Magnesium aluminate spinel (MgAl2O4) is a technologically important transparent ceramic with a broad optical window, high hardness, excellent thermal stability, and good chemical durability, making it attractive for infrared windows, transparent armor, and related optoelectronic components. However, pressureless densification of spinel remains difficult because the diffusion of Mg2+ and Al3+ ions is intrinsically sluggish, so conventional sintering typically requires long dwell times or pressure-assisted routes such as hot pressing and hot isostatic pressing. In this work, pressureless ultrafast high-temperature sintering (UHS) was employed to densify MgAl2O4 spinel ceramics. Starting from a green compact with an initial relative density of about 55%, the samples were rapidly heated to 1750 u2103 at rates exceeding 1000 u2103u00B7min-1, held for only 5 s, and then cooled in vacuum. The sintered body retained a single cubic spinel phase, with no detectable secondary phases in XRD. Archimedes measurements gave a relative density of 98.2%, corresponding to a low residual porosity of 1.8%. The microstructure consisted of fine equiaxed grains with an average size of 0.62 u00B1 0.13 u03BCm, together with a small amount of residual pores located mainly at grain boundaries and triple junctions. After polishing to a thickness of about 1 mm, the specimen exhibited an in-line transmittance of 64.7% at 5.3 u03BCm and showed a monotonic increase in transmittance with wavelength, consistent with residual pore scattering in the mid-infrared region. The enhanced densification achieved by UHS is attributed to two coupled effects. First, the extremely fast heating schedule suppresses the low-temperature stage dominated by surface diffusion, thereby limiting unnecessary grain coarsening and preserving a high sintering driving force at the peak temperature. This fine-grain retention is critical because the densification rate in grain-boundary-diffusion-controlled sintering depends strongly on grain size. Second, the severe thermal shock associated with UHS may freeze grain boundaries into high-energy, non-equilibrium states, which could accelerate grain-boundary diffusion and facilitate pore elimination, although this mechanism is presently supported only by indirect evidence and requires direct atomic-scale verification in future work. For comparison, a conventional pressureless sintering schedule of 10 u2103u00B7min-1 to the same peak temperature followed by a 5 s hold produced a much lower relative density of 74.2% and a coarser grain size of about 2.31 u03BCm. These results demonstrate that UHS provides a powerful pressureless route for rapidly densifying diffusion-limited spinel ceramics and offers a viable basis for the preparation of small-sized transparent MgAl2O4 components.
Ceramic-based dispersed matrix fuel(CDM)takes advantage of the excellent thermal conductivity and irradiation resistance of SiC materials,which can further enhance the operational safety of TRISO(Tristructural-isotropic)pellets and meet the requirements of higher temperatures and fuel consumption in reactors.In this work,the mechanical properties of the TRISO pellets coating and its interfacial bonding properties with the SiC matrix in CDM with zirconia simulated core were studied.The Young's modulus and Vickers' hardness of each coating,as well as the fracture toughness of the SiC coating and the SiC substrate,were tested by the micrometer indentation method.Furthermore,the bonding force of the relevant interfaces was evaluated by using the push-out method and the indentation method,and the crack propagation behavior at each coating and interface was investigated with microstructure characterization.The results show that considering the bonding force of each interface of the CDM sample and the strength of each coating area itself,the relatively loose Buffer layer and the core/Buffer interface with weak bonding are prone to damage and failure.The study has proposed feasible testing methods and analytical approaches for the characterization of the mechanical properties and interfacial bonding of fuel microsphere-coated coatings,providing an important reference for the improvement of the sample processing technology of TRISO and CDM.
