Advanced Materials Research Vols. 295-297

Abstract: Sample preparation is always a bottleneck in system for chemical analysis. In recent years, the development of methodologies for microextraction related techniques has progressed phenomenally. This review introduces and compares the various microextraction approaches for trace environmental analysis, and the advantages and disadvantages of current methods are proposed as well.

Abstract: The carbon complex film, Which consists of diamond grains, carbon nanotubes, amorphous carbon composition, were fabricated by microwave plasma chemical vapor deposition （MPCVD） method. The ceramic with a Ti mental layer was used as substrate. The carbon complex films were evaluated by Raman scattering spectroscopy, x-ray diffraction spectrum, scanning electron microscope. The field emission properties were tested by using a diode structure in a vacuum. A phosphor-coated indium tin oxide anode was used for observing and characterizing the field emission. The turn-on field was only 0.55V/μm and emission current density as high as 11mA/cm² was obtained under an applied field of 2.18V/μm for the first operation. The growth mechanism and field emission properties of the carbon complex films are discussed relating to microstructure and electrical conductivity.

Abstract: In this paper, a three-dimensional, complex seepage model of a proton exchange membrane fuel cell (PEMFC) is studied, the corresponding finite element method and numerical simulation are given as well, where species transport, fluid flow, charge transport, heat transfer and electrochemical reaction in the PEMFC are simultaneously addressed. The domain to be studied includes porous gas diffusion layers, catalyst layers, gas channels, bipolar plates, and membrane. The fluid transportation phenomena arising in the whole fuel cell are described by the referred model, different physical parameters and source terms are reflected in different areas. The chemical components, flow characteristics and distributions of temperature in the 3-D space are obtained by resolving the seepage control equation system coupled with electrochemical equations. The induced methods and results can guide the optimal design of PEMFC.

Abstract: PVP/ZnO-TiO₂ composite nanofibers were prepared by Sol-gel processing followed by electrospinning technique using Ti(OC₄H₉)₄ and polyvinglpyrrolidone ( PVP) as starting materials. ZnO-TiO₂ nanofibers of 100–200 nm diameter were obtained by high temperature calcinations of the inorganic organic PVP/ZnO-TiO₂ composite fibers.The materials were characterized by differential scanning calorimetry thermogravimetric analysis (DSC- TGA) , Fourier transform infrared (FT-IR),and scanning electron microscopy (SEM). The process of the photocatalytic degradation of methylene blue using ZnO-TiO₂ nanofiber as catalyst was investigated.The results show that the ZnO-TiO₂ nanofiber dopped 3% ZnO has better photocatalytic activity for methylene blue degradation, the degradation rate of methylene blue solution reached 99% under sunshine for 6 h., and it’s still 95% after eight times reuse.

Abstract: The length of a single fiber of hemp is 18mm or so, which is somewhat lower than that of flax. So it is possible to make the spun yarn with hemp. For the sake of high 7%~8% content of lignin in row fiber, even worse, it can not drop under the degree of 0.8% when treated by classical boiling off. That’s why the coarse stiff hemp fiber can not ever answer the demand of its spun yarn processing. The so called non-acid re-double-boiling out process developed on the renovation to the classic chemical boiling off of raw hemp can prevent the lignin from further fasculation under the inorganic acid preparation. At the same time, the OH^— boiling off agent and HS^— boiling off agent can cause a rapid thorough hydrolization of lignin, this undoubtedly will ensure the being of high quality refined dry hemp.

Abstract: A new cooling concept for high power LED by combining the heat release of high power LED with two-phase heat transfer heat pipes was proposed, and in this study a new type of heat pipe with specific fins structure was developed. Through experimental results, we found the new heat pipe heat exchanger has the features of high efficiency of heat dissipation and compact construction which meets the demand of heat dissipation for high power LED. We also found the heat dissipation performance of the HP heat exchanger changed with the work angle.

Abstract: Light weight , softness and comfort are becoming the development priority for the bast fabrics for apparel use. Therefore, some properties of the bast fabers related to these aspects become important. In this paper, the properties of bast fibers, including fiber length, fineness, tenacity, softness were tested and evaluated to determine which is better for developing fabrics pleased by the consumers by using optimal design theory. The results show that ramie fiber has high softness, great tenacity and is finest. It is the best material for the garments required light weight and comfort, hemp second, the next is flax and kenaf. Jute is the worst one.

Abstract: Consecutive PA6/MWNTs nanofiber filaments were successfully fabricated by an improved electrospining method in this paper. The microstructure and the arrangement of MWNTs in the nanofibers both with the conductivities of the filaments in different MWNTs contents were studied. The results show that the orientation arrangement of the nanofiber and MWNTs in the fibers were both fine at different MWNTs contents .Besides, with the increase of the MWNTs contents, the diameters of the nanofiber increased, while the conductivity of the filaments increased and MWNTs became gathered in the fibers.

Abstract: This research works for plain stitch of weft knitted stitch, mainly introduced the curling property of plain stitch and it’s influence factors were given. I will combine with plain stitch's structure characteristics and its unique fringe curling of style to design and produce suitable knitwear to satisfy the increasing needs of ourselves in the modern life. Drape, three dimentional cutting, also means stereo cutting, was taken to the research in order to design and make a middle and long tape skirt with black and gray, together with a white super short T-shirt, we can see the application of fringe culing in the collar, bottom margin, wristband and so on. In short, color in harmony, long and short matching brings to harmonious with nature.

Abstract: Electrochemical impedance (EI) plays a very important role on the characteristics of proton exchange membrane (PEM) fuel cell. In this paper, the effects of the cell temperature and the humidification temperature on the electrochemical impedance are analyzed by the equivalent circuit. The results show: when the cell temperature is higher than the gas humidification temperature, ohms impedance and Faraday impedance increase markedly, and electric double layer in the PEM fuel cell inclines to the specialty of capacitive reactance; the more than the cell temperature the gas humidification temperatures is, the more the extent of specialty of capacitive reactance the electric double layer shows. These results are very helpful to understand the operating principle of PEM fuel cell and improve its performance.