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Justification of the most rational method for the nanostructures synthesis on the semiconductors surface

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Suchikova Y. , Vambol S. , Vambol V. , Mozaffari N. , Mozaffari N.

Journal of Achievements in Materials and Manufacturing Engineering

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2019

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tom Vol. 92, nr 1-2

19--28

EN

Purpose: of this paper is to justification the most rational method for the nanostructures synthesis on the semiconductors surface, which is capable of providing high quality synthesized nanostructures at low cost and ease of the process. Design/methodology/approach: The choice of the optimal method of synthesis was carried out using the hierarchy analysis method, which is implemented by decomposing the problem into more simple parts and further processing judgments at each hierarchical level using pair comparisons. Findings: The article describes the main methods of synthesis of nanostructures, presents their advantages and disadvantages. The methods were evaluated by such criteria as: environmental friendliness, efficiency, stages number of the technological process, complexity, resources expenditure and time and effectiveness. Using the hierarchy analysis method, has been established that electrochemical etching is the most important alternative, and when choosing a nanostructures synthesis method on the semiconductors surface, this method should be preferred. Such studies are necessary for industrial serial production of nanostructures and allow reducing expenses at the realization of the problem of synthesis of qualitative samples. Research limitations/implications: In this research, the hierarchy analysis method was used only to select a rational method for synthesizing nanostructures on the semiconductors surface. However, this research needs to be developed with respect to establishing a correlation between the synthesis conditions and the nanostructures acquired properties. Practical implications: First, was been established that the optimal method for the nanostructures synthesis on the semiconductors surface is electrochemical etching, and not lithographic or chemical method. This allowed the theoretical and empirical point of view to justify the choice of the nanostructures synthesis method in the industrial production conditions. Secondly, the presented method can be applied to the synthesis method choice of other nanostructures types, which is necessary in conditions of resources exhaustion and high raw materials cost. Originality/value: In the article, for the first time, the choice of the nanostructures synthesis method on the semiconductors surface is presented using of paired comparisons of criteria and available alternatives. The article will be useful to engineers involved in the nanostructures synthesis, researchers and scientists, as well as students studying in the field of "nanotechnology".

2

Substantiation of expedience of application of high-temperature utilization of used tires for liquefied methane production

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Vambol S. , Vambol V. , Kondratenko O. , Koloskov V. , Suchikova Y.

Journal of Achievements in Materials and Manufacturing Engineering

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2018

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tom Vol. 87, nr 2

77--84

EN

Purpose: The purpose of this investigation is to substantiate by means of numerical simulation the expedience of high-temperature utilization of used tires with subsequent methanation of fuel gases and separation of multicomponent hydrocarbon mixtures to drain the liquefied methane. Design/methodology/approach: The investigation was carried out by means of numerical simulation. In mathematical description of gas processes relations of thermodynamics and heat and mass transfer were used. To determine the coefficients of thermal and physical parameters of working bodies the Peng-Robinson equation of state was used through the computer program REFPROP. The system of equations is represented as the interrelations between the functional elements according to the principle "output from the element A – input into the element B". Its solution was obtained by the method of successive approximations, namely by the Newton-Raphson iteration method. Using this method we have determined the values of temperature, pressure, mass flow rate and mass content of the hydrocarbon gas mixture components in each reference cross-section of the power facility. Findings: As a result of numerical simulation, it is determined that when the multicomponent hydrocarbon mixtures are separated, three flows of energy resources may be obtained: with a high mass content of methane of 91.5% and 83.4%, which may be used as motor fuel, and a gas flow suitable for maintaining the process of waste gasification. However, to remove heat in the condenser of the rectification column, it is necessary to use expensive liquid nitrogen. The cost of methane production may be reduced if the condenser is removed from the rectification column. However, such approach reduces the overall yield of commercial products almost in four times and significantly reduces the methane with the third product (molar percentage of 35%). Research limitations/implications: The investigation was carried out for the material of used tires without a metal frame. Practical implications: The implementation of the technology of high-temperature recycling of used tires gives the opportunity to use the generated synthetic gas to maintain the process of utilization, and gives the opportunity to produce liquefied methane, suitable for storage. Originality/value: The main problem of high-temperature recycling of tires is the emission of toxic gas to the atmosphere. It is proposed to allocate methane energy resource from this gas. For the first time an attempt was made to justify the expedience of the technology of high-temperature utilization of tires for liquefied methane production.

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Investigation of the porous GaP layers' chemical composition and the quality of the tests carried out

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Vambol S. , Vambol V. , Suchikova Y. , Bogdanov I. , Kondratenko O.

Journal of Achievements in Materials and Manufacturing Engineering

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2018

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tom Vol. 86, nr 2

49--60

EN

Purpose: The purpose of this study is to establish the quality of tests for determining the chemical composition of the porous surface obtained by the method of electrochemical etching, based on the indicators of convergence and reproducibility of the results. Design/methodology/approach: The method of electrochemical etching was used to obtain layers of porous gallium phosphide, which can be used as buffer layers for nitrides formation on their basis. Por-GaP was formed in a solution of hydrofluoric acid at a current density of j =100 mA/cm2, etching was carried out for 20 minutes. The resulting structures sulfide passivation was carried out, thus avoiding the formation of an oxide film on the samples surfaces. For this purpose, porous gallium phosphide samples were kept in a sulfide solution for 10 minutes and dried in a stream of nitrogen. The chemical composition of the porous GaP surface layers has been investigated. To do this, the method of electronprobe INCA Energy microanalysis was used. The research was carried out on the entire surface of the sample in order to calculate the total spectrum of the elemental composition of the sample under study. Findings: It was established that during anodizing, the stoichiometry of the crystals investigated did not shift significantly towards the excess of gallium atoms. Oxygen is present at an insignificant concentration of 0.3%. This indicates the effectiveness of conducting the sulfide passivation of the sample surface following the electrochemical treatment. The presence of fluorine atoms that appeared on the surface as a result of the reaction with the electrolyte during etching, is observed in extremely low concentration. Experimental studies have shown that the sample chosen can be used as a standard enterprise sample when analyzing the chemical composition of the surface of porous gallium phosphide due to its convergence, reproducibility, homogeneity. In addition, the given method for determining the standard sample can be applied to other porous semiconductors. Conducting such studies is an important technological task that will allow us to create a series of standard samples of porous semiconductors of A3B5 group. Research limitations/implications: The research was carried out for porous gallium phosphide samples synthesized in the solution of hydrofluoric acid, though, carrying out of similar experiments for por-GaP obtained in other conditions, is necessary. Practical implications: The studies of the reproducibility and convergence of the experiment have an important practical significance, since it is the reproducibility of the experiment results that is the main problem to modern material science, all the more to nanoengineering. Therefore, the technique proposed, will allow the synthesis of por-GaP layers with adjustable properties, will facilitate their widespread implementation in the real sectors of industry. The obtained porous layers can be used as standard samples. Originality/value: The main problem in the nanostructures synthesis is the adjustability of properties. The technique presented allows to form stable layers of the porous gallium phosphide with the surface chemical composition known in advance. In addition, carrying out the sulfide passivation allows to stabilize por-GaP properties, which is an important process task. For the first time, a study of the presented technique as to convergence, reproducibility and homogeneity, was conducted.