Silica Precursors Derived From TEOS

Two high-char-yield polysiloxane polymers developed. Designated as TEOS-A and TEOS-B with silica char yields of 55% and 22%, respectively. These free-flowing polymers are Newtonium liquids instead of thick gels. Easily synthesized by controlled hydrolysis of inexpensive tetraethoxysilane (TEOS). Adhesive properties of TEOS-A suggest its use as binder for fabrication of ceramic articles from oxide powders. Less-viscous and more-fluid lower-molecular-weight TEOS-B used to infiltrate already-formed porous ceramic compacts to increase densities without effecting shrinkage. Also used as paint to coat substrate with silica, and to make highly pure silicate powders.