CN117866366A - High-temperature-resistant wave-absorbing multilayer microsphere material and preparation method and application thereof - Google Patents
High-temperature-resistant wave-absorbing multilayer microsphere material and preparation method and application thereof Download PDFInfo
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- 239000000463 material Substances 0.000 title claims abstract description 54
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- 239000002041 carbon nanotube Substances 0.000 claims abstract description 45
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- 239000004332 silver Substances 0.000 claims abstract description 38
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims abstract description 37
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- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 claims description 13
- PLKATZNSTYDYJW-UHFFFAOYSA-N azane silver Chemical compound N.[Ag] PLKATZNSTYDYJW-UHFFFAOYSA-N 0.000 claims description 13
- 239000008103 glucose Substances 0.000 claims description 13
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 12
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Abstract
The invention provides a high-temperature-resistant wave-absorbing multilayer microsphere material, a preparation method and application thereof, and relates to the technical field of wave-absorbing materials. The high-temperature-resistant wave-absorbing multilayer microsphere material provided by the invention comprises polymethyl methacrylate microspheres, and a silver layer and a carboxyl carbon nano tube layer which are sequentially compounded on the surfaces of the polymethyl methacrylate microspheres from inside to outside, wherein the surfaces of the polymethyl methacrylate microspheres are adhered and grafted together through polydopamine between the silver layer and the carboxyl carbon nano tube layer. According to the invention, polymethyl methacrylate microspheres are used as cores, polydopamine with high hydroxyl activity is used as an adsorbent, silver films and carbon nanotube film layers with excellent conductivity are compounded on the surfaces of the microspheres, the excellent conductivity of the silver films and the carbon nanotube film layers provides conditions for absorbing electromagnetic waves, and the interface polarization effect of the material is enhanced by the multi-layer structural design, so that dielectric loss is improved to an extremely high position; meanwhile, the silver film and the carbon nano tube film layer provide excellent heat resistance for the microsphere.
Description
Technical Field
The invention relates to the technical field of wave-absorbing materials, in particular to a high-temperature-resistant wave-absorbing multilayer microsphere material, and a preparation method and application thereof.
Background
Along with the progress of electronic information technology, various electronic devices are applied to the aspects of life of people, so that on one hand, the life of people is facilitated, and on the other hand, the health of people is affected by electromagnetic pollution generated by the electronic devices. In order to solve the electromagnetic interference problem, high-performance electromagnetic wave absorbing materials have been widely paid attention to and developed. The conventional electromagnetic absorption materials are mainly divided into dielectric materials and magnetic materials, wherein the dielectric materials mainly comprise carbon materials, metal oxides, polymers and the like, and the magnetic materials mainly comprise ferrite, magnetic metals, alloys and the like. The single type of wave-absorbing material cannot achieve perfect impedance matching of electromagnetic wave materials, so that the magnetic material and the dielectric material are compounded to prepare the composite wave-absorbing material, and the composite wave-absorbing material can not only keep the advantages of the single type of material, but also play the synergistic effect of different materials.
However, existing composite wave-absorbing materials still rely on magnetic materials. The addition of the magnetic material can damage the electromagnetic field structure of the equipment, so that the working reliability of the electromagnetic material is affected, a plurality of electronic equipment uses magnetizable metal, the magnetic material added by the wave absorbing material is easy to be adsorbed on the surface of the metal alloy, and especially the microsphere material can be more easily adsorbed on the metal if the magnetic material is added, so that the equipment is damaged. Moreover, wave-absorbing materials are strictly speaking energy converting electromagnetic waves into thermal energy, which makes many intrinsically conductive materials and polymer base materials that are not resistant to high temperatures thermally decompose during use or cannot be applied in high temperature environments.
