Opaque silica glass fabricated by slip casting and sintering (Part 2) - Bubble formation

Bubbles are essential in the formation of opaque silica glass, because opac ity results from light scattering by bubbles dispersed throughout the glass matrix. In this sintering study of slip casting of a silica compact, the f ormation of bubbles was observed. In the final densification stage, a large number of small bubbles formed at around 1600 degrees C, With increasing s intering temperature, isolated bubbles became larger and, concurrently, the number of bubbles decreased. Opacity increased with increasing sintering t emperature up to 1800 degrees C, These results are discussed from the viewp oint of the critical bubble size which determines whether bubbles expand or shrink.