CN113956535B - Bead-type one-dimensional heterogeneous nanocomposite, preparation method and application thereof, and polymer-based wave-absorbing composite - Google Patents
Bead-type one-dimensional heterogeneous nanocomposite, preparation method and application thereof, and polymer-based wave-absorbing composite Download PDFInfo
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Abstract
The invention provides a bead-type one-dimensional heterogeneous nanocomposite, a preparation method and application thereof and a polymer-based wave-absorbing composite material, and belongs to the technical field of wave-absorbing materials. MOFs are strung in one-dimensional inorganic insulating nano materials through in-situ synthesis, and a Co-C@ one-dimensional inorganic heterogeneous nano composite material is constructed after high-temperature calcination. The wave absorbing performance of the Co-C@ one-dimensional inorganic heterogeneous nanocomposite can be regulated and controlled within a certain range by regulating the Co-C loading. On the basis, the one-dimensional heterogeneous nano composite material is filled into a polymer to prepare the polymer-based wave-absorbing composite material, and the rigid Co-C@ one-dimensional inorganic heterogeneous nano composite material with large length-diameter ratio is easy to disperse and lap in a polymer matrix to form a three-dimensional network structure, so that the wave-absorbing performance and the comprehensive performance of the composite material are improved.
Description
Technical Field
The invention relates to the technical field of wave-absorbing materials, in particular to a bead-type one-dimensional heterogeneous nano composite material, a preparation method and application thereof and a polymer-based wave-absorbing composite material.
Background
With the rapid development of electronic technology, living electronic equipment affects people's life at any time, and electromagnetic pollution causes damage to electronic communication equipment and also greatly damages to human health. In order to overcome the pollution problem caused by electromagnetic radiation, electromagnetic wave absorbing materials have been developed. The electromagnetic wave absorbing material has high absorption capacity and wide absorption bandwidth, and is favorable for weakening the harm of electromagnetic waves to electronic communication equipment and human health. On the other hand, electromagnetic absorbing materials are also widely used in the military field and have become an important indicator for measuring the military level of a country. Therefore, the development of the wave-absorbing material with excellent performance has important significance in the aspects of military use, civil use and the like.
The traditional wave-absorbing materials comprise graphite, barium titanate, ferrite, silicon carbide and the like, but the application of the traditional wave-absorbing materials is limited due to the defects of narrow absorption frequency band and high density. In recent years, porous carbon nanocomposites prepared from MOFs (metal organic framework compounds, english name Metal organic Framework) have been attracting attention. MOFs material is an organic-inorganic hybrid material formed by self-assembly of metal ions, clusters and organic ligands, and adjacent metal ions are connected through the organic ligands, so that the MOFs material is orderly and orderly in structure and has the characteristics of large specific surface area, high porosity and the like. MOFs precursors can be converted to metal/carbon composites by carbonization at different temperatures. The porous carbon material formed after MOFs calcination converts the insulating MOFs into a conductive material, and magnetic metal or metal oxide cluster nano particles formed in situ in the insulating MOFs can be used for widely adjusting magnetic loss and dielectric loss, so that the repeated reflection loss of electromagnetic waves in an absorber is greatly promoted, and the electromagnetic wave absorption effect is improved. However, the resistivity of the carbon-based material derived from the MOFs is greatly different from that of air, so that impedance mismatch is caused, and the metal particles contained in the carbon-based material derived from the MOFs affect the chemical stability of the carbon-based material derived from the MOFs, so that the application of the carbon-based material derived from the MOFs in the field of electromagnetic wave absorption is limited. In addition, the porous carbon material formed after MOFs calcination is a powdery material similar to a sphere, is not easy to disperse in a matrix such as a polymer, if the filling amount is too small, conductive carbon particles in the porous carbon material cannot be in close contact in a large amount, cannot form a large and wide conductive path, and cannot construct a conductive network, so that a large filling amount (more than 60 wt%) is required for forming the conductive network in the polymer matrix, which not only increases the cost of the material, but also reduces the original mechanical property and processing flow property of the polymer matrix material.
Disclosure of Invention
The invention aims to provide a bead-type one-dimensional heterogeneous nanocomposite, a preparation method and application thereof and a polymer-based wave-absorbing composite material, wherein the bead-type one-dimensional heterogeneous nanocomposite has excellent microwave absorption performance, and the wave-absorbing performance of the polymer-based composite material can be improved at a low filling amount.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a beaded one-dimensional heterogeneous nanocomposite, which comprises a one-dimensional inorganic insulating nanomaterial and Co-C particles penetrating through the one-dimensional inorganic insulating nanomaterial, wherein the Co-C particles are prepared by sintering a metal organic framework ZIF-67, and the Co-C particles and the one-dimensional inorganic insulating nanomaterial form a beaded structure; the one-dimensional inorganic insulating nano material comprises a boron nitride nano tube, a boron nitride whisker or an aluminum oxide nanowire.
