Special Session CB-9
Session CB-9.1 - Analysis and Modeling of SHS Processes and Structure Formation
CB-9.1:IL01 Mesoscale Modelling and Experimental Studies of Impact-initiated Reactions
N. THADHANI, School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, USA
The response of reactive intermetallic forming particulate materials and laminate structures under dynamic high-pressure and high-strain-rate deformation conditions is dominated by the configuration of reactants, in addition to their intrinsic and extrinsic material properties. We are employing time-resolved stress and particle velocity measurements, with gas-gun impact experiments to monitor the deformation states and obtain evidence of reaction based on changes in compressibility and shock-velocity. Meso-scale numerical simulations employing multimaterial hydrocodes on imported micrographs of reactive s powder or laminates are used to qualitatively and quantitatively probe the local configurational changes and their effects, following validation of macroscopic properties by correlations with experiments. The simulations reveals heterogeneous deformation in reactants of dissimilar properties and morphological characteristics. Processes such as forced or turbulent flo w, vortex formation, and dispersion of reactants are influenced by the reactive system configuration, orientation of wave propagation front and strain localizations at heterogeneities. Understanding these processes, and correlating those with microstructural constructs can be used to reverse design reactive materials.
CB-9.1:IL02 Peculiarities of Combustion and Structure Formation Routes in Multicomponent SHS-Systems with Participation of Gas Transport Reactions
E. LEVASHOV, E.I. PATSERA, A.YU. POTANIN, YU.S. POGOZHEV, V.V. KURBATKINA, N.A. KOCHETOV, National University of Science and Technology "MISIS", Moscow, Russia
The mechanisms of combustion and structure formation in systems Ti-Ta-C, Mo-Si-B, Cr-B were investigated. The contribution of mechanical activation with in Cr-B mixture drastically changes the combustion mode from a stationary to non-stationary, as a result of increased amount of adsorbed oxygen by boron. It was established that gas transport of boron oxide B2O2 to Cr is to control the combustion. In system (100%-X)(Ti+0,5C) + X(Ta+C) with X= 10 and 30% an abrupt increase of Uc and Tc occurs as a result of the transfer from separate mode to the spread mode, which is accompanied by an increase in heat release as a result of two parallel chemical reactions. The combustion stage goes from the break mode to the merging mode. In the case of X= 50%, dependences Tc(T0) and Uc(T0) are linear over an a wide range of T0. In Mo-Si-B system 2 stages of chemical transformations were observed. 1st, MoSi2 appears resulting from: melting Si; spreading the melt on Mo particles; interaction with forming Mo3Si layer; reaction diffusion through the product layer and appearance of MoSi2 phase. 2nd stage proceeds in the presence of oxygen via the volatile molybdenum oxide, chemisorptions with boron.
CB-9.1:L03 Modeling of Changes in the Macroscopic Structure of a Substance during Combustion of Gasless Systems under External Loading
V. PROKOFYEV, V. SMOLYAKOV, Tomsk State University, Department for Structural Macrokinetics, Tomsk Scientific Center, Tomsk, Russia
Managing the formation of condensed products during combustion of heterogeneous systems is one of the most important problems in structural macrokinetics. Modeling of this process at the macroscopic level should describe the change in the structural values such as porosity, length and geometry of the sample. This paper presents a theoretical study of the macroscopic changes in the structure of the substance during an exothermic reaction under uniaxial loading. To describe the structural transformations it is used a model of viscous compressible liquid. Formation of the macrostructure is considered under the action of surface and mass forces taking into account the melting of one of the agents. The final deformation of the sample and the linear combustion rate were calculated depending on the applied external pressure for various gasless systems. The calculations were compared with experimental data.