Disclosure of Invention
In view of the above, the invention aims to provide a high-temperature-resistant wave-absorbing multilayer microsphere material, and a preparation method and application thereof. The high-temperature-resistant wave-absorbing multilayer microsphere material provided by the invention has good thermal stability and wave-absorbing performance, and does not need to rely on magnetic materials.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a high-temperature-resistant wave-absorbing multilayer microsphere material, which comprises polymethyl methacrylate microspheres, and a silver layer and a carboxyl carbon nano tube layer which are sequentially compounded on the surfaces of the polymethyl methacrylate microspheres from inside to outside, wherein the surfaces of the polymethyl methacrylate microspheres are adhered and grafted together through polydopamine between the silver layer and the carboxyl carbon nano tube layer.
Preferably, the polymethyl methacrylate microsphere has a diameter of 8-10 μm.
Preferably, the silver layer in the high-temperature-resistant wave-absorbing multilayer microsphere material has a mass content of 1-58.61%, and the carboxyl carbon nanotube layer has a mass content of 5-10%.
The invention provides a preparation method of the high-temperature-resistant wave-absorbing multilayer microsphere material, which comprises the following steps:
mixing dopamine hydrochloride, tris and water to obtain a dopamine hydrochloride solution;
mixing polymethyl methacrylate microspheres with the dopamine hydrochloride solution to obtain polymethyl methacrylate/polydopamine microspheres;
mixing the polymethyl methacrylate/polydopamine microspheres with a silver ammonia solution and a glucose solution to perform silver mirror reaction to obtain polymethyl methacrylate/polydopamine@Ag microspheres;
mixing the polymethyl methacrylate/polydopamine@Ag microspheres with the dopamine hydrochloride solution to obtain polymethyl methacrylate/polydopamine@ Ag@ polydopamine microspheres;
and mixing the polymethyl methacrylate/polydopamine@ Ag@ polydopamine microsphere with a carboxyl carbon nano tube dispersion liquid to obtain the polymethyl methacrylate/polydopamine@ Ag@ polydopamine/CNT microsphere, namely the high-temperature-resistant wave-absorbing multilayer microsphere material.
Preferably, the mass ratio of the dopamine hydrochloride to the tris (hydroxymethyl) aminomethane to the water is (0.5-1): (0.3-0.6): (120-250), wherein the pH value of the dopamine hydrochloride solution is 7-9.
Preferably, the mass ratio of the polymethyl methacrylate microsphere to the dopamine hydrochloride in the dopamine hydrochloride solution is (0.5-1): (0.5-1); the mixing time of the polymethyl methacrylate microspheres and the dopamine hydrochloride solution is 2-4 h.
Preferably, the silver mirror reaction time is 2-4 hours.
Preferably, the carboxyl carbon nanotube dispersion liquid is prepared by ultrasonically dispersing carboxyl carbon nanotubes in water, and the mass ratio of the carboxyl carbon nanotubes to the water is (0.05-0.1): (100-150).
Preferably, the polymethyl methacrylate/polydopamine @ Ag@ polydopamine microsphere is mixed with the carboxyl carbon nano tube dispersion for 2-4 hours.
The invention provides the application of the high-temperature-resistant wave-absorbing multilayer microsphere material prepared by the technical scheme or the preparation method in the wave-absorbing electromagnetic shielding field.
The invention provides a high-temperature-resistant wave-absorbing multilayer microsphere material, which comprises polymethyl methacrylate microspheres, and a silver layer and a carboxyl carbon nano tube layer which are sequentially compounded on the surfaces of the polymethyl methacrylate microspheres from inside to outside, wherein the surfaces of the polymethyl methacrylate microspheres are adhered and grafted together through polydopamine between the silver layer and the carboxyl carbon nano tube layer. According to the invention, the polymethyl methacrylate microsphere with good adsorption performance is taken as a core, the polydopamine with high hydroxyl activity and environmental protection and no harm is taken as a bio-based adsorbent, the silver film and the carbon nano tube film layer with excellent conductivity are compounded on the surface of the polymethyl methacrylate microsphere, the excellent conductivity of the silver film and the carbon nano tube film layer provides conditions for absorbing electromagnetic waves, and the interface polarization effect of the material is enhanced by the multi-layer structural design, so that the dielectric loss is improved to an extremely high position; meanwhile, the silver film and the carbon nano tube film layer provide excellent heat resistance for the microsphere, so that the multi-layer microsphere has excellent heat stability, and therefore, the material can be well prevented from being decomposed by heat, and the influence of high Wen Dui wave absorbing performance is reduced. The high-temperature-resistant wave-absorbing multilayer microsphere material provided by the invention has good thermal stability and wave-absorbing performance, and does not need to rely on magnetic materials.