The proposed aluminum-plated LaMA dual ceramic thermal barrier coating life extension strategy significantly enhances the coating's high-temperature oxidation resistance through aluminum deposition on the LaMA coating surface.The coating was fabricated using a composite technique of plasma spraying and arc ion plating.Detailed characterization of the coating's phase composition,surface morphology,and cross-sectional structure was performed via X-ray diffraction(XRD),scanning electron microscopy(SEM),and energy-dispersive X-ray spectroscopy(EDS).Findings revealed that the aluminum plating treatment significantly reduced microcracks and pores on the coating surface,improved coating density,and enhanced oxidation resistance.In oxidation kinetics testing,the weight gain rate of the aluminum-coated LaMA coating was 4.84±0.23 mg/cm2,significantly lower than the 8.39±0.12 mg/cm2 of the uncoated sample,indicating that the aluminum layer effectively reduced weight gain under high-temperature oxidation.Further analysis of TGO layer evolution revealed that the aluminum-coated layer effectively retards rapid TGO thickening and mitigates interfacial stress accumulation during oxidation.This demonstrates the significant advantage of aluminum coating in enhancing high-temperature oxidation resistance.These findings provide an effective technical solution for ensuring the long-term reliability of dual-ceramic thermal barrier coatings in high-temperature environments.
The next-generation aero-engines impose increasingly stringent demands on the high-temperature resistance,lightweight nature,and long service life of hot-section components.Continuous silicon carbide fiber-reinforced silicon carbide(SiCf/SiC)ceramic matrix composites have emerged as core candidate materials owing to their excellent comprehensive performance.However,the efficient densification of complex-shaped components remains a critical bottleneck restricting their engineering applications.The combined chemical vapor infiltration(CVI)and precursor infiltration and pyrolysis(PIP)process,by synergistically leveraging the advantages of CVI in fabricating a SiC matrix with high crystallinity and few defects and the characteristics of PIP in efficient pore filling and near-net shaping,provides an optimal technical pathway to address the issues of low densification efficiency,high cost,and unbalanced performance associated with single processes.This paper focuses on the synergistic mechanism of the CVI+PIP combined process.It systematically analyzes the parameter optimization strategies for key processing steps,including fiber preform fabrication,interphase tailoring,initial CVI densification,deep PIP filling,and post-treatment.The core advantages of this combined process in enhancing material density,optimizing microstructure,shortening the fabrication cycle,and reducing cost are elaborated in depth.Furthermore,the application examples and performance of the process in typical hot-section components such as combustor liners,turbine guide vanes,and exhaust nozzles are reviewed in detail.Finally,considering current technical challenges including process optimization,precise microstructural control,and the development of durable environmental barrier coatings,future research directions are proposed.This paper provides important theoretical support and technical references for the scale-up fabrication of high-performance SiCf/SiC composite hot-section components and the performance leap of aero-engines.
Aero engines and gas turbines,as national strategic equipment,have a profound impact on national defense security,energy security,and technological innovation.With technological advancements and the pursuit for enhanced efficiency,the combustion chamber temperatures of aero engines and gas turbines continue to rise,subjecting hot-section components to severe challenges of high temperature,oxidation and corrosion.Surface coating technology is a key solution to increase the service temperature and corrosion resistance of components,among which thermal barrier coatings,environmental barrier coatings,and integrated thermal/environmental barrier coatings are the mainstream protective coating systems.Regardless of the various coating systems,a bond coat is required between the top coat and the substrate(superalloy/ceramic matrix composite).This layer,designed with a matched coefficient of thermal expansion,effectively alleviates thermal stress and reduces the risk of coating cracking;its active elements can also react with oxygen to form a dense oxide layer,preventing substrate oxidation and thus determining the overall lifespan of the coating system.This paper systematically summarizes the material characteristics,technical advantages,and limitations of bond coats for different coating systems,and reviews the research progress.It introduces the preparation techniques for bond coats,analyzes their suitability in service environments,and identifies current technical bottlenecks in research.Finally,it discusses the future development trends of bond coat technology.
The miniaturization and thinning of high-temperature co-fired ceramics(HTCC)present challenges for maintaining mechanical properties,which is critical for packaging reliability.This study employed direct ink writing(DIW)technology to fabricate alumina HTCC structures with varying interlayer deflection angles,resulting in improved mechanical performance.By incorporating only 3 wt％of organic additives,we developed a water-based alumina slurry with 86 wt％solid content that exhibits shear-thinning behavior.Our results demonstrate that the mechanical properties peak when the interlayer deflection angle is 15°,though this configuration exhibits a higher degree of anisotropy.Conversely,a 90° deflection angle minimizes anisotropy.This work elucidates how different printing filling methods influence the mechanical properties of alumina HTCC and offers valuable insights and experimental evidence for enhancing the mechanical performance of 3D-printed HTCC materials.
