CN115340744B - Electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment and preparation method and application thereof - Google Patents
Electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses an electromagnetic shielding composite material based on heterogeneous hollow microsphere layering enrichment, which comprises a polymer matrix, and magnetic conductive hollow microspheres and non-magnetic conductive hollow microspheres doped in the polymer matrix; wherein the polymer matrix has two surfaces that are opposite from top to bottom; the magnetic conductive hollow microspheres are enriched on one surface of the polymer matrix; and the non-magnetic conductive hollow microspheres are enriched on the other surface of the polymer matrix. The composite material structure can reduce the consumption of conductive hollow microsphere filler and solve the problem that the low density and the high strength of the electromagnetic shielding composite material are difficult to be compatible; the method also provides a scheme for regulating and controlling the comprehensive performance of the electromagnetic shielding composite material through the compounding process design of the conductive filler. The invention also discloses a preparation method and application of the electromagnetic shielding composite material.
Description
Technical Field
The invention relates to the technical field of composite materials. More particularly, relates to an electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment, and a preparation method and application thereof.
Background
The increasing severity of electromagnetic wave pollution makes the development and application of electromagnetic shielding materials important. The great demand for the weight reduction of materials for consumer electronics, civil protection equipment and high-end equipment is increasing, and the weight reduction of electromagnetic shielding materials is imperative. The polymer-based composite material is a novel material form with great competitive power under the large trend of light weight of functional and structural materials due to the characteristics of wide raw material sources, rich function selection, convenient strength design and easy molding, and the research and the application of the polymer-based composite material are also highly focused by researchers at home and abroad. However, for electromagnetic shielding composite materials, it is generally necessary to have strong electrical conductivity and/or magnetism to achieve direct reflection of incident electromagnetic waves through impedance mismatch of interfaces or to achieve shielding of electromagnetic waves through loss of electromagnetic waves entering the interior of the material.
Since most (especially technically and commercially valuable) polymeric materials do not have good electrical conductivity and/or magnetic properties, it is often necessary to impart the polymer matrix composite with a corresponding functionality by means of electromagnetically functional fillers to achieve an efficient shielding of incident electromagnetic waves. For the conventional electromagnetic functional filler and the electromagnetic shielding composite thereof, there are the following problems. Firstly, the density of the filler is high (particularly a metal material with good conductivity), which not only increases the density of the composite material, but also is not beneficial to lightweight design; and the sedimentation problem of the filler is also brought, so that the distribution uniformity is poor, and the performance is influenced. Secondly, the electromagnetic functional filler is generally added in a large proportion to obtain high electromagnetic shielding effectiveness, and the density of the composite material is greatly increased by considering the high density of the electromagnetic functional filler. Third, the price of part of high-performance conductive filler (such as silver) is high, and the large-scale filling can also lead to the increase of the production cost of the composite material.
Based on the analysis, the development of novel electromagnetic functional filler based on a hollow structure and the realization of the high shielding effectiveness of the composite material under the condition of low filler addition through the controllable distribution of the novel electromagnetic functional filler in the composite material have important scientific research and practical values. The lightweight hollow microsphere based on the internal cells can greatly reduce the density and the consumption of electromagnetic functional materials by utilizing the existence of the cells; on the other hand, the enrichment of the electromagnetic functional material in the hollow microsphere spherical shell area can be utilized to enable a contact network to be formed more easily, and the shielding effectiveness is improved. However, the prior hollow structure filler is adopted to reduce the density, and the defects of single function of the filler, difficult control of the distribution of the filler in a polymer matrix, higher filling quantity of the filler volume and the like exist.
Disclosure of Invention
The first aim of the invention is to provide an electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment.
The second aim of the invention is to provide a preparation method of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layering enrichment.
The third object of the invention is to provide an application of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment.
In order to achieve the first object, the present invention adopts the following technical scheme:
the composite material comprises a polymer matrix, and magnetic conductive hollow microspheres and non-magnetic conductive hollow microspheres doped in the polymer matrix;
wherein the polymer matrix has two surfaces that are opposite from top to bottom;
the magnetic conductive hollow microspheres are enriched on one surface of the polymer matrix; and is also provided with
The non-magnetic conductive hollow microspheres are enriched on the other surface of the polymer matrix.
In the technical scheme, the controllable enrichment of the conductive hollow microspheres with two different characteristics is utilized to realize high shielding effectiveness under the condition of low filler addition.
Further, the magnetic conductive hollow microspheres are enriched on one surface of the polymer matrix to form a magnetic conductive hollow microsphere layer; the nonmagnetic conductive hollow microspheres are enriched on one surface of the polymer matrix to form a nonmagnetic conductive hollow microsphere layer. It is understood that the magnetically conductive hollow microsphere layer and the non-magnetically conductive hollow microsphere layer are not in direct contact. The polymer matrix is filled between the magnetic conductive hollow microsphere layer and the non-magnetic conductive hollow microsphere layer, so that the part of the hollow cavity is less in cavity and high in mechanical strength, better mechanical support can be provided for the composite material, and the overall mechanical strength of the composite material is improved; meanwhile, repeated reflection oscillation of electromagnetic waves can be formed between the magnetic conductive hollow microsphere layer and the nonmagnetic conductive hollow microsphere layer, and the shielding effect is enhanced.
