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Search Results (247)

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Keywords = direct tinning

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18 pages, 6070 KiB  
Article
A Non-Vacuum Coating Process That Fully Achieves Technical Goals of Bipolar Plates via Synergistic Control of Multiple Layer-by-Layer Strategy
by Qiaoling Liu, Xiaole Chen, Menghan Wu, Weihao Wang, Yinru Lin, Zilong Chen, Shuhan Yang, Yuhui Zheng and Qianming Wang
Molecules 2025, 30(12), 2543; https://doi.org/10.3390/molecules30122543 - 11 Jun 2025
Viewed by 437
Abstract
The primary challenge associated with stainless steel in fuel cell operation is its susceptibility to corrosion, which leads to increased contact resistance and subsequent degradation of electrochemical performance. In general, the protective layers have been loaded onto the metal surface by widely used [...] Read more.
The primary challenge associated with stainless steel in fuel cell operation is its susceptibility to corrosion, which leads to increased contact resistance and subsequent degradation of electrochemical performance. In general, the protective layers have been loaded onto the metal surface by widely used traditional techniques such as physical vapor deposition (PVD), or cathode arc ion plating. However, the above sputtering and evaporation ways require a high-vacuum condition, complicated experimental setups, higher costs, and an elevated temperature. Therefore, herein the achievement for uniform coatings over a large surface area has been realized by using a cost-effective strategy through a complete wet chemical process. The synergistic regulation of two conductive components and a plastic additive has been employed together with the entrapment of a surfactant to optimize the microstructure of the coating surface. The assembly of layered graphite and a polystyrene sphere could maintain both the high corrosion resistance feature and excellent electrical conductivity. In particular, the intrinsic vacant space in the above physical barriers has been filled with fine powders of indium tin oxide (ITO) due to its small size, and the interconnected conductive network with vertical/horizontal directions would be formed. All the key technical targets based on the U.S. Department of Energy (DOE) have been achieved under the simulated operating environments of a proton exchange membrane fuel cell. The corrosion current density has been measured as low as 0.52 μA/cm2 (for the sample of graphite/mixed layer) over the applied potentials from −0.6 V to 1.2 V and its protective efficiency is evaluated to be 99.8%. The interfacial contact resistance between the sample and the carbon paper is much less than 10 mΩ·cm2 (3.4 mΩ·cm2) under a contact pressure of 165 N/cm2. The wettability has been investigated and its contact angle has been evolved from 48° (uncoated sample) to even 110°, providing superior hydrophobicity to prevent water penetration. Such an innovative approach opens up new possibilities for improving the durability and reducing the costs of carbon-based coatings. Full article
(This article belongs to the Special Issue Inorganic Chemistry in Asia)
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28 pages, 5977 KiB  
Review
Advances in Flotation Reagents for Cassiterite Separation: Challenges and Sustainable Solutions
by Xianchen Wang, Hong Li, Xinhong Liu, Yuan Tang and Chenquan Ni
Molecules 2025, 30(11), 2380; https://doi.org/10.3390/molecules30112380 - 29 May 2025
Viewed by 642
Abstract
Tin is a crucial strategic metal, extensively employed in aerospace, new energy materials, and other advanced fields. However, with the progressive depletion of high-grade tin ores, the utilization of low-grade tin ores for metal tin production has emerged as a significant trend. Nonetheless, [...] Read more.
