DESC:TECHNICAL FIELD
The present disclosure relates to the field of carbon materials and polymer composites. The disclosure particularly relates to carbon material and corresponding composite materials, their preparations and various applications thereof such as attenuation/shielding of electromagnetic radiations, and desalination or purification of water. The disclosure also relates to articles or devices comprising the carbon material capable of shielding electromagnetic radiations.

BACKGROUND OF THE DISCLOSURE
The world has been ruled by automation, wireless communications and use of various electronic equipment in miniaturized forms, which has led to the most unwanted offshoots like electromagnetic (EM) pollution. EM radiation is increasing day by day as more utilities/equipment are moving up in the EM spectrum towards higher frequency. The need to protect sophisticated electronics from nearby devices has also become very important as they directly interfere with the device’s reliability and performance. Particularly, EM radiation results in unwanted damage to the surrounding devices resulting in their malfunctioning and in addition affecting human health. Conventionally, for EM wave absorption, the industrial practice is to use metal plated/painted sheets to encapsulate precise electronics. Off-late, given the surge in wearable electronics, plastics have replaced metals as the primary/core build for electronics because of their corrosion free and light-weight nature. However, plastics are transparent to electromagnetic (EM) shielding and hence modifications become very important to meet the desired EM shielding targets. Towards the same, in the recent times, plastic based composites containing heavy loading of conducting particles have been explored. However, the problem with these composites is lack of creating complex patterns, difficulty in processability and poor shelf life.

Thus, exploring high-efficiency electromagnetic shielding materials thereby preventing electromagnetic wave pollution/leakage to protect the environment and human health has become an inevitable need in the society. Particularly, there is an utmost need for electromagnetic shielding materials that meet key attributes such as light weight, flexibility, durability, easy processability, economical, easy to adapt-integrate-process, industrial scalability and improved efficiency in electromagnetic shielding performance.

Further, over 97% of the water on earth is unsuitable for human consumption due to its salinity. The vast majority of this is seawater, with most of the remainder consisting of saline groundwater. Purification of this sea water holds great promise as water resource for human civilization and also for other industrial/commercial processes. However, desalination/purification of seawater is expensive, energy intensive and often has large adverse impacts on ecosystems. Thus, there is a dire need for simple, efficient, and eco-friendly material and method for desalination/purification of water, particularly, sea water.

The present disclosure tries to address the aforesaid needs.

SUMMARY OF THE DISCLOSURE
The present disclosure relates to carbon fibre unit or urchin of carbon fibres. More particularly, the present disclosure provides a carbon fibre unit comprising a carbon fibre core and a plurality of carbon fibres in a form of globular needles protruding out from the carbon fibre core, wherein diameter of each of the globular needle is in the range of about 5 µm to about 10 µm, wherein length of each of the globular needle is in the range of about 500 µm to about 1000 µm, and wherein the carbon fibre unit is in a shape of sea-urchin.

In some embodiments of the present disclosure, the carbon fibre unit comprises plurality of carbon fibres as an assembly or collection or network of long globular needles/spines/whiskers.

In some embodiments of the present disclosure, the globular needles protrude out from the core in all directions to form an assembly of the globular needles.

In some embodiments of the present disclosure, the plurality of carbon fibre units comprises an assembly of multiple units of carbon fibre units.

In some embodiments of the present disclosure, mass of each urchin of carbon fibres ranges from about 0.3 milligram (mg) to 25 mg, including all values and ranges therefrom.

The present disclosure further relates to a method of preparing the urchin of carbon fibres described above. In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises subjecting urchin of carbon fibres to a refluxing reaction in the presence of a solvent, and pH of the reflux reaction ranges from about 1 to 14.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprising a carbon fibre core and a plurality of carbon fibres in a form of globular needles protruding out from the carbon fibre core, the method comprising subjecting carbon fibres to a refluxing reaction in the presence of a solvent, and pH of the reflux reaction ranges from about 1 to 14.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the carbon fibres are selected from chopped carbon fibres, carbon fibre mat, carbon fibre woven fabric or knit, carbon fibre spun yarn, or any combinations thereof.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the chopped carbon fibres have an average diameter of about 5 to 7 µm and a length of about 5 mm to 6 mm.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the solvent is a polar solvent.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the solvent is water or alcohol.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
a) providing a reactant mixture in a reflux apparatus, wherein the reactant mixture comprises chopped carbon fibres and an aqueous solution which maintains a pH between 1-14,
wherein the aqueous solution is an acid solution, alkali solution, salt solution, sea water, or deionised (DI) water, or any combination thereof; and
b) refluxing the reactant mixture in presence of the polar solvent at a temperature ranging from about 50? to about 180? for a time-period ranging from about 2 hours to about 48 hours, to obtain carbon fibre units, and
wherein the polar solvent is selected from a group comprising water or ethanol.

The present disclosure also relates to a composite material comprising a polymer matrix and urchins of carbon fibres.

In some embodiments of the present composite material, the composite comprises a polymer matrix and a plurality of urchins of carbon fibres, wherein each of the unit of urchin of carbon fibre comprises a carbon fibre core and a plurality of carbon fibres in a form of globular needles protruding out from the carbon fibre core.

In some embodiments of the present composite material, the polymer matrix is made up of a thermosetting polymer, a thermoplastic polymer, or a combination there. In some embodiments of the composite material, the polymer matrix is in an amount ranging from about 93 wt% to 97 wt%, including all values and ranges therefrom.

In some embodiments of the composite material, the urchins of carbon fibres is in an amount ranging from about 3 wt% to 7 wt%, including all values and ranges therefrom.

In some embodiments of the present disclosure, the composite material demonstrates enhanced electromagnetic (EM) radiation shielding capacity (total shielding effectiveness) ranging from about -15 dB to -60 dB over entire Ku Band (12-18 GHz) and X band (8-12 GHz) having frequency ranging from about 8 GHz to 18 GHz.

The present disclosure also relates to a method of preparing the composite material comprising the polymer matrix and the urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the composite material comprising the polymer matrix and the urchins of carbon fibres, comprises mixing the urchins and the polymer matrix to obtain the composite material.

In some embodiments of the present disclosure, the curing is performed at a temperature ranging from about 50? to 200? for a time-period ranging from about 1 hour to 5 hours.

The present disclosure further relates to an article comprising the urchins of carbon fibres or the plurality of urchins of carbon fibres or the composite material described above.

The present disclosure also relates to use of the carbon urchins, the plurality of urchins of carbon fibres, the composite material or the article comprising the composite material described above.

The present disclosure further relates to a method for shielding of electromagnetic (EM) radiation, said method comprises contacting the electromagnetic (EM) radiation with the urchin of carbon fibres or the plurality of urchins of carbon fibres or the composite material as described above.

The present disclosure also provides a method of purifying water comprising the step of contacting the urchin of carbon fibres or the plurality of urchins of carbon fibres described herein with the water, to obtain purified water.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
In order that the present disclosure may be readily understood 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, where:

Figure 1 represents urchin product of the present disclosure. Figure 1A: a single urchin unit comprising carbon fibres structurally existing in a sea-urchin like structure; Figures 1B-D: various SEM images of urchins.

Figure 2 illustrates a representative method of preparing urchin of carbon fibres according to the present disclosure.

Figure 3 depicts: (a) SEM image of chopped carbon fibres, (b) SEM image of carbon urchins, and (c) various urchins obtained under different pH conditions.

Figure 4 illustrates the process and mechanism of formation of urchins of carbon fibres according to the present disclosure.

Figure 5 illustrates results of conductivity (AC, S/cm) and EM shielding effectiveness (SET, dB) of the composite material comprising epoxy polymer and urchins.

Figure 6 illustrates results of conductivity (AC, S/cm) and EM shielding effectiveness (SET, dB) of the composite material comprising EVA polymer and urchins.

Figure 7 illustrates epoxy based polymer composites. A: illustration of preparation of epoxy based polymer composites according to the present disclosure; B: digital photographs of the prepared epoxy based polymer composites.

Figure 8 illustrates digital photographs of the prepared EVA based polymer composites according to the present disclosure.

Figure 9 illustrates XRD pattern of the synthesized carbon urchins according to the present disclosure.

Figure 10 illustrates FTIR spectra of chopped carbon fibres (CF) and carbon urchins [acid and alkali].

Figure 11 illustrates EMI shielding effectiveness of carbon nanotubes (CNT) reinforced with ethylene-vinyl acetate (EVA) polymer.

DESCRIPTION OF THE DISCLOSURE
Unless otherwise defined, all terms used in the disclosure, including technical and scientific terms, have meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included for better understanding of the present disclosure.

As used herein, the singular forms ‘a’, ‘an’ and ‘the’ include both singular and plural referents unless the context clearly dictates otherwise.

The term ‘comprising’, ‘comprises’ or ‘comprised of’ as used herein are synonymous with ‘including’, ‘includes’, ‘containing’ or ‘contains’ and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps.

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

The term ‘about’ as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of ±10% or less, preferably ±5% or less, more preferably ±1% or less and still more preferably ±0.1% or less of and from the specified value, insofar such variations are appropriate to perform the present disclosure. It is to be understood that the value to which the modifier ‘about’ refers is itself also specifically, and preferably disclosed.

As used herein, the term/phrase ‘carbon fibre unit’, ‘carbon urchin’, ‘carbon fibre urchin’, ‘urchin’, ‘urchin of carbon fibres’, or ‘urchin-like structure’ are used interchangeably and means a product having carbon fibre core and an assembly of spiny and globular carbon fibres arising or protruding from the core to form a shape of urchin i.e., carbon fibres as a sea-urchin like structure having structural features/characteristics as described in this disclosure. In some embodiments of the present disclosure, carbon fibre units or urchins of carbon fibres is the product of the disclosure wherein said urchins are structurally and functionally distinguishable from other forms of carbon fibres including chopped carbon fibres or other conventionally known forms of carbon fibres.

As used herein, the term/phrase ‘carbon fibre unit’, ‘carbon urchin’, ‘carbon fibre urchin’, ‘urchin’, ‘urchin of carbon fibres’, or ‘urchin-like structure’ means a “single” unit.

