Chemical characterization of some substituted hydroxyapatites

Synthetic multi-substituted hydroxyapatite nano powders containing silicon and or carbonate prepared by a wet chemical method. The process parameters are set up to allow the simultaneous substitution of carbonate and silicon ions in the place of phosphorus. The chemical and structural characterizations of the prepared powders are determined with the aid of; XRF, ICP, XRD and FTIR. The results show that, the ion substitution in the crystal lattice of HA caused a change in the unit cell dimensions and affected the degree of crystallization of the produced powders. The apatite formation abilityy of the prepared discs from the synthesized powders is determined by immersing in SBF solution for different periods. The degree of ion release was determined in the obtained solutions. The examined surface of the immersed discs under SEM and analyzed by CDS showed a more dense HA layer than those of un-substituted ones. The HA with the substituted silicon and carbonate ions, showed the highest solubility with greater rate of ion release, compared with carbonate-free powder. All prepared powders took sodium ion from the SBF solution during immersion, which was not recorded before

Phase equilibria in the system Cu-Mn-O

\u3cp\u3eA T-x-section of the phase diagram is proposed for the system CuMnO in air between 750 and 1,400°C. From X-ray and chemical analyses on quenched samples and from high-temperature X-ray diffraction studies the occurrence of the following phases is deduced: a cubic phase α-Mn\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e, a phase Cu\u3csub\u3ex\u3c/sub\u3eMn\u3csub\u3e3−x\u3c/sub\u3eO\u3csub\u3e4+γ\u3c/sub\u3e (0 ⩽ x < 0.2 and 0 < γ < 0.02) with a tetragonally deformed spinel structure, a cubic spinel phase Cu\u3csub\u3ex\u3c/sub\u3eMn\u3csub\u3e3−x\u3c/sub\u3eO\u3csub\u3e4+γ\u3c/sub\u3e (0 ⩽ x ⩽ 1.03 and −0.08 < γ < 0.02), a crednerite-like phase Cu\u3csub\u3ey\u3c/sub\u3eMn\u3csub\u3e1−y\u3c/sub\u3eO (0.50 < y < 0.53) with monoclinic structure, a delafossite-like phase Cu\u3csub\u3ey\u3c/sub\u3eMn\u3csub\u3e1−y\u3c/sub\u3eO (0.54 < y < 0.60) with hexagonal structure, a liquid phase, the phase Cu\u3csub\u3e2\u3c/sub\u3eO and the phase CuO. CuMn\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e4\u3c/sub\u3e was found to be cubic or tetragonal at room temperature, depending on the temperature of quenching.\u3c/p\u3e\u3cp\u3eThe po\u3csub\u3e2\u3c/sub\u3e-x-section of the system CuMnO at 1,000°C, as determined by SCHMAHL and MÜLLER (1964), was confirmed and could be farther extended to lower oxygen pressures.\u3c/p\u3e\u3cp\u3eThe valencies of the cations, especially of those in the spinel structure, are discussed.\u3c/p\u3

Stoichiometry of potassium-containing and carbonate-containing apatites synthesized by solid-state reactions

In this study, a series of potassium- and carbonate-containing apatites is prepared by solid state reactions at high temperature in a nearly dry CO2 atmosphere. Chemical and physical analyses showed that the samples are single-phase and contain 4-12 wt % carbonate. Their stoichiometry conforms to Ca10-xKx[(PO4)(6-x)(CO3)(x)][(OH)(2-2y)(CO3)(y)] with 0 K+ + CO32-] and [2OH(-) CO32- + V-OH], where V-OH stands for a vacancy in the OH- sublattice. Although these mechanisms appear to occur independently of each other, they have a marked effect on the IR characteristics of the solid