سال انتشار: ۱۳۸۷

محل انتشار: دومین کنگره بین المللی علوم و فناوری نانو

تعداد صفحات: ۲

نویسنده(ها):

S Manafi – Materials Engineering Department, Islamic Azad University, Shahrood Branch, Shahrood
S Joughehdoust –

چکیده:

Apatites are a class of compounds of general formula M10(PO4)6X2, where M is a divalent metal cation (primarily Ca2+, Sr2+, Ba2+, Cd2+, or Pb2+), and X is a monovalent anion (OH, F-, Cl-, and Br-). The calcium derivatives are by far the most abundant, and they constitute one of the principal host phases for condensed phosphorus and halogens in the solar system, [1-3] at temperatures below ca. 700 K. Hydroxyapatite (HAp) is a major constituent of mammalian bone and teeth enamel, where it occurs as a nonstoichiometric, amorphous, and carbonated form, but it is also very important as a biomaterial for medical implants [3]. Fluorapatite (FAp) is the most commonly occurring calcium apatite, whereas both pure chlorapatite (ClAp) and bromapatite (BrAp) do not occur naturally on Earth, although they can be found in some astral bodies such as meteorites [3]. The structure of the apatites is basically a crystal lattice composed of tetrahedral phosphate anions and calcium cations, with the hydroxyl and halide ions lying on the crystallographic c-axis perpendicular to the planes defined by three calcium ions. The stacking of these planes results in a series of parallel hexagonal pipes where the substituents are located. While the fluoride ions are exactly located on the triangle centers, the hydroxyl, chloride, and bromide ions are increasingly shifted toward a position above those triangles [3], resulting in an overall hexagonal symmetry (P63/m). HA can be synthesized by a variety of methods such as solid-state reaction [4], co-precipitation [5], sol-gel [6], and sputtering [7]. In spite of the large amount of preparation procedures, only a few have been devoted to synthesizing apatitic compounds with morphology controlled. In contrast, hydrothermal methods using elevated temperature and pressure aqueous solutions [8] allow the synthesis of HA crystals with a certain shape. Although the needleshaped HA ceramics have been prepared by hydrothermal method, the procedure was relatively complicated or the treating temperature was comparatively high. In this paper, fine HA single crystals of high crystallinity with homogeneous rod shapes have been synthesized by a simple method at comparatively low temperature