CB-9.1:IL04 SHS in Nanofoils: A Molecular Dynamics Approach
F. BARAS, O. POLITANO, Laboratoire ICB, UMR 6303 CNRS-Université de Bourgogne, Dijon Cedex, France
Reactive multilayer nanofoils are obtained by the superposition of very thin layers of metal or non-metals. SHS in such nanofoils is extremely rapid (up to 10 m/s) and induces a localized increase of the temperature up to 1500-2000 K in a few milliseconds. Moreover SHS in nanofoils can be initiated by a relatively low local heating.
The control of exothermic properties of reactive multilayer nanofoils requires a better understanding of their specific behavior. During this lecture, we will show how molecular dynamics simulations can be used to study the development of interfacial reactions between nickel and aluminum in such nano-systems. The microstructure observed across a quenched reactive front by the TEM analysis of experimental samples are compared to MD results. MD can predict the formation of rounded shaped grains observed experimentally. Moreover MD allows to detect the elementary mechanisms on an atomic basis and shed some light on the phase competition during the process. We will underline how amorphization phase plays a crucial role in the kinetics and we will decompose the nucleation and growth process of seeds of intermetallic compounds step by step to understand their development. We will also demonstrate the role of the solid substrate in this process.
CB-9.1:IL05 New Results on Structural Macrokinetics Obtained on Multilayer Nanofoils
A.S. ROGACHEV, Institute of Structural Macrokinetics and Materials Science (ISMAN), Chernogolovka, Moscow region, Russia
SHS process in the multilayer nanofoils possesses many unique properties, such as unexpectedly high propagating rate (up to 102 m/s) and extremely short time of reaction and product phase formation (10-7 - 10-6 s). Understanding of the mechanism of this process has critical significance not only for the theory of SHS, but also for various applications of the reactive nanofilms, e.g., joining of dissimilar materials and items.
An overview of new experimental results shows existence of complex structure of the reaction waves in the multilayer foils and reveals some new "solid-flame" combustion phenomena at macroscopic level. Comparison of these data with the study of the micro- and nano-scale processes by different experimental methods sheds new light on the intrinsic mechanism of the process. The roles of the melts, reactive exothermic dissolution and methastable phases are discussed.
This work is supported by RFBR research Grant 13-03-01043a.
Session CB-9.2 - SHS Materials and Compounds
CB-9.2:IL01 Carbonaceous Refractory Materials on SHS-technology
Z. MANSUROV, Institute of Combustion Problems, Almaty, Kazakhstan
This study contains results of application of carbonaceous SHS-refractory materials for binding graphite products and melting metals in induction furnaces. The opportunity of producing strong graphite-graphite bond up to 5 MPa by means of the carbonaceous refractory material has been shown and established to demonstrate high chemical stability in the aggressive liquid metals and alloys environment. The results of the industrial tests of melting crucibles made of carbonaceous SHS-refractory materials have been presented in the case of aluminum melting. It has been shown that such crucibles stability is 5-6 times higher than that of standard graphite crucibles in aluminum melting conditions.
Obtained study results testify that developed carbonaceous material to be applied for lining of the induction furnace melting unit allows to increase the number of nonferrous metals (bronze) melting cycles 5 to 6 times in comparison with the traditional graphite crucible melting. High chemical stability of the material to oxidizing environment as well as to metal melts is provided by formation of high-melting compounds in the carbon containing exothermic systems during the SHS-process.
