CN115340744A - 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 layered 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 which are opposite up and down; 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 the 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 considered; and a scheme is provided 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 pollution of electromagnetic waves makes the development and application of electromagnetic shielding materials widely regarded. Facing to the great increasing demands of consumer electronics, civil protection equipment and high-end equipment on material lightweight, the lightweight of electromagnetic shielding materials is imperative. The polymer-based composite material is a novel material form with great competitiveness under the great trend of light weight of functional and structural materials due to the characteristics of wide raw material sources, rich functional selection, convenient strength design and easy forming, and the research and application of the polymer-based composite material are also highly concerned by researchers at home and abroad. However, for the electromagnetic shielding composite material, it is generally required to have strong electrical conductivity and/or magnetism to realize direct reflection of incident electromagnetic waves through impedance mismatch of interfaces or to realize shielding of electromagnetic waves through loss of electromagnetic waves entering the material.
Since most (especially, technically and commercially valuable) polymer materials do not have good electrical conductivity and/or magnetism, it is usually necessary to provide the polymer matrix composite with corresponding functionality by means of electromagnetic functional fillers to achieve efficient shielding of incident electromagnetic waves. The conventional electromagnetic functional filler and the electromagnetic shielding composite thereof have the following problems. Firstly, the density of the filler is high (especially the metal material with good conductivity), which not only increases the density of the composite material, but also is not beneficial to lightweight design; also brings about the problem of sedimentation of the filler, resulting in poor distribution uniformity and affecting the performance. Secondly, the electromagnetic functional filler is usually added in a large proportion to obtain high electromagnetic shielding effectiveness, and considering the high density of the electromagnetic functional filler, the large proportion of the electromagnetic functional filler is necessary to greatly increase the density of the composite material. Thirdly, the price of part of high-performance conductive fillers (such as silver) is higher, and the production cost of the composite material is increased due to the large-proportion filling.
Based on the analysis, the novel electromagnetic functional filler based on the hollow structure is developed, and the work of realizing the high shielding efficiency of the composite material under the condition of low filler addition amount through the controllable distribution of the filler in the composite material has important scientific research and practical value. On one hand, the lightweight hollow microspheres based on internal foam pores can greatly reduce the density and the using amount of electromagnetic functional materials by utilizing the existence of the foam pores; on the other hand, the enrichment of electromagnetic functional materials in the hollow microsphere shell area can be utilized to enable a contact network to be formed more easily, and the shielding efficiency is improved. However, the density reduction by adopting the hollow structure filler at present has the defects of single function of the filler, difficult control of the distribution of the filler in a polymer matrix, higher filling amount of the filler volume and the like.
Disclosure of Invention
The invention aims to provide an electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment.
The second purpose of the invention is to provide a preparation method of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment.
The third purpose 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 purpose, the invention adopts the following technical scheme:
the composite material comprises a polymer matrix, and magnetic conductive hollow microspheres and non-magnetic conductive hollow microspheres which are doped in the polymer matrix;
wherein the polymer matrix has two surfaces which are opposite up and down;
the magnetic conductive hollow microspheres are enriched on one surface of the polymer matrix; and is
The non-magnetic conductive hollow microspheres are enriched on the other surface of the polymer matrix.
In the technical scheme, the high shielding efficiency under the condition of low filler addition is realized by utilizing the controllable enrichment of two conductive hollow microspheres with different characteristics.
Further, the magnetic conductive hollow microsphere is enriched on one surface of the polymer matrix to form a magnetic conductive hollow microsphere layer; the non-magnetic conductive hollow microsphere is enriched on one surface of the polymer matrix to form a non-magnetic conductive hollow microsphere layer. It is understood that the magnetic conductive hollow microsphere layer and the non-magnetic 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, the hollow cavities of the polymer matrix are fewer, the mechanical strength is high, 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 non-magnetic 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 1.5-1:1, more preferably 1:1, and the comprehensive performance is better at this time.
