Advanced Materials Research Vols. 488-489

Abstract: Molybdenum oxide (M_oO₃) is a well known transition metal oxide with multi phase properties that permit novel applications in sensors and batter systems. In this paper, we report a new approach to synthesize meta-stable structured molybdenum oxide (M_oO₃) by microwave assisted solution precipitation method using a domestic microwave oven. The reaction is carried out in a short period of 5 min. The XRD results confirms that the powder exhibits single phase hexagonal M_oO₃ with lattice parameter a= 10.53 Å and c = 14.907 Å. SEM images show, the particles are one dimensional (1-D) structure with hexagonal cross section and EDX spectrum confirm that the particles comprise of only molybdenum and oxygen. Further, the thermal and electrical properties are investigated by thermo gravimetric and impedance analysis and the results are discussed.

Abstract: In this study, tensile properties, thermal stability and morphology of polypropylene/ethylene propylene diene rubber/wollastonite (PP/EPDM/wollastonite) thermoplastic elastomer composites were tested and evaluated as a function of their compositions in comparison with PP/EPDM blends and native PP. PP was melt mixed with two loadings of EPDM (20 and 30% (w/w)) and for the composites each of these with three loadings of wollastonite (10, 20 and 30 parts by weight per hundred of the PP/EPDM resin) on a twin screw extruder and then injection molded. Both PP/EPDM blends provided a higher elongation at break but a lower tensile strength and Young’s modulus as compared with those of the neat PP. However, the addition of wollastonite microparticles (particle size of 1200 mesh) into the blends increased the Young’s modulus in a dose-dependent manner with increasing wollastonite loadings, whilst the tensile strength and elongation at break were decreased. Moreover, the thermal stability was improved by the presence of either EPDM or wollastonite in the PP matrix.

Abstract: Polyaniline was synthesized by pulsed plasma polymerization using a theta-pinch device. The process was done using oxygen plasma at a voltage of 20 kV, a pressure of 2 Pa and a discharging current of 125 kA. The number of the plasma shots was varied from 10, 15, 20, 25, to 30 shots. This parameter significantly affected the chemical structures of the synthesized polyanilines as revealed by FTIR spectra. While all synthesized polyaniline exhibited the characteristic peaks of quinoid ring and benzenoid group, the peaks corresponding to the formation of oxygen containing groups was found when high numbers of plasma shots were employed. This also caused the difference in UV-VIS absorption of these polyanilines. The highest conductivity of polyaniline was obtained when 20 shots of oxygen plasma were used. At this condition, polyaniline had a semi-crystalline structure and the thermal decomposition temperature at 262oC.

Abstract: In this research a composite structure containing of a TiB₂ matrix with dispersed Al₂O₃ particles was obtained via mechanical alloying of Al, TiO₂ and B₂O₃ powder mixture. The mixture was milled for different lengths of time. Phase evolutions of the milled powder mixture were investigated. Powder particle characteristics were evaluated by XRD, SEM and TEM techniques. The XRD results reveal that the reaction begins during first 10 h milling by formation of TiB₂ and Al₂O₃¬ phases and further milling causes partial amorphization of powder mixture. SEM micrograph of the sample milled for 30 h exhibited ultrafine particles of Al₂O₃-TiB₂, but TEM images show that particles consist of some grains in the range of nano-size. The mean crystallite size of final product is about 25 nm.

Abstract: Aluminum alloys are used for mechanical parts, but the alloys have poor wear-resistance. To increase their wear resistance, a hard coating is applied to the surface of the alloys. Diamond-like carbon (DLC) is applied in surface modification technology due to its superior mechanical characteristics. In this study, in order to achieve effective surface modification to improve the wear resistance of the aluminum alloys, a new coatings-system was designed. This coating-substrate system is a multilayer coating-substrate system, which consists of nitriding pretreatment of the substrate, the intermediate layer of the silicon-based film and the outer layer of the DLC film. This new coating-system was used to deposit DLC film on three kinds of aluminum alloys that have different Si contents. In order to determine the influence of the Si contents on the mechanical properties of the DLC film, SEM observation of the cross section of the coating layer, the adhesion and the wear resistance of the layer were experimentally investigated. The results were as follows: (1) In the case of the DLC un-coated aluminum alloys, the rapid progress of the friction coefficient in the case of 10-N load was found at the short sliding distance. (2) The hardness of the DLC film was not decreased with the increase of Si contents. And the increase of Si contents did not have a negative influence upon the hardness of the DLC film. (3) The frictional coefficient of the Al-4%Si alloy was the smallest, the frictional coefficient of the DLC film was decreased with the increase of Si contents, and it was effective for improvement of the frictional coefficient to increase Si contents. The new coating-substrate system is effective for improving the adhesion between the substrate of the aluminum alloy and the DLC film. Moreover, the increase of Si contents was effective for the decrease in the frictional coefficient.

