Advanced Materials Research Vols. 415-417

Abstract: In this article, nanocomposites of BaTiO₃/CoFe₂O₄ have been prepared by sol-gel technique. The samples have been calcined at various temperatures ranging from 500 to 900 °C and then the microstructure of the composite nano-particles was studied. XRD, SEM analysis showed the powders can form the two phase composite system of BaTiO₃ and CoFe₂O₄ and the average particle size of the crystalline phases is 50nm at sintering temperature of 800 °C. In addition, we have studied the effects of different solvents and mixed solvents on the stability of the nanocomposites suspensions. Results of sediment volumes and conductivity showed under ultrasonic agitation for at least 25 min, suspensions of the BaTiO₃/CoFe₂O₄ in ethanol-acetylacetone (1:1 in volume) were most stable (the sediment volumes is 0.6cm3/0.4g, the conductivity is 9μS/cm). Electrophoretic deposition (EPD) was utilized for preparation of magnetoelectric (ME) composite films, the impact of deposition time and deposition voltage on electrophoretic deposition process was investigated. The obtained ME composite films exhibited good ferroelectric and ferromagnetic properties, which can meet the demand of ME devices.

Abstract: This work focus on the effects of C vacancy on wetting of Fe to TiC/Fe at the cermet interfaces. We do the whole work using the first-principles density functional theories. The ideal work of adhesion of the pure interface is not big enough, comparing with the expeimental value. Our calculations suggest that the C vacancy at the interface is a very important factor for interface banding of TiC/Fe cermet composite. An adequate quantities of C vacancies at the interface can improve the wetting of TiC/Fe interfaces.

Abstract: According to the related experimental standards, the finite element (FE) methodology to calculate the in-plane and out-of-plane moduli of hexagonal honeycombs (HHs) is designed by simulating the experimental loadings. Some simulations were carried out for the hexagonal honeycombs with different configuration parameters. The FE results are consistent with the theoretical ones, which verifies the reliability of FE methodology.

Abstract: This study demonstrates the surface modification of carbon fiber by grafting polyglycidyl methacrylate (PGMA) using atom transfer radical polymerization (ATRP). Firstly, the surface of carbon fiber was modified by using 3-aminopropyltriethoxysilane and 2-bromoisobutyryl bromide to immobilize ATRP initiators on the surface. Then the glycidyl methacrylate was initiated and propagated on the carbon fiber surface by ATRP. Characterization of these modified carbon fibers included Fourier transform infrared (FT-IR), Thermal gravimetric analysis (TGA) and 1H nuclear magnetic resonance (NMR). The results indicated that the grafting of PGMA from the carbon fiber surface was successful.

Abstract: This paper describes a basic method of mechanical design and virtual teaching of a two-leg walking mechanism, mainly including the assignment of the degree of freedom (DOF), the process of kinematics and Kinetics computing, the selection method of driving devices and the principle of the virtual teaching system. The fact proves that this two-leg walking mechanism is of high stability and efficient teaching.

Abstract: Based on the SrO-Al₂O₃-Fe₂O₃-B₂O₃ system, the nano-ferrimagnetic glass ceramics has been prepared through heat treating the melted glass. Using the aqueous solution solvent evaporation and melt method, we firstly obtained the molecular-scale homogenously mixed compound. And thus the glass specimen was produced by naturally cooling the batch melts. The crystallization of the glass systems with diffirent component has been systematically investigated by using X-ray diffraction (XRD), Thermo gravimetric (TG), Differential Thermal Analysis (DTA) as well as Vibrating Sample Magnetometer (VSM). It is found that Fe₃O₄ crystal precipitated during naturally cooling the melt from 1500°C to anneal temperature. Moreover, the nano-ferromagnetic glass ceramics with the main crystal phase of SrFe₁₂O₁₉ was obtained after heat-treated at 865°C for 2 hours. The size of crystal was 20-50nm. The magnetic properties of the obtained ferromagnetic glass ceramics indicated that the saturation magnetization and the intrinsic coercivity were 32A•m²/kg and 236KA/m, respectively.

Abstract: A new Modifier with Silicon radicals as anchoring group and poly(butyl acrylate) as solvatable chain was synthesized and its effect on the properties of HDPE/Anhydrite composites was investigated in this paper. Fourier transmission infrared spectroscopy (FT-IR) results show that the modifier react on the Anhydrite powder particles surface and the modified Anhydrite powder particles particles. compared with that of HDPE/Anhydrite (filled with same non-modified fraction), The impact strength, tensile strength, bending strength and Young’s modulus of modified HDPE/Anhydrite composites increased about 36.6%, 7.5%, 15.6% and 34% respectively. Based on surface analysis by scanning electron microscope (SEM), the Anhydrite powder particles buried well in HDPE matrix when Anhydrite powder particles was coated with the YB modifier. It was found that Anhydrite powder particles significantly increased the crystallization temperature and crystallization rate of HDPE by differential scanning calorimetry (DSC). At same time, through the X-ray diffraction (XRD) found the addition of the YB modifier modified Anhydrite powder particles can not change the formation of crystal HDPE, but can reduce the crystallite size.

Abstract: Experimental investigations were performed on strain characteristic of filament wound composite cylinder. Cylinders are wound with S-1 glass fiber and epoxy resin, and then subjected to an axial tension. During loading, strains at three fiber crossing position and one laminate region on cylinder’s surface are measured by gauges for better understanding strain field. For all specimens, strains at fiber crossing positions are larger than that of laminate region. This indicates that fiber undulation caused by winding process affects mechanical response of filament wound composites.

Abstract: Flame retardation of PP/EPDM blend containing ammonium polyphosphate or its microcapsule (MFAPP) combined with dipentaerythritol (DPER) was evaluated by LOI and UL -94 methods. It is found that MFAPP is better than APP in exerting flame retardation in the PP/EPDM. No apparent improvement in flame retardation for APP and MFAPP in combination with DPER in the PP/EPDM blend. SEM results show that microencapsulation of APP with the melamine–formaldehyde resin leads to some improvement in its dispersion in the blend. Moreover, mechanical properties of the flame retarded PP/EPDM composites are studied.

Abstract: Precision predicting is a new methodology for precision verification and validation of product. Considering the dimension and geometric deviation of assembled part, the precision predicting model is built by assembly deviation sources explaining and deviation propagation route modeling. The deviation source during assembly process is mainly explained by dimension torsor and deviation torsor that are built in common coordinate system, and the deviation propagation rout is modeled by weighted deviation graph. The weighted deviation graph contains vertexes that refer to functional geometry and mating geometry and edges that refer to dimension and geometric constraint; besides, the edge weight is calculated by tolerance evaluation along specific functional direction. In addition, the process of computer aided adaptive assembly method is introduced, and the proper index for assembly precision and accuracy is discussed.