| 摘要 |
<p>Large crystals of a silica polymorph having a characteristic X-ray diffraction pattern, a specific gravity of 1.70 +/- 0.05 g/cc. and a mean refractive index of 1.39 +/- 0.01 after calcination in air at 600 DEG C., are prepared by a hydrothermal process in which fluoride anions are included in the reaction mixture. The crystals, which can be as large as 200 microns, exhibit a substantial absence of infrared adsorption in the hydroxyl-stretching region and also exhibit an exceptional degree of hydrophobicity.</p> |
