Advanced Materials Research Vols. 148-149

Abstract: Highly-ordered titania nanotube arrays were fabricated in ethylene glycol polar organic electrolyte containing a certain amount of sodium fluoride. Series of patterned nanotube arrays with different outside diameter and aspect ratio were obtained via optimizing anodic voltage, the concentration of fluoride ion and reaction time. The as-prepared nanotube arrays were amorphous and transformed single anatase phase characterized by X-ray diffraction with annealing under the condition of 450oC for 3h. Cyclic voltammogram behaviors were discussed using electrochemical workstation. The pH value of electrolyte, the scanning rate, the crystal structure and morphology of the samples have a significant effect on the reductive/oxidative and H+ intercalation properties.

Abstract: The Single-walled carbon nanotubes were coated with Ni-P layers by an electroless plating technique. A Ni-P layers are thick and smooth and on individual nanotube with thickness of 20 nm can be obtained after the deposition process. The Single-walled carbon nanotubes were obtained in the suspension of purification solution. The samples have been characterized by X-ray diffraction, selected area electron diffraction, transmission electron microscopy and energy dispersive spectrometry.The coating layers after heat-treatment convert the amorphous Ni-P coated layers into the nanocrystalline Ni-P layers.

Abstract: In structural health monitoring, evaluation of bridge serviceability performance is based on vibration method. The vibration properties are influenced by temperature, humidity, wind and traffic load. Temperature differential in rigid frame bridge causes additional stress, which affects dynamic characteristics and induces concrete cracks. Thus analysis of temperature distribution is the basement of damage identification. Fiber Bragg grating (FBG) sensors are advanced materials for SHM. This paper introduces a temperature sensor monitoring system consisting of 52 temperature sensors on a twin-deck continuous rigid frame concrete bridge and analyzes temperature distribution on the twin decks of the bridge through August to December, 2006. Temperature at the same height sections differs little in the longitudinal direction along this bridge. The comparisons between maximum and minimum temperature each month reveal the asymmetry of transverse temperature distribution. The pavement has significant impact to the top slab temperature. In November the temperature declines sharply. The temperature on the external surface of top slab is lower than that of bottom for short box girders in winter because of shelters of flanges.

Abstract: In this work, Praseodymium (Pr) doped bismuth sodium titanate, (Bi0.5Na0.5)TiO3 (BNT) is successfully produced using the soft combustion technique. The effects of Pr doping on stoichiometry, microstructure, density and dielectric properties are studied. Pure phase can be obtained in all samples containing 0, 5, 10 and 20% Pr after calcination at 800°C for three hours. The powders are then pressed into pellets and sintered at 1050°C for three hours. The crystallite size and grain size decrease with increasing Pr amount because Pr acts as grain growth inhibitor. Maximum density is obtained in 5% Pr doped BNT, beyond which density decreasing. Maximum dielectric constant of 756 was obtained in 5% Pr doped BNT and decreases beyond that. Pr doped in BNT also causes dielectric loss to decrease. The result is in agreement with structural, microstructure and density analysis.

Abstract: Titanium dioxide powder co-doped by Fe 3+and N was prepared in sol-gel method with tetrabutyl titanate as raw material, iron(III) nitrate as source of ferrum, urea as source of nitrogen. The structure and properties of catalysts were characterized by XRD, XPS, DSC, FS, UV-Vis respectively, where XRD represents Fe/N-TiO2 species calcined at 500°C are classified into anatase pattern with average 17nm diameter of TiO2 crystal; XPS shows iron and nitrogen species dope into the lattice of TiO2 framework; DSC indicates phase transition temperature 440°C of the doped TiO2 from amphorous crystalline into anatase and the dopants have a limited effect on transition temperature; UV-Vis reveals stronger absorption of doped TiO2 than that of TiO2 in visible region and red shift of 70nm to 450nm; FS proves poorer electron-hole recombination. On basis of degradation of methylene blue, photocatalytic activities of various catalysts are investigated to identify maximum decolorization at 2g/L of the doped TiO2, i.e., 92% of decolorized efficiency at 2h ultraviolet illumination and 60% decolorized efficiency at 5h visible illumination.

Abstract: High surface area porous silicon carbide was synthesized by a modified sol-gel method. In the sol-gel method, furfuryl alcohol and tetraethoxysilane were used respectively as carbon and silicon precursors for preparing a carbonaceous silica xerogel. Polymethylhydrosiloxane (PMHS) was employed as pore-adjusting agent in the sol-gel process. SiC was obtained by the carbothermal reduction of the carbonaceous silica xerogel at 1300 oC in argon flow and then purified by removing excess silica, carbon and other impurities. XRD、FTIR、SEM、HRTEM and BET were used to characterize the SiC samples. The results show that the SiC products are found to have high specific surface area of 135 m2 /g. PMHS has important effect on the surface area, pore volume of the SiC products. It is therefore suggested that PMHS plays the role of structure-directing agent that enhances the production of mesoporous pores in the SiC products.

Abstract: After FBG was protected and embedded into cement mortar, the stresses and strains on the FBG ,protected layer and cement mortar under varied temperature were analyzed in theory. In order to verify the theoretical analysis of stress and strain,a finite element analysis software(ANSYS)was used to simulate the stresses and strains on the FBG ,protected layer and cement mortar. The results of theoretical analysis matches the ones form simulations well.

Abstract: The stresses and strains on the protected FBG and protected layer under varied temperature were analyzed in theory. In order to verify the theoretical analysis of stress and strain,a finite element analysis software(ANSYS) was used to simulate the stresses and strains on the protected FBG and protected layer. Both simulation and theoretical analysis are show that the strain and stress on protected layer in r direction decreases with the increasing of radius(r), while the strain and stress in direction increases with the increasing of radius(r) . The results of theoretical analysis matches the ones form simulations well.

Abstract: This paper presents a cylindrical Shape memory alloy (SMA) fan clutch for automobile cooling system application. The resilience of pre-strain 2% SMA alloy wire is analyzed in the processes of heating and cooling. The Design method of SMA helical spring is described. The expression of transmission torque provided by SMA spring is established. The relationship between transmission torque and temperature is analyzed in detail. The results indicate that the transmission torque increases gradually with the increasing of airflow temperature and decreases with the decreasing of airflow temperature, respectively. The cylindrical SMA fan clutch has the property that its transmission torque changes rapidly according to the temperature of airflow from radiator.

Abstract: Nano rice starch was synthesized by ultrasonic-assisted inverse suspension polymerization, using N,N-methylenebisacrylamide (MBAA) as the cross-linker, span 80 as the emulsifier and soybean oil as the oil phase. The effects of starch concentration, oil/water ratio, ultrasonic power and ultrasonic time on adsorption of methylene blue were studied separately. The optimal conditions were obtained as followings: starch concentration 2%, ultrasonic power 320W, ultrasonic time 30min and oil-water ratio 8:1. Under above conditions, the average diameter of the prepared nanoparticles tested by particle size analyzer was 96.2 nm.