Preparation method of gradient layered structure silicon nitride ceramic

Abstract

The invention discloses a preparation method of a gradient layered structure silicon nitride ceramic, the preparation method comprises the following steps: firstly, screening out a surface modifier capable of effectively reducing the refractive index difference of silicon nitride ceramic particles, and increasing the curing depth of the surface modifier; the applicant reveals a photocuring forming mechanism of the modified silicon nitride ceramic slurry by comparing rheological properties, dynamic stability, wettability and photocuring properties of the silicon nitride ceramic slurry before and after modification. By utilizing the mechanism, the rheological property, the dynamic stability, the wettability and the photocuring property of the silicon nitride ceramic slurry are improved, and the silicon nitride ceramic with high density, hardness and fracture toughness can be prepared.

Description

technical field [0001] The invention relates to the technical field of forming silicon nitride ceramics, in particular to a method for preparing silicon nitride ceramics with a gradient layered structure. Background technique [0002] Due to its high hardness, low thermal expansion coefficient and high fracture toughness, silicon nitride ceramics are widely used in industrial fields such as exhaust valves, valve springs, bucket tappets, and rocker pads. Silicon nitride ceramics have both high wear resistance and thermal shock resistance, making them widely used in the field of machining. Because of its excellent thermoelectric properties and corrosion resistance, it has also been widely used in the fields of thermal conductors, valves, catalyst carriers, spark plugs and other motors. In addition, its excellent comprehensive physical properties make it a candidate material for high-temperature gas-cooled reactor fusion reactors. [0003] At the same time, the silicon nitrid...

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Problems solved by technology

[0005] However, there are relatively few reports on the light-curing forming technology of nitride ceramics, especially gray or dark nitride ceramics.

This is due to the high UV absorption of silicon nitride ceramics, high refractive index, strong scattering, low curing depth of slurry, and difficulty in forming

At the same time, the strong covalent bond characteristics of nitride ceramics also make it difficult to sinter and densify

Only Huang et al. oxidized silicon nitride powder to generate nano-SiO on its surface. 2 film, which reduces the refractive index difference with the premix solution, and prepares Si with a density of 97.84%. 3 N 4 Ceramic, but SiO 2 The presence of can lead to a significant decrease in its mechanical properties

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