Study of bovine hydroxyapatite obtained by calcination at low heating rates and cooled in furnace air

This article focuses on the study of the thermal, vibrational, structural, and morphological changes of hydroxyapatite from bovine bone obtained by a three-step process: calcination at two different low heating rates (2.5 and 5 A degrees C/min), at different temperatures ranging from 600 to 1100 A degrees C, and cooled in the air furnace. Differential scanning calorimetric and thermogravimetry showed that for T > 700 A degrees C, no organic compounds were present in the bone matrix. Scanning electron microscopy images showed that the heating rates affect the morphology of the samples. The primary porosity originated by the presence of fat and protein disappears after the coalescence of the poly-hydroxyapatite crystals, and for T > 800 A degrees C, a disorder-order transition (poly-crystal-single crystal) occurs. Full-width at the half-maximum of X-ray diffraction patterns indicated that the heating rate affects the structure of the BIO-Hap. Diffraction peak corresponding to calcium carbonate disappears from X-ray patterns of the samples calcined above 700 A degrees C. The disorder-order (poly-crystal-single crystals) transition occurs for T > 900 A degrees C. Raman experiments showed that for T > 700 A degrees C, no organic phases are present in the samples. Dihydroxylation of hydroxyapatite is present for temperatures up to 800 A degrees C originated Whitlockite. The same thermal conditions during sample calcination process were assured by using a controlled computer system.