As a highly reliable dielectric material,the study of BaTiO3 ceramic grain boundary defects is very important for the reliability of multilayer ceramic capacitors(MLCC).In this paper,a series of amphoteric rare earth element Dy-doped BaTiO3 ceramics(Dy:0.2,0.5,1.0,2.0,and 5.0 mol％)were prepared by the solid-phase method,and the effects of the defect types induced by the differences in the doping sites of the rare earth element Dy on the crystal-boundary defect of BaTiO3 ceramics were investigated.The results indicate that ceramic doped with 0.2 mol％Dy2O3 exhibit a grain size of 330 nm,conductivity activation energy of 1.534 eV,grain boundary barrier of 0.4645 eV,bandgap of 3.193 eV,and oxygen vacancy concentration of 32.67％.Notably,this composition demonstrates higher grain boundary activation energy and barrier potential among the investigated systems.The enhanced insulating properties of grain boundaries align with the stringent requirements for high-reliability dielectric materials.The defect analysis reveals that when Dy3+doping is below 1.0 mol％,Dy3+substitutes Ti4+ions to form acceptor doping,generating oxygen vacancies as donor states.This increases carrier concentration within the system,reduces grain boundary activation energy and barrier potential,consequently diminishing impedance capability.In contrast,at Dy3+concentrations exceeding 1.0 mol％,partial Dy3+replaces Ba2+to form donor doping,inducing barium vacancies due to charge compensation.These vacancies trap electrons,enhance effective acceptor states,and elevate grain boundary activation energy and barrier potential.This study demonstrates the significant role of grain boundary defects in the grain boundary barriers of rare earth doped BaTiO3 ceramics,providing a way to achieve high reliability of BaTiO3-based MLCCs.
Hexavalent chromium(Cr(Ⅵ))is a highly toxic and carcinogenic heavy metal pollutant,posing serious threats to the environment and human health.The development of efficient and cost-effective adsorbents is crucial for treating Cr(Ⅵ)-containing wastewater.In this study,porous carbon aerogels(CAs)with a three-dimensional network structure were prepared using resorcinol-formaldehyde as precursors and polydiallyldimethylammonium chloride(PDADMAC)as a soft template via sol-gel method,ambient pressure drying,and high-temperature carbonization.The regulation of PDADMAC dosage on the microporous structure of the carbon aerogels was systematically investigated,and their performance as adsorbents for the removal of Cr(Ⅵ)from water,as well as their compressive properties,were thoroughly evaluated.The results demonstrated that by adjusting the amount of PDADMAC,the pore structure of the carbon aerogels could be effectively tailored,achieving a transition from microporous to mesoporous structures.Adsorption experiments revealed that the abundant mesoporous structure provided low-resistance mass transfer channels for Cr(Ⅵ)compounds,resulting in an adsorption capacity of 102.34 mg·g-1 while maintaining compressive strength up to 7.08 MPa.The adsorption kinetics followed the pseudo-second-order model and the intra-particle diffusion model,which indicated that the process was dominated by chemical adsorption and exhibited multi-stage adsorption characteristics.This study demonstrates the preparation of high-performance carbon aerogels through structural regulation,offering a feasible strategy for the efficient adsorption of heavy metal Cr(Ⅵ).
