The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jinzhu Tan - One of the best experts on this subject based on the ideXlab platform.
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chemical aging of the silicone rubber in a simulated and three accelerated proton exchange membrane fuel cell environments
Journal of Power Sources, 2012Co-Authors: Jinzhu Tan, Jianming GongAbstract:Abstract Long-term stability and durability of Gaskets in Proton Exchange Membrane (PEM) fuel cell are important to both sealing and the electrochemical performance of PEM fuel cells. In this paper, the time-dependent aging process of silicone rubber, which is one of the potential Gasket materials for PEM fuel cells, is investigated in one simulated PEM fuel cell environment and three accelerated durability test (ADT) media at 70 °C. Optical microscopy is employed to observe the topographical changes on the surfaces of samples. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) are used to study the surface chemistry of the samples before and after exposure to the test environments over time. The optical microscopy results indicate that the surface conditions of the samples change from initially smooth to rough, crack appearance and finally crack propagation. The ATR-FTIR and XPS results reveal that the degradation mechanisms of the silicone rubber are likely due to the de-crosslinking and chain scission in the backbone, and the acid has a significant effect on the degradation.
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chemical degradation of five elastomeric seal materials in a simulated and an accelerated pem fuel cell environment
Journal of Power Sources, 2011Co-Authors: Jinzhu Tan, Y J Chao, Chihwei Lin, Chihui Chien, J W Van ZeeAbstract:Abstract Polymer electrolyte membrane (PEM) fuel cell stack requires Gaskets and seals in each cell to keep the hydrogen and air/oxygen within their respective regions. The stability of the Gaskets/seals is critical to the operating life as well as the electrochemical performance of the fuel cell. Chemical degradation of five elastomeric Gasket materials in a simulated and an aggressive accelerated fuel cell solution at PEM operating temperature for up to 63 weeks was investigated in this work. The five materials are copolymeric resin (CR), liquid silicone rubber (LSR), fluorosilicone rubber (FSR), ethylene propylene diene monomer rubber (EPDM), and fluoroelastomer copolymer (FKM). Using optical microscopy, topographical changes on the sample surface due to the acidic environment were revealed. Weight loss of the test samples was monitored. Atomic absorption spectrometer analysis was performed to study the silicon, calcium, and magnesium leachants from the materials into the soaking solution. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the surface chemistry of the materials before and after exposure to the simulated fuel cell environment over time. Among the five materials studied, CR and LSR in the accelerated solution are not as stable as the other three materials. FSR appears to be the most stable.
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chemical and mechanical stability of a silicone Gasket material exposed to pem fuel cell environment
International Journal of Hydrogen Energy, 2011Co-Authors: Jinzhu Tan, Y J Chao, W K Lee, Min Yang, J W Van ZeeAbstract:Proton exchange membrane (PEM) fuel cell stack requires Gaskets in each cell to keep the reactant gas and liquid within their respective regions. Long-term chemical and mechanical stability and durability of the Gaskets are critical to both sealing and the electrochemical performance of the fuel cells. In this paper, the chemical and mechanical degradation of a commercially available elastomeric Silicone material were investigated. A simulated solution at two temperatures, that are close to actual PEM fuel cell environment, was used. Optical microscopy was used to show the topographical changes on the sample surface. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and atomic absorption spectrometer analysis were employed to study the surface chemical degradation of the samples after exposure to the simulated PEM fuel cell environment. Microindentation and dynamic mechanical analysis (DMA) were used to assess the change of mechanical properties of the samples exposed to the environment. The ATR-FTIR results indicate that the surface chemistry of the Silicone material was altered after exposure to the environment over time. In addition, atomic absorption spectrometry detected silicon and Calcium leached from the Gasket material into the soaking solution. Microindentation test results show that the sample surface hardening occurred and the elastic modulus increased for the Silicone material exposed to the environment.
