WO2021094836A1

WO2021094836A1 - Electromagnetic interference shielding composition, article and methods thereof

Info

Publication number: WO2021094836A1
Application number: PCT/IB2020/050030
Authority: WO
Inventors: Avinash RAJALAKSHMAN PAI; Sabu THOMAS; Nandakumar KALARIKKAL
Original assignee: Ministry Of Electronics & Information Technology (Meity); Mahatma Gandhi University
Priority date: 2019-11-14
Filing date: 2020-01-03
Publication date: 2021-05-20
Also published as: EP4058405A4; EP4058405A1

Abstract

The present disclosure relates to the field of polymer engineering, applied industrial technology and electromagnetic interference (EMI) shielding materials. Particularly, the present disclosure relates to a low-density EMI shielding composition comprising soft elastomer, conductive nanostructure and metal ferrite doped reduced graphene oxide (RGO) and method of preparing the composition. The composition of the present disclosure is useful for manufacturing EMI shielding articles such as coating, adhesive, sheet, absorber, gasket, Microwave Absorbing Material, Radar Absorbing Material, soft electromagnetic interference shielding material, etc. The present disclosure also relates to articles comprising the composition and methods of obtaining the same.

Description

“ELECTROMAGNETIC INTERFERENCE SHIELDING COMPOSITION, ARTICLE AND METHODS THEREOF”

TECHNICAL FIELD

The present disclosure generally relates to the field of polymer engineering, applied industrial technology and Electromagnetic interference (EMI) shielding materials. Particularly, the present disclosure relates to a low-density EMI shielding composition comprising soft elastomer, conductive nanostructure and metal ferrite doped reduced graphene oxide (RGO) and method of preparing the composition. The present disclosure also relates to articles comprising the composition and methods of obtaining the same.

BACKGROUND OF THE DISCLOSURE

The operation of electronic gadgets such as Bluetooth, Wi-Fi, radio, mobile phones and other telecommunication instruments works by transmitting and receiving electromagnetic signals in a particular bandwidth of electromagnetic spectrum as stipulated by the international telecommunication Union (ITU). The misdirected electromagnetic (EM) signals from these electronic modules develop a field that can interfere within the devices working in close proximities which is termed herein as electromagnetic interference. To attenuate the Electromagnetic interference (EMI) effects, EMI shields are typically inserted within electronic modules both to confine the EM energy within a source device and prevent it from interfering with other nearby devices. However, for achieving effective shielding, the spaces between the adjacent panels and openings inside the electronic modules should be properly sealed so as to prevent the leakage of electromagnetic energy.

The prior arts provide for high density EMI shielding compositions with lower efficiency in terms of total shielding effectiveness. The density of conventional EMI shielding gaskets is found to be more than 2.5 which adds to the weight of electronic gadgets. Also, the composition and methods of the prior art require higher concentration of nanomaterials, have higher costs, and lower shielding effectiveness. Therefore, there is a strong urge to develop low density gasket compositions which will also help to reduce the final weight of the electronic devices and achieve high shielding effectiveness. The present disclosure aims at overcoming the limitations of the prior art.

SUMMARY OF THE DISCLOSURE

Accordingly, the present disclosure relates to a composition comprising soft elastomer, conductive nanostructure and metal ferrite doped reduced graphene oxide (RGO); a method of preparing the said composition, comprising acts of: contacting the conductive nanostructure with the soft elastomer, and optionally mixing, to obtain a mixture; and adding the metal ferrite doped reduced graphene oxide (RGO) to the mixture, and optionally mixing, to obtain the composition; an article comprising the said composition; a method of obtaining an article comprising the said composition, comprising the act of compression moulding the said composition to obtain the article; and a method of obtaining an article comprising the said composition, comprising the act of combining and optionally mixing the said composition with an industrially acceptable excipient to obtain the article.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

In order that the present disclosure may be readily understood and put into practical effect, reference is now made to exemplary embodiments as illustrated with reference to the accompanying figure. However, the figure is purely for the purpose of exemplifying and is non-limiting in nature. The figure together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where:

FIGURES 1A & IB illustrate the transmission electron microscopic (TEM) images of the NiFdCft nanoparticle at 10 nm and 50 nm magnification respectively. FIGURE 2 illustrates the synthesis strategy of NiFdGi doped RGO.

FIGURE 3 A & B illustrates the transmission electron microscopic (TEM) images ofNiFe₂04 doped RGO at 50nm and 20 nm magnification respectively. FIGURE 4 illustrates the EMI shielding performance of silicone rubber gasket in X band region (8.2- 12.4 GHz).

DETAILED DESCRIPTION OF THE DISCLOSURE

The present disclosure pertains to a composition comprising soft elastomer, conductive nanostructure and metal ferrite doped reduced graphene oxide (RGO).

In an embodiment, the soft elastomer is silicone rubber or its analogue.

In embodiments of the present disclosure, soft elastomer refers to silicone rubber or its analogue which has a shore A hardness 30. Shore A hardness is the measure of softness.

