Papers by Author: Chuan Bin Wang

Abstract: In this research, the W-40wt.%Cu composite tape-casting films were prepared through the vacuum hot-press sintering method, and the effect of sintering temperature on the microstructures and properties of the W-40wt.%Cu composite samples was studied. Microstructures of the W-40wt.%Cu tape-casting film and the prepared samples were analyzed by field emission scanning electron microscopy (FE-SEM). The phase of the samples was investigated by X-ray diffraction (XRD). The relative density, Vickers hardness, bending strength and electrical conductivity of the samples were investigated. The results show that the relative density of the W-40wt.%Cu composite materials enhances with the increasing of the sintering temperature, at the same time the mechanical and electrical properties are better with the increasing of the sintering temperature. The W-40wt.%Cu composites prepared at the condition of 900°C-200MPa-2h have the relative density of 97%, the bending strength of 507.3MPa, the Vickers hardness of 376.2HV and the electrical conductivity of 32.5% IACS, respectively.

Abstract: La_1-xSr_xMnO₃ (LSMO) thin films were grown on (100)- and (110)-oriented MgO substrates by pulsed laser deposition, so as to control the preferential orientation of the films. At the optimum deposition temperature (T_d = 923K), LSMO thin films with a dense texture and a smooth surface were prepared. The XRD patterns and X-ray pole figures indicated that the LSMO thin films were epitaxially grown on MgO substrates, due to the small lattice mismatch between the films and substrates The possible orientation relationships were found to be LSMO (100) [100] // MgO (100) [100] and LSMO (110) [110] // MgO (110) [110], as for the (100) and (110) MgO substrates, respectively.

Abstract: Mg1 and 1060 Al were diffusion-bonded by using pure silver foil under different holding times (10 min~120 min). The interface of the joint consists of Mg-Ag diffusion zone, Ag foil interlayer and Ag-Al diffusion zone. The distributions of Mg, Ag and Al show ladder-like distributions at the interface of the joints. When the holding time is below 90 min, silver foil has impeded the inter-diffusion of Mg and Al. When the holding time is beyond 90 min, the brittle eutectic Mg-Al intermetallic compounds (IMCs) cannot be avoided. Mg₃Ag and MgAg intermetallic compounds formed on Mg base side. Ag₂Al intermetallic compound grew on Al base side. The thicknesses of Mg₃Ag, MgAg and Ag₂Al increased linearly with the increasing holding time, which is contrary to that of the silver foil. The growth rate relationship of the formed IMCs is MgAg > Ag₂Al > Mg₃Ag according the slope values of the fitted lines. The hardness sharply increased at the interface because of the formation of IMCs. The maximum hardness values of three IMCs Mg₃Ag, MgAg and Ag₂Al are 287.5 HV, 196.5 HV and 175.7 HV respectively. The hardness of each IMC layer increased with the extension of holding time. The shear strength of the joints decreased from 10.5 MPa to 4.6 MPa with the rising holding time.

Abstract: c-BN films were deposited on Si (100) substrates by magnetron sputtering followed by annealing at high temperatures. The effect of annealing temperature on the structure, surface morphology and mechanical property of the films were investigated. The structural characterization by FTIR showed an increasing in c-BN content with annealing temperature, and the surface morphology of the c-BN films became more homogeneous. The stress produced in the films was relaxed after annealing, and the hardness was increased with the increasing of c-BN content. At the optimum annealing temperature of 900°C, the hardness reached the maximum value of 13.32 GPa, where the films had the highest c-BN content of 64.3%.

Abstract: High-performance copper-coated tungsten composite powders were successfully prepared using electroless plating at an appropriate pH in the plating bath. The effect of pH value in the plating bath on the microstructure and purity of the coated Cu layer was studied systematically. With the increase of pH in the bath, the surface roughness, particle size and average grain size of coated Cu increased, and the particle shape gradually changed from round into square block. At pH 12–12.5, coated Cu was highly pure with very little oxygen content (less than 0.09 wt.%). The promotion effect of the increased pH on both main electroless plating reaction and side reactions causes the changes of surface morphology, average grain size of Cu and the oxygen content in the composite powders.

