O-2-01: Usage of Filtrational Combustion for Accelerated Synthesis
V.A.Borodulya1, L.M.Vinogradov1, S.A.Zhdanok1, V.S.Komarov2,
A.V.Krauklis1, N.K.Lunyova2, A.M.Safonova2
1HMTI named after A.V.Lykov of National Academy of Sciences of Belarus, Belarus
2IONCh of National Academy of Sciences of Belarus, E-mail:
Based on results of studies performed by the authors, specific one-stage technique of obtaining carbon adsorbents from timber wastes is proposed. It is based on thermocemical pyrolysis of raw material in the steam-gas flow from gas radiation porous burners. Under such conditions
cellulose containing materials are exposed simultaneously
to intensive heat radiation and interaction with gaseous products of combustion.
During contact heating high active radicals H, OH, HO2 which
are formed during gas filtrational combustion initiate destruction of bonds
in polymeric chains with forming liquid and gaseous products and char residue.
Combining pyrolysis and steam-gas activation under speedy heating (40 to
50 degrees per min) with short-term endurance at final processing temperature
(near 600 - 7000C) leads to carbonization of impregnated timber
and formation of porous absorbent's structure. Impregnating additives contain
catalysts of charring and pore-forming substances. Again char residue yield
increases 2 to 2.5 times and iongenic functional groups are introduced
at the same time. Chars obtained in such a manner possess high consumption
characteristics. They can absorb both organic compounds and ions of heavy
metals and are comparatively cheap in the production. The process is characterized
by high degree of ecological safety and is the basis to develop compact
mobile devices to produce carbon adsorbents from timber wastes and other
vegetation raw materials.
O-2-02: Kinetic Study of Synthesis of SiC Powders and Whiskers
J. A. Puszynski, Shuxia Miao
Chemistry and Chemical Engineering Department South Dakota School of Mines and Technology , Rapid City, SD 57701 USA
Tel: 605-394-1230, Fax: 605-394-1232, E-mail: firstname.lastname@example.org
The effect of KClO3 and Teflon on maximum combustion temperature, reaction heating rate, and the combustion front velocity have been studied in detail. With increasing concentrations of KClO3 (5 ~ 20 wt%) and Teflon (8 ~ 20 wt%), the maximum combustion temperature increases from 1400oC to approximately 2000oC. However, the combustion front velocity in the case of KClO3 varies from 0.5 cm/sec to 2 cm/sec, and it is ten times faster than that when Teflon is used as the additive.
It has been found that the gas pressure has a very significant effect on the combustion characteristics. When the concentration of additives is greater than the minimum concentration, three different combustion regimes might exist. If the gas pressure is lower than minimum pressure, no propagation can be achieved. However, when the gas pressure is higher, low-temperature and high-temperature combustion waves might be generated. The propagation regime depends on the absolute value of the gas pressure.
The activation energy of SiC formation in the presence of KClO3 and Teflon were estimated using non-isothermal technique and they were found to be 380 kJ/mole and 520 kJ/mole respectively.
It has also been demonstrated that SiC whiskers can be
formed in the presence of above discussed additives and other growth promoters,
such as Fe, Co and Ni. Mechanism of whisker growth and their morphology
will be presented in detail.
O-2-03: Magnesium Thermite Method for Preparing Hydrides of Alkali Metals
Institute of Chemical Physics Researches RAS, 142432,Chernogolovka,
The most known method for preparing hydrides of alkali metals is hydrogenation of molten alkali metals with molecular hydrogen at temperatures up to 700oC during long time and that is the principal disadvantage of such methods. Besides, in order to prepare some hydrides it is necessary to use stirring means. In some cases hydrogenation is performed in inert organic solvents and that makes the process significantly more complex.
The proposed magnesium thermite method for preparing hydrides
of alkali metals consists in reduction of hydroxides of alkali metals with
magnesium that is perfomed in the combustion regime after ignition of a
mixture and further hydrogenation of a formed in an active form alkali
metal with evolved hydrogen at cooling the combustion products. In fact,
both reactions proceed as a unique process.
MeOH + Mg = Me + MgO + 1/2H2 (1)
Me + 1/2 H2 = MeH (2)
MeOH + Mg = MeH + MgO (3)
The effect of various technological parameters (ratio of components, their dispersity, the relation between free volume and a mass mixture, etc.) on the yield and chemical activity of a hydride was studied. It was established that hydrides of alkali metals may be prepared by the proposed method with high yields (up to 90-95% LiH, 70-80% NaH and KH) at rather low hydrogen pressures
(5-10 ata) growing as a result of the reaction (1).
It was experimentally shown that inseparable mixtures
of hydrides of alkali metals with magnesium oxide possess higher chemical
activity than crystalline hydrides of alkali metals, which were prepared
by direct hydrogenation of alkali metals. in particular, in exchange reactions
with aluminium chloride at reduction of organic compounds and particularly
upon using solvents or gases as drying agents.
Jiang Guojian, Zhuang Hanrui, Li Wenlan, Wu Fengying, Zhang Baolin
Department of High Temperature Structural Ceramics, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi road, Shanghai 200050, China,
Tel:+86-21-625-129-90-6275,Fax: 86-21-62513903, Telex: 33309 ASSIC CN
Under high pressure nitrogen, AlN containing higher nitrogen content (33.5wt%) has been prepared by SHS method. The combustion reaction characteristics in the nitridation of Al was investigated by measuring nitrogen content. Based on calculating the free energy ((rGm() of reactions, the reaction mechanism of combustion synthesis of AlN is possibly the reactions between N2 and Al vapor and/or liquid Al. Based on experiments, the reaction mechanism of combustion synthesis of AlN is proposed. The primary structure of the combustion wave in the nitridation of Al is proposed. the reaction is divided into four zones, i.e. preheat zone, reaction zone (which, in turn, is divided into kinetics control stage, thermal explosion stage, transition stage and diffusion stage), after-burn zone and cold zone. The Activation Energy of the Kinetic Reaction Process is 6 KJ/mol.