Example results show that the high-temperature-resistant wave-absorbing multilayer microsphere material provided by the invention has better thermal stability (T) d5％ =316 ℃), a high dielectric constant (real part of dielectric constant e' =7.5 to 10.34), and good wave-absorbing performance (rl= -14 dB).
Drawings
FIG. 1 is a scanning electron microscope image of PMMA microspheres, PD microspheres prepared in example 1, PDA-200 microspheres and PDADT-200 microspheres prepared in example 5, wherein (a), (b), (c) and (d) in FIG. 1 correspond to PMMA microspheres, PD microspheres, PDA-200 microspheres and PDADT-200 microspheres in sequence;
FIG. 2 is a graph of TG curves of PMMA, PDA-200, PDADT-200 in the examples;
FIG. 3 is a two-dimensional projection of the reflection loss RL of PDADT-200 in example 5.
Detailed Description
The invention provides a high-temperature-resistant wave-absorbing multilayer microsphere material, which comprises polymethyl methacrylate microspheres, and a silver layer and a carboxyl carbon nano tube layer which are sequentially compounded on the surfaces of the polymethyl methacrylate microspheres from inside to outside, wherein the surfaces of the polymethyl methacrylate microspheres are adhered and grafted together through polydopamine between the silver layer and the carboxyl carbon nano tube layer.
In the present invention, the polymethyl methacrylate microsphere (PMMA microsphere) preferably has a diameter of 8 to 10. Mu.m. In the invention, the mass content of the silver layer in the high-temperature-resistant wave-absorbing multilayer microsphere material is preferably 1-58.61%, and the mass content of the carboxyl carbon nano tube layer is preferably 5-10%.
The poly (methyl methacrylate) microsphere is used as a polymer microsphere matrix and poly (dopamine) is used as an adhesive, wherein the poly (methyl methacrylate) microsphere has the advantages of high adsorption capacity, high cohesive force, high surface reaction activity, rich ester groups can react with hydroxyl groups on poly (dopamine), the hydroxyl groups of the poly (dopamine) provide good environment for silver ions and carboxyl carbon nano tube deposition adhesion, and the poly (dopamine) is a biological base material, and is environment-friendly, nontoxic and harmless. Silver is used as a wave-absorbing metal material, and has the excellent characteristics of high conductivity, good ductility, chemical stability and the like; the carbon nano tube has high conductivity, can effectively absorb electromagnetic waves, and is characterized in that electrons of the electromagnetic waves migrate along with the structure of the carbon nano tube to generate conductive loss and propagation loss, a large number of carbon nano tubes form a loss network on the surface of the microsphere, and meanwhile, the dielectric constant of the carbon nano tube is lower than that of silver metal, so that the impedance matching capability of the silver-plated microsphere can be improved, and reflection is reduced.
According to the invention, the polymethyl methacrylate microsphere with good adsorption performance is taken as a core, the polydopamine with high hydroxyl activity and environmental protection and no harm is taken as a bio-based adsorbent, the silver film and the carbon nano tube film layer with excellent conductivity are compounded on the surface of the polymethyl methacrylate microsphere, the excellent conductivity of the silver film and the carbon nano tube film layer provides conditions for absorbing electromagnetic waves, and the interface polarization effect of the material is enhanced by the multi-layer structural design, so that the dielectric loss is improved to an extremely high position; meanwhile, the silver film and the carbon nano tube film layer provide excellent heat resistance for the microsphere, so that the multi-layer microsphere has excellent thermal stability, and the material can be well prevented from being decomposed by heating. Therefore, the high-temperature-resistant wave-absorbing multilayer microsphere material provided by the invention has good thermal stability and wave-absorbing performance, and does not need to rely on magnetic materials. The thermal decomposition temperature T of the high-temperature-resistant wave-absorbing multilayer microsphere material provided by the invention d5％ The real part of the dielectric constant is at most 10.34 at 228-320 ℃, and the reflection loss is-14 dB.