Tin is a crucial strategic metal, extensively employed in aerospace, new energy materials, and other advanced fields. However, with the progressive depletion of high-grade tin ores, the utilization of low-grade tin ores for metal tin production has emerged as a significant trend. Nonetheless, low-grade tin ores present inherent challenges that hinder their direct application in tin extraction. Flotation remains an effective method to enhance ore grade, yet issues such as fine particle dispersion and ore complexity persist. In light of this, the present study provides a comprehensive review of cassiterite resource characteristics, surface chemistry, flotation reagents, and relevant case studies. By delving into the physicochemical properties of cassiterite, this paper elucidates its floatability and the distinctions among various flotation reagents. Furthermore, it identifies critical challenges in cassiterite flotation and proposes targeted, feasible strategies to support the efficient exploitation of tin resources, thereby fostering the sustainable development of the tin industry. Full article
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15 pages, 3612 KiB  
Article
The Effect of pH Solution in the Sol–Gel Process on the Process of Formation of Fractal Structures in Thin SnO2 Films
by Ekaterina Bondar, Igor Lebedev, Anastasia Fedosimova, Elena Dmitriyeva, Sayora Ibraimova, Anton Nikolaev, Aigul Shongalova, Ainagul Kemelbekova and Mikhail Begunov
Fractal Fract. 2025, 9(6), 353; https://doi.org/10.3390/fractalfract9060353 - 28 May 2025
Viewed by 450
Abstract
In this paper, we investigated fractal cluster structures of colloidal particles in tin dioxide films obtained from lyophilic film-forming systems SnCl4/EtOH/NH4OH with different pH levels. It was revealed that at the ratio Sn > Cl2 > O2 [...] Read more.
In this paper, we investigated fractal cluster structures of colloidal particles in tin dioxide films obtained from lyophilic film-forming systems SnCl4/EtOH/NH4OH with different pH levels. It was revealed that at the ratio Sn > Cl2 > O2, N2 = 0, and pH = 1.42, the growth of cross-shaped and flower-shaped structures of various sizes from several μm to tens of μm is observed. At the ratio Cl2 > Sn > O2 > N2 and pH = 1.44, triangular and hexagonal structures are observed, the sizes of which are on the order of several tens of micrometers. The growth of hexagonal structures is probably affected by the presence of nitrogen in the film, according to the elemental analysis data. At the ratio Sn > Cl2 > O2 > N2 and solution pH of 1.49, the growth of hexagonal and cross-shaped structures is observed, whereas flower-shaped structures are not observed. Hierarchical flower-like and cross-shaped structures are fractal. The shape of microstructures is directly related to the shape of the elementary cells of SnO2 and NH4Cl. A direct dependence of the formation of hierarchical structures on the volume of ammonium hydroxide additive was found. This allows for controlling the shape and size of the synthesized structures when changing the ratio of the initial precursors and influencing the final physicochemical characteristics of the obtained samples. Full article
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14 pages, 3791 KiB  
Article
Deposition of HfO2 by Remote Plasma ALD for High-Aspect-Ratio Trench Capacitors in DRAM
by Jiwon Kim, Inkook Hwang, Byungwook Kim, Wookyung Lee, Juha Song, Yeonwoong Jung and Changbun Yoon
Nanomaterials 2025, 15(11), 783; https://doi.org/10.3390/nano15110783 - 23 May 2025
Viewed by 1039
Abstract
Dynamic random-access memory (DRAM) is a vital component in modern computing systems. Enhancing memory performance requires maximizing capacitor capacitance within DRAM cells, which is achieved using high-k dielectric materials deposited as thin, uniform films via atomic layer deposition (ALD). Precise film deposition that [...] Read more.
