تحسين الخصائص الميكانيكية و البيوحيوية للهيدروكسيأباتيت الطبيعي

Abstract

The main objective of this research is to study the hydroxyapatite (HA: Ca10(PO4)6(OH)2,) which was extracted from cortical bovine. This latter because of both its abundance and high purity may be considered as an exciting starting material for cheap bioceramics production. The effect of milling time, sintring temperature and P2O5 and B203 additions on density, microhardness, bioactivity and compatibility of Hydroxyapatite have been studied. In order to accomplish the above objectives, many techniques have been used to study and characterize the chemical and physical properties of prepared samples. The most important of them are Scanning Electronic Microscope (SEM), Infra-Red (IR), X-ray Diffraction (XRD) and the Induced Coupled Plasma (ICP-OES). In the first part the effect of milling time on the natural hydroxyapatite particles size has been studied. In addition, we studied the effect of sintring temperature on natural hydroxyapatite stability. and found that this latter is stable, so that at all temperatures the only phase present was Hydroxyapatite. Also, this latter has significant mechanical properties. In addition, we studied the effect of the introduction of certain additives in Hydroxyapatite as P2O5 and B2O3 with a percentage of 3% at the following temperatures: 1050 ° C and 1250 ° C.. Although the introduction of the additions at 1050 ° C has not removed the percentage of sintering, but improved mechanical properties, in particular when B2O3 is added, where the value of microhardness increased to 0.96 GPa compared to 0.61 GPa obtained without additions and the value of the tensile strength increased from 6.7 MPa to 17 MPa. At 1250 ° C, the effect of additions was evident where the sintering percentage reached 93%, and the value of the tensile strength has jumped to 67 MPa in the samples containing 3% of B2O3 compared to a low value in the range of 13 MPa for samples without additions. these additives led to the transformation of the hydroxyapatite in ß-TCP, in different percentages. We can also observe that the ß-TCP percentage was higher when the sintering temperature is 1250 ° C. After the immersion of the different samples in SBF for different times, it was found that when the temperature is 1050 ° C, for the samples whithout additions and those containing P2O5 the apatite layer appears on the surface of samples after 14 days. But for samples containing B2O3 the appearance of the apatite layer was quicker, and that appears after only 3 days of immersion. While at the temperature 1250 ° C, any apatite layer has been observed on the surface of the different samples and this is due to the high relative density.