DESC:Field of the Invention
The present disclosure relates to graphene-carbon black hybrid material. Particularly, the present disclosure relates to a cost effective method of preparing said graphene-carbon black hybrid material.

Background
Carbon has inevitably been an astonishing element for the purpose of research, and has notable applications in its various forms in every possible field of science and technology. Polymer industries have been utilizing carbon from centuries primarily in the form of carbon black. Revolution started with the discovery of fullerene in 1985 followed by the discovery of carbon nanotubes in 1991. The forerunner of fullerene and carbon nanotubes was yet to come into light until in 2004, one atom thick single layer of graphene was isolated from graphite.
Graphene can be described as a one-atom thick layer of the layered mineral graphite. In graphene, carbon atoms are arranged in a substantially regular hexagonal pattern. Graphene is transparent, flexible, extraordinarily resistant, waterproof, abundant, economical and conducts electricity better than any known metal.
Also, graphene has been found to be superior to other carbon materials such as carbon black, in aspect of mass productivity, handleability, and performance, and accordingly attempts are being made to use graphene in various fields. Though graphene’s outstanding electrical properties raises the hope for widespread applications in electronics and other devices, it was predicted that the immediate possible application of graphene could be in composites.
Since its discovery, graphene has become an attractive filler material in polymer nanocomposites. Apart from its applications to impart conductivity into insulating plastics like polystyrene with only 0.1 volume percent filler loading, motion sensors based on graphene- natural rubber nanocomposites, extensive works have been done on the basis of mechanical reinforcement of polymers, especially rubbers using graphene. With the wonderful results obtained at very low filler loadings for the properties of graphene-elastomer nanocomposites, interests have grown to partially replace carbon black, which is the most popular filler for elastomer till date.
Various routes for synthesis of graphene has been a wide area of research for last two decades. It is known to prepare graphene using mechanical or thermal exfoliation, chemical vapor deposition (CVD), and/or epitaxial growth, etc. Graphene can also be produced via chemical reduction. Graphite oxide can be produced by combining graphite with an oxidizing agent such as one or more of sodium nitrate, potassium permanganate and sulphuric acid.
However, there are significant challenges remaining in producing graphene on a large or industrial scale, such as a high manufacturing cost, a large percentage of production losses and loss of their properties.

Brief Description of Drawings
Figure 1 shows a schematic representation of the synthetic technique for preparation of graphene-carbon black hybrid material in accordance with an embodiment of the present invention.
Figure 2(a) illustrates X-Ray Diffraction (XRD) pattern of G-CB obtained in accordance with an embodiment of the present invention and N220 carbon black (inset).
Figure 2(b) illustrates Raman spectrum of G-CB obtained in accordance with an embodiment of the present invention and N220 carbon black (inset).
Figures 3 (a) and 3(b) illustrates X-ray photoelectron spectroscopy (XPS) survey and C 1s analysis respectively, of G-CB obtained in accordance with an embodiment of the present invention, and Figure 3(c) and 3(d) illustrate XPS survey and C 1s analysis respectively, of N220 carbon black.
Figures 4(a)-(c) illustrate Field Emission Scanning Electron Microscopy (FESEM) images of graphene sheets covered with carbon black particles in G- CB at different magnification, in accordance with an embodiment of the present invention and Figure 4(d) illustrates FESEM image of particulate N220 carbon black.
Figure 5 illustrates Transmission electron microscopy (TEM) images of graphene sheets with dispersed carbon black particles obtained in accordance with an embodiment of the present invention.
Figures 6(a) and 6(b) illustrate high-resolution transmission electron microscopy (HRTEM) images of crystalline G-CB; Figure 6(c) illustrates Selected Area Electron Diffraction (SAED) pattern of G-CB, Figure 6(d) illustrates atomic fringes observed in G-CB, Figure 6(e) illustrates profile for (d) indicating the d002 spacing of G-CB, in accordance with an embodiment of the present invention.
Figure 7(a) illustrates reduction in specific capacitance with increasing current density, Figure 7 (b) illustrates three peaks fitted under the 2D band of the Raman spectra of G-CB, Figure 7 (c) illustrates Isothermal TGA plot; Figure 7 (d) illustrates plot for temperature scan in TGA, in accordance with an embodiment of the present invention.
Figures 8 (a) and 8(c) illustrate Galvanostatic charge-discharge profile and Cyclic voltammogram respectively, for G-CB obtained in accordance with an embodiment of the present invention, and Figures 8 (b) and 8(d) illustrate Galvanostatic charge- discharge profile and Cyclic voltammogram respectively, for N220 carbon black.

