Ln < 3 + >-induced multi-phase oxide modified CNT / cyanate composite wave-absorbing material and method

Abstract

The invention discloses an Ln < 3 + >-induced multi-phase oxide modified CNT / cyanate composite wave-absorbing material and a preparation method thereof.The Ln < 3 + >-induced multi-phase oxide modified CNT / cyanate composite wave-absorbing material is characterized in that a carbon oxide nanotube is used as a carrier, and multi-phase oxide nanoparticles with inverse spinel phase ferrite / perovskite phase orthoferrite / amorphous phase are uniformly modified through thermal decomposition of Ln < 3 + >, Fe < 3 + > and divalent transition metal salt in a specific proportion; and finally, mixing a cyanate monomer, and carrying out hot-pressing curing molding to obtain the multi-phase oxide modified carbon nanotube / cyanate resin composite wave-absorbing material. The composite wave-absorbing material combines conduction loss, magnetic loss, dipole polarization loss of lattice oxygen vacancies and polarization loss of rich heterogeneous interfaces, shows excellent wave-absorbing characteristics, and has high-temperature environment applicability and high base material adhesion due to the cyanate ester resin matrix.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave absorbing materials and particularly relates to a Ln 3+ A doping-induced multiphase oxide-modified CNT (carbon nanotube) / cyanate resin composite absorbing material and a preparation method thereof. Background Art

[0002] With the rapid development of microwave communication and radar detection technology, microwave absorbing materials play a vital role in the electromagnetic interference shielding of electronic equipment and the radar stealth of military equipment. Traditional single-component microwave absorbing materials often cannot meet the requirements of strong absorption and wide absorption band due to their poor impedance matching characteristics and weak microwave attenuation ability. Among the many developed composite microwave absorbing materials, carbon nanotube / ferrite composites are considered to have great application potential due to their tunable electromagnetic properties, high stability and low cost. However, these carbon nanotube / ferrite materials mainly rely on conduction loss and magnetic loss, and the role of polarization loss is weak, resulting in the effective absorption bandwidth often being less than 5GHz. If the dipole polarization and interface polarization losses of carbon nanotube / ferrite composites can be further optimized, wider absorption bandwidth and lower reflection loss can be achieved. Heteroatom doping strategies, especially lanthanide elements Ln with larger size and special electronic configuration 3+ , which can usually induce lattice deformation, introduce many defect centers, and promote the formation of electric dipoles. In addition, excessive doping can also derive heterogeneous grain boundaries, thereby accelerating charge accumulation and facilitating the formation of interface polarization. Therefore, on the basis of existing carbon nanotube / ferrite composite materials combined with Ln 3+ Doping engineering optimizes the crystal structure and phase composition of ferrite to obtain a wider electromagnetic response space.

[0003] The substrate material also affects the actual working performance of the absorbing coating. Traditional organic polymer carriers, such as polyurethane, synthetic rubber and polyvinyl chloride, do not have good heat resistance, decompose or deform at high temperatures, and are generally not suitable for the actual working environment of absorbing materials. The excellent heat resistance, substrate adhesion, low dielectric constant and low moisture absorption rate of thermosetting cyanate resin make it one of the competitive choices for microwave absorbing substrate materials in the aviation, aerospace and electronics industries. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a Ln 3+ The invention discloses a doping-induced multiphase oxide-modified carbon nanotube / cyanate composite wave-absorbing material and a preparation method thereof, which improves the impedance matching and polarization loss mechanism of the carbon nanotube composite material and obtains a better wave-absorbing effect.

[0005] Another object of the present invention is to solve the technical problem of the difficulty in dispersing carbon nanotube / metal oxide composite absorbing fillers in thermosetting resins, and to provide a method for well dispersing the above-mentioned absorbing fillers in a cyanate ester resin matrix, thereby obtaining an absorbing coating material with excellent environmental stability and substrate adhesion.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A Ln 3+ The preparation method of the composite absorber material of carbon nanotube / cyanate resin modified by induced heterogeneous oxide comprises: impregnating the oxidized carbon nanotube with Ln 3+ , Fe 3+ and divalent transition metal ions in a solution, and the defects of carbon nanotubes were modified by thermal decomposition to form multiphase oxide nanoparticles with inverse spinel ferrite / perovskite orthoferrite / amorphous phases. 3+ It plays a role in regulating the crystal form, defects and interfaces of the oxide. Finally, the cyanate monomer is mixed with the polar solvent for auxiliary dispersion and then cured by step-by-step heating and hot pressing to obtain a multiphase oxide-modified carbon nanotube / cyanate resin composite absorbing material.