Further, the density of the magnetic conductive hollow microsphere is 0.3-1.0g/cm 3 The grain diameter is 5-90 microns.
Furthermore, 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 nm.
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.
Furthermore, the magnetic metal shell layer is made of one or more of cobalt, nickel, iron and alloys thereof.
Further, the conductive metal shell layer is made of one or more selected from copper, silver and alloys thereof.
Further, the density of the non-magnetic conductive hollow microsphere is 0.3-0.95g/cm 3 The grain diameter is 5-90 microns.
Furthermore, 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.
Furthermore, 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 components of the conductive metal layer are 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 that: the liquid is in a flowable state before curing or in a flowable state 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.
Furthermore, the raw materials for forming the composite material also comprise an auxiliary agent, wherein the auxiliary agent is selected from one or more of a curing agent, an accelerator, a surfactant and a diluent. The selection and the dosage of each specific auxiliary agent can be selected by a person skilled in the art according to actual conditions. Taking an epoxy resin as an example, the curing agent includes but is not limited to methyl tetrahydrophthalic anhydride; the accelerator includes, but is not limited to, N-dimethylbenzylamine; the diluent includes, but is not limited to, aliphatic alcohol diglycidyl ether (V22).
In order to achieve the second purpose, the invention adopts the following technical scheme:
a preparation method of an electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment comprises the following steps:
respectively providing magnetic conductive hollow microspheres and non-magnetic conductive hollow microspheres;
mixing and pouring raw materials comprising a polymer matrix, magnetic conductive hollow microspheres and non-magnetic conductive hollow microspheres into a mold coated with a release agent in advance;
fixing a magnet at the bottom of the mold, and carrying out vibration layering treatment on the mold and the materials inside the mold;
and curing and demolding to obtain the electromagnetic shielding composite material.
In the preparation method, the oriented controllable enrichment of the conductive filler is realized through one-pot reaction with the assistance of buoyancy and an external magnetic field, and a layered composite structure of the magnetic conductive hollow microspheres and the non-magnetic 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 microspheres A with the assembly reaction liquid, heating, stirring, reacting, filtering and cleaning.
Furthermore, the assembly reaction liquid comprises ion source salt, a stabilizing agent, a reducing agent and a pH regulator.
Further, the ion source salt comprises iron 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 to 11, and the regulator is preferably an inorganic base.
Further, the adding amount of the hollow microspheres A is 1g/50ml-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 microspheres B and the assembly reaction solution at room temperature, and then filtering and cleaning.
In the preparation method, in the method for coating the conductive metal on the surface of the hollow microsphere B, whether further calcination heat treatment is performed or not can be selected according to actual needs.
Further, the assembly reaction solution consists of: 0.08-1.8mol/L of metal ions, 0.05-0.6mol/L, pH of complexing agent to 0.1-1mol/L of regulator and 0.01-2mol/L of reducing agent.
Further, the ion source salt includes copper salt, silver salt, preferably inorganic salt.
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 to 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 microspheres, the hollow microspheres a may be prepared as described above.
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 microspheres 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 or not can be selected according to actual needs.
Further, the assembly reaction solution consists of: 0.08-1.8mol/L of metal ions, 0.05-0.6mol/L, pH of complexing agent to 0.1-1mol/L of regulator and 0.01-2mol/L of reducing agent.
Further, the ion source salt includes copper salt, silver salt, preferably inorganic salt.
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 to 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 carrying out seed core adsorption on the hollow microspheres with coupled surfaces.
Preferably, the method for performing surface coupling treatment on the silicate glass hollow microspheres comprises the following steps:
and 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 coupled surfaces.
The solvent in the mixed solution for coupling treatment is a mixed solution of absolute ethyl alcohol and distilled water, and can be in any volume ratio, and the volume ratio of absolute ethyl alcohol to distilled water is preferably 3:1-1:6.
Further, the coupling treatment agent of the coupling treatment mixed solution is a conventional commercially available silane coupling agent.
