GREEN METHOD FOR PRODUCING A MIXTURE OF MULTIPLE NANO-CARBON POLYMORPHS FROM COAL

Abstract

The present disclosure relates to a green method for producing and exploiting multiple nano-carbon polymorphs from coal commonly known as anthracite, meta-anthracite, and semi-graphite. The method disrupts the prevalent environmentally unfriendly practices of burning coal with poor profitability and sustainability because the method yields an unexpectedly rich mixture of high-performance nano-materials, comprising carbon nano-fibers, carbon nano-tubes, carbon nano-onions, nano-graphite-plates, and nano-graphene-disks, by simply mechanically-comminuting coal to nano-size, with minimal sorting efforts. The resulting total-yield of nano-carbon polymorphs is over 50% by weight from properly selected coal. Innovative means are added to the prevalent comminution and sorting practices to further reduce energy and chemical consumption. More importantly, the method also refines the comminution and sorting details for producing the best custom-made formulations. This holistic engineering approach eliminates unnecessary separation and sorting steps because a custom-made formulation typically requires blending the sorted components. Formulations with mixed nano-carbon polymorphs are engineered as new and high-valued-added composite ingredients to critically raise the performance of cement-based, polymer-based, and metal-based composites.

Claims

1. A method for extracting from coal more than one nano-carbon polymorphs, wherein the method uses no oxidation nor any chemical etch but uses environmentally friendly processes comprising: the selection of a proper coal source; dry mechanical pulverization of the selected coal; float-sink separation of organic constituents from inorganic mineral constituents; wet-comminution of the separated organic constituents to 200-1000 nm with no grinding grit; follow-up wet-comminution of the sub-micron comminuted organic constituents, with the assistance of grinding agents, to yield nano-carbon polymorphs smaller than-100 nm; sorting of multiple nano-carbon polymorphs and amorphous organic nano-constituents; blending the sorted nano-dispersions comprising different coal constituents into an application-specific formulation as a custom-made high-performance product.

2. The method of claim 1, wherein the nano-carbon polymorphs comprise carbon nano-fibers, carbon nano-tubes, carbon nano-onions, nano-graphene, nano-graphite-plates, or a combination thereof.

3. The method of claim 1, wherein the nano-carbon polymorphs are sphere-like with diameter of 1 nm-50 nm, flake-like with thickness not more than 2 nm and edge-size not more than 100 nm, thread-like with cross-section dimension not more than 20 nm and length not less than 50 nm, and or a combination thereof.

4. The method of claim 1, wherein the nano-carbon polymorphs comprise carbon with a concentration more than 90% by weight.

5. The method of claim 1, wherein the nano-carbon polymorphs display diffraction features and comprise crystalline or turbostratic-crystalline structures.

6. The method of claim 1, wherein the nano-carbon polymorphs have density 1.5-2.1 g/cm.sup.3.

7. The method of claim 1, wherein the coal is selected from anthracite, meta-anthracite, semi-graphite, combinations thereof, or coal with mean random vitrinite reflectance 3-10%.

8. (canceled)

9. (canceled)

10. (canceled)

11. (canceled)

12. (canceled)

13. (canceled)

14. The method of claim 1, wherein the mechanical pulverization comprises milling, grinding, or a combination thereof, and the pulverized size ranges 50-500 microns.

15. The method of claim 1, wherein the wet comminution comprises solvation, dispersion, and comminution in a liquid medium with the additives of surfactants and dispersion-stabilizers to solvate and disperse the pulverized and sieved coal powder into nano-dispersions.

16. The method of claim 15, wherein the liquid medium comprises water, alkanol, glycerol, ethylene glycol, propylene glycol, ionic liquid, alkane liquid, ether, carbon tetrachloride, or a combination thereof.

17. The method of claim 15, wherein the surfactants and dispersion-stabilizers comprise tetrahydrofurfuryl ester, ethoxylated alcohols, alkyl sulfates, alkyl carboxylates, poloxamer, polysorbate, polyvinylpyrrolidone, or a combination thereof.

18. The method of claim 15, wherein the wet comminution is conducted with a high-speed spinner or a mixer.

19. (canceled)

20. (canceled)

21. (canceled)

22. The method of claim 1, wherein the grinding agents in the follow-up wet-comminution comprise grinding grits of alumina, silica, or yttrium-stabilized zirconia.

23. (canceled)

24. (canceled)

25. (canceled)

26. The method of claim 1, wherein the float-sink separation of the constituents of the pulverized coal comprises the use of liquid media having ZnCl.sub.2 aqueous-solution, alkane liquid, carbon tetrachloride, pyridine, chloroform, ether, alkanol, or a combination thereof; or the addition of hydrodynamic cavitation in a flotation column.

