Plasma Chemical Activity Research Articles

Development of technology for the production of all-purpose buckwheat malt using plasmochemically activated aqueous solutions

The result of the conducted research is the development of buckwheat malt production technology using plasma-chemically activated aqueous solutions. Buckwheat grain with high starch content became the object of research. The main technological problem is obtaining high-quality brewing malt suitable for the production of gluten-free beer. The expediency of using plasma-chemically activated aqueous solutions as an intensifier of the process of germination of buckwheat grains and an effective disinfectant of buckwheat malt has been experimentally proven. It is shown that the use of plasma chemical activation of technological solutions allows to speed up the process of moistening of buckwheat grain by more than 2 times. The energy and germination capacity of buckwheat grains, when using plasma-chemically activated aqueous solutions, underwent positive changes. The effect of increasing the energy of germination was from 8 to 14 %, and the ability to germinate was 2–9 %. The amylolytic activity of buckwheat malt was analyzed, an increase in amylolytic activity in the range of 30–77 units/g was noted. The extractability of buckwheat malt was investigated separately. This indicator increased by 2–9 % depending on the concentration of peroxides in the solution. The Kolbach index also increased by 2–10 %, which indicates an intensive course of proteolysis. The total amount of amino acids in the experimental samples increased by 619 mg/100 g. There was a significant decrease in the viscosity of the wort, which indicates the high solubility of the obtained buckwheat malt. The technology can be applied in the industrial production of brewing malt and sprouted buckwheat grain of functional purpose. The developed buckwheat malting technology will receive priority in the production of environmentally friendly buckwheat malts of universal purpose that are not contaminated with pathogenic microflora

Development of buckwheat groats production technology using plasma-chemically activated aqueous solutions

The result of the conducted research is the development of a technology for the production of buckwheat groats using plasma-chemically activated aqueous solutions. The research object was buckwheat grain. An urgent technological problem is the preservation of biologically valuable components of buckwheat during technological operations and optimization of the existing technology for the production of buckwheat groats. The expediency of using plasma-chemically activated aqueous solutions as an intensifier of the technological process of production of buckwheat groats and an effective groats disinfectant has been experimentally proven. It is shown that the use of plasma-chemical activation of technological solutions allows reducing the temperature and accelerating the course of hydrothermal treatment of buckwheat grain. The composition of buckwheat grain as a raw material was analyzed. The obtained buckwheat groats were studied separately. A reduction in tempering time from 6–10 to 2 h and a decrease in the optimal moistening temperature from 60 to 40 °C were recorded. This allows preserving a number of biologically important components in buckwheat grain. The groats yield increases from 68 to 74 %, i.e. by 1.9–6.0 %. The preservation of the maximum number of amino acids is observed, namely, 7.7 % more than in the control. That is, only 2 % is lost during technological processing, instead of 9.7 % in the control sample. The vitamin composition also remains stable and almost does not decrease in terms of B1, B2, B3, B4, B5, B6, K, E, PP, R. In addition, plasma-chemically activated solutions qualitatively disinfect grain raw materials during processing, which has a positive effect on further storage of buckwheat groats. The technology can be applied in the industrial production of high-quality buckwheat groats. The developed technology will receive special attention in the production of ecologically clean cereal products that are not contaminated with pathogenic microflora

Development of a technology for the production of germinated flaxseed using plasma-chemically activated aqueous solutions

