Advanced Materials Research Vols. 239-242

Abstract: The preparation of multi-walled carbon nanotube/polylactide (PLA)/Ecoflex^® biodegradable composites is described. Three modifiers, maleic anhydride ,methyl methacrylate and vinyltrimethoxysilane , were utilized to modify multiwall carbon nanotube. The dispersion of multi-walled carbon nanotube was enhanced by covalent or hydrogen bonding between modified multi-walled carbon and biodegradable blend. The tensile strengths of pristine PLA/Ecoflex^® resin and 4 wt% modified multi-walled carbon composites are 68 kgf/cm² and 257 kgf/cm², respectively (representing a difference of 380%). High electrical conductivity can be achieved at a low carbon nanotube loading. When 1wt% modified multi-walled carbon was added to PLA/Ecoflex^® matrix, the surface resistance of the composite fell from 1.46×10¹⁶ to 7.88 × 10² Ω/Υ (by 10¹³ order).

Abstract: The pulsed current of rectangular wave was used to electrolyzing zinc nitrate aqueous solution for the purpose of preparation of a transparent zinc oxide (ZnO) film by cathodic deposition. The current density of rectangular wave was 0.2 and 1.0 mA/cm² , respectively. The former plays a role to deposit homogenous ZnO particles on the substrate surface and the latter plays the role to promote further growth of the particles and film formation. The structural and optical characterizations of the deposited films were performed with x-ray diffraction, scanning electron microscope, and measurements of optical absorption in UV-vis range. Similar technique has been used to modify as prepared porous silicon, resulting a green photoluminescence after 1 h annealing at 1273 K under oxygen atomsphere.

Abstract: In order to find out the accident urea reactor explosion reasons, based on the accident investigation, the reactor structure was anatomyed, the macroscopic and microscopic fractures were sampled and observed, The results show that the trace sodium, potassium and other alkaline ions content in the liquid of liquefied steam is the stress corrosion medium reason; the leak detection pine and the 16MnR laminate connecting with screw joint is the structural reasons; typical stress corrosion had occurred on the accident urea reactor cylindrical segment base metal and welding. Some important suggestions were given

Abstract: A 2 wt % Pd/C catalyst has been prepared by chemical impregnation and used to catalyze the hydrogenation of o-chloronitrobenzene (o-CNB) to o-chloroaniline (o-CAN) in solvent-free conditions. The effects of reaction temperature, H₂ pressure, and stirring intensity on the hydrogenation kinetics have been investigated. The hydrogenation reaction showed very high selectivity with dehalogenation side products as low as 0.3% of total yield. The favorable reaction conditions were found to be temperature T = 383 K, stirring speed = 900 rpm, and feeding ratio CNB/catalyst = 200/1 (m/m). The recycled Pd/C still retained more than 98% of its original selectivity after 12 repeat used, indicating the catalyst had strong potentials for commercial application at industrial scale.

Abstract: Aluminium titanate, Al₂TiO₅ (AT) with the pseudobrookite structure is the only compound in the alumina-titania system. It is an excellent refractory and thermal shock resistant material due to its relatively low thermal expansion coefficient (1 ´10^-6 °C ^–1) and high melting point (1860°C). However, its low mechanical strength, hardness and fracture resistance together with susceptibility to decomposition in the temperature range 900–1200°C has limited its wider application. In this paper, the innovative tailored design of functionally- graded Al₂TiO₅ – based ceramics system was presented. This involves the use of a vacuum heat-treatment or die-pressing to form hard graded layers of alumina on Al₂TiO₅. These hard outer layers will provide hardness and wear resistance to protect the softer but damage resistant underlayers. The results will also explore unresolved issues concerning the effect of graded interfaces on their physical and mechanical performance properties.