As used herein, the term/phrase ‘carbon fibre units’, ‘carbon urchins’, ‘carbon fibre urchin’, ‘urchin’, ‘urchin of carbon fibres’, or ‘urchin-like structure’ means a “single” unit.

As used herein, the term ‘carbon fibres’ or ‘CFs’ are used interchangeably and refer to fibres composed substantially of carbon atoms, wherein said fibres have an average diameter of about 5 to 7 µm and a length of about 5 to 6 mm. In the context of the present disclosure, the carbon fibres are employed as raw materials/reactant to prepare the carbon urchin product described herein.

As used herein, the terms ‘shield’, ‘shielding’, ‘shielding effect’, ‘electromagnetic shielding’, ‘EM shielding’ or ‘electromagnetic shielding effect’ are used interchangeably and in the context of electromagnetic radiations, and refer to blocking or prevention of electromagnetic radiations from penetrating through carbon urchins, a composite material, an article or device exposed to them. In the context of the present disclosure, this shielding effect is provided by the carbon urchins or the composite material of the present disclosure.

As used herein, the terms ‘reflux’ or ‘refluxing’ or ‘refluxed’ are used interchangeably and generally refers to a process of heating a chemical reaction in a controlled manner, while continually cooling the vapour (for eg. by using a condenser) to ensure that the solvent doesn’t boil off. The vapours produced in the reaction continually undergo condensation, returning to the system as a condensate. This way, it is ensured that the temperature of the reaction remains constant. In the context of the present disclosure, the urchins of carbon fibres are prepared by reflux reaction.

As used herein, the term ‘sea water’ refers to the water from oceans and/or sea. In some embodiments, seawater is a complex mixture of about 96.5% water, about 2.5% salts, and smaller amounts of other substances, including dissolved inorganic and organic materials, particulates, and a few atmospheric gases.

As used herein, the term ‘deionized water’ or ‘DI water’ refers to water that has been treated to remove ions. In some embodiments, deionization removes dissolved particles such as salt (e.g. sodium chloride), minerals, carbon dioxide, organic contaminants, and other impurities from water.

An objective of the present disclosure is to develop effective and industrially scalable electromagnetic (EM) shielding materials.

Another objective of the present disclosure is to provide carbon fibres for preparation of polymer composite materials capable of shielding electromagnetic radiations.

Another objective of the present disclosure is to develop an efficient, cost-effective, eco-friendly, robust, and scalable method to produce carbon fibres.

Another objective of the present disclosure is to develop a simple and green process to produce carbon fibres that employ simple starting ingredients such as commercially available chopped carbon fibres and solvent.

Yet another objective of the present disclosure is to provide a polymer composite material comprising carbon fibres.

Another objective of the present disclosure is to provide a polymer composite material capable of shielding electromagnetic radiations.

Still another objective of the present disclosure is to develop a simple method of synthesis of polymer composite material comprising polymer and carbon fibres.

Another objective of the present disclosure is to provide article or device effective in shielding electromagnetic radiations.

Another objective of the present disclosure is to prepare carbon fibre material which can be employed in desalination/purification of water, such as sea water.

To achieve the aforesaid objectives, the present disclosure provides , effective and industrially scalable electromagnetic (EM) shielding materials. In particular, the present invention provides ‘urchin of carbon fibres’ or ‘carbon fibre unit’. Said urchin of carbon fibres are conducting materials and act as an EM shielding material which can be incorporated in various polymeric systems to design lightweight composites that can shield/block a wide spectrum of electromagnetic (EM) radiation.

Urchin(s) of carbon fibres or Carbon fibre unit(s)
The present disclosure relates to carbon fibre unit or urchin of carbon fibres. It is to be understood that the terms such as ‘carbon fibre unit’, ‘urchin of carbon fibres’, ‘carbon urchin’ and ‘urchin’ are used interchangeably in this disclosure and mean the same.

More particularly, the present disclosure provides a carbon fibre unit comprising a carbon fibre core and a plurality of carbon fibres in a form of globular needles protruding out from the carbon fibre core, wherein diameter of each of the globular needle is in the range of about 5 µm to about 10 µm, wherein length of each of the globular needle is in the range of about 500 µm to about 1000 µm, and wherein the carbon fibre unit is in a shape of sea-urchin.

In some embodiments of the present disclosure, the carbon fibre unit or urchin of carbon fibres are carbon fibres structurally existing in the shape or form of urchin. In some embodiments of the present disclosure, the urchin of carbon fibres are carbon fibres existing as a sea-urchin like structure.

In some embodiments of the present disclosure, the carbon fibre unit comprises plurality of carbon fibres as an assembly or collection or network of long globular needles/spines/whiskers protruding from the carbon fibre core. The terms ‘globular needles’, ‘spines’, ‘spikes’ and ‘whiskers’ have been used interchangeably throughout the specification.

In some embodiments of the present disclosure, the carbon fibre unit comprises plurality of carbon fibres as an assembly or collection or network of long globular needles/spines/whiskers in the shape or form of urchin.

In some embodiments of the present disclosure, the plurality of carbon fibres in the form of globular needles protrude out from the carbon fibre core in all directions to form an assembly of the globular needles.

In some embodiments of the present disclosure, the plurality of carbon fibres in the form of globular needles protrude out from the carbon fibre core in all directions and at all possible angles varying between 0o to 360 o to form an assembly of the globular needles. More particularly, the globular needles of the carbon urchin protrude out from the carbon fibre core in all directions and at all possible angles between 0o to 360 o to form an assembly or collection of the globular needles.

In some embodiments of the present disclosure, the carbon fibre unit comprises a single carbon fibre unit or multiple/plurality of carbon fibre units.

In some embodiments of the present disclosure, the carbon fibre unit or urchin of carbon fibres comprises a single urchin or unit. A representative single urchin or single carbon fibre unit is depicted in Figure 1A. As shown in Figure 1A, a single urchin unit comprises numerous needles/spines/whiskers. Each urchin unit comprises a carbon fibre core and numerous bristle-like spikes (needles/spines/whiskers) protruding out in all directions. The diameter of each spike ranges between 5 µm to 7 µm and the average length of each spike ranges between 550 µm to 700 µm. These needles are connected through inter-spine contacts and are structurally uniform. Highly dense and close packed spikes strongly hold each other through van der waals forces and thereby forming a sea-urchin like structure. Such close packing also helps in conducting and resulting in high EMI shielding. Additional scanning electron microscope (SEM) images of the needles forming the urchin structure are shown in Figures 1B and 1C, wherein Figure 1C shows clear and enlarged view of the needles forming the urchin structure.

In some embodiments of the present disclosure, each needle in the urchin of carbon fibres has an average diameter of about 5 µm to 10 µm, including all values and ranges therefrom.

In some embodiments of the present disclosure, each needle in the urchin of carbon fibres has an average diameter of about 5 µm to 7.7 µm, including all values and ranges therefrom.

In some embodiments of the present disclosure, each needle in the urchin of carbon fibres has an average diameter of about 6 µm to 8 µm, including all values and ranges therefrom.

In some embodiments of the present disclosure, each needle in the urchin of carbon fibres has an average diameter of about 6 µm to 7 µm, including all values and ranges therefrom.

In some embodiments of the present disclosure, each needle in the urchin of carbon fibres has an average diameter of about 5 µm, about 5.5 µm, about 6 µm, about 6.5 µm, about 7 µm, about 7.5 µm, about 7.7 µm, about 8 µm, about 8.5 µm, about 9 µm, about 9.5 µm or about 10 µm.

In some embodiments of the present disclosure, Figure 1D shows the diameter of representative needles in the urchin of carbon fibres. The needles shown therein have a diameter of 5.8 µm, 7.7 µm, 6.1 µm and 5.1 µm, respectively.

In some embodiments of the present disclosure, each needle in the urchin of carbon fibres has a length of about 500 µm to 1000 µm, including all values and ranges therefrom.

In some embodiments of the present disclosure, each needle in the urchin of carbon fibres has a length of about 550 µm to 900 µm, including all values and ranges therefrom.

In some embodiments of the present disclosure, each needle in the urchin of carbon fibres has a length of about 550 µm to 700 µm, including all values and ranges therefrom.

In some embodiments of the present disclosure, each needle in the urchin of carbon fibres has a length of about 500 µm, about 525 µm, about 550 µm, about 575 µm, about 600 µm, about 625 µm, about 650 µm, about 675 µm, about 700 µm, about 725 µm, about 750 µm, about 775 µm, about 800 µm, about 825 µm, about 850 µm, about 875 µm, about 900 µm, about 925 µm, about 950 µm, about 975 µm or about 1000 µm.

In some embodiments of the present disclosure, mass of each urchin of carbon fibres ranges from about 0.3 milligram (mg) to 25 mg, including all values and ranges therefrom.

In some embodiments of the present disclosure, mass of each urchin of carbon fibres ranges from about 0.3 mg to 15 mg, including all values and ranges therefrom.

In some embodiments of the present disclosure, mass of each urchin of carbon fibres is about 0.3 mg, about 0.5 mg, about 0.5 mg, about 0.6 mg, about 0.7 mg, about 0.8 mg, about 0.9 mg, about 1 mg, about 1.5 mg, about 2 mg, about 2.5 mg, about 3 mg, about 3.5 mg, about 4 mg, about 4.5 mg, about 5 mg, about 5.5 mg, about 6 mg, about 6.5 mg, about 7 mg, about 7.5 mg, about 8 mg, about 8.5 mg, about 9 mg, about 9.5 mg, about 10 mg, about 10.5 mg, about 11 mg, about 11.5 mg, about 12 mg, about 12.5 mg, about 13 mg, about 13.5 mg, about 14 mg, about 14.5 mg or about 15 mg.

In some embodiments of the present disclosure, mass of each urchin is illustrated in Figure 3(c), wherein said urchins of carbon fibres were synthesized/obtained under different pH conditions.

The present invention also relates to plurality of carbon fibre units or urchins of carbon fibres as a product comprising an assembly or collection of carbon fibre unit or urchin of carbon fibres, wherein each carbon fibre unit or urchin of carbon fibres is described as above.

