Browsing by Author "Somo, Thabang Ronny"

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    A comprehensive review on hydrogen absorption behaviour of metal alloys prepared through mechanical alloying
    (MDPI, 2020) Davids, Moegamat Wafeeq; Somo, Thabang Ronny; Maponya, Thabiso Carol
    Hydride-forming alloys are currently considered reliable and suitable hydrogen storage materials because of their relatively high volumetric densities, and reversible H2 absorption/desorption kinetics, with high storage capacity. Nonetheless, their practical use is obstructed by several factors, including deterioration and slow hydrogen absorption/desorption kinetics resulting from the surface chemical action of gas impurities. Lately, common strategies, such as spark plasma sintering, mechanical alloying, melt spinning, surface modification and alloying with other elements have been exploited, in order to overcome kinetic barriers. Through these techniques, improvements in hydriding kinetics has been achieved, however, it is still far from that required in practical application. In this review, we provide a critical overview on the effect of mechanical alloying of various metal hydrides (MHs), ranging from binary hydrides (CaH2, MgH2, etc) to ternary hydrides (examples being Ti-Mn-N and Ca-La-Mg-based systems), that are used in solid-state hydrogen storage, while we also deliver comparative study on how the aforementioned alloy preparation techniques affect H2 absorption/desorption kinetics of different MHs. Comparisons have been made on the resultant material phases attained by mechanical alloying with those of melt spinning and spark plasma sintering techniques.
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    High entropy hydrogen storage alloys and perspectives of their application in hydrogen storage systems operating at near-ambient temperatures
    (University of the Western Cape, 2024) Somo, Thabang Ronny
    Hydrogen (H2) storage in reversible metal hydrides (MH) is very promising for a number of stationary and mobile niche applications due to its safety, compactness, simplicity, as well as low cost of the associated H2 refuelling infrastructure. At the same time, further market penetration of MH H2 storage technologies is greatly dependent on the availability of advanced hydrogen storage materials characterised by high reversible H2 storage capacity per unit volume at near-ambient temperatures and H2 pressures. Easy activation, fast H2 absorption/desorption kinetics, low heat effect of hydrogenation, and a good cycle stability are also very important. High Entropy Alloys (HEAs) consisting of five or more individual metals in equal or close to equal atomic fractions is a new class of metallic materials discovered in early 2000s. Due to a number of structural-morphological, thermodynamic and electronic features, the HEAs often exhibit outstanding application-related properties including high strength and wear resistance, corrosion resistance, high-temperature stability, etc. Some HEAs are characterised by very good hydrogen sorption properties comparable with and exceeding the ones for the best hydrogen storage alloys on the basis of rare earth elements. Importantly, the hydrogen storage HEAs do not contain the rare earth metals characterised by high cost and limited availability. However, most of the studied to date hydrogen storage HEAs include only elements having a high affinity to hydrogen (Ti, Zr, Nb, etc.) and thus require too high temperatures to release the absorbed H2 that limits their application potential.