The formation of nanostructured materials by consolidating ultrafine amorphous alloy particles prepared by chemical reduction

Abstract

Amorphous (Fe, Co, Ni)-B binary and ternary alloy particles of diameter 20–50 nm can be prepared by chemical reduction using KBH 4 as a reduction agent. In the FeB binary system, structure and chemical concentration of particles depend on the mixing molar ration of KBH 4 to Fe 2+ ions M R. The structure is amorphous for M R⩾ 10.0 and with decreasing M R a crystalline α-phase is precipitated in an amorphous matrix. The B concentration in the amorphous phase is about 33 at.% for M R⩾ 9.0 and about 25 at.% for M R ⪕ 8.0 . The amorphous alloy particles in (Fe, Ni, Co)-B binary and ternary systems are consolidated to a cylindrical shape at various temperatures. The structure of hot-pressed compacts is amorphous for pressing temperatures below the crystallization temperature. T x. These crystalline phases are confirmed to have a nanometer-scale structure. It is concluded that these particles should form a fully dense amorphous bulk or a crystalline bulk consisting of nanometer-scale mixed phase.