FIELD OF INVENTION
[001] The present invention relates to development of Metal Molybdate Carbon Nanotube Composite for suppression of Electromagnetic Pollution or shielding of electromagnetic interference (EMI), and in particular, to composite comprising a Metal Molybdate i.e. Nickel Cobalt Molybdate and carbon nanotubes as 5 substrates. The present subject matter relates to development of high EMI shielding effectiveness materials with advantages of reduced weight, improved corrosion resistant and good electrical conductivity. These composites find applications of electromagnetic interference shielding or suppression of electromagnetic pollution in Ku-band. 10
Definitions of Terms and Phrases
[002] It may be noted that the abbreviations are not necessarily used commonly. For the facilitation of drafting, several abbreviations may be formulated strictly 15 for this specification describing the present invention.
OPV: Organic Photo Voltaic
OSC(s): Organic Solar Cell(s)
BHJ: Bulk Hetero Junction 20
HTL(s): Hole Transport Layer(s)
ITO: Indium Tin Oxide
QD’s: Quantum Dots
CNT: Carbon nanotube
P3HT: Poly-3-hexylthiophene 25
CdS: Cadmium Sulphide
TCB: Trichlorobenzene
TOP: Trioctylphosphine
MoO3: Molybdenum oxide
30
[003] It may be noted that as per the requirement of invention disclosure, terms or phrases are used in several combination.
3
BACKGROUND AND PRIOR ARTS OF INVENTION
[004] Current technologies have become a source of omnipresent electromagnetic pollution from generated electromagnetic fields and resulting electromagnetic radiation. In many cases this pollution is much stronger than any natural sources of electromagnetic fields or radiation. Wireless and radio 5 communication, power transmission, or devices in daily use such as smartphones, tablets, and portable computers every day expose people to electromagnetic pollution. The harm caused by this pollution is still open to question since there is no clear and definitive evidence of its negative influence on human beings. This is despite the fact that extremely low frequency electromagnetic fields were 10 classified as potentially carcinogenic. For these reasons, in recent decades a significant growth can be observed in the scientific research on the influence of electromagnetic fields and/or electromagnetic radiation on living organisms. Alarming reports of potentially harmful effects of electromagnetic pollution drew the attention of the World Health Organization (WHO), which in 2007 presented a 15 summary report of an international research program titled Electromagnetic Fields. Hence, high-performance electromagnetic interference (EMI) shielding materials are required to isolate the internal electronics from the surroundings. Based on these well-established attenuation principles, shielding materials are classified into two categories: wave-reflection dominant materials and wave-20 absorption dominant materials. Metals are typical wave-reflection dominant materials owing to their abundance in mobile charge carriers that can interact with the electric vector of incident EM radiation. Wave-absorption dominant materials are composed of magnetic materials like carbonyl iron and ferrites (including Fe3O4 and α-Fe2O3), dielectric materials such as barium titanate, carbon-based 25 materials (including carbon fibers, carbon black, graphite, graphene, single-/multi-wall carbon nanotubes and mesoporous carbon) and conductive polymers (including polyaniline (PANI), polyacetylene and polypyrrole). Combining two or three of these materials together may be an effective way to bypass these inherent shortcomings. As an alternative, binary- or ternary-component shielding 30 composites may have supplementary attenuation properties (not available from
4
their single peer) toward EM waves, i.e., an improved match degree between magnetic loss and dielectric loss; a synergistic effect between wave absorption and wave reflection.
[005] Following are the works done so far in the field of wave absorption or 5 reflection composite materials for protection from Electromagnetic pollution or EMI shielding application:
[006] US20120236528A1 reports a flexible multilayer electromagnetic shield is provided that includes a flexible substrate, a thin film layer of a first 10 ferromagnetic material with high magnetic permeability disposed upon the substrate and a multilayer stack disposed upon the first ferromagnetic material. The multilayer stack includes pairs of layers, each pair comprising a polymeric spacing layer and a thin film layer of at least a second ferromagnetic material disposed on the spacing layer. At least one or more of the spacing layers includes 15 an acrylic polymer. Also methods of making the flexible multilayer electromagnetic shield are provided.
