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Keywords = TiC coating

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14 pages, 2180 KiB  
Article
Study on Preparation of Nano-CeO2 Modified Aluminized Coating by Low Temperature Pack Aluminizing on γ-TiAl Intermetallic Compound
by Jiahui Song, Yunmei Long, Yifan He, Yichen Li, Dianqi Huang, Yan Gu, Xingyao Wang, Jinlong Wang and Minghui Chen
Coatings 2025, 15(8), 914; https://doi.org/10.3390/coatings15080914 (registering DOI) - 5 Aug 2025
Abstract
TiAl alloy offers advantages including low density, high specific strength and stiffness, and excellent high-temperature creep resistance. It is widely used in the aerospace, automotive, and chemical sectors, as well as in other fields. However, at temperatures of 800 °C and above, it [...] Read more.
TiAl alloy offers advantages including low density, high specific strength and stiffness, and excellent high-temperature creep resistance. It is widely used in the aerospace, automotive, and chemical sectors, as well as in other fields. However, at temperatures of 800 °C and above, it forms a porous oxide film predominantly composed of TiO2, which fails to provide adequate protection. Applying high-temperature protective coatings is therefore essential. Oxides demonstrating protective efficacy at elevated temperatures include Al2O3, Cr2O3, and SiO2. The Pilling–Bedworth Ratio (PBR)—defined as the ratio of the volume of the oxide formed to the volume of the metal consumed—serves as a critical criterion for assessing oxide film integrity. A PBR value greater than 1 but less than 2 indicates superior film integrity and enhanced oxidation resistance. Among common oxides, Al2O3 exhibits a PBR value within this optimal range (1−2), rendering aluminum-based compound coatings the most extensively utilized. Aluminum coatings can be applied via methods such as pack cementation, thermal spraying, and hot-dip aluminizing. Pack cementation, being the simplest to operate, is widely employed. In this study, a powder mixture with the composition Al:Al2O3:NH4Cl:CeO2 = 30:66:3:1 was used to aluminize γ-TiAl intermetallic compound specimens via pack cementation at 600 °C for 5 h. Subsequent isothermal oxidation at 900 °C for 20 h yielded an oxidation kinetic curve adhering to the parabolic rate law. This treatment significantly enhanced the high-temperature oxidation resistance of the γ-TiAl intermetallic compound, thereby broadening its potential application scenarios. Full article
(This article belongs to the Special Issue High-Temperature Protective Coatings)
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25 pages, 15569 KiB  
Article
Studies on the Chemical Etching and Corrosion Resistance of Ultrathin Laminated Alumina/Titania Coatings
by Ivan Netšipailo, Lauri Aarik, Jekaterina Kozlova, Aivar Tarre, Maido Merisalu, Kaisa Aab, Hugo Mändar, Peeter Ritslaid and Väino Sammelselg
Corros. Mater. Degrad. 2025, 6(3), 36; https://doi.org/10.3390/cmd6030036 - 2 Aug 2025
Viewed by 226
Abstract
We investigated the protective properties of ultrathin laminated coatings, comprising three pairs of Al2O3 and TiO2 sublayers with coating thicknesses < 150 nm, deposited on AISI 310 stainless steel (SS) and Si (100) substrates at 80–500 °C by atomic [...] Read more.