Detailed Description
The following explanation of terms is provided to better describe the present disclosure and to guide those of ordinary skill in the art in the practice of the present disclosure. As used herein, “comprising” means “including but not limited to” and the singular forms “a” or “an” or “the” include plural references unless the context clearly dictates otherwise. The term “or” refers to a single element of stated alternative elements or a combination of two or more elements, unless the context clearly indicates otherwise.
The devices, compositions, and methods described herein should not be construed as limiting in any way. Instead, the present disclosure is directed towards all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The disclosed devices, compositions, and methods are not limited to any specific aspect or feature or combinations thereof, nor do the disclosed devices, compositions, and methods require that any one or more specific advantages be present or problems be solved. Any theories of operation are to facilitate explanation, but the disclosed devices, compositions, and methods are not limited to such theories of operation.
Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed devices, compositions, and methods can be used in conjunction with other devices, compositions, and methods. Additionally, the description sometimes uses terms like “produce” and “provide” to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations that correspond to these terms will vary depending on the particular implementation and are readily discernible by one of ordinary skill in the art.
Unless explained otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Unless otherwise indicated, all numbers expressing quantities of components, molecular weights, percentages, temperatures, times, and so forth, as used in the specification or claims are to be understood as being modified by the term “about”. Accordingly, unless otherwise indicated, implicitly or explicitly, the numerical parameters set forth are approximations that can depend on the desired properties sought and/or limits of detection under standard test conditions/methods. When directly and explicitly distinguishing embodiments from discussed prior art, the embodiment numbers are not approximates unless the word “about” is recited. Furthermore, not all alternatives recited herein are equivalents.
In its broadest scope, the present disclosure relates to graphene-carbon black hybrid material. Particularly, the present disclosure relates to a method of preparing graphene-carbon black hybrid material. Said method comprises of subjecting a mixture of a sugar source and carbon black to pyrolysis at a temperature in a range of 600-1000? for a time period of 3-10 hours in an inert atmosphere in a reaction chamber. The resultant graphene-carbon black hybrid material comprises graphene sheets having carbon black particles deposited thereon.
Figure 1(a) shows the schematic representation of synthesis of the graphene-carbon black hybrid material.
In accordance with an embodiment, in the disclosed method, the sugar source and carbon black are mixed in a weight ratio ranging between 1:1 to 7:1. In accordance with a preferred embodiment, the sugar source and carbon black are mixed in a weight ratio ranging between 2:1 to 5:1.
In accordance with an embodiment, the sugar source and carbon black are mixed using any known mixing techniques. Preferably, the sugar source and carbon black are mixed manually using a mortar and a pestle.
In accordance with an embodiment, after mixing, the mixture of the sugar source and carbon black is subjected to pyrolysis in a reaction chamber. Said reaction chamber can include any furnace which has a facility of a constant nitrogen flow.
In accordance with an embodiment, pyrolysis is carried out at a temperature in a range of 600-1000 ? and preferably at a temperature in range of 700-900 ?. In accordance with yet another embodiment, pyrolysis is carried out for a time period in a range of 3-10 hours, and preferably 5-8 hours In accordance with an embodiment, the pyrolysis is performed at atmospheric pressure between 0.9-1.01 bar and in an inert gas atmosphere.
In accordance with an embodiment, said method further comprises cooling the product obtained after pyrolysis to room temperature in the reaction chamber. Upon cooling, the graphene-carbon black hybrid material is collected from the reaction chamber.
In accordance with an embodiment, the sugar source is selected from a group consisting of raw sugar, molasses, cane sugar, beet sugar, honey, coconut sugar, agave nectar, brown sugar, refined sugar, dates, maple syrup, fruit extracts and rice syrup. The fruit extracts include fruit puree, jam, and the like from a variety of fruits such as monk fruit, banana etc. Said sugar source may be in solid, semi-solid or liquid form. In accordance with a preferred embodiment, molasses is used as the sugar source. Said molasses is in a semi-solid form obtained from sugarcane. The molasses has been obtained from commercial sources in the United States (US).