Further, the true density of the composite material is 0.7-1.1g/cm 3 。
Further, the volume percentage of the magnetic conductive hollow microspheres and the non-magnetic conductive hollow microspheres in the composite material is 20-40%.
Further, the volume ratio of the magnetic conductive hollow microspheres to the non-magnetic conductive hollow microspheres is 3:1-1:3, preferably 1:0.5-1:1, more preferably 1:1, and the comprehensive performance is better.
Further, the density of the magnetic conductive hollow microsphere is 0.3-1.0g/cm 3 The grain size is 5-90 microns.
Further, the magnetic conductive hollow microsphere has a hollow structure, and a silicate glass shell layer, a magnetic metal shell layer and a conductive metal shell layer are sequentially arranged in the shell structure from inside to outside.
Further, the thickness of the silicate glass shell layer is 300-1200 nanometers.
Further, the thickness of the magnetic metal shell layer is 20-200 nanometers.
Further, the thickness of the conductive metal shell layer is 20-400 nanometers.
Further, the components of the magnetic metal shell layer are selected from one or more of cobalt, nickel, iron and alloys thereof.
Further, the component of the conductive metal shell layer is selected from one or more of copper, silver and alloys thereof.
Further, the density of the non-magnetic conductive hollow microsphere is 0.3-0.95g/cm 3 The grain size is 5-90 microns.
Further, the non-magnetic conductive hollow microsphere has a hollow structure, and a silicate glass layer and a conductive metal layer are sequentially arranged in the shell structure from inside to outside.
Further, the thickness of the silicate glass layer is 300-1500 nanometers, and the thickness of the conductive metal layer is 20-400 nanometers.
Further, the composition of the conductive metal layer is selected from one or more of copper, silver and alloys thereof.
Further, the polymer matrix is a common polymer matrix for preparing composite materials with rigid supporting performance, and the polymer matrix requires: before curing, or after dilution with a solvent.
Further, the polymer matrix is selected from one or more of epoxy resin, unsaturated polyester resin, phenolic resin, polyurethane resin and polystyrene.
Further, the raw materials for forming the composite material also comprise an auxiliary agent, wherein the auxiliary agent is one or more selected from curing agents, accelerators, surfactants and diluents. The choice and amount of the specific auxiliaries can be chosen by the person skilled in the art according to the actual situation. Taking epoxy resin as an example, the curing agent includes, but is not limited to, methyltetrahydrophthalic anhydride; such promoters include, but are not limited to, N-dimethylbenzylamine; the diluent includes, but is not limited to, fatty alcohol diglycidyl ether (V22).
In order to achieve the second object, the present invention adopts the following technical scheme:
the preparation method of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment comprises the following steps:
providing magnetic conductive hollow microspheres and non-magnetic conductive hollow microspheres respectively;
mixing and pouring raw materials comprising a polymer matrix, magnetic conductive hollow microspheres and nonmagnetic conductive hollow microspheres into a die coated with a release agent in advance;
fixing a magnet at the bottom of the die, and carrying out vibration layering treatment on the die and the materials in the die;
solidifying and demoulding to obtain the electromagnetic shielding composite material.
In the preparation method, the orientation controllable enrichment of the conductive filler is realized by one-pot reaction with the aid of buoyancy and an externally applied magnetic field, and the layered composite structure of the magnetic conductive hollow microspheres and the nonmagnetic conductive hollow microspheres in the polymer matrix is obtained.
Further, the preparation of the magnetic conductive hollow microsphere comprises the following steps:
pretreating silicate glass hollow microspheres to obtain hollow microspheres A;
assembling a magnetic metal spherical shell on the surface of the hollow microsphere A to obtain a hollow microsphere B;
and coating conductive metal on the surface of the hollow microsphere B to obtain a hollow microsphere C, namely the magnetic conductive hollow microsphere.
Further, the method for assembling the magnetic metal spherical shell on the surface of the hollow microsphere A comprises the following steps:
mixing the hollow microsphere A with the assembly reaction liquid, heating, stirring, reacting, filtering and cleaning.
Further, the assembly reaction liquid comprises ion source salt, a stabilizer, a reducing agent and a pH regulator.
Further, the ion source salt comprises ferric salt, nickel salt and cobalt salt, preferably inorganic salt, and the concentration is 0.1-50g/L.
Further, the stabilizer comprises ammonium sulfate, potassium sodium tartrate and EDTA, and the concentration is 10-90g/L.
Further, the reducing agent comprises sodium hypophosphite, hydrazine hydrate, formaldehyde and sodium borohydride, and the concentration is 2-80g/L.
