In the present work, biomimetic hydroxyapatite (BHAP) doped with silicate and carbonate anions in the presence of citrate ions are synthesized by chemical precipitation from aqueous solutions. According to the results of X-ray phase analysis (XRD), all the obtained materials are single-phase. Scanning electron microscopy (SEM) demonstrates that BHAP powders are a collection of agglomerated particles with similar morphology. Dynamic light scattering confirms that the synthesized BHAPs consist of agglomerates 1–4μm in size. For all samples, with an increase in the number of introduced citrate ions, decreases in the average crystallite size and degree of crystallinity are observed. With an increase in the concentration of citrate ions, the content of agglomerate fractions of 1–2μm in size increases from 70.16 to 75.43%. The solubility of hydroxyapatite samples in physiological saline (ω(NaCl) = 0.9%) at temperatures of 22°C and 37°C is studied. It is revealed that for all synthesized BHAPs, the amount of released Ca2+ ions into the liquid phase increases. The maximum yield of Ca2+ ions in physiological saline is recorded in BHAP with the highest content of citrate ions. The obtained results allow to consider the synthesized BHAP as a promising medical biomaterial for the regeneration of bone tissue.

The process of thermocatalytic conversion of polypropylene into liquid hydrocarbons using amorphous aluminum silicates with aluminum content of 1.6-12.9 wt.% as catalysts was studied. The aluminum silicates were synthesized by sol-gel method using hydrolysis of tetraethoxysilane in a presence of aluminum salt at pH=9. All samples possessed acidic sites with pKa value of 3.46-5.00 and had a developed surface. Textural properties of the aluminum silicates were determined. Thermocatalytic conversion of polypropylene was carried out in a flow fixed-bed reactor with a fixed layer of the mixture of the catalyst and the reagent at a mass ratio of polymer : catalyst of 3 : 1 in argon atmosphere with a gradual rise of temperature in the range of 300 – 450 ºС. The sample of silica, which did not contain aluminum, was demonstrated to be inactive in polypropylene degradation, while other catalysts provided conversion of polypropylene into liquid products. The highest yield of liquid products was 80% for a catalyst with an aluminum content of 8.1 wt.%. According to the results of GLC saturated hydrocarbons were identified among the products for all samples. The effect of the concentration of acidic centers on the chemical and fractional composition of the target products was shown. For the studied aluminum silicates with the same pKa values, an increase in the aluminum content favored the formation of a lighter hydrocarbon fraction. For the catalyst with the highest aluminum content the n-alkanes of С5-С10 composition were identified. These products were closest to gasoline oil fraction. This provides a possibility to consider secondary polyolefins as an alternative source of motor fuels. An influence of catalyst composition on maximal temperature of polyethylene degradation was determined by differential thermal analysis.

The present study investigated the phase composition, the structural, morphological, and bioactivity properties of silicon- and carbonate-doped biomimetic hydroxyapatite synthesized by precipitation from aqueous solutions in the presence of different amounts of citrate ions. The X-ray diffraction and Fourier transform infrared spectroscopy analyses confirmed that all the samples exhibited single-phase. Base on the results of the morphological study, all the obtained samples consisted of porous agglomerated particles made up of tiny crystallites in the nanometer range. The change in structural order, as well as the decrease in particle size and degree of crystallinity result from the presence of citrate ions were revealed by X-ray diffraction, dynamic light scattering, and scanning electron microscopy analyses. Bioactivity properties of samples were studied by analyzing their bioresorbability in physiological saline (ω (NaCl) = 0.9%) and evaluating their solubility in SBF solution after a certain period of soaking time. The amount of the released Ca2+ ions was found to increase with the increasing concentration of citrate ions introduced in the synthesis process. The better solubility of material with the presence of citrate ions was beneficial in the growth of apatite on its surface that made produced material more biocompatible.

Phase formation of calcium monoaluminate and calcium dialuminate in the СаО–Al2О3 system in the range 230–1450°C was studied using a model powder mixture comprising aluminum and calcium hydroxides. The onset of formation of an intermediate phase Ca12Al14O33 (С12А7) was observed at 430°С. At 1100°С, the appearance of CaAl4O7 (CA2) and the presence of κ-Al2O3 were observed. The onset of intense formation of the CaAl2O4 (СА) phase is at 1170°С. In the range 1250–1400°С, the CA amount increases notably, while the СА2 proportion remains almost unchanged. The final formation of the CA and CA2 target phases occurs in 2 h at 1450°С. The syntheses of CA and CA2 is controlled by Ca2+ diffusion inward the aluminum-enriched cores of spherulites. Energy dispersive X-ray spectroscopy elucidated the CA and CA2 distribution in the form of concentric layers.

Degradation of polyethylene in the presence of synthetic amorphous aluminosilicates as catalysts to form petroleum-like hydrocarbons was studiedyesBS