[Effects of additive oxide, repeating load on the fracture toughness of calcium phosphate crystalline ceramics (CPCC)].

This experimental study was performed to obtain fundamental data for the development of highly reinforced calcium phosphate crystalline ceramics (CPCC) by evaluation of fracture toughness by adding a single metal oxide such as B2O3, Na2O, Li2O, SiO2, MgO and Al2O3, which are thought to solidify and reinforce ceramics. In experiment I, values of fracture toughness for CPCC to which each oxide was added were determined by indentation method, and in experiment II dynamic test method by repeated loading was studied. The results are summarized as follows: 1) One half (a) of the diagonal of indentation was increased with an increase in indentation load, and the test fragment of CPCC with 4.7 mol% Na2O added at 10kgf of indentation load showed the maximum diagonal of indentation (145 microns), while the test fragment of CPCC containing 3.0mol% Al2O3 showed the minimum value (29 microns) at 1kgf. 2) One half (c) of the crack length was increased with an increase in indentation load, and the test fragment of CPCC containing 4.7mol% Li2O showed the maximum crack length (411 microns) at 10kgf, while the test fragment of CPCC with 4.7mol% B2O3 showed the minimum value (55 microns) at 1kgf. 3) The maximum value (2.98MNm-3/2) of fracture toughness (KIC) was observed in CPCC containing 4.7mol% B2O3 at 10kgf, while the minimum (1.02MNm-3/2) was observed in CPCC with 4.7mol% Li2O added, at 5kgf. 4) (a) was increased with an increase in the number of repetitions of loading, showing the maximum value (111 microns) for a test fragment at 10kgf with 100 repetitions and the minimum (31 microns) for a test fragment at 1kgf with just 1 repetition. 5) (c) was increased with an increase in the number of repetitions of loading, showing the maximum value (337 microns) for a test fragment at 10kgf with 100 repetitions and the minimum (64 microns) for a test fragment at 1kgf with 1 repetition. 6) KIC reached a maximum value (2.35MNm-3/2) at 5kgf and 1 of the repetition, and a minimum (1.54MNm-3/2) at 3kgf and 10 repetitions of loading.