Silica polymorph and process for preparing same
AssigneeUnion Carbide Corporation
InventorsEdith M. Flanigen, Robert L. Patton
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Abstract
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.degree. 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.
Claims6
A synthetic crystalline silica polymorph, said silica polymorph after calcination in air for at least 1 hour at 600.degree. C., having a mean refractive index of 1.39 .+-. 0.01, a specific gravity at 25.degree. C. of 1.70 .+-. 0.05 g./cc., an adsorptive capacity for water vapor at 23.degree. C and a water vapor pressure of 4.6 mm Hg of less than 1 weight percent, having an infrared absorption spectrum which exhibits a substantial absence of absorption in the region 3700 to 3100 cm.sup.-1 and having an X-ray powder diffraction pattern containing at least those d-spacings set forth in Table A, said X-ray diffraction pattern being further characterized by the absence of a reflection intermediate the reflections which correspond to the d-spacings, 3.82 .+-. 0.04.degree. A and 3.71 .+-. 0.02A.
Dependencies are inferred from the claim text.