We investigated the protective properties of ultrathin laminated coatings, comprising three pairs of Al2O3 and TiO2 sublayers with coating thicknesses < 150 nm, deposited on AISI 310 stainless steel (SS) and Si (100) substrates at 80–500 °C by atomic layer deposition. The coatings were chemically etched and subjected to corrosion, ultrasound, and thermal shock tests. The coating etching resistance efficiency (Re) was determined by measuring via XRF the change in the coating sublayer mass thickness after etching in hot 80% H2SO4. The maximum Re values of ≥98% for both alumina and titania sublayers were obtained for the laminates deposited at 250–400 °C on both substrates. In these coatings, the titania sublayers were crystalline. The lowest Re values of 15% and 50% for the alumina and titania sublayers, respectively, were measured for laminate grown at 80 °C on silicon. The coatings deposited at 160–200 °C demonstrated a delay in the increase of Re values, attributed to the changes in the titania sublayers before full crystallization. Coatings grown at higher temperatures were also more resistant to ultrasound and liquid nitrogen treatments. In contrast, coatings deposited at 125 °C on SS had better corrosion protection, as demonstrated via electrochemical impedance spectroscopy and a standard immersion test in FeCl3 solution. Full article
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14 pages, 6773 KiB  
Article
MoTiCo Conversion Coating on 7075 Aluminium Alloy Surface: Preparation, Corrosion Resistance Analysis, and Application in Outdoor Sports Equipment Trekking Poles
by Yiqun Wang, Feng Huang and Xuzheng Qian
Metals 2025, 15(8), 864; https://doi.org/10.3390/met15080864 (registering DOI) - 1 Aug 2025
Viewed by 130
Abstract
The problem of protecting 7075 Al alloy trekking poles from corrosion in complex outdoor environments was addressed using a composite conversion coating system. This system comprised Na2MoO4, NaF, CoSO4·7H2O, ethylenediaminetetraacetic acid-2Na, and H2(TiF [...] Read more.
The problem of protecting 7075 Al alloy trekking poles from corrosion in complex outdoor environments was addressed using a composite conversion coating system. This system comprised Na2MoO4, NaF, CoSO4·7H2O, ethylenediaminetetraacetic acid-2Na, and H2(TiF6). The influences of this system on the properties of the coating layer were systematically studied by adjusting the pH of the coating solution. The conversion temperature and pH were the pivotal parameters influencing the formation of the conversion coating. The pH substantially influenced the compactness of the coating layer, acting as a regulatory agent of the coating kinetics. When the conversion temperature and pH were set to 40 °C and 3.8, respectively, the prepared coating layer displayed optimal performance in terms of compactness and protective properties. Therefore, this parameter combination favours the synthesis of high-performance conversion coatings. Microscopy confirmed the formation of a continuous, dense composite oxide film structure under these conditions, effectively blocking erosion in corrosive media. Furthermore, the optimised process led to substantial enhancements in the environmental adaptabilities and service lives of the components of trekking poles, thus establishing a theoretical foundation and technical reference for use in the surface protection of outdoor equipment. Full article
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15 pages, 2324 KiB  
Article
Influence of Aluminum Alloy Substrate Temperature on Microstructure and Corrosion Resistance of Cr/Ti Bilayer Coatings
by Yuqi Wang, Tao He, Xiangyang Du, Alexey Vereschaka, Catherine Sotova, Yang Ding, Kang Chen, Jian Li and Peiyu He
Coatings 2025, 15(8), 891; https://doi.org/10.3390/coatings15080891 (registering DOI) - 1 Aug 2025
Viewed by 192
Abstract
Cr/Ti bilayer coatings were deposited on 7050 aluminum alloy via magnetron sputtering at substrate temperatures of room temperature (RT), 150 °C, and 300 °C to investigate temperature effects on microstructure, hardness, and corrosion resistance. All coatings exhibited Cr(110) and Ti(002) phases. Temperature significantly [...] Read more.
Cr/Ti bilayer coatings were deposited on 7050 aluminum alloy via magnetron sputtering at substrate temperatures of room temperature (RT), 150 °C, and 300 °C to investigate temperature effects on microstructure, hardness, and corrosion resistance. All coatings exhibited Cr(110) and Ti(002) phases. Temperature significantly modulated corrosion resistance by altering pore density, grain boundary density, and passivation film composition. Increasing temperature from RT to 150 °C raised corrosion rates primarily due to increased pore density. Further increasing to 300 °C reduced corrosion rates mainly through decreased grain boundary density, while passivation film composition changes altered electrochemical reaction kinetics. Substrate-coating interface defect density primarily influenced hardness with minimal effect on corrosion. Consequently, the RT-deposited coating, despite lower hardness, demonstrated optimal corrosion resistance: polarization resistance (7.17 × 104 Ω·cm2), charge transfer resistance (12,400 Ω·cm2), and corrosion current density (2.47 × 10−7 A/cm2), the latter being two orders of magnitude lower than the substrate. Full article
(This article belongs to the Special Issue Innovative Coatings for Corrosion Protection of Alloy Surfaces)
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21 pages, 14026 KiB  
Article
Development of PEO in Low-Temperature Ternary Nitrate Molten Salt on Ti6Al4V
by Michael Garashchenko, Yuliy Yuferov and Konstantin Borodianskiy
Materials 2025, 18(15), 3603; https://doi.org/10.3390/ma18153603 - 31 Jul 2025
Viewed by 157
Abstract
Titanium alloys are frequently subjected to surface treatments to enhance their biocompatibility and corrosion resistance in biological environments. Plasma electrolytic oxidation (PEO) is an environmentally friendly electrochemical technique capable of forming oxide layers characterized by high corrosion resistance, biocompatibility, and strong adhesion to [...] Read more.
