Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Reexamination Certificate
1999-11-30
2001-11-13
Wong, Edna (Department: 1741)
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
C204S157440
Reexamination Certificate
active
06315871
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for producing diamonds, and more specifically, this invention relates to a method for producing nanometer-sized diamonds from carbonaceous materials by ion irradiation.
2. Background of the Invention
Nanodiamonds have various technological applications, including as fine polishing and grinding abrasives. Other possible uses for nanodiamonds include their use as powders with high thermal conductivity for use as heat sinks. Inasmuch as such media are both chemically resistant and electrically nonconducting, their suspension in advanced coolant fluids will enhance heat transport.
Nanodiamonds also can be utilized as an admixture in advanced composite materials to enhance thermal conductivity or surface hardness.
Lastly, nanodiamonds may be utilized as seed crystals for growth of larger diamonds.
The free energy difference between diamond and graphite is small. However, transformation between the two allotropes is difficult. This is because the high stability of the basal graphite planes requires the presence of catalysts, or thermodynamic conditions deep within the diamond phase region, for solid-state transformation of graphite into diamond.
A myriad of techniques exist to produce nanodiamonds. However, these processes require extreme conditions, such as high pressure, high temperature, or high irradiation fluence. For example, efforts at the Max-Planck-Institut in Stuttgart Germany, Wesolowski et al.
Appl. Phys. Lett
. 71 (14), pp 1948-1950, Oct. 6, 1997, have produced nanodiamonds but only after soot is irradiated for 30 hour at temperatures of between 700 and 1100° C. at high ion fluences of more than 10
19
ions-cm
−2
.
Earlier research at the same institute, Banhart et al.,
Nature
382 pp 433-435 (1996) discloses a method for diamond production by irradiating carbon onions with high electron fluences of more than 10
24
e
−cm
−2
at a sample temperature of 700° C.
Explosive shock methods for nanodiamond formation are also known.
Nanometer-size diamonds are the detonation products of reactions described throughout the scientific literature, including “Diamonds in Detonation Soot,”
Nature
Vol. 333, pp 440 (Jun. 2, 1988). Additional methods for producing and modifying nanodiamonds are disclosed in “Influence of the Molecular Structure of Explosives on the Rate of Formation, Yield, and Properties of Ultradisperse Diamond,” Combustion, Explosion, and Shock Waves, Vol. 30, No. 2, pp 235-238 (Plenum Publishing Corp, New York, N.Y. 1994), which is a translation of
Fizika Goreniya i Vzryva
, Vol. 30, No. 2, pp. 102-106, March-April 1994. Diamonds ranging in size of from 2-20 nanometers are produced in methods described in “Synthesis of Ultradispersed Diamond in Detonation Waves” Combustion, Explosion, and Shock Waves, Vol 25, No. 3, pp 372-379, (Plenum Publishing Corp. New York, N.Y. 1994), which is a translation of
Fizika Goreniya i Vzryva
, Vol. 25, No. 3, pp 117-126, May-June, 1989.
Other sources and methods for obtaining nanodiamonds can be found in U.S. Pat. No. 5,709,577, issued on Jan. 20, 1998.
None of the prior art discussed supra provides a method for obtaining nanodiamonds under relatively mild conditions.
A need exists in the art for a process to produce nanometer sized diamonds at room temperature and at ambient pressures. The process should yield diamonds from a myriad of carbonaceous materials and in reasonably short periods of time. Furthermore, the process should isolate the product diamond from the carbonaceous starting material with a minimum of product loss and effort.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method for producing nanodiamonds that overcomes many of the disadvantages of the prior art.
Another object of the present invention is to provide an economical method for producing nanodiamonds. A feature of the invention is that any high carbon content carbonaceous material can be transformed to diamond at room temperature. Another feature of the invention is the use of acid dissolution to isolate the diamond product from the carbonaceous material. An advantage of the invention is the elimination of the need for high-temperature, high-pressure processing.
Still, another object of the present invention is to provide a process for producing diamonds using ion irradiation. A feature of the invention is the use of ion radiation at energies of at least approximately 50 MeV. An advantage of the invention it is thought that the ion-irradiation may lower the free energy barrier for transformation between carbonaceous starting material and the diamond product. In one embodiment, approximately 0.02 diamonds are produced per ion for 350±50 MeV Kr irradiation of graphite at 20° C. and at low ambient pressure, less than about 10
−1
Torr and preferably less than about 10
−3
Torr.
Briefly, the invention provides a method for producing diamonds, the method comprising exposing carbonaceous material to ion radiation at ambient temperature and reduced pressure conditions in a vacuum for a time sufficient to transform the carbonaceous material to diamond.
The invention also provides a method for producing diamonds comprising subjecting graphite to at least approximately 50 MeV ion radiation at room temperature and at a reduced pressure in a vacuum chamber for a time sufficient to transform the graphite into diamond.
REFERENCES:
patent: 5374318 (1994-12-01), Rabalais et al.
patent: 5773834 (1998-06-01), Yamamoto et al.
patent: 280198 (1988-08-01), None
Daulton Tyrone
Kirk Marquis
Lewis Roy
Rehn Lynn
Caress Virginia B.
Dvorscak Mark
LaMarre Mark
The United States of America as represented by the United States
Wong Edna
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