27. (canceled)

28. The method of claim 1, wherein the sorting processes for sorting nano-carbon-polymorphs comprise filtration processes for extracting particulates of 1-5 nm, 5-10 nm, 10-30 nm, 30-50 nm, 50-100 nm, and or a combination thereof.

29. The method of claim 1, wherein the nano-carbon polymorphs and other constituents of the pulverized coal are separated by differentiation in density and wettability.

30. The method of claim 1, wherein the nano-carbon-polymorphs are extracted from coal with each extract comprising a distribution of polymorph composition, shape, and size, and with each extract comprising dry powder, slurry, colloid, composite, or a combination thereof.

31. The method of claim 1, wherein the products of nano-carbon-polymorphs comprise application-specific product-formulations of nano-carbon-polymorphs by blending the sorted extracts of nano-carbon polymorphs.

32. The method of claim 1, wherein the products of nano-carbon polymorphs in application-specific formulations are utilized in cement-modification, concrete-modification, production of nano-particulate-reinforced composites, production of inks for 3D printing, production of coatings, production of lubricants, production of batteries, and ora combination thereof.

33. The method of claim 1, wherein the remaining constituents of coal in the processes of extracting the nano-carbon polymorphs are utilized in the production of chemicals, construction materials, or energy.

Description

DESCRIPTION OF THE FIGURES

[0071] FIG. 1 Commonly-known nano-carbon polymorphs

[0072] FIG. 2 The eighteen molecular models of coal as recently validated by Zhou et al. [29].

[0073] FIG. 3 A scheme of a green and low-cost method for producing nano-carbon polymorphs from coal and exploiting the best value of most constituents of coal with the lowest environmental load

[0074] FIG. 4 A high resolution TEM (HRTEM) image of a nano-grain of coal comprising a mixture of turbostratic carbon nano-crystals with the presence of carbon nano-onions, carbon nano-fibers, and a hexagonal nano-graphene. The majority of lattice fringes show lattice spacing of 0.32-0.39 nm. The chemical elemental identification by energy dispersive X-ray spectroscopy in the scanning TEM mode confirms the presence of carbon. The nano-grain of coal was found from the diluted slurry prepared by simply grinding two pieces of coa.1

[0075] FIG. 5 A high resolution TEM (HRTEM) image of a nano-carbon polymorph present in the hexane extract prepared by adding hexane to the aqueous colloid from simple grinding a piece of coal with 50 nm alumina-grits. The presence of abundant nano-carbon graphitic-polymorphs with an average size of about 2 nm is evident. The diffraction signals fit the carbon crystal structure known as PDS #046-943 in the database released under the Joint Committee on Powder Diffraction Standards. The most intense diffraction signals are attributed to the presence of repetitive lattice planes with an average lattice spacing of 0.32 nm.

[0076] FIG. 6 A high resolution TEM (HRTEM) image of a nano-carbon polymorph present in the hexane extract prepared by adding hexane to the aqueous slurry which was prepared by simple grinding a piece of coal with 50 nm alumina-grits. The nano-carbon graphitic-polymorph was present amid an amorphous carbon grain with the chemical elemental identification confirmed by energy dispersive X-ray spectroscopy in the scanning TEM mode. The lattice imaging picture shows graphite basal-planes packed vertically into a rectangular graphitic carbon nano-crystal (about 6 nm×25 nm). The average lattice spacing is 0.33 nm.

DETAILED DESCRIPTION OF THE INVENTION

[0077] Coal was formed with an age as old as 200-400 million years and has been a major and rich natural resource for human. However, the prevalent utilization of coal is burning merely for its energy contents with little attention to the other values in coal and to the environmental loads incurred by burning coal. A revolutionary social conscience has recently emerged to curb such misuse and mismanagement of coal. Ideally, most of the current energy production by burning coal should be replaced with clean energy production by harvesting solar, hydro, and wind energy. When this green energy management becomes prevalent, coal can then be preserved as raw materials for green chemical engineering of high-value-added carbon-based products. To implement such an ideal, innovative science and technology must be developed for the articulation of the diverse variations in coal's physical/chemical nature, and for the green extraction and applications of all functional constituents in coal. The present disclosure is developed with this mission of using and managing the coal resources on earth in compliance to the principles of green chemistry and engineering. As such, the contents of green chemistry and engineering in the disclosure must first be clarified.

[0078] Among the well-known 12 principles of green chemistry[1], those most relevant to the present disclosure are summarized and articulated as follows: [0079] Preventing waste; [0080] Incorporation of all materials used in the production process into the final products; [0081] Energy requirements are minimized, with the elimination of heating/pressuring procedures, and with the consideration of energy requirements incurred in the production of raw materials.

