To enhance the high-temperature oxidation resistance of carbon-based materials through optimized ceramic coating structures, a borosilicate glass (BSG)-modified ZrB2-MoSi2-BSG gradient composite coating was successfully fabricated via in-situ self-assembly induced by thermal expansion mismatch. The influence of densification temperature on the oxygen-blocking microstructure and oxidation resistance of the composite coating was systematically investigated. Results indicate that when the densification temperature exceeds 1300 degrees C, a gradient oxygen-blocking structure is formed via self-assembly during high-temperature oxidation protection. With increasing densification temperature, the interfacial bonding strength between the coating and the substrate initially increases and then decreases, reaching an optimum performance at a specific temperature. The maximum bonding strength achieved was 84.6 N, accompanied by a minimal oxidation weight gain of 0.24 x 10-2 g center dot cm- 2 after 100 min at 1700 degrees C. Additionally, the oxygen transmission rate was as low as 0.04 %, the carbon loss rate was 0.13 x 10-6 g center dot cm- 2 center dot s- 1, and the cumulative protection efficiency reached 99.95 %. However, further increasing the sintering temperature leads to excessive accumulation of self-assembled SiO2 layers at the coating interface, resulting in structural defects such as pores and cracks within the coating. These defects provide pathways for oxygen permeation, thereby degrading the oxidation resistance of the coating. This study demonstrates that thermal expansion mismatch can be effectively utilized to induce gradient in-situ selfassembly in BSG-modified ZrB2-MoSi2 composite coatings, enabling effective regulation of glass phase distribution and interfacial structure through optimized sintering temperatures. This approach provides a viable strategy for the controllable structural design and highly efficient oxygen-blocking protection of ultra-high temperature ceramic coatings.

To improve the oxidation resistance and self-healing ability of ZrB2 based coatings, ZrB2-ZrSi2 coatings modified by powder alloying were successfully prepared, and the effect of different proportions of ZrB2-ZrSi2 alloy composition on the oxygen barrier layer was studied. The results showed that the 90 vol.% ZrB2- 10 vol.% ZrSi2 coating exhibited the lowest oxygen permeability (3.66%) and the highest cumulative protective efficiency (95.77%) among all components. The synergistic strengthening effect of ZrB2-ZrSi2 alloying significantly improved the stability and oxygen barrier performance of the coating at high temperatures. The dispersed distribution of Zr oxides helps to expand the crystallization region, enhance the structural densification of the glassy layer, suppress oxygen permeability, and reduce oxygen-induced damage to the glassy layer. The Zr-Si-O multiphase glass layer spontaneously formed during the oxidation process could effectively hinder the oxygen diffusion channel, which enhances the structural integrity of the coating in the oxidation environment and prolongs its protective function.

Abstract Ti/Cr nanoscale multilayers (∼1.5 μm) with individual layer thicknesses (h) from 5 to 150 nm were deposited on AZ91D magnesium alloy by unbalanced magnetron sputtering. Regarding wear reduction, the 10 nm coating proved most efficient. In contrast, substrate wear increased progressively as h shifted from 150 nm down to 5 nm (excluding the 10 nm peak). The 10 nm coating exhibited the highest adhesion (L C = 12.43 N) and Ti/Cr retention, attributed to coherent/semi-coherent interfaces that homogenize stress and suppress damage. Although the 150 nm coating achieved peak hardness (∼12.5 GPa), its wear resistance was inferior due to columnar grain coarsening and poor interfacial bonding (L C = 5.33 N). The 5 nm coating, despite the lowest roughness (Rq = 0.403 nm), failed prematurely via “interface softening.” All systems underwent oxidative–adhesive–abrasive composite wear, underscoring that interfacial design—not hardness alone—dictates tribological performance.

