[001] The present invention relates to polymer composites capable of absorbing electromagnetic interference using barium ferrite and a dielectric material (T^Os) that effectively operates over a wide range of frequencies. The electromagnetic interference shielding composite comprises: a high permittivity polymer; a plurality of magnetic particles dispersed within the high permittivity polymer; and a plurality of dielectric particles dispersed within the high permittivity polymer.
BACKGROUND AND PRIOR ARTS OF THE INVENTION
[002] Electrical and electronic devices are very reactive to electromagnetic pollution present in the environment due to many sources. These EMI sources may be self-induced or externally induced. Electromagnetic energy may propagate by conduction through wires or conductive surfaces or through radiation or reactive coupling. EMI often disrupts the performance of a device and may lead to failure. In order to prevent the electronic device from EMI, electronic devices must be shielded in such a way that both incoming and outgoing interferences are filtered. Typically metals have been used for this purpose but they have some disadvantages like heavy weight, corrosion etc. Conducting polymers has been used for shielding the electromagnetic interference to overcome the disadvantages seen in the metals.
[003] Polypyrrole is a promising conducting polymer for EMI shielding due to its ease of synthesis, environmental stability and good conductivity. A number of different metal and metal oxide particles have so far been encapsulated into the polymer matrix giving rise to composites with exciting chemical and physical properties . Dielectric constant for Tantalum Pentoxide (Ta205) is high. Environmental compatibility of Ta205 is most excellent. The hexagonal barium ferrite is suitable for shielding material due to good dielectric properties as well as large value of permeability and magnetization. By combining the extraordinary properties of pyrrole, barium ferrite and tantalum pentaoxide, the nanocomposite would be very attractive for EMI shielding applications.

[004] CN 102977366B provides a method of preparing a ferrite NiCoZn polypyrrole composite absorbing materials -Si02 / DBSA doped. A new shielding material is prepared by using a novel particle. The particle is a conductive polymer disposed over a metal-coated, ferromagnetic particle to form a three-layered, conductive, ferromagnetic particle. The new three-layered particle is blended into a polymer matrix and processed in a magnetic field or without a magnetic field to form single-layered coatings and freestanding films and sheets. The blends are magnetically processed, such that a conductive network of particles in the matrix is obtained. The composite material exhibits excellent magnetic properties and electrical conductivity, thereby producing superior overall performance microwave absorbing material.
[005] CN102532890A imparts a preparation method of a fluorinated and oxidized graphene/polyaniline composite material. Fluorinated and oxidized graphene/polyaniline composite material is obtained by performing in-situ polymerization on fluorinated and oxidized grapheme and aniline monomer. The preparation method is a simple process. The prepared fluorinated and oxidized graphene/polyaniline composite material have applications in the fields of lithium ion batteries super capacitors etc.
[006] US20130146801A1 provides a composite material with conductive and ferromagnetic properties. The composite material includes: 5 to 90 parts by weight of a conductive polymer matrix; and 0.1 to 40 parts by weight of iron oxide nanorods. The iron oxide nanorods are ferromagnetic and have a length-to-diameter ratio of larger than 3. Hybrid slurry is also provided. The hybrid slurry includes a conductive polymer, and iron oxide nanorods and a solvent. The conductive polymer is wrapped outside a surface of the iron oxide nanorods to form a core-shell structure which enhances the continuity of the ferromagnetic and conductive biphase. Due to which the hybrid slurry or a composite material have improved ferromagnetic and conductive properties.

[007] US 4474676A relates to an EMI shielding material having a high shielding effectiveness (SE), when it is used to shield an electronic device from electromagnetic waves from MHz to GHz range, and it is durable when used for various electronic devices. The provided shielding material is a ferromagnetic
9 1 1
amorphous alloy having a conductivity of 10 Q" . cm" or more and a permeability of 100 or more at 1 kHz incorporated into a polymeric organic substance in the form of short fibers, short pieces, grains or flakes. This ferromagnetic amorphous alloy provides good electromagnetic shielding characteristics. When the ferromagnetic amorphous alloy, in the form of short pieces is dispersed in a polymeric organic substance, the resulting material has a good formability. Since the ferromagnetic amorphous alloy has a selected shape therefore it has a high aspect ratio. The high aspect ratio renders the demagnetization field in the alloy very small, due to which high effective permeability is obtained. The demagnetization field is particularly small in a ferromagnetic amorphous alloy in the form of short pieces, short fibers, and flakes. Short fibers advantageously have a high conductivity and permeability.
[008] US20150287486A1 includes a radiation attenuation shield. The radiation shield is composed of a polymer, a radiation attenuating material, and a magnetic material. It is composed of 10 to 70 percent by volume of magnetic material, 5 to 55 percent by volume of attenuating material, and 20 to 85 percent by volume of polymer. The radiation attenuating material and magnetic material may be dispersed within the polymer to form an attenuation layer of the shield. Further, a magnetic material layer may be positioned adjacent to the attenuation layer. The radiation shield and system of the present invention provide additional attenuation and vibration damping and/or thermal insulation benefits.
[009] CN1867243A discloses hexagonal ferrite, the metal phase and an organic polymer is used to constitute a series of electromagnetic shielding composite. In such materials, hexagonal ferrites not only acts as an insulating phase, isolating the high conductance of the nickel particles, but effectively reduces the influence of the eddy current effect on ferromagnetic composite material. The frequency

range of application of such materials has greatly improved in the range 8.2-12.4GHz.Total electromagnetic shielding effectiveness achieved is between 30-70dB.
OBJECTS OF THE INVENTION:
[0010] The main objective of the present invention is to fabricate efficient ferrite and tantalum oxide incorporated polymer composite for mitigation of electromagnetic pollution or EMI shielding application.
Another object of the present invention is to develop light weight, corrosion resistant materials with excellent shielding behaviour towards electromagnetic noise.
SUMMARY OF THE INVENTION
[0011] Thus the present invention discloses a polymer ferrite-tantalum oxide composite as a protective shielding material, said composite comprising pyrrole monomer, hexagonal ferrite, preferably a M-type hexagonal ferrites: BaFe^Oig and tantalum oxide as filler material, wherein pyrrole (Py) monomer is polymerized to yield polypyrrole (PPy), wherein further the polymer has a nitrogen group in the cyclic ring structure.
[0012] In addition, an in situ polymerization method for preparing a composite material shield, wherein: said composite material prepared using the different weight ratio of Py:B:T 1:0.2:0.2, 1:0.2:0.5, 1:0.5:0.2, 1:0.5:0, 1:0:0.5, wherein further the process comprising obtaining final composite after washing and filtering, wherein the obtained composite is dried in vacuum oven at 60° C.
[0013] Precisely, the present invention grossly discloses and claims a process for the preparation of a Nano-Ferrite Ta20s polypyrrole composite comprising the steps of synthesizing of BaFe^Oig by dissolving Ba(NC>3)2 and Fe(NC>3)3 in

