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Unidirectional SiCf/SiC minicomposite with a scheelite (CaWO4) interphase coating was fabricated through the precursor infiltration and pyrolysis method. Fractography of the SiCf/SiC minicomposites indicated that weak fiber/matrix bonding can be provided by the CaWO4 interphase. Furthermore, interfacial debonding stress of SiCf/CaWO4/SiC minicomposite was evaluated through the fiber push-out test, and estimated to be 80.7 ± 4.6 MPa. In-situ tensile SEM observation of SiCf/CaWO4/SiC minicomposite after oxidation at 1000–1100 °C was carried out, and thermal compatibility between CaWO4 interphase coating and SiC fiber or matrix after heat treatment at 1300 °C was investigated. [ABSTRACT FROM AUTHOR]

To heighten the oxidation inhibition capacity of HfB 2 -SiC coating, film-forming regulation of the self-formed compound layer was utilized to enhance the dynamic stability and the oxygen hindering capacity of the coating. The oxidation process of the HfB 2 -SiC coating in air from room temperature to 1700 °C can be divided into the lower temperature oxidation zone, the medium temperature protection zone and the high temperature corrosion zone. The oxidation activity of the coatings was significantly weakened in the medium temperature oxidation protection zone from 1100 °C to 1400 °C, which was selected as the film-forming regulation temperature region to ensure the lower film-forming wastage of the coatings. When the film-forming temperature was 1200 °C, the coating was uniformly covered by the glass layer with fewer defects. The values of active factor and inerting factor of the HfB 2 -SiC coating after film-forming at 1200 °C were 0.151 and 0.953 × 10−6 g cm−2 s−1, respectively, which show the lowest film-forming wastage of the coating. With further ascending the film-forming temperature, a large number of pores and cracks generated on the glass layer owing to the evaporation and release of the gaseous byproducts, which destroyed the structure of the glass layer and aggravated the oxidation wastage of the coating. With increasing the film-forming time at 1200 °C for 360 min, the protection efficiency of the HfB 2 -SiC coating increased to 99.13%, the oxygen permeability and carbon loss rate decreased by 79.6% and 67.8%, respectively, which slowed down the oxidation activity and improved the dynamic stability of the coating during oxidation. [ABSTRACT FROM AUTHOR]

Scheelite coating was deposited on SiC fiber tows from various liquid-phase precursors followed by heat treatments between 900 °C and 1100 °C in different atmospheres. The tensile strength was fully retained for the coated fibers treated at 900 °C in vacuum. Subsequent heat treatment at 1100 °C in Ar had little effect on the fiber strength, which is explained by the excepted good thermal stability between the scheelite coating and SiC fiber. However, larger strength degradation and poor spool ability of coated fibers prepared in Ar/air were found. Assisted oxidation of SiC fiber by calcium salts is suggested to be responsible for the much larger strength degradation of fibers prepared in Ar/air. [ABSTRACT FROM AUTHOR]

ZrB 2 -SiC coatings with varied porous structures were deposited on SiC fiber tows using the sol-gel method and cured at 1400 ℃ in vacuum. Tensile strength of the coated SiC fibers were much lower than that of the uncoated fibers. The bimodal distribution in the Weibull plot of the coated SiC fibers demonstrated that the fracture of the coated fiber can be attributed to two types of defects: the porous structure of the coating and the fiber defects. Detailed morphology and microstructure characterization of the coating and fiber combined with strength calculation were carried out to investigate the individual contribution of the fiber defects and the porous coating layer respectively. The results revealed that apart from the fiber damage during the coating process the porous structure of the fiber coating has a non-negligible effect on the fiber strength, presumably due to a relatively strong bonding between the fiber and coating. [ABSTRACT FROM AUTHOR]

To suppress the oxidation loosening of HfB 2 -SiC coating, the HfB 2 was alloyed with HfSi 2 in the form of composite powders through self-propagating high-temperature synthesis (SHS) technique, which was then used to prepare HfB 2 -HfSi 2 -SiC coatings. Compared to the 60HfB 2 -SiC coating, the 60(HfB 2 -HfSi 2) SHS -SiC coating exhibited lower oxidation activity and better inert oxygen blocking at 1700 °C. The addition of HfSi 2 promoted the homogenization of the Hf-oxides distribution on the glass layer and the formation of the protective phase HfSiO 4 , further inhibiting oxygen diffusion. The 60(80HfB 2 -20HfSi 2) SHS -SiC coating exhibited optimal oxygen blocking protection after oxidation at 1700 °C, with 87.96% and 92.33% reductions in oxygen permeability and carbon loss rate, respectively. [ABSTRACT FROM AUTHOR]

