EPOXY MEDIATED ALIGNMENT OF SINGLE WALL CARBON NANOTUBES UNDER HIGH MAGNETIC FIELDS

Transcription

1 EPOXY MEDIATED ALIGNMENT OF SINGLE WALL CARBON NANOTUBES UNDER HIGH MAGNETIC FIELDS H. Garmestani, M.S. A-Haika, D. Lia, K. Dahmen, Georgia Institute of Technoogy, Atanta, Georgia a Department of Mechanica Engineering, FAMU-FSU Coege of Engineering, Forida State Uniersity, Taahassee, Forida

2 Outine Carbon Nanotubes Reorientation of Carbon nanotubes and Poymers Experimenta work: Magnetic fied-induced aignment of a buk epoxy nanotube sampes Resuts for aignment process (ESEM), atomic force microscopy (AFM) and wide ange x-ray diffraction (WAXD). Concusions

3 Carbon Nanotubes Carbon nanotubes are near idea whiskers consisting of fodedgraphene ayers with cyindrica hexagona attice structure Singe waed: 0.4-1nm diameter Muti-waed: nm diameter Length: nm-mm

4 Chemica Vapor Deposition for in-fied Processing Furnace Upper Thermocoupe we 503mm 654 mm 305 mm mm HOT ZONE Lower Thermocoupe we In-fied & 0-fied Processing (1200C) Thin fim Nano-tubes..

5 Prototype For Nano-tube CVD Production

6 Scae bar: 500nm, HV: 200KV, TEM Mag: 50000X Scae bar: 500nm, HV: 200KV, TEM Mag: 50000X Scae bar: 100nm, HV: 200KV, TEM Mag: X HRTEM Scae bar: 5nm, HV: 200KV, TEM Mag: X

7 Carbon Nanotubes Attractions High Young s moduus (~1.2 TPa) High fracture strains (10-30%) Fexibiity Low density Large aspect ratio Thermay stabe up to 2800 C in acuum Therma conductiity about twice as high as diamond Eectriccurrent-carrying-capacity 1000 times higher than copper wires

8 Aigned Nanotubes 1. We-aigned carbon nanotubes hae been synthesized through: Hot fiament chemica apor deposition, [Y. Chen,Et a., Journa Of Materias Science, 2000; 35: Met processing [R. Haggenmueer, et a., Chemica Physics Letters, 2000; 330: Mechanica stretching [L. Jin, C. Bower, O. Zhoua, Appied Physics Letters, 1998; 73(9): Eectrophoresis [K. Yamamoto, S. Akita, Y. Nakayama, Japan Journa of Appied Physics, 1996; 35: ]. When introduced to poymeric matrix, carbon nanotubes disperse randomy, oosing their orientations. Hence, the reorientation process shoud take into consideration the rearrangement of the poymeric matrix.

9 Poymer Orientation In Magnet Fieds Poymeric materias interact with magnetic fied through the diamagnetic anisotropy of the constituent chemica units. The energy that the chemica unit gains through the interaction with magnetic fied is dependent on the orientation of the unit reatie to the magnetic fied There wi be a tendency for poymer moecues to aign with their chain axes parae to a magnetic fied speciay when the randomizing infuence of therma energy is reduced as a consequence of the moecues being orientationay ordered within a mesophase. The tendency of a unit to aign is suppressed by the therma agitation if the energy reduction is insufficient compared to the therma energy.

10 Magnetic Processing Nonmagnetic sampe hoder Thermocoupe Epoxy sampe Epoxy mixed with S W C N The sampe was eft to cure at 25 C under 25 T fied for 2 hrs to keep the iscosity as ow as possibe. Then the furnace was heated up to 60 C and the sampe is eft to cure under the magnet fied for another 2 hours. After then the magnetic fied was reduced to 0 Tesa, the sampes were paced in another furnace at 60 C for another 2 hours to fuy cure. The experiment was repeated at 15 Tesa fied with same magnetic processing and curing cyces as before.

11 ESEM Resuts: Epoxy Aone ESEM micrographs for the morphoogy of the fracture surface for the magneticay processed epoxy sampes at (a) 0 Tesa, (b) 15 Tesa and (C) 25 The arrows represent the direction of the magnetic fied.

12 0 Tesa ESEM image for the morphoogy of the fracture surface of SWCNEpoxy composite processed at 0 Tesa Fied. The fracture surface was captured at two magnifications: (a) 50 mm and (b) 10mm.

13 25 Tesa ESEM image for the morphoogy of the fracture surface of SWCN-Epoxy composite. The arrow is the direction of the magnetic fied. The darkest spots are custers of the nanotubes The fracture surface was captured at two magnifications; (a) 50mm and (b) 10mm.

14 AFM Resuts AFM microscopy for the SWCN-epoxy composite cured inside a 25 Tesa magnetic fied.

15 diffractometer axis Wide Ange X-Ray Diffraction (WAXD) f q Transerse direction counter Norma direction source Poished sections of the processed sampes were obtained by sectioning parae to the magnetic fied direction. The 2q scan data were coected from 2q =1º to 30º in 0.01º steps for a period of 1s per step. A series of radia scans were obtained at arious azimutha anges (f) by rotating the sampe on its own pane between f=0 and f=360. f scans were performed in 0.1º steps for a period of 0.5s per

16 WAXD-2q Scan f = 0 f = 90 (A) 2-q diffraction aong the azimutha direction (f=0, norma to the magnetic fied direction) for the 0, 15, and 25 Tesa cured epoxy sampes. (B) 2-q diffraction aong the azimutha direction (f=90, parae to the magnetic fied direction) for the 0, 15, and 25 Tesa cured epoxy sampes. Sampes don t contain any SWCN.

17 WAXD:f -Scan Azimutha (f) scans of diffraction intensity for different magneticay- processed epoxy sampes. A scans carried out for fixed 2q =19.

18 Poe-Figures Poe figure of the (a) 0 T, (b) 15 T, and (c) 25 T magneticay processed epoxy sampes. The normaized raw poe densities potted in units of time random distribution in which 1 corresponds to compete random orientation distribution.

19 Concusions The microstructures of the poymer sampes processed inside 15 and 25 Tesa fieds were shown to hae oca orientation aong the fied s directions. The WAXD show a high degree of aignment when the azimutha scan is parae to the fied direction f=90 and 2q=19. The aignment was proportiona to the strength of the magnetic fied. The poe figures anaysis confirmed this obseration. The fied-assisted reorientation in the epoxy sampes used to utiize the aignment of SWCNs in the buk sampes based on the magnetic anisotropy between the composite two components. The carbon nanotubes are shown to be aigned at the nano-ee, whie the carbon nanotubes ropes did not aign gobay mainy because the ength of the carbon nanotubes.