CA2517965C - New form of carbon - Google Patents
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- CA2517965C CA2517965C CA002517965A CA2517965A CA2517965C CA 2517965 C CA2517965 C CA 2517965C CA 002517965 A CA002517965 A CA 002517965A CA 2517965 A CA2517965 A CA 2517965A CA 2517965 C CA2517965 C CA 2517965C
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Abstract
C60 and C70 carbon atom compounds are prepared by evaporating graphite in an inert quenching gas. The vapor of carbon is collected and is selectively extracted with an organic non-polar solvent.
Description
NEW FORM OF CARBON
This application is a divisional of co-pending Canadian Application Serial No. 2,072,117.
This invention relates tQ new forms of carbon as well as methods for the production and recovery thereof from carbon sources.
In 1985, Kyoto et al. postulated the existence of a highly stable molecule composed of 60 carbon atoms based solely on mass spectroscopic analysis of vaporized graphite (Ii.W. Kyoto, et al., Nature, Vol. 318, 162, 14 November 1985). More specifically, all that was observed --was a peak in the mass spectra of said carbon vapor.
Ilowever, Kyoto et al. did not isolate any of said compound.
A rnodel for this compound was proposed in wr~ich 60 carbon atoms are placed at the vertices of a truncated 2p icosahedron forming a perfect "soccerball" structure.
Subsequent thereto, many publications have strengthened the evidence for the existence of this molecule. The 60 carbon atom compound (hereinafter C60) was~presumably produced in situ for the spectroscopic determination 25 reported in these publications. Yet, to date, no one has been successful in verifying the existence of this molecule since no one has been successful in isolating the molecule in measurable amounts. Thus, no processes for producing recoverable amounts of this new compound 30 have been described to the present time.
Tn the aforesaid publication by Kyoto, et al., the authors proposed many uses for the new substance, C60 if it could be produced in quantity such as C60 transition metal compounds, e.g., C60Fe; or halogenated 35 - species like C60F60 which might be a super lubricant;
molecules including oxygen and lanthanum in the C60 interior; C60 would provide a topologically novel
This application is a divisional of co-pending Canadian Application Serial No. 2,072,117.
This invention relates tQ new forms of carbon as well as methods for the production and recovery thereof from carbon sources.
In 1985, Kyoto et al. postulated the existence of a highly stable molecule composed of 60 carbon atoms based solely on mass spectroscopic analysis of vaporized graphite (Ii.W. Kyoto, et al., Nature, Vol. 318, 162, 14 November 1985). More specifically, all that was observed --was a peak in the mass spectra of said carbon vapor.
Ilowever, Kyoto et al. did not isolate any of said compound.
A rnodel for this compound was proposed in wr~ich 60 carbon atoms are placed at the vertices of a truncated 2p icosahedron forming a perfect "soccerball" structure.
Subsequent thereto, many publications have strengthened the evidence for the existence of this molecule. The 60 carbon atom compound (hereinafter C60) was~presumably produced in situ for the spectroscopic determination 25 reported in these publications. Yet, to date, no one has been successful in verifying the existence of this molecule since no one has been successful in isolating the molecule in measurable amounts. Thus, no processes for producing recoverable amounts of this new compound 30 have been described to the present time.
Tn the aforesaid publication by Kyoto, et al., the authors proposed many uses for the new substance, C60 if it could be produced in quantity such as C60 transition metal compounds, e.g., C60Fe; or halogenated 35 - species like C60F60 which might be a super lubricant;
molecules including oxygen and lanthanum in the C60 interior; C60 would provide a topologically novel
-2-aromatic nucleus for new branches of organic and inorganic chemistry; and Cso being especially stable and symmetrical provides possible catalyst andlor intermediate in modelling prebiotic chemistry.
Another form of carbon containing 70 carbon atoms (C~o) has also been postulated (Kroto, Chemistry in Britain, 40-45 (1990), Kroto, Science, 1139-(1988)). Like the Cso to date, no one has been successful in verifying the existence of the C,o. Heretofore, no one has been successful in obtaining the molecule in any appreciable amounts.
A process has now been developed for the production of recoverable amounts of Cso and C,o. The present invention relates to a method of producing Cso and Coo compounds which comprises evaporating graphite in an atmosphere of an inert quenching gas at effective pressures in an evacuated reactor, collecting the quenched carbon product produced therefrom and contacting the quenched carbon product with an extracting non-polar organic solvent under effective conditions to separate the Cso and C,o compounds therefrom. The present new process is accomplished by evaporating carbon rods in an atmosphere of an inert quenching gas maintained at reduced pressure in a reactor therefor. This process produces a sooty carbon product which is graphitic carbon including a few percent of Cso and low levels of Coo which are recoverable from the product. However, an increase in the fraction of C,o molecules can be produced if the pressure is raised to greater than atmospheric pressures.
The recovery process is preferably accomplished by selective extraction of Cso and C,o with non-polar organic solvents from the sooty graphitic carbon.
Such products can be characterized as being amorphous or crystalline particulate matter comprised of Cso or C,o.
In accordance with an embodiment of the present invention there is provided a method of producing C6o and Coo compounds which comprises evaporating graphite in an atmosphere of an inert quenching gas at pressures effective to quench the vaporized carbon in a reactor that had previously been evacuated, collecting the quenched carbon product produced therefrom and -2a-contacting the quenched carbon product with an extracting non-polar organic, solvent under effective conditions to separate the coo and Coo compounds therefrom.
In accordance with another embodiment of the present invention there is provided a carbon product, the mass spectrum of which shows a strong peak at mass 720 amu, the infrared bonds to which have four intense lines at 1424', 1183, 577 and 528 cm'', absorption peaks in the UV at 264 and 339 nm, soluble in non-polar organic solvents and sublimes at a temperature of from about 300°
to 400°C, present in amounts sufficient to be discerned as a solid.
Another embodiment of the present invention provides a formed or molded product comprising Cso and C,o.
Yet another embodiment of the present invention provides a free flowing particulate comprised of Cso and Coo.
A substantially pure Cso and C,o is provided in another embodiment of the present invention.
Still another embodiment of the present invention provides an isolated carbon product, the mass spectrum of which shows a molecular ion at 840 amu, a broad peak in the ultraviolet at 276 nm, and soluble in non-polar organic solvents.
Other embodiments of the present invention provide isolated Coo or isolated C,o as well as the vapor of Coo and C,o.
In accordance with yet another embodiment of the present invention there is provided a method of extracting Cso and Coo from a carbon source containing same which comprises contacting the carbon source with a non-polar organic solvent.
A still further embodiment of the present invention provides a process for preparing C6o comprising: (a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising Cso molecules, the Cso molecules being present in the sooty carbon product in amounts capable of extracting and recovering predominantly therefrom the Cso as a visible solid form; and (b) recovering Cso from the sooty carbon product.
-2b-An embodiment of the present invention provides a process for preparing Cso comprising: (a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising C~ molecules, said Cso molecules being present in said sooty carbon product in amounts sufficient to be capable of providing a visibly coloredrsolution when extracted with sufficient amounts of benzene; and (b) recovering Cso from said sooty carbon product.
Another embodiment of the present invention provides a process for preparing C fio comprising: (a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising Cso molecules, the Cso molecules being present in said sooty carbon product in macroscopic amounts; and (b) recovering macroscopic amounts of the Cso from said sooty carbon product.
In accordance with one embodimenf of the present invention there is provided a process for preparing fullerenes~comprising: (a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising fullerene molecules, the fullerene molecules being present in the sooty carbon product in macroscopic amounts;
and (b) recovering macroscopic amounts of fullerene from the sooty carbon product.
In accordance with another embodiment of the present invention there is provided a process for preparing a carbon allotrope comprising caged molecules consisting solely of carbon atoms which are soluble in non-polar organic solvents, the process comprising: (a) vaporizing a carbon source in the present of an inert gas to produce a carbon vapor; (b) quenching the vapor of carbon in the inert gas under conditions effective to nucleate. and condense the carbon allotrope, the allotrope being present in the sooty carbon~product in amounts sufficient to be capable of extracting and revering therefrom the allotrope in solid form; and (c) recovering the carbon allotrope form the sooty carbon product.
In accordance with a further embodiment of the present invention there is -2c-provided a method of extracting Cso from a carbon source containing same which comprises contacting the carbon source with a non-polar organic solvent.
fn accordance with a still further embodiment of the present invention there is provided a carbon product comprising Coo, Coo or a mixture of Cso and Coo.
Various other embodiments of the present invention provide far solid Cso, solid Coo, crystalline Cso, crystalline Coo, substantially pure solid Coo, substantially pure solid C,o, substantially pure crystalline Cso, substantially pure crystalline C,o.
Also provided by embodiments of the present invention are Cso in amounts sufficient to isolate as a visible solid, Clo in amounts sufficient to isolate as a visible solid, macroscopic amounts of Cso, macroscopic amounts of C,o, substantially pure Coo in amounts sufficient to isolate as a visible solid, substantially pure Coo in amounts sufficient to isolate as a visible solid.
A still further embodiment of the present invention provides a solution of a carbon allotrope selected from the group consisting of Cso and C,o being dissolved in an organic non-polar solvent, the allotrope being present therein in amounts sufficient to be capable of recovering it as a solid when the solvent is evaporated.