In some embodiments of the present disclosure, the urchins of carbon fibres comprise an assembly of plurality of urchins, wherein a single urchin is as depicted in Figure 1A. Additional SEM images of the needles forming the urchin structure are shown in Figures 1B and 1C, wherein Figure 1C shows clear and enlarged view of the needles forming the urchin structure.

Without wishing to be bound by any theory, the present inventors have surprisingly found that the urchins of carbon fibres provide enhanced/improved electromagnetic (EM) shielding compared to chopped carbon fibres i.e., conventionally known carbon fibres. Particularly, due to the isometric/asymmetric structure of the urchins, there are multiple internal scattering and reflections from each urchin which lead to high/improved degree of EM shielding.

An individual spike/needle existing outwards the urchin structure can be considered as protruding rod to absorb EM waves. The urchin morphology distinctly shows that the spikes assembly is converged with different distribution densities with large aspect ratio. Based on the conducting nature of carbon fibres, the electric field intensity at the tip of the spike is concentrated under EM radiation with an alternating polarization vector direction. These concentrated tips might act as mutlipoles couple with the incident electric field due to the EM resonance effect resulting in strong microwave absorption.

Further, the present carbon urchins which are conducting in nature are employed as composites with polymers such as epoxy or EVA wherein the host matrix (i.e., polymer such as epoxy or EVA) is insulating in nature, and the shielding efficiency is because of the network of conducting carbon urchins.

Preparation of Carbon fibre Urchin
The present disclosure further relates to a method of preparing the urchin of carbon fibres described above.

While the subsequent embodiments focus on method of obtaining the urchin of carbon fibres, the features and characteristics of said product (urchin of carbon fibres) are as described by any of the embodiments above. For the sake of brevity, and avoiding repetition, each of those embodiments are not being reiterated here again. However, each of the said embodiments completely fall within the purview of the method of preparing the said urchin of carbon fibres.

The method of preparing the urchin of carbon fibres comprises subjecting urchin of carbon fibres to a refluxing reaction in the presence of a solvent, and pH of the reflux reaction ranges from about 1 to 14.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprising a carbon fibre core and a plurality of carbon fibres in a form of globular needles protruding out from the carbon fibre core, comprises subjecting carbon fibres to a refluxing reaction in the presence of a solvent, wherein pH of the reflux reaction ranges from about 1 to 14.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the carbon fibres are selected from chopped carbon fibres, carbon fibre mat, carbon fibre woven fabric or knit, carbon fibre spun yarn, or any combinations thereof.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the chopped carbon fibres have an average diameter of about 5 to 7 µm and a length of about 5 mm to 6 mm.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the solvent is a polar solvent.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the polar solvent is a compound having high polarity.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the solvent is a polar solvent selected from a group comprising water, alcohol, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), acetonitrile and combinations thereof. In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the alcohol solvent is methanol, ethanol, or a combination thereof.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the solvent is water or alcohol.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the pH of the reflux reaction ranges from about 1 to 14.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the pH of the reflux reaction is maintained at about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, about 11, about 12, about 13, or about 14.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the pH of 1 to 6.9 is acidic pH.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the acidic pH is maintained by an acid selected from the group comprising sulphuric acid (H2SO4), hydrochloric acid (HCl), nitric acid (HNO3), acetic acid (CH3COOH) and combinations thereof.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the pH of 7.1 to 14 is alkaline pH.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the alkaline pH is maintained by an alkali selected from the group sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide [Ca(OH)2], ammonium hydroxide (NH4OH) and combinations thereof.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the pH of 7 is neutral pH.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the neutral pH is maintained by salt.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, a neutral to moderately alkaline pH of 7.5 is maintained by salt.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, a weakly acidic pH to a weakly alkaline pH range of 6.5 to 7.5 is maintained by deionized (DI) water.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, an alkaline pH of 8.2 is maintained by seawater.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the pH is maintained by a salt selected from the group chloride salt, sulphate salt, carbonate salt, phosphate salt, nitrate salt and combinations thereof.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the pH is maintained by a chloride salt selected from the group comprising sodium chloride (NaCl), ammonium chloride (NH4Cl), or a combination thereof.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the pH is maintained by a nitrate salt selected from the group comprising potassium nitrate (KNO3), aluminium nitrate [Al(NO3)3], or a combination thereof.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the pH is maintained by a sulphate salt selected from the group comprising ammonium sulphate [(NH4)2SO4], magnesium sulphate (MgSO4), or a combination thereof.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the pH is maintained by a carbonate salt which is calcium carbonate (CaCO3).

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the pH is maintained by a phosphate salt which is ammonium phosphate [(NH4)3PO4].

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the pH of the reflux reaction is strongly acidic pH ranging from pH of 1 to 3, neutral to moderately basic pH ranging from 7 to 8.5, or strong alkaline pH of 14.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out at a temperature corresponding to boiling point of the solvent.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out at a temperature ranging from about 50? to 180?, including all values and ranges therefrom.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out at a temperature ranging from about 70? to 180?, including all values and ranges therefrom.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out at a temperature ranging from about 70? to 180? in presence of a polar solvent.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out at a temperature ranging from about 70? to 180? in presence of a polar solvent selected from a group comprising methanol, ethanol, water, DMSO, DMF and acetonitrile.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out at a temperature of about 50?, about 51?, about 52?, about 53?, about 54?, about 55?, about 56?, about 57?, about 58?, about 59?, about 60?, about 61?, about 62?, about 63?, about 64?, about 65?, about 66?, about 67?, about 68?, about 69?, about 70?, about 71?, about 72?, about 73?, about 74?, about 75?, about 76?, about 77?, about 78?, about 79?, about 80?, about 81?, about 82?, about 83?, about 84?, about 85?, about 86?, about 87?, about 88?, about 89?, about 90?, about 91?, about 92?, about 93?, about 94?, about 95?, about 96?, about 97?, about 98?, about 99?, about 100?, about 105?, about 110?, about 115?, about 120?, about 125?, about 130?, about 135?, about 140?, about 145?, about 150?, about 155?, about 160?, about 165?, about 170?, about 175?, or about 180?, including all values and ranges therefrom.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out at a temperature of about 65? in presence of methanol.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out at a temperature of about 78? in presence of ethanol.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out at a temperature of about 100? in presence of water.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out at a temperature of about 180? in presence of DMSO.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out at a temperature of about 150? in presence of DMF.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out at a temperature of about 80? in presence of acetonitrile.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out for a time period ranging from about 2 hours to 48 hours, including all values and ranges therefrom.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out for a time period ranging from about 6 hours to 48 hours, including all values and ranges therefrom.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out for a time period ranging from about 2 hours to 24 hours, including all values and ranges therefrom.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out for a time period ranging from about 2 hours to 6 hours, including all values and ranges therefrom.

In some embodiments of the present disclosure, in the method of preparing the urchin of carbon fibres, the refluxing is carried out for a time period of about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours, about 10 hours, about 11 hours, about 12 hours, about 13 hours, about 14 hours, about 15 hours, about 16 hours, about 17 hours, about 18 hours, about 19 hours, about 20 hours, about 21 hours, about 22 hours, about 23 hours, about 24 hours, about 25 hours, about 26 hours, about 27 hours, about 28 hours, about 29 hours, about 30 hours, about 31 hours, about 32 hours, about 33 hours, about 34 hours, about 35 hours, about 36 hours, about 37 hours, about 38 hours, about 39 hours, about 40 hours, about 41 hours, about 42 hours, about 43 hours, about 44 hours, about 45 hours, about 46 hours, about 47 hours or about 48 hours.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises subjecting chopped carbon fibres to refluxing reaction in presence of a polar solvent at a pH selected from acidic pH, alkaline pH and neutral pH.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises subjecting chopped carbon fibres to refluxing reaction in presence of a polar solvent at a pH selected from acidic pH, alkaline pH and neutral pH, and at a temperature ranging from about 50? to 180? for a time-period ranging from about 2 hours to 48 hours.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises subjecting chopped carbon fibres to refluxing reaction in presence of a polar solvent at a pH selected from acidic pH, alkaline pH and neutral pH, and at a temperature ranging from about 70? to 180? for a time-period ranging from about 2 hours to 48 hours.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising carbon fibres and an aqueous solution to maintain a pH between 1-14, in a reflux system or apparatus; and
- refluxing the reactant mixture in presence of a polar solvent at a temperature ranging from about 50? to 180? for a time-period ranging from about 2 hours to 48 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising carbon fibres and an aqueous solution to maintain a pH between 1-14, in a reflux system or apparatus; and
- refluxing the reactant mixture in presence of a polar solvent at a temperature ranging from about 50? to 180? for a time-period ranging from about 2 hours to 48 hours, to obtain urchins of carbon fibres,
wherein the aqueous solution maintaining the pH is selected from acid solution, alkali solution, salt solution, sea water or DI water,
and wherein the polar solvent is selected from a group comprising methanol, ethanol, water, DMSO, DMF and acetonitrile.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
a) providing a reactant mixture in a reflux apparatus, wherein the reactant mixture comprises chopped carbon fibres and an aqueous solution which maintains a pH between 1-14,
wherein the aqueous solution is an acid solution, alkali solution, salt solution, sea water, or deionised (DI) water, or any combination thereof; and
b) refluxing the reactant mixture in presence of the polar solvent at a temperature ranging from about 50? to about 180? for a time-period ranging from about 2 hours to about 48 hours, to obtain carbon fibre units, and
wherein the polar solvent is water or ethanol.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and an aqueous solution to maintain acidic pH, alkaline pH or neutral pH, in a reflux system or apparatus,
wherein the aqueous solution is an acid solution, alkali solution, salt solution, sea water, deionised (DI) water, or any combinations thereof; and
- refluxing the reactant mixture in presence of a polar solvent at a temperature ranging from about 70? to 180? for a time-period ranging from about 6 hours to 48 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and an aqueous solution to maintain acidic pH, alkaline pH or neutral pH, in a reflux system or apparatus,
wherein the aqueous solution is an acid solution, alkali solution, salt solution, sea water, deionised (DI) water, or any combinations thereof; and
- refluxing the reactant mixture in presence of a polar solvent selected from water and alcohol, at a temperature ranging from about 50? to 180? for a time-period ranging from about 2 hours to 48 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and an aqueous solution to maintain acidic pH, alkaline pH or neutral pH, in a reflux system or apparatus,
wherein the aqueous solution is an acid solution, alkali solution, salt solution, sea water, deionised (DI) water, or any combinations thereof; and
- refluxing the reactant mixture in presence of water at a temperature of about 100? for a time-period ranging from about 2 hours to 48 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and an aqueous solution to maintain acidic pH, alkaline pH or neutral pH, in a reflux system or apparatus,
wherein the aqueous solution is an acid solution, alkali solution, salt solution, sea water, deionised (DI) water, or any combinations thereof; and
- refluxing the reactant mixture in presence of water at a temperature of about 100? for a time-period ranging from about 2 hours to 6 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and acid solution; and
- refluxing the reactant mixture in presence of water at a temperature of about 100? for a time-period of about 2 hours to 6 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and acid solution; and
- refluxing the reactant mixture in presence of water at a temperature of about 100? for a time-period of about 2 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and alkali solution; and
- refluxing the reactant mixture in presence of water at a temperature of about 100? for a time-period of about 4 hours to 6 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and alkali solution; and
- refluxing the reactant mixture in presence of water at a temperature of about 100? for a time-period of about 4 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and salt solution; and
- refluxing the reactant mixture in presence of water at a temperature of about 100? for a time-period of about 4 hours to 6 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and salt solution; and
- refluxing the reactant mixture in presence of water at a temperature of about 100? for a time-period of about 6 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and sea water; and
- refluxing the reactant mixture in presence of water at a temperature of about 100? for a time-period of about 2 hours to 6 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and sea water; and
- refluxing the reactant mixture in presence of water at a temperature of about 100? for a time-period of about 6 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and deionised (DI) water; and
- refluxing the reactant mixture in presence of water at a temperature of about 100? for a time-period of about 2 hours to 6 hours, to obtain urchins of carbon fibres.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres comprises:
- providing a reactant mixture comprising chopped carbon fibres and deionised (DI) water; and
- refluxing the reactant mixture in presence of water at a temperature of about 100? for a time-period of about 6 hours, to obtain urchins of carbon fibres.

