Chief Editor’s note
Merzhanov A.G. Self-propagating high-temperature synthesis: about the past, nowadays, and future (instead of Preface)
Amosov A.P., Borovinskaya I.P., Merzhanov A.G., Sychyov A.E. Procedures to control dispersed structure of SHS-powders: from monocrystalline grains to nanosized particles.
A review of the procedures to control the dispersed SHS-powder structure (particle size, shape, and structure as well their size distribution) and produce submicrometer and nanosized monocrystalline powders is given. The process of product crystal generation and growth in combustion wave is briefly described. The general principles of SHS-product grain size reduction are formulated. The principles are used for explanation and classification of SHS-nanopowder producing methods.
Pogozhev Yu.S., Levashov E.A., Kudryashov A.E., Ul’yanova T.M., Dedov N.V., Matyukha V.A. On the effect of nanocrystalline powders of refractory compounds on combustion process, structure formation, phase composition, and properties of TiC–TiAl based SHS-alloy.
Macrokinetic features of the production process (according to forced SHS-compacting technique), phase composition, structure, and physical-mechanical properties of SHIM-40TA hard alloy have been studied. The alloy is of 60%TiC–40%TiAl composition alloyed by nanocristalline ZrO2, Al2O3, NbC, W, WC, and WC–Co powders. Their introduction into the starting charge is shown to result in SHIM-40TA SHS-alloy structure modifying when the average size of carbide phase grains is reduced 1,5–2,0 times. Addition of nanocrystalline ZrO2 powders (of different fineness) and Al2O3 powders results in decreasing the combustion temperature and rate. It is found that application of ultrasonic treatment in the preparation process of charge mixtures, which contain nanoparticles, favorably affects the properties of finished material. Taking the whole results obtained in mind, the optimal version is found to alloy SHIM-40TA by ЧСЦ (in Russian writing) grade zirconium dioxide nanoparticles using ultrasonic mixing of nanocomponent with the starting charge mixture.
Grigoryan A.E., Illarionova E.V., Loginov B.A., Nosyrev A.N., Rogachyov A.S., Sachkova N.V., Tsygankov P.A., Yagubova I.Yu. Structure peculiarities of thin multilayered Ti/Al films for self-propagating high-temperature synthesis.
Micro- and nanostructures of multilayered films were studied. The films were obtained by plasma-assisted sputtering technique and composed of alternating titanium and aluminum layers, in a wide range of layer thickness. Microscopic features of propagation of gasless combustion wave in multilayered films are considered. Studying the structure of samples has shown that they are strongly textured, nonporous polycrystalline materials, which consist of two mutually perpendicular systems of borders: between layers and intergranular ones. The size of effective diffusion coefficient during synthesis was evaluated. It was found that the effective diffusion coefficient is more than the order of magnitude of that in b -titanium and five orders of magnitude of that in a -titanium. It gives the basis to suppose that the gasless combustion reaction occurs due to abnormal fast diffusion along the grain boundaries.
Vadchenko S.G., Borovinskaya I.P., Merzhanov A.G. SHS in thin films. Opportunities of technological application.
Combustion of the films produced by rolling of Ti + 2B charge mixture was investigated. The dependencies of lengthwise combustion rate of single samples on their width, applied load, initial temperature and number of bands in the layered system were established. A model of researching the mechanism and formation of porous structure of combustion products in heterogeneous metal–gas systems was proposed. It was found that the products with regular structure, in which transversal pores alternate with the regions of flat band, are formed as a result of combustion of the titanium powder rolled bands in the air and nitrogen. Regular porous structure generation areas and the main macrokinetic parameters of band combustion were found. A possibility of applying the SHS in thin films was shown to produce coatings, gradient materials, manufacture of filters and catalyst carriers with directional porosity.
Shkodich N.F., Kochetov N.A., Rogachyov A.S., Kovalev D.Yu., Sachkova N.V. On the effect of mechanical activation on SHS-composition Ni–Al and Ti–Al.