In other preferred embodiments, there are provided a fullerene present in an amount sufficient to isolate as a solid and a macroscopic amount of fullerene.
In accordance with a further embodiment of the present invention there is provided a solid that consists essentially ~of a fullerene, the fullerene being isolated from a sooty carbon product formed from vaporizing a carbon source in the presence of an inert quenching gas, wherein the fulferene is recovered therefrom in macroscopic amounts.
In accordance with a still further embodiment of the present invention there is provided a cage carbon molecule consisting solely of carbon atoms that is isolated from a sooty carbon product formed from the vaporization of a carbon source in the presence of an inert quenching gas, the cage carbon molecule being recovered therefrom in amounts sufficient to be isolated as a visible solid.
In another embodiment of the present invention there is provided a cage -2d-carbon molecule product consisting solely of carbon atoms which is prepared by (a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to produce a sooty carbon containing the caged carbon molecule product the inert gas providing a non-reactive atmosphere; (b) collecting the sooty carbon product; (c) separating the product from the sooty carbon product, the separated product being free of any sooty carbon product and consisting solely of carbon atoms, the product being present in amounts sufficient for the product to be perceived as a visible solid in solid form.
In accordance with a further embodiment of the present invention, there is provided fullerenes in an amount at least as large as that amount which is sufficient to see under an optical microscope.
In accordance with a further embodiment of the present invention, there is provided a process for preparing cage molecules consisting solely of carbon atoms comprising vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to form a sooty carbon product containing the cage molecules of carbon, the cage molecules being present in the sooty carbon product in sufficient amounts to be capable of extracting and recovering therefrom the cage molecules as a solid; and extracting the cage molecule of carbon from the sooty carbon product.
In accordance with a further embodiment of the present invention, there is provided a process for preparing cage molecules consisting solely of carbon atoms comprising vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to provide a sooty carbon product comprising the cage molecules of carbon, the cage molecules being present in the sooty carbon product in amounts sufficient to be capable of extracting and recovering therefrom the cage molecules in solid form; depositing the sooty carbon product on a collecting surface; removing the sooty product from the collecting surface; and extracting a product which comprises cage molecules consisting solely of carbon atoms from the sooty carbon product.
-2e-In accordance with a further embodiment of the present invention, there is provided a process for preparing caged molecules consisting solely of carbon atoms comprising vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising the cage molecules, the cage molecule being present in the sooty carbon product in amounts sufficient to provide a visibly colored solution when extracted with effective amounts of benzene; and extracting the cage molecule from the sooty carbon product.
In accordance with a further embodiment of the present invention, there is provided a process for preparing a carbon allotrope comprising vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to provide a sooty carbon product comprising the carbon allotrope, the carbon allotrope being present in the sooty carbon product in amounts sufficient to be capable of providing a visibly colored solution when dissolved in sufficient amounts of benzene depositing the sooty carbon product on a collecting surface;
removing the sooty carbon product from the collecting surface; and extracting a product which comprises the carbon allotrope.
In accordance with a further embodiment of the present invention, there is provided a process for preparing a carbon allotrope comprising vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising the carbon allotrope, the carbon allotrope being capable of being dissolved in a non-polar organic solvent and the carbon allotrope being present in the sooty carbon product in sufficient quantities to be capable of extracting and recovering therefrom the allotrope in solid form; and extracting the allotrope from the sooty carbon product.
-2f-In accordance with a further embodiment of the present invention, there is provided a process for preparing a carbon allotrope consisting solely of carbon atoms which is soluble in non-polar organic solvent comprising vaporizing elemental carbon in the presence of an inert quenching gas under a pressure ranging from less than 1 atmosphere up to 10 atmospheres under conditions effective to form a sooty carbon product comprising the carbon allotrope, the product being present in the sooty carbon product in quantities sufficient to be recovered as a visible solid; and separating the carbon allotrope from the sooty carbon product.
Another form of carbon containing 70 carbon atoms (C~o) has also been postulated (Kroto, Chemistry in Britain, 40-45 (1990), Kroto, Science, 1139-(1988)). Like the Cso to date, no one has been successful in verifying the existence of the C,o. Heretofore, no one has been successful in obtaining the molecule in any appreciable amounts.
A process has now been developed for the production of recoverable amounts of Cso and C,o. The present invention relates to a method of producing Cso and Coo compounds which comprises evaporating graphite in an atmosphere of an inert quenching gas at effective pressures in an evacuated reactor, collecting the quenched carbon product produced therefrom and contacting the quenched carbon product with an extracting non-polar organic solvent under effective conditions to separate the Cso and C,o compounds therefrom. The present new process is accomplished by evaporating carbon rods in an atmosphere of an inert quenching gas maintained at reduced pressure in a reactor therefor. This process produces a sooty carbon product which is graphitic carbon including a few percent of Cso and low levels of Coo which are recoverable from the product. However, an increase in the fraction of C,o molecules can be produced if the pressure is raised to greater than atmospheric pressures.
The recovery process is preferably accomplished by selective extraction of Cso and C,o with non-polar organic solvents from the sooty graphitic carbon.
Such products can be characterized as being amorphous or crystalline particulate matter comprised of Cso or C,o.
In accordance with an embodiment of the present invention there is provided a method of producing C6o and Coo compounds which comprises evaporating graphite in an atmosphere of an inert quenching gas at pressures effective to quench the vaporized carbon in a reactor that had previously been evacuated, collecting the quenched carbon product produced therefrom and -2a-contacting the quenched carbon product with an extracting non-polar organic, solvent under effective conditions to separate the coo and Coo compounds therefrom.
In accordance with another embodiment of the present invention there is provided a carbon product, the mass spectrum of which shows a strong peak at mass 720 amu, the infrared bonds to which have four intense lines at 1424', 1183, 577 and 528 cm'', absorption peaks in the UV at 264 and 339 nm, soluble in non-polar organic solvents and sublimes at a temperature of from about 300°
to 400°C, present in amounts sufficient to be discerned as a solid.
Another embodiment of the present invention provides a formed or molded product comprising Cso and C,o.
Yet another embodiment of the present invention provides a free flowing particulate comprised of Cso and Coo.
A substantially pure Cso and C,o is provided in another embodiment of the present invention.
Still another embodiment of the present invention provides an isolated carbon product, the mass spectrum of which shows a molecular ion at 840 amu, a broad peak in the ultraviolet at 276 nm, and soluble in non-polar organic solvents.
Other embodiments of the present invention provide isolated Coo or isolated C,o as well as the vapor of Coo and C,o.
In accordance with yet another embodiment of the present invention there is provided a method of extracting Cso and Coo from a carbon source containing same which comprises contacting the carbon source with a non-polar organic solvent.
A still further embodiment of the present invention provides a process for preparing C6o comprising: (a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising Cso molecules, the Cso molecules being present in the sooty carbon product in amounts capable of extracting and recovering predominantly therefrom the Cso as a visible solid form; and (b) recovering Cso from the sooty carbon product.
-2b-An embodiment of the present invention provides a process for preparing Cso comprising: (a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising C~ molecules, said Cso molecules being present in said sooty carbon product in amounts sufficient to be capable of providing a visibly coloredrsolution when extracted with sufficient amounts of benzene; and (b) recovering Cso from said sooty carbon product.
Another embodiment of the present invention provides a process for preparing C fio comprising: (a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising Cso molecules, the Cso molecules being present in said sooty carbon product in macroscopic amounts; and (b) recovering macroscopic amounts of the Cso from said sooty carbon product.
In accordance with one embodimenf of the present invention there is provided a process for preparing fullerenes~comprising: (a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising fullerene molecules, the fullerene molecules being present in the sooty carbon product in macroscopic amounts;
and (b) recovering macroscopic amounts of fullerene from the sooty carbon product.
In accordance with another embodiment of the present invention there is provided a process for preparing a carbon allotrope comprising caged molecules consisting solely of carbon atoms which are soluble in non-polar organic solvents, the process comprising: (a) vaporizing a carbon source in the present of an inert gas to produce a carbon vapor; (b) quenching the vapor of carbon in the inert gas under conditions effective to nucleate. and condense the carbon allotrope, the allotrope being present in the sooty carbon~product in amounts sufficient to be capable of extracting and revering therefrom the allotrope in solid form; and (c) recovering the carbon allotrope form the sooty carbon product.
In accordance with a further embodiment of the present invention there is -2c-provided a method of extracting Cso from a carbon source containing same which comprises contacting the carbon source with a non-polar organic solvent.
fn accordance with a still further embodiment of the present invention there is provided a carbon product comprising Coo, Coo or a mixture of Cso and Coo.
Various other embodiments of the present invention provide far solid Cso, solid Coo, crystalline Cso, crystalline Coo, substantially pure solid Coo, substantially pure solid C,o, substantially pure crystalline Cso, substantially pure crystalline C,o.
Also provided by embodiments of the present invention are Cso in amounts sufficient to isolate as a visible solid, Clo in amounts sufficient to isolate as a visible solid, macroscopic amounts of Cso, macroscopic amounts of C,o, substantially pure Coo in amounts sufficient to isolate as a visible solid, substantially pure Coo in amounts sufficient to isolate as a visible solid.