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microindentation test for assessing the mechanical properties of silicone rubber exposed to a simulated polymer electrolyte membrane fuel cell environment
Journal of Fuel Cell Science and Technology, 2009Co-Authors: Jinzhu Tan, Y J Chao, J W Van ZeeAbstract:The elastomeric materials used as seals and Gaskets in polymer electrolyte membrane (PEM) fuel cells are exposed to acidic environment, humid air, and hydrogen, and subjected to mechanical compressive load. The long-term mechanical and chemical stability of these materials is critical to both sealing and the electrochemical performance of the fuel cell. In this paper, mechanical degradation of two elastomeric materials, Silicone S and Silicone G, which are potential Gasket materials for PEM fuel cells, was investigated. Test samples were subjected to various compressive loads to simulate the actual loading in addition to soaking in a simulated PEM fuel cell environment. Two temperatures, 80°C and 60°C, were selected and used in this study. Mechanical properties of the samples before and after exposure to the environment were studied by microindentation. Indentation load, elastic modulus, and hardness were obtained from the loading and unloading curves. Indentation deformation was studied using Hertz contact model. Dynamic mechanical analysis was conducted to verify the elastic modulus obtained by Hertz contact model. It was found that the mechanical properties of the samples changed considerably after exposure to the simulated environment over time. The temperature and the applied compressive load play a significant role in the mechanical degradation. The microindentation method is proved to provide a simple and efficient way to evaluate the mechanical properties of Gasket materials.
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degradation of elastomeric Gasket materials in pem fuel cells
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Jinzhu Tan, Y J Chao, J W Van Zee, W K LeeAbstract:Polymer electrolyte membrane (PEM) fuel cell stack requires Gaskets in each cell to keep the reactant gases within their respective regions. Long-term durability of the fuel cell stacks depends heavily on the functionality of the Gaskets. Both the leachants from the seal materials and the cracking of the seals are of great concern to the overall durability of the fuel cell stacks. The degradation of four commercially available Gasket materials was investigated in a PEM fuel cell environment in this study. Optical microscopy reveals that the degradation starts with surface roughness from the early stage of exposure and finally results in cracks over time. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to study the surface chemistry of the Gasket materials before and after exposure to the PEM fuel cell environment over time. Results from these analyses indicate that the surface chemistry changed initially as a manifestation of the chemical degradation and proceeded via de-cross-linking and chain scission in the backbone. Atomic adsorption spectrometry analysis was used to identify the leachants in the soaking solution from the Gasket materials. The effect due to applied stress is reported as well.
J W Van Zee - One of the best experts on this subject based on the ideXlab platform.
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chemical degradation of five elastomeric seal materials in a simulated and an accelerated pem fuel cell environment
Journal of Power Sources, 2011Co-Authors: Jinzhu Tan, Y J Chao, Chihwei Lin, Chihui Chien, J W Van ZeeAbstract:Abstract Polymer electrolyte membrane (PEM) fuel cell stack requires Gaskets and seals in each cell to keep the hydrogen and air/oxygen within their respective regions. The stability of the Gaskets/seals is critical to the operating life as well as the electrochemical performance of the fuel cell. Chemical degradation of five elastomeric Gasket materials in a simulated and an aggressive accelerated fuel cell solution at PEM operating temperature for up to 63 weeks was investigated in this work. The five materials are copolymeric resin (CR), liquid silicone rubber (LSR), fluorosilicone rubber (FSR), ethylene propylene diene monomer rubber (EPDM), and fluoroelastomer copolymer (FKM). Using optical microscopy, topographical changes on the sample surface due to the acidic environment were revealed. Weight loss of the test samples was monitored. Atomic absorption spectrometer analysis was performed to study the silicon, calcium, and magnesium leachants from the materials into the soaking solution. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the surface chemistry of the materials before and after exposure to the simulated fuel cell environment over time. Among the five materials studied, CR and LSR in the accelerated solution are not as stable as the other three materials. FSR appears to be the most stable.