Further, the pH of the assembly reaction solution is preferably 9-11, and the regulator is preferably an inorganic base.
Further, the hollow microsphere A is added in an amount of 1g/50ml to 1g/300ml.
Further, the temperature of the assembly reaction is 40-90 ℃.
Further, the method for coating the conductive metal on the surface of the hollow microsphere B comprises the following steps:
mixing and stirring the hollow microsphere B and the assembly reaction liquid at room temperature, and then filtering and cleaning.
In the preparation method, in the method of coating the conductive metal on the surface of the hollow microsphere B, whether further calcination heat treatment is performed can be selected according to actual needs.
Further, the assembly reaction liquid comprises: 0.08-1.8mol/L of metal ion, 0.05-0.6mol/L, pH of complexing agent, 0.1-1mol/L of regulator and 0.01-2mol/L of reducing agent.
Further, the ion source salts include copper salts, silver salts, preferably inorganic salts.
Further, the complexing agent is selected from one or more of potassium sodium tartrate, sodium citrate and EDTA.
Further, the pH of the assembly reaction solution is preferably 9-11, and the regulator is preferably an inorganic base.
Further, the reducing agent is selected from one or more of formaldehyde, hydrazine hydrate, sodium hypophosphite and sodium borohydride.
Further, the preparation of the non-magnetic conductive hollow microsphere comprises the following steps:
pretreating silicate glass hollow microspheres to obtain hollow microspheres A;
and assembling a conductive metal spherical shell on the surface of the hollow microsphere A to obtain a hollow microsphere D, namely the nonmagnetic conductive hollow microsphere.
In the preparation of the non-magnetic conductive hollow microsphere, the hollow microsphere A can be prepared as described in the preparation method.
Further, the method for assembling the conductive metal spherical shell on the surface of the hollow microsphere A comprises the following steps:
mixing and stirring the hollow microsphere A and the assembly reaction liquid at room temperature, and then filtering and cleaning.
In the preparation method, in the method for assembling the conductive metal spherical shell on the surface of the hollow microsphere A, whether further calcination heat treatment is carried out can be selected according to actual needs.
Further, the assembly reaction liquid comprises: 0.08-1.8mol/L of metal ion, 0.05-0.6mol/L, pH of complexing agent, 0.1-1mol/L of regulator and 0.01-2mol/L of reducing agent.
Further, the ion source salts include copper salts, silver salts, preferably inorganic salts.
Further, the complexing agent is selected from one or more of potassium sodium tartrate, sodium citrate and EDTA.
Further, the pH of the assembly reaction solution is preferably 9-11, and the regulator is preferably an inorganic base.
Further, the reducing agent is selected from one or more of formaldehyde, hydrazine hydrate, sodium hypophosphite and sodium borohydride.
Preferably, the pretreatment method comprises the following steps:
carrying out surface coupling treatment on the silicate glass hollow microspheres to obtain surface-coupled hollow microspheres;
and (3) performing seed nucleus adsorption on the hollow microsphere with the coupled surface.
Preferably, the method for carrying out surface coupling treatment on the silicate glass hollow microspheres comprises the following steps:
adding the silicate glass hollow microspheres into the coupling treatment mixed solution, uniformly mixing, filtering, drying, and screening out agglomerates to obtain the hollow microspheres with surface coupling.
Further, the solvent in the coupling treatment mixed solution is a mixed solution of absolute ethyl alcohol and distilled water, and the volume ratio of the absolute ethyl alcohol to the distilled water can be any, preferably 3:1-1:6.
Further, the coupling treatment agent of the coupling treatment mixed solution is a conventional commercially available silane coupling agent.
Further, the addition amount of the silicate glass hollow microspheres relative to the coupling treatment mixed solution is 1g/10ml-1g/50ml.
Further, the surface coupling treatment is carried out at a temperature of 20-50 ℃.
Further, the seed core adsorption includes the steps of: adding the hollow microsphere with the coupled surface into the adsorption solution, uniformly mixing, filtering and drying to obtain the nano-porous silica gel.
Further, the adsorption solution is an aqueous solution, more preferably an acidic aqueous solution. Wherein the acid in the acidic aqueous solution is preferably an inorganic acid with a concentration of 0.2-1.5mol/L.
Further, the adsorption solution ions comprise one or more of palladium, silver and gold, and the ion concentration is 0.003-0.2mol/L.
Further, the addition amount of the surface-coupled hollow microspheres relative to the adsorption solution is 1g/10ml-1g/100ml.
Further, the temperature of the seed nucleus adsorption is 10-80 ℃.
To achieve the third object, the present invention also protects the application of the electromagnetic shielding composite material as described in the claims in the field of electromagnetic shielding.
