Abstract
Highly-densified and fine-grained hydroxyapatite (Ca10(PO4)6(OH)2: HAp) ceramics with and without 3.0 mol% B2O3 addition were fabricated by pulse-current pressure firing at 1000°C for 10 min under a pressure of 50 MPa. The tensile elongations of HAp ceramics with and without 3.0 mol% B2O3 addition were examined by changing the strain rate from 0.15 to 2.4 × 10−3 s−1 at the test temperature of 1000°C. The tensile elongation of HAp ceramic with no B2O3 addition showed a maximum (474%) at the strain rate of 0.59 × 10−3 s−1. On the other hand, the tensile elongation of HAp ceramic increased to 583% at the strain rate of 2.4 × 10−3 s−1 due to the addition of 3.0 mol% B2O3. Microscopic observation of fractured surfaces of HAp ceramic with 3.0 mol% B2O3 addition showed that the mean grain size decreased from 5.1 to 1.9 μm with increasing strain rate from 0.15 to 2.4 × 10−3 s−1 and that notable amounts of cavities were created among the grains. The time required to achieve the maximum tensile elongation (∼580%) of the HAp ceramic could thus be significantly reduced (approximately 1/16, i.e., 12 h to 45 min), due to increasing the strain rate from 0.15 to 2.4 × 10−3 s−1.
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