Description:FORM 2
THE PATENT ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See section 10, rule 13)

TITLE
BODY-CENTERED TETRAGONAL CARBON FROM COCONUT RACHIS AND METHOD OF PREPARATION THEREFOR

INVENTORS
CHANDRASEKHARANNAIR OMANAAMMA, Sreekala, Indian Citizen
Amrita Vishwa Vidyapeetham, Amritapuri, Kollam, Kerala 690525, India.
RAJAN, Jose, Indian Citizen
Universiti Malaysia Pahang, 26300 Kuantan, Malaysia

BINDHU, Devu, Indian Citizen
Amrita Vishwa Vidyapeetham, Amritapuri, Kollam, Kerala 690525, India.

APPLICANT
Amrita Vishwa Vidyapeetham
Amritapuri PO, Kollam 690525, Kerala India

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

BODY-CENTERED TETRAGONAL CARBON FROM COCONUT RACHIS AND METHOD OF PREPARATION THEREFOR
CROSS-REFERENCES TO RELATED APPLICATIONS
None.
FIELD OF THE INVENTION
The present invention generally relates to carbonaceous material and more particularly relates to carbonaceous material from a bio-precursor materialand methods of preparation thereof.
BACKGROUND OF THE RELATED ART
Carbon is the most extensively utilized material, a material with distinctive physical and chemical characteristics. They are useful for many applications due to their low density, strong mechanical strength, good thermal and electronic conductivity, high stability, and capacity to exist in various forms. Carbon, with its unique ability to form allotropes like graphene, graphite, carbon nanotubes, fullerene, and diamond etc. enables them to be the backbone of coming generation technological scientific era. Due to their wide network of sp3, sp2, and sp hybridization, these allotropes offer unique properties such as hardness, lubricating behavior, thermal conductivity, and electrical conductivity. The prediction and synthesis of various carbon allotropes have been the specific attention of materials researchers due to these fascinating features. Numerous unique carbon allotropes, including T carbon, Cco-C8, R carbon, Penta -C20, P carbon, BCT C4, etc., have been theoretically predicted in recent years. Among them, tetragonal body-centered carbon allotropes are the subject of extensive study due to their sp3 hybridized bonding character.
Eventhough there are many theoretically predicted carbon allotropes but most of them are not experimentally synthesized. The carbon allotrope with tetragonal phase ie; the tetragonal body centered carbon is getting more attention from the researchers due to its fascinating properties. Theoretical studies revealed that they are highly stable and can have high mechanical stability at ambient conditions, which is more rigid than most carbon materials but less rigid than diamond. High thermal stability and an excellent electronic properties were also predicted for these carbon phase. Thus they can have widened applications in both electronic devices and super hard material field. The synthesis of these tetragonal phase carbon structure experimentally that too from a biomass precursor material can open the paths toward a wide sustainable technological advancement.
Researchers from all across the world have used a variety of naturally occurring biomass materials for the synthesis of valuable functional carbon materials.Among the different biomass materials coconut palm is considered as the significant source of carbon production because it is the most common agriculture all around the world. For the production of 1 tons of carbon, 50000 coconutsare used. Thus from the above data, it is observed that 5% of the global demand for carbon can be met from coconut shell itself. This confirmed the importance of coconut as a suitable precursor for carbon production.In one of the research, graphitic-type activated carbon from coconut shell (DOI: 10.1039/d0ra09182k) has been reported to show high degree of crystallinity, suitable morphologyandspecific surface area ranging from 586 m2g-1 to 1998 m2g-1. Patent application, CN114455950A,discloses a method for preparing a graphite boat from lignin-rich plant bodies such as bamboo, pine, corn stover, coconut shell or tea seed oil shell using pyrolysis and volatilization.
However, fabrication of the carbonmaterials with above-mentioned processes involves use of strong acids, high temperatures and cannot be performed without complex machineries. Furthermore, coconut rachis has not been readilyused in preparing graphite or activated carbonfor COD and BOD reduction in liquid waste. Hence, there has long been a need in the art for preparation ofcarbon precursors from coconut waste that is easy to fabricate, cost-effective and is suitable for energy storage application. In this regard, the method and products according to the present invention substantially departs from the conventional concepts and designs of the prior art.
This and other aspects are described herein.
SUMMARY OF THE INVENTION