In another embodiment, the conductive nanostructure is selected from a group comprising single walled carbon nanotubes (SWCNTs), double walled carbon nanotubes (DWCNTs), multiwalled carbon nanotubes (MWCNTs) or any combinations thereof.

In yet another embodiment, the metal ferrite is selected from a group comprising nickel ferrite, copper ferrite, silver ferrite, cobalt ferrite, and manganese ferrite or any combination thereof.

In still another embodiment, the conductive nanostructures is at a concentration ranging from about 1 to 2.88 weight percent. In still another embodiment, the metal ferrite doped reduced graphene oxide is at a concentration ranging from about 0.1 to 0.96 weight percent.

In still another embodiment, the soft elastomer is at a concentration ranging from about 96.16 to 98.9 weight percent. In still another embodiment, the composition is used for manufacturing an article selected from a group comprising coating, adhesive, sheet, absorber, gasket, Microwave Absorbing Material, Radar Absorbing Material and soft electromagnetic interference shielding material or any combination thereof.

The present disclosure also pertains to the use of the said composition for manufacturing an article selected from a group comprising coating, adhesive, sheet, absorber, gasket, Microwave Absorbing Material, Radar Absorbing Material and soft electromagnetic interference shielding material or any combination thereof.

The present disclosure also pertains to a method of preparing the said composition, comprising acts of: contacting conductive nanostructure with soft elastomer, and optionally mixing, to obtain a mixture; and adding metal ferrite doped reduced graphene oxide (RGO) to the mixture, and optionally mixing, to obtain the composition.

In an embodiment, the mixing is carried out at a temperature ranging from about 95°C to about 120°C, preferably about 100°C for a time period ranging from about 15 to about 30 minutes, preferably about 25 minutes at about 60 rpm to about 100 rpm, preferably about 80 rpm.

The present disclosure also pertains to an article comprising the said composition.

In an embodiment, the article is selected from a group comprising coating, adhesive, sheet, absorber, gasket, Microwave Absorbing Material, Radar Absorbing Material and soft electromagnetic interference shielding material or any combination thereof.

In another embodiment, density of the afore -described composition or article is less than 2.5, preferably ranging from about 1.14 to 1.25. In yet another embodiment, the article has total shielding effectiveness of at least -20 dB at frequency range of about 8.2 to about 12.4 GHz.

In still another embodiment, the article has total shielding effectiveness of about -74 dB at frequency range of about 8.2 to about 12.4 GHz.

The present disclosure also pertains to a method of obtaining an article comprising the said composition, wherein the method comprises the act of compression moulding the said composition to obtain the article. In an exemplary embodiment, the article is selected from a group comprising sheet, absorber, gasket, Microwave Absorbing Material, Radar Absorbing Material and a soft electromagnetic interference shielding gasket material.

In an embodiment, the compression moulding is carried out at a temperature ranging from about 130°C to about 160°C, preferably about 150°C.

The present disclosure also pertains to a method of obtaining an article comprising the said composition, wherein the method comprises the act of combining, and optionally mixing, the said composition with an industrially acceptable excipient to obtain the article. In an exemplary embodiment, the article is a coating or an adhesive.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results. Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising” or “containing” or “has” or “having” wherever used, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

As used herein, the term "about" means to be nearly the same as a referenced number or value. As used herein, the term "about" should be generally understood to encompass ± 10% of a specified amount or value.

As used herein, the terms ‘method’ and ‘process’ are used interchangeably.

As used herein, the term “hybrid nanomaterial” or “hybrid combination” are used interchangeably and refer to combination of the conductive nanostructure and metal ferrite doped reduced graphene oxide employed in the present disclosure. The conductive nanostructure includes but are not limited to single walled carbon nanotubes (SWCNTs), double walled carbon nanotubes (DWCNTs), multiwalled carbon nanotubes (MWCNTs) or any combinations thereof. The metal ferrite doped reduced graphene oxide include reduced graphene oxide doped with dopents such as but not limited to metal ferrites selected from a group comprising nickel ferrite, copper ferrite, silver ferrite, cobalt ferrite, manganese ferrite, etc. or any combination thereof.

In a non-limiting embodiment of the present disclosure, the ferrite particles are less than 50 nm.

In an exemplary and non-limiting embodiment of the present disclosure, the ferrite particles are ranging from about 5-50 nm.

As used herein, “total shielding effectiveness” refers to the shielding value in decibel (dB) offered by a shield material at a particular frequency and thickness to measure attenuation.

As used herein, “specific EMI shielding effectiveness” means shielding effectiveness value in (db) divided by density of the composition. In embodiments of the present disclosure, the density indicated herein is Relative Density.

The present disclosure overcomes the non-limited drawbacks of the prior art and provides for cost-effective, efficient composition, articles and methods thereof.

