Synthesis of Mg–Zn–Ca metallic glasses by gas-atomization and their excellent capability in degrading azo dyes

•Mg–Zn–Ca metallic glass powders were synthesized by gas-atomization.•The phase structure of powders was affected by the composition and the size.•Degradation capacity of powders is determined by phase constituents and Mg content.•Nano-whiskers are distributed loosely on the reacted surface of the glassy powder. Mg–Zn–Ca powders of Mg63+xZn32−xCa5 (x=0, 3, 7 and 10) with the diameter from 2μm to 180μm were synthesized by gas-atomization. The relationship among powder morphology, the composition, glass forming ability, thermal stability, corrosion resistance and the capacity in degrading azo dyes for these powders was investigated. It is shown that fully glass powders with the particle diameter