Preferably, the diameter of the boron nitride nano tube is 30-50 nm, the length-diameter ratio is 180-300, and the specific surface area is 65-75 m 2 /g, average pore radius of 10.86nm; the mass ratio of the one-dimensional inorganic insulating nano material to the Co-C particles is 1 (1-3).
The invention provides a preparation method of the beaded one-dimensional heterogeneous nanocomposite, which comprises the following steps:
mixing a one-dimensional inorganic insulating nano material, a cobalt source, a surfactant, 2-methylimidazole and an organic solvent, and performing in-situ synthesis to obtain a ZIF-67@one-dimensional inorganic insulating nano composite material; the one-dimensional inorganic insulating nano material comprises a boron nitride nano tube, a boron nitride whisker or an aluminum oxide nanowire;
and sintering the ZIF-67@one-dimensional inorganic insulating nanocomposite material to obtain the beaded one-dimensional heterogeneous nanocomposite material.
Preferably, the cobalt source comprises cobalt nitrate; the mole ratio of the cobalt source to the one-dimensional inorganic insulating nano material is 1 (0.1-1.2).
Preferably, the surfactant comprises polyvinylpyrrolidone, sodium stearyl sulfate, sodium dodecylbenzenesulfonate or sodium dodecylsulfate.
Preferably, the mole ratio of the surfactant to the one-dimensional inorganic insulating nano material is 1 (20-800).
Preferably, the molar ratio of the 2-methylimidazole to the cobalt source is 1 (0.05-0.2).
Preferably, the in-situ synthesis temperature is 25-30 ℃ and the time is 3-8 h; the sintering temperature is 500-900 ℃ and the sintering time is 2-5 h.
The invention provides the application of the bead-type one-dimensional heterogeneous nanocomposite material prepared by the technical scheme or the bead-type one-dimensional heterogeneous nanocomposite material prepared by the preparation method in the microwave absorption field.
The invention provides a polymer-based wave-absorbing composite material, which comprises a blended bead-type one-dimensional heterogeneous nanocomposite material and a polymer matrix material; the bead-type one-dimensional heterogeneous nanocomposite is prepared by the bead-type one-dimensional heterogeneous nanocomposite according to the technical scheme or the preparation method according to the technical scheme.
The invention provides a beaded one-dimensional heterogeneous nanocomposite, which comprises a one-dimensional inorganic insulating nanomaterial and Co-C particles penetrating through the one-dimensional inorganic insulating nanomaterial, wherein the Co-C particles are prepared by sintering a metal organic framework ZIF-67, and the Co-C particles and the one-dimensional inorganic insulating nanomaterial form a beaded structure; the one-dimensional inorganic insulating nano material comprises a boron nitride nano tube, a boron nitride whisker or an aluminum oxide nanowire. According to the invention, MOFs derived carbon-based material particles are strung on the one-dimensional inorganic insulating nano material, disordered Co-C particles are orderly arranged on the one-dimensional inorganic insulating nano material by means of the supporting function of the rigid one-dimensional inorganic insulating nano material to form a stable three-dimensional conductive network, the Co-C particles can be uniformly distributed in the network and are tightly combined with the one-dimensional inorganic insulating nano material so as not to be easy to separate, meanwhile, widely distributed one-dimensional nano materials can be mutually overlapped to form polygonal holes with different sizes but stable, and the polygonal holes not only can support the Co-C particles of the carbon-based material, but also can form complex conductive paths, so that the dielectric loss and the magnetic loss of the composite material are enhanced, and the microwave absorption performance is improved.
According to the invention, an insulated boron nitride nanotube, boron nitride whisker or alumina nanowire is used as a support, co-C particles are strung together to form a Co-C@ one-dimensional heterogeneous nanocomposite, and the Co-C@ one-dimensional heterogeneous nanocomposite with large length-diameter ratio is easy to disperse and lap in a polymer matrix, so that a three-dimensional conductive network is constructed, dielectric loss and magnetic loss of the three-dimensional conductive network are enhanced, and microwave absorption performance is improved; the boron nitride nanotube is an insulating hollow material, has high rigidity, is easy to disperse to form a passage, and can dissipate microwaves for many times in the hollow nanotube to improve the microwave absorption performance.
The invention can regulate the wave absorbing performance of the bead-shaped one-dimensional heterogeneous nanocomposite by regulating and controlling the load capacity of Co-C particles on the one-dimensional nanomaterial to obtain the one-dimensional heterogeneous nanocomposite with the controllable microwave absorbing performance.