CB-9.2:L02 Synthesis and Luminescence Properties of a Red Nitride Phosphor (CaAlSiN3:Eu2+) for White Light LED Applications
SHYAN-LUNG CHUNG1, 2, S.C. HUANG1, 1Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan, ROC; 2Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan, Taiwan, ROC
A combustion synthesis method has been developed for synthesis of Eu2+-doped CaAlSiN3 phosphor and its photoluminescence properties and thermal quenching behavior were investigated. Ca, Al, Si, and Eu2O3 powders were used as the Ca, Al, Si and Eu sources. NaN3 was added as both solid-state nitrogen source and reducing agent and NH4Cl was added as catalytic agent. These powders were mixed and pressed into a compact which was then wrapped up with an igniting agent (Mg+Fe3O4). The wrapped reactant compact was ignited by electrical heating under a N2 pressure of 0.2-1.0 MPa. Effects of the experimental parameters on product yield and photoluminescence properties were investigated. The synthesized CaAlSiN3:Eu2+ phosphor absorbs light in the region of 250-520 nm and shows a broad band emission in the region of 500-800 nm due to the 4f65d1→4f7 transition of Eu2+. With excitation at 460nm, the peak emission wavelength was found to increase from 606nm to 670nm as the Eu concentration(i.e.,X in Ca1-xAlSiN3:Eux) is increased from x=0.01 to x=0.72. However, the peak emission intensity increases with increasing x to a maximum at x=0.09 and then begins to decrease with a further increase in X. The peak emission intensity was measured to be ~106 % of a commercially available phosphor, YAG:Ce3+ with X=0.09.
CB-9.2:L03 Salt-assisted Combustion Synthesis of Aluminium Nitride and Aluminium Oxynitride Powders
A. WILMANSKI, J. DOMAGALA, M.M. BUCKO, AGH University of Science and Technology, Faculty of Materials Science and Ceramics, Krakow, Poland
Aluminium nitride, AlN, and aluminum oxynitride with spinel-type structure, γ-alon Al3O3N, are well known functional ceramic materials. On the other hand, both phases due to their high thermal and chemical stability have a great potential as a structural and refractory materials. In both case synthesis of good sinterable powders is usually energy and time consuming. Aluminium nitride powders can be prepared using self-sustain high-temperature reaction (SHS) between aluminum and nitrogen. Similar reaction performed with a presence of aluminium oxide leads to γ-alon synthesis. A relatively small efficiency of such reactions is a main disadvantage of the method. High adiabatic temperature of the aluminium nitridation causes evaporation of aluminium and weak penetration of nitrogen into reactive bed. Some progress of the synthesis can be associated with dilution of the substrates by a simple, easy decomposed inorganic salt. In the present work mixtures of aluminum and/or aluminum oxide powders with different amounts of ammonium salt were used as precursors. The SHS reaction were performed in pure nitrogen at different pressure. An influence of salt content and nitrogen pressure on phase composition of the SHS products were observed.
CB-9.2:L04 Combustion and Microwave Methods for the Synthesis of Carbide Catalysts
A.R. ZURNACHYAN, R.A. MNATSAKANYAN, A.B. Nalbandyan Institute of Chemical Physics NAS RA, Yerevan, Armenia
Tungsten and molybdenum carbides have a wide range of application, particularly, as noble metal like catalysts. During the last years they are greatly used as catalysts in different reactions. Carbides of tungsten and molybdenum and catalytic systems based on them have been synthesized. Synthesis has been carried out by methods of modified self-propagating high temperature synthesis (SHS) and microwave oven (MO). In the first case carbidization of metal under combustion mode has been performed in the presence of magnesium. In the case of MO carbidization was possible without magnesium, which solved the problem of leaching, as well as increased yield of process. Thermal regimes of processes of reducing and carbidization were regulated by changing combustion temperature and got products: tungsten and molybdenum carbides (WC, W2C, Mo2C), as well as systems with different carriers (WC/C, Mo2C/C, WC/Al2O3 etc.). Both methods allow get nanopowder and homogeneous carbides with developed specific surface areas. These carbide catalysts have been applied in important practical reactions: hydrazine decomposition, naphthalene hydrogenation and methane dry reforming. Molybdenum carbide (Mo2C) exhibits higher catalytic activity and 100% selectivity in the mentioned reactions.
CB-9.2:L05 Surfacing of Protective Coatings on Titanium, Steel Substrates by SHS Metallurgy
D.E. ANDREEV, V.I. YUKHVID, V.N. SANIN, Institute of Structural Microkinetiks and Materials Science, RAS, Chernogolovka, Moscow region, Russia
Foundations of centrifugal SHS metallurgy of cast ceramics, alloys and composite materials, centrifugal SHS surfacing on steel substrates, etc. were developed on the base of the basic research results.