[0082] The present disclosure relates to a green method for extracting and exploiting the high-value-added nano-carbon polymorphs in coal, and the method starts with the process of selecting a proper coal source. In compliance to the principles of green chemistry and engineering, the present disclosure picks only certain types of coal for the production of nano-carbon polymorphs. Made-made coke, artificial graphitized coal, carbon black, activated carbon, and any derivatives of coal with considerable environmental loads are not selected because of the high energy consumption and environmental load in their product life-cycles. Natural graphite is not selected because it is well known that a high energy barrier of about 1000 kJ/mol is present against the conversion of coal and coal-like materials to graphite; as such, the cleavage and exfoliation of graphite to nano-carbon polymorphs must also be energy intensive procedures and should be excluded. Similarly, the disclosure rejects those coke, carbon black, activated carbon, and derivatives of coal whenever they comprise large micron-size graphite domains because breaking these domains down to nano-carbon polymorphs are energy-consuming. Members of low-rank coal like peat, sub-bituminous coal, bituminous coal, and lignite are not included because they contain too many aliphatic C—C, C—O, C—H, C—S, C—N, and C—P bonds, and the cleavages of them, together with the diffusion and re-organization of the resultant carbon atoms towards the formation of nano-carbon polymorphs, requires high energy consumption and imposes environmental loads.

[0083] With these considerations, the present disclosure goes against the prevalent choices of a broad range of coal ranks in the production of nano-graphene and graphene-quantum-dots and is discriminating in selecting its raw materials. Specifically, the present disclosure favors the group of anthracite, meta-anthracite, semi-graphite, and combinations thereof. Under the ISO 11760 coal classification, anthracite and meta-anthracite are named Anthracite C, Anthracite B, and Anthracite A. In this classification, meta-anthracite is grouped into Anthracite A, and Anthracite B is a mixture of anthracite and meta-anthracite. Semi-graphite is not well-defined in the literature and is technically referred in the present disclosure as meta-anthracite having more nanometer- and micron-size graphite contents than Anthracite A. More specifically, in ISO 11760, Anthracite A is defined as anthracite with mean random vitrinite reflectance of 4-6% (mean maximum vitrinite reflectance of up to 8%); in this context, the present disclosure refers semi-graphite as anthracite with mean random vitrinite reflectance of 6-10%. Coal with such unusually high reflectance is present in coal-beds around the world, and is still referred as anthracite in China.

[0084] The global reserve of anthracite and meta-anthracite is huge, with rich deposits in all continents. Hence, the transformation of them to high-performance nano-carbon polymorphs and application-specific formulations comprising such nano-carbon polymorphs with green and low-cost processes will certainly disrupt the present coal industry and fundamentally change the financial and social issues relevant to coal.

[0085] In the course of developing the present disclosure, Applicants have indeed diligently verified with high resolution TEM analyses the presence of multiple nano-carbon polymorphs in coal. Specifically, Applicants have verified, with experimental data articulated in Examples 1 and 2 in the present disclosure, that Anthracite A typically has a high concentration (more than 50% in volume) of multiple nano-carbon polymorphs comprising more than one polymorphs from the group of carbon nano-fiber, carbon nano-tube, carbon nano-onion, nano-graphene, and nano-graphite plate. With the same analysis method, Applicants have also verified that Anthracite C typically has abundant nano-graphene, with other nano-carbon polymorphs as minor polymorph constituents. In short, the selection of special sources of coal is very important in producing multiple nano-carbon polymorphs in coal with the lowest environmental loads and with the best product performance at low costs. These results and conclusion are new and break the ground of the prevalent knowledge about coal. Technically, since measurements of reflectance are simple, fast and low-cost, they can be integrated in automated production as a real-time in-line coal-selection means.

[0086] The present disclosure is novel because the main-stream literature of coal has taught against the contemplation of the presence and the production of multiple nano-carbon polymorphs in coal. First, there are about 345 known structural models of coal in the main-stream literature since 1942 and 18 of them have been validated recently with the most updated and reliable scientific data from known coal analyses [27-29], and none of these 18 validated models indicate the presence of multiple nano-carbon polymorphs in coal. In fact, these 18 models, as shown in FIG. 3, consistently imply the presence of nano-graphene with a short-range-order resembling the crystalline structure of graphene, and with a graphene-domain of 1-2 nm across the basal-plane and at the most 2-3 basal-plane layers. Second, in the large volume of literature about experimental studies of coal including anthracite, abundant data from XRD and TEM also consistently conclude the presence of nano-size graphene-like domains of 1-2 nm across the basal-plane and 1-3 basal-plane layers. Third, the recent discoveries of nano-graphene in coal by Tour et al. and other groups, also show nano-graphene domains of 1-2 nm across the basal-plane and 1-3 basal-plane layers. These recent discoveries further reinforce the perception that only nano-graphene, with no other nano-carbon polymorphs, is present in coal and can be produced from coal.

