The Experts below are selected from a list of 180 Experts worldwide ranked by ideXlab platform

Dongil Kwon - One of the best experts on this subject based on the ideXlab platform.

  • assessment of thin film hardness through elastic plastic stress analysis in a Microindentation Test
    Journal of Applied Physics, 1997
    Co-Authors: Jeong-hoon Ahn, Dongil Kwon
    Abstract:

    The true hardness of thin film is assessed through micromechanical analysis of the composite hardness measured by a Microindentation Tester. In partitioning the respective contributions of the film and the substrate to the composite hardness, we apply the modified plastic-zone volume-law-of-mixtures theory by analyzing the indentation stress field of a film/substrate system. At this time, while the substrate is assumed to undergo radial deformation, the film is assumed to be deformed mainly parallel to the surface. On the basis of these stress analyses, the influence of interface is incorporated; the deformation in the softer material is constrained by interface bonding and the plastic-zone radii are modified by considering the respective virtual pressures that the film and the substrate actually support. When an interface has perfect bonding, the hardness value for a film can be calculated analytically from the condition of strain matching at the interface—approximately 2200 kgf/mm2 for diamondlike carbo...

  • Assessment of thin-film hardness through elastic/plastic stress analysis in a Microindentation Test
    Journal of Applied Physics, 1997
    Co-Authors: Jeong-hoon Ahn, Dongil Kwon
    Abstract:

    The true hardness of thin film is assessed through micromechanical analysis of the composite hardness measured by a Microindentation Tester. In partitioning the respective contributions of the film and the substrate to the composite hardness, we apply the modified plastic-zone volume-law-of-mixtures theory by analyzing the indentation stress field of a film/substrate system. At this time, while the substrate is assumed to undergo radial deformation, the film is assumed to be deformed mainly parallel to the surface. On the basis of these stress analyses, the influence of interface is incorporated; the deformation in the softer material is constrained by interface bonding and the plastic-zone radii are modified by considering the respective virtual pressures that the film and the substrate actually support. When an interface has perfect bonding, the hardness value for a film can be calculated analytically from the condition of strain matching at the interface—approximately 2200 kgf/mm2 for diamondlike carbo...

Y J Chao - One of the best experts on this subject based on the ideXlab platform.

  • 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, 2009
    Co-Authors: Jinzhu Tan, Y J Chao, J.w. Van Zee
    Abstract:

    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.

  • Chemical and mechanical stability of EPDM in a PEM fuel cell environment
    Polymer Degradation and Stability, 2009
    Co-Authors: Jinzhu Tan, Y J Chao, Haifeng Wang, Jianming Gong, J.w. Van Zee
    Abstract:

    Proton exchange membrane (PEM) fuel cell stack requires elastomeric 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 elastomeric gasket material. Chemical and mechanical stability of the elastomeric material is of great concern to the overall performance of the fuel cell stacks. The degradation of a commercially available gasket material, ethylene-propylene-diene monomer (EPDM), was investigated in a simulated PEM fuel cell environment in this work. One solution and two temperatures, based on actual fuel cell operation, were used in this study. Optical microscopy was used to show the topographical changes on the sample surface. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the surface chemistry of the gasket material before and after exposure to the simulated PEM fuel cell environment over time. Atomic absorption spectrometry was used to identify the leachants in the soaking solution from the elastomeric material. Microindentation Test and dynamic mechanical analysis (DMA) were conducted to assess the change of mechanical properties of the samples exposed to the environment. The atomic absorption spectrometer analysis shows that silicon and calcium were leached from the material into the soaking solution. The ATR-FTIR results indicate that the chemical changes were not apparent. The Microindentation Test and DMA results reveal that mechanical properties were not changed significantly.

  • Assessment of Mechanical Properties of Fluoroelastomer and EPDM in a Simulated PEM Fuel Cell Environment by Microindentation Test
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008
    Co-Authors: Y J Chao, Xinnan Wang, Xiaodong Li, Min Yang
    Abstract:

    Abstract The elastomeric materials used as seals/gaskets in Polymer Electrolyte Membrane (PEM) fuel cells are exposed to acidic environment, humid air and hydrogen, and subjected to mechanical compressive load. Both sealing and electrochemical performance of the fuel cell depend heavily on the long-term mechanical and chemical stability of these materials. In this paper, mechanical property degradation of two elastomeric materials, Fluoroelastomer and EPDM, which are being considered as gasket materials for PEM fuel cells, was investigated using Microindentation. 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, based on actual fuel cell operation, 80 and 60 °C, were selected in this study. Mechanical properties of the samples before and after exposure to the environment were assessed. Hysteresis loss energy, indentation load, elastic modulus and hardness were obtained from the loading and unloading curves. Indentation deformation was studied using Hertz contact model. It was found that the mechanical properties of the Fluoroelastomer samples changed significantly after exposure to the simulated environment over time. The exposure medium, temperature and applied compressive load contributed to the degradation of the material. On the other hand, the change of mechanical properties for the EPDM samples was not apparent. It is concluded that EPDM is much more stable than Fluoroelastomer for PEM seal applications.

