Synthetical bone-like and biological hydroxyapatites: a comparative study of crystal structure and morphology

Abstract

Phase composition, crystal structure and morphology of biological hydroxyapatite (BHAp) extracted from human mandible bone, and carbonated hydroxyapatite (CHAp), synthesized by the chemical precipitation method, were studied by x-ray powder diffraction (XRD), Fourier transform infrared (FTIR) and Raman (R) spectroscopy techniques, combined with transmission electron microscopy (TEM). Structural and microstructural parameters were determined through Rietveld refinement of recorded XRD data, performed using the FullProf computing program, and TEM. Microstructural analysis shows anisotropic extension along the [00l] crystallographic direction (i.e. elongated crystallites shape) of both investigated samples. The average crystallite sizes of 10 and 8 nm were estimated for BHAp and CHAp, respectively. The FTIR and R spectroscopy studies show that carbonate ions substitute both phosphate and hydroxyl ions in the crystal structure of BHAp as well as in CHAp, indicating that both of them are mixed AB-type of CHAp. The thermal behaviour and carbonate content were analysed using thermogravimetric and differential thermal analysis. The carbonate content of about 1 wt.% and phase transition, at near 790 °C, from HAp to β-tricalcium phosphate were determined in both samples. The quality of synthesized CHAp powder, particularly, the particle size distribution and uniformity of morphology, was analysed by a particle size analyser based on laser diffraction and field emission scanning electron microscopy, respectively. These data were used to discuss similarity between natural and synthetic CHAp. Good correlation between the unit cell parameters, average crystallite size, morphology, carbonate content and crystallographic positions of carbonate ions in natural and synthetic HAp samples was found.

Effect of preparation conditions on the nanostructure of hydroxyapatite and brushite phases

“…The characteristic bands of PO 4 3-appeared at 566, 604 and 1032 cm -1 where the bands at 566 and 604 cm -1 were assigned to the vibration of the O-P-O mode (Markovic et al 2011). It is observed that the intensities of the bands were increased by increasing the pH value, as a result of the improvement of the crystallinity of the investigated samples.…”

“…3b for the samples prepared at pH (7, 9, 12), the absorption bands at 3435 and 1606 cm -1 were assigned to the absorbed water (Markovic et al 2011). The bands at 1424 and 844 cm -1 were attributed to the vibrations of CO 3 2-groups absorbed from the ambient atmosphere (Alobeedallah et al 2011).…”

Improving the Radiopacity of Calcium Aluminate Cement Based Blends

“…In the range between 900 and 1100 cm -1 , the presence of the functional groups PO 4 3-and CO 3 2-derived from carbonate hydroxyapatite is expected 33,34 . The latter is the main mineral phase of bone, which is a bioceramic composite that also comprises the organic phase, mainly collagen 22 .…”

Estudo, caracterização e propriedades de ortofosfatos multifuncionais

“…Bandas referentes as outras possíveis fases de ortofosfatos não foram observadas em nenhum caso, confirmando a estabilidade estrutural do material na faixa de temperatura estudada. A banda ampla entre 3000-3600 cm -1 está associada a presença de H2O adsorvida [51].…”

“…e está relacionado a substituição tipo-AB [33,51]. As bandas nessa região também podem estar associadas a presença de NH4 + e HPO4 2- [111,173].…”