[0008] The preparation method comprises the following steps:

[0009] Step 1: Ln 3+ Preparation of induced heterogeneous oxide-modified carbon nanotubes:

[0010] Oxidized carbon nanotubes were added to an organic solvent, and then Ln 3+ , Fe 3+ and other transition metal ions (M 2+ ) salt. The mixture was dispersed by ultrasound and then transferred to an oven for drying to remove the solvent, and then transferred to a tube furnace and calcined under an inert gas atmosphere to obtain Ln 3+ Induced heterogeneous oxide modified carbon nanotubes (CNT@MLn x Fe 2-x O4);

[0011] Step 2: Ln 3+ Preparation of induced heterogeneous oxide-modified carbon nanotube / cyanate ester composites:

[0012] The CNT@MLn prepared in step 1 x Fe 2-x O4 was added to a polar organic solvent and ultrasonically dispersed in a water bath at room temperature. Then, a cyanate resin monomer was subsequently added to the above dispersion and stirred vigorously. The mixed solution was vacuum dried at 80°C to remove the solvent. The paste mixture was then poured into a preheated mold and Ln was obtained through a step-by-step temperature curing process.3+ Induced heterogeneous oxide modified carbon nanotube / cyanate composites.

[0013] In the preparation method, the oxygen content of the oxidized carbon nanotubes used in step 1 is optimally 3-6 at.%, the oxygen-containing groups can provide attachment sites for metal ions, and the defects generated after calcination provide dipole polarization in the wave absorption effect without significantly affecting its conduction loss.

[0014] The preparation method, in step 1, Ln 3+ is a combination of one or more, the transition metal ion is Fe 2+ ,Co 2+ , Ni 2+ , Zn 2+ , Mn 2+ , Cu 2+ The metal salt is a nitrate, phosphate or acetate which can be thermally decomposed into a metal oxide.

[0015] The preparation method, in step 1, M 2+ , Ln 3+ and Fe 3+ The molar ratio of metal salt is 1:0.1-0.4:1.6-1.9, and their ratio determines the type, ratio and distribution of the crystal phase in the metal oxide particles modified on the carbon nanotubes. x Fe 2-x The mass ratio of O4 multiphase oxides is calculated to be 1:1~4.

[0016] In the preparation method, in step 1, the dispersed mixture is transferred to an oven, heated at a temperature slightly higher than the boiling point of the solvent until the mixture becomes a paste, and then heated at a temperature slightly lower than the boiling point of the solvent for several hours to completely remove the solvent and crystal water. After being transferred to a tube furnace, the temperature is raised from room temperature to 400-900° C., maintained for 2 hours, and then naturally cooled to room temperature, and then the product is ground.

[0017] In the preparation method, in step 2, the organic solvent is one or more of tetrahydrofuran, N,N-dimethylformamide or acetone, which assists in fully dispersing the oxide-modified carbon nanotubes in the resin monomer and is easy to remove.

[0018] In the preparation method, in step 2, the resin monomer is one or more of bisphenol E cyanate monomer, bisphenol F cyanate monomer or epichlorohydrin, and the mass ratio of the heterogeneous oxide-modified carbon nanotubes to the resin monomer is 10% to 40%: 60% to 90%.

[0019] In the preparation method, in step 2, the pressure applied by the hot press is 2Mpa-50Mpa. The curing reaction is carried out under step-by-step temperature increase, with the first stage curing temperature being 60-100°C and the time being 1-5h; the second stage curing temperature being 80-150°C and the time being 1-5h; the third stage curing temperature being 150-190°C and the time being 1-5h; and the fourth stage curing temperature being 190-230°C and the time being 1-5h.

