Effect of process control agents on synthesizing nano-structured 2Mg–9Ni–Y catalyst by mechanical milling and its catalytic effect on desorption capacity of MgH2

• Sample prepared by toluene had smaller crystallite size than those of stearic acid.
• After heating of the samples prepared by stearic acid, Mg2Ni9Y compound appeared.
• Particle size of the catalyst was more effective than the amount of Mg2Ni9Y phase.
• MgH2 doped with toluene desorbed 1 wt% more H2 than MgH2 doped with stearic acid.

Synthesizing 2Mg–9Ni–Y catalyst was investigated by mechanical alloying of Mg, Ni, and Y elemental powder mixture and subsequent heat treatment. Accordingly, effects of milling time, process control agent (PCA) type (stearic acid and toluene), and heat treatment time on the powder microstructure, phase composition, and powder morphology were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and laser particle size analyzer (LPSA). Results showed that particle size of the samples prepared by toluene were smaller than those of the samples prepared by stearic acid. Also, it was found that the ternary Mg2Ni9Y compound was not formed by mechanical milling alone. This intermetallic compound was partially formed after the heat treatment of ball milled powders for 8 h at 800 °C. Effect of toluene on powder particle was higher than that of stearic acid. According to XRD patterns, it seems that the amount of formed Mg2Ni9Y in the samples which were ball milled for 15 h using stearic acid and subsequently heat treated at 800 °C for 8 h was more than the powders that used toluene in the same conditions. Furthermore, results of hydrogen desorption tests of MgH2 doped with 10 wt% sample prepared by toluene after the desorption time of 2500 s at 300 °C showed that it desorbed 1 wt% more hydrogen than MgH2 doped with 10 wt% sample prepared by acid stearic.

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