The strain-dependent electrical resistance characteristics of multi-walled carbon nanotube (MWCNT)/polymer composite films were investigated. In this research, polyethylene oxide (PEO) is used as the polymer matrix. Two representative volume fractions of MWCNT/PEO composite films were selected: 0.56 vol% (near the percolation threshold) and 1.44 vol% (away from the percolation threshold) of MWCNT. An experimental setup which can measure electrical resistance and strain simultaneously and continuously has been developed. Unique and repeatable relationships in resistance versus strain were obtained for multiple specimens with different volume fractions of MWCNT. The overall pattern of electrical resistance change versus strain for the specimens tested consists of linear and nonlinear regions. A resistance change model to describe the combination of linear and nonlinear modes of electrical resistance change as a function of strain is suggested. The unique characteristics in electrical resistance change for different volume fractions imply that MWCNT/PEO composite films can be used as tunable strain sensors and for application into embedded sensor systems in structures.
REVIEW 781 wileyonlinelibrary.com www.MaterialsViews.com www.advenergymat.dean electrochemical reaction; [ 30 ] importance of nano-structured materials and their utilization for Li-air batteries is emphasized; [ 33 ] issues of aqueous vs. nonaqueous electrolytes (solubility and diffusivity of oxygen) are addressed; [ 34 ] today's challenges of Li-air batteries are rooted in material discovery and optimization. [ 36 ] One of the most valuable insights gained from these review articles is that the signifi cant challenge is the lack of fundamental understanding on each Li-air cell component, as well as on the whole system performing together as an electrochemical device. The reason for this lack of understanding partly comes from the fact that the amount of research effort on Li-air cells is relatively small compared to that on the other mainstream batteries, i.e., Li-ion cells. This could also explain why, at the current stage, it is diffi cult to construct reproducible and reliable Li-air cells, which is the basis for the commercialization of Li-air cells in the foreseeable future. Note that the operating mechanism of Li-air cells is inherently different from that of Li-ion batteries, which are based on an intercalation/ deintercalation reaction; Li-air cells, however, are based upon a classical type of oxidation/reduction reaction. The graphical description of cell operating mechanisms of Li-air and Li-ion cells are shown in Figure 1 , [ 1 , 27 , 28 , 38 ] Figure 2 [ 27 , 29 , 34 , 38 ] and Figure 3 . [ 39 ] Previously published articles are a very good starting point for any scientist or engineer who starts looking at this particular battery system. However there were no review papers published on utilized cell confi gurations (or cell types) vs. performance of the Li-air cell, which is an important aspect from an industrial point of view. For example, which cell is the most suitable for the initial stage of research? Does any schema exist for a reliable and reproducible Li-air system construction? Therefore, we set up an overall objective of this study: to understand the current issues of the Li-air cell in relation to automotive applications. To achieve this goal, throughout this study we will execute the following items as sub-level objectives. The results are presented in the subsequent sections:1. To establish and maintain our own view point for the current review; battery industry-point-of-view 2. To conduct thorough reviews on previous publications including journal papers, book chapters, patents and industrial reports based on the established view point 3. To extract reasonable conclusions and perspectives from the results of item 2There are some limitations of the current research, such as a limited study time period. Due to time constraints, we might miss some potentially important aspects related to the current survey, i.e., depending on search conditions and options in gathering materials, there is a chance that some of the published materials could be inadvertently missed. It is also probable th...
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 , an 80% 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)
A simple, reliable and potentially cost-effective composite film casting procedure is presented using the evaporation of solvent (water) from a dilute mixture of multiwalled carbon nanotubes (MWCNTs) and polyethylene oxide (PEO) polymer. It is found that the fabrication method develops excellent dispersion of MWCNTs in PEO confirmed by morphology observations, final crystallinity of polymer (amorphous) and a lower percolation threshold (closer to theoretical value) as well as higher electrical conductivity. A film thickness prediction model is derived based upon the fact that final film thickness is mainly dependent upon the dimensions of the casting mold and the loading of the MWCNTs and polymer. This simple model provides important insight that the material loss and the actual density of the base polymer are critical factors making the current casting method truly cost effective and controlling final thickness.
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