Influence of Milling Conditions on the Hydriding Properties of Mg‐C Nanocomposites

Abstract

Mg75 at.%, CB25 at.% (CB: carbon black) composites were synthesized at different ball milling conditions (milling energy, milling duration, and environment) and their hydriding properties were characterized by high-pressure DSC. The SEM observations revealed that the samples consist of 5–15 μm Mg particles, surrounded and in some cases coated by carbon particles. X-ray diffraction analysis showed that the Mg phase of all as-obtained composite powders is nanocrystalline with average crystallite size in the range 20–30 nm, depending on the milling conditions. The best hydriding properties, expressed in low-temperature hydriding (below 150°C) and improved cycle life, showed the composites milled at dry conditions. This is obviously due mainly to the successful Mg surface protection by the carbon. Additional decrease of the hydriding temperature (<100°C) was achieved applying higher-energy milling, but at the same time the cycling stability deteriorated, due to the extremely fine particles and microstructure achieved under these conditions. The composites milled in the presence of heptane showed rapid capacity decline during cycling as well. The observed difference in the hydriding behavior of the Mg-CB composites is attributed to the different coating efficiency of the carbon milled under different conditions with Mg, which is supposed to protect magnesium from oxidation and plays a catalytic role for the hydriding reaction.

The Effect of High-Energy Ball Milling Conditions on Microstructure and Hydrogen Desorption Properties of Magnesium Hydride and Single-Walled Carbon Nanotubes

“…A high rotation speed leads to particle friction and destruction of CNTs, which contributes to the formation of smoother particles [35,36]. However, such high rotational speeds can lead to a decrease in the concentration of carbon/graphite particles on the surface of MgH 2 particles due to their incorporation into the particles and because of the formation of amorphous carbon [37,38].…”

“…However, the decrease in the activation energy of desorption in this case is insignificant and is practically within the error limits. A decrease in the activation energy of hydrogen desorption, as well as the temperature of hydrogen desorption, can occur due to the influence of several factors, such as due to the high thermal conductivity of CNTs [43] and their incorporation into magnesium particles, which allows hydrogen atoms to be diffused more easily from the bulk of the material [37,44]. It can also be related to the distribution of metal catalysts contained in nanotubes [20].…”

Artificial Intelligence Application in Solid State Mg-Based Hydrogen Energy Storage

“…The composites milled in dry conditions showed that the hydriding kinetics improved significantly at low temperatures. The melted composites showed a rapid deterioration in capacity during the cycling period in the presence of heptane, which showed an efficient carbon coating process [44].…”

Hydrogen absorption in carbon allotropes and talc

“…The authors concluded that the addition of more than 9 wt.% of graphite to Mg-V fine powder did not lead to any further acceleration of hydrogen absorption. The newest results are reported in studies [1,[24][25][26].…”