Focused Session CA-11
CA-11.2:L03 SHS-derived Powders Obtained by Coupled Reactions and Thermal Dilution for Subsequent Consolidation
S. AYDINYAN, I. Hussainova, S. Kharatyan, A.B. Nalbandyan Institute of Chemical Physics, Yerevan, Armenia and Tallinn University of Technology, Tallinn, Estonia
Thermokinetic coupling and thermal dilution approaches to produce ceramic composite powders of high sintering ability by self-propagating high-temperature synthesis (SHS) have wide potential to garner the interest of industry. SHS-derived powders comprise a significant defect concentration in order to effectively enhance the mass transfer processes during the sintering, which allows for the successful consolidation of difficult-to-sinter materials at relatively low temperatures. From another hand, reactions’ coupling and thermal dilution contribute to the preparation of powders with a tuned degree of fineness and a high-homogeneity by regulating the thermal regime of combustion. From these perspectives, the design of precursors, synthesis in controlled thermal regime and the optimization of microstructure of the potential feedstock for the sintering are of key importance. The SH synthesis of the composite materials in the systems Me’O3(WO3,MoO3)-Me’’O(CuO,NiO)-Mg-C, Ti-B-Al12Mg17, Mo-Si, MoSi2-Al, TiB2-Si and their sintering peculiarities were comparatively discussed. SHS-derived powders obtained by coupled reactions and thermal dilution approach, owing to specific microstructural features, demonstrated themselves as good candidates for the subsequent consolidation.
CA-11.2:L04 Combustion Synthesis of Nanoscale Boron and Silicon Carbides
M. ZAKARYAN1, N. Amirkhanyan1, H. Kirakosyan1, A. Zurnachyan1, S. Aydinyan1, 2, 1A.B. Nalbandyan Institute of Chemical Physics, Yerevan, Armenia; 2Tallinn University of Technology, Tallinn, Estonia
Currently there is a growing interest in boron carbide (B4C) and silicon carbide (SiC), stemming largely from the express search for super-strong and lightweight hierarchical structures for next generation applications. The mechanical properties of these carbides are quite exceptional relying on morphological features and may depend on the preparation pathway. In this work, the combustion synthesis (CS) method was used for the preparation of target materials. Its distinctiveness allowed for the production of innovative structures which are difficult to fabricate by conventional methods. For the preparation of B4C, B2O3 and MgB12 were utilized as boron source. The latter served as an efficient reagent for overcoming the difficulties at CS of low caloric mixtures with a moderate driving force. For the preparation of SiC, negligible amount of tetrafluoroethylene (PTFE) was used to promote the Si+C interaction. After finding the optimum compositions of the initial mixtures, the obtained nanopowders were subjected to consolidation by spark plasma sintering (SPS). Sintered specimens exhibited high relative density and improved mechanical properties.
CA-11.2:L05 Solution Combustion Synthesis and Spark Plasma Sintering of Magnetic High Entropy Materials
H. KIRAKOSYAN1, A. Sargsyan1, S. Aydinyan1, 2, S. Kharatyan1, 1A.B. Nalbandyan Institute of Chemical Physics, Yerevan, Armenia; 2Tallinn University of Technology, Tallinn, Estonia
Studies on high entropy materials (HEMs) have been mostly conducted for high-entropy alloys (HEA) of simple crystal structures, and random studies have been done for making crystalline high-entropy oxides (HEO) with more complex crystal structures. Solution combustion synthesis (SCS) was performed aimed at preparation of the both CoCuFeMnNi high entropy alloy and (CoCuFeMnNi)3O4 high entropy oxide with a single-phase and stable nanostructure. Homogeneous solution of metals’ nitrates as oxidizing agents, alanine and glycine - as reducing agents, and ammonium nitrate as an auxiliary promoter of the exothermicity of the reaction were utilized for the SCS process. As a result, the possibility of obtaining a single-phase, pure and fine-grained CoCuFeMnNi and (CoCuFeMnNi)3O4 materials by SCS was manifested, the optimal conditions for the preparation of alloy and oxide were determined according to the composition of the precursors’ mixture, solution pH, solvent amount, preheating temperature, etc. The obtained materials exhibit enhanced magnetic properties. For the bulk samples, consolidated by spark plasma sintering technique at 1000°C, Archimedes and geometric densities, as well as Vickers microhardness and compressive strength were determined.
