Effect of dispersion on graphite nanosheet composites

Abstract

By intercalating and exfoliating natural graphite flakes, expanded graphite was obtained and used as the additive for making composites. The expanded graphite was composed of partly connected graphite nanosheets. Three types of composites were made, representing three levels of dispersing the graphite nanosheets. The first was the impregnation of epoxy resin to the expanded graphite by resin transfer molding. No dispersion was applied, and the expanded graphite can retain its original shape. The second was the use of a high-power sonication to break apart the expanded graphite. The thickness of the sonicated expanded graphite was reduced to about 100 times. The third method was to use a high-shear strain rate to separate the graphite nanosheets from the expanded graphite and to disperse them into the resin. The thickness range of the graphite nanosheets was 20-50 nm, about 100 times thinner than the sonicated ones. Compression and impact tests were conducted. The influence of dispersion on the material behavior was studied. Some fracture modes associated with the layered microstructures of the graphite nanosheets were observed. A simple model was used to study the stress transfer and frictional energy consumption of the pullout of the nanosheet.

Surface Modification of Graphite Particles Coated by Atomic Layer Deposition and Advances in Ceramic Composites

“…Graphite doped composites and alloys have been created that utilize the superior thermal and mechanical properties of graphite to produce bulk materials with enhanced characteristics . However, poor dispersability and oxidation at temperatures above 600°C limit graphite's utilization as a high‐temperature ceramic additive . It is desirable to improve particle dispersion and wettability in suspensions and mixtures, to achieve more homogeneous properties in bulk materials.…”

“…[1][2][3][4] However, poor dispersability and oxidation at temperatures above 600°C limit graphite's utilization as a high-temperature ceramic additive. 5,6 It is desirable to improve particle dispersion and wettability in suspensions and mixtures, to achieve more homogeneous properties in bulk materials.…”

“…The incorporation of graphite into composite materials has been shown to impart several beneficial properties, specifically thermal properties. [3][4][5] As process temperatures and material demands continue to increase, there is cause to try improving the thermal shock resistance of high-temperature ceramics. Industries such as nuclear and concentrated solar energy production push the limits of conventional materials.…”

Processing and failure behavior of carbon‐nanotube composites in sheet forms

“…For a dense CNT packing, resin becomes difficult to flow, and small voids in nanoscales can be formed. Because of the direct resin infiltration, the CNT contents of the present materials can be much higher, typically between 10 and 12 wt%, much higher than the value in typical bulk CNT composites .…”

“…Beyond a certain CNT fraction, the mixture will become too sticky to be processed by typical dispersion facilities, such as high‐speed mixers, sonication, and three‐roller mills . The previous works indicated that when the CNT loading reached 5 wt%, the mixture became a visco‐elastic material, and dispersion of CNTs becomes difficult for the three‐roller mill . Without proper dispersion, many CNTs are unable to be wetted and bonded by the resin, and the resulting mechanical behavior can be deteriorated.…”