[007] US 6870092B2 dealt with respect to methods and apparatus for improving the resiliency and airflow through a honeycomb air vent filter while providing 20 EMI shielding. In one embodiment, the honeycomb can be manufactured from a dielectric (e.g., plastic) substrate to provide improved resistance to deformation as compared to conventional aluminum honeycomb. The dielectric honeycomb substrate is metalized to provide EMI shielding capability. The metalized honeycomb substrate is cut slightly oversize to fit an opening in an electronic 25 enclosure, which results in elastic deformation of resilient perimeter spring fingers that are used to hold the metalized dielectric honeycomb in place and provide electrical conductivity between the metalized dielectric substrate and the enclosure, thereby eliminating the use of a frame. In another embodiment, additional conductive layers can be added to the metalized dielectric honeycomb. 30
5
In yet another embodiment, the metalized dielectric honeycomb substrate can be utilized in a framed configuration to provide improved durability.
[008] US 20100188833A1 relates to designing of a composite material for electromagnetic interference shielding. The composite material comprises a stack 5 including at least two electrically conductive nanoscale fiber films, which are spaced apart from one another by at least one insulating gap positioned between the at least two nanoscale fiber films. The stack is effective to provide a substantial multiple internal reflection effect. An electromagnetic interference shielded apparatus and a method for shielding an electrical circuit from 10 electromagnetic interference is provided.
[009] CN103266542A relates to a method for preparing carbon nanotube electromagnetic wave shielding paper, which comprises the following steps: (a) adding a carbon nanotube into solvent, then adding resin and surfactant, 15 performing dispersion treatment, and uniformly stirring, thus preparing carbon nanotube ink; and (b) by taking the carbon nanotube ink as a raw material, designing a printed mesh line pattern according to the requirements for shielding performance, printing carbon nanotube electromagnetic wave shielding paper in an ink jet printing mode, drying, and finishing, wherein the carbon nanotube ink 20 contains 10-95wt% of solvent, 0.1-20wt% of carbon nanotube, 2-50wt% of resin and 0.1-5wt% of surfactant; the line width W1 of the mesh line pattern is 1-500mu m, the width W2 of the blank part is 1-500mu m, and the area ratio of the mesh lines is 20-99.9%. The method provided by the invention can be used for preparing electromagnetic wave shielding paper, and has the advantages of simple 25 process and raw material saving; and the shielding paper is wide in shielding wave band, adjustable in property, portable and easy to use, and can be widely used hopefully.
[0010] US20100000770A1 relates to the preparation of an electromagnetic 30 interference (EMI) shielding material which includes a matrix of a dielectric or
6
partially conducting polymer, such as foamed polystyrene, with carbon nanotubes or other nanostructures dispersed therein in sufficient concentration to make the material electrically conducting. The composite is formed by dispersing the nanotube material in a solvent in which the dielectric or partially conducting polymer is soluble and mixing the resulting suspension with the dielectric or 5 partially conducting polymer. A foaming agent can be added to produce a lightweight foamed material. An organometallic compound can be added to enhance the conductivity further by decomposition into a metal phase.