deionized water while mixing an aqueous solution of citric acid with molar ratio of total moles of nitrate ions to citric acid fixed at 2:1 to 1:2 at pH 10, vaporized with continuous stirring; calcinating said powder at 700 - 1000°C in air, milling by mechanical ball mill at a speed of 200 - 600 rpm; synthesizing polypyrrole nanocomposites through in situ emulsion polymerization by dissolving BaFei20i9 nanoparticles and tantalum oxide in an aqueous medium of 0.1 - 0.5 M SLS wherein 0.05 - 0.2 M of pyrrole is added further, stirred continually for again half an hour; and adding 0.05 - 0.3 M FeCb dropwise and stirring for 4-5 hours to complete emulsion polymerization, then filtering, and washing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In the drawings accompanying this specification-Fig. 1: XRD pattern of PBT-122, PBT-125, PBT-152, PB-15, and PT-15 composites.
Fig. 2: FTIR spectra of PBT-122, PBT-125, PBT-152, PB-15, and PT-15 composites.
Fig. 3: UV-Vis spectra of PBT-122, PBT-125, PBT-152, PB-15, and PT-15 composites.
Fig. 4: SEM images of PBT-122, PBT-125, PBT-152, PB-15, and PT-15 composites.
Fig. 5: Variation of total shielding effectiveness with frequency of Composites
Fig. 6: Shielding effectiveness due to absorption and due to reflection of Composites
DETAILED DESCRIPTION OF THE INVENTION
[0015] 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 intended to be taken restrictively.
[0016] 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, 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.
[0017] 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, 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 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.
[0018] The reader's attention is directed to all papers and documents which are 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.
[0019] The present invention relates to a process of fabricating ferrite i.e. barium ferrite, tantalum pentaoxide and polypyrrole composite and their application in EMI shielding thereof. The method of preparation of polypyrrole/ferrite/tantalum oxide composites comprising steps of: barium ferrite was synthesized by citrate precursor method. In a typical procedure required amounts of Ba(NC>3)2 and Fe(NC>3)3 were dissolved in minimum amount of deionized water and an aqueous solution of citric acid was mixed with this Nitrate solution. The molar ratio of Ba to Fe was kept 1:12 whereas the molar ratio of total moles of nitrate ions to citric acid was fixed at 1:1. PH was balanced at 9 by adding Ammonia solution gradually. This solution was then allowed to vaporize by heating at 100 °C with continuous stirring. The solution became viscous as water vaporized and finally it was converted in brown gel. With continuous heating a brown colored porous powder was formed. This powder was calcinated at 900 °C for 2h in air to obtain the BaFel2019 phase. The resultant powder of the combustion was milled by mechanical ball mill at a speed of 400 rpm. The ball-to-powder weight (gm) ratio was 10:1. The grinding was operated by using rigid steel balls with a diameter of 10mm.
[0020] Synthesis of polypyrrole nanocomposites has been carried out by in situ emulsion polymerization. For this, first BaFei20i9 nanoparticles and tantalum oxide in an aqueous medium of 0.2 M sodium lauryl sulfate (SLS) have been homogenized for half an hour. To this solution, 0.1 M of pyrrole has been added and stirred continually for again half an hour to form an emulsion. The oxidant and dopant FeC13 (0.2 M) was added dropwise to the above solution at room temperature and continually stirred for 4-5 h to complete emulsion polymerization. The reaction mixture has been filtered by means of a Buchner funnel of G-2 specification. The product thus obtained has been washed repeatedly with distilled water to remove any traces of initiator left out. Several nanocomposites having different weight ratios of pyrrole(Py), BaFe^Oig (B), and

tantalum oxide (T) have been synthesized and are abbreviated as PBT-122 where Py, BaFei20i9, and T are taken in a 1:0.2:0.2 wt. ratio, PBT-125 where Py, B, and T are taken in a 1:0.2:0.5 wt.ratio, PBT-152 where Py, ferrite, and T are in a 1:0.5:0.2 wt. ratio, PBT-125 where Py, B, and T are taken in a 1:0.2:0.5 wt.ratio, PB-15 where Py, B, and T are taken in a 1:0.5:0 wt.ratio, PT-15 where Py, B, and T are taken in a 1:0:0.5 wt.ratio. All samples have been synthesized by the same procedure as discussed above in order to check the effect of barium ferrite and tantalum oxide constituents in the polymer matrix on the microwave absorption properties. The 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 sample holder connected between the wave¬guide flanges of the network analyzer in the X-band (8.2-12.4 GHz) waveguide.
[0021] In the present invention electromagnetic interference shielding composite is provided. The electromagnetic interference shielding composite comprises a high permittivity polymer; a plurality of magnetic particles dispersed within the high permittivity polymer; and a plurality of dielectric particles dispersed within the high permittivity polymer.
[0022] Barium ferrite was synthesized by citrate precursor method. In a typical procedure required amounts of Ba (N03)2 and Fe (N03)3 were dissolved in minimum amount of deionized water and an aqueous solution of citric acid was mixed with this Nitrate solution. The molar ratio of Ba to Fe was kept 1:10- 1:15 whereas the molar ratio of total moles of nitrate ions to citric acid was fixed in a range 1:2 to 2:1. PH was balanced at 7-10 by adding Ammonia solution gradually. This solution was then allowed to vaporize by heating at 100 °C with continuous stirring. The solution became viscous as water vaporized and finally it was converted in brown gel. With continuous heating a brown colored porous powder was formed. This powder was calcinated at 700 - 1000 °C for 2h in air to obtain the BaFei20i9 phase. The resultant powder of the combustion was milled. The ball-to-powder weight (gm) ratio was 10:1. The grinding was operated by using rigid steel balls with a diameter of 10 mm.

