Cementless refractory castable. Part 9. HCBS and ceramic concretes in the Al2O3‒SiO2‒SiC system

The priority-chronological aspect of research and technological development in the field of SiC-containing HCBS and ceramic castables in the systems Al2O3‒SiO2‒SiC and Al2O3‒SiO2‒SiC‒C is characterized. The results of studies on the effect of the firing temperature and prolonged (up to 100 h) high-temperature heat treatment on the oxidation kinetics of SiC of different dispersion and content are considered. A noticeable oxidation, accompanied by an increase in the mass and growth of samples, is noted after 1200 °C and significant at 1300‒1400 °C. The effect of the firing temperature in the range of 1000‒1400 °C and long holding in a tunnel furnace (60 h at 1300‒1400 °C) on the dynamics of phase transformations and the structure of samples of the matrix system based on HCBS of composite composition (bauxite + 11 % VFQG), as well as with an additional content of 15% SiC. In contrast to firing in air, during the service of monolithic gutter masses in the Al2O3‒SiO2‒SiC‒C system, the working surface of concrete is largely isolated from the air due to cast iron and slag. This drastically reduces the rate of both SiC oxidation and carbon burnout. The zonal structure of the lining is characterized. The data on the effect of heating and cooling on the modulus of elasticity of ceramic castable are presented.

Spontaneously formed gradient chemical compositional structures of niobium doped titanium dioxide nanoparticles enhance ultraviolet- and visible-light photocatalytic performance

Semiconductor photocatalysts showing excellent performance under irradiation of both ultraviolet (UV)- and visible (VIS)-light are highly demanded towards realization of sustainable energy systems. TiO2 is one of the most common photocatalysts and has been widely investigated as candidate showing UV/VIS responsive performance. In this study, we report synthesis of Nb doped TiO2 by environmentally benign mechanochemical reaction. Nb atoms were successfully incorporated into TiO2 lattice by applying mechanical energy. As synthesized Nb doped TiO2 were metastable phase and formed chemical compositional gradient structure of poorly Nb doped TiO2 core and highly Nb doped TiO2 surface after high temperature heat treatment. It was found that formed gradient chemical compositional heterojunctions effectively enhanced photocatalytic performance of Nb doped TiO2 under both of UV- and VIS-light irradiation, which is different trend compared with Nb doped TiO2 prepared through conventional methods. The approach shown here will be employed for versatile systems because of simple and environmentally benign process.

Immunomodulating sauces

Deficiency of most micronutrients, imbalance in nutrition, together with a dangerous environmental situation in Ukraine, has led to a decrease in the immunity of the population and the spread of alimentary-dependent diseases. Due to the damaged immunological picture of the population in recent years, the relevance of the creation of immunomodulating products is significantly increasing. About 70% of dishes served in restaurant are released with sauces, which allows not only to improve the aroma, appearance and taste of the finished dish, but also to increase the content of the essential substances of the dish. In the assortment of sauce products on the Ukrainian market, most of the sauces contain preservatives, artificial stabilizers and emulsifiers that negatively affect the human body and are not recommended for daily consumption. The subject of research is sauce products for preventive nutrition with increased nutritional value, without the presence of artificial food additives in the composition. The purpose of the study is to develop formulations of immunomodulating sauces using natural raw materials. Methods. The object of the study - developed immunomodulating sauces. In the finished product, the following parameters were determined: titratable acidity (DSTU 4957:2008), microbiological indicators (GOST 10444.15-94, GOST 54728-92, GOST 10444.2-94, GOST 30519-97). The results of the study. As a result of a literature search, the substances were determined, their bigger content in dies being important for improvement in the state of the immune system. These substances include, first of all, antioxidant vitamins (C, A and E), polyunsaturated fatty acids (especially omega-3), mineral elements and other minor substances. During developing the formulations of immunomodulating sauces, twelve requirements were formulated.. As a result of the raw materials selection, three formulations of immunomodulating sauces have been proposed. In their technology, there is a high-temperature heat treatment, which allows maximizing the preservation of useful thermolabile components. Scope of research results. Ready-made sauces are sold in restaurant establishments and consumed locally. Due to their simplicity of preparation, they can also be recommended for making at home. The developed immunomodulating sauces have a pleasant appearance and harmonious taste, which is confirming the data of sugar-acid indices.

