Hafnium carbide ceramic material additive

At present, the method of synthesis of hafnium carbide at home and abroad is not much reported, the original method, generally need to be above 1900℃ to react, high energy consumption, high requirements for equipment, and grow out of the particle size, need to use other methods to reduce the reaction temperature. (2) Liquid phase precursor conversion method. Wang Yanbin et al. used HfoCl2, HCl, HNO3, n-propanol, isopropanol, ethanol, acetyl and other HFC powders with sizes ranging from tens of nanometers to hundreds of nanometers, and the particles had serious agglomeration. KarlsruheGmbh et al. successfully prepared hafnium carbide by vapor deposition with HfCl4 and appropriate amount of CH4 and H2 as raw materials. This method has a long reaction time.
The hafnium carbide block was prepared by firing 8 hours in atmosphere atmosphere. The hafnium carbide block is decarburized in an oxidizing atmosphere at 550℃ for 12 hours to form hafnium carbide powder. [0049] The raw materials used are 99.99% pure. Nanometer hafnium carbide powder by aerosol ablation method, powder activity is high, the surface energy is large, widely used in powder metallurgy, hafnium carbide (HFC)=185.501, containing 6.47% carbon, belongs to the sodium chloride cubic crystal system, theoretical density 12.7g/cm3, melting point 3890℃, is a single compound in the high melting point. Volume resistivity Ω 1.95 x 10-4 cm (2900 ℃), thermal expansion coefficient of 6.73 x 10-6 / ℃. With very high elastic coefficient, good electrical and thermal conductivity, small thermal expansion coefficient and good impact resistance, ultra-fine hafnium carbide and many compounds (such as ZrC, TAC, etc.) to form a solid solution.
Ali hafnium carbide ceramic additive has been widely used in aerospace and other national defense fields. The coating technology is an effective means to solve the bottleneck problem. Among them, oxidation resistance and good physical and chemical compatibility with C/C composite material, material. However, the brittleness of ceramic coating is the bottleneck problem which is difficult to break through in practical application. The main reason of anti-oxidation failure is that the thermal expansion coefficient of ceramic coating and matrix does not match, which leads to the existence of large thermal stress, which leads to the ceramic coating cracking easily in the process of high and low temperature alternating process, resulting in the failure of the coating. In order to alleviate the tendency of coating cracking, degree coating, composite coating and the introduction of second-phase toughening coating technology have attracted great attention of researchers. The porous SiC inner coating was prepared by two-step embedding method. Secondly, the pores in the inner SiC coating are filled with Si and SiC particles by embedding method. Technology, however, reduces the thermal stress in the coating to a certain extent.
In order to improve the mechanical properties, the preparation methods of boron nitride, zirconia and yttrium oxide materials are improved compared with the pure reaction sintered Si3N4 materials, but fail to achieve a more ideal effect. Therefore, it is a difficult point for engineering ceramics to continue to find a method to improve the mechanical properties of the reaction sintered Si3N4 multiphase ceramics. The purpose of the invention is to provide a preparation method of silicon nitride – hafnium carbide multiphase ceramics, which is simple in operation, industrial production, and the product is non-shrinkage and has good performance. The preparation method of the silicon nitride – hafnium carbide multiphase ceramic is obtained by mixing with spinel. The preparation method of the silicon nitride – hafnium carbide multiphase ceramics described in the invention is: (1) the raw materials and media are ball mashed to get a evenly mixed slurry, the slurry is dried and screened, and the powder is formed; (2) The preformed powder is put in the die to press the blank, and the blank is treated by cold isostatic pressing to get the presintered body; (3) Put the pre-sintered body into the vacuum sintering furnace and pass nitrogen into it.

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