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chemical and mechanical stability of a silicone Gasket material exposed to pem fuel cell environment
International Journal of Hydrogen Energy, 2011Co-Authors: Jinzhu Tan, Y J Chao, W K Lee, Min Yang, J W Van ZeeAbstract:Proton exchange membrane (PEM) fuel cell stack requires Gaskets in each cell to keep the reactant gas and liquid within their respective regions. Long-term chemical and mechanical stability and durability of the Gaskets are critical to both sealing and the electrochemical performance of the fuel cells. In this paper, the chemical and mechanical degradation of a commercially available elastomeric Silicone material were investigated. A simulated solution at two temperatures, that are close to actual PEM fuel cell environment, was used. Optical microscopy was used to show the topographical changes on the sample surface. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and atomic absorption spectrometer analysis were employed to study the surface chemical degradation of the samples after exposure to the simulated PEM fuel cell environment. Microindentation and dynamic mechanical analysis (DMA) were used to assess the change of mechanical properties of the samples exposed to the environment. The ATR-FTIR results indicate that the surface chemistry of the Silicone material was altered after exposure to the environment over time. In addition, atomic absorption spectrometry detected silicon and Calcium leached from the Gasket material into the soaking solution. Microindentation test results show that the sample surface hardening occurred and the elastic modulus increased for the Silicone material exposed to the environment.
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microindentation test for assessing the mechanical properties of silicone rubber exposed to a simulated polymer electrolyte membrane fuel cell environment
Journal of Fuel Cell Science and Technology, 2009Co-Authors: Jinzhu Tan, Y J Chao, J W Van ZeeAbstract:The elastomeric materials used as seals and Gaskets in polymer electrolyte membrane (PEM) fuel cells are exposed to acidic environment, humid air, and hydrogen, and subjected to mechanical compressive load. The long-term mechanical and chemical stability of these materials is critical to both sealing and the electrochemical performance of the fuel cell. In this paper, mechanical degradation of two elastomeric materials, Silicone S and Silicone G, which are potential Gasket materials for PEM fuel cells, was investigated. Test samples were subjected to various compressive loads to simulate the actual loading in addition to soaking in a simulated PEM fuel cell environment. Two temperatures, 80°C and 60°C, were selected and used in this study. Mechanical properties of the samples before and after exposure to the environment were studied by microindentation. Indentation load, elastic modulus, and hardness were obtained from the loading and unloading curves. Indentation deformation was studied using Hertz contact model. Dynamic mechanical analysis was conducted to verify the elastic modulus obtained by Hertz contact model. It was found that the mechanical properties of the samples changed considerably after exposure to the simulated environment over time. The temperature and the applied compressive load play a significant role in the mechanical degradation. The microindentation method is proved to provide a simple and efficient way to evaluate the mechanical properties of Gasket materials.
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degradation of elastomeric Gasket materials in pem fuel cells
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Jinzhu Tan, Y J Chao, J W Van Zee, W K LeeAbstract:Polymer electrolyte membrane (PEM) fuel cell stack requires Gaskets in each cell to keep the reactant gases within their respective regions. Long-term durability of the fuel cell stacks depends heavily on the functionality of the Gaskets. Both the leachants from the seal materials and the cracking of the seals are of great concern to the overall durability of the fuel cell stacks. The degradation of four commercially available Gasket materials was investigated in a PEM fuel cell environment in this study. Optical microscopy reveals that the degradation starts with surface roughness from the early stage of exposure and finally results in cracks over time. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to study the surface chemistry of the Gasket materials before and after exposure to the PEM fuel cell environment over time. Results from these analyses indicate that the surface chemistry changed initially as a manifestation of the chemical degradation and proceeded via de-cross-linking and chain scission in the backbone. Atomic adsorption spectrometry analysis was used to identify the leachants in the soaking solution from the Gasket materials. The effect due to applied stress is reported as well.
Zhaolei Sun - One of the best experts on this subject based on the ideXlab platform.