In some embodiments of the present method of preparing the urchin of carbon fibres, the obtained urchin of carbon fibres comprises carbon fibre core and plurality of carbon fibres in the form of globular needles which protrude out from the core in all directions to form an assembly of the globular needles, wherein the diameter of each of the globular needle is in the range of about 5 µm to about 10 µm, and wherein the length of each of the globular needle is in the range of about 500 µm to about 1000 µm, and wherein mass of the urchin of carbon fibres is in the range of about 0.3 mg to about 25 mg.

In some embodiments of the present method of preparing the urchin of carbon fibres, the obtained urchin of carbon fibres comprises carbon fibre core and plurality of carbon fibres in the form of globular needles which protrude out from the core in all directions to form an assembly of the globular needles, wherein the diameter of each of the globular needle is in the range of about 5 µm to about 7 µm, and wherein the length of each of the globular needle is in the range of about 550 µm to about 700 µm, and wherein mass of the urchin of carbon fibres is in the range of about 0.3 mg to about 25 mg.

In some embodiments of the present disclosure, the method of preparing the urchin of carbon fibres is illustrated in Figure 2.

In some embodiments of the present disclosure, various urchins obtained from the above described reflux reaction by employing different pH conditions are illustrated in Figure 3(c). As seen from Figure 3(c), employing any of the pH between 1-14 such as acidic pH, alkaline pH or neutral pH under reflux reaction conditions in presence of a polar solvent result in the formation of carbon urchins. While all the different pH conditions lead to the formation of urchins, the variation is only in terms of weight of the formed urchins. In some embodiments, the weight of carbon urchins is higher when sea water is employed followed by DI water, salt solution, alkaline solution and acid solution, respectively. In some embodiments, the weight of each carbon urchin is 12 mg ± 2 mg when sea water is employed followed by 8 mg ± 2 mg (DI water), 5 mg± 1 mg (salt solution), 4 mg ± 1 mg (alkaline solution) and 0.7 mg ± 0.3 mg (acid solution), respectively.

Without wishing to be bound by any theory, the present inventors have surprisingly found that when the present method of preparation of carbon urchin is employed, the formation of urchin of carbon fibres occur by vaporisation followed by condensation. Particularly, the possible mechanism is vaporisation and condensation due to the high temperature spark generated by the heat waves from the reflux of the solvent(s).

In some embodiments of the present disclosure, the mechanism of formation of carbon urchin is illustrated in Figure 4. The formation mechanism can be further explained as follows: the isotropic and aligned chopped carbon fibres begin to aggregate and self-assemble into microsphere structures under heating so that the rate of vaporisation of solvent and the rate of condensation maintain a stable equilibrium or near-equilibrium condition. It is believed that Van der Waals forces drive the aggregation of the chopped carbon fibres and enable the growth of urchin microstructures. During the condensation process, a large number of isotropic nuclei assemble and aggregate into microspheres in order to reduce the total energy of the system. Due to the existence of a large number of surface defects, they could act as the sites for further growth on the surface of carbon fibre and finally form/evolve into the sea urchin-like architectures.

As discussed above, the formation of carbon urchins follows a conversion of the linearly aligned carbon fibres to randomly aligned carbon fibres which make the urchin structure. In an embodiment, SEM images showing the differences in alignment of carbon fibres before forming urchin-like structure and the alignment of the synthesized carbon urchins is depicted in Figure 3(a) and 3(b). The linear array alignment of as such used chopped carbon fibres [Figure 3(a)] is converted to random array alignment during the process of making urchins [Figure 3(b)].

The present disclosure also relates to urchins of carbon fibres or plurality of carbon fibre units prepared by a process comprising subjecting carbon fibres to refluxing reaction in presence of a solvent at a pH between 1-14. The features and characteristics of the urchins of carbon fibres (product) and the method/process of preparing the same are as described by any of the embodiments above. For the sake of brevity, and avoiding repetition, each of those embodiments are not being reiterated here again. However, each of the said embodiments completely fall within the purview of said urchin of carbon fibres prepared by the process described above.

Composite
The present disclosure also relates to a composite comprising a polymer matrix and urchins of carbon fibres (i.e., a plurality of carbon fibre units).

In some embodiments of the present composite material, said composite comprises a polymer matrix and urchins of carbon fibres, wherein each of the urchin comprises a carbon fibre core and a plurality of carbon fibres in a form of globular needles protruding out from the carbon fibre core.

In some embodiments of the present composite material, the urchin comprises a carbon fibre core and a plurality of carbon fibres in the form of globular needles which protrude out from the core in all directions to form an assembly of the globular needles, wherein the diameter of each globular needle is in the range of about 5 µm to about 10 µm, and wherein the length of each globular needle is in the range of about 500 µm to about 1000 µm, and wherein mass of each of the unit of urchin of carbon fibre is in the range of about 0.3 mg to about 25 mg.

In some embodiments of the present composite material, urchin comprises a carbon fibre core and a plurality of the carbon fibres in the form of globular needles which protrude out from the core in all directions and at all possible angles between 0o and 360o to form an assembly of the globular needles, wherein the diameter of each globular needle is in the range of about 5 µm to about 7 µm, and wherein the length of each globular needle is in the range of about 550 µm to about 700 µm, and wherein mass of each of the unit of urchin of carbon fibre is in the range of about 0.3 mg to about 25 mg.

In some embodiments of the present composite material, the polymer matrix is made up of a thermosetting polymer, a thermoplastic polymer, or a combination thereof.

In some embodiments of the present composite material, the thermosetting polymer is selected from a group comprising epoxy resin, silicone, polyurethane, phenolic resin and combinations thereof.

In some embodiments of the present composite material, the thermosetting polymer is epoxy resin.

In some embodiments of the present composite material, the thermoplastic polymer is selected from a group comprising ethylene vinyl acetate (EVA), polypropylene (PP), polyethylene terephthalate (PET), low density polyethylene (LDPE), high density polyethylene (HDPE) and combinations thereof.

In some embodiments of the present composite material, the features and characteristics of the urchins of carbon fibres are as described by any of the embodiments above. For the sake of brevity, and avoiding repetition, each of those embodiments are not being reiterated here again. However, each of the said embodiments completely fall within the purview of the composite material described herein.

In some embodiments of the composite material, the polymer matrix is present in an amount from about 75 wt% to about 99 wt% and the urchins of carbon fibres are present in an amount from about 1 wt% to about 25 wt%.

In some embodiments of the composite material, the polymer matrix is present in an amount from about 93 wt% to about 97 wt% and the urchins of carbon fibres are present in an amount from about 3 wt% to about 7 wt%.

In some embodiments of the composite material, the polymer matrix is in an amount ranging from about 75 weight percentage (wt%) to 99 wt%, including all values and ranges therefrom.

In some embodiments of the composite material, the polymer matrix is in an amount ranging from about 90 weight percentage (wt%) to 99 wt%, including all values and ranges therefrom.

In some embodiments of the composite material, the polymer matrix is in an amount ranging from about 93 wt% to 97 wt%, including all values and ranges therefrom.

In some embodiments of the composite material, the polymer matrix is present in an amount of about 90 wt%, about 91 wt%, about 92 wt%, about 93 wt%, about 94 wt%, about 95 wt%, about 96 wt%, about 97 wt%, about 98 wt% or about 99 wt%.

In some embodiments of the composite material, the polymer matrix is present in an amount of about 93 wt%, about 94 wt%, about 95 wt%, about 96 wt% or about 97 wt%.

In some embodiments of the composite material, the urchins of carbon fibres is in an amount ranging from about 1 wt% to 25 wt%, including all values and ranges therefrom.

In some embodiments of the composite material, the urchins of carbon fibres is in an amount ranging from about 1 wt% to 10 wt%, including all values and ranges therefrom.