[0023] Synthesis of polypyrrole nanocomposites has been carried out by in situ emulsion polymerization. For this, BaFe12O19 nanoparticles and tantalum oxide in an aqueous medium of 0.1 – 0.5 M sodium lauryl sulfate (SLS) have been 5 homogenized for half an hour. To this solution, 0.05 – 0.2 M of pyrrole has been added and stirred continually for again half an hour to form an emulsion. The oxidant and dopant FeCl3 (0.05 – 0.2 M) was added dropwise to the above solution at room temperature and continually stirred for 4-5 h to complete emulsion polymerization. Pyrrole (Py), BaFe12O19 (B), and tantalum oxide (T) are 10 taken in a definite weight ratio. The reaction mixture has been filtered by means of a Buchner funnel of G-2 specification. The product thus obtained has been washed repeatedly with distilled water to remove any traces of initiator left out.
[0024] In typical reaction PBT-125 composite was synthesized by using emulsion 15 polymerization technique. An aqueous solution of 0.05 – 0.2 M sodium lauryl sulfate (SLS) has been homogenized for half an hour. BaFe12O19 nanoparticles and tantalum oxide in the weight ratio 0.2:0.5 w.r.t. monomer have been added and homogenized for one hour to form an emulsion followed by addition of 0.05 – 0.2 M pyrrole monomer. 0.1 – 0.5 M FeCl3 was added dropwise to the above 20 solution at room temperature and continually stirred for 4-5 h to complete emulsion polymerization. The reaction mixture has been filtered by means of a Buchner funnel of G-2 specification. The product thus obtained has been washed repeatedly with distilled water. Powdered polymer composite was obtained after drying at 60oC
25 [0025] PBT-152 composite was synthesized by in situ emulsion polymerization using FeCl3 as oxidant. For this, BaFe12O19 nanoparticles and tantalum oxide are dispersed in an aqueous solution of 0.1 – 0.5 sodium lauryl sulfate (SLS) and is homogenized for half an hour. To this solution, 0.05 – 0.2 M of pyrrole has been added and stirred continually for again half an hour to form an emulsion. FeCl3
30 (0.1 – 0.5 M) was added drop by drop to the above solution at room temperature.
10

The solution was continually stirred for 4-5 h. Pyrrole (Py), BaFe12O19 (B), and tantalum oxide (T) are taken in a 1:0.5:0.2 wt. ratio. The resultant precipitate was filtered, washed and dried to get the composite.
[0026] Pyrrole/ BaFe12O19 composite is synthesized by polymerizing 0.05 – 0.2 5 M pyrrole in 0.1 – 0.5 M of SLS. BaFe12O19 nanoparticles and tantalum oxide are taken in 1:0.5:0 wt. ratio to the monomer and homogenized in aqueous medium. This solution was polymerized at room temperature by using FeCl3 as oxidant. The reaction mixture was stirred continually for 4-5 h to complete emulsion polymerization. The reaction mixture has been filtered washed, and dried to get 10 the desired product.
[0027] Synthesis of the polypyrrole/ tantalum oxide composite has been carried out by in situ emulsion polymerization. For this purpose, tantalum oxide is homogenized for half an hour in an aqueous medium of 0.1 – 0.5 SLS followed by addition of 0.5 – 0.2 M pyrrole monomer. The oxidant and dopant FeCl3 (0.1 – 15 0.5 M) was added dropwise to the above solution and is continually stirred for 4-5 h. Pyrrole and tantalum oxide are taken in a 1:0.5 wt. ratio. The reaction mixture has been filtered. The product thus obtained has been washed repeatedly with distilled water and dried in vacuum oven.
20 Embodiments:
[0028] In the present subject matter, the ferrite chosen for study is barium ferrite.
[0029] In another embodiment of the present subject matter, the dielectric material used for making the composite is tantalum pentoxide.
[0030] In another embodiment of the present subject matter, the polymer used for 25 study is polypyrrole.
[0031] In another embodiment of the present subject matter, citrate precursor method is used for synthesis of ferrite.
11

[0032] In yet another embodiment of the present subject matter, molar ratio of Ba to Fe was kept 1:12.
[0033] In yet another embodiment of the present subject matter, molar ratio of total moles of nitrate ions to citric acid was kept 1:1.
5 [0034] In yet another embodiment of the present subject matter, in situ polymerization method is used for synthesis of composites.
[0035] In still another embodiment of the present subject matter, the prepared composites were washed by deionized water.
[0036] In still another embodiment of the present subject matter, measurement of
10 the EMI shielding effectiveness of the composite samples by using a vector
network analyzer (VNA E8263B Agilent Technologies) by placing pellet inside a
copper sample holder connected between the wave-guide flanges of the network
analyzer in the X-band (8.2–12.4 GHz) waveguide.
[0037] The following examples are given to illustrate the process of the present 15 invention and should not be construed to limit the scope of the present invention:
Example 1
Synthesis of barium ferrite (BaFe12O19)
[0038] Barium ferrite was synthesized by citrate precursor method. In a typical procedure required amounts of Ba (NO3)2 and Fe (NO3)3 were dissolved in
20 minimum amount of deionized water and an aqueous solution of citric acid was mixed with this Nitrate solution. The molar ratio of Ba to Fe was kept 1:12 whereas the molar ratio of total moles of nitrate ions to citric acid was fixed at 1:1. pH was balanced at 9 by adding Ammonia solution gradually. This solution was then allowed to vaporize by heating at 100 °C with continuous stirring. The
25 solution became viscous as water vaporized and finally it was converted in brown gel. With continuous heating a brown colored porous powder was formed. This powder was calcinated at 900 °C for 2h in air to obtain the BaFe12O19 phase. The
12

