Abstract
This paper focuses on the study of the effect of the change of the crystal size on the shape and width of the X-ray diffraction patterns for defatted and deproteinized bones as well as incinerated biogenic hydroxyapatite obtained from bovine, porcine, and human bones. Inductively Couple Plasma showed the presence of some ions such as Mg, K, Al, Fe, Zn, and Na for all samples. The nanometric size of the crystals was determined through High Resolution Transmission Electron Microscopy in which ordered crystals were found. The calcination of raw clean bones at 720 °C produced a transition of crystal size from nano to micro due to a coalescence phenomenon, this was accompanied by a decrease of the peak width of the X-ray diffraction patterns due to the decrease of the inelastic scattering contribution from the microcrystals. A simulation of the effect of the crystallite size on the shape and width of the X-ray patterns was done using PDF-4 software which confirmed that raw ordered bone crystals produce broad peaks which so far have been erroneously assigned to polycrystalline hydroxyapatite with low crystalline quality.
Highlights
It is well established that the above-mentioned biogenic sources are formed by nanocrystals of HAp that contains minor elements such as Mg, Na, S, and K
Ca levels are higher for human than for bovine and porcine bone; it could be due to the human diet rich in calcium, and that this HAp is carbonated
The shape and width of the X-ray diffraction pattern for ordered crystals are governed by the crystal size
Summary
It is well established that the above-mentioned biogenic sources are formed by nanocrystals of HAp that contains minor elements such as Mg, Na, S, and K. Even with the presence of these ions, the XRD patterns of the raw bone mineral phase almost exhibit the same positions as those of synthetic hydroxyapatite[4]. The structural properties of hydroxyapatite from several sources have been studied by X-ray diffraction, in which information about the determination of crystalline structures, crystalline quality, crystal size, and lattice defects can be obtained. Ooi et al.[13] showed that the X-ray pattern of raw bovine bone exhibits the presence of nanocrystalline apatite. Their results indicate that in annealed samples between 700 to 1000 °C, a substantial increase in the height and a decrease in the width of the peaks occur which were associated with an increment in crystallinity and crystallite size. If the initial state of the hydroxyapatite of the bovine bone corresponds to nanocrystals, the width and the height of the peaks cannot be correlated with crystalline quality due to elastic and inelastic scattering phenomena governing them
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