Preparation And Oxidation Properties Of (Ta,Zr)C Solid Solution Ceramics

With the rapid development of the aerospace industry,the performance of various high-temperature thermal structural materials has put forward higher requirements.（Ta,Zr）C solid solution ceramics have excellent high temperature mechanical properties and antioxidant ablation properties,and are one of the ideal thermal structural material systems suitable for aerospace applications.In this paper,several（Ta,Zr）C solid solution ceramic powders with different solid solution ratios were prepared by a solvent heat-carbon heat reduction process.The effects of the process parameters of the solvothermal and carbothermal reduction processes on the composition and structure of the powders were investigated in detail.The（Ta,Zr）C solid solution ceramic powders with specific composition points were selected and rapidly densified using discharge plasma sintering（SPS）to obtain（Ta,Zr）C solid solution ceramic bulk,and the oxidation properties of（Ta,Zr）C solid solution ceramics were investigated.The main conclusions are as follows.（1）Thermodynamic calculations show that the synthesis temperature of（Ta,Zr）C ceramic powder gradually increases with the increase of Zr C content;the actual reaction results show that the synthesis temperature of（Ta,Zr）C ceramic powder has a tendency to increase and then decrease with the increase of Zr C content.The deviation of the thermodynamic calculation is mainly due to the influence of the diffusion kinetics between atoms not considered.（2）The solvent heat and carbon thermal reduction process parameters have a great influence on the microscopic morphology,crystal structure,particle size and dispersion of the powder.The results show that the precursors synthesized with atomic concentrations of Ta and Zr of 0.16mol·L^-1 and 0.44 mol·L^-1,a solvothermal temperature and time of 200°C and 20 h,a molar ratio of Ta and Zr atoms to acetylacetone of 1:3,and ethanol as solvent at 1700°C under vacuum.The（Ta,Zr）C solid solution ceramic powder with fine particle size,good dispersion,high purity and single-phase structure can be obtained.（3）Several（Ta,Zr）C solid solution ceramic powders with different solid solution ratios were prepared using the optimal process parameters.The grain size of the powder particles was between 21 and 31 nm,which belonged to the category of nanocrystals,with an average particle size of about 148 nm,a monodisperse particle size distribution,a specific surface area of 39.7 m²/g,and a uniform distribution of elements in the micro-nano scale.（4）Three（Ta,Zr）C ceramic blocks with specific composition points,namely Ta₄Zr C₅,Ta Zr C₂,and Ta Zr_2.75C_3.75,were rapidly prepared by SPS process using the prepared solid solution ceramic powder as raw material.the densities of the prepared solid solution ceramics were 98.06%,98.15%,and 96.74%,respectively.The oxidation properties of the three（Ta,Zr）C solid solution ceramic blocks were investigated by static and dynamic oxidation methods.The results showed that the oxidation rate constant decreased and the oxidation activation energy increased with the increase of Zr C solid solution amount in the three（Ta,Zr）C solid solution ceramics.Among them,Ta Zr_2.75C_3.75 has the lowest oxidation rate constant and the highest oxidation activation energy,which are 0.74-1.77×10-5g²/（cm⁴·min）and 113.43 KJ/mol,respectively.a study of the physical phase of the oxidized oxide layer found that with the increase of Zr C content,the ternary oxide in the oxide layer Ta Zr_2.75O₈ content increases.Ta Zr_2.75O₈ has a lower oxygen diffusion coefficient,which correspondingly decreases the diffusion coefficient of oxygen in the oxide layer,thus making Ta Zr_2.75C_3.75 have a better oxidation resistance.There are 58 pictures,13 tables and 100 references in this study...