Characterization of initial activation behavior for hydrogen storage alloys by acoustic emission technique

We have monitored the physical processes linked to electrochemical processes in situ occurring at MmNi 3.6Mn 0.4Al 0.3Co 0.7 and TiCr 0.3V 1.8Ni 0.3 electrodes using an acoustic emission (AE) technique. The difference in initial activation behavior between both alloy electrodes was characterized by waveforms, power spectra and time history of the AE signals. In the first charging process, the cracking based on hydrogen absorption occurred intensively on the MmNi 3.6Mn 0.4Al 0.3Co 0.7 electrode in the first half, while the cracking on the TiCr 0.3V 1.8Ni 0.3 negative electrode occurred after hydrogen evolution. In the initial activation, the MmNi 3.6Mn 0.4Al 0.3Co 0.7 particles were broken down with many large and small cracks, while the TiCr 0.3V 1.8Ni 0.3 particles were not pulverized although a few cracks were observed.