This paper shows new results of SHS centrifugal surfacing of composite materials based on intermetallic and carbide compounds on titanium, steel and other substrates. Highly exothermic mixtures of nickel, molybdenum, aluminum and carbon oxides with functional additives were used in the work. Green mixtures were placed on the surface of the substrates in graphite molds. The syntheses were carried out under centrifugal overloading ranging from 1 to 500 g at the mode of steady-state rotation. For experimental investigation we used image acquisition, methods of thermocouple and optical measurements, quenching and local analysis of the area of chemical conversion, SEM, metallography, X-ray diffractometry, etc. Thermodynamic calculations were used for selecting chemical schemes of the synthesis and mixture compositions, estimation of combustion temperature and product.
CB-9.2:L06 Peculiarity of the Formation of Oxide Ceramics under the Action of Centrifugal Acceleration
G. KSANDOPULO, A. BAIDELDINOVA, K. OMAROVA, Institute of Combustion Problems, Almaty, Kazakhstan
The study purpose is to observe a combustion wave in the active layer, identify co-ordinates of its transition to the adiabatic mode, and allocate a less active layer with the purpose to produce the ceramic, gradient and composite materials. We have intentionally chosen stoichiometric mixtures of tungsten, cobalt, and nickel. These mixtures have been put into the high-temperature centrifuge reactors. When rotation frequency reached a preset value we initiated an electric impulse based ignition.
We have used a high-speed video shooting, splitted it into separate frames, and identified a co-ordinate of the combustion wave transition to the adiabatic mode i.e. sharp increase of the front shift velocity. There is placed a less active layer such as a mixture of boron oxide with aluminum. Based on this video record we have managed to build up a diagram of the co-ordinate dependent front advance along the reactor axis. Noteworthy that combustion process in the second less active layer develops similarly to the first one. The synthesis product structure changes from metal (tungsten) to ceramics (aluminum oxide, corundum). The basic phases take 91.9 %. Other involved substances are boron-containing solid tungsten and boron compounds. Performed studies allowed for production of materials with various structures and compositions, namely spinels and mullites.
CB-9.2:L07 In Situ Consolidation Via Spark Plasma Sintering and Self-Propagating High Temperature Synthesis of SiC
D.O. MOSKOVSKIKH1, A.S. ROGACHEV1, 3, A.S. MUKASYAN1, 2, 1National University of Science and Technology «MISIS», Moscow, Russia; 2Department of Chemical & Biomolecular Eng., University of Notre Dame, Notre Dame, IN, USA; 3Institute of Structural Macrokinetics and Materials Science, RAS, Chernogolovka, Moscow Region, Russia
Ceramic materials based on silicon carbide (SiC) have a set of unique properties, such as thermal and chemical stability, refractoriness and high hardness. Due to these properties, SiC has a wide range of applications, including abrasives and cutting materials, structural ceramics and crystals for microelectronics, catalysts, and coatings.
In the present work, we report self-propagating high temperature synthesis (SHS) of a submicron nanocrystalline SiC powder and In situ consolidation via spark plasma sintering (SPS) and SHS of SiC.
It is shown that initial micro-scalled mixture of silicon and graphite powders after 15 minutes of high-energy ball milling (HEBM) transformers to the nano-size media of composite particles, which consist of amorphous carbon and crystalline silicon. It is also demonstrated that self-sustained reaction can be accomplish in such nano media in argon atmosphere and reaction front propagates with velocity of ~ 5 mm/s and maximum temperature 1800 K.