SEM morphology of combustion products and its production mechanism have also been studied simply.
To apply AlN whisker commercially, it is necessary to
produce it by an economic means. The AlN whiskers used in this investigation
have been produced by SHS technique. Here, the morphology, chemistry, and
growth mechanism of AlN whiskers have been investigated using high-resolution
electron microscopy, and X-ray diffraction techniques. Emphasis has been
placed on the crystallographic aspect of the mechanism of growth of the
whiskers. The growth mechanisms of AlN whiskers are VLS and VS mechanism.
O-2-05: About Possibility of Use of SHS Nitrided Alloys for Production of
Tomsk Branch of the Institute of Structural Macrokinetics and Materials Science Russian Academy of Sciences,Tomsk, 634021, pr. Academicheskii, 10/3, Russia.
To extract the nitride phases through the acid enrichment, the solutions by hydrochloric and sulphuric acids in a wide concentration range (5-25%) were used. The kinetic curves of accumulation of iron, chromium, niobium, vanadium, titanium in the solutions of various concentrations are presented. Owing to the results of the acid enrichment investigation, treatment conditions of SHS nitrided ferroalloys were chosen; under these conditions the content of iron in metal nitrides and the losses of the latter are minimal.
Physical and chemical properties of the nitrides, being extracted, were investigated. Phase and elementary composition of obtained niobium, chromium, vanadium, titanium nitrides was determined with X-ray-phase and chemical analysis. The oxidation nitrides in air up to 1000oC was investigated with the help of complex thermal analysis. The specific surface of the nitrides obtained was determined.
Thus, the nitrides of chromium, niobium, vanadium and
titanium were produced through acid enrichment of SHS nitrided ferroalloys.
Some of their physical and chemical properties were investigated.
O-2-06: Combustion Synthesis of Ternary Carbides TixSc-xCy Scandium
Hydride, Ti and C
Institute of Chemical Physics of National Academy of Sciences of Republic of Armenia, 5/2, Paruir Sevak Str., Yerevan 375014, Republic of Armenia.Phone:(374 2)28-17-80,
28-16-41; Fax:(8 3742)28-17-42; E-mail:email@example.com
The investigation of the combustion systems xTi + (1-x)ScH2-z(Sc) + yC in hydrogen and argon atmosphere were carried out in wide ranges of Ti/ScH2-z and Ti/Sc ratios at various carbon content (z<1; 0.4 < y < 1) .
Preliminary, the combustion process in Sc-H system was studied. The hydride of Sc (fcc structure, a = 4.76A, H-content - 2.0 %) was synthesized.
The thermal dissociation of ScH2-z was studied using Derivatograph Q-1500. It was established that the dissociation began at 600oC. The complete dissociation occured at 1000oC. The powder of Sc of hcp structure (a=3.308; c=5.268) was obtained.
In this work ScH2-z and Sc were used as initial reagents.The obtained experimental data prove that the combustion process in the above mentioned system is a two-stage process. In the first, high temperature stage, Ti + xC reaction takes place (when x > 5 and Ti/Sc > 0.5). Because of high temperature arised in the reaction zone, the dissociation of scandium hydride and its interaction with carbon begin. As a result, the scandium carbide is formed. Then depending on combustion temperture, full or partial dissolvation of ScC in TiC takes place. It has been found that the full dissolvation of this carbides is possible at Ti/ScH2-z < 4. On the solubility of these carbides, the content of carbon in the initial mixture also influences.
This work was supported by ISTC. Grant A-192.
O-2-07: Hydriding Shs of Mg2Nih4
Sendai, 980-8577, Japan
2 Research Institute of Electric Light Source Material, 5 Jinchuanmenwai, Nanjing 210015, P. R. China
two pairs of the modifications of Mg2NiH4.
O-2-08: Transition Metal Nitrides Prepared by HP-SHS
1INFM and Dip.to di Chimica e Chimica Industriale, via Dodecaneso 31,
I-16146 Genoa, Italy,E-mail:firstname.lastname@example.org
2Istituto di Chimica Fisica Applicata dei Materiali,CNR,via
De Marini 6,1-16149 Genoa,Italy
1. L.E. Toth,Transition Metal Carbides and Nitrides, Academic Press, 1971.
2. K. Schwarz, N. Rysch, J. Phys. C: Solid State Phys., 9 (1976) L433.
3. G. Ries, H. Winter, J. Phys. F: Metal Phys., 10 (1980) 1-7.
4. V.N. Lipatnikov, W. Lengauer, P. Ettmayer, E. Keil, G. Groboth, E. Kny, J. Alloys Comp., 261 (1997) 192-197.
5. K. Frisk, CALPHAD, 15 (1991) 79-106.
6. W. Mayr, W. Lengauer, P. Ettmayer, D. Rafaja, J. Bauer, M. Bohn, Def. Diff. For., 143-147 (1997) 569-574.
7. W. Huang, Metall. Trans. A, 27A (1996) 3591-3600.
8. M. Joguet, W. Lengauer, M. Bohn, J. Bauer, J. Alloys Comp., 269 (1998) 233-237.
9. Y. Du, R. Schmid-Fetzer, H. Ohtani, Z. Metallkd., 88 (1997) 545-556.
10.V. Buscaglia, F. Caracciolo, M. Ferretti, M. Minguzzi, R. Musenich, J. Alloys Comp., 266 (1998) 201-206.