A still further embodiment of the present invention provides a solution of a carbon allotrope selected from the group consisting of Cso and C,o being dissolved in an organic non-polar solvent, the allotrope being present therein in amounts sufficient to be capable of recovering it as a solid when the solvent is evaporated.
In other preferred embodiments, there are provided a fullerene present in an amount sufficient to isolate as a solid and a macroscopic amount of fullerene.
In accordance with a further embodiment of the present invention there is provided a solid that consists essentially ~of a fullerene, the fullerene being isolated from a sooty carbon product formed from vaporizing a carbon source in the presence of an inert quenching gas, wherein the fulferene is recovered therefrom in macroscopic amounts.
In accordance with a still further embodiment of the present invention there is provided a cage carbon molecule consisting solely of carbon atoms that is isolated from a sooty carbon product formed from the vaporization of a carbon source in the presence of an inert quenching gas, the cage carbon molecule being recovered therefrom in amounts sufficient to be isolated as a visible solid.
In another embodiment of the present invention there is provided a cage -2d-carbon molecule product consisting solely of carbon atoms which is prepared by (a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to produce a sooty carbon containing the caged carbon molecule product the inert gas providing a non-reactive atmosphere; (b) collecting the sooty carbon product; (c) separating the product from the sooty carbon product, the separated product being free of any sooty carbon product and consisting solely of carbon atoms, the product being present in amounts sufficient for the product to be perceived as a visible solid in solid form.
In accordance with a further embodiment of the present invention, there is provided fullerenes in an amount at least as large as that amount which is sufficient to see under an optical microscope.
In accordance with a further embodiment of the present invention, there is provided a process for preparing cage molecules consisting solely of carbon atoms comprising vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to form a sooty carbon product containing the cage molecules of carbon, the cage molecules being present in the sooty carbon product in sufficient amounts to be capable of extracting and recovering therefrom the cage molecules as a solid; and extracting the cage molecule of carbon from the sooty carbon product.
In accordance with a further embodiment of the present invention, there is provided a process for preparing cage molecules consisting solely of carbon atoms comprising vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to provide a sooty carbon product comprising the cage molecules of carbon, the cage molecules being present in the sooty carbon product in amounts sufficient to be capable of extracting and recovering therefrom the cage molecules in solid form; depositing the sooty carbon product on a collecting surface; removing the sooty product from the collecting surface; and extracting a product which comprises cage molecules consisting solely of carbon atoms from the sooty carbon product.
-2e-In accordance with a further embodiment of the present invention, there is provided a process for preparing caged molecules consisting solely of carbon atoms comprising vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising the cage molecules, the cage molecule being present in the sooty carbon product in amounts sufficient to provide a visibly colored solution when extracted with effective amounts of benzene; and extracting the cage molecule from the sooty carbon product.
In accordance with a further embodiment of the present invention, there is provided a process for preparing a carbon allotrope comprising vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to provide a sooty carbon product comprising the carbon allotrope, the carbon allotrope being present in the sooty carbon product in amounts sufficient to be capable of providing a visibly colored solution when dissolved in sufficient amounts of benzene depositing the sooty carbon product on a collecting surface;
removing the sooty carbon product from the collecting surface; and extracting a product which comprises the carbon allotrope.
In accordance with a further embodiment of the present invention, there is provided a process for preparing a carbon allotrope comprising vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising the carbon allotrope, the carbon allotrope being capable of being dissolved in a non-polar organic solvent and the carbon allotrope being present in the sooty carbon product in sufficient quantities to be capable of extracting and recovering therefrom the allotrope in solid form; and extracting the allotrope from the sooty carbon product.
-2f-In accordance with a further embodiment of the present invention, there is provided a process for preparing a carbon allotrope consisting solely of carbon atoms which is soluble in non-polar organic solvent comprising vaporizing elemental carbon in the presence of an inert quenching gas under a pressure ranging from less than 1 atmosphere up to 10 atmospheres under conditions effective to form a sooty carbon product comprising the carbon allotrope, the product being present in the sooty carbon product in quantities sufficient to be recovered as a visible solid; and separating the carbon allotrope from the sooty carbon product.
- 3 -In the accompanying figures, Fig. 1 is a micrograph of typical crystals of the 98 % Coo, 2 % Coo material showing thin platelets, rods and stars of hexagonal symmetry.
Fig. 2 is an x-ray diffraction of a microcrystalline powder of the 98% C6o, 2% Coo solid material. Tnset at upper left is a single crystal electron diffraction pattern indexed with Miller indices compatible with the x-ray pattern, taken on a thin platelet as in Figure 1 with the electron beam perpendicular to the flat face.
Fig. 3 is an infrared absorption spectrum of an approximately 2 micrometer thick coating of the 98~ Cso, 2% C
material on a silicon substrate, referenced to a clean silicon substrate. Absorption is given as optical density=logo (1/T), where T is transmission. Apparent negative absorptions are due to the coating acting in part as a non-reflecting layer.
Fig. 4 is a visible-ultraviolet absorption spectrum of an approximately 0.1 micrometer thick coating of the 98%
C6o, 2 % C-,o material on quartz. Shown. at the bottom are positions and relative oscillator strengths for allowed transitions calculated for the C6Q molecule by Larsson, et al.
The first step in the production of C6o and C-,o molecules is vaporizing carbon from any source containing carbon in its various forms, e.g. graphite, amorphous and glassy carbon. It is preferred that this vaporization takes place in an evacuated reactor (e. g., a bell jar). The carbon is vaporized by heating in the presence of an inert quenching gas. The carbon vapor is nucleated in the presence of the inert quenching gas to form smoke particles.
l In the production of C60 and C~~, and procedure Lor vapori::in9 carbon can be used, although the preferred method relics on the use of a high intensity electrical current with graphite rods as electrodes. These rods are constructed to permit vaporization of.carbon at tire tip of the rod to produce a high density vapor of carbon.
For best results, the end of one of the rods is reduced in diameter so that the vaporization occurs at the reduced tip. The rods can be prepared using any of the various forms of carbon, such as graphite, amorphous and glassy carbon.
The inert quenching gas can be any of the usual inert gases such as the noble gas. Argon and helium are preferred, the latter being most preferred. Other inert gases commonly employed to provide a non-reactive atmosphere can also be used as quenching gas.
The amount of C60 and C~0 produced from this carbon source is dependent upon the pressure of the quenching gas. At lower pressures relatively pure.C60 molecules can be produced~in high yield with uinor concentrations of CEO. For the production of predominantly C~0 molecules, the pressure at which the quenching gas is maintained should be subatmospheric and preferably about 50-400 torr. Especially preferred is a pressure of approximately 100 torr. The use of any lower pressure may result in reduced yield of C60' However, as the pressure is raised, the ratio of C-,o:C~o is also increased.
. If the pressure is increased to at least two atmospheres, the greatest percentage of C.,o product is formed. Theoretically, the pressure can be raised to any level just below the point where the reactor would 1 explode from tie increased pressure. Iiowever, at the higher pressures, the yield of the overall product (C6o and C-,o) is reduced even though the ratio of C~~,:C~o is also increased. Therefore, as a practical consideration, the pressure of the quenching gas should not be greater than 10 atmospheres. The preferred pressure for maximizing the amount of C-,o produced is 2-3 atmospheres.
The produced quenched vapor of carbon, i.e., the smoked particles coats the internal surface of the reactor and of collecting substrates as black soot.
These collecting surfaces are inert to the vaporized carbon. They can be transparent and/or coated with an inert metal. Examples include glass, or gold coated glass surfaces and the like. These collecting surfaces are located in the reactor in the . path of the carbon smoke. The black coating can be removed by any suitable means, e.g., by scraping the solids from the coated surfaces. The C60 and C~0 molecules can be removed from this collected quenched product by contacting sold quenched product with an extracting solvent. In other words, the black soot is placed in a container containing the extracting solvent, or the extracting solvent is poured onto the black soot placed in a container. In either case, the C60 and C~0 molcules become dissolved in the solvent, while the remainder of the black soot remains insoluble. The insoluble material is separated from the solution containing the C60 and C~0 molecules, e.g., by decanting, or by filtration, and the like.
Suitable solvents include non-polar organic solvents, such as the alkanes containing S-10 carbon atoms (e. g. pentanes, hexanes, heptanes, octaves), benzene and alkyl-benzenes (e. g. toluene, xylene), carbon disulfide, carbon tetrachloride, naphtha,l,l,l-1 trichloroethane, and the like. Simple solubility determinations using classical laboratory methods will permit selection of other suitable solvents. The.
preferred solvents are carbon disulfide, benzene, carbon tetrachloride and toluene. Especially preferred are benzene, carbon tetrachloride and carbon disulfide.
The product obtained contains a mixture of C60 and C70. As described hereinabove, the amounts of C~0 and C~0 present is dependent upon the pressure used. If subatmospheric pressures are used, such as 50-400 torr, the product is predominatly pure C60 with a minor amount of C~0 present. Thus, when the collected product is dispersed in the extracting solvent, the product obtained is a mixture of C60 and CEO. For example, 4rhen the' pressure is 100 torr, the product formed is about 98o C60 and about Za C.,o. This product can be separated from the organic solvent solution by standard methods as by evaporation of the solvent or by dilution of the solvent solution with a non-solvent for C60. The product can be crystallized by careful evaporation of the organic solvent or by sublimation~procedures.
