Chlorapatite to hydroxiapatite ion-exchanging, single-crystal point of view

Abstract

Poster Sessions C576 hierarchical level is formed. In the same way the cluster of the 2 nd level is formed, etc.Thus, we interpreter the formation of silica spheres as the process of hierarchical self-organization of matter at nanolevel.This work is supported by The new mineral galuskinite (IMA2010-63) was detected in small, a few meters in diameter, altered silicate-carbonate xenoliths within the Birkhin gabbro massif in Eastern Siberia. Most surprisingly a synthetic analogue of galuskinite Ca 7 (SiO 4 ) 3 CO 3 is not known, neither from cement clinker production nor from studies of the CaO-SiO 2 -CO 2 system.The structure was solved on the basis of X-ray single-crystal data and refi ned to R 1 = 3.1%. The mineral crystallizes in the monoclinic space group P2 1 /c: a = 18.7872(5), b = 6.7244(2), c = 0.4673(2) Å, β = 90.788(1)º, V = 1322.24(6) Å 3 , Z = 4. The structure of galuskinite represents an orthosilicate with additional CO 3 groups. There are 7 symmetry independent Ca sites with O coordination between seven and eight. The arrangement of the coordination polyhedra indicates modular character with strong similarities to spurrite Ca 5 (SiO 4 ) 2 CO 3 [1] and larnite β-Ca 2 SiO 4 [2]. A polyhedral model of the crystal structure of galuskinite is presented in fi gure 1. Dashed contours intersect the structure in layered modules parallel to (100). The structure is composed of three alternating modules. The central module with composition Ca 2 SiO 4 contains eight-coordinate Ca polyhedra with SiO 4 tetrahedra and is analogues to a corresponding one in spurrite. The adjacent module on both sides is a mixed anion layer of Ca 2 SiO 4 × CaCO 3 composition with topologically different front-(Ca 2 SiO 4 ) and backside (CaCO 3 ). The sequence is completed by one perfect larnite layer of Ca 2 SiO 4 composition. Adding up the modular units, the composition of galuskinite becomes Ca 7 (SiO 4 ) 3 CO 3 .The mineral galuskinite is named in honour of the couple Irina O. Galuskina and Evgeny V. Galuskin, University of Silesia, Poland for their outstanding contributions to skarn mineralogy. There is an interest in obtaining biocompatible crystals of Calcium phosphates (CaPs) because they have a composition very similar to the mineral component of bones, [1]. This property makes them excellent candidates for very broad applications such as a reinforcing phase in composite bioceramics, [2]. Elliot and Young, [3] have provided the fi rst evidence of solid-state ion exchange in CaPs into the apatite crystal structure.Chlorapatite (ClAp) millimeter-size crystals were heated in atmosphere conditions from 1300 to 1500ºC, leading to a systematic conversion from ClAp to Hydroxyapatite (HA) structure by an ion exchange reaction. Under these experimental conditions, the ClAp and annealed samples are single crystals suitable for SXRD analysis. We provide a detailed description of the evolution of Ca 5 (PO 4 ) 3 Cl x (OH) 1-x single-crystals decreasing systematically its chlorine content. The results obtained from SXRD were extrapolated...