A study on the electric property of buckypaper by eddy current testing

Since 1991, Carbon nanotubes (CNTs) have been caused a worldwide wave of research interests because of its excellent characteristics of physical and chemical. But to the present, it's rarely being applied to daily life due to its hard-handling, tiny-size and the nature of difference between each tube (even on one tube, actually). In this study, in order to overcome the limit above, with the idea of bottom up, for the purpose of accumulating and averaging the singularity, we filtrate the suspension of multi-walled CNTs (MWCNTs) and make it as a sheet-like bulk material, so called random buckypaper (RBP); that make plenty of CNTs as an isotropic material, and this allows the applications of CNTs in macro-scale achieve. Besides, in order to vary the property of RBP, we (1) add a vortex power to disturb suspension when filtration, that makes the direction of tube body align along the circumference, and it becomes as an alignment BP (ABP). And, (2) coat some kinds of metal (Fe, Co, Ni, Mn) oxide on it for modification, and called modify BP (MBP). According to some basic test, RBP possesses the features of lightweight, sheet-like, robust, high specific surface area and 78 % porosity. Under four probes resistivity test, it shows that the resistivity of ABP along the vortex direction (horizontally) is decreased when vortex speed increased. The results were opposite when the direction is perpendicular. And, after low temperature resistance test, RBP and ABP both show the negative temperature effect phenomenon. It was assumed that BP is a semimetal material with great conductivity ability. Eddy current measurement was employed as an index to tell the metallic degree of BP. Under the condition of 250 mT/s flux rate of magnetic field, the eddy current (because of electromagnetic induction) of ABP is 5.13 times than RBP do. Besides, Co-coating ABP is 5.06 times than pristine ABP do, and multi-metal coating (Fe, Co, Ni, Mn) is 9.9 times than pristine ABP do and just like pure metal copper do (with same thickness). It would be possible of BP to make a same revolution in material history as semiconductor did (to replace ferroalloy), because of its excellent and controllable electric properties.