In an embodiment, the present disclosure provides for low density, cost-effective, efficient composition, articles and methods thereof for efficient absorption and attenuation of electromagnetic (EM) waves in X band frequency region (8.2-12.4 GHz) and/or providing technical enhancement in the shielding effectiveness value.

The present disclosure relates to a composition comprising a soft elastomer and a process for obtaining the said composition.

The present disclosure also relates to an article made from the composition comprising soft elastomer, methodology of obtaining the said article and applications thereof.

In an exemplary embodiment of the present disclosure, the article drawn from the composition comprising the soft elastomer is selected from group comprising but not limiting to coating, adhesive, sheet, absorber, gasket, Microwave Absorbing Material, Radar Absorbing Material and soft electromagnetic interference shielding material or any combination thereof.

In embodiments of the present disclosure, the composition and the article drawn from the said composition has total shielding effectiveness of at least -20 dB at frequency range of about 8.2 to about 12.4 GHz. -20 dB is the minimum shielding requirement for application in electronics devices. In an embodiment, the composition and the article drawn from the said composition has total shielding effectiveness ranging from about -63 dB to about -74 dB at frequency range of about 8.2 to about 12.4 GHz.

In an exemplary embodiment, the composition and the article drawn from the said composition has a maximum total shielding effectiveness of about -74 dB at frequency range of about 8.2 to about 12.4 GHz.

In embodiments of the present disclosure, the composition and the article drawn from the said composition is capable of absorbing microwave radiations, electromagnetic radiations, radio waves in frequency ranging from about 8.2 GHz to about 12.4 GHz.

In embodiments of the present disclosure, the composition and the article drawn from the said composition is capable of absorbing microwave (MW) radiation of at least about -20 decibels in frequency range of about 8.2 GHz to about 12.4 GHz.

In embodiments of the present disclosure, the composition and the article drawn from the said composition is capable of absorbing electromagnetic radiation of at least about -20 decibels in frequency range of about 8.2 GHz to about 12.4 GHz.

In embodiments of the present disclosure, the composition and the article drawn from the said composition is capable of absorbing radio waves of at least about -20 decibels in frequency range of about 8.2 GHz to about 12.4 GHz.

In an embodiment, the composition and the article of the present disclosure is a flexible Electromagnetic interference (EMI) shielding composition.

Electromagnetic shielding refers to reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. In an embodiment, the composition and the article of the present disclosure has a specific EMI shielding effectiveness value ranging from 63/1.1148 which is 55 db.g Vcm ³ to -74/1.148 which is -64 (db.g Vcm ³). The composition of the present disclosure comprises a soft elastomer, conductive nanostructure and metal ferrite doped reduced graphene oxide (RGO).

In embodiments of the present disclosure, the conductive nanostructure provides electric dipoles and the metal ferrite present in the doped RGO provides magnetic dipoles for the electromagnetic waves to interact with. Magnetic nanomaterial such as metal ferrites tend to agglomerate if added alone. In embodiments of the present disclosure, doping the metal ferrites on RGO aids its uniform dispersion in the rubber matrix (soft elastomer).

In embodiments of the present disclosure, the soft elastomer employed in the present disclosure has a Shore A hardness of 35-45.

In an embodiment of the present disclosure, the soft elastomer is silicone rubber/ polydimetyl siloxane (PDMS) or its analogue.

In embodiments of the present disclosure, the conductive nanostructure is selected from a group comprising single walled carbon nanotubes (SWCNTs), double walled carbon nanotubes (DWCNTs), multiwalled carbon nanotubes (MWCNTs) or any combinations thereof.

In preferred embodiments of the present disclosure, the conductive nanostructure is single walled carbon nanotubes (SWCNTs).

In preferred embodiments of the present disclosure, the conductive nanostructure is double walled carbon nanotubes (DWCNTs).

In preferred embodiments of the present disclosure, the conductive nanostructure is multiwalled carbon nanotubes (MWCNTs). In embodiments of the present disclosure, the reduced graphene oxide is doped with metal ferrites wherein the metal is selected from a group comprising nickel, copper, silver, cobalt, manganese, or any combination thereof.

In embodiments of the present disclosure, the reduced graphene oxide is doped with metal ferrite selected from a combination of copper ferrite, silver ferrite, nickel ferrite, cobalt ferrite, manganese ferrite, etc. and combinations thereof.

In an exemplary embodiment, the metal ferrite/magnetically doped RGO is NiFdCri doped RGO.

In an exemplary embodiment, the present disclosure relates to low density soft elastomer composition comprising of hybrid nanostructures with multi walled carbon nanotubes and nickel ferrite doped graphene for efficient absorption and attenuation of electromagnetic waves in X band frequency region (8.2-12.4 GHz).

In embodiments of the present disclosure, the soft elastomer is at a concentration ranging from about 96.16 to 98.9 weight percent of the total weight of the composition.

In embodiments of the present disclosure, the conductive nanostructure (such as MWCNT) is at a concentration ranging from about 1 to 2.88 weight percent of the total weight of the composition.

