Crossover from localized to diffusive water dynamics in carbon nanohorns: A comprehensive quasielastic neutron-scattering analysis

Marie-Claire Bellissent-Funel, Katsumi Kaneko, Tomonori Ohba, Marie-Sousai Appavou, Antti J. Soininen, and Joachim Wuttke
Phys. Rev. E 93, 022104 – Published 2 February 2016

Abstract

Incoherent neutron scattering by water confined in carbon nanohorns was measured with the backscattering spectrometer SPHERES and analyzed in exemplary breadth and depth. Quasielastic spectra admit δ-plus-Kohlrausch fits over a wide q and T range. From the q and T dependence of fitted amplitudes and relaxation times, however, it becomes clear that the fits do not represent a uniform physical process, but that there is a crossover from localized motion at low T to diffusive α relaxation at high T. The crossover temperature of about 210 to 230 K increases with decreasing wave number, which is incompatible with a thermodynamic strong-fragile transition. Extrapolated diffusion coefficients D(T) indicate that water motion is at room temperature about 2.5 times slower than in the bulk; in the supercooled state this factor becomes smaller. At even higher temperatures, where the α spectrum is essentially flat, a few percentages of the total scattering go into a Lorentzian with a width of about 1.6μeV, probably due to functional groups on the surface of the nanohorns.

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  • Received 2 February 2015
  • Revised 1 December 2015

DOI:https://doi.org/10.1103/PhysRevE.93.022104

©2016 American Physical Society

Physics Subject Headings (PhySH)

  1. Research Areas
  1. Physical Systems
Statistical Physics & Thermodynamics

Authors & Affiliations

Marie-Claire Bellissent-Funel

  • LLB, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France

Katsumi Kaneko

  • Center for Energy and Environmental Science, Shinshu University, 1-17-1 Wakasato, Nagano, Japan

Tomonori Ohba

  • Graduate School of Science, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan

Marie-Sousai Appavou, Antti J. Soininen, and Joachim Wuttke*

  • Forschungszentrum Jülich GmbH, JCNS at MLZ, Lichtenbergstraße 1, 85747 Garching, Germany

  • *To whom correspondence should be addressed: j.wuttke@fz-juelich.de

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Vol. 93, Iss. 2 — February 2016

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