Furthermore, 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 to 50 ℃.
Further, the seed adsorption comprises the following steps: and adding the hollow microspheres with coupled surfaces into an adsorption solution, uniformly mixing, filtering and drying to obtain the nano-composite adsorbent.
Further, the adsorption solution is an aqueous solution, more preferably an acidic aqueous solution. Wherein, the acid in the acidic aqueous solution is preferably inorganic acid, and the concentration is 0.2-1.5mol/L.
Furthermore, the ions of the adsorption solution 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 to the adsorption solution is 1g/10ml-1g/100ml.
Further, the temperature of the seed core 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 above in the field of electromagnetic shielding.
The invention has the following beneficial effects:
in the composite material provided by the invention, the high shielding efficiency under the condition of low filler addition amount is realized by utilizing the controllable enrichment of two conductive hollow microspheres with different characteristics; meanwhile, the polymer enrichment middle layer with low filler content is positioned between the two different conductive hollow microsphere enrichment layers, the electromagnetic loss capacity of the polymer enrichment middle 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, a 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, the electromagnetic performance of the obtained composite material can be conveniently regulated and controlled by preferably selecting the conductive hollow microspheres with different spherical shell compositions and thicknesses; further combining the proportion of the three-layer structure and the resin matrix design, the serialized composite materials with different densities, mechanical properties and shielding properties can be obtained.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
Fig. 1 shows a schematic structural view of the magnetic conductive hollow microsphere of the present invention.
Fig. 2 shows a schematic structural view of the non-magnetic conductive hollow microsphere of the present invention.
Fig. 3 is a schematic structural view showing a light-weight high-strength electromagnetic shielding composite material of a layered structure according to the present invention.
FIG. 4 is a schematic diagram showing a process for preparing a light-weight high-strength electromagnetic shielding composite material with a layered structure based on magnetic and non-magnetic conductive hollow microspheres.
Fig. 5 shows a photograph of the magnetic conductive hollow microsphere in the present invention.
Fig. 6 shows a photograph of non-magnetic conductive hollow microspheres in the present invention.
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below with reference to preferred embodiments and the accompanying drawings. Similar parts in the figures 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 is not to be taken as limiting the scope of the invention.
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 ) Dispersion in 400ml of solution a: the silane coupling agent KH550 g/L, the solvent is the mixed liquid of absolute ethyl alcohol and distilled water 2:1 with volume ratio; 500ml of solution B, 0.5mol/L of hydrochloric acid and 0.008mol/L of palladium chloride, is stirred at 40 ℃ for reaction for 20min, is filtered, is dried at 50 ℃, and is sieved to remove agglomerated particles, thus obtaining the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microspheres A obtained in the step (1) in 1500mL of magnetic metal assembly reaction liquid, adjusting the pH to be approximately equal to 9.5 by using concentrated ammonia water, stirring and reacting at 60 ℃, and filtering and collecting the hollow microspheres B after the reaction is finished, wherein the reaction liquid contains 26g/L of nickel sulfate, 40g/L of sodium hypophosphite, 60g/L of potassium sodium tartrate and 40g/L of ammonium sulfate. Dispersing the obtained hollow microsphere 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 microsphere C.
(3) The preparation process of the non-magnetic conductive hollow microsphere comprises the following steps: and (3) dispersing 10g of the hollow microsphere A in 1000mL of conductive metal assembly reaction liquid which is the same as the step (2), and reacting under the same condition to obtain the non-magnetic conductive hollow microsphere D.
