Electrothermal Explosion Research Articles

Synthesis of double carbide (Ti,Cr)C with a different Cr content produced by electro thermal explosion

In this paper we report the preparation of double carbide (Ti,Cr)C with a chromium content of 10 ÷ 30 at% by electrothermal explosive synthesis (ETE). This method allows synthesis to be carried out at high temperature with minimal holding time. The ETE method is favourable for the formation of dense carbide ceramics. The synthesized samples were characterized by X-ray diffraction and scanning electron microscopy. It was found experimentally that the unit cell parameter of the double carbide decreases linearly with increasing chromium content. The DFT calculations also confirmed the dependence of the unit cell parameter (Ti,Cr)C on the chromium content according to Vegard's law and show changes in the cell shape and distance between Cr–Cr layers with increasing chromium content. The pDOS diagram shows that an increase in chromium content leads to an excess of d∗ electrons on the π∗ orbitals, which has a destabilizing effect on the double carbide structure.Crystal Orbital Hamiltonian (COHP) analysis of the electronic structure of the double carbide, partitioning the energy of the band structure into bonding, non-bonding and anti-bonding energy regions, showed the influence of chromium content on its stability.

Rapidly Synthesizing Cu2Sb Phase of Tetragonal Structure by Electrothermal Explosion

Rapidly Synthesizing Cu2Sb Phase of Tetragonal Structure by Electrothermal Explosion

Simulation of an Electrothermal Explosion of a Gas-Free System. Effect of Conductive Heat Exchange and Joule Heating Power

Simulation of an Electrothermal Explosion of a Gas-Free System. Effect of Conductive Heat Exchange and Joule Heating Power

Tungsten Carbide by Electrothermal Explosion under Pressure: Accompanying Phase Transformations

Tungsten Carbide by Electrothermal Explosion under Pressure: Accompanying Phase Transformations

The influence of mechanical activation on the structure and phase formation of an electro-thermal explosion in the Ti–Zr–C system

The TixZr1-xC solid solutions were synthesized by electro-thermal explosion under pressure in the (Ti + Zr + C) blends mechanically activated in hexane (MA-ETE). The effect of mechanical activation (MA) duration on reaction blend characteristics, ETE parameters, phase composition, and microstructure formation in solid solutions was investigated. At MA, the Ti + Zr blend deforms metal crystal lattices for 20 min, complete amorphization occurs for 40 min, and the carbide grains form a cubic structure for 90 min. The single-phase Zr0.50Ti0.50C solid solution with a grain size of 3–5 μm and a submicron composite with a grain size of 0.1–0.2 μm containing the Ti0.86Zr0.14C and Zr0.74Ti0.26C solid solutions were synthesized in a one-stage process for the first time without any additional thermotreatment. The influence of mechanical activation on diffusional mass transfer of reactants, structure, and phase formation is discussed.

Синтез ультратугоплавкого композита Ta4HfC5 — HfB2 методом электротеплового взрыва под давлением

An ultra-high-temperature ceramic Ta4HfC5 — HfB2 with a submicron structure and a relative density of 0.9 was synthesized by electro-thermal explosion (ETE) under pressure. A mixture of Ta, Hf, C and B powders prepared by mechanical activation (HEBM) in a planetary ball mill was used for synthesis. The heat resistance of composites was searched at heating in the flame of an oxygen-acetylene burner.

Synthesis of TiС–ZrC Composite with Submicron Structure by Electro-Thermal Explosion under Pressure

Synthesis of TiС–ZrC Composite with Submicron Structure by Electro-Thermal Explosion under Pressure

Activation energy of phase transformations at high-temperature synthesis of tungsten carbide by electrothermal explosion under pressure