The invention provides a preparation method of the high-temperature-resistant wave-absorbing multilayer microsphere material, which comprises the following steps:
mixing dopamine hydrochloride, tris and water to obtain a dopamine hydrochloride solution;
mixing polymethyl methacrylate microspheres with the dopamine hydrochloride solution to obtain polymethyl methacrylate/polydopamine microspheres;
mixing the polymethyl methacrylate/polydopamine microspheres with a silver ammonia solution and a glucose solution to perform silver mirror reaction to obtain polymethyl methacrylate/polydopamine@Ag microspheres;
mixing the polymethyl methacrylate/polydopamine@Ag microspheres with the dopamine hydrochloride solution to obtain polymethyl methacrylate/polydopamine@ Ag@ polydopamine microspheres;
and mixing the polymethyl methacrylate/polydopamine@ Ag@ polydopamine microsphere with a carboxyl carbon nano tube dispersion liquid to obtain the polymethyl methacrylate/polydopamine@ Ag@ polydopamine/CNT microsphere, namely the high-temperature-resistant wave-absorbing multilayer microsphere material.
In the present invention, unless otherwise specified, all the materials involved are commercially available products well known to those skilled in the art.
According to the invention, dopamine hydrochloride (DA), tris (hydroxymethyl) aminomethane (Tris) and water are mixed to obtain a dopamine hydrochloride solution. In the present invention, the mass ratio of dopamine hydrochloride, tris (hydroxymethyl) aminomethane and water is preferably (0.5 to 1): (0.3-0.6): (120 to 250), more preferably 0.5:0.3:125, the pH value of the dopamine hydrochloride solution is preferably 7-9, more preferably 8.5. In the invention, the trihydroxymethyl aminomethane is used as a buffer agent of dopamine hydrochloride to adjust the pH.
After obtaining the dopamine hydrochloride solution, the invention mixes the polymethyl methacrylate microsphere with the dopamine hydrochloride solution to obtain the polymethyl methacrylate/polydopamine microsphere. In the present invention, the polymethyl methacrylate microsphere is preferably a monodisperse polymethyl methacrylate microsphere having a diameter of 10 μm. In the invention, the mass ratio of the polymethyl methacrylate microsphere to the dopamine hydrochloride in the dopamine hydrochloride solution is preferably (0.5-1): (0.5 to 1), more preferably 1:1.
in the present invention, the time for mixing the polymethyl methacrylate microspheres with the dopamine hydrochloride solution is preferably 2 to 4 hours, more preferably 3 to 4 hours, and the mixing is preferably performed at room temperature under stirring. In the mixing process, dopamine can be polymerized into polydopamine by itself and is attached to the surface of the polymethyl methacrylate microsphere to form a compact polydopamine membranous layer, so that favorable conditions are provided for subsequent implantation of silver particles. After the mixing, the resulting material is preferably washed and dried sequentially, the drying temperature is preferably 60 to 80 ℃, the time is preferably 4 hours, and the drying is performed under normal pressure. After each film layer is covered, the microspheres are washed and dried, so that residual reagents are prevented from affecting subsequent experiments.
After polymethyl methacrylate/polydopamine microspheres are obtained, the polymethyl methacrylate/polydopamine microspheres, a silver ammonia solution and a glucose solution are mixed for silver mirror reaction, and polymethyl methacrylate/polydopamine@Ag microspheres are obtained.