resultant powder of the combustion was milled by mechanical ball mill at a speed of 400 rpm. The ball-to-powder weight (gm) ratio was 10:1. The grinding was operated by using rigid steel balls with a diameter of 10mm.
5 Example 2
[0039] Synthesis of polypyrrole/barium ferrite/tantalum pentaoxide (PBT-122) Composite
[0040] Synthesis of polypyrrole nanocomposites has been carried out by in situ emulsion polymerization. For this, BaFe12O19 nanoparticles and tantalum oxide in
10 an aqueous medium of 0.2 M sodium lauryl sulfate (SLS) have been homogenized for half an hour. To this solution, 0.1 M of pyrrole has been added and stirred continually for again half an hour to form an emulsion. The oxidant and dopant FeCl3 (0.2 M) was added dropwise to the above solution at room temperature and continually stirred for 4-5 h to complete emulsion polymerization. Pyrrole (Py),
15 BaFe12O19 (B), and tantalum oxide (T) are taken in a 1:0.2:0.2 wt. ratio. The reaction mixture has been filtered by means of a Buchner funnel of G-2 specification. The product thus obtained has been washed repeatedly with distilled water to remove any traces of initiator left out.
20 Example 3
[0041] Synthesis of polypyrrole/barium ferrite/tantalum pentaoxide (PBT-125) Composite
[0042] In typical reaction PBT-125 composite was synthesized by using emulsion polymerization technique. An aqueous solution of 0.2 M sodium lauryl sulfate 25 (SLS) has been homogenized for half an hour. BaFe12O19 nanoparticles and tantalum oxide in the weight ratio 0.2:0.5w.r.t. monomer have been added and homogenized for one hour to form an emulsion followed by addition of 0.1M pyrrole monomer. 0.2 M FeCl3 was added dropwise to the above solution at room
13

temperature and continually stirred for 4-5 h to complete emulsion polymerization. The reaction mixture has been filtered by means of a Buchner funnel of G-2 specification. The product thus obtained has been washed repeatedly with distilled water. Powdered polymer composite was obtained after 5 drying at 60oC.
Example 4 [0043] Synthesis of polypyrrole/ barium ferrite/ tantalum pentaoxide (PBT-152) Composite
10 [0044] PBT-152 composite was synthesized by in situ emulsion polymerization using FeCl3 as oxidant. For this, BaFe12O19 nanoparticles and tantalum oxide are dispersed in an aqueous solution of 0.2 sodium lauryl sulfate (SLS) and is homogenized for half an hour. To this solution, 0.1 M of pyrrole has been added and stirred continually for again half an hour to form an emulsion. FeCl3 (0.2 M)
15 was added drop by drop to the above solution at room temperature. Thesolution was continually stirred for 4-5 h. Pyrrole(Py), BaFe12O19 (B), and tantalum oxide (T) are taken in a 1:0.5:0.2 wt. ratio. The resultant precipitate was filtered, washed and dried to get the composite.
Example 5 20 [0045] Synthesis of polypyrrole/ barium ferrite (PB-15) Composite
[0046] Pyrrole/ BaFe12O19 composite is synthesized by polymerizing 0.1M pyrrole in 0.2M of SLS. BaFe12O19 nanoparticles and tantalum oxide are taken in 1:0.5:0 wt. ratio to the monomer and homogenized in aqueous medium. This solution was polymerized at room temperature by using FeCl3 as oxidant. The 25 reaction mixture was stirred continually for 4-5 h to complete emulsion polymerization. The reaction mixture has been filtered washed, and dried to get the desired product.
Example 6
30 [0047] Synthesis of polypyrrole/tantalum oxide (PT-15) Composite
14

5

[0048] Synthesis of the polypyrrole/tantalum oxide composite has been carried out by in situ emulsion polymerization. For this purpose, tantalum oxide is homogenized for half an hour in an aqueous medium of 0.2 SLS followed by addition of 0.1 M pyrrole monomer. The oxidant and dopant FeCl3 (0.2 M) was added dropwise to the above solution and is continually stirred for 4-5 h. Pyrrole and tantalum oxide are taken in a 1:0.5 wt. ratio. The reaction mixture has been filtered. The product thus obtained has been washed repeatedly with distilled water and dried in vacuum oven.

10 Example 7
[0049] EMI Shielding Data of Composites
[0050] To explore the EMI shielding dielectric measurements of the composite Agilent E8362B Vector Network Analyzer was used in the Xband. The Powder samples were pelletized in rectangular shape of thickness ~2mm and inserted into
15 copper sample holder connected between the wave-guide flanges of network analyzer. The EM parameters, i.e., relative complex permittivity and relative complex permeability have been measured at room temperature for the study of microwave absorption properties of composites. These obtained complex parameters have been estimated from experimental scattering parameters (S11 &
20 S21) by standard Nicholson-Ross and Weir theoretical calculations.
Table 1: EMI shielding data of Composites

S. No. Sample SET (dB) SEA (dB) SER (dB)
1. PBT-122 22.27 17.55 5.45
2. PBT-125 50.06 42.98 8.96
3. PBT-152 23.88 18.85 6.47
4. PB-15 37.13 29.57 9.63
5. PT-15 19.03 13.65 6.13
15

[0051] From the result, it is evident that PBT-125 at serial no.: 2 is the best in terms of EMI shielding data above, said EMI shielding being the principal object of the present invention. Therefore, the process for preparation of PBT-125 under example 3 may be accepted as the best mode available, said mode is claimed further.

We Claim:

