GRINDING EFFECT OF POWDER ON THERMAL-EXPA NSION OF SILICA GLASS POWDER COMPACTS

A thermal expansion ten times larger than that of silica glass was obs erved for the pressed compacts of silica glass powder, which was groun d with a planetary pot mill. The extent of the thermal expansion incre ased with increasing the grinding time. Since quartz powder compacts d id not undergo much thermal expansion after grinding, such a large the rmal expansion behavior of the silica glass powders seemed to be uniqu e for the silica glass. Solid state Si-29 NMR and IR spectra showed a reduction in the Si-O-Si bonding angle, which resulted due to a distor tion of the silica glass network.