Environmental Barrier Coatings(EBCs)critically determine the performance of SiC ceramic matrix composites(CMCs)in high-temperature water-oxygen environments.As a key component of EBCs,the bond coat must ensure adhesion between the coating and substrate while effectively blocking the penetration of oxidizing/corrosive media to the SiC substrate.Current widely studied bond coat materials,such as Si and Si+HfO2,are limited by the relatively low melting point of Si(～1410℃),restricting their upper service temperature.Oxide materials with higher melting points and inherent oxidation resistance have emerged as promising candidates for high-temperature bond coats.This article reviews the research progress on oxide-based bond coats,including mullite,SiO2-HfO2,HfO2-Al2O3-SiO2,cordierite and Yb2Si2O7,focusing on their fabrication techniques,material properties and oxidation/corrosion resistance.Among these,mullite and SiO2-HfO2 systems demonstrate significant application potential under specific conditions.Building on these findings,this work further addresses challenges in oxide bond coats,such as brittleness,controllable synthesis,limited oxidation resistance and interfacial bonding strength.The analysis provides foundational insights and guidance for the design,development,and performance optimization of next-generation oxide-based bond coats for ultra-high-temperature environments(≥1400℃).
Nd:LuAG transparent ceramics,due to their excellent optical,mechanical,and thermodynamic properties,as well as their moderate saturation fluence,demonstrate greater development potential as a gain medium in high repetition rate high-energy solid-state lasers.The co-precipitation method for synthesizing nano-powders offers advantages such as high chemical homogeneity and low synthesis temperature.Nano-powders with high sintering activity can significantly reduce the densification temperature and time,as well as greatly decrease the grain size of ceramics.It is a commonly used and effective method for preparing garnet-based transparent ceramic powders.Using nitrate as raw material and ammonium bicarbonate as precipitant,lat.％Nd:LuAG nano-powders were prepared via the co-precipitation method.The nano-powders exhibit a single LuAG phase with an average primary particle size of approximately 97nm.The lat.％Nd:LuAG transparent ceramics were prepared by vacuum pre-sintering at 1450～1650℃ for 3h and HIP post-treated at 1500℃for 3h under 200MPa.The effect of the vacuum pre-sintering temperature on the microstructure and optical transmittance was investigated.The experimental results indicate that when the vacuum pre-sintering temperature is 1550℃,the in-line transmittance of the 1.5mm thickness lat.％Nd:LuAG transparent ceramics with an average grain size of 927nm is 83.6％at 1064nm.The successful preparation of fine-grained,high-optical-quality Nd:LuAG transparent ceramics is of great significance for enhancing the performance of high repetition rate nanosecond high-energy solid-state lasers.
12CaO·7Al2O3(C12A7),known as mayenite,is a major phase in calcium aluminate cement and an intermediate formed during Portland cement production.In recent years,the electride derived from C12A7 has exhibited substantial potential in catalysis and related domains.This review focuses on advances in catalysis enabled by the mayenite electride(C12A7:e-).We first introduce the basic concept of electrides and their historical development,and elucidate the structural features of C12A7:e-alongside its distinctive position in materials science.We then systematically summarize its crystal-structural characteristics and principal synthesis strategies,analyzing how different preparation routes influence the resulting material properties.Subsequently,we highlight the performance of C12A7:e-across multiple catalytic reactions,including ammonia synthesis and ammonia decomposition(cracking),and delineate its advantages in enhancing catalytic activity and selectivity.Finally,we identify key challenges for practical deployment—such as chemical stability and scalable production-and offer an outlook on expanding its applications in energy and environmental catalysis through structural tuning and process optimization.
The basic mechanical properties of advanced ceramics are crucial for the design,preparation,and safe application of ceramic components.Although there are various standards at home and abroad to specify the testing of these properties,young researchers and designers of ceramics often have some problems in terms of operation or sample preparation during the performance testing process.In order to facilitate accurate understanding and acquisition of the basic mechanical properties of advanced ceramics,the main testing principles and standard testing methods by bending for elastic modulus,bending strength,and fracture toughness of advanced ceramics were summarized in this paper.The most commonly used standard testing methods,as well as related sample requirements,testing devices,testing procedures,and calculation methods are discussed.It is helpful and for accurate characterization and evaluation of the mechanical properties of advanced ceramic materials.
