Indian Patents. 268800:"A PROCESS FOR THE SYNTHESIS OF DOUBLE HELICAL CARBON MICROCOILED BY CATALYTIC CHEMICAL VAPOUR DEPOSITION (CCVD) METHOD"

Title of Invention	"A PROCESS FOR THE SYNTHESIS OF DOUBLE HELICAL CARBON MICROCOILED BY CATALYTIC CHEMICAL VAPOUR DEPOSITION (CCVD) METHOD"
Abstract	The present invention relates to a method for the synthesis of double helical carbon microcoils by catalytic chemical vapour deposition (CCVD). The method disclosed herein induces coiled configuration in the absence of magnetic field by using thiophene as promoter. In particular aspect the present invention provides double helical carbon microcoils (DHCMCs).

Full Text	TITLE: A Process for the Synthesis of Double Helical Carbon Microcoiled by Catalytic Chemical Vapour Deposition (CCVD) Method FIELD OF INVENTION: The disclosure relates to a method for the synthesis of helical carbon microcoils by catalytic chemical vapour deposition (CCVD). More specifically, the disclosure relates to a method for the synthesis of double helical carbon microcoils (DHCMCs) using CCVD method. The method disclosed herein induces coiled configuration in the absence of magnetic field by using thiophene as promoter. The term 'Carbon nanofibres (CNFs)' summarizes a large family of different filamentous nanocarbons. They could be either well graphitic or amorphous depending on their crystalline aspects. They also could be either solid tubular or hollow tubular. But in general way, all of them consist of either sp3 or sp2 or both sp3 / sp2 forms of carbons. However, irrespective of their crystalline aspects, all types of CNFs are very good candidates for fiber reinforcement applications, as electrically conducting fillers, catalyst support and electrochemical energy storage matrices (in particular for gas storage applications), With the development of nanomaterial based technologies, carbon coils of nanometer-scale size or carbon nanocoils (CNCs) are required in the fabrication of nanodevices such as a generator or detector of magnetic field, an inductive circuit, an actuator, a spring etc. Materials with 3D-helical / spiral structure have attracted more and more interests in recent years. Such a structure is expected to have new and unique functional properties. Researchers have been trying to synthesize 3D helical materials and explore their mechanism of formation, nature, morphological features and properties of these materials. It is also expected that these 3D helical / spiral materials could have wide potential applications in near future. Three dimensional carbon coils are very fascinating materials regarding their peculiar helical morphology, which can be used as high performance electromagnetic Many efforts have been made for the synthesis and property study of carbon coils of micron size, which are also called carbon micro coils (CMCs). The formation of CMCs and their morphology have been described in a number of papers. They are synthesized by the high temperature catalytic decomposition of hydrocarbons on finely divided metallic catalysts such as Fe, Co, Ni or their alloys. Motojima et al. [Ij also reported the synthesis of double helical carbon microcoils using fine Ni powder as catalysts via CCVD route with acetylene as carbon source. It should be noted that Motojima et al. [1] got the coiled morphology in presence of magnetic field in the reaction zone. Pan and coworkers [2] have used iron-coated indium tin oxide as catalyst and acetylene as hydrocarbon source via CCVD route at 700oC. It has been found that iron plays an important role for tube morphology while indium, tin and oxygen play major role for coiled morphology. Varadan et al \|3] also have reported the synthesis of carbon coiled nano/micro fiber by microwave CVD route. Double helical microcoils find applications in electronic devices, electromagnetic absorbers and filters. In addition, smart devices can be conceived using tunable films on these fibers and tunable host materials. SUMMARY OF THE INVENTION: An object of the present disclosure is to provide a method for the synthesis of Carbon double helical microcoils by catalyst chemical vapour deposition (CCVD). The method makes possible the synthesis of DHCMCs at large scale and in an easier way. Another object of the present disclosure is to synthesize DHCMCs in the absence of magnetic field by using thiophene as a coiling inducer. An aspect of the present invention provides a method of synthesizing double helical carbon microcoils in the absence of magnetic field by using thiophene, wherein the method comprises: introducing a mixture of catalyst and thiophene in a reactor; supplying nitrogen gas over the above mixture; supplying hydrocarbon gas over the above; heating the above to generate double helical carbon microcoils. In a particular aspect the present disclosure provides double