Decomposition Of Solution Research Articles

A STUDY OF PROPERTIES OF AUSTENITIC STEEL IN THE INITIAL STATE

High-manganese steel is used in the rocket, space, and defense industries due to its low specific gravity, stable austenitic structure over a wide temperature range, and ability to strengthen under mechanical deformation. However, the wider application of this steel is hindered by such factors as: instability of mechanical properties in the initial state, tendency to thermal embrittlement and very poor machinability. Therefore, the work is aimed at solving the problems of eliminating the above-mentioned negative factors. Conducted studies of the effect of temperature-time parameters on the structure and properties of steel made it possible to establish the mechanism of thermal embrittlement of 9Г28Ю9МВБ steel. During slow cooling from hot deformation temperatures with speeds of the order of 0.03 º/s in steel, a large number of gray-blue coarse phase particles are released, which are located on the grain boundaries, which causes a sharp decrease in impact viscosity. It was established that in the temperature range of 500-800 ºС, the solid solution disintegrates with the release of particles of the strengthening K-phase - (Fe, Mn)3 AL, Cx. It was determined that the simultaneous decrease in hardness and impact strength in the temperature range of 750-950ºС provides a significant improvement in machinability. The lowest values of mechanical properties are achieved during aging at 700 ºС, the improvement of machinability in this case is maximal compared to exposure to other temperatures. So, for example, with an increase in the temperature of isothermal holding at 650ºС for 35 hours. machinability improves by almost 1.7 times, and for the same time at 700 ºС – by 2.4 times. When the holding temperature is increased to 950ºС for 35 hours. the machinability of steel increases only 1.6 times, which is due to the less intense decomposition of the saturated solid solution. Significant anisotropy of mechanical properties is formed as a result of the development of liquid chemical heterogeneity and its imitation during further thermomechanical processing. The value of the coefficient of anisotropy in sample bars of different grades of initial steel reaches values from 1.5 for a bar with a cross section of 105x105 mm to 3.9 units for a bar with a diameter of 120 mm. The study of the influence of the annealing temperature on the homogeneity of austenitic steel made it possible to develop a mode of heat treatment of austenitic steel 9Г28Ю9МВБ, which consists of heating to 1250°С, holding for 2 hours. at this temperature and subsequent cooling in water, in order to fix a homogeneous supersaturated solid solution. After such heat treatment, the striated microchemical heterogeneity is significantly reduced, the anisotropy coefficient does not exceed 1.1 units for all types of steel assortment.

Decomposition solutions and Bäcklund transformations of the B-type and C-type Kadomtsev–Petviashvili equations

This paper introduces a modified formal variable separation approach, showcasing a systematic and notably straightforward methodology for analyzing the B-type Kadomtsev–Petviashvili (BKP) equation. Through the application of this approach, we successfully ascertain decomposition solutions, Bäcklund transformations, the Lax pair, and the linear superposition solution associated with the aforementioned equation. Furthermore, we expand the utilization of this technique to the C-type Kadomtsev–Petviashvili (CKP) equation, leading to the derivation of decomposition solutions, Bäcklund transformations, and the Lax pair specific to this equation. The results obtained not only underscore the efficacy of the proposed approach, but also highlight its potential in offering a profound comprehension of integrable behaviors in nonlinear systems. Moreover, this approach demonstrates an efficient framework for establishing interrelations between diverse systems.

Degradation mechanism and decomposition of sulfamethoxazole aqueous solution with persulfate activated by dielectric barrier discharge

