Room-Temperature Switching Behavior in CNT/Hexadecane Composites
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.531
Room-Temperature Switching Behavior in CNT/Hexadecane Composites Yulong Wu1, Peng Meng1, Quan Zhang1, Zhiyuan Tan1, Guoan Cheng1,2, Xiaoling Wu1,2, 1,2 Ruiting Zheng ͳKey Laboratory of Radiation Beam Technology and Materials Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875, P. R. China 2
Beijing Radiation Center, Beijing 100875, P. R. China
ABSTRACT
The room-temperature switching effect is of great interest for many applications, such as smart buildings, sensors, thermal energy storage and automatic temperature control. In this paper, we report a room-temperature switchable carbon nanotube (CNT)/hexadecane composites. Electrical conductivity, thermal conductivity and permittivity of the CNT/hexadecane composites can be regulated around 18˚C and the maximal switching ratio reaches 5 orders of magnitude, 3 times and 106.4, respectively. The switching behavior of composites is caused by rearrangement of the carbon nanotube fillers in hexadecane matrix during liquid-solid phase transition. It is found that surface modification is necessary to improve dispersion stability. Effects of filler properties on switching behaviour are also discussed.
INTRODUCTION Temperature-sensitive material (TSM) attracted many researchers’ interest because their physical or chemical properties can be changed in the specific temperature range. The TSMs include thermochromism materials [1], heat induced shape memory materials [2], temperature sensitive resistors (thermistors) [3-8] and so on. Thermistors are one of the most popular TSMs due to their potential applications in sensor, temperature control, thermal energy storage and other fields. In the past years, researchers developed several
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thermistors such as vanadium oxide [4], titanate [6] and polymer composites [7]. However, the regulation temperatures of these thermistors are far from room temperature. It is still a challenge to develop a kind of smart material that works near room temperature for the purpose of energy-saving and automatic-control in our daily life. Liquid-solid phase transition can be an alternative route for room temperature regulation because fillers can be rearranged during phase transition. Phase transition temperatures of some organics is near room temperature and could be used for developing room-temperature TSMs. Hexadecane is adopted as base fluid in this paper due to its nontoxicity, high chemical inertness and stability. The phase transition temperature of hexadecane is around 18°C, which is suitable for many applications such as smart building, air conditioner, temperature-sensitive power switch, drug storage cabinet, bacteriological incubator and so on. Carbon n
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