Papers by Author: Lei Wang

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Authors: Xue Tao Yuan, Xu Dong Lv, Zhi Qiang Hua, Lei Wang, Tao Li
Abstract: Anodic polarization behavior of ternary alloy Pb-0.08%Ca-1%Sn is studied by potentiodynamic polarization measurements, corrosion rate, the products on electrode surface after polarization, and microstructure of anode mud after polarization in electrowinning cell. The results show that Pb-Ca-Sn anode is easy to be passivated in electrolyte for copper electrowinning, the maintaining passivity current density is 97.72 µA•cm-2 and the corrosion products on the surface of Pb-Ca-Sn electrode present loose scaly, being composed of α-PbO2, β- PbO2 and PbSO4 after polarization.
Authors: Xue Tao Yuan, Zhi Qiang Hua, Lei Wang, Dong Bai Sun, Song Lin Chen
Abstract: Composite coatings were prepared using electroless nickel bath containing different concentrations of Al2O3 nano-particles. The analyses of coating compositions, carried out by EDS, showed that there is marginal difference between phosphorus contents of NiP and NiP/nano-Al2O3 deposits. The structure of the coatings was examined by scanning electron microscopy (SEM), and X-ray diffraction (XRD). It has been found that the co-deposition of nano-Al2O3 particles with Ni disturbs the NiP coating’s regular surface structure and increases its surface roughness. DC and AC electrochemical tests were carried out on such coatings in a 3.5wt.% solution of NaCl in order to evaluate their corrosion resistance. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests both showed that, the corrosion resistance of NiP-Al2O3 coatings firstly increases and then decreases when Al2O3 concentration in electroless bath is increasing, but the corrosion resistance of NiP-Al2O3 composite coating is better than that of amorphous NiP coating.
Authors: Yun Yi Wu, Lei Wang, Zhi Qiang Hua, Tao Li, Xue Tao Yuan, Xu Dong Lv
Abstract: Pure, La3+ doped at A site, V5+ doped at B site, and La3+ and V5+ co-doped ferroelectric Bi4Ti3O12 (BTO), Bi3.25La0.75Ti3O12 (BLT), Bi4Ti2.98V0.02O3 (BTV) and Bi3.25La0.75Ti2.98V0.02O12 (BLTV) were successfully prepared by conventional sintering technique. The structures of the ceramics were investigated by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. X-ray diffraction indicated that assemblages of all sintered ceramics consist of a single phase of Bi4Ti3O12, implying that the A-site La3+ and B-site V5+ substitutions in this case do not affect the layered structure. Among these ceramics, BLTV ceramic exhibited the best electrical properties. The leakage current density of BLTV ceramic was only 1.3×10-4 Acm-2 at 40 KVcm-1, two orders of magnitude lower than BTO ceramic. Besides, a saturated ferroelectric hysteresis loops with largest remnant polarization 2Pr of 30.6μC/cm2 was observed for this sample. These suggested that the co-doped Bi4Ti3O12 ceramic by La3+ and V5+ at A and B sites showed advantages in application over the pure BTO, doped BLT and BTV ceramic, respectively.
Authors: Yun Yi Wu, Xue Tao Yuan, Zhi Qiang Hua, Tao Li, Lei Wang
Abstract: The Bi3.25La0.75O12 films were prepared on the Pt/TiO2/SiO2/Si substrate using RF-magnetron sputtering method. The effects of sputtering conditions, including sputtering pressure, oxygen partial pressure and substrate temperature on microstructure, ferroelectric properties were investigated. When deposited at low substrate temperature (room temperature), the BLT thin film exhibits preferentially c-axis oriented. With the increasing of substrate temperature, the (117) diffraction peak become stronger, indicating the changing of the microstructure in the BLT films. The BLT film samples deposited at 4.5-6Pa exhibit desired bismuth-layered structure, with no any preferred orientation. However, when BLT films were deposited above 5 Pa, some weak pyrochlore diffraction peaks appear in the X-ray diffraction pattern. The Pr is a maximum for the BLT film deposited at 5 Pa with O2/Ar ratio 1/5 and decreases with both decreasing and increasing deposition pressure.
Authors: Xu Dong Lv, Xue Tao Yuan, Zhi Qiang Hua, Lei Wang, Tao Li, Yu Gao Zhou, Zhi Wei Wei
Abstract: Prepared lead dioxide(PbO2) coating on a Ti substrate by pulse current technique. The effect of the pulse current density, pulse time and relaxation time on the morphology and electrochemistry properties of the coating was studied by means of scanning electron microscopy and electrochemistry station. Compared with lead dioxide fabricate by common electroplate technique, lead dioxide coating prepared by pulse current technique is more dense, without hole, better corrosion resisting property and more stable electrochemistry properties.
Authors: Xue Tao Yuan, Dong Bai Sun, Zhi Qiang Hua, Lei Wang
Abstract: The growth morphology and structure of deposits during the initial stages of amorphous Ni-P electrodeposition was studied using atomic force microscopy (AFM), X-ray diffraction (XRD) and transmission electron microscope (TEM). Combined electrochemical and surface analytical measurements showed that the electrocrystallization process follows a three-dimensional instantaneous nucleation and growth mechanism. The structure of the Ni-P deposits progressively changed from polycrystalline to amorphous state with increasing electroplating time. Additional electrodeposition was carried out on amorphous carbon film at potential -650mV (SCE) for 5s in the same bath for plating Ni-P alloy. It was confirmed that the formation of crystal Ni at initial stage of electroplating Ni-P amorphous alloy was not caused by the epitaxial relationship between the crystal Ni and the crystal substrate and there was a nucleation process in the electrodeposition of amorphous alloy.
Authors: Yun Yi Wu, Lei Wang, Zhi Qiang Hua, Tao Li
Abstract: A series of ferroelectric BIT ceramics with various V2O5 dopants were prepared by conventional solid-state route. The influence of V2O5 dopant on microstructural and electrical properties of BIT ceramic were investigated in detail, which were examined by XRD, Raman spectra and P-E hysteresis loops, etc. X-ray Photoelectron Spectroscopy was used to examine the chemical state of the vanadium ions inside the BIT ceramics. Vanadium added to the BIT system can enhance the ferroelectric property due to the decrease of the concentration of space charge occurred during calcinations and weaken the polarization property due to the decrease of grain size and the change of chemical valence for vanadium ion. The BIT ceramic with 3 mol% V2O5 dopant exhibits a remnant polarization 2Pr of 25.6 μC/cm2, and coercive field Ec of 47.4 KV/cm. Besides, the conductivity of BTV was obviously lower than that of the undoped BIT, which was accord with donor dopants decreasing the conductivity of a material with a p-type mechanism.
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