Preparation Of Hydroxyapatite Sol And Its Liquid Crystal

Hydroxyapatite, (HAp or HA in short) a typical biomaterial, has excellent biocompatibility and bioactivity, and the bone and the teeth of we human being are natural composites composed of nano-hydoxyapatite, which is systematically organized in collagen fiber with excellent physical property. As we can see, this self-assembled three-dimension nano-structure is similar to that of inorganic liquid crystal.In this paper, HA particles (n-HA) with high aspect ratio were prepared by chemical deposition. The reacting temperature, pH, the concentration and Ca/P molar ratio of the materials, and the amountof diffierent dispensants determine the shape and size of n-HA and the quality of n-HA aqueous colloids;The conditions for prepartion of n-HA sol and its liquid crystal were studied by controlling the proportion of n-HA in sol. The results are as follows:HA nano particles, 200nm in length, 20-30nm in diameter, 15-20 in aspect ratio could be obtained by the reacting between Ca(NO3)2 and (NH4)PO4 solutions in 0.2mol/L concentration at 90℃, pH 8. As the reaction temperature goes, it was discovered that as the reaction temperature went high, the sizes of n-HA were enlarged and crystallinity is improved while the shapes were still very simillar to the original.Found out the proper dispersant such as Gelatin, low molecular weight Polyacrylate sodium, sodium citrate and sodium hexame taphospha for preparation of n-HA colloid. Compared with these dispersants for their stability and dispensilility, it is obvious that gelatin has a particular function of the coating n-HA and it has a certain function on the stability of HAp in aqueous solution; low molecular weight polyacrylate sodium, by chemical absorption on the surface, is also functional for the dispense of n-HA in solution; sol with good quality could be prepared by using sodium citrate and sodium hexame taphospha as multiplex dispersant.Inspection on liquid crystal state was carried out in the solution that was prepared by using sodium citrate and sodium hexame taphospha as multiplex dispersant, Gelatin respectively. It was found that the birefringence would be obvious when the non-volatile matter content of the sol was over 20%, when it was over 10% the birefringence would become less obvious, while below 5%, there would be no such phenomenon. It was also figured out that the concentration of gelatin is 8%, that is to say; the sol should be concentrated into gel state if there should be obvious phenomena of birefringence.