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Keywords:

  • hydrogen storage;
  • MgH2;
  • TiC;
  • nanoparticles;
  • mechanical milling;
  • microstructure;
  • absorption/desorption kinetics

Abstract

BACKGROUND: Magnesium hydride is considered to be a promising hydrogen storage material because of its high gravimetric and volumetric storage capacities. However, its slow kinetics and high desorption temperature of > 300 °C limit practical applications. In this work, TiC nanoparticles were selected to modify the hydrogen storage properties of MgH2. Composite mixtures (MgH2 + TiC) were prepared using both cryogenic milling and high-energy ball milling.

RESULTS: The resulting morphology and crystallite structure of the composites were identified by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The milled samples show good mixing of the hydride and carbide particles, with MgH2 particles around 0.09–1 µm and TiC particles 10–20 nm. The (MgH2 + TiC) composites consist of γ-MgH2, β-MgH2 and TiC. MgH2 nano-crystallites of 25 nm were formed after cryomilling. Thermogravimetry reveals that the composites release ∼6.5 mass % hydrogen from 190–400 °C at a heating rate of 10 °C min−1 under He flow, with the onset and peak temperatures at 190 and 280 °C, respectively, for the (MgH2 + TiC) after 8 h cryomilling and 60 h ball milling.

CONCLUSION: Results indicate that TiC is an effective catalyst for hydrogen desorption of MgH2. Copyright © 2010 Society of Chemical Industry