DEPENDENCE OF PHYSICAL PROPERTIES OF PIEZOELECTRIC ALUMINUM-SCANDIUM NITRIDE ON SCANDIUM CONCENTRATION

In this work the physical properties of the piezoelectric aluminum-scandium nitride (ASN) solid solution as a function of scandium concentration were studied using the density functional theory and experimental methods. The phase transition from the wurtzite phase to the rock salt phase at a Sc concentration of 43% was shown. The barriers of transformation from the wurtzite phase to the rock salt phase for various Sc concentrations were obtained. The behavior of the ASN piezoelectric constant d33 calculated by the piezoelectric constants e33, e31, and e15 shows a sharp increase with increasing Sc concentration compared to aluminum nitride AlN. The relationship between the increase in the piezoelectric response of ASN and the softening of the lattice, accompanied by a decrease in the main elastic constants C11, C33, C44 and C66, as well as a decrease in the c/a ratio with increasing Sc concentration, is shown. ASN films with a predominance of the crystal orientation (00·2) were obtained experimentally by magnetron sputtering. The structural properties of the films were studied by X-ray diffraction analysis. A comparison of the experimentally obtained dependence of the c/a ratio on the Sc concentration with the theoretical values showed a good correspondence. Studies of the physical properties of ASN thin films were performed using microwave multi-overtone composite resonators on diamond substrates with a longitudinal bulk acoustic wave (BAW) as the operating mode in the range of 0.5 – 20 GHz. The frequency dependences of the Q-factor of BAW-resonators with different ASN films were obtained, and the frequency dependences of the square of the modulus of the form factor as |m|2 were calculated. The dependences of the elastic constant С33 and the piezoelectric constant e33 for the ASN films with different Sc concentrations were calculated. The calculated and measured values of these constants are agreed within the experimental error.

KINETICS OF GRINDING OF VEGETABLE RAW MATERIALS DURING ELECTRIC DISCHARGE EXTRACTION

The influence of the degree of grinding of the particles of growing raw materials during electric discharge extraction on the quality of the obtained extracts was studied. Each discharge during electro-discharge extraction contributes to the grinding of a part of the raw material, which is confirmed by granulometric analysis. The particle size of the raw material should be controlled, since excessive grinding of the extracts results in cloudy, difficult to clarify and poorly filtered. The design of the extraction chamber is proposed, in which the grounded electrode is made in the form of a perforated plate, called a false bottom, with the optimal size of the holes and their density, which eliminates the over-grinding of the raw material particles, which leads to the production of turbid and difficult-to-filter extracts. Since the extraction of raw materials is carried out at a certain ratio of solid-liquid phases, the volume of the chamber from the sieve to the bottom does not significantly affect the kinetics of the extraction process itself, since it is intended for collecting the smallest particles of processed raw materials, the mass of which does not exceed 15-16% of the loaded mass of raw materials. The device of the extraction chamber, due to the high turbulence and intensive mixing of the suspension under the action of cavitation and shock waves initiated by the discharge in the liquid, allows you to remove small particles of raw materials less than 1 mm in size from the working area of the chamber. The results of the study show that the extraction of target components from various raw materials using a chamber with a false bottom can significantly reduce the content of the smallest particles of raw materials in the extract. It facilitates the filtration of the extract, reduces the filtration time, significantly reduces the likelihood of turbidity of the solution due to suspension, which improves the quality of the extract. Experimental studies of the developed electric discharge chamber with a false bottom, conducted with various types of plant raw materials, confirm the effectiveness of extraction in the chamber of the proposed design.

SORPTION PURIFICATION OF WASTEWATER FROM ORGANIC DYES USING GRANULATED BLAST-FURNACE SLAG

The properties of granulated blast-furnace slag from “ArcelorMittal Krivoy Rog”, which stipulate its sorption activity, have been determined. The following minerals were identified in the slag fractions: akermanite Ca2MgSi2O7, helenite Ca2Al(Al,Si)2O7, rankinite Ca3Si2O7, pseudowollastonite CaSiO3, merwinite Ca3MgSi2O8, microcline КAlSi3O8, calcite CaCO3, aldhamite CaS with > 50% of calcium and magnesium aluminosilicates. Some phases are in an amorphous sorption-active state. The expediency of activation with water for 1 day is shown, due to which hydroxyl and silanol groups are formed and dissociated on the surface with the formation of a negative charge on the surface of slag particles, which is typical for Ca and Mg aluminosilicates as well as minerals calcite and aldhamite. The shape of the adsorption isotherm indicates the formation of polymolecular layers of the methylene blue (MB) organic dye, which increases the efficiency of the slag sorbent. The adsorption value of MB is not less than 2 mg/g. There is obviously no desorption of MB from the slag, which ensures the safety of both the disposal of the waste sorbent and its utilization as a filler for construction materials. The radiation safety of the slag has been proven. The specific effective activity of slag fractions does not exceed 370 Bq/kg, which allows using them as technical materials without restrictions. A technological scheme of adsorption purification of wastewaters from organic synthesis enterprises and textile industry containing organic dyes, is suggested using a slag sorbent. The stages of the technological process are the following: receiving the slag from the dump, analysis of the mineral composition of the slag, water activation of the slag, static sorption of dyes in the sump, further utilization of the slag and the inflow of purified water into the primary production. The technology provides for the removal of organic dyes from wastewater and its repeated usage, which ensures the closed cycle of water reuse, no need for chemical reagents for the activation of the slag sorbent, improvement of the environmental situation in the locations of the slag dumps due to the use of slags as sorbents.

