Irma Bogdanoviciene

pH impact on the sol-gel preparation of calcium hydroxyapatite, Ca10(PO4)6(OH)2, using a novel complexing agent, DCTA

Aqueous sol-gel chemistry routes — based on ammonium hydrogen phosphate as the phosphorus precursor, calcium acetate monohydrate as the source of calcium ions, and 1,2-diaminocyclohexanetetraacetic acid monohydrate (DCTA) as the complexing agent — have been used to prepare calcium hydroxyapatite (HA). The sol-gel process was performed in aqueous solution at different pH values followed by calcination of the dry precursor gels for 5 h at 1000°C. Phase transformations, composition, and structural changes in the polycrystalline samples were studied by thermoanalytical methods (TG/DTA), infrared spectroscopy (IR), X-ray powder diffraction analysis (XRD), and scanning electron microscopy (SEM). It was shown that pH adjustment has significant impact on the apatite formation process and on the morphology and phase purity of the ceramic samples.

Formation of Ca–Zn–Na phosphate bioceramic material in thermal processing of EDTA sol–gel precursor

In this study, investigation of the Ca–P–O, Ca:Zn–P–O, Ca:Na–P–O, and Ca:Zn:Na–P–O precursor gels prepared using EDTA as complexing agent and slightly different starting materials was performed. For this purpose, thermal decomposition of the gels was studied by TG/DTA-EGA/MS with following evolvement of H2O, CO2, NH3, and NOx gases. Besides, thermal decomposition products were characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. It was demonstrated that thermal decomposition of Ca–P–O acetate and Ca:Zn–P–O, Ca:Zn:Na–P–O acetate-nitrate gels is different. Thus, the results of thermal decomposition of Ca:Zn–P–O and Ca:Zn:Na–P–O gels showed that Zn and Na additives accelerate decomposition of the gels. In addition, Na substitution at Ca sites creates conditions for the formation of the orthophosphate composites at lower temperatures.

Sol-Gel Synthesis and Characterization of Lanthanide-Substituted Nanostructured Calcium Hydroxyapatite

In this study, nanostructured Ce- and Sm-substituted Ca10(PO4)6(OH)2 samples have been synthesized using an aqueous sol-gel chemistry route. For the characterization of obtained specimens, the XRD, SEM, UV-visible reflection and IR spectroscopy and luminescence measurements were recorded. It was shown that phase purity of the end products highly depends on the amount of lanthanide element. The reflectance of lanthanide-substituted calcium hydroxyapatite samples is wavelength independent in the wavelength range of 450-800 nm and equal almost 100%. The cerium-substituted samples show a significant decrease of transmission at ~300 nm. The characteristic samarium absorption line (~430 nm) is evident in the UV-vis reflection spectra of samarium-substituted hydroxyapatites.

Purity test of precipitated apatites by TG/DTA/EGA–MS

AbstractnPure Ca hydroxyapatites (CaHAp) and Na-, Mg-, Zn- and Sr-substituted precipitated apatites were characterized by X-ray diffraction analysis, Fourier transformed infrared spectroscopy and element, chemical, and TG/DTA–EGA–MS analysis at their heating up to 1200xa0°C in Ar atmosphere. The evolvement of H2O, CO2, NH3, and NxOy was followed by mass spectroscopy (MS). Comparison of thermal behavior of pure CaHAps and cation-substituted apatites indicates that the exact temperatures of the release of gases (thermal stability) depend strongly on the chemical composition and crystallinity of sample. The presence of nitrogen species was detected by TA–MS in all precipitated apatites, and its content (0.01–1xa0%) depends on the synthesis conditions, the washing profoundness as well as on the cationic composition of apatite.

Synthesis of Bio-Cation-Substituted Ca-Apatites by Precipitation

Nanosize Mg2+, Zn2+, Sr2+, and Na+ mono- and di-substituted calcium hydroxyapatites were synthesized using an aqueous precipitation route under controlled conditions. The chemical composition and the micro-structural features of the polycrystalline samples were characterized by chemical analysis, thermal analysis (TG/DTA) combined with MS for evolved gas analysis, FTIR and XRD spectroscopy as well as SEM. The correlations between chemical composition and the crystal morphology were elucidated.