The present subject matter relates to a method of experimentally synthesizing body centered tetragonal carbon from a bio-precursor coconut rachis.
According to one embodiment of the invention, a method of synthesizng body centered tetragonal (BCT) carbon from coconut rachis is disclosed. The method comprises steps of providing sun dried coconut rachis and the coconut rachis is sun dried for 48 hours. The method next includes powdering the sun dried coconut rachis followed by oven dryingat 110°C for 48 hours. The oven dried powder is then pre-carbonised at a temperature of 250 °C for 2 hrs. The method next includes pulverizing the pre-carbonized oven dried powder using a mortar and pestle. The pulverised powder is carbonized in a muffle furnace under nitrogen flow at 450°C for 2-3 hrs to form a crystalline body centered tetragonal carbon.
According to one embodiment of the invention, crystalline carbon (200) from coconut rachis, comprising a crystallographic structure with a degree of graphitization in the range of 98% or more, a BET surface area of 38 m2 g-1 or more, and a pore size of 2.81 or more is disclosed. The crystalline carbon as claimed in claim 10, wherein the crystalline BCT carbon comprises a crystal size of 23.04 nm, or a pore volume of 0.027 cm³/g or more. The crystalline body centered tetragonal (BCT) carbon as claimed in claim 10, wherein the crystalline carbon gives an XRD pattern with peaks at 2? = 28.65º, 40.73º, 58.83º , 66.65º and 73.86º corresponding to (110), (200), (211), (310) and (301) planes respectively, corresponding to tetragonal phase of graphite.The tetragonal carbon gives two distinctive absorption peaks at 1333 and 1582 cm-1, corresponding to D-band and G-band respectively in the Raman spectra. The BCT carbon shows a peak of O1 spectrum at a binding energy of 531.4 eV and three peaks of C1 spectrum at 282.8, 284.6 and 286.7 eV corresponding to sp2, sp3, and oxidized states of the carbon atom, respectively in the XPS spectra. The body centered tetragonal carbon has a density of 3.121 g/cm3exhibits ahardness of 88 GP.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention has other advantages and features which will be more readily apparent from the following detailed description of the invention and the appended claims, when taken in conjunction with the accompanying drawings, in which:
FIG.1: represents a method of the present invention for synthesizing body centered tetragonal (BCT) carbon.
FIG. 2: is a graphical representation of three dimensional crystal structure of the synthesized BCT carbon.
FIG. 3 shows the XRD pattern of the synthesized tetragonal carbon: is a graphical representation showing XPS survey spectra.
FIG. 4A shows the HRTEM image of the synthesized tetragonal carbon.
FIG. 4B shows the SAED pattern of the synthesized BCT carbon.
FIG. 5 shows the Raman spectra of the synthesized tetragonal carbon.
FIG. 6. shows the XPS spectra of the synthesized BCT carbon.
FIG. 7 shows the differential scanning calorimetry analysis of synthesized BCT carbon.
DETAILED DESCRIPTION OF THE EMBODIMENTS
While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope.
Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of "a", "an", and "the" include plural references. The meaning of "in" includes "in" and "on." Referring to the drawings, like numbers indicate like parts throughout the views. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein.
The present disclosure provides for synthesis of body centered tetragonal (BCT) carbon from coconut rachis waste. The invention in various embodiments includes a method 100of preparing body centered tetragonal (BCT) carbon200 from coconut rachis. The method 100 involves various steps of preparation, as shown in FIG. 1.The invention also discloses a crystalline carbon obtained from coconut rachis200.
In various embodiments, the method 100of preparing body centered tetragonal carbon200 from coconut rachis includes providing in step 101sun dried coconut rachis. The coconut rachis is sundried for 48 hours or more. In the next step, powdering102 of the sun dried coconut rachis is carried out. In step 103, oven drying of the sun dried coconut rachis powder is carried out. In various embodiments, the oven drying 103 is performed at 110°C for 48 hours. In various embodiments, the oven dried powder is pre-carbonized in step104. The pre-carbonization is performed at a temperature of 250 °C for 2 hrs. In various embodiments, step 104 is followed by step 105 of pulverizing the pre-carbonized powder. In various embodiments, the pulverizing 105 of the pre-carbonized powder is carried out using a mortar and pestle, ball mill, or other similar process.
In various embodiments, in step 106 carbonizing of the pulverized powderis carried out. The carbonizing 106 of the pulverized powder is performed in a suitable furnace, such as a furnace. In various embodiments, the carbonizing 106 of the pulverized powder is performed under nitrogen flowto form a crystalline carbon. In one embodiment,the crystalline carbon is formed by carbonizing 106 of the pulverised powder at 450°Cin the muffle furnace for 2-3 hoursunder nitrogen flow.The crystalline carbon 200may be used in various applications such as crucibles, electrodes etc.
The crystalline body centered tetragonal carbon 200 from coconut rachis comprises a tetragonal crystallographic structure as shown in FIG. 2. The crystalline carbon 200 gives an XRD diffraction pattern with peaks at 2? = 28.65º, 40.73º, 58.83º , 66.65º and 73.86º corresponding to (110), (200), (211), (310) and (301) planes as shown in FIG. 3. In various embodiments, the crystal size of the product is in the range of 20-25 nm. In various embodiments, the crystal carbon200comprises a degree of graphitization in the range of98% or more. The crystalline carbon 200 comprises a BET surface area of 38 m2 g-1 or more. In various embodiments, the crystalline carbon comprises a pore size of 2.81 or more. In various embodiments, the average void diameter on the surface of the crystalline carbon is calculated as 8µm or more. In various embodiments, the pore volume of the surface of the activated carbon is 0.027cm³/g.

