Improved Oxidation Resistance Research Articles

Polysiloxane encapsulating strategy to enhance the high-temperature electromagnetic wave absorption performance of carbon-rich SiOC ceramics

Carbon-enriched polysiloxane-derived SiOC (C-SiOC) ceramics are promising electromagnetic wave absorption (EMA) materials. However, oxidation and impedance mismatch severely deteriorate their EMA performance at high temperatures. In this study, we used polysiloxane (PSO) to encapsulate the crosslinked precursor of C-SiOC ceramics. After pyrolysis, PSO-derived SiOC-encapsulated C-SiOC (here named PSO-C-SiOC) ceramics were obtained. The PSO-C-SiOC ceramics exhibit an improved oxidation resistance compared with C-SiOC ceramics and basically retain their original dielectric and EMA properties after exposure to air at high temperatures. Moreover, the ceramics can maintain excellent EMA properties at elevated temperatures with good impedance matching. The remarkable high-temperature EMA properties of PSO-C-SiOC ceramics in air are attributed to the protective outer-layer of PSO-derived SiOC ceramic, which enhances oxidation resistance and simultaneously controls the impedance matching. These findings underscore the potential of PSO-C-SiOC ceramics as high-temperature EMA materials.

The Effect of Y Addition on Oxidation Resistance of Bulk W-Cr Alloys

The self-passivating tungsten-based alloy W-11.4Cr-0.6Y (in wt.%) is a potential plasma-facing material for the first wall of future fusion reactors, which has been shown to suppress oxidation of tungsten and withstand temperatures of up to 1000 °C. In this study, the effect of Y addition on the microstructure and oxidation behavior of W-11.4Cr alloy at 1000 °C is analyzed by comparing it with W-11.4Cr-0.6Y, both prepared using identical synthesis routes. While the binary W-Cr alloy already exhibits improved oxidation resistance over pure W due to the formation of an outer Cr2WO6 layer, it still shows a tendency for spallation and, hence, is not protective. A continuous passivating chromia layer is only obtained with the addition of Y, and we demonstrate that it results in a 50-fold decrease in the oxide growth rate and eliminates the preferred growth of the oxide at edges seen in the binary alloy. Although a porous, complex oxide scale containing mixed oxide layers and WO3 is formed in both cases, the addition of Y results in lower porosity, which makes the oxide scale more adherent.

All-In-One Additive Enabled Efficient and Stable Narrow-Bandgap Perovskites for Monolithic All-Perovskite Tandem Solar Cells.

Hybrid tin-lead (Sn-Pb) perovskites have garnered increasing attention due to their crucial role in all-perovskite tandem cells for surpassing the efficiency limit of single-junction solar cells. However, the easy oxidation of Sn2+ and fast crystallization of Sn-based perovskite present significant challenges for achieving high-quality hybrid Sn-Pb perovskite films, thereby limiting the device's performance and stability. Herein, an all-in-one additive, 2-amino-3-mercaptopropanoic acid hydrochloride (AMPH) is proposed, which can function as a reducing agent to suppress the formation of Sn4+ throughout the film preparation. Furthermore, the strong binding between AMPH and Sn-based precursor significantly slows down the crystallization process, resulting in a high-quality film with enhanced crystallinity. The remaining AMPH and its oxidation products within the film contribute to improves oxidation resistance and a substantial reduction in defect density, specifically Sn vacancies. Benefiting from the multifunctionalities of AMPH, a power conversion efficiency (PCE) of 23.07% is achieved for single-junction narrow-bandgap perovskite solar cells. The best-performing monolithic all-perovskite tandem cell also exhibits a PCE of 28.73% (certified 27.83%), which is among the highest efficiency reported yet. The tandem devices can also retain over 85% of their initial efficiencies after 500 hours of continuous operation at the maximum power point under one-sun illumination.

