Effect of Microstructure on Hydrogen Permeation in EA4T and 30CrNiMoV12 Railway Axle Steels

A comparative study was conducted to reveal the effect of microstructure on hydrogen permeation in the EA4T and 30CrNiMoV12 railway axle steels. Unlike the EA4T with its sorbite structure, 30CrNiMoV12 steel shows a typical tempered martensitic structure, in which a large number of fine, short, rod-like, and spherical carbides are uniformly dispersed at boundaries and inside laths. More importantly, this structure possesses plentifully strong hydrogen traps, such as nanosized Cr7C3, Mo2C, VC, and V4C3, thus resulting in a high density of trapping sites (N = 1.17 × 1022 cm−3). The hydrogen permeation experiments further demonstrated that, compared to EA4T, the 30CrNiMoV12 steel not only delivered minimally effective hydrogen diffusivity but also had a high hydrogen concentration. The activation energy for hydrogen diffusion of the 30CrNiMoV12 steel was greatly increased from 23.27 ± 1.94 of EA4T to 47.82 ± 2.14 kJ mol−1

Microstructure characterization and hydrogen storage properties study of Mg2Ni0.92M0.08 (M = Ti, V, Fe or Si) alloys

In the present study Mg2Ni-type compounds alloyed independently with Ti, V, Fe and Si were successfully prepared by wet-milling followed by sintering. Although these alloyed Mg2Ni compounds exhibited a similar hydrogen storage mechanism as that of pure Mg2Ni, the dissolution of Ti, V or Fe into the Mg2NiH4 lattice had a considerable catalytic effect on hydrogen desorption from additional MgH2. The further structure investigations clearly indicated that the substitution of Ti for Ni could suppress the formation of the micro-twined low-temperature phase (LT2) and promote the formation of the high-temperature phase (HT), thus resulting in remarkably improved hydrogen desorption kinetics for the Mg2Ni0.92Ti0.08–H system. Keywords: Hydrogen storage, Mg-based alloys, Elemental substitution, Kinetic

Thermal Dehydrogenation Characteristics of Li-Sr-Al-N-H Hydrogen Storage System

<div><p>Thermolysis behavior of the Li-Sr-Al-N-H hydrogen storage system prepared by ball milling of Sr2AlH7 + LiNH2 mixture was investigated in this paper. The results show that thermal decomposition of the Li-Sr-Al-N-H system proceeds mainly in two steps with only hydrogen desorption. The thermal stability of this system is lowered as compared to the individual starting material, resulting in the hydrogen desorption initiating from about 125 °C. In addition, about 0.91 and 1.53 wt.% of hydrogen can be isothermally desorbed within 180 min at 180 and 330 °C, respectively. The decreased thermal stability of the Li-Sr-Al-N-H system might be attributed to the chemical reactions between the starting materials during the heating process with the formation of LiSrH3 and N-containing amorphous phases.</p></div

Thermal Dehydrogenation Characteristics of Li-Sr-Al-N-H Hydrogen Storage System

<div><p>Thermolysis behavior of the Li-Sr-Al-N-H hydrogen storage system prepared by ball milling of Sr2AlH7 + LiNH2 mixture was investigated in this paper. The results show that thermal decomposition of the Li-Sr-Al-N-H system proceeds mainly in two steps with only hydrogen desorption. The thermal stability of this system is lowered as compared to the individual starting material, resulting in the hydrogen desorption initiating from about 125 °C. In addition, about 0.91 and 1.53 wt.% of hydrogen can be isothermally desorbed within 180 min at 180 and 330 °C, respectively. The decreased thermal stability of the Li-Sr-Al-N-H system might be attributed to the chemical reactions between the starting materials during the heating process with the formation of LiSrH3 and N-containing amorphous phases.</p></div