helical carbon microcoils. The DHCMCs of the present disclosure are amorphous in nature and their diameter depends on the diameter distribution of the catalyst used in the method of their production. BRIEF DESCRIPTION OF THE DRAWINGS: FIGURE 1: Schematic Diagram of the electrically heated horizontal CCVD reactor FIGURE 2: Magnified view of the double helical carbon microcoils at 2000x magnification. FIGURE 3: Magnified view of the double helical carbon microcoils at 16000x magnification. DESCRIPTION OF THE INVENTION While the present disclosure has been particularly described herein with reference to embodiments thereof, the embodiments mentioned below of the present invention are for illustrative purposes and are not intended to limit the scope of the invention. In the present invention, the terms double helical carbon microcoils (DHCMCs) is used as a comprehensive meaning to include various kinds of DHCMCs, for example, hollow tubular, solid tubular. The DHCMCs may also be graphitic or amorphous depending on their crystalline aspects. The present invention discloses a method of synthesizing double helical carbon microcoils by Catalytic Chemical Vapour Deposition, wherein the method comprises: introducing a mixture of catalyst and thiophene in a reactor; supplying nitrogen gas over the above mixture; supplying hydrocarbon gas over the above mixture; heating the above to generate carbon microcoils. The method of the present disclosure is easier to perform and can be utilized for the synthesis of DHCMCs on a larger scale. The double helical microcoiled carbon fiber could be an interesting and useful material in many applications such as EM wave absorbers, tunable micro devices, electron emitters, hydrogen storage materials, chiral materials etc. The method provided in the present disclosure relates to the synthesis of the DHCMCs by CCVD route without using magnetic field in the reaction chamber. In particular, the present disclosure relates to a method of synthesizing DHCMCs, wherein the double helical configuration of the carbon microcoils is induced by anisotropy. The anisotropy in the method as disclosed in the present invention is achieved in the absence of magnetic field in the reaction chamber / reactor. The method to synthesis DHCMCs encompasses simple procedure, wherein the raw materials comprise Catalyst, Source of Sulphur, Carbon Source gas, Nitrogen gas and Ceramic boat. The reaction is carried out in a horizontal furnace inside which the temperature gradient is maintained, regulated and measured accurately by thermocouples. Depending on the reaction requirements, the temperature inside the furnace is maintained selectively and locally, differing at the entrance point, centre of the furnace and right of the furnace. Further, the method for synthesizing carbon microcoils comprises mixing catalyst and sulphur source in the quartz boat to obtain a semi solid mass; exposing the semisolid mass to high temperature in the central zone of reaction reactor; supplying nitrogen gas in the reactor at a flow rate which is gradually increased after about 30 minutes; starting the flow of carbon source gas simultaneously with the increase in flow of nitrogen gas; simultaneously stopping the flow of carbon source gas and lowering down the flow of nitrogen gas; collecting the black powder which gets deposited at the surface of the existing catalyst particles. (Refer Figure 1 for details) In an embodiment the disclosure provides a method of synthesizing DHCMCs by CCVD, wherein the method comprises: introducing a mixture of catalyst and thiophene in a reactor; supplying nitrogen gas over the above mixture; supplying hydrocarbon gas over the above; heating the above to generate DHCMCs. In a preferred embodiment the method described in the present disclosure provides DHCMCs of 1-5 microns diameter. However, it may be noted that the diameter distribution of the microcoils will depend on the diameter distribution of catalyst particles. In yet another embodiment of the present disclosure the method described utilizes catalyst which is a transition metal, a transition metal salt or a metal alloy or a compound containing a transition metal. In still another embodiment the transition metal is selected from a group consisting of iron, nickel and cobalt, tungsten and titanium In still another embodiment of the present disclosure the method disclosed utilizes nickel as catalyst. The size of the Nickel particle used as catalyst ranges from I microns to 5 microns. As stated earlier the diameter distribution of double helical carbon micro-coils will depend on the diameter distribution of catalyst particles. Since the catalyst particles (in the present case Ni powders) have the diameter distribution of 1-5 microns so the synthesized double helical carbon microcoils have almost the same diameter