Titanium alloys are frequently subjected to surface treatments to enhance their biocompatibility and corrosion resistance in biological environments. Plasma electrolytic oxidation (PEO) is an environmentally friendly electrochemical technique capable of forming oxide layers characterized by high corrosion resistance, biocompatibility, and strong adhesion to the substrate. In this study, the PEO process was performed using a low-melting-point ternary eutectic electrolyte composed of Ca(NO3)2–NaNO3–KNO3 (41–17–42 wt.%) with the addition of ammonium dihydrogen phosphate (ADP). The use of this electrolyte system enables a reduction in the operating temperature from 280 to 160 °C. The effects of applied voltage from 200 to 400V, current frequency from 50 to 1000 Hz, and ADP concentrations of 0.1, 0.5, 1, 2, and 5 wt.% on the growth of titanium oxide composite coatings on a Ti-6Al-4V substrate were investigated. The incorporation of Ca and P was confirmed by phase and chemical composition analysis, while scanning electron microscopy (SEM) revealed a porous surface morphology typical of PEO coatings. Corrosion resistance in Hank’s solution, evaluated via Tafel plot fitting of potentiodynamic polarization curves, demonstrated a substantial improvement in electrochemical performance of the PEO-treated samples. The corrosion current decreased from 552 to 219 nA/cm2, and the corrosion potential shifted from −102 to 793 mV vs. the Reference Hydrogen Electrode (RHE) compared to the uncoated alloy. These findings indicate optimal PEO processing parameters for producing composite oxide coatings on Ti-6Al-4V alloy surfaces with enhanced corrosion resistance and potential bioactivity, which are attributed to the incorporation of Ca and P into the coating structure. Full article
(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, 3rd Edition)
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23 pages, 3795 KiB  
Article
Structural Analysis of the Newly Prepared Ti55Al27Mo13 Alloy by Aluminothermic Reaction
by Štefan Michna, Jaroslava Svobodová, Anna Knaislová, Jan Novotný and Lenka Michnová
Materials 2025, 18(15), 3583; https://doi.org/10.3390/ma18153583 - 30 Jul 2025
Viewed by 169
Abstract
This study presents the structural and compositional characterisation of a newly developed Ti55Al27Mo13 alloy synthesised via aluminothermic reaction. The alloy was designed to overcome the limitations of conventional processing routes for high–melting–point elements such as Ti and Mo, enabling the formation of a [...] Read more.