The present work is devoted to studying the effect of mechanical activation (duration and mode) in powder mixtures Ni + 31,5 wt % Al and Ti + 36 wt % Al on the SHS process and product parameters. It is shown that the combustion of the above compositions occurs in the micro-heterogeneous mode, and the process rate is determined by composite particle warming-up time. Using X-ray diffraction and electronic microscopy, the qualitative dynamics of composite particle formation is determined depending on the parameters (duration and mode) of mechanical activation.
Kvanin V.L., Balikhina N.T. Production of large-size hard-alloy products is one of technological trends using SHS-process.
The history concerned with implementing the process of production of hard-alloy and composite large-sized products (LSP) by forced SHS-compacting technique is given. Economic and technological advantages of the new method over the conventional powder metallurgical techniques are considered. The most large-scale examples of SHS-LSP application and testing under the industrial conditions are given. A necessity of development of new specialized equipment for LSP production (compression mold reactors in particular) is shown and the examples of scientific and design solutions in its development are given. Requirements to the materials to produce LSP are specified. It is shown that radically new materials with different functional properties are required for such products in scattered instances. The methods of compacting process examination and optimization as well as arising problems during implementation of forced SHS-compaction and some way of their overcoming are briefly described. Prospects of the method under the modern conditions are shown.
Yukhvid V.I. High-temperature liquid-phase SHS-processes: new trends and missions.
The three trends: 1) study of high-temperature liquid-phase combustion regularities and mechanism; 2) chemical synthesis carrying out, investigation of structure formation mechanism, and properties of cast SHS-products; and 3) technological works to produce cast materials, products, and coatings (protective surfacing, production of ingots, pipe products, and others) and their practical realization are now realizing and develop on in the Institute of Structural Macrokinetics and Problem of Materials Science (Chernogolovka city) within the frame of SHS-metallurgy. In recent years (1991–2005), the emphasis was on the development of new experimental methods and processes, study of the effect of “low” and “high” gravitation on SHS-processes in elemental and hybrid systems as well as the investigations of SHS-processes in the thermit type systems were proceeded. The present work is devoted to the review of the most important experimental results of this period.
Barinova T.V., Borovinskaya I.P., Ratnikov V.I., Belikova A.F. Some structural peculiarities and properties of cermet materials in the Zn–Ni–Sn–O system.
Experimental investigations of possibility to synthesize cermet material in the Zn–NiO–SnO2 system have been carried out. The cermet was produced by direct synthesis from compacted samples with the SHS-compacting technique. The optimal conditions were found. The product is monolithic cylindrical blocks consisting of ZnO based dense outer layer and electrically conductive central part where the metal phase is protected chemically and thermally by Zn2SnO4 based resisting phase. Using as the initial reagent of coarse nickel oxide was shown to allow significant decrease of specific electrical resistance of cermet at the cost of formation of structure peculiarities in it as metal-clad particles oriented perpendicularly to compaction axis. A complex of investigations of the product properties (structure, phase and chemical compositions, electric conductivity, thermal resistance, corrosion stability) has been carried out.
Itin V.I., Kirdyashkin A.I., Minin R.V., Gabbasov R.M., Naiden E.P., Maksimov Yu.M. Self-propagating high-temperature synthesis of hexagonal oxide ferrimagnetic of W-structure.
The effect of mechanical activation and magnetic field on the velocity, maximum temperature, and product phase composition of the self-propagating high-temperature synthesis (SHS) was investigated in the mixtures of reagents forming hexagonal oxide ferrimagnetic BaCo0,7Zn1,3Fe16O27 with W-structure. It was found that complete conversion of SHS-product into W-phase can be reached only after ferritizing process at Tf = 1180÷1190 ° C for 2 h. Magnetic characteristics of synthesized hexaferrite with W-structure were determined. A new method of producing oxide hexagonal ferrimagnetics with W-structure was proposed. It comprises mechanical activation of initial reaction mixture, SHS in magnetic field, and ferritization of finished product. Compared with the conventional method, the new one allows us to reduce the number of process steps and essentially decrease power and material consumptions of the production at the cost of ferritization temperature and duration reducing.
Kuznetsov M.V. Self-propagating high-temperature synthesis of alkali metal ferrites and lithium ferrite-chromite.
Various aspects of the effect of iron substitution by chromium on the processes of production and physical-chemical characteristics of spinel ferrites, being SHS-products are considered. Improvements of ferrite material preparation processes are proposed at the cost of using combustion reactions at the stage of primary ferritization, solid intra-reaction oxidizers as well as magnetic fields applied to the reaction zone. The transformations of structural, magnetic and spectroscopic parameters of synthesized materials including under the dynamic conditions depending on the degree of iron substitution by chromium and application of magnetic fields in the combustion reactions are explained. For the first time, by the example of ferrites, simultaneous effect of chromium (chemical factor) and magnetic fields (physical factor) on Moessbauer parameters of SHS-products were investigated in detail. The nature of chemical interaction during synthesis of ferrites of different classes in magnetic field was concluded. The first discovered effects of magnetic field on the parameters of unsubstituted and doping magnetic materials such as compression of elementary cells of ferrites under the effect of external magnetic fields, magnetophoresis in reacting magnetic compositions, and others are studied and described.
Pisklov A.V., Prokofiev V.G., Smolyakov V.K. Gasless combustion of layered package under nonadiabatic conditions.
Numerical simulation of two-dimensional combustion process of gasless layered composition was carried out. Being a strip of finite dimensions, the specimen consisted of two layers of different chemical activity – the model of “chemical furnace”. The combustion process of the internal layer was shown to vary from front process to induction one depending on the ratio of layer sizes. The effect of heat-conductive element on firing and combustion of samples was considered. Introduction of an inert material layer of high heat-conductive properties can expand the area of firing layered composition by glowing surface under the conditions of outer heat removal.
Levashov E.A., Zamulaeva E.I., Kudryashov A.E., Vakaev P.V., Sviridova T.A., Petrzhik M.I. Formation processes and properties of titanium-substrate deposited electrospark coatings produced using nano- and microstructural WC–Co electrodes.
Composition and structure of electrospark coatings produced with using micro- (VK8) and nanostructural electrodes (92%WC–8%Co) were investigated with the help of X-ray crystallography, X-ray microspectroscopy, X-ray photoelectron spectrometry, scanning electron microscopy, and ion microscopy. The physical-chemical processes on the working end of electrodes and substrate in the course of electrospark deposition are considered. It was found that the presence of secondary structure (electrode material and substrate interaction product as a result of back mass transfer) is the limiting factor of the electrospark coating formation process. The coatings made of VK8 electrode in all range of energies of pulse discharge constitute carbide (Ti,W)C distributed in the matrix of W–Ti solid solution. When using nanostructural electrode, the phase composition and structure of coatings vary with a rise in energy. The surface layer of the coatings consists of (Ti,W)C and W2C carbide grains. Under the optimal surfacing conditions (E = 0,13 J), the nanostructural electrode provides deposition of harder wear-resisting coating with fine-grain structure and low friction factor as compared with the coating made of microstructural VK8.
Pribytkov G.A., Khramogin M.N. Oxygen sorption from residual gases during vacuum SHS with preliminary heating of titanium-containing powdered mixtures.
The problem concerning the titanium powder oxidation in the processes of self-propagating high-temperature synthesis of titanium carbide and composites on its basis is discussed with using the literature data and the analysis of simple model describing gas filtration through open pores of a pressed-powder compact. It is shown that the oxidation rate of titanium powder inside compact during heating in vacuum is limited by oxygen filtration on the surface through open pores, while the role of oxygen being initially in the pores is negligibly small. The quantity of oxygen absorbed by titanium during heating in vacuum is inversely proportional to the depth of vacuum.
Chronicle
To 100-year anniversary of Anatoly Ivanovich Belyaev’s birth (1906–1967)
In memoriam of Anatoly Ivanovich Orlov (1921–1976)
Gennady Grigorievich Mineev is 70 years old
