Papers by Keyword: Deposition

Abstract: The intensity of neutralization of dangerous gases (chlorine, sulfur dioxide, hydrogen cyanide, phosgene, hydrochloric acid, ammonia) is researching during deposition with small-dispersion water. For this purpose, a mathematical model of neutralization of a dangerous gas, which is lighter than air, with fine water was modified for use in neutralizing a dangerous gas, which is heavy relative to air. The model takes into account the main parameters of sorption (environmental conditions, physical and chemical properties of the dangerous gas, parameters of the liquid flow supplied for deposition), which minimizes the forecasting time and is critical in the elimination of an accident with a release of dangerous gases. It was found that when dangerous gases are deposited in a finely dispersed water stream, the determining parameter is the Henry's constant of the dangerous gas, rather than the intensity of the fine water stream. It is confirmed that for dangerous gases that are poorly soluble in water (have small values of Henry's constant), it is necessary to add additives to the water stream that increase the chemical activity of the solution.

Abstract: This study optimizes 28 nm planar MOSFET technology to reduce device leakage current and enhance switching speed. The specific aims are to decrease subthreshold swing (S.S.) and mitigate drain-induced barrier lowering (DIBL) effect. Silvaco TCAD software is used for process (Athena) and device (Atlas) simulations. For the further development of MOSFET technology, we implemented our device (planar 28 nm n-MOSFET) with high-k metal-gate (HK/MG), lightly doped drain (LDD), multi-spacers, and silicide. Simulation validation shows improvements over other 28 nm devices, with lower static power consumption and notable optimizations in both S.S. (69.8 mV/dec) and DIBL effect (30.5 mV/V).

Abstract: An algorithm for predicting the intensity of sorption of gaseous materials released into the atmosphere as a result of an accident is proposed. The algorithm consists of three hierarchical levels: monitoring the parameters of gaseous material emission, predicting the consequences of gaseous material emission before and after sorption, and making a management decision. The first hierarchical level includes 4 blocks: obtaining information from the chemical reconnaissance group and the facility representative on the type, amount of hazardous gaseous materials, release intensity and scale of the accident; obtaining information from the hydrometeorological service on temperature, atmospheric pressure, wind direction and speed in the accident area; processing the information received; information on the availability of forces and means for sorption of hazardous gaseous materials. The second hierarchical level also includes 4 blocks: readiness of forces and means for sorption of hazardous gaseous materials; calculation with sorption; calculation without sorption; determination of the boundaries of the chemical damage zone according to the established criteria. At the third hierarchical level, there is 1 block: making a management decision. The software implementation of the proposed algorithm was carried out. The use of the developed algorithm and its software implementation will increase the speed and accuracy of predicting the consequences of the release of hazardous gaseous materials in an accident.

Abstract: This study aimed to evaluate filter efficiency for TiO₂ nanoparticle deposition across varied water chemistry and simulated conditions. The experimental results provided collision attachment efficiencies (α) of 0.001, 0.002, and 0.01 and filter coefficients (λ) of -0.003, -0.01, and -0.02. The authors used these collision attachment efficiencies to assess filter efficacy under simulated conditions, mainly removing naturally occurring nanoparticles spanning sizes from 1 to 100 nm. This experiment uncovered a strong correlation between TiO₂ nanoparticle deposition and water ionic strength, with aggregation becoming more pronounced as ionic strength increased. This phenomenon was especially prominent in instances lacking alum addition. Notably, the presence of alum resulted in the nanoparticles maintaining a dispersed state in the water, attaining enhanced stability by introducing excessive positive charges. Consequently, this study underscores how manipulating water's ionic strength can effectively induce nanoparticle destabilization during filtration. The implications of these findings are significant, as practical data about the behavior of diminutive like TiO₂ nanoparticles has been notably lacking.

Abstract: Inorganic thermoelectric (TE) materials have gained significant attention because of their salient properties. However, they possess some significant drawbacks, including high production costs, high heat loss, and fragility. Recently, Organic conducting polymers presented a promising platform as an alternative TE material because of their great mechanical flexibility, high stretchability, and environmental friendliness. In this work, we report for the first time on the TE properties of n-PEDOT:PSS film prepared using spray coating technique. The structural, optical and TE properties of the obtained n-PEDOT:PSS thin film was investigated using X-ray diffraction spectroscopy, UV-vis spectroscopy and Seebeck coefficient measurement systems, respectively. The n-PEDOT:PSS layer showed excellent optical properties with a band gap ranges from 3.91 to 3.78. In addition, the Seebeck coefficient and power factor (PF) were obtained to be 1096.77 µVK^-1 and 298.59 µWm^-1K^-2 respectively, making n-PEDOT:P PSS to be regarded as efficient TE material.

Abstract: An experimental study has been undertaken to investigate the effect of flow velocity and ionic strength on the transport of suspended particles (SP) and their deposition in a saturated porous medium. The SP injections were carried out using a laboratory column filled with sand and a pulse injection method. Ionic strengths varying between 0 and 600 mM (NaCl) have prospected. Two velocities were tested: 0.15 and 0.30 cm/s. Selected polydisperse particles diameters ranging from 0.27 to 5 μm and a median diameter (d_p50) equal to 2.25 μm were used. An analytical solution of the convection–dispersion equation with first-order deposition kinetics was used to describe the experimental breakthrough curves and to identify the transport parameters. The results show that the increase of ionic strength promotes the retention of the SP in the porous medium. In addition, retention is more important when the flow velocity is low. The deposition kinetics coefficient increases with increasing ionic strength and flow velocity.

