Zhi-you Li

Fabrication and characterization of electrodeposited nanocrystalline Ni–Fe alloys for NiFe2O4 spinel coatings

Abstract Nanocrystalline Ni–Fe FCC alloy coatings with Fe content of 1.3%–39% (mass fraction) were fabricated on the nickel substrates using a DC electrodeposition technique. The crystal structure, lattice strain, grain size and lattice constant of the Ni–Fe alloy coatings were studied by X-ray diffraction technique. The chemical composition and surface morphology of the FCC Ni–Fe alloy coatings were investigated with the energy dispersive X-ray spectroscopy (EDS) and atomic force microscopy (AFM). The results show that the Fe content of the Ni–Fe alloy coatings has a great influence on the preferred orientation, grain size, lattice constant and lattice strain. FCC Ni–Fe alloy coatings exhibit preferred orientations of (200) or (200)(111). With an increase of Fe content, the preferred growth orientation of (200) plane is weakened gradually, while the preferred growth orientation of (111) increases. An increase of the Fe content in the range of 1.3%–25% (mass fraction) results in a significant grain refinement of the coatings. Increasing the Fe content beyond 25% does not decrease the grain size of FCC Ni–Fe alloys further. The lattice strain increases with increasing the Fe content in the FCC Ni–Fe alloys. Since the alloys with Fe content not less than 25% has similar grain size (∼11 nm), the increase in the lattice strain with the increase of Fe content cannot be attributed to the change in the grain size.

Phase evolution of 17(Cu-10Ni)-(NiFe2O4-10NiO) cermet inert anode during aluminum electrolysis

17(Cu-10Ni)-(NiFe2O4-10NiO) cermets were prepared by cold pressing and sintering in nitrogen atmosphere, and tested as inert anode for aluminum electrolysis at 960 °C for 10 and 40 h, respectively. Microstructures and phase compositions of the as-sintered and post-electrolyzed samples were investigated. The impurity contents in the electrolyte and the cathode metal were detected in order to investigate the corrosion characteristic of the elements of Fe, Ni and Cu in the anode. A dense NiFe2O4 layer was observed on the surface of anode and thickened with prolonging the electrolysis time. In the newly formed dense ceramic layer, NiO phase disappeared as a result of being swallowed by NiFe2O4 phase, and the metal phase was oxidized during the electrolysis in which Cu element showed a higher dissolution rate than Fe and Ni elements. The formation process of the dense ceramic layer during the electrolysis was presented and explained by using the corrosion mode of the metal phase and the transformation mechanism from NiO phase to NiFe2O4 phase.

Soft-chemical synthesis and high-temperature electrochemical characteristics of VO2

Abstract VO 2 powder was synthesized by a new soft-chemical method using formaldehyde as a reductant. The influences of pyrolysis temperature and time on the phase and morphology of grains were investigated by using thermal gravimeter/differential thermal analysis(TG/DTA), X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy and scanning electron microscope(SEM). The positive electrode discharge performances of Li-B/LiCl-KCl/VO 2 thermal battery at 500 °C were studied. The results show that the product is mainly non-crystal when the precursor of VO 2 is heated below 300 °C. VO 2 (B) appears and transits into VO 2 (R) irreversibly as the heating temperature rises. The open-circle voltage of VO 2 is 2.6 V (vs Li-B), and the initial discharge voltage of 100 mA/cm 2 at 500 °C is 2.52 V. The specific capacities of 100 mA/cm 2 and 200 mA/cm 2 at cut-off voltage of 1.4 V are 449 A·s/g and 539 A·s/g, respectively.

Effect of BaO addition on electric conductivity of xCu/10NiO-NiFe2O4 cermets

Abstract The effects of BaO addition on the phase composition, relative density and electric conductivity of x Cu/10NiO-NiFe 2 O 4 ( x =5, 10) cermets were studied, which were prepared with cold isostatic pressing-sintering process. The results show that the relative densities of 5Cu/10NiO-NiFe 2 O 4 cermet doped with 1% BaO (mass fraction) and 10Cu/10NiO-NiFe 2 O 4 cermet doped with 1% BaO sintered at 1 473 K in nitrogen atmosphere, are increased by about 9.86% and 9.75% compared with the undoped BaO cermets, respectively. And the electric conductivities 22.79 S/cm of 5Cu/10NiO-NiFe 2 O 4 cermets adding 1% BaO and 23.10 S/cm of 10Cu/10NiO-NiFe 2 O 4 cermets adding 1% BaO are obtained, which are 2.21 times and 1.47 times of those of undoped samples, respectively. Moreover, the 10Cu/10NiO-NiFe 2 O 4 cermets doped with 1% BaO have a maximum σ 0 of 58.91 S/cm and electric conductivity of 23.10 S/cm at 1 233 K. Maybe low melting-point phases of BaFe 2 O 4 and Ba 2 Fe 2 O 5 have an excellent electric conductivity in x Cu/10NiO-NiFe 2 O 4 ( x =5, 10) cermets at 1 233 K.

