Nanocrystalline nickel dispersed with nano-size WO3 particles synthesized by electrodeposition

Abstract

A new class of bulk nanocrystalline nickel dispersed with nano-scale WO 3 particles has been synthesized by conventional electrodeposition to clarify the effect of the presence of nano-size dispersions on the strength and thermal stability of nanocrystalline structures. It was found that WO 3 particles of an initial size of 0.1 lm, when suspended in an electrolyte, fragmented into smaller nano-size particles, and were embedded into nanocrystalline nickel matrix of an average grain size of 45 nm during deposition. X-ray diffraction and transmission electron microscopy analyses revealed that phase transition of WO 3 particles occurred from an initial monoclinic to a tetragonal structure. The cause-and-effect relation between the fragmentation and the phase transition of WO 3 particles was discussed. Further hardening was confirmed in comparison with nanocrystalline pure nickel, but its increment was less than that predicted by the classical Orowan-type hardening of the particle-dislocation interaction. The discrepancy may be associated with a different dominant deformation mode which operates in a nanocrystalline regime.

Preparation of WO3/CNT catalysts in presence of ionic liquid [C16mim]Cl and catalytic efficiency in oxidative desulfurization

“…The catalysts WO 3 /CNT‐1 and WO 3 /CNT‐2 improved by [C 16 mim]Cl had strong characteristic diffraction peaks at 2 θ = 22.95, 23.82, 28.58, 33.29 and 34.03°, indexed as the (0 0 1), (2 0 0), (2 1 0), (2 0 1) and (2 2 0) reflections of tetragonal phase WO 3 (PDF No. 89‐1287) respectively . However, in the absence of [C 16 mim]Cl, the calcined catalysts showed characteristic peaks of monoclinic phase WO 3 .…”

“…89-1287) respectively. 28 However, in the absence of [C 16 mim]Cl, the calcined catalysts showed characteristic peaks of monoclinic phase WO 3 . This indicated that the addition of [C 16 mim]Cl would transform monoclinic phase WO 3 on CNT into tetragonal phase WO 3 .…”

Novel Synthesis of Nanocrystalline Nickel Dispersed with Nano-size WO3 Particles by Electrodeposition

“…During electrodeposition, it is possible that the plate of the surface rises above this temperature locally by the discharge of electricity. In our previous study [22,23], original WO 3 particles suspended in the electrolyte were monoclinic, but were identified as tetragonal structures in the electrodeposits by XRD and TEM.…”

“…In view of a possible change in the dominant deformation mechanism from conventional dislocation slip to deformation mediated by grain boundaries, additional hardening by WO 3 particles is of interest. Thus, as was performed in the previous report [22], the result was compared with the theoretical strengthening by classical dislocation-pinning. According to the Orowan dislocation bowing model [26], yield stress σOR can be described as:…”

“…During an effort to synthesize nanocrystalline nickel with very fine dispersed particles, the authors discovered that WO3 particles suspended in an electrolyte were fragmented into finer particles accompanying phase transition from a monoclinic to a tetragonal structure during electrodeposition [22,23]. The phenomenon has been successfully applied to synthesize bulk nanocrystalline metals with dispersed nano-size particles.…”