Focused Session CB-10
SHS Ceramics


Session CB-10.1 - Theory and Modeling of SHS Processes and Structural Transformations
CB-10.1:IL01  Concurrent and Complementary Methods in the Theory of SHS: Partial Differential Equations vs Molecular Dynamics
F. BARAS, Laboratoire ICB, CNRS-Université Bourgogne Franche-Comté, Dijon, France

From the seminal contribution of Merhanov to the understanding of solid flame, most of theoretical works in SHS topic have been based on coupled partial differential equations. This approach offers a relevant description of the phenomena observed during SHS, from stationary propagation to highly complex front. On the other hand, Molecular Dynamics simulations offer an atomistic-level description of the elemental mechanisms involved. During this talk, we will show how large scale simulations may reproduce macroscopic behaviors that are compared to the usual theory predictions. Two cases will illustrate our purpose: the propagation of a reactive front, driven by exothermic dissolution, in a nanometric metallic multilayer and the random initiation of the combustion mode in metallic glasses.

CB-10.1:IL03  A Molecular Dynamics Simulation of SHS in Nanofoils
O. POLITANO, Laboratoire ICB UMR 6303 CNRS-Universite de Bourgogne, Dijon Cedex, France

Nanometric metallic multilayers (N2M) are structured as a succession of interfaces separated by a few nanometers. N2Ms are made of thin layers (4-100 nm) of metals deposited alternately. By igniting locally one edge of the sample, a self-sustaining reactive front propagates along the foil, without any further supply of heat. The exothermic processes are the interdiffusion of the two metals together with the formation of new phases such as intermetallics. We studied by means of molecular dynamics (MD) simulations the products formed after the reaction that occurs in NiAl nanometric metallic multilayers. MD is a valuable tool to study those systems, since the typical length scale (a few nanometers) corresponds precisely to the scale accessible in the simulation. The formation of the new phase, here the NiAl intermetallic compound, develops in non-equilibrium conditions. Underlying microscopic processes and some specific properties such as nucleation and growth of the new intermetallic phase are revealed, while well-established experimental characteristics are observed. Depending on the stoichiometry and initial temperature, several types of nucleation and growth are observed: grain formed at the solid-liquid interfaces or crystallization directly from the melt.

CB-10.1:IL04  Influence of Mechanical Activation on Microstructure, Reactivity and Kinetic Parameters of SHS-mixtures
A.S. ROGACHEV, Merzhanov Institute of Structural Macrokinetics and Materials Science (ISMAN), Chernogolovka Moscow region, Russia

Mechanical activation of reactive powder mixtures, caused by high-energy ball milling (HEBM), is an intriguing factor that alter reaction properties of SHS-green mixtures. It is commonly agreed that HEBM results in decreasing of reaction onset temperature (self-ignition), however, data about reaction wave propagation velocities are contradictory. In this work, we consider experimental data of different researchers concerning influence of HEBM on the microstructure, kinetic parameters of the reaction (activation energy, onset temperature), and reaction routes of the SHS-processes. Major theoretical explanations of the observed phenomena are critically overviewed, including “pumping” of energy, increasing contact surface area, cleaning of the contact boundaries, etc. A conclusion is made that formation of nano-sized precursors of the reactive products during intense sliding and shear deformation of the reactants causes abnormal reactivity of the mechanically activated SHS mixtures. Prospective of using HEBM for producing ceramic products and materials by SHS are presented.

