Electrical behavior and water phase transformation in multi-walled carbon nanotube/polytetrafluoroethylene composite films

초록

Multi-walled carbon nanotubes (MWCNTs) with excellent physiochemical properties have been recently applied to energy/power generation and storage systems encompassing polymer electrolyte membrane fuel cells (PEMFCs). However, there is a lack of investigations of the properties of MWCNT composites themselves under the actual operating conditions of systems. In this paper, MWCNTs/polytetrafluoroethylene (PTFE) composites were fabricated as electric and hydrophobic components for energy/power systems. The electrical properties, heating behavior, hydrophobicity, and water evaporation behavior of the composites are characterized within the operating voltage ranges of PEMFC. With 50% MWCNT content, the conductivity and the contact angle were 11.83 S/cm, and the contact angle 128.1 degrees, respectively. The MWCNT/PTFE composite film showed a linear temperature rise with voltages and rapid temperature saturation within 40 s. The rate in the initial heating range was measured at 0.5 degrees C/s for the voltage of 0.5 V. The voltage increase induced an exponential decrease in the height of water droplets on the composite surface. The evaporation rate increased almost 10-fold, from 0.013 mm/min at 0.0 V to 0.12 mm/min at 1.0 V. The proposed characteristics of the functional composite provide insights into the material requirements for electrochemical devices, including PEMFC.Highlights Multi-walled carbon nanotube/polytetrafluoroethylene composites can be applied to energy storage and power generation. Key properties of the composites are proposed for polymer electrolyte membrane fuel cell (PEMFC) operating conditions. The composite has a fast heating by high conductivity and temperature uniformity. Water-vapor transformation under PEMFC operating voltage is quantified. Electric heating and water droplet vaporization behavior of MWCNT/PTFE composite film. image

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