Improvement of the reactivity of triethyl phosphate and structural behavior of hydroxyapatite versus the synthesis conditions by sol-gel route

Hydroxyapatite (HA) is a biocompatible and bioactive material used as bone-substitute materials in both orthopedics and dentistry. This work is devoted to studying the synthesis of hydroxyapatite (HA) by sol-gel route using triethyl phosphate (TEP) and calcium nitrate tetrahydrate as calcium and phosphor precursors. In order to optimize the hydrolysis of TEP, each prepared solution was aged in a closed Teflon(R) container. Several factors were tested in order to improve the synthesis conditions of well-crystallized HA. The effect of aging time (4 h, 16 h, and 24 h), aging temperature (25 degrees C, 50 degrees C, 70 degrees C, and 90 degrees C) of the prepared solutions, and the type of solvents (ethanol and/or distilled water) were tested. All dried gels were calcined at 700 degrees C for 1 h. The obtained results showed that the crystallinity degree of hydroxyapatite increases with aging time and temperature, which must not exceed 70 degrees C. When the prepared solutions were aged at 90 degrees C, the tri-calcium phosphate (TCP) was formed as a major phase and HA was present as a very minor phase. It was remarked that the aging of sols in a closed Teflon container(R) leads to an important decrease of the aging time and temperature. It was found that 24 h and 70 degrees C are the optimal conditions for the synthesis of well-crystallized HA. Also, it was deduced that a sufficient amount of water was needed to hydrolyze the triethyl phosphate and consequently, to obtain a well-crystallized HA.

Automated summary

This study focused on the synthesis of hydroxyapatite (HA) by sol-gel method, finding that aging time and temperature have a significant impact on the crystallinity of HA, with the optimal conditions being 24 hours and 70 degrees Celsius. Aging in a closed container was shown to decrease aging time and temperature effectively.