The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
H Feng - One of the best experts on this subject based on the ideXlab platform.
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A New Type of High Pressure System for a Tian-Calvet Calorimeter
Journal of Thermal Analysis and Calorimetry, 1998Co-Authors: D.e.g. Jones, P. Handa, H FengAbstract:A Tian-Calvet heat flux calorimeter has been modified for use with High Pressures in measurements of thermal hazards of materials. The System comprising a specially designed High Pressure vessel and an associated manifold is described. With this System, comparative measurements using both standard and High Pressure vessels can be made, different materials and/or liners can be used for the High Pressure vessel and an assessment of the influence of the gaseous environment on thermal behaviour can be made. Calibration was carried out in the range 25 to 300°C at different Pressures and heating rates, using sapphire and the calibration results were verified with benzoic acid, both reference grade materials. With the new vessel, Pressures up to about 70 MPa can be used or recorded during the thermal decomposition of energetic materials. The reproducibility of the baseline, as illustrated by standard error results, was about 0.02% compared with 0.13% for the standard vessel, over the entire temperature range. The corresponding results for the baseline of the Pressure vessel at 5.5 MPa (in air and Ar) and in a calibration experiment with sapphire were 0.08%. Experimental data obtained for ammonium nitrate and 2,3-dimethyl-2,3-dinitrobutane in the standard and Pressure vessels are compared and discussed. The effect of Pressure and the nature of the gaseous environment (inert or oxidizing) on the results for these two materials will be described.
Stephen Yue - One of the best experts on this subject based on the ideXlab platform.
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Metallization of Various Polymers by Cold Spray
Journal of Thermal Spray Technology, 2018Co-Authors: Hanqing Che, Phuong Vo, Xin Chu, Stephen YueAbstract:Previous results have shown that metallic coat-ings can be successfully cold sprayed onto polymeric substrates. This paper studies the cold sprayability of var-ious metal powders on different polymeric substrates. Five different substrates were used, including carbon fiber reinforced polymer (CFRP), acrylonitrile butadiene styrene (ABS), polyether ether ketone (PEEK), polyethylenimine (PEI); mild steel was also used as a benchmark substrate. The CFRP used in this work has a thermosetting matrix, and the ABS, PEEK and PEI are all thermoplastic poly-mers, with different glass transition temperatures as well as a number of distinct mechanical properties. Three metal powders, tin, copper and iron, were cold sprayed with both a low-Pressure System and a High-Pressure System at vari-ous conditions. In general, cold spray on the thermoplastic polymers rendered more positive results than the ther-mosetting polymers, due to the local thermal softening mechanism in the thermoplastics. Thick copper coatings were successfully deposited on PEEK and PEI. Based on the results, a method is proposed to determine the feasi-bility and deposition window of cold spraying specific metal powder/polymeric substrate combinations.
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Metallization of carbon fibre reinforced polymers by cold spray
Surface and Coatings Technology, 2017Co-Authors: Hanqing Che, Phuong Vo, Stephen YueAbstract:Carbon fibre reinforced polymer (CFRP) is a very competitive alternative to aluminum for aircraft structures for lightweighting purposes, but this leaves vulnerability against lightning strike. Cold spray is one coating approach to metallize the polymers, making them lightning strike proof. The aim of this work is to investigate the viability of metallizing aircraft quality CFRPs by cold spray. Copper, aluminum and tin were cold sprayed onto the CFRPs with both a High-Pressure and a low-Pressure cold spray System. A number of different combinations of the gas Pressure and gas preheating temperature were used for the cold spray process. Erosion was found to be the key obstacle to developing continuous coatings on the CFRP substrates with the High-Pressure System. On the other hand, continuous tin coatings were successfully obtained on CFRP with the low-Pressure System, due to the very soft tin coating the substrate through a “crack filling” mechanism. Based on the results, it was proposed that when cold spraying metals on CFRP, it is necessary to differentiate between the development of the first layer and the build-up of subsequent layers. Last but not least, the effect of particle velocity and gas temperature was discussed and the deposition window of tin on CFRP was developed.
D. W. Hess - One of the best experts on this subject based on the ideXlab platform.
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UltraHigh vacuum surface analysis coupled with a High Pressure System for the study of near critical and supercritical fluid processing
Review of Scientific Instruments, 1997Co-Authors: G L Bakker, D. W. HessAbstract:A System has been constructed for ultraHigh vacuum analysis investigation of surfaces after High Pressure fluid processing. The System features a cell capable of withstanding Pressures up to 400 bar that opens directly into an ultraHigh vacuum (10−10 Torr) System to allow transfer of samples for analysis. Temperature control of the cell and fluid is possible to within ±1 °C up to temperatures of 400 °C. The High Pressure System design allows the preparation and study of supercritical fluid mixtures as well as of pure components. X-ray photoelectron spectroscopy, Auger electron spectroscopy, sputter etching, and vacuum anneal capabilities comprise the surface analysis System. The fluids investigated include supercritical carbon dioxide, methanol, water, and their mixtures; these are applied to processes such as surface cleaning and thin film etching using High Pressure fluids.