In embodiments of the present disclosure, the metal ferrite doped RGO is at a concentration ranging from about 0.1 to 0.96 weight percent of the total weight of the composition.

In embodiments of the present disclosure, the hybrid combination is at a concentration ranging from about 1.1 to 3.84 weight percent of the total weight of the composition. In embodiments of the present disclosure, the hybrid combination is at a concentration ranging from about 3.5 Parts per Hundred Rubber (Phr)- to 5 Phr. The soft elastomer’s concentration is always 100 phr or 100 parts to which the hybrid combination is added.

In embodiments of the present disclosure, the conductive nanostructure is at a concentration ranging from about 3 Phr to 4 Phr.

In embodiments of the present disclosure, the metal ferrite doped RGO is at a concentration ranging from about 0.5 Phr to 1 Phr.

In an embodiment, a percolating network of the conductive nanostructure aids in proper distribution of the metal ferrite doped RGO. Further, the present disclosure provides for a uniform distribution of the metal ferrite doped RGO and conductive nanostructure with the soft elastomer. This allows employing lower loading of the metal ferrite on the elastomer, which retains the flexibility of the elastomer and results in a product having much lower density compared to products known in the art.

In embodiments of the present disclosure, the density of the composition and/or the article drawn from the composition is very low. This reduces the overall weight of the final product, such as electronic product, into which it is inserted to serve as EMI shield.

The density of the composition and/or the article drawn from the composition of the present disclosure is less than 2.5. The composition and/or the article of the present disclosure thus has high specific EMI shielding value i.e. shielding per unit density (db.g-d/cnG).

In embodiments of the present disclosure, the density of the composition and/or the article drawn from the composition is less than 1.25. In embodiments of the present disclosure, the density of the composition and/or the article drawn from the composition ranges from about 1.14 to 1.25, preferably 1.148.

In an embodiment of the present disclosure, Graphite oxide is synthesized by oxidation of graphite according to Hummer’s method, wherein H2SO4 is cooled and added to a mixture of graphite flakes and NaNCb. The mixture is then kept at 0 °C followed by addition of KMnOu The reaction mixture is then heated and stirred followed by slow addition of water to increase the temperature. The reaction mixture is then cooled followed by the addition of water and H2O2 in order to terminate the reaction. The resulting solution is then allowed to settle down and washed with double distilled water until the pH becomes neutral. The solution is filtered. The filtrate is collected and vacuum -dried to obtain graphite oxide (GO).

In an embodiment of the present disclosure, the metal ferrite employed in the present disclosure may be prepared in accordance to any standard protocol known in the art.

In an exemplary embodiment of the present disclosure, the process for preparing the metal ferrite comprises: contacting salts (such as nitrates) of metal selected from a group comprising nickel, copper, silver, cobalt, and manganese or any combinations thereof with salts of iron (preferably iron (III) nitrate) and dissolving in a suitable solvent such as water, the pH of the above reaction mixture is maintained to about 10-11 to aid precipitation of the iron and the metal hydroxides, the solution along with the precipitate thus obtained is heated and subsequently cooled, the resulting solid product is collected, washed, dried and optionally calcined to obtain the metal ferrite. In an exemplary embodiment of the present disclosure, spinal NiFciOr is prepared by mixing Fe(NC>3)2 · 9FhO and Ni(NC>3)2 · 6H2O and dissolved in water preferably deionized water. The pH is maintained at 10-11 by addition of KOH solution, to aid precipitation of iron and nickel hydroxides. The solution along with the precipitate is transferred into an autoclave. The autoclave is sealed and kept in an oven and subsequently cooled. The resulting solid product is collected and washed. The washed particles are then dried and calcined to obtain the spinal NiFerCh.

In another embodiment, the solid product is washed with deionized water and ethanol.

In embodiments of the present disclosure, the metal ferrite doped RGO is obtained by Solvothermal Synthesis for decorating the metal ferrite on graphene.

In an embodiment of the present disclosure, metal ferrite doped RGO is in situ- synthesized by coprecipitation of the metal ferrite in the presence of GO using hydrothermal reaction, wherein the metal ferrite is added to GO and dispersed in water. The mixture obtained is optionally sonicated and combined with NaBHr, transferred into a hydrothermal reactor half filled with water and heated. The mixture is then left to cool down to room temperature. The obtained metal ferrite doped RGO powder is filtered, rinsed with double distillated water several times, and optionally dried.

In another embodiment, the metal ferrite is selected from a group comprising nickel ferrite, copper ferrite, silver ferrite, cobalt ferrite, manganese ferrite, or any combination thereof.

In an embodiment, the composition of the present disclosure is prepared by contacting the conductive nanostructure with soft elastomer, and then adding metal ferrite doped reduced graphene oxide (RGO) to obtain the composition. In embodiments of the present disclosure, the method of preparing the EMI shielding composition comprises acts of:

- contacting the conductive nanostructure with soft elastomer, and optionally blending/mixing, to obtain a mixture;

- adding metal ferrite doped reduced graphene oxide (RGO) to the mixture, and optionally blending/mixing, obtain the composition.