In a preferred embodiment of producing C00 and O, pure graphite rods are vaporized by passing high electrical current (either do or ac) through narrowed tips of graphite rods. Electron beam, laser and RF
heating can be used in lieu of electrical heating. This is done in a reactor (such as a bell jar) that has been evacuated, purged and filled with inert gas at or preferably below atmospheric pressure, e.g., pressures ranging from about 50 to about X00 torr. and even higher.
The graphite rods are typically 1/4 inch in diameter with _7_ 1 about 1 cm length of one rod reduced in diameter to about nun. The electrical heating vaporizes the constricted tip of the graphite rod producing a high density vapor of carbon, which quickly condenses into a smoke consisting of very fine particles (of the order of 0.1 microns) of graphitic carbon with an admixture of a few percent of the desired C60 molecule. At this point in the process there is a heavy black coating on collecting substrates and/or on the walls of the chamber which can be easily ' scraped oft for the recovery step.
For recovery, the sooty product is treated with benzene to provide a brownish-red solution. After separation of the undissolved graphitic carbon, the benzene solution is evaporated to obtain microcrystalline product. Alternatively, the product can be sublimed from the sooty carbon at 300° to A00'C. and the sublimation product obtained by condensation on a conventional substrate.
When the pressure of inert quenching gas is 100 torr, the product formed is 9B% C6o~and 2% C.,o. This product, as obtained from the solvent extract of the sooty graphitic carbon, is a dark brown to black crystalline material. When obtained by sublimination in vacuum or inert atmosphere, the product is obtained as a brown to gray coating depending on thickness.
On analysis by mass spectroscopy, the spectrum clearly shows a strong peak at mass 720 amu (i.e., the mass of C60) and a clean peak at F3A0 amu (i.e., the mass of C~0). Significant differences in the spectra occur only in the abundances in the mass domain lower than 300 amu. Most of these differences seem to originate from the different ionization techniques in the mass spectrometer and from the different kinds of sample desorption. So far, the cleanest mass spectra have been obtained when the material was evaporated and ionized in the vapor phase by electrons. In such spectra the mass range above 40 amu is dominated by the Cso mass along with its expected isotope lines. The only other large mass found in any abundance corresponds to Coo, with a ratio of Coo to C6o of about .02.
Studies by optical microscopy of the Cso material which is left after evaporating the benzene solution show a variety of what appear to be crystals -- mainly rods, platelets, and star-like flakes. Figure 1 shows a micro-photograph of such a crystal assemblage. AlI crystals tend to exhibit six-fold symmetry. In transmitted light they appear red to brown in color; in reflected Light the larger crystals have a metallic appearance, whereas the platelets show interference colors consistent with an index of refraction of about 2.
The platelets can be rather thin and thus are ideally suited for electron diffraction studies in an electron microscope. (See the insert in Figure 2).
In order to determine if the C6o molecules form a regular lattice, electron and x-ray diffraction studies on the individual crystals and on the powder were carried out. A
typical X-ray diffraction pattern of the purified C6o powder is shown in Figure 2. To aid in comparing the electron diffraction results with the X-ray results the electron diffraction pattern is inserted into the corner of Figure 2.
From the hexagonal array of diffraction spots indexed as shown in the Figure, a d-spacing of 8.7 A was deduced corresponding to the (100) reciprocal lattice vector of a hexagonal lattice.
The most obvious correspondence between the two types of .
diffraction is between- the 5.01 A peak of the X-ray pattern and the (100) spot of the electron diffraction pattern, which a gives a spacing of about 5.0 A. Assuming that the Coo _ g molecules are behaving approximately as spheres stacked in a hexagonal close packed lattice with a c/a ratio of 1.633, d-spacings can be calculated. The results are shown in Table I.
Table I: X-Ray Diffraction Results and Assignments For a Hexagonal Lattice Using a o a = 10.02 A, = 16.36 A
c 1 = 4 (h2 + hk kz) + QZ
-d2 3 ( a2 ) c2 , Measured Measured Calculated Assignment d-spacing d-spacing (hlcl) ydegreesy (A) (A) 10.2 shoulder 8.7 8.68 (100) 10.81 8.18 8.18 (002) 7.57 (101) 20 17.69 5.01 5.01 (110) 20.73 4.28 4.27 (112) 21.63 4.11 4.09 (004) 28.1 3.18 3.17 (114) 30.8 2.90 2.89 (300) 32.7 2.74 2.73 (006) The values derived from this interpretation are a =
20.02 A and c = 16.36 A. The nearest neighbor distance is thus 10.02 A. For such a crystal structure the density is calculated to be 1.678 g/cm3, which is consistent with a value of 1.65 +/- .05 determined by suspending crystal samples in aqueous GaCl3 solutions of known densities. Although the agreement shown in Table 1 is good, the absence of the characteristically strong (101) diffraction in hcp and the broad continuum in certain regions suggest a less than perfect crystalline order. Furthermore, X-ray diffraction patterns obtained on carefully grown crystals up to S00 micrometers in size with well developed faces yielded no clear spot pattern (in contrast to the electron diffraction pattern on micron-size crystals). It thus appears that these larger ~ crystals do not exhibit long range periodic order in all directions.
A likely explanation for the unusual diffraction lies in the disordered stacking arrangement of the molecules in planes normal to the c-axis. It is well known that the position taken by spheres in the third layer of~stacking determines which of the close-packed structures occurs, the stacking arrangement in fcc being ABCABC while that in hop is AHABA~. If the stacking sequence varies, the X-ray lines due to certain planes will be, broadened by the disorder while other lines will remain sharp. Such disordered crystalline behavior was observed long ago in the close packed structure of cobalt, where X-ray diffraction lines such as (101), (102) and (202) were found to be substantially broadened due to the stacking disorder. Reflections from planes such as (002 remain sharp since these planes have identical spacings in both fcc and hcp structures. A
general expression for which peaks are broadened by this kind of disorder have been given in terms of Miller indices (h,k,l) as h - k = 3t ~ 1, 1 # 0, where t is an integer. None of these broadened reflections are apparent in the X-ray pattern of Figure 2. This may explain the weakness of the characteristically strong 1 (101) peak. Whether or not this stacking disorder is related to the presence of the possibly elongated Coo molecules is yet to be determined.
In.small crystals at least, the C6~ molecules appear to be assembling themselves into a somewhat ordered array as though they are effectively spherical, which is entirely consistent with the soccer ball hypothesis for their structure: The additional diameter over the calculated 7.1 ~ value for the carbon cage 'itself must represent the effective van der Waals diameter set by the repulsion of the pi electron clouds extending outward from each carbon atom. Scanning tunnelling spectroscopy of the C6Q molecules clearly shows the spherical nature of the C6o molecules.
Some scanning tunnelling microscope images of a carbon sample prepared in accordance with the procedure described hereinabove at pressures of helium at 100 torr show a spherical molecule of twice the diameter of the C6o molecules. This is evidence of the existence of a caged molecule containing 240 carbon atoms or a C2d4 molecule.
Samples were prepared for spectroscopy by subliming pure material onto transparent substrates for transmission measurements. Depending on the pressure of helium in the sublimination chamber, the nature of the coatings can range from uniform films (at high vacuum) to coatings of C60 smoke (i.e., sub-micron microcrystalline particles of solid C60) with. the particle size depending to some extent on the pressure.
, rigure 3 shows the transmission spectrum of an approximately 2 micrometer thick C60 coating on a silicon substrate. The infrared bands show the four tnost intense lines at 1429, 1183, 577, and 52~ cm 1, with no 1 underlying continuum remaining from the soot. In early tries at purifying C60 material, the infrared spectrum showed a strong band in the vicinity of 3.0 micrometers, which is characteristic of a CI1 stretching mode. After much effort, this contaminant was successfully removed by washing the soot with ether and using distilled benzene in the extraction. The spectrum in Figure 3 was obtained when the material cleaned in such a manner was sublimed under vacuum onto the substrate. The spectrum shows very little indication of CII impurities.
The presence of only four strong bands is what is expected for the free, truncated icosahedral molecule with its unusually high symmetry. Also present are a number of other weak infrared lines which may be due to other causes, among which may be absorption by the C?0 molecule or symmetry breaking produced, for example, by isotopes other than C12 in the C60 molecule or by mutual interaction of the C60 molecules in the solid.
Noteworthy, are weaker features at about 2330 and 2190 cm 1 which are located in the near vicinity of the free C02 and CO stretching modes. This may imply some attachment of C02 or CO to a small fraction of the total number of C60 molecules. Another noteworthy effect can be observed in the feature at 675 cm 1, which is weak in the thin film samples but almost as strong as the four main features in the crystals. This vibrational mode may be of solid state rather than rnolecular origin.
Figure 4 shows an absorption spectrum taken on a uniform film coated onto a quartz glass substrate. The ultraviolet features are no longer obscured by the graphitic carbon background as in our previous spectra.
Hroad peaks at 216, 264 and 339 nm dominate the spectra.