Fiber reinforced ceramic matrix composites(FRCMCs)exhibit exceptional properties,including high strength,fracture toughness,thermal stability,corrosion resistance,and oxidation resistance,rendering them highly promising for applications in aerospace,energy,and advanced manufacturing sectors.However,their extreme hardness,brittleness,intrinsic anisotropy,and heterogeneous microstructure pose significant machining challenges,often leading to machining-induced defects such as burrs,chipping,and delamination.Conventional machining technologies such as grinding,cutting,drilling,and milling are widely employed for FRCMCs but suffer from issues like severe tool wear and low machining efficiency.In contrast,non-traditional machining technologies such as laser machining(LM),ultrasonic assisted machining(UAM),electrical discharge machining(EDM),and abrasive water jet machining(AWJM)offer advantages like non-contact operations and reduced mechanical stress.Despite these benefits,they face limitations including high equipment requirements,complex parameter optimization,and immature process technologies.This paper comprehensively reviews the current research progress in both conventional and non-traditional machining technologies for FRCMCs.The machining mechanisms,critical influencing factors,and comparative advantages/disadvantages of these technologies are also systematically analyzed.Looking forward,research directions in machining of FRCMCs should focus on in-depth exploration of material removal mechanisms,optimization of process parameters,and development of high-precision hybrid machining technologies.
Transparent spinel-type aluminum oxynitride(γ-AlON)ceramics have emerged as a highly promising material for military protection(e.g.,infrared windows,armor materials)and civilian optics(e.g.,lenses,semiconductor devices)due to their excellent optical properties(high transmittance,broad transmission band),outstanding chemical stability,and superior mechanical strength.Transparent ceramics require not only high optical transmittance but also high mechanical properties,which is the fundamental prerequisites for the practical application of AlON ceramics.The incorporation of sintering aids is a critical strategy in fabricating transparent AlON ceramics,as optimizing their type and content allows precise control over microstructural evolution during sintering,including grain nucleation and growth,phase distribution,and overall densification.Consequently,these microstructural modifications directly influence the ceramic's properties,such as,optical transmittance,mechanical strength,and chemical stability,enabling their effective regulation and optimization for advanced applications.This paper comprehensively reviews the research progress on sintering aids for preparing high-quality AlON transparent ceramics.The sintering aids are categorized into rare earth oxides(Y2O3,La2O3,and Pr2O3),alkaline earth oxides(CaCO3and MgO),and silicon-based compounds(SiO2 and Si3N4).The review delves into the effects of these aids on the optical and mechanical properties of AlON transparent ceramics and details their mechanisms in promoting densification,optimizing grain size distribution,suppressing phase decomposition,and lowering sintering temperature.Optimal sintering aids facilitate pore elimination and suppress abnormal grain growth via liquid-phase formation or pinning effects,thereby enhancing optical transmittance while simultaneously improving mechanical properties(hardness,fracture toughness,and strength)through microstructural refinement.The mechanisms of sintering aids in AlON densification vary significantly depending on their chemical nature.Specifically,rare-earth additives predominantly facilitate liquid-phase sintering,alkali metals induce grain-boundary pinning effects,while silicon-based compounds primarily form solid solutions.This review also analyzes the existing problems and challenges in current research and looks forward to future research directions,aiming to provide theoretical guidance and technical reference for the preparation of high-performance AlON transparent ceramics.
With the continuously increasing performance requirements for high-temperature structural materials in aerospace,energy,and other fields,traditional 8YSZ(8 wt％yttria-stabilized zirconia)thermal barrier coating(TBC)materials have gradually revealed limitations such as insufficient phase stability at elevated temperatures and rising thermal conductivity,making them inadequate for extreme service environments like next-generation high thrust-to-weight ratio engines.La2Zr2O7,as a typical A2B2O7-type rare-earth zirconate,exhibits promising potential in TBC applications due to its low thermal conductivity,(～1.2 W·m-1·K-1@1000℃),high melting point(～2300℃),high-temperature structural stability,and excellent sintering resistance.High-performance powder serves as the foundation for preparing high-quality coatings,and extensive research has been conducted on La2Zr2O7 powder synthesis.This paper systematically reviews the main synthesis methods for La2Zr2O7 powder,including solid-state reaction,chemical co-precipitation,sol-gel,self-propagating high-temperature synthesis(SHS),and molten salt synthesis,analyzing their characteristics and applicability in terms of synthesis conditions,powder morphology,and phase structure control.Furthermore,the influence mechanisms of La2Zr2O7's crystal structure on its thermophysical properties are explored,with emphasis on the intrinsic relationship between preparation processes and structural evolution,as well as the impact of crystal structure variations on its TBC performance parameters(e.g.,thermal conductivity,thermal stability,and thermal shock resistance).Current challenges and unresolved issues in research are identified,and future directions are proposed.This work aims to provide theoretical insights and technical references for advancing La2Zr2O7 powder research and engineering applications.
