Advanced Materials Research Vols. 47-50

Abstract: The carbon fiber (CF) reinforced butadiene rubber (BR) electromagnetic shielding composite has been prepared by mechanical agitation and roll mixing methods. The composites have been characterized and tested. As shown in the experimental results, the mechanical properties was increased with the increase of CF, and the electromagnetic shielding effectiveness (SE) of BR based composite with 15 wt% CF content has been tested, the maximum SE was about 60 dB.

Abstract: Si3N4/polyimide hybrid films based on 4,4-oxydianiline (ODA) and pyromellitic dianhydride(PMDA) were prepared by incorporation with different content of nano-sized Si3N4. In this study, the effect of Si3N4 on the microstructure of the Si3N4/polyimide film was characterized by Fourier Transform Infrared Spectrometry (FTIR), scanning electron microscope (SEM). The dependence of mechanical properties and thermal stability of the Si3N4/polyimide film were also investigated. The hardness from unload of the Si3N4/polyimide film were expressly investigated for the first time.

Abstract: Phlogopite with layered silicate structure had been firstly chemically modified via an in situ intercalation method, and phlogopite-polymer nanocomposite films were prepared from 2,2'-bis (3,4-dicarboxyphenyl) hexafluropropane dianhydride (6FDA) and oxydimethyl aniline (ODA) in N,N-dimethylacetamide as a solvent by using in-situ polymerization process combined with ultrasonic dispersion and multi-step curing. The structure of phlogopite minerals and its polymer nanocomposites were characterized by X-ray diffraction (XRD) and infrared spectra (FTIR) respectively. The experimental results indicated that the phlogopites with layered nanostructure had lost their ordered structure and had been exfoliated or intercalated. Thereafter, they were dispersed randomly in the polyimide matrix. The dependence of dielectric properties and thermal stabilities of the nanocomposite films on the phlogopite content and frequency were studied.

Abstract: This work presented the electrochemical reduction of platinum (Pt) and ruthenium (Ru) nanoparticles within multiwalled carbon nanotube-Nafion (MWCNT-Nafion) composite for electrochemical oxidation of methanol. The structure of the resulting Pt-Ru-MWCNT-Nafion nanocomposite was characterized by scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. Electrochemical properties of Pt-Ru-MWCNT-Nafion nanocomposite were investigated by cyclic voltammetry in a 2 M CH3OH + 1 M H2SO4 aqueous solutions. The Pt-Ru-MWCNT-Nafion nanocomposite modified electrode had high electrocatalytic activity and performance toward the methanol electrooxidation as compared with Pt-MWCNT-Nafion nanocomposite modified electrode.

Abstract: Using commercial Ti powders and recycled TiH2 powders made from titanium turning chips, the effects of hydrogen on microstructures and oxygen reduction were investigated. Each powder was hot-pressed at 750oC and 1100oC, which are below and above β-transition temperature (880oC), respectively. The TiH2 and Ti samples of sintered at 1100oC showed equiaxed α phase. However, TiH2 sample sintered at 750oC consist of primary α phase, secondary α phase and titanium hydride (TiH2), though Ti sample represented single α phase. The formation of complex microstructure in TiH2 sample sintered at 750oC is due to hydrogen remained after sintering. The oxygen contents after sintering in TiH2 samples were relatively lower than Ti samples, although those before sintering were higher than Ti. This result can be explained that hydrogen gas generated from dehydrogenation of TiH2 leads to the reduction of oxygen contents and protection of re-oxidation during sintering.

Abstract: This research described the optimization of the process parameters for clad coating of alumina (Al2O3) powder on AISI 1018 mild steel utilizing plasma non-transferred arc cladding process using Taguchi method and Pareto ANOVA analysis. Four factors were selected which were plasma arc current, plasma torch velocity, distance between nozzle and layer and ratio of alumina powder to binder. The analysis of the results showed that the optimal combination for high microhardness were distance between nozzle and layer at 3 mm and plasma torch velocity at 0.03 mm.

Abstract: Experimental results showed that both of commercial pure titanium (CP-Ti) and yttria-stabilized zirconia (YSZ) intermediate layers significantly enhanced the bonding strength of HACs (one-way ANOVA test, p < 0.05). On the basis of fracture morphologies and bonding strength data fluctuation, the Weibull model provided a powerful statistical analysis for assessing the failure mechanism and the reliability of composite coatings. Plasma-sprayed HACs were reliable materials with a right-shift wear-out failure model (m > 3) of increasing failure rate (IFR). The HA composite coatings remained in tack on the substrate, which represented better reliability and less dissociation for further applications. The measured bonding strength of HACs was a combination of adhesive and cohesive strength of a coating layer. The area fraction of adhesive failure tended to decrease with introducing the reinforced intermediate layer, especially for the HA/YSZ composite coating. The decrease of adhesive failure area fraction represented good interlocking between the coating/substrate interfaces. The knowledge of fracture behaviour in HACs with reinforced intermediate layers will be very helpful for the understanding and prediction of the bonding strength.

Abstract: Electric field-polarization interaction shows nonlinear effects in the constitutive relations. In this study, an attempt is made to include these interaction effects in the finite element formulation. A layer-by-layer finite element code is developed to handle the linear and nonlinear problems. Linear and nonlinear analysis is carried out for a smart plate with surfacemounted distributed piezo layer. The nonlinearity leads to a significant increase in the transverse deformation.

Abstract: A 2.45 GHz microwave atmospheric pressure torch is employed to prepare cuprous oxide films. The sputtered copper films are firstly deposited on slide glass. After that, the films are annealed in air at 500°C for 12 h, which would directly oxidize into cupric oxide. The annealed films are then treated by atmospheric nitrogen plasma at 800 W for 10 min. The color changed significantly from black to reddish brown after nitrogen plasma treatment. The X-ray diffraction patterns show that annealed films are cupric oxide which is vanished after plasma treatment. The cuprous oxide films appeared after nitrogen plasma treatment. The resistivity of annealed films is 16.7 --cm, which reduce to 2.08 --cm after plasma treatment. The optical band gap of annealed films, cupric oxide phase, is 2.1 eV but the value shifts toward 2.4 eV after plasma treatment. The novel microwave plasma torch posses a fast and easy way to fabricate cuprous oxide films.