In an embodiment of the present disclosure, the method of preparing the EMI shielding composition comprises acts of:

- adding the soft elastomer in a blender/mixer and contacting it with the conductive nanostructure followed by blending/mixing to obtain a mixture;

- adding metal ferrite doped reduced graphene oxide (RGO) to the mixture and blending/mixing to obtain the composition.

In embodiments of the present disclosure for preparation of the EMI shielding composition, the blending/mixing is carried out at temperature ranging from about

95°C to about 120°C, preferably about 100°C for a time period of about 15 minutes to about 30 minutes, preferably about 25 minutes at about 60 rpm to about 100 rpm, preferably about 80 rpm. In embodiments of the present disclosure, the mixer is selected from a group comprising Haake mixer or barbender.

In embodiments of the present disclosure for preparation of the EMI shielding composition, the soft elastomer is silicone rubber or its analogue, the conductive nanostructure is selected from a group comprising single walled carbon nanotubes (SWCNTs), double walled carbon nanotubes (DWCNTs), multiwalled carbon nanotubes (MWCNTs) or any combinations thereof, and/or the reduced graphene oxide is doped with metal ferrite selected from a group comprising nickel ferrite, copper ferrite, silver ferrite, cobalt ferrite, and manganese ferrite or any combination thereof. In embodiments of the present disclosure for preparation of the EMI shielding composition, the conductive nanostructures is at a concentration ranging from about 1 to 2.88 weight percent; the metal ferrite doped reduced graphene oxide is at a concentration ranging from about 0.1 to 0.96 weight percent; and the soft elastomer is at a concentration ranging from about 96.16 to 98.9 weight percent.

In a preferred embodiment, a percolating network of carbon nanotubes (CNTS) is obtained at about at least 3 phr of conductive nanostructure and followed by addition of magnetically doped RGO.

In an embodiment of the present disclosure, the metal ferrite nanoparticles are stacked uniformly in between the graphene sheets in the metal ferrite doped RGO. The metal nanoparticles are not coated on graphene but stacked in between the sheets of graphene via weak Vander walls forces of interaction.

In an embodiment, the article of the present disclosure is prepared by compression moulding the well dispersed soft elastomer composition at about 130°C to 160°C to make EMI shielding articles with desired thickness.

In a non-limiting embodiment of the present disclosure, the thickness of the article may be varied as desired to provide at least -20 db shielding effectiveness, and hence a wide range of thickness may be employed. In an exemplary non-limiting embodiment, the thickness of the article is ranging from about 0.1 mm to 10 mm.

In an exemplary embodiment, the article is compression molded to different forms.

In another exemplary embodiment, the gasket is compression molded to different forms.

In embodiments of the present disclosure, the composition is manufactured into an article selected from a group comprising coating, adhesive, sheet, absorber, gasket, Microwave Absorbing Material, Radar Absorbing Material and soft electromagnetic interference shielding material or any combination thereof

In embodiments of the present disclosure, the total shielding effectiveness of an article of the composition is -74 dB at 12 Ghz.

In embodiments of the present disclosure, the method of obtaining the article such coating, adhesive etc. comprises the act of combining and optionally mixing the afore-described composition of the present disclosure with an industrially acceptable excipient to obtain the said article.

In an embodiment, the excipient used in the process of obtaining the article may be any industrially acceptable excipient such as but not limited to resin, solvent or any combination thereof.

In an exemplary embodiment, the resin is liquid silicone resin.

In another exemplary embodiment, the solvent is selected from a group comprising chloroform, THF, xylene, toluene, pentane, n-heptane, diisoproplyamine or any combination thereof.

In embodiments of the present disclosure, heating during the process is carried out in a hot water bath.

In embodiments of the present disclosure, cooling during the process is carried out in an ice bath.

In embodiments of the present disclosure, room temperature is about 28°C.

In an embodiment of the present disclosure, the coating is prepared by combining the soft elastomer, the conductive nanostructure (such as SWCNT, DWCNT, and/or MWCNT) and the metal ferrite doped RGO in a suitable solvent. In an exemplary embodiment, the solvent is selected from a group comprising chloroform, tetrahydrofuran (THF), xylene, toluene, pentane, n-heptane, and diisoproplyamine or any combination thereof.

In embodiments of the present disclosure, the silicone rubber based coating is prepared by dispersing the hybrid nanostructures in a solvent, and mixed with liquid silicone rubber to form the coating. The coating on drying at the desired thickness has total shielding effectiveness of at least -20 dB at frequency range of about 8.2 to about 12.4 GHz.

In exemplary and non-limiting embodiment of the present disclosure, the solvent for use in preparation of the coating is selected from a group comprising chloroform, tetrahydrofuran (THF), xylene, toluene, pentane, n-heptane and diisoproplyamine or any combination thereof.