This study presents the structural and compositional characterisation of a newly developed Ti55Al27Mo13 alloy synthesised via aluminothermic reaction. The alloy was designed to overcome the limitations of conventional processing routes for high–melting–point elements such as Ti and Mo, enabling the formation of a complex, multi–phase microstructure in a single high–temperature step. The aim was to develop and characterise a material with microstructural features expected to enhance wear resistance, oxidation behaviour, and thermal stability in future applications. The alloy is intended as a precursor for composite nanopowders and surface coatings applied to aluminium–, magnesium–, and iron–based substrates subjected to mechanical and thermal loading. Elemental analysis (XRF, EDS) confirmed the presence of Ti, Al, Mo, and minor elements such as Si, Fe, and C. Microstructural investigations using laser confocal and scanning electron microscopy revealed a heterogeneous structure comprising solid solutions, eutectic regions, and dispersed oxide and carbide phases. Notably, the alloy exhibits high hardness values, reaching >2400 HV in Al2O3 regions and ~1300 HV in Mo– and Si–enriched solid solutions. These results suggest the material’s substantial potential for protective surface engineering. Further tribological, thermal, and corrosion testing, conducted with meticulous attention to detail, will follow to validate its functional performance in target applications. Full article
(This article belongs to the Section Metals and Alloys)
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19 pages, 4569 KiB  
Article
Tailored Magnetic Fe3O4-Based Core–Shell Nanoparticles Coated with TiO2 and SiO2 via Co-Precipitation: Structure–Property Correlation for Medical Imaging Applications
by Elena Emanuela Herbei, Daniela Laura Buruiana, Alina Crina Muresan, Viorica Ghisman, Nicoleta Lucica Bogatu, Vasile Basliu, Claudiu-Ionut Vasile and Lucian Barbu-Tudoran
Diagnostics 2025, 15(15), 1912; https://doi.org/10.3390/diagnostics15151912 - 30 Jul 2025
Viewed by 167
Abstract
Background/Objectives: Magnetic nanoparticles, particularly iron oxide-based materials, such as magnetite (Fe3O4), have gained significant attention as contrast agents in medical imaging This study aimsto syntheze and characterize Fe3O4-based core–shell nanostructures, including Fe3O4 [...] Read more.
Background/Objectives: Magnetic nanoparticles, particularly iron oxide-based materials, such as magnetite (Fe3O4), have gained significant attention as contrast agents in medical imaging This study aimsto syntheze and characterize Fe3O4-based core–shell nanostructures, including Fe3O4@TiO2 and Fe3O4@SiO2, and to evaluate their potential as tunable contrast agents for diagnostic imaging. Methods: Fe3O4, Fe3O4@TiO2, and Fe3O4@SiO2 nanoparticles were synthesized via co-precipitation at varying temperatures from iron salt precursors. Fourier transform infrared spectroscopy (FTIR) was used to confirm the presence of Fe–O bonds, while X-ray diffraction (XRD) was employed to determine the crystalline phases and estimate average crystallite sizes. Morphological analysis and particle size distribution were assessed by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) and transmission electron microscopy (TEM). Magnetic properties were investigated using vibrating sample magnetometry (VSM). Results: FTIR spectra exhibited characteristic Fe–O vibrations at 543 cm−1 and 555 cm−1, indicating the formation of magnetite. XRD patterns confirmed a dominant cubic magnetite phase, with the presence of rutile TiO2 and stishovite SiO2 in the coated samples. The average crystallite sizes ranged from 24 to 95 nm. SEM and TEM analyses revealed particle sizes between 5 and 150 nm with well-defined core–shell morphologies. VSM measurements showed saturation magnetization (Ms) values ranging from 40 to 70 emu/g, depending on the synthesis temperature and shell composition. The highest Ms value was obtained for uncoated Fe3O4 synthesized at 94 °C. Conclusions: The synthesized Fe3O4-based core–shell nanomaterials exhibit desirable structural, morphological, and magnetic properties for use as contrast agents. Their tunable magnetic response and nanoscale dimensions make them promising candidates for advanced diagnostic imaging applications. Full article
(This article belongs to the Section Medical Imaging and Theranostics)
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10 pages, 2670 KiB  
Article
High-Temperature-Resistant High-Entropy Oxide Protective Coatings for Piezoelectric Thin Films
by Huayong Hu, Jie Liu, Liqing Chao, Xiangdong Ma, Jun Zhang, Yanbing Zhang and Bing Yang
Coatings 2025, 15(8), 861; https://doi.org/10.3390/coatings15080861 - 22 Jul 2025
Viewed by 300
Abstract
By introducing oxygen doping, the structure of an AlCrNbSiTiN coating was optimized, and its high-temperature oxidation resistance was improved. As the oxygen content incorporated increases, the coating changes from an FCC structure to an amorphous or spinel structure. Meanwhile, stress relaxation occurred, and [...] Read more.
