A kind of preparation method of conductive network structure si3n4 ceramics

Abstract

The invention discloses a making method for Si3N4 ceramic of a conductive network structure. The making method comprises the steps that 1, Si powder is used as a raw material, Al2O3-Re2O3 is used as a sintering aid, and mixing, ball-milling and drying are carried out to obtain Si-Al2O3-Re2O3 mixed powder, wherein Re refers to the rare earth element; 2, the Si-Al2O3-Re2O3 mixed powder obtained in the step 1 is shaped and pre-sintered in a nitrogen atmosphere, and a green body obtained after pre-sintering is soaked in MO2 sol for 0.5-24 hours, dried and subjected to secondary sintering in the nitrogen atmosphere to make the Si3N4 ceramic of the conductive network structure. The relative density of the obtained Si3N4 ceramic is larger than 95%, the conductivity reaches 1,000-3,000 Sm-1, the hardness is 8-20 GPa, the breaking tenacity is 6-12 MPa m<1 / 2>, and the bending strength is 800-1,200 MPa. The Si3N4 ceramic can be processed into workpieces in any shape by means of electrical discharge machining, especially workpieces with complicated shapes like ceramic turbine blades, and common Si3N4 ceramic on the market currently does not have the characteristic.

Description

technical field [0001] The invention specifically relates to a conductive network structure Si 3 N 4 Methods of preparation of ceramics. Background technique [0002] Si 3 N 4 Ceramics have excellent properties such as wear resistance and high temperature resistance, and are widely used in high-speed cutting tools and key parts of engines. Usually Si 3 N 4 Ceramics with high purity Si 3 N 4 The powder is prepared by hot pressing and sintering as raw material, the cost is high, and samples with complex shapes cannot be prepared. [0003] In order to reduce costs and prepare complex shapes, Si powder was used as raw material to prepare Si by reactive pressure sintering. 3 N 4 ceramics. On the one hand, the powder preparation and ceramic densification are combined in one step, which significantly reduces the cost; on the other hand, through gas pressure sintering, Si 3 N 4 Preparation of ceramics. However, since the nitriding speed of Si powder is relatively slow,...

AI Technical Summary

Problems solved by technology

Preparation of Si by reactive pressure sintering of Si powder 3 N 4 There are two main problems in ceramics: (1) The nitriding time of Si powder is long, and it needs to be kept at 1400°C for 8 hours; (2) Si powder 3 N 4 Densification conditions are too harsh, high nitrogen pressure (10atm), high sintering temperature (1900°C), long holding time (12h)

In addition, Si 3 N 4 Because of its high hardness and high brittleness, ceramics are difficult to process, especially they cannot be used for EDM to form workpieces with complex shapes, thus limiting their industrial application

[0004] If in Si 3 N 4 Ceramics are added to the conductive network structure. The traditional method is to directly mix the conductive phase, such as TiN or TiCN, etc., and there are the following problems: 1) It needs a large amount of mixing to achieve a good conductive effect, usually about 40%, and the existing technology is difficult. A network-like distribution is formed when less conductive phases are introduced; 2) Adding too much conductive phase is not conducive to the sintering and densification of ceramics, and ceramics are prone to agglomeration, resulting in uneven distribution