Phosphorus/Calcium-Containing Oxide Layer on Titanium and Its Hydrothermal Treatment
Date Issued
2008
Date
2008
Author(s)
Un, Fu-Wa
Abstract
This study employed micro-arc oxidation (MAO) and hydrothermal treatment (HT) to modify the surface characteristics of commercial pure Titanium (c.p.Ti) for improving the biocompatibility of the test material for human implants application. The parameters investigated include voltage for MAO and pH value, treatment temperature and duration for HT. The surface characteristics were analyzed by SEM, EPMA and XRD, and the bonding strength of the coating was also tested. The results indicate that a dense Ca, P-containing anatase TiO2 layer was formed by micro-arc oxidation, and HA (Ca10(PO4)6(OH)2) was crystallized on the oxide layer by the subsequent hydrothermal treatment. As a result, HA/TiO2 was formed on the surfaces of the treated material. It has been observed that both the thickness of the oxide layer and the size of pores increase with increasing MAO voltage. In addition, the Ca and P contents in the oxide layer increase from the substrate/oxide interface toward the outmost surface. On the other hand, the bonding strength decreases with increasing MAO voltage. The rather wide variation in bonding strength for voltages exceeding 250V is due to relatively thick oxide layer, large pores and the presence of micro-cracks. Regarding the effect of hydrothermal treatment, HA will form only when the MAO voltage is above 200V and the HT temperature is above 250oC. For MAO voltage below 250V (but above 200V), increasing treatment time promote the diffusion of Ca and P and hence the formation of HA, due to relatively low Ca and P contents in the oxide layer. On the other hand, for MAO voltage of 300V, the results show that the treatment time of 2 hours is sufficient to form HA, due to relatively high Ca and P contents in the oxide layer. However, HA will transform to tricalcium phosphate by means of thermal decomposition if the treatment time is too long. Based upon the results obtained herein, the optimal treatment conditions are: 230V-deionized water/pH9-250oC-6hours.
Subjects
Pure Ti
Micro-arc oxidation
Hydrothermal treatment
biocompatibility
Type
thesis
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