Dynamic random-access memory (DRAM) is a vital component in modern computing systems. Enhancing memory performance requires maximizing capacitor capacitance within DRAM cells, which is achieved using high-k dielectric materials deposited as thin, uniform films via atomic layer deposition (ALD). Precise film deposition that minimizes electronic defects caused by charged vacancies is essential for reducing leakage current and ensuring high dielectric strength. In this study, we fabricated metal–insulator–metal (MIM) capacitors in high-aspect-ratio trench structures using remote plasma ALD (RP-ALD) and direct plasma ALD (DP-ALD). The trenches, etched into silicon, featured a 7:1 aspect ratio, 76 nm pitch, and 38 nm critical dimension. We evaluated the electrical characteristics of HfO2-based capacitors with TiN top and bottom electrodes, focusing on leakage current density and equivalent oxide thickness. Capacitance–voltage analysis and X-ray photoelectron spectroscopy (XPS) revealed that RP-ALD effectively suppressed plasma-induced damage, reducing defect density and leakage current. While DP-ALD offered excellent film properties, it suffered from degraded lateral uniformity due to direct plasma exposure. Given its superior lateral uniformity, lower leakage, and defect suppression, RP-ALD shows strong potential for improving DRAM capacitor performance and serves as a promising alternative to the currently adopted thermal ALD process. Full article
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21 pages, 19032 KiB  
Article
Synthesis of Copper Nanowires Using Monoethanolamine and the Application in Transparent Conductive Films
by Xiangyun Zha, Depeng Gong, Wanyu Chen, Lili Wu and Chaocan Zhang
Nanomaterials 2025, 15(9), 638; https://doi.org/10.3390/nano15090638 - 22 Apr 2025
Viewed by 698
Abstract
Copper nanowires (Cu NWs) are considered a promising alternative to indium tin oxide (ITO) and silver nanowires (Ag NWs) due to their excellent electrical conductivity, mechanical properties, abundant reserves, and low cost. They have been widely applied in various optoelectronic devices. In this [...] Read more.
Copper nanowires (Cu NWs) are considered a promising alternative to indium tin oxide (ITO) and silver nanowires (Ag NWs) due to their excellent electrical conductivity, mechanical properties, abundant reserves, and low cost. They have been widely applied in various optoelectronic devices. In this study, Cu NWs were synthesized using copper chloride (CuCl2) as the precursor, monoethanolamine (MEA) as the complexing agent, and hydrated hydrazine (N2H4) as the reducing agent under strongly alkaline conditions at 60 °C. Notably, this is the first time that MEA has been employed as a complexing agent in this synthesis method for Cu NWs. Through a series of experiments, the optimal conditions for the CuCl2–MEA–N2H4 system in Cu NWs synthesis were determined. This study revealed that the presence of amines plays a crucial role in nanowire formation, as the co-ordination of MEA with copper in this system provides selectivity for the nanowire growth direction. MEA prevents the excessive conversion of Cu(I) complexes into Cu2O octahedral precipitates and exhibits an adsorption effect during Cu NWs formation. The different adsorption tendencies of MEA at the nanowire ends and lateral surfaces, depending on its concentration, influence the growth of the Cu NWs, as directly reflected by changes in their diameter and length. At an MEA concentration of 210 mM, the synthesized Cu NWs have an average diameter of approximately 101 nm and a length of about 28 μm. To fabricate transparent conductive films, the Cu NW network was transferred onto a polyethylene terephthalate (PET) substrate by applying a pressure of 20 MPa using a tablet press to ensure strong adhesion between the Cu NW-coated mixed cellulose ester (MCE) filter membrane and the PET substrate. Subsequently, the MCE membrane was dissolved by acetone and isopropanol immersion. The resulting Cu NW transparent conductive film exhibited a sheet resistance of 52 Ω sq−1 with an optical transmittance of 86.7%. Full article
(This article belongs to the Section Nanoelectronics, Nanosensors and Devices)
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26 pages, 6666 KiB  
Review
Recent Advance on Metal Carbides Reinforced Laser Cladding Coatings
by Dazhi Jiang, Guangjin Wang, Wei Dong, Xiaodong Hong and Chenguang Guo
Molecules 2025, 30(8), 1820; https://doi.org/10.3390/molecules30081820 - 18 Apr 2025
Viewed by 629
Abstract
The laser cladding technique can be adapted to fabricate composite coatings on the surface of the metal substrate, which not only effectively improves the surface properties of materials, but also greatly expands their application range. Metal carbides exhibit extremely high hardness, melting point, [...] Read more.