Second, to obtain a compact material used SPS techniques, homogeneous nano- structures of silicon SiC ceramics were obtained by sintering of silicon and graphite reaction mixtures. The results show that an additional electric current is essential for achieving a large number of evenly distributed ignition points that ensure that the self-propagating reaction. The effects of the electric current and the heating rates on the resulting SiC ceramic densities and microstructures are discussed.
The aim of this work is to examine the influence of electric current on the self-propagation reaction Si-C using reaction mixtures after HEBM. Studied the effect of DC current under SPS conditions on nonconductive reactants. The resulting solidification and microstructures of the SiC ceramics formed were studied.
Session CB-9.3 - SHS as Alternative Technology
CB-9.3:IL01 SHS and Casting
V.I. YUKHVID, Institute of Structural Macrokinetics and Materials Science, RAS, Chernogolovka, Moscow Region, Russia
Three bas directions were develop in SHS-metallurgy: 1-study of regularities and mechanisms of high-temperature liquid-phase combustion, 2-study of chemical conversion, phase and structure formation and its relationship with properties of cast ceramics and composite materials; 3-applied research for solution of practical problems. Much attention has been paid to the fundamental problems recently: effect of «low» and «high» gravity on SHS processes in elemental, thermite and hybrid systems; energy stimulation of synthesis in low-caloric systems; effect of convective processes on combustion and chemical transformation; dynamics of of high temperature SHS products interaction with inert and active bases, etc. Modeling of SHS castings based on the experimental results was carried out. Several important processes useful for practice were proposed and studied: SHS of cast titanium aluminide; SHS surfacing on titanium base; SHS impregnation for obtaining composite materials, etc.
The most important experimental and theoretical research results are reviewed in the lecture.
CB-9.3:L03 Ultra-fast Densification of Nano- and Submicro-grain Ceramics Based on SHS Reaction
ZHENGYI FU, WEIMING WANG, HAO WANG, JINYONG ZHANG, YUCHENG WANG, Wuhan University of Technology, Wuhan, China
Densification of nano- or ultrafine grain ceramics is important, because smaller grain size results in the enhanced mechanical and functional properties. However, preparing fully-dense fine-grained ceramics is difficult by traditional sintering procedures, while the high temperature required for sintering results in excessive grain growth. A new method based on combustion reaction plus quick pressing (SHS/QP) for producing dense nano- and submicro-grain ceramics was developed. The heat generated by combustion reaction is applied to act as a heating source, which supplies a heating rate of 1300-1600℃/min to the sample. The densification can be performed within a few minutes. Dense nano- and submicro-grain Al2O3 ceramics and nano-grain Y2O3 and MgO ceramics were obtained under pressure of 100-120MPa inseveral minutes. The process has higher heating rate and shorter densification time than traditional sintering processes, which leads to no or limited grains coarsening. The densification process is likely different from traditional sintering techniques. It is suggested that the plastic flow mechanism may play an important role in the densification. The method is promising in the fabrication of nano- or ultrafine grain ceramics.
Session CB-9.4 - SHS Products Characterization, Application, Industrialization, Commercialization
CB-9.4:IL02 Space Applications of SHS
R. LICHERI1, G. CORRIAS1, R. ORRU'1, A. CONCAS2, M. PISU2, G. CAO1, 2, 1DIMCM, UniCA, Italy; 2CRS4, Italy
A review of the results related to experiments concerning the self-propagating high-temperature synthesis (SHS) technology operated under microgravity conditions is presented. The corresponding mechanism of combustion and phase/structure formation of final products are discussed. It has been shown that welding and joining can be successfully performed by SHS onboard the International Space Station. The potential application of SHS for the development of novel technologies for robotic and human space exploration of Moon and Mars are also discussed in the framework of some results recently obtained.
