Reactivity of 2,3-Dichloropropene in free-radical copolymerization reactions

The copolymers of 2,3-Dichloropropene with vinyl chloride, methyl methacrylate, and styrene of different compositions were obtained via free-radical copolymerization. The copolymerization constants for the comonomers were found from the dependence of the copolymer composition on the initial mixture content. An increase in the content of 2,3-Dichloropropene in the initial mixture was found to decrease the yield and intrinsic viscosity of the copolymer for all systems. The reactivity of 2,3-Dichloropropene in copolymerization reactions was assessed according to the reciprocals of the copolymerization constants of vinyl chloride, methyl methacrylate, and styrene, which indicate the reactivity of the dichlorinated monomer when interacting with comonomer radicals. It was found that 2,3-dichloropropene is the most active in the reaction with a styrene radical. However, its reactivity with a methyl methacrylate radical decreases by a factor of 0.88 as compared to the styrene radical. The lowest reactivity of 2,3-Dichloropropene is observed when interacting with a vinyl chloride radical. The synthesized copolymers can be further modified by replacing chlorine atoms with functional groups.

The Structure and Properties of Ceramics, Obtained from Mixtures of the System ZrO2–Al–C

The paper presents the results of the analysis of the structures of materials obtained as a result of hot pressing of mixtures of the ZrO2(m) –Al – С system of various compositions. The nature of the change in the composition and physical and mechanical properties of the obtained materials was established depending on the concentration of aluminum and carbon in the initial mixture, as well as the parameters of hot pressing.

Enhanced Metakaolin Reactivity in Blended Cement with Additional Calcium Hydroxide

This study aims to increase the pozzolanic reactivity of metakaolin (MK) in Portland cement (PC) blends by adding additional calcium hydroxide (CH_add) to the initial mixture. Cement paste samples were prepared with PC, MK and water with a water-to-binder ratio of 0.6. Cement replacement ratios were chosen from 5 to 40 wt.% MK. For higher replacement ratios, i.e., 20, 30 and 40 wt.% MK, CH_add was included in the mixture. CH_add-to-MK ratios of 0.1, 0.25 and 0.5 were investigated. Thermogravimetric analysis (TGA) was carried out to study the pozzolanic reactivity after 1, 7, 28 and 56 days of hydration. A modified mass balance approach was used to normalize thermogravimetric data and to calculate the calcium hydroxide (CH) consumption of samples with CH_add. Results showed that, without CH_add, a replacement ratio of 30 wt.% or higher results in the complete consumption of CH after 28 days at the latest. In these samples, the pozzolanic reaction of MK turned out to be restricted by the amount of CH available from the cement hydration. The increased amount of CH in the samples with CH_add resulted in an enhanced pozzolanic reaction of MK as confirmed by CH consumption measurements from TGA.

Power units with full CO2 utilization

The forecasts for the development of renewable energy and conventional energy with fossil fuels have significant discrepancies in quantitative indicators, but agree on the need to reduce CO2 emissions. In this direction, a great number of developments are associated with hydrogen energy. Alternative proposals are cycles on methane-oxygen fuel with CO2 capture from the concentrated stream at the outlet of the condenser-separator: high-temperature gas-steam turbine unit of CJSC SPC «Turbocon», Allam, and JIHT RAS cycle. A 100 kW gas-steam turbine with an initial mixture temperature of up to 800° C has been developed and tested. To develop a method for calculating steam condensers from a mixture with CO2 (common to all three schemes), tests were carried out on a special stand; the heat transfer coefficient experimental data have been used to design a highly efficient steam condenser from a mixture with a converging flow path to maintain its high speed, a heat transfer coefficient of 2700 W/m2K was achieved. It is planned to create a prototype installation containing a steam boiler, a gas-steam turbine and a steam condenser with CO2 capture from the concentrated stream at the compressor outlet.

An experimental study of flow boiling heat transfer of zeotropic mixture R32/R134a in a microchannel heat exchanger

This paper presents experimental data on heat transfer of a binary zeotropic mixture of refrigerants R32/R134a in a microchannel heat exchanger with a high specific surface within a range of parameters that is practically important for the development of cooling systems for microelectronics and space technology. The experiments were carried out in a horizontal heat exchanger with one-sided heating of a copper microchannel plate 20x40 mm, containing 21 rectangular microchannels with a cross-section of 335x930 μm, within the range of mass fluxes from 80 to 250 kg/m2s, and at an absolute pressure in the system ranged from 12 to 14 bar. A zeotropic mixture of refrigerants R32/R134a with a molar concentration of the initial mixture of 65%/35% was used as a working fluid. Experimental data were compared with model-based calculations that take into account the influence of changes in the concentrations of components in the liquid and gas phases.

Collectivism in a Replication Network of Minimal Nucleobase Sequences

A major challenge for understanding the origins of life is to explore how replication networks can engage in an evolutionary process. Herein, we shed light on this problem by implementing a network constituted by two different types of extremely simple biological components: the amino acid cysteine and the canonical nucleobases adenine and thymine, connected through amide bonds to the cysteine amino group and oxidation of its thiol into three possible disulfides. Supramolecular and kinetic analyses revealed that both self- and mutual interactions between such dinucleobase compounds drive their assembly and replication pathways. Those pathways involving sequence complementarity led to enhanced replication rates, suggesting a potential bias for selection. The interplay of synergistic dynamics and competition between replicators was then simulated in an open reactor with experimental kinetic data, showing the selective amplification of different species depending on the initial mixture composition. Overall, this network configuration can favor a collective adaptability to changes in the availability of feedstock molecules, with disulfide exchange reactions serving as 'wires' that connect the different individual auto- and cross-catalytic pathways.