In an embodiment of the present disclosure, the adhesive is prepared by combining the soft elastomer, the conductive nanostructure (such as SWCNT, DWCNT, and/or MWCNT) and the metal ferrite doped RGO in a suitable solvent. In an exemplary embodiment, the solvent is selected from a group comprising chloroform, tetrahydrofuran (THF), xylene, toluene, pentane, n-heptane, and diisoproplyamine or any combination thereof.

In embodiments of the present disclosure, the composition of the present disclosure comprising the soft elastomer, the conductive nanostructure, and the metal ferrite doped reduced graphene oxide is synergistic in nature.

In embodiments of the present disclosure, replacement of the soft elastomer with hard rubber such as natural rubber or styrene -butadiene rubber (SBR) does not result in the desired shielding effectiveness due to increased hardness of the rubber matrix. Thus, replacing the soft elastomer in the composition of the present disclosure with an alternate rubber does not result in the desired properties in the composition and article of the present disclosure.

In embodiments of the present disclosure, excluding conductive nanostructures from the composition of the present disclosure i.e. resulting in a composition having only the soft elastomer and metal ferrite doped RGO does not result in the desired properties in the composition/ article. Thus, if only metal doped RGO is added to the silicone rubber, in absence of conductive nanostructures, it does not result in the percolation which is created only on using the conductive nanostructures of the present disclosure. Thus, in preferred embodiments of the present disclosure, the conductive nanostructures are added first to form a percolating network followed by addition of the metal ferrite doped RGO.

In embodiments of the present disclosure, excluding metal ferrite doped RGO from the composition of the present disclosure i.e. resulting in a composition having only the soft elastomer and conductive nanostructure does not result in the desired properties in the composition article as the shielding value is found to be much lesser than -74 db.

In an exemplary embodiment, advantages of the present disclosure include but are not limiting to:

• The composition and articles of the present disclosure provide for efficient absorption and attenuation of electromagnetic waves in X band frequency region (8.2-12.4 GHz)

• The composition is advantageous as articles such as coating, adhesive, sheet, absorber, gasket, Microwave Absorbing Material, Radar Absorbing Material and soft electromagnetic interference shielding material or any combination thereof.

• The composition and articles of the present disclosure provide for high shielding materials with lower hybrid combination loadings. Lower loading of the hybrid combination of the nanomaterials, results in reduction of costs. • The present disclosure provides for composition and articles having low density of about 1.14 to 1.25, preferably about 1.148.

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.

Any possible combination of two or more of the embodiments described herein is comprised within the scope of the present disclosure.

The foregoing descriptive matter is illustrative of the disclosure and not a limitation. While considerable emphasis has been placed herein on the 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.

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

EXAMPLES:

Example 1: Preparation of graphite oxide (GO)

Graphite oxide was synthesized by oxidation of graphite according to Hummer’s method with slight modifications. 69 ml of H2SO4 was cooled to 0 °C in an ice bath and after 45 min of cooling, it was added to a mixture of graphite flakes (3.0 g) and NaNCb (1.5 g). The mixture was again kept in the ice bath at 0 °C followed by the slow addition of KMnCft (9.0 g). The slow addition process takes place for about 2-3 h. The reaction mixture was then heated to 35 °C in a hot water bath and stirred for 30 min followed by slow addition of double distilled water (138 ml) to increase the temperature to 95°C. The heating of the reaction mixture at 95 °C was continued for 15 min, after which the heat was removed. The reaction mixture was then cooled using an ice bath for 10 min followed by the addition of 420 ml double distilled water and 30 ml H2O2 in order to terminate the reaction. The resulting solution was allowed to settle down for 24 h and washed with double distilled water several times until the pH became neutral through settling and decantation process. The reaction mixture is allowed to slowly settle down the bottom of the flask post which it can be easily decanted. The solution was filtered with Whatman^® Grade 41 filter paper. The filtrate was collected and vacuum -dried at 60°C for 24 h to obtain GO.

Example 2: i) Preparation of NiFe₂Q₄ nanoparticles

Spinal NiFe204 was prepared by using about 3.5 g of Fe(N03)2 · 9¾0 and about 1.4 g of Ni(N03)2 · 6H2O which were mixed together in 2:1 molar ratio and dissolved in 20 ml deionized water. The pH was maintained at 10-11 with KOH solution, where iron and nickel hydroxides were precipitated. The solution along with the precipitate was transferred into a 100-ml Teflon-lined stainless steel autoclave. The autoclave was sealed and kept in an oven at 180°C for 6h and then cooled to room temperature. The resulting solid product was collected and washed with deionized water and ethanol. The washed particles were then dried at 70°C for 6 h followed by calcination at 600°C for 3h in air. The TEM images of the NiFdCU nanoparticle is shown in figure 1A & B. ii) Preparation of nanoparticles

