ИСТИНА

Materials for bone implants are of great importance due to growing demands from orthopedic surgery. Essential attention is paid to composite materials containing bioresorbable phase. Calcium-deficient and/or carbonate-containing hydroxyapaptite (HAp), amorphous calcium phosphate (ACP), tricalcium phosphate (TCP), phosphate glass, and calcium pyrophosphate (CPP) can be regarded as such phases. Calcium pyrophosphate β-Ca2P2O7 is one of the intermediate products in bone mineralization process. The biological response with respect to new bone formation is quite similar for CPP and HAp. Sintered CPP has better biological responses, and, thus, a great potential as a biodegradable bone substitute [ ]. Several sources for CPP phase in ceramics can be assumed. CPP phase may come from frit (CaO-P2O5, Ca/P=0.2-0.75) and may be used as a sintering additive [ ].. Ceramics can be fabricated from powder of CPP with Na4P2O7 as sintering additive [ ]. In work [ ], phase of α-CPP forms due to interaction between H3PO4 or (NH4)2HPO4 and porous HAp at high temperature after soaking it in the former solutions. In ceramic fabrication, powders of brushite CaHPO4•2H2O, monetite CaHPO4 and CPP may be used as components for the composite materials. The aim of present work was focused on fabrication of powdered samples of calcium phaphates with Ca/P=1 demonstrating enhanced reactivity to sintering. Powders of brushite, monetite and CPP were synthesized by means of wet chemical precipitation from aqueous solutions of Ca(NO3)2, Ca(CH3COO)2, CaCl2, and (NH4)2HPO4, K2HPO4, Na2HPO4. Synthesized dried powders were disaggregated in acetone. Powders of the materials were tested by means of XRD, TG, SEM/EDX. Density and microstructure evolution of samples of ceramic materials sintered at 700-1100˚C with isothermal holding during 6 hours were tested. Complicated consequence of phase transformations took place during heating the mixtures from 20 to 1200 C. Decrease in size of the particles of the materials under study was observed with increase of the concentration of stock solutions. Among precursors mentioned above, calcium acetate gives rise to the smallest plate-like particles being less than 2 μm according to SEM.