To enhance the anti-oxidation performance of ultra-high temperature ceramic (UHTC) coatings applied on carbon-based materials under extremely high-temperature conditions, HfB2-HfSi2 powders modified with a Zr-based borosilicate glass (BSG) were employed to fabricate HfB2-HfSi2-BSG(ZrO2) composite coatings via self-propagating high-temperature synthesis (SHS) and spark plasma sintering (SPS). A systematic investigation was conducted into the microstructural changes and the oxygen-barrier strengthening mechanism of the Zr-based borosilicate-modified HfB2-HfSi2 coating when exposed to 1700 °C. The findings indicated that the introduction of ZrO2 facilitated the in-situ development of an oxidized Zr-Hf-Si-O multiphase glassy layer on the surface, which significantly reinforced the blocking of inward oxygen diffusion and the retention of volatile reaction products. The optimal overall oxidation resistance of the coating was achieved when the BSG:ZrO2 proportion was set to 1:1. The average oxidation rate and the average oxygen permeability were 0.41 × 10−7 g cm−2 s−1 and 0.09%, which were 61.68% and 82.0% lower than those of the coating without ZrO2 addition. However, doping with an excess of ZrO2 caused the glass layer to exhibit an overly high viscosity and induced dendritic precipitation, which consequently compromised self-healing sealing capability. This study reveals the oxygen-barrier mechanism of HfB2-HfSi2-BSG(ZrO2) coatings, offering a new strategy for long-life oxidation-resistant coatings in extreme environments.

To enhance the oxygen barrier capability of Y2O3-ZrSi2-ZrB2-SiC coatings under ultra-high temperature conditions, a preformed glass layer was prepared on the coating surface by lossless film formation technology, aiming to reduce the consumption of the self-generate film during the oxidation process. The influence of different film formation treatment time on the oxygen barrier performance was investigated, along with the coating micro-structural evolution at 1700 degrees C in the oxygen containing atmosphere. Results indicate that the composite coating with a 360 min film formation treatment exhibited final oxygen permeability and average oxygen permeability of merely 0.60 % and 1.04 %, respectively, after oxidation 100 min at 1700 degrees C. Compared to the coating without preformed glass layer, the final oxygen permeability and average oxygen permeability were reduced 26.31 % and 31.41 %, while the structural factor and inertization factor decreased by 28.09 % and 6.35 %, respectively. The improved oxidation resistance is attributed to the effective suppression of cracking in the glass layer by YSZ (Y2O3 partially stabilized ZrO2), which acts as a pining phase in the composite glass layer prepared by solution combustion synthesis. Ceramic nanocrystals phases such as YSZ and ZrSiO4, uniformly distributed within the preformed glass layer, increase the viscosity of the glass layer, heal structural defects that arise during oxidation, and facilitate the formation of a stable Zr-Y-Si-O multiphase glass layer.

At high temperatures, oxidation is generally regarded as an unavoidable degradation process for ceramic protective coatings. Here, oxidation is shown to drive dynamic glass evolution and form a robust self-sealing barrier under extreme thermal conditions. An in situ alloyed borideu2013silicide composite coating is constructed, and the controlled incorporation of HfSi2 is found to change oxide-scale development by providing additional Hf and Si sources during oxidation and promoting the early formation and continuous reconstruction of a highly sealing Hfu2013Siu2013O glassy layer. The optimized coating exhibits exceptional oxidation resistance at 1700 u00B0C, with the oxygen permeability and carbon loss rate reduced by 61.67% and 75.26%, respectively, corresponding to an average protection efficiency of 99.94%. Mechanistically, oxidation-driven glass evolution seals pores and microcracks and slows inward oxygen diffusion, whereas appropriate HfSi2 incorporation helps compact and stabilize the glassy layer, while excessive glass stiffening reduces high-temperature fluidity and weakens scale integrity. These findings provide a general design method for improving self-sealing oxidation protection at high temperatures.

To address the issues of loose oxide scale and insufficient protective performance in ZrB2-MoSi2 composite ceramics under ultra-high temperature oxidizing environments, caused by the volatilization of B2O3 and the self-depletion of MoSi2, A novel Hf-based borosilicate glass modification strategy is proposed by this work. The effects of varying HfO2 contents on the oxidation resistance and mechanical properties of the ceramics after oxidation at 1700 °C for 100 min were systematically investigated. The results indicate that, with an appropriate amount of HfO2 modification, a continuous Zr-Hf-Si-O multiphase glass layer forms in situ during oxidation, significantly suppressing the inward diffusion of oxygen. Compared with the unmodified sample, the ZMGH30 sample exhibits a 23.73% reduction in oxidation weight gain, a 70.38% decrease in average oxidation rate, and an increase in hardness retention to 61.17%. Excessive HfO2 leads to excessively high viscosity of the glass layer, Hf element agglomeration, and dendritic precipitation, thereby weakening the self-healing ability and deteriorating the oxidation resistance. A new approach for developing ultra-high temperature ceramics that combine excellent oxidation resistance and mechanical reliability is provided by this work.