Abstract: Recently, attention has been given to base heterogeneous catalysis reactions and have attracted broad field of scientific researches. Alkaline earth metal oxide calcium oxide (CaO) having rock salt crystal structure, with surface defect and cavities are important for their basic catalytic reactivity. In this study CaO with high surface area and at nano level was prepared by hydration-dehydration method, calcined at various temperatures and of high vacuum of 10-3 mbar. The effect of thermal decomposition of the samples towards the morphology and chemical reactivity was characterized using Thermogravimetry-Derivative Thermogravimetry (TG-DTG) analysis, X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM). The effect of hydration-dehydration on the basic strength was then analysed using back titration method. It was found, by increasing the calcinations temperature, the morphology of nano CaO changes from hexagonal to cubic. The basic strength, on the other is doubled compared to the CaO commercially available.

Abstract: Biomass energy is a typical renewable energy. It is of great significance to develop and utilize biomass as it can solve the problems of rural energy, ease pressure on the environment and implement the strategy of sustainable development. Abundant biomass energy can be found in rural areas of Chongqing, but its use is still in the initial development stage. Chongqing rural energy structure is based on the original straw and firewood, whose combustion is direct and has low thermal efficiency. This paper gives some strategies and suggestions on the use of biomass energy in rural area of Chongqing.

Abstract: In this research, the feasibility to obtain cellulose film from rice straw was investigated. After delignification and bleaching of rice straw, the rice straw pulp was treated by acid hydrolysis in order to obtain rice straw cellulose powder. After that, the esterification of rice straw cellulose was carried out by using lauroyl chloride as an esterifying agent, toluene and pyridine as a solvent and a catalyst, respectively. The optimum condition for esterification was examined in terms of temperature and reaction time. Chemical structure and properties of modified cellulose such as morphology, thermal stability, and solubility were investigated. The rice straw cellulose ester film was prepared by casting method and the films obtained were tested for their tensile properties.

Abstract: The paper aims to develop a bio-rapid prototyping system based on air pressure-aided deposition technique for fabricating scaffolds with pore size in the range of 50 to 420 µm. The material used are thermal-sensitive polymers consisting of poly(ethylene glycol) and poly(-caprolactone), and synthesized with different molecular weights for investigating the viscosity effect on deposition stability in regarding to varying scanning speed. The experimental results show that at the molecular weight of 10,000, the molten form can be stably deposited through a heating nozzle at an air pressure of 0.3 MPa and no crack occurs after it solidifies. The scaffolds with mean pore size of 420 µm (porosity 89%) were fabricated and its average compressive strength was 9.28 MPa. The study also suggested that the developed bio-rapid prototyping system is suitable for fabricating micro-porous cellular scaffold, especially for thermal-sensitive copolymers.

Abstract: The purpose of this study was to investigate the influence of Temporomandibular Joint implant geometry on stress distribution in total reconstruction of temporomandibular joint. A three dimensional model of a lower jaw of a patient was developed from a Computed Tomography scan images. Anatomical curvature and flat contact surface of implant design and fixation screws were modeled. Two implanted mandibles were then compared by means of finite element analysis. The muscle forces for incisal clenching were applied. The equivalent stress resulted in contact surface region of the bone and implant and in fixation screw holes were investigated to evaluate the designs. In applied loading condition, The results showed that anatomical design of implant was more preferred and it will lead to long-term success of implant.