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numerical and experimental study on heat transfer characteristic and thermal load of the freezer Gasket in frost free refrigerators
International Journal of Refrigeration-revue Internationale Du Froid, 2016Co-Authors: Gang Yan, Qi Chen, Zhaolei SunAbstract:Abstract The present study has been carried out to analyze the heat transfer characteristics and thermal load near the freezer Gasket region of a 649 L domestic frost-free refrigerator/freezer. Both 3D numerical simulations and experimental test were performed. The numerical models for different freezer Gasket sections were developed, while considering the non-uniform distribution of temperature inside the freezer cabinet. The calculated temperatures showed acceptable agreement with the measured temperatures. The total thermal load of Gasket region is 10.57/6.68 W, in the status of compressor on/off. Thermal load of cold-bridge accounts for 23.8%/25.8% of the total thermal load, and thermal load of Gasket bulk holds 76.2%/74.2%, respectively. When the compressor on–off time ratio is 7:3, total thermal load near the freezer Gasket region is 9.40 W during an on–off cycling operation of compressor, accounting for 17.1% of the total thermal load in the freezer cabinet.
Y J Chao - One of the best experts on this subject based on the ideXlab platform.
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chemical degradation of five elastomeric seal materials in a simulated and an accelerated pem fuel cell environment
Journal of Power Sources, 2011Co-Authors: Jinzhu Tan, Y J Chao, Chihwei Lin, Chihui Chien, J W Van ZeeAbstract:Abstract Polymer electrolyte membrane (PEM) fuel cell stack requires Gaskets and seals in each cell to keep the hydrogen and air/oxygen within their respective regions. The stability of the Gaskets/seals is critical to the operating life as well as the electrochemical performance of the fuel cell. Chemical degradation of five elastomeric Gasket materials in a simulated and an aggressive accelerated fuel cell solution at PEM operating temperature for up to 63 weeks was investigated in this work. The five materials are copolymeric resin (CR), liquid silicone rubber (LSR), fluorosilicone rubber (FSR), ethylene propylene diene monomer rubber (EPDM), and fluoroelastomer copolymer (FKM). Using optical microscopy, topographical changes on the sample surface due to the acidic environment were revealed. Weight loss of the test samples was monitored. Atomic absorption spectrometer analysis was performed to study the silicon, calcium, and magnesium leachants from the materials into the soaking solution. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the surface chemistry of the materials before and after exposure to the simulated fuel cell environment over time. Among the five materials studied, CR and LSR in the accelerated solution are not as stable as the other three materials. FSR appears to be the most stable.
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chemical and mechanical stability of a silicone Gasket material exposed to pem fuel cell environment
International Journal of Hydrogen Energy, 2011Co-Authors: Jinzhu Tan, Y J Chao, W K Lee, Min Yang, J W Van ZeeAbstract:Proton exchange membrane (PEM) fuel cell stack requires Gaskets in each cell to keep the reactant gas and liquid within their respective regions. Long-term chemical and mechanical stability and durability of the Gaskets are critical to both sealing and the electrochemical performance of the fuel cells. In this paper, the chemical and mechanical degradation of a commercially available elastomeric Silicone material were investigated. A simulated solution at two temperatures, that are close to actual PEM fuel cell environment, was used. Optical microscopy was used to show the topographical changes on the sample surface. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and atomic absorption spectrometer analysis were employed to study the surface chemical degradation of the samples after exposure to the simulated PEM fuel cell environment. Microindentation and dynamic mechanical analysis (DMA) were used to assess the change of mechanical properties of the samples exposed to the environment. The ATR-FTIR results indicate that the surface chemistry of the Silicone material was altered after exposure to the environment over time. In addition, atomic absorption spectrometry detected silicon and Calcium leached from the Gasket material into the soaking solution. Microindentation test results show that the sample surface hardening occurred and the elastic modulus increased for the Silicone material exposed to the environment.