In the present invention, the silver ammonia solution is preferably prepared by the following method: preparing silver nitrate solution, then dropwise adding ammonia water into the silver nitrate solution while stirring, so that the clarified solution becomes turbid first, and then dropwise adding the solution until the clarified solution becomes clear again, thus obtaining the silver ammonia solution. In the invention, the concentration of the silver nitrate solution is preferably 50-200 g/L, and can be specifically 50g/L, 100g/L, 150g/L and 200g/L; the mass ratio of the ammonia water (analytically pure) to the silver nitrate in the silver nitrate solution is preferably (0.3-0.5) to (1-5).
In the present invention, the solvent in the glucose solution is preferably water, the glucose solution is preferably in excess relative to the silver ammonia solution, so that silver ions and polydopamine are well adhered to the microspheres, specifically, the concentration of the glucose solution is preferably 200 to 400g/L, and the mass ratio of glucose in the glucose solution to silver nitrate used for preparing the silver ammonia solution is preferably (5 to 10): (1 to 5). In the invention, the ratio of the mass of the polymethyl methacrylate microsphere to the volume of the silver ammonia solution in the polymethyl methacrylate/polydopamine microsphere is preferably 0.5-1 g:25mL.
In the invention, the method for mixing the polymethyl methacrylate/polydopamine microspheres with the silver ammonia solution and the glucose solution is preferably as follows: and adding the polymethyl methacrylate/polydopamine microspheres into silver ammonia solution, performing ultrasonic treatment for 30min, and then adding glucose solution.
In the present invention, the time for the silver mirror reaction is preferably 2 to 4 hours, and the time for the silver mirror reaction is calculated from the completion of the addition of the glucose solution. In the present invention, the silver mirror reaction is preferably performed under stirring. After the silver mirror reaction is completed, the obtained material is preferably washed and dried sequentially.
The method for preparing the silver film has the defects of high energy consumption, high cost and the like due to various film plating methods such as magnetron sputtering, vacuum evaporation and the like.
After polymethyl methacrylate/polydopamine@Ag microspheres are obtained, the polymethyl methacrylate/polydopamine@Ag microspheres are mixed with the dopamine hydrochloride solution to obtain polymethyl methacrylate/polydopamine@ Ag@ polydopamine microspheres. In the present invention, the method and conditions for mixing the polymethyl methacrylate/polydopamine@ag microspheres with the dopamine hydrochloride solution are the same as those described in the above technical scheme, and are not described herein.
After polymethyl methacrylate/polydopamine @ Ag@ polydopamine microspheres are obtained, the polymethyl methacrylate/polydopamine @ Ag@ polydopamine microspheres are mixed with a carboxyl carbon nanotube dispersion liquid to obtain polymethyl methacrylate/polydopamine @ Ag@ polydopamine/CNT microspheres, namely the high-temperature-resistant wave-absorbing multilayer microsphere material.
In the present invention, the carboxyl carbon nanotube dispersion is preferably prepared by ultrasonically dispersing carboxyl Carbon Nanotubes (CNTs) in water. In the invention, the carboxyl carbon nano tube is provided with carboxyl groups, has good dispersibility, and can well react with the hydroxyl groups of the polydopamine, so that the carboxyl carbon nano tube can be well attached to the microsphere surface. In the present invention, the mass ratio of the carboxyl carbon nanotubes to water is preferably (0.05 to 0.1): (100 to 150), more preferably 0.05:100. in the present invention, the time of the ultrasonic dispersion is preferably 5 to 10 minutes, the power of the ultrasonic dispersion is preferably 800W, and the ultrasonic dispersion is preferably performed using an ultrasonic cleaner. In the present invention, the ultrasonic dispersion is preferably carried out while stirring. After ultrasonic dispersion, the dispersion liquid is preferably placed into an ice bath to be cooled for 3-5 min, and the ice bath can reduce heat energy generated by ultrasonic waves and eliminate bubbles on the surface of the liquid. In the present invention, the ultrasonic dispersing and cooling operations are preferably performed in cycles, and the number of cycles is preferably 3 to 5.
