Journal of Materials Science and Engineering A 1 (2011) 374-379
Formerly part of Journal of Materials Science and Engineering, ISSN 1934-8959
CALS-Technology for Synthesis of Oxide Nanomaterials in Low-Temperature Plasm
Bessarabov Arkadiy1, Kvasyuk Aleksey1, Kochetygov Aleksey1 and Ivanov Mark2
1. The State Scientific-Research Institute of Chemical Reagents and High Purity Chemical Substances (IREA), Moscow 107076, Russia
2. LOHR PLASMA, Hangenbieten 67980, France
Received: January 19, 2011 / Accepted: March 01, 2011 / Published: August 10, 2011.
Abstract: It is shown that for synthesis of nanodispersed oxide materials (silicon, tin, tungsten, etc.) application of low-temperature plasm is prospectively. Information CALS-technology (Continuous Acquisition and Life cycle Support) for design of universal plasmachemical apparatus was developed. Thermodynamic modeling of the process in a wide range of temperature, pressure and rate of components proportion was carried out. For analytic monitoring of target oxide nanomaterials the Computer Quality-Management system was used.
Key words: Nanomaterials, oxides, plasmachemistry, CALS-technology, thermodynamic modeling.
1. Introduction
Development of nanotechnologies is one of the key directions for the industry growth and progress of society. At the same time the availability of compute technologies application for nanostructures modeling, for prediction of the properties of new nanomaterials, as well as for scaling-up, design and industrialization of nanotechnologies is important problem [1].
In the last years, a special interest was generated by some nanomaterials which are used in production of ceramic products, such as: tungsten carbide, tantalum, niobium, hafnium, molybdenum, silicon; silicon nitride, titanium nitride, aluminum nitride; silicon oxide, ferric oxide, aluminum oxide, zircon oxide, titanium oxide and tin oxide. In our works special attention has been given to producing of oxide nanomaterials. Synthesis of oxide nanomaterials in the low temperature stream of plasma becomes a promising industrial method. The low temperature plasma allows
Corresponding author: Bessarabov Arkadiy, professor, research fields: nanotechnologies, system analysis, chemistry, innovations.E-mail:*******************.ru.to create a modern technology at the temperatures of 2
× 103-2 × 104 K, at different pressure values and at duration of 10-5-10-3sec. The low temperature plasma can be used in cases, where the balance is shifted towards high temperatures. High output is produced in extremely none quilibrium conditions and the speed of reactions rises rapidly with the rise of temperature [2]. When developing the technology it is important that
a by-product of synthesis does not pollute target products and does not interact with the technology apparatus, taking additional contamination. To solve this problem it is very promising to use the low temperature plasma, which allows creating a complex
of current apparatus with minimum level of micro-contamination.
Development of the plasmachemical process was carried out in the context of the most current and perspective system of computer support– CALS-technology (Continuous Acquisition and Life cycle Support). An information model of the plasmachemical process for the producing of nanodisperse oxides was developed. Thermodynamic
modeling of the process in a wide range of temperature,
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CALS-Technology for Synthesis of Oxide Nanomaterials in Low-Temperature Plasm 375
pressure and rate of components proportion was carried out. For analytic monitoring of target oxide nanomaterials the Computer Quality-Management system (CQM-system) was used, which was worked out in the context of CALS-technology.
2. Universal Plasmachemical Apparatus for Obtaining of Oxide Nanomaterials
To obtain nanodisperse oxides, the universal plasmachemical apparatus was developed, which allows applying not only initial hardphase product by means of powder feeder, but liquid-phase reagents with the help of special sprayer. Universality of the plant allows obtaining nanodisperse oxide of metals of 2nd, 3rd and 4th group of the periodic system. Depending on amount of the parent material, plasma-formation gas flow and power insertion it is possible to obtain nanopowders of different dimension series.
The plasmachemical process was developed in the
framework of the most modern and promising computer-support system, CALS technology [3]. The CALS concept is based on a set of unified information models and on standardization of access ways to information and its adequate interpretation in conformity with international standards (ISO-10303 STEP). This provides unified methods for control over processes and enables interaction between all those involved in the development process. According to prognoses of foreign specialists, it will be impossible to sell at the foreign market any high-tech products without electronic documentation conforming to international CALS standards (ISO-10303 STEP). Thus, use of CALS technologies is a must for promising domestic projects.
In the development of a plasmachemical process for synthesis of nanodispersed tin oxide, a type scheme (application protocol) “Initial data for designing” was created in the framework of the CALS project (Fig. 1).
Fig. 1  Element of design CALS-project of universal plasmachemical apparatus for synthesis of nanomaterials: reactor.
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CALS-Technology for Synthesis of Oxide Nanomaterials in Low-Temperature Plasm 376
In conformity with the chemical industry’s standard, the structure of the input data includes 17 necessary sections [4]. All these sections are incorporated in the CALS project. In the screen form (Fig. 1), additional subitems are only displayed in section no. 12 (data for calculation and choice of the process equipment). However, additional, specific to chemical industry, information is actually input into the CALS project for all the sections.
Designing electronic description according to STEP standard (Fig. 1) contains the structure and variants of item configuration, geometrical models and drawings, properties and features of components. At the element of this scheme universal plasmachemical apparatus shown allows transferring to reactor not only the initial solid product by means of powder feeder, but the liquid reagents (chlorides and alchoxides) with a special sprayer.
For this CALS-project of apparatus (Fig. 1) includes metering device for the transfer of initial materials powders, pulverizer for transfer of plasma-creating gas, filter for the product recovery and plasma torch. Apparatus universality allows obtaining nanodisperse compounds of tin, iron, silicon, titan, tungsten on it.