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UltraHigh vacuum surface analysis coupled with a High Pressure System for the study of near critical and supercritical fluid processing
Review of Scientific Instruments, 1997Co-Authors: G L Bakker, D. W. HessAbstract:A System has been constructed for ultraHigh vacuum analysis investigation of surfaces after High Pressure fluid processing. The System features a cell capable of withstanding Pressures up to 400 bar that opens directly into an ultraHigh vacuum (10-10) Torr) System to allow transfer of samples for analysis. Temperature control of the cell and fluid is possible to within ±1 degrees C up to temperatures of 400 oC. The High Pressure System design allows the preparation and study of supercritical fluid mixtures as well as of pure components. X-ray photoelectron spectroscopy, Auger electron spectroscopy, sputter etching, and vacuum anneal capabilities comprise the surface analysis System. The fluids investigated include supercritical carbon dioxide, methanol, water, and their mixtures; these are applied to processes such as surface cleaning and thin film etching using High Pressure fluids.
D.e.g. Jones - One of the best experts on this subject based on the ideXlab platform.
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A New Type of High Pressure System for a Tian-Calvet Calorimeter
Journal of Thermal Analysis and Calorimetry, 1998Co-Authors: D.e.g. Jones, P. Handa, H FengAbstract:A Tian-Calvet heat flux calorimeter has been modified for use with High Pressures in measurements of thermal hazards of materials. The System comprising a specially designed High Pressure vessel and an associated manifold is described. With this System, comparative measurements using both standard and High Pressure vessels can be made, different materials and/or liners can be used for the High Pressure vessel and an assessment of the influence of the gaseous environment on thermal behaviour can be made. Calibration was carried out in the range 25 to 300°C at different Pressures and heating rates, using sapphire and the calibration results were verified with benzoic acid, both reference grade materials. With the new vessel, Pressures up to about 70 MPa can be used or recorded during the thermal decomposition of energetic materials. The reproducibility of the baseline, as illustrated by standard error results, was about 0.02% compared with 0.13% for the standard vessel, over the entire temperature range. The corresponding results for the baseline of the Pressure vessel at 5.5 MPa (in air and Ar) and in a calibration experiment with sapphire were 0.08%. Experimental data obtained for ammonium nitrate and 2,3-dimethyl-2,3-dinitrobutane in the standard and Pressure vessels are compared and discussed. The effect of Pressure and the nature of the gaseous environment (inert or oxidizing) on the results for these two materials will be described.
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A New Type of High Pressure System for a Tian-Calvet Calorimeter
Journal of Thermal Analysis and Calorimetry, 1998Co-Authors: D.e.g. Jones, P. Handa, H. T. FengAbstract:A Tian-Calvet heat flux calorimeter has been modified for use with High Pressures in measurements of thermal hazards of materials. The System comprising a specially designed High Pressure vessel and an associated manifold is described. With this System, comparative measurements using both standard and High Pressure vessels can be made, different materials and/or liners can be used for the High Pressure vessel and an assessment of the influence of the gaseous environment on thermal behaviour can be made. Calibration was carried out in the range 25 to 300°C at different Pressures and heating rates, using sapphire and the calibration results were verified with benzoic acid, both reference grade materials. With the new vessel, Pressures up to about 70 MPa can be used or recorded during the thermal decomposition of energetic materials.
Michael Joshua Cunningham - One of the best experts on this subject based on the ideXlab platform.
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Air System Management for Fuel Cell Vehicle Applications
Fuel Cell, 2001Co-Authors: Michael Joshua CunninghamAbstract:Research and development of fuel cell Systems for multiple applications has dramatically increased in the past few years. The vehicular application of the fuel cell System as the powertrain leads to a number of unique challenges, namely physical packaging within the vehicle, durability and operation under extreme environmental conditions, and demanding duty cycles that include High peak power requirements and a rapid response time. The focus of this research is on the air management System of the fuel cell powertrain in the vehicular application. Specifically, the work has solely focused on numeric simulation (modeling) using fundamental calculations and characterization of existing laboratory data. The motivation for the modeling project has been to create a tool for supplementing physical System research. As may be expected, the full System can be quite complex and the optimum configuration choice is not always clear. Using a modeling tool, a System designer can experiment with various configurations and analyze their relative tradeoffs prior to physically building the System of choice. Specific to the air System, various types of compressors and energy recovery devices exist, and with each component comes a unique optimum control scheme for the fuel cell System. This research, therefore, is designed to address the following motivating questions. First, what model design will realistically characterize the performance of the laboratory-tested air System? And second, what are the relative differences in System performance when the air System configuration is altered? Both of these questions are addressed in this thesis. v Much of the work from this research was published in three independent papers, which are included in this thesis. A few of the research findings are included here. Section 2.1 Highlights an analysis comparing an air System with and without the use of an expander (turbine). It is shown that the use of the expander (turbine) results in an improvement to the System efficiency at peak power levels. However, under normal driving conditions, peak power levels are demanded only a small fraction of the time. Therefore, it becomes less clear as to whether the added complexity and cost of an expander (turbine) would be beneficial. For example, for a fixed fuel cell stack size, the net efficiency is improved by approximately 4 % in the Higher power region above 24kW net compared to the System without the expander. However, net efficiency is almost unchanged in the lower power region used most of the time. Alternatively, for a fixed peak power, the stack size can be reduced by about 13% using an expander compared to the fuel cell stack size required in a System without an expander. Section 2.2 presents findings from a study comparing a low Pressure air System to that of a High Pressure System. The results of the study demonstrate that equivalent direct hydrogen fuel cell peak net System power values (86kW) can be obtained with both types of air supply configurations but require different stack sizes. For the blower application, the stack size had to be increased by 16.3% (500 vs. 430 cells in this example) for the same peak net power of 86kW. Finally, Section 2.3 Highlights research focused solely on the modeling structure of an air System in the context of the fuel cell engine. It was found that to maximize the performance of a particular fuel cell System configuration, it is useful to have a model that can compare various air supply technologies in the context of the System operation.