Consolidated amorphous carbon materials, their manufacture and use

Abstract

A carbon based material produced from the consolidation of amorphous carbon by elevated temperature compression. The material having unique chemical and physical characteristics that lend themselves to a broad range of applications such as in electrical, electrochemical and structural fields.

Description

RELATED APPLICATIONS [0001] This is a continuation of U.S. patent application Ser. No. 10 / 315,747, filed Dec. 10, 2002 and issued Sep. 7, 2004 as U.S. Pat. No. 6,787,235, which is a continuation of U.S. patent application Ser. No. 09 / 675,031, filed Sep. 28, 2000 and issued Apr. 8, 2003 as U.S. Pat. No. 6,544,648, which is a divisional of U.S. Pat. application Ser. No. 09 / 365,642, filed Aug. 2, 1999 and issued Feb. 26, 2002 as U.S. Pat. No. 6,350,520, which claimed the benefit of U.S. Provisional Patent Application No. 60 / 097,862, filed Aug. 26, 1998 and U.S. Provisional Patent Application No. 60 / 097,960, filed Aug. 26, 1998.FIELD OF THE INVENTION [0002] This invention relates to a new carbon based material, its manufacture and use. More particularly, the invention relates to a carbon based material produced from the consolidation of amorphous carbon under elevated temperature compression having a broad range of applications, such as for example, as electrode material and as structur...

AI Technical Summary

Benefits of technology

[0020] The novel carbon based material of the present invention is versatile so as to be used in a broad range of applications such as in the manufacture of structural materials and of electrode materials. The process of the present invention is an inexpensive manufacturing method that produces materials that are near net shape or are readily machinable to specifications and the process is effective at generating monolithic carbon material without the use of binders, or any noxious or toxic chemicals. Carbon source material can be selected based on any combination of properties such as available surface area, particle size distribution, and conductivity to produce material with optimal properties for the specific application desired. Additionally, the process parameters can be optimized to produce specific material properties, such as degree of densification, internal porosity, available surface area, or other property that the end user may require. The process of the present invention provides for the making of large billets of activated carbon so that production costs could be reduced.

[0021] After consolidation at elevated pressures and temperatures, novel carbon material can be produced with desired surface areas, porosity, density, strength and resistivity. Cyclic voltammetry (CV) curves demonstrate that the novel material is stable over a wide potential range in aqueous solution and therefore suitable for electrochemical applications. A capacitive feature of the CV curves indicates that the novel material is capable of storing a great amount of charge. The novel material is suitable for application of ultracapacitors. For example, test cells using electrodes of the novel material demonstrated that the capacitor had a specific capacitance of 53 F / g in an aqueous electrolyte and 23 F / g in an organic electrolyte, based upon the electrode material only. Electrodes of the novel material can be used for deionization, such as desalination. Such electrodes are effective at removing ions at a low energy consumption rate.

[0024] It is another feature of the present invention to provide a manufacturing process whose parameters can be altered to obtain the novel material having optimized characteristics for a particular application.

[0039] It is another feature of the present invention to provide the application of this novel material in uses in applications requiring materials of high strength, low density and / or specific porosity.

Problems solved by technology

The basic operating principles of carbon electrodes are readily understood, but the manufacturing techniques for producing activated carbon electrode material have been limited.

It is difficult to make such an electrode that is maintained under constant high pressure, the system would be unacceptably bulky and dangerous.

Disadvantages exist with the use of binders to form the electrodes.

Binders block a large portion of carbon surfaces, causing some pores to be blinded, and occlusion therefore is inevitable, thus lowering the available surface area of the carbon.

Binders also deteriorate the conductivity of the electrodes because most binders are themselves nonconductive.

The contamination from the binders also hinders their uses in electroanalytical applications.

The resulting carbon has relatively large surface area, but the manufacturing technique requires the use of toxic and environmentally dangerous chemicals.

The volume of carbon formed is considerably smaller than the original resin size which leads to low product yield.

This is a significant problem if specific geometric shapes or sizes are required.

This manufacturing technique also has the disadvantages of high material cost and weak material strength due to the “shrinking” of the precursor carbon at high carbonization temperatures.

However, this manufacturing technique includes extremely high manufacturing costs and leads to the release of organic solvents such as acetone, formaldehyde and aromatic compounds as the substrate is thermally changed to carbon.

These can pose serious health hazards to workers near the furnaces.

Although prototype and commercial ultracapacitors have been made with activated carbon, overall performance has not been satisfactory mainly due to the inevitable problem of occlusion from binders used or the high cost of material manufacturing.

As a consequence, the electrical and mass transfer resistance is very high and the overall performance is poor.

These materials have unique high temperature strength properties which retain stiffness and strength even at temperatures exceeding 1650° C. These are very expensive materials because of the complex manufacturing process.

These materials are then subjected to a long and complicated densification process known as chemical vapor deposition to produce the final product.

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