Advanced Materials Research Vols. 152-153

Abstract: B4C/CNTs and B4C/Ccomposites were prepared by reaction-sintering technique. The density and porosity of the samples were determined and three-points bending strengths of the composites were measured. Wear resistance tests were performed using a HT-500 pin-on-disc tribometer with the sample placed horizontally on a turning table. The morphology of the worn surfaces and fracture of the composites were examined by means of scanning electron microscopy so as to explore the wear mechanisms. The results indicate that B4C/CNTs composites show improved friction and wear properties as compared with B4C/C composites. It is found that CNTs in the specimens play important role in improving the wear properties of the composites. The wear mechanism of the B4C/CNTs composites is characterized by micro-cutting and plowing at ambient temperature, and sub-surface cracking and the resultant localized spalling on the worn surface at the temperatures higher than 500°C.

Abstract: Above all, it is discussed about vibration mechanism of the pipe system being filled with liquid ammonia in a chemical ship, the mathematic equations of pipe vibration are deduced, and finite element model of the pipe system is constructed by means of CAESARⅡ software, then according to constructed model, vibration emulating of the pipe system is done with the help of MATLAB software, and field measuring of vibration is also done in the connection and elbow of the pipe system, dynamic damping project is put forward after the results of emulating are compared with measuring values of vibration in a chemical ship, original pipe system being filled with liquid ammonia is improved on the basis of the dynamic damping project, in the end, vibration values of improved pipe system are tested and analyzed again, the results of testing indicate that adopted dynamic damping project is feasible.

Abstract: In this paper, series of mortar tests with Aeolian sand as its fine aggregate were launched. Result shows that the admixture flyash can effectively improve the liquidity and water capacity, hence to improve the workability of the mortar. As the mortar age increases, with the surface activity of flyash gradually brought into full play, the long-term mortar strength can be ensured. The compound additive with polycarboxylic as the water reducing agent, neopelex as the gas-forming agent and the sodium silicate, reduced the required water by about 15% without changing the consistency of the mortar mixture. United Expansive Agent (UEA) was used to reduce the shrinkage rate of the mortar mixture. The Cost Performance Indicator (CPI) was introduced to evaluate the cost performance of the mix mortar, suggesting that the CPI of the mix mortar is 1.38 times of that of the mortar with river sand. Test results of various index value shows that the mortar mix ratio obtained in this paper can meet the need of plastering and masonry engineering.

Abstract: The surface morphology of the non-conducting granular materials was analysis by SEM under low vacuum conditions. The effects of the incident electron voltage, electronic beam spot size and atmosphere pressure on the SEM image quality and EDX analysis were investigated systematically. The results show that the quality and the resolution of the SEM images both reduce with the increase of the incident electron voltage, the electronic beam spot size and the atmosphere pressure; the errors of the EDS analysis decrease when measured under low vacuum conditions.

Abstract: Influence of different pretreatment methods applied on anaerobic mixed inoculum was evaluated for selectively enriching the hydrogen (H2) producing mixed culture using glucose as substrate. The cumulative H2 yield and H2 production rate were found to be dependent on the type of pretreatment procedure adopted on the parent inoculum. They could be increased by appropriate pretreatment methods, including use of heat, alkaline or acidic conditions. Along with the processing temperature and time of heat pretreatment and alkaline of alkali pretreatment increasing, the H2 yield increased and then declined, but it declined and then increased as the acidity of acid pretreatment increasing. Among the studied pretreatment methods, the heat pretreatment methods procedure enabled higher H2 yield and the maximum H2 production rate, then were alkali and acid pretreatment methods. When the inoculum was heat-treated at 80°C for 30 min, the highest cumulative H2 yield was obtained at 2152.0 mL, which was 53.20% higher than the control, and the maximum H2 production rate was 178.0 mL h-1, which was 122.0% higher than that of the Ctrl (138.0mL h-1).

Abstract: Flower-like CuO nanostructures have been prepared via cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal method. Here, CuCl2•2H2O was used as copper raw material, and sodium hydroxide was used as precipitate. The resulting CuO powders were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). X-ray diffraction (XRD) pattern exhibited the nanocrystalline nature with monoclinic structure for the as-synthesized nanostructures. FESEM images indicated that the flower-like CuO nanostructures are composed of many interconnected nanosheets in size of several micrometers in length and width and 60-80 nm in thickness. The possible formation mechanism of flower-like CuO nanostructures was discussed.

Abstract: Diamond films were deposited on (111) silicon wafers by microwave plasma chemical vapor deposition (MPCVD). The deposition parameters included a system power of 1200 W, chamber pressure of 110 torr, H2 flowing rate of 300 sccm, and a CH4 flowing rate of 15 sccm. The diamond particles measured about 5-6 μm, and morphology analysis revealed a rectangular structure stacked regularly on diamond films after deposition. X-ray diffraction (XRD) analysis detected (220) square structures. Annealing at 600 °C improved the quality of diamond film, making the peak of the Raman spectra at 1350 cm-1 sharper and higher. The (220) and (311) orientation structures on the diamond films decreased after annealing broke the surface morphology. To conduct electric and optical experiments conveniently, the deposited samples were immersed in acid (HNA, HF：HNO3：CH3COOH = 3：25：10) to remove the silicon layers. The HNA acid did not corrode diamond films seriously, but slightly damaged the incomplete (220) and (311) structures.

Abstract: Optically active films were built up from poly(allylamine hydrochloride) (PAH) and R-(+)--phenylethylamine derivatives of poly(ethylene-alt-maleic acid) (PEMA-PEA) with substituting degrees (DS) ranging from 0.48 to 0.97. The growth of the film was monitored with the circular dichroism (CD) and the UV spectrophotometer and the effect of DS of PEMA-PEA on the film was investigated. UV and CD data show the growth regime of the multilayer changing from exponential to linear. Deposition amounts of PEMA-PEA in multilayer films decrease with the increase in DS of PEMA-PEA, which was explained based on the conformation of the polyelectrolyte and the charge overcompensation as the polyelectrolyte was deposited on the surface of the film. These results are of benefit to the development of multilayer films for the chiral separation of enantiomers.

Abstract: Modified Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] was prepared by melt reactive blending P(3HB-co-4HB) with chain extenders (ADR-4367). Thermal transitions, spherulitic and freeze-fracture morphology, mechanical and rheological properties of the chain extended bio-materials were investigated. The results show that glass transition temperatures and crystallization temperatures increase, crystallinity and diameters of spherulites decrease, there are amorphous parts dispersed among the crystalline phase, and the bio-materials transfer from brittleness to toughness and ductility. Steady shear viscosity of the modified P(3HB-co-4HB) increases by about one order of magnitude, melts of the modified P(3HB-co-4HB) behave more viscoelasticity by storage modulus and loss modulus correlated with oscillatory shear frequency. Addition of ADR-4367 with contents of 4~6 wt% in the blends is enough to branching and coupling the co-polymer chains and brings remarkable effect on improving mechanical properties, steady shear viscosity and viscoelasticity.

Abstract: The electronic transport properties of pyrrole trimer sandwiched between two electrodes are investigated by using nonequilibrium Green’s function formalism combined first-principles density functional theory. Theoretical results show that the system manifests negative differential resistance (NDR) behavior. A detailed analysis of the origin of negative differential resistance has been given by observing the shift in transmission resonance peak across the bias window with varying bias voltage.