[0011] CN104093787A relates to resin composition for electromagnetic 10 interference shielding. More particularly, provided is a resin composition having superior dispersibility and impact relaxation and high conductivity, the resin comprising: (a) 100 parts by weight of a resin; based on 100 parts by weight of the resin, (b) 0.1 to 15 parts by weight of a carbon nanotube surface-modified in a condition of the absence of oxidant; and (c) 1 to 40 parts by weight of a carbon 15 compound, a metal, a metal compound, or a mixture thereof. The resin composition for electromagnetic interference shielding, comprising a carbon hydride composite, is specifically useful in an electronic control unit material for weight reduction of car, and thus can be replaced with a high-priced heavy metal material. 20
[0012] US20080057265A1 relates to designing electromagnetic interference (EMI) shielding structure and methods of making such structures are provided. In one case, a method is provided for making a lightweight composite structure for electromagnetic interference shielding, including the steps of providing a 25 nanoscale fiber film which comprises a plurality of nanoscale fibers; and combining the nanoscale fiber film with one or more structural materials to form a composite material which is effective as an electromagnetic interference shielding structure. In another case, a method is provided for shielding a device which includes an electrical circuit from electromagnetic interference comprising the 30 steps of providing a nanoscale fiber film which comprises a plurality of nanoscale
7
fibers; and incorporating the nanoscale fiber film into an exterior portion of the device to shield an interior portion of the device from electromagnetic interference.
[0013] US20060241236A1 describes an electromagnetic radiation attenuating 5 material or coating consistent with certain embodiments of the present invention uses a binding matrix with an operative quantity of electromagnetic radiation attenuating nano-particles suspended in the binding matrix, wherein, the electromagnetic radiation attenuating nano-particles comprise onion-like-carbon (OLC) particles. In other embodiments, freestanding structures, aerosols and 10 powders or suspensions contained within an enclosure provide EM or Radar absorption, particularly in the range of about 500 MHz to about 30 THz.
[0014] US7008563B2 relates to new compositions of matter and articles of manufacture comprising SWNTs as nanometer scale conducting rods dispersed in 15 an electrically-insulating matrix. These compositions of matter have novel and useful electrical, mechanical, and chemical properties including applications in antennas, electromagnetic and electro-optic devices, and high-toughness materials. Other compositions of matter and articles of manufacture are disclosed, including polymer-coated and polymer wrapped single-wall nanotubes (SWNTs), 20 small ropes of polymer-coated and polymer-wrapped SWNTs and materials comprising same. This composition provides one embodiment of the SWNT conducting-rod composite mentioned above, and also enables creation of high-concentration suspensions of SWNTs and compatibilization of SWNTs with polymeric matrices in composite materials. This solubilization and 25 compatibilization, in turn, enables chemical manipulation of SWNT and production of composite fibers, films, and solids comprising SWNTs.
OBJECTS OF THE INVENTION
8
[0015] An object of the invention is to fabricate efficient metal molybdate incorporated carbon nanotube composite for suppression of electromagnetic pollution or EMI shielding application.
[0016] Another object of the invention is to develop light weight, corrosion 5 resistant, and easily process able materials with excellent shielding behavior towards electromagnetic noise.
SUMMARY OF THE INVENTION
[0017] The present invention discloses and claims a process of preparation of a 10 flexible multilayer electromagnetic interference shield comprising the steps of functionalizing CNTs by oxidation in a mixture of H2SO4 acid and HNO3 acid in 1:3 volume ratios for 4 hours with ultrasonication; vacuum filtering, washing with deionized water and absolute alcohol 3-5 times followed by drying; dissolving 2-3 g, preferably 2.417g of 0.04 M of ammonium molybdenum in 50 ml of deionized 15 water; dissolving 0.2 – 0.5 g, preferably 0.365 g of 0.04 M of cobalt nitrate in 50 ml of deionized water; dissolving 0.2 – 0.5 g, preferably 0.365 g of 0.04 M of nickel nitrate in 50 ml of deionized water; adding said cobalt nitrate and nickel nitrate solution in ammonium molybdenum solution with magnetic stirring; adding 0.1 gm of CNT as obtained previously to said cobalt nitrate, nickel nitrate, 20 and ammonium molybdenum solution; autoclaving in a Teflon lined stainless autoclave the resultant mixture solution at 140 - 170°C , preferably 160°C for 24 hours followed by vacuum filtering, washing with deionized water and absolute alcohol 3-5 times; and collecting grey colored precipitate of nickel cobalt molybdate/ carbon nanotubes composite after drying at 60°C for 12 hours. 25
[0018] The present invention thus relates to a process of fabricating Metal Molybdate i.e. Nickel Cobalt Molybdate and multiwalled carbon nanotubes composite and their application in EMI shielding thereof. The method of prepare of Metal Molybdate i.e. Cobalt Molybdate, Nickel Cobalt Molybdate and carbon 30
9
nanotubes composites comprising steps of: The cobalt-Molybdate (Co-
MoO4)/composite was synthesized by hydrothermal method. In a typical
procedure 0.04M of ammonium molybdenum solution was dissolved in 50ml deionized
water and 0.04M of cobalt nitrate was dissolved in 50ml de-ionized water.