The laser cladding technique can be adapted to fabricate composite coatings on the surface of the metal substrate, which not only effectively improves the surface properties of materials, but also greatly expands their application range. Metal carbides exhibit extremely high hardness, melting point, and outstanding chemical stability. The hardness of carbides is much higher than that of general metal materials. Therefore, various metal carbides serve as reinforcing agents for enhancing the overall performance of metal-based coatings. To date, there is no special review about metal carbide-reinforced laser cladding coatings. In view of the outstanding performance and wide application of metal carbides in laser cladding coatings, herein, recent advances in various metal carbide-reinforced metal coatings are highlighted. According to the type of metal carbides, the whole review is classified into five sections: WC-reinforced coatings, TiC-reinforced coatings, NbC-reinforced coatings, Tin+1AlCn (MAX) reinforced coatings, and Cr3C2, TaC-reinforced coatings. The preparation method, microstructure feature, and application performance of various carbide-reinforced composite coatings are summarized. At last, some prospects are put forward on the current issues and future development directions, aiming to provide comprehensive and in-depth references for the research and application in the field of composite coatings. Full article
(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry—2nd Edition)
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10 pages, 5038 KiB  
Communication
ITO Meta-Absorber-Loaded Conformal UHF Monopole Antenna with Wide-Angel RCS Reduction
by Pan Lu, Jiuhao Gong, Xiaona Liu, Yuanxi Cao, Anxue Zhang and Sen Yan
Materials 2025, 18(6), 1379; https://doi.org/10.3390/ma18061379 - 20 Mar 2025
Cited by 1 | Viewed by 506
Abstract
In this paper, a conformal UHF antenna with a wide-angle radar cross section (RCS) reduction capability is proposed. The radiator of the design is a planar monopole antenna. Since the large physical size of the antenna in UHF band can generate a scatter [...] Read more.
In this paper, a conformal UHF antenna with a wide-angle radar cross section (RCS) reduction capability is proposed. The radiator of the design is a planar monopole antenna. Since the large physical size of the antenna in UHF band can generate a scatter beam with a large RCS in the high operating frequency of radars and other sensing applications, i.e., the X band, two types of ITO (Indium Tin Oxide) meta-absorber are proposed and loaded onto the monopole antenna to suppress the scatter. For the incident beam around the direction orthogonal to the radiator plane, the periodical meta-absorber can realize around a 20 dB RCS reduction in the X band. The incident wave around the parallel direction of the radiator is absorbed by the taper meta-absorber, which can greatly suppress the surface and then reduce the RCS in the horizontal plane. The combined effect means the antenna can achieve a wide-angle RCS reduction. It should be noted that the antenna can still produce a high-efficiency omnidirectional beam after the lossy meta-absorber is loaded. In our opinion, the advantages of the proposed antenna design, including good radiation performance in UHF band and high RCS reduction in X band, make it a suitable candidate for airborne and drone applications. Full article
(This article belongs to the Special Issue Advancements in Optical Materials and Photonic Device Technologies)
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24 pages, 6645 KiB  
Article
Assessing the Impacts of Transition and Physical Climate Risks on Industrial Metal Markets: Evidence from the Novel Multivariate Quantile-on-Quantile Regression
by Ousama Ben-Salha, Mourad Zmami, Sami Sobhi Waked, Bechir Raggad, Faouzi Najjar and Yazeed Mohammad Alenazi
Atmosphere 2025, 16(2), 233; https://doi.org/10.3390/atmos16020233 - 18 Feb 2025
Cited by 2 | Viewed by 720
Abstract
Climate change and global warming have been shown to increase the frequency and intensity of extreme weather events. Concurrently, substantial efforts are being directed toward fostering the transition to a low-carbon economy. These concurrent trends result in the emergence of both physical and [...] Read more.