distribution as that of catalyst powders. In yet another embodiment of the present disclosure Nickel is provided at the concentration of 0.15gm per ml of thiophene. It should be noted that in absence of thiophene, straight carbon fiber has been obtained during synthesis as observed under SHM (Table I). It has been already proposed that the driving force behind the coiling factor is the presence of catalytic anisotropy between the crystal faces of the catalyst grain. This catalytic anisotropy is caused by the differing chemical compositions of the crystal faces. Motojima et al. [1 j has achieved this anisotropy by applying a magnetic field in the reaction zone although he used Ni powder as catalyst. Ni metal exhibits ferromagnetism with a Curie temperature of 358°C. This suggests that Ni metal is paramagnetic with a weak magnetic susceptibility at the reaction temperature. In an illustration the catalyst is provided in the form of powder with particle size of diameter in the range of 1-5 microns. Yet another embodiment of the present disclosure relates to the method of synthesizing DHCMCs, wherein the method utilizes nitrogen gas supply at the flow rate in the range of 10 ml/min to 500 ml/min. In preferred embodiment, nitrogen gas is supplied at the flow rate of 100 ml/min and continued for till the reaction temperature had reached. Then the flow of nitrogen gas has been increased up to 200ml/min. Still another embodiment of the present disclosure provides a method of synthesizing DHCMCs, wherein the method utilizes hydrocarbon gas as a carbon source gas selected from a group comprising of propane, acetylene, ethylene, methane and benzene. Yet another embodiment of the present disclosure relates to the method of synthesizing DHCMCs, wherein the method utilizes hydrocarbon supply at the flow rate of 10 ml/min to 1000 ml/min. In preferred embodiment the flow rate of acetylene is started when the flow rate of nitrogen gas is increased from 100 ml/min to 200 ml/min. In preferred embodiment the hydrocarbon is acetylene. In a particular embodiment the present disclosure provides double helical carbon microcoils. The DHCMCs of the present disclosure are amorphous in nature and their diameter depends on the diameter distribution of the catalyst used in the method of their production. Figure 2 shows the magnified view of the double helix microcoiled carbon fiber. . It should be noted that in absence of thiophene, straight carbon fiber has been obtained during synthesis as observed under SHM. It should be noted that when thiophene vapour has been passed in combination with hydrogen and acetylene, the product is single helical carbon micro coiled structure as revealed by electron microscopy analysis. Figure 3 (a and b) and Figure 4 (a and b) shows the magnified view of the double helical carbon microcoils observed under electron microscope (SEM) As already known regarding the growth of carbon nanotubes (CNTs) - the same could be extended in the present case too. The growth of CMCs has been started by the decomposition of precursor gas molecules and subsequent deposition of the resulting carbon radicals on the surface of the existing catalyst particles at that particular reaction temperature. This is followed by the growth of the CMCs having almost the same diameter distribution of originating catalysts particles. Thiophene after getting pyrolysed in the reaction zone of the reactor gives rise to fine sulphur powder. It should be noted that these sulphur particles have been formed in situ and are in highly reactive state similar to Ni powders -present at the reaction temperature. This may lead to a possible chemical / physical absorption / alloy formation between Ni particles and chemical species (here sulphur particles). Hence a chemical reaction based on the diffusion of solid particles occurs on the catalyst surface - leading to the proposed catalytic anisotropy on the crystal faces of the catalyst grains. Depending on the degree of the anisotropy (which depends on the degree of in situ reactions/combinations between Ni particles and sulphur particles) the coil diameters also vary. Larger the anisotrophy, smaller is the diameter and vice versa which also reflect on the difference in morphology as observed in the coiled structure. it should be noted that when thiophene vapour has been passed in combination with hydrogen and acetylene, the product is single helical carbon micro coiled structure as revealed by SEM images. But when liquid thiophene has been mixed with Ni powder and synthesis has been performed in presence of acetylene and nitrogen but in absence of hydrogen, DHCMCs have been obtained. Figure 2 and Figure 3 shows the magnified view of the double helical carbon microcoils. The double helical configuration can be attributed here to thiophene vapour. The thiophene vapour