The influence of CeO2 on the oxidation resistance of TaC/Ni composites

The in-situ TaC/Ni composites with different CeO2 content (0 wt%, 1 wt%, 2 wt%) were prepared by reactive sintering method, and their oxidation behavior in air at 1073 K was analyzed by static cyclic oxidation method to investigate the influence mechanism of CeO2 on the oxidation resistance of composites. The results show that the CeO2 particles are distributed around the TaC particles in the Ni matrix, and the oxidation behavior of composites with different CeO2 content conforms to the linear kinetic law. The oxide film is mainly composed of NiTa2O6 and a small amount of NiO. The generation reactions of Ta2O5 and NiTa2O6 induce a high expansion and compressive stress in oxide scale, leading to the formation of nonprotective oxide film with pores and cracks on the surface. As the addition of CeO2 increases from 0 wt% to 2 wt%, the thickness of oxide scale on composites obviously reduces from 505 μm to 122 μm, and the Ni and Ta oxides content decreases, leading to the reduction of pores and cracks in oxide scale. The Ce ion generated from the dissolution of CeO2 particles mainly distributes in the Ta oxides during the oxidation process, which hinders the outward diffusion of Ni and Ta ions, resulted in the improved oxidation resistance of TaC/Ni composites.

Rare earth-doped ZrB2-MoSi2 ceramics: Densification and oxidation behavior

The effect of rare earth oxides (REO), Nd2O3 and Eu2O3, on the densification and oxidation behavior of pressureless sintered ZrB2-MoSi2 ceramic composites was investigated. Addition of REO results in the formation of REO-silicates which are liquid at the sintering temperature and contribute to matter transfer mechanisms. Oxidation studies at 1500 °C for 0.5–4 h evidenced that Eu2O3 can improve oxidation resistance in the ZrB2-MoSi2 system, especially after prolonged exposition, whilst Nd2O3 induces faster degradation of the ceramic. It was found that the Eu dispersed both in silica and in zirconia modifies the rheological properties of the glassy phase thus playing an important role in hindering oxygen inward from the atmosphere to the subsurface, resulting in a noticeable improvement of the oxidation resistance.

Oxidation Behaviour of TiC/TiN Coatings Deposited by Chemical Vapor Deposition (CVD): Mechanisms, Structures, and Properties

This review explores the oxidation behavior of Titanium Carbide (TiC) and Titanium Nitride (TiN) coatings deposited by Chemical Vapor Deposition (CVD), with a focus on their industrial applications as wear-resistant coatings for cutting tools. It examines effect of process parameters—such as temperature, pressure, precursor composition, and substrate preparation—on formation and performance of TiC/TiN coatings. The review evaluates the microstructural characteristics of these coatings, including crystal structure, using X-ray diffraction analysis. Also, estimates the mechanical properties such as hardness, wear resistance, and adhesion strength. Additionally, the review covers the thermal stability of TiC/TiN coatings, emphasizing their ability to maintain structural integrity at high temperatures, which is essential for the performance of cutting tools and other industrial components. A major focus is the oxidation behavior of TiC/TiN coatings, including the impact of coating composition, deposition methods, and environmental conditions. The review details oxidation kinetics and mechanisms, revealing various stages of oxidation at different temperatures. It also examines oxide scale morphology and its effect on coating properties. Finally, this review reveals the importance of alloying elements, like silicon, in improving oxidation resistance. Composite coatings such as TiSiN and TiSiCN are shown to offer better high-temperature stability compared to traditional TiN coatings. The effects of coating thickness and the benefits of multilayer coatings for enhanced oxidation resistance are also discussed.

Synthesis and oxidation behavior of Ti-Zr-Ta(Hf) high entropy carbide nanopowders by sol-gel method

Multi-component solid solution carbide is a promising material due to its excellent mechanical strength, thermal stability, and resistance to chemical corrosion. In this study, we intentionally designed and synthesized three types of solid solution carbide powders using the sol-gel method: (Ti1/3Zr1/3Ta1/3)C, (Ti1/3Zr1/3Hf1/3)C and (Ti1/4Zr1/4Ta1/4Hf1/4)C. The results show that the liquid-phase precursor undergoes pyrolysis at 800 °C and subsequently form homogeneous single face-centered cubic structure solid solutions upon thermal treatment at temperatures exceeding 1800 °C. The obtained powders exhibited ultra-fine and uniform particle sizes of 340 nm, 248 nm, and 401 nm, respectively. Furthermore, the oxidation behavior of the three types of carbide powders in air shows that Hf and Ta elements are of great significance in improving oxidation resistance. The solid solution of Hf increases the initial oxidation temperature, while Ta tends to form a complex oxide with Zr, which helps to improve the oxidation temperature resistance. This work therefore contributes filling the gap of employing the sol-gel method in the fabrication of multi-component solid solution carbide materials and provides novel insights into their synthesis mechanism and oxidation behaviours.

