The current approach in bone tissue engineering requires resorbable biomaterials that enhance bone formation while maintaining sufficient mechanical stability. In this work, the influence of three levels of B-type carbonate substitution in hydroxyapatite lattice on mechanical strength and degradation rate is analyzed. The inverse aqueous route has been selected as a synthesis method of four powders with carbonate substitution between 4 and 6 wt.%. X-ray fluorescence (XRF), (C-S)-Analysis, FT-Infrared, X-ray diffraction, DTA-TG and TEM were used to investigate chemical composition, type of substitution, thermal behaviour, and morphology of the powders. Disc shaped specimens were processed by uniaxial pressing and sintering in argon/CO2 flow. Maximum temperatures of thermal treatment between 750 and 850 °C were selected to obtain similar porosity levels for the different compositions. The highest carbonate substituted material (5.3 wt.%) presented higher compressive strength and dissolution rate than the other materials showing the beneficial effect of B-type substitution in hydroxyapatite materials for bone repair.
This study investigated the transformation of cancrinite-type zeolite, together with secondary phases, in a hydrothermal system. The mineral kaolin and NaOH were used as precursors under self-generated pressure at 140 °C, varying the reaction time at intervals of 0 to 10 hours. The kaolin, the main precursor, was subjected to X-ray diffraction (XRD), elemental chemical composition (XRF) and Fourier Transform IR Spectroscopy (FT-IR) analyses. The resulting solids were characterized by XRD. Initially, crystalline phases such as Na-P2 zeolites, gismondine, analcime, natrolite and sodalite were formed, but with time they became unstable and dissolved to form new phases. At 8 hours of reaction, the cancrinite zeolite predominated, fulfilling the main objective of the study. The solid material was analyzed by scanning electron microscopy (SEM) and FT-IR. The behavior of Na, Si and Al in the solutions was evaluated over time by inductre coupled plasma (ICP). It was conclusively demonstrated that kaolin from Hidalgo is a feasible precursor to synthesize zeolites, cancrinite type as predominant phase in 8 hours at 140 °C, using moderate concentrations of NaOH.