University of Manchester

Imaging 3D Printed Graphene Capillary Suspensions

Hui Ding

Scientific Case

Capillary suspensions of graphene can be used to 3D print porous structures with possible applications as electrodes in energy storage devices e.g. Li-batteries or supercapacitors. A capillary suspension of graphene is a mixture of two immiscible liquids, here water and octanol, in which the graphene phase segregates to the octanol because of its greater work of adhesion to graphene. The suspensions are > 80% water and display strong shear thinning behaviour because of the presence of a continuous interpenetrating water/octanol phase that disrupts during flow and reforms rapidly once shear is removed. After printing the drying of the suspension is a two stage process, with the water phase being removed rapidly because of its high vapour pressure at room temperature, followed by a slower evaporation of the octanol. There is some shrinkage during drying but the final material has a density of about 10% of graphite, indicating a total porosity of ≈90 %. The resulting structure is believed to contain two scales of porosity, one controlled by the water phase on a scale > 10-6 m, and another nanoporous scale that is controlled by the chaotic restacking of the graphene once the octanol is removed. The resulting structures show a reasonable mechanical strength, > 1 MPa, and a reasonable level of porosity, < 10 m2g-1.
To date, our understanding of the internal structure of the dried capillary suspensions has been confined to surface image using SEM and studies of mechanically sectioned samples. This gives an inadequate representation of the internal structure because of surface drying artefacts or excessive damage during sectioning. X-Ray tomographic imaging will enable a full representation of the internal structure of these porous solids and allow a quantification of the larger scale porosity to complement data on the nanoscale obtained via BET measurements. We believe that key macroscopic properties of the printed structures, including mechanical strength and electrical conductivity are controlled by the microstructure at this scale and the data obtained through this study will be used to validate microstructural models that predict these properties.
Graphene and 3D Printing

Experiment Design

An SEM image of the surface of a sample dried capillary suspension was obtained from a GNP – water/octanol fluid. Macroporosity is > 10 um, thus we expect a resolution of ≈ 4 um will be sufficient for the initial study.
Experiments will be image acquisition under normal laboratory conditions using extruded specimens of approximately 3-5 mm diameter. We wish to investigate 12 conditions with a duplicate of each condition – 24 scans. We also wish a singl proof of principle study of a wet specimen – a further single scan.
Scanners and Rigs
Xradia VersaXCT
Not Required

Sample & Safety

Sample Description: Extruded 3D graphene structures of crosslinked cylinders.
Whole dimension: 3 mm x 3 mm x 3 mm
Low Hazard

Scan Records

Project Report