Long-time oxidation resistance of KD-SiC fibers with different composition and structure in air atmosphere

Continuous silicon carbide (SiC) fibers, as reinforcement of ceramic matrix composites, have broad application prospects in the fields of aviation, aerospace and nuclear energy. Three typical KD-SiC fibers were adopted to explore the relationship of the composition and structure with their long-term oxidation (1–100 h) resistance in air environment. The mechanical strength retention of the nearly stoichiometric polycrystalline SiC fiber (C-1) was generally higher than that of the SiC fiber (C-3) with excess carbon and low oxygen, also higher than the nearly stoichiometric SiC fiber (C-2), especially under oxidation conditions of higher temperature and longer holding time. By comparing the high-temperature resistance with oxidation resistance at 1200–1600 °C, it was found that the oxidation reaction was the dominant factor affecting the mechanical properties. This work could provide theoretical and practical references for improvement of oxidation resistance of SiC fibers and their composites.

Significantly enhanced electrochemical performance of Al-Ti3C2Tx MXene synthesized from Al-Ti3AlC2 MAX phase

MXenes, a type of two-dimensional nanomaterials consisting of transition metal carbides/nitrides, have emerged as promising electrode materials for supercapacitors. Especially, Ti3C2Tx MXene prepared from Ti3AlC2 MAX phase shows great application potential in flexible supercapacitors due to its facile synthesis, excellent conductivity and film-forming property. In contrast to conventional Ti3AlC2, excessive aluminum is incorporated in the synthesis process to produce Al-Ti3AlC2. In this study, Ti3AlC2 and Al-Ti3AlC2 MAX phases are used to synthesize Ti3C2Tx and Al-Ti3C2Tx MXenes, respectively, by the same method of HF:HCl etching and LiCl intercalation. The freestanding Ti3C2Tx and Al-Ti3C2Tx film electrode is separately prepared through simple vacuum filtration. The presence of excess aluminum during the Al-Ti3AlC2 synthesis facilitates to form more homogeneous grains structure with relatively larger particle sizes and an improved stoichiometric MAX phase with a Ti:C ratio closer to 3:2. The resulting Al-Ti3C2Tx nanosheets show improved oxidation resistance with relatively uniform and larger dimensions, which facilitate the higher conductivity with slightly increased interlayer spacing for the Al-Ti3C2Tx film. Therefore, the Al-Ti3C2Tx film electrode shows more efficient ions transport and charge transfer, and thus achieves significantly enhanced capacitance (399 F g−1 at 1 A g−1) and rate performance (63.6 % retention from 1 to 10 A g−1) compared to the Ti3C2Tx film electrode (342 F g−1 at 1 A g−1, 55.6 % retention from 1 to 10 A g−1). Moreover, the Al-Ti3C2Tx-based flexible sandwiched supercapacitor also exhibits superior energy storage performance. The impressive results indicate that Al-Ti3C2Tx MXene synthesized from Al-Ti3AlC2 MAX phase possesses the great application potential in flexible supercapacitors.

Exceptional hardness in multiprincipal element alloys via hierarchical oxygen heterogeneities

Refractory multiprincipal element alloys (RMPEAs) are potential successors to incumbent high-temperature structural alloys, although efforts to improve oxidation resistance with large additions of passivating elements have led to embrittlement. RMPEAs containing group IV and V elements have a balance of properties including moderate ductility, low density, and the necessary formability. We find that oxidation of group IV-V RMPEAs induces hierarchical heterogeneities, ranging from nanoscale interstitial complexes to tertiary phases. This microstructural hierarchy considerably enhances hardness without indentation cracking, with values ranging between 12.1 and 22.6 GPa from the oxide-adjacent metal to the surface oxides, a 3.7 to 6.8× increase over the interstitial-free alloy. Our fundamental understanding of the oxygen influence on phase formation informs future alloy design to enhance oxidation resistance and obtain exceptional hardness while preserving plasticity.