[0087] Nevertheless, scarce pieces of information on coal hint the presence of some of the common nano-carbon polymorphs shown in FIG. 1, other than nano-graphene. For example, a high resolution TEM image of nearly half of a carbon nano-onion is revealed in the study of using lithium to violently reduce anthracite by Sun et al. [30]. No details were given by Sun et al. regarding the exact anthracite treatment prior to the TEM imaging. Nevertheless, in the section showing the image of carbon nano-onion, Sun et al. said “exfoliation of anthracite has been investigated and shown that strong oxidants are required” [30]. This casts some uncertainty if the presence of carbon nano-onion is natural or artificial. On the other hand, a report on TEM [31] dated to 1965 shows the presence of well-crystallized and relatively large nano-graphite with an average domain-size of 80 nm in meta-anthracite samples taken from the Leoben coal-field in Austria. Unfortunately, the TEM imaging clarity was not good enough in 1965 to pin the presence of multiple nano-carbon polymorphs. Since then, no relevant data have been reported except the works of Kumanek et al. [32] in 2018 on thermally treated anthracite. There, a high resolution TEM image of an alleged-anthracite sample taken from the Doneck Basin (Donbas) coal-field of Svierdlovski in Ukraine was shown. Although the authors did not pay any attention to the detailed structure in this image, Applicants of the present disclosure opine that the image reveals the presence of multiple nano-carbon polymorphs. Interestingly, Kumanek et al. [32] also reported that the sample had an extremely high carbon content of 95% by weight. A careful track of coal from the Donbas coal-field reveals that Donbas is well known for its rich meta-anthracite reserve and the Donbas meta-anthracite typically has a carbon content of 94-95% [33]. From all known data on anthracite, the carbon contents are typically 91-93% and are certainly lower than 95%. Hence, a verdict can be reached that Kumanek et al. [32] erroneously referred metal-anthracite of the Donbas coal-field to anthracite. In short, speculative evidence of the presence of multiple nano-carbon polymorphs in coal, particularly in meta-anthracite, is hidden in several past reports despite the fact that the main-stream literature is against the contemplation of such presence.

[0088] The science governing the formation of multiple nano-carbon polymorphs in anthracite and meta-anthracite is further explained in this section. Thermodynamically, coal is not as stable as graphite; as such, coal can be fully graphitized at around 3000° C. Such a high temperature is required because the phase transformation is blocked by an extremely high energy barrier of about 1000 kJ/mol [11, 32-35]. Experimentally, the formation of intermediate precursors of graphite as a function of energy input in the slow graphitization process has been tracked by several groups [32, 34, 35]. In general, multiple nano-carbon polymorphs emerge during thermal treatments around 1000° C. [34,35]. The temperature threshold of this onset of phase transformation decreases to around 300-900° C. when press or shear is applied. On earth, natural formation of meta-anthracite and graphite are facilitated by both temperature and stress in the processes of coalification and graphitization. As such, the feasibility of searching and extracting multiple nano-carbon polymorphs from coal are supported by the global presence of coal-fields which have experienced transient geological rises in pressure and temperature, such as about 0.3-0.6 GPa and 300-1000° C. Typically, meta-anthracite is found in these coal fields. Therefore, the present disclosure scientifically clarifies that multiple nano-carbon polymorphs are precursors for the formation of micro-graphite and graphite.

[0089] The most cost-effective and environmental-friendly way to produce nano-carbon polymorphs is thus to extract them from anthracite and meta-anthracite because these nano-materials are naturally present in these coal sources. Alternatively, low-rank coal can be modified with thermal processes around 1000° C. in atmospheric pressure or around 500° C. under press and shear to improve the yield in producing multiple nano-carbon polymorphs; but these energy-demanding processes are costly and noncompliant to the principles of green chemistry and engineering. The formation and production of nano-carbon polymorphs from coal-derivatives produced by any means of carbonized or graphitized processes which are typically noncompliant to the principles of green chemistry and engineering are different from the contents of the present disclosure and are rejected by the present disclosure.

[0090] In the coal industry, the extraction of coal constituents typically begins with the pulverization and sieve of coal into appropriate coal powder as a function of powder-size. The typical powder-size for starting the extraction processes in the present disclosure is around 50-500 microns.

[0091] To further break down the primary pulverized coal powder to fine particles and ultrafine particles, wet-comminution and dispersion are adopted to prevent health hazard and environmental pollution imposed by processing dry powder in such powder sizes. Practical techniques and production equipment are readily available for these processes. Particularly, technology advancements and market demands have already enabled the successful production of nano-dispersions of drugs and pesticides in industry, with adequate machines facilitating wet-comminution and dispersion for laboratory-based R&D and for mass production [36]. Relatively safe surfactants and stabilizers have also been developed and accepted in the trade. In the known practices [36], milling beads of down to 0.05 mm have been newly introduced to the market and adopted to mill carbofuran, as a pesticide, down to 29 nm. In the present disclosure, coal constituents are grinded down below 10 nm with the innovative adoption of grinding grits as small as 10 nm to drive the required nano-comminution. Such grinding grits are readily available at low cost in the trade of metallurgy and nanotechnology. The grit composition chosen by the present disclosure is alumina which is commonly present in coal as a mineral constituent. While most fragments of anthracite and meta-anthracite are hydrophobic, alumina is hydrophilic; hence, recycling alumina from the nano-dispersion production is relatively easy and inexpensive.