ABSTRACT The present study focused on the degradation of sulfamethoxazole (SMX) aqueous solution and the toxicity of processing aqueous by the dielectric barrier discharge (DBD) activated persulfate (PS). The effects of input voltage, input frequency, duty cycle, and PS dosage ratio on the SMX degradation efficiency were measured. Based on the results of the Response Surface Methodology (RSM), SMX degradation efficiency reached 83.21% which is 10.54% higher than that without PS, and the kinetic constant was 0.067 min−1 in 30 min when the input voltage at 204 V (input power at 110.6 W), the input frequency at 186 Hz, the duty cycle at 63%, and the PS dosage ratio at 5.1:1. The addition of PS can produce more active particles reached 1.756 mg/L (O3), 0.118 mg/L (H2O2), 0.154 mmol/L (·OH) in 30 min. Furthermore, the DBD plasma system effectively activated an optimal amount of PS, leading to improved removal efficiency of COD, and TOC to 30.21% and 47.21%, respectively. Subsequently, eight primary by-products were pinpointed, alongside the observation of three distinct pathways of transformation. Predictions from the ECOSAR software indicated that most of the degradation intermediates were less toxic than SMX. The biological toxicity experiments elucidated that the treatment with the DBD/PS system effectively reduced the mortality of zebrafish larvae caused by SMX from 100% to 20.13% and improved the hatching rate from 55.69% to 80.86%. In particular, it is important to note that the degradation intermediates exhibit teratogenic effects on zebrafish larvae.

Nanoparticle morphology and magnetic properties modified by synthesis conditions

In this paper, we present a comparative analysis of the physicochemical properties of magnetite nanoparticles synthesized via two primary methods: (i) co-precipitation of iron (II) and (III) chloride in an ammonia solution and (ii) thermal decomposition of Fe(acac)3 in an organic solvent. In each case, variable synthesis conditions were used (mixing, temperature, inert gas presence, time of synthesis), which significantly influenced the resulting nanoparticle characteristics, including size, size distribution, shape, and magnetic properties. By utilization of such techniques as transmission electron microscopy, X-ray diffraction, infrared spectroscopy, and Mössbauer spectroscopy, we demonstrate the ability to exert control over particle growth to a considerable extent. Our findings underscore the innovative aspect of our work, revealing quantitative insights into the precise manipulation of nanoparticle properties, thus offering promising ways for tailored applications in diverse fields.

Parameter‐robust higher‐order time‐accurate computational method for singularly perturbed time‐dependent semilinear convection‐diffusion PDEs with discontinuous data

This article is concerned with a class of singularly perturbed semilinear parabolic convection‐diffusion partial differential equations (PDEs) with discontinuous source function. Solutions of these PDEs usually exhibit a weak interior layer at one side of the point of discontinuity along with a boundary layer at one side of the spatial domain. We begin our study by proving existence of the analytical solution of the considered nonlinear PDE by means of the upper and lower solutions approach; and the ‐uniform stability of the analytical solution is established by using the comparison principle for the continuous nonlinear operator. In order to realize the asymptotic behavior of the analytical solution, we derive a priori bounds of the solution derivatives via decomposition of the solution into the smooth and the layer components. For an efficient numerical solution of the nonlinear PDE, the time‐derivative is approximated by the Crank–Nicolson method on an equidistant mesh, and we approximate the spatial derivative by a finite difference scheme on a suitable layer‐adapted mesh. We establish the comparison principle for the nonlinear difference operator to prove the ‐uniform stability of the discrete solution and further construct a suitable decomposition of the discrete solution for pursuing the convergence analysis. The computational method is proven to be parameter‐robust with second‐order time accuracy in the discrete supremum norm. The theoretical estimate is finally verified by the numerical experiments.

Higher-order composition of short- and long-period effects for satellite analytical ephemeris computation

The construction of an analytic orbit theory in closed form of the eccentricity that takes into account the main effects of the Geopotential is notably simplified when splitting the removal of periodic effects in several stages. Conversely, this splitting of the closed-form analytical solution into several transformations reduces the evaluation efficiency for dense ephemeris output. However, the advantage is twofold when the different parts of the mean-to-osculating transformation are composed into a single transformation. To show that, Brouwer’s solution is extended to the second order of the zonal harmonic of the second degree by the sequential elimination of short and long period terms. Then, the generating functions of the different transformations are composed into a single one, from which a single mean-to-osculating transformation is derived. The new, unique transformation notably speeds up the evaluation process, commonly improving evaluation efficiency by at least one third with respect to the customary decomposition of the analytical solution into three different parts.

Numerical analysis of a singularly perturbed 4th order problem with a shift term

We consider a one-dimensional singularly perturbed 4th order problem with the additional feature of a shift term. An expansion into a smooth term, boundary layers and an inner layer yields a formal solution decomposition, and together with a stability result we have estimates for the subsequent numerical analysis. With classical layer adapted meshes we present a numerical method that achieves supercloseness and optimal convergence orders in the associated energy norm. We also consider coarser meshes in view of the weak layers. Some numerical examples conclude the paper and support the theory.

