— We have studied the effect of doping with lithium cations on the phase composition, lattice parameters, and crystallite size of hydroxyapatite at different heat treatment temperatures (900,...

Mesoporous hydroxyapatite (HA) materials demonstrate advantages as catalysts and as support systems for catalysis, as adsorbent materials for removing contamination from soil and water, and as nanocarriers of functional agents for bone-related therapies. The present research demonstrates the possibility of the enlargement of the Brunauer–Emmett–Teller specific surface area (SSA), pore volume, and average pore diameter via changing the synthesis medium and ripening the material in the mother solution after the precipitation processes have been completed. HA powders were investigated via chemical analysis, X-ray diffraction analysis, Fourier-transform IR spectroscopy, transmission electron microscopy (TEM), and scanning (SEM) electron microscopy. Their SSA, pore volume, and pore-size distributions were determined via low-temperature nitrogen adsorption measurements, the zeta potential was established, and electron paramagnetic resonance (EPR) spectroscopy was performed. When the materials were synthesized in water–ethanol and water–acetone media, the SSA and total pore volume were 52.1 m²g⁻¹ and 116.4 m²g⁻¹, and 0.231 and 0.286 cm³g⁻¹, respectively. After ripening for 21 days, the particle morphology changed, the length/width aspect ratio decreased, and looser and smaller powder agglomerates were obtained. These changes in their characteristics led to an increase in SSA for the water and water–ethanol samples, while pore volume demonstrated a multiplied increase for all samples, reaching 0.593 cm³g⁻¹ for the water–acetone sample.

The dependence of the sintering of zirconium dioxide on the aluminum oxide content and the use of additives forming the liquid phase during sintering is studied. Dense nanostructured ceramic materials based on zirconium dioxide containing aluminum oxide are synthesized. It is shown that the use of additives based on sodium silicate contributes to the sintering and the formation of a nonporous structure at 1330°C. It is revealed that aluminum oxide in the amount of 1 and 5 wt % increases the density of materials, while at the content of 16 wt % the sintering until the dense state does not occur even at temperatures up to 1550°C.