11. R. Musenich, P. Fabbricatore, G. Gemme, R. Parodi, M. Viviani, B. Zhang, V. Buscaglia, C. Bottino, J. Alloys Comp., 209 (1994) 319-328.
12. M.W. Williams, K.M. Ralls, M.r. Pickus, J. Phys. Chem. Solids, 28 (1967) 333.
13. K.S. Keskar, T. Yamashita, Y. Onodera, Jap. J.
Appl. Phys., 10 (1971) 370.
O-2-09: Peculiarities of SHS Fine-Dispersive Complex Titanium-
Chromium Carbide in Complex System
S.S. Mamyan, D. Belov, I.P. Borovinskaya
Russian Academy of Sciences, Chernogolovka, 142432, Russia
Thermodynamic researches have shown the possibility of the formation of that complex compound at the combustion of Ti - Cr - C - TiO2 - NiO system. The experimental researches have shown that we can regulate the particle size, replace elementary Ni by its oxide and replace approximately to 20-30% elementary Ti by TiO2 at SHS of this system.
The effect of the initial synthesis parameters on the
product quality (particles morphology, size and distribution components,
chemical composition, etc.) has also been shown.
O-2-10: Formation of Metal Sulfides in Combustion of Metal Nitrates Complex
Compounds with Sulfur-Containing Organic Ligands
Complex compounds of metal nitrates with hydrazine and its derivatives are knows as energy-rich substances able to undergo self-sustaining combustion [1, 2]. The presence of metal atoms in the complexes leads to the formation of solid products during combustion, along with gas-phase ones. This allows to consider these complexes as initial substances to obtain definite target products during combustion.
It was shown earlier that the combustion of complex compounds of nickel and copper nitrates with some hydrazine derivatives, e.g. semicarbazide, aminoguanidine, and oxalyl dihydrazide, leads to the formation of metal nickel and copper with porous, carcass structure [3-5].
In the present work we demonstrate the possibility to obtain sulfides of different metals during the combustion of such complexes. The formation of sulfides occurs if a sulfur-containing hydrazine derivative, thiosemicarbazide, is used as a ligand. Nickel, cobalt, copper, zinc and cadmium sulfides were obtained by this method. We also found that complexes of some metal nitrates with thiocarbamide (which are not so rich in energy) are also able to burn. Their combustion is also accompanied by the formation of the sulfides of corresponding metals.
It is important that the morphology and dispersity of
the combustion products can be governed. This can be done by changing the
conditions of their formation in the combustion wave by varying some parameters,
e.g. external pressure, temperature and combustion rate. This effect is
especially vivid in obtaining sublimable sulfides with rather high vapour
pressure at the temperature of complex combustion.
O-2-11: SHS of Metal Carbides; Reactions of Calcium Carbide with Anhydrous
1 Department of Chemistry, University College London,20 Gordon Street, London WC1H OAJ, UK
(> 2,000°C) under controlled atmospheres for prolonged time periods. We have developed two new routes to a wide range of transition metal carbides (TiC, ZrC, HfC, V8C7, NbC, TaC, Cr3C2, Mo2C, WC, Fe3C) from the self propagating reactions of aluminium carbide or calcium carbide with anhydrous metal chlorides (Eqn.1, Eqn.2). In the calcium carbide reactions crystalline metal carbides such as TaC can be made in less than ten seconds and the reaction promoted in air. The solid state metathesis reactions have been extended to the synthesis of solid solutions of mixed metal carbides and metal carbonitrides. Microstructure of the metal carbides has been investigated in detail by TEM and ELNES studies.
Al4C3 + 3WCl4 --------> 3WC + 4AlCl3 Eqn.2
I. G. Cano, S. Purez, M. A. Rodriguez, S. de Aza
Instituto de Cerámica y Vidrio (CSIC),
Arganda del Rey (Madrid), Spain
In the present work, the effect of the amount and chemical composition of the ammonium salt used, on the physic-chemical characteristics of the final products are studied.
Compositions using different amounts of Ammonium Chloride,
Ammonium Fluoride and mixes of them are added to the raw materials to improve
the Synthesis. Final products are characterized by SEM and XRD.
O-2-13: Chemistry and Technology of Combustion Synthesis of Complex
2 University of Houston, Dept of Chemical Engineering,
Houston, TX, USA
O-2-14: Synthesis of Perovskites (ABO3) by Combustion Process
CEP 13565-905, São Carlos, Spain – Brazil,
The development of ceramic materials with characteristic of laser properties, electrical conductivity, electro-optical and piezoelectric behaviour is a quite attractive subject of fundamental and technological research of the last years, due the properties highly peculiar that has been observed in these classes of materials. The work searches through the synthesis by combustion reaction the preparation of ABO3 perovskite-type compounds, namely, LaAlO3, LaCoO3, LaCrO3, LaNiO3, LiNbO3 powders, with adapted characteristics of high crystallinity and phase stability. The main objective is to evaluate the combustion technique for powder preparation as an alternative method to the sophisticated and complex processes, which involve high costs, besides the acquaintance conventional mixing of oxides that produces powders of low reactivity and/or with the presence of undesired secondary phases. Powder’s characteristics prepared by combustion reaction are presented and discussed. The purpose of this work is to attempt to bring together the information obtained from this study and to evaluate the combustion process as an alternative rote for preparing new perovskite compounds with new and improved properties.
The authors are thankful
to FAPESP - State of São Paulo Research Support Foundation - Brazil.