[0092] The technology and production-equipment for separating and sorting coal constituents are well established and readily available. Various filtration separation techniques for nano-materials processing, including dialysis and cross-flow ultrafiltration, have been used successful in the health-care industry for separating and sorting nano-biomaterials, and is adopted in the present disclosure.

[0093] In the following section, some embodiments are given and explained to further illustrate the technical details of the present disclosure.

[0094] In some embodiments, the present disclosures pertain to processes of producing various forms of multiple nano-carbon polymorphs from coal comprising anthracite, meta-anthracite, semi-graphite, and combinations thereof. In the coal industry, anthracite, meta-anthracite, and other coal materials like anthracite are classified under ISO 11760 as Anthracite A, Anthracite B, and Anthracite C. In some embodiments, Anthracite C under the ISO 11760 coal classification is selected for the production of multiple nano-carbon polymorphs comprising nano-graphene as the main polymorphs and with other polymorphs as shown in FIG. 1 as minor polymorphs. In some embodiments, Anthracite A under the ISO 11760 coal classification is selected for the production of multiple nano-carbon polymorphs comprising nano-graphene as minor polymorphs and with other polymorphs as shown in FIG. 1 as major polymorphs. In some embodiments, Anthracite A, Anthracite B, Anthracite C, and combinations thereof are selected as the coal source for the production of multiple nano-carbon polymorphs.

[0095] In some embodiments, the method of the present disclosure involves, as shown in FIG. 2, the proper selection of a coal source and the comminution and dispersion of the coal source to various products comprising nano-carbon polymorphs. In some embodiments, the method involves pulverizing and sieving the coal source into coal powder of proper sizes for the production of nano-carbon polymorphs. In some embodiments, the coal source is pulverized and sieved to 50-500 microns. In some embodiments, the coal source is pulverized and sieved to 50-100 microns. In some embodiments, flotation processes are used to separate residual minerals from organic coal constituents. In some embodiments, hydrodynamic cavitation is integrated with flotation to reduce energy consumption and to optimize the performance of flotation separation. In some embodiments, other float-sink processes are used to separate residual minerals from organic coal constituents. In some embodiments, wet-comminution and dispersion processes are used to reduce the particulate size of the coal powder for the production of nano-carbon polymorphs. In some embodiments, multiple cycles of comminution plus separation, with separation comprising flotation separation, float-sink separation and combinations thereof, are used for increasing the yield and reducing the energy and chemical consumption in the production of nano-carbon polymorphs.

[0096] In some embodiments, surfactants and stabilizers are added in the wet-comminution processes and the separation processes for improving the yield of comminution and dispersion, and for reducing energy consumption in these processes with the maintenance of their high yields. In some embodiments, common and safe surfactants and stabilizers widely accepted by both industrial users and environmental protection agencies are used. In some embodiments, surfactants and stabilizers comprising tetrahydrofurfuryl ester, ethoxylated alcohols, alkyl sulfates, alkyl carboxylates, poloxamer, polysorbate, polyvinylpyrrolidone, and combinations thereof are used.

[0097] In some embodiments, dry pulverized coal powder is dispersed and comminuted by common wet milling processes using milling beads [36]. In some embodiments, the coal powder is wet-milled with zirconia milling beads. In some embodiments, the coal powder is wet-milled to 100-500 nm with milling beads. of 100-500 microns. In some embodiments, the coal powder is wet-milled to 20-300 nm with milling beads of 10-100 microns.

