Characterisation of borosilicate glass matrix composites reinforced with SiC or ZrO2

Two kinds of glass/ceramic composites were prepared. The first contained borosilicate glass with SiC ceramic: batches designated SG10, SG20, SG30 and SG40 consisted of 10: 90, 20: 80, 30: 70 and 40: 60 SiClglass (wt-%) respectively. The second contained borosilicate glass with ZrO2: batches designated ZG5, ZG10, ZG20 and ZG40 consisted respectively of 5: 95, 10: 90, 20: 80, 40: 60 ZrO2/glass (wt-%). The densification parameters (bulk density and apparent porosity) were measured by the Archimedes method Scanning electron microscopy and X-ray diffraction were used to investigate the microstructure and phase composition of the prepared composites. Cold crushing strength was also measured. The results reveal that in composites containing SiC, apparent porosity increases with increasing SiC content, while with increasing firing temperature from 800 to 1000degreesC, apparent porosity decreases to a minimum at 875degreesC before increasing again. As SiC content increases, the inhibition of cristobalite formation increases, as shown by XRD. The appearance of cristobalite causes the opposite effect on thermal properties: cold crushing strength increases with increasing SiC content, reaching a maximum at 30 wt-%SiC, and decreases again with 40 wt-%SiC In ZrO2 containing composites, apparent porosity increases with increasing ZrO2 content. With increasing firing temperature, apparent porosity decreases, reaching a minimum at 1000degreesC The effect of ZrO2 on the inhibition of cristobalite formation is more obvious than with SiC. Also, the cold crushing strength of ZrO2 containing composite is higher than for those containing SiC.