The tetragonal carbon gives two distinctive absorption peaks in the Raman spectra at 1333 and 1582 cm-1, corresponding to D-band and G-band respectively. The BCT carbon shows a peak of O1 spectrum at a binding energy of 531.4 eV and three peaks of C1 spectrum at 282.8, 284.6 and 286.7 eV corresponding to sp2, sp3, and oxidized states of the carbon atom, respectively in the XPS spectra. The synthesized body centered tetragonal carbon exhibits a hardness of 88 GP and has a density of 3.121 g/cm3.
In various embodiments, the method 100 provides a cost efficient means for preparing crystalline body-centered tetragonal carbon from biomass waste such ascoconut rachis wherein the used ingredient is renewable and abundantly available in nature. In various embodiments, the method 100 disclosed address some of the drawbacks of conventional chemical based methods for preparing activated carbon of high quality. In various embodiments, the method 100 disclosed produces body centered tetragonal carbon with narrow pore size distribution. In various embodiments, the method 100 provides a pore size distribution in the range of 2.81nm. In various embodiments, the method 100 leads to synthesis of carbon with narrow pore size distribution, suitable for energy storage applications such as supercapacitors, battery electrodes and hydrogen storage.
In various embodiments, the crystalline carbon 200 obtained by this method 100is a graphitic carbon of high quality. The obtained graphitic carbon has a high carbon content of ~90% which is very high comparing with other parts of coconut palm or carbon content of any other biomass waste material. Owning to the high carbon content and a high graphitic value, the crystalline carbon obtained by this method may be used in various applications such as crucibles, electrodes etc.The BCT carbon synthesised from coconut rachis may be used as filtration medium for water filtration and purification. The synthesised BCT carbon may also be used as a replacement for silicon.
While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material the teachings of the invention without departing from its scope, as defined by the claims.
EXAMPLES
Example 1: Procedure for synthesis of BCT carbon- To synthesize the tetragonal carbon structure, locally sourced coconut rachis was initially sun-dried for 48 hours, powdered, and oven-dried at 110 °C for 48 hours. The dried sample was pre-carbonized at a temperature of 250 °C for 2 hours, then pulverized using a mortar and pestle. The carbonization process was performed in a laboratory muffle furnace under nitrogen flow at 450°C for 2-3 hours.

Characterization of BCT carbon:
Example 2: X-ray diffraction (XRD) pattern of pyrolyzed carbon sample obtained from coconut rachis before activation:Structural analysis of the prepared sample was analysed using XRD. FIG. 3 shows the XRD pattern of the biomass carbon synthesised from coconut rachis.The XRD pattern of the product shown sharp and crystalline diffraction peaks at 2? = 28.65º, 40.73º, 58.83º , 66.65º and 73.86º , corresponding to (110), (200), (211), (310) and (301) planes, respectively, of the tetragonal phase of carbon (space group: I4/mmm [139]). The lattice parameters “a” and “c” of carbon was calculated as 0.44 and 0.24 nm, respectively. The obtained values of lattice parameters were consistent with the standard reported data. The (110) diffraction peak was found to be predominant over all other diffraction peaks. This XRD pattern confirmedtetragonal phase of graphite for crystalline carbon. Further, the crystal size of crystalline carbon was calculated to be 23.04 nmusing Debye Scherer’s formula, as shown in (1).
D=0.9?/ßcos?…..(1)
where,?=1.54 Å is the wavelength of the X-ray (Cu-ka), ? is the Bragg diffraction angle and ß is the full width at half maximum (FWHM) of the diffraction peak.
To further analyze the structural transition, Rietveld refinement of XRD patterns have been performed by the Fullprof Suite program. The pseudo-Voigt function was used for the refinement. An excellent match of peak positions was obtained from refinement including lattice and background parameters, instrument factors and R-factors and are listed in Table 1. Atomic positions parameters were held constant to the values provided by previous studies while the lattice parameters and profile parameters were refined. Residuals (R-values) from the refinement were calculated to be 31.4 for residual of least- squares refinement, RP, 12.71 for weighted profile factor, Rexp, and 27.8 for weighted profile factor, Rwp. The Bragg factor (RBragg) and crystallographic factor (Rf) were obtained as 0.7516 and 1.957. The chi-square value (?2) was obtained as 4.77. The low R-value of refinements and chi-square value indicates that the simulated parameters can fit with the experimentally acquired XRD pattern. The density of the synthesized sample was also observed after refinement, and a higher density value of 3.121 g/cm3 was obtained. This value is only 10.8% less than that of diamond, making the synthesized sample the only experimentally synthesized carbon allotrope after lonsdaleite whose density is closest to that of diamond.
Table 1: Rietveld refined structural parameters of carbon simulated based on the measured XRD patterns.