The invention provides a preparation method of the beaded one-dimensional heterogeneous nano composite material, which adopts an in-situ synthesis method to load a metal organic framework compound ZIF-67 on a one-dimensional inorganic insulating nano material in situ, ZIF-67 crystals grow on the one-dimensional inorganic insulating nano material in a serial connection mode to form a beaded structure of the ZIF-67@one-dimensional inorganic insulating nano material, and then the organic framework in the ZIF-67 is decomposed into a porous carbon material by sintering, co 2+ Is reduced into Co to form Co-C to be strung on the one-dimensional inorganic insulating nano material to prepare the beaded Co-C@ one-dimensional inorganic insulating nano material heterogeneous nano composite material. The bead-type one-dimensional heterogeneous nano composite material not only endows insulated boron nitride nano tubes, boron nitride whiskers and aluminum oxide nano wires with high conductivity (the high conductivity is endowed by carbon particles and metal cobalt particles, co-C particles are strung on one-dimensional nano materials to form a conductive path), but also generates interface polarization loss and multiple reflection loss due to the special bead-type structure, combines the magnetic loss of magnetic Co particles, the conductivity loss of carbon materials and the dielectric loss of one-dimensional inorganic insulating nano materials, and the multiple energy dissipation form greatly increases the capability of the materials for absorbing microwaves, thus being a brand-new and high-wave-absorbing composite material, and the brand-new composite material has a mutually strung coating structure with large specific surface area (150-430 m 2 And/g), small pore radius (2.1-5.5 nm) and the like, the existence of the holes increases the path of microwave reflection inside the material and improves the wave absorbing performance of the material. Wherein, the one-dimensional inorganic insulating nano material connects a plurality of ZIF-67 particles in series to form a bead-shaped structure, and the one-dimensional inorganic insulating nano material is one-dimensional inorganic insulating nano materialThe good mechanical strength and rigidity of the nano material enable the formed Co-C@ one-dimensional inorganic insulating nano material heterogeneous nano composite material not to be easy to agglomerate, a continuous conductive network is easier to form in a polymer matrix, and the composite material can achieve more excellent microwave absorption performance than a Co-C material under the condition of lower filling quantity. Meanwhile, the high thermal conductivity of the one-dimensional inorganic insulating nano material reduces adverse effects caused by eddy effect heating in the wave absorbing process. The method expands the application of the one-dimensional inorganic insulating nano material, improves the application value of the MOFs and the calcined product Co-C composite material thereof, and provides a new thought for solving electromagnetic pollution.
The one-dimensional heterogeneous nanocomposite prepared by the method is nontoxic and pollution-free, does not generate harmful gas to human bodies in the preparation process, and has the advantages of simple and convenient operation process, short synthesis period, environmental protection, safety and controllable morphology.
The beaded one-dimensional heterogeneous nanocomposite is used in a polymer matrix, the reflection loss of the polymer matrix composite is adjustable within the range of-20 to-70 dB by adjusting the loading capacity of Co-C on the one-dimensional nanocomposite and the addition amount of the one-dimensional heterogeneous nanocomposite in the polymer matrix, the wave absorption is adjustable, the application value is very good, and a new thought is provided for the innovative development of microwave absorbing materials.
The bead-type one-dimensional heterogeneous nanocomposite is used in a polymer matrix, the filling amount of the composite in the polymer matrix can be as low as 10%, the bead-type one-dimensional heterogeneous nanocomposite has a multiple loss mechanism, the conduction loss of a carbon material, the magnetic loss of cobalt particles and the dielectric loss of a one-dimensional nanomaterial form multiple dissipation of microwaves, and meanwhile, a plurality of interface polarizations and microwave losses are generated due to a plurality of interfaces formed by a bead-type structure; and the bead-type structure is used for stringing Co-C particles on the one-dimensional nano material, and a three-dimensional conductive network is formed after the Co-C particles are filled into a polymer matrix, so that the microwave dissipation is greatly enhanced, and the low filling quantity is realized, and the high wave absorbing performance is realized.
Drawings
FIG. 1 is an SEM image of Co-C material prepared in comparative example 1;
FIG. 2 is an SEM image of a ZIF-67@BNT one-dimensional nanocomposite prepared in example 1;
FIG. 3 is an SEM image of a Co-C@BNT one-dimensional heterogeneous nanocomposite prepared in example 1;
FIG. 4 is a graph showing the electromagnetic wave reflection of the Co-C@BNT one-dimensional heterogeneous nanocomposite prepared in example 1 at a matching thickness of 3 mm.
Detailed Description
The invention provides a beaded one-dimensional heterogeneous nanocomposite, which comprises a one-dimensional inorganic insulating nanomaterial and Co-C particles penetrating through the one-dimensional inorganic insulating nanomaterial, wherein the Co-C particles are prepared by sintering a metal organic framework ZIF-67, and the Co-C particles and the one-dimensional inorganic insulating nanomaterial form a beaded structure; the one-dimensional inorganic insulating nano material comprises a boron nitride nano tube, a boron nitride whisker or an aluminum oxide nanowire.
In the present invention, the required raw materials or reagents are commercially available products well known to those skilled in the art unless specified otherwise.