In some embodiments of the composite material, the urchins of carbon fibres is in an amount ranging from about 2 wt% to 8 wt%, including all values and ranges therefrom.

In some embodiments of the composite material, the urchins of carbon fibres is in an amount ranging from about 3 wt% to 7 wt%, including all values and ranges therefrom.

In some embodiments of the composite material, the urchins is present in an amount of about 1 wt%, about 1.5 wt%, about 2 wt%, about 2.5 wt%, about 3 wt%, about 3.5 wt%, about 4 wt%, about 4.5 wt%, about 5 wt%, about 5.5 wt%, about 6 wt%, about 6.5 wt%, about 7 wt%, about 7.5 wt%, about 8 wt%, about 8.5 wt%, about 9 wt%, about 9.5 wt% or about 10 wt%.

In some embodiments of the composite material, the urchins is present in an amount of about 3 wt%, about 3.5 wt%, about 4 wt%, about 4.5 wt%, about 5 wt%, about 5.5 wt%, about 6 wt%, about 6.5 wt% or about 7 wt%.

In some embodiments of the composite material, the urchins is present in an amount of about 3 wt%.

In some embodiments of the composite material, the urchins is present in an amount of about 7 wt%.

In some embodiments of the present disclosure, the composite material comprises epoxy polymer matrix and urchins of carbon fibres.

In some embodiments of the present disclosure, the composite material comprises epoxy polymer matrix and urchins of carbon fibres, wherein said urchins are prepared from chopped carbon fibres under reflux conditions in presence of a polar solvent at a pH between 1-14.

In some embodiments of the present disclosure, the composite material comprises epoxy polymer matrix and urchins of carbon fibres, wherein said urchins are prepared from chopped carbon fibres under reflux conditions in presence of a polar solvent at a pH selected from acidic pH, alkaline pH and neutral pH.

In some embodiments of the present disclosure, the composite material comprises epoxy polymer matrix and urchins of carbon fibres, wherein said urchins are prepared from chopped carbon fibres under reflux conditions in presence of a polar solvent and employing acid, alkali, salt, sea water or DI water.

In some embodiments of the present disclosure, the composite material comprises epoxy polymer matrix at 97 wt% and urchins of carbon fibres at 3 wt%.

In some embodiments of the present disclosure, the composite material comprises epoxy polymer matrix at 93 wt% and urchins of carbon fibres at 7 wt%.

In some embodiments of the present disclosure, the composite material comprises EVA polymer matrix and urchins of carbon fibres.

In some embodiments of the present disclosure, the composite material comprises EVA polymer matrix and urchins of carbon fibres, wherein said urchins are prepared from chopped carbon fibres under reflux conditions in presence of a polar solvent at a pH selected from 1-14.

In some embodiments of the present disclosure, the composite material comprises EVA polymer matrix and urchins of carbon fibres, wherein said urchins are prepared from chopped carbon fibres under reflux conditions in presence of a polar solvent and employing acid, alkali, salt, sea water or DI water.

In some embodiments of the present disclosure, the composite material comprises EVA polymer matrix at 97 wt% and urchins of carbon fibres at 3 wt%.

In some embodiments of the present disclosure, the composite material comprises EVA polymer matrix at 93 wt% and urchins of carbon fibres at 7 wt%.

In some embodiments of the present disclosure, the composite material comprises thermoplastic polymer or thermosetting polymer in the form of nanoparticles.

In some embodiments of the present disclosure, the composite material has a thickness ranging from about 1 mm (millimetre) to 5 mm, including all values and ranges therefrom.

The composite material of the present disclosure provides effective shielding against electromagnetic (EM) radiations across X Band and Ku Band having frequency ranging from about 8 to 18 GHz.

In some embodiments of the present disclosure, the composite material demonstrates enhanced electromagnetic (EM) radiation shielding capacity (total shielding effectiveness) ranging from about -15 dB to -60 dB over entire Ku Band (12-18 GHz) and X band (8-12 GHz) having frequency ranging from about 8 GHz to 18 GHz.

In some embodiments of the present disclosure, the composite material demonstrates enhanced electromagnetic (EM) radiation shielding capacity ranging from about -20 dB to -60 dB over entire Ku Band and X band having frequency ranging from about 8 GHz to 18 GHz.

In some embodiments of the present disclosure, the composite material demonstrates enhanced electromagnetic (EM) radiation shielding capacity ranging from about -30 dB to -60 dB over entire Ku Band and X band having frequency ranging from about 8 GHz to 18 GHz.

In some embodiments of the present disclosure, the composite material demonstrates electromagnetic (EM) radiation shielding capacity of about -20 dB, about -21 dB, about -22 dB, about -23 dB, about -24 dB, about -25 dB, about -26 dB, about -27 dB, about -28 dB, about -29 dB, about -30 dB, about -31 dB, about -32 dB, about -33 dB, about -34 dB, about -35 dB, about -36 dB, about -37 dB, about -38 dB, about -39 dB, about -40 dB, about -41 dB, about -42 dB, about -43 dB, about -44 dB, about -45 dB, about -46 dB, about -47 dB, about -48 dB, about -49 dB, about -50 dB, about -51 dB, about -52 dB, about -53 dB, about -54 dB, about -55 dB, about -56 dB, about -57 dB, about -58 dB, about -59 dB or about -60 dB over entire Ku Band and X band having frequency ranging from about 8 GHz to 18 GHz.

Figure 5 of the present disclosure demonstrates conductivity (AC, S/cm) and EM shielding effectiveness (SET, dB) of the composite material comprising epoxy polymer and urchins, wherein the shielding effectiveness range from about -16 dB to -58 dB over a frequency ranging from about 8 GHz to 12 GHz.

Figure 6 of the present disclosure illustrates conductivity (AC, S/cm) and EM shielding effectiveness (SET, dB) of the composite material comprising EVA polymer and urchins, wherein the shielding effectiveness ranges from about -19 dB to -45 dB over a frequency ranging from about 8 GHz to 12.5 GHz.

In some embodiments of the present disclosure, the composite material comprising the polymer matrix and the urchins of carbon fibres demonstrates enhanced electromagnetic radiation shielding capacity for over a period of about 1 month to 60 months over entire Ku Band and X band having frequency ranging from about 8 GHz to 18 GHz.

In some embodiments of the present disclosure, the composite material comprising the polymer matrix and the urchins of carbon fibres demonstrates enhanced electromagnetic radiation shielding capacity over entire Ku Band and X band having frequency ranging from about 8 GHz to 18 GHz, for over a period of about 1 month, about 2 months, about 3 months, about 4 months, about 5 months, about 6 months, about 7 months, about 8 months, about 9 months, about 10 months, about 11 months, about 12 months, about 13 months, about 14 months, about 15 months, about 16 months, about 17 months, about 18 months, about 19 months, about 20 months, about 21 months, about 22 months, about 23 months, about 24 months, about 25 months, about 26 months, about 27 months, about 28 months, about 29 months, about 30 months, about 31 months, about 32 months, about 33 months, about 34 months, about 35 months, about 36 months, about 37 months, about 38 months, about 39 months, about 40 months, about 41 months, about 42 months, about 43 months, about 44 months, about 45 months, about 46 months, about 47 months, about 48 months, about 49 months, about 50 months, about 51 months, about 52 months, about 53 months, about 54 months, about 55 months, about 56 months, about 57 months, about 58 months, about 59 months or about 60 months.

In some embodiments of the present disclosure, the composite material comprising the polymer matrix and the urchins of carbon fibres retains original flexibility for at least about 10000 bending cycles.

In some embodiments of the present disclosure, the composite material comprising the polymer matrix and the urchins of carbon fibres retains original flexibility for about 10000 cycles to 20000 cycles.

In some embodiments of the present disclosure, the composite material comprising the polymer matrix and the urchins of carbon fibres retains original stretchability for at least about 200 stretching cycles.

In some embodiments of the present disclosure, the composite material requires very low loading of urchins of carbon fibres in the polymer matrix to achieve an electromagnetic (EM) radiation shielding capacity of at least -20 dB when compared to the loading of conventional carbon fibres in the polymer matrix.

In some embodiments of the present disclosure, the composite material requires a loading of 1 wt% to 10 wt% urchins in the polymer matrix to achieve an electromagnetic (EM) radiation shielding capacity of at least -20 dB when compared to higher loading of chopped carbon fibres in the polymer matrix to achieve EM radiation shielding capacity of at least -20 dB.

The present disclosure also relates to a method of preparing the composite comprising the polymer matrix and the urchins of carbon fibres (i.e. the plurality of carbon fibre units).

While the subsequent embodiments focus on method of preparing the composite, the features and characteristics of the composite material are as described by any of the embodiments above. For the sake of brevity, and avoiding repetition, each of those embodiments are not being reiterated here again. However, each of the said embodiments completely fall within the purview of the method of preparing the said composite.

In some embodiments of the present disclosure, the method of preparing the composite material comprising the polymer matrix and the urchins of carbon fibres, comprises mixing the urchins and the polymer matrix to obtain the composite material.

In some embodiments of the present disclosure, the composite material comprising polymer matrix and urchins of carbon fibres is prepared by -
- mixing the polymer and a hardener to obtain a mixture;
- adding urchins to the mixture to form a mould; and
- curing the mould to obtain the composite material.

In some embodiments of the present disclosure, the composite material comprising polymer matrix and urchins of carbon fibres is prepared by -
- mixing the polymer and a hardener to obtain a mixture, wherein the polymer is a thermosetting polymer selected from a group comprising epoxy resin, silicone, polyurethane, phenolic resin and combinations thereof;
- adding urchins to the mixture to form a mould; and
- curing the mould to obtain the composite material.

In some embodiments of the present disclosure, the hardener is selected from an amine-based hardener, ___________, _____________ and ___________. In some embodiments, the amine-based hardener is cyclohexylamine.

In some embodiments of the present disclosure, the composite material comprising polymer matrix and urchins of carbon fibres is prepared by -
- mixing the polymer and urchins to form a mould; and
- curing the mould to obtain the composite material.

