Tham khảo tài liệu 'carbon nanotubes episode 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 148 R. s. Ruoff and D. c. Lorents buckling be accommodated on the surface of a carbon nanotube For a MWNT it seems very unlikely that the outer tube can buckle in this way because of the geometric constraint that the neighboring tube offers in graphite expansion in the c direction occurs readily as has been shown by intercalation of a wide range of atoms and molecules such as potassium. However Tanaka el al. 25 have shown that samples of MWNTs purified by extensive oxidation and removal of other carbon types present such as carbon polyhedra do not intercalate K because sufficient expansion of the interlayer separation in the radial direction is impossible in a nested MWNT. Achieving a continuous high strength bonding of defect-free MWNTs at their interface to the matrix as in the discussion above may simply be impossible. If our argument holds true efforts for high-strength composites with nanotubes might better be concentrated on SWNTs with open ends. The SWNTs made recently are of small diameter and some of the strain at each c atom could be released by local conversion to tetravalent bonding. This conversion might be achieved either by exposing both the inner and outer surfaces to a gas such as F2 g or through reaction with a suitable solvent that can enter the tube by wetting and capillary action 26-28 . The appropriately pretreated SWNTs might then react with the matrix to form a strong continuous interface. However the tensile strength of the chemically modified SWNT might differ substantially from the untreated SWNT. The above considerations suggest caution in use of the rules of mixtures eqn 3 to suggest that ultrastrong composites will form just because carbon nanotube samples distributions are now available with favorable strength and aspect ratio distributions. Achieving a high strength continuous interface between nano tube and matrix may be a high technological hurdle to leap. On the other hand other applications where reactivity should be minimized .
