1005 exhibited a spongy-type structure, as illustrated in
Fig. 1. The bubbles ranged from 2 to 100lm in diameter
and were found uniformly throughout the glass. Large
bubbles were produced when glass G-1004 was in contact
with SiC as shown in Fig. 2. In Fig. 2(b) a bubble
has formed, exploded and then collapsed under its
own weight because of the low viscosity of the glass at
the firing temperature. Fig. 3 shows two SEM images
illustrating the results obtained using glass Corning
1723. Again, bubbles fill the entire volume of the glass
and are clearly visible on the surface. The presence of
bubbles suggests that gaseous products must have
evolved from the glass/SiC interface. Some of the constituents
of the glasses must therefore have reacted with
SiC.