Prof. Dr. S. A. Abdel-Aal, spent two months at Chemnitz University, Germany funded by the German Research Community (DFG). The research was conducted in the field of preparation and coating of hydroxyapatite. Because the main concern for the rule of hydroxyapatite as the main component of human bones (about 70%). This material is used in many medical areas, where they have high critical consensus is an ideal substitute for bone, especially in the parts of a more load, such as weak bones of the ear bones. In case of high load parts such as the bones of the hand or the thigh or neck bands can be replaced by a layer of titanium-coated materials as hydroxyapatite. These segments are biocompatible with human body and make a layer adherent and coherent interface between the titanium alloy and the surrounding bone tissue. Preparation was done using chemical precipitation method for the coating powder which then coated on titanium slides using plasma spraying. The study of the overlapping between the various factors affecting the coating process. The most important achievement through this collaboration work is the development of a relationship between the conditions of preparation and mechanical properties and the degree of purity of the hydroxyapatite.