Structural and dynamic investigations of graphite based materials

• Main Author: Bailey, A. M.
• Published: University of Salford 2014
• Subjects: 620.1; Energy
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.644751

Graphite based materials are of particular interest as energy materials. Graphite is used as a moderator in nuclear reactors and there have been investigations into the ability of modified graphites, such as expanded or intercalated graphite, to store hydrogen. Poly-crystalline coherent inelastic neutron scattering(poly-CINS) is used to give information on the dynamic properties of materials. typically poly-CINS produces large and difficult to interpret data sets. Neutronplot, a novel analysis software suite described in this work, is used in conjunction with predicted dynamic information to analyse poly-CINS data. X-ray diffraction measurements taken by Keens[1] were used to investigate the bulk structural properties of several natural graphites, one of which was chosen for poly-CINS analysis using IN5 experimental data, simulated data and Neutronplot. These investigations were also replicated with an exfoliated graphite sample. Both x-ray and neutron diffraction were used to investigate the structure of a C60 intercalated graphite sample derived from the exfoliated graphite and a Poly-CINS experiment was conducted using the NEAT spectrometer. We have found that the current IUPAC lattice values for rhombohedral stacking in graphite do not fit with experimental measurements. Also the interlayer spacing of rhombohedrally stacked graphite in natural graphite samples tends to be larger than that of hexagonal graphite. The investigations of exfoliated graphite show how interactions other than the graphene interlayer begin to dominate as disorder is added into the system. Successful C60 intercalation in graphite layers is confirmed by neutron diffraction. Measurements of the elastic constant C33 for natural and exfoliated graphite show good agreement with other graphite measurements. The intercalate poly-CINS measurement suffered from low statistics and shows how Neutronplot can be used for less than ideal data sets. The data shows diffuse C60 in the graphite matrix, this result is reflected in the diffraction measurements.