Rapidly solidified magnesium: nickel alloys as hydrogen storage materials

Yi, Xiaodong (2014). Rapidly solidified magnesium: nickel alloys as hydrogen storage materials. University of Birmingham. Ph.D.

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Abstract

Due to high hydrogen capacity, good reversibility and low cost, magnesium hydride is one of the most promising hydrogen storage materials. However, the high desorption temperature and slow hydriding kinetics hinder the application of magnesium hydrides. To improve the hydrogen storage characteristics of magnesium hydrides, many effective treatments have been developed and applied, such as ball milling, melt spinning, alloying with other metals, adding catalysts and using thin film technique. In this work, melt spinning and alloying with Ni were the main sample modification methods used to improve hydrogen storage properties for magnesium hydrides. At the beginning of this project, it was found that it was difficult to repeat the methodology of sample preparation in the literature. Therefore, sample synthesis method was developed after numerous preliminary trials and a series of Mg-Ni alloys were melt-spun successfully.
The structural characterization and analysis of hydrogen storage property were performed on the melt-spun Mg-Ni samples in a range of compositions. It was found that a nanocrystalline / amorphous structure was produced by melt spinning, and a metastable intermediate phase, Mg\(_6\)Ni, was discovered in the melt-spun materials. The melt-spun Mg-Ni ribbons exhibited fast kinetics of both absorption and desorption at 300 °C, with a high capacity. Moreover, they exhibited low temperature and even room temperature hydrogen sorption, with slow kinetics.\(\gamma\)-MgH\(_2\) phase, which forms usually under high pressure, has been found in the samples, which probably caused the ambient hydrogen absorption.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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