Papers by Author: Dong Yan Tang

Abstract: Zinc acetate (ZnAc)/PVP composite fibers were prepared by electrospinning technique and pure inorganic ZnO nanofibers were then obtained after the calcination of the composite fibers at 600°C for 2.5h. The effects of the parameters during the spinning process on the composite fibers and ZnO nanofibers were investigated. Uniform in diameters and continuous nanofibers without liquid beads could be obtained with the polymer concentration of 15%, the spinning voltage of 11kV, the receiving distance of 20cm and the rate of sample propulsion of 1.5uL/min. The XRD detection demonstrated the construction of ZnO for nanofibers after the calcinations of the composite fibers.

Abstract: Corrosion behaviors of ultra high strength steel 22MnB5 and its weld were studied based on electrochemical method in the present work. Electrochemical measurements such as Tafel polarization curve and electrochemical impedance spectroscopy were performed to investigate the corrosion mechanisms of 22MnB5 steel and its weld. The testing results indicated the weld metal possessed less corrosion resistance than the base metal, and the main reason for this phenomenon is the microstructure variation of the weld metal.

Abstract: Fluorinated silica nanoparticles (FSNs) were synthesized by the hydrolysis of tetraethyl orthosilicate and fluoroalkyl siloxane, and by the assistance of surfactant of cetyltriammonium bromide (CTAB) under basic condition. Through adjusting the synthesis conditions, the better particles distribution of fluorinated silica could be obtained. Then the FSNs were used to prepare liquid marble with water and the stability of the liquid marble was tested to investigate the wetting prevention ability of the fluorinated silica nanoparticles.

Abstract: Single ion conducting polymer electrolytes synthesized through a copolymer poly(lithium 2-acrylamido-2-methylpropanesulfonic acid-co-vinyl triethoxysilane) and a crosslinker poly(etheylene glycol) dimethacrylate (PEGDMA) were prepared. Scanning electron microscope (SEM) was used to observe the morphology of the surface and cross-section of the polymer electrolyte membrane. AC impedance and linear sweep voltammetry were used to investigate the electrochemical properties of the polymer electrolytes. It was found that the obtained membrane had a typical amorphous structure and possessed a smooth surface. The bulk resistance of the polymer electrolyte increased with the increase in the plasticizer uptake. The electrochemical stability increased with the increase in the content of VTES.

Abstract: By the Langmuir-Blodgett(LB) technique, the zinc ion containing multilayer was prepared by transferring the zinc acetate, spread on the surface of subphase of ultrapure water and stearic acid-chloroform mixtures, onto a hydrophilic silicon wafer or glass plate. Then the multilayer was converted into ZnO ultrathin films after pre-heating and annealing. The optimized parameters for monolayer formation, such as concentration of subphase, barrier speed and spreading volume, were determined by the measurement of the surface pressure-surface area (Π-A) isotherms. The expended areas after deposition with zinc ions inferred the interaction of stearic acid with zinc ion during the formation of monolayer at air-water interface. The optimized parameters for multilayer deposition, such as surface pressure and lifting speed were determined by the measurement of the transfer coefficient. The X-ray diffraction(XRD) was used to investigate the crystal structures of ZnO nanoparticles and ultrathin film. The surface morphologies of the LB multilayer and ultrathin film were observed by the atomic force microscopy (AFM). A uniform and flat surface of ZnO ultrathin film within nanometer ranges(<35nm) were obtained.

Abstract: To prevent the potential cracking of gel fibers, La modified lead zirconate titanate (PLZT) ceramic fibers with diameter within 50µm were achieved by embedding into PLZT powders during the heat treatment. Then the 1-3 PLZT fiber/interpenetrating polymer network (IPN) piezoelectric composites were prepared by casting the IPN precursors onto the well aligned ceramic fibers. The influences of the heating temperatures and La amounts on the dielectric constant, dielectric loss with frequencies and piezoelectric constant of PLZT were investigated in detail. The morphologies of fibers and composites were observed by biological microscope. And also, the dielectric constant of PLZT fibers and PLZT fiber/IPN piezoelectric composites were detected.

Abstract: The oriented La modified PZT thin films were prepared on Pt/Ti/SiO2/Si substrate by the LB technique. The pre-sintering temperatures and the annealing temperatures for La modified PZT were determined by TG-DTA curves and XRD detect results. XRD detection of PZT and PZT with different La amount illustrated the crystal constructions and the effects by modification. The AFM observation of PLZT thin films with organic acid indicated that the LB technique could obtain smooth and flat film with the deposition of PLZT particles within nanometers on substrate. The detection results of the electrical properties indicated that the modification of La had great influence on the electric properties of LB thin film. PLZT thin film by annealing at 650°C had better dielectric constant of 569.2 and dielectric loss of 0.4915 at 5 kHz. And the amount of La of 2% in mass gave the piezoelectric constant of 14pC/N.

Abstract: (PU/UP IPNs)-BaTiO3 nanocomposites with different amounts of BaTiO3 nanopowder are prepared and polarized. The ferroelectric and dielectric properties are detected and the relationship between electric properties and damping properties are discussed in detail. Results indicate that the synergistic effects can be created successfully by elastic damping of polymer, frictional damping of BaTiO3, and piezoelectric damping of nanocomposites after poling. The nanocomposites increase the damping property evidently and sustain mostly ferroelectric and dielectric characters of inorganic phase. The introduction of BaTiO3 into IPNs decreases the resistivity, and this has advantages to enlarge the damping loss factor (tanδ).

Abstract: In present work, sol-gel process is used to direct the organization of high quality and pore-free parasite PZT thin films with a composition near the morphotropic phase boundary (Zr/Ti = 52/48). The PZT transparent sol can be obtained by dissolving the zirconium oxynitrate, butyl titanate and lead acetate in ethylene glycol with the molar ratio of 0.52:0.48:1 and the PZT gel can be gained by spin-coating. In such process, PZT thin films can be readily prepared by hydrolysis on hot plate at 350°C for 20min and annealing in RTA at 650°C for 1 minute. The structural and electric characteristics of the films have been carried out by XRD, AFM and the C-V measurements, etc. Experimental results have indicated that by treating film RTA at 6508 for 1 minute film with perfect crystallization and good surface morphology with a RMS roughness of 2.0nm can be obtained, and the remnant polarization Pr (28.5 μC/cm2) and coercive field Ec (39.8kV/cm) are obtained in the P-E hysteresis loops. The films have a dielectric constant ε of 1080 and a dielectric loss tanδ of 0.01 at 1 kHz. Ferroelectric polarization fatigue test of the films has shown that high fatigue resistance up to 3 × 1010 cycles before Pr is decreased by 50%.

Abstract: By adding methyl alcohol/water solution with certain concentration into sol to hydrolysis directly and sintering the fresh sol directly, lead titanate(PbTiO3) ceramics doped with magnesium are prepared by using magnesium acetate as doper to prohibit the disadvantages contained in conventional sol-gel method, such as low hydrolytic rate, high sintering temperature, long preparation period. The changes of structure, microstructure, synthesis process and electric properties of modified ceramics are studied in detail. The sizes and morphology of high purely and high density magnesium doped lead titanate nanocrystals thus obtained are observed by TEM photographs and the structures and affection of sintering temperature of to lattice constant and sizes of nanocrystals are detected by XRD. Electric properties detection results show that doped lead titanate ceramics exhibite excellent dielectric, ferroelectric and pyroelectric properties compare with pure lead titanate.