(4) The density of the magnetic conductive hollow microsphere prepared by the method is 0.69g/cm 3 (ii) a The density of the non-magnetic conductive hollow microsphere is 0.47g/cm 3 。
The specific embodiment of the preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment is as follows:
the resin matrix selected in this example is E-51 epoxy resin, the curing agent is methylhexahydrophthalic anhydride, and the accelerator is N, N-dimethylbenzylamine. Weighing 40 parts of epoxy resin and 30 parts of curing agent methyl hexahydrophthalic anhydride, stirring and mixing uniformly, and adding 0.75 part of accelerator N, N-dimethylbenzylamine and 0.45 part of coupling agent KH550 to obtain a resin matrix. Then 10.5 parts of magnetic conductive hollow microspheres and 9.5 parts of non-magnetic conductive hollow microspheres are added into the matrix, and stirred for 30 minutes to be fully mixed. And then pouring the uniformly stirred mixed material into a mold treated by a mold release agent, and fixing a magnet at the bottom of the mold. The material and the mould were then placed on a vibrating platform for a vibrating layering process, wherein the vibrating process lasted 20 minutes. Then putting the mould and the magnet into a curing box together for curing treatment, and treating the four stages: the first stage of 80 ℃ treatment for 2 hours, the second stage of 125 ℃ treatment for 2 hours, the third stage of 170 ℃ treatment for 4 hours, and the fourth stage of cooling process, and the temperature is cooled to room temperature within 18 hours.
In the electromagnetic shielding composite material based on the conductive hollow microsphere prepared by the method, the volume of the hollow microsphere accounts for 35 percent (the volume of the magnetic conductive hollow microsphere and the magnetic conductive hollow microsphere are combined together)The volume ratio of 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 ) Dispersion in 400ml solution a: the silane coupling agent KH550 g/L, the solvent is the mixed liquid of absolute ethyl alcohol and distilled water 2:1 with volume ratio; 500ml of solution B, 0.5mol/L of hydrochloric acid and 0.008mol/L of palladium chloride, is stirred at 40 ℃ to react for 20min, then is filtered, is dried at 50 ℃, and is screened to remove agglomerated particles, thus obtaining the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microspheres A obtained in the step (1) in 1000mL of magnetic metal assembly reaction liquid, adjusting the pH to be approximately equal to 9.5 by using concentrated ammonia water, stirring and reacting at 65 ℃, and filtering and collecting the hollow microspheres B after the reaction is finished, wherein the reaction liquid contains 13g/L of nickel sulfate, 14g/L of cobalt sulfate, 40g/L of sodium hypophosphite, 60g/L of potassium sodium tartrate and 40g/L of ammonium sulfate. Dispersing the obtained hollow microsphere 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 microsphere C.
(3) The preparation process of the non-magnetic conductive hollow microsphere comprises the following steps: and (3) dispersing 10g of the hollow microsphere A in 1500mL of conductive metal assembly reaction liquid which is the same as the step (2), and reacting under the same condition to obtain the non-magnetic conductive hollow microsphere D.
(4) The density of the magnetic conductive hollow microsphere prepared by the method is 0.47g/cm 3 (ii) a The density of the non-magnetic conductive hollow microsphere is 0.37g/cm 3 。
The preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment is carried out according to example 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 ) Dispersion in 300ml of solution a: silane coupling agent KH550 12g/L, and the solvent is a mixed solution of absolute ethyl alcohol and distilled water 1:1 in volume ratio; 400ml of solution B, 0.4mol/L of hydrochloric acid and 0.01mol/L of palladium chloride, stirring and reacting at 45 ℃ for 20min, filtering, drying at 50 ℃, and screening to remove agglomerated particles to obtain the hollow microspheres A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microspheres 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, adjusting the pH to be approximately equal to 10 by using concentrated ammonia water, stirring and reacting at 75 ℃, and filtering and collecting the hollow microspheres B after the reaction is finished. Dispersing the obtained hollow microsphere 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 microsphere C.
(3) The preparation process of the non-magnetic conductive hollow microsphere comprises the following steps: and (3) dispersing 10g of the hollow microsphere A in 1500mL of conductive metal assembly reaction liquid which is the same as the step (2), and reacting under the same condition to obtain the non-magnetic conductive hollow microsphere D.