The beneficial effects of the invention are as follows:
in the composite material provided by the invention, the controllable enrichment of the conductive hollow microspheres with two different characteristics is utilized to realize high shielding effectiveness under the condition of low filler addition; meanwhile, a polymer enrichment middle layer with low filler content is positioned between two different conductive hollow microsphere enrichment layers, the electromagnetic loss capacity of the layer is weak, repeated reflection oscillation of electromagnetic waves can be formed between the two conductive hollow microsphere enrichment layers, and the shielding effect is enhanced; in addition, the polymer matrix enrichment middle layer between two layers of different conductive hollow microspheres forms a region with fewer cavities and higher mechanical strength, so that better mechanical support can be provided for the composite material, and the overall mechanical strength of the composite material is improved; finally, preferably, the electromagnetic performance of the obtained composite material can be conveniently regulated and controlled by selecting conductive hollow microspheres with different spherical shell compositions and thicknesses; the three-layer structure proportion and the resin matrix design are further combined, and the series composite materials with different densities, mechanical properties and shielding properties can be obtained.
Drawings
The following describes the embodiments of the present invention in further detail with reference to the drawings.
FIG. 1 shows a schematic structural diagram of a magnetic conductive hollow microsphere in the present invention.
FIG. 2 shows a schematic structural diagram of a non-magnetic conductive hollow microsphere in the present invention.
Fig. 3 shows a schematic structural diagram of a layered structure light-weight high-strength electromagnetic shielding composite material in the invention.
Fig. 4 shows a schematic preparation flow of a layered structure light-weight high-strength electromagnetic shielding composite material based on magnetic and non-magnetic conductive hollow microspheres in the invention.
Fig. 5 shows a photograph of a magnetic conductive hollow microsphere in the present invention.
Fig. 6 shows a photograph of a non-magnetic conductive hollow microsphere in the present invention.
Detailed Description
In order to more clearly illustrate the present invention, the present invention will be further described with reference to preferred embodiments and the accompanying drawings. Like parts in the drawings are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and that this invention is not limited to the details given herein.
Example 1
(1) The preparation process of the hollow microsphere A comprises the following steps: 20g of silicate glass hollow microspheres (density 0.30 g/cm) 3 ) Disperse in 400ml solution a: 550 g/L of silane coupling agent KH, wherein the solvent is a mixed solution of absolute ethyl alcohol and distilled water in a volume ratio of 2:1; 500ml of solution B, 0.5mol/L hydrochloric acid and 0.008mol/L palladium chloride, stirring and reacting for 20min at 40 ℃, filtering, drying at 50 ℃, and sieving to remove agglomerated particles to obtain the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microsphere A obtained in the step (1) in 1500mL of magnetic metal assembly reaction liquid, wherein the reaction liquid contains 26g/L nickel sulfate, 40g/L sodium hypophosphite, 60g/L potassium sodium tartrate and 40g/L ammonium sulfate, regulating the pH to approximately 9.5 by using concentrated ammonia water, stirring and reacting at 60 ℃, and filtering and collecting the hollow microsphere B after the reaction is finished. Dispersing the obtained hollow microspheres B in 1000mL of conductive metal assembly reaction liquid, wherein the reaction liquid contains 0.1mol/L copper sulfate, 0.08mol/L potassium sodium tartrate, 0.06mol/L EDTA, 0.5mol/L sodium hydroxide and 5mL/L formaldehyde, reacting under stirring at room temperature, filtering after the reaction is finished, and drying at 50 ℃ to obtain the hollow microspheres C.
(3) The preparation process of the nonmagnetic conductive hollow microsphere comprises the following steps: dispersing 10g of hollow microspheres A in 1000mL of the same conductive metal assembly reaction liquid as in the step (2), and reacting under the same conditions to obtain nonmagnetic conductive hollow microspheres D.
(4) The density of the magnetic conductive hollow microsphere prepared by the method is 0.69g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the non-magnetic conductive hollow microsphere is 0.47g/cm 3 。
The specific implementation scheme of the preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layering enrichment is as follows:
the resin matrix selected in this example is E-51 epoxy resin, the curing agent is methyl hexahydrophthalic anhydride, and the accelerator is N, N-dimethylbenzylamine. 40 parts of epoxy resin and 30 parts of curing agent methyl hexahydrophthalic anhydride are weighed, stirred and mixed uniformly, and 0.75 part of accelerator N, N-dimethylbenzylamine and 0.45 part of coupling agent KH550 are added to obtain a resin matrix. And then 10.5 parts of the magnetic conductive hollow microspheres and 9.5 parts of the non-magnetic conductive hollow microspheres are added into the matrix, and the mixture is stirred for 30 minutes to be fully mixed. And pouring the uniformly stirred mixture into a mold treated by a release agent, and fixing a magnet at the bottom of the mold. The material and the mould were then placed together on a vibration platform for a vibration layering arrangement, wherein the vibration process lasted 20 minutes. Then, the die and the magnet are put into a curing box for curing treatment, and four stages are adopted: the first stage is treated at 80 ℃ for 2 hours, the second stage is treated at 125 ℃ for 2 hours, the third stage is treated at 170 ℃ for 4 hours, and the fourth stage is a cooling process, and the temperature is cooled to room temperature within 18 hours.
