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High Power Densities (high + power_density)
Selected Abstracts157 nm fluorine laser ablation of wooden surfaces as an improved preparation technique for microscopyLASER PHYSICS LETTERS, Issue 1 2005M. Kopp Abstract By means of 157 nm VUV short-wavelength laserirradiation the wood layer of damaged cells near the surface as well as deeper wood regions can be removed. As this is a nonthermal laser ablation-process, oxidation of the wood surface exposed to 157 nm under N2 -atmosphere is avoided even with high power densities. By applying a mechanical pre-treatment process the wood structure is compressed and can then be removed with almost no damage. Four types of wood - spruce, pine, beech and oak - were ablated in all three main cutting directions prescribed for an anisotropic material such as wood. Several microscopic techniques were used. To measure the ablation depth LSM was applied. The surface roughness as well as the quality of the laser ablation was determined by using LV-SEM. CAM was used to measure the contact angle and thereby calculate the surface energy. Ablation can be carried out regardless of the cutting direction used to obtain clean and open surfaces free of artefacts. (© 2005 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Functional properties of microstructured cylinder liner surfaces for internal combustion enginesLUBRICATION SCIENCE, Issue 4 2005R. Golloch Abstract Internal combustion engines are still of major importance as propulsion systems. To fulfil future market and legislative demands it is necessary to improve engine performance, reduce fuel consumption, and limit exhaust emissions. Mechanical and thermodynamic losses, wear, and the emissions caused by lubricating oil combustion are principally influenced by the tribological behaviour of the piston assembly. The trend towards compact engines with high power densities and increased thermomechanical loads increases the importance of this tribological system and requires new approaches. One promising possibility is the utilisation of liner surfaces with specially machined microstructures. This paper describes a comparison between a conventional liner surface and a laser-structured liner as regards their tribological behaviour. Measurements of wear as well as of oil film thickness and friction force in operation have been carried out. The results show better tribological behaviour for the laser-structured liner surface than for the conventional plateau-honed surface. This leads to lower fuel consumption and less wear. [source] GaAs converters for high power densities of laser illuminationPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2008E. Oliva Abstract Photovoltaic power converters can be used to generate electricity directly from laser light. In this paper we report the development of GaAs PV power converters with improved conversion efficiency at high power densities. The incorporation of a lateral conduction layer (LCL) on top of the window layer resulted in a considerable gain in efficiency at high illumination levels. Additional performance improvements were obtained by using a metal electrode grid design and antireflection coating optimised for monochromatic and inhomogeneous laser light. Maximum monochromatic (810,nm) optical-to-electrical conversion efficiency of 54·9% at 36·5,W/cm2 has been achieved. The characteristics of laser power converters with p/n and n/p polarity are discussed in this paper. Moreover, different materials and doping levels were applied in the LCL. The performance of these different device structures at high laser intensity is presented and discussed. It is shown that the lateral series resistance of the cell has a major impact on the overall device performance. Copyright © 2008 John Wiley & Sons, Ltd. [source] Design and Synthesis of Hierarchical Nanowire Composites for Electrochemical Energy StorageADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Zheng Chen Abstract Nanocomposites of interpenetrating carbon nanotubes and vanadium pentoxide (V2O5) nanowires networks are synthesized via a simple in situ hydrothermal process. These fibrous nanocomposites are hierarchically porous with high surface area and good electric conductivity, which makes them excellent material candidates for supercapacitors with high energy density and power density. Nanocomposites with a capacitance up to 440 and 200,F g,1 are achieved at current densities of 0.25 and 10 A g,1, respectively. Asymmetric devices based on these nanocomposites and aqueous electrolyte exhibit an excellent charge/discharge capability, and high energy densities of 16,W h kg,1 at a power density of 75,W kg,1 and 5.5,W h kg,1 at a high power density of 3,750,W kg,1. This performance is a significant improvement over current electrochemical capacitors and is highly competetive with Ni,MH batteries. This work provides a new platform for high-density electrical-energy storage for electric vehicles and other applications. [source] Redox-Active Polypyrrole: Toward Polymer-Based Batteries,ADVANCED MATERIALS, Issue 13 2006H.-K. Song An energy-storage device consisting of polypyrrole (pPy) doped with indigo carmine (IC) and 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS) has been fabricated. These redox-active conducting polymers (see figure) form the basis of a battery that depends on the faradaic reactions of the redox-active dopants, and performs better than conventional batteries and ultracapacitors at high power density. [source] | |||||||||||||