Climate change and global warming have been shown to increase the frequency and intensity of extreme weather events. Concurrently, substantial efforts are being directed toward fostering the transition to a low-carbon economy. These concurrent trends result in the emergence of both physical and transition climate risks. This study investigates the impacts of climate risks, both physical and transition, on the return of major industrial metals (aluminum, copper, iron, lead, tin, nickel, and zinc) between January 2005 and December 2023. Employing the novel multivariate quantile-on-quantile regression (m-QQR) approach, this study examines how climate risks affect metal markets under different market conditions and risk levels. The results reveal that transition risks exert a more significant adverse impact on metal returns during bearish markets conditions, particularly for metals linked to high-emission industries, while physical risks affect metal returns across a wider range of quantiles, often increasing volatility during extreme market conditions. Furthermore, copper and nickel, both of which are crucial for renewable energy development, demonstrate resilience at higher quantiles, highlighting their role in the transition to a low-carbon economy. Finally, these two metals may serve as effective hedges against losses in other metals that are more vulnerable to transition risks, like aluminum and lead. Full article
(This article belongs to the Special Issue Climate Change and Extreme Weather Disaster Risks)
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16 pages, 36325 KiB  
Article
Effect of Annealing in Air on the Structural and Optical Properties and Efficiency Improvement of TiO2/CuxO Solar Cells Obtained via Direct-Current Reactive Magnetron Sputtering
by Grzegorz Wisz, Maciej Sibiński, Mirosław Łabuz, Piotr Potera, Dariusz Płoch, Mariusz Bester and Rostyslav Yavorskyi
Materials 2025, 18(4), 888; https://doi.org/10.3390/ma18040888 - 18 Feb 2025
Viewed by 712
Abstract
In this study, four various titanium dioxide/cuprum oxide (TiO2/CuxO) photovoltaic structures deposited on glass/indium tin oxide (ITO) substrates using the direct-current (DC) reactive magnetron sputtering technique were annealed in air. In our previous work, the deposition parameters for different [...] Read more.
In this study, four various titanium dioxide/cuprum oxide (TiO2/CuxO) photovoltaic structures deposited on glass/indium tin oxide (ITO) substrates using the direct-current (DC) reactive magnetron sputtering technique were annealed in air. In our previous work, the deposition parameters for different buffer layer configurations were first optimized to enhance cell fabrication efficiency. In this paper, the effects of post-deposition annealing at 150 °C in air on the optical properties and I-V characteristics of the prepared structures were examined. As a result, significant changes in optical properties and a meaningful improvement in performance in comparison to unannealed cells were observed. Air annealing led to an increase in the reflection coefficient of the TiO2 layer for three out of four structures. A similar increase in the reflection of the CuxO layer occurred after heating for two out of four structures. Transmission of the TiO2/CuxO photovoltaic structures also increased after heating for three out of four samples. For two structures, changes in both transmission and reflection resulted in higher absorption. Moreover, annealing the as-deposited structures resulted in a maximum relative increase in open-circuit voltage (Voc) by 294% and an increase in short-circuit current (Isc) by 1200%. The presented article gives some in-depth analysis of these reported changes in character and origin. Full article
(This article belongs to the Special Issue Advances in Solar Cell Materials and Structures—Second Edition)
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18 pages, 5286 KiB  
Article
Synthesis and Characterization of Tetrasubstituted Porphyrin Tin(IV) Complexes and Their Adsorption Properties over Tetracycline Antibiotics
by Hanifi Yaman, Mirza Talha Baig and Asgar Kayan
Reactions 2025, 6(1), 12; https://doi.org/10.3390/reactions6010012 - 6 Feb 2025
Cited by 4 | Viewed by 1276
Abstract
New tetrasubstituted porphyrin tin complexes (514) were prepared in two different ways: In the first preparation procedure, tin porphyrin complexes were prepared by a direct reaction of butyltin trichloride and dibutyltin dichloride with tetra/tetrakis(4-X-phenyl)porphyrins (X = H, F, Cl, [...] Read more.