1.A process for the preparation of a Nano-Ferrite Ta2O5 polypyrrole composite for the suppression of electromagnetic radiation, said process comprising the steps of:
a) synthesizing of barium ferrite (BaFe12O19) by dissolving Ba(NO3)2 and Fe(NO3)3 in deionized water while mixing an aqueous solution of citric acid was mixed with this solution in a way so that the molar ratio of total moles of nitrate ions to citric acid was fixed at 2:1 to 1:2 at pH -10, vaporized with continuous stirring in order to form a brown colored porous powder;
b) calcinating said powder at 700 - 1000°C for 2 h in air to obtain the BaFe12O19 phase, milling by mechanical ball mill at a speed of 200 – 600 rpm;
c) synthesizing polypyrrole nanocomposites through in situ emulsion polymerization by dissolving BaFe12O19 nanoparticles and tantalum oxide in an aqueous medium of 0.1 – 0.5 M sodium lauryl sulfate (SLS) wherein 0.05 – 0.2 M of pyrrole is added further and stirred continually for again half an hour to form an emulsion; and
d) adding 0.05 – 0.3 M FeCl3 dropwise at room temperature and continually stirring for 4-5 hours to complete emulsion polymerization, filtering, and washing.
2. The process as claimed in claim 1, wherein the molar ratio of Ba to Fe was kept 1:12.
3. The process as claimed in claim 1, wherein the molar ratio of total moles of nitrate ions to citric acid was fixed at 1:1.
4. The process as claimed in claim 1, wherein the pH is fixed at 9 by gradual addition of ammonia solution.
5. The process as claimed in claim 1, wherein said calcination is performed at 900 °C for 2 h in air to obtain the BaFe12O19 phase.
6. The process as claimed in claim 1, wherein said milling is performed through mechanical ball mill at a speed of 400 rpm, wherein further the ball-to-powder weight (gm) ratio was 10:1.
7. The process as claimed in claim 1, wherein for synthesizing polypyrrole nanocomposites through in situ emulsion polymerization, 0.2 M sodium lauryl sulfate (SLS) has been homogenized for half an hour.
8. The process as claimed in claim 1, wherein BaFe12O19 nanoparticles and tantalum oxide in the weight ratio 0.2: 0.5 w.r.t. monomer have been added and homogenized for one hour to form an emulsion followed by addition of 0.1 M pyrrole monomer.
9. The process as claimed in claim 1, wherein 0.2 M FeCl3 is added dropwise.
10. The process as claimed in claim 1, wherein the powdered polymer composite was obtained after drying at 60oC. , Description:FIELD OF THE INVENTION
[001] The present invention relates to polymer composites capable of absorbing electromagnetic interference using barium ferrite and a dielectric material (Ta2O5) that effectively operates over a wide range of frequencies. The electromagnetic interference shielding composite comprises: a high permittivity polymer; a plurality of magnetic particles dispersed within the high permittivity polymer; and a plurality of dielectric particles dispersed within the high permittivity polymer.
BACKGROUND AND PRIOR ARTS OF THE INVENTION
[002] Electrical and electronic devices are very reactive to electromagnetic pollution present in the environment due to many sources. These EMI sources may be self-induced or externally induced. Electromagnetic energy may propagate by conduction through wires or conductive surfaces or through radiation or reactive coupling. EMI often disrupts the performance of a device and may lead to failure. In order to prevent the electronic device from EMI, electronic devices must be shielded in such a way that both incoming and outgoing interferences are filtered. Typically metals have been used for this purpose but they have some disadvantages like heavy weight, corrosion etc. Conducting polymers has been used for shielding the electromagnetic interference to overcome the disadvantages seen in the metals.
[003] Polypyrrole is a promising conducting polymer for EMI shielding due to its ease of synthesis, environmental stability and good conductivity. A number of different metal and metal oxide particles have so far been encapsulated into the polymer matrix giving rise to composites with exciting chemical and physical properties . Dielectric constant for Tantalum Pentoxide (Ta2O5) is high. Environmental compatibility of Ta2O5 is most excellent. The hexagonal barium ferrite is suitable for shielding material due to good dielectric properties as well as large value of permeability and magnetization. By combining the extraordinary properties of pyrrole, barium ferrite and tantalum pentaoxide, the nanocomposite would be very attractive for EMI shielding applications.
[004] CN 102977366B provides a method of preparing a ferrite NiCoZn polypyrrole composite absorbing materials -SiO2 / DBSA doped. A new shielding material is prepared by using a novel particle. The particle is a conductive polymer disposed over a metal-coated, ferromagnetic particle to form a three-layered, conductive, ferromagnetic particle. The new three-layered particle is blended into a polymer matrix and processed in a magnetic field or without a magnetic field to form single-layered coatings and freestanding films and sheets. The blends are magnetically processed, such that a conductive network of particles in the matrix is obtained. The composite material exhibits excellent magnetic properties and electrical conductivity, thereby producing superior overall performance microwave absorbing material.
[005] CN102532890A imparts a preparation method of a fluorinated and oxidized graphene/polyaniline composite material. Fluorinated and oxidized graphene/polyaniline composite material is obtained by performing in-situ polymerization on fluorinated and oxidized grapheme and aniline monomer. The preparation method is a simple process. The prepared fluorinated and oxidized graphene/polyaniline composite material have applications in the fields of lithium ion batteries super capacitors etc.
[006] US20130146801A1 provides a composite material with conductive and ferromagnetic properties. The composite material includes: 5 to 90 parts by weight of a conductive polymer matrix; and 0.1 to 40 parts by weight of iron oxide nanorods. The iron oxide nanorods are ferromagnetic and have a length-to-diameter ratio of larger than 3. Hybrid slurry is also provided. The hybrid slurry includes a conductive polymer, and iron oxide nanorods and a solvent. The conductive polymer is wrapped outside a surface of the iron oxide nanorods to form a core-shell structure which enhances the continuity of the ferromagnetic and conductive biphase. Due to which the hybrid slurry or a composite material have improved ferromagnetic and conductive properties.
[007] US 4474676A relates to an EMI shielding material having a high shielding effectiveness (SE), when it is used to shield an electronic device from electromagnetic waves from MHz to GHz range, and it is durable when used for various electronic devices. The provided shielding material is a ferromagnetic amorphous alloy having a conductivity of 102 O-1. cm-1 or more and a permeability of 100 or more at 1 kHz incorporated into a polymeric organic substance in the form of short fibers, short pieces, grains or flakes. This ferromagnetic amorphous alloy provides good electromagnetic shielding characteristics. When the ferromagnetic amorphous alloy, in the form of short pieces is dispersed in a polymeric organic substance, the resulting material has a good formability. Since the ferromagnetic amorphous alloy has a selected shape therefore it has a high aspect ratio. The high aspect ratio renders the demagnetization field in the alloy very small, due to which high effective permeability is obtained. The demagnetization field is particularly small in a ferromagnetic amorphous alloy in the form of short pieces, short fibers, and flakes. Short fibers advantageously have a high conductivity and permeability.
[008] US20150287486A1 includes a radiation attenuation shield. The radiation shield is composed of a polymer, a radiation attenuating material, and a magnetic material. It is composed of 10 to 70 percent by volume of magnetic material, 5 to 55 percent by volume of attenuating material, and 20 to 85 percent by volume of polymer. The radiation attenuating material and magnetic material may be dispersed within the polymer to form an attenuation layer of the shield. Further, a magnetic material layer may be positioned adjacent to the attenuation layer. The radiation shield and system of the present invention provide additional attenuation and vibration damping and/or thermal insulation benefits.
[009] CN1867243A discloses hexagonal ferrite, the metal phase and an organic polymer is used to constitute a series of electromagnetic shielding composite. In such materials, hexagonal ferrites not only acts as an insulating phase, isolating the high conductance of the nickel particles, but effectively reduces the influence of the eddy current effect on ferromagnetic composite material. The frequency range of application of such materials has greatly improved in the range 8.2-12.4GHz.Total electromagnetic shielding effectiveness achieved is between 30-70dB.