Weaker structures show up in the visible, including a 1 plateau with ends at about 960 and 500 nm and a very weal:
peak near 625 nm. At the bottom of Figure 4 are snown pos?tions and relative oscillator strengths taken from Larsson, et al. CChem. Phys. Lett. 137, 501-504) calculated for the C60 molecule. This reference also shows a variety of forbidden bards with the lowest energy ones in the vicinity of 500 nm. There seems to be a rough correspondence between the present measurements on thin films and the allowed transitions predicted for the molscule. There was no band at 386 nm in our films of C60, a disclosed by Fieath, et al. (J. Chem. Phys. 87, 4236-4238 (1987)) using a laser depletion spectroscopy method and attributed to the C60 molecule. Quite similar spectra to that in Figure 4 have been recorded for microcrystalline coatings deposited at helium pressures of 100 tort, for example. The peaks occur at the 5liC;-ttly shifted positions o~ 219, 268, and 345 nm.
The C.,o molecule is larger than the C6o molecule. The C~o molecule shows a molecular ion peak at g40 amu. Furthermore, a noticeable peak in the ultraviolet spectrum of the_C~o molecule taken on a uniform film coated onto a guartz glass substrate is exhibited at about 216 nm. This is a broad peak.
Suprisingly, it appears that the C70 molecule is more stable than C60' Thus, using the procedures described hereinabove, at quenching pressures of less than 1 atmospheric pressure and especially at pressures of 50-400 tort, a product is produced which is predominantly C60 and car~tains minor amounts of C70. The C60 product can be used or can be further purified.
Further purification and separation of C60 and C70 can be made by many conventional techniques known to 1 one sl:filled in the art, e.g., fractional crystallization, column chromatography, capillary electrophoresis, IIPLC, preparative thin-layer chromatographf, and the lil:e.
Because the molecular figuration of C~0 end C~0 are different, the attractive intermolecular iorces~are different which allows for the two molecules to be readily separated.
Furthermore, the solubility of C60 and C~0 in pure solvents and mixed solvents are also different from each other, which also makes the two compounds separable by using conventional techniques known to one spilled in the art, such as crystallization, extraction, and the like.
For example, pure C00 and pure C~0 molecules can be isolated as follows. The black sooty tniy:ture of C60 and C~0 which is produced according to the procedure described hereinabove is placed in the extracting solvent, such as benzene. The insoluble residue is removed and the resulting benzene solution containing.C60 and C~0 molecules is concentrated. 'fhe C60 and solution is added to a packed column with an adsorbent, such as alumina. The column is eluted with an eluent such as benzene or a mixture of benzene and toluene.
Various fractions of set volume e.g., 10 mL, are collected. The eluent i.e., the solvent is removed from each fraction such as by evaporation to dryness. The fractions faith product will contain microcrystals, the identity of which can be confirmed by spectroscopy, e.g., mass spectroscopy.
Thus, the process of the present invention can ' produce a product which is predominantly C60, which, if desired, can be further purified by the purification and separation techniques described liereinabove.
Furthermore, the present invention contemplates two different variations of the procedure described hereinabove to make C~0 molcules. First, if subatmospheric pressures of quenching gases are used in the initial step, small amounts of C70 are produced, which can be separated from the C60 molecules using the' purification techniques described hereinabove. However, if the pressure of the quenching gas is raised to at least 2 atmospheres, after separation and purification, a 'greater percentage of substantially pure Coo would be produced from each vaporization of carbon.
The present new products, Cso, Coo, or mixtures thereof have the similar utilities as graphite. liowever, they are particularly valuable for forming products of a higher order of stability than those formed from graphitic carbon, and can be processed into formed or molded products such as C60 fibers, C~0 fibers, or mixtures thereof using standard processing techniques.
In this regard, free-flowing, particulate C60 anc C~0 are of special value particularly for use in producing molded products, especially those extended .in at least one direction. C60, and C~0 are also useful for producing a low temperature C60 vapor (300°-400°C.) and C70 vapor of the respective molecules to produce low temperature atomic and molecular beams of carbon which is not now possible using graphite as the carbon source. Further, the synthesis of compounds such as C60~;60 and C60F60 can be accomplished by introducing hydrogen and fluorine, respectively, into a reactor containing C60 vapor.
Furthermore, the C60 product and the C~0 product may be used as an industrial paint pigment or as a lubricant.
Moreover, since the C60 and C~0 molecule are hollow, they could be used for binding and/or storing molecules e.g., toxic material.
C60-containing carbon dust was produced in a conventional bell-jar carbon evaporator which was first evacuated to 10 4 tore by either an oil diffusion pump or a turbo pump, both equipped with liquid nitrogen trap's , and then filled with an inert quenching gas, lielium and argon were used at pressures ranging up to 400 torr.
Then graphite rods (as'previously described herein) were evaporated using a current of about 100 amps (either AC
or DC) .
The smoke which formed in the vicinity of the evaporating carbon rods was collected on substrates which were placed within 5 cm to 10 cm of the evaporating carbon rods.
The evaporator was opened after a cool down period of 10-30 min. and the carbon dust samples removed by scraping substrate surfaces and the internal surfaces of the bell-jar. After washing with ether, the collected dust samples were then extracted with benzene to produce a wine-red to brown solution. On evaporation of the solution, C60 was obtained,as a microcrystalline residue.
The crystals were sublimed by heating in vacuo or in a quenching inert gas to 400°C. and collected on a substrate. The sublimed product was brown to gray in color.
In powder form, the present new carbon allotrope is brownish-red.
-17_ The procedure of Example 1 is repeated except, in the original step, the graphite rods are evaporated at 2 or more atmospheres of helium pressure in the chamber.
The product obtained from this procedure contains a greater percentage of C.,o than does the product in Example 1.
3o wrrnnr c o Pure C6~ and pure C~~ are obtained as follows:
The C~~ and C.,o mixtures prepared in either examples 1 or 2 are dissolved in benzene and added to an alumina column. Using benzene as the eluent,~the fractions,.are collected and each elute traction is evaporated to . dryness. The presence of Cso or C~o.in the traction can be determined by taking mass spectroscopy thereof.
1 The above embodiments and examples are given to illustrate the scope and spirit of the instant invention.
These embodiments and examples are within the contemplation of the present invention. Therefore, the present invention should be limited'only by the appended claims.
Fig. 2 is an x-ray diffraction of a microcrystalline powder of the 98% C6o, 2% Coo solid material. Tnset at upper left is a single crystal electron diffraction pattern indexed with Miller indices compatible with the x-ray pattern, taken on a thin platelet as in Figure 1 with the electron beam perpendicular to the flat face.
Fig. 3 is an infrared absorption spectrum of an approximately 2 micrometer thick coating of the 98~ Cso, 2% C
material on a silicon substrate, referenced to a clean silicon substrate. Absorption is given as optical density=logo (1/T), where T is transmission. Apparent negative absorptions are due to the coating acting in part as a non-reflecting layer.
Fig. 4 is a visible-ultraviolet absorption spectrum of an approximately 0.1 micrometer thick coating of the 98%
C6o, 2 % C-,o material on quartz. Shown. at the bottom are positions and relative oscillator strengths for allowed transitions calculated for the C6Q molecule by Larsson, et al.
The first step in the production of C6o and C-,o molecules is vaporizing carbon from any source containing carbon in its various forms, e.g. graphite, amorphous and glassy carbon. It is preferred that this vaporization takes place in an evacuated reactor (e. g., a bell jar). The carbon is vaporized by heating in the presence of an inert quenching gas. The carbon vapor is nucleated in the presence of the inert quenching gas to form smoke particles.
l In the production of C60 and C~~, and procedure Lor vapori::in9 carbon can be used, although the preferred method relics on the use of a high intensity electrical current with graphite rods as electrodes. These rods are constructed to permit vaporization of.carbon at tire tip of the rod to produce a high density vapor of carbon.
For best results, the end of one of the rods is reduced in diameter so that the vaporization occurs at the reduced tip. The rods can be prepared using any of the various forms of carbon, such as graphite, amorphous and glassy carbon.
The inert quenching gas can be any of the usual inert gases such as the noble gas. Argon and helium are preferred, the latter being most preferred. Other inert gases commonly employed to provide a non-reactive atmosphere can also be used as quenching gas.
The amount of C60 and C~0 produced from this carbon source is dependent upon the pressure of the quenching gas. At lower pressures relatively pure.C60 molecules can be produced~in high yield with uinor concentrations of CEO. For the production of predominantly C~0 molecules, the pressure at which the quenching gas is maintained should be subatmospheric and preferably about 50-400 torr. Especially preferred is a pressure of approximately 100 torr. The use of any lower pressure may result in reduced yield of C60' However, as the pressure is raised, the ratio of C-,o:C~o is also increased.
. If the pressure is increased to at least two atmospheres, the greatest percentage of C.,o product is formed. Theoretically, the pressure can be raised to any level just below the point where the reactor would 1 explode from tie increased pressure. Iiowever, at the higher pressures, the yield of the overall product (C6o and C-,o) is reduced even though the ratio of C~~,:C~o is also increased. Therefore, as a practical consideration, the pressure of the quenching gas should not be greater than 10 atmospheres. The preferred pressure for maximizing the amount of C-,o produced is 2-3 atmospheres.