CoFdC nanoparticles were prepared by using about 3.5g of Fe(NC>3)2 · 9FhO and about 1.4 g of CO(NC>3)2 · 6FhO which were mixed together in 2:1 molar ratio and dissolved in 20 ml deionized water. The pH was maintained at 10-11 with KOH solution, where iron and cobalt hydroxides were precipitated. The solution along with the precipitate was transferred into a 100-ml Teflon-lined stainless steel autoclave. The autoclave was sealed and kept in an oven at 180°C for 6h and then cooled to room temperature. The resulting solid product was collected and washed with deionized water and ethanol. The washed particles were then dried at 70°C for 6 h followed by calcination at 600°C for 3h in air. iii) Preparation of MnFe_2Q4 nanoparticles

MnFe204 nanoparticles were prepared by using about 3.5 g of Fe(NC>3)2 · 9H2O and about 1.4 g of Mh(Nq3)2· 6H2O which were mixed together in 2:1 molar ratio and dissolved in 20 ml deionized water. The pH was maintained at 10-11 with KOH solution, where iron and manganese hydroxides were precipitated. The solution along with the precipitate was transferred into a 100-ml Teflon-lined stainless steel autoclave. The autoclave was sealed and kept in an oven at 180°C for 6h and then cooled to room temperature. The resulting solid product was collected and washed with deionized water and ethanol. The washed particles were then dried at 70°C for 6 h followed by calcination at 600°C for 3h in air.

Example 3: i) Solvothermal Synthesis of NiFe_2Q4 doped RGO

NiFe2C>4 doped RGO was in situ-synthesized by coprecipitation of Ni(N03)2 · 6H2O, and Fe(N03)3 9¾0 in the presence of GO using hydrothermal reaction. 3.5 g of [Fe3 (NO)3 9HO2], 1.4 g ofNi(N0₃)26H2O were added to 200 mg of GO dispersed in 400 ml of double distilled water. The mixture was sonicated with a frequency of 20 KHz and power of 1500 Watt for lh. An ice bath was used in order to avoid increase in temperature during the sonication process. Then, the mixture was combined with 70 ml of NaBH4 (37.5 mg/ml) and transferred into a hydrothermal reactor which is half filled with double distilled water and kept in an oven at 160 °C for 6 h. The mixture was then left to cool down at room temperature for 12 h. The obtained NiFdCU doped RGO powder (with black color) was filtered with Whatman^® Grade 41 filter paper, rinsed with double distillated water several times, and dried in an oven at 80 °C for 24 h. The synthesis protocol of NiFdCri doped RGO is shown in figure 2.

It can be observed from TEM images shown in figure 3A & B, that NiFe204 nanoparticles are stacked uniformly in between the graphene sheets. The NiFe204 nanoparticles are not coated on graphene but stacked in between the sheets of graphene via weak Vander walls forces of interaction. ii) Solvothermal Synthesis of CoFe_2Q4 doped RGO

CoFe204 doped RGO was in situ-synthesized by coprecipitation of Co(N03)2· 6H2O and Fe(N03)3 · 9H2O in the presence of GO using hydrothermal reaction. 3.5 g of [Fe₃ (N0)₃ · 9HO2], 1.4 g of Co(N0₃)2 · 6H2O were added to 200 mg of GO dispersed in 400 ml of double distilled water. The mixture was sonicated with a frequency of 20 KHz and power of 1500 Watt for lh. An ice bath was used in order to avoid increase in temperature during the sonication process. Then, the mixture was combined with 70 ml of NaBHi (37.5 mg/ml) and transferred into a hydrothermal reactor which is half filled with double distilled water and kept in an oven at 160 °C for 6 h. The mixture was then left to cool down at room temperature of about 28°C for 12 h. The obtained CoFerCri doped RGO powder (with black color) was filtered with Whatman^® Grade 41 filter paper, rinsed with double distillated water several times, and dried in an oven at 80 °C for 24 h. iii) Solvothermal Synthesis of MnFe_2Q4 doped RGO

MnFdC doped RGO was in situ-synthesized by coprecipitation of Mn(N03)2 · 6H2O and Fe(N03)3 · 9FhO in the presence of GO using hydrothermal reaction. 3.5 g of [Fe₃ (N0)₃ 9HO2], 1.4 g of Mn(N0₃)2 · 6FhO were added to 200 mg of GO dispersed in 400 ml of double distilled water. The mixture was sonicated with a frequency of 20 KHz and power of 1500 Watt for lh. An ice bath was used in order to avoid increase in temperature during the sonication process. Then, the mixture was combined with 70 ml of NaBHi (37.5 mg/ml) and transferred into a hydrothermal reactor which is half filled with double distilled water and kept in an oven at 160 °C for 6 h. The mixture was then left to cool down at room temperature of about 28°C for 12 h. The obtained MnFe204 doped RGO powder (with black color) was filtered with Whatman^® Grade 41 filter paper, rinsed with double distillated water several times, and dried in an oven at 80 °C for 24 h. Example 4: Preparation of silicone rubber based EMI shielding composition and gasket

The silicone rubber based EMI shielding composition was prepared by blending 100 PHR -silicone rubber (PDMS) with 3 PHR multi walled carbon nanotubes in a Haake mixer, followed by adding 1 PHR NiFe204 doped RGO to the mixture and mixing at 100°C for 25 min at 80 rpm.

