Papers by Keyword: Self-Propagating High-Temperature Synthesis (SHS)

Abstract: The aim of this study was an investigation of the influence of technological parameters of the process of self-propagating high-temperature synthesis (SHS) on the formation of nanoparticles of titanium carbide from a mixture of powders of titanium and carbon in molten aluminum and on the properties of the obtained composite Al-10 wt. %TiC. The results show that the application of such techniques as the use of titanium powder of coarse fraction, the integrated flux of composition 30-35% NaCI, 52-57% KCI, 10-13% Na₂SiF₆ and adding aluminum powder to the initial charge can reduce the size of most of the synthesized particles of the carbide phase TiC to ultrafine sizes. At the same time, the replacement of 20% titanium metal powder in the charge with the titanium-containing salt Na₂TiF₆ makes it possible to synthesize nanoparticles of titanium carbide with size less than 0.1 μm in the composite Al-10%TiC. The produced SHS composite Al-10%TiC is characterized by a high level of physico-mechanical and tribological properties with good corrosion resistance. Reinforcement with ultrafine and nanosized particles of TiC enhances the strength characteristics of the composite Al-10%TiC by 2.5-2.9 times in comparison with pure aluminum, while the reinforcement with microsized particles of TiC (2-4 μm) only by 1.5-1.7 times; resistance to corrosion increases by 4-5 times.

Abstract: Structural properties of porous TiNi-based materials produced by SHS method and sintering have been investigated. The material having different pore wall surface topography, porosity and pore size distribution was shown to be produced depending on the powder metallurgy method for porous TiNi-based alloy. All the materials having porosity of 55-70%, mean pore size 90-150 μm, as well as normal pore size distribution are most preferable. Ultimate strength and breaking point were determined to depend on porosity, pore size distribution, pore intersections and phase chemical composition of the material. Strength properties of the sintered alloy are twice as much compared to the SHS-produced ones due to homogeneity of its macrostructure, low chemical heterogeneity and TiNi₃ precipitations strengthening the TiNi matrix.

Abstract: It has been calculated that the introduction of nickel-aluminum additives leads to an increase in the heat effect and allows for the development of materials with the desired phase composition. A comparative analysis of the results of design and instrumentation experiments has shown a satisfactory agreement which allows us to speak about the correctness of the developed numerical model as well as the possibility of selecting optimal initial values ​​of the heat energy source as a factor which allows for controlling the reaction of self-propagating high-temperature synthesis and eventually the phase composition of the final product.

Abstract: The article describes the development of a model for controlling self-propagating high-temperature synthesis. The model is based on computation and theoretical analysis of temperature field dynamics for a propagating combustion wave. The work proves the applicability of this model for the synthesis of boron-containing materials implemented at nuclear power plants. The discrepancy of the model amounts to 20 - 25%, and the satisfactory agreement between the calculation and experimental data testifies the validity of the numerical method and allows calculating any two-component SHS systems.

Abstract: This paper is devoted to the actual topic of increasing wear resistance of working parts soil cultivating machines. Established that the introduction in welding layer carbides of metal via powder electrodes of SHS materials increases the wear resistance of the deposited layer, which will significantly increase the service life of the working bodies of tillage equipment.

Abstract: FSUE Radon deals with collection, transportation, treatment, conditioning, and interim storage and final disposal of conditioned low-and intermediate-level radioactive wastes (LILW) as well as radiation monitoring, decontamination and environmental remediation of Moscow and Moscow area. Liquid LILW with high salinity is subject to vitrification at the Radon full scale vitrification plant using a cold crucible inductive melting (CCIM) at temperatures of 1150-1200 °C. The bench-scale cold crucible based unit is used for research works and feasibility study on new promising ceramic and glass-ceramic waste forms based on incinerator slag and ash. Solid and liquid organic LILWs are treated in a plasma shaft furnace with liquid slagging at temperatures of 1400-1500 °C. Molten slag is solidified in containers yielding a glass-crystalline material with high chemical durability and strong mechanical integrity suitable for safe long-term storage and disposal in both interim repositories and underground sites. One of the promising methods for LILW treatment is application of thermochemical reactions – self-propagating high-temperature synthesis (SHS) with high energy release which is considered as a potential technology for treatment of spent ion-exchange resins, silts and grounds and some specific wastes.

Abstract: The consolidation of refractory ceramic powders at relatively milder conditions with respect to conventional methods represents an important target to achieve. 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 of the ceramic powders by SHS 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.

Abstract: Controlling the formation of condensed products during combustion of heterogeneous systems is one of the key problems in structural macrokinetics [1]. Modeling of this process at the macroscopic level should describe the change of macrostructural variables: porosity, size and shape of specimens. This paper provides the results of research in macrostructural transformations obtained using the model of a viscous compressible fluid [2].

Abstract: The technique of synthesis of Ni+16mass%Al open cell type porous intermetallic materials that can be treated in inert or regenerative atmospheres at temperature up to 1600 K without changing their functional properties has been developed. Materials with Ni₃Al + NiAl phase composition, porosity of 42 %, sizes of transport pores up to 10 μm, sizes of core elements equal to 40 μm, and specific surface of open porosity of 90 mm^-1 have been produced. It is demonstrated that after complete oxidation of the given materials, the NiO-NiAl₂O₄ composite is formed, whose reduction in hydrogen flux results in the formation of Ni-NiAl₂O₄ cermet; the shape of the porous material in the course of oxidation/reduction does not change.

Abstract: An investigation is performed of the filtrational combustion of gaseous hydrocarbons inside a spherical nozzle manufactured from porous Ni-Al material. The porous material is produced using the process of self-propagating high temperature synthesis, which allows an article of the desired configuration, chemical composition and porosity to be fabricated within a single technological stage. A combustion mode is demonstrated, wherein the combustion wave is localized inside the wall of the porous nozzle. Under this condition, up to 70 % of the total heat value of the fuel mixture is converted into IR flux radiated from the surface of the nozzle, with the maximum lying within the wavelength region 3–11 μm. A number of promising applications of new porous materials for designing new energy conversion devices are shown.