The produced quenched vapor of carbon, i.e., the smoked particles coats the internal surface of the reactor and of collecting substrates as black soot.
These collecting surfaces are inert to the vaporized carbon. They can be transparent and/or coated with an inert metal. Examples include glass, or gold coated glass surfaces and the like. These collecting surfaces are located in the reactor in the . path of the carbon smoke. The black coating can be removed by any suitable means, e.g., by scraping the solids from the coated surfaces. The C60 and C~0 molecules can be removed from this collected quenched product by contacting sold quenched product with an extracting solvent. In other words, the black soot is placed in a container containing the extracting solvent, or the extracting solvent is poured onto the black soot placed in a container. In either case, the C60 and C~0 molcules become dissolved in the solvent, while the remainder of the black soot remains insoluble. The insoluble material is separated from the solution containing the C60 and C~0 molecules, e.g., by decanting, or by filtration, and the like.
Suitable solvents include non-polar organic solvents, such as the alkanes containing S-10 carbon atoms (e. g. pentanes, hexanes, heptanes, octaves), benzene and alkyl-benzenes (e. g. toluene, xylene), carbon disulfide, carbon tetrachloride, naphtha,l,l,l-1 trichloroethane, and the like. Simple solubility determinations using classical laboratory methods will permit selection of other suitable solvents. The.
preferred solvents are carbon disulfide, benzene, carbon tetrachloride and toluene. Especially preferred are benzene, carbon tetrachloride and carbon disulfide.
The product obtained contains a mixture of C60 and C70. As described hereinabove, the amounts of C~0 and C~0 present is dependent upon the pressure used. If subatmospheric pressures are used, such as 50-400 torr, the product is predominatly pure C60 with a minor amount of C~0 present. Thus, when the collected product is dispersed in the extracting solvent, the product obtained is a mixture of C60 and CEO. For example, 4rhen the' pressure is 100 torr, the product formed is about 98o C60 and about Za C.,o. This product can be separated from the organic solvent solution by standard methods as by evaporation of the solvent or by dilution of the solvent solution with a non-solvent for C60. The product can be crystallized by careful evaporation of the organic solvent or by sublimation~procedures.
In a preferred embodiment of producing C00 and O, pure graphite rods are vaporized by passing high electrical current (either do or ac) through narrowed tips of graphite rods. Electron beam, laser and RF
heating can be used in lieu of electrical heating. This is done in a reactor (such as a bell jar) that has been evacuated, purged and filled with inert gas at or preferably below atmospheric pressure, e.g., pressures ranging from about 50 to about X00 torr. and even higher.
The graphite rods are typically 1/4 inch in diameter with _7_ 1 about 1 cm length of one rod reduced in diameter to about nun. The electrical heating vaporizes the constricted tip of the graphite rod producing a high density vapor of carbon, which quickly condenses into a smoke consisting of very fine particles (of the order of 0.1 microns) of graphitic carbon with an admixture of a few percent of the desired C60 molecule. At this point in the process there is a heavy black coating on collecting substrates and/or on the walls of the chamber which can be easily ' scraped oft for the recovery step.
For recovery, the sooty product is treated with benzene to provide a brownish-red solution. After separation of the undissolved graphitic carbon, the benzene solution is evaporated to obtain microcrystalline product. Alternatively, the product can be sublimed from the sooty carbon at 300° to A00'C. and the sublimation product obtained by condensation on a conventional substrate.
When the pressure of inert quenching gas is 100 torr, the product formed is 9B% C6o~and 2% C.,o. This product, as obtained from the solvent extract of the sooty graphitic carbon, is a dark brown to black crystalline material. When obtained by sublimination in vacuum or inert atmosphere, the product is obtained as a brown to gray coating depending on thickness.
On analysis by mass spectroscopy, the spectrum clearly shows a strong peak at mass 720 amu (i.e., the mass of C60) and a clean peak at F3A0 amu (i.e., the mass of C~0). Significant differences in the spectra occur only in the abundances in the mass domain lower than 300 amu. Most of these differences seem to originate from the different ionization techniques in the mass spectrometer and from the different kinds of sample desorption. So far, the cleanest mass spectra have been obtained when the material was evaporated and ionized in the vapor phase by electrons. In such spectra the mass range above 40 amu is dominated by the Cso mass along with its expected isotope lines. The only other large mass found in any abundance corresponds to Coo, with a ratio of Coo to C6o of about .02.
Studies by optical microscopy of the Cso material which is left after evaporating the benzene solution show a variety of what appear to be crystals -- mainly rods, platelets, and star-like flakes. Figure 1 shows a micro-photograph of such a crystal assemblage. AlI crystals tend to exhibit six-fold symmetry. In transmitted light they appear red to brown in color; in reflected Light the larger crystals have a metallic appearance, whereas the platelets show interference colors consistent with an index of refraction of about 2.
The platelets can be rather thin and thus are ideally suited for electron diffraction studies in an electron microscope. (See the insert in Figure 2).
In order to determine if the C6o molecules form a regular lattice, electron and x-ray diffraction studies on the individual crystals and on the powder were carried out. A
typical X-ray diffraction pattern of the purified C6o powder is shown in Figure 2. To aid in comparing the electron diffraction results with the X-ray results the electron diffraction pattern is inserted into the corner of Figure 2.
From the hexagonal array of diffraction spots indexed as shown in the Figure, a d-spacing of 8.7 A was deduced corresponding to the (100) reciprocal lattice vector of a hexagonal lattice.
The most obvious correspondence between the two types of .
diffraction is between- the 5.01 A peak of the X-ray pattern and the (100) spot of the electron diffraction pattern, which a gives a spacing of about 5.0 A. Assuming that the Coo _ g molecules are behaving approximately as spheres stacked in a hexagonal close packed lattice with a c/a ratio of 1.633, d-spacings can be calculated. The results are shown in Table I.
Table I: X-Ray Diffraction Results and Assignments For a Hexagonal Lattice Using a o a = 10.02 A, = 16.36 A
c 1 = 4 (h2 + hk kz) + QZ
-d2 3 ( a2 ) c2 , Measured Measured Calculated Assignment d-spacing d-spacing (hlcl) ydegreesy (A) (A) 10.2 shoulder 8.7 8.68 (100) 10.81 8.18 8.18 (002) 7.57 (101) 20 17.69 5.01 5.01 (110) 20.73 4.28 4.27 (112) 21.63 4.11 4.09 (004) 28.1 3.18 3.17 (114) 30.8 2.90 2.89 (300) 32.7 2.74 2.73 (006) The values derived from this interpretation are a =
20.02 A and c = 16.36 A. The nearest neighbor distance is thus 10.02 A. For such a crystal structure the density is calculated to be 1.678 g/cm3, which is consistent with a value of 1.65 +/- .05 determined by suspending crystal samples in aqueous GaCl3 solutions of known densities. Although the agreement shown in Table 1 is good, the absence of the characteristically strong (101) diffraction in hcp and the broad continuum in certain regions suggest a less than perfect crystalline order. Furthermore, X-ray diffraction patterns obtained on carefully grown crystals up to S00 micrometers in size with well developed faces yielded no clear spot pattern (in contrast to the electron diffraction pattern on micron-size crystals). It thus appears that these larger ~ crystals do not exhibit long range periodic order in all directions.
A likely explanation for the unusual diffraction lies in the disordered stacking arrangement of the molecules in planes normal to the c-axis. It is well known that the position taken by spheres in the third layer of~stacking determines which of the close-packed structures occurs, the stacking arrangement in fcc being ABCABC while that in hop is AHABA~. If the stacking sequence varies, the X-ray lines due to certain planes will be, broadened by the disorder while other lines will remain sharp. Such disordered crystalline behavior was observed long ago in the close packed structure of cobalt, where X-ray diffraction lines such as (101), (102) and (202) were found to be substantially broadened due to the stacking disorder. Reflections from planes such as (002 remain sharp since these planes have identical spacings in both fcc and hcp structures. A
general expression for which peaks are broadened by this kind of disorder have been given in terms of Miller indices (h,k,l) as h - k = 3t ~ 1, 1 # 0, where t is an integer. None of these broadened reflections are apparent in the X-ray pattern of Figure 2. This may explain the weakness of the characteristically strong 1 (101) peak. Whether or not this stacking disorder is related to the presence of the possibly elongated Coo molecules is yet to be determined.
In.small crystals at least, the C6~ molecules appear to be assembling themselves into a somewhat ordered array as though they are effectively spherical, which is entirely consistent with the soccer ball hypothesis for their structure: The additional diameter over the calculated 7.1 ~ value for the carbon cage 'itself must represent the effective van der Waals diameter set by the repulsion of the pi electron clouds extending outward from each carbon atom. Scanning tunnelling spectroscopy of the C6Q molecules clearly shows the spherical nature of the C6o molecules.
Some scanning tunnelling microscope images of a carbon sample prepared in accordance with the procedure described hereinabove at pressures of helium at 100 torr show a spherical molecule of twice the diameter of the C6o molecules. This is evidence of the existence of a caged molecule containing 240 carbon atoms or a C2d4 molecule.