CB-9.4:IL03 SHS Technology Applied to Renewable Energy Efficient for Exergy Loss Minimization
O. ODAWARA, Tokyo Institute of Technology, Nagatsuta, Yokohama, Japan
Self-propagating high-temperature synthesis (SHS) technologies have advantageously progressed not only for high-temperature compounds synthesis but also as super-heating chemical ovens. The SHS technology has a rapid, versatile and near net shaping characteristics that can sustainably proceed without any oxygen supply other than the system, which can establish high temperature environments with reaction heat generation and simply operate in various conditions of even low gravity and high vacuum. By carrying out the SHS reaction processes under mass-force effect, self-pressure control, self-heat recycling and/or reactant phase/shape design, some advanced results relating with SHS technologies have been performed through our research activities as follows; (1) long ceramic-lined pipe production under centrifugal forces, (2) in-situ resource utilization in materials refinement and heat energy supply, (3) simultaneous nitride synthesis/sintering with liquid nitrogen and (4) self-heat circulation emulsion combustion. These R&D achievements would lead the stage of quality concerning the characteristics of SHS technology from 'economical and energy saving benefit' to 'low exergy loss profit', which is analysed and discussed in the present work.
Session CB-9.5 - SHS-coupled Processes
CB-9.5:IL01 Kinetics of Rapid High-temperature Reactions
A.S. MUKASYAN, A.S. SHTEINBERG, S.L. KHARATYAN, University of Notre Dame, Notre Dame, IN, USA; ALOFT Corporation, Berkeley, CA, USA; Institute of Chemical Physics, National Academy of Sciences of Armenia, Yerevan, Armenia
A variety of engineering technologies involve chemical reactions under essentially non-isothermal high temperature conditions. It has been reported that heating rates have an important effect on different processes, including the kinetics of chemical reactions and phase transformation mechanisms. Thus it is understood that under high heating rates, kinetics of interaction between the reactants may differ significantly as compared to chemical kinetic laws obtained in near-isothermal conditions. The problem becomes even more complicated for the conditions, typical for various combustion and plasma syntheses or laser induced processes, where rate of temperature change reaches values 104-106 K/s. In many such cases, the observed reaction rates appear to be greater than obtained isothermally. There are a few techniques which allow the measuring of the kinetics of chemical reactions under such conditions, including the so-called electro thermography and the electro-thermal explosion analyses. In this work we overview the results obtained by these methods on high-temperature kinetics for different heterogeneous reaction systems, such as metal-metal, metal-nonmetal, thermite and gas-solid. The general trends on influence of the heating rate on the reaction mechanism are also discussed.
CB-9.5:IL02 Single Mechanochemistry Impact Investigation by Synchrotron Radiation Methods with Nanosecond Time Resolution for Optimization of SHS Precursors Preparation
B.P. TOLOCHKO, M.R. SHARAFUTDINOV, N.Z. LYAKHOV, Institute of Solid State Chemistry and Mechanochemistry SB RAS, Novosibirsk, Russia; K.A. TEN, E.R. PRUUEL Institute of Hydrodynamics SB RAS, Novosibirsk, Russia
The nanosecond time resolution X-ray diffraction experiment on synchrotron radiation (SR) beams was realized for crystal lattice behavior investigation under dynamical (shock impact) loading. Experiment was realized for model systems. In an experiment modeling an elementary act of mechanochemical impact, when a sample was subjected by a shock impact by a bullet (aluminum, copper or nickel disc), shot from a gas-dynamic gun. An aluminum bullet can accelerate up to a velocity of 3 km/s (a minimum velocity is 0.5 km/s). Upon knocking a sample, also plate-shaped, the striker produces a shock wave in the sample. X-ray photography (32 frames) is performed ~ 100 ns after the shock wave generation. A series of X-ray pictures was recorded with a time resolution of 125 ns and an exposure of 1 ns. Diffraction data obtained in this experiment allows getting information on the loading of a sample under study with a shock wave, i.e., on the energy transmission to a crystal lattice with using of equation of state. The resulting data is used to optimize the mechanisms and processes of mechano-chemical preparation of samples for SHS synthesis of ceramics. SHS synthesis depends strongly on the used machines and mechano-chemical processes.