Revealing the oxidation behavior of AlCrxFeNi lightweight multi-principal element alloys via experimental and first-principles calculations

Developing alloys capable of withstanding high temperatures is crucial for modern engineering applications. Introducing multi-component alloys (MPEAs) has provided new strategies for designing high-temperature alloys. We have successfully prepared a series of AlCrxFeNi lightweight MPEAs in this study. The oxidation behavior of AlCxFeNi lightweight at 800 °C was investigated systematically through a combination of experimental methods and first-principles calculations. The microstructure characterization before oxidation reveals that the lightweight AlCrxFeNi MPEAs consist of BCC and B2 phases. In contrast, the AlCrFeNi alloy exhibited a microstructure characterized by typical eutectic features. Oxidation tests indicate that all three alloys exhibited oxidation kinetics following a parabolic law, with oxidation rates decreasing as the Cr content increased. Post-oxidation microstructural characterization revealed an oxide layer composed primarily of Al2O3 and Cr2O3 on the alloy surfaces. First-principles calculations provided insights into the microscopic mechanisms underlying the oxidation process. The results demonstrate that the adsorption energy of the O atom at the top position of the Cr atom is significantly lower than that of the Al atom at the top position. Electronic structure analysis shows that the Cr-O covalent bonding is stronger than the Al-O covalent bonding, which accounts for the oxidation resistance improvement as the Cr element content increases. This study advances MPEAs for high-temperature environments by elucidating these microscopic mechanisms.

Improved oxidation behavior of Hf0.11Al0.20B0.69 in comparison to Hf0.28B0.72 magnetron sputtered thin films

The oxidation resistance of Hf0.28B0.72 and Hf0.11Al0.20B0.69 thin films was investigated comparatively at 700 °C for up to 8 h. Single-phase solid solution thin films were co-sputtered from HfB2 and AlB2 compound targets. After oxidation at 700 °C for 8 h an oxide scale thickness of 31 ±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pm$$\\end{document} 2 nm was formed on Hf0.11Al0.20B0.69 which corresponds to 14% of the scale thickness measured on Hf0.28B0.72. The improved oxidation resistance can be rationalized based on the chemical composition and the morphology of the formed oxide scales. On Hf0.28B0.72 the formation of a porous, O, Hf, and B-containing scale and the formation of crystalline HfO2 is observed. Whereas on Hf0.11Al0.20B0.69 a dense, primarily amorphous scale containing O, Al, B as well as approximately 3 at% of Hf forms, which reduces the oxidation kinetics significantly by passivation. Benchmarking Hf0.11Al0.20B0.69 with Ti–Al-based boride and nitride thin films with similar Al concentrations reveals superior oxidation behavior of the Hf-Al-based thin film. The incorporation of few at% of Hf in the oxide scale decelerates oxidation kinetics at 700 °C and leads to a reduction in oxide scale thickness of 21% and 47% compared to Ti0.12Al0.21B0.67 and Ti0.27Al0.21N0.52, respectively. Contrary to Ti–Al-based diborides, Hf0.11Al0.20B0.69 shows excellent oxidation behavior despite B-richness.

Improved oxidation resistance of boron nitride nanotubes with protective alumina nano-coatings

Boron nitride nanotubes (BNNTs) are gaining interest for high temperature applications due to their thermal stability at elevated temperatures. Although BNNT temperature limits are well studied, there remains a gap in quantifying the high temperature failure mechanisms and oxidation kinetics. This study characterizes the oxidation mechanisms and kinetics of BNNTs and Al2O3-coated BNNTs, via atomic layer deposition (ALD), at temperatures between 850 and 1000 °C. ALD Al2O3 surface coatings improved BNNT oxidation resistance by over an order of magnitude for coating thicknesses between 7 and 56 nm. However, the improved oxidation resistance of Al2O3-coated BNNTs decayed after prolonged exposure to oxygen at elevated temperatures, gradually reaching the same extent of oxidation as uncoated BNNTs after approximately 200 min at 900 °C. This behavior is attributed to the crystallization of as-deposited amorphous Al2O3 coatings at elevated temperatures leading to densification, cracking, and exposure of BNNTs to the oxidizing environment. While Al2O3 coatings did not completely prevent oxidation, a significant improvement in oxidation resistance was observed, extending the thermal stability of BNNTs.