By introducing oxygen doping, the structure of an AlCrNbSiTiN coating was optimized, and its high-temperature oxidation resistance was improved. As the oxygen content incorporated increases, the coating changes from an FCC structure to an amorphous or spinel structure. Meanwhile, stress relaxation occurred, and the hardness of the coating dropped to 12 gpa. Oxygen-doped coatings exhibit excellent oxidation resistance; this is especially the case for oxidized coatings, whose structure remains stable up to 900 °C in an oxidizing environment. Full article
(This article belongs to the Special Issue Advanced Thin Films of High-Entropy Alloys)
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18 pages, 13429 KiB  
Article
Formation of Intermetallic Coatings on Titanium by Explosive Welding and Subsequent Heat Treatment of the Layered Metal Composite
by Artem Igorevich Bogdanov, Vitaliy Pavlovich Kulevich, Roman Evgenevich Novikov and Victor Georgievich Shmorgun
J. Compos. Sci. 2025, 9(7), 379; https://doi.org/10.3390/jcs9070379 - 21 Jul 2025
Viewed by 411
Abstract
An approach for the formation of intermetallic coatings on the titanium surface based on titanium aluminides is proposed. The approach involves producing a layered steel-aluminum-titanium metal composite via explosive welding, followed by heat treatment to form a diffusion zone at the steel–aluminum interface [...] Read more.
An approach for the formation of intermetallic coatings on the titanium surface based on titanium aluminides is proposed. The approach involves producing a layered steel-aluminum-titanium metal composite via explosive welding, followed by heat treatment to form a diffusion zone at the steel–aluminum interface with a thickness of more than 30 μm, sufficient for the spontaneous separation of the steel layer. As a result, an aluminum layer approximately 0.3 mm thick remains on the titanium surface. Subsequent heating at temperatures of 700–850 °C, below the allotropic transformation temperature of titanium, results in the transformation of the aluminum layer into titanium aluminides. The formation of the intermetallic coating structure occurs as a result of the upward transportation of TiAl3 fragments separated from the reaction zone by circulating melt flows. With increasing heat treatment time, these fragments become separated by the Al2O3 oxide phase. Full article
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24 pages, 15762 KiB  
Article
Performance of TiSiN/TiAlN-Coated Carbide Tools in Slot Milling of Hastelloy C276 with Various Cooling Strategies
by Ly Chanh Trung and Tran Thien Phuc
Lubricants 2025, 13(7), 316; https://doi.org/10.3390/lubricants13070316 - 19 Jul 2025
Viewed by 491
Abstract
Nickel-based superalloy Hastelloy C276 is widely used in high-performance industries due to its strength, corrosion resistance, and thermal stability. However, these same properties pose substantial challenges in machining, resulting in high tool wear, surface defects, and dimensional inaccuracies. This study investigates methods to [...] Read more.
Nickel-based superalloy Hastelloy C276 is widely used in high-performance industries due to its strength, corrosion resistance, and thermal stability. However, these same properties pose substantial challenges in machining, resulting in high tool wear, surface defects, and dimensional inaccuracies. This study investigates methods to enhance machining performance and surface quality by evaluating the tribological behavior of TiSiN/TiAlN-coated carbide inserts under six cooling and lubrication conditions: dry, MQL with coconut oil, Cryo-LN2, Cryo-LCO2, MQL–Cryo-LN2, and MQL–Cryo-LCO2. Open-slot finishing was performed at constant cutting parameters, and key indicators such as cutting zone temperature, tool wear, surface roughness, chip morphology, and microhardness were analyzed. The hybrid MQL–Cryo-LN2 approach significantly outperformed other methods, reducing cutting zone temperature, tool wear, and surface roughness by 116.4%, 94.34%, and 76.11%, respectively, compared to dry machining. SEM and EDS analyses confirmed abrasive, oxidative, and adhesive wear as the dominant mechanisms. The MQL–Cryo-LN2 strategy also lowered microhardness, in contrast to a 39.7% increase observed under dry conditions. These findings highlight the superior performance of hybrid MQL–Cryo-LN2 in improving machinability, offering a promising solution for precision-driven applications. Full article
(This article belongs to the Special Issue High Performance Machining and Surface Tribology)
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20 pages, 4241 KiB  
Article
Strontium-Doped Ti3C2Tx MXene Coatings on Titanium Surfaces: Synergistic Osteogenesis Enhancement and Antibacterial Activity Evaluation
by Yancheng Lai and Anchun Mo
Coatings 2025, 15(7), 847; https://doi.org/10.3390/coatings15070847 - 19 Jul 2025
Viewed by 385
Abstract
To improve implant osseointegration while preventing infection, we developed a strontium (Sr)-doped Ti3C2Tx MXene coating on titanium, aiming to synergistically enhance bone integration and antibacterial performance. MXene is a family of two-dimensional transition-metal carbides/nitrides whose abundant surface terminations [...] Read more.