C a=4.456
b=4.56
c=2.57
?=??=??=900
C
C
C
C
C
C
C
C
0.68028800

0.81971200

0.81971200

0.68028800

0.18028800

0.31971200

0.31971200

0.18028800
0.81971200 0.68028800
0.18028800
0.31971200
0.18028800
0.3197120
0.68028800
0.81971200
0.50000000
0.00000000
0.00000000
0.50000000
0.00000000
0.50000000
0.50000000
0.00000000 RP=31.4
Rwp=27.8
Rexp=12.7
?2=4.77
0.7516 1.957
Example 4: High Resolution Transmission Electron Microscopy and Selected Area Electron Diffraction (HRTEM and SAED Analysis) The High Resolution TEM image of the tetragonal carbon material is shown in FIG. 4A The inset of clearly shows the lattice fringes with an interplanar spacing of 0.30 nm, which is close to the (110) plane of synthesized tetragonal carbon material. The selected area electron diffraction (SAED) of the carbon material consist of both spots and diffraction ring patterns, indicating the crystalline nature of material as shown in FIG. 4B. The diffraction patterns were consistent with tetragonal phase of carbon from XRD. The SAED indexed data is given in Table 2. Thus by HRTEM imaging combined with SAED data analysis, confirmed the tetragonal phase of the synthesized carbon in an atomic-scale.
Table 2: d-space calculation from SAED pattern of the synthesised sample
Sl. No: 1/2r
( nm-1) 1/r
(nm-1) r
(nm) d-spacing (A0) (hkl) XRD
peak d-spacing from XRD
(A0)
1 8.97 4.485 0.2296 2.296 (200) 40.734 2.213
2 12.661 6.3305 0.157 1.57 (220) 58.83 1.568
3 15.579 7.7895 0.1283 1.283 (301) 73.86 1.282
4 6.094 3.047 0.3281 3.281 (110) 28.659 3.112
5 13.636 6.818 0.1466 1.46 (310) 66.65 1.402

Example 5: Raman spectroscopic analysis of the synthesized BCT carbon: The chemical structure of the tetragonal carbon sample was analyzed using Raman spectroscopy over a spectral range of 4000-50 cm-1. In FIG. 5, two distinctive absorption peaks can be observed at 1333 and 1582 cm-1, corresponding to the D-band and G-band, respectively. The D-band arises from the sp3-hybridization and defect state of the carbon atom, whereas the G-band originated from the in-plane vibration of the sp2-hybridized carbon. The higher Raman intensity for D-band indicates that a higher population of carbon atoms were sp3-hybridized, where the presence of sp2-hybridized carbon atoms cannot be neglected, considering the almost identical Raman intensity for the G-band peak.
Example 6: X-Ray Electron spectroscopy (XPS) of the synthesiszed tetragonal carbon: The XPS analysis of the sample is given in FIG. 6. The XPS scan concludes that carbon and oxygen are the major constituents on the surface of the synthesized BCT carbon, with low concentrations of other metal elements such as calcium and potassium. The occurrence of other elements at low concentrations was typical for biomass carbon. The composition of the synthesized sample as obtained in the XPS analysis is shown in Table 3.