The effect of activation energy on phase transformations (transitions) in the W–C system during the synthesis induced by an external heat source was investigated by electrothermal explosion (ETE) under pressure. The ETE technology combines self-propagating high-temperature synthesis (SHS) with additional sample heating by Joule heat – electric current passing through the synthesized mixture, and it makes it possible to determine the chemical reaction rate that is highly susceptible to external impacts such as pressure, concentration, sample shape, any film present on combustion products, etc. The chemical reaction rate, i.e. external source current, may be controlled by changing the activation energy. The study was conducted in the following conditions: temperature Т = 293÷3700 K; carbon concentration of 49.8–50.2 at.%; quasi-static compression at P = 96 MPa; external source voltage and current density V = 10 V, I = 20 МА/m2, respectively; samples 8 mm in diameter weighing 6 g. The Т–τ thermogram of the W–C system was used to determine the following parameters: four stages of the synthesis process, temperatures of special points of phase transformations, temperature boundaries of phases and process activation energy. Thermograms of intermediate states are presented as isothermal plateaus of phase transformations. The analysis of experimental results and the physical representation of the process make it possible to assert that temperature plateau parameters are the effective value of activation energy for synthesis mode maintenance. Each of the 4 W–C mixture synthesis stages is described. Pre-explosion stage I – sample heating in the temperature range of Т = 293÷563К, endothermic reaction, effective activation energy for synthesis mode maintenance Q = 2.96 kJ, and taking into account 1-mole mass Еа = 111.6 kJ/mol. Low-temperature (563–1190 К) stage II – ignition, Q = 5.46 kJ, Еа = 109.2 kJ/mol. High-temperature stage (III) in the range of Т = 1190÷2695К, order–disorder transformation, Q = 14.25 kJ, Еа = 424 kJ/mol. Finally, Stage IV occurs in the range of Т = 2695÷3695К, Q = 14.31 kJ, Еа = 143.2 kJ/mol. It was shown that the limiting stage with the highest activation energy is the melting process.

Structural and Magnetic Properties of MgCu2 Laves Phase Alloys Synthesized by Electrothermal Explosion

Structural and Magnetic Properties of MgCu2 Laves Phase Alloys Synthesized by Electrothermal Explosion

Study of the effect of continuous loading and compaction on the electrical resistance of powder materials

The electrical conductivity of powder media depends on the composition, impurities, oxide films, morphology and the nature of the contact surface. We present the results of studying the electrical resistance of powder materials and their compounds under continuous loading by the four-contact method. The electrical resistance is determined using a special experimental cell. Industrial powders Al (ASD-1), Ti (PTK), Hf (GFM-1), soot and their mixtures, as well as TaC and HfC powders obtained by self-propagating high-temperature synthesis were studied. It is shown that an increase in the mechanical pressure up to 80 MPa leads to a decrease in the electrical resistance of the materials under study. The morphology of the particles (spherical or fragmentary shape), their dispersion affects the quality of the contact surface and, accordingly, the magnitude of the electrical resistance. Moreover, the electrical resistance of the material depends on the degree of cleaning of the particle surface from oxide films. The proposed method in combination with other analytical methods used for studying powder media allows us to reveal the regularities of this relationship, characteristic of all morphological features, composition and electrophysical properties of powders of various compositions under loading conditions. The results obtained can be used to select the optimal characteristics of consolidation by electric current depending on the initial pressure, as well as in case of high-voltage electric pulse consolidation of powder materials by spark plasma sintering and electrothermal explosion methods.

Ta4HfC5 Ceramic by Electro-Thermal Explosion under Pressure: Thermal and Electrical Parameters of the Process

Ta4HfC5 Ceramic by Electro-Thermal Explosion under Pressure: Thermal and Electrical Parameters of the Process

Exothermic synthesis of binary solid solutions based on hafnium and zirconium carbides

The paper presents the results of an experimental study into the possibility of producing ultra-high temperature ceramics constituting solid solutions of HfC and ZrC carbides by the single-stage electro-thermal explosion (ETE) method under pressure. Adiabatic flame temperature and phase composition of the equilibrium final product were calculated based on thermodynamic data. It was shown that when the ZrC content in the final product is less than 20 wt.%, adiabatic flame temperature reaches 3800– 3900 K, and the combustion product contains hafnium and zirconium carbides. The effect of mechanical activation modes in an AGO-2 planetary centrifugal mill used for a reaction mixture containing Hf, Zr and C powders on its properties, phase composition formation and the microstructure of carbide solid solutions was studied. It was shown that high-energy mixing in hexane leads to the destruction of the crystal structure of Hf and Zr particles and the formation of amorphous composite particles. The synthesized samples of ultra-high temperature ceramics were studied by X-ray phase and microstructure analyzes. It was shown that exothermic synthesis leads to the formation of single-phase solid solutions of HfC and ZrC carbides with the average particle size of 0.2–1.5 μm. The residual porosity of the binary carbides obtained is 10–12 %. It was found that, despite the high temperature of sample heating during ETE under pressure, the particle size of the resulting solid solutions is significantly (by an order of magnitude) smaller than the particle size of similar complex carbides (20–50 μm) obtained by other methods (SPS and hot pressing). This is associated with the rapidity of the exothermic interaction of the reagents (10–50 ms) during ETE.