The bead-type one-dimensional heterogeneous nanocomposite provided by the invention comprises a one-dimensional inorganic insulating nanomaterial, wherein the one-dimensional inorganic insulating nanomaterial comprises a boron nitride nanotube (BNT), a Boron Nitride Whisker (BNW) or an aluminum oxide nanowire (ANW).
In the present invention, the diameter of the boron nitride nanotube is preferably 30 to 50nm, the aspect ratio is preferably 180 to 300, and the specific surface area is preferably 65 to 75m 2 The average pore radius is preferably 10.86nm; the diameter of the boron nitride whisker is preferably 100-500 nm, the length-diameter ratio is preferably 10-100, and the specific surface area is preferably 10-15 m 2 /g; the diameter of the alumina nano wire is preferably 2-8 nm, the length-diameter ratio is preferably 200-800, and the specific surface area is preferably 150-160 m 2 /g。
The invention improves the loading rate of MOFs by means of the high specific surface area, ion adsorption capacity and excellent mechanical property of the one-dimensional nano material, and realizes the adjustable and controllable wave absorbing performance of the Co-C@ one-dimensional inorganic heterogeneous nano composite material in a certain range by adjusting the loading capacity of ZIF-67. And the Co-C@ one-dimensional inorganic heterogeneous nano composite material is easy to construct a three-dimensional network structure by supporting the rigid one-dimensional inorganic insulating nano material, so that the stability and the dispersibility of the composite material are improved. The one-dimensional inorganic insulating nano material has the advantages that the insulating property and the high contact area of the one-dimensional inorganic insulating nano material optimize impedance matching, are beneficial to the generation of electronic polarization and interface polarization, and are beneficial to the improvement of dielectric loss and magnetic loss capacity of MOFs particles; the Co-C and the one-dimensional inorganic insulating nano material construct a complex microwave transmission channel, which is beneficial to the energy dissipation of microwaves in the material; the addition of the one-dimensional inorganic insulating nano material effectively improves the heat conductivity and corrosion resistance of the material, effectively reduces the influence of vortex effect, and avoids the structural damage and the reduction of wave absorbing performance caused by the vortex effect.
The bead-type one-dimensional heterogeneous nano composite material provided by the invention comprises Co-C particles which are penetrated and strung on the one-dimensional inorganic insulating nano material; the Co-C particles are prepared by sintering a metal-organic framework ZIF-67, and the Co-C particles and the one-dimensional inorganic insulating nano material form a bead-shaped structure.
In the bead-type one-dimensional heterogeneous nanocomposite, an inorganic insulating one-dimensional nanomaterial, conductive porous carbon and metallic cobalt form a heterostructure.
In the invention, the metal-organic framework ZIF-67 has regular dodecahedron microcosmic morphology, and the surface of the Co-C material formed by high-temperature sintering has rich protrusions, contains magnetic metal Co in the interior and is microporous.
The process of preparing Co-C particles from the metal-organic framework ZIF-67 by sintering is not particularly limited in the present invention, and may be carried out according to the processes well known in the art.
In the present invention, the mass ratio of the one-dimensional inorganic insulating nanomaterial to the co—c particles is preferably 1 (1 to 3), more preferably 1: (1.3-2.6).
In the present invention, the Co-C particles preferably have a specific surface area of 100 to 300m 2 /g, more preferably 200m 2 The pore radius is preferably 3 to 4nm, more preferably 3.76nm, the conductivity is preferably 4 to 9S/cm, more preferably 8S/cm.
The invention provides a preparation method of the beaded one-dimensional heterogeneous nanocomposite, which comprises the following steps:
mixing a one-dimensional inorganic insulating nano material, a cobalt source, a surfactant, 2-methylimidazole and an organic solvent, and performing in-situ synthesis to obtain a ZIF-67@one-dimensional inorganic insulating nano composite material; the one-dimensional inorganic insulating nano material comprises a boron nitride nano tube, a boron nitride whisker or an aluminum oxide nanowire;
and sintering the ZIF-67@one-dimensional inorganic insulating nanocomposite material to obtain the beaded one-dimensional heterogeneous nanocomposite material.
The invention mixes one-dimensional inorganic insulating nano material, cobalt source, surfactant, 2-methylimidazole and organic solvent, and carries out in-situ synthesis to obtain ZIF-67@one-dimensional inorganic insulating nano composite material. In the present invention, the cobalt source preferably comprises cobalt nitrate, more preferably cobalt nitrate hexahydrate; the molar ratio of the cobalt source to the one-dimensional inorganic insulating nanomaterial is preferably 1 (0.1 to 1.2), more preferably 1 (0.2 to 1), and even more preferably 1 (0.875 to 1).
In the present invention, the surfactant preferably includes polyvinylpyrrolidone, sodium octadecyl sulfate, sodium dodecylbenzene sulfonate or sodium dodecyl sulfate, and the molar ratio of the surfactant to the one-dimensional inorganic insulating nanomaterial is preferably 1 (20 to 800), more preferably 1 (32 to 700), and still more preferably 1 (140 to 500). According to the invention, the combination of cobalt ions and the one-dimensional nano material is promoted by using the surfactant, so that the cobalt ions are wrapped on the one-dimensional nano material, and ZIF-67 crystals grow in situ.
