Nanopowders of hydroxyapatite (HA), modified by magnesium (MgHA) and by silicon (SiHA) were obtained by liquid-phase microwave synthesis method. X-ray diffraction and IR spectroscopy results showed that Mg2+ and SiO44− ions were present in the synthesized products both as secondary phases and as part of the HA phase. Whitlockite was found in the magnesium-modified HA (MgHA) and larnite was found in the silicon-modified HA (SiHA); ion substitution for both materials resulted in solid solutions. In the synthesized samples of modified HA, the increase of particle size of powders was in the order HA < SiHA < MgHA, which was calculated through data specific surface area and measured pycnometric density of the powders. The Lewis acid sites (Ca2+, Mg2+, Si4+) were present using spectral probes on the surface of the samples of HA, MgHA, and SiHA, and the acidity of these sites decreased in the order SiHA > MgHA > HA. The rates of calcium phosphate layer deposition on the surface of these materials at 37 °C in the model simulated body fluid solution showed similar dependence.

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The calcium phosphate spherical material with a hierarchical structure has been used as a bone implantation material. To improve the properties of the implant material, the compositions of calcium phosphate, silicon, and titanium are crucial. The presence of silicon on the surface of the phosphate–calcium material accelerates the bonding of the implant with the bone (osseointegration). The aim of this work was to develop a sol–gel method to prepare spherical calcium-phosphate@TiO 2 –SiO 2 biomaterials for bone implantation. The CaO@TiO 2 –SiO 2 biomaterial with a core–shell structure was synthesized by the sol–gel method. The biological properties of the materials were studied with a simulated body fluid (SBF). The sample had a spherical shape. The sample exhibited bioactive properties because an increase in the content of calcium and phosphorus ions in the shell and the presence of precipitated ions from the solution were detected on the surface. The TiO 2 –SiO 2 framework was uniformly fixed on the CaO core. Heat treatment of the hybrid mesostructure led to the formation of mesoporous materials with a specific regular structure in the nanometer size in the shell, which is necessary for the fixation of biological cells when the sample is introduced into the biological medium. The formation of a calcium–phosphate layer on the materials and the release of soluble silicon and calcium ions into the SBF are the key factors for the rapid connection of these materials with tissue. The results demonstrate that the CaO@TiO 2 –SiO 2 biomaterial with a core–shell structure is a good candidate for bone implantation.

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Preferential oxidation of carbon monoxide in the presence of hydrogen (PROX) is a promising method to remove CO from a hydrogen-containing gas mixture. Nanosized gold catalyst supported on CeO 2 and modified with Mg(OH) 2 was used for preferential oxidation of carbon monoxide in hydrogen-rich stream in this study. Mg(OH) 2 was added on CeO 2 by incipient-wetness impregnation. Au was loaded on Mg(OH) 2-CeO 2 by deposition-precipitation method. PROX reaction was carried out in a continuous flow, fixed bed reactor. CO/O 2 feed ratio was fixed at 1 to magnify the difference of various catalysts. The catalysts were characterized by N 2 sorption, TEM, HR-TEM and XPS. Mg(OH) 2 formed a thin layer on the surface of CeO 2. CeO 2 was in the crystalline phase and Mg(OH) 2 was amorphous. Au particles were homogeneously dispersed on the support with a size of 2-5 nm. Using CeO 2 as a support could increase the dispersion of Mg(OH) 2 and thus increase the interaction between Au and Mg(OH) 2. Adding Mg(OH) 2 on Au/CeO 2 could suppress H 2 oxidation and therefore increase CO oxidation activity.