Rare‐earth compositional screening of high‐entropy diborides for improved oxidation resistance

AbstractCompositional screening is an important strategy to improve the oxidation resistance of high‐entropy diborides (HEB2), yet the related studies are limited. Here, we report a rare‐earth (RE) element compositional screening strategy to improve the oxidation resistance of HEB2. To be specific, the single‐phase (Hf0.28Zr0.28Ta0.28RE0.16)B2 (HEB2‐RE) samples with 12 different RE elements are fabricated via ultrafast ultrahigh‐temperature synthesis and spark plasma sintering techniques, and their oxidation resistance is explored by isothermal oxidation tests. The results show that the as‐obtained HEB2‐Sc samples possess the best oxidation resistance among all the as‐fabricated HEB2‐RE samples. Such outstanding oxidation resistance is ascribed to the enhanced viscosity of the generated B2O3 glass originating from the solid solution of (Zr, Me)0.84Sc0.16O2 complex oxides, as confirmed by transmission electron microscope observations and first‐principles calculations.

Improved Oxidation Resistance and Cr Retention of Coated AISI441 for SOC Application

Improved Oxidation Resistance and Cr Retention of Coated AISI441 for SOC Application

Strategies to improve oxidation resistance of MgO–C refractories by decreasing oxygen potential through MgSiN2

AbstractMgO–C refractories are of paramount importance in the converter side blowing system, requiring outstanding oxidation resistance under harsh conditions including high temperature, oxygen atmosphere, and high‐speed airflow. In this study, MgSiN2 phase reconstruction was used to improve the oxidation resistance of MgO–C refractories, as well as the mechanical properties and oxidation resistance of MgO–C refractories were evaluated. The results indicated that the cold modulus of rupture of the sample with 9 wt% MgSiN2 was increased by 93.3% compared with the MgO–C refractories without MgSiN2. After oxidation tests, the oxidation index and rate constant (k) of the sample with 9 wt% MgSiN2 were reduced by 38.9% and 35.3%. Furthermore, incorporating MgSiN2 facilitated the formation of layered dense structures consisting of plate‐like Mg‐Sialon and MgO–Mg2SiO4–MgAl2O4. This structural optimization effectively inhibited oxygen diffusion and reaction within the material, resulting in gradual oxygen potential mitigation.

Tannic acid one-step induced quaternized chitin-based edible and easy-cleaning coatings with multifunctional preservation for perishable products

The development of biomass hydrogel coatings is significant for fruit preservation. This paper presents the facile development of a multifunctional polysaccharide-based hydrogel produced from quaternized chitin (QC) and tannic acid (TA) by in situ rapid cross-linking with high-density hydrogen bonding using the sample mixing method. The Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) spectra, and thermogravimetric analysis (TGA) proved that QC-TA hydrogel was formed by physical interactions (hydrogen bonding, electrostatic interaction, etc.). Moreover, the cross-linking density of the QC-TA hydrogels was analyzed by rheological property measurements and scanning electron microscope (SEM) morphology observations. This polysaccharide-based hydrogel, QC-TA, was evaluated as an edible coating for perishable food items, demonstrating significant improvements in physic-chemical properties, oxidation resistance, and antimicrobial activity against key pathogens (E. coli, S. aureus, and C. albicans). Notably, the hydrogel formed a protective film that effectively shields fruits from mechanical damage, maintaining freshness and extending shelf life, and also featuring with easy cleaning. Applied to cherry tomatoes, the QC-TA coating ensured a smooth, uniform surface, reducing dehydration and flavor loss while inhibiting microbial growth. These findings underscore the potential of employing polyphenol induced polysaccharide forming green hydrogel coatings as an economical, efficient strategy for enhancing the quality and safety of perishable foods, representing an advancement in the field of sustainable food packaging.

