We are reporting the atomic force microscope (AFM) nanomanipulation of ultrasonically dispersed and reflux-oxidized multiwalled carbon nanotubes (MWCNT) and single walled carbon nanotubes (SWCNT) by controlling the AFM tip with a NanoManipulator on a silicon substrate. The structure and the morphology of the carbon nanotubes (CNT) were confirmed with AFM interfaced with NanoManipulator and transmission electron microscope. The modifying parameter, which controls the force exerted by AFM tip, was set to be 0.5 nA in each case (0.5 nA = 20 nN). Bending was observed in ultrasonically dispersed MWCNTs, whereas, cutting was observed for reflux-oxidized MWCNTs along with the lateral movements. Similar observations were found for SWCNTs with sharp cuts and lateral displacements. The results show that CNTs deform by combining bending and distortion when subjected to large mechanical forces exerted by the tip of the AFM. The magnitude of the force, required to deform the reflux-oxidized CNTs is less than that for the ultrasonically dispersed CNTs, for both MWCNTs and SWCNTs.
The Fe-doped PZT, Pb (Zr, Ti) 1-x Fe x O 3 , ceramics have gathered plenty of attention because of the interplay of ferroelectric and ferromagnetic properties. In the present study, we report the properties of Pb(Zr 0.52 Ti 0.48) 1-x Fe x O 3 , x = 0, 0.05, 0.10, 0.15 and 0.20, prepared by conventional solid state reaction route with varying Fe 3+ doping concentrations. Study of X-ray diffraction patterns confirmed the tetragonal crystal structure with reduction in tetragonality and unit cell size with doping. It also showed formation of secondary magneto-plumbite phase at higher doping concentrations. The SEM micrographs exhibited decrease in grain size with increase in doping concentration (for x > 0.05). The increase in oxygen vacancies and the formation of secondary magneto-plumbite phase and Fe 3+-VO 2−-Fe 3+ defect dipole complexes introduced with the acceptor (Fe 3+) doping, caused clamping of the domain walls and hence reduced the room temperature dielectric constant as the doping concentration was increased. The coexistence of electrical polarization and magnetic moment at room temperature in all PFZT compositions confirmed the multiferroic characteristic in the ceramic samples. Electric polarization (P r) and coercive fields (E c) decreased with increase in Fe 3+ concentration in PFZT sample. However, magnetization (M) and magnetic coercive fields (E c) increased with the increasing Fe 3+ concentration due to the dominant effect of F-center exchange mechanism in Fe 3+-VO 2−-Fe 3+ and formation of ferromagnetic secondary magneto-plumbite phase.
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