Abstract
The elastic moduli of densified fused silica were determined by using the cubic resonance method capable of measuring the shear wave velocity and Poisson's ratio of small cubic specimens. The thermal expansivity and Vickers hardness were also determined, and an attempt was made to interpret the changes in these physical properties of fused silica due to densification on the basis of glass structure. The main results obtained were as follows:
(1) The bulk modulus and Young's modulus increased about 60% and 40%, respectively, when fused silica was densified about 20%. The densified fused silica had higher bulk modulus (about 60%) and Young's modulus (about 20%) than α-quartz, even though both specimens had the same density.
(2) The thermal expansion coefficient increased slightly with densification, but its value was considerably smaller than common crystals or glasses. Hardness increased about 60% with densification, which is comparable to the change in elastic moduli.
(3) The increase in elastic moduli was not proportional to density but a sudden increase appeared at 2.4g/cm3 and 2.6g/cm3. This behavior may be interpreted in terms of the decrease in average bond length and the change in bonding angle of Si-O-Si.
