The effect of CF4 gaseous plasma exposure to single-wall carbon nanotubes (CNTs) has been studied. Raman spectroscopy results show that CNTs have gained more disordered sp3 bonds associated with functionalization, as both the flow rates of gas in the plasma and exposure time in the plasma are increased. Scanning electron microscopy images indicate the CNTs have been preserved after CF4 plasma exposure. X-ray photoelectron spectroscopy provides evidence of carbon to fluorine bonds (C–F) on the CNTs samples after CF4 plasma exposure. Semi-ionic and covalent C–F bonds are prevalent on the CNTs after CF4 exposure with the intensity ratio of the semi-ionic to covalent C–F bond decreasing as the flow rate of CF4 and exposure time in the CF4 plasma is increased.

No abstract

We report the results of a neutron diffraction study of structural evolution in sodium niobate, NaNbO 3 , which is the parent compound for lead-free ferroelectric material, as a function of temperature from 15 to 930 K over six phases. The Rietveld analysis of the high resolution powder neutron diffraction data shows the variation in the structure from cubic to rhombohedral ferroelectric structures. However, the refinements on local structure by the PDF method indicates that there are only three basic patterns of the local structure, and the ground states of NaNbO 3 in the low-temperature antiferroelectric and ferroelectric phases have the R3c symmetry, even though in the long range the system shows the Pbcm symmetry or the coexistence of two phases. The origin of the complex phase behavior and its implications on the performance as lead-free ferroelectrics are discussed.