In some embodiments of the present disclosure, the composite material comprising polymer matrix and urchins of carbon fibres is prepared by -
- mixing the polymer and urchins to form a mould, wherein the polymer is a thermoplastic polymer selected from a group comprising ethylene vinyl acetate (EVA), polypropylene (PP), polyethylene terephthalate (PET), low density polyethylene (LDPE), high density polyethylene (HDPE) and combinations thereof; and
- curing the mould to obtain the composite material.

In some embodiments of the present disclosure, the curing is performed at a temperature ranging from about 50? to 200? for a time-period ranging from about 1 hour to 5 hours.

In some embodiments of the present disclosure, the composite material comprising EVA polymer matrix and urchins of carbon fibres is prepared by: a) mixing the ethylene vinyl acetate polymer and the urchins of carbon fibres, and subjecting the mixture to compression moulding to form a mould; and b) curing the mould at a temperature of about 170ºC.

In some embodiments of the present disclosure, the composite material comprising epoxy polymer matrix and urchins of carbon fibres is prepared by a) mixing the epoxy polymer with a hardener to obtain a mixture, followed by addition of the urchins of carbon fibres to form a mould; and b) curing the mould at a temperature ranging from about 60ºC to about 120ºC.
In some embodiments of the present disclosure, in the method of preparing the polymer composite material comprising the polymer matrix and the urchins of carbon fibres, mixing is performed using an overhead stirrer and curing is carried out in an oven.

Figures 7(B) and 8 provide digital photographs of the prepared epoxy and EVA based composites respectively. As seen from these figures, urchins prepared under different pH conditions were successfully employed for synthesizing epoxy and EVA polymer composites. Urchin structures were mechanically strong during processing at relatively high temperature during composite preparation with epoxy or EVA polymers. Further, urchins did not undergo any deformation as clearly visible in Figures 7(B) and 8, respectively.

Article or device
The present disclosure further relates to an article or device comprising the urchins of carbon fibres or the composite described above.

In some embodiments of the present disclosure, the article or device is an electronic equipment including but not limited to mobile phone or components thereof, computer or components thereof, laptop or components thereof, wearable electronics, medical, aerospace and military electronics and train signalling and control systems.

In some embodiments of the present disclosure, the article or device has electromagnetic radiation shielding capacity ranging from about -15 dB to -60 dB, including all values and ranges therefrom, over a frequency ranging from about 8 GHz to 18 GHz.

In some embodiments of the present disclosure, the composite material in the article or device is present at a thickness ranging from about 1 mm to 5 mm, including all values and ranges thereof.

In some embodiments of the present disclosure, the article comprising the composite material described above is an article emitting the electromagnetic radiation. In alternate embodiments, the article comprising the composite material described above is an article receiving or required to be shielded from the electromagnetic radiation.

Thus, in some embodiments of the present disclosure, in order to protect an article or device from harmful effects of electromagnetic radiation, or in other words to provide shielding of electromagnetic radiation, an article or device is appropriately covered, contacted or layered with the composite material of the present disclosure. Once the electromagnetic radiations are directed, converged or contacted with the composite material, shielding of electromagnetic radiation occurs. Further, and as mentioned above, the degree of this shielding depends on the type of polymer matrix and urchins employed. A person skilled in the art upon reading the present disclosure will understand that, based on the end use, device, or article in question, appropriate modifications including type of polymer matrix and/or urchins can be employed.

The features and characteristics of the urchins and composite material, and the manner in which it is prepared is as described by any of the embodiments above. For the sake of brevity, and avoiding repetition, each of those embodiments are not being reiterated here again. However, each of the said embodiments, completely fall within the purview of the article or device described herein.

Use
The present disclosure also relates to use of the carbon urchins, the composite material, or the article or device comprising the composite material described above.

In some embodiments of the present disclosure, the carbon urchin or the plurality of carbon urchins are used for providing electromagnetic shielding effect.

In some embodiments of the present disclosure, the composite material is used for providing electromagnetic shielding effect.

In some embodiments of the present disclosure, the article or device is used for providing electromagnetic shielding effect.

In some embodiments of the present disclosure, the composite material or the article has electromagnetic radiation shielding capacity ranging from about -15 dB to -60 dB, including all values and ranges therefrom, over a frequency ranging from about 8 GHz to 18 GHz.

Thus, the present disclosure focuses on unique conducting carbon materials (urchin of carbon fibres) and corresponding lightweight polymer composite materials that can be employed as EM radiation shielding materials for effectively blocking the incoming EM radiation. The disclosure provides fabrication/preparation of said conducting urchins from chopped carbon fibres following a green and sustainable strategy. Particularly, though the existing carbon based materials/systems provide EM radiation shielding, but synthesizing them at industrial scale is highly challenging. Said existing carbon based materials/systems also require high loading in polymer composites to achieve desired EM shielding effect. Hence, the present disclosure successfully provides a facile, economical, efficient and industrially scalable approach to synthesize ‘carbon urchins’ which can be incorporated in various polymeric systems to design composites that can shield/block a wide spectrum of EM radiation. The ‘carbon urchins’ are synthesized from carbon fibres by a green strategy and following a robust chemistry route. Said carbon urchins prepared from chopped carbon fibres result in enhanced EMI shielding when compared with chopped carbon fibres at relatively low loadings. These urchins are easy to handle during processing and offers high loading easily which otherwise is cumbersome in conventional composites.

Additionally, the urchins of carbon fibres described herein are used in desalination i.e. removing salt from a sample. Particularly, in some embodiments of the present disclosure, the urchins of carbon fibres described herein are employed for desalination of a water sample. In some embodiments of the present disclosure, the urchins of carbon fibres described herein are employed for water purification. Thus, the urchins described herein have immense/significant utility including purifying or desalinating sea water wherein said carbon fibre urchins trap salt or other contaminants from sea water thereby purifying/desalinating the sea water.

Methods for electromagnetic radiation shielding and water desalination
The present disclosure further relates to a method for shielding of electromagnetic (EM) radiation, said method comprising contacting the electromagnetic (EM) radiation with the urchin(s) of carbon fibres or the composite material as described above.

In some embodiments of the present disclosure, in the method of shielding of electromagnetic radiation, the shielding effect ranges from about -15 dB to -60 dB, including all values and ranges therefrom, over a frequency ranging from about 8 GHz to 18 GHz.

Figures 5 and 6 illustrate the EM shielding effectiveness of the present composite material comprising the polymer matrix and urchins, wherein the overall shielding effectiveness ranges from about -16 dB to -58 dB over a frequency ranging from about 8 GHz to 12.5 GHz.

In some embodiments of the present disclosure, the urchins or the composite material of the present disclosure is sufficient to provide minimum electromagnetic shielding of about -20 db which is industrially relevant and significant. The said shielding can be enhanced by employing different polymer matrices in combination with the urchins of carbon fibres obtained under reflux conditions in presence of a polar solvent at different pH conditions. Based on the information and results provided in the present disclosure, a person skilled in the art would be able to readily arrive at such modifications/permutations/combinations of polymer matrix and urchins to arrive at an appropriate composite material for desired purpose or end use. All such modifications/permutations/combinations therefore fully fall within the purview of the present disclosure.

The features and characteristics of the urchins and composite material, and the manner in which it is prepared is as described by any of the embodiments above. For the sake of brevity, and avoiding repetition, each of those embodiments are not being reiterated here again. However, each of the said embodiments, completely fall within the purview of the method for shielding of electromagnetic radiation.

Further, the present disclosure provides a method of desalinating or purifying water comprising the step of contacting the urchin(s) of carbon fibres described herein with the water, to obtain purified water.

In some embodiments of the method of purifying water, the water is sea water.

In some embodiments of the method of purifying water, the water is sea water and the method purifies or removes salt content to obtain purified or desalinated water.

In some embodiments of the method of purifying water, the water is a water contaminated with salt or any other contaminant/undesirable compound(s).

In some embodiments of the method of purifying water, urchins trap salt or other contaminants from water thereby purifying the water.

In embodiments relating to the method of purifying water, the features and characteristics of the urchins and the manner in which it is prepared is as described by any of the embodiments above. For the sake of brevity, and avoiding repetition, each of those embodiments are not being reiterated here again. However, each of the said embodiments, completely fall within the purview of the method of purifying water described herein.

Overall, the present invention possesses at least the following advantages:
a) the urchin of carbon fibres and the corresponding composites of the present invention are effective and industrially scalable electromagnetic (EM) shielding materials;
b) the method of preparing the urchin of carbon fibres is a simple, efficient, eco-friendly/green, robust, and a scalable method that can be carried out any pH;
c) the composites of the present invention require a very low loading of urchin of carbon fibres (e.g. up to ~7%) to exhibit an enhanced shielding of electromagnetic radiations ranging from about -15 dB to about -60 dB over a frequency ranging from about 8 GHz to about 18 GHz.

It is to be understood that the foregoing description is illustrative not a limitation. While considerable emphasis has been placed herein on particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. Those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. Similarly, additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based upon description provided herein.

Descriptions of well-known/conventional methods/steps and techniques are omitted so as to not unnecessarily obscure the embodiments herein. Further, the disclosure herein provides for examples illustrating the above-described embodiments, and in order to illustrate the embodiments of the present disclosure, certain aspects have been employed. The examples used herein for such illustration are intended merely to facilitate an understanding of ways in which the embodiments may be practiced and to further enable those of skill in the art to practice the embodiments. Accordingly, following examples should not be construed as limiting the scope of the embodiments herein.

