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A pinboard by
Amol Kamble

PhD Scholar, IIT-Bombay

PINBOARD SUMMARY

Investigation on hydrogen absorption in doped BCC alloys for hydrogen storage varying particle size

I am working on Ti-V-Cr based materials(metal hydrides) for storing hydrogen at room temperature under 2 bar(very low compared to other metal types of metal hydrides). We choose the composition which has body centered cubic crystal structure as has high void. These materials absorbs/desorbs hydrogen so quickly after first time exposure for hydrogenation but first time hydrogen absorption is very difficult. There is some waiting period before first time hydrogen absorption. This waiting period may be couple of minutes or days. My task is to find out parameters affecting this waiting period and optimize the favorable material synthesizing technique for quicK hydrogenation. The waiting period during first hydrogenation is mainly affected by chemical composition, phase system, phase compositions, crystal structure, surface properties. In this investigation, I searched for effect of particle size and doping on hydrogen absorption of 52Ti-12V36Cr doped with 4wt%Zr. We found

  1. doped samples absorbs hydrogen quickly due to presence of secondary phase. 2.chemical composition has strong impact on reduced waiting period and increased kinetics.
  2. waiting time depends on the average particle size and not on the distribution of particle sizes.
7 ITEMS PINNED

Batteries, Vol. 2, Pages 15: Studies on the Synergetic Effects in Multi-Phase Metal Hydride Alloys

Abstract: The electrochemical reactions of multi-phase metal hydride (MH) alloys were studied using a series of Laves phase-related body-centered-cubic (BCC) Ti15.6Zr2.1V43Cr11.2Mn6.9Co1.4Ni18.5Al0.3X (X = V, B, Mg, Y, Zr, Nb, Mo, La, and Nd) alloys. These alloys are composed of BCC (major), TiNi (major), C14 (minor), and Ti2Ni (minor) phases. The BCC phase was found to be responsible for the visible equilibrium pressure plateau between 0.1 MPa and 1 MPa. The plateaus belonging to the other phases occurred below 0.005 MPa. Due to the synergetic effects of other non-BCC phases, the body-centered-tetragonal (BCT) intermediate step is skipped and the face-centered-cubic (FCC) hydride phase is formed directly. During hydrogenation in both gaseous phase and electrochemistry, the non-BCC phases were first charged to completion, followed by charging of the BCC phase. In the multi-phase system, the side with a higher work function along the grain boundary is believed to be the first region that becomes hydrogenated and will not be fully dehydrided after 8 h in vacuum at 300 °C. While there is a large step at approximately 50% of the maximum hydrogen storage for the equilibrium pressure measured in gaseous phase, the charge/discharge curves measured electrochemically are very smooth, indicating a synergetic effect between BCC and non-BCC phases in the presence of voltage and charge non-neutrality. Compared to the non-BCC phases, the C14 phase benefits while the TiNi phase deteriorates the high-rate dischargeability (HRD) of the alloys. These synergetic effects are explained by the preoccupied hydrogen sites on the side of the hydrogen storage phase near the grain boundary.

Pub.: 19 May '16, Pinned: 30 Jul '17