(4) The density of the magnetic conductive hollow microsphere prepared by the method is 1.04g/cm 3 (ii) a The density of the non-magnetic conductive hollow microsphere is 0.74g/cm 3 。
The preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment is carried out according to example 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 ) Dispersion in 300ml of solution a: the silane coupling agent KH550 g/L, and the solvent is a mixed solution of absolute ethyl alcohol and distilled water 1:1 in volume ratio; 300ml of solution B, 0.4mol/L of hydrochloric acid and 0.01mol/L of palladium chloride, stirring and reacting at 45 ℃ for 20min, filtering, drying at 50 ℃, and screening to remove agglomerated particles to obtain the hollow microspheres A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microspheres A obtained in the step (1) in 1000mL of magnetic metal assembly reaction liquid, adjusting the pH to be approximately 10.5 by using concentrated ammonia water, stirring and reacting at 75 ℃, and filtering and collecting the hollow microspheres B after the reaction is finished, wherein the reaction liquid contains 13g/L of nickel sulfate, 7g/L of cobalt sulfate, 30g/L of sodium hypophosphite, 50g/L of potassium sodium tartrate and 30g/L of ammonium sulfate. Dispersing the obtained hollow microsphere 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 microsphere C.
(3) The preparation process of the non-magnetic conductive hollow microsphere comprises the following steps: and (3) dispersing 10g of the hollow microspheres A in 2000mL of conductive metal assembly reaction liquid which is the same as the conductive metal assembly reaction liquid obtained in the step (2), and reacting under the same condition to obtain the non-magnetic conductive hollow microspheres D.
(4) The density of the magnetic conductive hollow microsphere prepared by the method is 0.97g/cm 3 (ii) a The density of the non-magnetic conductive hollow microsphere is 0.78g/cm 3 。
The preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment is carried out according to example 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 ) Dispersion in 500ml solution a: the silane coupling agent KH550 g/L, the solvent is the mixed liquid of absolute ethyl alcohol and distilled water 2:1 with volume ratio; 600ml of solution B, 0.5mol/L of hydrochloric acid and 0.008mol/L of palladium chloride, is stirred at 40 ℃ for reaction for 20min, is filtered, is dried at 50 ℃, and is sieved to remove agglomerated particles, thus obtaining the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microspheres 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, adjusting the pH to be approximately equal to 11 by using concentrated ammonia water, stirring and reacting at 70 ℃, and filtering and collecting the hollow microspheres B after the reaction is finished. Dispersing the obtained hollow microsphere B in 1000mL of conductive metal assembly reaction liquid, adding 0.1mol/L silver nitrate (dropwise adding concentrated ammonia water to colorless) into the reaction liquid, 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 non-magnetic conductive hollow microsphere comprises the following steps: and (3) dispersing 10g of the hollow microsphere A in 1000mL of conductive metal assembly reaction liquid which is the same as the step (2), and reacting under the same condition to obtain the non-magnetic conductive hollow microsphere D.
The density of the magnetic conductive hollow microsphere prepared by the method is 0.55g/cm 3 (ii) a 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 layered enrichment is carried out according to example 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 0.25 g/cm) 3 ) Dispersion in 500ml of solution a: the silane coupling agent KH550 g/L, the solvent is the mixed liquid of absolute ethyl alcohol and distilled water 2:1 with volume ratio; 600ml of solution B, 0.5mol/L of hydrochloric acid and 0.008mol/L of palladium chloride, is stirred at 40 ℃ to react for 20min, then is filtered, is dried at 50 ℃, and is screened to remove agglomerated particles, thus obtaining the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microspheres A obtained in the step (1) in 1000mL of magnetic metal assembly reaction liquid, wherein the reaction liquid contains 14g/L of cobalt sulfate, 14g/L of ferrous sulfate, 25g/L of sodium hypophosphite, 50g/L of potassium sodium tartrate and 30g/L of ammonium sulfate, adjusting the pH to be approximately equal to 11 by using concentrated ammonia water, stirring for reaction at 70 ℃, and filtering and collecting the hollow microspheres B after the reaction is finished. Dispersing the obtained hollow microsphere B in 1000mL of conductive metal assembly reaction liquid, adding 0.1mol/L silver nitrate (dropwise adding concentrated ammonia water to colorless) into the reaction liquid, 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 non-magnetic conductive hollow microsphere comprises the following steps: and (3) dispersing 10g of the hollow microsphere A in 1000mL of conductive metal assembly reaction liquid which is the same as the step (2), and reacting under the same condition to obtain the non-magnetic conductive hollow microsphere D.