Abstract: A two-channel temperature-control CVI scheme was proposed to fabricate thicker and denser composites. The two-channel structure helps to densify a thick preform, and a precise temperature control will guarantee a low and uniform porosity distribution. Validation simulations containing hydrodynamics, mass transfer, heat transfer and pore structure evolution were first carried out. Modeling results confirm that a two-step densification based on the new scheme can work well: At step I, all gases pass through the preform and the high-temperature bottom-preform is densified; At step II, by altering the outlet, temperature and infiltration time, part of gases are sucked into the preform and the remaining coarse preform is densified. The scheme can fabricate tick, uniform and dense composite, it can also avoid huge pump pressure thus protecting fibers from cracking. It is hoped to enlighten the CVI processing of ceramic matrix composites.

Abstract: Modified stepwise model of gas sorption process with finely dispersed water flow. The sorption model allows forecasting the intensity of hazardous gases deposition with adequate for the emergency recovery conditions accuracy using minimum input parameters. This allows using the sorption model under the conditions of emergency and increasing the forecasting promptness. Use of chemical neutralizer is proposed to increase the effectiveness of chlorine hazardous gas deposition. Use of sodium hydroxide is proposed as the chlorine chemical neutralizer, which is easily dissolved in water, non-toxic and easy to store. An experimental laboratory facility was developed and created with the purpose of experimental verification of the sorption processes, which allows researching the sorption processes by liquid aerosols within a wide range of dispersity. Adequacy of the existing models as well as the modified one was verified experimentally. The verification results showed a 5% indicator of the theoretical and experimental results compliance.

Abstract: Cold spray (CS) is a solid-state deposition technique of micron-sized metallic powder in an ultra-high velocity gas using a de Laval nozzle. CS is a unique deposition technique due to its use of relatively lower gas temperatures in comparison to other thermal processes. Consequently, high-temperature oxidation and phase transformations of deposited powders are largely restricted while the operating cost of CS is much lower than that of other thermal processes. Generally, the low pressure cold spray (LPCS) technique is used for the deposition of metallic powders on metallic substrates, while only a few studies of metallic particle deposition on ceramic substrates have been conducted, and it was found that the deposition of metallic powders on ceramic substrates was quite difficult. In this study, improved LPCS deposition of copper coatings on zirconia substrates was investigated. It is known that deposition of a metallic powder on a ceramic substrate is difficult due to the differences in material bonding and several properties of the two materials. These difficulties in LPCS deposition were solved using three different approaches, namely 1) use of copper and aluminum composite powders and 2) laser pre-treatment and 3) laser texturing of zirconia substrates. It was found that pure copper powder coatings on the as-received and various treated substrates were delaminated in the interface as expected. However, the deposition was improved for all substrates by using the copper and aluminum composite powder. While the laser pre-treated substrate was not effective for the deposition of the copper and aluminum composite powder, thick coatings were obtained for the deposition on the laser pre-treated with heat treatment substrate and the laser-textured substrate.

Abstract: Development of a waste-free technology for lignite slurry upgrading at briquetting factories, which provides for getting cleared water for closed-loop water supply and transportable product for burning or briquetting with sustainable equipment application. Detection and study of peculiarities of lignite coal and slurry of briquetting factories, as well as research on slurry surface properties for substantiating a separation ratio. Determination of the separation ratio of lignite coal slurry taking into account its surface properties to estimate technological efficiency of reagentless flotation separation. Research on kinetics of settling and influence of different flocculants on efficiency of the slurry thickening process for sludge collection and getting circulating water. Development of waste-free technology for lignite slurry upgrading with the purpose of slurry recycling based on the substantiation of rational technological parameters and appropriate equipment. Regularities of the process of reagentless flotation separation of lignite coal slurry, kinetics of settling are defined, which is the basis of technological solutions on separate briquetting waste treatment. A waste-free technology for upgrading lignite slurry and cinders with closed-cycle of water supply and transportable final product for burning and briquetting with moisture content of 26% ... 28 % is developed. Floating and sinking fractions of lignite slurry are studied and necessity of separate treatment of these fractions is substantiated. Kinetic regularities of deposition of heat-treated lignite particles are determined; rational modes which provide for efficient deposition of particles of the sinking fraction with minimum flow of a flocculant are defined. A phenomenon of hydrophobic behaviour of mineral particle surface after heat treating and briquetting of lignite coal is revealed, which is taken as a separation ratio; this allowed substantiating the waste-free technology for lignite slurry upgrading through reagentless flotation separation. The practical value of the results obtained involves development of a waste treatment technology at a briquetting factory (slurries and cinders) and its conversion into closed-loop water supply, which will allow obtaining 23 t/year of transportable final product additionally as well as decreasing consumption of pure water considerably and eliminating environment pollution.