J.w. Van Zee - One of the best experts on this subject based on the ideXlab platform.

  • 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, 2009
    Co-Authors: Jinzhu Tan, Y J Chao, J.w. Van Zee
    Abstract:

    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.

  • Chemical and mechanical stability of EPDM in a PEM fuel cell environment
    Polymer Degradation and Stability, 2009
    Co-Authors: Jinzhu Tan, Y J Chao, Haifeng Wang, Jianming Gong, J.w. Van Zee
    Abstract:

    Proton exchange membrane (PEM) fuel cell stack requires elastomeric 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 elastomeric gasket material. Chemical and mechanical stability of the elastomeric material is of great concern to the overall performance of the fuel cell stacks. The degradation of a commercially available gasket material, ethylene-propylene-diene monomer (EPDM), was investigated in a simulated PEM fuel cell environment in this work. One solution and two temperatures, based on actual fuel cell operation, were used in this study. Optical microscopy was used to show the topographical changes on the sample surface. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the surface chemistry of the gasket material before and after exposure to the simulated PEM fuel cell environment over time. Atomic absorption spectrometry was used to identify the leachants in the soaking solution from the elastomeric material. Microindentation Test and dynamic mechanical analysis (DMA) were conducted to assess the change of mechanical properties of the samples exposed to the environment. The atomic absorption spectrometer analysis shows that silicon and calcium were leached from the material into the soaking solution. The ATR-FTIR results indicate that the chemical changes were not apparent. The Microindentation Test and DMA results reveal that mechanical properties were not changed significantly.

Min Yang - One of the best experts on this subject based on the ideXlab platform.

  • Assessment of Mechanical Properties of Fluoroelastomer and EPDM in a Simulated PEM Fuel Cell Environment by Microindentation Test
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008
    Co-Authors: Y J Chao, Xinnan Wang, Xiaodong Li, Min Yang
    Abstract:

    Abstract The elastomeric materials used as seals/gaskets in Polymer Electrolyte Membrane (PEM) fuel cells are exposed to acidic environment, humid air and hydrogen, and subjected to mechanical compressive load. Both sealing and electrochemical performance of the fuel cell depend heavily on the long-term mechanical and chemical stability of these materials. In this paper, mechanical property degradation of two elastomeric materials, Fluoroelastomer and EPDM, which are being considered as gasket materials for PEM fuel cells, was investigated using Microindentation. 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, based on actual fuel cell operation, 80 and 60 °C, were selected in this study. Mechanical properties of the samples before and after exposure to the environment were assessed. Hysteresis loss energy, indentation load, elastic modulus and hardness were obtained from the loading and unloading curves. Indentation deformation was studied using Hertz contact model. It was found that the mechanical properties of the Fluoroelastomer samples changed significantly after exposure to the simulated environment over time. The exposure medium, temperature and applied compressive load contributed to the degradation of the material. On the other hand, the change of mechanical properties for the EPDM samples was not apparent. It is concluded that EPDM is much more stable than Fluoroelastomer for PEM seal applications.

Jeong-hoon Ahn - One of the best experts on this subject based on the ideXlab platform.

  • assessment of thin film hardness through elastic plastic stress analysis in a Microindentation Test
    Journal of Applied Physics, 1997
    Co-Authors: Jeong-hoon Ahn, Dongil Kwon
    Abstract:

    The true hardness of thin film is assessed through micromechanical analysis of the composite hardness measured by a Microindentation Tester. In partitioning the respective contributions of the film and the substrate to the composite hardness, we apply the modified plastic-zone volume-law-of-mixtures theory by analyzing the indentation stress field of a film/substrate system. At this time, while the substrate is assumed to undergo radial deformation, the film is assumed to be deformed mainly parallel to the surface. On the basis of these stress analyses, the influence of interface is incorporated; the deformation in the softer material is constrained by interface bonding and the plastic-zone radii are modified by considering the respective virtual pressures that the film and the substrate actually support. When an interface has perfect bonding, the hardness value for a film can be calculated analytically from the condition of strain matching at the interface—approximately 2200 kgf/mm2 for diamondlike carbo...

  • Assessment of thin-film hardness through elastic/plastic stress analysis in a Microindentation Test
    Journal of Applied Physics, 1997
    Co-Authors: Jeong-hoon Ahn, Dongil Kwon
    Abstract:

    The true hardness of thin film is assessed through micromechanical analysis of the composite hardness measured by a Microindentation Tester. In partitioning the respective contributions of the film and the substrate to the composite hardness, we apply the modified plastic-zone volume-law-of-mixtures theory by analyzing the indentation stress field of a film/substrate system. At this time, while the substrate is assumed to undergo radial deformation, the film is assumed to be deformed mainly parallel to the surface. On the basis of these stress analyses, the influence of interface is incorporated; the deformation in the softer material is constrained by interface bonding and the plastic-zone radii are modified by considering the respective virtual pressures that the film and the substrate actually support. When an interface has perfect bonding, the hardness value for a film can be calculated analytically from the condition of strain matching at the interface—approximately 2200 kgf/mm2 for diamondlike carbo...