The density of the magnetic conductive hollow microsphere prepared by the method is 0.61g/cm 3 (ii) a 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 layered enrichment is carried out according to example 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 ) Dispersion in 400ml solution a: the silane coupling agent KH550 g/L, the solvent is the mixed liquid of absolute ethyl alcohol and distilled water 1:4 with volume ratio; 400ml of solution B, 0.5mol/L of hydrochloric acid and 0.008mol/L of palladium chloride, is stirred at 40 ℃ for reaction for 20min, is filtered, is dried at 50 ℃, and is sieved to remove agglomerated particles, thus obtaining the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: dispersing 10g of the hollow microspheres 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, adjusting the pH to be approximately equal to 10 by using concentrated ammonia water, stirring and reacting at 75 ℃, and filtering and collecting the hollow microspheres B after the reaction is finished. Dispersing the obtained hollow microsphere B in 1000mL of conductive metal assembly reaction liquid, adding 0.05mol/L of silver nitrate (dropwise adding concentrated ammonia water until colorless), 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 non-magnetic conductive hollow microsphere comprises the following steps: and (3) dispersing 10g of the hollow microsphere A in 1000mL of conductive metal assembly reaction liquid which is the same as the step (2), and reacting under the same condition to obtain the non-magnetic conductive hollow microsphere D.
The density of the magnetic conductive hollow microsphere prepared by the method is 0.6g/cm 3 (ii) a The density of the non-magnetic conductive hollow microsphere is 0.38g/cm 3 。
The preparation process of the electromagnetic shielding composite material based on heterogeneous hollow microsphere layered enrichment is carried out according to example 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 ) Dispersion in 500ml solution a: the silane coupling agent KH550 g/L, the solvent is the mixed liquid of absolute ethyl alcohol and distilled water 1:4 with volume ratio; 500ml of solution B, 0.5mol/L of hydrochloric acid and 0.008mol/L of palladium chloride, is stirred at 40 ℃ to react for 20min, then is filtered, is dried at 50 ℃, and is screened to remove agglomerated particles, thus obtaining the hollow microsphere A.
(2) The preparation process of the magnetic conductive hollow microsphere comprises the following steps: and (2) dispersing 10g of the hollow microspheres A obtained in the step (1) in 1000mL of magnetic metal assembly reaction liquid, wherein the reaction liquid contains 13g/L of nickel sulfate, 14g/L of ferrous sulfate, 14g/L of cobalt sulfate, 40g/L of sodium hypophosphite, 80g/L of potassium sodium tartrate and 40g/L of ammonium sulfate, adjusting the pH to be approximately 10 by using concentrated ammonia water, stirring and reacting at 75 ℃, and filtering and collecting the hollow microspheres 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 non-magnetic conductive hollow microsphere comprises the following steps: and (3) dispersing 10g of the hollow microsphere A in 2000mL of conductive metal assembly reaction liquid which is the same as the step (2), and reacting under the same condition to obtain the non-magnetic conductive hollow microsphere D.
(4) The density of the magnetic conductive hollow microsphere prepared by the method is 0.7g/cm 3 (ii) a The density of the non-magnetic conductive hollow microsphere is 0.5g/cm 3 。
The preparation process of the electromagnetic shielding composite material based on the layered enrichment of the heterogeneous hollow microspheres is carried out according to example 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 the electromagnetic shielding composites of examples 2-9
The test method comprises the following steps:
1. processing the material into a sample with the size of 22.8 × 10.1 × 3mm in the process of testing the electromagnetic shielding effectiveness of the composite material; the S parameter in the 8.2-12.4GHz frequency band is tested by a vector network analyzer through a waveguide method, and the shielding performance is calculated by the measured S parameter through the following formula (A) is the total shielding performance, formula (B) is the reflection shielding performance, and formula (C) is the absorption shielding performance).
