Research Progress on Colloidal Silica for Ceramic Shells in Investment Casting

Author of the article:LI Qian1 , LIU Zhipeng2 , ZHAO Wei3 , LI Yong1 , ZHANG Qiang1 , SHEN Bin1 , ZHOU Hankun1 , LYU Yongl

Author's Workplace：1. Science and Technology on Advanced High Temperature Structural Materials Laboratory, Beijing Institute of Aeronautical Materials, Beijing 100095, China; 2. Leicester International Institute, Dalian University of Technology, Dalian 124000, China; 3. The Sixth Military Representative Office of Airforce in Beijing, Beijing 100013, China; 4. School of Materials Science and Engineering, Beijing University of Science and Technology, Beijing 100083, China

Key Words：colloidal silica; investment casting; gel; ceramic shell

Abstract：Colloidal silica is defined as a dispersed suspension of silica nanoparticles with the advantages of high viscosity, high thermal stability and environmental friendliness. The ceramic shell in investment casting is mainly composed of refractory material and binder (colloidal silica). In this review, various methods for preparing colloidal silica (including electrodialysis, silicon dissolving, ion exchange and sol-gel process) have been displayed and discussed. The gelation behavior of colloidal silica (including gelation/drying time and shell strength) is controlled by regulating the colloidal silica concentration, colloidal size, pH value, temperature, and ion concentration. Meanwhile, other influencing factors for gelation have been reviewed, and future trends of colloidal silica in ceramic shells have been discussed.