Advanced Materials Research Vols. 399-401

Abstract: Abstract: Using laboratory-made nano-scale r–AlOOH as nanophase raw material, the compounding method characterized by direct solution-blending was adopted to prepare epoxy resin/AlOOH nano-composite material; the influences of various factors, such as the dispersion characteristics of nano-scale AlOOH and its content in composite material, on mechanical and flame retardant properties of composite material were studied. The result indicated that the epoxy resin/AlOOH nano-composite material, compared with the ordinary Al(OH)₃/epoxy resin composite material, possessed excellent mechanical and flame retardant properties. When the content of AlOOH was 10%, the tensile strength and the breaking elongation rate of composite material was increased by 189% and 468%, respectively. When the mass ratio of AlOOH/epoxy resin was 70/100, the impact strength was increased by 59%; after it decreased to about 60/100, the vertical combustion reached the level of V-0.

Abstract: Hollow sodalite spheres were prepared in water-soluble polymer polyacrylamide hydrogels (PAM) which were used as "soft template". The samples were characterized by XRD and SEM. The influence of the contents of initiator (ammonium persulfate) and crosslinker (N,N’-methylene-bis-acrylamide) on the size and morphology of hollow sodalite spheres was investigated. The results showed that the pore sizes of hollow sodalite spheres significantly decreased and the shell thicknesses thickened as the amount of initiator increased. The amount of MBAM affected the crystallization of sodalite, stacked arrangement and hollow structure. When the amounts range of MBAM was 0.8%-1.6%, hollow sodalite spheres were non-friable and smaller than the others, and their arrangement was uniform and orderly.

Abstract: Nanoscale copper particles were synthesized by chemical reduction with polyvinyl pyrrolidone as dispersant, ascorbic acid as reduction agent, copper sulfate pentahydrate and ammonia as reagent. X-ray diffraction (XRD) analysis revealed that as-prepared copper nanoparticle was well crystallized without other impurities. Transmission electron microscopy (TEM) displayed that nanoscale coppers had homogenous distribution and the particle size was about 30~50 nm. Uniform and stable Cu-nanofluids were prepared by general stirring, high speed shear stirring and ultrasonic, with water/ethylene glycol as base fluid and as-synthesized copper nanoparticles as additives. The thermal conductivity of Cu-nanofluid was measured by a short-hot wire method. The results showed that the thermal conductivity of Cu-nanofluid was increased 8~9% compared to base fluid and the temperature had little effect on the enhancement of the thermal conductivity.

Abstract: This As a new type of nano-carbon materials , CNTs have special structure and exhibit excellent mechanical properties, electrical properties, electromagnetic properties, the unique micro-structure, high aspect ratio and high specific surface area. So CNTs have great potential value in many areas. However, there are a large number of catalyst particles and amorphous carbon particles in CNTs during preparation. So carbon nanotubes must be purified before used. This thesis studied the purity of CNTs by microwave technology, improved the surface of the carbon nanotubes, strengthen the structure and properties of carbon nanotubes, reduced the impurities of CNTs, the pretreatment of CNTs has been expanded and got the best parameter of microwave technology

Abstract: X-ray diffraction (XRD) and differential thermal analysis (DTA) as well as heat treating method etc have used to study the material characteristics of ultra-fine serpentine powder and analyze its material science bases for the improvement of tribological intervention behaviors of friction pair surface. The ultra-fine serpentine powders are taken as lube oil additive in present experiment. The friction coefficient is tested on the four-ball and ring-on-block friction pairs under different working conditions, and the surface topography of friction pair are observed and measured with scanning electron microscopy (SEM) and three dimensional white light interfering profilometer. The results indicate that the ultra-fine serpentine powders as lube oil additive can significantly improve the antifriction properties of the lube oil. The content of the added ultra-fine serpentine powders can affect on the antifriction performance of the lube oil.

Abstract: The (Co₂MnSi)_1-x-(NiO)_x (x = 0.0, 0.1, 0.2, 0.3) nanocomposites were fabricated by mechanical alloying using Co₂MnSi Heusler alloy and NiO nanoparticles. It is revealed that antiferromagnetic NiO nanocrystallines dramatically enhances the magnetoresistance of the nanocomposites more than 20 times larger than that of the NiO-free Co₂MnSi alloys at 300 K. The Exchange bias effect of the nanocomposites suggests that the spin-dependent tunneling and scattering at the interfaces of ferromagnetic/antiferromagnetic are responsible for the enhancement of the magnetoresistance.

Abstract: Mesostructured nickel phosphate was synthesized with urea as alkali by sol-gel method. The obtained material nominated as NiPO-3 was characterized by means of XRD, ICP, FT-IR, TEM, and N₂ adsorption. In contrast to mesoporous nickel phosphate NiPO-1 and NiPO-2 we reported before, NiPO-3 exhibits relatively longer nanotubes reached up to 400~600 nm. N2 adsorption shows that NiPO-3 possesses high BET surface area (345.8 m²g^-1) and pore volume (0.46 cm³g^-1). The catalytic performance of NiPO-3 showed that the total selectivity of epoxycyclohexane and hexadienol was as high as 83.38%.

Abstract: An InGaN/GaN-based photodetector with nano-structure on the surface is present. Surface nano-structure was formed by nanoimprint lithography (NIL) and reactive ion etching (RIE) techniques. The NIL technique and nano-structure etching by employing RIE were demonstrated in details. The nano-pattern was designed as regular triangles consisting of columns, whose diameter and period were around 105 and 210 nm, respectively. The height of nano-columns was around 66 nm. The photo-voltage of this type of photodetector had very good wave characteristics with 60° period, and it presented different waveform at different angles and wavelengths of incident light. The periodic characteristics took not only on minimum voltage but also peak voltage. We demonstrated this characteristic by employing Bragg formulation.

Abstract: NdPO₄•nH₂O nanorods with a pure hexagonal and monoclinic phase were controlled synthesized through a hydrothermal route at low temperature. By simply increasing the molar ratio of PO₄/Nd, pure monoclinic NdPO₄ can be obtained at lower temperature of 180 °C. Furthermore, NdPO4•nH2O nanorods can be assembled into flower- or bundle-shape. The reactant molar ratio played key roles in the formation of the products with different morphologies and structures. The possible formation mechanism for NdPO4 nanorods with different morphologies and structures was discussed. In addition, low-cost preparation of NdPO4 nanorods could be achieved through cycling use of phosphoric acid. Furthermore, this synthesis strategy will open a novel approach to rare earth phosphates with multiple structures.

Abstract: Based on the surface morphology, a model is presented to investigate the heat transfer in anodic aluminum oxide (AAO) porous thin films. The extra thermal resistance from the micropores will inevitably cause a change in thermal properties, which can be analyzed by the Fourier law. The effect of the characteristic size on the thermal conductivity is discussed in details by means of the theory of phenomenological model of phonon scattering. Considering the effects of porosity and the distribution of micropores reflected by parameter D, the function of the effective thermal conductivity of AAO porous thin films expressed by two independent variables, ε_p and D. The temperature field is simulated with the effective thermal conductivity and the result demonstrates a bigger temperature rise in AAO porous thin films.