Advanced Materials Research Vols. 123-125

Abstract: Cerium-iron oxide composite nanorods were synthesized by a surfactant free precipitation method. The synthesized products were characterized by XRD, FESEM, BET and TEM. Increase in the mole concentration causes the morphology of the cerium oxide to change from nanorods into nanocubes. X-ray diffraction pattern shows a diffraction peak at 28.5° corresponding to (111) reflection plane normal to c axis of a cubic fluorite structure of CeO2 and also hexagonal phase of Fe2O3 and orthorhombic phase of FeO (OH). EDAX analysis on individual nanorod conform the presences of Iron, which supports the XRD spectra. From transmission electron microscopy (TEM), the length and width of the nanorods were estimated in the range of ~100-350 nm and ~20-40 nm respectively. The Brunauer Emmett Teller (BET) analysis showed the increase in surface area for the obtained nanorods with respect to the increase in Fe concentration which in turn enhanced the formation and growth of nanorods.

Abstract: A dense nanostructured 5NbSi2-SiC-Si3N4 composite was synthesized by the high-frequency induction-heated combustion synthesis (HFIHCS) method within 1 minute in one step from mechanically activated powders of 4NbN, NbC and 14Si. A highly dense 5NbSi2-SiC-Si3N4 composite with relative density of up to 98% was produced under the simultaneous application of a pressure of 80 MPa and the induced current. The average grain size and mechanical properties (hardness and fracture toughness) of the composite were investigated.

Abstract: Fiber reinforced composite materials have been used in main parts of structures; an accurate evaluation of their erosion behavior becomes very important. In this study, short glass fibre reinforced polyester based isotropic polymer composites are fabricated with five different fibre weight-fractions. The effect of various operational variables, material parameters and their interactive influences on erosive wear behavior of these composites has been studied systematically. After systematic analysis of solid particle erosion for all the five composites, 30wt% short glass fiber reinforced polyester based composite shows better erosion resistance. In order to improve the erosion resistance further ceramic silicon carbide particle is reinforced with the 30wt% glass-polyester based hybrid composites. A finite element (FE) model (LS-DYNA) of erosive wear is established for damage assessment and validated by a well designed set of experiments. For this, the design of experiments approach using Taguchi’s orthogonal arrays design is used. It is recognized that there is a good agreement between the computational and experimental results, and that the proposed simulation method is very useful for the evaluation of damage mechanisms.

Abstract: This paper investigated the stiffness reduction of the plate spring made of CFRP (Carbon cloth and epoxy) subjected to ultra high cyclic fatigue loading under high relative humidity. For practical uses, this paper proposes a new design which prevents the significant degradation with stiffness change of the plate spring at high humidity. Remarkable stiffness reduction of the plate spring due to cracks and delaminations around inter layer could be prevented by using CFRTP rather than that by using CFRP, when ultra high cyclic loading was applied to the plate spring under high humidity condition.

Abstract: The composite materials of LiFePO4 powder coated with polyacenic semiconductor materials (PAS) were successful prepared. Effects of the preparation conditions, such as precursor material, annealing temperature et al., on the structure and electrochemical properties of LiFePO4 were studied. SEM images and TG thermogravimetric analysis of the obtained carbon coating microspheres suggest that LiFePO4 powder was successfully encased within the carbon gel microspheres. The electrical conductivity of the composite materials could get to 10-2 S•cm-1. It was found that the composite LiFePO4 material exhibits excellent capability with initial discharge capacity more than 210 mAhg–1. The discharge capacity goes up to 340 mAh/g after ten times of cycle.

Abstract: The cheaper plant materials such as wheat straws and corn stalks, which contain a lot of celluloses, were used to synthesize the new GPE by graft copolymerization with acrylic acid (AA). A kind of thinner film was prepared by coating the mixture of above precursor with polyvinyl alcohol (PVA). The new polymer film was expected to have larger uptake of standard liquid electrolyte. Therefore, its ionic conductivity could reach to 6.7×10-3 S•cm-1, which was near to the conductivity of liquid electrolyte (~10-3 S•cm-1). So the lithium batteries containing the new GPE could have better charge-discharging efficiency with larger current density. The new GPE was also expected to be degradable as it was made of plant stem materials.