upon decomposition at high temperature results in highly activated sulphur powder on the surface of the catalyst. Since the sulphur powder is directly in touch with Ni powder and because of generation of above mentioned catalytic anisotropy at higher rate, DHCMCs have been formed. However, when thiophene vapour has been used along with acetylene, hydrogen and nitrogen gas, the generation and attachment of highly activated sulphur particles with Ni particles is less because thiophene vapour competes with acetylene, hydrogen and nitrogen vapour and as a result the resulting catalytic anisotropy is much less, generating single helical carbon micro coiled. Synthesis of Double Helical Micro-Coils: The chemicals and raw materials used for the synthesis are as follows: • Micron sized Nickel powder (99.8%) • Thiophene (99+%) • Acetylene gas (99.9% pure) • Nitrogen gas (96% pure) • Quartz/Ceramic boat The schematic diagram of experimental set-up has been described in Figure 1. It consists of a meter long horizontal furnace which is the reactor having an inner diameter of 10cm. The temperature gradient maintained inside is regulated and measured precisely by three thermocouples. At the gas entrance point the temperature is 500°C. At the reactive center of the reactor the temperature is maintained in the range of 900°C. On the right hand corner near the gas outlet, the temperature is kept constant at 600°C. In the quart/, boat, 1.5 grams of micron sized nickel powder is thoroughly mixed with 10 ml of thiophene to get a semisolid mass. The boat containing the mass is placed in the central zone of the furnace where the temperature is maintained at 900°C. The flow of nitrogen (96% pure) is started at the flow rate of 100 ml/min and continued for 30 minutes. Then the flow of nitrogen gas is increased up to 200 ml/min and acetylene flow has been started at the flow rate of lOOtnl/min. The (low rates of nitrogen and acetylene have been measured by digital mass How controller. After 30 mins, the flow of acetylene has been switched oFfbut the furnace has been allowed to cool down to room temperature with nitrogen How at the rate 50 ml/min. The resulting black powder was collected and directly observed under microscope without carrying any further purification process. Figure 2 shows the magnified view of the double helix microcoiled carbon fiber. . It should be noted that in absence of thiophene, straight carbon fiber has been obtained during synthesis as observed under SEM. It should be noted that when thiophene vapour has been passed in combination with hydrogen and acetylene, the product is single helical carbon micro coiled structure as revealed by electron microscopy analysis. The above analysis indicates that the thiophene vapour is mainly responsible for coiling factor. It will be understood by those skilled in the art that advantageously, the overall process is simple and can be applied to mass-scale production at low costs. Relerences. \|l\| Ku/.uya C. Kohda M. Hishikawa Y. Motojima S. Preparation of carbon micro-coils with the application of outer and inner electromagnetic fields and bias voltage. Carbon 2002: 40: 1991-2001. (Table Removed)[21 Pan L, /hang M, Nakayama Y. Growth mechanism of carbon nanocoils. J Appl Phys 2002; 91:10058-61. \|3\| Varadan VK. Hollinger RD. Varadan VV. Xie J. Sharma PK. Development and characterization of micro-coil carbon fibers by a microwave CVD system. Smart Mater. Struct. 2000: 9:413 - 20. 1 / We claim: 1 A method of synthesizing double helical carbon microcoils in the absence of magnetic Held by using thiophene, wherein the method comprises introducing hydrocarbon gas over a mixture of catalyst and thiophene at a temperature in the range of 500 °C to 1000°C. 2 The method as claimed in claim I, wherein nitrogen gas is supplied before the introduction of hydrocarbon gas. 3 The method as claimed in claim 1, wherein the catalyst is provided at the concentration of about 0.05 to about 0.25gm per ml of thiophene. 4 The method of claim 1, wherein the catalyst is a transition metal, a transition metal salt or a metal alloy or a compound containing a transition metal. 5 The method of claim 4, wherein the transition metal is selected from a group consisting of iron, nickel, cobalt and tungsten. 6 The method as claimed in claim 1, wherein the nitrogen gas is supplied/provided at the (low rale of 10 ml / min - 500 ml/min 7. The method as claimed in claim 1, wherein the hydrocarbon gas is provided/supplied at the flow rate of 10 ml/min - 1000 ml/min 8. The method as claimed in claim 1, wherein the hydrocarbon gas is selected from a group consisting of propane, acetylene, ethylene, benzene and methane. 9. The method as claimed in claim 8, wherein the hydrocarbon gas is acetylene. 10 Double helical carbon microcoils produced by the method as claimed in claim 1.

