CRYSTALLIZATION OF AL2O3-SIO2 GLASS-FIBER AND EFFECT OF ZRO2 AND CR2O3 ADDITIONS ON THE CRYSTALLIZATION

Crystallization of Al2O3-SiO2 glass fiber (AS) and the effect of ZrO2 and Cr2O3 addition on the crystallization were investigated by DTA, XR D and density measurement. Mullite crystallized in the AS at 995 degre es C. The mullite crystal grew and its amount increased with rising te mperature. Cristobalite crystallized in the AS at 1450 degrees C and a bove. Mullite crystallized at 1015 degrees C with t-ZrO2 and spinel ph ase in fibrous glass containing ZrO2 (ASZ). The mullite crystal grew a nd its amount increased with rising temperature. At 1500 degrees C, cr istobalite crystallized and the t-ZrO2 partly transformed into m-ZrO2. The amount of cristobalite in this fibers was larger than that in the AS. Only spinel phase crystallized at 990 degrees C in fibrous glass containing Cr2O3 (ASC). The amount of spinel phase increased up to 110 0 degrees C, but slightly decreased at 1200 degrees C and disappeared at 1300 degrees C. Mullite appeared from 1100 degrees C and increased with rising temperature. Cr2O3 dissolved in the mullite and suppressed the crystallization rate and grain growth. The addition of Cr2O3 rais ed the temperature at which the amount of mullite reached the calculat ed value by 105 degrees C compared to that of the AS. Although the amo unt was smaller than that of the AS, cristobalite also crystallized in the ASC by firing at 1500 degrees C.