A comparative study on the crystallization behavior of electroless NiP and NiCuP deposits
ABSTRACT The crystallization behavior of electroless NiP and NiCuP was studied comparatively by using differential scanning calorimetry and X-ray diffractometry. It is apparent that low-P NiP deposits transform to the stable phase Ni3P directly, but low-P (high-Cu) NiCuP deposits transform to the metastable phase Ni5P2 first, and then to the stable Ni3P. Both the hypereutectic amorphous NiP deposits and amorphous NiCuP deposits with high phosphorus content transform to the metastable phases Ni5P2 and Ni12P5 first, then to the stable phase Ni3P. For the amorphous NiP and NiCuP deposits with P content of approximately 10 wt.%, the crystallization temperature of the latter is markedly higher than that of the former. In addition, the crystallization temperature of the hypereutectic NiP deposit is nearly the same as that of the amorphous NiCuP deposit with a similar P content. For the crystalline NiP and NiCuP deposits with low P content, the temperature at which the stable Ni3P forms in the latter is obviously higher than that of the former.
- Wood Science and Technology 09/2014; 48(5):961-979. · 1.87 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Ni-W-P-Al2O3 electroless composite coating was successfully co-deposited on 45 steel substrate using electroless plating. Optical microscope (OM), X-ray diffraction (XRD) and potentiodynamic polarization were used to analyze the morphology, microstructure and corrosion resistance of the composite coating. The results show that Al2O3 particles co-deposit homogeneously, and the structure of the composite coating as deposited is amorphous and crystallite. After heat treatment, the amorphous structure of the composite coating appears a precipitation transformation. When annealing at 400°C, because of the emergence of crystal defects brought out by the precipitation of crystal phases, the composite coating exhibits the lowest corrosion resistance. As the annealing temperature rising to 600°C, the crystalline structure continually grows up and the precipitation transformation tends to be completed. Then the crystal defects decreases which results in an improvement to the corrosion resistance of the composite coating.Advanced Materials Research. 02/2012; 468-471:1177-1180.
- [Show abstract] [Hide abstract]
ABSTRACT: Nanoporous Ni-Cu-P amorphous alloy (NP-NiCuP) and nanoporous Ni-Cu crystalline alloy (NP-NiCu) are prepared by the linear sweep voltammetry (LSV) etching of copper from the electroless Ni-Cu-P and Ni-Cu alloy coatings, respectively. The results of X-ray diffraction (XRD) analysis show that the nanoporous Ni-Cu-P alloy is amorphous structure. The scanning electron microscopy (SEM) analysis demonstrates the NP-NiCuP shows a 3-D bi-continuous porous structure with the pore size of 150–200 nm and the ligament size of around 100 nm. Electrochemical performances are measured by cyclic voltammetry (CV) and chronoamperometry (CA). The results prove that the NP-NiCuP electrode exhibits higher the proton diffusion coefficient (D0) of Ni(OH)2 and surface coverage (Γ*) of the redox species than those on smooth electroless Ni-Cu-P amorphous alloy (S-NiCuP) and NP-NiCu electrodes in alkaline solution obviously. Moreover, electro-oxidation of methanol suggests that the NP-NiCuP electrode holds higher anodic current density and lower onset potential than the S-NiCuP and NP-NiCu electrodes. Finally, the NP-NiCuP electrode has stable redox behavior and superior catalytic stability for methanol oxidation.Electrochimica Acta 02/2015; 154. · 4.09 Impact Factor