A kind of non-melting pretreatment of polycarbosilane and its cracking conversion method for three-dimensional ceramics

Abstract

A polycarbosilane non-melting pretreatment and its cracking transformation method for three-dimensional ceramics relate to the preparation of ceramic materials. Synthesize the three-dimensional silicon carbide polymer precursor first, prepare SiC(Al,rGO)p ceramic particles by pyrolysis at high temperature under the protection of an inert atmosphere, mix with the precursor powder by ball milling, then dry, press into tablets and sinter at high temperature again to obtain 3D‑SiC (Al,rGO) ceramics, and finally modify the surface morphology of ceramics. The three-dimensional ceramic material contains four elements: Si, C, O, and Al, and Al is evenly distributed in SiO in an atomic state. x C y In the amorphous phase, β-SiC nanocrystals are embedded in SiO composited with rGO x C y / C free In the amorphous phase, there is SiO 2 Microcrystalline. Expand the crosslinking degree and molecular weight of the precursor to form a three-dimensional network structure, reduce the evaporation of small molecule gas during cracking, improve the fracture toughness and high temperature stability of ceramics, and meet the harsh environment applications such as high temperature.

Description

technical field [0001] The invention relates to the preparation of ceramic materials, in particular to a polycarbosilane non-melting pretreatment and a method for cracking and transforming three-dimensional ceramics. Background technique [0002] Silicon carbide (SiC), as an advanced ceramic material, has excellent mechanical properties, wide band gap, high electron mobility, chemical stability, high temperature resistance, corrosion resistance, etc. Power and other harsh environmental conditions also show excellent performance, often used to make corrosion-resistant materials, wear-resistant materials, high-temperature structural components, diodes, etc., in microelectronic systems, machinery, petroleum, chemical industry, metallurgy, aerospace, It is widely used in national defense and other fields. [0003] At present, silicon carbide ceramics can be obtained by normal pressure sintering, hot pressing sintering, reaction sintering and other preparation methods. Chinese ...

AI Technical Summary

Problems solved by technology

Despite the significant advantages of the precursor conversion method, there are certain difficulties in the preparation of SiC 3D ceramics

Low molecular weight polycarbosilane precursors are not easy to form at room temperature, and it is difficult to convert into three-dimensional ceramics

Polycarbosilane releases a large amount of H during pyrolysis 2 、CH 4 , SiO, CO and other small molecular gases shrink the ceramics, and there are defects inside, resulting in poor mechanical properties such as fracture toughness of the ceramics, resulting in a large number of cracks, which eventually cause serious damage and cannot be molded.

Chinese patent ZL 201711494377.7 discloses a method for preparing graphene / silicon carbide monolithic ceramics by high-temperature pyrolysis of graphene oxide-vinyltriethoxysilane-polycarbosilane precursors, which has made new achievements in the field of precursor ceramics. Breakthrough, but the resulting monolithic ceramics have poor overall performance

Chinese patent CN 110467467 A discloses a method of blending and re-cracking, which enables graphene / silicon carbide monolithic ceramics to have higher ceramic yield and lower linear shrinkage, but high-temperature cracking of the silicon carbide precursor is still inevitable A large number of small molecular gases are produced, and there are still many pores and defects on the ceramic surface on the microscopic scale, and the high temperature resistance and fracture toughness need to be improved, which limits the application of silicon carbide ceramics.

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