Size distribution of precipitated Ni clusters on the surface of an alkaline-treated LaNi5-based alloy

Anisotropic Nanoporous Nickel Obtained through the Chemical Dealloying of Y2Ni7 for the Comprehension of Anode Surface Chemistry of Ni‐MH Batteries

“…As mentioned in the introduction, other authors have already reported the formation of such nickel layer as corrosion product of electrode materials and partially characterized it. For LaNi 5 , Li et al . have identified the presence of Ni clusters, smaller than 25 nm.…”

“…Indeed, Ovshinsky and Fetcenko reported the existence of catalytically active Ni nanoparticles dispersed at the surface of ZrMn 2 ‐type alloys after a discharge reaction . Other authors reported nanometric nickel at AB 5 surfaces during charge‐discharge cycles in KOH solution . Some authors have also developed surface treatments with KOH and NaBH 4 for AB 5 alloys to favor this catalytic np‐Ni layer formation, or to produce nickel coatings on A 2 B 7 alloys .…”

Comparisons of metallic clusters imbedded in the surface oxide of AB2, AB5, and A2B7 alloys

“…The metallic nickel clusters embedded in the surface oxide layer of the AB 2 [21][22][23][24][25][26] and AB 5 [27][28][29][30][31][32][33][34][35][36][37][38] MH electrodes as the product of a self restoration [27,30] are known to play a very important role in catalyzing the electrochemical reaction powering Ni/MH batteries. These Ni-based clusters not only control the high-rate dischargeability (HRD) of the electrodes but also increase the corrosion/passivation resistance of the alloy [13,39].…”

“…These Ni-based clusters not only control the high-rate dischargeability (HRD) of the electrodes but also increase the corrosion/passivation resistance of the alloy [13,39]. Extensive measurements of magnetization together with transmission electron microscopy (TEM) studies were used to investigate the properties of these superparamagnetic Ni-based clusters [25,28,30,31,34,38,40]. Based on fits of the sample magnetization to the Langevin function, the sizes of these Ni clusters were estimated to range from a 2 to 20 nm, depending on the alkaline treatment conditions [38].…”

“…Extensive measurements of magnetization together with transmission electron microscopy (TEM) studies were used to investigate the properties of these superparamagnetic Ni-based clusters [25,28,30,31,34,38,40]. Based on fits of the sample magnetization to the Langevin function, the sizes of these Ni clusters were estimated to range from a 2 to 20 nm, depending on the alkaline treatment conditions [38]. The total volume percentage of these Ni rich clusters, reaching up to 5 wt.% [41], can be extracted from the value of the saturation magnetization, M S , normalized to the magnetization for pure nickel metal.…”