| Summary: | 碩士 === 東海大學 === 電機工程學系 === 102 === Abstract
Since carbon nanotubes (CNTs) were discovered in 1991, its mechanical, optical, electrical and magnetic properties of excellent features that make research in recent years in the popular direction. The decoration of CNTs with various compounds and various structures could increase their surface functionality and the tunability of their properties, such as their electrical and magnetic characteristics. Recent reports described the attachment of various inorganic nanoparticles to either the external surface of the CNTs, or to the internal surface of the CNT cavity, through several experimental methods. To enable us to study the nanotubes at the macroscopic level, by the aqueous solution of CNTs and the filtration method to make into a paper like structure called as buckypaper (BP). Magnetoresistance (MR) has been used as a sensitive tool to assess the transport phenomena in several CNT networks, as doped/undoped, which was fabricated in films, or sheets, of uncontrolled mixtures of metallic and semiconducting CNTs.
This study deals with the fabrication of multi-layer of MWCNT-BP containing magnetic (cobalt-Co) and non-magnetic (copper-Cu) nanopowders synthesized by the thermal evaporation technique. We used two and four-probe Hall measurements for analysis the magnetoresistive behavior (MR), at room temperature. The measurements carried out in two different directions of sample and magnetic field such as P (parallel) and T (perpendicular). The findings show that the MR behavior is due to the giant magnetoresistance (GMR) that takes place in layered or cluster systems consisting of magnetic and nonmagnetic materials. We obtained the higher value of 20% MR in a sandwich model, in the direction of T, at 8000 Gauss compared with 2% observed in the pure buckypaper. We also obtained the anisotropic magnetoresistance which is characteristic of ferromagnetic metals in the BP sample containing Co nanopowders.
We fabricated the flexible MWCNT-BP sheets, with exceptional magnetic properties to make them very attractive for many applications, including consumer electronics, sensing, or conducting sheets for shielding.
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