SCIENTIFIC AND TECHNOLOGICAL FEATURES OF SYNTHESIS OF NEW ESTER PLASTICIZERS BASED ON RENEWABLE RAW MATERIALS

Methods for the synthesis of ester non-toxic biodegradable plasticizers (hazard class 4) using renewable raw materials have been developed: glycerine-containing waste generated in the production of biofuels; citric acid 244, by microbial synthesis from molasses sugar production waste; polyatomic alcohol (neopoliol) – trimethylolpropane – a product of oxosynthesis obtained on the basis of natural gas. The target products are esters with a molecular weight range of 250-600, with low saturated vapor pressure, good thermal stability and polymer compatibility, and chemical inertia. The results of complex researches of processes of esterification of carboxylic acids with hydroxyl compounds in industrial homogeneous catalysts of different acidity (sulfuric acid, p-toluensulfonate, phosphoric acid) allowed determining the main approaches to the selection of raw materials chemical composition. This took into account the availability and toxicological characteristics and evaluation of the technological characteristics of esterification process to increase the conversion of raw materials and achieve a high selectivity for the target product. It is shown that to overcome the thermodynamic limitation in all processes, it is necessary to use a 6-7-fold molar excess of the second reagent: acid or alcohol. A solvent (benzene, toluene) is added to the initial mixture, which maintains a constant temperature and removes the reaction water in the form of an azeotrope. To isolate the target products from the reaction mass, it is proposed to use a film evaporator operating under vacuum (p=5-10 mm Hg, t=105-120 ℃). Samples of tributyrin glycerin, triamyl citrate and triethanoate purity ≥ 98% were obtained. The main physical-chemical properties were determined. A comparison with known industrial analogues was carried out. Evaluation of key quality indicators confirms the possibility of their use as plasticizers in the formulation of PVC pastes.

MATHEMATICAL AND STATISTICAL MODEL OF CLEANING IN A HIGH-GRADIENT MAGNETIC FIELD OF HYDROGENATED FAT FROM SUSPENDED CATALYST

The introduction specifies the object of the study - hydrogenated fat subjected to purification from suspended nickel-containing catalyst in a high-gradient magnetic field. The nickel-containing catalyst, due to the presence of nickel salts in it, is paramagnetic and can be effectively extracted from hydrated fat in the magnetic field by a method of highly gradient magnetic separation. In the experiment technique the magnetic field strength was not less than 600 kA/m, the gradient not less than (20-30)∙104 kA/m2. Based on the results and their discussion, the analysis of empirical dependencies on each factor basis is carried out separately, as well as the construction of classical types of one-dimensional non-linear regression models for each of them. It is shown that the most statistically reliable are the exponential models. It was found that after purification the content of suspended nickel-containing catalyst in the hydrogenated fat has an inverse proportional dependence on the magnetic field strength, height (length) of the filtration zone and filtration rate. A two-dimensional exponential regression model of the content of the nickel-containing catalyst in the hydrogenated fat in the complex dependence on the rate and height of the filtration zone is built. Based on the experimental data at a certain height of the filtration zone and the selected filtration rate, a mathematical-statistical model of change in the concentration of nickel-containing catalyst depending on the magnetic field strength is made. Using the resulting two-dimensional exponential regression model, it is possible to predict the degree of purification of the salomas from the suspended catalyst depending on the specific tension of the magnetic field and to determine the tension of the magnetic field, at which the concentration of nickel as a result of cleaning will reach an advance value.