The well dispersed silicone rubber composition obtained was then compression moulded at 150°C to make EMI shielding gaskets with 5mm thickness. The moulded gasket samples were measured for EMI shielding effectiveness by using a vector network analyzer coupled with a wave guide operating in X band (8.2 to 21.4 Ghz)

The total shielding effectiveness of the silicone rubber based gasket composition was -74 dB at 12 Ghz and 5mm gasket thickness as evident from figure 4. Example 5: Preparation of coating

The silicone rubber based coating is prepared by dispersing the hybrid nanostructures (comprising the multi walled carbon nanotubes and NiFdGi doped RGO or CoFdCU doped RGO or MnFdCU doped RGO) in the solvent chloroform, adding liquid silicone rubber (PDMS) and mixing to form the coating. The process is repeated for each of the metal ferrite doped RGO by replacing the chloroform with alternate solvents viz. THF, xylene, toluene, pentane, n-heptane or diisoproplyamine. Each coating thus obtained has total shielding effectiveness of at least -20 dB at frequency range of about 8.2 to about 12.4 GHz. The coating was found to have the same EMI shielding performance as the gasket.

Therefore, it is evident that the present disclosure is able to successfully overcome the various deficiencies of prior art and provide for a composition a method for preparing the composition comprising a soft elastomer, conductive nanostructures, and magnetically doped reduced graphene oxide (RGO), that exhibit efficient absorption and attenuation of electromagnetic waves in X band frequency region (8.2-12.4 GHz).

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.

Claims

We Claim:

1. A composition comprising soft elastomer, conductive nanostructure and metal ferrite doped reduced graphene oxide (RGO).

2. The composition as claimed in claim 1, wherein the soft elastomer is silicone rubber or its analogue, wherein the conductive nanostructure is selected from a group comprising single walled carbon nanotubes (SWCNTs), double walled carbon nanotubes (DWCNTs), multiwalled carbon nanotubes (MWCNTs) or any combinations thereof, and wherein the metal ferrite is selected from a group comprising nickel ferrite, copper ferrite, silver ferrite, cobalt ferrite and manganese ferrite or any combinations thereof.

3. The composition as claimed in claim 1, wherein the conductive nanostructures is at a concentration ranging from about 1 to 2.88 weight percent; wherein the metal ferrite doped reduced graphene oxide is at a concentration ranging from about 0.1 to 0.96 weight percent; and wherein the soft elastomer is at a concentration ranging from about 96.16 to 98.9 weight percent.

4. The composition as claimed in claim 1, wherein the composition is used for manufacturing an article selected from a group comprising coating, adhesive, sheet, absorber, gasket, Microwave Absorbing Material, Radar Absorbing Material and soft electromagnetic interference shielding material.

5. A method of preparing the composition as claimed in any of claims 1 to 4, comprising acts of: contacting conductive nanostructure with soft elastomer, and optionally mixing, to obtain a mixture; and adding metal ferrite doped reduced graphene oxide (RGO) to the mixture, and optionally mixing, to obtain the composition.

6. The method as claimed in claim 5, wherein the mixing is carried out at a temperature ranging from about 95°C to about 120°C, preferably about 100°C for a time period of about 15 minutes to about 30 minutes, preferably about 25 minutes at about 60 rpm to about 100 rpm, preferably about 80 rpm.

7. An article comprising the composition as claimed in any of claims 1 to 4.

8 The article as claimed in 7, wherein the article is selected from a group comprising coating, adhesive, sheet, absorber, gasket, Microwave Absorbing Material, Radar Absorbing Material and soft electromagnetic interference shielding material.

9. The article as claimed in 8, wherein the article has total shielding effectiveness of at least -20 dB at frequency range of about 8.2 to about 12.4 GHz.

10. The composition as claimed in claim 1 or the article as claimed in 8, wherein density of the composition or the article is less than 2.5, preferably ranging from about 1.14 to 1.25.

11. A method of obtaining an article comprising a composition as claimed in any of claims 1-4, comprising act of compression moulding the said composition to obtain the article.

12. The method as claimed in claim 11, wherein the compression moulding is carried out at a temperature ranging from about 130°C to about 160°C, preferably about 150°C.

13. The method as claimed in claim 11, wherein the article is selected from a group comprising sheet, absorber, gasket, Microwave Absorbing Material, Radar Absorbing Material and soft electromagnetic interference shielding gasket material.

14. A method of obtaining an article comprising a composition as claimed in any of claims 1-4, comprising act of combining and optionally mixing the said composition with an industrially acceptable excipient to obtain the article.

15. The method as claimed in claim 14, wherein the article is a coating or an adhesive.