Microstructural Investigation of Nanocrystalline Hydrogen-Storing Mg-Titanate Nanotube Composites Processed by High-Pressure Torsion

Marcell Gajdics,Viktória Kovács Kis,Ádám Révész,Ferenc Béke,Erhard Schafler,Tony Spassov,Zoltán Novák

doi:10.3390/en13030563

Abstract

A high-energy ball milling and subsequent high-pressure torsion method was applied to synthesize nanocrystalline magnesium samples catalyzed by TiO2 or titanate nanotubes. The microstructure of the as-milled powders and the torqued bulk disks was characterized by X-ray diffraction. The recorded diffractograms have been evaluated by the convolutional multiple whole profile fitting algorithm, which provided microstructural parameters (average crystal size, crystallite size distribution, average dislocation density). The morphology of the nanotube-containing disks has been examined by high-resolution transmission electron microscopy. The effect of the different additives and preparation conditions on the hydrogen absorption behavior was investigated in a Sieverts’-type apparatus. It was found that the ball-milling route has a prominent effect on the dispersion and morphology of the titanate nanotubes, and the absorption capability of the Mg-based composite is highly dependent on these features.

Highlights

The coupling between continuing growth of the world’s population and industrialization means that the transportation segment of the economy is responsible for significant part of petroleum consumption, and transportation is one of the main source of global CO2 emission [1].In addition, the world’s energy consumption is expected to be doubled by 2050, which requires the introduction of alternative energy sources to the energy grid [2]
In a recent work we investigated the influence of simultaneous mixing of transition metal oxide and carbon nanotube catalysts on the hydrogen storage performance of severely deformed nanocrystalline magnesium [40]
We present the effect of the preparation conditions on the microstructure, morphology and hydrogen storage properties of these materials

Summary

Introduction

The world’s energy consumption is expected to be doubled by 2050, which requires the introduction of alternative energy sources to the energy grid [2]. Even though these alternative renewable sources are not competitive with fossil fuels at the moment [3], hydrogen as a secondary energy carrier has gained increasing attention in the last decade; significant technical and economical challenges, such as efficient production and storage need to be solved [4]. The poor thermodynamics, high thermal stability of MgH2 and the sluggish kinetics of dehydrogenation below 300 ◦ C are significant obstacles which still hinder the practical utilization of the Mg-H system [11,12,13]

Methods

Results

Conclusion