X-ray determination of crystalline hydroxyapatite to amorphous calcium-phosphate ratio in plasma sprayed coatings.
A method to measure the amorphous calcium phosphate (ACP) content of plasma sprayed hydroxyapatite (HA) coatings is presented. The areas of the crystalline peaks and the broad amorphous "hump" in an X-ray diffraction scan of a mixture of crystalline and amorphous HA can be fitted using conventional nonlinear least-squares methods. The weight fraction of the amorphous component in a mixture of unknown proportions is obtained from the measured hump fraction using a linear expression requiring a single calibration constant. This calibration constant may be determined by applying the same sample preparation, X-ray measurement, and least-squares fitting methods to a single standard of known (weighed) proportions as used to measure the unknown(s). Application of this method to a set of 12 samples yields an "index of crystallinity" for plasma sprayed HA coatings with an estimated standard deviation of 1 wt % ACP across the entire compositional range.
Keller
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CAMET Research, Inc., 6409-F Camino Vista, Goleta, California 93117, USA.
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D001672:Biocompatible Materials; D002118:Calcium; D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; D017886:Durapatite / Q000737:chemistry; D006801:Humans; D010710:Phosphates; D014961:X-Ray Diffraction
D001672:Biocompatible Materials; D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; D010710:Phosphates; C519480:amorphous calcium phosphate; D017886:Durapatite; D002118:Calcium