EXAMPLES

Example 1: Synthesis of Carbon Urchins
Hierarchically assembled urchins of carbon fibres were prepared from chopped carbon fibres as follows:

Chopped carbon fibres was obtained from SGL carbon company. The carbon fibres had a length of about 6 mm and a diameter of about 7 µm. Typically, 500 mg of said pristine chopped carbon fibres were added to about 40 mL of distilled water and about 360 mL of HNO3 aqueous solution, and was subjected to refluxing. Particularly, the solution was bath sonicated for about 30 minutes and kept for stirring for about 24 hours at about 80°C in an oil bath. The resultant solution was filtered and washed repeatedly with distilled water and kept for drying in the oven at 80°C and stored for further usage. Said protocol using water (polar solvent) was followed to synthesize urchins at all pH conditions, namely: a) acidic pH (pH=1) by employing nitric acid (HNO3), b) alkaline pH (pH=14) by employing sodium hydroxide (NaOH), c) neutral pH (pH=7.5) by employing sodium chloride (NaCl), d) sea water (obtained from Mangalore beach, Karnataka, India) to maintain pH = 8.1, and e) distilled water to maintain a pH = 6.8. A schematic representation of synthesis of urchins is illustrated in Figure 2 and Figure 4(A).

During the reflux reaction, the condensed vapors aid in clustering of chopped carbon fibre to form urchins. The mechanism of formation of urchins is illustrated in Figure 4. The formation mechanism can be further explained as follows: the isotropic chopped carbon fibres begin to aggregate and self-assemble into microsphere structures under heating so that the rate of vaporisation of solvent and the rate of condensation maintain a stable equilibrium or near-equilibrium condition. It is believed that Van der Waals force will drive the aggregates of chopped carbon fibre and enable the growth of urchin microstructures. During the condensation process, a large number of isotropic nuclei will assemble and aggregate into microspheres in order to reduce the total energy of the system. Due to the existence of a large number of surface defects, they could act as the sites for further growth on the surface of carbon fibre and finally evolve into the sea urchin-like architectures.

Figure 3 depicts various urchins derived from different pH conditions. As seen from Figure 3(c), employing any of the acidic pH, alkaline pH or neutral pH result in the formation of carbon urchins. While all the different pH conditions lead to the formation of urchins of carbon fibres, the variation is only in terms of weight of the formed carbon urchins. The weight of carbon urchins was higher when sea water (12 mg ± 2 mg) was employed followed by 8 mg ± 2 mg (DI water), 5 mg± 1 mg (salt solution), 4 mg ± 1 mg (alkaline solution), and 0.7 mg ± 0.3 mg (acid solution), respectively.

Additionally, experiments were also performed using ethanol (a polar solvent) at a pH of 7.3 and cyclohexane (a non-polar solvent) at a pH of 14. While urchins formed when ethanol was employed, urchins did not form in cyclohexane (non-polar solvent) (boiling point: 80.7°C) under reflux conditions for 48 hours. This non-polar solvent (cyclohexane) was chosen to maintain uniformity in temperature as continued in the case of polar solvents. These results further suggest that the conversion of chopped carbon fibres to urchin structures require polar solvents.

Further, the synthesis of urchins was also attempted in other ways. Particularly, the above described protocol under same conditions was alternatively performed by: a) heating at 80°C with DI water on hot plate, or b) hydrothermal reaction at 80°C with DI water. These alternate methods were employed to understand the effect of the condensation process. However, the formation of urchin did not occur in hot plate and hydrothermal techniques, whereas the urchin formation occurred only in refluxing conditions. These results also establish the importance of the present method (refluxing) to synthesize carbon urchins from chopped carbon fibres.

Example 2: Characterization of Carbon Urchins
Characterization of the synthesized urchins according to Example 1 was performed. X-ray diffraction (XRD) analysis was performed using XPERT Pro from PANalytical in the Scattering range 5-80°using CuKa radiation source (? = 1.5406 A°, 40kV & 30mA). The structural change in carbon urchins (C-urchins) was assessed by XRD; the XRD pattern of the synthesized C-urchins is shown in Figure 9. The C-urchins showed a peak around 25° which corresponds to (002) plane representing the carbon matrix. Chopped carbon fibre showed the similar pattern as the raw fibre and urchin are chemically same but differ by structure and shape.

The carboxylic functionalization of C-urchins was confirmed by Fourier transform infrared (FTIR) spectroscopy using a Perkin-Elmer GX in the range of 4000-400 cm-1. The carboxylic functionalization of carbon fibres (CF) was confirmed by FTIR spectra. Figure 10 shows the FTIR of chopped CF, C-urchin by acid and alkali. The new peak at 1704 cm-1 in the spectra of C-urchins corresponds to C=O carbonyl stretching. The pristine carbon fibre exhibited the C-H peak at 2831 cm-1.

The surface morphology of urchins was observed through microscopy. The SEM images of as prepared urchin (single urchin or carbon fibre unit) is shown in Figure 1. The urchin comprises a carbon fibre core and a lot of bristle-like spikes protruding out in all directions. The diameter of each spike varies from 5-7 µm, and the average length of spike is about 550-700 µm. These rod like spikes are connected through inter-spine contacts and are structurally uniform. Highly dense and close packed spikes strongly hold each other through van der waals force and depicts a sea-urchin like structure. This close packing helps in conducting and resulting into high EMI shielding.

Example 3: Preparation of Polymer Composite material
The urchins prepared in Example 1 were employed for developing polymer composites based on thermoplastic or thermoset polymers. Epoxy or Ethylene-vinyl acetate (EVA) based composites containing urchins were prepared.

Various epoxy composites containing control epoxy, epoxy with carbon fibre (CF) urchins were prepared by adding epoxy and an amine-based hardener [(2,2'-dimethyl-4,4'methylene bis (cyclohexylamine)] with 100:37 ratio followed by about 15 minutes of mixing at 500 rpm by mechanical mixing using an overhead stirrer (Heidolph RZR 2102) as this procedure results in better mixing. The mixture was kept in presence of vacuum to remove bubbles. A bed of urchin was arranged manually in the mould (with no overlap) and thereafter the mixed mixture of epoxy and hardener was carefully poured in Teflon coated aluminium mould. Similarly, a bed of urchins was laid (wherein the urchins touch each other) and infused with epoxy and hardener. The mould was then kept in the oven for curing and post-curing. It was pre-cured at about 60?, 80? and 100? each for about 1 hour followed by post-curing at about 120°C for about 2 hours. The rectangular samples were fabricated for EMI and conductivity measurements. An illustration of epoxy- CF urchin composite preparation is provided in Figure 7A.

Similar experiment was performed for preparing EVA based composite in the absence of hardener. The curing temperature here was maintained at about 170°C for about 2 hours.

Figures 7B and 8 provide digital photographs of the prepared epoxy and EVA based composites, respectively. As seen from these figures, urchins prepared under different pH conditions were successfully employed for synthesizing epoxy and EVA polymer composites. Urchin structures were mechanically strong during processing at relatively high temperature during composite preparation with epoxy or EVA polymers. Further, urchins did not undergo any deformation as clearly visible in Figures 7 and 8, respectively.

Example 4: Conductivity and EM radiation shielding capacity
The prepared epoxy and EVA polymer composites of Example 3 were analysed for conductivity and EMI shielding properties.

Conductivity and EMI shielding properties of both thermoplastics (EVA based polymer composite) and thermoset (Epoxy based polymer composite) filled with urchins in the 8 GHz to 12 GHz frequency range was analysed. The results are shown in Figure 5, Figure 6 and Table 1. The total shielding effectiveness SET (dB) of 1 mm thick epoxy/EVA composites incorporated with urchins was very high. A typical shielding effectiveness of about -20 dB indicates a shielding of 99% of the incoming EM radiation. The neat polymers (EVA and Epoxy) were transparent to EM radiation and polymer composites containing chopped carbon fibres having diameter of about 5 µm to about 7 µm and length of about 5 mm to about 6 mm showed -10 dB and -21 dB for Epoxy and EVA, respectively. However, most of the polymer composites according to present disclosure containing various urchins showed greater than -20 dB of shielding at urchin loading of as low as 7 wt%. Further, the composites showed a very high EM shielding of -45 dB and -58 dB when urchin loading was 22 wt% and 23 wt% (high content urchins) for EVA and Epoxy, respectively.

Table 1: Conductivity and EM shielding effectiveness of various polymer composites

Composites prepared with EVA and Epoxy
Urchins (wt %)
Polymer Matrix (wt %)
Conductivity (S/cm)
EMI SET (dB)

in EVA composite in Epoxy composite EVA Epoxy EVA Epoxy EVA Epoxy
Carbon Fibres (CF) 7 7 93 93 2E-2 4E-10 -21 -10
Acid urchins
7 7 93 93 1E-3 5E-2 -30
-16
Alkali urchins 7 7 93 93 4E-3 4E-2 -24 -19
Salt urchins 7 7 93 93 1E-2 2E-2 -27 -29
Sea water urchins 7 7 93 93 2E-1 3E-2 -19 -27
D.I water urchins 7 7 93 93 3E-2 1E-2 -24 -30
High content urchins 22 23 78 77 1E-1 3E-2 -45 -58

The data in Figures 5/6 and Table 1 demonstrate that polymer composite materials containing urchins of carbon fibres at different wt% according to the present disclosure have enhanced electromagnetic shielding. Further, very low urchin loadings of about 3 wt% to 7 wt% is enough to meet the standard EM shielding targets of -20 dB or above.

Further, the EMI shielding effectiveness of carbon nanotube (CNT) reinforced with EVA polymer at 3, 5 and 10 wt% was studied and the results are given in Figure 11. When compared with the results of Table 1, most of urchins-polymer composites possess enhanced EMI shielding at 7 wt% itself in comparison with CNT-polymer material which shows relatively lesser EMI shielding even at 10 wt%.

The above experimental results demonstrate the importance and advantages of the present carbon urchins and corresponding composite materials in achieving excellent EM shielding effect vis-à-vis conventional carbon materials (such as chopped carbon fibres or carbon nanotubes) containing composites.

The foregoing description of the specific embodiments reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Throughout this specification, the term ‘combinations thereof’ or ‘any combination thereof’ or ‘any combinations thereof’ are used interchangeably and are intended to have the same meaning, as regularly known in the field of patents disclosures.

