Materials Science Forum Vols. 620-622

Abstract: In the present work, the effect of plasma treated ZnO nanoparticle on crystallization behavior and properties of polypropylene（PP）/ polylactic acid （PLA）composites filaments has been intensively researched. Our results show that, although the interfacial interaction between PP/PLA and nano ZnO is very weak, addition of nano ZnO and the proportional relations of PP/PLA in composites induced the increase of percent crystallinity. Tensile results showed that nano ZnO /PP/PLA nanocomposites filaments were strain rate sensitive materials and the activation volumes of the nano ZnO /PP/PLA nanocomposite filaments by following Eyring’s equation could be evaluated.

Abstract: In this article, the microstructure, mechanical properties and machinability of the B4C/BN microcomposites and the B4C/BN nanocomposites were investigated. Homogenous distribution of the h-BN particles in the B4C ceramics appeared. The mechanical properties decreased gradually with the increasing content of h-BN for the both composites, while the nanocomposites demonstrated high performance. Machinability increased gradually with the increasing content of h-BN, and excellent machinability exhibited for both composites with more than 20wt% h-BN. The weak interface between the B4C matrix grains and the h-BN particles as well as the cleavage behavior of the laminate structured h-BN particles significantly attributed to the machinability of the B4C/BN composites.

Abstract: A novel and simple approach has been developed for a large-scale synthesis of ZnO nanorods using ultrasound radiation. Double-pod-like ZnO nanorods were directly grown from the starting precursors of zinc nitrate hydrate [Zn(NO3)26H2O] and hexamethylene tetramine (HMT) in deionized water without any templates or seeds. The obtained double-pod-like product had a diameter ranging from 80 to 150 nm and length ranging from 1 to 5 um. Scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM) revealed that these products are of high purity, hexagonal and of single-crystalline structure. The ZnO nanorods synthesized were utilized for gas sensing application. Alumina plate consists of Pt interdigitated electrode was used as sensor substrate. The as-prepared products were transferred to the surface of substrate by screen printing method to fabricate the gas sensor. The sensing properties of the sensor were investigated toward methyl mercaptan (CH3SH). The sensor shows good and fast response towards methyl mercaptan at a fixed operating temperature. The high sensitivity may be ascribed to the high surface area and aspect ration of the double-pod-like nanomaterial.

Abstract: After a preliminary investigation on the binary asphalt/clay binder, the ternary binder was prepared by adding the nanoclay and TAFPACK-SUPER (TPS) to the original asphalt. The previous research shows that exfoliated/intercalated layers homogeneously are dispersed in the asphalt matrix and the nanocomposite has formed. Rotation Thin Film Oven Test (RTFOT) and Pressure Age Vessel Test (PAV) results indicate that the modified asphalt with 3% organic nano-montmorillonite (OMMT) present better performance of aging resistance. The purpose of this research is to attain ternary asphalt binder with better rheological performance and aging resistance. The ternary modified asphalt binder containing 4% OMMT and 12% TPS by weight were prepared at the laboratory scale using high speed shearing mixer. The rheological properties of OMMT/TPS modified asphalt binders were evaluated before and after aging in present paper. Temperature sweep tests and frequency sweep tests were conducted to characterize the rheological properties of modified asphalt using Dynamic Shear Rheometer (DSR). According to the frequency sweep tests, complex modulus master curves were plotted to analysis the rheological properties. The results indicate that nanoclay/TPS/asphalt ternary binders have more excellent performance of rheological and aging resistance at both high and low temperatures, compared with the virginal bitumen and TPS modified asphalt.

Abstract: Single-walled carbon nanotubes (SWCNTs) were dispersed in water with the assistance of polyphenols (resorcinol and pyrogallol). SWCNTs have intrinsic tendency to adsorb aromatic compounds due to π-π dispersion interactions, which leads to SWCNTs noncovalently dispersed in water by adsorption of resorcinol or pyrogallol. The concentration of SWCNT suspension was determined by the absorbance value at 500 nm using UV-Vis spectrometer. The effects of polyphenol concentration and ultrasonication time on the dispersion state have been investigated. Resorcinol of 0.5 mg/mL was found to be most effective for solubilizing SWCNTs in water. Over 60 % of SWCNTs were well dispersed with ultrasonication time for 4 hours. However, SWCNTs were cut shorter and damages could be introduced with prolonged ultrasonication time. TEM images showed that SWCNT bundles became thinner with the presence of polyphenols. These aromatic compounds provide an effective way to disperse SWCNTs in water and might have potential application in nanocomposite preparation.

Abstract: We report the synthesis and characterization of FePt nanoparticles (NPs)/single walled carbon nanotube (SWNTs) nanocomposites, which might have important potential applications to orient CNTs and the development of new catalysts. The crystallite size of FePt NPs is about 2.5-4 nm and the Fe atom content ranges from 50% to 65%. HiPCO SWNTs have been decorated with FePt nanoparticles under mild conditions without any pretreatment. When the bundle size of HiPCO SWNTs is about 20 nm, FePt NPs mostly attach on the sidewalls of SWNTs. The loading of FePt nanoparticles on the SWNTs bundles can be conveniently controlled by adjusting the initial amount of FePt NPs. The nanocomposite showed magnetic properties in a magnetic field. TEM, HRTEM, and EDS spectra were performed to observe the nanostructure of these nanocomposites.

Abstract: X-ray irradiation was applied to control the size of metal colloids in a silicate glass to make a high precise photosensitive glass containing K2O, Na2O, ZnO BaO, 0.01-0.05wt.% Au metal as sensitizer, <1.2wt.% Sb2O3 and SnO2 as thermal reducer. Colorimetry showed that X-ray irradiation effectively works to make the color of red system. Transmission electron microscopy revealed that the metal colloids were oxided and had uniform and spherical shape of 10-20 nm. Au colloid made various colors like pink after heating at 400°C, red at 500°C and dark-red at 600°C. Ag colloid made them like yellow-green at 400°C, yellow at 500°C and dark-brown, respectively.

Abstract: SiC/h-BN nano-composites powder was synthesized using an in-situ reaction method and SiC/h-BN nano-composites were fabricated by hot-pressing. Damage resistance and R-curve behavior of machinable SiC/h-BN nano-composites was evaluated using the indentation- strength-in-bending technique and compared with that of SiC/h-BN micro-composites and monolithic SiC. The results showed that SiC/h-BN nano-composites have better damage resistance and R-curve behavior than SiC/h-BN micro-composites and monolithic SiC.

Abstract: The SWNT/Pt composite with high electrocatalytic property was successfully fabricated through pretreating SWNTs by acid and NH3 treatment. According to the hydrodynamic voltammograms and the current response for H2O2, the SWNT/Pt composite was demonstrated to have faster and more sensitive response than SWNTs, indicating the enhanced electrocatalytic property of SWNT/Pt composite.

Abstract: An aluminization process with controlled Al activity to form surface Ni(Al) zone was applied to fabricate ceramic nanorod array structures by using internal oxidation. The pack cementation with NaCl, Ni3Al and Al2O3 was adapted as the aluminization process to form surface Ni(Al) zone. With increasing Ni3Al concentration in pack powder mixture, Al content of surface Ni(Al) zone was increased. Nanorod array structures can be successfully obtained on Ni components with designed shape.