[0098] In some embodiments, the coal powder is wet-comminuted with the trade-marked technology of FILMIX which is at present marketed globally by the PRIMIX Corporation in Japan. Briefly, a powder slurry is placed in a mixer comprising a turbine spinning at high speed along the axis of a cylindrical container. The centrifugal force concentrates the particulates in the slurry to the wall of the cylindrical vessel. A film is thus formed in which crowded particulates are pressed and sheared [U.S. Pat. No. 5,582,484]; as such, comminution is accomplished. The FILMIX technology has actually been exploited for the comminution and dispersed coal in water [U.S. Pat. No. 9,574,151B2] to a particle size-mode of about 200-300 nm, for enhancing the combustion efficiency of coal. In the present disclosure, modified FILMIX techniques are revealed for the production of multiple nano-carbon polymorphs from coal, with polymorphs as small as 1-2 nm. In some embodiments, coal powder is directly wet-comminuted and dispersed in a FILMIX mixer for the production of multiple nano-carbon polymorphs with a particle-size of 100-1000 nm. In some embodiments, a mixture of coal powder and nano-grinding-grits is wet-comminuted and dispersed in a FILMIX mixer for the production of multiple nano-carbon polymorphs with polymorphs as small as 1-2 nm. In some embodiments, a mixture of coal powder and nano-grinding-grits of 10-100 nm is used in conjunction with a FILMIX mixer for the production of multiple nano-carbon polymorphs with polymorphs as small as 1-2 nm. In some embodiments, coal powder is wet-comminuted and dispersed by this method integrating FILMIX with nano-grit-grinding, by the common wet-milling technology with milling beads, and by combinations thereof, to optimize the yield and reduce the energy consumption and environmental load in the production of nano-carbon polymorphs with polymorphs as small as 1-2 nm.

[0099] In some embodiments, the present disclosure pertains to processes of making products comprising nano-carbon polymorphs with other coal constituents as additives, for industrial applications requiring such mixtures. In some embodiments, such processes involve first the partition of the coal source to its mineral constituents, aliphatic organic constituents comprising amorphous organic polymers, and aromatic organic constituents comprising multiple nano-carbon polymorphs. Then, these partitioned extracts are mixed to form the application-oriented products. In some embodiments, such partition processes are partly omitted or totally omitted in order to yield a mixture of these coal constituents with the best functional performance for a specific engineering application. All these embodiments are developed with the common goal of increasing the yield and reducing the energy and chemical consumption in the production of application-specific formulations comprising nano-carbon polymorphs with appropriate additives. In some embodiments, application-specific formulations comprising nano-carbon polymorphs with appropriate additives are made for the production of new cement composites comprising multiple nano-carbon polymorphs for optimizing the performance of cements and concretes at low cost. In some embodiments, application-specific formulations comprising nano-carbon polymorphs with appropriate additives are made for the production of new polymer composites comprising multiple nano-carbon polymorphs for optimizing the performance of the new polymer composites at low cost. In some embodiments, such new polymer composites are rubber composites. In some embodiments, application-specific formulations comprising nano-carbon polymorphs with appropriate additives are made for the production of metal composites comprising multiple nano-carbon polymorphs for optimizing the performance of metal and alloy at low cost. In some embodiments, application-specific formulations comprising nano-carbon polymorphs with appropriate additives are made for the production of ink composites comprising multiple nano-carbon polymorphs for optimizing the ink performance for printing and 3D printing applications at low cost.

[0100] In one embodiment of the present disclosure, anthracite (Anthracite C in accord to the ISO011760 classification) with a carbon content (dry ash free basis) of 89-93% by weight and mean random vitrinite reflectance of 2.0-3.0% is pulverized to about 100 microns. Multiple steps of wet comminution are applied. Between these wet-comminution and dispersion processes, flotation and float-sink techniques are used to separate hydrophilic and high-density mineral particles from the organic coal constituents. Finally, the organic coal extract is mixed with alumina grits of 10-100 nm and wet-comminuted with the modified FILMIX method precedingly described. Again, flotation and float-sink techniques are used to separate low-density aliphatic coal-constituents from high-density nano-carbon graphitic polymorphs. In this case of anthracite processing, the main extract-products are nano-dispersions of nano-graphene-disks with average size of 1-2 nm in diameter and 1 nm in thickness. Minority extract-products are nano-dispersions of other nano-carbon polymorphs with different shapes and larger sizes. Low-density aliphatic coal constituents are sorted as ink additives and other nanotechnology applications.

[0101] In another embodiment of the present disclosure, meta-anthracite (Anthracite A in accord to the ISO11760 classification) with a carbon content (dry ash free basis) of 93-97% by weight and mean random vitrinite reflectance of 4-6% is pulverized to about 100 microns. Multiple steps of wet comminution are applied. Between these wet-comminution and dispersion processes, flotation and float-sink techniques are used to separate hydrophilic and high-density mineral particles from the organic coal constituents. Finally, the organic coal extract is mixed with alumina grits of 10-100 nm and wet-comminuted with the modified FILMIX method precedingly described. Again, flotation and float-sink techniques are used to separate low-density aliphatic coal-constituents from high-density nano-carbon graphitic polymorphs. In this case of anthracite with a low reflectance, the product mixes are like those of Anthracite C as shown in the preceding embodiment descriptions. For meta-anthracite with a high reflectance, the majority extract-products are nano-dispersions mainly comprising nano-carbon polymorphs including carbon nano-fibers multi-wall carbon nanotubes, carbon nano-onions, and nano-graphite-plates. Nano-dispersions mainly comprising nano-graphene-disks with average size of 1-2 nm in diameter and 1 nm in thickness are also produced as minority products. Low-density aliphatic coal constituents are sorted as ink additives and other nanotechnology applications.