Photocatalytic dye decomposition by bio-enzyme enriched TiO2/g-C3N4 nanocomposite and assessment of toxicity of resultant water using Catla catla fish

Nanocomposite of TiO2/g-C3N4 enriched with enzyme prepared from bio-wastes (fruit and vegetable peels) was synthesized for the photocatalytic decomposition of toxic dye solution and the toxicity, if any, of the resultant water obtained after treatment was tested by exposing freshwater Catla catla fish to the treated water. The result was compared with the toxicity of the untreated test dye solution. The bio-enzyme powered TiO2/g-C3N4 nanocomposite exhibits enhanced degradation efficiency of 99% for methylene blue (MB) and 95% for methyl orange (MO) in 45 min, whereas the bare TiO2/g-C3N4 exhibits efficiencies of only 92% for MB and 90% for MO. The quantitative study showed that enzymes present in the system viz., protease, peroxidase, cellulase, amylase and lipase act as supporting catalyst and thereby improve the photocatalytic ability of the synthesized nanocomposite for effective dye degradation. The results showed the combined effects of composite partners and the bio-cocatalyst. Characterization of the prepared samples was performed using XRD, FTIR, SEM, RAMAN, UV, EDS and XPS and the results are correlated with the application concerned. The histology study was performed through paraffin wax method to evaluate the toxic effects of the industrial dyes on Catla catla fish by exposing the fish to different aquarium systems (Dye, Control and Treated water).

Phase transformation and strengthening of the gas-atomized FeCoCrNiMo0.5Al1.3 high-entropy alloy powder during annealing

Phase evolution and strengthening of the FeNiCoCrMo0.5Al1.3 powder alloy produced via inert gas atomization and annealed in the temperature interval of 300–800 °C have been studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and microhardness testing. It was found that annealing at 300–600 °C leads to an increase of the element segregations between the several solid solutions with a rise of the lattice misfit (ε) to 1.5 % and microhardness growth to 1070 HV. It was assumed that elastic stress caused by the element partitioning is the main strengthening mechanism: microhardness rises linearly with misfit rise with dHV/dε = 43400 MPa. Sigma arises after the maximum elastic deformation (in 1.5 %) was reached. Formation of the dispersed coherent sigma phase in the annealing interval 600–800 °C results in the microhardness rise. Oxidation that began at 800 °C in 27 h is accompanied with FCC formation due to a depletion of the B2 in Al caused by Al2O3 formation. Estimation of the activation energy of the initial stage of the solid solution decomposition gives a very low value in 0.65eV, apparently caused by the high concentration of quenched vacancies. The activation energy of sigma formation approximately coincides with the activation energy of self-diffusion in BCC metals (about 2.60 eV).

Effect of zinc(II) and caustic content on the decomposition of sodium aluminate solutions and relevance to the Bayer process

The impact of zinc (Zn) on the seed decomposition process of sodium aluminate solution at different caustic concentrations was investigated. The results showed that as the concentration of Zn(II) in sodium aluminate solution increased from 0 to 1000 mg/L, the decomposition efficiency of the solution and average grain size of the resulting aluminum tri-hydroxide (ATH) changed little at a caustic concentration of 141 g/L. At caustic concentrations of 160 g/L and 177 g/L, the decomposition efficiency increased from 35.8% and 21.6% to 40.6% and 24.9%, respectively, while average grain size of the ATH crystal seeds increased from 14.2 and 9.25 μm to 17.9 and 15.9 μm, respectively. The XRD, FT-IR, and SEM analyses showed that zinc can enter the ATH seeds and interact with the α-ATH crystal planes. It may also form interactions with the AlO octahedral growth structure, thus promoting solution decomposition and influencing crystal growth. The research results will provide valuable references for improving the quality of alumina products.

