Claims:WE CLAIM:
1. A method for synthesizing reduced graphene oxide (rGO) from coal tar pitch, said method comprising heating the coal tar pitch at a temperature ranging from about 700ºC to 900ºC in presence of air, followed by cooling to a temperature ranging from about 20ºC to 40ºC to obtain the reduced graphene oxide, wherein the method involves minimal interaction of the coal tar pitch with the air.

2. The method as claimed in claim 1, wherein the heating is carried out in a furnace having a closed end and an open end, wherein the furnace permits the air to enter and exit from the open end, allowing minimal interaction of the coal tar pitch with the air.

3. The method as claimed in any one of claims 1 to 2, wherein the heating is carried out for a duration ranging from about 15minutes to 30minutes.

4. The method as claimed in claim 1, wherein the coal-tar pitch is optionally mixed with graphene.

5. The method as claimed in any one of claims 1 to 4, wherein the reduced graphene oxide comprises carbon content ranging from about 94% to 96% and oxygen content ranging from about 4% to 6%.

6. The method as claimed in any one of claims 1 to 4, wherein the reduced graphene oxide has conductivity ranging from about 0.125mS/cm to 500 S/cm.

7. The method as claimed in any one of claims 1 to 4, wherein the reduced graphene oxide has resistance ranging from about 0.5O to 2.0MO.

8. A reduced graphene oxide (rGO) synthesized by the method of claim 1 comprising carbon content ranging from about 94% to 96% and oxygen content ranging from about 4% to 6%.

9. The reduced graphene oxide as claimed in claim 8, wherein the reduced graphene oxide has conductivity ranging from about 0.125mS/cm to 500S/cm.

10. The reduced graphene oxide as claimed in claim 8, wherein the reduced graphene oxide has resistance ranging from about 0.5O to 2.0MO.

11. An apparatus for synthesizing reduced graphene oxide (rGO) from coal tar pitch comprising-
a mold for holding the coal tar pitch, optionally along with graphene, having a closed end and an open end, allowing air to enter and exit from the open end, and
a furnace, wherein cast is prepared by heating the coal tar pitch in the mold

12. The apparatus as claimed in claim 11, wherein the furnace accommodates the mold and is configured to heat the mold to a temperature ranging from about 700ºC to 900ºC, followed by cooling to a temperature ranging from about 20ºC to 40ºC to obtain the reduced graphene oxide.

13. The apparatus as claimed in claim 11, wherein the furnace is having a closed end and an open end, allowing air to enter and exit from the open end.

14. The apparatus as claimed in claim 11, wherein the furnace is external heating system.

Dated this 20th day of August 2019
Signature:
Name: Durgesh Mukharya
To: Of K&S Partners, Bangalore
The Controller of Patents Agent for the Applicant
The Patent Office, at Kolkata IN/PA No. 1541
, Description:TECHNICAL FIELD
The present disclosure relates to a field of material science. The present disclosure particularly relates to a method of synthesizing reduced graphene oxide (rGO). The disclosure relates to a method of synthesising reduced graphene oxide from coal tar pitch. The present disclosure also relates to the reduced graphene oxide having higher conductivity and reduced resistance. The disclosure also relates to an apparatus for synthesising said reduced graphene oxide.

BACKGROUND OF THE DISCLOSURE
Coal tar pitch (CTP) is an industrial by-product of steel production and is mainly composed of complex mixture of aromatic hydrocarbons and heterocyclics. Every year, steel works produce huge amount of CTP which is toxic and causes severe environmental problems. Recycling of CTP has always been a concern and various approaches have been attempted to recycle the CTP to a value-added product, particularly into graphene or graphene oxide. However, the available methods of converting CTP to graphene or graphene oxide suffers from various limitations including quality, yield, efficiency and cost. The present disclosure addresses these limitations existing in converting CTP to graphene or graphene oxide.

SUMMARY OF THE DISCLOSURE
An object of the present disclosure is to provide a simple, inexpensive, environmentally friendly and single-step method for synthesising reduced graphene oxide (rGO) having high conductivity and reduced resistance from coal tar pitch (CTP).

Accordingly, the present disclosure relates to a method for synthesising reduced graphene oxide from coal tar pitch, optionally along with graphene, wherein the method comprises heating the coal tar pitch at a temperature ranging from about 700ºC to 900ºC in presence of air, followed by cooling to a temperature ranging from about 20ºC to 40ºC to obtain the reduced graphene oxide, wherein the method involves minimal interaction of the coal tar pitch with the air.

The present disclosure further relates to the reduced graphene oxide comprising carbon content ranging from about 94% to 96% and oxygen content ranging from about 4% to 6%, wherein the reduced graphene oxide has conductivity ranging from about 0.125mS/cm to 500S/cm and resistance ranging from about 0.5? to 2.0M?.

The present disclosure further relates to an apparatus for synthesising the reduced graphene oxide from the coal tar pitch comprising a mold to hold the coal tar pitch, optionally along with graphene, having a closed end and an open end, allowing air to enter and exit from the open end, and a furnace, wherein the furnace accommodates the mold and is configured to heat the mold to a temperature of about 700ºC to 900ºC, followed by cooling to a temperature ranging from about 20ºC to 40ºC to obtain the reduced graphene oxide.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
For the purpose that the disclosure may be easily perceived and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where:

FIGURE 1 X-ray powder diffraction (XRD) patterns of coal tar pitch heated at 700ºC and at 900ºC.

FIGURE 2 illustrates Raman spectra for rGO cast sample at various locations.

FIGURE 3 X-ray powder diffraction (XRD) patterns of coal tar pitch at 900ºC.

FIGURE 4 Field emission scanning electron microscopy (FE-SEM) and Energy-dispersive X-ray spectroscopy (EDX) of reduced graphene oxide cast.

FIGURE 5 Schematic representation of 4-probe experimental method for analysing conductivity of the reduced graphene oxide.

FIGURE 6 illustrates Raman spectra for rGO cast with 1wt% of graphene sample at various locations.

FIGURE 7 a) illustrates schematic illustration of process flow of rGO cast preparation and b) illustrates digital image of cylindrical mold and rGO cast.

FIGURE 8 illustrates digital image of square mold and rGO cast.

FIGURE 9 illustrates flow chart depicting the method of synthesising reduced graphene oxide.

DETAILED DESCRIPTION
The present disclosure relates to a method of synthesising reduced graphene oxide from coal tar pitch.

In an embodiment of the present disclosure, the method of synthesising reduced graphene oxide from coal tar pitch is simple, inexpensive and environmentally friendly.

In an embodiment of the present disclosure, the method of synthesising reduced graphene oxide from coal tar pitch comprises heating the coal tar pitch at a temperature ranging from about 700ºC to 900ºC in presence of air, followed by cooling to a temperature ranging from about 20ºC to 40ºC to obtain the reduced graphene oxide, wherein the method involves minimal interaction of the coal tar pitch with the air.

In an embodiment of the present disclosure, the coal tar pitch is heated to a temperature of about 700ºC, about 720ºC, about 740ºC, about 760ºC, about 780ºC, about 800ºC, about 820ºC, about 840ºC, about 860ºC, about 880ºC or about 900ºC.

In an embodiment of the present disclosure, the coal tar pitch is heated for a duration ranging from about 15minutes to 30minutes.

In another embodiment of the present disclosure, the coal tar pitch is heated for a duration of about 15minutes, about 16minutes, about 17minutes, about 18minutes¸ about 19minutes¸ about 20minutes¸ about 21minutes¸ about 22minutes¸ about 23minutes¸ about 24minutes¸ about 25minutes¸ about 26minutes¸ about 27minutes¸ about 28minutes¸ about 29minutes or about 30minutes.

In an embodiment of the present disclosure, the heated coal tar is cooled to a temperature ranging from about 20ºC to 40ºC.

In another embodiment of the present disclosure, the coal tar pitch is cooled to a temperature of about 20ºC, about 22ºC, about 24ºC, about 26ºC, about 28ºC, about 30ºC, about 32ºC¸ about 34ºC¸ about 36ºC¸ about 38ºC or about 40ºC.

In an embodiment of the present disclosure, the heating of the coal tar pitch is carried out in a furnace having a closed end and an open end, wherein the furnace permits the air to enter and exit from the open end, allowing minimal interaction of the coal tar pitch with the air.

In an embodiment of the present disclosure, the successful conversion of coal tar pitch to reduced graphene oxide having high conductivity according to the method is because of minimal interaction of the coal tar pitch with air during heating and that the top layer of the coal tar pitch acting as a barrier for oxygen penetration.

In an embodiment of the present disclosure, the method does not require any expensive instrumentation or any gaseous sources, such as hydrogen and methane for obtaining reduced graphene oxide with high conductivity from coal tar pitch.

In an embodiment of the present disclosure, the reduced graphene oxide obtained by the method has conductivity ranging from about 0.125mS/cm to 500 S/cm.

In an embodiment of the present disclosure, the reduced graphene oxide obtained by the method has resistance ranging from about 0.5O to 2.0MO.

In an embodiment of the present disclosure, the reduced graphene oxide obtained by the method has carbon content ranging from about 94% to 96% and oxygen content ranging from about 4% to 6%. The obtained reduced graphene oxide having 4% to 6% of oxygen content is closer to intrinsic graphene and therefore it exhibits better conductivity of about 500 S/cm. Higher the oxygen content in the reduced graphene oxide will be more closer to graphene oxide and will considerably not have properties exhibited by the reduced graphene oxide.

In another embodiment of the present disclosure, the reduced graphene oxide obtained by the method has carbon content of about 94%, about 95% or about 96% and has oxygen content of about 4%, about 5% or about 6%.

In an embodiment of the present disclosure, the method is a high throughput method, wherein the reduced graphene oxide can be synthesised at a rate of about 5kg/hour.

In an embodiment of the present disclosure, the method of synthesising reduced graphene oxide with high conductivity is a one-step reduction method by thermal annealing in ambient atmosphere.

In an exemplary embodiment of the present disclosure, the reduced graphene oxide obtained by the method preferably has the conductivity of about 500S/cm which is at least about 3 orders high when compared to the conductivity observed in the reported reduced graphene oxide.

In an exemplary embodiment of the present disclosure, the reduced graphene oxide obtained by the method preferably has the resistance as low as about 1?/square according to sheet resistance extracted from 4-probe measurement.

In an exemplary embodiment of the present disclosure, the reduced graphene oxide obtained by the method preferably has carbon content ranging from about 94% to 96% and has oxygen content ranging from about 4% to 6%, wherein the percentage of carbon content is higher and the oxygen content is lesser when compared to carbon and oxygen content of the reported reduced graphene oxide.

In an exemplary embodiment of the present disclosure, the method of synthesising reduced graphene oxide from coal tar pitch comprises- grinding coal tar pitch; loading the coal tar pitch to a mold and placing the mold in a furnace; heating the furnace to a temperature of about 900ºC with a ramp of about 12ºC/minute, causing evaporation of solvent, such as toluene, benzene, xylene and dimethyl naphthalene; heating the quartz tube containing coal tar pitch at a temperature of about 900ºC for about 15 minutes in ambient atmosphere to obtain reduced graphene oxide.

In an embodiment of the present disclosure, the method of synthesising reduced graphene oxide is not carried out under vacuum or inert atmosphere. In other words, the synthesising of reduced graphene oxide by the method described above completely avoids vacuum or inert atmosphere.

In an alternate embodiment, the method of synthesising reduced graphene oxide comprises heating coal tar pitch along with graphene, including but not limiting to graphene powder and graphene flakes, wherein the coal tar pitch is mixed with graphene, followed by dispersing the mixture in a solvent, such as toluene and then drying the mixture and subjecting the mixture to heating at a temperature ranging from about 700ºC to 900ºC in presence of air, followed by cooling to a temperature ranging from about 20ºC to 40ºC to obtain the reduced graphene oxide, wherein the method involves minimal interaction of the coal tar pitch with the air

In another embodiment of the present disclosure, the mixture of coal tar pitch and graphene is heated to a temperature of about 700ºC, about 720ºC, about 740ºC, about 760ºC, about 780ºC, about 800ºC, about 820ºC, about 840ºC, about 860ºC, about 880ºC or about 900ºC.

In an embodiment of the present disclosure, the mixture of coal tar pitch and graphene is heated for a duration ranging from about 15minutes to 30minutes.

In another embodiment of the present disclosure, the mixture of coal tar pitch and graphene is heated for a duration of about 15minutes, about 16minutes, about 17minutes, about 18minutes¸ about 19minutes¸ about 20minutes¸ about 21minutes¸ about 22minutes¸ about 23minutes¸ about 24minutes¸ about 25minutes¸ about 26minutes¸ about 27minutes¸ about 28minutes¸ about 29minutes or about 30minutes.

In an embodiment of the present disclosure, the heated mixture of coal tar pitch and graphene is cooled to a temperature ranging from about 20ºC to 40ºC.

In another embodiment of the present disclosure, mixture of coal tar pitch and graphene is cooled to a temperature of about 20ºC, about 22ºC, about 24ºC, about 26ºC, about 28ºC, about 30ºC, about 32ºC¸ about 34ºC¸ about 36ºC¸ about 38ºC or about 40ºC.

In an embodiment of the present disclosure, the heating of the coal tar pitch along with graphene, including but not limiting to graphene powder and graphene flake is carried out in a furnace having a closed end and an open end, wherein the furnace permits the air to enter and exit from the open end, allowing minimal interaction of the coal tar pitch with the air.

In an embodiment of the present disclosure, the successful conversion of mixture of coal tar pitch and graphene, including but not limiting to graphene powder and graphene flake to reduced graphene oxide having high conductivity according to the method is because of minimal interaction of the mixture of coal tar pitch graphene with air during heating and that the top layer of the mixture acting as a barrier for oxygen penetration.

In an embodiment of the present disclosure, the mixture of coal-tar pitch and graphene comprises about 0.1wt% to 1 wt% graphene and remaining component is the coal-tar pitch in the mixture.

The present disclosure further relates to a reduced graphene oxide obtained by the method described above.

In an embodiment of the present disclosure, the reduced graphene oxide has carbon content ranging from about 94% to 96% and has oxygen content ranging from about 4% to 6%.

In another embodiment of the present disclosure, the reduced graphene oxide has carbon content of about 94%, about 95% or about 96% and has oxygen content of about 4%, about 5% or about 6%.

In an embodiment of the present disclosure, the reduced graphene oxide has conductivity ranging from about 0.125mS/cm to 500 S/cm.

In an embodiment of the present disclosure, the reduced graphene oxide has resistance ranging from about 0.5O to 2.0MO.

In an exemplary embodiment of the present disclosure, the reduced graphene oxide preferably has the conductivity of about 500S/cm which is at least about 3 orders high when compared to the conductivity observed in the reported reduced graphene oxide.

In an exemplary embodiment of the present disclosure, the reduced graphene oxide preferably has the resistance as low as about 1?/squad according to sheet resistance extracted from 4-probe measurement.

In an embodiment of the present disclosure, the reduced graphene oxide is a porous mesh structure with improved surface area and very low oxygen content.

The present disclosure further relates to an apparatus for synthesising the reduced graphene oxide from coal tar pitch.

In an embodiment of the present disclosure, the apparatus for synthesising the reduced graphene oxide from coal tar pitch comprises- a mold for holding the coal tar pitch, optionally along with graphene including but not limited to graphene powder and graphene flake, having a closed end and an open end, allowing air to enter and exit from the open end; and a furnace, wherein the furnace accommodates the mold and is configured to heat the mold to a temperature ranging from about 700ºC to 900ºC, followed by cooling to a temperature ranging from about 20º to 40ºC to obtain the reduced graphene oxide.

In an exemplary embodiment of the present disclosure, the mold is in a form of a square having an illustrative dimension of about 5cm x 5cm x 5cm.

In another exemplary embodiment of the present disclosure, the mold is in a form of a cylinder having illustrative dimensions r= about 1.25cm, h= about 5cm and r=about 0.5cm, h=about 5cm.

In an embodiment of the present disclosure, the mold having shapes including but not limited to cylindrical shape and square shape yield reduced graphene oxide (rGO) casts having shapes including but not limited to cylindrical shape and square shape, wherein the reduced graphene oxide is porous in nature and is highly conductive, having conducting of about 500S/cm.

In an embodiment of the present disclosure, the furnace is an external heating system, such as tube furnace, including but not limited to quartz tube.

In an embodiment of the present disclosure, the furnace is having a closed end and an open end, allowing air to enter and exit from the open end.

The present disclosure further relates to use of the reduced graphene oxide described above in immersion heater application.

The present disclosure furthermore relates to use of the reduced graphene oxide described above in super capacitor application.

The present disclosure furthermore relates to use of the reduced graphene oxide described above in water-oil separation.

In the present specification, the expression ‘mold’ and ‘container’ are interchangeably used. The expression mold or container means an object to hold coal tar pitch and/or mixture of coal tar pitch and graphene and which can sustain temperature greater than 500ºC.

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based upon the description provided. The embodiments provide various features and advantageous details thereof in the description. Description of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments. The examples provided herein are intended merely to facilitate an understanding of ways in which the embodiments provided may be practiced and to further enable those of skilled in the art to practice the embodiments provided. Accordingly, the following examples should not be construed as limiting the scope of the embodiments.

