# Patent

## Title
Composite material and method for preparing the same

## Abstract

Disclosed are a composite material and a method for preparing the same. The composite material is consisted of TiO2 and BaZn1.2Co0.8Fe16O27. The composite material of the invention has the advantages of high absorption frequency band, good compatibility and wide frequency band, and it is applicable for the shell protection material of a mobile phone or a TV set, thereby absorbing the electromagnetic wave band that is the most harmful to human bodies, without influencing the normal communication function of an electronic device, for example, a mobile phone.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
The present application claims priority to and incorporates by reference the entire contents of Chinese priority document 201510197778.0, filed in China on Apr. 23, 2015.
TECHNICAL FIELD
The present invention relates to a composite material and a method for preparing the same, and in particular, to a W-type Ba-Ferrite/TiO2 composite material and a method for preparing the same.
BACKGROUND
In daily life, electromagnetic waves exist everywhere, for example, radio broadcast, TV set, mobile communication, radio telecontrol, navigation and high-voltage distribution line, etc., all radiate strong electromagnetic waves energy to the surroundings. Since the electronic industry made its appearance, revolutionary changes do have been made to the science and technology and the industry, and great convenience have been made to people's life; however, the electromagnetic waves radiated by various electronic products sometimes may pollute the environment, this has become one of the significant environment pollution factors, and it may endanger human health, thus it has become another public nuisance to human environment in the train of exhaust gas, waste water, waste residue and noise. Wherein, 3 MHz ̃30 MHz is the military short-wave band, which has little relation with the public and is thus unconcerned. Because of the popularization of devices such as mobile phone, TV set, high-voltage electricity, etc., in people's daily life, the electromagnetic wave frequency band is in the range of 30 MHz ̃30 GHz, wherein, the higher the frequency is, the more harmful it will be to human bodies. At present, there is little research on the reduction of radiation caused by electronic products (for example, mobile phone, TV set and the like), and the application area of high-frequency radiation products are limited, therefore, it seems necessary to develop novel wave-absorbing materials. Titanium dioxide (TiO2) has a high dielectric constant and a good stability, thus it is an important dielectric material, which can absorb electromagnetic waves via dielectric loss. A composite wave-absorbing material with both good dielectric loss capability and good magnetic loss capability may be obtained by compounding TiO2 and W-type Ba-Ferrite.
SUMMARY
One embodiment of the present invention relates to a composite material comprising TiO2 and BaZn1.2Co0.8Fe16O27. In the text below, BaZn1.2Co0.8Fe16O27 is shorted as BaW. The composite material of the invention has the advantages of high absorption frequency band, good compatibility and wide frequency band.
The composite material of one embodiment of the invention comprises TiO2 and BaZn1.2Co0.8Fe16O27, and specifically, it is composed of TiO2-coated BaZn1.2Co0.8Fe16O27 particulates. Wherein, a weight ratio of TiO2 to BaZn1.2Co0.8Fe16O27 is (0.1-10):(1-10), and optionally, (0.1-1):(5-10); for example, in one embodiment of the invention, the weight ratio is 0.469:7.94.
In one embodiment of the invention, the composite material is a powder with a micrometer-level grain size.
In one embodiment of the invention, a reflection loss of the composite material at 7.76-13.68 GHz is less than −10 dB, and a reflection loss thereof at 10.3 GHz is −47.6 dB.
The invention further provides a method for preparing a composite material, which includes the steps of:
dissolving Ba(NO3)2, Zn(NO3)2.6H2O, Co(NO3)2.6H2O and Fe(NO3)3.9H2O in distilled water at a molar ratio of 1:1.2:0.8:16, adding a citric acid at a molar ratio of 10:1 relative to Ba(NO3)2, stirring till complete dissolution, adjusting a pH value of a resultant solution to neutrality, evaporating the solution to prepare a sol, drying to obtain a gel, and then calcining the gel to obtain BaZn1.2Co0.8Fe16O27; and
adding BaZn1.2Co0.8Fe16O27 into a TiO2 sol, stirring and filtering, washing the obtained filter residue, drying the obtained filter residue to obtain a precursor, and drying the precursor to obtain the composite material; wherein, a weight ratio of TiO2 to BaZn1.2Co0.8Fe16O27 is (0.1-10):(1-10), and preferably, (0.1-1):(5-10); for example, in one embodiment of the invention, the weight ratio is 0.469:7.94.
Optionally, Ba(NO3)2 is analytically pure Ba(NO3)2, Zn(NO3)2.6H2O is analytically pure Zn(NO3)2.6H2O, Co(NO3)2.6H2O is analytically pure Co(NO3)2.6H2O, Fe(NO3)3.9H2O is analytically pure Fe(NO3)3.9H2O.
Optionally, the evaporation of the solution is constant-temperature evaporation in a 70° C. water bath.
Optionally, before being calcined at 1300° C., the gel is ground into powder.
Optionally, the filter residue is washed with absolute ethyl alcohol.
Optionally, the filter residue washed with absolute ethyl alcohol is dried at 80° C.
Optionally, the TiO2 sol is prepared by: dissolving 2 parts by weight of butyl titanate and 1 part by weight of glacial acetic acid in 10 parts by weight of absolute ethyl alcohol, and stirring to obtain a transparent solution; and adding 4 parts by weight of an ethanol solution with a volume fraction of 75% dropwise into the transparent solution slowly, and stirring to obtain the TiO2 sol.
Optionally, the calcining is performed at 1300° C.
The composite material of the invention may be used as a material for manufacturing the shell of an electronic device such as a mobile phone, etc., thereby absorbing the electromagnetic wave band that is the most harmful to human bodies, without influencing the normal communication function of an electronic device, for example, a mobile phone.
It is another object of the invention to provide an electronic device shell, which is made from a raw material that includes the composite material.
Optionally, the electronic device is a mobile phone.
In the invention, a composite material with both good dielectric loss capability and good magnetic loss capability is obtained by compounding TiO2 and BaW material. The composite material of the invention has the advantages of high absorption frequency band, good compatibility and wide frequency band, and it may be used as the material of the shell of an electronic device such as a mobile phone, etc., thereby absorbing the electromagnetic wave band that is the most harmful to human bodies, without influencing the normal communication function of an electronic device, for example, a mobile phone.