OBJECTS OF THE INVENTION:
[0010] The main objective of the present invention is to fabricate efficient ferrite and tantalum oxide incorporated polymer composite for mitigation of electromagnetic pollution or EMI shielding application.
Another object of the present invention is to develop light weight, corrosion resistant materials with excellent shielding behaviour towards electromagnetic noise.

SUMMARY OF THE INVENTION
[0011] Thus the present invention discloses a polymer ferrite-tantalum oxide composite as a protective shielding material, said composite comprising pyrrole monomer, hexagonal ferrite, preferably a M-type hexagonal ferrites: BaFe12O19 and tantalum oxide as filler material, wherein pyrrole (Py) monomer is polymerized to yield polypyrrole (PPy), wherein further the polymer has a nitrogen group in the cyclic ring structure.
[0012] In addition, an in situ polymerization method for preparing a composite material shield, wherein: said composite material prepared using the different weight ratio of Py:B:T 1:0.2:0.2, 1:0.2:0.5, 1:0.5:0.2, 1:0.5:0, 1:0:0.5, wherein further the process comprising obtaining final composite after washing and filtering, wherein the obtained composite is dried in vacuum oven at 60o C.
[0013] Precisely, the present invention grossly discloses and claims a process for the preparation of a Nano-Ferrite Ta2O5 polypyrrole composite comprising the steps of synthesizing of BaFe12O19 by dissolving Ba(NO3)2 and Fe(NO3)3 in deionized water while mixing an aqueous solution of citric acid with molar ratio of total moles of nitrate ions to citric acid fixed at 2:1 to 1:2 at pH 10, vaporized with continuous stirring; calcinating said powder at 700 - 1000°C in air, milling by mechanical ball mill at a speed of 200 – 600 rpm; synthesizing polypyrrole nanocomposites through in situ emulsion polymerization by dissolving BaFe12O19 nanoparticles and tantalum oxide in an aqueous medium of 0.1 – 0.5 M SLS wherein 0.05 – 0.2 M of pyrrole is added further, stirred continually for again half an hour; and adding 0.05 – 0.3 M FeCl3 dropwise and stirring for 4-5 hours to complete emulsion polymerization, then filtering, and washing.

BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In the drawings accompanying this specification:-
Fig. 1: XRD pattern of PBT-122, PBT-125, PBT-152, PB-15, and PT-15 composites.

Fig. 2: FTIR spectra of PBT-122, PBT-125, PBT-152, PB-15, and PT-15 composites.

Fig. 3: UV-Vis spectra of PBT-122, PBT-125, PBT-152, PB-15, and PT-15 composites.

Fig. 4: SEM images of PBT-122, PBT-125, PBT-152, PB-15, and PT-15 composites.

Fig. 5: Variation of total shielding effectiveness with frequency of Composites
Fig. 6: Shielding effectiveness due to absorption and due to reflection of Composites

DETAILED DESCRIPTION OF THE INVENTION
[0015] 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 intended to be taken restrictively.
[0016] 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, 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.
[0017] 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, 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 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.
[0018] The reader's attention is directed to all papers and documents which are 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.
[0019] The present invention relates to a process of fabricating ferrite i.e. barium ferrite, tantalum pentaoxide and polypyrrole composite and their application in EMI shielding thereof. The method of preparation of polypyrrole/ferrite/tantalum oxide composites comprising steps of: barium ferrite was synthesized by citrate precursor method. In a typical procedure required amounts of Ba(NO3)2 and Fe(NO3)3 were dissolved in minimum amount of deionized water and an aqueous solution of citric acid was mixed with this Nitrate solution. The molar ratio of Ba to Fe was kept 1:12 whereas the molar ratio of total moles of nitrate ions to citric acid was fixed at 1:1. PH was balanced at 9 by adding Ammonia solution gradually. This solution was then allowed to vaporize by heating at 100 °C with continuous stirring. The solution became viscous as water vaporized and finally it was converted in brown gel. With continuous heating a brown colored porous powder was formed. This powder was calcinated at 900 °C for 2h in air to obtain the BaFe12O19 phase. The resultant powder of the combustion was milled by mechanical ball mill at a speed of 400 rpm. The ball-to-powder weight (gm) ratio was 10:1. The grinding was operated by using rigid steel balls with a diameter of 10mm.
[0020] Synthesis of polypyrrole nanocomposites has been carried out by in situ emulsion polymerization. For this, ?rst BaFe12O19 nanoparticles and tantalum oxide in an aqueous medium of 0.2 M sodium lauryl sulfate (SLS) have been homogenized for half an hour. To this solution, 0.1 M of pyrrole has been added and stirred continually for again half an hour to form an emulsion. The oxidant and dopant FeCl3 (0.2 M) was added dropwise to the above solution at room temperature and continually stirred for 4-5 h to complete emulsion polymerization. The reaction mixture has been ?ltered by means of a Buchner funnel of G-2 speci?cation. The product thus obtained has been washed repeatedly with distilled water to remove any traces of initiator left out. Several nanocomposites having different weight ratios of pyrrole(Py), BaFe12O19 (B), and tantalum oxide (T) have been synthesized and are abbreviated as PBT-122 where Py, BaFe12O19, and T are taken in a 1:0.2:0.2 wt. ratio, PBT-125 where Py, B, and T are taken in a 1:0.2:0.5 wt.ratio, PBT-152 where Py, ferrite, and T are in a 1:0.5:0.2 wt. ratio, PBT-125 where Py, B, and T are taken in a 1:0.2:0.5 wt.ratio, PB-15 where Py, B, and T are taken in a 1:0.5:0 wt.ratio, PT-15 where Py, B, and T are taken in a 1:0:0.5 wt.ratio. All samples have been synthesized by the same procedure as discussed above in order to check the e?ect of barium ferrite and tantalum oxide constituents in the polymer matrix on the microwave absorption properties. The 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 sample holder connected between the wave-guide flanges of the network analyzer in the X-band (8.2–12.4 GHz) waveguide.
[0021] In the present invention electromagnetic interference shielding composite is provided. The electromagnetic interference shielding composite comprises a high permittivity polymer; a plurality of magnetic particles dispersed within the high permittivity polymer; and a plurality of dielectric particles dispersed within the high permittivity polymer.
[0022] Barium ferrite was synthesized by citrate precursor method. In a typical procedure required amounts of Ba (NO3)2 and Fe (NO3)3 were dissolved in minimum amount of deionized water and an aqueous solution of citric acid was mixed with this Nitrate solution. The molar ratio of Ba to Fe was kept 1:10 – 1:15 whereas the molar ratio of total moles of nitrate ions to citric acid was fixed in a range 1:2 to 2:1. PH was balanced at 7-10 by adding Ammonia solution gradually. This solution was then allowed to vaporize by heating at 100 °C with continuous stirring. The solution became viscous as water vaporized and finally it was converted in brown gel. With continuous heating a brown colored porous powder was formed. This powder was calcinated at 700 - 1000 °C for 2h in air to obtain the BaFe12O19 phase. The resultant powder of the combustion was milled. The ball-to-powder weight (gm) ratio was 10:1. The grinding was operated by using rigid steel balls with a diameter of 10 mm.