Full Text

TITLE: A Process for the Synthesis of Double Helical Carbon Microcoiled by Catalytic Chemical Vapour Deposition (CCVD) Method
FIELD OF INVENTION:
The disclosure relates to a method for the synthesis of helical carbon microcoils by catalytic chemical vapour deposition (CCVD). More specifically, the disclosure relates to a method for the synthesis of double helical carbon microcoils (DHCMCs) using CCVD method. The method disclosed herein induces coiled configuration in the absence of magnetic field by using thiophene as promoter.
The term 'Carbon nanofibres (CNFs)' summarizes a large family of different filamentous nanocarbons. They could be either well graphitic or amorphous depending on their crystalline aspects. They also could be either solid tubular or hollow tubular. But in general way, all of them consist of either sp3 or sp2 or both sp3 / sp2 forms of carbons. However, irrespective of their crystalline aspects, all types of CNFs are very good candidates for fiber reinforcement applications, as electrically conducting fillers, catalyst support and electrochemical energy storage matrices (in particular for gas storage applications), With the development of nanomaterial based technologies, carbon coils of nanometer-scale size or carbon nanocoils (CNCs) are required in the fabrication of nanodevices such as a generator or detector of magnetic field, an inductive circuit, an actuator, a spring etc.
Materials with 3D-helical / spiral structure have attracted more and more interests in recent years. Such a structure is expected to have new and unique functional properties. Researchers have been trying to synthesize 3D helical materials and explore their mechanism of formation, nature, morphological features and properties of these materials. It is also expected that these 3D helical / spiral materials could have wide potential applications in near future. Three dimensional carbon coils are very fascinating materials regarding their peculiar helical morphology, which can be used as high performance electromagnetic

Many efforts have been made for the synthesis and property study of carbon coils of micron size, which are also called carbon micro coils (CMCs).
The formation of CMCs and their morphology have been described in a number of papers. They are synthesized by the high temperature catalytic decomposition of hydrocarbons on finely divided metallic catalysts such as Fe, Co, Ni or their alloys.
Motojima et al. [Ij also reported the synthesis of double helical carbon microcoils using fine Ni powder as catalysts via CCVD route with acetylene as carbon source. It should be noted that Motojima et al. [1] got the coiled morphology in presence of magnetic field in the reaction zone.
Pan and coworkers [2] have used iron-coated indium tin oxide as catalyst and acetylene as hydrocarbon source via CCVD route at 700oC. It has been found that iron plays an important role for tube morphology while indium, tin and oxygen play major role for coiled morphology.
Varadan et al |3] also have reported the synthesis of carbon coiled nano/micro fiber by microwave CVD route.
Double helical microcoils find applications in electronic devices, electromagnetic absorbers and filters. In addition, smart devices can be conceived using tunable films on these fibers and tunable host materials.
SUMMARY OF THE INVENTION:
An object of the present disclosure is to provide a method for the synthesis of Carbon double helical microcoils by catalyst chemical vapour deposition (CCVD). The method makes possible the synthesis of DHCMCs at large scale and in an easier way. Another object of the present disclosure is to synthesize DHCMCs in the absence of magnetic field by using thiophene as a coiling inducer.
An aspect of the present invention provides a method of synthesizing double helical carbon microcoils in the absence of magnetic field by using thiophene, wherein the method comprises: introducing a mixture of catalyst and thiophene in a reactor; supplying nitrogen gas over the above mixture; supplying

hydrocarbon gas over the above; heating the above to generate double helical carbon microcoils.
In a particular aspect the present disclosure provides double helical carbon microcoils. The DHCMCs of the present disclosure are amorphous in nature and their diameter depends on the diameter distribution of the catalyst used in the method of their production.
BRIEF DESCRIPTION OF THE DRAWINGS:
FIGURE 1: Schematic Diagram of the electrically heated horizontal CCVD reactor
FIGURE 2: Magnified view of the double helical carbon microcoils at 2000x magnification.
FIGURE 3: Magnified view of the double helical carbon microcoils at 16000x magnification.
DESCRIPTION OF THE INVENTION
While the present disclosure has been particularly described herein with reference to embodiments thereof, the embodiments mentioned below of the present invention are for illustrative purposes and are not intended to limit the scope of the invention.
In the present invention, the terms double helical carbon microcoils (DHCMCs) is used as a comprehensive meaning to include various kinds of DHCMCs, for example, hollow tubular, solid tubular. The DHCMCs may also be graphitic or amorphous depending on their crystalline aspects.
The present invention discloses a method of synthesizing double helical carbon microcoils by Catalytic Chemical Vapour Deposition, wherein the method comprises: introducing a mixture of catalyst and thiophene in a reactor; supplying nitrogen gas over the above mixture; supplying hydrocarbon gas over the above mixture; heating the above to generate carbon microcoils.