O-2-15: Self-Propagating High-Temperature Synthesis of Complex Chromium-
Containing Alkaline and Alkaline-Earth Metals Oxides
Institute of Structural Macrokinetics and Materials Science RAS,
Chernogolovka, 142432 Russia
Synthesizing SHS products can be used in pigment mixtures;
in the tunnery industry; like dry electrolytes; corrosion inhibitors etc.
O-2-16: Synthesis of Lattice Matched Cd-In-Ga Oxides for Gan Thin Film
1 NASA Center of Applied Radiation Research, Prairie View A&M University
Prairie View, TX 77446. E-mail: email@example.com
1 Institute of Structural Macrokinetics and Materials Science,
3 Chemical Engineering Department, University of Houston,Houston,
TX 77204, USA
Gallium nitride and associated III-N materials have various
potential electro-optical applications. The lack of cost-effective latticed-matched
substrates for growing these nitride films is a recognized problem. CdIn2-dGadO4,
with lattice constants from 8.39 Å (d
=2) to 9.17 Å (d
=0) may be suitable substrates for growing various nitride thin films.
For examples, CdIn1.673Ga0.327O4, having a lattice constant of 9.04 Å (2x
cubic GaN), and CdIn0.952Ga1.048O4, having a lattice constant of 8.76 Å
(2x AlN), may be substrates for growth of GaN and AlN thin films, respectively.
The sointering/calcination processes to produce Cd-In-Ga oxides are time
consuming and expensive. We studied the use of Self-propagating High-temperature
Synthesis (SHS) to fabricate Cd-In-Ga oxides to circumvent these synthesis
problems. We studied the impact of the standard SHS variables on the product
quality at normal pressures using various precursor powders, pellet diameters
and densities, oxygen flow rates, and additives. A high-pressure reactor
was used to investigate the impact of oxygen pressure on product quality.
The crystal structure and local stoichiometry of the product were determined
by XRD and EMPA. The thermal behavior of the reactants at high temperatures
was determined by TG/DTA. The reaction network and kinetics for the reaction
were deduced from the temperature history during the combustion.
O-2-17: Disilicides Elaboration by Combustion Synthesis: Interest
of Using a Mechanical Activation Step
1 “Far from equilibrium phase transition” group UPR CNRS AO423 IPSé F-90010 Belfort
2 “ fine grained materials ” group LRRS UMR 5613 CNRS-University of Burgundy
BP 47870 –F 21078 Dijon Cédex, France
CNRS av. J-B. Clément F 93430 Villetaneuse, France
The mechanically activated SHS process is able to produce via a very fast combustion front (> 20 mms-1) a pure “ bulk ” a-MoSi2 with a nanometric structure (66nm). In addition, the nanostructure of the starting powder mixture (Mo+2Si) influences the propagation of the combustion front and modifies the values of thermal parameters during the process. In the case of Fe-Si system, mechanical activation allows to initiate a self-sustaining reaction after heating up to 400°C a cylindrical sample.
Thermal and structural informations describing the combustion
front initiated in Fe-Si or in Mo-Si green samples were clearly determined
using a Time-Resolved X-ray Diffraction (TRXRD) experiment coupled to an
infrared camera. Mo+2Si-> MoSi2 appears to be the only reaction,
which is monitored with a temporal resolution of 30 ms inside the combustion
front during SHS process. The existence of a combustion wave in Fe-Si system
was assumed to be linked to the formation of FeSi compounds during gasless
O-2-18: The Effect of Mechanical Treatment on the Rate and Combustion
Limits of Shs Processes
630128 Novosibirsk, Kutateladze 16, Russia, e-mail: firstname.lastname@example.org
It is known that it is difficult (or even impossible)
to obtain a single-phase product by means of SHS in many intermetallic
systems. MT of SHS products allows to carry out phase homogenisation. For
example, the mixture of Ni2Al3 with NiAl after MT
for 3 min is transformed into a single-phase product composed only of NiAl
with the size of coherent scattering domains 8-10 nm. Electron microscopic
studies of the changes in the morphology of particles in the reaction mixture
during MT have been conducted.
O-2-19: Effect of High-Energy Milling Reactant on the Combustion Synthesis of
1Department of Materials Engineering, Federal University of Sao Carlos, Sao Carlos, 13565-905, Brazil. E-mail:email@example.com
2 Department of Chemical Engineering and Materials Science, Facility for Advanced Combustion synthesis,University of California,Davis,CA 95616,USA.
O-2-20: Shs Synthesis of the Oxide Systems Based on the "Mechanochemical"
Quartz Modified by Organometallic Compounds
Combustion Problems Institute, Almaty, Kazakhstan, e-mail firstname.lastname@example.org
The use of divers alcohols and other organic additives in the mechanical quartz processing as a surface active substances makes possible the formation of polymer compound particles on the surfaces. During further heating of the particles having their modificated surfaces there are occurred organic compound decomposition and high-active radicals formation which participate in the redox processes and effect on the starting and kinetics of such processes running out.
In this paper the evaluation analysis of energy saturation of the quartz particles resulted of the mechanochemical processing in the centrifuge-planetary mills is carried out. This investigation showed that the variations of mechanical action conditions and its time duration (5-100 minutes) result in the observed stage-by-stage modification of the processed material structure and state. The quartz activation during 15 minutes results in the most pronounced effects, the synthesis starting temperature being decreased and making possible the most complete reaction running out at minimum charge content of aluminum (up to 6%). The energy saturation of the quartz processed individually or in the mixture with other oxides substantially depends on the used organic additions. The buthanol as a modifying additive is the most efficient to speed up the reactions between quartz and aluminum.