A dual strategy combining high-entropy composition design and microstructural engineering is employed to optimise the overall performance of protective coatings. A series of (TiCrVAl)1-xNx coatings (0.15 < x < 0.46) is prepared by pulsed magnetron sputtering. Precise nitrogen regulation is utilised as a microstructural engineering tool to achieve the controlled transformation of coating structures within a fixed equiatomic metallic component framework. Increasing x from 0.15 to 0.46 causes a pronounced structural evolution, from an amorphous state to a nanocomposite structure, and ultimately to a well-crystallized structure. The nanocomposite structure was achieved in the (TiCrVAl)(0.6)2N(0.38) coating, delivering the highest hardness of 37.6 GPa, superior toughness (reflected by H/E* of 0.084), and ultralow wear rate of 4.7 & times; 10(-9) mm(3) N- 1 m(- 1). Oxidation tests further reveal that the (TiCrVAl)0.62N0.38 coating possesses the strongest oxidation resistance, attributed to the formation and retention of the continuous Al2O3 scale.

Focusing on the problem of oxygen barrier structure degradation in ZrB2-SiC coatings resulting from selfconsumption during the initial oxidation, Hf-Si-B-O glass films with controllable HfO2 content were prepared on the surface by pre-filming method. As the HfO2 content increased, the thermal expansion coefficient (CTE) of the composite glass film showed a progressive increase, from 1.90 & times; 10-6/degrees C to 4.50 & times; 10-6/degrees C, reducing the thermal mismatch with the underlying coating. The volatilization of the glass matrix is inhibited due to the "pinning" effect, which is induced by the HfO2 nanocrystals and the HfSiO4 and ZrSiO4 silicate phases. The sample with 50 wt% HfO2 (H3) exhibited the optimal performance: after 100 min of exposure to 1700 degrees C for oxidation testing, the oxidation rate dropped to 0.76 & times; 10-6 g & sdot;cm-2 & sdot;s-1, the cumulative protection efficiency reached a high level of 99.95%, and the average oxygen permeability was only 0.37%. The final weight gain was reduced by 94.75% compared to the uncoated sample. However, excessive HfO2 (70 wt%, H4) led to overpolymerization of the glass network, and excessive consumption of SiO2 hindered high-temperature self-healing, leading to increased surface defects and decreased oxidation resistance. In this study, low-consumption film formation is achieved by pre-filming method, providing a new idea for solving the "self-consumption" problem of ZrB2-SiC coatings. Meanwhile, this technology provides theoretical reference for developing and optimizing nextgeneration ultra-high-temperature oxidation-resistant coatings through composition design.

At high temperatures, oxidation is generally regarded as an unavoidable degradation process for ceramic protective coatings. Here, oxidation is shown to drive dynamic glass evolution and form a robust self-sealing barrier under extreme thermal conditions. An in situ alloyed boride–silicide composite coating is constructed, and the controlled incorporation of HfSi2 is found to change oxide-scale development by providing additional Hf and Si sources during oxidation and promoting the early formation and continuous reconstruction of a highly sealing Hf–Si–O glassy layer. The optimized coating exhibits exceptional oxidation resistance at 1700 °C, with the oxygen permeability and carbon loss rate reduced by 61.67% and 75.26%, respectively, corresponding to an average protection efficiency of 99.94%. Mechanistically, oxidation-driven glass evolution seals pores and microcracks and slows inward oxygen diffusion, whereas appropriate HfSi2 incorporation helps compact and stabilize the glassy layer, while excessive glass stiffening reduces high-temperature fluidity and weakens scale integrity. These findings provide a general design method for improving self-sealing oxidation protection at high temperatures.