Abstract: Polydicyclopentadiene (PDCPD)/montmorillonite Clay (MMT) nanocomposites were synthesized through reaction injection molding with a Gusmer-Decker machine by in situ polymerization. The results of X-ray diffraction (XRD) diagrams of the nanocomposites showed that MMT were completely exfoliated within the range of 0.25% to 4% MMT. The erosion wear behaviors of PDCPD/MMT nanocomposites were studied using an MCF-30 water and sand erosion wear tester. The worn surface of PDCPD/MMT nanocomposites was exami-ned with a scanning electron microscope (SEM) and the wear mechanism was discussed.It was found that when the content of MMT is 0.25%, the erosion rate of nanocompositesreach the minimum; the erosion rate of nanocomposites increases with the increase of MMT content compared with neat PDCPD. The important wear mechanism of neat PDCPD was tearing and ploughing-cutting, And the results showed that wear mechanism of PDCPD/MMT nanocomposites was dominated by ploughing-cutting, with the increase of MMT the severe mechanical cutting, fatigue wear and slight brittle rupture appear. PDCPD/MMT nanocomposites with a lower content of MMT were thus a promising structural material candidate for engineering application.

Abstract: From the impact experiment for the nonlinear plastic behavior with the dynamically loaded adhesively-bonded TDCB specimens, there is the range of load from 1 to 2 kN or pin displacement from 4 to 10 mm for the most part in case of the impact rates 1, 2.5, 5, 7.5 and 12.5m/s. There is also the range of energy from 5 to 10 J or energy release rate(fracture energy) from 3000 to 6000 J/m2 for the most part in case of all impact rates. The fracture energy on automotive adhesive joints can be estimated by using the fracture toughness, GIC, experimental results under high rates of loading in this study. The key fracture mechanics parameter, namely the fracture energy, GIC, was ascertained as a function of test rate and may be used to assess and model the joint performance.

Abstract: By means of melt compounding method, the Glycidyl methacrylate (GMA) grafted HDPE modified Polyamide 66 (PA66) with ultra high molecular weight polyethylene (UHMWPE) blends were prepared via the co-rotating twin screw extruder．The effects of different UHMWPE/HDPE contents on properties of PA66/UHMWPE blends were investigated．Meanwhile, the mechanical properties such as tensile and impact strength etc. were investigated. By using the differential scanning calorimetry (DSC) and scanning electron microscope (SEM), the crystalline and morphology of PA66/UHMWPE blends were analyzed. The results show that UHMWPE toughened PA66 samples exhibit significantly enhanced impact strength and elongation at break comparison with natural PA66. The samples of PA66 with 30% of UHMWPE/HDPE (mass ratio 3/7) blends show impact strength about 2 times and elongation at yield 7 times more than those of natural PA66．The behavior of HDPE-g-GMA shows an effective compatibilizer for PA66/UHMWPE blends, when the mass ratio of PA66/(UHMWPE/HDPE) at 70:30, the blend indicates the best comprehensive property. The investigation on crystallization and morphology of PA66 and their blends show that the behaviors of melting about the two components are independent either PA66 or UHMWPE/HDPE. There are independent melting behaviors, meanwhile, interacted each other between PA66 and UHMWPE. Due to the good compatibility which HDPE-g-GMA contributed, the homogenous PA66/UHMWPE blends could be achieved. The photographs of SEM analysis indicate that the interface action of PA66 and polyethylene is enhanced by compatibilizer HDPE-g-GMA.

Abstract: In recent years, the influence of surface modification of carbon nanotubes (CNTs ) on CNT’s dispersion among epoxy resin, mechanical properties and electrical conductivities of CNTs has been observed. On account of above-mentioned effects, that CNTs treated with oxidizing in organic acids, a kind of surface modification, generates functional groups on the surface of CNTs is a major investigation in this study to enhance mechanical properties and electrical conductivities of CNTs. In this study, CNTs dispersed among epoxy resin well by adopting ultrasonication method and then the nano-prepreg was fabricated by mixing CNTs/Epoxy resin into carbon fiber. The influence of the different proportion contents of CNTs added into Epoxy resin on mechanical properties and electrical conductivities of composites is investigated. The strength of material tested under different circumstance is also observed. Furthermore, the creep behavior of carbon fiber/epoxy resin thermosetting composites tested under different circumstance and stress is also concerned to be analyzed.