It is shown that the kinetic combustion characteristics, phase composition, structure and properties of the end synthesis products of the analyzed materials based on the SiO2 + Al system depend on the organic and organometallic compound types formed on the surfaces of the quartz particles during preliminary mechanochemical processing and that the most pronounced effects on the SH-synthesis are attributed to the action of aluminum and organic compounds.
O-2-21: Mechanically Stimulated Self-Propagating Syntheses of
In the course of systematic investigations we have shown wide possibilities of solid-state mechanochemical methods in the synthetic chemistry of coordination compounds such as metallocenes, b -diketonates, carboxylates, metallocarboranes etc. Physico-chemical (IR, XRD, TGA, DTA etc.) and preparative investigations of the reaction mixtures consisting of solid metal chlorides and salts of organic ligands allowed us to draw a corollary that all systems studied can be divided into three main groups depending on their response to mechanical loading.
The first group includes ordinary mechanochemical reactions, formation of products in which takes place directly in the course of mechanical loading, as, for example, formation of ferrocene in the system “FeCl3 — TlC5H5”. The second group consists of the systems, mechanical loading of which leads initially to the formation and accumulation of activated mixture without formation of the final products. Formation and relative quantity of activated mixture can be detected by the appearance of a new exothermic event on DTA curves of mechanically loaded reaction mixtures. Prolongation of mechanical treatment after accumulation of the activated mixture in the systems leads to “explosive mechanochemical synthesis” - a sudden initiation of a fast exchange reaction leading to a vigorous self-heating and formation of final products. Bulk heating of the activated reaction mixtures leads to the exothermic interaction of reactants with formation of final products which can occur in the form of heat explosion. Exothermic interaction of reactants in such systems can be organized in the self-propagating mode: the action of a local thermal impulse on an end face of the specimen formed from the activated mixture causes the appearance of reaction zone which propagates along the specimen up to a full exhaustion of a material with formation of final products. “CrCl3 — NaC5H7O2” is an example of such systems.
The majority of the systems investigated takes an intermediate position between these extreme cases. That is, formation of final products and intermediate activated mixture occurs in the course of mechanical loading. Further transformation of mechanically activated mixtures to the products can be organized in various modes, including self-propagating, depending on conditions of the mechanical loading, organization of the process and chemical identity of reactants.
Characteristic features of self-propagating syntheses of coordination compounds are discussed.
We acknowledge support from RFBR (grants No 99-03-32253;
O-2-22: Mechanism of Interaction and Combustion Limits for Niobium and
A.V. Kostanyan, H.H. Nersisyan, S.L. Kharatyan
Nalbandyans Institute of Chemical Physics NAS RA Yerevan, 375044,
Republic of Armenia. E-mail: Suren@ichph.sci.am
The purpose of presented work is to study the interaction mechanism and expansion of combustion limits of Nb-C system on various parameters in conditions of activation.
Combustion limits of Nb-C system on following parameters are experimentally investigated: the size of metal particles, ratio of initial reagents, tablet diameter, amount of inert additive. Various activators of combustion with the purpose of activation both metal, and carbon were tested.
It was shown, that at introduction in an initial mixture Nb with C a few (less than 1%) chemical activator successfully selected for the given system - polytetrafluoroethylene, steady-state combustion in a wide range of values of various parameters takes place: the size of niobium particles (m Nb£ 80 mm), initial tablet diameter (d³ 10 mm), ratio of initial reagents (0,3£ a £ 1,0), amount of the inert additive in a mixture (up to 50 % mass.) etc.
It was shown, that the observable expansion of combustion limits is result of intensification of gas-transport transfer of niobium to carbon particles, by means of niobium fluorides. The similar studies on activation of carbon using various gas-generating additives, including of oxalates of metals, appreciable results have not brought.
It was established by X-ray and SEM analyses, that it’s possible to synthesize single-phase carbide NbC in the form of half-perfect crystallites by the sizes 5 ¸15 microns at rather wide range of process parameters.
Complete distributions of temperature on combustion zones
for Nb - aC mixtures in conditions of activation are received. Leading
stages of process are established, sizes of reaction zones are estimated.
O-2-23: Shs in Fabrication of Composites
State Key Lab of Advanced Technology for Materials Synthesis and
Processing Wuhan University of Technology, Wuhan 430070,China
O-2-24: SHS of Composite Materials in Thin Multilayer Systems
Combustion Problems Institute, 172 Bagenbay Bat., Almaty, Kazakstan, 480012
O-2-25: Reactive-Casting of NiAl-Base Intermetallic Compounds
Division of Materials Science and Engineering Graduate School of Engineering
Hokkaido University Kita 13 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan
O-2-26: Processing of in-situ Nitride Reinforced Aluminum Matrix
H.J. Brinkman, J.Duszczyk, L. Katgerman
Rotterdamseweg 137, 2628 AL Delft, The Netherlands
O-2-27: Hybrid SHS Technologies Based for Production of
Composite Materials and Coatings
1Center of SHS of the Moscow Steel and Alloys Institute
and the Institute of Structural Macrokinetics and Materials Science
2Institute of Physical Chemistry of RAS, Moscow 117915,
- the development of new materials and chemical products using known technological types of the SHS processes;
- the development of novel technological versions and hybrid SHS-based technologies which in combination with other methods allows achieving super effects.
Let's take as super effect the creation of unique materials
with a new, earlier inaccessible, level of properties and also a considerable
growth of the technological process efficiency with a heightened product
quality. Taking this point of view the method ofthermoreactive electrospark
surface strengthening (TRESS) developed at the SHS- Center of the Moscow
Steel and Alloys Institute can be classified with the hybrid technologies.