The result of the research is the development of a technology for the production of germinated flaxseed using plasma-chemically activated aqueous solutions. The object of research was flaxseed. An urgent technological problem is the intensification of the bioactivation process of flaxseed and its effective disinfection. The expediency of using plasma-chemically activated aqueous solutions as an intensifier of the process of flaxseed germination and an effective disinfectant of food raw materials was experimentally proven. It is shown that the use of plasma-chemical activation of process solutions not only accelerates flaxseed germination, but also contributes to a more active accumulation of biologically valuable components in flax raw materials. The composition of flaxseed as a raw material derivative was analyzed. Germinated flaxseed, which is considered a high-value component of food products, was studied separately. An increase in the moisture content of flaxseed during the soaking process by 0.7–1.7 % was recorded. Seedling development increases by 2–9 mm. The germination energy and capacity increase by 5–12 %. The biomass of germinated seeds increases by 39–56 %. In the process of germination, the content of proteins in flaxseed increases from 21.88 to 23.71 %, reducing sugars from 2.37 to 4.02 %. The total content of amino acids increases from 3.64 to 10.38 % compared to the control, and 10 times compared to the raw material. A significant accumulation of vitamins was noted: B1, B2, B3, B5, B6, B7, B9, C, E. In addition, plasma-chemically activated solutions effectively disinfect germinated flaxseed. The technology can be applied in the production of enrichment components of food products. The developed technology will receive special attention in the production of functional food products

STUDY OF USE OF ANTISEPTIC ICE OF PLASMA-CHEMICALLY ACTIVATED AQUEOUS SOLUTIONS FOR THE STORAGE OF FOOD RAW MATERIALS

Scientists and specialists of food processing industry are increasingly focused on the technology of storage of raw materials of animal origin in antiseptic ice. The paper presents the peculiar features of plasma-chemical activation of solutions to produce antiseptic ice and their further use in the storage of meat and fish. The process of treatment leads to formation of micro-particles of hydrogen peroxide, which in contact with the raw materials are capable of generating active oxygen, allowing to disinfect the raw material surface. Concentration of hydrogen peroxide in the solutions further used to produce antiseptic ice has been determined. Study of the features of use of antiseptic ice made of plasma-chemically activated aqueous solutions showed unchanged organoleptic properties of raw materials after using the presented antiseptic agent. Suppression of viable microflora owing to antimicrobial action of plasma-chemically activated aqueous solutions was recorded. Antiseptic ice contributes to long-term disinfection of raw materials. For example, the samples show absence of microflora of mesophilic aerobic and facultative anaerobic microorganisms and bacteria of the Escherichia coli group, which allows improving the quality of stored food raw materials. At the concentration of peroxides at the level of 600-700 mg/l, pathogenic microflora in meat and fish samples is not present at all. When meat and fish raw materials are stored in ice for 30 days, pathogenic microflora does not appear, and it confirms the long-term disinfecting action of antiseptic ice. Slower accumulation of amino-ammonia nitrogen is observed during long-term storage of meat and fish raw materials. The use of plasma-chemically activated aqueous solutions for the production of antiseptic ice and storage of meat and fish raw materials in it can partially prevent the processes of protein breakdown and, accordingly, increase the product shelf life. The paper describes technological parameters of the process of storage of meat and fish in antiseptic ice, which can be used in the industrial storage of raw materials, and provides the guidance for use of ice of plasma-chemically activated aqueous solutions in the process of storage of raw materials of animal origin.

Neutral dissociation of methane by electron impact and a complete and consistent cross section set

We present cross sections for the neutral dissociation of methane, in a large part obtained through analytical approximations. With these cross sections the work of Song et al (2015 J. Phys. Chem. Ref. Data 44 023101) can be extended, which results in a complete and consistent set of cross sections for the collision of electrons with up to 100 eV energy with methane molecules. Notably, the resulting cross section set does not require any data fitting to produce bulk swarm parameters that match with experiments. Therefore consistency can be considered an inherent trait of the set, since swarm parameters are used exclusively for validation of the cross sections. Neutral dissociation of methane is essential to include (1) because it is a crucial electron energy sink in methane plasma, and (2) because it largely contributes to the production of hydrogen radicals that can be vital for plasma-chemical processes. Finally, we compare the production rates of hydrogen species for a swarm-fitted data set with ours. The two consistent cross section sets predict different production rates, with differences of 45% (at 100 Td) and 125% (at 50 Td) for production of H2 and a similar trend for production of H. With this comparison we underline that the swarm-fitting procedure, used to ensure consistency of the electron swarm parameters, can possibly degrade the accuracy with which chemical production rates are estimated. This is of particular importance for applications with an emphasis on plasma-chemical activation of the gas.

