New development of graphene nanoplatelets-from Prof. Guahua Chen
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- Time of issue:2011-09-03 18:02
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New development of graphene nanoplatelets-from Prof. Guahua Chen
- Categories:Knano News
- Author:
- Origin:
- Time of issue:2011-09-03 18:02
- Views:
16 June 2010
Guohua Chen, Lwei Wang, and Jiangbin Hong
FROM SPE "Graphite nanosheets act as conducting filler for high-density polyethylene"
http://www.4spepro.org/view.php?article=003007-2010-06-12
Nanocomposites containing graphite nanosheets exhibit a very low percolation threshold and significantly enhanced mechanical and processing properties compared with those containing carbon black.
Conductive carbon black (CB) is used extensively in industrial applications to increase polymer conductivity. However, the mechanical properties of CB-filled polymer composites decrease due to the high level of inorganic filler used. Graphite, an alternative to carbon black, possesses excellent electrical conductivity of 104S/cm and is an abundant resource. Graphite's layered structure consists of carbon sheets bound by weak van der Waals forces, which can be exfoliated into thin sheets with large areas. These graphite nanosheets (GNs), which are intrinsically made of stacks of multi-layer graphene, can be used at lower addition levels without sacrificing mechanical properties. It is known that graphene's mechanical strength and flexibility as well as its high electrical conductivity are advantageous compared with most other fillers.1 These advantages have attracted much attention to GNs as a conductive filler. For instance, Xiamen Knano Graphite Technology Co.Ltd.2 recently achieved mass-production of GNs, demonstrating the feasibility of commercial use.
We fabricated GNs using an ultrasonic powdering technique in 2003 and found that conducting composites containing GNs showed good electrical conductivity and a low percolation threshold (the critical loading of a conductive filler where a continuous pathway conducts an electrical charge) as evidenced by reaching a threshold resistivity.3 We found that a large GN aspect ratio and uniform dispersion of GNs in the matrix were key factors for obtaining a low percolation threshold.
In recent experiments, we incorporated GNs and CB respectively into pure high-density polyethylene (HDPE) and found that resistivity of both nanocomposites greatly decreases (see Figure 1). The critical percolation threshold of HDPE/GN nanocomposites occurs at a filler loading of about 6wt.% (2.528vol.%), which is much lower than that of conventional HDPE/graphite composites. The drop in resistivity levels off when the GN content reaches 8wt.%, indicating the formation of a conductive network throughout the HDPE matrix. HDPE/CB nanocomposites exhibit a similar S-shaped curve. However, they also exhibit a much higher percolation threshold (about 22wt.%).
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