Samples were prepared for spectroscopy by subliming pure material onto transparent substrates for transmission measurements. Depending on the pressure of helium in the sublimination chamber, the nature of the coatings can range from uniform films (at high vacuum) to coatings of C60 smoke (i.e., sub-micron microcrystalline particles of solid C60) with. the particle size depending to some extent on the pressure.
, rigure 3 shows the transmission spectrum of an approximately 2 micrometer thick C60 coating on a silicon substrate. The infrared bands show the four tnost intense lines at 1429, 1183, 577, and 52~ cm 1, with no 1 underlying continuum remaining from the soot. In early tries at purifying C60 material, the infrared spectrum showed a strong band in the vicinity of 3.0 micrometers, which is characteristic of a CI1 stretching mode. After much effort, this contaminant was successfully removed by washing the soot with ether and using distilled benzene in the extraction. The spectrum in Figure 3 was obtained when the material cleaned in such a manner was sublimed under vacuum onto the substrate. The spectrum shows very little indication of CII impurities.
The presence of only four strong bands is what is expected for the free, truncated icosahedral molecule with its unusually high symmetry. Also present are a number of other weak infrared lines which may be due to other causes, among which may be absorption by the C?0 molecule or symmetry breaking produced, for example, by isotopes other than C12 in the C60 molecule or by mutual interaction of the C60 molecules in the solid.
Noteworthy, are weaker features at about 2330 and 2190 cm 1 which are located in the near vicinity of the free C02 and CO stretching modes. This may imply some attachment of C02 or CO to a small fraction of the total number of C60 molecules. Another noteworthy effect can be observed in the feature at 675 cm 1, which is weak in the thin film samples but almost as strong as the four main features in the crystals. This vibrational mode may be of solid state rather than rnolecular origin.
Figure 4 shows an absorption spectrum taken on a uniform film coated onto a quartz glass substrate. The ultraviolet features are no longer obscured by the graphitic carbon background as in our previous spectra.
Hroad peaks at 216, 264 and 339 nm dominate the spectra.
Weaker structures show up in the visible, including a 1 plateau with ends at about 960 and 500 nm and a very weal:
peak near 625 nm. At the bottom of Figure 4 are snown pos?tions and relative oscillator strengths taken from Larsson, et al. CChem. Phys. Lett. 137, 501-504) calculated for the C60 molecule. This reference also shows a variety of forbidden bards with the lowest energy ones in the vicinity of 500 nm. There seems to be a rough correspondence between the present measurements on thin films and the allowed transitions predicted for the molscule. There was no band at 386 nm in our films of C60, a disclosed by Fieath, et al. (J. Chem. Phys. 87, 4236-4238 (1987)) using a laser depletion spectroscopy method and attributed to the C60 molecule. Quite similar spectra to that in Figure 4 have been recorded for microcrystalline coatings deposited at helium pressures of 100 tort, for example. The peaks occur at the 5liC;-ttly shifted positions o~ 219, 268, and 345 nm.
The C.,o molecule is larger than the C6o molecule. The C~o molecule shows a molecular ion peak at g40 amu. Furthermore, a noticeable peak in the ultraviolet spectrum of the_C~o molecule taken on a uniform film coated onto a guartz glass substrate is exhibited at about 216 nm. This is a broad peak.
Suprisingly, it appears that the C70 molecule is more stable than C60' Thus, using the procedures described hereinabove, at quenching pressures of less than 1 atmospheric pressure and especially at pressures of 50-400 tort, a product is produced which is predominantly C60 and car~tains minor amounts of C70. The C60 product can be used or can be further purified.
Further purification and separation of C60 and C70 can be made by many conventional techniques known to 1 one sl:filled in the art, e.g., fractional crystallization, column chromatography, capillary electrophoresis, IIPLC, preparative thin-layer chromatographf, and the lil:e.
Because the molecular figuration of C~0 end C~0 are different, the attractive intermolecular iorces~are different which allows for the two molecules to be readily separated.
Furthermore, the solubility of C60 and C~0 in pure solvents and mixed solvents are also different from each other, which also makes the two compounds separable by using conventional techniques known to one spilled in the art, such as crystallization, extraction, and the like.
For example, pure C00 and pure C~0 molecules can be isolated as follows. The black sooty tniy:ture of C60 and C~0 which is produced according to the procedure described hereinabove is placed in the extracting solvent, such as benzene. The insoluble residue is removed and the resulting benzene solution containing.C60 and C~0 molecules is concentrated. 'fhe C60 and solution is added to a packed column with an adsorbent, such as alumina. The column is eluted with an eluent such as benzene or a mixture of benzene and toluene.
Various fractions of set volume e.g., 10 mL, are collected. The eluent i.e., the solvent is removed from each fraction such as by evaporation to dryness. The fractions faith product will contain microcrystals, the identity of which can be confirmed by spectroscopy, e.g., mass spectroscopy.
Thus, the process of the present invention can ' produce a product which is predominantly C60, which, if desired, can be further purified by the purification and separation techniques described liereinabove.
Furthermore, the present invention contemplates two different variations of the procedure described hereinabove to make C~0 molcules. First, if subatmospheric pressures of quenching gases are used in the initial step, small amounts of C70 are produced, which can be separated from the C60 molecules using the' purification techniques described hereinabove. However, if the pressure of the quenching gas is raised to at least 2 atmospheres, after separation and purification, a 'greater percentage of substantially pure Coo would be produced from each vaporization of carbon.
The present new products, Cso, Coo, or mixtures thereof have the similar utilities as graphite. liowever, they are particularly valuable for forming products of a higher order of stability than those formed from graphitic carbon, and can be processed into formed or molded products such as C60 fibers, C~0 fibers, or mixtures thereof using standard processing techniques.
In this regard, free-flowing, particulate C60 anc C~0 are of special value particularly for use in producing molded products, especially those extended .in at least one direction. C60, and C~0 are also useful for producing a low temperature C60 vapor (300°-400°C.) and C70 vapor of the respective molecules to produce low temperature atomic and molecular beams of carbon which is not now possible using graphite as the carbon source. Further, the synthesis of compounds such as C60~;60 and C60F60 can be accomplished by introducing hydrogen and fluorine, respectively, into a reactor containing C60 vapor.
Furthermore, the C60 product and the C~0 product may be used as an industrial paint pigment or as a lubricant.
Moreover, since the C60 and C~0 molecule are hollow, they could be used for binding and/or storing molecules e.g., toxic material.
C60-containing carbon dust was produced in a conventional bell-jar carbon evaporator which was first evacuated to 10 4 tore by either an oil diffusion pump or a turbo pump, both equipped with liquid nitrogen trap's , and then filled with an inert quenching gas, lielium and argon were used at pressures ranging up to 400 torr.
Then graphite rods (as'previously described herein) were evaporated using a current of about 100 amps (either AC
or DC) .
The smoke which formed in the vicinity of the evaporating carbon rods was collected on substrates which were placed within 5 cm to 10 cm of the evaporating carbon rods.
The evaporator was opened after a cool down period of 10-30 min. and the carbon dust samples removed by scraping substrate surfaces and the internal surfaces of the bell-jar. After washing with ether, the collected dust samples were then extracted with benzene to produce a wine-red to brown solution. On evaporation of the solution, C60 was obtained,as a microcrystalline residue.
The crystals were sublimed by heating in vacuo or in a quenching inert gas to 400°C. and collected on a substrate. The sublimed product was brown to gray in color.
In powder form, the present new carbon allotrope is brownish-red.
-17_ The procedure of Example 1 is repeated except, in the original step, the graphite rods are evaporated at 2 or more atmospheres of helium pressure in the chamber.
The product obtained from this procedure contains a greater percentage of C.,o than does the product in Example 1.
3o wrrnnr c o Pure C6~ and pure C~~ are obtained as follows:
The C~~ and C.,o mixtures prepared in either examples 1 or 2 are dissolved in benzene and added to an alumina column. Using benzene as the eluent,~the fractions,.are collected and each elute traction is evaporated to . dryness. The presence of Cso or C~o.in the traction can be determined by taking mass spectroscopy thereof.
1 The above embodiments and examples are given to illustrate the scope and spirit of the instant invention.
These embodiments and examples are within the contemplation of the present invention. Therefore, the present invention should be limited'only by the appended claims.
Claims (26)
1. A process for preparing fullerenes comprising:
(a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising fullerene molecules, said fullerene molecules being present in said sooty carbon product in macroscopic amounts; and (b) recovering macroscopic amounts of fullerene from said sooty carbon product.
(a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising fullerene molecules, said fullerene molecules being present in said sooty carbon product in macroscopic amounts; and (b) recovering macroscopic amounts of fullerene from said sooty carbon product.
2. The process according to Claim 1, wherein the fullerene is recovered in solid form.
3. The process according to claim 1, wherein the fullerene is recovered in solution.
4. A fullerene present in an amount sufficient to isolate as a solid.
5. A macroscopic amount of fullerene.
6. A solid that consists essentially of a fullerene, said fullerene being isolated from a sooty carbon product formed from vaporizing a carbon source in the presence of an inert quenching gas, wherein said fullerene is recovered therefrom in macroscopic amounts.
7. A cage carbon molecule consisting solely of carbon atoms that is isolated from a sooty carbon product formed from the vaporization of a carbon source in the presence of an inert quenching gas, said cage carbon molecule being recovered therefrom in amounts sufficient to be isolated as a visible solid.
