Quick preparation and thermal transport properties of nanostructured β-FeSi 2 bulk material

This paper reports that the nanostructured β-FeSi2 bulk materials are prepared by a new synthesis process by combining melt spinning (MS) and subsequent spark plasma sintering (SPS). It investigates the influence of linear speed of the rolling copper wheel, injection pressure and SPS regime on microstructure and phase composition of the rapidly solidified ribbons after MS and bulk production respectively, and discusses the effects of the microstructure on thermal transport properties. There are two crystalline phases (α-Fe2Si5 and ∊-FeSi) in the rapidly solidified ribbons; the crystal grains become smaller when the cooling rate increases (the 20 nm minimum crystal of e-FeSi is obtained). Having been sintered for 1 min above 1123 K and annealed for 5min at 923 K, the single-phase nanostructured β-FeSi2 bulk materials with 200–500 nm grain size and 98% relative density are obtained. The microstructure of β-FeSi2 has great effect on thermal transport properties. With decreasing sintering temperature, the grain size decreases, the thermal conductivity of β-FeSi2 is reduced remarkably. The thermal conductivity of β-FeSi2 decreases notably (reduced 72% at room temperature) in comparison with the β-FeSi2 prepared by traditional casting method.