The effects of R2O-Al2O3-B2O3-SiO2 system glass and superfine alpha-Al2O3 on the sintering and phase transition of hydroxyapatite (HAP) ceramics were assessed. The results showed that alpha-Al2O3 impeded the sintering of HAP and raised the sintering temperature. When glass and alpha-Al2O3 were used together to reinforce HAP ceramics, better results could be obtained; the bending strength of multiphase HAP ceramics approached 106 MPa when 10% (wt) alpha-Al2O3 and 20%(wt) glass were used and sintered at 1200 for 1 h.
Aluminum Oxide ; chemistry ; Biocompatible Materials ; Boron Compounds ; chemistry ; Ceramics ; chemical synthesis ; chemistry ; Durapatite ; chemical synthesis ; chemistry ; Glass ; chemistry ; Materials Testing ; Silicon Dioxide ; chemistry ; Tensile Strength

HAP-Glass-alpha-Al2O3 gradient coating on alumina ceramics substrate was prepared by multi-layer slurry-dipping and sintering process, effects of the composition of the coating on the microstructure and adhesion strength of the gradient coating were studied. R2O-Al2O3-B2O3-SiO2 system glass with low softening temperature and thermal expansion was used in the gradient coating. The composition of the coating was varied from interface to surface layer, i.e. the HAP concentration increased and glass concentration decreased gradually from the under layer to the surface layer. A suitable amount superfine alpha-Al2O3 was added in the gradient coating to reinforce the bonding strength between the coating and substrate. The results show that the use of R2O-Al2O3-B2O3-SiO2 system glass is propitious to sintering the coating at low temperature and to combination between the coating and substrate. The addition of superfine alpha-Al2O3 can reinforce the bonding strength between the coating and substrate, the highest bonding strength is about 48.2 MPa.
Adhesiveness ; Aluminum Oxide ; chemistry ; Ceramics ; chemistry ; Coated Materials, Biocompatible ; chemistry ; Durapatite ; chemistry ; Glass ; chemistry

In this paper, alpha-tricalcium phosphate (alpha-TCP) and tetracalcium phosphate (TTCP) respectively were chosen as basic compositions of phosphate bone cements. Other auxiliary materials such as hydroxyapatite (HAP), dicalcium phosphate dihydrate (DCPD), calcium carbonate (CaCO3), calcium oxide (CaO) and amorphous calcium silicate (CaSiO3) were added in the cements. Six kinds of composite bone cements were decided with 1.50 as their Ca/P ratio. Then the primary properties of them were studied. Ringer's simulated body fluid (SBF) tests were carried out for the samples. The changes of pH value in SBF and the compressive strength of the samples with the immersion time were studied. The results showed: the mixing liquid 0.25 M K2HPO4/KH2PO4 and amorphous CaSiO3 were effective for accelerating the setting of the cements; the initial setting time (It) was about 4-5.5 min and the final setting time (Ft) was about 18-19. 5 min. Amorphous calcium silicate can increase the compressive strength of the bone cements remarkably; the compressive strength of the alpha-TCP bone cement with the addition of suitable amount amorphous CaSiO3 reached 45.3 MPa after immersion in SBF for 14 days.
Bone Cements ; chemical synthesis ; chemistry ; Calcium Compounds ; chemistry ; Calcium Phosphates ; chemistry ; Compressive Strength ; Humans ; Silicates ; chemistry