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AssigneeUniversity of Louisville Research Foundation, Inc.
InventorsMahendra Sunkara, Gopinath Bhimarasetti
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A method of synthesizing and controlling the internal diameters, conical angles, and morphology of tubular carbon nano/micro structures. Different morphologies can be synthesized included but not limited to cones, straight tubes, nozzles, cone-on-tube (funnels), tube-on-cone, cone-tube-cone, n-staged structures, multijunctioned tubes, Y-junctions, dumbbell (pinched morphology) and capsules. The process is based on changing the wetting behavior of a low melting metals such as gallium, indium, and aluminum with carbon using a growth environment of different gas phase chemistries. The described carbon tubular morphologies can be synthesized using any kind of gas phase excitation such as, but not limited to, microwave excitation, hot filament excitation, thermal excitation and Radio Frequency (RF) excitations. The depositions area is only limited by the substrate area in the equipment used and not limited by the process. The internal diameters of the carbon tubular structures can be varied from a few nm to as high as about 20 microns. The wall thickness is about 10-20 nm. The carbon tubular structures can be formed open on both ends are directly applicable to micro-fluidics. Gallium required for the growth of the carbon tubes can be supplied either as a thin film on the substrate or could be supplied through the gas phase with different precursors such as Tri-methyl gallium. Seamless Y-junctions with no internal obstructions can be synthesized without the need of templates. Multi-channeled junctions can also be synthesized without any internal obstructions. Gallium that partially fills the carbon structures can be removed from the tubes by simple heating in vacuum at temperature above 600°.
The present invention comprises a technique to synthesize and control the (a) internal diameters (b) conical angles and ©) morphology of tubular carbon nano/micro structures. Using this technique different morphologies can be synthesized:
The technique is based on changing the wetting behavior of low melting metals such as gallium, indium, and aluminum with carbon using different gas phase chemistries.
The described carbon tubular morphologies can be synthesized using any kind of gas phase excitation such as, but not limited to, microwave excitation, hot filament excitation, thermal excitation and Radio Frequency (RF) excitations.
The depositions area is only limited by the substrate area in the equipment used and not limited by the process.
The internal diameters of the carbon tubular structures can be varied from a few nm to almost as high as 20 microns. The wall thickness is about 10-20 nm.
The carbon tubular structures are open on both ends directly applicable to micro-fluidics.
Gallium required for the growth of the carbon tubes can be supplied either as a thin film on the substrate or could be supplied through the gas phase with different precursors such as Tri-methyl gallium.
Seamless Y-junctions with no internal obstructions can be synthesized without the need of templates.
Multi-channeled junctions can also be synthesized without any internal obstructions.
Gallium that partially fills the carbon structures can be removed from the tubes by simple heating in vacuum at temperature 600° C. or above.
Any gas phase dosing that cause variations in the wetting behavior of low melting metals can be used to control the morphologies just as oxygen or nitrogen.
Any kind of carbon source for the growth of carbon tubes could be used, although we illustrated the growth of carbon tube using methane.
In this invention we described the controlled synthesis of carbon tubes. However, this growth concept can be extended to synthesize tubular morphologies of other material systems.
Dependencies are inferred from the claim text.