Advanced Materials Research Vols. 79-82

Abstract: A visible-light-active nitrogen and gadolinium codoped TiO2 catalyst was synthesized by the sol-gel route. For comparison, Gd-doped sample, N-doped sample, and pure titania were prepared through the same method, without adding the corresponding dopants. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD) and Uv-vis spectra. The results showed that the codoped photocatalyst exhibited a smaller size than the undoped titania. The transformation from anatase to rutile was suppressed by doping with N and Gd atoms. Furthermore, the absorbance spectra of N, Gd-codoped TiO2 exhibited a significant red shift to the visible region. The photocatalytic activity of N, Gd-codoped TiO2 was evaluated by photodegradation of methyl orange under visible light irradiation. This codoped sample exhibited enhanced photocatalytic activity compared to N-doped TiO2, Gd-doped TiO2, and pure TiO2. The improvement of the photocatalytic activity was ascribed to the synergistic effects of the N and Gd co-doping.

Abstract: This study investigates the use of the microwave thermo-ethanol method to recover cuprous oxide from waste liquid that contains heavy metals, formed by the leaching of acid from sludge of printed circuit boards. An XRD analysis yields main peaks of cuprous oxide 2θ = 36.45° and 42.35°. SEM analysis indicates that the cuprous oxide was octahedral when 0.1 M glucose, or a higher concentration, was added to the waste liquid. The purity of prepared powder of cuprous oxide was analyzed using an inductively coupled plasma-optical emission spectrometer (ICP-OES), and the purity of the prepared powder of cuprous oxide was found to exceed 70%. Accordingly, in this study, metallic resources were regenerated.

Abstract: , 1,3-bis(3-aminopropyl) tetramethyl disiloxane (DS) is used as liquid epoxy curing agent of epoxy molding compounds(EMCs) for high-reliability semiconductor devices. Experimental results indicated that DS could be effectively used as epoxy curing agent and greatly lower the viscosity of epoxy system, in which way, the coefficient of thermal expasion(CTE) of EMCs can be lowered effectively by increasing the filler loading. The concentration of DS strongly affected the mechanical properties of the thermally cured epoxy composites. As expected, the flexural modulus of epoxy composite decreased and the toughness was improved.

Abstract: The microstructure of a twin roll cast (designated as TRC in short) and warm rolled Mg-4.5Al-1.0Zn (designated as AZ41 in short) alloy was investigated using OM and TEM after annealing treatment at the temperature range of 300oC~400oC. Tensile test was performed to show the influence of the annealing treatment on mechanical properties. The microstructure of AZ41 alloy sheet consisted of fibrous structure of elongated grains and shear bands along the rolling direction. Static recrystallization (SRX) was observed at and above 300oC during annealing treatment process. Shear bands, dislocations and twins play an important role during SRX and serve as nucleation sites, this leads to grain refinement. The sheet had higher strength and lower elongation after warm rolling. However annealing treatment after warm rolling induced the decrease of strength and increase of elongation. This results in the balance of strength and elongation in AZ41 alloy sheet. Annealing treatment at 400oC for 40min can be considered to be the optimum annealing treatment, and at this condition the tensile strength, yield strength and elongation are 375MPa, 285MPa and 17.7%, respectively.

Abstract: Ca2Co2O5 ceramic powders were synthesized by the coprecipitation method and consolidated by spark plasma sintering (SPS) technique.The observation by the SEM indicated that the ceramics body showed fine and layer microstructure.The density of the body increased with an increase of the fritting temperature.XRD patterns showed that the ceramics sample exhibits inpure phase with increasing the sintering temperayure to 850°C and that the grain was preferentially oriented.The electrical conductivity was reduce and the Seebeck coefficient slightly increased with an increase of the sintering temperature.As a result,the thermoelectric properties of the sample prepared by SPS at 800 °C for 5 min was better than the sample prepared by SPS at 750 °C for 5 min at high temperature.The sample treated by the SPS process under the condition of 800 °C,40 MPa and 5 min showed the maximum power factor (PF) of 3.85×10-4W∙m-1∙K-2 at 923 K.

Abstract: This paper introduces a sound absorption structure named as MPA/MR which is a combination of the MPA and Metal Rubber (MR) material. On the basis of Rayleigh model and sound propagation theory in pipe, according to the acoustoelectric analogy method, the theoretical acoustic model of MPA/MR is established, and the formula of absorption coefficient is derived. The multi-function standing wave tube with two microphones was used to obtain acoustic characteristics of MPA/MR experimentally, and the effects of the parameters were analyzed as well. The investigation indicates that MPA/MR can be applied with a broad range of application prospects.

Abstract: In this study, the aluminizing of high silicon cast iron by hot-dipping in pure Al melt was performed and their high temperature oxidation behaviour was tested at 750 °C for virous exposure time. After high temperature oxidation tests, the microstructure analysis of all samples were investigated by means of metallographical examination, scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectrometer (EDS) and X-ray diffractometry (XRD).The results showed that the coating layers consisted of three layer, in the sequence of Al, Fe-Al and Si-rich layers from external topcoat to substrate. Nodules graphite had a blocking effect to retard the outward diffusion of Fe atoms and impeded the growth of Fe2Al5 in C-axis. Eventually, the cast iron substrate was oxidized directly by oxygen penetration via the greater cracks and pores to form Fe oxide nodules after 750 °C oxidation for 48h.

Abstract: A 3, 4-dihydroxyphenethylamine (dopamine) polymer film has been prepared on copper surface from 2.0g/L dopamine solution in tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffer solution at pH 8.5 by a simple solution-immersion method. The dopamine self-polymerized and adhered to the copper surface firmly in aqueous environment. The film surface was evaluated through SEM, EDS, XPS and contact angle measurement. The results have shown that the film was indeed formed on copper surface. And this research offers a versatile approach for the surface modification.

Abstract: SrTiO3- (STO) thin film has been deposited epitaxially on the (100) oriented, 0.1 wt % Nb-doped SrTiO3 (NSTO) substrate using the pulsed laser deposition technique. The current-voltage (I-V) characteristics of STO/NSTO heterojunction at various temperatures had been measured. A rectifying behavior similar to conventional diodes was observed. For the forward bias, the conduction mechanism changes from Ohmic-like for the low bias voltages to space charge limited current for the high bias voltages. The results were explained by considering the band structures of the heterojunction and the role of space charge layer formed at the interface between STO and NSTO. Our results demonstrate that the interface formed between two oxide materials plays an important role on transport characters of the system and can lead to some potential applications in future microelectronic devices based on combination of two perovskite oxide materials.

Abstract: This paper describes an effect of fluctuation in fiber orientation on Young’s modulus of the so-called green composites. The composites were reinforced with slivers of high-strength natural fibers extracted from plants named curaua. Then a surface optical micrograph of the composites with the fiber fluctuation was obtained. The micrograph was divided into many fine segments, and the fiber orientation angle in each segment was measured. Then, a new concept which takes account of the fiber orientation angles as a probability distribution, was proposed for prediction of the Young’s modulus. The results showed that the predicted Young’s moduli were in a good agreement with the experimental results.