In accordance with an embodiment, carbon black particles have a statistical thickness surface area (STSA) ranging between 25 m2/g to 160 m2/g, and preferably 70 m2/g to 150 m2/g. In accordance with an embodiment, carbon black has an oil absorption number (OAN) ranging between 55 m3/kg to 150 m3/kg, and preferably 70-130 m3/kg. In accordance with an embodiment, the carbon black can be any ASTM grade carbon black, such as N774, N772 N660, N683, N650, N550, N375, N347, N339, N330, N326, N234, N220, N110, N121, N134 carbon black or a mixture thereof, and preferably N375, N347, N339, N330, N326, N234, N220, N110, N121, N134 carbon black is used. In accordance with an exemplary embodiment, N110 carbon black, N220 carbon black and N330 carbon black obtained from Birla Carbon India Private Limited were used in the present disclosure.
The present disclosure also concerns a graphene-carbon black hybrid material obtained using the disclosed method. Said material comprises graphene sheets having carbon black particles deposited thereon.
In accordance with an aspect, said material comprises graphene in an amount ranging from about 30 weight % to 70 weight % and carbon black ranging from about 70 weight % to 30 weight %. In accordance with an embodiment, said material comprises graphene in an amount ranging from about 40 weight % to 60 weight % and carbon black ranging from about 60 weight % to 40 weight %, and preferably said material comprises graphene in an amount of about 50 weight % and carbon black in an amount of about 50 weight %.
In accordance with an embodiment, graphene sheets comprise at least two layers, and preferably three- five layers of graphene. When analyzed by Raman spectrometry, scanning electron microscopy, high-resolution transmission electron microscopy and X-Ray diffraction, said material has Raman D-peak, G-peak and 2D-peak at approximately 1340 cm-1, 1590 cm-1, and 2650 cm-1, respectively, that form the peaks where it is clearly known that the result is multi-layer (three) graphene.
In accordance with an embodiment, said graphene sheets have an inter-plane spacing d002 ranging between 0.33-0.40 nanometers as measured by X-ray Diffraction. Preferably, said graphene sheets have an inter-plane spacing d002 ranging between 0.340-0.370 nanometers as measured by X-ray diffraction. In accordance with yet another embodiment, graphene sheets have a lateral size ranging between 0.1-10 micrometers, and preferably 0.2-5 micrometer micrometers.
The graphene obtained using disclosed process has no or is substantially free of graphene oxide. Additionally, the graphene formed are substantially free of impurities and residual defects.
In accordance with an embodiment, said graphene-carbon black hybrid material is a solid powder.
Specific Embodiments
A method of preparing graphene-carbon black hybrid material, the method comprising subjecting a mixture of a sugar source and carbon black to pyrolysis at a temperature in a range of 600-1000? for a time period of 3-10 hours in an inert atmosphere in a reaction chamber, such that graphene-carbon black hybrid material comprising graphene sheets having carbon black particles deposited thereon is obtained.
Such method, wherein the sugar source and carbon black are mixed in a weight ratio ranging between 1:1 to 7:1.
Such method, further comprising cooling the product obtained after pyrolysis to room temperature in the reaction chamber.
Such method, wherein the sugar source is selected from a group consisting of cane sugar, beet sugar, honey, coconut sugar, agave nectar, brown sugar, refined sugar, dates, maple syrup, fruit extracts and rice syrup.
Such method, wherein the sugar source is molasses.
A graphene-carbon black hybrid material comprising graphene sheets having carbon black particles deposited thereon, said material comprising graphene in an amount ranging from about 30 weight % to 70 weight % and carbon black ranging from about 70 weight % to 30 weight %.
Such graphene-carbon black hybrid material, wherein graphene sheets comprise at least three layers of graphene.
Such graphene-carbon black hybrid material, wherein said graphene sheets have an inter-plane spacing d002 ranging between 0.30-0.40 nanometers as measured by X-ray diffraction.
Such graphene-carbon black hybrid material, wherein graphene sheets have a lateral size ranging between 0.1-10 micrometers.
Such graphene-carbon black hybrid material, wherein carbon black particles have a statistical thickness surface area (STSA) ranging between 25 m2/g to 150 m2/g and oil absorption number (OAN) ranging between 55 m3/kg to 150 m3/kg