Session CB-10.2 - SHS of Powders from the Micro- to Nano-scale. Consolidation of the SHS-powders

CB-10.2:IL01  Ultra-refractory Ceramics by Combination of SHS and SPS: Recent Advances
R. ORRU', G. TALLARITA, R. LICHERI, G. CAO, Dipartimento di Ingegneria Meccanica, Chimica e dei Materiali, Università degli Studi di Cagliari, Cagliari, Italy

Ultra-High Temperature Ceramics (UHTCs) based on transition metal borides and carbides are very attractive materials in several application areas (aerospace, nuclear, solar energy fields, etc.). Such interest can be readily associated to their peculiar chemico-physical and mechanical properties, like melting point > 3000 °C, high hardness, chemical inertness, good electrical and thermal conductivity, neutron and selective solar energy absorption capabilities, etc. Nonetheless, UHTC powders obtained via standard synthesis routes display low sintering ability, so that their consolidation by conventional hot-pressing requires temperature levels above 2000°C, unless certain sintering aids are introduced in the mixture. In contrast, it is generally found that relatively milder processing conditions are needed when the Spark Plasma Sintering (SPS) technique is used to consolidate UHTC powders obtained by Self-propagating High-temperature Synthesis (SHS). A wide variety of monolithic, binary and ternary composites, as well as solid solution phases have been successfully produced using such two-stage processing method. The obtained products display suitable thermo-mechanical and optical properties in view of their potential application in the aerospace and the solar energy fields.

CB-10.2:L02  Design, Combustion Synthesis and Consolidation of the Borides in Zr-Ta-B System
V.V. KURBATKINA, E.I. PATCERA, E.A. LEVASHOV, National University of Science and Technology “MISIS”, Moscow, Russia

Macrokinetics of the combustion synthesis in the Ta-Zr-C mixtures has been studied. Peculiarity of the combustion in Zr-Ta-B system lies in the spin regime, which contributes the gas-phase mechanism to the wave propagation. The mechanism of chemical transformation and final products structure formation were proposed. The formation of tantalum and zirconium borides starts in preheating zone at the temperature below the melting point of zirconium. In combustion zone, after achievement of zirconium and boron melting points, primary ZrB2 crystals were appeared from the melt. TaB2 and ZrB2 do not melt in the combustion zone. The final structure of the (Zr,Ta)B2 forms in post combustion zone due to the interphase diffusion processes. SHS powder was used for consolidation and the dense UHTCs using hot pressing and SPS were obtained. Mechanical properties, thermal conductivity and oxidation resistance were measured.
This work was carried out in the framework of state assignment No.11.1207.2017 ПЧ

CB-10.2:L03  NiO and WO3 Coreduction by Combined Reducers Mg/C and Preparation of W-Ni Alloy
M.K. ZAKARYAN1, 2, S.V. AYDINYAN3, S.L. KHARATYAN1, 2, 1A.B. Nalbandyan Institute of Chemical Physics NAS RA, Yerevan, Armenia; 2Yerevan State University, Yerevan, Armenia; 3Tallinn University of Technology, Tallinn, Estonia

Tungsten and its alloys have attracted considerable interest for various applications because of their specific tribological, magnetic, electrical and electro-erosion properties. Ni-W alloys successfully vie even with ceramics and graphite by virtue of high thermo-resistance. Another perspective is their application in magnetic heads, bearings, magnetic relays, electrodes etc. Ni-W alloys are usually electroplated from aqueous solutions. In this work for preparation of fine Ni-W composite materials it has been suggested to use the method of self-propagating high temperature synthesis (SHS) or combustion synthesis (CS) by using thermo-kinetic coupling approach with Mg/C combined reducers. To our knowledge, the combustion synthesis of Ni-W nanopowders has not been explored so far. Optimum compositions were found for joint and complete reduction of oxide precursors. For exploring the mechanism of the reduction process occurring in the combustion wave copper-wedge technique was used. For complete clarification of the process it was studied at non-isothermal conditions by carrying out simultaneous differential thermal (DTA) and thermogravimetric (TG) analyses. These methods allow investigating not only the final but the intermediate products too, by suing X-ray diffraction analysis.

