CHED 1573 |
| Carbon, the sixth most abundant element in the universe, has been known since ancient times and its appeal is due to its versatile nature of chemical bonding results in various forms where diamond (tetragonal) and graphite (trigonal) are the most well-known allotropes. Unprecedented worldwide activity in the investigation of nanostructured carbons was initiated by the discovery of the C60 molecule in 1985 and the development of the arc-discharge technique in 1990 producing elongated members of fullerenes (C60) known as nanotubes followed by nanocrystalline diamond in 1999 synthesized by varying the traditional gas phase chemistry for polycrystalline diamond. The talk will present the recent activities related to nanodiamond and nanotubes wherein materials science played a vital role in discovering these novel carbons with tailored physical properties [1,2]. Electron field emitting materials known as cold cathodes are of vital importance enabling a variety of applications such as flat panel displays, RF amplifiers for communication and radar, electric propulsion for microsatellites, and portable X-ray sources for medical and security diagnostics. Nanodiamond and carbon nanotubes proved to be potential candidate materials as planar cold cathodes yet having nanoscale heterogeneity. Starting with a brief introduction on the materials syntheses, the traditional field emission (I-V) and temperature dependent field emission microscopy (T-FEEM) properties enabling real-time imaging of electron emission with high spatial resolution providing evident information on emission site density, temporal variation or flicker of the emission intensity, and insight into the role of adsorbates from nanotube films will be presented. Temperature dependent field emission findings will be related to vacuum thermionic energy converters. Sulfur doping in diamond will be briefly mentioned in the context of n-type doping in diamond and providing almost equivalent field emission properties to those of nanotubes. [1] Gupta et. al. APL 86, (2005); [2] Gupta, et. al. JAP 95, (2005). |
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Research and Education in Material Science
8:00 AM-11:25 AM, Thursday, April 10, 2008 Hilton New Orleans Riverside -- HEC B, Oral
Division of Chemical Education |