The cobalt nitrate solution was added into t 5 he ammonium molybdenum solution
and magnetic stirred for 12 hours. Which produces a homogenous solution (pH =
6). The reaction mixture was then transferred to a Teflon lined stainless autoclave.
The autoclave was maintain at 160°C for 24 hours in an oven and then cooled
naturally to room temperature. The dark purple coloured precipitate was collected,
10 filtered and washed with deionized water and ethanol several times. Then the
sample was dried in oven at 60°C for 6 hours. Hydrothermal synthesis reaction
was adopted to synthesize nickel-cobalt molybdate/ CNTs composite by two
processes: In the first step, CNTs was functionalized by oxidation in a mixture of
H2SO4 acid and HNO3 acid (1:3 ratios) for 4 hours with ultrasonication. The acid
15 treated CNTs were vacuum filtered and washed with deionized water and absolute
ethanol 3-5 times, then dried in an oven at 60°C for 6 hours. Thus acid treated
CNTs were obtained. 2.417g ammonium molybdenum was dissolved in 50ml of
deionized water. Equal moles 0.365g of cobalt nitrate and nickel nitrate solution
was prepared each in 50ml of deionized water. The cobalt nitrate solution was
20 added into the ammonium molybdenum solution and magnetic stirred for 12
hours. Then 0.1g of CNTs was added in the prepared solution and the mixture was
ultrasonicated for 1hour.Then the reaction mixture was transferred to a Teflon
lined stainless autoclave. The hydrothermal reaction was kept at 180°C for 24
hours. After the autoclave cool down to room temperature the precipitate was
25 filtered and repeatedly washed with deionized water and ethanol 3-4 times.
Finally, grey coloured precipitate was obtained and then dried in an oven at 60°C
for 12h. Thus, Nickel Cobalt molybdate /Carbon nanotubes composite was
obtained. The measurement of the EMI shielding effectiveness of the composite
samples by using a vector network analyzer (VNA E8263B Agilent Technologies)
30 by placing pellet inside a copper sample holder connected between the waveguide
flanges of the network analyzer in the Ku-band (12.4–18.0 GHz)
10
waveguide. In order to further understand the characteristics and technical
contents of the present subject matter, a description relating thereto will be made
with reference to the accompanying drawings. However, the drawings are
illustrative only but not used to limit scope of the present subject matter.
BRIEF DESCRIPTION O 5 F THE ACCOMPANYING FIGURES
Fig. 1: Schematic illustration of Preparation of Cobalt Molybdate, Nickel Cobalt
Molybdate and Nickel Cobalt molybdate / carbon nanotubes composites,
in accordance with the present subject matter;
Fig. 2: FTIR spectra of (a) Cobalt Molybdate, (b) Nickel Cobalt Molybdate and
10 (c) Nickel Cobalt Molybdate /CNTs Composite
Fig. 3: XRD pattern of (a) CoMoO4, (b) NiCoMoO4 and (c) NiCoMoO4/CNTs
composite
Fig. 4: FESEM images of (a) CoMoO4, (b) NiCoMoO4 and (c) NiCoMoO4/CNTs
composite
15 Fig. 5: Variation of total shielding effectiveness with frequency of Composites
Fig. 6: Shielding effectiveness due to absorption loss of Composites
Fig. 7: Shielding effectiveness due to reflection loss of Composite
DETAILED DESCRIPTION OF THE INVENTION
20 [0019] At the very outset of the detailed description, it may be understood that the
ensuing description only illustrates a particular form of this invention. However,
such a particular form is only exemplary embodiment, and without intending to
imply any limitation on the scope of this invention. Accordingly, the description is
to be understood as an exemplary embodiment and teaching of invention and not
25 intended to be taken restrictively.