Synthesis of Ta4HfC5 Ceramics with a Submicron Structure by Electro-Thermal Explosion under Pressure

Synthesis of Ta4HfC5 Ceramics with a Submicron Structure by Electro-Thermal Explosion under Pressure

Effect of Carbon on the Electrical Resistivity of Ni–Al Intermetallic Alloy Synthesized by an Electrothermal Explosion under Pressure

Effect of Carbon on the Electrical Resistivity of Ni–Al Intermetallic Alloy Synthesized by an Electrothermal Explosion under Pressure

Modeling of an Electrothermal Explosion with Account for Changes in the Thermoelectric Characteristics of a Gasless System

Modeling of an Electrothermal Explosion with Account for Changes in the Thermoelectric Characteristics of a Gasless System

Synthesis of the Ni–Al–C Composite with Multilayer Carbon Nanostructures by an Electrothermal Explosion under Pressure

A composite material based on the Ni–Al–C system is synthesized by the method of an electrothermal explosion at a pressure of 96 MPa. During the electrothermal explosion in a reactive powder medium (Ni + Al + C), a Ni- and Al-based melt is formed, in which carbon dissolves. In the process of crystallization of the final product, carbon, due to its low solubility in NiAl, is located on the surface of intermetallic grains of NiAl in the form of multilayer graphite nanofilms 50–80 nm thick and fills the intergranular space. The microhardness of the synthesized material is 3084 MPa.

Ultra-High-Temperature Composite Hf4ZrC5 Produced by Electrothermal Explosion under Pressure

Ultra-High-Temperature Composite Hf4ZrC5 Produced by Electrothermal Explosion under Pressure

Влияние углерода на удельное электросопротивление интерметаллидного сплава системы Ni – Al, синтезированного методом электротеплового взрыва под давлением

In this paper, we studied the effect of carbon (3 wt. %) on the electrical resistivity of materials based on Ni − Al and Ni – Al − C synthesized by the electrothermal explosion in the temperature range 300 – 1300 K in a vacuum of 2·10–3 Pa. During an electrothermal explosion, a Ni – Al-based melt is formed in a powder reactive medium, in which carbon is dissolved. It is shown that during the crystallization of the final product, due to its low solubility in NiAl, carbon is located on the surface of intermetallic NiAl grains in the form of multilayer graphite nanofilms 50 – 80 nm thick, filling the intergranular space. It is shown that the synthesized materials have a metallic conductivity, and the electrical resistivity in the measured temperature range of 300 – 1300 K increases monotonically for the Ni – Al-based alloy from 16 to 40 mW·cm and for the carbon-containing Ni – Al – C material from 22 to 60 mW·cm. The temperature coefficient of resistance (TCS) also increases from 1.45·10–3 K–1 for NiAl to 1.77·10–3 K–1 for NiAl/C. The slope of the resistivity curves in the studied temperature range of 300 – 1300 K remains constant and is well described by a linear function.

Cu–Sb Solder Alloy by Combustion Synthesis: Structural Characterization and Magnetic Properties

Lead-free Cu–Sb solder alloys of nominal composition Cu–20 at % Sb were fabricated by SHS and electrothermal explosion (ETE) and characterized by XRD, SEM, and vibrating sample magnetometry (VSM). Combustion products were found to represent a mixture of δ-Cu11Sb3, β-Cu3Sb, and Cu. The ETE and SHS methods were recommended as a facile route to synthesis of Cu–Sb intermetallics.

Synthesis of a Ni-Al-C Composite with Multilayer Carbon Nanostructures by an Electrothermal Explosion under Pressure

Synthesis of a Ni-Al-C Composite with Multilayer Carbon Nanostructures by an Electrothermal Explosion under Pressure