Table 3: XPS characterization of synthesized sample.
Name of elements Atomic %
K 1
C 87.05
O 10/06
Ca 1.89

The high-resolution spectra of both C1s and O1s shown as inset in FIG. 6 were deconvoluted. The O1s spectrum shows only one peak at a binding energy of 531.4 eV, corresponding to the O-H bonding from the adsorbed surface moisture. Different from the O1s, the C1s spectrum can be deconvoluted into three individual peaks positioned at 282.8, 284.6, and 286.7 eV, corresponding to the sp2, sp3, and oxidized states of the carbon atom, respectively. Comparing the area fraction of the deconvoluted peaks, the ratio between the sp2, sp3, and oxidized carbon species can be determined as 32.5%, 58.8%, and 8.7%, respectively. Despite showing a higher concentration of sp3-hybridized carbon species, the XPS measurement concluded that sp2-hybridized species also exist on the surface of the synthesized BCT carbon. Correlating with the crystallography analyses, the data on chemical structure conclude that the synthesis BCT carbon has a body-centered tetragonal structure with high vacancy (defect) concentration. The vacancy could induce the formation of C=C (sp2-hybridization) when annealed under an inert atmosphere, explaining the presence of sp2-hybridized species in an sp3-dominated crystal structure.
Example 7: Analysis of the sample byDifferential Scanning Calorimetry (DSC): The temperature stability of the synthesized BCT carbon was analyzed using Differential Scanning Calorimetry analysis in a temperature ranging from 0 to 13000C, given in FIG. 7. The DSC curve showed a broad endothermic peak between 300 to 900oC with a minimum of 600oC during the temperature treatment of the carbon sample. A small endothermic peak is observed at 685 0C, indicating a phasetransition.
Brunauer-Emmett-Teller (BET) surface area analysis of thesample: Brunauer-Emmett-Teller surface area (BET) measurement was carried out to study the surface properties tetragonal carbon obtained from coconut rachis.The surface area was found to be ~38 m²/g, pore volume of 0.027 cm³/g and pore size of 2.81 nm.
The surface morphology of the BCT carbon synthesized from coconut rachis was studied using SEM analysis and is shown in FIG. 8. Pores were observed on the surface and the average void diameter was calculated as 8.6?m. The analysis shows a honey comb structure of the surface.The multitubular structure obtained in the analysis finds application in water filtration, among others.
, Claims:We claim:
1. A method (100) of synthesizing body centered tetragonal (BCT) carbon (200) from coconut rachis, the method comprising the steps of:
a) providing sun dried coconut rachis (101), wherein the coconut rachis is sun dried for 48 hours;
b)powdering the sun dried coconut rachis (102) followed by oven drying (103) at 110°C for 48 hours;
c)pre-carbonizing(104) the oven dried powderat a temperature of 250 °C for 2 hrs;
d) pulverizing(105) the pre-carbonized oven dried powder using a mortar and pestle;
e) carbonizing (106) the pulverized powder in a muffle furnace under nitrogen flow at 450°C for 2-3 hrs to form a crystalline body centered tetragonal carbon;

2. A crystalline body-centered tetragonal (BCT) carbon (200) from coconut rachis, comprising
a crystallographic structure with a degree of graphitization in the range of 98% or more,
a BET surface area of 38 m2 g-1 or more, or
a pore size of 2.81nm or more.

3. The crystalline body centered tetragonal (BCT) carbon as claimed in claim 2, wherein the crystalline carbon gives an XRD pattern with peaks at 2? = 28.65º, 40.73º, 58.83º , 66.65ºand 73.86ºcorresponding to (110), (200), (211), (310) and (301) planes respectively, corresponding totetragonal phase of graphite.

4. The crystalline carbon as claimed in claim 2, wherein the crystalline BCT carbon has a crystal size of 23.04 nm,or a pore volume of 0.027 cm³/g or more.

5. The crystalline BCT carbon as claimed in claim 2, wherein the tetragonal carbon gives two distinctive absorption peaks in Raman spectra at 1333 and 1582 cm-1, corresponding to D-band and G-band respectively.

6. The crystalline carbon as claimed in claim 2, wherein the BCT carbon shows a peak of O1 spectrum at a binding energy of 531.4 eV and three peaks of C1 spectrum at 282.8, 284.6 and 286.7 eV corresponding to sp2, sp3, and oxidized states of the carbon atom, respectively in the XPS spectra.

7. The crystalline BCT carbon as claimed in claim 2, wherein the BCT carbon has a density of 3.121 g/cm3 and a hardness of 88 GP.

Sd.- Dr V. SHANKAR
IN/PA-1733
For and on behalf of the Applicants