8. A cage carbon molecule product consisting solely of carbon atoms which is prepared by (a) vaporizing a carbon source in the presence of an inert quenching gas under conditions effective to produce a sooty carbon containing said cage carbon molecule product, said inert gas providing a non-reactive atmosphere;
(b) collecting said sooty carbon product;
(c) separating said product from said sooty carbon product, said separated product being free of any sooty carbon product and consisting solely of carbon atoms, said product being present in amounts sufficient for the product to be perceived as a visible solid in solid form.
(b) collecting said sooty carbon product;
(c) separating said product from said sooty carbon product, said separated product being free of any sooty carbon product and consisting solely of carbon atoms, said product being present in amounts sufficient for the product to be perceived as a visible solid in solid form.
9. The product according to Claim 8, wherein the inert quenching gas is a noble gas.
10. The product according to Claim 8 or 9, wherein the carbon source is vaporized in a reaction vessel which has been evacuated prior to the vaporization step.
11. The product according to Claim 8, 9, or 10, wherein the inert quenching gas is present in amounts sufficient to quench the vaporized carbon source, said inert quenching gas being present at a pressure ranging from subatmospheric to torr.
12. The product according to any one of Claims 8 to 11, wherein the inert quenching gas is helium or argon.
13. The product according to any one of Claims 7 to 12, wherein the cage carbon molecule product consisting solely of carbon atoms is hollow.
14. Fullerenes in an amount at least as large as that amount which is sufficient to see under an optical microscope.
15. A process for preparing a carbon allotrope comprising cage molecules consisting solely of carbon atoms which are soluble in non-polar organic solvents, said process comprising:
(a) vaporizing a carbon source in the presence of an inert gas to produce a carbon vapor;
(b) quenching said vapor of carbon in said inert gas under conditions effective to nucleate and condense said carbon allotrope, said allotrope being present in said sooty carbon product in amounts sufficient to be capable of extracting and recovering therefrom said allotrope in solid form; and (c) recovering said carbon allotrope from said sooty carbon product.
(a) vaporizing a carbon source in the presence of an inert gas to produce a carbon vapor;
(b) quenching said vapor of carbon in said inert gas under conditions effective to nucleate and condense said carbon allotrope, said allotrope being present in said sooty carbon product in amounts sufficient to be capable of extracting and recovering therefrom said allotrope in solid form; and (c) recovering said carbon allotrope from said sooty carbon product.
16. A process for preparing cage molecules consisting solely of carbon atoms comprising:
(a) vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to form a sooty carbon product containing said cage molecules of carbon, said cage molecules being present in said sooty carbon product in sufficient amounts to be capable of extracting and recovering therefrom said cage molecules as a solid; and (b) extracting said cage molecule of carbon from said sooty carbon product.
(a) vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to form a sooty carbon product containing said cage molecules of carbon, said cage molecules being present in said sooty carbon product in sufficient amounts to be capable of extracting and recovering therefrom said cage molecules as a solid; and (b) extracting said cage molecule of carbon from said sooty carbon product.
17. A process for preparing cage molecules consisting solely of carbon atoms comprising:
(a) vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to provide a sooty carbon product comprising said cage molecules of carbon, said cage molecules being present in said sooty carbon product in amounts sufficient to be capable of extracting and recovering therefrom said cage molecules in solid form;
(b) depositing the sooty carbon product on a collecting surface;
(c) removing the sooty product from the collecting surface; and (d) extracting a product which comprises cage molecules consisting solely of carbon atoms from said sooty carbon product.
(a) vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to provide a sooty carbon product comprising said cage molecules of carbon, said cage molecules being present in said sooty carbon product in amounts sufficient to be capable of extracting and recovering therefrom said cage molecules in solid form;
(b) depositing the sooty carbon product on a collecting surface;
(c) removing the sooty product from the collecting surface; and (d) extracting a product which comprises cage molecules consisting solely of carbon atoms from said sooty carbon product.
18. A process for preparing caged molecules consisting solely of carbon atoms comprising:
(a) vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising said cage molecules, said cage molecule being present in said sooty carbon product in amounts sufficient to provide a visibly colored solution when extracted with effective amounts of benzene; and (b) extracting said cage molecule from said sooty carbon product.
(a) vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising said cage molecules, said cage molecule being present in said sooty carbon product in amounts sufficient to provide a visibly colored solution when extracted with effective amounts of benzene; and (b) extracting said cage molecule from said sooty carbon product.
19. A process for preparing a carbon allotrope comprising:
(a) vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to provide a sooty carbon product comprising said carbon allotrope, said carbon allotrope being present in said sooty carbon product in amounts sufficient to be capable of providing a visibly colored solution when dissolved in sufficient amounts of benzene;
(b) depositing the sooty carbon product on a collecting surface;
(c) removing the sooty carbon product from the collecting surface;
and (d) extracting a product which comprises said carbon allotrope.
(a) vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to provide a sooty carbon product comprising said carbon allotrope, said carbon allotrope being present in said sooty carbon product in amounts sufficient to be capable of providing a visibly colored solution when dissolved in sufficient amounts of benzene;
(b) depositing the sooty carbon product on a collecting surface;
(c) removing the sooty carbon product from the collecting surface;
and (d) extracting a product which comprises said carbon allotrope.
20. A process for preparing a carbon allotrope comprising:
(a) vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising said carbon allotrope, said carbon allotrope being capable of being dissolved in a non-polar organic solvent and said carbon allotrope being present in said sooty carbon product in sufficient quantities to be capable of extracting and recovering therefrom said allotrope in solid form; and (b) extracting said allotrope from said sooty carbon product.
(a) vaporizing elemental carbon in the presence of an inert quenching gas under conditions effective to form a sooty carbon product comprising said carbon allotrope, said carbon allotrope being capable of being dissolved in a non-polar organic solvent and said carbon allotrope being present in said sooty carbon product in sufficient quantities to be capable of extracting and recovering therefrom said allotrope in solid form; and (b) extracting said allotrope from said sooty carbon product.
21. A process for preparing a carbon allotrope consisting solely of carbon atoms which is soluble in non-polar organic solvent comprising:
(a) vaporizing elemental carbon in the presence of an inert quenching gas under a pressure ranging from less than 1 atmosphere up to 10 atmospheres under conditions effective to form a sooty carbon product comprising said carbon allotrope, said product being present in said sooty carbon product in quantities sufficient to be recovered as a visible solid; and (b) separating said carbon allotrope from said sooty carbon product.
(a) vaporizing elemental carbon in the presence of an inert quenching gas under a pressure ranging from less than 1 atmosphere up to 10 atmospheres under conditions effective to form a sooty carbon product comprising said carbon allotrope, said product being present in said sooty carbon product in quantities sufficient to be recovered as a visible solid; and (b) separating said carbon allotrope from said sooty carbon product.
22. The process according to Claim 21 wherein separating comprises subliming said carbon allotrope from said sooty carbon product and condensing said sublimed carbon allotrope.
23. The process according to Claim 21 wherein separating further comprises:
b(i) contacting said sooty carbon product with a non-polar organic solvent effective to dissolve said carbon allotrope, said solvent being present in an amount effective to dissolve the carbon allotrope in said sooty carbon product; and b(ii) separating the solvent containing the dissolved carbon allotrope from the sooty carbon product that is insoluble in said solvent, and separating said allotrope from the non-polar organic solvent.
b(i) contacting said sooty carbon product with a non-polar organic solvent effective to dissolve said carbon allotrope, said solvent being present in an amount effective to dissolve the carbon allotrope in said sooty carbon product; and b(ii) separating the solvent containing the dissolved carbon allotrope from the sooty carbon product that is insoluble in said solvent, and separating said allotrope from the non-polar organic solvent.
24. The process according to Claim 23 wherein separating comprises evaporating the solvent.
25. The process according to Claim 23 wherein the non-polar organic solvent is benzene, toluene, carbon tetrachloride, 1,1,1-trichloroethane, xylene or an alkane having 5-10 carbon atoms.
26. The process according to Claim 23, 24 or 25 wherein the insoluble sooty carbon product is separated from the solution containing dissolved carbon allotrope by filtration or by decanting.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US57525490A | 1990-08-30 | 1990-08-30 | |
| US572,254 | 1990-08-30 | ||
| US580,246 | 1990-09-10 | ||
| US07/580,246 US7494638B1 (en) | 1990-08-30 | 1990-09-10 | Form of carbon |
| CA002072117A CA2072117C (en) | 1990-08-30 | 1991-08-21 | Form of carbon |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002072117A Division CA2072117C (en) | 1990-08-30 | 1991-08-21 | Form of carbon |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2517965A1 CA2517965A1 (en) | 1992-03-19 |
| CA2517965C true CA2517965C (en) | 2006-06-27 |
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ID=35431147
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002517965A Expired - Lifetime CA2517965C (en) | 1990-08-30 | 1991-08-21 | New form of carbon |
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| Country | Link |
|---|---|
| CA (1) | CA2517965C (en) |
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1991
- 1991-08-21 CA CA002517965A patent/CA2517965C/en not_active Expired - Lifetime
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| Publication number | Publication date |
|---|---|
| CA2517965A1 (en) | 1992-03-19 |
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