[0023] Synthesis of polypyrrole nanocomposites has been carried out by in situ emulsion polymerization. For this, BaFe12O19 nanoparticles and tantalum oxide in an aqueous medium of 0.1 – 0.5 M sodium lauryl sulfate (SLS) have been homogenized for half an hour. To this solution, 0.05 – 0.2 M of pyrrole has been added and stirred continually for again half an hour to form an emulsion. The oxidant and dopant FeCl3 (0.05 – 0.2 M) was added dropwise to the above solution at room temperature and continually stirred for 4-5 h to complete emulsion polymerization. Pyrrole (Py), BaFe12O19 (B), and tantalum oxide (T) are taken in a definite weight ratio. The reaction mixture has been ?ltered by means of a Buchner funnel of G-2 speci?cation. The product thus obtained has been washed repeatedly with distilled water to remove any traces of initiator left out.

[0024] In typical reaction PBT-125 composite was synthesized by using emulsion polymerization technique. An aqueous solution of 0.05 – 0.2 M sodium lauryl sulfate (SLS) has been homogenized for half an hour. BaFe12O19 nanoparticles and tantalum oxide in the weight ratio 0.2:0.5 w.r.t. monomer have been added and homogenized for one hour to form an emulsion followed by addition of 0.05 – 0.2 M pyrrole monomer. 0.1 – 0.5 M FeCl3 was added dropwise to the above solution at room temperature and continually stirred for 4-5 h to complete emulsion polymerization. The reaction mixture has been ?ltered by means of a Buchner funnel of G-2 speci?cation. The product thus obtained has been washed repeatedly with distilled water. Powdered polymer composite was obtained after drying at 60oC
[0025] PBT-152 composite was synthesized by in situ emulsion polymerization using FeCl3 as oxidant. For this, BaFe12O19 nanoparticles and tantalum oxide are dispersed in an aqueous solution of 0.1 – 0.5 sodium lauryl sulfate (SLS) and is homogenized for half an hour. To this solution, 0.05 – 0.2 M of pyrrole has been added and stirred continually for again half an hour to form an emulsion. FeCl3 (0.1 – 0.5 M) was added drop by drop to the above solution at room temperature. The solution was continually stirred for 4-5 h. Pyrrole (Py), BaFe12O19 (B), and tantalum oxide (T) are taken in a 1:0.5:0.2 wt. ratio. The resultant precipitate was filtered, washed and dried to get the composite.
[0026] Pyrrole/ BaFe12O19 composite is synthesized by polymerizing 0.05 – 0.2 M pyrrole in 0.1 – 0.5 M of SLS. BaFe12O19 nanoparticles and tantalum oxide are taken in 1:0.5:0 wt. ratio to the monomer and homogenized in aqueous medium. This solution was polymerized at room temperature by using FeCl3 as oxidant. The reaction mixture was stirred continually for 4-5 h to complete emulsion polymerization. The reaction mixture has been ?ltered washed, and dried to get the desired product.
[0027] Synthesis of the polypyrrole/ tantalum oxide composite has been carried out by in situ emulsion polymerization. For this purpose, tantalum oxide is homogenized for half an hour in an aqueous medium of 0.1 – 0.5 SLS followed by addition of 0.5 – 0.2 M pyrrole monomer. The oxidant and dopant FeCl3 (0.1 – 0.5 M) was added dropwise to the above solution and is continually stirred for 4-5 h. Pyrrole and tantalum oxide are taken in a 1:0.5 wt. ratio. The reaction mixture has been ?ltered. The product thus obtained has been washed repeatedly with distilled water and dried in vacuum oven.

