Effect of ZrO2 and Cr2O3 Addition on Softening and Sintering of Al2O3-SiO2 Quenched Glass

Softening and sintering behavior of Al2O3-SiO2(AS), Al2O3-SiO2-ZrO2(ASZ) and Al2O3-SiO2-Cr2O3(ASC) glass fibers that are generally called ceramic fibers were investigated by dilatometric measurement. Thermal linear change of a single fiber was measured with an optical microscope with a hot stage. All the fibers showed sharp shrinkage at about 1000°C due to crystallization. Glass spheres that have the same composition as the glass fibers and compacted bodies of the crushed glass fibers showed shrinkage at about 1200°C in addition to the shrinkage at about 1000°C. The shrinkage at 1200°C for the glass spheres was governed by softening, and the shrinkage of the compacted body of crushed glass fibers was governed by sintering and softening. Softening of the glass spheres was in the order of ASC≥AS>ASZ and sintering of glass fiber was in the oder of ASZ=AS>ASC at 1400°C. Sintering of glass fibers was governed by the viscous flow mechanism and its apparent activation energy changed at about 1300°C.