Synthesis of a Mg-based alloy with a hydrogen-storage capacity of over 7 wt% by adding a polymer CMC via transformation-involving milling

Abstract

Carboxymethylcellulose sodium salt (CMC) was added to magnesium via milling in hydrogen (transformation-involving milling), and samples with compositions of 95 wt% Mg + 5 wt% CMC (named Mg-5CMC) and 90 wt% Mg + 10 wt% CMC (Mg-10CMC) were prepared. At the cycle number (CN) of three, Mg-5CMC had a very high initial hydrogenation rate (1.45 wt% H/min) and a very large effective hydrogen-storage capacity of about 7.2 wt%. It is believed that the CMC melted during milling, and that because the melted CMC was highly viscous, sliding between the Mg particles and hardened steel balls was prevented, which led to effective milling (the generation of defects and cracks and the reduction of particle sizes). To the best of our knowledge, this study is the first in which a polymer CMC was added to Mg in order to improve the hydrogenation and dehydrogenation properties of Mg.