Reactive synthesis of porous FeSi intermetallic compound

Abstract

Porous FeSi intermetallic compound was prepared by reactive synthesis of elemental powders. The evolutions of phase composition, microstructure and pore structure of Fe–Si compacts during the synthesis procedure were investigated, as well as the corrosion resistivity of the porous material against sulfuric acid solution. The results show that the major phases are generated in the order of α-Fe, Fe3Si, η-Fe5Si3 and ε-FeSi during the sintering process. The skeletons of Fe5Si3 and FeSi phases are formed successively, resulting in a large number of connected pores in the compact. The final synthesized porous compound has the FeSi phase purity of 95.4 wt%. The open porosity, maximum pore size and gas permeability of porous FeSi are 53.8%, 14.1 μm and 92.20 m3 m−2 kPa−1·h−1, respectively. The radial dimension variation ratio, pore size and permeability show the linear change regulation with the sintering temperature with the change rate constants being 1.51 × 10−2%·°C−1, 5.3 × 10−2 μm·°C−1, 1.45 × 10−1 m3·m−2·kPa−1·h−1·°C−1, respectively. The pore size and permeability show the linear change law with the initial Fe powder size with the change rate constants being 5.4 × 10−2 μm·μm−1 and 3.05 × 10−1 m3·m−2·kPa−1·h−1·μm−1, respectively. The corrosion kinetics of the synthesized porous FeSi compound in 160 g·L−1 sulfuric acid solution shows a characteristic of two stages with the average corrosion rates being 2.11 × 10−3%·h−1 and 1.18 × 10−4%·h−1, respectively, in which porous FeSi shows good pore structure and microstructure stability.