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Calcium Hydroxyapatite (calcium + hydroxyapatite)
Selected AbstractsPhase Relations Between ,-Tricalcium Phosphate and Hydroxyapatite with Manganese(II): Structural and Spectroscopic PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2006Isaac Mayer Abstract The preparation of Mn-containing ,-tricalcium phosphate (,-TCP) samples was achieved in two ways: a) transformation of precipitated Mn-containing calcium hydroxyapatite (HA) to ,-TCP by heating at 1100 °C, and b) preparation by solid-state reaction of a mixture of CaCO3, (NH4)2HPO4, and Mn(NO3)2 at 1100 °C. Powder X-ray diffraction (XRD) analyses of the samples, obtained by both methods, show well-defined patterns with structural data of the rhombohedral R3c, ,-TCP phase. The calculated lattice constants are smaller than those known for ,-Ca3(PO4)2 because of substitution of Ca2+ by Mn2+. EPR spectroscopy indeed reveals that manganese is divalent in the samples. Apparently, the Ca(5) site in the ,-TCP structure is occupied by Mn2+. The distribution of Mn2+ between the ,-TCP and the HA phase in the case of preparation (b) was studied by EPR spectroscopy, and a pronounced preference for the former lattice was found. Micron- and submicron-sized crystals with visible faces were observed by TEM in the case of ,-TCP prepared by solid-state reaction, and large micron-sized, droplike-shaped crystals, sensitive to beam radiation, were found in the case of samples prepared by heating HA at elevated temperatures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Metathetic Reaction in Reverse Micelles: Synthesis of Nanostructured Alkaline-Earth Metal PhosphatesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007Purnendu Parhi For the past few years, hydroxyapatite (HAp) has been identified as a potential biomaterial due to its excellent biocompatibility and bioactivity. The preparation of nanostructured HAp with controlled powder characteristics is a pre-requisite for processing it into useful biocomposites. Here, the synthesis of nanorods of calcium hydroxyapatite (Ca-HAp), strontium hydroxyapatite (Sr-HAp), and barium hydroxyapatite (Ba-HAp) by exploiting the metathetic reaction taking place in reverse micelles in the presence of cetyltrimethylammonium bromide has been reported. Powder X-ray diffraction analysis and thermogravimetric measurements confirm the formation of monophasic Ca-HAp and Sr-HAp. The growth of nanorods was further confirmed using transmission electron microscopy studies. The average lengths of Ca-HAp and Sr-HAp were ,60 and 30 nm, respectively. However, the preparation of Ba-HAp invariably yielded a multiphasic mixture with other competitive phases like BaHPO4 and Ba(H2PO4)2. [source] Preparation of Porous Ca10(PO4)6(OH)2 and ,-Ca3(PO4)2 BioceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2000N. Özgür Engin Submicrometer-sized, pure calcium hydroxyapatite (HA, (Ca10(PO4)6(OH)2)) and ,-tricalcium phosphate (,-TCP, Ca3(PO4)2) bioceramic powders, that have been synthesized via chemical precipitation techniques, were used in the preparation of aqueous slurries that contained methyl cellulose to manufacture porous (70%,95% porosity) HA or ,-TCP ceramics. The pore sizes in HA bioceramics of this study were 200,400 ,m, whereas those of ,-TCP bioceramics were 100,300 ,m. The pore morphology and total porosity of the HA and ,-TCP samples were investigated via scanning electron microscopy, water absorption, and computerized tomography. [source] STRAFI imaging of paramagnetic solids: 31P paramagnetic displacements,,MAGNETIC RESONANCE IN CHEMISTRY, Issue 1 2002Edward W. Randall Abstract One-dimensional stray field (STRAFI) profiles of 31P in phantoms containing, variously, calcium hydroxyapatite, calcium orthophosphate and cobaltous phosphate octahydrate were obtained in a STRAFI field of 11.7 T on a 19.6 T magnet at 206 MHz. The intrinsic spatial resolution with the apatite and orthophosphate samples was about 100 mum. The profile of the image from the paramagnetic cobaltous sample was displaced to high field by 1.2 MHz. The spatial resolution for the cobalt component was degraded because of the large linewidth of ,0.6 MHz. Copyright © 2001 John Wiley & Sons, Ltd. [source] Hydroxyapatite as a filler for biosynthetic PHB homopolymer and P(HB,HV) copolymersPOLYMER INTERNATIONAL, Issue 7 2003Antje Bergmann Abstract This paper deals with some of the fundamental problems encountered when using a semicrystalline polymer as the matrix phase for a particulate-filled composite. As our model system we adopted poly-(R)-3-hydroxybutyrate, PHB, and two copolymers of (R)-3-hydroxybutyrate and (R)-3-hydroxyvalerate, P(HB,HV), for the matrix phase, and the mineral calcium hydroxyapatite as a particulate filler. The structure and properties of compression-moulded films of various compositions were investigated by polarized light microscopy, wide-angle X-ray scattering and mechanical testing. It was found that the degree of crystallinity of the matrix was lower in filled samples, and that the spherulitic crystallization of the matrix appeared to cause the filler particles to form agglomerates, which would not be as effective a reinforcement as finely dispersed primary filler particles. The tensile strength, strain-to-break and tensile modulus of samples of different compositions were analysed using well-known theories for composite behaviour. Copyright © 2003 Society of Chemical Industry [source] | |||||||||||||