The production of gradient ceramic and metal ceramic substrates for the
subsequent precipitation of highly adhesive thick film coatings on them
is another way of the effective SHS application. The report presents the
results of the research connected with the synthesis of diamond containing
graded materials with a thick diamond film. According to the force SHS-
pressing technology poreless plates are produced with a variable through
the thickness concentration of diamond grains from 0 to 60 vol. ^o in the
cramic binder based on TiB2, TiC etc. Then polycrystalline diamond
films more then 30 u,m in thickness were precipitated on the plate surface
by the CVD technology (in an arc discharge). A high adhesion of a coating
to the substrate is an advantage of such composites. In contrast to the
other technologies (powder metallurgy, HIP, HTHP) SHS allows to "seal up"
a diamond grain into various ceramic binders, in particular into a highly
heat conductive binder of titanium diboride. The composite's structure
and properties were studied in the paper.
O-2-28: Multilayer Component Prepared by Combining Tape
Casting and SHS Process
J.P. Bonnet, S. Desiles, A.L. Dumont, T. Chartier, D.S. Smith
E-mail : email@example.com
MoSi2-Al2O3 based composites can be prepared by S.H.S. reactions between MoO3, Al and Si or SiO2. Addition of Al2O3 or MoSi2 to the reactants allows to the relative amount of each phase in the final product to be controlled. It is then possible to obtain either electrically conducting (addition of MoSi2) or insulating composites (addition of Al2O3).
The addition of additives, which contribute to a decrease in the maximum temperature reached during the process, allows the amount of transient liquid to be altered. Therefore this parameter can be used as a processing variable.
Tapes of about 250 m m thickness of both MoSi2-rich and Al2O3-rich compositions are prepared by tape casting. Ten layers of each composition are then stacked alternately. After debinding, the S.H.S. reaction is initiated in the self-propagating mode and densification is achieved by the application of a small mechanical load.
The quality of the multilayer structure, as well as the efficiency of the densification step, are strongly dependent on the amount of transient liquid formed during the S.H.S. process. After optimisation of this parameter, dense multilayer plates were obtained. The final layers thickness is about 120 m m. Local electrical measurements confirmed the presence of alternating conducting
(0.1 W ) and insulating (10
MW ) layers.
O-2-29: Preparation of Carbide Fiber-Reinforced Composites
Jondo Yun, Hwancheol Bang, Cheolho Go, Tae-Hyeon Choi, and Bongseob Kim
Department of Inorganic Materials Engineering, Kyungnam University,
449 Weolyeong-dong, Masan, 631-701, Korea, E-mail:firstname.lastname@example.org
O-2-30: Characterization of Li-Cu Ferrite Powders Prepared by Self-
propagating High Temperature Synthesis
1 Department of Metallurgical and Materials Engineering, Sunmoon University, #100 Kalsan-Ri, Tangjeoung-Myun, Asan, Chung Nam, 336-840 Korea
2 Korea Institute of Metal and Machinery, Changwon, Kyung
O-2-31: Mathematical Model of SHS Welding
Chernogolovka, 142432, Russia
The whole of SHS- welding process may be divided into two stages. The first stage is complited out with electrothermal explosion with forming a charge melt. The second one involved in charge melt squeezing with simultaneous cooling and solidifying. Itis supposed that there is no reaction before melting temperature of charge metallic component is reached and heating is realized by Joule heat. The electrothermal explosion takes place when this temperature is reached. A reaction is proceeded instantly and the melt or suspension of reaction products are formed. Two postprocesses are realized after the electrothermal explosion: a) squeezing of a part of SHS-products; b) cooling and solidifying.
Squeezing in one’s turn may be divided into two stages.
Simultaneously with melt squeezing melt cooling is occured. The first stage
involved a period up to reaching of solidifying temperature. In this stage
the problem is two-layer (solid electrode – liquid charge melt). After
reaching of solidification temperature the problem transforms inton three
layer (solid electrode – solidified reaction product – charge melt) with
mooving boundary at which there is phase change. The systems of differential
equations discribing different stages of SHS-welding process are developed.
O-2-32: In-Situ Joining of Nickel monoaluminide to Ni-base Superalloys
C.Pascal, R.M. Marin-Ayral, N. Frety, J.C. Tedenac
Laboratoire de Physicochimie de la Matière Condensée,(L.P.M.C. UMR 5617) c.c.003
University Montpellier II, Pl. E. Bataillon, 34095 Montpellier Cedex France
Phone (04 67 14 33 55) Fax (04 67 14 42 90)
High gas pressure combustion synthesis is a new way for welding. In this process, a Ni-base braze is placed between a substrate of Ni-base superalloy and a compact made of 50at% Ni-50at% Al mixture. The heat released during the combustion synthesis of the Ni+Al compact gives rise to interdiffusion of the elements and consequently to a joining interface. The main advantage of this new process is an important decrease of welding temperature which allows to increase the number of repairs by turbine blade.
In this presentation, we will develop the results obtained for a Ni-base superalloy. In a first part, we will describe the main experimental conditions to optimise the joint’s quality. Then, using scanning electron microscope (SEM) and electron probe microanalyser, we have studied microstructures and concentration distributions across the joining interface. Finally, we will present first results of mechanical characterisation of the joining interface by distribution of hardness across the interface, three point bending test and shear test.
This work was supported by DGA (n°97-2527A/DSP/STTC) and by Sochata-SNECMA service (Chatellerault-France)
O-2-33: Influences of Mechanical Vibration on SHS Ceramic -Lined Pipes
Dept.of Mater.Sci.and Eng., Shi Jia Zhuang Machenical Engineering College
Shi Jia Zhuang, He Bei, P.R. China, 050003
and ceramic solidification process.
