The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jack S Hu - One of the best experts on this subject based on the ideXlab platform.
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estimation of Contact Resistance in proton exchange membrane fuel cells
Journal of Power Sources, 2006Co-Authors: Lianhong Zhang, Ying Liu, Haimin Song, Shuxin Wang, Y Zhou, Jack S HuAbstract:The Contact Resistance between the bipolar plate (BPP) and the gas diffusion layer (GDL) is an important factor contributing to the power loss in proton exchange membrane (PEM) fuel cells. At present there is still not a well-developed method to estimate such Contact Resistance. This paper proposes two effective methods for estimating the Contact Resistance between the BPP and the GDL based on an experimental Contact Resistance–pressure constitutive relation. The constitutive relation was obtained by experimentally measuring the Contact Resistance between the GDL and a flat plate of the same material and processing conditions as the BPP under stated Contact pressure. In the first method, which was a simplified prediction, the Contact area and Contact pressure between the BPP and the GDL were analyzed with a simple geometrical relation and the Contact Resistance was obtained by the Contact Resistance–pressure constitutive relation. In the second method, the Contact area and Contact pressure between the BPP and GDL were analyzed using FEM and the Contact Resistance was computed for each Contact element according to the constitutive relation. The total Contact Resistance was then calculated by considering all Contact elements in parallel. The influence of load distribution on Contact Resistance was also investigated. Good agreement was demonstrated between experimental results and predictions by both methods. The simplified prediction method provides an efficient approach to estimating the Contact Resistance in PEM fuel cells. The proposed methods for estimating the Contact Resistance can be useful in modeling and optimizing the assembly process to improve the performance of PEM fuel cells.
Hyonny Kim - One of the best experts on this subject based on the ideXlab platform.
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effects of a carbon nanotube layer on electrical Contact Resistance between copper substrates
Nanotechnology, 2006Co-Authors: Myounggu Park, Baratunde A Cola, Thomas Siegmund, Jun Xu, Matthew R Maschmann, Timothy S Fisher, Hyonny KimAbstract:Reduction of Contact Resistance is demonstrated at Cu–Cu interfaces using a multiwalled carbon nanotube (MWCNT) layer as an electrically conductive interfacial material. The MWCNTs are grown on a copper substrate using plasma enhanced chemical vapour deposition (PECVD) with nickel as the catalyst material, and methane and hydrogen as feed gases. The MWCNTs showed random growth directions and had a bamboo-like structure. Contact Resistance and reaction force were measured for a bare Cu–Cu interface and a Cu–MWCNT–Cu interface as a function of probe position. For an apparent Contact area of 0.31 mm 2 ,a n80% reduction in Contact Resistance was observed when the MWCNT layer was used. Resistance decreased with increasing Contact force, thereby making it possible to use this arrangement as a small-scale force sensor. Also, the Cu–MWCNT–Cu interface was roughly two times stiffer than the bare Cu–Cu interface. Contact area enlargement and van der Waals interactions are identified as important contributors to the Contact Resistance reduction and stiffness increase. A model based on compaction of the MWCNT layer is presented and found to be capable of predicting Resistance change over the range of measured force. (Some figures in this article are in colour only in the electronic version)
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effects of a carbon nanotube layer on electrical Contact Resistance between copper substrates
Nanotechnology, 2006Co-Authors: Myounggu Park, Baratunde A Cola, Thomas Siegmund, Matthew R Maschmann, Timothy S Fisher, Hyonny KimAbstract:Reduction of Contact Resistance is demonstrated at Cu–Cu interfaces using a multiwalled carbon nanotube (MWCNT) layer as an electrically conductive interfacial material. The MWCNTs are grown on a copper substrate using plasma enhanced chemical vapour deposition (PECVD) with nickel as the catalyst material, and methane and hydrogen as feed gases. The MWCNTs showed random growth directions and had a bamboo-like structure. Contact Resistance and reaction force were measured for a bare Cu–Cu interface and a Cu–MWCNT–Cu interface as a function of probe position. For an apparent Contact area of 0.31 mm 2 ,a n80% reduction in Contact Resistance was observed when the MWCNT layer was used. Resistance decreased with increasing Contact force, thereby making it possible to use this arrangement as a small-scale force sensor. Also, the Cu–MWCNT–Cu interface was roughly two times stiffer than the bare Cu–Cu interface. Contact area enlargement and van der Waals interactions are identified as important contributors to the Contact Resistance reduction and stiffness increase. A model based on compaction of the MWCNT layer is presented and found to be capable of predicting Resistance change over the range of measured force. (Some figures in this article are in colour only in the electronic version)
Lianhong Zhang - One of the best experts on this subject based on the ideXlab platform.