In the electromagnetic shielding composite material based on the conductive hollow microspheres, which is prepared according to the method, the volume ratio of the hollow microspheres is 35 percent (the volume ratio of the magnetic conductive hollow microspheres to the non-magnetic conductive hollow microspheres is 1:1), and the density is 0.94g/cm 3 The uniaxial compression strength is 121.3MPa, and the electromagnetic shielding effectiveness is 56-67dB.
Example 2
(1) The preparation process of the hollow microsphere A comprises the following steps: 20g of silicate glass hollow microspheres (density 0.20 g/cm) 3 ) Disperse in 400ml solution a: 550 g/L of silane coupling agent KH, wherein the solvent is a mixed solution of absolute ethyl alcohol and distilled water in a volume ratio of 2:1; 500ml of solution B, 0.5mol/L hydrochloric acid and 0.008mol/L palladium chloride, stirring and reacting for 20min at 40 ℃, filtering, drying at 50 ℃, and sieving to remove agglomerated particles to obtain the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microsphere A obtained in the step (1) in 1000mL of magnetic metal assembly reaction liquid, wherein the reaction liquid contains 13g/L nickel sulfate, 14g/L cobalt sulfate, 40g/L sodium hypophosphite, 60g/L potassium sodium tartrate and 40g/L ammonium sulfate, regulating the pH to approximately 9.5 by using concentrated ammonia water, stirring and reacting at 65 ℃, and filtering and collecting the hollow microsphere B after the reaction is finished. Dispersing the obtained hollow microspheres B in 1500mL of conductive metal assembly reaction liquid, wherein the reaction liquid contains 0.1mol/L copper sulfate, 0.08mol/L potassium sodium tartrate, 0.06mol/L EDTA, 0.5mol/L sodium hydroxide and 5mL/L formaldehyde, reacting under stirring at room temperature, filtering after the reaction is finished, and drying at 50 ℃ to obtain the hollow microspheres C.
(3) The preparation process of the nonmagnetic conductive hollow microsphere comprises the following steps: dispersing 10g of hollow microsphere A in 1500mL of the same conductive metal assembly reaction liquid as in the step (2), and reacting under the same conditions to obtain the nonmagnetic conductive hollow microsphere D.
(4) The density of the magnetic conductive hollow microsphere prepared by the method is 0.47g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the nonmagnetic conductive hollow microsphere is 0.37g/cm 3 。
The preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layering enrichment is carried out according to the embodiment 1, and specific distinguishing conditions and performance parameters of the obtained composite material are shown in table 1.
Example 3
(1) The preparation process of the hollow microsphere A comprises the following steps: 20g of silicate glass hollow microspheres (density 0.40 g/cm) 3 ) Dispersed in 300ml of solution A: 550 g/L of silane coupling agent KH, wherein the solvent is a mixed solution of absolute ethyl alcohol and distilled water in a volume ratio of 1:1; 400ml of solution B, 0.4mol/L hydrochloric acid and 0.01mol/L palladium chloride, stirring and reacting for 20min at 45 ℃, filtering, drying at 50 ℃, and sieving to remove agglomerated particles to obtain the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microsphere A obtained in the step (1) in 1000mL of magnetic metal assembly reaction liquid, wherein the reaction liquid contains 19.5g/L nickel sulfate, 21g/L cobalt sulfate, 60g/L sodium hypophosphite, 80g/L potassium sodium tartrate and 50g/L ammonium sulfate, regulating the pH to about 10 by using concentrated ammonia water, stirring and reacting at 75 ℃, and filtering and collecting the hollow microsphere B after the reaction is finished. Dispersing the obtained hollow microspheres B in 1500mL of conductive metal assembly reaction liquid, wherein the reaction liquid contains 0.1mol/L copper sulfate, 0.08mol/L potassium sodium tartrate, 0.06mol/L EDTA, 0.5mol/L sodium hydroxide and 7mL/L formaldehyde, reacting under stirring at room temperature, filtering after the reaction is finished, and drying at 50 ℃ to obtain the hollow microspheres C.
(3) The preparation process of the nonmagnetic conductive hollow microsphere comprises the following steps: dispersing 10g of hollow microsphere A in 1500mL of the same conductive metal assembly reaction liquid as in the step (2), and reacting under the same conditions to obtain the nonmagnetic conductive hollow microsphere D.
(4) The density of the magnetic conductive hollow microsphere prepared by the method is 1.04g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the nonmagnetic conductive hollow microsphere is 0.74g/cm 3 。
The preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layering enrichment is carried out according to the embodiment 1, and specific distinguishing conditions and performance parameters of the obtained composite material are shown in table 1.
