Single thermite-type combustion synthesis of Fe2VAl for thermoelectric applications from Fe, V2O5 and Al powders

Abstract

Single thermite-type combustion synthesis (STCS) for synthesizing Heusler alloy Fe2VAl from Fe, V2O5, and Al powders for thermoelectric applications was proposed and investigated, in which the microstructure and the thermoelectric properties of the product were mainly examined. Macroscopically, STCS was successfully carried out to produce metallic product of Fe2VAl in lower part and alumina as slag in upper part. According to SEM observation and FE-EPMA-analyzed, elemental mapping images, the product contained dispersed inclusions of spherical Al2O3 with 0.4 mol% and angulated AlN with 1.0 mol%. In comparison to the reported data on Fe2VAl, the thermal conductivity at room temperature became about half. It could be because of increased phonon scattering due to dispersed AlN&Al2O3 and non-stoichiometry of the product; Fe2.06V1.01Al0.93. As a result, the maximum values for the product were 99.6 mu W m K-1 (2) in power factor and 2.19 x 10 (3) at 309 K in dimensionless figure of merit

Preparation of Eco-Friendly Fe₂VAl-Based Thermoelectric Materials Using Cast Iron Scrap Chips as a Source Material

“…using cast-iron scrap chips exhibits a rather semiconductorlike dependence on temperature. Furthermore, the electrical conductivity values of p-type 2C.I.VAl prepared using cast-iron scrap chips were approximately 30% 13,24,25) higher than those previously reported. 22,23) The temperature dependence of the electrical conductivity could be attributed to carrier mobility, which decreased with the temperature increase, since the acceptors were exhausted due to the movement of the carrier by lattice vibration.…”

“…Additionally, the PF values of undoped 2C.I.VAl prepared using cast-iron scrap chips showed an approximate two-fold improvement (967 µWm ¹1 K ¹2 at 200°C, the highest PF value at a certain temperature) compared to those previously reported. 24,25) It is interesting to note that the performance of undoped and p-type 2C.I.VAl made from cast-iron scrap chips is comparable to that of Fe 2 VAl prepared using pure Fe, especially at temperatures higher than 200°C, which has been reported in the literature. Unfortunately, in this study, the n-type 2C.I.VAl specimen made from cast-iron scrap chips could not be fabricated due to the effect of impurities in the cast-iron scrap chips, such as O, Si, Mn and C.…”

“…The reduction of the thermal conductivity of the 2C.I.VAl specimens prepared using castiron scrap chips is believed to be related to an increase in phonon scattering by the increase in grain boundary regions due to the dispersal of impurity phases and the small difference in stoichiometry in the composition. 25) Thus, the thermal conductivity values of undoped and p-type 2C.I. VAl prepared using cast-iron scrap chips were about 10% smaller than those previously reported.…”

Ultrafast Iron-Making Method: Carbon Combustion Synthesis from Carbon-Infiltrated Goethite Ore

“…It is also possible to make iron via the attractive “combustion synthesis (CS)” method for carbon-infiltrated goethite ores with high carbon content. CS utilizes strong exothermic reactions to self-propagate the combustion wave to complete the reaction spontaneously; several different types of materials have been prepared by this method. − For carbon-infiltrated goethite ore, the CS reaction consists of carbon combustion and the reduction of iron oxides. When the total reaction is strongly exothermic, the CS reaction will be self-propagating and rapidly reach completion.…”

Salt-assisted combustion synthesis of Ca-α-SiAlON:Eu2+ phosphors

“…This method is a proven effective energy-and time-saving process for producing various industrial materials, owing to advantages such as high-purity products, low energy investment, and short processing time. Therefore, the SHS process has been applied to the powder production of various kinds of materials including metallic alloys [20,21], and ceramics [22,23], etc.…”