Inhibition mechanism of aspartic acid on crystal growth of hydroxyapatite

Abstract The effects of aspartic acid on the crystal growth, morphology of hydroxyapatite(HAP) crystal were investigated, and the inhibition mechanism of aspartic acid on the crystal growth of hydroxyapatite was studied. The results show that the crystal growth rate of HAP decreases with the increase of the aspartic acid concentration, and the HAP crystal is thinner significantly compared with that without amino acid, which is mainly due to the (10

Synthesis and characterization of arginine-modified and europium-doped hydroxyapatite nanoparticle and its cell viability

1 0) surface of HAP crystal being inhibited by the aspartic acids. The calculation analysis indicates that the crystal growth mechanism of HAP, following surface diffusion controlled mechanism, is not changed due to the presence of aspartic acid. AFM result shows that the front of terrace on vicinal growth hillocks is pinned, which suggests that the aspartic acid is adsorbed onto the (10

Preparation and mechanism of calcium phosphate coatings on chemical modified carbon fibers by biomineralization

1 0) surface of HAP and interacts with the Ca 2+ ions of HAP surface, so as to block the growth active sites and result in retarding of the growth of HAP crystal.

Oxidation behaviors of electrodeposited nickel-cobalt coatings in air at 960 °C

Abstract The arginine-modified and europium-doped hydroxyapatite nanoparticles (HAP-Eu) were synthesized by hydrothermal synthesis. The prepared nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffractometry (XRD), Fourier transform infrared (FTIR) and zeta potential analyzer. The cell viability of HAP-Eu was tested by image flow cytometry. The results indicated that HAP-Eu is short column shapes and its size is approximately 100 nm, its zeta potential is about 30.10 mV at pH of 7.5, and shows no cytotoxicity in human epithelial cells and endothelial cells.

Influence of Yb2O3 addition on microstructure and corrosion resistance of 10Cu/(10NiO-NiFe2O4) cermets

In order to prepare HA coatings on the carbon fibers, chemical modification and biomineralization processes were applied. The phase components, morphologies, and possible growth mechanism of calcium phosphate were studied by infrared spectroscopy(IR), X-ray diffractometry(XRD) and scanning electron microscopy(SEM). The results show that calcium phosphate coating on carbon fibers can be obtained by biomineralization. But the phase components and morphologies of calcium phosphate coatings are different due to different modification methods. Plate-like CaHPO4·2H2O (DCPD) crystals grow from one site of the active centre by HNO3 treatment. While on the para-aminobenzoic acid treated fibers, the coating is composed of nano-structural HA crystal homogeneously. This is because the —COOH functional groups of para-aminobenzoic acid graft on fibers, with negative charge and arranged structure, accelerating the HA crystal nucleation and crystallization on the carbon fibers.

Microstructure and formation process of Ni-pool defect in WC–8Ni cemented carbides

Abstract Ni coating and Ni-Co alloy coatings were produced by adjusting the composition of the plating solution using a direct current electrodepositing process. The oxidation behaviors of nickel and nickel-cobalt alloys in air at 960 °C were studied by thermogravimetric (TG) analyzer and then the formed oxide scales were examined by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), X-ray diffractometry (XRD), and Raman spectroscopy. The scale morphologies, composition, grain size and mechanism of oxidation were discussed in detail. The results show that oxidation rates of Ni, Ni-7%Co (mass fraction) and Ni-15%Co generally follow parabolic relationship, whereas that of Ni-30% Co alloy follows cubic relationship. The higher the Co content of the alloys is, the faster the oxidation rate is. Metal concentration profiles reveal cobalt depletion in the alloy surface beneath oxide scales, and a progressive enrichment in cobalt towards the outer surface of the scale.