Surface modification method for ruthenium in situ wrapping ultramicro high purity Si3N4 powder

Abstract

The present invention discloses an improved method with a ruthenium enveloped with super-micro and high-pure Si3N4 powder; because of the much less grain diameter of the super-micro and high-pure Si3N4 powder, the powder is easy to be reunited after being collected. The present invention is characterized in that: the method uses the super-micro powder to compose in the high-distributed situation in the lasting stage to make the chemical treatment on the surface directly; a ruthenium amorphism phase much inerter to oxidation is enveloped on the surface of the high-distributed one-off Si3N4 grain; the improved method on the surface of super-micro powder is with the especial advantage, which can not only improve the distribution character for the super-micro powder and avoid the hard solid reuniting, but also can change the physical and chemical performance for the powder surface. The material satisfies the requirement of the grain size for silicon nitride. The method can add the component separately and evenly in the farthest degree without needing other expensive device and establishment; the method has the advantages of simple technical and low cost; the method can enchance the density of the elementary blank and the baking activity; compared with the physical phase aggradation method, chemical phase aggradation, vacuum spraying and ion plating and so on, the method is with much lower cost.

Description

technical field [0001] The invention relates to the technical field of high-performance structural ceramic materials, in particular to a ruthenium in-situ wrapping ultrafine high-purity Si 3 N 4 Surface modification method of powder Background technique [0002] The unique characteristics of silicon nitride ceramics, such as high temperature resistance, oxidation resistance, thermal shock resistance, and high temperature self-lubrication, make it an outstanding representative of extreme high temperature structural materials. Due to the strong covalent nature of the silicon-nitride (Si-N) bond, Si 3 N 4 In the sintering process, the self-diffusion coefficient of Si and N atoms is very low, and it is extremely difficult to sinter and densify, which leads to the increase of the sintering temperature to close to Si. 3 N 4 decomposition temperature. In order to change this situation, the more typical method is by adding metal oxides (Al 2 o 3 , Y 2 o 3 , MgO, etc.) to f...

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Problems solved by technology

In order to change this situation, the more typical method is by adding metal oxides (Al 2 o 3 , Y 2 o 3 , MgO, etc.) to form a liquid phase co-solution, lower the sintering temperature, and promote sintering densification, but the low melting point liquid phase surrounds Si in the form of a glass phase during cooling 3 N 4 Grains, most of the additive cations are often enriched in the glass phase of the grain boundary, and the glass phase has a disordered loose structure, which is prone to structural relaxation and creep at high temperatures, and is likely to evolve into a fast channel for the diffusion of internal and external ions. High-temperature performance of highly degraded materials

Some researchers proposed to use rare earth oxides as additives to make Si 3 N 4 Grain boundary crystallization, the coarse grains produced by liquid phase sintering cannot be improved, and the improvement of material performance is limited

[0003] With the development of nanotechnology, the sintering temperature is lowered by reducing the particle size of the powder, and the dense green body is obtained by ultra-high pressure, hot isostatic pressing, hot pressing and other methods to promote densif