The method of the present disclosure is easier to perform and can be utilized for the synthesis of DHCMCs on a larger scale.
The double helical microcoiled carbon fiber could be an interesting and useful material in many applications such as EM wave absorbers, tunable micro devices, electron emitters, hydrogen storage materials, chiral materials etc.
The method provided in the present disclosure relates to the synthesis of the DHCMCs by CCVD route without using magnetic field in the reaction chamber.
In particular, the present disclosure relates to a method of synthesizing DHCMCs, wherein the double helical configuration of the carbon microcoils is induced by anisotropy. The anisotropy in the method as disclosed in the present invention is achieved in the absence of magnetic field in the reaction chamber / reactor.
The method to synthesis DHCMCs encompasses simple procedure, wherein the raw materials comprise Catalyst, Source of Sulphur, Carbon Source gas, Nitrogen gas and Ceramic boat.
The reaction is carried out in a horizontal furnace inside which the temperature gradient is maintained, regulated and measured accurately by thermocouples. Depending on the reaction requirements, the temperature inside the furnace is maintained selectively and locally, differing at the entrance point, centre of the furnace and right of the furnace.
Further, the method for synthesizing carbon microcoils comprises mixing catalyst and sulphur source in the quartz boat to obtain a semi solid mass; exposing the semisolid mass to high temperature in the central zone of reaction reactor; supplying nitrogen gas in the reactor at a flow rate which is gradually increased after about 30 minutes; starting the flow of carbon source gas simultaneously with the increase in flow of nitrogen gas; simultaneously stopping the flow of carbon source gas and lowering down the flow of nitrogen gas; collecting the black powder which gets deposited at the surface of the existing catalyst particles. (Refer Figure 1 for details)

In an embodiment the disclosure provides a method of synthesizing DHCMCs by CCVD, wherein the method comprises: introducing a mixture of catalyst and thiophene in a reactor; supplying nitrogen gas over the above mixture; supplying hydrocarbon gas over the above; heating the above to generate DHCMCs.
In a preferred embodiment the method described in the present disclosure provides DHCMCs of 1-5 microns diameter. However, it may be noted that the diameter distribution of the microcoils will depend on the diameter distribution of catalyst particles.
In yet another embodiment of the present disclosure the method described utilizes catalyst which is a transition metal, a transition metal salt or a metal alloy or a compound containing a transition metal.
In still another embodiment the transition metal is selected from a group consisting of iron, nickel and cobalt, tungsten and titanium
In still another embodiment of the present disclosure the method disclosed utilizes nickel as catalyst.
The size of the Nickel particle used as catalyst ranges from I microns to 5 microns. As stated earlier the diameter distribution of double helical carbon micro-coils will depend on the diameter distribution of catalyst particles. Since the catalyst particles (in the present case Ni powders) have the diameter distribution of 1-5 microns so the synthesized double helical carbon microcoils have almost the same diameter distribution as that of catalyst powders.
In yet another embodiment of the present disclosure Nickel is provided at the concentration of 0.15gm per ml of thiophene. It should be noted that in absence of thiophene, straight carbon fiber has been obtained during synthesis as observed under SHM (Table I). It has been already proposed that the driving force behind the coiling factor is the presence of catalytic anisotropy between the crystal faces of the catalyst grain. This catalytic anisotropy is caused by the differing chemical compositions of the crystal faces. Motojima et al. [1 j has achieved this anisotropy by applying a magnetic field in the reaction zone although he used Ni powder as