Examples:
In order that this invention may be better understood, the following examples are set forth. These examples are for the purpose of illustration only and the exact compositions, methods of preparation and embodiments shown are not limiting of the invention, and any obvious modifications will be apparent to one skilled in the art.
Also described herein are method for determining the properties of the graphene-carbon black hybrid material, formed using embodiments of the claimed process. Some examples highlight the benefits of using the presently disclosed graphene-carbon black hybrid material.

Graphene-Based Materials Structure Analysis:
The characterization of graphene-based materials makes use of electron microscopy techniques, XRD (X-ray diffraction), Raman spectroscopy, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM), as discussed below:

1. X-Ray Diffraction (XRD): The XRD technique is used to evaluate the average structural parameters (such as lateral size and thickness), and can also be used to estimate the relative content of graphitic materials. Powder samples were used for performing XRD. XRD of the samples was done using wide angle X-ray diffractometer (model: X'Pert PRO, made by PANalytical B.V., The Netherlands) using Ni-altered Cu Ka radiation (?=1.5418 ?).

Interlayer spacing d002 (or d002 spacing) between the (002) planes were deduced by the Bragg’s law which relates d-spacing (d) with the wavelength of X-ray?, with the sin of diffraction angle O by equation. In the Bragg’s law equation (Eqn. 1), n is the degree of reflection which is always a positive integer, considered as unity for calculation. Cu-Ka radiation was incident on the sample which had a wavelength of 1.54 Å.
n?=2dsin?…(1)
Additionally, Crystallite size was calculated by Scherrer equation (Eqn. 2) where t is the crystallite size, K is shape factor, the value of which is close to unity, ? is the wavelength of X-ray, and ß is the FWHM value in radians. Crystallite size, in the case of graphite, graphene or graphene is the height or thickness of the layers which are stacked together.

2. Raman Spectroscopy: This technique is used to evaluate defects in graphene-based materials. Samples were prepared by dispersing 1 mg of powder in 3 mL of N,N-dimethylforamide (DMF) by sonication and drop casting the dispersions onto cleaned glass slides followed by overnight drying inside an oven at 50 °C. Raman spectra of the samples were taken at 514 nm wavelength by Trivista 555 spectrograph (Princeton Instruments) using Ar laser (Coherent, Sabre Innova SBRC-DBWK).

3. X-ray photoelectron spectroscopy (XPS): XPS indicates the surface chemical analysis of graphene based material.

4. Scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM): The SEM technique can be used to assess the overall morphology of the graphene-based materials. Additionally, the HRTEM technique can be used to get more detailed structural information via fringes structure.

Structures of the graphene-carbon black hybrid material were studied, first by Field emission scanning electron microscope (FESEM) (MERLIN with tungsten filament; Carl ZEISS, SMT, Germany), followed by JEOL JEM-2100F field emission high resolution transmission electron microscope (HRTEM). Samples were prepared by dispersing 1 mg of powder in 3 mL of DMF by sonication. Dispersions were drop cast on cleaned aluminum surface for SEM analysis and dropped on Copper grids for TEM analysis.

5. Thermal gravimetric analysis (TGA): Isothermal TGA of the mixture of the sugar source and carbon black was carried out at 750 °C for to understand the reaction kinetics for conversion of the sugar source into graphene.