Example 4
(1) The preparation process of the hollow microsphere A comprises the following steps: 20g of silicate glass hollow microspheres (density 0.50 g/cm) 3 ) Dispersed in 300ml of solution A: 550 g/L of silane coupling agent KH, wherein the solvent is mixed solution of absolute ethyl alcohol and distilled water in a volume ratio of 1:1; 300ml of solution B, 0.4mol/L hydrochloric acid and 0.01mol/L palladium chloride, stirring and reacting for 20min at 45 ℃, filtering, drying at 50 ℃, and sieving to remove agglomerated particles to obtain the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microsphere A obtained in the step (1) in 1000mL of magnetic metal assembly reaction liquid, wherein the reaction liquid contains 13g/L nickel sulfate, 7g/L cobalt sulfate, 30g/L sodium hypophosphite, 50g/L potassium sodium tartrate and 30g/L ammonium sulfate, regulating the pH to about 10.5 by using concentrated ammonia water, stirring and reacting at 75 ℃, and filtering and collecting the hollow microsphere B after the reaction is finished. Dispersing the obtained hollow microspheres B in 2000mL of conductive metal assembly reaction liquid, wherein the reaction liquid contains 0.05mol/L copper sulfate, 0.06mol/L potassium sodium tartrate, 0.4mol/L sodium hydroxide and 4mL/L formaldehyde, reacting under stirring at room temperature, filtering after the reaction is finished, and drying at 50 ℃ to obtain the hollow microspheres C.
(3) The preparation process of the nonmagnetic conductive hollow microsphere comprises the following steps: dispersing 10g of hollow microsphere A in 2000mL of the same conductive metal assembly reaction liquid as in the step (2), and reacting under the same conditions to obtain the nonmagnetic conductive hollow microsphere D.
(4) The density of the magnetic conductive hollow microsphere prepared by the method is 0.97g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the nonmagnetic conductive hollow microsphere is 0.78g/cm 3 。
The preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layering enrichment is carried out according to the embodiment 1, and specific distinguishing conditions and performance parameters of the obtained composite material are shown in table 1.
Example 5
(1) The preparation process of the hollow microsphere A comprises the following steps: 20g of silicate glass hollow microspheres (density 0.25 g/cm) 3 ) Disperse in 500ml solution a: 550 g/L of silane coupling agent KH, wherein the solvent is a mixed solution of absolute ethyl alcohol and distilled water in a volume ratio of 2:1; 600ml of solution B, 0.5mol/L hydrochloric acid and 0.008mol/L palladium chloride, stirring and reacting for 20min at 40 ℃, filtering, drying at 50 ℃, and sieving to remove agglomerated particles to obtain the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microsphere A obtained in the step (1) in 1000mL of magnetic metal assembly reaction liquid, wherein the reaction liquid contains 6.5g/L nickel sulfate, 7g/L ferrous sulfate, 25g/L sodium hypophosphite, 50g/L potassium sodium tartrate and 30g/L ammonium sulfate, regulating the pH to about 11 by using concentrated ammonia water, stirring and reacting at 70 ℃, and filtering and collecting the hollow microsphere B after the reaction is finished. Dispersing the obtained hollow microsphere B in 1000mL of conductive metal assembly reaction liquid, wherein the reaction liquid contains 0.1mol/L silver nitrate (colorless by dropwise adding concentrated ammonia water), then dropwise adding 8mL of hydrazine hydrate under stirring, reacting under stirring at room temperature, filtering after the reaction is finished, and drying at 50 ℃ to obtain the hollow microsphere C.
(3) The preparation process of the nonmagnetic conductive hollow microsphere comprises the following steps: dispersing 10g of hollow microspheres A in 1000mL of the same conductive metal assembly reaction liquid as in the step (2), and reacting under the same conditions to obtain nonmagnetic conductive hollow microspheres D.
The density of the magnetic conductive hollow microsphere prepared by the method is 0.55g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the non-magnetic conductive hollow microsphere is 0.49g/cm 3 。
The preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layering enrichment is carried out according to the embodiment 1, and specific distinguishing conditions and performance parameters of the obtained composite material are shown in table 1.
Example 6
(1) The preparation process of the hollow microsphere A comprises the following steps: 20g of silicate glass hollow microspheres (density 0.25gcm 3 ) Disperse in 500ml solution a: 550 g/L of silane coupling agent KH, wherein the solvent is a mixed solution of absolute ethyl alcohol and distilled water in a volume ratio of 2:1; 600ml of solution B, 0.5mol/L hydrochloric acid and 0.008mol/L palladium chloride, stirring and reacting for 20min at 40 ℃, filtering, drying at 50 ℃, and sieving to remove agglomerated particles to obtain the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microsphere A obtained in the step (1) in 1000mL of magnetic metal assembly reaction liquid, wherein the reaction liquid contains 14g/L cobalt sulfate, 14g/L ferrous sulfate, 25g/L sodium hypophosphite, 50g/L potassium sodium tartrate and 30g/L ammonium sulfate, regulating the pH to about 11 by using concentrated ammonia water, stirring and reacting at 70 ℃, and filtering and collecting the hollow microsphere B after the reaction is finished. Dispersing the obtained hollow microsphere B in 1000mL of conductive metal assembly reaction liquid, wherein the reaction liquid contains 0.1mol/L silver nitrate (colorless by dropwise adding concentrated ammonia water), then dropwise adding 8mL of hydrazine hydrate under stirring, reacting under stirring at room temperature, filtering after the reaction is finished, and drying at 50 ℃ to obtain the hollow microsphere C.