catalyst. Ni metal exhibits ferromagnetism with a Curie temperature of 358°C. This suggests that Ni metal is paramagnetic with a weak magnetic susceptibility at the reaction temperature.
In an illustration the catalyst is provided in the form of powder with particle size of diameter in the range of 1-5 microns.
Yet another embodiment of the present disclosure relates to the method of synthesizing DHCMCs, wherein the method utilizes nitrogen gas supply at the flow rate in the range of 10 ml/min to 500 ml/min. In preferred embodiment, nitrogen gas is supplied at the flow rate of 100 ml/min and continued for till the reaction temperature had reached. Then the flow of nitrogen gas has been increased up to 200ml/min.
Still another embodiment of the present disclosure provides a method of synthesizing DHCMCs, wherein the method utilizes hydrocarbon gas as a carbon source gas selected from a group comprising of propane, acetylene, ethylene, methane and benzene.
Yet another embodiment of the present disclosure relates to the method of synthesizing DHCMCs, wherein the method utilizes hydrocarbon supply at the flow rate of 10 ml/min to 1000 ml/min. In preferred embodiment the flow rate of acetylene is started when the flow rate of nitrogen gas is increased from 100 ml/min to 200 ml/min. In preferred embodiment the hydrocarbon is acetylene.
In a particular embodiment the present disclosure provides double helical carbon microcoils. The DHCMCs of the present disclosure are amorphous in nature and their diameter depends on the diameter distribution of the catalyst used in the method of their production. Figure 2 shows the magnified view of the double helix microcoiled carbon fiber. . It should be noted that in absence of thiophene, straight carbon fiber has been obtained during synthesis as observed under SHM. It should be noted that when thiophene vapour has been passed in combination with hydrogen and acetylene, the product is single helical carbon micro coiled structure as revealed by electron microscopy analysis. Figure 3 (a

and b) and Figure 4 (a and b) shows the magnified view of the double helical carbon microcoils observed under electron microscope (SEM)
As already known regarding the growth of carbon nanotubes (CNTs) - the same could be extended in the present case too. The growth of CMCs has been started by the decomposition of precursor gas molecules and subsequent deposition of the resulting carbon radicals on the surface of the existing catalyst particles at that particular reaction temperature. This is followed by the growth of the CMCs having almost the same diameter distribution of originating catalysts particles.
Thiophene after getting pyrolysed in the reaction zone of the reactor gives rise to fine sulphur powder. It should be noted that these sulphur particles have been formed in situ and are in highly reactive state similar to Ni powders -present at the reaction temperature. This may lead to a possible chemical / physical absorption / alloy formation between Ni particles and chemical species (here sulphur particles). Hence a chemical reaction based on the diffusion of solid particles occurs on the catalyst surface - leading to the proposed catalytic anisotropy on the crystal faces of the catalyst grains. Depending on the degree of the anisotropy (which depends on the degree of in situ reactions/combinations between Ni particles and sulphur particles) the coil diameters also vary. Larger the anisotrophy, smaller is the diameter and vice versa which also reflect on the difference in morphology as observed in the coiled structure.
it should be noted that when thiophene vapour has been passed in combination with hydrogen and acetylene, the product is single helical carbon micro coiled structure as revealed by SEM images. But when liquid thiophene has been mixed with Ni powder and synthesis has been performed in presence of acetylene and nitrogen but in absence of hydrogen, DHCMCs have been obtained. Figure 2 and Figure 3 shows the magnified view of the double helical carbon microcoils. The double helical configuration can be attributed here to thiophene vapour. The thiophene vapour upon decomposition at high temperature results in highly activated sulphur powder on the surface of the catalyst. Since the sulphur powder is directly in touch with Ni powder and because of generation of above

mentioned catalytic anisotropy at higher rate, DHCMCs have been formed. However, when thiophene vapour has been used along with acetylene, hydrogen and nitrogen gas, the generation and attachment of highly activated sulphur particles with Ni particles is less because thiophene vapour competes with acetylene, hydrogen and nitrogen vapour and as a result the resulting catalytic anisotropy is much less, generating single helical carbon micro coiled.
Synthesis of Double Helical Micro-Coils: The chemicals and raw materials used for the synthesis are as follows:
• Micron sized Nickel powder (99.8%)
• Thiophene (99+%)
• Acetylene gas (99.9% pure)
• Nitrogen gas (96% pure)
• Quartz/Ceramic boat
The schematic diagram of experimental set-up has been described in Figure 1. It consists of a meter long horizontal furnace which is the reactor having an inner diameter of 10cm. The temperature gradient maintained inside is regulated and measured precisely by three thermocouples. At the gas entrance point the temperature is 500°C. At the reactive center of the reactor the temperature is maintained in the range of 900°C. On the right hand corner near the gas outlet, the temperature is kept constant at 600°C.
In the quart/, boat, 1.5 grams of micron sized nickel powder is thoroughly mixed with 10 ml of thiophene to get a semisolid mass. The boat containing the mass is placed in the central zone of the furnace where the temperature is maintained at 900°C. The flow of nitrogen (96% pure) is started at the flow rate of 100 ml/min and continued for 30 minutes. Then the flow of nitrogen gas is increased up to 200 ml/min and acetylene flow has been started at the flow rate of lOOtnl/min. The (low rates of nitrogen and acetylene have been measured by digital mass How controller. After 30 mins, the flow of acetylene has been

