Study On The Preparation Of Porous Hydroxyapatite

This paper deals with preparation of porous hydroxyapatite and some relative aspects as follows: the preparation of porous HA by the dipping technology and by the gel-casting and polymer sponge methods were researched. The factors in the two technologies were investigated in order to improve the structure and properties of porous HA. The effect of different processes on porous structure and on the phase changes of porous HA was studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric (TG) and differential thermal analyses (DTA). The porosity, the pore size and the compressive strength of porous HA were also tested.The research on the preparation of HA powder by the liquid deposition method with two reactants of Ca (NO3)24H2O and (NH4)2HPO4 indicated that, the best Ca/P molar ratio was 1.67, the best pH value was bigger than 12.4, the best sintering temperature was 900℃. The temperature affected the crystallization degree and reuniter of HA powder. The powder that was dried by spraying was better than that after the treatment of 900℃ in the modality, size and size distributing. This process was simple and low-costed.The pore size of porous HA by the dipping method was 15~40um and the porosity was 65%~75%. The results of measure and computing indicated that the opening porosity approximated to the general porosity and the pores were three-dimensional connective. The compressive strength was 3.743MPa. The quality ratio of HA powder, gooey, dispersant, deionized (DI) water in the solution was 50:5:3:42. The quality of the solution was an important effect on this process. The pore of porous HA by the solution blended with gooey and dispersant had better connective, bigger strength and littler shrinkage. The gooey can enhance the strength of porous HA and prevent a dent. The dispersant can improve the stability of the solution and avoid reuniting.The pore size of porous HA by the gel-casting and polymer sponge methods was 100~150um and the porosity was 60%~70%. The compressive strength was 6.127MPa. The ration of HA powder, AM, MB AM, APS, TEMED, deionized (DI) water was 50: 4: 0.5: 0.1: 0.1: 100. The size and the size distributing of HA powder were important effects on this process. Narrower the size distributing was and smaller the size was, the quality of porous HA was better. The process means was also important. Extrusion was more advantageous to molding and to reserve the frame of polymer sponge than pumping. Extrusion can also decrease tiny pores and increase the strength of porous HA.Polymer sponge determined the capability and structure of porous HA, including pore size, porosity, girder size and components of polymer sponge. The pore size of porous HA was smaller than that of polymer sponge, but the porosity was similar. The girder size affected the number of tiny pore. If the girder size was bigger, the number of tiny pore was more and the strength of porous HA was smaller.Temperature should be strictly controlled. The test proved that the dry temperature was 60 T2 and the sintering temperature was 1000'C.