Simultaneous x-ray and neutron diffraction Rietveld refinements of nanophase Fe substituted hydroxyapatite.Reportar como inadecuado


 Simultaneous x-ray and neutron diffraction Rietveld refinements of nanophase Fe substituted hydroxyapatite.


Simultaneous x-ray and neutron diffraction Rietveld refinements of nanophase Fe substituted hydroxyapatite. - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.



Type of Resource: text

Genre: Electronic Thesis or Dissertation

Date Issued: Florida Atlantic University

Publisher: Florida Atlantic University

Physical Form: electronic

Extent: xviii, 117 p. : ill. (some col.)

Language(s): English

Summary: The effect of Fe substitution on the crystal structure of hydroxyapatite (HAp) is studied by applying simultaneous Rietveld refinements of powder x-ray and neutron diffraction patterns. Fe is one of the trace elements replacing Ca in HAp, which is the major mineral phase in bones and teeth. The morphology and magnetic properties of the Fe-HAp system are also studied by transmission electron microscopy and magnetization measurements. Samples of Ca(5-x)Fex(PO4)3OH with 0< x < 0.3 were prepared. Single phase HAp was identified in x-ray diffraction patterns (XRD) of samples with x < 0.1 inferring that the solubility limits are less than 0.1. Hematite ((Sa(B-Fe2O3) is identified as a secondary phase for higher Fe content. The refined parameters show that Fe is incorporated in the HAp structure by replacing Ca in the two crystallographic sites with a preference at the Ca2 site. This preference explains the small effect of the Fe substitution on the lattice constants of HAp. The overall decrease of the lattice constants is explained by the ionic vi size difference of Ca and Fe. The increasing trend of the a-lattice constant with x in the Fe substituted samples is attributed to a lattice relaxation caused by the substitution of the 4- and 6-fold Fe at the 7- and 9-fold Ca1 and Ca2 sites. This Ca local geometry reduction is indicated by a slight increase of the Ca1-O3 and Ca2-O1 bond lengths. Above the solubility limit x = 0.05, the Fe is partitioned in and out of the HAp structure with increasing nominal Fe content x. The excess Fe is oxidized to hematite. The TEM analysis and magnetic measurements support the results of the simultaneous Rietveld refinements. The TEM images show no significant effect on the morphology and size of the HAp particles upon Fe incorporation. The particles are either spheres or short rods of dimensions 20-60 nm. Hematite particles are imaged in the samples with x exceeding the solubility limit. These particles

Identifier: 794746457 (oclc), 3342204 (digitool), FADT3342204 (IID), fau:3875 (fedora)

Note(s): by Andreas Kyriacou.Thesis (Ph.D.)--Florida Atlantic University, 2012.Includes bibliography.Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

Subject(s): X-rays -- DiffractionRietveld methodNanostructured materialsBiomedical materials

Persistent Link to This Record: http://purl.flvc.org/FAU/3342204

Owner Institution: FAU



Autor: Kyriacou, Andreas.

Fuente: http://fau.digital.flvc.org/islandora/object/fau%3A3875



DESCARGAR PDF




Documentos relacionados