Environmental barrier coatings (EBCs) are expected to be applied to the hot-end components of new generation of highthrust-toweight ratio aircraft engines.Rare-earth pyrosilicates， especially Yb2 Si2 O7， have been considered excellent EBCs materials.However， the corrosion of calcium-magnesium-aluminum-silicate (CMAS) under service conditions has become a bottleneck limiting their application.The CMAS component has a significant impact on the corrosion behaviors of rare-earth silicate coatings.Herein， Yb2Si2O7 coatings were prepared by vacuum plasma spraying technology， the corrosion behaviors and mechanisms of the coatings exposed to different CMAS components(Ca/Si＝1.00， 0.75， 0.60) in air atmosphere at 1 350 ℃ were investigated.Results showed that the CMAS composition had a significant impact on the corrosion behaviors.After CMAS corrosion with high Ca/Si ratio (1.00 or 0.75)， a porous apatite phase corrosion layer was formed on the Yb2Si2O7 coating.Beneath the corrosion layer， there existed an infiltration layer comprising both apatite phase and Yb2 Si2 O7 phase.After CMAS corrosion with low Ca/Si ratio (0.60)， a dense Yb2Si2O7 layer was formed on the surface of the coating， but it failed to effectively prevent CMAS infiltration， resulting in the formation of an infiltration layer within the coating.As the corrosion time increased， the thickness of the infiltration layer grew significantly.

Mg-Al-Zn-Mn series alloys have been widely used due to their cost advantages and good comprehensive properties， but their application remains limited by poor corrosion resistance.Taking the Mg-8Al-0.8Zn-0.2Mn-0.3Ca (AZMX810203) alloy as the research object，this study systematically investigated the effects of different extrusion temperatures (350， 400， 450 ℃) on the microstructure and corrosion resistance of T6-treated AZMX810203 alloy using metallographic microscopy，XRD，SEM，XPS，and electrochemical tests.Results showed that under the optimized solution treatment (420 ℃ heat treatment for 24 h followed by 450 ℃ for 3 h) and aging treatment (300 ℃ heat treatment for 12 h) processes， the alloy achieved microstructural homogenization and precipitation phase dispersion.All three extruded alloys exhibited fully recrystallized microstructures.As the temperature increased， the grains gradually grew and the volume fraction of secondary phases decreased.With the rise in extrusion temperature， the corrosion resistance showed a “first increase followed by decrease” trend.Moreover， the corresponding corrosion rates for the E350℃， E400℃ and E450℃ alloys were 3.95，0.14，0.42 mm/a， respectively.The E350℃ alloy exhibited intensified corrosion due to intense micro-galvanic effects between secondary phases and fine-grained microstructure，along with the inability to form an effective protective film.In contrast， the E400℃ alloy improved Al content in the matrix by dissolving nano-scale Mg17Al12 phases and promoting the formation of dense and stable Al2O3-rich films.However， the E450℃ alloy showed slightly inferior corrosion resistance compared to the E400℃ alloy， as the significant reduction of secondary phases and grain growth weakened the inhibition of corrosion propagation.Overall， the optimized heat treatment and extrusion processes for AZMX810203 alloy can significantly enhance the corrosion resistance of AZMX810203 alloy， thereby establishing a solid theoretical and practical foundation for its engineering applications.

The oxidation behavior of high-entropy borides and the influence mechanism of SiC secondary phases are critical for their applications in extreme environments， yet related research remains relatively limited to date.In this work， (Hf1/4Zr1/4Ta1/4Ti1/4)B2-SiC multiphase ceramics with SiC contents (volume fractions) of 10%and 20%were fabricated using spark plasma sintering technology， and oxidation tests were conducted using a high-temperature tube furnace to characterize their oxidation behavior at 1 500 ℃， including oxidation weight gain，phase composition and structural features of the oxidation products， with comparisons made to the single-phase (Hf1/4Zr1/4Ta1/4Ti1/4)B2.Results showed that the SiC secondary phase significantly reduced oxidation mass loss of (Hf1/4Zr1/4Ta1/4Ti1/4)B2， decreased the thickness and internal defects of the oxide layer， and enhanced its oxygen barrier capability.Furthermore， combined with thermodynamic calculations， the possible oxidation processes and the action mechanism of the SiC additive were analyzed to provide references for the high-temperature applications of high-entropy borides.

To address the urgent demand for stray light suppression in high-precision space optical systems， an ultra-black high-absorptance thermal control coating suitable for the space service environment was designed and fabricated.The coating was formulated using carbon black nanoparticles as the filler and inorganic potassium silicate as the binder.Based on the Maxwell-Garnett effective medium model and the Fresnel equations，the influence of filler volume fraction on the spectral absorption characteristics of the coating was calculated.Furthermore，the finitedifference time-domain method was employed to simulate the electromagnetic field of coatings with randomly rough surfaces， and the absorption behavior of smooth and rough coatings under different incident angles was compared.Finally， a thermal control coating with ultra-black and high-absorption properties was successfully fabricated.Computational results demonstrated that within the wavelength range of 250～2 500 nm，at a carbon black volume fraction of 2%and a surface roughness of σrms ＝2.0 μm，the coating maintained an optical absorptance of 99.9%even at a 60° incidence angle.Experimental results confirmed that the sprayed ultra-black coating achieved an absorptance of 99.2%under the same 60° large incidence angle， showing high consistency with the simulation.This study provides a promising technical solution for developing advanced stray light suppression coatings in space optical systems， which is of significant importance for enhancing imaging contrast， detection sensitivity， and the overall performance of the system in complex space environments.

Poor high-temperature oxidation resistance remains a major limiting factor hindering the application of niobium(Nb) alloys. Silicide coatings applied to the surface of Nb-based alloys have proven to be an effective solution for enhancing their oxidation resistance. This paper reviewed recent research progress in silicide coatings, introduced the commonly used preparation techniques for silicide coatings and their research advancements, summarized current methods for enhancing the oxidation resistance of silicide coatings, and outlined mechanistic studies related to silicide coating failure. Finally, the future development directions of silicide coatings were summarized.