New tetrasubstituted porphyrin tin complexes (514) were prepared in two different ways: In the first preparation procedure, tin porphyrin complexes were prepared by a direct reaction of butyltin trichloride and dibutyltin dichloride with tetra/tetrakis(4-X-phenyl)porphyrins (X = H, F, Cl, Br, CF3, CH3O, and (CH3)2N). In the second procedure, the same tin porphyrin complexes were synthesized from the reaction of butyltin trichloride and dibutyltin dichloride with lithium porphyrinato derivatives. These novel tin complexes were characterized by elemental analysis, 1H, 13C NMR, FTIR, UV-Vis spectroscopy, and mass spectrometry. Among these complexes, tin porphyrin containing methoxy group [Bu2Sn(TMOPP)] was tested as an adsorbent to remove tetracycline antibiotics from wastewater. The TTC antibiotic removal efficiency (R%) of this complex was measured using UV-Vis spectroscopy. After 120 min of equilibration, the final R% and adsorption capacity (qt) were measured at 60.15% and 18.10 mg/g, respectively. Full article
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12 pages, 3506 KiB  
Article
Photoluminescence and Stability of Dion–Jacobson Tin-Based Halide Perovskites with Different Spacer Cation Chain Length
by Muhammad Umair Ali, Wen Ting Sun, Aleksandr A. Sergeev, Atta Ur Rehman, Kam Sing Wong, Aleksandra B. Djurišić and Jasminka Popović
Molecules 2025, 30(3), 703; https://doi.org/10.3390/molecules30030703 - 5 Feb 2025
Viewed by 911
Abstract
Two-dimensional tin halide perovskites are of significant interest for light emitting applications. Here, we investigate the effect of organic cation A on the stability of different Dion–Jacobson tin-based halide perovskites. The ASnBr4 materials using diammonium cation A with shorter alkyl chains are [...] Read more.
Two-dimensional tin halide perovskites are of significant interest for light emitting applications. Here, we investigate the effect of organic cation A on the stability of different Dion–Jacobson tin-based halide perovskites. The ASnBr4 materials using diammonium cation A with shorter alkyl chains are found to exhibit improved stability, exhibiting dramatic stability difference between the most stable HDASnBr4, where HDA denotes 1,6-hexanediammonium, and two materials with 8- and 10-carbon alkyl chain ammonium cations. The HDASnBr4 powders were thermally stable at 100 °C in an argon environment but exhibited decreasing photoluminescence with time in ambient air at 100 °C. The sample degradation at 100 °C is accelerated compared to room temperature, but it proceeds along similar pathways, namely phase transformation followed by perovskite decomposition. Light emission from HDASnBr4 thin films could be further enhanced by methanol vapor treatment, and warm white emission with Commission Internationale de l’Eclairage (CIE) coordinates (0.37, 0.34) could be obtained by combining HDASnBr4 with a blue-emitting polymer film, while direct mixing of blue phosphor and HDASnBr4 powder yields white emission with CIE coordinates of (0.34, 0.32). Full article
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17 pages, 13348 KiB  
Article
Structure Modulation and Self-Lubricating Properties of Porous TiN–MoS2 Composite Coating Under Humidity–Fluctuating Conditions
by Tiancheng Ye, Kai Le, Ganggang Wang, Zhenghao Ren, Yuzhen Liu, Liwei Zheng, Hui Tian and Shusheng Xu
Lubricants 2025, 13(2), 61; https://doi.org/10.3390/lubricants13020061 - 1 Feb 2025
Cited by 1 | Viewed by 1328
Abstract
To improve the friction performance and service life of protective coatings in humidity-fluctuating environments, porous hard titanium nitride (TiN)–molybdenum disulfide (MoS2) composite coatings were prepared by using direct current magnetron sputtering (DCMS) with the mode of oblique angle deposition (OAD) and [...] Read more.