CB-9.5:L03 Some Specific Features at Rapid Heating of Mechanochemically Activated Ni-Al System
KH.G. KIRAKOSYAN, S.L. KHARATYAN, Institute of Chemical Physics NAS RA, Yerevan, Armenia; A.A. NEPAPUSHEV, D.O. MOSKOVSKIKH, A.S. ROGACHEV, National University of Science and Technology, Moscow, Russia; A.S. MUKASYAN, Depart. Chem. & Biomolec. Eng., University of Notre Dame, Notre Dame, IN, USA
Recently a new approach and the related technique was developed by the research group in the Institute of Chemical Physics NAS RA for study kinetic features of exothermic reactions in powdered mixture at high heating rates (up to 104 o/min). In this lecture we report the results of preliminary studies for mechanically activated (MA) nanostructured Ni-Al mixtures depending on activation time and heating rate. It was shown that:
. For MA mixtures, unlike to non activated one, there is a critical value of heating rate, above which an abrupt increase in the self-heating is observed: mixture ignites;
. The dependence of the self-heating on the duration of MA is expressed by the curve with a maximum;
. The reaction starting temperature for non activated mixtures increases with heating rate, while for activated mixtures - vice versa, decreases.
This work is partially supported by SCS RA and RFBR joint Armenian Russian research Grant AR 13RF-057 // 13-03-90604.
CB-9.5:IL04 Coupling SHS and SPS Processes
R. ORRU', R. LICHERI, C.MUSA, G. CAO, Dipartimento di Ingegneria Meccanica, Chimica e dei Materiali, Università degli Studi di Cagliari, Cagliari, Italy
The consolidation of ultra-refractory ceramic powders at relatively milder conditions with respect to conventional methods represents an important target to achieve. In this context, based on results recently reported in the literature, it is possible to state that the combination of the Self-propagating High-temperature Synthesis (SHS) with the Spark Plasma Sintering (SPS) technologies provides a useful contribution in this direction. Specifically, the two-steps processing route consisting in the synthesis by SHS of the ceramic powders and their subsequent densification by SPS is successfully utilized to obtain various dense MB2-based materials (M= Zr, Hf, Ta). In this regard, an important role is played by the SHS process, particularly for the synthesis of composite powders. Indeed, stronger interfaces are established among the different phases formed in-situ, so that diffusion phenomena are promoted during SPS. Additional benefits are produced by the use of the latter technology, due to the direct passage of the electric current through the powders undergoing sintering and the die containing them.
CB-9.5:L06 Combustion Synthesis of Copper - Refractory Metal Composites by Co-reduction Approach
S.V. AYDINYAN, S.L. KHARATYAN, Institute of Chemical Physics NAS RA, Yerevan, Armenia
Copper - Refractory Metal (Cu-W, Cu-Mo) composites are promising materials for fusion reactor and microelectronic applications due to prominent thermal and electrical properties of copper, and the low vapor pressure, low tritium retention and high melting point of W and Mo. However, it is difficult to fabricate such type of composites due to the distinct differences in melting point and insolubility between W(Mo) and Cu. We developed a new way to fabricate W( Mo)-Cu composites of various compositions directly from the oxide precursors by energy efficient combustion synthesis method. In order to perform joint reduction of oxides in controlled combustion mode, it was proposed to use coupling of low exothermic reduction reactions (e.g. MeO+C(CH polymer)) with a high-energetic one (e.g. MeO+Mg) as important lever to control combustion temperature, morphology and microstructure of the final product.
The proposed approach allowed to perform complete joint reduction of oxides in combustion mode and to obtain W(Mo)-Cu composite materials in a single technological stage.
The authors acknowledge the financial support of the State Committee of Science of the Republic of Armenia (Project no. 13_1D192) and ISTC (Partner project # A-2097).
