Synthesis of TTCP by using inverse micelle method

Abstract

Tetracalcium phosphate (TTCP, Ca4(PO4)2O) is one of the major powder components of self-setting orthopedic and dental cements. Traditionally, TTCP powders are produced by a solid-state reaction of Ca- and P-containing precursors between 1350 and 1500 °C. Such procedures require expensive high-temperature furnaces and subsequent grinding of sintered particles. Grinding not only leads to the contamination but also alters the structure of TTCP, thereby reducing its bioactivity. The present paper offers an innovative approach to the inverse micelle method of TTCP synthesis, with a subsequent thermal treatment to obtain purer TTCP phase. The obtained powder was a mixture of TTCP and octacalcium phosphate (OCP) phases for thermally untreated sample, while for the sample thermally treated at 800 °C it was a mixture of TTCP and β-TCP phases. The TTCP phase was prevailing phase in both cases. A typical shape of TTCP nanoparticles was needle-like. Somewhere, needles are joined together forming platelet-like structures. Investigations of the obtained phases were made by XRD and TEM. The mechanism of chemical synthesis and structural arrangements of the obtained phases were particularly investigated.The specific surface area and mechanical properties (compressive and flexural strength) of cements based on needle like TTCP (n-TTCP) and irregular shape TTCP (i-TTCP), as the most frequent form of TTCP appeared in literature, were compared. It was shown, by corresponding calculations, that the specific surface area of n-TTCP (determined from TEM micrographs) was much higher than in the case of i-TTCP (determined from SEM micrographs). Beside, compressive and flexural strength of n-TTCP based cement were significantly improved, because n-TTCP whiskers considerably reinforced structure of hardened cement paste.