To improve the friction performance and service life of protective coatings in humidity-fluctuating environments, porous hard titanium nitride (TiN)–molybdenum disulfide (MoS2) composite coatings were prepared by using direct current magnetron sputtering (DCMS) with the mode of oblique angle deposition (OAD) and chemical vapor deposition (CVD) technologies. The structure and chemical component were characterized by field emission scanning electron microscopy (FESEM), energy dispersive spectrometer (EDS), grazing incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The tribological properties of these TiN–MoS2 composite coatings were investigated. The results indicate that the porous TiN–MoS2 composite coating exhibited outstanding friction performance and long service life under humidity-fluctuating environments. At the initial 20% relative humidity (RH) stage, the MoS2 on the porous TiN–MoS2 composite coating surface worked as an effective lubricant; thus, the coating demonstrated excellent lubrication performance, and the friction coefficient (COF) was about 0.05. As the humidity was alternated to 70% RH, the lubrication effect diminished due to the production of molybdenum oxide (MoO3), and the COF was about 0.2, which was attributed to the degradation of MoS2 on the wear track and the release of fresh MoS2 from the porous TiN matrix. After the environmental conditions shifted from 70% to 20% RH, the MoO3 was removed, and the lubrication effect was restored. In summary, TiN–MoS2 porous composite coating offers a promising approach for lubrication in humidity-fluctuating environments. Full article
(This article belongs to the Special Issue Coatings and Lubrication in Extreme Environments)
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20 pages, 11085 KiB  
Article
High-Pressure Hydrogen Charge Check-Valve Energy Loss-Based Correlation Analysis Affecting Internal Flow Characterizations
by Seung-Hun Oh, Sun-Min Jang and Hyun-Kyu Suh
Appl. Sci. 2025, 15(3), 1428; https://doi.org/10.3390/app15031428 - 30 Jan 2025
Viewed by 727
Abstract
In this study, we analyzed changes in flow characteristics and energy-dissipation characteristics due to changes in hydrogen temperature and inlet/outlet differential pressure in a check valve, which affect the storage safety and reliability of high-pressure hydrogen refueling systems. The effects of flow separation [...] Read more.
In this study, we analyzed changes in flow characteristics and energy-dissipation characteristics due to changes in hydrogen temperature and inlet/outlet differential pressure in a check valve, which affect the storage safety and reliability of high-pressure hydrogen refueling systems. The effects of flow separation and recirculation flow generation at the back end of the valve were investigated, and the pressure, flow rate, pressure coefficient, and energy dissipation at the core part (where the hydrogen inflow is blocked) and the outlet part (where the hydrogen is discharged) were numerically analyzed. The hydrogen-inlet temperature (Tin) was selected as 233 K, 293 K, and 363 K, and the differential pressure (∆P) was selected in the range of 2 to 10 MPa in 2 MPa steps. To ensure the reliability of the numerical results, mesh dependence was performed, and the effect of the mesh geometry on the results was less than 2%. The numerical simulation results showed that the hydrogen introduced into the core part is discharged into the discharge part, and the pressure decreases by up to 6% and the velocity increases by up to 16% at the 95 mm position of the L-shaped curved tube. In addition, for the hydrogen-inlet temperature of 233 K in the L-shaped curved tube, the flow velocity decreases by up to 60% and the pressure coefficient increases at the 2.3 mm point in the Y-axis direction, indicating that the main flow area is biased towards the bottom of the valve due to the constriction of the veins caused by flow separation. The TDR results showed that the hydrogen discharge to the discharge region increased by 96% at 95 mm compared to 90 mm, and the turbulent kinetic energy of the hydrogen was dissipated, resulting in a temperature increase of up to 4.5 K. The exergy destruction was maximized in the core region where flow separation occurs, indicating that the pressure, velocity, and TDR changes due to flow separation and recombination have a significant impact on the energy loss of the flow in the check valve. Full article
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25 pages, 2189 KiB  
Review
Advancements in Surface Modification of NiTi Alloys for Orthopedic Implants: Focus on Low-Temperature Glow Discharge Plasma Oxidation Techniques
by Justyna Witkowska, Jerzy Sobiecki and Tadeusz Wierzchoń
Int. J. Mol. Sci. 2025, 26(3), 1132; https://doi.org/10.3390/ijms26031132 - 28 Jan 2025
Cited by 3 | Viewed by 1518
Abstract
Nickel–titanium (NiTi) shape memory alloys are promising materials for orthopedic implants due to their unique mechanical properties, including superelasticity and shape memory effect. However, the high nickel content in NiTi alloys raises concerns about biocompatibility and potential cytotoxic effects. This review focuses on [...] Read more.
