直接凝固注模成型Si_3N_4及SiC陶瓷──基本原理及工艺过程

MOULDING OF Si_3N_4 AND SiC CERAMICS VIA DIRECT COAGULATION CASTING──BASIC PRINCIPLES AND PROCESSING

直接凝固注模成型（ｄｉｒｅｃｔｃｏａｇｕｌａｔｉｏｎｃａｓｔｉｎｇ，ＤＣＣ）是一种崭新的（准）净尺寸陶瓷成型方法。本文报道了采用此法成型Ｓｉ_３Ｎ_４及ＳｉＣ陶瓷的基本原理和工艺过程。ＤＣＣ成型工艺过程为把高固相含量低粘度的陶瓷浆料浇注到无孔模具中，事先加入到浆料中的生物酶及化学物质通过改变浆料的ｐＨ或电解质浓度来改变浆料的胶体化学行为，从而使浆料原位凝固，得到有足够脱模强度的陶瓷坯体。ＤＣＣ成型的特点为坯体密度高（理论密度的５５％～７０％），坯体均匀，不用或只需少量的有机添加剂（少于１％），可成型大尺寸、复杂形状、高可靠性的陶瓷部件。

Direct coagulation casting (DCC)is a novel ceramic net shape forming technique for ceramic green bodies. The basic principles and processing of Si_3N_4 and SiC moulding by DCC are reported in this paper. During processing, high solid loading ceramic slurry of high solid content and low viscosity was cast into a non-porous mould. The salt concentration in slurry was changed by the enzyme catalyzed reactions. The colloidal behaviours of the slurry was changed due to these reactions and an in-situ coagulation of the slurry happened.The green body with sufficient strength for demoulding was obtained. Direct coagulation casting is characterized by high green body density, high homogeneity, no or less than 1% organic additives needed and capable to form large size, complicated shape ceramic parts of high reliability.