The influence of nano-scale silicon nitride additions on the physical and magnetic properties of iron sheathed magnesium boride wires

The enhancement of flux line pinning in magnesium boride wires is a critical issue for their future applications in devices and machines. It is well known that small size dopants can significantly influence the current densities of these materials. Here, the influence of nanometric (< 30nm) silicon nitride on physical properties and cur-rent density is presented. The iron-sheathed powder in tube wires were prepared using pure magnesium and boron powders with silicon nitride additions. The wires were rolled flat and treated at up to 900 degrees C in flowing argon. SEM and XRD were used to identify phases 2 and microstructures. Magnetization critical currents, up to several 100 of thousands A/cm(2), at various temperatures and fields (5K-20K and up to 3 tesla) show that there are competing mechanisms from chemical and flux pinning effects.