[0020] Throughout the description and claims of this specification, the phrases
“comprise” and “contain” and variations of them mean “including but not limited
to”, and are not intended to exclude other moieties, additives, components,
11
integers or steps. Thus, the singular encompasses the plural unless the context otherwise requires. Wherever there is an indefinite article used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.
5
[0021] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, 10 abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this 15 specification including any accompanying claims, abstract and drawings or any parts thereof, or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
[0022] The reader's attention is directed to all papers and documents which are 20 filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. Post filing patents, original peer reviewed research paper shall be published. 25
[0023] The present subject matter relates to a process for fabrication efficient Metal Molybdate-Carbon nanotubes composites for EMI shielding application. The present subject matter relates generally to electromagnetic (EM) radiation absorbing composites containing Metal Molybdate and carbon nanotubes. These 30 prepared composites found enormous applications as EM shielding materials, for
12
example, EM-sensitive electronic equipment, stealth vehicles, aircraft, etc., having low radar profiles, protection of electronic components from interference from one another on circuit boards, protection of computer equipment from emitting RF radiation causing interference to navigation systems, medical life support systems, etc. Without being bound by theory, it is believed that in composites of this 5 invention, EM shielding is achieved through absorption of radiation rather than reflection.
[0024] The cobalt-Molybdate (Co-MoO4)/ composite are synthesized by hydrothermal method. In a typical procedure 0.02 – 0.06 M of ammonium 10 molybdenum solution was dissolved in 30 – 70 ml de-ionized water and 0.02 – 0.06 M of cobalt nitrate was dissolved in 50 ml de-ionized water. The cobalt nitrate solution was added into the ammonium molybdenum solution and magnetic stirred for 12 hours. Which produces a homogenous solution (pH = 6). The reaction mixture was then transferred to a Teflon lined stainless autoclave. 15 The autoclave was maintain at 140 – 170°C for 24 hours in an oven and then cooled naturally to room temperature. The dark purple coloured precipitate was collected, filtered and washed with deionized water and ethanol several times. Then the sample was dried in oven at 60°C for 6 hours.
20
[0025] The nickel-cobalt-molybdate (Ni-Co-MoO4)/ composite are synthesized by hydrothermal method. Here 0.02 – 0.06 M of ammonium molybdenum solution was dissolved in 30 – 70 ml de-ionized water and equal moles 0.02 – 0.06 M of cobalt nitrate and nickel nitrate was prepared each in 50 ml deionized water. The cobalt nitrate solution was added into the ammonium molybdenum 25 solution and magnetic stirred for 12 hours. The mixture was transferred to a Teflon lined stainless autoclave. The autoclave was maintained at 140 – 170°C for 24 hours. The light coloured purple precipitate was obtained, filtered and washed with deionized water and ethanol several times. After drying in an oven at 60°C for 6 hours the final powder were obtained. 30
13
[0026] Hydrothermal synthesis reaction was adopted to synthesize nickel-cobalt-molybdate/ CNTs composite by two processes. In the first step, CNTs was functionalized by oxidation in a mixture of H2SO4 acid and HNO3 acid for 4 hours with ultrasonication. The acid treated CNTs were vacuum filtered and 5 washed with deionized water and absolute ethanol 3-5 times. Then dried in an oven at 60°C for 6 hours .Thus acid treated CNTs was obtained. In the second step, 2-3 g ammonium molybdenum was dissolved in 50 ml of deionized water. Equal moles 0.2 – 0.5 g of cobalt nitrate and nickel nitrate solution was prepared each in 50 ml of deionized water. The cobalt nitrate solution was added into the 10 ammonium molybdenum solution and magnetic stirred for 12 hours. Then 0.1g of CNTs was added in the prepared solution and the mixture was ultrasonicated for 1 hour. Then the reaction mixture was transferred to a Teflon lined stainless autoclave. The hydrothermal reaction was kept at 140 - 170°C for 24 hours. After the autoclave cool down to room temperature the precipitate was filtered and 15 repeatedly washed with deionized water and ethanol 3-4 times. Finally, grey coloured precipitate was obtained and then dried in an oven at 60°C for 12 hours. Thus, nickel cobalt molybdate/ Carbon nanotubes composite was obtained.