6. Electrochemical measurements: The samples as obtained from the tube furnace, without any purification were used for the electrochemical experiments. Electrochemical performance tests such as galvanostatic charge-discharge, and cyclic voltammetry tests were performed CH760D electrochemical work station (CH instrument). Electrochemical tests were performed using a standard three electrode system. The powder materials were individually mixed with Polyvinylidene fluoride (PVDF) in a weight ratio of 90:10 (sample: PVDF) and taken in a mortar. N-Methylpyrrolidone (NMP) was added dropwise to this mixture and mixed thoroughly with the help of a pestle to obtain a thick slurry. Samples were coated on glass carbon electrodes and dried properly and were used as working electrodes. Pt plate of dimension 1 cm*1 cm was used as counter electrode. Ag/AgCl with saturated KCl solution was used as the reference electrode. 1 M KCl solution was used as the electrolyte.

Potential range in which cyclic voltammetry and galvanostatic charge-discharge experiments were carried out was set at -0.05V to +0.7 V at varying scan rates (10, 20, 50, 100, 200 mV/s) and current densities (0.1, 0.2, 0.3, 0.5, 1 A/g) respectively. The specific capacitance Cs was calculated from the slope of discharge curve excluding the IR drop from the potential difference using the following formula:
Cs = (I × ?T)/(m × ?V) …(3)
Example 1: Preparation of graphene-carbon black hybrid material (G-CB) using molasses as the sugar source and N220 carbon black

15 grams of molasses was mixed with 3 grams of N220 carbon black using a mortar and a pestle. The mixture was placed in a silica crucible and kept inside the tube furnace. A steady nitrogen flow was maintained inside the furnace. The temperature of the furnace was set at 750 °C and 6 hours of pyrolysis time was given after said temperature was reached. The product was cooled inside the furnace under the same inert atmosphere and was taken out when room temperature was reached.

The graphene-carbon black hybrid material (G-CB) was then assessed to determine its structure and properties. The observations of each of aforesaid analysis is summarized below:

Observations:

XRD pattern of G-CB was compared with that of N220 carbon black. As illustrated in Figure 2 (a), four peaks were identified for N220 carbon black at 2? values 24.3, 42.1, 43.6 and 49.1 representative of (002), (100), (101) and (102) planes respectively. In the XRD profile of G-CB, a broad peak at 2? = 24.6 was obtained for (002) diffraction, and a wide band like pattern at 2?=43, probably arising from the cumulative diffraction from (100), and (101) planes were obtained, which are characteristic of graphene.

The value of d002 spacing of G-CB was found to be 3.61Å which was comparable to the d002 spacing value of reduced graphene oxide existing in literature. The crystallite size of G-CB was 13.6 Å. The value of crystallite size when divided by the value of d-spacing obtained for G-CB gives the average number of layers. Herein, average number of graphene layers was found to be 3.76 i.e. between 3 to 4.

Figure 2(b) illustrates the Raman spectrum of G-CB in comparison with N220 carbon black. Two broad and fused signals were noticed in the case of N220 carbon black, at 1350 cm-1 and 1580 cm-1 identified as D and G peaks respectively. G-CB showed D band at 1340 cm-1, G band at 1590 cm-1 along with a broad 2D signal at 2650 cm-1. Graphite is known to show strong characteristic Raman peak at 1575-1580 cm-1 namely the G peak. Introduction of defects in the structure may broaden this peak and another peak nearly at 1350 cm-1 known as the D peak may appear whereas activated carbon samples such as carbon blacks show broad D and G bands, often fused together. As the structure proceeds to smaller length scale towards graphene, D peak is expected to become more intense and on an addition 2D band appears near at 2700 cm-1. However, the peak positions are not fingerprints and may vary as a result of strain, oxidation, and presence of impurities as reported in many studies. Redshift in G peak in graphene is reported in literature to be caused by uniaxial strain. Peak shift towards higher values of wavenumber i.e., blue shift was observed to be influenced by nature the substrate on which graphene is grown and on the presence of impurities in graphene. Graphene nanosheets synthesized by Hummer’s method (See Hummers W.S., Offeman R.E. "Preparation of Graphitic Oxide," J. Am. Chem. Soc, 1958, 80 (6), 1339-1339) followed by reduction with hydrazine was reported to display the G peak at 1595 cm-120. Another possible reason behind the blue shift of G peak could be the appearance of D’ peak nearly at 1620 cm-1 caused by activation of Raman inactive phonons due to the presence of defects, and this peak may sometimes merge with G peak giving rise a shifted band. The D band is indicative of defects like edges, structural disorders or presence of functional groups. Higher intensity of G band compared to D band indicates low degree of defects. The ID/IG ratio is expected to increase as the flakes of graphite becomes smaller i.e., lower size of sp2 network and presence of defects. ID/IG value of G-CB was found to be 0.85 and hence indicates low degree of defects.