CB-10.2:L04  Mechanically Activated SHS in Ta-Si-C System
S. VOROTILO, E.A. LEVASHOV, National University of Science and Technology "MISiS", Moscow, Russia

Ceramic composites based on tantalum silicides have a high oxidation resistance up to 1600 °C and they are prospective for aerospace, automotive and energy-generating industries. To increase the mechanical properties, SiC additions are used. Adiabatic temperatures of combustion for this system are low (1589 - 1690 K) and mechanical activation was useful to realize to layer-by-layer mode.  Thermodynamic calculations, investigation of stopped combustion front and time-resolved XRD  the mechanism of combustion and structure formation in Ta-Si-C system.
Ceramic having hierarchical structure with the size of primary grains of TaSi2 and SiC 1-3 µm and the secondary grains 30-50 nm was obtained. Hot pressed TaSi2-SiC composite high is characterized by record-high hardness of 19,1 GPa and toughness till 6,7 MPa*m1/2
This work was carried out with financial support from the Russian Science Foundation in the framework of the project No. 14-19-00273-П.

CB-10.2:IL05  Contribution of SHS in Development and Production of Super-refractory Ceramic Materials
E.A. LEVASHOV, YU.S. POGOZHEV, V.V. KURBATKINA, I.V. IATSYUK, YU.YU. KAPLANSKII, S. VOROTILO, National University of Science and Technology “MISIS”, Moscow, Russia

The hybrid off-line technologies SHS + HP (hot pressing), SHS + SPS and online technologies such as reaction SPS or reaction HP were applied for synthesizing refractory carbide and boride compounds. The kinetics and the mechanism of combustion in systems Ta-Zr-C, Ta-Hf-C, Ta-Si-C, Zr-Ta-B, Hf-Ta-B, Zr-B-Si, Zr-B-Si-C have been studied. It was shown that mechanical activation of initial mixtures play a keynote role in SHS of the refractory compounds. Samples (Ta,Hf)C with density till 98%, hardness of 24–27 GPa, Young’s modulus of 423–484 GPa, and elastic recovery of 44–46 have been produced. Hot pressed combust products exhibits superior hardness, fracture toughness, heat resistance due to hierarchical  structure.  
The work was financially supported by the FTP "Research and development in priority areas for the development of the scientific and technological complex of Russia for 2014-2020", Agreement on granting subsidy No. 14.578.21.0227 (Unique identifier of the project RFMEFI57817X0227).

CB-10.2:L06  Selective Laser Melting of Ti-B-Si System produced by SHS
S.V. AYDINYAN, L. LIU, I. HUSSAINOVA, Tallinn University of Technology, Tallinn, Estonia

Silicon nitride is known as one of the best structural ceramics due to its excellent mechanical and chemical properties. Many potential applications are, however, still limited by lack of toughness and reliability at elevated temperatures, which can be resolved by the incorporation of TiB2 reinforcement. The aim of the present study is to improve the sinterability of the components, as well as to expand the application fields of composite through synthesis of TiB2/Si3N4 using advanced additive manufacturing technology, particularly - selective laser melting (SLM). Sintering of ceramics by SLM is limited by the low absorption of laser beam energy and poor thermal shock resistance. These challenges can be overcome with preliminary design of 3D shape via SLM of a combustion-synthesized TiB2/Si powder followed by a process of nitridation. As a result, a 3D object can be built in complex 3D geometry, including completely dense materials and porous structures. The work is focused onto development of the technology to fabricate TiB2/Si3N4 using a method not requiring further machining. In addition, the synthesized material can exhibit enhanced mechanical properties due to (i) combination of properties of both ceramics, and (ii) additional self-functionalization.

CB-10.2:L07  MoSi2 based Composites Preparation by Combustion Synthesis with Subsequent Selective Laser Sintering
T. MINASYAN1, M.A. RODRIGUEZ2, LE LIU1, M. AGHAYAN1, L. KOLLO1, I. HUSSAINOVA1, 3, 4, 1Tallinn University of Technology, Tallinn, Estonia; 2Instituto de Ceramica y Vidrio (ICV-CSIC), Madrid, Spain; 3ITMO University, St. Petersburg, Russia; 4University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, Urbana, IL, USA

