Papers by Keyword: Thermodynamic Analysis

Abstract: Based on the idea of material genetic engineering, according to the innovative design of the whole material chain and taking high-strength and high conductivity copper alloy as the research object and carrier, this paper carries out high-throughput integrated calculation and design methods such as alloy characteristic microstructure, interface chemistry, thermodynamics and kinetics, establishes the prediction model of material composition structure process performance relationship, and realizes the high-throughput preparation and characterization technology of materials, Form a low-cost and rapid development capability oriented by application objectives. In this paper, the mixed matrix and characteristic microstructure sequence are optimized by high-throughput calculation, the thermodynamic and kinetic conditions of material preparation and synthesis are analyzed, and the phase diagram and solidification technology are calculated by CALPHAD to optimize the content, morphology and distribution of characteristic microstructure in the alloy. By designing polycrystalline and peritectic platforms, the microstructure type, morphology and content of characteristic microstructure can be controlled. At the same time, the type, content and distribution of the second phase are regulated by multi-element alloy equilibrium calculation phase diagram and non-equilibrium solidification path calculation, so as to realize the integrated calculation of materials and the selection of composition and process sequence range.

Abstract: The work is devoted to the study of the specific features of the structure of vacuum ion-plasma coatings, called by the authors substructural defects. Formed during the deposition of coatings of various compositions by the mechanism of helical growth, these surface crystalline formations, after reaching a certain size, spontaneously extruded (pushed out) from the coating. The cavities (niches) remaining at the site of the defect are filled (healed) by the deposited ions in the process of further growth of the coating. On the basis of thermodynamic analysis, theoretical estimates of the extrusion conditions were obtained in the work, which give a satisfactory agreement between the calculated and experimental data.

Abstract: In conventional vapor compression and absorption refrigeration systems, a compressor or a mechanical pump, respectively circulates the refrigerant. Mechanical input, which is required by the compressor or the pump operation, contributes significantly to the noise level and lessens its reliability and portability. In contrast, diffusion absorption refrigeration (DAR) systems are heat-driven and contain no moving parts. Solar-driven diffusion absorption cooling system uses a low-grade heat to produce a cooling effect, and it's specially tuned for remote locations with high levels of solar radiation. This article studies the performance of a DAR system in Ashdod, Israel. Based on existing models in the literature and on experimental measurement of quantities such as the solar irradiance and the air temperature, the cooling capacity and the COP were simulated. Cooling capacity of the DAR system varies between 100 and 140 W, and COP between 0.09 and 0.17.

Abstract: Carbonate decomposition with significant heat energy absorption takes place at siderite ore oxidizing roasting in a shaft furnace. Thermal dissociation of complex carbonates comprising the siderite ore was studied. Thermodynamic analysis was carried out for a sideroplesite decomposition process. Formulas allowing determination of the carbonate dissociation and exchange energy rates were obtained using the regular ion solution theory. The ion composition and thermodynamic activity simulation results were described for sideroplesites as well as iron and magnesium cation shares. The work output is of certain interest as knowing the initial sideroplesite decomposition temperature and the carbonate dissociation rate the optimal dimensions of various zones throughout the shaft furnace height may be defined, the roasting process time may be calculated and the optimal heat treatment conditions as well as the firing rate may be established.

Abstract: In the present report, a two dimensional (2D) model was developed to describe the fluid dynamics, heat and mass transfer of a Chemical Vapor Deposition activated by a Hot Filament (HFCVD) reactor, as well as the chemical generation of the precursor species which are present in the growth of non-stoichiometric silicon rich oxide (SRO) films. The SRO is known for have excellent photo luminescent properties which are useful in optoelectronic applications. This material can be obtained by the HFCVD technique which offers important advantages such as the easily to obtain thin films with diverse structural, compositional and optical characteristics. During deposition is a priority to control key parameters as inlet flow, substrate temperature and pressure so it compels to know previous theoretical information about these parameters which can be obtained by computational simulation. Therefore, by means of commercial Computational Fluid Dynamics (CFD) were solved the continuity, momentum and energy equations in steady state. Also, a thermodynamic equilibrium study of the SiO₂(s) + H₂ (g) reaction was carried out with the Factsage software. The thermodynamic equilibrium results provide the main chemical species which are present during the deposit process of the SRO films. The 2D model was used to simulate the temperature and velocity distribution of the hydrogen in the deposit process. The theoretical calculated temperatures were compared with those obtained experimentally by thermocouple measurements. From the simulation results, the temperature and gas velocity profiles were obtained at different hydrogen flow levels (50, 75, 100 sccm) and temperature source-substrate distances (5, 6 and 7mm) for a 50 sccm level. SEM micrographs and profilometry measurements disclose that the outlet configuration affects substantially both the thickness and surface uniformity of the SRO films. This parameter was modified to obtain a better quality (thickness and uniformity) and a large deposit area.