Natural Rubber Biocomposites Filled with Phyto-Ashes Rich in Biogenic Silica Obtained from Wheat Straw and Field Horsetail

The rich structural hierarchy of plants permits the obtainment of porous structures which can be expected to show improved performances in fields such as pharmaceuticals and cosmetics, catalysis, drug delivery, adsorption, separation or sensors in various chemical reactions. On the other hand, porous materials can be an active additive to polymer composites. The aim of the study was to obtain natural rubber (NR) biocomposites with the addition of phyto-ashes reach in biogenic silica from plant biomass. For the production of bioadditives, a two-stage method of high-temperature heat treatment was used, preceded by acid hydrolysis of plant tissues in the form of horsetail and wheat straw. Hydrolysis was performed with hydrochloric and citric acid. The efficiency of the processes and their influence on the elemental composition, surface morphology, thermal stability and particle size of the fillers were determined. Modified bioadditives were introduced into the elastomer matrix and their processing properties, as well as the vulcanization characteristics, were examined. Static mechanical properties (tensile strength, elongation at break, stress at 100%, 200% and 300% elongation), dynamic-mechanical analysis and the influence of additives on the cross-link density of the composites were determined. Structural analysis was performed using scanning electron microscopy. It was found that the field horsetail and cereal straw are plants rich in many valuable chemical compounds, especially silica. The specific and appropriate treatment of these plants can lead to bioadditives that significantly affect the properties of rubber materials.

Study on the Effect of High-Temperature Heat Treatment on the Microscopic Pore Structure and Mechanical Properties of Tight Sandstone

The investigation of changes in physical properties, mechanical properties, and microscopic pore structure characteristics of tight sandstone after high-temperature heat treatment provides a theoretical basis for plugging removal and stimulation techniques, such as high energy gas fracturing and explosive fracturing. In this study, core samples, taken from tight sandstone reservoirs of the Yanchang Formation in the Ordos Basin, were first heated to different temperatures (25-800°C) and then cooled separately by two distinct cooling methods—synthetic formation water cooling and natural cooling. The variations of wave velocity, permeability, tensile strength, uniaxial compressive strength, and microscopic pore structure of the core samples were analyzed. Experimental results demonstrate that, with the rise of heat treatment temperature, the wave velocity and tensile strength of tight sandstone decrease nonlinearly, yet its permeability increases nonlinearly. The tight sandstone’s peak strength and elastic modulus exhibit a trend of the first climbing and then declining sharply with increasing temperature. After being treated by heat at different temperatures, the number of small pores varies little, but the number of large pores increases obviously. Compared to natural cooling, the values of physical and mechanical properties of core samples treated by synthetic formation water cooling are apparently smaller, whereas the size and number of pores are greater. It can be explained that water cooling brings about a dramatic reduction of tight sandstone’s surface temperature, generating additional thermal stress and intensifying internal damage to the core. For different cooling methods, the higher the core temperature before cooling, the greater the thermal stress and the degree of damage caused during the cooling process. By taking into consideration of changes in physical properties, mechanical properties, and microscopic pore structure characteristics, the threshold temperature of tight sandstone is estimated in the range of 400-600°C.

Improvement of the technology of production of table grainy sterlet (Acipenser ruthenus (Linnaeus, 1758)) caviar