Further, the nature of the 2D band was studied for an apprehension of the number of layers stacked together in the graphene sample. The 2D or G’ band near 2700 cm-1 is a result of double resonance Raman process in graphene. Monolayer graphene gives a single peak under the 2D band. Four peaks can be fitted under the 2D band of a bilayer graphene, arising from four electron- phonon scattering processes in the conduction band. Knowledge acquired from the group theories postulates that fifteen peaks are allowed under the 2D band of tri-layer graphene. Negligible energy separations between these transitions makes it difficult to identify fifteen of these peaks, but at least six could possibly be identified for three-layer graphene. The feature of high-intensity peak at higher frequency under 2D band which differentiates a few-layers’ graphene from bulk graphite actually appears from four-layer graphene. In a four-layer graphene intensity of 2D band is somewhat higher than in lower frequency, whereas in bulk graphite 2D band shows two peaks and the higher frequency one having a sharper head. The 2D band of G-CB had the nature of a four-layer graphene, and three peaks were fitted under the 2D peak by Gaussian peak fitting in OriginPro 8.5 software as shown in Figure 6(b).Small disorder induced bumps at higher wavenumbers are observed for G-CB as D+G or D+D’ combination modes in G-CB at 2935 cm-1.

Figure 3 illustrates the XPS survey and C 1s analysis of G-CB and N220 carbon black. For G-CB, carbon C 1s, oxygen O 1s and traces of nitrogen N 1s were detected. N220 carbon black contained higher percentage of carbon which decreased in G-CB. As an obvious consequence, the percentage of oxygen increased in the reversed order. N220 carbon black contained 94.51% carbon, 4.58% oxygen and 0.91% nitrogen. On the other hand, G-CB showed 92.11% carbon content, 6.92% oxygen and 0.95% content of nitrogen. XPS results were found in accordance with the fact that G-CB was derived from an organic source with fair presence of oxygen-containing functional groups, and on the other hand N220 carbon black was a commercial product containing mostly sp2 carbon clusters. The percentage of oxygen in G-CB was found to be inferior than that in graphene oxide, and comparable to the oxygen contents in reduced graphene oxide synthesized by hummers method with subsequent chemical reduction, indicating that graphene oxide was not formed in the process of pyrolysis of molasses. Hence, the possibility of formation of graphene oxide was excluded. As illustrated in Table 1, G-CB comprises a very high percentage of sp2 carbon and a low percentage of sp3. Further, percentage of C-O was found to be higher than that of carbonyl group (C=O).

Sample Group Peak position Percentage
G-CB C=C 284.0 69.35
C-C 285.0 13.90
C-O 286.1 13.74
C=O 288.1 2.99
N220 C=C 284.2 60.68
C-C 285.0 17.15
C-O 286.0 8.85
C=O 288.4 13.30
Table 1: Percentage of different groups by XPS analysis

Referring to Figure 4, FESEM revealed wrinkled sheet-like morphology for G-CB. The particles of N220 carbon black were found dispersed randomly over wrinkled graphene sheet. Figure 5 depicts the TEM images of graphene sheets with dispersed carbon black particles in G-CB. The lateral size of the graphene sheets was found to be a few micrometers. SAED pattern of G-CB in Figure 6, shows the typical six-fold symmetry expected for graphene and graphite. Additionally, highly crystalline zones in the graphene sheets of G-CB were found at higher magnification under HRTEM. Fringes were observed from which the d002 spacing was found to be 0.3 nm.

