Volume 16, Issue 21 (November-1 2023) – 235 articles

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