Advanced Materials Research Vols. 306-307

Abstract: We report an easy and scaleable approach to produce single and double layer graphene (Gr)-sheet from re-exfoliation of expanded graphite (EG) with large area. Transmission and scanning electron microscopic observations show that the Gr-sheets have an area of ~ (12 x 10) μm². Raman spectroscopy has confirmed the presence of single and double layer Gr-sheet with I_2D/I_G ratio as ~ 1.7. Scanning probe microscopy studies reveals that on re-exfoliation of EG, thickness of Gr-layer decreases from 6-7 nm to 0.8-1.1 nm. This infers that re-exfoliation overcomes the problem of insufficient oxidation or inadequate pressure buildup during heat treatment.

Abstract: A flow injection chemiluminescence (CL) method has been developed for the determination of indoleacetic acid (IAA). It is based on the fact that the weak CL of Ce(IV)-Ru(phen)32+ system is strongly enhanced in the presence of silver nanoparticles. Optimum conditions and possible mechanisms have been investigated. Under optimum experimental conditions, the linear range is from 1.0×10-8 – 6.0×10-7 g mL-1 with a detection limit 9.0×10-9 g mL-1

Abstract: This paper investigates mechanism of tribological behavior of carbon nanotubes by using universal tribometer-II and molecular dynamics simulations. The experiment results indicate that multi-walled carbon nanotubes film with mixed acid treatment has better surface quality and less impurities but higher friction than pristine carbon nanotubes film. The reason is that mixed acid treatment introduces carboxyl group and more defects which increases dangling bonds of carbon nanotubes. Breaking of dangling bonds increases friction force when sliding and shearing occurs. Molecular dynamics simulation of shearing between silicon surfaces and single-walled carbon nanotube bundles without defect shows low lateral forces because only van der walls force exists between silicon surfaces and carbon nanotubes owing to no dangling bonds. The result is consistent to the conclusion inferred from experiment. Therefore excellent performance is expected when carbon nanotubes treated with little defects are used as lubricant or addictives.

Abstract: In this paper, the precursors were synthesized by microwave hydrothermal method using SnCl4•5H2O and Ce(NO3)3·6H2O as raw material, CO(NH2)2 as precipitants, respectively. Pure SnO2 nanoparticles and cerium-doped SnO2 nanoparticles were obtained. Furthermore, five kinds of SnO2 thick film gas sensors were fabricated from the above SnO2 nanoparticles (the sensors denoted as sensor SC0, SC2, SC3, SC4 and SC6, respectively). The experiment results showed that, compared with pure SnO2 thick film gas sensor, the intrinsic resistance of cerium-doped SnO2 thick film gas sensors decreased, and their sensor responses to acetone vapor increased, which are discussed in relation to the SEM micrographs of thick film sensors.

Abstract: Wormhole-shaped F-doped TiO₂/Ti photoelectrodes were prepared by microarc oxidation method in NaF solution. The morphology and structure of the photoelectrodes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray fluorescence (XRF). It was found that F-doped TiO₂/Ti photoelectrodes were porous and composed of anatase TiO₂. The photocatalytic properties of F-doped TiO₂/Ti photoelectrodes were investigated by photodiscoloration rate of Rhodamine B(Rh.B) under different conditions. All results showed that the photoelectrodes prepared at voltage of 160V, NaF concentration of 0.01mol/L and oxidation time of 10min have optimal photocatalytic performance. Rh.B was almost completely removed by F-doped TiO₂/Ti photoelectrodes after 120min under the illumination of artificial visible light.

Abstract: A research program was simulated to study the effects of pouring temperature, squeeze pressure and die temperature on the tensile, elongation and hardness properties of AZ91D magnesium alloys using anycasting software. The curves with different processing parameters on mechanical properties have been painted. The results indicated that mechanical properties increased firstly, then decreased when the pouring temperature increased to 670°C, and gradually increased with the increasing of squeeze pressure. The affect laws of mould temperature are similar as ones of pouring temperature. Eventually found that the squeeze casting got better mechanical properties(σb= 225MPa, δ= 3.6%, Vickers hardness=62) on the pouring temperature 670°C, mold temperature 180°C, holding pressure 120Mpa, pressure duration 25s.

Abstract: A series of La₂Sn_2-xFe_xO₇ (x=0, 0.2, 0.6, 1.0, 1.4, 1.8, 2.0) catalysts were prepared by a constant pH co-precipitation method, and their catalytic activity was investigated for simultaneous removal of NOx and soot. The incorporation of Fe strongly influences the crystal phase composition, surface area and redox properties of the catalysts. All the catalysts displayed soot oxidation activity with nearly 100% selectivity towards CO₂. The doped solids exhibit higher activities than the undoped one, which may be related to the enhancement of reducibility derived from structure defects induced by doping. LSF0.6 may be a good catalyst with high soot oxidation activity (T_i = 334 °C) and a high maximum productivity of N₂ (P_N2= 12.4%).

Abstract: One new kind of cementitious material, which is suited to paste filling in coal mine, was introduced. The paste filling slurry, which is mixed with extremely small amount(about 50 kg/m³) of the material, can be solidified quickly and reach the strength requirement of none -village-relocation coal extraction engineering. The solidified body is provided with typical plasticity, high elastic modulus and strain hardening even under the condition of very small surrounding stress.

Abstract: In this paper, an Infrared Sulfur Analyzer is set to measure the desulphurization degree during thermal decomposition of phosphor-gypsum, which provides a much quick, convenient, continuous and accurate method. It might be considered as an effective way to study kinetics of phosphor-gypsum (or phosphogypsum) thermal decomposition (or pyrolysis). With the help of this method, the desulphurization degree and desulphurization rate of broadly constituted phosphor-gypsum samples in the temperature range of 1250-1400°C were studied. The experimental results show that the desulphurization degree increase with the rising of temperature in the range of 1250-1300°C quickly, however, this increase is not obvious when the temperature is above 1300°C. Besides, the corresponding regression equations are obtained. The decomposition degree of phosphor-gypsum could be judged according to the regression equations mentioned above.

Abstract: Ecological crystal glass with no toxic compounds, especially lead, was based on soda-lime-silica glass that fabricated mainly from 50 wt% local dressing sand, 22 wt% barium carbonate and doped with various concentrations of zirconium dioxide. Density (ρ), refractive index (RI), thermal expansion coefficient (CoE) and hardness (HV) were measured. It was found that the values of ρ, RI and HV increased linearly as the increasing of zirconium dioxide contents, whereas the CoE was decreased. This type of glass was ecologically friendly material.