abstract
An extended use of synchrotron-based X-ray diffraction microtomography (XRD-mu CT) to study simultaneously the phase distribution and microstructure in phase-transformation processes is proposed. This three-dimensional non-invasive imaging approach has been applied to understand the phase transformation of C60 rhombohedral polymer (C60R) into disordered graphite (DG) at high pressure and high temperature. The heterogeneous sample was synthesized (5 GPa, 1100 K) using a Paris-Edinburgh cell and selective image reconstructions were achieved for all different phases present in this sample. The XRD-mu CT analysis evidences elongated DG domains with a fiber texture where nested (002)(DG) planes show +/- 70 degrees preferential orientation relative to the compression axis. In contrast C60R domains are found to be small and spotty, preferentially in the middle of the sample. The parent and product phases are mutually interpenetrative and exhibit a crystallographic relationship. This study evidences that formation of (002)(DG) planes occurs parallel to {111}(C60C) pseudo-cubic planes. Among these four possible alignments, uniaxial pressure favors one [111](C60C) direction. Transmission electron microscopy observations validate these nondestructive XRD-mu CT results.
keywords
FULLERITE C-60; SINGLE-CRYSTAL; STRUCTURAL REFINEMENT; POLYMERIZED FULLERITE; HIGH-TEMPERATURE; SOLID C-60; CARBON; SYNCHROTRON; TOMOGRAPHY; FULLERENES
subject category
Chemistry; Crystallography
authors
Alvarez-Murga, M; Bleuet, P; Marques, L; Lepoittevin, C; Boudet, N; Gabarino, G; Mezouar, M; Hodeau, JL
our authors
Leonel Marques Vitorino Joaquim
Assistant Professoracknowledgements
We wish to thank J.-P. Perrillat and R. Tucoulou for their comments and discussions. The authors are also grateful to the personnel of ID22, ID27 and D2AM at ESRF for their help during experiments. The European Synchrotron Radiation Facility is acknowledged for provision of synchrotron radiation beamtime. MA-M acknowledges CONACYT grant 211996; LM acknowledges 'Fundacao para a Ciencia e Tecnologia', Lisbon (project No. PTDC/FIS/104310/2008).