HfB 2 -MoSi 2 -based ultra-high temperature ceramic (UHTC) coatings have shown remarkable antioxidant effects owing to the formation of silicate glass layers with low oxygen permeability in high-temperature environments, which shows great potential in the antioxidation of carbon structural materials. To further enhance the oxidation resistance of the HfB 2 -MoSi 2 -based coating in a wide temperature region, the influence of volume ratio between HfB 2 and TaB 2 on the antioxidant capacity of the HfB 2 -MoSi 2 -TaB 2 coatings was investigated. The addition of 15 vol% TaB 2 in the 60HfB 2 -40MoSi 2 coating delays the initial oxidation temperature of the 60HfB 2 -40MoSi 2 sample from 300 °C to 500 °C, which decreased the oxidation loss by 75.85% during dynamic oxidation. In oxidation process at 900 °C and 1700 °C, the weight gains of the 45HfB 2 -40MoSi 2 –15TaB 2 coating reduced by 78.56% and 63.14%, respectively. Due to the coexistence of 45 vol%HfB 2 and 15 vol%TaB 2 , the suitable Ta5+ promoted the homogenization and dispersion of Hf/Ta-oxides, which forms the coral-like Hf/Ta oxides skeleton in the glass layer, thus preventing the oxygen penetration and decreasing the inert factor of the HfB 2 -MoSi 2 coating at 1700 °C by 51.19%. However, excessive TaB 2 weakened the self-healing ability of the Ta-Hf-Si-O glass layer and inhibited the oxygen barrier effect of the HfB 2 -MoSi 2 -TaB 2 coating. [ABSTRACT FROM AUTHOR]

To suppress the oxidation of TaB 2 -SiC coatings, the effects of pre-oxidation temperature on the oxygen hindering properties of TaB 2 -SiC coatings were investigated to prepare TaB 2 -SiC coatings with enhanced oxidation behavior. The addition of 40 wt% TaB 2 made the oxygen permeability of the coating decrease by 62.16%. However, excessive TaB 2 weakened the oxygen hindering ability of the coating due to the large ion complex ability of Ta5+. The pre-oxidation temperature at 1500 °C led to a homogeneous dispersion of Ta-oxide nanocrystal particles in the Ta-B-Si-O complex-phase glass layer. In contrast with the untreated samples, the active factor and inert factor values of the TaB 2 -SiC coating after pre-oxidation treatment at 1500 °C decreased by 43.12% and 17.33%, respectively, which improved the dynamic stability of the coating during oxidation. [ABSTRACT FROM AUTHOR]

• Regulating the dominant exposure plane of TiN to change the electronic properties of the electrode interface. • Interface induction promotes the formation of rigid-flexible SEI. • The difference of adsorption energy of LiF on various TiN crystal planes reveals the regulation mechanism. The performance of SiO anodes is critically dependent on the characteristics of the solid-electrolyte interface (SEI). However, the properties of SEI are challenging to control due to the complexity of its generation mechanisms. Among them, the electrode interface property is one of the crucial but easily neglected factors influencing the formation of SEI. Herein, considering the strong reaction tendency of HF with SiO, TiN is used as a coating to isolate HF from SiO to investigate the mechanism of influence of electrode interface on SEI. The dominant exposed crystalline planes of the TiN coatings are modified by tuning supersaturation during the coating process, and the changes in electrode interface properties were achieved. The variation of mechanical properties of SEI under different interface properties are discussed and analyzed, and the SiO/TiN-{1 0 0} electrode with a rigid-flexible SEI is preferred. Furthermore, the adsorption states of LiF on different TiN crystal planes are calculated and analyzed by the first-principle method to reveal the effect of the electrode interfacial property on SEI. Electrochemical tests show that the performance of the SiO/TiN-{1 0 0} electrode is significantly better than others. Finally, the electrochemical-mechanical coupled correlation between SEI and cycling performance was deeply revealed based on differential capacity analyses. [ABSTRACT FROM AUTHOR]

The film-forming regulation at 1100–1400 °C was utilized to suppress the dynamic evolution and enhance the oxidation inhibition capacity of the ZrB 2 -SiC coating during oxidation. The excessive film-forming temperature would make the generated glass porous, thus provoking the oxidation consumption of the ZrB 2 -SiC coating. Compared with the coating without film-forming regulation, the coating film-forming treated at 1200 °C for 120 min shows the best oxidation inhibition ability, whose value of structural factor and inertia factor decreased by 33.36% and 82%, respectively. With extending the film-forming time at 1200 °C to 360 min, the oxygen permeability of the coating decreased by 57.52%. • Oxygen barrier ability of ZrB2-SiC coating was enhanced by film-forming treatment. • Film-forming treatment at 1100–1400 ℃ can inhibit the dynamic evolution of coating. • A glass film is formed under low consumption conditions by film-forming treatment. • Oxygen permeability decreased by 57.52% after treatment at 1200 ℃ for 6 h. • Excessive film-forming treatment can weaken the integrity of the glass film. [ABSTRACT FROM AUTHOR]