Energy efficiency of atmospheric pressure plasma-aided porous media surface finishing

Atmospheric pressure plasma pretreatment based on dielectric barrier discharge technology at industrial frequency (50 Hz) has been used for surface activation (oxidation, functionalization) of four species of European and tropical wood samples in a multi-step plasma enhanced capillary process of flame retardancy. Plasma-chemical activation is an effective surface alteration by attaching polar or functional groups to wood and cellulosic surfaces. Oxygen containing functional groups enhance effectively capillary impregnation processes for flame retardation of wood as porous media finishing. Oxidation level was studied by wettability in order to follow the increased surface free energy. For each species, a critical active power surface density was necessary to obtain the best impregnation results more quickly. The relationship between the penetration-spreading parameter and the active power density has been investigated experimentally as process quality parameter.

Investigation of air gasification of micronized coal, mechanically activated using the plasma control of the process

Combination of the processes of coal combustion and gasification into a single technology of mechano-chemical and plasma-chemical activation is of a considerable scientific and technological interest. Enhancement of coal reactivity at their grinding with mechanical activation is associated with an increase in the reaction rate of carbon material, and at plasma-chemical effect, the main is an increase in reactivity of the oxidizing agent caused by the high plasma temperatures of atomic oxygen. The process of gasification was studied on the 1-MW setup with tangential scroll supply of pulverized coal-air mixture and cylindrical reaction chamber. Coal ground by the standard boiler mill is fed to the disintegrator, then, it is sent to the scroll inlet of the burner-reactor with the transport air. Pulverized coal is ignited by the plasmatron of 10-kW power. In experiments on air gasification of micronized coal, carried out at the temperature in the reaction chamber of 1000-1200°C and air excess α = 0.3-1, the data on CO concentration of 11% and H 2 concentration of up to 6% were obtained. Air and air-steam gasification of mechanically-activated micronized coals with plasma control was calculated using SigmaFlow software package.

Chemical activation and changes in surface morphology of poly(ε-caprolactone) modulate VEGF responsiveness of human endothelial cells.

The high degree of clinical routine in percutaneous transluminal coronary angioplasty (PTCA) with and without stenting has not changed the fact that a large number of coronary heart disease patients are still affected by post-operative complications such as restenosis and thrombosis. Because re-endothelialization is the crucial aspect of wound healing after cardiovascular implant surgery, there is a need for modern biomaterials to aid endothelial cells in their adhesion and functional recovery post-stenting. This study systematically examines the potential of numerous chemical polymer modifications with regard to endothelialization. Poly(ε-caprolactone) (PCL) and its chemically activated forms are investigated in detail, as well as the impact of polymer surface morphology and precoating with matrix protein. Human umbilical vein endothelial cells (HUVECs) are used to characterize endothelial cell responses in terms of in vitro viability and adhesion. As a potential component in drug eluting implants, VEGF is applied as stimulus to boost endothelial cell proliferation on the polymer. In conclusion, plasma chemical activation of PCL combined with VEGF stimulation best enhances in vitro endothelialization. Examining the impact of morphological, chemical and biological modifications of PCL, this study makes an important new contribution towards the existing body of work on polymer endothelialization.

The catalytic role of tungsten electrode material in the plasmachemical activity of a pulsed corona discharge in water

The effects of tungsten material used as a high-voltage needle electrode on the production of hydrogen peroxide and the degradation of dimethylsulfoxide (DMSO) caused by a pulsed corona discharge in water were investigated. A reactor of needle–plate electrode geometry was used. The erosion of the tungsten electrodes by the discharge was evaluated. The yields of H2O2 production and the decomposition of DMSO by the discharge, which were obtained using the tungsten electrodes, were compared with those determined for titanium electrodes. The electrode erosion increased significantly with an increase in the solution conductivity. A large fraction (50–70%) of the eroded tungsten electrode material was released into the solution in dissolved form as tungstate ions. A correlation between the amount of eroded tungsten material released into the solution and the chemical effects induced by the discharge was determined. Lower yields of H2O2 and a higher degradation of DMSO by the discharge were obtained using the tungsten electrodes than were determined using titanium electrodes. Tungstate ions were shown to play a dominant role in the decomposition of H2O2, which was produced by the discharge using a tungsten electrode. The higher degradation of DMSO that was determined for tungsten was attributed to the tungstate-catalyzed oxidation of DMSO by H2O2, in addition to the oxidation of DMSO by OH radicals. Such a mechanism was supported by the detection of degradation by-products of DMSO (methanesulfonate, sulfate and dimethyl sulfone). The catalytic role of tungstate ions in the plasmachemical activity of the discharge generated using a tungsten electrode was also demonstrated on a pH-dependent decomposition of H2O2 and DMSO.