MASTERING THE PROCESSES OF SYNTHESIS OF OXIDE COMPOUNDS WITH THE USE OF A POWERFUL SOURCE OF FAST HEATING OF THE INITIAL INGREDIENTS

The creation of new materials with predetermined properties is perhaps the mostimportant issue and problem of modern materials science. Increasingly harsh conditions for the useof materials in modern, and especially - promising technological processes, the need to ensure andimplement the safest conditions for humanity and the environment of modern industrial production,the importance and increasing role of economic factors – all these factors necessitate improvingknown and creating new materials, as well as technologies for their production and use. Furthereconomically justified, socially attractive and technologically safe use of nuclear technologies andoperation of modern complex technical facilities, which undoubtedly include nuclear power devices,further development of nuclear and in the future thermonuclear energy is impossible withoutmodernization.The article implements the method of electron beam heating of a mixture of yttrium andzirconium oxides for the synthesis of complex oxides. The initial mixture contained ingredients in anamount corresponding to the compound Y2Zr2O7. The mixture was heated in a tantalum containeralmost to the melting point of tantalum (2915 C). The high temperature of the process is provided bythe use of a system with a plasma electron emitter. The purpose of the vacuum high-temperature effect on the powder mixture was to implement conditions sufficient to initiate reactions for the synthesis ofcomplex oxides. The analysis of the obtained samples recorded after the initial high-temperaturetreatment a fluorite-type phase (Y, Zr) Ox with a lattice parameter of 5.2 Å and technologicalimpurities of tantalum oxide. After additional annealing in air at 1200 C for 7 hours, another phasewith a lattice parameter of 5.17 Å was recorded, as well as impurities of tantalum oxide. The testedsynthesis conditions lead to the formation of multi-element oxides with a structure of only fluorite,pyrochlore phase in the heat is not detected.

A Starch-Milk Paste Enables the Incorporation of Ripened Cheese in Novel Fresh Cheese

Research background: Fresh cheese varieties represent an important share of the whole cheese market. Although with great variability in terms of composition and method of preparation, fresh cheese varieties are bland in flavor and their production originates whey drainage. On the other hand, the cheese market is also responsible for a significant amount of food waste. These motivated the development of a novel fresh cheese incorporating ripened cheese, which can then represent a valorization of ripened cheese surpluses. Experimental approach. A variable amount of ripened cheese was dispersed in a paste of gelatinized starch (normal corn or waxy rice) in milk, producing melted cheese bases. These cheese bases were diluted with milk, sometimes enriched with skim milk powder, and then renneted. The resultant fresh cheese was characterized for macronutrients content, and physical properties. Sensory analyses of samples incorporating mature Cheddar, goats’, or ewes’ cheese were carried out. Results and conclusions. Gel formation of the initial mixture was hindered above 8 % (m/m) incorporation of ripened cheese, which could be overcome by the addition of skim milk powder. These observations are corroborated by the hardness values from texture analysis tests. Evaluation of syneresis of different samples enabled to conclude that addition of 2 % (m/m) starch and of 2.8 % (m/m) skim milk powder contribute to reduce its magnitude by half. Sensory analysis with a consumer panel indicated a preference for a more consistent texture of the fresh cheese, and for the Cheddar flavor. Novelty and scientific contribution. A novel fresh cheese variety incorporating dispersed ripened cheese was prepared. The proposed method is versatile and quite straightforward and does not use polyphosphate salts or originate whey wastage. The fresh cheese physical and sensorial properties can be manipulated by the amounts and types of starch, ripened cheese, and skim milk powder added; such tailoring of fresh cheese properties widens product portfolio capacity for a larger number of consumer groups. The ripened cheese added can come from non-sellable pieces and unsold stocks from the retail sector, contributing to a reduction of food waste.

Carbon Monoliths with Hierarchical Porous Structure for All-Vanadium Redox Flow Batteries

Carbon monoliths were tested as electrodes for vanadium redox batteries. The materials were synthesised by a hard-templating route, employing sucrose as carbon precursor and sodium chloride crystals as the hard template. For the preparation process, both sucrose and sodium chloride were ball-milled together and molten into a paste which was hot-pressed to achieve polycondensation of sucrose into a hard monolith. The resultant material was pyrolysed in nitrogen at 750 °C, and then washed to remove the salt by dissolving it in water. Once the porosity was opened, a second pyrolysis step at 900 °C was performed for the complete conversion of the materials into carbon. The products were next characterised in terms of textural properties and composition. Changes in porosity, obtained by varying the proportions of sucrose to sodium chloride in the initial mixture, were correlated with the electrochemical performances of the samples, and a good agreement between capacitive response and microporosity was indeed observed highlighted by an increase in the cyclic voltammetry curve area when the SBET increased. In contrast, the reversibility of vanadium redox reactions measured as a function of the difference between reduction and oxidation potentials was correlated with the accessibility of the active vanadium species to the carbon surface, i.e., was correlated with the macroporosity. The latter was a critical parameter for understanding the differences of energy and voltage efficiencies among the materials, those with larger macropore volumes having the higher efficiencies.