Abstract: The basis of modern materials science is multicomponent systems, on their basis it is possible to create various combinations of phases in structural materials with a set of specified properties. The investigated system MgO-Al₂O₃-FeO-TiO₂ is promising for the production of periclase-spinel refractories used as lining of rotary kilns during cement clinker firing, which are highly resistant to chemical corrosion when exposed to a gas environment and cement clinker components; thermomechanical stresses. However, in the reference literature and scientific articles, no information was found on the structure of the four-component diagram of the state of the MgO-Al₂O₃-FeO-TiO₂ system, partial elements of its structure are given only in the composition of multicomponent systems [1-3]. Thus, research to the study of the subsolidus structure of the MgO-Al₂O₃-FeO-TiO₂ system, which is the physicochemical basis for the development of compositions of periclase-spinel refractories, is urgent.

Abstract: The microstructure of coatings with different graphene content and the hardness of cladding layer under different distance between coil and samples were investigated. The results showed that with the increase of graphene, the mean particle size of the powder did not get significantly coarser. The defects and oxides were appeared in the cladding layer and graphene diffused into the substrate. Distance between induction coil and sample has great impact on the hardness of coating, the higher hardness was measured in the distance between 6-8cm. The thermodynamic analysis of coating nucleation was carried out.

Abstract: Amine-modified solid sorbents have attracted extensive interests in post-combustion carbon capture for power plants. Among various amines, polyethyleneiemine (PEI) is likely to be the most effective and promising candidate. However, previous studies have mainly focused on examining various supports to increase PEI loading and then enhance CO₂ adsorption capacity. In this study, one rare earth element (Ce) and 6 first-row transition metals (from V to Cu) in the oxidation states impregnated on PEI incorporated γ-Al₂O₃ were prepared and investigated as potential catalyst/promotor for base-catalyzed reaction. Thermodynamic analysis, including isothermal and quasi-static CO₂ adsorption tests, were implemented to evaluate the performances amongst the 7 metal oxides. The results showed that MnO₂, CeO₂ and Fe₂O₃ showed a better performance in isothermal CO₂ adsorption at 75°C. Upon quasi-static tests, the results also indicates that the peak adsorption temperatures (T_{peak, a}) of V₂O₅ and Cr₂O₃ shifted to high temperature region, whilst opposite behavior of MnO₂ was observed. In preliminary study, density functional theory (DFT) was also adopted to assist the screening of metal oxide in terms of bond length and adsorption energies.

Abstract: When re-melting scrap in electric arc furnaces (EAF), dust is formed. This dust is a rich zinc-containing raw material. The composition of the EAF-dust from JSC “Pervouralsk New Pipe Plant” was investigated. Dust contains 18 wt.% of zinc, more than 1/3 of zinc is a part of the slightly soluble in acids and alkalis of zinc ferrite ZnFe₂O₄. The aim of the work is to study the effect of roasting temperatures of 700, 850 and 1000 °C and the effect of CaO and Na₂CO₃ additives on the decomposition of zinc ferrite. Thermodynamic analysis of chemical transformations in dust during roasting showed that the additions of CaO and Na₂CO₃ provide destruction of zinc ferrite and promote the transfer of zinc into the acid-soluble form of ZnO. The effect of the roasting temperature, the duration of roasting and the amount of calcium oxide and sodium carbonate additions on the degree of zinc transition into acid-soluble form was studied experimentally. The best results were obtained at 1000 oС. The increase in the roasting time in the interval from 1 to 3 hours promotes an increase in the concentration of acid-soluble zinc in the cinder. The combined additions of 36 wt.% of Na₂CO₃ and 19 wt.% of CaO above the dust mass are optimal. The proportion of acid-soluble zinc in the cinder increased to 97–99 %, as a result of roasting under optimal conditions.

Abstract: The complex approach based on the combination of methods of equilibrium thermodynamics and x-ray electron spectroscopy for layer-by-layer analysis of the composition of surface layers of amorphous alloys is described on the example of Fe-Si-B-Nb-Cu alloy.