EXAMPLES
Materials and Methods

Raman spectra were acquired from Horiba Jobin Yvon Xp1oRA PLUS V2.1 Multiline confocal Raman microscope. An excitation laser of about 532 nm is focused on the samples through a 50x objective. The acquisition time was 30seconds for each sample.

XRD patterns are obtained using Brucker D8 Discover diffractometer with Cu Ka (? = 1.5419 Å) source.

The morphology of the grown rGO is examined using a field-emission SEM (Nova Nano SEM 600, FEI company).

EXAMPLE 1: Method of synthesizing reduced graphene oxide
Solid C-pitch was powdered and then transferred on to the tube furnace with a mold, by placing the mold in a hot plate. The temperature of the tube furnace was set at a temperature of about 900ºC and maintained for about 30 minutes to evaporate all unwanted solvents with boiling point less than about 700ºC, such as toluene, benzene, xylene and dimethyl naphthalene, to obtain reduced graphene oxide (rGO). The converted coal tar pitch into rGO was collected at room temperature and subjected to examination, such as Raman spectroscopy analysis, XRD analysis, FE-SEM and EDX analysis and conductivity.

a. Raman Spectroscopy analysis
Raman spectroscopy was employed to characterize the structural properties in rGO casts. In Raman spectra, rGO formation can be manifested by significant characteristic peaks shifts of two main D and G peaks. As shown in Figure 2, D and G peaks of rGO were located at 1,360 cm-1 and at 1,600 cm-1,respectively, indicating a defect-induced breathing mode of sp2 rings common to an sp2-bonded carbon lattice, which originates from the stretching of C–C bonds. The intensity of the D band is related to the size of the in-plane sp2 domains, and the increase in D peak intensity indicates the formation of additional sp2 domains. The intensity ratio of the two peaks (ID/IG) is a measure of disorder degree and is inversely proportional to the average size of the sp2 clusters. Higher ID/IG values along with prominent 2D peak at 2860 cm-1 were observed due to the increase in the number of sp2 clusters, confirming that coal tar pitch was successfully converted to rGO casts.

b. XRD analysis
The crystallographic phase of rGO casts were examined by XRD. Usually, for graphene oxide (GO), a strong diffraction peak will appear at 2? at about 10°. However, this peak was absent in the coal tar pitch converted rGO casts, and a peak at 2? at about 26° with d-spacing 0.339 nm emerged due to graphene diffraction. Thus, was concluded that coal tar pitch was effectively converted into rGO casts (illustrated in Figure 3). There was no obvious diffraction peaks of graphene observed in rGO profile, indicating that graphene sheets were homogeneously dispersed.

c. FE-SEM and EDX analysis
Figure 4 shows the FE-SEM image of rGO casts synthesized from the coal tar pitch. A randomly aggregated, thin, crumpled graphene sheets with wavy structures was observed in figure 4. The EDX spectra shown in Figure 4 also confirmed the presence of carbon and oxygen in rGO casts. Majority of oxygen-containing functional groups were removed from rGO casts, and the atomic ratio of carbon to oxygen was found to be 4.61.

d. Conductivity analysis
To quantify the electrical properties of the rGO, conductivity was estimated with the in-line 4-probe experimental setup as illustrated in Figure 5. The estimated electrical conductivity was found to be about 500S/cm.

EXAMPLE 2:
a. Method of synthesizing rGO with external heating at 12ºC/minute in ambient atmosphere.
About 25g of the coal-tar pitch filled was filled in a quartz tube having one sealed end and another open end. The said quartz tube having the coal-tar pitch is placed inside a furnace at temperature of about 25ºC and heated to a temperature of about 700ºC to 900ºC with a ramp of about 12ºC/minute in ambient atmosphere (pressure of about 1bar) for about 30 minutes to obtain the reduced graphene oxide. The rGO casts obtained showed significant reduction in GO phase and the rGO showed improved conductivity.

Figure 1(a) and 1(b) illustrates the XRD profile of the coal tar pitch heated at 700ºC and at 900ºC, respectively. Figure 1(a) correspond to coal-tar pitch heated up to temperature at 700ºC, two peaks were observed, one around 10º and other around 26º representing graphene oxide (GO) and reduced graphene oxide (rGO), respectively. Figure 1(b) correspond to coal tar-pitch heated up to 900ºC wherein only one peak was observed at around 26º representing reduced graphene oxide (rGO) peak. The figure 1(b) indicates significant reduction in GO phase as the temperature is increased, as a result the obtained reduced graphene oxide is highly conductive.

b. Rapid heating of coal-tar pitch under ambient atmosphere.
About 25g of coal-tar pitch was filled in a quartz tube having one sealed end and another open end. The said quartz tube is placed inside a furnace maintained at temperatures ranging from about 700ºC to about 900ºC in ambient atmosphere (pressure of about 1 bar) and heated for about 5minutes to 30 minutes to obtain reduced graphene oxide (rGO).