Significant improvement of oxidation resistance and slag penetration resistance of MgO-SiC-C refractories with Si3N4-Fe addition

MgO-SiC-C refractories demonstrate distinguished thermal shock resistance and slag resistance, making them a promising alternative to magnesia-chrome refractories in matte smelting furnaces. Herein, we propose a novel approach to enhance both oxidation resistance and slag penetration resistance of such refractories by incorporating Si3N4-Fe powder. The results demonstrated that adding Si3N4-Fe powder effectively enhanced their overall performance. The oxidation resistance of the specimen with 6 wt% Si3N4-Fe was greatly improved because Si3N4 in Si3N4-Fe could promote in-situ reactions to form more forsterite, and the FeO formed by iron oxidation could react with SiC to form Fe-Si alloys; the formed forsterite and Fe-Si alloys worked together to prevent oxygen intrusion. Meanwhile, Si3N4 in Si3N4-Fe promoted the formation of forsterite layer in the corrosion area of refractories, and the reaction of Si3N4 and Fe in Si3N4-Fe formed Fe-Si alloys to prevent slag penetration, which greatly improved the resistance to matte slag penetration of the refractories.

Co–Ni–Al–W γ/γ′ superalloy with Cr and Ti additions fabricated via laser fusion of elemental powders

A Co-based superalloy (Co-0.20Ni-0.11Al-0.07W-0.04Cr-0.03Ti, mole fraction) was synthesized by laser powder-bed fusion of a blend of elemental powders. The as-built alloy shows a γ-FCC matrix where the high-melting Ti and Cr powders are fully dissolved, but the refractory W particles are only partially melted. Full dissolution of the W particles is achieved after homogenization at 1150 °C, resulting in a homogeneous, single-phase γ microstructure. Upon aging at 900 °C, a two-phase γ/γ′ microstructure forms, with a high-volume fraction of sub-micron γ′ precipitates with cuboidal shape. Compared to a control quaternary alloy without Cr and Ti fabricated by the same method, the present alloy has increased γ′ fraction and microhardness after aging for 300 h, maintaining a strong γ′ strengthening effect without forming γ′-depleted zone at grain boundaries. Micrometer-size γ′-precipitates at grain boundaries also shift the transition between diffusional and dislocation creep to lower stress levels, by inhibiting diffusional creep and grain-boundary sliding. However, overall creep resistance is lowered, consistent with a reduction of lattice mismatch due to Cr additions and rafting of γ′ precipitates. Furthermore, Cr and Ti additions improve oxidation resistance at 900 °C, due to the formation of a continuous Cr-, Ti- and Al-rich oxide layer.

Invited Article: The oxidation kinetics and mechanisms observed during ultra-high temperature oxidation of (HfZrTiTaNb)C and (HfZrTiTaNb)B2

Ultra-high temperature ceramics (UHTCs), most notably transition metal carbides and borides, exhibit melting temperatures exceeding 3000 °C, making them appropriate candidates to withstand the extreme temperatures (∼2000 °C) expected to occur at the leading edges of hypersonic vehicles. However, their propensity to react rapidly with oxygen limits their sustained application. The high entropy paradigm enables the exploration of novel UHTC compositions that may improve on the oxidation resistance of conventional refractory mono-carbides and -diborides. The oxidation kinetics of candidate high entropy group IV + V (HfZrTiTaNb)C and (HfZrTiTaNb)B2 materials were evaluated at 1500–1800 °C using Joule heating in one atmosphere 0.1%–1% oxygen/argon gas mixtures for times up to 15 min. Possible mechanisms based on the resulting complex time, temperature, and oxygen partial pressure dependencies are discussed. The carbides formed porous and intergranular oxides. Oxidation resistance was improved upon a continuous external scale formation. The diborides formed dense external scales and exhibited better oxidation resistance compared to the carbides. This improvement was attributed to the formation of liquid boria. Both compositions showed an unexpected reduction in material consumption at 1800 °C for all times tested, compared to results at lower temperatures. An in-depth analysis of the composition and morphology of the oxide scale and sub-surface regions for specimens tested at 1800 °C revealed that the formation of denser group IV-rich (Hf, Zr, Ti) oxides mitigated the formation of the otherwise detrimental liquid-forming group V (Ta, Nb) oxides, leading to the improved oxidation resistance.