The antibacterial activity of non-stoichiometric calcium phosphate particles prepared by precipitation under controlled experimental conditions at pH∼9 and sintered at high temperature was studied against Staphylococcus aureus bacteria. The effects of operating parameters developed according to an experimental design of Plackett-Burman type on the physicochemical characteristics and the capacity to inhibit bacterial growth were identified using a thermal analysis (TGA-DTA-DSC), x-ray Diffraction (XR), Raman Spectroscopy, Scanning Electron Microscope (SEM) and the Kirby Bauer Method. The XRD spectrum shows that the synthetic crystalline nanoparticles powders consist of multiphasic calcium phosphate β-TCP/β-CPP/OCP/HA and that the average particle size is between 56 and 123 nm calculated by the Debay-Shearer equation. The Raman spectrum of sintered powder shows the main absorption bands that are assigned to the asymmetric / symmetric P-O stretching vibrations in PO 4 −3 and the symmetric O-H stretching mode of the hydroxyl group in addition of Ca-PO 4 and Ca-OH modes. The samples were found to possess different morphologies consisting of nano-rods of different lengths, semi / spherical structures and fine granules, in addition to irregular clusters. The antibacterial tests results showed that the high concentration calcium phosphate powder exhibited better antibacterial activity against Staphylococcus aureus bacteria with inhibition zones ranging from 0.2-0.7 cm.

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Selection of calcium phosphate base materials in reconstructive bone surgery is justified by the surprising similarities in chemical compositions with human bones. The closest to natural apatite material is the hydroxyapatite (HAp) which has a chemical composition based on calcium and phosphate (Ca10(PO4)6(OH)2). In this study, HAp is synthesized using the wet precipitation method from hydrated calcium chloride (CaCl2,12H2O) and di-sodium hydrogen phosphate di-hydrate (HNa2PO4,2H2O). The powder is calcinated at 900°C and 1200°C in order to compare with sintered condition at 1150°C. Vickers microhardness tests and X-ray diffraction analyzes are used for the characterization of the crystalline material. Mechanical properties (HV, σe, σr, and KC) and the degree of crystallinity (Xc) are discussed according to heat treatment temperatures. Results indicate that heat treating the powder at 1200°C increased crystallinity up to 72%. At the same time, microhardness increased with temperature and even outmatched the sintered case at 1150°C. Fracture toughness is ameliorated with increasing heat treatment temperature by more than two folds. * Calculated (when needed) using Eq. 6. **Calculated (when needed) from compressive strength using Eq. 7.