Powders Based on Ca2P2O7-CaCO3-H2O System as Model Objects for the Development of Bioceramics

Abstract

Nanoscale powders of hydrated Ca2P2O7, CaCO3, and a product of mixed-anionic composition containing P2O74− and CO32− anions were synthesized from aqueous solutions of Ca(CH3COO)2, pyrophosphoric acid (H4P2O7), and/or (NH4)2CO3. Pyrophosphoric acid was previously obtained on the basis of the ion exchange process from Na4P2O7 solution and H+-cationite resin for further introduction into the reactions as an anionic precursor. The phase composition of powders after the syntheses was represented by bioresorbable phases of X-ray amorphous Ca2P2O7 phase, calcite and vaterite polymorphs of CaCO3. Based on synthesized powders, simple cylindrical constructions were prepared via mechanical pressing and fired in the temperature range of 600–800 °C. Surface morphology observation showed the presence of bimodal porosity with pore sizes up to 200 nm and 2 μm, which is likely to ensure tight particle packing and roughness of the sample surface required for the differentiation of osteogenic cells. Thus, the prepared ceramic samples can be further examined as model objects for bone tissue repair.

Powder Synthesized from Aqueous Solution of Calcium Nitrate and Mixed-Anionic Solution of Orthophosphate and Silicate Anions for Bioceramics Production

“…There are some examples of powders synthesized from mix-anionic HPO 4 /P 2 O 7 [43] P 2 O 7 /CO 3 [44], HPO 4 /CO 3 [45,46], or mix-cationic K/Na [47] aqueous solutions with appropriate homogeneity that were used for the ceramic materials preparation. Preservation of reaction by-product as a component of the powder mixture also can be used as a method of preparation of powder mixtures with high homogeneity [25,48,49].…”

“…However, an approach involving synthesis from mixed-anionic solutions is more interesting, since this method leads to a more homogeneous distribution of components in the powder mixture [43][44][45][46]. In addition, a chemical approach to the synthesis of mixedanionic powders makes it possible to obtain more dispersed powders with a larger specific surface area, which are more active, and the sintering process is more effective [48,49].…”

Microporous Ceramics Based on β-Tricalcium Phosphate

“…Powder mixtures with a given molar ratio Ca/P = 1.5 intended for the synthesis of tricalcium phosphate Ca 3 (PO 4 ) 2 , in addition to the calcium phosphates with Ca/P = 1 (i.e., calcium pyrophosphate Ca 2 P 2 O 7 , hydrated calcium pyrophosphate Ca 2 P 2 O 7 •xH 2 O, brushite CaHPO 4 •2H 2 O, or monetite CaHPO 4 ) may contain tetracalcium phosphate Ca 4 (PO 4 ) 2 O, hydroxyapatite Ca 10 (PO 4 ) 6 (OH) 2 [27], calcium oxide CaO, or precursors of calcium oxide CaO, such as calcium carbonate CaCO 3 [28,29] or calcium salts of carboxylic acids [30][31][32]. Calcium carbonate CaCO 3 or calcium salts of carboxylic acids can be treated as reagents convenient for synthesis due to the stability of their chemical composition in storage.…”