나노 탄소 기반 지능형 소재의 특성 연구

Abstract

In this study, a nano carbon based smart material composite and their characteristics to develop strain sensor, new actuators and corrosion sensor. The resistance change of the composites was measured with respect to the change of strain and the gauge factors of the composite were derived and were compared with others. It is deduced that the largest contribution of piezoresistivity of the composite comes from slippage of overlaying or bundled MWCNT in the matrix from a macroscopic standpoint. The graphene / epoxy composite strain sensor showed much higher strain sensitivity than both carbon nanotubes (CNTs) composite strain sensors and the strain gauge made of high-quality graphene films. A contact area & resistance model of graphene was introduced to explain the higher piezoresistivity of graphene composites compared to CNTs composites. The electrochemical actuation characteristics of nano carbon materials were experimentally studied to develop electrochemical actuators. The electrochemical actuators were composed of aqueous NaCl electrolyte and their actuating electrodes were made of multi-walled carbon nanotube (MWCNT) / polystyrene composite and graphene respectably. Actuation is proportional to charging transfer rate, and the electrolysis with an AC voltage input has very complex characteristics. To quantify the actuation property, the strain responses and output model were studied based on electrochemical effects between the nano carbon films and the electrolyte. The nano composite sensor can detect structural deterioration, chemical contamination and bio signal by means of its impedance measurement (resistance and capacitance). For a structural application, the change of impedance shows specific patterns depends on the structural deterioration and this characteristic is available for an in-situ multifunctional sensor, which can simultaneously detect multi symptoms of the structure. This study is anticipated to develop a new nano sensor detecting multiple symptoms in structural, chemical and bio applications with simple electric circuits.