[0102] In another embodiment of the present disclosure, Anthracite B in accord to the ISO11760 classification) with a carbon content (dry ash free basis) of 90-95% by weight and mean random vitrinite reflectance of 3.0-4.0 is pulverized to about 100 microns. Multiple steps of wet comminution are applied. Between these wet-comminution and dispersion processes, flotation and float-sink techniques are used to separate hydrophilic and high-density mineral particles from the organic coal constituents. Finally, the organic coal extract is mixed with alumina grits of 10-100 nm and wet-comminuted with the modified FILMIX method precedingly described. Again, flotation and float-sink techniques are used to separate low-density aliphatic coal-constituents from high-density nano-carbon graphitic polymorphs. In this case of anthracite with a low reflectance, the product mixes are like those of Anthracite C as shown in the preceding embodiment descriptions. For anthracite with a high reflectance, the majority extract-products are nano-dispersions mainly comprising nano-carbon polymorphs including carbon nano-fibers, multi-wall carbon nanotubes, carbon nano-onions and nano-graphite-plates. Nano-dispersions mainly comprising nano-graphene-disks with average size of 1-2 nm in diameter and 1 nm in thickness are also produced as minority products. Low-density amorphous coal constituents are sorted as ink additives and other nanotechnology applications.

EXAMPLES

[0103] By way of non-limiting illustration, examples of certain specific embodiments of the present disclosure are given below.

Example 1

[0104] The Production of Multiple nano-carbon polymorphs by Grinding Coal with Coal

[0105] Some preceding embodiment descriptions of multiple nano-carbon polymorphs by wet-comminution of coal, with no grinding beads nor grinding grits, to nano-dispersions is validated in this first example. Here, a piece of Anthracite A under the ISO 11760 classification was split to two pieces. The two pieces were pressed and sheared against each other in water by hand repetitively to form a diluted slurry. A drop of the diluted slurry was placed on a TEM grid. Two high resolution TEM (HRTEM) images of a nano-grain of coal on this grid are shown in FIG. 4. The HRTEM images clearly confirm the presence of a mixture of turbostratic carbon nano-crystals in this nano-grain of coal. More specifically, the presence of several carbon nano-onions, many carbon nano-fibers, an imperfect multiwall carbon nano-tube, and a hexagonal nano-graphene-disk are evident. Their presences are identified by their shapes and by their lattice fringes with lattice spacing of 0.32-0.39 nm. These lattice fringes are stacks of basal planes of turbostratic graphite. The chemical elemental identification by energy dispersive X-ray spectroscopy in the scanning TEM mode also confirms the presence of carbon.

[0106] This example demonstrates that coal is soft and brittle enough to chip off nano-grains in a simple pressing and shearing process involving two pieces of coal in water without any chemical additives and reagents. HRTEM unambiguously shows the presence of multiple nano-carbon polymorphs comprising some carbon nano-onions and abundant carbon nano-fibers, with a few nano-graphene-disks and multiwall carbon nano-tubes, in such nano-grains.

Example 2

[0107] The Production of Multiple nano-carbon polymorphs by Grinding Coal with nano-grits of alumina

[0108] Some preceding embodiment descriptions of multiple nano-carbon polymorphs by wet-comminution of coal, with grinding beads or grinding grits, to nano-dispersions is validated in this second example. Here, a grain of coal powder milled from a piece of Anthracite C under the ISO 11760 classification was simply wet-comminuted with 50 nm alumina grinding-grits in a mortar by hand to form a diluted slurry. Some of the slurry was placed in a test tube and hexane was mixed with the slurry to finally form two layers of immiscible liquids. A drop of the hexane extract was placed on a TEM grid. The high resolution TEM (HRTEM) image of a nano-grain of coal on this grid is shown in FIG. 5. This TEM image clearly shows the presence of abundant nano-carbon graphitic-polymorphs with an average size of about 2 nm. The diffraction signals fit the carbon crystal structure known as PDS #046-943 in the database released under the Joint Committee on Powder Diffraction Standards. The most intense diffraction signals are attributed to the presence of repetitive lattice planes with an average lattice spacing of 0.33 nm which matches the lattice spacing of graphitic basal-planes. The chemical elemental identification by energy dispersive X-ray spectroscopy in the scanning TEM mode confirms the presence of carbon.

