Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1994-04-15
2001-02-27
Raimund, Christopher (Department: 1771)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S398000, C428S401000
Reexamination Certificate
active
06194066
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the manufacture of devices using microscopic hollow tubes which are particularly useful as lightweight, thermal barrier and heat exchange materials.
Lightweight, low mass material is widely used for thermal barrier protection shields and for lightweight structural components in devices such as aircraft components that place a premium on structurally strong lightweight materials. A variety of manufacturing methods are used to produce lightweight, structural materials. These methods include production of composite, non-metallic components and production of components having a reduced weight through the inclusion of spaces and holes. There are, however, limitations to the production of such reduced weight materials since conventional drilling of spaces and holes and electric die machining of holes are costly operations that raise the price of the final component. Other lightweight materials make use of fibers and laminations for producing components having good structural rigidity without the attendant weight of comparable metallic components. Production of materials having layers of fibers or fibrous material with ceramic or epoxy binders is also an expensive manufacturing procedure.
A need therefore exists for a new and inexpensive lightweight material suitable for use in lightweight components.
A need also exists for an improved method of manufacturing hollow materials that are particularly useful for thermal insulation and alternately for gas separation applications.
A further need exists for an inexpensive and efficient method of producing lightweight raw materials for use in the above-mentioned lightweight and thermal insulating components.
A further need exists for producing devices having microscopic hollow tubes therein having walls with multiple layers, having coatings thereon, etc.
SUMMARY OF THE INVENTION
The invention comprises a device composed of at least one microscopic hollow tube having a wall of single or multiple layers with a thickness of at least one nanometer and a diameter of at least 5 nanometers. The tubes can be formed from a wide variety of materials, some of the preferred materials include metals, polymers, silica, carbon, carbides, nitrides and oxides.
The invention also comprises a method for forming the microscopic hollow tube devices. The method begins with the step of positioning fibers having a predetermined rate of reaction or salvation at specific temperatures in a preform corresponding to a desired tube configuration. Although a random orientation may be used. The fibers are then cleaned and the temperature of the fibers is adjusted to a preferred deposition temperature in an inert environment. A tube material is then deposited on the fibers to coat them. Additional layers may be deposited of the same or different materials. The tube material has a lower rate of reaction or solvation at specific temperatures than the fibers. The coated fibers may then be heated in a solvent or reactive environment to a temperature at which is at least 10 times faster than the rate at which the fiber is removed at a rate which the fiber coating is removed. During this reaction or salvation, there is no ignition of the fiber material or build up of gas pressure that would damage the tubes which remain after the fiber is removed.
In a preferred embodiment of the invention, the tube material is deposited on the fibers by chemical vapor deposition after the fibers have been cleaned in a high vacuum environment. In one preferred embodiment of the invention the initial fibers comprise carbon fibers, however, practically any other microscopic fibers may be used. Silica and other high temperature oxides are preferred coating materials for the fibers in the preferred embodiment of the invention which utilizes carbon fibers.
In another preferred embodiment of the method of this invention, the metal or polymer fibers used for forming microscopic tubes are removed from the deposited tube material by means of a solvent or a dissolving acid. The solvent or dissolving acid dissolves the inner fiber but is incapable of dissolving the tube material.
REFERENCES:
patent: 4257157 (1981-03-01), Pollock et al.
patent: 4900483 (1990-02-01), Witzke et al.
patent: 4982068 (1991-01-01), Pollock et al.
patent: 5011566 (1991-04-01), Hoffman
patent: 5094906 (1992-03-01), Witzke
patent: 5298298 (1994-03-01), Hoffman
patent: 5352512 (1994-10-01), Hoffman
Collier Stanton E.
Raimund Christopher
Stover Thomas C.
The United States of America as represented by the Secretary of
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