3. Regulation of Nanopowders Dispersity
To the work and CALS-project researches, dealing with influence for nanodispersity of two parametrical complexes: aggregate condition of initial substance; ratio of speed pressures of plasma stream and stream of input gas (SIG) were included. Research of influence of aggregate condition was carried out for plasmachemical synthesis of nanopowders of silicon oxide (required granulated content: d = 10 nm). To the proper subcategory of information CALS-project the table of obtained results (Fig. 2а)  was  included. It is
Fig. 2 Element of CALS-project «Modeling of nanopowders dispersity: silicon oxide» (influence on dispersity: а – aggregate
condition; b - ratio of SIG/PS).
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shown that for obtaining of required granulated content when using of initial substance (tetraethoxysilane –TEOS) ratio of SIG/PS is enough to 1. When input through sprayer of liquid TEOS ratio of SIG/PS equal to 12 is required. When input through feeder of quartz powder (d0 = 10 mcm) for obtaining of nanodisperse silicon oxide (10 nm) high ratio of SIG/PS equal to 50 is required.
In CALS-project researches of influence for dispersity of final product of ratio of SIG/PS (Fig. 2-b) are shown. Quartz powder was used as initial product (d0= 10 mcm). Ratio of SIG/PS varied from 20 till 50. As the result there were nanopowders with the diameter form 10 till 60 nm. This relation is approximated by the next exponential relation: ln(d) = a0 + a1. Linear equation of correlation of ratio of SIG/PS and input power (W) also is included to the model: W = W0 + b1. Application in the CALS-project of methods of computer modeling and forecasting allows to create optimum flexible structure of high technology plasmachemical production and to provide full post sell support, including the documentation in electronic form.
4. Thermodynamic Researches
Section no. 11 (mathematical description of the process) of the CALS project (Fig. 1) presents the resu
lts obtained in simulating the plasmachemical synthesis. Analysis of chemical and heat-and-mass exchange processes at elevated temperatures leads to severe difficulties already in the stage of formulation of the simulation problem. It is appropriate to use thermodynamic simulation methods as a first approximation. These methods presume that, in the processes under consideration, the working body forms a conditionally closed, isolated system in which a local thermodynamic equilibrium (LTE) is attained. In this approximation, the state of the system is only determined by the content of chemical elements in the system and by values of two parameters of state. The use of the thermodynamic equilibrium approximation is justified by the high concentration of energy in the volumes under consideration and by the resulting high rates of conversion processes, which instantaneously bring the system in the LTE state.
A calculation of equilibrium for isolated multicomponent thermodynamic systems can be reduced to a problem of determination of a state with the minimum entropy. Therefore, to compose the sought-for system of equations, it is necessary to find an analytical relationship between the entropy of a unit mass of the working body and the thermodynamic parameters determining its composition, properties, and existence conditions.
In the general case, a gaseous system is constituted by neutral and electrically charged (ionized) com
ponents of the gas phase and separate condensed phases. The equation of state for an ideal gas is valid for the gas phase as a whole and for each of its components. The condensed phase will be considered single-component and immiscible. The content of the components of the gas phase and of separate condensed phases in the system will be expressed in moles per unit mass.
Determination of the parameters of the equilibrium state consists in finding all the dependent variables, including the number of moles of the components and the number of phases at which entropy reaches a maximum. This problem of a search for the extremum of the entropy of the system with account of constriction equations was solved using Astra-4 software developed at Bauman Higher Technical School in Moscow [5].reactor technology 文章翻译
A thermodynamic calculation of the equilibrium states of the system is performed in a wide range of basic parameters of the plasmachemical process: starting component ratios, temperatures, and pressures (Fig. 3). A thermodynamic simulation makes it possible to choose the synthesis conditions, analyze the environmental safety of the production process, and assess the mechanism of thermal dissociation of the starting compounds.
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CALS-Technology for Synthesis of Oxide Nanomaterials in Low-Temperature Plasm 378
Fig. 3 Screen form of the results of thermodynamic simulation of the plasmachemical synthesis (tin oxide).
5. Analytical Quality Monitoring
Low-temperature plasm allows obtaining of high purity nanomaterials. It is connected with the fact that by-product of synthesis does not pollute target products and does not interact with the technology apparatus, taking additional contamination. For a choice and the analysis of initial reagents and target high purity nanodispersed products of plasmachemical synthesis there was developed a system of computer quality management (CQM). The system (Fig. 4) has hierarchical structure of databases. Three basic information categories are allocated: «Analysis object»; «Analytical Method» and «Impurity» [6]. The developed information structure allows choosing optimum methods of the analytical control for as much as possible exact definition of qualitative characteristics of analyzed products.
On the basis of information model the program complex of the CALS-project of analytical monitoring is developed. The program interface is performed taking into account an optimality of work of the user. Special procedures and the screen forms including a complex of modern elements of representation of
the information and interaction with the user are developed for each stage of functioning of system.
For assortment of initial reagents considered by us and target products of plasmachemical synthesis the following inorganic clusters are entered into the first category (Fig. 4): «alchoxides» (tetraethoxysilane, tetrabuthoxytitan); «oxides» (oxides of silicon, titan, tin, iron, and tungsten); «salts» (tungsten carbide).
The chosen structure of classification of nanomaterials corresponds to the applied All-Russian qualifier of standards, a part of Uniform system of classification and coding of the technical and economic and social information of the Russian Federation. The qualifier is harmonized with the International qualifier of standards and the Interstate qualifier of standards.
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