Advanced Materials Research Vols. 160-162

Abstract: To have a fundamental understanding on the principle of carbon aerogels when it is used as electrode materials in power battery, the effects of density and structural properties on the electrical conductivity of carbon aerogels was investigated in this paper. Carbon aerogels with different density were prepared via adjusting the chemical conditions of the primary solution. The morphology of carbon aerogels were observed by field emission scanning electron microscopy (FE-SEM). Experimental results show that the electrical conductivity of carbon aerogels is ranged from 10-6 Ω/cm to 10 Ω/cm, and that not only the density but also the carbon particle size and porosity of carbon aerogels effect the transport property greatly. With the increasing of the density the electrical conductivity of carbon aerogels increases. This indicates that larger particle size and lower porosity of the nano-structure lead to higher conductivity.

Abstract: The purpose of the present study is to evaluate the processing property of Mg96Zn2Y2 of casting material. Mg96Zn2Y2 is a high strength magnesium alloy material newly developed by Mr. Kawamura in Japan. The name of this alloy is called as 'Kumadai Goukin'. For this purpose, cylinder upsetting tests were performed. In addition, the marketing community of AZ31 magnesium alloy collates the information with the new material. We examined and compared the deformation resistance and ductility of the two materials. Furthermore, the dependence of deformation resistance and ductility of these materials to processing temperature and speed was evaluated [1].

Abstract: Highlighted with its advantage of convenience, low energy consumption and sanitation, low temperature floor radiate heating system has been favored and been used in most heating areas since it was introduced into china in mid 80’s,But it is generally believed that floor heating system alone can not meet heating design requirement for large room located in cold area and is only deemed as an assistant heating methods.This article has proved by monitoring data collected from low temperature floor radiate heating system designed for large room in cold area that it is well enough to apply low temperature floor radiate heating system alone with reasonable design and running control and modification of heat exchanger.

Abstract: In this paper, we report the deposition of nano-crystalline silicon flexible solar cells on stainless steel (SS) substrates for application in solar roof. The influence of substrate treatment on the properties of material and the solar cells was studied by Raman spectroscopy, scanning electron microscope, current-voltage (I-V), and Quantum efficiency (QE) measurements. Results suggest that the properties of the Si:H thin films and solar cells were greatly improved by the substrate treatment with surface polishing and the followed Ag/ZnO electrodes deposition.

Abstract: . In the range of 1200°C to 1500°C, the transient hot-wire method was applied to measure the thermoconductivity of boron-containing slag, and the characteristics relationship of thermoconductivity with temperature was obtained. The thermoconductivity decreased rapidly with the elevation of temperature in the concerned temperature zone. The effect of thermoconductivity from compositions was obtained in the concerned temperature zone. The thermoconductivity increased with the increase of component of SiO2 and MgO. This is in favor of realization of quick cooling and increasing efficiencies of extraction of boron. This study not only provides an important properties parameter for the integrated utilization of boron-containing slag and helps to understand the conductivity mechanism of boron-containing slag, but also has a reference significance and practical value about the development of heat conduction theory in silicate system.

Abstract: Polyaniline(PANI) nanofibers were firstly prepared by rapid mixture method, EP/PANI nanocomposite was obtained by in-situ adding the PANI nanofibers to epoxy resin(EP). Scanning electron microscopy(SEM) proves that the type of doped acids has a little effect on the morphologies of PANI, and the PANI doped by different acids present nanofiber structures with the diameter of about 50 nm. The thermal behaviour of EP/PANI nanocomposites were investigated in detail by using a dynamic rate mode of thermogravimetric analyser (TGA) in inert atmosphere, and the results show that the PANI nanofibers obviously improve thermal stability of pure EP. Compared with EP/PANI doped by nitric acid or sulfuric acid, EP/PANI doped by phosphoric acid has best thermal stability.

Abstract: In this study, galling behavior in macro-scale is investigated in the square cup drawing of a high tensile strength steel in semi-dry and dry condition on laboratory experiments. The drawing dies are set two types: the non-coated (SKD11, ADI and SLD) and coated (TiC and DLC-Si). When using the non-coated dies in semi-dry, the macro-scale galling can clearly observed on die and drawn cup surface after a few drawing cycles. As a result, the galling on the die surface occurs at the bottom point of the boundary between the straight and corner edge, and grows upward with the drawing cycles; on the drawn cup, the galling starts at the top of the same boundary and grows downward. Simultaneously, the finite element method (FEM) with DEFORM-3D was used to simulate the square cup drawing process with the respect to the drawing force distribution and volume change analysis, which gave us a rational interpretation of the galling phenomena and illustrated the galling behavior and seizing tumour theoretically. Furthermore, a continued experiment with coated dies for TiC (CVD) and DLC-Si (DC -PACVD) was carried out to seek a anti-galling tool material for the high tensile strength steel.

Abstract: Laser thermal stress forming is a flexible forming process that forms sheet metal by means of stresses induced by external heat instead of by means of external force. Based on the analyzing of the influence of temperature on the thermal and mechanical properties of the materials, a 3D thermal-mechanical coupling model of laser thermal stress forming of thin steel sheet is set up in this paper. Based on ANSYS APDL developing platform, the stress field, temperature field and deformation field are obtained by numerical simulation of laser scanning of Q235 mild steel sheet for one time. Moreover, the forming progress and mechanism have been analyzed. The results show that the laser thermal stress forming is a quasi-steady-state process and its forming mechanism belongs to temperature gradient mechanism.

Abstract: In order to determine and actively design the vibration characteristics of micro-cantilever in the MEMS devices, it is highly necessary to research on the modal analysis of micro-cantilever which is driven by electrostatic force. This paper analyzes the coupling of mechanical and electrical coupling beam based on the direct coupling method, applies ANSYS software into creating the model of the micro-cantilever to simulation of electromechanical coupling, and establishes the quantitative impact analysis model between natural frequency of vibration and the thickness of a micro-beam with Trans126 transducer element, through directly embedding intrinsic characteristic length of micro-cantilever beam to the scale effect of vibration mode. The main conclusion is that when the thickness of micro-beam is close to the characteristics size of the materials, the natural frequency will show a significant scale effect phenomenon.

Abstract: Most soil constitutive models were developed based on the traditional triaxial tests with isotropic assumption, in which the load is applied as the major principal stress direction and the other two principal stresses are symmetric. When such isotropic models are applied to practical analysis, stress induced anisotropy under complex stress state and the middle principal stress effects are often neglected, thus there are many disagreements between the calculated results and the infield testing data. To simulate the practical loading process, true triaxial tests were carried out on geomaterial under three-dimensional stress state. It was found that the stress induced anisotropy effects are remarkable and the middle principal stress effects are obvious because of the initial three-dimensional stress state. Such kind of stress-induced anisotropy could have important impact on the numerical analysis results and should be taken into consideration when developing the constitutive model.