The resistance value of the reduced graphene oxide (rGO) vary depending on the treatment temperature and processing time. The details of employed process parameters and resistance values of obtained rGO at ambient pressure is described in Table 1.

Table 1 illustrates the resistance of the rGO with various parameters employed according to Example 2.

Method used Environment Temperature (?C) Time in minutes Resistance in ?
External heating Ambient atmosphere 700 30 ~0.5-2M
800 30 ~1-20k
850 30 ~10-100
900 5 ~5-20
900 10 ~2-10
900 15 ~0.5-2
900 30 ~0.5-1

Table 1: Resistance of rGO casts obtained from different process parameters.

Further, Table 2 illustrates conductivity of the reduced graphene oxide of the present disclosure and that of the commercially available reduced graphene oxide. From the data in the Table 2 it is apparent that the conductivity of reduced graphene oxide of the present disclosure has greater conductivity than the commercially available reduced graphene oxide.

Sample Conductivity (S/cm)
Reduced graphene oxide from Graphenea 66.67
Reduced graphene oxide from Sigma Aldrich 6
Reduced graphene oxide of present disclosure 500

Table 2: Conductivity of reduced graphene oxide of present disclosure and commercially available reduced graphene oxide.

Example 3: Heating at temperature of about 900ºC in ambient atmosphere with 0.1wt% to 1wt% graphene flakes.
About 9.9g of coal-tar pitch was finely grounded and 0.1g graphene powder was added to the grounded coal-tar pitch to obtain a mixture. The mixture was dispersed in about 40ml of toluene solvent and sonicated for about 30 minutes. The dispersion was then transferred to a petri dish and the solvent was evaporated naturally. The dried mixture was then transferred to a quartz tube with one sealed end. The mixture was then heated to a temperature of about 900ºC with a ramp of about 12ºC/minute and maintained at that temperature for about 30 minutes. The sample was cooled down to temperature of about 25ºC naturally and characterized by Raman Spectroscopy. From Figure 6 it can be observed that the quality of rGO produced looks similar to rGO produced from coal-tar pitch alone at about 900ºC for about 30minutes in ambient atmosphere (see figure 1(b)).

The reduced graphene oxide (rGO) obtained by heating the coal tar pitch, optionally along with graphene powder at a temperature of about 900ºC for about 30 minutes possesses good conductivity and the corresponding process conditions are employed for bulk production of reduced graphene oxide.

Example 4: Cylindrical shaped reduced graphene oxide (rGO) cast preparation
To prepare cylindrical rGO cast in one step, a quartz tube with one end sealed to hold coal-tar pitch and sustain temperature of about 900ºC heating is used.

About 25g of coal-tar pitch was loaded into cylindrical shaped (r=1.25cm, h=40cm) quartz tube (mold). The quartz tube loaded with coal-tar pitch was loaded into the furnace and heated to a temperature of about 900ºC for about 30minutes as described in Example 1 and further cooled to room temperature to obtain rGO cast. Once the tube was cooled to a temperature of about 25ºC, rGO cast was taken out by overturning the quartz tube. Figure 7a shows the schematic illustration of the process flow and Figure 7b shows a cylindrical mold and rGO cast obtained after the treatment. rGO casts obtained are porous in nature and are electrically conducting.

Example 5: Square shaped reduced graphene oxide (rGO) cast preparation
To prepare cylindrical rGO cast in one step, a square shaped stainless-steel mold with one end sealed to hold coal-tar pitch and sustain temperature of about 900ºC heating is used.

About 25g of coal tar-pitch was loaded into square shaped stainless-steel mold (1=5cm, w=5cm, h=15cm) (mold). The mold loaded with coal tar pitch was loaded into the furnace and heated to a temperature of about 900ºC for about 30minutes as described in Example 1 and further cooled to room temperature to obtain rGO. Once the mold was cooled to room temperature, rGO cast taken out by overturning the stainless-steel mold. Figure 8a illustrates the stainless-steel mold and rGO obtained after the treatment. rGO casts are porous in nature and are electrically conducting.