In the invention, the mass ratio of the polymethyl methacrylate microsphere to the carboxyl carbon nanotube in the carboxyl carbon nanotube dispersion liquid in the polymethyl methacrylate/polydopamine @ Ag@ polydopamine microsphere is preferably (0.5-1): (0.05 to 0.1), more preferably 0.5:0.05.
in the present invention, the time for mixing the polymethyl methacrylate/polydopamine Ag@ polydopamine microsphere with the carboxyl carbon nanotube dispersion is preferably 2 to 4 hours, and the mixing is preferably performed under stirring. In the mixing process, the hydroxyl on the polydopamine can be subjected to esterification reaction with the carboxyl on the carbon nano tube, and as the reactivity of the two groups is very strong, no additional catalyst and temperature rise are needed, and meanwhile, the carboxyl carbon nano tube can be well dispersed on the surface of the microsphere to form a final layer of covered film.
The invention provides the application of the high-temperature-resistant wave-absorbing multilayer microsphere material prepared by the technical scheme or the preparation method in the wave-absorbing electromagnetic shielding field. The high-temperature-resistant wave-absorbing multilayer microsphere material provided by the invention has excellent thermal stability and high wave-absorbing characteristic, and has high thermal weightlessness temperature (T) d5％ ) The high dielectric constant and excellent Reflection Loss (RL) have wide application prospect in the field of wave-absorbing electromagnetic shielding. The method of application of the present invention is not particularly limited, and methods well known to those skilled in the art may be employed.
In order to further illustrate the present invention, the following describes the high temperature resistant wave absorbing multilayer microsphere material provided by the present invention in detail, and the preparation method and application thereof, but they should not be construed as limiting the scope of the present invention.
Example 1
Adding 0.5g of dopamine hydrochloride, 0.3g of tris (hydroxymethyl) aminomethane and 125g of ultrapure water into a 250mL beaker, regulating the pH value to be about 8.5, then adding 0.5g of monodisperse polymethyl methacrylate microspheres (PMMA microspheres, purchased from Korea high molecular materials) with the diameter of 10 mu m, rapidly stirring for 4h by using a magnetic stirrer, washing, filtering and drying the microspheres, carefully preserving for later use, and preventing the structure of the microspheres from being damaged by rolling. The obtained microsphere is polymethyl methacrylate/polydopamine microsphere, and is named as PD.
Example 2
1.25g of silver nitrate is added into a 100mL beaker, then a proper amount of ultrapure water is added to prepare 25mL of silver nitrate solution with the concentration of 50g/L, and then ammonia water is added dropwise into the solution under stirring, so that the clarified solution becomes turbid first and then is added dropwise until the clarified solution becomes clear again, and finally the silver-ammonia solution with the corresponding concentration is obtained.
Adding the polymethyl methacrylate/polydopamine microspheres prepared in the embodiment 1 into an ammonia silver solution, carrying out ultrasonic treatment for 30min, adding excessive glucose solution, stirring and reacting for 4h by using a magnetic stirrer until the solution is clear, collecting the microspheres at the bottom after the reaction is finished, washing and drying to obtain the polymethyl methacrylate/polydopamine@Ag microspheres, and naming the microspheres as PDA-50.
And covering a polydopamine membranous layer on the surface of the silver membranous layer in the same way as in the embodiment 1, and utilizing the reaction of hydroxyl groups on polydopamine and carboxyl carbon nanotubes to enable the polydopamine to be better attached to the surface of the microsphere, so as to obtain the polymethyl methacrylate/polydopamine@ Ag@ polydopamine microsphere.
0.05g of a carboxyl carbon nanotube (CNT, XFM06, available from Nanjing Xianfeng nanomaterial technologies Co., ltd.) was added to a beaker containing 100g of ultra pure water, sonicated with an ultrasonic cleaner for 5 minutes while stirring the dispersion with a glass rod, and then cooled in an ice bath for 3 minutes to eliminate bubbles, and circulated 5 times. Then, adding polymethyl methacrylate/polydopamine @ Ag@ polydopamine microspheres into the carboxyl carbon nano tube dispersion liquid, and stirring and reacting for 4 hours to obtain a final product polymethyl methacrylate/polydopamine @ Ag@ polydopamine/CNT microspheres, which is named PDADT-50.