BRIEF DESCRIPTION
FIG. 1 shows XRD diagrams of a BaW/TiO2 composite material, BaW and TiO2 according to Embodiment 1;
FIG. 2 shows an SEM diagram of a sample of the BaW/TiO2 composite material according to Embodiment 1; and
FIG. 3 shows reflection loss curves of the BaW/TiO2 composite material and BaW according to Embodiment 1.



DETAILED DESCRIPTION
The composite material of the embodiment of the invention comprises TiO2 and BaZn1.2Co0.8Fe16O27. Optionally, the composite material is a powder with a micrometer-level grain size. Optionally, the reflection loss of the composite material at 7.76-13.68 GHz is less than −10 dB, and the reflection loss thereof at 10.3 GHz is −47.6 dB.
The composite material of the embodiment of the invention has the advantages of high absorption frequency band, good compatibility and wide frequency band, and it may be used as the material of the shell of an electronic device such as a mobile phone, etc., thereby absorbing the electromagnetic wave band that is the most harmful to human bodies, without influencing the normal communication function of an electronic device, for example, a mobile phone.
The specific implementation modes of the invention will be further described in detail below in conjunction with the drawings and embodiments. The embodiments below are used for illustrating the invention, rather than limiting the scope of the invention.
Embodiment 1
1) Preparation of BaZn1.2Co0.8Fe16O27:
First Step: 2.61 g Ba(NO3)2, 2.97 g Zn(NO3)2.6H2O, 2.91 g Co(NO3)2.6H2O and 3.42 g Fe(NO3)3.9H2O are dissolved in 50 mL distilled water, and after sufficient dissolution, 19.5 g analytically pure citric acid is added thereto and is stirred sufficiently till complete dissolution, and then the pH of the solution is adjusted to neutrality with ethylene diamine.
Second Step: The above solution is placed in a 70° C. water bath for constant-temperature evaporation to prepare a sol, and it is dried to obtain a gel. The gel is ground to powder and calcined at 1300° C. for 3 h to obtain BaW particulates.
Third Step: 2 mg butyl titanate and 1 mg glacial acetic acid are dissolved in 10 mg absolute ethyl alcohol and stirred sufficiently to obtain a transparent solution A, and 4 mg ethanol solution with a volume fraction of 75% is added dropwise into solution A, and it is stirred for 30 min to obtain a light yellow TiO2 sol. 7.94 g BaW powder is weighted out and added into the sol, and it is filtered after being stirred for 3 h at room temperature, the obtained filter residue is washed with absolute ethyl alcohol, and then the obtained filter residue is dried at 80° C. for 10 h to obtain a precursor. The precursor is dried at 500° C. for 3 h to obtain a BaW/TiO2 composite material powder that is composed of TiO2-coated BaZn1.2Co0.8Fe16O27 particulates, wherein the grain size of the powder is at micrometer-level (1-1000 um).
2) The structure, compositions, appearance, magnetic performance and wave-absorbing performance of the composite material BaW/TiO2:
The BaW/TiO2 composite material obtained in Embodiment 1 is mixed with paraffin with a mass ratio of 2.4:1, and pressed into an annular sample with an outer diameter of 7 mm, an inner diameter of 3 mm and a thickness of about 4 mm via a mould.
The BaW/TiO2 composite material sample is observed via a scanning electron microscope, and the result is as shown in FIG. 2. The BaW/TiO2 composite material is a micrometer-level wave-absorbing material.
The BaW/TiO2 composite material sample is analyzed via X-ray diffraction, the result is as shown in FIG. 1, and it indicates that the composite material obtained is truly a BaW/TiO2 composite material.
The electromagnetic parameters thereof, i.e., real part of magnetic permeability (μ′)imaginary part of magnetic permeability (μ′′), real part of dielectric constant (ε′) and imaginary part of dielectric constant (ε′′), are tested in a range of 2-18 GHz via a vector network analyzer.
The reflectivity R(dB) of the sample is finally simulated via complex magnetic permeability μr=μ′−jμ′′, complex dielectric constant εr=ε′−jε′′ and formula