EXTRACTION OF RUBBER FROM LATEX BY HYBRID COAGULANT BASED ON POLYDIMETHYLDIALLYLAMMONIUM CHLORIDE AND VISCOSE FIBER

In the proposed work, the possibility of using a hybrid coagulant based on a polymer cationic electrolyte-VPK – 402 (poly-N,N-dimethyl-N, N-diallylammonium chloride) in combination with viscose fiber in the technological process of separating SKS-30 ark rubber from latex is considered. The influence of the consumption of a hybrid coagulating agent, viscose fiber and its dosage, as well as the process temperature on the reduction of the aggregate stability of styrene-butadiene latex is considered. The influence of viscose fiber on the physical and mechanical properties of vulcanizates is established. At the same time, a number of features were noted consisting in a decrease in the aggregate stability of latex butadiene-styrene rubber during its coagulation with a hybrid coagulant. It was found that the use of a hybrid coagulant can reduce the consumption of cationic polyelectrolyte by up to 30%. It is shown that in the multicomponent system under consideration, several processes can occur simultaneously, which lead to the destabilization of latex dispersions. The use of a hybrid coagulant, including cationic polyelectrolyte, provides a combined effect of the bridging and neutralization mechanisms of violation of the aggregate stability of the dispersion. The presence of viscose fiber in the dispersed phase leads to an additional coagulating effect-adagulation, which is a kind of heterocoagulation. This may be due to the difference in surface potentials between the latex globules and the fiber additive. It is established that the temperature regime of the process of isolation of rubber from latex does not significantly affect the completeness of the extraction of rubber from latex. A decrease in the content of components of the emulsion system in wastewater discharged from the shops producing rubbers by emulsion polymerization was noted. According to the main physical and mechanical parameters, rubbers, rubber mixtures and vulcanizates prepared on their basis meet the requirements.

TECHNOLOGICAL ADDITIVES FOR OIL AND PETROL RESISTANCE RUBBERS BASED ON BUTADIENE-NITRILE CAOUTCHOUCS

The article investigated the influence of various technological additives (zincolet BB 222, lubstab-01 and MA-L22) on the technological properties of the rubber mixture, physical, mechanical and operational characteristics of rubber based on nitrile butadiene caoutchouc BNKS-40AMN. Basic rubber mixture studied included caoutchouc, BC-FF percadox, zinc monomethacrylate, maleide F, triallyl isocyanurate, acetonanil N, MGF-9 and THM-3 oligoester acrylates, carbon black P 514 and other ingredients. The rubber mixture was prepared on laboratory rolls LB 320 160/160 in two stages. At the first stage, BNKS-40AMN caoutchouc was mixed with ingredients and processing aids. As technological additives, zincolet BB 222, lubstab-01 and MA-L22 were used. In the second mixing step, BC-FF percadox and vulcanization coagents were introduced. For the obtained variants of the rubber mixture the vulcanization characteristics were studied on an MDR 3000 Basic rheometer at a temperature of 170 °C. The rubber mixture prepared was vulcanized in a P-V-100-3RT-2-PCD type vulcanizing press at 150 °C for 40 min. Determination of elastic-strength and operational properties of rubber were carried out according to the standards existing for the rubber industry. The oil resistance of the vulcanizates was evaluated by changing their elastic strength after exposure to standard liquid SZHR-1 at a temperature of 125 °C, as well as by changing the mass of the samples after exposure to a mixture of isooctane with toluene at room temperature. It was found that the introduction of technological additives in the rubber compound improves the distribution of carbon black P 514 and powdered ingredients (zinc monomethacrylate, maleide F, triallyl isocyanurate, acetonanil H) in the caoutchouc matrix. Increased elastic strength indicators and their smallest changes after exposure to aggressive hydrocarbon media is characterized a rubber containing technological additive MA-L22. A comparison of technological, elastic-strength properties and resistance to aggressive media for rubbers containing butadiene-nitrile caoutchoucs BNKS-18AMN, BNKS-28AMN and BNKS-40AMN with optimal technological additives for them was done. It has been established that rubber containing BNKS-40AMN and technological additive MA-L22 is characterized by improved vulcanization properties, increased elastic strength indicators and their smallest changes after exposure to aggressive hydrocarbon media.