[0027] In the present subject matter, the metals chosen for study are Cobalt and 20 Nickel.
[0028] In another embodiment of the present subject matter, the metal molybdate chosen for above study was cobalt molybdate and nickel cobalt molybdate.
25
[0029] In another embodiment of the present subject matter, the carbon nanotubes taken act as carbon substrates for deposition of metal molybdate.
[0030] In another embodiment of the present subject matter, the hydrothermal synthesis reaction is used and solvent used was aqueous solution. 30
14
[0031] In another embodiment of the present subject matter, the temperature of the hydrothermal synthesis reaction was kept 160°C.
[0032] In another embodiment of the present subject matter, molar ratio of nickel nitrate and cobalt nitrate was kept 1:1. 5
[0033] In another embodiment of the present subject matter, the hydrothermal reaction time was kept 24 hours.
[0034] In another embodiment of the present subject matter, the prepared 10 composites were washed by ethanol, deionized water and dried at 60 °C.
[0035] In another embodiment of the present subject matter, measurement of the EMI shielding effectiveness of the composite samples by using a vector network analyzer (VNA E8263B Agilent Technologies) by placing pellet inside a copper 15 sample holder connected between the wave-guide flanges of the network analyzer in the Ku-band (12.4–18.0 GHz) waveguide.
Table 1: EMI shielding data of Metal Molybdate/ CNTs Composites
Sr. No.
Sample
SET(dB)
SEA(dB)
SER(dB)
1.
CoMoO4
31.54
25.43
6.10
2.
NiCoMoO4
39.04
30.30
8.74
3.
NiCoMoO4/ CNTs
48.84
40.56
8.27
20
[0036] The following examples are given to illustrate the process of the present invention and should not be construed to limit the scope of the present invention:
Example 1
Synthesis of Co-MoO4/Composite
15
[0037] The cobalt-Molybdate (Co-MoO4)/ composite are synthesized by hydrothermal method. In a typical procedure 0.04 M of ammonium molybdenum solution was dissolved in 50 ml de-ionized water and 0.04 M of cobalt nitrate was dissolved in 50ml de-ionized water. The cobalt nitrate solution was added into the ammonium molybdenum solution and magnetic stirred for 12 hours, which 5 produces a homogenous solution (pH = 6). The reaction mixture was then transferred to a Teflon lined stainless autoclave. The autoclave was maintain at 160°C for 24 hours in an oven and then cooled naturally to room temperature. The dark purple coloured precipitate was collected, filtered and washed with deionized water and ethanol several times. Then the sample was dried in oven at 60°C for 6 10 hours.