CA-11.2:IL06 SHS High-entropy Ceramics
R. ORRU'1, S. Barbarossa1, M. MURGIA1, R. Licheri1, S. Garroni2, G. Cao1, 1Dipartimento di Ingegneria Meccanica, Chimica e dei Materiali, Università degli Studi di Cagliari, Cagliari, Italy; 2Dipartimento di Chimica e Farmacia, Università degli Studi di Sassari, Sassari, Italy
The synthesis and consolidation of High Entropy-Ultra-High Temperature Ceramics (HE-UHTCs) based on transition metal borides is addressed in this work. This emerging class of ceramics is based on the combination, in near equimolar proportions, of at least four constituents to generate single-phase crystalline solid solutions with maximum configurational entropy, i.e. (Hf0.2Ti0.2Ta0.2Nb0.2Mo0.2)B2, (Hf0.2Ti0.2Ta0.2Zr0.2Mo0.2)B2, etc. The studies conducted so far evidenced that HE-UHTCs often exhibit superior oxidation resistance and mechanical properties, with respect to their individual constituents. Therefore, these materials have gained a significant interest for their high-temperature applications in several innovative and traditional industrial fields. Unfortunately, the obtainment of dense single phase HE-UHTCs represents quite a difficult goal. In this work, a two-steps process, consisting in the combination of the SHS technique with Spark Plasma Sintering (SPS), is successfully adopted for the preparation of various HE-UHTCs. In this regard, the use of the SHS method is found to highly promote the obtainment of the single-phase HE ceramic during the subsequent SPS stage. The introduction of different additives on SHS powder prior the SPS step is also considered.
CA-11.2:IL07 Combustion Synthesis of Metastable Ceramic Phases
A.S. MUKASYAN, University of Notre Dame, Notre Dame, IN, USA
The combustion synthesis (CS) approach allows the fabrication of a wide variety of ceramics: powders, bulk materials, coatings, and net shape articles. In this work, we focus on a specific feature of CS, i.e. ability to fabricate the metastable phases. Two specific examples are considered. The first is the shock-induced synthesis of cubic boron nitride. It is shown that exchange reactions in TiN-B and GaN-B systems can be not only initiated by the shock wave but what is more important, take place in the microsecond’s time span of high pressure (15-20GPa) presence in the reactive media, leading to the formation of c-BN phase [1,2]. The second is a single-step method for the preparation of metastable ε-Fe3N nanoparticles by the combustion of reactive gels. It is demonstrated that the exothermic decomposition of a coordination complex formed between metal nitrite and HMTA is responsible for the formation of metastable ε-Fe3N nanoparticles .
1. MT. Beason, JM. Pauls, IE. Gunduz, S. Rouvimov, KV. Manukyan, K. Matous, SF. Son, AS Mukasyan, APL, 112(17) 171903 (2018).
2. W. W. Chapman, M. Örnek, J.M. Pauls, M. Zhukovskyi, S. F. Son, A.S. Mukasyan, Scripta Materialia, 189 58-62 (2020);
3. AS. Mukasyan, S. Roslyakov, JM. Pauls, et al., Inorg. Chem., 58(9), 5583-5592 (2019).
CA-11.3:IL06 Self-propagating High-temperature Synthesis (SHS) in Joining Technologies
L.P.H. JEURGENS, B. Rheingans, L. Dörner, P. Schmutz, J. Janczak-Rusch, Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Joining Technologies and Corrosion, Dübendorf, Switzerland
This talk addresses current developments and applications of self-propagating high-temperature synthesis (SHS) reactions for joining of dissimilar materials and miniaturized components at room-temperature in air. First, the application of commercial Ni-Al nanofoils© for reactive joining of a wide variety of dissimilar materials at room temperature in air is presented, emphasizing the dominant role of the thermal properties of the base components on the reactive joining characteristics [1,2]. General guidelines for tailoring the exothermal reaction, solders and metallizations are given in order to achieve optimum reactive joining processes for different material combinations. Next, our latest research on the development of novel thermite nanocomposites for reactive SHS joining technologies is presented, which aims at the direct incorporation of the filler metal or alloy into the reactive SHS foil (or coating).
References:  B. Rheingans et al., Reactive Joining of Thermally and Mechanically Sensitive Materials, Journal of Electronic Packaging 140 (2018) 041006.  B. Rheingans et al, “Joining iwith Reactive Nano-Multilayers: Influence of Thermal Properties of Components on Joint Microstructure and Mechanical Performance”, Applied Sciences, 9 (2019) 262.