Magnetron sputtering hcp/bcc Ti/Ta multilayers with different modulation ratios (eta) were systematically investigated, to understanding intrinsic role of constituent structures on interfaces and mechanical properties, and revealing the underlying deformation mechanisms, especially rate-related behaviors in multilayers with unequal layer thicknesses. Transmission electron microscopy and X-ray analyses suggested that Ti partially transformed from hcp to bcc metastable phase at Ti/Ta interfaces, therefore coherent or semi-coherent interfaces appeared. Hardness and strain rate sensitivity of Ti/Ta multilayers was well evaluated by nanoindentation experiments, both of which exhibit an increasing trend with increasing eta. Several related deformation mechanisms were discussed, as a result, partial-dislocations emission from grain boundaries of Ti participate in the deformation at eta< 1 and dislocations confined slipping dominant deformation at eta > 1. A negative m is presented at eta < 1, which is caused by metastable bcc to hcp phase transformation under the indentation. Meanwhile, the double-kink dislocations nucleation in nanocrystalline Ta is responsible for the deformation at eta > 1, therefore m becomes positive and increases slightly with eta.

To reduce the oxidation damage during the initial active oxidation stage of ZrB2-SiC coating, this paper employed a slurry-brushing method to prepare a self-healing Zr-Si-B-O biomimetic glass film on the surface of the ZrB2-SiC coating. Furthermore, the oxidation resistance behavior of biomimetic glass films with varying ZrO2 contents was investigated. Experimental results indicate that the Zr-Si-B-O biomimetic glass film can significantly reduce the oxidation weight gain of ZrB2-SiC coating. The biomimetic glass film sample with 70 wt% ZrO2 exhibits the best oxidation protection effect. After oxidation treatment in the temperature range of 600-1600 degrees C, the weight gain is only 0.081 & times; 10-2 g cm- 2, which is 95.35% lower than that of the sample without the biomimetic glass film; after oxidation at 1700 degrees C, the final protection efficiency and average carbon loss rate reach the optimal values of 99.97% and 0.34 & times; 10- 6 g cm-2 s-1, respectively, and the average oxygen permeability is only 0.35%. The presence of Zr-Si-B-O biomimetic glass film can significantly reduce the oxidation activity and improve the oxidation resistance of the coating. This is attributed to the pre-introduction of a flowable and self-healing glass on the coating surface, which prevented the intense oxidation of the coating at the initial stage.

To mitigate the degradation of oxidation protection performance in ZrB2-SiC-based ultra-high-temperature ceramic coatings caused by porosity and loosening of the oxygen-barrier structure during service at 1700 degrees C in an oxygen-rich environment, alloying modification using ZrB2-ZrSi2-based powders was employed to enhance the self-healing efficiency of the in-situ generated glass layer in loosened regions. The research revealed that alloying with ZrB2-ZrSi2 powder shortened the repair pathway of the in-situ formed glass layer produced by silicide oxidation in loosened areas, thereby improving the oxidation resistance of ZrB2-ZrSi2-based coatings under ultra-high-temperature conditions. ZrB2 powder modified with 10 vol% ZrSi2 exhibited optimal selfhealing performance, reducing oxygen permeability by 4.25%, decreasing the structural factor by 26.20%, and lowering the passivation factor by 57.43% and achieving a cumulative protection efficiency of 96.36%. When the ZrSi2 content exceeded 10 vol%, excess ZrSi2 acted as a corrosion phase at high temperatures, accelerating ZrB2 oxidation and weakening its self-healing capability. This effect is primarily ascribed to the excessive generation of ZrO2, which disrupts the structural stability of the SiO2 glass matrix, leading to localized volume contraction and an increase in the thermal expansion coefficient. Consequently, oxide segregation and accumulation occur within the protective layer, degrading its oxidation resistance. Additionally, the ZrB2-ZrSi2SiC-based composite coating modified with 10 vol% ZrSi2 markedly improved oxidation resistance; relative to the unmodified ZrB2-SiC coating, its structural factor decreased by 43.94%, and its passivation factor decreased by 12.31% and its cumulative protection efficiency reached 98.62%. This study provides a novel methodology for enhancing the oxygen barrier protection performance of ultra-high-temperature ceramic coatings.