3E τ ＝3E R +3E A (A)；
2. Reference national standard test of uniaxial compressive strength: resin cast body property test method (GBT 2567-2008).
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.
Claims (9)
1. The electromagnetic shielding composite material based on the layered enrichment of heterogeneous hollow microspheres is characterized by comprising a polymer matrix, and magnetic conductive hollow microspheres and non-magnetic conductive hollow microspheres which are doped in the polymer matrix;
wherein the polymer matrix has two surfaces which are opposite up and down;
the magnetic conductive hollow microspheres are enriched on one surface of the polymer matrix; and is
The non-magnetic conductive hollow microspheres are enriched on the other surface of the polymer matrix.
2. The electromagnetically shielding composite as claimed in claim 1, wherein said composite has a true density of 0.7 to 1.1g/cm 3 ；
The total volume percentage of the magnetic conductive hollow microspheres and the non-magnetic conductive hollow microspheres in the composite material is 20-40%;
preferably, the volume ratio of the magnetic conductive hollow microspheres to the non-magnetic conductive hollow microspheres is 3:1-1:3, more preferably 1.5-1:1.
3. The electromagnetically shielding composite as claimed in claim 1, wherein said layer formed of magnetically conductive hollow microspheres and said layer formed of non-magnetically conductive hollow microspheres are not in direct contact.
4. The electromagnetically shielding composite as claimed in claim 1, wherein said magnetically conductive hollow microspheres have a density of 0.3 to 1.0g/cm 3 The grain diameter is 5-90 microns;
preferably, 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;
preferably, the thickness of the silicate glass shell layer is 300-1200 nm;
preferably, the thickness of the magnetic metal shell layer is 20-200 nm;
preferably, the thickness of the conductive metal shell layer is 20-400 nm;
preferably, the magnetic metal shell layer is made of one or more of cobalt, nickel, iron and alloys thereof;
preferably, the conductive metal shell layer has a composition selected from one or more of copper, silver and alloys thereof.
5. Electromagnetic shield according to claim 1The composite material is characterized in that the density of the non-magnetic conductive hollow microsphere is 0.3-0.95g/cm 3 The grain diameter is 5-90 microns;
preferably, 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;
preferably, the thickness of the silicate glass layer is 300-1500 nm, and the thickness of the conductive metal layer is 20-400 nm;
preferably, the conductive metal layer has a composition selected from one or more of copper, silver and alloys thereof.
6. The electromagnetically shielding composite material as claimed in claim 1, wherein said polymer matrix is one or more selected from the group consisting of epoxy resin, unsaturated polyester resin, phenol resin, polyurethane resin and polystyrene.
7. The electromagnetically shielding composite as claimed in claim 1, wherein the raw materials for forming said composite further comprise an auxiliary;
the auxiliary agent comprises a curing agent and one or more of an accelerator, a surfactant and a diluent.
8. The method for preparing an electromagnetically shielding composite as claimed in any one of claims 1 to 7, comprising the steps of:
respectively providing magnetic conductive hollow microspheres and non-magnetic conductive hollow microspheres;
mixing and pouring raw materials comprising a polymer matrix, magnetic conductive hollow microspheres and non-magnetic conductive hollow microspheres into a mold coated with a release agent in advance;
fixing a magnet at the bottom of the mold, and carrying out vibration layering treatment on the mold and the materials inside the mold;
and curing and demolding to obtain the electromagnetic shielding composite material.
9. Use of the electromagnetically shielding composite as claimed in any one of claims 1 to 7 in the field of electromagnetic shielding.
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