In the present invention, the molar ratio of the 2-methylimidazole to the cobalt source is preferably 1 (0.05 to 0.2), more preferably 1:0.1.
In the present invention, the organic solvent is preferably anhydrous methanol; the invention has no special limit to the dosage of the organic solvent, and can ensure that the materials are fully mixed and the reaction is smoothly carried out.
In the invention, the mixing process of the one-dimensional inorganic insulating nano material, the cobalt source, the surfactant, the 2-methylimidazole and the organic solvent is preferably as follows: dispersing one-dimensional inorganic insulating nano material in a first part of organic solvent, dissolving surfactant in a second part of organic solvent, and uniformly mixing and stirring the obtained surfactant solution and the one-dimensional inorganic insulating nano material dispersion liquid to obtain a first solution; dissolving a cobalt source in a third part of organic solvent, and adding the obtained cobalt source solution into the first solution after uniform oscillation to obtain a second solution; dissolving 2-methylimidazole in the residual organic solvent, dropwise adding the obtained 2-methylimidazole solution into the second solution, and uniformly stirring to obtain a mixed material. The stirring speed is not particularly limited, and the materials can be uniformly mixed.
In the present invention, the concentration of the cobalt source solution is preferably 30 to 85mmol/L, more preferably 40mmol/L; the concentration of the 2-methylimidazole solution is preferably 700 to 900mmol/L, more preferably 800mmol/L.
In the invention, the in-situ synthesis temperature is 25-30 ℃, more preferably 28 ℃, and the time is preferably 3-8 h, more preferably 6h; the in-situ synthesis is preferably carried out under stirring conditions and standing conditions in sequence, the time ranges of the stirring conditions and the standing conditions are not particularly limited, and the in-situ synthesis is adjusted according to actual requirements, so that the total synthesis time is satisfied.
After the in-situ synthesis is completed, the obtained product is preferably subjected to centrifugal separation, drying and grinding in sequence to obtain the ZIF-67@one-dimensional inorganic insulating nanocomposite. In the present invention, the drying means is preferably vacuum drying, and the drying temperature is preferably 60 ℃. The process of centrifugal separation and grinding is not particularly limited in the present invention, and may be performed according to a process well known in the art.
After the ZIF-67@one-dimensional inorganic insulating nanocomposite is obtained, the ZIF-67@one-dimensional inorganic insulating nanocomposite is sintered to obtain the bead-type one-dimensional heterogeneous nanocomposite. The sintering is preferably carried out in a muffle furnace; the sintering temperature is preferably 500-900 ℃, more preferably 600-800 ℃; the time is preferably 2 to 5 hours, more preferably 3 hours. The invention controls the structure and the composition of the product through the sintering temperature and the shielding gas, so that the product has good electromagnetic wave absorption effect.
Compared with the prior art, the invention has the following advantages:
(1) According to the invention, co-C particles are strung on the one-dimensional inorganic insulating nano material, and the three-dimensional conductive network is easily constructed in the polymer matrix by the larger length-diameter ratio of the one-dimensional inorganic insulating nano material, so that low filling and high absorption can be realized, and the defects that the Co-C particles are filled in the polymer matrix, have small particle size, are easy to agglomerate, are difficult to form a conductive path in the polymer matrix, and can form a conductive network by the Co-C particles only by a large filling amount, so that the composite material has poor wave absorbing performance are overcome.
(2) Improving impedance matching and enhancing microwave absorption: co-C has good conductivity and magnetic conductivity, so that conductivity loss and magnetic loss can be generated, but when the resistivity of Co-C is too much different from that of air, electromagnetic waves are reflected when the electromagnetic waves are injected into the surface of a material, and the material with high conductivity enables the electromagnetic waves to be reflected on the surface of the material in a large amount and not enter the interior of the material effectively, so that impedance mismatch is caused, and the wave absorbing performance is limited. The invention combines the insulated one-dimensional inorganic nano material with Co-C with higher conductivity, reduces the difference value between the insulating one-dimensional inorganic nano material and air resistivity, optimizes impedance matching and enhances the absorption of the composite material to electromagnetic waves. The Co-C@ one-dimensional inorganic insulating nanocomposite integrates the conductivity loss, the dielectric loss and the magnetic loss, and combines the impedance matching, so that the Co-C@ one-dimensional inorganic insulating nanocomposite has excellent wave absorbing performance. In addition, co-C particles are small, have high structural performance and multiple gaps, can form multiple reflection points for electromagnetic waves, and consume energy due to multiple scattering of the electromagnetic waves, so that the purpose of absorbing the electromagnetic waves is achieved.
