Ming Ya Li

Ferromagnetic Properties of Ni0.2Cu0.2Zn0.6Fe2O4-PZT Composites

A series of novel composites with the composition of xNiCuZn-(1-x)PZT (NiCuZn: Ni0.2Cu0.2Zn0.6Fe2O4; PZT: PbZr0.52Ti0.48O3.) were prepared by solid-state reaction methods. The presence of ferromagnetic NiCuZn ferrite phase and ferroelectric PZT phase was confirmed by XRD analysis. It was revealed that composite materials exhibit typical ferromagnetic hysteresis behaviors. With the increase of phase fraction of NiCuZn ferrite, the permeability of composites increases and the natural resonance peak appears. Meanwhile, the maximum of quality factors shifts to the lower frequency.

Fabrication of Bi-2212 Films on Ag Substrate by Dip-Coating Method

In this study, Bi2Sr2CaCu2Ox (Bi-2212) thick films on Ag substrate were fabricated using the dip-coating method. Firstly, the Bi-2212 powders were prepared by Sol-Gel process. Metal nitrates were used as starting materials and ethylenediaminetetracetic acid (EDTA) was used as chelating agent. Secondly, the resulting powders were used as solute, and polyvinyl butyral (PVB) was used as solvent to prepare suspension via stirring and ultrasonic vibration. Then the suspension was dip-coated on Ag substrate. After heat treatments, the phase compositions of the samples were characterized using the XRD. The microstructure was observed using SEM. Experimental results show that the sintering temperature strongly influence the phase formation of Bi–2212.

Fabrication and luminescence properties of Y2SiWO8 : Dy3+ phosphors via sol-gel process

Y2SiWO8:Dy3+ phosphors were prepared through a sol-gel process. XRD and photoluminescence spectra were used to characterize the resulting phosphors. The results indicated that the phosphors crystallized completely at 1000°C. In Y2SiWO8:Dy3+ phosphors, the Dy3+ showed its characteristic yellow emission at 483nm (4F9/2-6H5/2) and 575nm (4F9/2-6H13/2) upon excitation into 275nm.

Cofiring Behavior of Ferroelectric Ferromagnetic Composites

Cofiring behavior of composites consisting of ferroelectric PMZNT and ferromagnetic NiCuZn ferrite was investigated via X-ray diffractometer (XRD), thermomechanical analysis (TMA) and scanning electron microscopy (SEM). Mismatch of sintered camber consisting of two layered structure of ferroelectric PMZNT and NiCuZn ferrite was observed. Mismatched sintering behavior was modified by adopting PMZNT and NiCuZn powders to form composite materials. The temperature of appearance pyrochlore phase in prepared composite materials is lower than that of sintering pure PMZNT material. The grain size of PMZNT and NiCuZn in prepared composites is smaller than that of sintering pure PMZNT and NiCuZn ferrite, respectively.

The Synthesis and Properties of the Inverse Opals Structure Used in Dye-Sensitized Solar Cells

In this paper, the inverse opal structures used in dye-sensitized solar cells were prepared by Sol-Gel method. The TiO2 inverse opal photonic crystal was formed by coating glass slices using dip-coating process. The structure, surface morphology and the optical properties were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet spectrograph (UV-is). The structural characteristics of the films were investigated by the SEM showed that inverse opal titanium dioxide could trap electrons, thus enhance the photoelectric current in the dye-sensitized solar cells. By use of the inverse opals into TiO2 photo anodes with the screen printing method, I-V testing measurement showed that the highest photoelectric conversion efficiency is 1.2%. And the best preparation process of inverse opal titanium dioxide is using Ti (OC4H9)4 as precursor, ethanol as the solvent, nitric acid as inhibitor, and dipping-lift number for 3 times. The result of the test showed that this inverse opals structure has the most appropriate thickness and the optimal performance. Based on the research, the results indicate that the TiO2 inverse opals structure could apply in dye-sensitized solar cells.