To address the issue of electromagnetic pollution exacerbated by new wireless communication technologies, the development of efficient electromagnetic wave (EMW) absorption materials is crucial. MXenes, as a typical class of two-dimensional nanomaterials, have gained attention as efficient EMW absorbers due to their abundant surface chemistry, large specific surface area, excellent electrical conductivity, and good mechanical properties. However, the preparation of novel MXenes and the elucidation of their electromagnetic wave absorption mechanisms remain to be further explored. This paper first provides a review of the preparation processes of MXene materials, with a focus on traditional MXene preparation methods such as HF etching, HF in-situ etching, and molten salt etching, and also discusses the prospects for the preparation of high-quality MXenes and new multi-component MXenes. In terms of EMW absorption, the paper emphasizes the impact of MXene morphology design, defect engineering (such as doping and vacancies), and the construction of heterogeneous structures (composites with magnetic, dielectric, and polymeric materials) on the EMW absorption performance. Based on these factors, design strategies for MXene-based EMW absorption materials are proposed. Additionally, the electromagnetic wave absorption mechanisms of MXene-based materials are clarified, and future prospects for multifunctional and ultra-broadband EMW absorption applications of MXene-based materials are discussed.
Silicon nitride (Si3N4) bioceramics exhibit promising potential in bone tissue engineering and implant materials due to their outstanding mechanical properties, biocompatibility, bioactivity, and remarkable antibacterial characteristics. This review systematically summarizes the crystalline phase structure, microstructure, and surface chemical properties of silicon nitride ceramics. It discusses the effects of grain size, grain boundary characteristics, and sintering processes on mechanical strength and toughness, as well as the mechanisms through which surface oxidation and hydrolysis release bioactive compounds such as silicates and ammonia, promoting osteogenesis and inhibiting pathogens. Moreover, composite materials of silicon nitride with graphene, silicon carbide whiskers, and other nanomaterials have significantly improved mechanical performance and have been successfully applied in spinal fusion, hip joint replacement, and dental restoration, demonstrating superior osseointegration, low wear, and excellent antimicrobial effects. However, inherent brittleness and slow degradation rates still limit wider clinical applications. Future research should focus on developing novel silicon nitride composites with graphene and carbon nanotubes to precisely regulate degradation rates, employing artificial intelligence to optimize sintering processes for accurate microstructural control, and conducting multicenter clinical trials to comprehensively evaluate long-term safety and effectiveness, thereby offering more efficient, safe, and reliable solutions for bone defect repair and regenerative medicine.
