THE IDENTITY, DEVELOPMENT AND QUANTIFICATION OF PHASES IN DEVITRIFIED, COMMERCIAL-GRADE, ALUMINOSILICATE, REFRACTORY CERAMIC FIBERS - AN X-RAY-POWDER DIFFRACTOMETRY STUDY

Aluminosilicate, refractory ceramic fibres devitrify to form cristobal ite and mullite in high-temperature applications. The identity of phas es and their development with temperature and time has been determined using x-ray powder diffractometry, and the internal standard method w ith fluorite reference and mullite, beta-cristobalite and amorphous st andards, has provided phase quantification. The formation of mullite a nd cristobalite as a function of exposure temperatures and times are m apped, and the presence of beta-, alpha- and disordered cristobalite a nd of tridymite and alpha-quartz are confirmed in samples measured at room temperature. The authors are confident that well-developed cristo balite and mullite phases can be quantified and fibres devitrified at 1400-degrees-C for greater than 50 h exposure contained (51 +/- 2) wt- % mullite and (36 +/- 2) wt-% beta-cristobalite with the remainder bei ng attributed to other silica phases and remnant glass.