The development of advanced ceramics for high-performance applications is one of the most challenging tasks of modern engineering. The wide industrial use of advanced ceramic materials depends on the technological availability to fabricate near-net-shaped three-dimensional ceramic-based parts with the required geometry. 3D printing by selective laser sintering is well suited to generate complex-shaped ceramic matrices directly from powder materials. In this regard, it is promising to develop MoSi2 based ceramic-matrix composites with SiC, Si3N4 to improve high temperature creep strength and room temperature toughness. However, for direct synthesis of MoSi2/Si3N4(SiC), the SLS technique was disabled because of low sintered density and crack formation due to thermal stresses. Here we report an approach for the preparation of MoSi2 based composites by SLS via (i) self propagating high-temperature synthesis of MoSi2/Si powders, (ii) shaping by SLS and (iii) functionalization in the nitrogen or carbon containing gas atmosphere. The effect of process parameters to the strength and surface finish of sintered parts was investigated and a set of parameters has been optimized. It was shown that auxiliary fiber reinforcing occurs enhancing toughness and strength of net-shaped composites.
Session CB-10.3 - SHS of Bulk Materials

CB-10.3:IL01  Hot Shock Welding Applications for Layered Composite Consisting of Non-oxide Ceramics and Metal
RYUICHI TOMOSHIGE, KANAKO SONODA, TAKUMI NAKAMURA, TAKUMA TANAKA, Sojo University, Japan; Seiichiro Ii, National Institute for Materials Science, Japan; Yasuhiro Morizono, National Institute of Technology, Kurume College, Japan

Demonstrative experiments have been performed to get multilayered joints consisting of titanium diboride, titanium nickel and steel by a novel hot explosive welding technique. The technique is a combined combustion synthesis, which is a spontaneous exothermic reaction with very high temperature, with explosive shock welding. TiNi intermetallic layer was inserted between ceramics and steel layers for relaxation of thermal stress at elevated temperatures. Obtained joints showed cohesive and strong bonded interfaces. Successful joining depended upon the conditions of time window from initiation of combustion synthesis to blasting of explosives, the kinds of materials to buffer the reflective shock waves, and a quantity of explosives. After rapid quenching test of the specimen from a furnace kept at 500 °C to water at ambient temperature, no exfoliation was observed at the interfaces. From these results, it was revealed that TiNi with pseudo elastic effect was effective to relax the thermal stress generated at the interface between different materials.

CB-10.3:IL02  Recent Progress in SHS Ceramics
A.S. MUKASYAN, Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN, USA, and National University of Science and Technology MISiS, Moscow, Russia

Combustion synthesis (CS) is an attractive technique to fabricate a wide variety of advanced compounds in forms of powders, bulk materials and near-net shape articles [1]. The characteristic feature of the CS approach is the self-sustained propagation of a chemical reaction through the heterogeneous mixture of precursors. The temperature in the combustion front can reach quite high values (2000-4000 K) and the velocity of its propagation typically in the range 0.1-10 cm/s. Ceramics were among the first materials produced by SC [2]. They include boron and silicon nitrides (BN, Si3N3), boron and silicon carbides (B4C, SiC). The goal of this review is summarized and critically discussed the results direct CS of the ceramics, including synthesis conditions, mechanism of microstructure formation, as well as material’s properties. Special attention is paid to the last achievements in the field, including analysis of such novel directions as combustion synthesis + spark plasma sintering; combustion synthesis + high-energy ball milling; CS of nanostructured ceramics and composites. It is also an attempt to prove that combustion-based technologies provide an efficient route for productions of such variety of ceramics.
[1] Rogachev AS and Mukasyan AS, (2015) Combustion for Materials Synthesis, CRC Press, Taylor & Francis, Boca Raton, London, New York; [2] Merzhanov AG, and Borovinskaya IP, Self-propagating high-temperature synthesis of refractory inorganic compounds. (1972) Dokl. Chem., 204:429. 