(3) Co-C is strung on one-dimensional inorganic insulating nano material, and forms a local conductive network in the material, and at the same time, the heat conductivity of the material is effectively improved (the maximum heat conductivity coefficient can reach 1.42 W.m -1 ·K -1 Under the same filler ratio, the thermal conductivity coefficient of the pure boron nitride filling system is 1.13 W.m -1 ·K -1 ) Because the lap joint also forms a heat conduction network, the one-dimensional inorganic insulating nano material adopted by the inventionThe materials have very high large heat coefficient (20-300 W.m -1 ·K -1 ) Therefore, heat caused by energy loss generated by electromagnetic wave absorption can be effectively emitted, and the safety and stability of the material are improved.
The invention provides the application of the bead-string type one-dimensional heterogeneous nanocomposite material prepared by the technical scheme or the preparation method in the microwave absorption field. The method of application of the present invention is not particularly limited, and may be applied according to methods well known in the art.
The invention provides a polymer-based wave-absorbing composite material, which comprises a blended bead-type one-dimensional heterogeneous nanocomposite material and a polymer matrix material; the bead-type one-dimensional heterogeneous nanocomposite is prepared by the bead-type one-dimensional heterogeneous nanocomposite according to the technical scheme or the preparation method according to the technical scheme. In the present invention, the polymer matrix material preferably includes Thermoplastic Polyurethane (TPU), polyvinyl butyral (PVB), or polyvinylidene fluoride (PVDF); the mass ratio of the bead-type one-dimensional heterogeneous nanocomposite to the polymer matrix material is preferably 1: (1 to 9), more preferably 1: (2-4).
In the present invention, the preparation method of the polymer-based wave-absorbing composite material preferably includes the steps of: mixing the beaded one-dimensional heterogeneous nano composite material with polymer material dispersion liquid, and carrying out tape casting on the obtained mixture to form a film so as to obtain the polymer matrix composite material.
In the present invention, the solvent used for the dispersion of the polymer material is preferably N, N-Dimethylformamide (DMF). The concentration of the polymer material dispersion liquid is not particularly limited, and the polymer material and the bead-type one-dimensional heterogeneous nanocomposite can be fully mixed.
In the invention, the mixing process of the bead-type one-dimensional heterogeneous nanocomposite and the polymer material dispersion liquid is preferably performed under the stirring condition, and the stirring speed is not particularly limited, so that the materials can be fully mixed.
In the present invention, the film formation is preferably performed on a substrate, and the present invention preferably forms a film by casting on a substrate, which is preferably a glass plate or a stainless steel plate; the specific type and source of the substrate are not particularly limited, and commercially available products known in the art may be used.
The process of casting the film and the thickness of the resulting film are not particularly limited in the present invention, and the film may be formed according to a process well known in the art and the film thickness may be determined according to the amount of the material.
The technical solutions of the present invention will be clearly and completely described in the following in connection with the embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the following examples, boron nitride nanotubes (BNT) having a diameter of 30 to 50nm, an aspect ratio of 180 to 300 and a specific surface area of 65 to 75m were used 2 /g, average pore radius of 10.86nm; the diameter of the Boron Nitride Whisker (BNW) is 100-500 nm, the length-diameter ratio is 10-100, and the specific surface area is 10-15 m 2 /g; the diameter of the Alumina Nano Wire (ANW) is 2-8 nm, the length-diameter ratio is 200-800, and the specific surface area is 150-160 m 2 /g。
Example 1
Dispersing 0.7mmol of boron nitride nanotubes in 60mL of absolute methanol, dispersing 0.005mmol of polyvinylpyrrolidone in 60mL of absolute methanol, and mixing the two obtained dispersions to obtain a first solution; dissolving 0.8mmol of cobalt nitrate hexahydrate in 20mL of absolute methanol, uniformly stirring, and adding the solution into the first solution to obtain a second solution; 8mmol of 2-methylimidazole is added into 10mL of absolute methanol, the mixture is rapidly stirred and gradually added into the second solution to obtain a third solution, the third solution is stirred for 3 hours, the mixture is stood and aged for 3 hours at 28 ℃, in-situ synthesis is carried out, after the obtained product is centrifuged, the obtained purple precipitate is dried in a 60 ℃ oven in vacuum, and is ground to powder, the obtained ZIF-67@BNT one-dimensional nano composite material is placed into a muffle furnace and sintered for 3 hours at 800 ℃, and the Co-C@BNT one-dimensional heterogeneous nano composite material is obtained, wherein the mass ratio of the one-dimensional inorganic insulating nano material to Co-C particles is 1:2.6.
Example 2
The only difference from example 1 is that: 0.005mmol of polyvinylpyrrolidone is replaced by 0.001mmol of polyvinylpyrrolidone to obtain the Co-C@BNT heterogeneous nanocomposite, and the mass ratio of the one-dimensional inorganic insulating nanomaterial to the Co-C particles is 1:1.3 otherwise.