O-2-34: SHS Process for Manufacturing Aluminum Master Alloys by Use
Samara State Technical University, 141 Galaktionovskaya, 443010, Samara,Russia
Tel.: (8462) 42-22-68, 42-28-89; Fax: (8462) 42-22-68, 32-42-35
The influence of flux agents on the SHS process, technological and structural parameters of the master alloy has been studied. The flux function is based on the SHS process activation through the dissolution of oxide films from a surface of aluminum powder particles. It is determined that the increase in flux quantity leads to the rise of the SHS reaction temperature and reduction of its delay time. It makes possible to reduce the temperature of master alloy production by 100-2000C without the degradation of its quality, to increase the completeness of the running reaction. The quantity variation of the flux and aluminum powder in a SHS mixture provides a wide range of different morphologies of TiAl3 particles- from needle-like, mixed to blocky and globular ones with the size of 10...15 m m. The small difference in the use of the two kinds of fluxes has been revealed. The NOCOLOK flux gives higher temperature of the SHS reaction (by 15-200C), rises the melt fluidity, results in a finer structure of master alloy.
The optimal modes of the master alloy production with the cheaper Russian flux Na3AlF6. have been found. The flux application makes possible to control the SHS process in an aluminum melt and thereby effect on structural and technological parameters of a grain refiner.
NOCOLOKTM is a registered trademark of Alcan
Aluminum Ltd, Canada
O-2-35: Reaction Characteristics of the Fillers for SHS Welding of SiC Ceramic
Shujie Li, Huiping Duan, Shuhua Li, Shen Liu
Beijing University of Aeronautics and Astronautics, Department of Materials
Science and Engineering, Beijing 100083, People*s Republic of China
O-2-36: Influence of Plastic Deformation on Microstructure and Properties
2Institute of Structural Macrokinetics of RAS, Chernogolovka,
The formation of a microstructure and mechanical properties in the nonstoichiometric titanium carbide was investigated by using three various methods of processing (C/Ti ratio was equal to 0.47): 1) the samples were prepared by SHS-reaction with the subsequent force compacting at high strain rates; 2) the samples were received after hot deformation of billets prepared by the 1st method; 3) the samples were prepared by combining SHS-reaction and hot deformation under temperature-rate conditions of superplasticity of nonstoichiometric titanium carbide. The porosity of the samples processed by the given methods did not exceed 3%.
The processing of titanium carbide by the first method led to formation of an extremely non-equilibrium two-phase microstructure. The average size of carbide grains was 10-12 m m and the volume fraction of excess titanium phase amounted to 12%. The ductile-brittle transition (DBT) of such material was observed at the temperature 750° C.
The subsequent deformation of such material showed its microstructure is non-equilibrium. Concurrent development in titanium carbide of phase transformation TiC0,47 ® b -Ti and dynamic recrystallization resulted in formation of a "microduplex" type microstructure with the average grain sizes of carbide and titanium phase about 2 m m at deformation in conditions of the enhanced strain rate sensitivity of flow stress (T=950° C, e =10-3 s-1). At that the volume fraction of titanium phase increased up to 30 vol.%, and the DBT-temperature decreased up to 650° C. Such material showed a much lower flow stress level, than that flow stress of titanium carbide produced by the 1st method.
The processing of titanium carbide by the third method promoted the formation of an equilibrium microstructure with an average size of carbide grains of 10-12 m m. The DBT-temperature of such material was observed at 750° C. This material showed an essentially higher level of flow stress at high temperatures (900° C and higher). The chemical composition of titanium carbide did not change during the further deformation, and the microstructure retained its stability.
Thus, the comparison of three methods of preparation of
nonstoichiometric titanium carbide using SHS-reaction and plastic deformation
showed that the temperature-rate conditions of plastic deformation essentially
influence the formation of microstructure during self-propagating high-temperature
synthesis. The control of conditions of plastic deformation might allow
us to influence the completeness of chemical reaction during SHS.
O-2-37: Densification of Condensed Systems During Combustion
1Institute of Structural Macrokinetics and Materials Science Russian Academy of Sciences
1Insitute of Chemical Physics Problems Russian Academy of Sciences
142432, Chernogolovka, Russia
Is allowed, that the capacity of combustion products to compaction is controlled by process of viscous flow at the expense of formation of hyperthermal fluid phases. In a general problem on combustion and densification the problems on a place of compacting are esteemed: behind front, in front and before combustion front.
The dependencies of combustion rate and final porosity on pressing efforts, and also on different ratio of characteristic times of densification both chemical reaction and cooling of products are analyzed. Influencing the fusible component on compaction of a material is during combustion. The analysis of transformation in time of initial distribution of density allows to observe propagation of densification boundary at moving of combustion wave along pattern.
This work was supported by
RFBR Grant ¹98-03-32110a.
O-2-38: Formability of SHS-Materials
Institute of Structural Macrokinetics and Materials Science Russian Academy of Sciences
142432, Chernogolovka, Russia
In the present activity the outcomes on usage of a method of free SHS-compaction for analysis of capacity to forming some widespread classes of SHS- materials are set up.
Are investigated of regularity of forming of some classes of SHS-systems with a different ratio of combustion temperature and melting of initial reactants. As the characteristic of capacity to forming it is offered to use parameter - degree of deformation having sense of relation final to the initial area of a sample. The analysis of relations of this testimonial from of quantity and structure of flow bundle is conducted.
This work was supported by
RFBR Grant ¹98-03-32110a.