CB-10.3:IL03  Shedding New Light on the Microstructure of SiBOC Based Ceramics
G.D. SORARU', University of Trento, Trento, Italy
SiBOC ceramics, a sub-set the SiOC system, belong to the family of Polymer Derived Ceramics and have been proposed as high temperature structural fibers and/or chemical sensors. In this work the micro-nanostructure of SiBOCs has been studied as a model to describe the structure of SiOCs. The study has been performed, before and after HF-etching the silica nanoclusters, using several complementary techniques including SS NMR and 3D TEM. Accordingly, information on different length scales from local -around the Si and B atoms- to mid to long range have been obtained. It will be shown that SiBOC ceramic is formed a by silica-rich and a C-rich interpenetrating nanometer sized networks. In particular 3D TEM allowed sheding new light on the interface between the two nanosized networks. The information are useful to rationalize the behavior of SiOCs when used as anode for Li-ion batteries.

Session CB-10.4 - Solution Combustion Synthesis of Ceramic Nanopowders and Materials, and Applications

CB-10.4:IL02  Solution Combustion Synthesis of Nanomaterials for Various Applications
Z.A. MANSUROV, G.T. SMAGULOVA, Institute of Combustion Problems, Kazakhstan, Almaty Al-Farabi Kazakh National University, Almaty, Kazakhstan

Solution combustion synthesis of nanomaterials (SCS) is a simple and fast combustion method which is suitable for production of various nano-dimensional materials. The solution combustion method was proposed in 1988 by Patil and widespread for synthesis of nanomaterials. The article gives an analysis of the current state in this field and results of the authors. Solution combustion synthesis found application for obtaining of carbon nanotubes growth catalysts. In this work presents results of the synthesis of carbon nanotubes on catalysts based on glass-fibers for obtaining of flexible heating elements. On the surface of glass-fibers obtained of metal oxide nanoparticles (10 – 50 nm) which are catalytic centers for growth of CNT. The model of soldier with a heated jacket was made. The catalytic activity of polyoxide-based catalysts on glass cloth in the process of carbon dioxide conversion of methane was investigated. Various reducing agents, MgO-NiO-CoO-citric acid, MgO-NiO-Cr2O3-glycine; NiO-Al2O3-glycine were used. And also with separate and co-deposited components, Al2O3-NiO-CoO - carbamide and glycine, La-NiO-CoO with reducing agents: citric acid, carbamide and glycine. It was found that catalysts with nickel and cobalt oxides are the most active in the process carbon dioxide conversion. The catalyst of 0.5 wt. % Ce2O3/CaA exhibiting the best catalytic activity was prepared by the "solution combustion" method and tested in the conversion of bioethanol. Catalysts of 0.5 wt. % CeO2/CaA were prepared by the capillary impregnation method, and also by the «solution combustion» method. Investigation showed the most effective is the "solution combustion". In the conversion of bioethanol on catalyst of 0.5 wt. % CeO2/CaA, the ethylene concentration prepared by the «solution combustion» method is increased to 89 vol. %.

CB-10.4:IL03  Branding Study on SHS Technologies toward Efficient In-situ Resource Utilization Scenario

With the key features of SHS in economical and energy saving standing-points, the technology is recognized as one of typical methods useful in exergy loss minimization, which has lead to active research areas for branding the SHS technology toward less or limited supplies under extreme environments such as “space”, “underwater” and “disaster-stricken area”. In space exploration, none would be enough to develop the technology with the resources on the earth. It is expected that the resources such as metal oxides that exist on planets or satellites could be refined, and utilized as useful supplies of heat energy, where the SHS technologies can stand as hopeful ones for such requirements, i.e., in-situ resource utilizations. By making clear optimum parameters of the SHS technology under fundamental understanding about the process controls, one can simply apply and operate the SHS technology under various conditions of space environment, for example, such as low gravity and high vacuum not only for synthesizing high-temperature materials but also for super-heating chemical ovens. For establishing useful SHS branding, the present work specially focuses on the SHS technology applicable to a “live off the land” scenario.

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