Mechanism of solid-state conversion of non-stoichiometric hydroxyapatite to diphase calcium phosphateстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Two non-stoichiometric hydroxyapatites (n-HA) with Ca/P molar ratios of 1.50 and 1.58 and one stoichiometric hydroxyapatite (s-HA) with Ca/P = 1.67 were prepared from chemically pure CaHPO4.2H(2)O and KOH. After sintering at 1050 degreesC for 4 h, n-HA with Ca/P = 1.50 was transformed into beta-Ca-3(PO4)(2), n-HA with Ca/P = 1.58 was converted to dipliase calcium phosphate (DCP), while s-HA underwent no chemical transformations. The sintered and unsintered samples of hydroxyapatite were studied by IR spectroscopy, chemical analysis, and X-ray diffraction analysis. The crystallite dimensions were calculated, and a model for the DCP structure was proposed. The mechanism of the solid-state n-HA to DCP conversion was proposed on the basis of this model and published values of the volume diffusion coefficients of the OH-, Ca2+, and PO43- ions at 1000 degreesC.