(3) The preparation process of the nonmagnetic conductive hollow microsphere comprises the following steps: dispersing 10g of hollow microspheres A in 1000mL of the same conductive metal assembly reaction liquid as in the step (2), and reacting under the same conditions to obtain nonmagnetic conductive hollow microspheres D.
The density of the magnetic conductive hollow microsphere prepared by the method is 0.61g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the non-magnetic conductive hollow microsphere is 0.49g/cm 3 。
The preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layering enrichment is carried out according to the embodiment 1, and specific distinguishing conditions and performance parameters of the obtained composite material are shown in table 1.
Example 7
(1) The preparation process of the hollow microsphere A comprises the following steps: 20g of silicate glass hollow microspheres (density 0.3 g/cm) 3 ) Disperse in 400ml solution a: silane coupling agent KH550 g/L, solvent is mixed solution of absolute ethyl alcohol and distilled water in a volume ratio of 1:4; 400ml of solution B, 0.5mol/L hydrochloric acid and 0.008mol/L palladium chloride, stirring and reacting for 20min at 40 ℃, filtering, drying at 50 ℃, and sieving to remove agglomerated particles to obtain the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microsphere A obtained in the step (1) in 1000mL of magnetic metal assembly reaction liquid, wherein the reaction liquid contains 13g/L nickel sulfate, 14g/L ferrous sulfate, 14g/L cobalt sulfate, 35g/L sodium hypophosphite, 60g/L potassium sodium tartrate and 40g/L ammonium sulfate, regulating the pH to approximately 10 by using concentrated ammonia water, stirring and reacting at 75 ℃, and filtering and collecting the hollow microsphere B after the reaction is finished. Dispersing the obtained hollow microsphere B in 1000mL of conductive metal assembly reaction liquid, wherein the reaction liquid contains 0.05mol/L silver nitrate (colorless by dropwise adding concentrated ammonia water), then dropwise adding 8mL of hydrazine hydrate under stirring, reacting under stirring at room temperature, filtering after the reaction is finished, and drying at 50 ℃ to obtain the hollow microsphere C.
(3) The preparation process of the nonmagnetic conductive hollow microsphere comprises the following steps: dispersing 10g of hollow microspheres A in 1000mL of the same conductive metal assembly reaction liquid as in the step (2), and reacting under the same conditions to obtain nonmagnetic conductive hollow microspheres D.
The density of the magnetic conductive hollow microsphere prepared by the method is 0.6g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the nonmagnetic conductive hollow microsphere is 0.38g/cm 3 。
The preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layering enrichment is carried out according to the embodiment 1, and specific distinguishing conditions and performance parameters of the obtained composite material are shown in table 1.
Example 8
(1) The preparation process of the hollow microsphere A comprises the following steps: 20g of silicate glass hollow microspheres (density 0.27 g/cm) 3 ) Disperse in 500ml solution a: silane coupling agent KH550 g/L, solvent is mixed solution of absolute ethyl alcohol and distilled water in a volume ratio of 1:4; 500ml of solution B, 0.5mol/L hydrochloric acid and 0.008mol/L palladium chloride, stirring and reacting for 20min at 40 ℃, filtering, drying at 50 ℃, and sieving to remove agglomerated particles to obtain the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microsphere A obtained in the step (1) in 1000mL of magnetic metal assembly reaction liquid, wherein the reaction liquid contains 13g/L nickel sulfate, 14g/L ferrous sulfate, 14g/L cobalt sulfate, 40g/L sodium hypophosphite, 80g/L potassium sodium tartrate and 40g/L ammonium sulfate, regulating the pH to approximately 10 by using concentrated ammonia water, stirring and reacting at 75 ℃, and filtering and collecting the hollow microsphere B after the reaction is finished. Dispersing the obtained hollow microsphere B in 2000mL of conductive metal assembly reaction liquid, wherein the reaction liquid contains 0.075mol/L copper sulfate, 0.09mol/L potassium sodium tartrate, 0.6mol/L sodium hydroxide and 6mL/L formaldehyde, reacting under stirring at room temperature, filtering after the reaction is finished, and drying at 50 ℃ to obtain the hollow microsphere C.
(3) The preparation process of the nonmagnetic conductive hollow microsphere comprises the following steps: dispersing 10g of hollow microsphere A in 2000mL of the same conductive metal assembly reaction liquid as in the step (2), and reacting under the same conditions to obtain the nonmagnetic conductive hollow microsphere D.
(4) The density of the magnetic conductive hollow microsphere prepared by the method is 0.7g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the nonmagnetic conductive hollow microsphere is 0.5g/cm 3 。
The preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layering enrichment is carried out according to the embodiment 1, and specific distinguishing conditions and performance parameters of the obtained composite material are shown in table 1.