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estimation of Contact Resistance in proton exchange membrane fuel cells
Journal of Power Sources, 2006Co-Authors: Lianhong Zhang, Ying Liu, Haimin Song, Shuxin Wang, Y Zhou, Jack S HuAbstract:The Contact Resistance between the bipolar plate (BPP) and the gas diffusion layer (GDL) is an important factor contributing to the power loss in proton exchange membrane (PEM) fuel cells. At present there is still not a well-developed method to estimate such Contact Resistance. This paper proposes two effective methods for estimating the Contact Resistance between the BPP and the GDL based on an experimental Contact Resistance–pressure constitutive relation. The constitutive relation was obtained by experimentally measuring the Contact Resistance between the GDL and a flat plate of the same material and processing conditions as the BPP under stated Contact pressure. In the first method, which was a simplified prediction, the Contact area and Contact pressure between the BPP and the GDL were analyzed with a simple geometrical relation and the Contact Resistance was obtained by the Contact Resistance–pressure constitutive relation. In the second method, the Contact area and Contact pressure between the BPP and GDL were analyzed using FEM and the Contact Resistance was computed for each Contact element according to the constitutive relation. The total Contact Resistance was then calculated by considering all Contact elements in parallel. The influence of load distribution on Contact Resistance was also investigated. Good agreement was demonstrated between experimental results and predictions by both methods. The simplified prediction method provides an efficient approach to estimating the Contact Resistance in PEM fuel cells. The proposed methods for estimating the Contact Resistance can be useful in modeling and optimizing the assembly process to improve the performance of PEM fuel cells.
Muammer Koc - One of the best experts on this subject based on the ideXlab platform.
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effect of manufacturing processes on Contact Resistance characteristics of metallic bipolar plates in pem fuel cells
International Journal of Hydrogen Energy, 2011Co-Authors: Cabir Turan, Omer Necati Cora, Muammer KocAbstract:Abstract In this study, metallic bipolar plate (BPP) samples manufactured with stamping and hydroforming under different process conditions were tested for their electrical Contact Resistance characteristics to reveal the effect of manufacturing type and conditions. Punch speed and force in stamping, and pressure and pressure rate in hydroforming were selected as variable process parameters. In addition, two different channel sizes were tested to expose the effect of BPP micro-channel geometry and its consequences on the Contact Resistance. As a general conclusion, stamped BPPs showed higher Contact conductivity than the hydroformed BPPs. Moreover, pressure in hydroforming and geometry had significant effects on the Contact Resistance behavior of BPPs. Short term corrosion exposure was found to decrease the Contact Resistance of bipolar plates. Results also indicated that Contact Resistance values of uncoated stainless steel BPPs are significantly higher than the respective target set by U.S. Department of Energy. Conforming to literature, proper coating or surface treatments are necessary to satisfy the requirements.
Rafael Reif - One of the best experts on this subject based on the ideXlab platform.
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abnormal Contact Resistance reduction of bonded copper interconnects in three dimensional integration during current stressing
Applied Physics Letters, 2005Co-Authors: Kuanneng Chen, Chuan Seng Tan, A Fan, Rafael ReifAbstract:Bonded copper interconnects were stressed with current to measure the specific Contact Resistance. For bonded copper interconnects without a prebonding HCl clean, the corresponding specific Contact Resistance did not change while increasing the stress current. However, for some interconnects with the prebonding HCl clean, an abnormal Contact Resistance reduction was observed during the increase of the stress current. The rise of temperature at the bonding interface area due to Joule heating under high current density may have caused the decrease of Contact Resistance. This behavior may be one option for quality enhancement in 3D integration at low temperature.
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relation of Contact Resistance reduction and process parameters of bonded copper interconnects in three dimensional integration technology
Copper Interconnects New Contact Metallurgies Structures and Low-k Interlevel Dielectrics II - Proceedings of the International Symposium, 2003Co-Authors: Kuanneng Chen, Chuan Seng Tan, A Fan, Rafael ReifAbstract:Contact Resistances of bonded copper interconnects in three-dimensional integration technology under different bonding conditions are investigated by using a novel test structure. A reduction in specific Contact Resistance is obtained by longer anneal time. The specific Contact Resistance of bonded interconnects with longer anneal time does not change with the interconnect sizes. Underlying physical mechanism is discussed. The relationship between specific Contact Resistance and bonded wafer location is discussed as well. The specific Contact Resistance shows a lower value at the center of the wafer. Stability and reversibility tests show that the specific Contact Resistance does not change when the stress current is increased gradually or decreased after that. The excellent stability and reversibility of specific Contact Resistances shows that the microstructure of bonded Cu interconnects has reached a stable state.