Example 3
The procedure of example 2 was followed, wherein the concentration of 25mL of the silver nitrate solution was 100g/L, and the remainder was the same as in example 2, and the obtained polymethyl methacrylate/polydopamine @ Ag microsphere was designated as PDA-100, and the obtained polymethyl methacrylate/polydopamine @ Ag@ polydopamine/CNT microsphere was designated as PDADT-100.
Example 4
The procedure of example 2 was followed, wherein the concentration of 25mL of the silver nitrate solution was 150g/L, and the remainder was the same as in example 2, and the obtained polymethyl methacrylate/polydopamine @ Ag microsphere was designated as PDA-150, and the obtained polymethyl methacrylate/polydopamine @ Ag@ polydopamine/CNT microsphere was designated as PDADT-150.
Example 5
The procedure of example 2 was followed, wherein the concentration of 25mL of the silver nitrate solution was 200g/L, and the remainder was the same as in example 2, and the obtained polymethyl methacrylate/polydopamine @ Ag microsphere was designated as PDA-200, and the obtained polymethyl methacrylate/polydopamine @ Ag@ polydopamine/CNT microsphere was designated as PDADT-200.
Surface morphology characterization:
FIG. 1 is a scanning electron microscope image of PMMA microspheres, PD microspheres prepared in example 1, PDA-200 microspheres and PDADT-200 microspheres prepared in example 5, and (a), (b), (c) and (d) in FIG. 1 correspond to PMMA microspheres, PD microspheres, PDA-200 microspheres and PDADT-200 microspheres in order.
As can be seen from the scanning electron microscope image in FIG. 1, the PMMA microsphere purchased initially has a diameter of about 10 μm, and has a certain degree of roughness on the surface, which is favorable for adhesion of polydopamine (FIG. 1 (a)). The diameter of the coated microsphere after polydopamine did not change much because polydopamine was more in the form of a solution than attached to the microsphere surface to form a solid film, but this already provides excellent conditions for Ag particle deposition (fig. 1 (b)). After the Ag particles are attached, the microsphere surface becomes extremely rough and exhibits an irregular morphology, but a large number of particles are stacked and bridged to form a film layer (fig. 1 (c)). After the polydopamine is covered by the same method, the polydopamine is grafted with carboxyl carbon nano-tubes by utilizing hydroxyl groups with strong activity of polydopamine, so that the carbon nano-tubes can be well attached to the surfaces of the microspheres (fig. 1 (d)). The microscopic scanning electron microscope can well observe that the preparation of the multi-layer microsphere is very successful, has obvious tendency that the diameter increases with the increase of the film layer, and shows the surface topography characteristics of different coatings.
Characterization of thermal stability:
thermal gravimetric analysis (TG) was performed on PMMA, PDA-200, PDADT-200, and the results are shown in FIG. 2.
As can be seen from FIG. 2, PMMA has poor thermal stability and undergoes decomposition at lower temperatures (T d5％ =228℃). With the coverage of DA (polydopamine)/Ag film, the thermal stability of PDA-200 is improved to a certain extent (T) d5％ =257℃. With the addition of the final DA/CNT, the PDADT-200 has improved thermal stability (T) by utilizing the strong heat insulation performance and the increased film thickness of the CNT material d5％ =316℃). This demonstrates that the Ag film and CNT film layer provide excellent heat resistance to the microspheres. T of microsphere with coating of multilayer film d5％ With the improvement, the multi-layer microsphere has extremely excellent thermal stability, and the thermal decomposition of the material is well avoided.
Reflection loss RL characterization:
PDADT-200 of example 5 was tested for its absorptive capacity RL in the frequency range of 2 to 18GHz, and its absorptive capacity was calculated from the transmission line theory. The results are shown in FIG. 3.