O-2-39: Production of Dense Molybdenum Disiliside Materials
P.Lintula1, J.Maunu1, M. Sundberg2,
1VTT Manufacturing Technology, P.O. Box 17031, FIN-33101,Tampere, Finland
Nearly fully dense (95 - 99 %) MoSi2 materials
were produced by combustion synthesis (SHS mode) of the elemental powders.
Formation reaction for MoSi2 has rather low adiabatic temperature
(1627oC), which makes it more difficult to obtain full density.
Both the manufacturing process and the material composition have been developed
to get high density and good high temperature properties. Experiments to
alloy MoSi2 by zirconium oxide, titanium carbide and silicon
carbide were also carried out. The phase composition, impurity content
and density of the materials were evaluated. Depending on the composition
and process parameters, small amounts of Mo5Si3 phase
were found in some samples but most samples had a single phase MoSi2
structure. The materials have homogeneous microstructure and fine grain
size. The microstructure and mechanical properties are compared to those
manufactured by conventional processes.
O-2-40: New Technical Decisions Improving SHS Pressing Method
Technology University, Galaktionovskaya 141, 443010 Samara, Russia,
Phone:(846-2)33-3473, E-mail: mvm. @ mc. sstu. samara. ru.
New technical decisions are developed and patented to improve the dimension accuracy of the article. To reduce the nonuniformity of the thermal field the side edges of the green compact are chamfered with dimension of 2 to 3 mm. To increase the axis contact stiffness of the tool: 1) the sheath thickness is reducer up to 2-3 mm simultaneously with cladding the green compact by a layer of heat-generating substance or 2) the sheath of the compact is performed thin rigid steel sheets.
At SHS pressing two objects are deformed plastically:
the article and the sheath. The pressing power is distributed proportionally
with energy consumption for deformation of the SHS product and the ring
sheath around the article. To reduce the stiffness of the ring sheath and
increase the press efficiency: 1) the ring sheath is made of material with
a low stiffness or 2) the height of the ring sheath is increased in comparison
with the central zone to reduce the rate of the axis deformation and compaction
of the zone.
O-2-41: Metal-Like SHS Catalysts as Analogues of Noble Metals
D. reidel Publ. Comp., The Netherlands, 1983.
3. Grigoryan E.H., Borovinskaya I.P., Merzhanov A.G., " SHS Catalysts for Neutralization of Exhaust Gases from Internal Combustion Engines", Intern. J. of SHS, 1997, v.6, N 4, p. 439
of SHS Catalysts
Institute of Materials Science, NCSR “Demokritos”, Athens, Greece
The proportion of spinels to simple oxides in Cu-Cr-O
catalysts did not appear to depend to a substantial extent on the quenching
media used. But significant differences were observed for their catalytic
activity in the processes of deep methane oxidation and carbon monoxide
and hydrocarbon oxidation. Detailed investigations using Scanning Electron
Miscroscopy, EDX analysis and XRD showed that the underlying reason for
the activity variation is the significant changes that take place in the
microstructure in the materials.
O-2-43: Chemistry Reaction Processing and Microstructure Formation
W.M.Wang, Z.Y.Fu, H.Wang, R.Z.Yuan
State Key Lab of Advanced Technology for Materials Synthesis and
Processing Wuhan University of Technology ,Wuhan 430070,China
In this paper, the TiO22 B2O33
Mg SHS reaction system was chose as research objective ,the chemistry
reaction processing and microstructure formation mechanism of this SHS
reaction system were studied by DTA-TG,X-ray diffraction ,SEM ,EDS and
Combustion Front Quenching (CFQ) . It was found that the B2O3
was reduced to B at the first step, and TiO2 was reduced to
Ti through following step: TiO22wTi3O55iTi2OOiTi
. In this combustion processing ,the Mg content have a key role .The microstructure
formation processing was studied in detail by SEM and EDS.
O-2-44: Nanocrystalline Ti (Zr) Hydrides Produced Combustion Synthesis
Institute of Chemical Physics of National Academy of Sciences of Republic of Armenia, 5/2, Paruir Sevak Str., Yerevan 375014, Republic of Armenia.Phone:(374 2)28-17-80,
28-16-41; Fax:(8 3742)28-17-42; E-mail:email@example.com
For obtaining the nanocrystalline hydrides the SHS is very advantageous in compare with the known methods i.e. reactive mechanical grinding or alloy under H2 gas pressure of 1 MPa. We were successfull in synthesizing SHS nanohydrides. Nanocrystallization of hydrides of metals and alloys directly at combustion of metals in H2 is an unusual phenomenon. Why does it take place, what is the SHS hydrogenation kinetic? These questions are discussed in the present work.
The results of analysis of materials by TEM, SEM and XRD methods are presented. It was established that for SHS technique the crystal grain of sizes smaller than 0.1 mkm are available. The complete mechanisms of event are not known yet, but these preliminary results can become the starting point of future experiments directed to explain the conditions of SHS process resulting in nanocrystalline hydride formation (hydrogen pressure, grain size, temperature and rate of combustion etc.) Nevertheless, now we are ready to say that apparently excellent peculiarities of SHS-hydrides are the results of instataneous rapid formation of nanocrystalls in combustion regime. From this point of view it will be useful and important to turn to the study of their physico-chemical properties (thermal, mechanical, magnetic, electrochemical, electrical resistance).
This work was supported by ISTC. Grant A-192.
O-2-45: SHS prepared BaSnO3; Comparison of SHS and Conventionally Prepared Materials as Sensors for CO2
Dept. of Chemistry, University College London, 20 Gordon Street,
London, WC1H OAJ, UK