Aluminum oxide(Al2O3),as a high-performance structural ceramic material with high melting point,high toughness,good chemical stability,and excellent wear resistance,is one of the best candidate materials for high-temperature wear resistant components.It has been widely used in aerospace materials,military industry,and biomedical fields.However,most ceramic materials do not have lubrication functions,especially under dry friction and high temperature conditions,where the friction coefficient and wear rate are relatively high.Therefore,the main strategy for preparing ceramic lubricating composite materials is to introduce single or complex solid lubricating components into the ceramic matrix,in order to form a lubricating film or transfer film during the friction process to achieve anti friction and anti-wear effects.Meanwhile,the inherent brittleness and high wear performance of Al2O3 ceramic materials greatly limit their applications in related fields.Therefore,how to improve the mechanical properties of Al2O3 ceramics is crucial for their application.In order to clarify the influence of different lubricating phases on the composition,microstructure,and mechanical properties of AlO3 ceramics,three different lubricants,graphite,Mo,and LaF3,were selected to be added to the Al2O3 ceramic lubricating material matrix.A series of Al2O3 ceramic lubricating materials were prepared by hot pressing sintering method.Then,the properties of the material were studied using X-ray diffraction(XRD),scanning electron microscopy(SEM),BET,and three-point bending methods,and the influence of lubricant type and content on the microstructure and mechanical properties of Al2O3 was analyzed.The results indicate that the type and content of lubricants have a significant impact on the microstructure and mechanical properties of the material.As the content of non-metallic lubricating phases increases,the hardness,bending strength,and fracture toughness of the composite material decrease significantly.Adding Mo can significantly improve the strength and toughness of composite materials,mainly because Mo not only makes Al2O3 denser,but also plays a role in ductile phase toughening.
C/SiC composites are regarded as ideal candidate materials for aerospace hot-section components due to their excellent high-temperature properties.However,carbon fibers undergo rapid oxidation in environments above 400 ℃,which severely limits their service temperature.Therefore,improving the high-temperature oxidation resistance of C/SiC composites is of significant practical importance for promoting their engineering application in aerospace thermal systems.Based on coating system design principles,this study selected ZrB2 as the main component of the coating,with SiC and B incorporated to enhance oxidation resistance.The coating was prepared through a two-step process of low-temperature curing and high-temperature sintering,resulting in a ZrB2-SiC composite coating.Orthogonal experimental design was employed to investigate the effect of composition ratio on coating performance and to optimize the coating formulation.The composition and microstructure of the coating were characterized by XRD and SEM,and the oxidation resistance of the coated composites was evaluated.The results indicate that the coating applied on the C/SiC composite consists of ZrB2 and SiC,with a thickness of approximately 200 μm.It is uniform and dense,without obvious through-thickness cracks.The content of SiC has the most significant influence on the oxidation weight loss rate and the interfacial bonding strength between the coating and the composite.The optimized composition was determined as follows:60wt.％ZrB2,4wt.％SiC,6wt.％PCS,4wt.％B,and 26wt.％DVB.The interfacial bonding strength between the coating and the substrate reached 2.01 MPa.The coated C/SiC composite exhibited an oxidation weight loss rate of only 0.54％and a strength retention rate of 97.3％.Under high-temperature oxidizing conditions,SiC reacts with oxygen to form a SiO2 protective layer.Compared to B2O3,SiO2 exhibits higher viscosity,higher melting point,lower oxygen diffusion coefficient,and lower vapor pressure,resulting in superior oxidation resistance.The combined action of the SiO2 and ZrO2 layers effectively inhibits oxygen inward diffusion,preventing further oxidation of the material and significantly improving the overall oxidation resistance of the composite.At 1200 ℃,SiO2 can react with B2O3 to form borosilicate glass,which enhances the density and adhesion strength of the coating.The developed coating system demonstrates excellent anti-oxidation performance.
Zirconia has broad application prospects in the industry,but unlike metal materials,it is difficult to control the microstructure and improve mechanical properties of ceramics through post heat treatment.This article proposes a plasma treatment technique at room temperature and studies the effects of plasma treatment and applying current on the microstructure of ceramics,achieving grain size control of dense 3YSZ(3mol％yttria stabilized zirconia)ceramics.The results indicate that plasma treatment can promote the grain size of 3YSZ ceramics from submicron(0.45 μm)to tens of microns(＞90 μm)in a short period of time.Applying current has a promoting effect on the rapid grain growth of ceramics.When the current is 1.0 A,the maximum grain size of zirconia can reach 255 μm,which is approximately 565 times larger than the initial grain size.The rapid grain growth caused by this plasma treatment can be attributed to the enrichment of oxygen vacancies induced by the electric field and the influence of plasma action on the rapid migration of grain boundaries.Compared with traditional heat treatment,plasma treatment technology has the advantages of high efficiency and low energy consumption,providing new ideas for ceramic microstructure control and single crystal material preparation.