CuFasterTucker: A Stochastic Optimization Strategy for Parallel Sparse FastTucker Decomposition on GPU Platform

The amount of scientific data is currently growing at an unprecedented pace, with tensors being a common form of data that display high-order, high-dimensional, and sparse features. While tensor-based analysis methods are effective, the vast increase in data size has made processing the original tensor infeasible. Tensor decomposition offers a solution by decomposing the tensor into multiple low-rank matrices or tensors that can be efficiently utilized by tensor-based analysis methods. One such algorithm is the Tucker decomposition, which decomposes an N -order tensor into N low-rank factor matrices and a low-rank core tensor. However, many Tucker decomposition techniques generate large intermediate variables and require significant computational resources, rendering them inadequate for processing high-order and high-dimensional tensors. This paper introduces FasterTucker decomposition, a novel approach to tensor decomposition that builds on the FastTucker decomposition, a variant of the Tucker decomposition. We propose an efficient parallel FasterTucker decomposition algorithm, called cuFasterTucker, designed to run on a GPU platform. Our algorithm has low storage and computational requirements and provides an effective solution for high-order and high-dimensional sparse tensor decomposition. Compared to state-of-the-art algorithms, our approach achieves a speedup of approximately 7 to 23 times.

Unified wavefront singularity characterization of three-dimensional elastodynamic time-domain half-space Green's function under impulsive boundary and internal loads

Founded on a novel analytical formulation that led to a rigorous yet compact path-integral representation of the time-domain elastodynamic half-space Green's function, a unified analysis of the possible occurrence of different singular wavefront behaviour in the response under arbitrary impulsive internal or surface point loads at arbitrary source-receiver locations is presented. With the decomposition of the general solution into distinct initiating and reflected wave group integrals that share a common factored format and simple contour definitions, the mathematical framework is shown to allow a straightforward identification of the specific conditions and the particular wave groups that are responsible for the singular wavefront phenomena without resorting to advanced analytic function theories or asymptotic methods. Analytic characterizations of the nature, strength and direction of all intrinsic singular wavefront behaviours of the three-dimensional Green's function in three canonical cases of source-receiver configurations are given in a dual integral-closed form format to facilitate their theoretical understanding as well as computational applications. Graphical illustrations of their variation with the source-receiver configuration and the medium's Poisson's ratio together with relevant comparison and clarifications of some classical treatments are included.

Synthesis of Hydroxylammonium Nitrate and Its Decomposition over Metal Oxide/Honeycomb Catalysts

The objectives of this study were to prepare a high-purity hydroxylammonium nitrate (HAN) solution and evaluate the performance of various types of metal oxide/honeycomb catalysts during the catalytic decomposition of the HAN solution. Hydroxylammonium nitrate was prepared via a neutralization reaction of hydroxylamine and nitric acid. FT-IR was used to analyze the chemical composition, chemical structure, and functional groups of the HAN. The aqueous HAN solution obtained from pH 7.06 showed the highest concentration of HAN of 60% and a density of 1.39 g/mL. The concentration of HAN solution that could be obtained when the solvent was evaporated to the maximum level could not exceed 80%. In this study, catalysts were prepared using a honeycomb structure made of cordierite (5SiO2-2MgO-2Al2O3) as a support, with Mn, Co, Cu, Pt, or Ir impregnated as active metals. The pore structure of the metal oxide/honeycomb catalysts did not significantly depend on the type of metal loaded. The Cu/honeycomb catalyst showed the strongest effect of lowering the decomposition onset temperature in the decomposition of the HAN solution likely due to the intrinsic activity of the Cu metal being superior to that of the other metals. It was confirmed that the effect of the catalyst on the decomposition mechanism of the aqueous HAN solution was negligible. Through a repetitive cycle of HAN decomposition, it was confirmed that the Cu/honeycomb catalyst could be recovered and reused as a catalyst for the decomposition of an aqueous HAN solution.