Nickel–titanium (NiTi) shape memory alloys are promising materials for orthopedic implants due to their unique mechanical properties, including superelasticity and shape memory effect. However, the high nickel content in NiTi alloys raises concerns about biocompatibility and potential cytotoxic effects. This review focuses on the recent advancements in surface modification techniques aimed at enhancing the properties of NiTi alloys for biomedical applications, with particular emphasis on low-temperature glow discharge plasma oxidation methods. The review explores various surface engineering strategies, including oxidation, nitriding, ion implantation, laser treatments, and the deposition of protective coatings. Among these, low-temperature plasma oxidation stands out for its ability to produce uniform, nanocrystalline layers of titanium dioxide (TiO2), titanium nitride (TiN), and nitrogen-doped TiO2 layers, significantly enhancing corrosion resistance, reducing nickel ion release, and promoting osseointegration. Plasma-assisted oxynitriding processes enable the creation of multifunctional coatings with improved mechanical and biological properties. The applications of modified NiTi alloys in orthopedic implants, including spinal fixation devices, joint prostheses, and fracture fixation systems, are also discussed. Despite these promising advancements, challenges remain in achieving large-scale reproducibility, controlling process parameters, and reducing production costs. Future research directions include integrating bioactive and antibacterial coatings, enhancing surface structuring for controlled biological responses, and expanding clinical validation. Addressing these challenges can unlock the full potential of surface-modified NiTi alloys in advanced orthopedic applications for safer, longer-lasting, and more effective medical implants. Full article
(This article belongs to the Special Issue Biomaterials for Dental and Orthopedic Applications)
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15 pages, 6055 KiB  
Article
Hot-Pressing of Ti-Al-N Multiphase Composite: Microstructure and Properties
by Ryszard Sitek, Kamil Bochenek, Piotr Maj, Michał Marczak, Krzysztof Żaba, Mateusz Kopec, Grzegorz Piotr Kaczmarczyk and Janusz Kamiński
Appl. Sci. 2025, 15(3), 1341; https://doi.org/10.3390/app15031341 - 27 Jan 2025
Viewed by 796
Abstract
This study focuses on the development and characterization of a bulk Ti-Al-N multiphase composite enriched with BN addition and sintered through hot pressing. The research aimed to create a material with optimized mechanical and corrosion-resistant properties suitable for demanding industrial applications. The composite [...] Read more.
This study focuses on the development and characterization of a bulk Ti-Al-N multiphase composite enriched with BN addition and sintered through hot pressing. The research aimed to create a material with optimized mechanical and corrosion-resistant properties suitable for demanding industrial applications. The composite was synthesized using a powder metallurgy approach with a mixture of AlN, TiN, and BN powders, processed under a high temperature and pressure. Comprehensive analyses, including microstructural evaluation, hardness testing, X-ray tomography, and electrochemical corrosion assessments, were conducted. The results confirmed the formation of a multiphase microstructure consisting of TiN, Ti₂AlN and Ti₃AlN phases. The microstructure was uniform with minimal porosity, achieving a hardness within the range of 500–540 HV2. Electrochemical tests revealed the formation of a passive oxide layer that provided moderate corrosion resistance in chloride-rich environment. However, localized pitting corrosion was observed under extreme conditions. The study highlights the potential of a BN admixture to enhance mechanical and corrosion-resistant properties and suggests directions for further optimization in sintering processes and material formulations. Full article
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