Abstract
Densities, elastic moduli, Vickers hardnesses, fracture toughnesses and fracture energies of Ca3(PO4)2-Al2O3-SiO2 glasses have been studied. Bulk, Young's and shear moduli were 55.26-62.19, 79.92-86.24 and 31.74-33.94GPa, respectively. If Ca3(PO4)2 and Al2O3 contents were kept constant, elastic moduli of these glasses decreased with increasing mean atomic volumes. On the other hand, if SiO2 contents were kept constant, there was an abnormal tendency that bulk modulus increased with increasing mean atomic volumes. If Ca3(PO4)2 contents were kept constant, Young's modulus decreased with increasing mean atomic volumes. Furthermore, if SiO2 or Al2O3 contents were kept constant, Young's elastic moduli increased with increasing mean atomic volumes. The elastic moduli of Ca3(PO4)2-Al2O3-SiO2 glasses (50-60% SiO2, 20-30% Al2O3) were higher than those of CaO-P2O5-SiO2 (0-15% SiO2) and CaO-P2O5-Al2O3 (0-7% Al2O3) which have been reported in the previous papers, and close to those of silicate glasses containing 50-60% SiO2. Vickers hardness was 510-580kg/mm2 and larger than that of CaO-P2O5-SiO2 and CaO-P2O5-Al2O3 glasses. The hardness increased with substitution of Al2O3 or SiO2 for Ca3(PO4)2. Al2O3 was the most effective component for increasing the hardness of these glasses. Fracture toughness and fracture energy were 0.99-1.47MPa·m1/2 and 5.6-12.2J/m2, respectively, and decreased with increasing Ca3(PO4)2 contents. It is estimated that fracture toughness and fracture energy of glasses related to the number of weak bonds. The weak bonds in Ca3(PO4)2-Al2O3-SiO2 glasses are Ca-O bond, and Si-O bond in P-O-Si bond. Because the number of these weak bonds increase with increasing Ca3(PO4)2 contents, fracture toughness and fracture energy decreased with increasing Ca3(PO4)2 contents.