CB-9.5:L07 New Methods for Consolidation of Highly Dense Cu-Cr Nanocomposites: MA and SPS
N.F. SHKODICH, A.S. ROGACHEV, S.G. VADCHENKO, A.S. MUKASYAN, D O. MOSKOVSKIKH, S. ROUVIMOV, 1Institute of Structural Macrokinetics and Materials Science, RAS, Chernogolovka, Russia; 2Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN, USA; 3National University of Science and Technology MISiS, Moscow, Russia
Nanocrystalline Cu-Cr composites are a novel kind of advanced materials due to excellent combination of high mechanical strength, electrical and thermal conductivities. They are considered to have great potential for their use as electric contact and brush materials.
To produce Cu-Cr materials with the grain size in nano- and sub meter scale and exceptional mechanical properties by conversional methods is limited because of the low solubility Cr in Cu at ambient temperature.
Combination of mechanical activation (MA) and spark plasma sintering (SPS) methods has been shown to be suitable for the production of nanostructured dense bulk materials
MA leads to deformation and multiple flattening of Cu particles, while the Cr particles are crushed into smaller ones. The initial components Cu and Cr intermixed and formed agglomerates. It has been shown that after 60 min of MA the grain size of Cr was in the range of 3-5 nm.
SPS is a newly developed process which mak es it possible for sintering at low temperature, inhibiting of grain growth and preservation of microstructure.
Combination of high-energy ball milling followed by SPS method leads to the formation of highly dense (95-99%) Cu-Cr bulk materials with the grain size in nanometer range at low sintering temperature (700-800ºC).
CB-9:P02 Self-propagating High Temperature Synthesis of Composition Materials using Boron Containing Ore
R. ABDULKARIMOVA, K. KAMUNUR, M.K. SKAKOV, Z.A. MANSUROV, Institute of Combustion Problems, Almaty, Kazakhstan
Development of modern science and engineering are closely linked with the development and production of materials, improvement of their properties and a reduction in the value of their industrial production. In this connection, the use of available mineral raw materials and effective SHS method to obtain composite materials is actual.
In this work, in order to obtain boron containing composition materials, SHS was carried out in the systems B2O3-Mg-MeO, B2O3-Al-MeO (where MeO are titanium, chromium, vanadium, zirconium oxides) using borate ores of Inder deposit of the Republic of Kazakhstan containing up to 40% of boron oxide. The regularities of aluminothermal and magnesiumthermal combustion of the systems depending on SHS conditions of the initial composition charge were studied.
Multicomponent composition materials containing borides, high temperature oxides, spinels which contribute both mechanical strength and refractorine ss to the synthesized SHS- materials were received.
CB-9:P03 Features of Oxide Systems Aluminothermic Combustion in the Conditions of High Nitrogen Pressure
S. FOMENKO, Z. MANSUROV, Combustion Problems Institute, Almaty, Kazakhstan
This paper describes the results of study of certain nitride-containing composite formation features in the pressed samples within AL - TiO2 - C - Si and АІ - ZrSiO4 - C - Zr systems at various nitrogen pressure values. The experiments have been carried out in a 45 litre steel reactor equipped with the heating furnace. Preliminary heating of the studied samples up to 1000 °С guaranteed steady spontaneous initiation of the aluminothermic reaction in the self-propagating high-temperature synthesis (SHS) mode.
Study of the microstructures at the observed samples facets within АІ - ZrSiO4 -С- N2 system has revealed that, according to the elemental analysis, rachislike structures mainly consist of zircon nitride. Round shape structures with more complex composition including silicides, nitrides and aluminum and zirconium oxides are observed at the rachies ends in the raphite containing samples. Such roundish shape is formed when crystals grow according to «steam - liquid - crystal» mechanism.
Obtained study results show that the SHS processes occurring in the multicomponental systems in the nitrogen environment at high pressure allow for synthesis of nitride-containing composite materials that have not only high fire resistance but also high mechanical properties.