Controlled Rate Thermal Analysis (CRTA) as New Method to Control the Specific Surface in Hydroxyapatite Thin Coatings

Abstract

The control of the texture in synthetic hydroxyapatite ceramics had limited their application in the ield of the materials for bone implantation, even more when it is used as a illing in cements and other formulations in orthopedic surgery. The present article shows preliminary results demonstrating the efectiveness of a modiication of the controlled rate thermal analysis (CRTA), developed by J. Rouquerol, used for the preparation of ceramic materials with controlled textural characteristics, during the formation of ceramic powders of synthetic hydroxyapatite at low temperatures. The thermal treatments of the hydroxyapatite were carried out in a device connected to a computer, to control temperature and pressure system, keeping the decomposition speed constant. Results, reported when preparing ceramic powders of hydroxyapatite at 300 and 850°C under controlled pressure, using synthetic hydroxyapatite with a Ca/P molar ratio equal to 1.64, were checked using IR spectroscopy and X-ray difraction, showed that the formed phase corresponds to that of crystalline hydroxyapatite, even at 300°C of maximum temperature. Values of speciic surface (BET) between 17 and 66 m 2 /g, with pore size in the range of 50-300 Å in both cases are obtained by N 2 absorption isotherms, when analyzing the isotherms of nitrogen absorption.

Sol-gel deposition of hydroxyapatite coatings on porous titanium for biomedical applications

“…Finally, the green compacts were sintered in a Carbolyte® STF 15/75/450 ceramic furnace, with a horizontal tube at 1250°C for 2h using high vacuum (~10-5 mbar). The protocol used for the HA coating is a variant of one procedure shown in the literature [20][21][22][23]. The precursor was triethyl phosphite, hydrolyzed during 24h with distilled water under vigorous stirring.…”

Biocompatibility and Corrosion Protection Behaviour of Hydroxyapatite Sol-Gel-Derived Coatings on Ti6Al4V Alloy

“…The HAp can be synthesized by many methods [ 7 , 8 ]. The sol-gel synthesis of HA ceramics has attracted much attention because it offers a molecular-level mixing of the calcium and phosphorus precursors, which is capable of improving chemical homogeneity of the resulting HAp to a significant extent, in comparison with conventional methods such as solid state reactions, wet precipitation and hydrothermal synthesis [ 9 , 10 , 11 , 12 ]. The HAp synthesized by sol-gel will form strong chemical bonds with bone in vivo.…”