switched oFfbut the furnace has been allowed to cool down to room temperature with nitrogen How at the rate 50 ml/min. The resulting black powder was collected and directly observed under microscope without carrying any further purification process. Figure 2 shows the magnified view of the double helix microcoiled carbon fiber. . It should be noted that in absence of thiophene, straight carbon fiber has been obtained during synthesis as observed under SEM. It should be noted that when thiophene vapour has been passed in combination with hydrogen and acetylene, the product is single helical carbon micro coiled structure as revealed by electron microscopy analysis.
The above analysis indicates that the thiophene vapour is mainly responsible for coiling factor.

It will be understood by those skilled in the art that advantageously, the overall process is simple and can be applied to mass-scale production at low costs.
Relerences.
|l| Ku/.uya C. Kohda M. Hishikawa Y. Motojima S. Preparation of carbon micro-coils with the application of outer and inner electromagnetic fields and bias voltage. Carbon 2002: 40: 1991-2001.
(Table Removed)[21 Pan L, /hang M, Nakayama Y. Growth mechanism of carbon nanocoils. J Appl Phys 2002; 91:10058-61.
|3| Varadan VK. Hollinger RD. Varadan VV. Xie J. Sharma PK. Development and characterization of micro-coil carbon fibers by a microwave CVD system. Smart Mater. Struct. 2000: 9:413 - 20.

1 / We claim:
1 A method of synthesizing double helical carbon microcoils in the absence of
magnetic Held by using thiophene, wherein the method comprises introducing
hydrocarbon gas over a mixture of catalyst and thiophene at a temperature in the
range of 500 °C to 1000°C.
2 The method as claimed in claim I, wherein nitrogen gas is supplied before the
introduction of hydrocarbon gas.
3 The method as claimed in claim 1, wherein the catalyst is provided at the
concentration of about 0.05 to about 0.25gm per ml of thiophene.
4 The method of claim 1, wherein the catalyst is a transition metal, a transition
metal salt or a metal alloy or a compound containing a transition metal.
5 The method of claim 4, wherein the transition metal is selected from a group
consisting of iron, nickel, cobalt and tungsten.
6 The method as claimed in claim 1, wherein the nitrogen gas is supplied/provided
at the (low rale of 10 ml / min - 500 ml/min

7. The method as claimed in claim 1, wherein the hydrocarbon gas is
provided/supplied at the flow rate of 10 ml/min - 1000 ml/min
8. The method as claimed in claim 1, wherein the hydrocarbon gas is selected from
a group consisting of propane, acetylene, ethylene, benzene and methane.
9. The method as claimed in claim 8, wherein the hydrocarbon gas is acetylene.
10 Double helical carbon microcoils produced by the method as claimed in claim 1.

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Patent Number

268800

Indian Patent Application Number

188/DEL/2007

PG Journal Number

38/2015

Publication Date

18-Sep-2015

Grant Date

17-Sep-2015

Date of Filing

31-Jan-2007

Name of Patentee

DIRECTOR GENERAL, DEFENCE RESEARCH & DEVELOPMENT ORGANISATION

Applicant Address

MINISTRY OF DEFENCE, GOVT OF INDIA ROOM NO 348, B-WING DRDO, RAJAJI MARG, NEW DELHI 110011

Inventors:

#	Inventor's Name	Inventor's Address
1	KINGSUK MUKHOPADHYAY	DEFENCE MATERIALS & GOVT. OF INDIA, ROOM NO 348, B-WING DRDO, RAJAJI MARG, NEW DELHI-110011
2	KONDEPUDI UDAYA BHASKER	DEFENCE MATERIALS & GOVT. OF INDIA, ROOM NO 348, B-WING DRDO, RAJAJI MARG, NEW DELHI-110011

PCT International Classification Number

C01B 31/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA