| This work analyzed the influence of stoichiometry, method of production and heat treatment on nickel metal hydride alloys. The arc melting process is described in details for Mm{dollar}rmsb{lcub}x{rcub}(Ni{dollar}-Co-Al){dollar}sb5{dollar}, x = 0.88-1.09; Mm(Ni-Co-Al){dollar}rmsb{lcub}x{rcub}{dollar} x = 4.76-5.376; Mm{dollar}rmsb{lcub}x{rcub}{dollar} (Ni-Co-Mn-Al){dollar}sb5{dollar} x =0.92-1.065 and Mm(Ni-Co-Mn-Al){dollar}rmsb{lcub}x{rcub}{dollar} x =4.77-5.42. The induction melting process is described for two stoichiometric alloys, Mm(Ni-Co-Al){dollar}sb5{dollar} and Mm(Ni-Co-Mn-Al){dollar}sb5{dollar}. Melting points were determined by DTA. Heat treatment was conducted in vacuum furnaces at 800{dollar}spcirc{dollar}C and 1000{dollar}spcirc{dollar}C. P-C-T curves were measured for two commercial and two stoichiometric in house made alloys at 30{dollar}spcirc{dollar}C and 40{dollar}spcirc{dollar}C using Sievert's apparatus built in Westaim Co. These alloys were also measured electrochemically at room temperature using a standard Hg/HgO electrode. EDS was used for chemical analysis of matrix and grain boundaries of NiMH alloys. A new understanding of the influence of stoichiometry on crystal structure of NiMH alloys and crystal structure on discharge capacity and rate of discharge capability was achieved. Four new alloys compositions were produced and tested. One of them has a discharge capacity above 300 mAh/g and excellent rate capability. Some of them are not at all sensitive to high current discharge rate. |
PDF Full Text Request