OXIDATION KINETIC AND ANODIC BEHAVIOR OF Zn22Al ALLOY DOPED WITH NICKEL

The article presents the results of the study of the oxidation kinetics and the anodic behavior of the zinc-aluminum alloy Zn22Al, doped with nickel, in various corrosive environments. The kinetic and energy parameters of the process of high-temperature oxidation of alloys are determined. It is shown that the process of high-temperature oxidation of samples of Zn22Al-Ni alloys is characterized by a monotonic decrease in the true oxidation rate and an increase in the effective activation energy at the content of the alloying component in the initial Zn0.5Al alloy up to 0.5 wt.%. It was found that nickel additives within the studied concentration (0.01-0.5 wt.% ) slightly increases the oxidability of the base alloy Zn22Al at temperatures of 523, 573 and 623 K. It is shown that the dependence of the corrosion potential of zinc-aluminum alloys on the nickel content in them is of the same type, i.e. the additives of the alloying component contribute to the displacement of the corrosion potential in the region of positive values. The influence of the aggressiveness of the corrosive medium on the anodic behavior of alloys when comparing concentrated electrolytes with the increasing concentration of chloride ions in the sodium chloride solution is established. It is determined that the potentials of pitting formation and repassivation of the initial alloys shift to a more positive region with an increase in the nickel concentration in the alloys. The greatest shift of these potentials to the positive region is observed when alloying alloys containing small nickel additives. It is shown that the corrosion products of the studied alloys consist of a mixture of protective oxide films Al2O3, ZnO, NiO, Al2O3·ZnO and Al2O3·Ni2O3. It was found that the alloying of zinc-aluminum alloys with nickel (in the range of 0.01–0.05 wt.%) reduces the corrosion rate of the base alloy by 2-3 times. The proposed alloy compositions can be used as an anode coating for corrosion protection of steel products and structures.

ANALYSIS OF ENERGY CONSUMPTION OF EXTRACTIVE DISTILLATION FLOWSHEETS OF FOUR-COMPONENT SOLVENT MIXTURE

A comparative analysis of energy consumption for extractive distillation flowsheets was carried out. This was done by the example of methanol - ethanol - acetonitrile - mixture. These solvents are used in pharmaceutical industries. The basic system methanol - ethanol - acetonitrile - water contains four binary and one ternary minimum-boiling azeotropes. Pressure change has almost no effect on the location of separatric surfaces. Therefore, extractive distillation should be used to separate solvents mixtures of any composition. Industrial entrainers dimethyl sulfoxide and glycerol are considered as selective agents. The effect of entrainer on vapor-liquid equilibrium at 30 and 101.32 kPa was evaluated by the relative volatility of the components forming azeotropes and the selectivity of the agents. The simulation was carried out on the Aspen Plus V.10.0 program environment. Two extractive distillation flosheets for the methanol - ethanol - acetonitrile - water separation are investigated. Both schemes include a two-column complex for the extractive distillation of the base mixture: in the first column, organic solvents are separated from water, and in the second column, the agent is regenerated. For subsequent separation of acetonitrile, extractive distillation with dimethyl sulfoxide or glycerol is also used. But separation of methanol-ethanol - entrainert zeotropic mixtures differs in the order of separation of components in schemes I and II. In scheme I, regeneration of the agent and further separation of the alcohol mixture is provided, in scheme II, methanol is first isolated, and then ethanol is separated from the agent. The optimized results for both schemes at columns pressures 30 and 101.32 kPa are performed. Different sets of selective agents introduced into extractive distillation columns are considered. The concept of an effective set of entrainers is introduced. The evaluation of the design alternatives need the assessment of energy demands. Total energy consumption for separation (reboiler duty) for the scheme II at 35-38% higher than values for scheme I. On the criterion of the minimum total energy consumption for the separation the scheme I was recommended: pressure columns 30 kPa, effective set of entrainers: glycerol for dehydration of the base mixture and dimethyl sulfoxide for acetonitrile isolation.

APPLICATION OF SUPERCRITICAL EXTRACTION FOR ISOLATION OF CHEMICAL COMPOUNDS

This paper provides a review of the scientific literature on the study of the supercritical extraction process. The use of substances in a supercritical state as an extractant is the basis of the supercritical extraction process. In a supercritical fluid, there is a high intensity of mass transfer, which allows the supercritical fluid to easily penetrate into the raw material and efficiently extract the target components. Carbon dioxide is of particular interest, since its use as an extractant in the process of supercritical extraction meets the basic principles of «green chemistry». The paper presents the mechanisms of mass transfer of target components from plant raw materials that arise during the process of supercritical extraction using carbon dioxide. The kinetics of the supercritical extraction process is considered. During the process, three main periods are distinguished: a period of a constant extraction rate, a period of a falling extraction rate, and a period of a low extraction rate. The influence of temperature and pressure, the influence of water in the raw material on the yield of target components in the process of supercritical extraction is shown. Supercritical extraction requires special high-pressure equipment. The paper presents the main technological solutions for the implementation of the process. A comparison of the process of supercritical extraction with extraction in the Soxhlet apparatus is carried out. The supercritical extraction process makes it possible to obtain an extract of high purity, which is promising for the production of biologically active medicinal components and the separation of impurities from difficult-to-separate mixtures. Examples of the application of supercritical extraction in industry are given. In addition, the paper presents studies on the extraction of aralosides from Aralia mandshurica plant raw materials using the supercritical extraction process. Supercritical extraction is considered as a safe and more efficient way to extract target components from plant materials.