Novel SiC synthesis method applicable to SiC solid phase sintering

Abstract

Most of the present production processes of SiC sintered bodies require some powder mixing using a mechanical milling process (ball milling, and so on). In this case, relatively long hours are required, and there is the problem of contamination during the preparation process. To avoid these problems, we developed a new process for obtaining a self-sinterable, stoichiometric SiC powder, whose precursor material is water-soluble; the precursor material was synthesized from aqueous silica and citric acid containing a small amount of aluminum compound. In order to obtain the stoichiometric SiC composition, the above aqueous precursor material was adequately cured in air (200°C-400°C); subsequently carbonization reaction (~800°C) in nitrogen atmosphere, carbothermal reduction (~1600°C) in argon atmosphere, and pressureless sintering (~1900°C) were performed. Among these processes, the curing process (cross-linking process) is very important for obtaining the equivalent composition (silica and carbon) for the subsequent carbothermal reduction. In this study, the adequate curing temperature and suitable preparation condition for the carbothermal reduction were investigated for the production of stoichiometric self-sinterable SiC powder. The pressureless sintered body achieved using the obtained SiC powder demonstrated a desirable trans-crystalline fracture behavior. K E Y W O R D Sprecursors, silicon carbide, sinter/sintering

A new process for creating a solid‐phase sintered body using a unique densification process between powders

“…Regarding the composition of the interstice, we have another solution to prevent the above undesirable phenomena. That is, aqueous silica‐compound 10 containing equivalent carbon with aqueous aluminum compound is useful.…”

“…This article is protected by copyright. All rights reserved aqueous silica-compound [10] containing equivalent carbon with aqueous aluminum compound is useful.…”

“…Regarding the composition of the interstice, we have another solution to prevent the above undesirable phenomena. That is, aqueous silica-compound 10 containing equivalent carbon with aqueous aluminum compound is useful. We explain the abovementioned aqueous silica compound containing equivalent carbon as an organic polymer with aqueous aluminum compound.…”

Morphological changes and their thermal conductivities of MgO crystals containing various impurities (B, Ca, Si)

“…The concentrations of the impurities were controlled within the range of 0‐3 wt% as B 2 O 3 , CaO, and SiO 2 in the MgO powder. The aqueous silica was prepared by the condensation reaction of tetraethoxysilane (44.2 mL) (Wako Pure Chemical Corporation, Japan) and ethylene glycol (44.6 mL) (Wako Pure Chemical Corporation, Japan) 10 . In the obtained mixture, citric acid (0.3 mol) (Wako Pure Chemical Corporation, Japan), distilled water (50 mL), and ethylene diamine (20 mL) (Wako Pure Chemical Corporation, Japan) were sequentially added with constant stirring.…”

Pressureless solid-state sintering of SiC ceramics with BN and C additives

“…Solid-state sintered SiC ceramics are important hightemperature structural materials because of their useful engineering properties such as strength retention at high temperatures, high oxidation resistance, high hardness, high thermal conductivity, and excellent thermal shock resistance [1,2,3,4,5,6,7,8,9]. Owing to the high covalency (~88%) of Si-C bonds, the selfdiffusion coefficient of SiC is very low.…”