The results show that the material has lower reflection loss than-10 dB in the range of 14-18 GHz when the material accounts for 50% and the mixed thickness of the material and paraffin is 1.5mm and 4.5mm, and the minimum reflection loss can reach RL= -14dB. The multi-layer microsphere PDADT-200 has certain wave-absorbing performance under high frequency and has the advantages of low thickness (the microsphere has excellent wave-absorbing performance when the thickness of the microsphere is increased by 2.51 mu m) due to the dielectric loss, the transmission loss and the strong interface polarization among the multi-layer structure of the carbon nano tube and the Ag, and can be prepared into a hollow mesoporous structure or added into other matrixes in a filler mode, thereby having certain effect in the field of wave-absorbing electromagnetic shielding.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be comprehended within the scope of the present invention.
Claims (10)
1. The high-temperature-resistant wave-absorbing multilayer microsphere material is characterized by comprising polymethyl methacrylate microspheres, and a silver layer and a carboxyl carbon nano tube layer which are sequentially compounded on the surfaces of the polymethyl methacrylate microspheres from inside to outside, wherein the surfaces of the polymethyl methacrylate microspheres are adhered and grafted with the silver layer and the carboxyl carbon nano tube layer through polydopamine.
2. The high temperature resistant wave absorbing multilayer microsphere material according to claim 1, wherein the polymethyl methacrylate microsphere has a diameter of 8-10 μm.
3. The high-temperature-resistant wave-absorbing multilayer microsphere material according to claim 1 or 2, wherein the mass content of the silver layer in the high-temperature-resistant wave-absorbing multilayer microsphere material is 1-58.61%, and the mass content of the carboxyl carbon nano tube layer is 5-10%.
4. A method for preparing the high temperature resistant wave-absorbing multilayer microsphere material according to any one of claims 1 to 3, which is characterized by comprising the following steps:
mixing dopamine hydrochloride, tris and water to obtain a dopamine hydrochloride solution;
mixing polymethyl methacrylate microspheres with the dopamine hydrochloride solution to obtain polymethyl methacrylate/polydopamine microspheres;
mixing the polymethyl methacrylate/polydopamine microspheres with a silver ammonia solution and a glucose solution to perform silver mirror reaction to obtain polymethyl methacrylate/polydopamine@Ag microspheres;
mixing the polymethyl methacrylate/polydopamine@Ag microspheres with the dopamine hydrochloride solution to obtain polymethyl methacrylate/polydopamine@ Ag@ polydopamine microspheres;
and mixing the polymethyl methacrylate/polydopamine@ Ag@ polydopamine microsphere with a carboxyl carbon nano tube dispersion liquid to obtain the polymethyl methacrylate/polydopamine@ Ag@ polydopamine/CNT microsphere, namely the high-temperature-resistant wave-absorbing multilayer microsphere material.
5. The preparation method according to claim 4, wherein the mass ratio of dopamine hydrochloride, tris (hydroxymethyl) aminomethane and water is (0.5-1): (0.3-0.6): (120-250), wherein the pH value of the dopamine hydrochloride solution is 7-9.
6. The preparation method of claim 4, wherein the mass ratio of the polymethyl methacrylate microsphere to the dopamine hydrochloride in the dopamine hydrochloride solution is (0.5-1): (0.5-1); the mixing time of the polymethyl methacrylate microspheres and the dopamine hydrochloride solution is 2-4 h.
7. The method according to claim 4, wherein the silver mirror reaction time is 2 to 4 hours.
8. The method according to claim 4, wherein the carboxyl carbon nanotube dispersion is prepared by ultrasonically dispersing carboxyl carbon nanotubes in water, and the mass ratio of the carboxyl carbon nanotubes to the water is (0.05-0.1): (100-150).
9. The preparation method according to claim 4 or 8, wherein the polymethyl methacrylate/polydopamine Ag@ polydopamine microsphere is mixed with the carboxyl carbon nanotube dispersion for 2-4 h.
10. The application of the high-temperature-resistant wave-absorbing multilayer microsphere material prepared by the preparation method of any one of claims 1 to 3 or any one of claims 4 to 9 in the field of wave-absorbing electromagnetic shielding.
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