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microindentation test for assessing the mechanical properties of silicone rubber exposed to a simulated polymer electrolyte membrane fuel cell environment
Journal of Fuel Cell Science and Technology, 2009Co-Authors: Jinzhu Tan, Y J Chao, J W Van ZeeAbstract:The elastomeric materials used as seals and Gaskets in polymer electrolyte membrane (PEM) fuel cells are exposed to acidic environment, humid air, and hydrogen, and subjected to mechanical compressive load. The long-term mechanical and chemical stability of these materials is critical to both sealing and the electrochemical performance of the fuel cell. In this paper, mechanical degradation of two elastomeric materials, Silicone S and Silicone G, which are potential Gasket materials for PEM fuel cells, was investigated. Test samples were subjected to various compressive loads to simulate the actual loading in addition to soaking in a simulated PEM fuel cell environment. Two temperatures, 80°C and 60°C, were selected and used in this study. Mechanical properties of the samples before and after exposure to the environment were studied by microindentation. Indentation load, elastic modulus, and hardness were obtained from the loading and unloading curves. Indentation deformation was studied using Hertz contact model. Dynamic mechanical analysis was conducted to verify the elastic modulus obtained by Hertz contact model. It was found that the mechanical properties of the samples changed considerably after exposure to the simulated environment over time. The temperature and the applied compressive load play a significant role in the mechanical degradation. The microindentation method is proved to provide a simple and efficient way to evaluate the mechanical properties of Gasket materials.
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degradation of elastomeric Gasket materials in pem fuel cells
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Jinzhu Tan, Y J Chao, J W Van Zee, W K LeeAbstract:Polymer electrolyte membrane (PEM) fuel cell stack requires Gaskets in each cell to keep the reactant gases within their respective regions. Long-term durability of the fuel cell stacks depends heavily on the functionality of the Gaskets. Both the leachants from the seal materials and the cracking of the seals are of great concern to the overall durability of the fuel cell stacks. The degradation of four commercially available Gasket materials was investigated in a PEM fuel cell environment in this study. Optical microscopy reveals that the degradation starts with surface roughness from the early stage of exposure and finally results in cracks over time. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to study the surface chemistry of the Gasket materials before and after exposure to the PEM fuel cell environment over time. Results from these analyses indicate that the surface chemistry changed initially as a manifestation of the chemical degradation and proceeded via de-cross-linking and chain scission in the backbone. Atomic adsorption spectrometry analysis was used to identify the leachants in the soaking solution from the Gasket materials. The effect due to applied stress is reported as well.
Alexander Teplyaev - One of the best experts on this subject based on the ideXlab platform.
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vibration modes of 3n Gaskets and other fractals
Journal of Physics A, 2008Co-Authors: N Bajorin, Tao Chen, Alon Dagan, C Emmons, Mohamed Hussein, M Khalil, P Mody, Benjamin Steinhurst, Alexander TeplyaevAbstract:We rigorously study eigenvalues and eigenfunctions (vibration modes) on the class of self-similar symmetric finitely ramified fractals, which include the Sierpinski Gasket and other 3n-Gaskets. We consider the classical Laplacian on fractals which generalizes the usual one-dimensional second derivative, is the generator of the self-similar diffusion process, and has possible applications as the quantum Hamiltonian. We develop a theoretical matrix analysis, including analysis of singularities, which allows us to compute eigenvalues, eigenfunctions and their multiplicities exactly. We support our theoretical analysis by symbolic and numerical computations. Our analysis, in particular, allows the computation of the spectral zeta function on fractals and the limiting distribution of eigenvalues (i.e., integrated density of states). We consider such examples as the level-3 Sierpinski Gasket, a fractal 3-tree, and the diamond fractal.
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spectral analysis on infinite sierpinski Gaskets
Journal of Functional Analysis, 1998Co-Authors: Alexander TeplyaevAbstract:We study the spectral properties of the Laplacian on infinite Sierpin ski Gaskets. We prove that the Laplacian with the Neumann boundary condition has pure point spectrum. Moreover, the set of eigenfunctions with compact support is complete. The same is true if the infinite Sierpin ski Gasket has no boundary, but is false for the Laplacian with the Dirichlet boundary condition. In all these cases we describe the spectrum of the Laplacian and all the eigenfunctions with compact support. To obtain these results, first we prove certain new formulas for eigenprojectors of the Laplacian on finite Sierpin ski pre-Gaskets. Then we prove that the spectrum of the discrete Laplacian on a Sierpin ski lattice is pure point, and the eigenfunctions are localized. 1998 Academic Press