As regards the embodiments characterized in this specification, it is intended that each embodiment be read independently as well as in combination with another embodiment. For example, in case of an embodiment 1 reciting 3 alternatives A, B and C, an embodiment 2 reciting 3 alternatives D, E and F and an embodiment 3 reciting 3 alternatives G, H and I, it is to be understood that the specification unambiguously discloses embodiments corresponding to combinations A, D, G; A, D, H; A, D, I; A, E, G; A, E, H; A, E, I; A, F, G; A, F, H; A, F, I; B, D, G; B, D, H; B, D, I; B, E, G; B, E, H; B, E, I; B, F, G; B, F, H; B, F, I; C, D, G; C, D, H; C, D, I; C, E, G; C, E, H; C, E, I; C, F, G; C, F, H; C, F, I, unless specifically mentioned otherwise.

Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
,CLAIMS:1. A carbon fibre unit comprising a carbon fibre core and a plurality of carbon fibres in a form of globular needles protruding out from the carbon fibre core,
wherein diameter of each of the globular needle is in the range of about 5 µm to about 10 µm;
wherein length of each of the globular needle is in the range of about 500 µm to about 1000 µm; and
wherein the carbon fibre unit is in a shape of sea-urchin.

2. The carbon fibre unit as claimed in claim 1, wherein the globular needles protrude out from the core in all directions to form an assembly of the globular needles.

3. The carbon fibre unit as claimed in claim 1, wherein the diameter of each of the globular needle is in the range of about 5 µm to about 7 µm, and length of each of the globular needle is in the range of about 550 µm to about 700 µm.

4. The carbon fibre unit as claimed in any of the claims 1 to 3, wherein mass of the carbon fibre unit is in the range of about 0.3 mg to about 25 mg.

5. A plurality of carbon fibre units, wherein each of the carbon fibre unit is as defined in any of the claims 1-4.

6. A method of preparing a carbon fibre unit comprising a carbon fibre core and a plurality of carbon fibres in a form of globular needles protruding out from the carbon fibre core,
the method comprising subjecting carbon fibres to a refluxing reaction in presence of a solvent,
wherein pH of the reaction is maintained between 1 to 14.

7. The method as claimed in claim 6, wherein the carbon fibres subjected to the refluxing reaction is selected from a group comprising chopped carbon fibres, carbon fiber mat, carbon fiber woven fabric, carbon fiber knit, carbon fiber spun yarn, and combinations thereof.

8. The method as claimed in claim 7, wherein the chopped carbon fibres have a diameter of about 5 µm to about 7 µm and a length of about 5 mm to about 6 mm.

9. The method as claimed in claim 6, wherein the solvent is a polar solvent selected from a group comprising water, alcohol, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), acetonitrile, and combinations thereof; and wherein the polar solvent is preferably water or alcohol.

10. The method as claimed in claim 9, wherein the alcohol is methanol, ethanol, or a combination thereof.

11. The method as claimed in claim 6, wherein:
a) a pH of 1 to 6.9 is acidic pH, wherein the acidic pH is maintained by an acid selected from a group comprising sulphuric acid (H2SO4), hydrochloric acid (HCl), nitric acid (HNO3), acetic acid (CH3COOH), and combinations thereof;
b) a pH of 7 is neutral pH, wherein the neutral pH is maintained by a salt selected from a group comprising chloride salt, sulphate salt, carbonate salt, phosphate salt, nitrate salt and combinations thereof; and
c) a pH of 7.1 to 14 is alkaline pH, wherein the alkaline pH is maintained by an alkali selected from a group comprising sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide [Ca(OH)2], ammonium hydroxide (NH4OH), and combinations thereof.

12. The method as claimed in claim 6 or claim 11, wherein:
a. a neutral to moderately alkaline pH of 7.5 is maintained by the salt;
b. an alkaline pH of 8.2 is maintained by sea water; and
c. a weakly acidic pH to a weakly alkaline pH range of 6.5 to 7.5 is maintained by deionized (DI) water.

13. The method as claimed in claim 6, wherein the refluxing reaction is carried out at a temperature ranging from about 50? to about 180?, and for a time period ranging from about 2 hours to about 48 hours.

14. The method as claimed in any of the claims 6 to 13, said method comprising:
a) providing a reactant mixture in a reflux apparatus, wherein the reactant mixture comprises chopped carbon fibres and an aqueous solution which maintains a pH between 1-14; and
b) refluxing the reactant mixture in presence of the polar solvent at a temperature ranging from about 50? to about 180? for a time-period ranging from about 2 hours to about 48 hours, to obtain carbon fibre units,
wherein the aqueous solution maintaining the pH between 1-14 is selected from a group comprising acid solution, alkali solution, salt solution, sea water and deionized (DI) water,
and wherein the polar solvent is selected from a group comprising methanol, ethanol, water, DMSO, DMF and acetonitrile.

15. The method as claimed in any of the claims 6 to 14, said method comprising:
a) providing a reactant mixture in a reflux apparatus, wherein the reactant mixture comprises chopped carbon fibres and an aqueous solution which maintains a pH between 1-14,
wherein the aqueous solution is an acid solution, alkali solution, salt solution, sea water, or deionised (DI) water, or any combination thereof; and
b) refluxing the reactant mixture in presence of the polar solvent at a temperature ranging from about 50? to about 180? for a time-period ranging from about 2 hours to about 48 hours, to obtain carbon fibre units, and
wherein the polar solvent is water or ethanol.

16. The method as claimed in claim 6, wherein the globular needles protrude out from the core in all directions to form an assembly of the globular needles;
wherein diameter of each of the globular needle is in the range of about 5 µm to about 10 µm, and length of each of the globular needle is in the range of about 500 µm to about 1000 µm; and
wherein mass of the carbon fibre unit is in the range of about 0.3 mg to about 25 mg.

17. A composite comprising a polymer matrix and a plurality of carbon fibre units,
wherein each of the carbon fibre unit comprises a carbon fibre core and a plurality of carbon fibres in a form of globular needles protruding out from the carbon fibre core,
and wherein the carbon fibre unit is in a shape of sea-urchin.

18. The composite as claimed in claim 17, wherein the globular needles protrude out from the core in all directions to form an assembly of the globular needles;
wherein diameter of each globular needle is in the range of about 5 µm to about 10 µm, and length of each globular needle is in the range of about 500 µm to about 1000 µm;
and wherein mass of each of the carbon fibre unit is in the range of about 0.3 mg to about 25 mg.

19. The composite as claimed in claim 17, wherein the polymer matrix comprises a thermosetting polymer, or a thermoplastic polymer, or a combination thereof;
wherein the thermosetting polymer is selected from a group comprising epoxy resin, silicone, polyurethane, phenolic resin, and combinations thereof; and
wherein the thermoplastic polymer is selected from a group comprising ethylene vinyl acetate (EVA), polypropylene (PP), polyethylene terephthalate (PET), low density polyethylene (LDPE), high density polyethylene (HDPE), and combinations thereof.

20. The composite as claimed in any of the claims 17 to 19, wherein the polymer matrix is present in an amount from about 75 wt% to about 99 wt% and the carbon fibre units are present in an amount from about 1 wt% to about 25 wt%.

21. The composite as claimed in claims 20, wherein the polymer matrix is present in an amount from about 93 wt% to 97 wt% and the carbon fibre units are present in an amount from about 3 wt % to about 7 wt%;
and wherein the polymer matrix comprises epoxy resin or ethylene vinyl acetate.

22. The composite as claimed in any of the claims 17 to 21, wherein the thermosetting polymer or the thermoplastic polymer is in the form of nanoparticles; and wherein the composite has a thickness ranging from about 1 mm to 5 mm.

23. The composite as claimed in any of the claims 17 to 22, wherein said composite has electromagnetic radiation shielding capacity measured as total shielding effectiveness in the range from about -15 dB to about -60 dB over frequency ranging from about 8 GHz to about 18 GHz and for over a period of about 1 month to about 60 months.

24. A method of preparing the composite as claimed in any of the claims 17 to 22, comprising:
a) mixing the polymer matrix and the carbon fibre units to form a mould; and
b) curing the mould to obtain the composite material.

25. The method as claimed in claim 24, wherein the curing is carried out at a temperature ranging from about 50? to about 200? for a time-period ranging from about 1 hour to about 5 hours.

26. The method as claimed in claim 24, wherein the composite comprising the ethylene vinyl acetate polymer matrix and the carbon fibre units is prepared by: a) mixing the ethylene vinyl acetate polymer and the carbon fibre units, and subjecting to compression moulding to form a mould, and b) curing the mould at a temperature of about 170ºC; or
wherein the composite comprising the epoxy polymer matrix and the carbon fibre units is prepared by: a) mixing the epoxy polymer with a hardener to obtain a mixture, followed by addition of the carbon fibre units to form a mould, and b) curing the mould at a temperature ranging from about 60ºC to about 120ºC.

27. An article or a device comprising the carbon fibre unit of any of the claims 1-4, the plurality of carbon fibre units of claim 5, or the composite of any of the claims 17-23, wherein the article or the device has an electromagnetic radiation shielding capacity measured as total shielding effectiveness ranging from about -15 dB to about -60 dB over a frequency ranging from about 8 GHz to about 18 GHz.

28. Use of the carbon fibre unit as claimed in claims 1-4, the plurality of carbon fibre units of claim 5, the composite of claims 17-23, or the article of claim 27 for shielding of electromagnetic radiation; or
use of the carbon fibre unit as claimed in claims 1-4 or the plurality of carbon fibre units of claim 5 for desalination or purification of water.

29. A method for shielding of electromagnetic radiation, comprising contacting the electromagnetic radiation with the carbon fibre unit as claimed in any of the claims 1-4, the plurality of carbon fibre units of claim 5, the composite of any of the claims 17-23, or the article of claim 27;
wherein the electromagnetic radiation shielding capacity measured as total shielding effectiveness ranges from about -15 dB to about -60 dB over a frequency ranging from about 8 GHz to about 18 GHz.

30. A method of desalinating or purifying water, comprising contacting the carbon fibre unit as claimed in any of the claims 1-4 or the plurality of carbon fibre units of claim 5 with water.

31. The method as claimed in claim 30, wherein the water subjected to desalination or purification is: a) sea water, or b) water contaminated with salt or a contaminant;
and wherein the method removes salt or contaminant from the water to obtain desalinated or purified water.