Properties and Optimization of Photoanode in Dye-Sensitized Solar Cells

In order to improve the photoelectric conversion efficiency of dye-sensitized solar cells (DSSC), the photoanode process conditions were optimized in this work. The effects on photoelectric conversion efficiency of three methods were mainly investigated, including magnetron sputtering barrier layer, printing scattering layer and post-treatment with TiCl4. The microstructure of TiO2 thin films was measured by scanning electron microscope (SEM). The results showed that porous photoanode benefited to electronic transmission. The photoelectric conversion efficiency and performance of DSSC were measured by I-V testing instrument. The results indicated that the short circuit current and photoelectric conversion efficiency were improved. Finally, the best result was obtained by combining the three optimal conditions. A high photoelectric conversion efficiency of 7.31% was achieved under illumination of simulated AM 1.5 sunlight (100mW/cm2). Compared to the previous result of 5.48%, the improvement of 33.4% was achieved.

Preparation at Low-Temperature and Characterization of TiO2 Film Used for Solar Cells

In this work, nanocrystalline TiO2 powder was prepared by the sol-gel method via tetrabutyl titanate as raw material, non-ion surfactant TO8 as a template. Then the nanocrystalline TiO2 thin film electrodes which were coated on FTO glass substrates via the slurry consiting of TiO2 powder prepared by us and the trabutyl titanate precursor were successfully prepared by using a simple and convenient hydrothermal method at low temperature. The structure and morphology of powders and films were characterized by X-ray diffraction, scanning electric microscopy. The influence factors on the samples were discussed. The photoelectric properties of cells assembled by the films were measured. The results show that, at 25°C and under 1000W/m2 light intensity，open voltage is 708mV, Jsc is 14.648mA/cm2, fill factor is 53.788, the conversion efficiency is 5.5988%.

Study on the Fabrication and Properties of Ni-P Composite Coating

In this paper, the method of electroless deposition of nickel-phosphorous composite coating on the sample surface is employed. The effect of the complexing agent ratio on the surface morphology and phase composition of nickel-phosphorus coating when the main salt and reducing agent concentration unchanged has been studied. The influence of heat treatment on properties and microstructure of coatings are also investigated. Experimental results show that in the case of salt and reducing agent concentration unchanged, complexing agent concentration has strong effect on the morphology of the coatings and the crystal structure of the composite coating. During heat treatment, the morphology of the composite coating changed significantly, and the hardness was improved a certain degree for all the samples, which is related to the precipitation of Ni3P.

Synthesis and Characterization of Magnetite Particles by Co-Precipitation Method

The Fe3O4 nanoparticles with different diameters were prepared by co-precipitation method in this paper. Magnetite particles with different diameters were fabricated by changing the concentration of the reactants and the reaction temperature. The influences of process parameters on the microstructure and properties of magnetic nanopariticles were studied. The obtained samples were characterized by X-ray powder diffraction and scanning electronic microscopy. Besides, vibrating sample magnetmeter was used to characterize the magnetic properties. The results show that all the as-synthesized magnetite nanoparticles are well crystallized and can be indexed into spinel structure. The appearance and magnetism of the particles with different diameter are different from each other. When the ratio of Fe3+ and Fe2+ is 2:1 or 4:3, the product was pure and good crystalline. Furthermore, higher saturation magnetization was obtained in a higher bath temperature.

Finite Element Analysis on Dynamic Characteristics of Hybrid Bearing Spindle System

Due to having the features of high accuracy, high stiffness, high load capacity and longer service life, the hybrid bearing spindle system is widely used in grinding. This paper presents an analysis method of hybrid bearing spindle dynamic characteristics. The method uses CFD method to solve the oil film pressure field, instead of Reynolds equation, in order to obtain the oil film stiffness and damping. With the obtained oil film stiffness and damping to build the appropriate constraints, 3D finite element model of the hybrid bearing spindle system is established, and the modal analysis of the spindle system is carried out. Compared the analysis results with the theoretical calculation results, the feasibility and correction of the method are proved.