Non-Crystalline Excrescences from Heated Silica

Abstract

THREE different forms of filamentary silica have been discussed recently. Jaccodine and Kline¹ reported the growth of whiskers on the devitrified surface of vitreous silica which had been heated in a nitrogen stream for 24 hr. at 1,425° C. Abrahams and Stockbridge² showed that these growths were proper whiskers (Nabarro and Jackson³) of high-cristobalite with [111] as whisker axis. They also examined whiskers found on hydrothermally grown crystals of α-quartz⁴, and showed that these were α-quartz crystals elongated along [0001]. Haller⁵ grew fibres of silica, non-crystalline and optically isotropic, on heated platinum surfaces (temperature about 1,100°C.) exposed to a mixture of silicon tetrafluoride and water vapour in a nitrogen stream.