To improve implant osseointegration while preventing infection, we developed a strontium (Sr)-doped Ti3C2Tx MXene coating on titanium, aiming to synergistically enhance bone integration and antibacterial performance. MXene is a family of two-dimensional transition-metal carbides/nitrides whose abundant surface terminations endow high hydrophilicity and bioactivity. The coating was fabricated via anodic electrophoretic deposition (40 V, 2 min) of Ti3C2Tx nanosheets, followed by SrCl2 immersion to incorporate Sr2+. The coating morphology, phase composition, chemistry, hydrophilicity, mechanical stability, and Sr2+ release were characterized. In vitro bioactivity was assessed with rat bone marrow mesenchymal stem cells (BMSCs)—with respect to viability, proliferation, migration, alkaline phosphatase (ALP) staining, and Alizarin Red S mineralization—while the antibacterial efficacy was evaluated against Staphylococcus aureus (S. aureus) via live/dead staining, colony-forming-unit enumeration, and AlamarBlue assays. The Sr-doped MXene coating formed a uniform lamellar structure, lowered the water-contact angle to ~69°, and sustained Sr2+ release (0.36–1.37 ppm). Compared to undoped MXene, MXene/Sr enhanced BMSC proliferation on day 5, migration by 51%, ALP activity and mineralization by 47%, and reduced S. aureus viability by 49% within 24 h. Greater BMSCs activity accelerates early bone integration, whereas rapid bacterial suppression mitigates peri-implant infection—two critical requirements for implant success. Sr-doped Ti3C2Tx MXene thus offers a simple, dual-function surface-engineering strategy for dental and orthopedic implants. Full article
(This article belongs to the Section Surface Coatings for Biomedicine and Bioengineering)
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11 pages, 809 KiB  
Article
Antimicrobial Behavior of Surface-Treated Commercially Pure Titanium (CpTi) for Dental Implants in Artificial Saliva—In Vitro Study
by Roshni Bopanna, Neetha J. Shetty, Ashith M. Varadaraj, Himani Kotian, Sameep Shetty and Simran Genescia
Antibiotics 2025, 14(7), 715; https://doi.org/10.3390/antibiotics14070715 - 16 Jul 2025
Viewed by 300
Abstract
Background/Objectives:Titanium implant surface modifications enhance osseointegration and prevent microbial colonization, improving implant longevity. Antimicrobial coatings, particularly cerium- and bismuth-doped hydroxyapatite (CeHAp and BiHAp), have gained attention for reducing infection-related complications. This study evaluates the antimicrobial activity of CeHAp and BiHAp coatings on [...] Read more.