Example 3
The only difference from example 1 is that: sintering for 3 hours at 600 ℃ to obtain the Co-C@BNT one-dimensional nanocomposite.
Example 4
The only difference from example 1 is that: and replacing 0.7mmol of boron nitride nanotube with 0.16mmol of alumina nanowire to obtain the Co-C@ANW one-dimensional heterogeneous nanocomposite, wherein the mass ratio of the one-dimensional inorganic insulating nanomaterial to the Co-C particles is 1:2.6.
Comparative example 1
Dissolving 0.8mmol of cobalt nitrate hexahydrate in 140mL of absolute methanol, and uniformly stirring to obtain solution A; 8mmol of 2-methylimidazole is placed in 10mL of absolute methanol, and the solution A is rapidly stirred and gradually dripped into the solution A to obtain solution B; stirring the solution B for 3 hours, standing and aging for 3 hours, centrifuging, vacuum drying the obtained precipitate in a 60 ℃ oven, grinding to powder, and sintering in a muffle furnace at 800 ℃ for 3 hours to obtain the Co-C material.
In the following application examples, the filler ratio is the mass ratio of the one-dimensional heterogeneous nanocomposite to the polymer matrix.
Application example 1
The Co-C@BNT one-dimensional heterogeneous nanocomposite prepared in example 1 was added to the TPU matrix in a filler ratio of 1:2: dissolving TPU with DMF to make the concentration of TPU be 91mmol/L, adding the Co-C@BNT one-dimensional heterogeneous nanocomposite prepared in example 1, stirring uniformly, pouring into a casting die for molding, and drying to form a film.
Application example 2
The Co-C@BNT heterogeneous nanocomposite prepared in example 2 was added to a PVDF matrix at a filler ratio of 1:2, and a composite material was prepared in accordance with the method of application example 1.
Application example 3
The Co-C@BNT one-dimensional nanocomposite prepared in example 3 was added to a TPU matrix at a filler ratio of 1:2, and a composite was prepared in accordance with the method of application example 1.
Application example 4
The Co-C@BNT heterogeneous nanocomposite prepared in example 1 was added to a TPU matrix at a filler ratio of 1:1, and a composite was prepared in accordance with the method of application example 1.
Application example 5
The Co-C@ANW one-dimensional heterogeneous nanocomposite prepared in example 4 was added to a PVB matrix at a filler ratio of 1:2, and a composite was prepared in accordance with the method of application example 1.
Application example 6
The Co/C@BNT one-dimensional heterogeneous nanomaterial prepared in example 1 is added into a TPU matrix at a filler ratio of 1:9, and a composite material is prepared according to the method of application example 1.
Comparative application example 1
The Co-C material prepared in comparative example 1 was added to the TPU matrix at a filler ratio of 1:2, and a polymer matrix composite was prepared in the same manner as in application example 1.
Comparative application example 2
The polymer matrix composite was prepared by adding boron nitride nanotubes to the TPU matrix at a filler ratio of 1:2, according to the method of application example 1.
Comparative application example 3
Comparative application 3 was made with a pure TPU matrix.
Characterization and performance testing
1) SEM test of the Co-C material prepared in comparative example 1, and the results are shown in FIG. 1; as can be seen from FIG. 1, co-C is a spheroidal and readily agglomerated powder material. The structure of the Co-C material prepared in comparative example 1 was tested by BET method, and the result showed that the specific surface area of the Co-C material was 200m 2 /g, average pore radius of 3.76nm; and refers to a four-probe method in the determination method of the powder conductivity in GBT 30835-2014 carbon composite lithium iron phosphate cathode Material for lithium ion batteriesConductivity was measured, indicating that the conductivity of the Co-C material prepared in comparative example 1 was 8S/cm.
2) SEM test is carried out on the ZIF-67@BNT one-dimensional nanocomposite prepared in example 1, and the obtained result is shown in FIG. 2; as can be seen from FIG. 2, ZIF-67 is strung on boron nitride nanotubes.
3) SEM test is carried out on the Co-C@BNT one-dimensional heterogeneous nanocomposite prepared in example 1, and the obtained result is shown in FIG. 3; as can be seen from FIG. 3, co-C formed by decomposition of ZIF-67 after carbonization was still strung on the boron nitride nanotubes, indicating successful preparation of beaded composites.
4) BET test and conductivity test were performed on the Co-C@BNT nanotubes prepared in example 1, and the results showed that the specific surface area thereof was 150 to 200m 2 And/g, average pore radius of 3nm, conductivity of 4S/cm.
5) FIG. 4 is a graph showing the microwave reflection of the Co-C@BNT one-dimensional heterogeneous nanocomposite prepared in example 1 at a thickness of 3 mm; as can be seen from fig. 4, when the matching thickness is 3mm, the maximum wave absorbing effect is rl= -54.2dB in the frequency range of 8-12.4 GHz.