Plasma-solution modification of poly(ethylene terephthalate) fibre material

Plasma-chemical modification of polyester thread ensures formation of active hydroxyl and carboxyl groups on its surface, necessary for fixation of functional preparations whose application on the surface of fibre material gives it new properties — water-repellent, antimicrobial, deodorizing, etc. A comparison of the efficacy of plasma-chemical and chemical methods of surface activation of polyester fibre material shows that in the first case, greater losses of strength are observed in the thread. However, in the case of plasma-chemical activation, an additional number of carbonyl/carboxyl groups is formed, which is an important advantage in selecting the method of activating polyester materials.

Plasma-chemical processes in microwave plasma-enhanced chemical vapor deposition reactors operating with C/H/Ar gas mixtures

Microwave (MW) plasma-enhanced chemical vapor deposition (PECVD) reactors are widely used for growing diamond films with grain sizes spanning the range from nanometers through microns to millimeters. This paper presents a detailed description of a two-dimensional model of the plasma-chemical activation, transport, and deposition processes occurring in MW activated H/C/Ar mixtures, focusing particularly on the following base conditions: 4.4%CH4/7%Ar/balance H2, pressure p=150 Torr, and input power P=1.5 kW. The model results are verified and compared with a range of complementary experimental data in the companion papers. These comparators include measured (by cavity ring down spectroscopy) C2(a), CH(X), and H(n=2) column densities and C2(a) rotational temperatures, and infrared (quantum cascade laser) measurements of C2H2 and CH4 column densities under a wide range of process conditions. The model allows identification of spatially distinct regions within the reactor that support net CH4→C2H2 and C2H2→CH4 conversions, and provide a detailed mechanistic picture of the plasma-chemical transformations occurring both in the hot plasma and in the outer regions. Semianalytical expressions for estimating relative concentrations of the various C1Hx species under typical MW PECVD conditions are presented, which support the consensus view regarding the dominant role of CH3 radicals in diamond growth under such conditions.

Application of a distributed gold catalyst to increase the output power and efficiency of a sealed off CO2 laser pumped by a transverse rf discharge in tubes

It is shown experimentally that a transverse rf discharge in tubes has a higher plasmachemical activity than a dc discharge, which deteriorates the parameters of rf discharge-pumped CO2 lasers. The output power and efficiency of a sealed off CO2 laser were substantially increased by using a distributed gold catalyst facilitating CO2 regeneration. The output power of 0.77 W cm-1 per unit length of an active medium with efficiency of 18.5% was obtained in an experimental CO2 laser with tubes with a distributed gold catalyst pumped by a 27.1 MHz rf discharge.

Degradation of phenol by underwater pulsed corona discharge in combination with TiO2 photocatalysis

Non-thermal plasma-induced degradation of phenol by pulsed high-voltage discharge generated in water using point to plane geometry of electrodes was investigated in the presence of photocatalytically active TiO2. The phenol removal attributed directly to the effects of plasma chemical activity of the discharge was enhanced in the presence of TiO2. At the same time, higher formation of 1,4-benzoquinone as the main primary aromatic by-product and increased accumulation of hydrogen peroxide in the solution were found. The main effect of TiO2 addition was in the utilizing of ultraviolet radiation from the plasma resulting in the photocatalytical formation of OH radicals on the surface of TiO2 particles and, thus, in the increase of the yield of OH radicals available for phenol degradation.