Background/Objectives:Titanium implant surface modifications enhance osseointegration and prevent microbial colonization, improving implant longevity. Antimicrobial coatings, particularly cerium- and bismuth-doped hydroxyapatite (CeHAp and BiHAp), have gained attention for reducing infection-related complications. This study evaluates the antimicrobial activity of CeHAp and BiHAp coatings on CpTi compared to untreated CpTi in artificial saliva at pH levels of 4.5, 6.5, and 8. Methods: Antibacterial efficacy against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Candida albicans (C. albicans) was assessed using the broth dilution method. Titanium rods coated with test compounds were incubated in inoculated nutrient broth, and microbial inhibition was determined via optical density at 600 nm. A statistical analysis was performed using the Kruskal–Wallis ANOVA test, the median and Interquartile Range were determined for the variables, and a Dwass–Steel–Critchlow–Fligner intergroup pairwise comparison was conducted. Results: The results showed that both the CeHAp and BiHAp coatings demonstrated significant antimicrobial activity against S. aureus (OD = 0.01) at pH 6.5, which was more pronounced than the activity observed against E. coli (OD = 0.05), with the difference being statistically significant (p = 0.001). The least antimicrobial activity was observed against C. albicans (0.21) at pH 8 (p = 0.001). Conclusion: These findings highlight the pH-dependent effectiveness of BiHAp and CeHAp coatings in inhibiting microbial growth. Their application on titanium implants may enhance antimicrobial properties, contributing to improved dental implant success and broader biomedical applications. Full article
(This article belongs to the Section Antimicrobial Materials and Surfaces)
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13 pages, 4656 KiB  
Article
High-Speed and Hysteresis-Free Near-Infrared Optical Hydrogen Sensor Based on Ti/Pd Bilayer Thin Films
by Ashwin Thapa Magar, Tu Anh Ngo, Hoang Mai Luong, Thi Thu Trinh Phan, Minh Tuan Trinh, Yiping Zhao and Tho Duc Nguyen
Nanomaterials 2025, 15(14), 1105; https://doi.org/10.3390/nano15141105 - 16 Jul 2025
Viewed by 503
Abstract
Palladium (Pd) and titanium (Ti) exhibit opposite dielectric responses upon hydrogenation, with stronger effects observed in the near-infrared (NIR) region. Leveraging this contrast, we investigated Ti/Pd bilayer thin films as a platform for NIR hydrogen sensing—particularly at telecommunication-relevant wavelengths, where such devices have [...] Read more.
Palladium (Pd) and titanium (Ti) exhibit opposite dielectric responses upon hydrogenation, with stronger effects observed in the near-infrared (NIR) region. Leveraging this contrast, we investigated Ti/Pd bilayer thin films as a platform for NIR hydrogen sensing—particularly at telecommunication-relevant wavelengths, where such devices have remained largely unexplored. Ti/Pd bilayers coated with Teflon AF (TAF) and fabricated via sequential electron-beam and thermal evaporation were characterized using optical transmission measurements under repeated hydrogenation cycles. The Ti (5 nm)/Pd (x = 2.5 nm)/TAF (30 nm) architecture showed a 2.7-fold enhancement in the hydrogen-induced optical contrast at 1550 nm compared to Pd/TAF reference films, attributed to the hydrogen ion exchange between the Ti and Pd layers. The optimized structure, with a Pd thickness of x = 1.9 nm, exhibited hysteresis-free sensing behavior, a rapid response time (t90 < 0.35 s at 4% H2), and a detection limit below 10 ppm. It also demonstrated excellent selectivity with negligible cross-sensitivity to CO2, CH4, and CO, as well as high durability, showing less than 6% signal degradation over 135 hydrogenation cycles. These findings establish a scalable, room-temperature NIR hydrogen sensing platform with strong potential for deployment in automotive, environmental, and industrial applications. Full article
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22 pages, 5400 KiB  
Article
Polyaniline/Ti3C2 MXene Composites with Artificial 3D Biomimetic Surface Structure of Natural Macaw Feather Applied for Anticorrosion Coatings
by Chen-Cheng Chien, Yu-Hsuan Liu, Kun-Hao Luo, Ting-Yun Liu, Yi-Ting Kao, Shih-Harn Yang and Jui-Ming Yeh
Biomimetics 2025, 10(7), 465; https://doi.org/10.3390/biomimetics10070465 - 15 Jul 2025
Viewed by 331
Abstract
In this paper, a series of polyaniline (PANI)/Ti3C2 MXene composites (PMCs) with a biomimetic structure were prepared and employed as an anticorrosion coating application. First, the PANI was synthesized by oxidative polymerization with ammonium persulfate as the oxidant. Then, 2D [...] Read more.