Referring to Figures 7(c) and 7(d), it was observed that the mixture of molasses and carbon black mixture lost 50% of its initial weight within 30 minutes. By this time, the temperature reached till 250 °C. It took 72 minutes for the temperature to reach 750 °C and within that time the reaction mixture retained only 35% of its initial weight. The rate of reduction in weight was rapid at the beginning but became low as the isothermal process began. At the end of 200 minutes, 28.8 % of the initial weight was retained. TGA of G- CB shows a mild weight loss of about 8% at 75 °C, and no significant weight loss was observed for the sample till 900 °C. The sample retained 86% of its initial weight. To the contrary, molasses lost 10 % of its initial weight within the temperature range of 120 °C to 180 °C, followed by a rapid weight loss till 225 °C and lost 40% of its initial weight. Weight loss was visible all throughout the total temperature for molasses and at 900 °C, it retained only 15% of the initial weight. No significant weight loss was noted for N220 carbon black till 500 °C temperature, but weight loss started afterward and at 900 °C, 33% of the initial weight was retained by N220 carbon black. From the TGA temperature scans it was perceived that N220 carbon black retains 54% of the initial weight at the reaction temperature, i.e. at 750 °C and molasses retained 19 % weight at the same temperature.

Figure 8 illustrates Galvanostatic charge-discharge profile and Cyclic voltammogram for G-CB and N220 carbon black. Said discharge profiles depicts IR drop in G-CB as well as N220 carbon black. The specific capacitance calculated from the discharge profile was found to be 24 F/g for G-CB whereas it was only 9 F/g for N220. The cyclic voltammetry plots for G-CB show typical electrostatic double layer capacitor (EDLC) behavior without any redox reaction in presence of electrolyte and hence without any peak in the cyclic voltammograms. Referring to Figure 7 (a), it was observed that here was a tendency to lose their specific capacitance with increasing current density.

Industrial Applicability

The disclosed method is a cost-effective method of preparing graphene-carbon black hybrid material. Using the disclosed method, graphene-carbon black hybrid material was successfully obtained from sugar source in its crude and cheap form.

Graphene-carbon black hybrid material thus produced was of good quality. Graphene-carbon black hybrid material contains highly crystalline graphene structure with fair thermal stability up to a temperature of 900 °C. Said material also exhibits improved capacitance compared to carbon black.

The disclosed graphene-carbon black hybrid material finds application in polymer nanocomposites.
,CLAIMS:We Claim:

1. A method of preparing graphene-carbon black hybrid material, the method comprising:
subjecting a mixture of a sugar source and carbon black to pyrolysis at a temperature in a range of 600-1000? for a time period of 3-10 hours in an inert atmosphere in a reaction chamber, such that graphene-carbon black hybrid material comprising graphene sheets having carbon black particles deposited thereon is obtained.

2. The method as claimed in claim 1, wherein the sugar source and carbon black are mixed in a weight ratio ranging between 1:1 to 7:1.

3. The method as claimed in claim 1, further comprising cooling the product obtained after pyrolysis to room temperature in the reaction chamber.

4. The method as claimed in claim 1 or 2, wherein the sugar source is selected from a group consisting of raw sugar, molasses, cane sugar, beet sugar, honey, coconut sugar, agave nectar, brown sugar, refined sugar, dates, maple syrup, fruit extracts and rice syrup.

5. The method as claimed in claim 4, wherein the sugar source is molasses.

6. A graphene-carbon black hybrid material comprising:
graphene sheets having carbon black particles deposited thereon, said material comprising graphene in an amount ranging from about 30 weight % to 70 weight % and carbon black ranging from about 70 weight % to 30 weight %.

7. The graphene-carbon black hybrid material as claimed in claim 4, wherein graphene sheets comprise at least three layers of graphene.

8. The graphene-carbon black hybrid material as claimed in claim 4 or 5, wherein said graphene sheets have an inter-plane spacing d002 ranging between 0.30-0.40 nanometers as measured by X-ray diffraction.

9. The graphene-carbon black hybrid material as claimed in claim 4 or 5, wherein graphene sheets have a lateral size ranging between 0.1-10 micrometers.

10. The graphene-carbon black hybrid material as claimed in claim 4, wherein carbon black particles have a statistical thickness surface area ranging between 25 m2/g to 150 m2/g and oil absorption number (OAN) ranging between 55 m3/kg to 150 m3/kg.

Dated this 29th day of March 2019

Essenese Obhan
Of Obhan & Associates
Agent for the Applicant
Patent Agent No. 864