サブマイクロメーターサイズ粉体を用いたSiCのプロセッシングと力学特性へ及ぼすナノメーターサイズSiC粉体の混合効果

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An 800nm-SiC powder (75vol%) was mixed with a 30nm-SiC powder (25vol%) in a 0.05-0.3 M-Y (NO_3)_3 solution containing an Al_2O_3 powder of median size 0.2μm at pH 5 to distribute homogeneously the sintering additives (Al_2O_3+yttrium ions) around the SiC particles. In a 20vol% SiC suspension, the network structure of negatively charged SiC particles was formed by the heterocoagulation through the positively charged Al_2O_3 and yttrium ions. Addition of polyacrylic acid increased the dispersibility of colloidal SiC particles and the amount of yttrium ion fixed to the SiC surfaces owing to the electrostatic interaction among negatively charged polymer, yttrium ions and SiC surfaces. The aqueous suspension of the SiC (800nm SiC 75%-30nm SiC 25%)-Al_2O_3 (1.2vol%)-Y^<3+> ions (1.2-3.2vol% Y_2O_3) system was consolidated by casting in a gypsum mold and formed green compacts of 36-38% theoretical density. These SiC compacts were hot-pressed to relative density 96.8-100% at 1950℃ in an Ar atmosphere. The addition of 30nm-SiC to 800nm-SiC decreased the grain size and flaw size of the hot-pressed SiC and improved the flexural strength and fracture toughness. The dense SiC with 2.0μm of average grain size, prepared from the mixed powder system, showed the following excellent mechanical properties: average four-point flexural strength of 812MPa, fracture toughness of 6.0MPa・m^<1/2> and Vickers hardness of 18-20GPa.
社団法人日本セラミックス協会の論文
2005-07-01

サブマイクロメーターサイズ粉体を用いたSiCのプロセッシングと力学特性へ及ぼすナノメーターサイズSiC粉体の混合効果

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