  
    
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It is measured that the reflection loss of the BaW/TiO2 composite material sample at 7.76-13.68 GHz is less than −10 dB, and the reflection loss thereof at 10.3 GHz is −47.6 dB (as shown in FIG. 3). The bandwidth of the BaW/TiO2 composite material sample at which the electromagnetic wave reflectivity is less than −10 dB may reach 3.92 GHz and the minimum reflectivity is −47.6 dB, which indicates that the BaW/TiO2 composite material has the advantages of high absorption frequency band, good compatibility and wide frequency band.
The above description only shows some preferred embodiments of the invention. It should be noted that, various improvements and substitutions may also be made by one of ordinary skills in the art without departing from the technical principles of the invention, and all these improvements and substitutions should be regarded as falling into the protection scope of the invention.

## Claims

1. A composite material, comprising TiO2-coated BaZn1.2Co0.8Fe16O27 particulates.

2. The composite material according to claim 1, wherein, a weight ratio of TiO2 to BaZn1.2Co0.8Fe16O27 is (0.1-10):(1-10).

3. The composite material according to claim 1, wherein, the composite material is a powder with a micrometer-level grain size.

4. The composite material according to claim 1, wherein, a reflection loss of the composite material at 7.76-13.68 GHz is less than −10 dB, and a reflection loss thereof at 10.3 GHz is −47.6 dB.

5. An electronic device shell, which is made from a raw material comprising the composite material according to claim 1.

6. The electronic device shell according to claim 5, wherein, the weight ratio of TiO2 to BaZn1.2Co0.8Fe16O27 is (0.1-10):(1-10).

7. The electronic device shell according to claim 5, wherein, the composite material is a powder with a micrometer-level grain size.

8. The electronic device shell according to claim 5, wherein, the reflection loss of the composite material at 7.76-13.68 GHz is less than −10 dB, and the reflection loss thereof at 10.3 GHz is -47.6 dB.

9. The electronic device shell according to claim 5, wherein, the electronic device is a mobile phone.

10. A method for preparing a composite material, comprising the steps of:
dissolving Ba(NO3)2, Zn(NO3)2.6H2O, Co(NO3)2.6H2O and Fe(NO3)3.9H2O in distilled water at a molar ratio of 1:1.2:0.8:16, adding a citric acid at a molar ratio of 10:1 relative to Ba(NO3)2, stirring till complete dissolution, adjusting a pH value of a resultant solution to neutrality, evaporating the solution to prepare a sol, drying to obtain a gel, and then calcining the gel to obtain BaZn1.2Co0.8Fe16O27; and
adding BaZn1.2Co0.8Fe16O27 into a TiO2 sol, stirring and filtering, washing the obtained filter residue, drying the obtained filter residue to obtain a precursor, and drying the precursor to obtain the composite material which comprises TiO2-coated BaZn1.2Co0.8Fe16O27 particulates.

11. The method according to claim 10, wherein, Ba(NO3)2 is analytically pure Ba(NO3)2, Zn(NO3)2.6H2O is analytically pure Zn(NO3)2.6H2O, Co(NO3)2.6H2O is analytically pure Co(NO3)2.6H2O, Fe(NO3)3.9H2O is analytically pure Fe(NO3)3.9H2O.

12. The method according to claim 10, wherein, the evaporation is constant-temperature evaporation in 70° C. water bath.

13. The method according to claim 10, wherein, before being calcined at 1300° C., the gel is ground into powder.

14. The method according to claim 10, wherein, the filter residue is washed with absolute ethyl alcohol.

15. The method according to claim 14, wherein, the filter residue washed with absolute ethyl alcohol is dried at 80° C.

16. The method according to claim 10, wherein, the TiO2 sol is prepared by: dissolving 2 parts by weight of butyl titanate and 1 part by weight of glacial acetic acid in 10 parts by weight of absolute ethyl alcohol, and stirring to obtain a transparent solution; and adding 4 parts by weight of an ethanol solution with a volume fraction of 75% dropwise into the transparent solution slowly, and stirring to obtain the TiO2 sol.

17. The method according to claim 10, wherein, the calcining is performed at 1300° C.

18. The method according to claim 10, wherein, a weight ratio of TiO2 to BaZn1.2Co0.8Fe16O27 is (0.1-10):(1-10).