Embodiments:
[0028] In the present subject matter, the ferrite chosen for study is barium ferrite.
[0029] In another embodiment of the present subject matter, the dielectric material used for making the composite is tantalum pentoxide.
[0030] In another embodiment of the present subject matter, the polymer used for study is polypyrrole.
[0031] In another embodiment of the present subject matter, citrate precursor method is used for synthesis of ferrite.
[0032] In yet another embodiment of the present subject matter, molar ratio of Ba to Fe was kept 1:12.
[0033] In yet another embodiment of the present subject matter, molar ratio of total moles of nitrate ions to citric acid was kept 1:1.
[0034] In yet another embodiment of the present subject matter, in situ polymerization method is used for synthesis of composites.
[0035] In still another embodiment of the present subject matter, the prepared composites were washed by deionized water.
[0036] In still 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 sample holder connected between the wave-guide flanges of the network analyzer in the X-band (8.2–12.4 GHz) waveguide.
[0037] 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 barium ferrite (BaFe12O19)
[0038] Barium ferrite was synthesized by citrate precursor method. In a typical procedure required amounts of Ba (NO3)2 and Fe (NO3)3 were dissolved in minimum amount of deionized water and an aqueous solution of citric acid was mixed with this Nitrate solution. The molar ratio of Ba to Fe was kept 1:12 whereas the molar ratio of total moles of nitrate ions to citric acid was fixed at 1:1. pH was balanced at 9 by adding Ammonia solution gradually. This solution was then allowed to vaporize by heating at 100 °C with continuous stirring. The solution became viscous as water vaporized and finally it was converted in brown gel. With continuous heating a brown colored porous powder was formed. This powder was calcinated at 900 °C for 2h in air to obtain the BaFe12O19 phase. The resultant powder of the combustion was milled by mechanical ball mill at a speed of 400 rpm. The ball-to-powder weight (gm) ratio was 10:1. The grinding was operated by using rigid steel balls with a diameter of 10mm.

Example 2
[0039] Synthesis of polypyrrole/barium ferrite/tantalum pentaoxide (PBT-122) Composite
[0040] Synthesis of polypyrrole nanocomposites has been carried out by in situ emulsion polymerization. For this, BaFe12O19 nanoparticles and tantalum oxide in an aqueous medium of 0.2 M sodium lauryl sulfate (SLS) have been homogenized for half an hour. To this solution, 0.1 M of pyrrole has been added and stirred continually for again half an hour to form an emulsion. The oxidant and dopant FeCl3 (0.2 M) was added dropwise to the above solution at room temperature and continually stirred for 4-5 h to complete emulsion polymerization. Pyrrole (Py), BaFe12O19 (B), and tantalum oxide (T) are taken in a 1:0.2:0.2 wt. ratio. The reaction mixture has been ?ltered by means of a Buchner funnel of G-2 speci?cation. The product thus obtained has been washed repeatedly with distilled water to remove any traces of initiator left out.

Example 3
[0041] Synthesis of polypyrrole/barium ferrite/tantalum pentaoxide (PBT-125) Composite
[0042] In typical reaction PBT-125 composite was synthesized by using emulsion polymerization technique. An aqueous solution of 0.2 M sodium lauryl sulfate (SLS) has been homogenized for half an hour. BaFe12O19 nanoparticles and tantalum oxide in the weight ratio 0.2:0.5w.r.t. monomer have been added and homogenized for one hour to form an emulsion followed by addition of 0.1M pyrrole monomer. 0.2 M FeCl3 was added dropwise to the above solution at room temperature and continually stirred for 4-5 h to complete emulsion polymerization. The reaction mixture has been ?ltered by means of a Buchner funnel of G-2 speci?cation. The product thus obtained has been washed repeatedly with distilled water. Powdered polymer composite was obtained after drying at 60oC.

Example 4
[0043] Synthesis of polypyrrole/ barium ferrite/ tantalum pentaoxide (PBT-152) Composite
[0044] PBT-152 composite was synthesized by in situ emulsion polymerization using FeCl3 as oxidant. For this, BaFe12O19 nanoparticles and tantalum oxide are dispersed in an aqueous solution of 0.2 sodium lauryl sulfate (SLS) and is homogenized for half an hour. To this solution, 0.1 M of pyrrole has been added and stirred continually for again half an hour to form an emulsion. FeCl3 (0.2 M) was added drop by drop to the above solution at room temperature. Thesolution was continually stirred for 4-5 h. Pyrrole(Py), BaFe12O19 (B), and tantalum oxide (T) are taken in a 1:0.5:0.2 wt. ratio. The resultant precipitate was filtered, washed and dried to get the composite.
Example 5
[0045] Synthesis of polypyrrole/ barium ferrite (PB-15) Composite
[0046] Pyrrole/ BaFe12O19 composite is synthesized by polymerizing 0.1M pyrrole in 0.2M of SLS. BaFe12O19 nanoparticles and tantalum oxide are taken in 1:0.5:0 wt. ratio to the monomer and homogenized in aqueous medium. This solution was polymerized at room temperature by using FeCl3 as oxidant. The reaction mixture was stirred continually for 4-5 h to complete emulsion polymerization. The reaction mixture has been ?ltered washed, and dried to get the desired product.
Example 6

[0047] Synthesis of polypyrrole/tantalum oxide (PT-15) Composite
[0048] Synthesis of the polypyrrole/tantalum oxide composite has been carried out by in situ emulsion polymerization. For this purpose, tantalum oxide is homogenized for half an hour in an aqueous medium of 0.2 SLS followed by addition of 0.1 M pyrrole monomer. The oxidant and dopant FeCl3 (0.2 M) was added dropwise to the above solution and is continually stirred for 4-5 h. Pyrrole and tantalum oxide are taken in a 1:0.5 wt. ratio. The reaction mixture has been ?ltered. The product thus obtained has been washed repeatedly with distilled water and dried in vacuum oven.

Example 7
[0049] EMI Shielding Data of Composites
[0050] To explore the EMI shielding dielectric measurements of the composite Agilent E8362B Vector Network Analyzer was used in the Xband. The Powder samples were pelletized in rectangular shape of thickness ~2mm and inserted into copper sample holder connected between the wave-guide flanges of network analyzer. The EM parameters, i.e., relative complex permittivity and relative complex permeability have been measured at room temperature for the study of microwave absorption properties of composites. These obtained complex parameters have been estimated from experimental scattering parameters (S11 & S21) by standard Nicholson-Ross and Weir theoretical calculations.
Table 1: EMI shielding data of Composites

S. No. Sample SET (dB) SEA (dB) SER (dB)
1. PBT-122 22.27 17.55 5.45
2. PBT-125 50.06 42.98 8.96
3. PBT-152 23.88 18.85 6.47
4. PB-15 37.13 29.57 9.63
5. PT-15 19.03 13.65 6.13

[0051] From the result, it is evident that PBT-125 at serial no.: 2 is the best in terms of EMI shielding data above, said EMI shielding being the principal object of the present invention. Therefore, the process for preparation of PBT-125 under example 3 may be accepted as the best mode available, said mode is claimed further.