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CAMP June Newsletter: Page 7

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Synthesis and Characterization of Silicon Carbide Nanowhiskers



CAMP Professor Weiqiang Ding and his group, of Clarkson's Department of Mechanical and Aeronautical Engineering, have synthesized silicon carbide nanowhiskers and nanoribbons through a vapor-solid process by using a home-built low pressure chemical vapor deposition system. The synthesis strategy is based on the reaction of silicon vapor with solid carbon powder at an elevated temperature in an argon environment at atmospheric pressure. The morphology and the crystal structure of the silicon carbide nanomaterials were characterized with scanning electron microscopy, high-resolution transmission electron microscopy and X-ray powder diffraction. The chemical composition and chemical state of the nanomaterials were investigated with energy dispersive X-ray spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The resulting nanomaterials were determined to be hexagonal wurtzite-type silicon carbide nanocrystalline structures. Compared with other reported silicon carbide nanomaterial synthesis methods, the main advantages of this approach are the relatively-low growth temperature and the catalyst-free synthesis. The mechanical properties of the silicon carbide nanowhiskers have been characterized with nanoscale tensile testing and mechanical resonance methods by using a home-built nanomanipulation system inside the vacuum chamber of a scanning electron microscope.  See Figure 3.

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Figure 3.  Scanning electron microscope images of (a) silicon carbide nanowhiskers and(b) tensile testing of a single silicon carbide nanowhisker inside a scanning electron microscope vacuum chamber.



Fabrication and Characterization of Cellulose Nanofiber-Reinforced Polymer Nanocomposites


CAMP Professors Weiqiang Ding and Daryush Aidun and graduate student Nimitt Patel, of Clarkson's Department of Mechanical and Aeronautical Engineering, are working on the fabrication and characterization of cellulose nanofiber-reinforced polymer nanocomposites. See Figure 4. Cellulose is the main component of many natural fibers such as wood, cotton and flax. It is among the most abundant natural renewable resources on earth. Cellulose nanofiber, because of its excellent mechanical property, biocompatible and biodegradable characteristics, is a promising nanomaterial for various engineering, biomedical and environmental applications. In this project, cellulose nanofibers were extracted from commercial cellulose microcrystals through high intensity ultrasonication. Cellulose nanofiber-reinforced polyvinyl alcohol (PVA) composites were fabricated by a direct casting method. The mechanical and thermal properties of the nanocomposites were studied with tensile testing, nanoindentation, dynamic mechanical analysis and thermogravimetric analysis methods. The influences of filler fiber dimension, volume fraction and surface chemistry on the mechanical and thermal properties of the resulting nanocomposites were investigated. Compared with cellulose microcrystals, cellulose nanofibers were found to be more effective in reinforcing the polymer matrix.

 

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Figure 4. (a) Scanning electron microscope image of cellulose nanofibers deposited on a holey carbon film substrate;(b) Stress-strain curves of cellulose microfiber- and nanofiber-reinforced polyvinyl alcohol composites.

 

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