TABLE 1 preparation conditions and Performance parameters of electromagnetic shielding composite materials in examples 2-8
The testing method comprises the following steps:
1. processing the material into a sample with the size of 22.8-10.1-3 mm in the electromagnetic shielding effectiveness test process of the composite material; s parameters in the frequency band of 8.2-12.4GHz are tested by a waveguide method by using a vector network analyzer, and the shielding performance of the shielding device is calculated by using the measured S parameters through the following formula (A) is total shielding effectiveness, formula (B) is reflection shielding effectiveness, and formula (C) is absorption shielding effectiveness).
…(A)；
2. Reference national standard test of uniaxial compressive strength: resin casting performance test method (GBT 2567-2008).
It should be understood that the foregoing examples of the present invention are provided merely for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention, and that various other changes and modifications may be made therein by one skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.
Claims (16)
1. An electromagnetic shielding composite material based on heterogeneous hollow microsphere layering enrichment is characterized by comprising a polymer matrix, and magnetic conductive hollow microspheres and non-magnetic conductive hollow microspheres doped in the polymer matrix;
wherein the polymer matrix has two surfaces that are opposite from top to bottom;
the magnetic conductive hollow microspheres are enriched on one surface of the polymer matrix; and is also provided with
The non-magnetic conductive hollow microspheres are enriched on the other surface of the polymer matrix;
the total volume percentage of the magnetic conductive hollow microspheres and the non-magnetic conductive hollow microspheres in the composite material is 20-40%;
the volume ratio of the magnetic conductive hollow microspheres to the non-magnetic conductive hollow microspheres is 3:1-1:3;
the layer formed by the magnetic conductive hollow microspheres is not in direct contact with the layer formed by the nonmagnetic conductive hollow microspheres;
the magnetic conductive hollow microsphere has a hollow structure, and a silicate glass shell layer, a magnetic metal shell layer and a conductive metal shell layer are sequentially arranged from inside to outside in a shell structure;
the non-magnetic conductive hollow microsphere has a hollow structure, and a silicate glass layer and a conductive metal layer are sequentially arranged in the shell structure from inside to outside.
2. The electromagnetic shielding composite of claim 1 wherein the composite has a true density of 0.7-1.1g/cm 3 。
3. The electromagnetic shielding composite of claim 1 wherein the volume ratio of the magnetically conductive hollow microspheres to the non-magnetically conductive hollow microspheres is from 1:0.5 to 1:1.
4. The electromagnetic shielding composite of claim 1 wherein the density of the magnetically conductive hollow microspheres is 0.3-1.0g/cm 3 The grain size is 5-90 microns.
5. The electromagnetic shielding composite of claim 1 wherein the silicate glass shell layer has a thickness of 300-1200 nanometers.
6. The electromagnetic shielding composite of claim 1 wherein the magnetic metal sheath has a thickness of 20-200 nanometers.
7. The electromagnetic shielding composite of claim 1 wherein the conductive metal shell has a thickness of 20-400 nanometers.
8. The electromagnetic shielding composite of claim 1 wherein the composition of the magnetic metal sheath is selected from one or more of cobalt, nickel, iron, and alloys thereof.
9. The electromagnetic shielding composite of claim 1 wherein the composition of the conductive metal shell is selected from one or more of copper, silver, and alloys thereof.
10. The electromagnetic shielding composite of claim 1 wherein the density of the non-magnetic conductive hollow microspheres is 0.3-0.95g/cm 3 The grain size is 5-90 microns.
11. The electromagnetic shielding composite of claim 1 wherein the silicate glass layer has a thickness of 300-1500 nanometers and the conductive metal layer has a thickness of 20-400 nanometers.
12. The electromagnetic shielding composite of claim 1 wherein the composition of the conductive metal layer is selected from one or more of copper, silver, and alloys thereof.
13. The electromagnetic shielding composite of claim 1, wherein the polymer matrix is selected from one or more of epoxy resin, unsaturated polyester resin, phenolic resin, polyurethane resin, polystyrene.
14. The electromagnetic shielding composite of claim 1 wherein the raw materials forming the composite further comprise an auxiliary agent;
the auxiliary agent comprises a curing agent and one or more of an accelerator, a surfactant and a diluent.
15. The method of preparing an electromagnetic shielding composite according to any one of claims 1 to 13, comprising the steps of:
providing magnetic conductive hollow microspheres and non-magnetic conductive hollow microspheres respectively;
mixing and pouring raw materials comprising a polymer matrix, magnetic conductive hollow microspheres and nonmagnetic conductive hollow microspheres into a die coated with a release agent in advance;
fixing a magnet at the bottom of the die, and carrying out vibration layering treatment on the die and the materials in the die;
solidifying and demoulding to obtain the electromagnetic shielding composite material.
16. Use of an electromagnetic shielding composite according to any of claims 1-4 in the field of electromagnetic shielding.
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