In this paper, a series of polyaniline (PANI)/Ti3C2 MXene composites (PMCs) with a biomimetic structure were prepared and employed as an anticorrosion coating application. First, the PANI was synthesized by oxidative polymerization with ammonium persulfate as the oxidant. Then, 2D Ti3C2 MXene nanosheets were prepared by treating the Ti3AlC2 using the optimized minimally intensive layer delamination (MILD) method, followed by characterization via XRD and SEM. Subsequently, the PMC was prepared by the oxidative polymerization of aniline monomers in the presence of Ti3C2 MXene nanosheets, followed by characterization via FTIR, XRD, SEM, TEM, CV, and UV–Visible. Eventually, the PMC coatings with the artificial biomimetic surface structure of a macaw feather were prepared by the nano-casting technique. The corrosion resistance of the PMC coatings, evaluated via Tafel polarization and Nyquist impedance measurements, shows that increasing the MXene loading up to 5 wt % shifts the corrosion potential (Ecorr) on steel from −588 mV to −356 mV vs. SCE, reduces the corrosion current density (Icorr) from 1.09 µA/cm2 to 0.035 µA/cm2, and raises the impedance modulus at 0.01 Hz from 67 kΩ to 3794 kΩ. When structured with the hierarchical feather topography, the PMC coating (Bio-PA-MX-5) further advances the Ecorr to +103.6 mV, lowers the Icorr to 7.22 × 10−4 µA/cm2, and boosts the impedance to 96,875 kΩ. Compared to neat coatings without biomimetic structuring, those with engineered biomimetic surfaces showed significantly improved corrosion protection performance. These enhancements arise from three synergistic mechanisms: (i) polyaniline’s redox catalysis accelerates the formation of a dense passive oxide layer; (ii) MXene nanosheets create a tortuous gas barrier that cuts the oxygen permeability from 11.3 Barrer to 0.9 Barrer; and (iii) the biomimetic surface traps air pockets, raising the water contact angle from 87° to 135°. This integrated approach delivers one of the highest combined corrosion potentials and impedance values reported for thin-film coatings, pointing to a general strategy for durable steel protection. Full article
(This article belongs to the Section Biomimetic Design, Constructions and Devices)
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15 pages, 2902 KiB  
Article
Synergistic Integration of MXene Photothermal Conversion and TiO2 Radiative Cooling in Bifunctional PLA Fabrics for Adaptive Personal Thermal Management
by Tianci Han and Yunjie Yin
Solids 2025, 6(3), 37; https://doi.org/10.3390/solids6030037 - 12 Jul 2025
Viewed by 306
Abstract
Polylactic acid (PLA) fabrics exhibit significant sunlight reflectivity and high emissivity within the atmospheric window, making them suitable as the foundational material for this study. This research involves the modification of one side of the fabric with hydrophilic agents and titanium dioxide (TiO [...] Read more.
Polylactic acid (PLA) fabrics exhibit significant sunlight reflectivity and high emissivity within the atmospheric window, making them suitable as the foundational material for this study. This research involves the modification of one side of the fabric with hydrophilic agents and titanium dioxide (TiO2), while the opposite side is treated with MXene and subsequently coated with polydimethylsiloxane (PDMS) to inhibit oxidation of the MXene. Through these surface modifications, a thermal management fabric based on PLA was successfully developed, capable of passively regulating temperature in response to environmental conditions and user requirements. The study discusses the optimal concentrations of TiO2 and MXene for the fabric, and characterizes and evaluates the functional surface of the PLA. Surface morphology analyses and tests indicate that the resulting functional PLA fabrics possess excellent ultraviolet (UV) resistance, favorable air permeability, high sunlight reflectivity on the TiO2-treated side, and superior photothermal conversion capabilities on the MXene-treated side. Furthermore, photothermal effect tests conducted under a light intensity of 1000 W/m2 reveal that the MXene-treated fabric exhibits a heating effect of approximately 25 °C, while the TiO2-treated side demonstrates a cooling effect exceeding 5 °C. This study developed PLA functional fabrics with heating and cooling capabilities. Full article
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