The development of protective coatings with simultaneously enhanced mechanical, tribological, and antioxidant properties remains a major challenge for micro-electro-mechanical systems operating under harsh environments. In this work, HfCx/a-C:H coatings with varying carbon contents were deposited by magnetron sputtering. Increasing the C2H2 flow rate from 12 to 20 sccm drove the coating structure to undergo two-stage evolution, from a composite structure dominated by HfC nanograins with a-C:H distributed at triple junctions of HfCx grain boundaries to a typical nanocomposite structure with similar to 8 nm HfCx nanograins embedded in a continuous a-C:H matrix. The coating deposited at 18 sccm exhibited the highest hardness (31.3 GPa) and effective Young's modulus (392.3 GPa), owing to enhanced interface-mediated strengthening effect induced by the optimized nanocomposite structure. The coating prepared at 20 sccm showed the lowest friction coefficient (0.28), the lowest wear rate (6.82 x 10(-6) mm(3)/N.m), and the best oxidation resistance. These improvements were supported by the enhanced mechanical properties and a-C:H fraction, the increased interface density and tortuosity, and the regulation of oxidation kinetics by the a-C:H matrix. This work provides an effective strategy for designing multi-functional protective coatings with balanced mechanical, tribological, and oxidation performance.

To reduce the oxidation loss of ZrB2-SiC ceramic coatings in the early stage of oxidation and minimize coating oxidation defects, a Hf-Ta-Si-B-O outer layer glass film was coated on the surface of ZrB2-SiC coatings by the slurry brushing method, and oxidation tests were conducted. The experimental results showed that the coating with the Hf-Ta-Si-B-O outer layer glass film formed a continuous protective layer in the early stage of oxidation, and the final weight gain in the wide temperature range from 600 to 1600 degrees C was suppressed to 4.60% of that of the pure ZrB2-SiC coating. The Hf-Ta-Si-B-O/ZrB2-SiC coating with 10 wt.% Ta2O5 addition had the best oxidation protection effect, with an average oxygen permeation rate of only 0.34%, a final carbon loss rate of only 0.12 x 10-6 gcm-2s-1, and a final protection efficiency of 99.97% after oxidation at 1700 degrees C for 100 min. The Hf-Ta-Si-B-O/ZrB2-SiC coating showed a dual protection mode of "low-temperature dense barrier + high-temperature dynamic healing" during cyclic oxidation in the wide temperature range from 600 to 1700 degrees C.

The ZrB2-SiC-LaB6 coating was prepared by spark plasma sintering method. To investigate the oxidation resistance and mechanism of ZrB2-SiC-LaB6 coating in a wide temperature range, oxidation tests were conducted in different-temperature isothermal environments and dynamic variable temperature environments. The results indicate that the protection efficiency of the ZrB2-SiC-LaB6 coating exceeded 98 % after oxidation for 100 min at 800, 1000, 1200, 1400, 1500 and 1600 degrees C, and the protection efficiency reached 95.9% after dynamic oxidation from room temperature to 1700 degrees C. LaB6 and ZrB2-SiC have good synergistic oxidation protection effect in a wide temperature range, which is mainly attributed to the self-healing La-Zr-Si-B-O glass film.

To enhance the oxidation resistance of the LaB6-modified HfB2-SiC coating, low-loss film-forming treatment (LFT) was used to form a dense protective film (LFT film) on the surface, which significantly delayed hightemperature oxidation and reduced the coatings' structural defects. After LFT at 1100 degrees C, the Hf-La oxide dendrites were uniformly dispersed in the LFT film, which exerted a particle enhancement effect. As the treatment time extended to 360 min, La element enriched on the surface of the coating, providing a basis for forming an Hf-La-Si-O layer. After oxidation at 1700 degrees C, the coating generated a smooth and continuous La2Si2O7 and La2Hf2O7 evenly distributed complex phase glass layer surface, which effectively inhibited oxygen erosion. Compared with the coating without LFT, the oxygen permeability and carbon loss rate of the coating after LFT were only 0.065 % and 0.211 x 10- 6 g & sdot;cm- 2 & sdot;s- 1, which were reduced by 84.1 % and 73.3 %, respectively.