[0109] This set of data confirms the presence of nano-graphene disks in coal. Although they are found with little perturbation of their natural occurrence in coal, their morphologies and structures are very much like those reported by Tour et al. [12-16; U.S. Pat. No. 9,919,927] and their followers [17-26] who treated coal with very strong oxidants. The similarity may be due to the fact that in the basic molecular structure of coal characterized by all these groups, as shown in the bottom of FIG. 2, stacks of nano-graphene with basal-plane of 1-2 nm in size are present. The morphologies and shapes of nano-graphene are not fundamentally altered, no matter whether the extraction processes are destructive oxidation of non-graphitic constituents or mild physical cleavages of weak links between nano-constituents.

[0110] When another drop of the hexane extract was placed on a TEM grid, a different scenario was observed as shown in FIG. 6. The HRTEM image in this figure clearly shows the presence of a nano-carbon graphitic-polymorph amid an amorphous grain. The chemical elemental identification by energy dispersive X-ray spectroscopy in the scanning TEM mode confirms the presence of carbon. The lattice imaging picture shows a stack of graphite basal-planes packed vertically into a rectangular graphitic carbon nano-crystal (about 6 nm×25 nm). The thickness of the crystal in the viewing direction is about 1-2 nm. The average lattice spacing in the basal-plane stack is 0.33 nm.

[0111] The HRTEM image clearly confirms the presence of a nano-graphite-plate in coal. In the perspective of materials microstructural analysis, the observed nano-graphite-plate is very much different from nano-graphene. The explicit difference is that the nano-graphite-plate comprises a stack of about 20 graphitic basal-planes with each basal-plane having a peculiar rectangular shape of about 25 nm×2 nm. Such a stack of long and narrow graphitic basal-planes is most likely hetero-epitaxially grown on a piece of mineral crystal facet with the facet lattice matching closely with the lattice of the growth front of the observed nano-graphite. The hetero-epitaxial growth must have been driven by appropriate hydrothermal activation for local graphitization of minute organic remains pressed between two closely packed mineral crystal facets in the long process of coalification. The mineral growth-substrates were than leached and consumed; this leaves the lone nano-graphite-plate embedded in a matrix of amorphous carbon in coal.

[0112] When a drop of the aqueous extract in this example was placed on a TEM grid, many nano-crystals of alumina were found and imaged. This set of data and those data from the hexane extract collectively corroborate that the hydrophobic (nonpolar) organic constituents of coal can be easily separated from the hydrophilic (polar) mineral impurities in coal.

[0113] The experimental TEM images of the nano-carbon polymorphs shown in Examples 1 and 2 clearly support the assertion of the present disclosure regarding the presence of multiple nano-carbon polymorphs in coal. More importantly, these images of the nano-carbon polymorphs with atomic resolution, together with the molecular models shown in FIG. 2, also depict graphically that most nano-carbon polymorphs are macro-molecules with aromatic molecular domains binding with neighboring coal constituents by van der Waals bonds and other physical adhesive interactions. As such, extracting these nano-carbon polymorphs from coal through energy-demanding and violent chemical-dissociation of strong covalent bonds in coal is both illogical and wasteful. The production of nano-carbon polymorphs from coal can be simply facilitated by solvation and dispersion, with physical agitation and comminution. These Examples and experimental results thus also support the present disclosure regarding the feasibility and practicality of producing multiple nano-carbon polymorphs from coal with physical and green processes.

[0114] TEM measurements were also performed on wet-comminuted Anthracite A, with dark-field imaging of nano-carbon polymorphs in comminuted grains of such coal samples. TEM dark-field imaging has been used to find the locations of graphitic crystalline carbon in coal [34,35]. Under dark-field imaging, nano-carbon polymorphs are bright in contrast and the amorphous carbon constituents are dark. This approach eases the statistical pattern-recognition analysis of the concentration of crystalline nano-carbon polymorphs in the background presence of amorphous carbon in coal [34,35]. The relevant data in the literature [34,35] and the experimental results obtained by Applicants of the present disclosure all consistently support that coal sources identified as highly mature coal with their coal ranks between meta-anthracite (Anthracite A under ISO 11760) and semi-graphite typically have an extremely high carbon concentration (over 90% by weight), an extremely high ratio of aromatic carbon to aliphatic carbon, a relative high mean random vitrinite reflectance of over 6%, and abundant nano-carbon polymorphs with their overall concentration over 50% of all carbon in the coal sources. The present disclosure reveals such criteria and processes for selecting the proper sources of coal for the most cost-effective production of multiple nano-carbon polymorphs from coal.

[0115] Without further elaboration, it is believed that one skilled in the art can, using the description herein, utilize the present disclosure to its fullest extent. The embodiments described herein are to be construed as illustrative and not as constraining the remainder of the disclosure in any way whatsoever. While the embodiments have been shown and described, many variations and modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims, including all equivalents of the subject matter of the claims. The disclosures of all patents, patent applications and publications cited herein are hereby incorporated herein by reference, to the extent that they provide procedural or other details consistent with and supplementary to those set forth herein.