Hydrothermal synthesis and characterization of hydroxyapatite microstructures

Abstract

In the present work, hydroxyapatite (HAp, Ca <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</inf> (PO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> ) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> (OH) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) synthesis was carried out using hydrothermal method with calcium hydroxide (Ca(OH) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) and ammonium phosphate((NH4)2HPO4) as precursors. Two different HAp powders were obtaining by varying pH by adding nitric acid (pH =9) and ammonium hydroxide (pH = 10). All the synthesis was carried out in an autoclave at 200 °C for 24 h. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. The results obtained by XRD confirms that the diffraction peaks correspond to pure hydroxyapatite phase. The results of SEM show the formation of hydroxyapatite agglomerates, with an approximate size ranging from 5 to 40 μm, with a rough surface. EDS analysis show a Ca / P ratio ∼1.95. powders obtained in this work, with the above characteristics can be utilized in gas sensors and thermoluminescence applications.