Post‐Mortem Gas Chromatography‐Mass Spectrometry Analysis of Aging Processes in Acetonitrile‐based Supercapacitors

AbstractAn ongoing challenge in the field of supercapacitors revolves around comprehending their failure mechanisms. The aging processes occurring at the electrode/electrolyte interphase of these devices are complex. Thus far, much attention has been directed toward examining the aging of electrodes, while fewer studies have been dedicated to the electrolyte's aging. This study aims to address this point and to gain a deeper understanding of the importance of individual decomposition products on the overall decomposition of the electrolytic solution of electric double‐layer capacitors. Therefore, the decomposition of the state‐of‐the‐art electrolyte 1 m solution of tetraethylammonium‐tetrafluoroborate in acetonitrile and that of the same electrolyte doped with compounds known to form during its aging, such as acetamide, 2,4,6‐trimethyl‐1,3,5‐triazine, and triethylamine has been investigated post‐mortem. The results of this study show that GC‐MS is a useful technique to interpret and understand the degradation processes taking place in the electrolytes of supercapacitors.

Oxidation Behavior of FeNiCoCrMo0.5Al1.3 High-Entropy Alloy Powder.

One of the most promising applications of FeNiCoCrMoAl-based high-entropy alloy is the fabrication of protective coatings. In this work, gas-atomized powder of FeNiCoCrMo0.5Al1.3 composition was deposited via high-velocity oxygen fuel spraying. It was shown that in-flight oxidation of the powder influences the coating's phase composition and properties. Powder oxidation and phase transformations were studied under HVOF deposition, and during continuous heating and prolonged isothermal annealing at 800 °C. Optical and scanning electron microscopy observation, energy dispersive X-ray analysis, X-ray diffraction analysis, thermogravimetric analysis, differential thermal analysis, and microhardness tests were used for study. In a gas-atomized state, the powder consisted of BCC supersaturated solid solution. The high rate of heating and cooling and high oxygen concentration during spraying led to oxidation development prior to decomposition of the supersaturated solid solution. Depleted Al layers of BCC transferred to the FCC phase. An increase in the spraying distance resulted in an increase in α-Al2O3 content; however, higher oxide content does not result in a higher microhardness. In contrast, under annealing, the supersaturated BCC solid solution decomposition occurs earlier than pronounced oxidation, which leads to considerable strengthening to 910 HV.

Crystalline phase transformation of Sr-Fe based oxygen carriers modulate the cyclic performance for syngas and CO coproduction in chemical looping ethanol reforming coupled with CO2 splitting

The chemical looping reforming coupled with CO2 splitting (CLR-CS) offers a promising solution for syngas production and simultaneous decomposition of CO2. In this study, the Sr-Fe based oxygen carriers (OCs) were evaluated in CLR-CS using ethanol as fuel. The presence of Sr significantly improved the oxidation performance of iron oxides. The Sr element in fresh Sr-Fe based OCs mainly formed two crystal phases, including SrFe12O19 and Sr4Fe6O13. Increasing the amount of Sr element made it easier to form Sr4Fe6O13 crystal phase. The Sr4Fe6O13 was favorable for syngas production, due to the higher surface oxygen vacancy formation energy with a range of 3.13–3.37 eV. However, the lower oxygen transfer capacity (OTC) of Sr4Fe6O13 resulted in a lower CO yield in the of stage of CO2 decomposition. Compared with Sr4Fe6O13, SrFe12O19 exhibited the higher OTC and the higher reactivity of lattice oxygen, which was preferable to produce more CO2 in the stage of ethanol reforming in fuel reactor. During the cycle tests, the crystalline phase of SrFe12O19 didn’t regenerate under the CO2 atmosphere but transformed into Sr4Fe6O13. It was attributed to the lower energy barrier of CO2 oxidation on the oxygen defect surface of Sr4Fe6O13. The phase transformation of SrFe12O19 accompanied the formation of Fe3O4. The excessive Fe3O4 had poor stability and inactivated easily due to sintering and agglomeration in Sr1Fe4 and Sr1Fe6 samples. The Sr1Fe2, namely the molar ratio of SrO to Fe2O3 of 1:2, exhibited the better performance for syngas (0.291 Nm3/kg OC) and CO (0.141 Nm3/kg OC) coproduction at 800 °C. Additionally, the Sr1Fe2 presented an excellent cyclic stability in 30 cycles due to the suitable proportion of Sr4Fe6O13 and iron oxides formed, which maintained a high syngas yield and avoided sintering of iron oxides. Overall, the Sr1Fe2 is a promising OC candidate in CLR-CS process.

