Materials Science Forum Vols. 675-677

Abstract: High current pulsed electron beam (HCPEB) has been developed as a useful tool for surface treatment of materials. In the present work, the fundamental principle of HCPEB source was described along with the device configuration and working parameters. Through the different kinds of HCPEB surface treatment experiments conducted, the enhanced surface properties induced by HPCEB treatment were illustrated and explained with their microstructure characterization results.

Abstract: Indium Tin Oxide (ITO) films on PET substrate sandwiching Al2O3 buffer layers with different thickness have been prepared by magnetron sputtering at low deposition temperature. The crystal structures, electrical and optical properties of ITO films have been investigated by XRD, four-point probe technology and UV-Vis spectrophotometer as a function of different Al2O3 buffer layers thickness, respectively. XRD reveals that there is an amorphous structure in ITO films with no buffer layer. However, ITO films became crystalline after sandwiching the buffer layer. It can be found that there are two major peaks, (222) and (400) of ITO film. A smallest resistivity of 3.53×10-4 Ω.cm was obtained for ITO film with Al2O3 buffer layers thickness 75nm. The average transmittance of ITO/Al2O3/PET films in the visible range of 400-760nm wavelength was around 80%. It can be conclude that the (222) orientation of ITO film is more in favor of low resistivity.

Abstract: In this paper, a new method named infiltration was applied to fabricate W-Cu surface modified layers of copper mould firstly in order to promote the life span of the continuous casting machine (CCM) mould. Our efforts concentrated on fabricating the W-Cu modified layers on the surface of mould copper plate by presintering and infiltration under inert gases. The W particle size and sintering temperature of W skeleton were adjusted to gain homogeneous microstructure of W-Cu modified layers. The results show that homogeneous microstructure of W-Cu modified layers can be obtained with the method of presintering and infiltration. For the excellent microstructure of W-Cu modified layers, the suitable tungsten particle size is 300 meshes and the optimal presintering temperature is about 1300°C. W-Cu modified layers have good bonding strength with copper substrate.

Abstract: This paper provides a nondestructive method for determination of the density, thickness and velocity of homogeneous coating from an inversion of experimental ultrasonic reflection coefficient amplitude spectrum (URCAS). The detailed analyses of the inverse algorithm and sensitivity of URCAS to the density, thickness and velocity are presented, and the sensitivity is identified as a basis for selecting the experimental data used in inversion. An example of the method and experimental measurement for comparison was given for an epoxy coating with the thickness of 0.277 mm. The relative errors between the inversion and reference value of the density, thickness and velocity were found to be 0.5 %, 3.97 %, and 0.97 %, respectively.

Abstract: Ultrasonic testing porosity of TBC (thermal barrier coating) has been investigated by numerical simulation based on the implementation of FDTD (Finite Difference Time Domain) method for the RPM (random pores model). Numerical simulations of measuring ultrasonic longitudinal and transverse velocities were carried out for the plasma sprayed ZrO2 coatings with porosities ranging from 0.5 % to 4 %. The results show both longitudinal and transverse velocity decrease with the increase of porosity, which is similar to the experimental results in the reference (J. Thermal Spray Technol 12 (2003) 530-535). The investigation proves that the combination of the RPM and FDTD method is available for simulating ultrasonic testing of TBC porosity.

Abstract: ZrC-Zr2Si coating was prepared on carbon fiber reinforced silicon carbide matrix composites (C/SiC) by pack cementation method to prevent these composites from oxidation. SEM, EDS and XRD were applied to analyze the surface and cross-section morphologies, element distribution and phase composition of the coating, respectively. The results show that the coating made by the technique exhibits excellent oxidation resistance. The optimizing infiltration composition and process was: 60wt.%Zr-Si, 30wt.%PCS-DVB, 10wt.%Al2O3, holding 8 hours at 1400°C in Ar protecting atmosphere, ZrC-Zr2Si coating is obtained, homogeneous and density. The weight loss percentage of the coated C/SiC is only 1.52％after oxidation in air at 1500°Cfor 30min.

Abstract: In the present work, 2-step mechanical coating technique (2-step MCT), an advanced MCT, was proposed and carried out to form TiO2/Ti composite photocatalyst film with anatase TiO2. The microstructures and photocatalytic activity of the composite film were investigated. The results show that the proposed 2-step MCT is a simple process for forming TiO2/Ti composite film. The composite film has a microstructure with a nonuniform thickness, like random distribution islands. The TiO2/Ti composite film has high photocatalytic activity, which is related with crystallinity and volume of the TiO2 in the composite film.

Abstract: In the present work, heat oxidation treatment was carried out for improving the photocatalyst activity of TiO2/Ti composite film. The microstructures and photocatalytic activity of the composite film were investigated. Effect of heat oxidation treatment was discussed. The results show that crystallinity of TiO2 in the composite film was improved by heat oxidation treatment. The photocatalyst activity was increased owing to the improvement of TiO2 crystallinity by heat oxidation treatment.

Abstract: The polyimide/multi-walled carbon nanotubes (MWNTs) nanocomposite films were prepared by means of ultrasonic blending and in-situ polymerization. MWNTs were modified with mixed strong acid in order to improve the chemical compatibility between polyimide matrix and MWNTs. The effects of the incorporation of MWNTs on the electrical property were researched in this study. The results showed that with the increase of the content of acid-modified MWNTs, the dielectric strength decreased gradually and had a sharp drop when the addition content was close to 0.6 wt%, the dielectric constant and the dielectric loss factor increased obviously. With the rise of the test frequency, the dielectric constant declined slowly and the dielectric loss factor increased. The corona resistance time of the nanocomposite films was all higher than that of the pure polyimide.

Abstract: In this paper, MWNTs (multi-walled carbon nanotubes) were modified by the mixture acid of H2SO4 and HNO3, the PI (polyimide)/MWNTs nano-hybrid films were prepared by means of ultrasonic vibration and in-situ polymerization. The surface morphology was characterized by SEM, the chemical structure was characterized by FT-IR. The tensile strength and Young’s modulus increased at first and then decreased with the increase of MWNTs content. The dielectric constant was tested at a frequency of 1 kHz. The dielectric constant had no obvious variation when MWNTs content was less than 2.9 wt%, as the MWNTs content exceeded 5.36 wt%, the dielectric constant increased rapidly. In general, the dielectric loss of PI/MWNTs nano-hybrid films was higher than the dielectric loss of pure polyimide films. The dielectric loss increased slowly in low frequency region but rapidly in high frequency region. All the test results were attributed to the dispersion degree of MWNTs doping and the combination degree between PI matrix and modified MWNTs in PI/MWNTs nano-hybrid films.