Abstract: Cellulose/magnetic nanocomposites were prepared by an ultrasound-assisted in-situ composition using cellulose fibers as matrices. The effects of pretreatment and maturing method on the composite efficiency were comparatively studied. Firstly the effects of ultrasound wave and mercerization pretreatment on the composite efficiency were investigated. Then the influences of ultrasound-assisted maturing on the composite efficiency were also discussed. Finally the nanocomposites’ structures were investigated by means of SEM, AFM and X-ray diffraction and the magnetic properties of the nanocomposites were determined by superconducting quantum interference device (SQUID). Results showed that ultrasound wave pretreatment was more efficient for the in-situ composition compared to the mercerization pretreatment. The amount of magnetic particles (valued as mass fraction of Fe) for untreated, ultrasound wave treated and mercerization treated cellulose fibers were 6.70%, 7.67% and 3.14%, respectively. The mass fraction of Fe increased from 5.04% for the mechanical agitation-maturing prepared sample to 5.61% for the ultrasound-assisted maturing prepared sample. Both ultrasound pretreatment and ultrasound-assisted maturing can remarkably raise the composite efficiency and magnetic particles’ yields. This reveals that ultrasound wave assisted-maturing is an effective method to control both the size and the distribution of magnetic iron oxide within the composites. Cellulose/magnetic nano-composite fibers with ferrite particles in size between 10 nm to 100 nm were obtained. XRD analysis indicates that the iron oxide synthesized is mainly in the C phase of g-Fe₂O₃. SQUID results reveal that the ultrasound-assisted in-situ synthesized cellulose/magnetic nanocomposites are superparamagnetic.

Abstract: Solid super acid (S₂O₈^2-/Fe_xO_y-CuO_x) was prepared and used as a heterogeneous Fenton-like catalyst to decompose H₂O₂ for the degradation of refractory dye Orange IV in water. The factors that affected the degradation of Orange IV were discussed in this heterogeneous Fenton-like system. The catalytic activity of S₂O₈^2-/Fe_xO_y-CuO_x was evaluated by the degradation of Orange IV and the decomposition of H₂O₂. The results show that the catalyst S₂O₈^2-/Fe_xO_y-CuO_x has a good catalytic activity. The reaction follows pseudo-first-order kinetics; the reaction rate constant has a good relationship with the concentration of H₂O₂. The degradation rate of Orange IV and the decomposition rate of H₂O₂ increase with the increase of temperature and the dosage of catalyst whereas it decreases with the increase of the initial concentration of Orange IV and the initial pH.

Abstract: In order to improve the corrosion resistance of Mg alloys in applications as degradable implant material. Fluoride conversion coating was synthesized on Mg alloy AZ31 by immersion in hydrofluoric acid (HF) with various concentrations. The effect of hydrofluoric acid (HF) treatment on the corrosion behavior of the Mg alloy AZ31 was investigated by potentiodynamic electrochemical technique and immersion tests. The XRD analysis indicated the fluoride conversion coating was amorphous, with smooth and compact surface. Electrochemical and immersion tests proved that the fluoride conversion coatings significantly improved the corrosion resistance of AZ31. The most improved corrosion protection was achieved using the concentrations of 40 % and 72 h of treatment time, resulting in corrosion rates 20 times lower than those of untreated samples, showing that fluoride coating by conversion treatment is a simple and promising way of enhancing the corrosion resistance of Mg in Hanks' solution.

Abstract: In this study, the activated crumb rubbers (ACR) and these ACR modified asphalts were prepared. Effects of the preparation technology of modified asphalt and properties of activated crumb rubber on performance of modified asphalt have been investigated. The activated crumb rubber powder was characterized by the Rubber NMR Crosslink Density (RNCD). The mechanism of the activated crumb rubber modified asphalt (ACRMA) was analyzed by microcosmic measures and tests such as Fluorescence Microscope (FM) etc. The experimental results indicated that the chemical and physical activating methods can improve the swelling capacity of crumb rubber in the asphalt by destroying the three-dimensional network and decreasing the cross-linking density; ACRMA have better performance compared with the crumb rubber modified asphalt. Micrograph of the ACRMA demonstrated that the structure of ACRMA is more uniform and compact, and the performances of modified asphalt were improved significantly.

Abstract: Fe₅₆Co₄₄ alloy nanowires were fabricated by electrodeposition with aluminum oxide template. Transmission Electron Microscope photographs show the nanowires are separate and have no twist with each other. Mossbauer spectroscopy results show the values of the isomer shift, hyperfine splitting and linewidth all decrease with increasing annealing temperature. Vibrating sample magnetometer (VSM) results of the alloy nanowire show that the coercive fields increase with increasing heat treatment temperature when the direction of applied magnetic field perpendicular to the axis of nanowires.