Composition‐Dependent NiS‐Enriched FeNi2S4/ZnCr2O4 Catalyst for Electrochemical Oxygen Evolution Reaction

AbstractTransition metal sulfide and oxide nanomaterials are gaining popularity as catalysts for electrochemical water splitting because of their cost effectiveness, durability, and stability without using noble metals. Our study focuses on a hybrid electrocatalyst, NiS‐enriched FeNi2S4/ZnCr2O4, which is synthesized in two steps by sol‐gel followed through thermal decomposition in an aqueous solution by a hydrothermal process. We investigated its potential application in the electrochemical oxygen evolution reaction (OER). Powder X‐ray diffraction and X‐ray photoelectron spectroscopy analyses were used to determine the chemical composition and structure. The results showed that the FeNi2S4 structure has an enriched NiS phase. Additionally, the morphology of the synthesized FeNi2S4/ZnCr2O4 was revealed by field emission scanning electron microscopy (FE‐SEM). Under alkaline (1 M KOH) conditions, the FeNi2S4/ZnCr2O4 hybrid nanostructure showed a low overpotential value of 295 mV (Tafel slope, 59 mV dec−1) for OER activities due to the synergistic effects of FeNi2S4 and ZnCr2O4. Furthermore, the hybrid nanostructure demonstrated its long‐term stability and efficiency as an electrocatalyst for OER activities, surpassing previously reported superior electrocatalysts and state‐of‐the‐art materials.

Structure and Microchannel Catalytic Bed Performance of Silver Thin Films Prepared by Electroplating

The morphology of catalysts in microchannels plays a crucial role in the orbital maneuvering and networking applications of micro/nano satellites using hydrogen peroxide as a unit propellant. In this paper, a microfluidic reaction chip was designed and fabricated to detect the reaction rate of the catalytic decomposition of hydrogen peroxide solution by a microchannel catalytic bed. In addition, a silver thin film prepared by constant-current electroplating was used as a substrate for the microchannel catalyst. The results show that the ratio of surface area to area of silver film and the average particle size of silver particles have a significant positive correlation on the reaction rate of catalytic decomposition, while the thickness, silver content, and surface roughness of the silver film have no significant effect on the reaction rate of catalytic decomposition. The catalytic performance of the microchannel catalytic bed of silver thin film is greatly influenced by the conditions of electroplating, namely, the electroplating temperature (T), time (t), and current (I). And when I = 0.3 mA, t = 180 s, and T = 60 °C, the microchannel catalytic bed of the silver film prepared by electroplating reaches the optimal reaction rate for the catalytic decomposition of hydrogen peroxide solution. This study has the best process parameters for the design and optimization of heterogeneous catalysts applied to microfluidic reactors.

Experimental studies on effects of electrode material and voltage on electrolytic decomposition of Hydroxylammonium nitrate solution

Hydroxylammonium nitrate (HAN)-based propellants have been attracting attention as future low-toxicity liquid propellants owing to their ionic properties. HAN-based propellants are primarily decomposed via catalytic reactions. However, this method has several drawbacks, such as catalyst preheating and deactivation. Therefore, in this study, the electrical characteristics of the electrolysis process of a HAN solution, as well as the by-product gases and reaction residues were analyzed considering the electrode material and applied voltage as the controlling variables. SUS (a designation of stainless steel) electrodes have higher durability than Cu electrodes; however, their decomposition proceeds more slowly because of the suppression of the initial reaction at low voltages. This study confirmed that this suppression could be significantly addressed at a high voltage of 400 V. The investigated electrolytic decomposition mechanism of the HAN solution was validated by analyzing the gases generated during the electrolysis and residue after the reaction, using Fourier-transform infrared spectroscopy. This study has important implications for the development of volume-limited propulsion systems, such as micro-thrusters.

Structurally Constrained Fuzzy Selective LQ WADC Based on the Spectral Decomposition of Gramians

We propose a number of improvements for a previously presented method of selective wide-area damping control (WADC) using spectral decomposition of Lyapunov equation solutions. Namely, accounting for structural constraints, fuzzy selectivity, and compatibility with global optimization methods. We demonstrate that the improved method is capable of providing useful WADC strategies when the availability of measurement data is severely limited.