Abstract
The composites consisting of α-quartz crystallites and amorphous SiO2 were prepared by HIP technique, imitating the structure of natural agate. In the previous study, the KIC of the composite prepared from the mixed powder of crystallites and amorphous SiO2 was comparable to that of the natural agate (0.56 MN/m1.5). In this study, to increase the toughness of the composite, (1) the mixture of silica sol and α-quartz powder and (2) silica sol including nucleation promoter were examined as starting materials respectively. These starting materials were pressed into powder compacts with φ10×50mm in size. The Pyrex glass capsule containing the compact was hipped at 800-1200°C for 0-120 minutes under the pressure of 200MPa. The KIC of the composite obtained from the mixture of silica sol and α-quartz powder was equivalent to that obtained in the previous study, while the maximum KIC (0.63 MN/m1.5) was obtained when PbCl2 was used as a nucleation promoter. The nucleation promoter having low solubility in water was useful for the homogeneous generation of the crystallites.
