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 covalency of silicon-nitride (Si-N) bonds, 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 form a liq...

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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 densification, but these methods also have certain limitations. On the one hand, the surface properties of ultrafine powder particles are lively, easy to adsorb and agglomerate, and difficult to disperse. Although methods such as ultra-high pressure, hot isostatic pressing, and hot pressing can overcome the soft agglomeration of powder, the problem of hard agglomeration of powder has not been solved. Can be solved, but hard agglomeration causes uncontrollable grain growth, can not obtain the ideal microstructure, and affects the final performance

On the other hand, the addition of additives makes it difficult to disperse evenly on the surface of the substrate, resulting in uneven distribution of additives, often making the doping effect fail to meet the expected requirements. Some impurity ions will cause secondary pollution and affect the sintering performance and reliability of silicon nitride ceramics

Further developed physical vapor deposition, chemical vapor deposition, vacuum sputtering, ion plating and other methods for Si 3 N 4 Although the surface modification of powder has a certain effect, the equipment is complicated and the cost is high, and large-scale production cannot be realized