6) Performing performance tests on the materials of application examples 1-6 and comparative application examples 1-3, testing the wave absorbing performance according to a method for measuring the shielding effectiveness of the military standard SJ 20524-1995 material, and placing a sample in two conductors for testing by using an ASTM-ES-7 coaxial transmission line (far field) method; the heat conductivity coefficient is measured according to a flash method described in GB/T22588-2008, and the flash light source is a laser pulse.
Table 1 performance data of materials of application examples 1 to 6 and comparative application examples 1 to 3
As can be seen from table 1, at low filler ratios (bead Co-c@bnnt filler: polymer=1:2), the microwave absorption properties of the polymer matrix composite are greatly improved, and the maximum wave absorption is achievedSexual effect R L -54.2dB; and under the condition of lower filler ratio (bead type Co-C@BNT filler: polymer=1:9), the maximum wave-absorbing effect RL= -15.4dB, can meet the commercial application requirements (general R L <-10 dB), and meanwhile, the polymer matrix composite material prepared by the invention has excellent thermal conductivity, and overcomes the defect of poor heat dissipation of the common wave-absorbing material.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (9)
1. The bead-type one-dimensional heterogeneous nanocomposite comprises a one-dimensional inorganic insulating nanomaterial and Co-C particles penetrating through the one-dimensional inorganic insulating nanomaterial, wherein the Co-C particles are prepared by sintering a metal organic framework ZIF-67, and the Co-C particles and the one-dimensional inorganic insulating nanomaterial form a bead-type structure; the one-dimensional inorganic insulating nano material comprises a boron nitride nano tube, a boron nitride whisker or an aluminum oxide nanowire;
the preparation method of the bead-string type one-dimensional heterogeneous nanocomposite comprises the following steps:
mixing a one-dimensional inorganic insulating nano material, a cobalt source, a surfactant, 2-methylimidazole and an organic solvent, and performing in-situ synthesis to obtain a ZIF-67@one-dimensional inorganic insulating nano composite material; the one-dimensional inorganic insulating nano material comprises a boron nitride nano tube, a boron nitride whisker or an aluminum oxide nanowire;
sintering the ZIF-67@one-dimensional inorganic insulating nanocomposite material to obtain a bead-type one-dimensional heterogeneous nanocomposite material;
the sintering temperature is 500-900 ℃;
the diameter of the boron nitride nano tube is 30-50 nm, the length-diameter ratio is 180-300, and the specific surface area is 65-75 m 2 /g, average pore radius of 10.86nm; the mass ratio of the one-dimensional inorganic insulating nano material to the Co-C particles is 1 (1-3);
the diameter of the boron nitride whisker is 100-500 nm, the length-diameter ratio is 10-100, and the specific surface area is 10-15 m 2 /g; the diameter of the alumina nano wire is 2-8 nm, the length-diameter ratio is 200-800, and the specific surface area is 150-160 m 2 /g。
2. The method for preparing the beaded one-dimensional heterogeneous nanocomposite material according to claim 1, comprising the following steps:
mixing a one-dimensional inorganic insulating nano material, a cobalt source, a surfactant, 2-methylimidazole and an organic solvent, and performing in-situ synthesis to obtain a ZIF-67@one-dimensional inorganic insulating nano composite material; the one-dimensional inorganic insulating nano material comprises a boron nitride nano tube, a boron nitride whisker or an aluminum oxide nanowire;
sintering the ZIF-67@one-dimensional inorganic insulating nanocomposite material to obtain a bead-type one-dimensional heterogeneous nanocomposite material;
the sintering temperature is 500-900 ℃.
3. The method of preparing according to claim 2, wherein the cobalt source comprises cobalt nitrate; the mole ratio of the cobalt source to the one-dimensional inorganic insulating nano material is 1 (0.1-1.2).
4. The method of preparation according to claim 2, wherein the surfactant comprises polyvinylpyrrolidone, sodium stearyl sulfate, sodium dodecylbenzenesulfonate or sodium dodecylsulfate.
5. The preparation method according to claim 4, wherein the molar ratio of the surfactant to the one-dimensional inorganic insulating nanomaterial is 1 (20-800).
6. The method according to claim 2 or 3, wherein the molar ratio of the 2-methylimidazole to the cobalt source is 1 (0.05 to 0.2).
7. The method according to claim 2, wherein the in situ synthesis is carried out at a temperature of 25-30 ℃ for a period of 3-8 hours; the sintering time is 2-5 h.
8. The application of the beaded one-dimensional heterogeneous nanocomposite material prepared by the beaded one-dimensional heterogeneous nanocomposite material of claim 1 or the preparation method of any one of claims 2 to 7 in the field of microwave absorption.
9. A polymer-based wave-absorbing composite material comprises a blended bead-type one-dimensional heterogeneous nanocomposite material and a polymer matrix material; the bead-type one-dimensional heterogeneous nanocomposite is prepared by the bead-type one-dimensional heterogeneous nanocomposite of claim 1 or the preparation method of any one of claims 2 to 7.
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