Purpose. Tosubstantiate scientifically and improve the technology of producing table caviar from ovulated sterlet eggs, which ensures the preservation of natural biologically active compounds and the stability of quality parameters. To investigate table caviar for microbiological, toxicological and toxico-biological safety. To determine the prospect of using the data in the practice of caviar sturgeon breeding. Methodology. Primary materials were obtained in the conditions of «Oasis Bisan» JSC. The results obtained were processed by organoleptic, biochemical, microbiological, toxicological, toxic-biological methods, as well as by the method of variation statistics using MS Excel with an emphasis on standard errors. Findings. Application of the heat treatment mode (78°C) of ovulated sterlet eggs while reducing the total time of the technological process to 1.0 minute contributes to the preservation of the integrity of food product components. Sterlet eggs from recirculated aquaculture system differed from a similar product from fish from natural waters by a lower mineral content (by 1.2%), an increased content of dry matter (by 8.1%), protein (by 7.5%) and lipids (by 3.7%). This fact indicates a decrease in the water content of the product and the acquisition of optimal gastronomic qualities. Sterlet caviar proteins were found to contain a full set of essential amino acids, the chemical score of which exceeded 100%; no limiting amino acids were found. Comparative analysis of sterlet caviar from recirculated aquaculture systems and from natural habitats showed the absence of significant differences in the amino acid composition, which demonstrated the biological value of the product. The use of the mode of short-term high-temperature heat treatment allows ensuring sufficient safety of the food product. The absence of E. coli and yeast in caviar was found. Pb, Cd, As and Hg contents in sterlet caviar were significantly lower than the maximum permissible levels. The total value of hexachloran and isomers was 0,0027mg/kg; DDT and metabolites – 0,016 mg/kg, polychlorinated biphenyls – 0,017 mg/kg and corresponded to permissible limits. The absence of altered forms, growth inhibition or death of tetrachimens confirms the toxicological safety of the finished product. The shelf life of the finished product without preservative is 6 months at a storage temperature of minus 2°C – minus 4°C, which parametrically meets the requirements of TU U 10.2-37758242-002: 2018. Originality. The technology of processing ovulated sterlet caviar has been scientifically substantiated and experimentally tested. New data on the comparison of the results of classical pasteurization and short-term high-temperature heat treatment of caviar are presented. For the first time, the amino acid composition of sterlet caviar was studied under conditions of recirculated aquaculture systems, and the analysis of grainy caviar for hexachloran and isomers, DDT and metabolites, and polychlorinated biphenyls was carried out. Information on the chemical composition of caviar in the process of technological processing was clarified and supplemented. Practical value. The advantage of the improved technology of processing raw caviar over the classical method of pasteurization was determined. The expediency of using an alternative technology in order to save energy and preserve traditional organoleptic properties, nutritional value and safety of the finished product were experimentally confirmed. On the basis of the results of the studies carried out, the technical documentation of TU «Technological instruction for the production of granular sturgeon caviar» and «Working instruction for the selection of caviar» were developed and agreed in accordance with the established procedure with the bodies and institutions of the State Sanitary and Epidemiological Surveillance and the State Standard. The developed technology was tested in the development of pilot batches of food sterlet caviar, which made it possible at the «Oasis Bisan» enterprise to introduce a food safety management system and conduct a certification audit by the International certification body TUV SUD for compliance with the International standard ISO 22000: 2005. Commission, the «Oasis Bisan» enterprise received an EU registration number: a-UA-14-20-121-VIII-PP, in connection with which it has the right to export products (sturgeon caviar) to the countries of the European Union. Key words: technology, heat treatment, pasteurization, food caviar, biological value, safety, finished product.

Phase Stability and Transport Properties of (ZrO2)0.91−x(Sc2O3)0.09(Yb2O3)x Crystals (x = 0–0.01)

Phase stability and transport properties of (ZrO2)0.91−x(Sc2O3)0.09(Yb2O3)x crystals (x = 0–0.01) have been studied before and after air annealing at 1000 °C for 400 h. The crystals have been grown by radio frequency (RF) heating in a cold crucible. The microstructure, phase composition, and electrical conductivity of the crystals have been studied using optical microscopy, X-ray diffraction, Raman spectroscopy, and impedance spectroscopy. Phase stability and degradation of ionic conductivity of the crystals upon long-term high-temperature heat treatment have been discussed. We show that the stabilization of ZrO2 co-doped with 9 mol.% Sc2O3 and 1 mol.% Yb2O3 provides transparent uniform crystals with the pseudocubic t″ phase structure having high phase stability. Crystals of this composition had the highest conductivity in the entire temperature range. Long-term high-temperature annealing of these crystals did not lead to conductivity degradation.