Example 2
Synthesis of Ni-Co-MoO4 /Composite
[0038] The nickel-cobalt-molybdate (Ni-Co-MoO4)/ composite were synthesized 15 by hydrothermal method. Here 0.04 M of ammonium molybdenum solution was dissolved in 50 ml de-ionized water and equal moles (0.04M) of cobalt nitrate and nickel nitrate was prepared each in 50 ml deionised water and then both solution was added into the ammonium molybdenum solution and magnetic stirred for 12 hours. The mixture was transferred to a Teflon lined stainless autoclave. The 20 autoclave was maintained at 160°C for 24 hours. The light coloured purple precipitate was obtained, filtered and washed with deionized water and ethanol several times. After drying in an oven at 60°C for 6 hours the final powder were obtained.
25
Example 3
Synthesis of Ni-Co-MoO4 / CNTs Composite
[0039] Hydrothermal synthesis reaction was adopted to synthesize nickel-cobalt-molybdate/ CNTs composite by two processes: In the first step, CNTs was 30
16
functionalized by oxidation in a mixture of H2SO4 acid and HNO3 acid (1:3
volume ratios) for 4 hours with ultrasonication. The acid treated CNTs were
vacuum filtered and washed with deionized water and absolute ethanol 3-5 times.
Then dried in an oven at 60°C for 6 hours .Thus acid treated CNTs was obtained.
In the second step, 0.04 M of ammonium molybdenum 5 solution was prepared in
deionized water. Equal moles of cobalt nitrate and nickel nitrate solution (0.04 M)
was prepared in 50 ml of deionized water and then added into the ammonium
molybdenum solution and magnetic stirred for 12 hours. Then 0.1g of CNTs was
added in the prepared solution and the mixture was ultrasonicated for 1 hour.
10 Then the reaction mixture was transferred to a Teflon lined stainless autoclave.
The hydrothermal reaction was kept at 160°C for 24 hours. After the autoclave
cool down to room temperature the precipitate was filtered and repeatedly washed
with deionized water and ethanol 3-4 times. Finally, grey coloured precipitate was
obtained and then dried in an oven at 60°C for 12 hours. Thus, nickel cobalt
15 molybdate/ Carbon nanotubes composite was obtained.
We Claim:
1. A process of preparation of a flexible multilayer electromagnetic interference shield comprising the steps of:
a) functionalizing CNTs by oxidation in a mixture of H2SO4 acid and HNO3 acid for 4 hours with ultrasonication; 5
b) vacuum filtering, washing with deionized water and absolute alcohol 3-5 times followed by drying;
c) dissolving 2-3 g of ammonium molybdenum in 50 ml of deionized water;
d) dissolving 0.2 – 0.5 g of cobalt nitrate in 50 ml of deionized water; 10
e) dissolving 0.2 – 0.5 g nickel nitrate in 50 ml of deionized water;
f) adding said cobalt nitrate and nickel nitrate solution in ammonium molybdenum solution with magnetic stirring;
g) adding 0.1 gm of CNT as obtained previously to said cobalt nitrate, nickel nitrate, and ammonium molybdenum solution; 15
h) autoclaving the resultant mixture solution at 140 - 170°C for 24 hours followed by vacuum filtering, washing with deionized water and absolute alcohol 3-5 times; and
i) collecting grey colored precipitate of nickel cobalt molybdate/ carbon nanotubes composite after drying at 60°C for 12 hours. 20
2. The process as claimed in claim 1, wherein the CNTs was functionalized by oxidation in a mixture of H2SO4 and HNO3 in 1:3 volume ratios.
3. The process as claimed in claim 1, wherein 2.417g of 0.04 M of 25 ammonium molybdenum was dissolved in 50 ml of deionized water.
4. The process as claimed in claim 1, wherein 0.365 g of 0.04 M of cobalt nitrate solution was prepared in 50 ml of deionized water.
30
5. The process as claimed in claim 1, wherein 0.365 g of 0.04 M of nickel nitrate solution was prepared in 50 ml of deionized water.
6. The process as claimed in claim 1, wherein autoclaving of the mixture of cobalt nitrate, nickel nitrate and ammonium molybdenum was performed 5 in a Teflon lined stainless autoclave for hydrothermal reaction at 160°C for 24 hours.