Abstract: Sr-doped lanthanum manganite (La_1-xSr_xMnO₃) is characteristic of thermochromic, which can act as a smart thermal control material used in the variable-emittance devices. In the present study, La_1-xSr_xMnO₃ thin films were prepared on MgO(100) substrates by pulsed laser deposition, and the effect of Sr-doping (x = 0 ~ 0.4) on the structure and infrared emissivity was investigated. Single-phased La_1-xSr_xMnO₃ films with (100)-orientation were obtained, which showed a dense texture with smooth surface. The ratio of Mn⁴⁺/Mn³⁺ in the films was increased with increasing Sr doping, leading to the enhancement in double-exchange interaction and electrical conductivity. As a result, the phase transition from metal to insulator was observed with the increasing of test temperature. For the La_0.8Sr_0.2MnO₃ thin film, a large value of emittance (De = 0.28) was obtained, indicating good variable-emittance by appropriate Sr doping.

Abstract: Ferroelectric BiFeO₃ (BFO) thin films were prepared on Pt (111)/Ti/SiO₂/Si substrates by pulsed-laser deposition under various oxygen partial pressures (P_O2). The effects of P_O2 on the phase, orientation, surface morphology, and ferroelectric properties of the films were investigated, particularly in regard to relationships between structure and properties. It was found that the crystallographic orientation and surface morphology of the BFO thin films strongly depended on P_O2. Films prepared at P_O2=10 Pa had a high degree of (111) orientation and densely packed grains. A maximum of twice the remanent polarization for the BFO thin film was 68 μC/cm².

Abstract: Transparent conducting antimony doped tin oxide (ATO) films have been prepared on quartz glass substrate by pulsed laser deposition (PLD) method which is distinctive to maintain the elemental components between the targets and the obtained thin films under optimal conditions. The effect of annealing temperature on the electrical and optical properties of the ATO thin films has been discussed. The annealing treatments have been often employed to reduce the defects and enlarge the grain size for more desirable crystalline structure. As the annealing temperature increases, the ATO thin films exhibited a slightly enhanced crystallinity. Furthermore, annealing treatment can promote both conductivity and transmittance significantly, especially for conductivity. The X-ray photoelectron spectroscopy is used to explore the variation of Sb5+/Sb3+ ratio against the annealing temperature. The optimal resistivity is 2.7×10-3 Ω cm and the average transmittance is about 92% at annealing temperature of 550 oC.

Abstract: Hot-Press Sintering, a Method that Could Effectively Decrease the Densification Temperature due to the Applied Pressure, Was Employed to Prepare a New Kind of Ho³⁺ Doped Bi₄Ti₃O₁₂ Ceramics, Bi_3.6Ho_0.4Ti₃O₁₂. The Effect of Preparation Parameters on the Crystal Phase, Density and Microstructure of the Ceramics Were Investigated. at First, Single-Phased Bi_3.6Ho0.4Ti3O12 Powders Were Synthesized from Bi2o3, Tio2 and Ho2o3 Raw Powders by Solid-State Reaction and the Optimum Calcined Temperature Should Be 900 °C. The as-Synthesized Powders Were Further Densified at 750-900 °C to Prepare Bi_3.6Ho_0.4Ti₃O₁₂ Ceramics. Dense (relative Density Was 99.4 %) Bi_3.6Ho_0.4Ti₃O₁₂ Ceramics with a Compact Texture Were then Obtained by Hot-Press at 850 °C, about 150-200 °C Lower as Compared with Pressureless Sintering.

Abstract: Transparent Conducting Antimony Doped Tin Oxide (ATO) Films Have Been Prepared on Quartz Substrate by Pulsed Laser Deposition (PLD) Technology. Despite of Extensive Researches of ATO Films Prepared by other Methods, the Study of PLD Technology Is Relatively few. PLD Technology Is Distinctive to Maintain the Elemental Components between the Targets and the Obtained Thin Flms under Optimal Conditions Contributing to Precise Control of Composition and Doping Ratio of ATO Films. The Effect of Sb₂O₃ Doping on the Electrical and Optical Properties of the ATO Films Was Investigated with Various Sb₂O₃ Doping Ratio (mol%) as 2, 4, 6, 8, 10 at 500 °C in an Oxygen Pressure of 8 Pa. The Results Suggest that the Electrical Resistivity Is Firstly Decreased and then Increased with the Increase of Sb₂O₃ Doping Ratio. When the Sb₂O₃ Doping Ratio Is about 6 mol%, the Optimal Electrical Resistivity Is 3.5×10-3 Ω.cm and the Average Optical Transmittance Is 83.1%. It Is Significant to Clarify the Impact Mechanism of Sb₂O₃ Doping Ratio to Get the Best Electrical and Optical Physical Properties. it Is Supposed that the Carrier Concentration Dominates at a Low Sb₂O₃ Doing Ratio while a Scattering Effect Is Performed at a High Sb₂O₃ Doing Ratio.