[0020] The second technical solution of the present invention is to provide a Ln 3+ The induced multiphase oxide modified carbon nanotube / cyanate resin composite wave absorbing material is prepared by the preparation method as described above. The oxidized carbon nanotube is used as a carrier, and multiphase oxide particles having inverse spinel phase ferrite / perovskite phase rare earth orthoferrite / amorphous phase are modified at the defects by impregnation of precursors and calcination and pyrolysis, and finally mixed with cyanate resin monomers and cured by step-by-step temperature increase and hot pressing to obtain a multiphase oxide modified carbon nanotube / heat-resistant resin composite wave absorbing material.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. Ln provided by the present invention 3+ Induced multiphase oxide modified carbon nanotube cyanate resin composite absorber material, multiphase oxide nanoparticles with inverse spinel phase ferrite / perovskite phase rare earth orthoferrite / amorphous phase are loaded on the defects of oxidized carbon nanotubes, which are prepared by impregnation and pyrolysis of Ln 3+ , Fe 3+ and divalent transition metal ions (M 2+ ) salt. Carbon nanotubes and ferrites provide efficient conduction loss and magnetic loss, respectively. Ln 3+ Doping induces lattice deformation, introduces many defect centers, and promotes the formation of electric dipoles. Excessive doping can also derive heterogeneous grain boundaries, and the formed carbon nanotube phase / spinel phase / perovskite phase / amorphous phase has abundant heterogeneous interfaces, which accelerates charge accumulation and is conducive to the formation of interface polarization. Therefore, Ln 3+ The induced heterogeneous oxide modified carbon nanotube / cyanate ester resin composite absorber shows better performance than that without Ln 3+ The samples have a wider electromagnetic response range.

[0023] 2. Ln provided by the present invention 3+ Induced heterogeneous oxide modified carbon nanotube / cyanate composite absorber, filler Ln 3+The induced heterogeneous oxide-modified carbon nanotubes are uniformly dispersed in the cyanate resin monomer matrix with the assistance of solvents and are completely removed in the subsequent vacuum drying. The excellent environmental stability and substrate adhesion broaden the application range of the resulting composite resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the preparation method steps of the present invention.

[0025] Figure 2 The multiphase oxide CoNd prepared in Example 3 of the present invention 0.3 Fe 1.7 XRD spectrum of O4 modified carbon nanotubes.

[0026] Figure 3 The multiphase oxide CoNd prepared in Example 3 of the present invention 0.3 Fe 1.7 TEM image of O4-modified carbon nanotubes.

[0027] Figure 4 The multiphase oxide CoNd prepared in Example 3 of the present invention 0.3 Fe 1.7 HRTEM image of O4 modified carbon nanotubes.

[0028] Figure 5 The multiphase oxide CoNd prepared in Example 3 of the present invention 0.3 Fe 1.7 Cross-sectional SEM image of O4-modified carbon nanotube / bisphenol E-type cyanate resin composite material.

[0029] Figure 6 ad are respectively the reflection loss graphs of the samples prepared in Comparative Example 1, Comparative Example 2, Example 2 and Example 3 of the present invention. DETAILED DESCRIPTION

[0030] The present invention is described in detail below in conjunction with specific embodiments.

[0031] Example 1: Preparation of oxidized carbon nanotubes:

[0032] Weigh 1.0g of carbon nanotubes and add a small amount of 80wt.% sulfuric acid solution to fully wet it to a paste, then evenly apply it on a titanium plate, and then place a layer of polytetrafluoroethylene film and another identical titanium plate. It is completely immersed in a sulfuric acid electrolyte of the same concentration. Subsequently, the titanium electrode plate with carbon nanotubes attached is connected to the positive pole of a DC regulated power supply, and the other titanium electrode is connected to the negative pole. A 30V DC voltage is applied and maintained for 4 hours. The oxidized carbon nanotubes are transferred to deionized water, vacuum filtered after ultrasonic dispersion, and washed with deionized water to remove residual sulfuric acid. The residual water is then removed by freeze drying to obtain pure oxidized carbon nanotubes.

[0033] Example 2: ZnNd 0.1 Fe 1.9 Preparation of O4 modified carbon nanotube bisphenol E type cyanate resin composites:

[0034] Step 1: Take 0.1g of oxidized carbon nanotubes and add them to 20mL of ethanol, then add 0.263g of Zn(CH3COO)2·2H2O, 0.921g of Fe(NO3)3·9H2O and 0.053g of Nd(NO3)3·6H2O. The mixture is dispersed by ultrasound and then transferred to an oven at 80°C for drying. It is then transferred to a tube furnace and heated to 550°C in an argon atmosphere for 2h to obtain neodymium-doped zinc ferrite modified carbon nanotubes CNT@ZnNd 0.1 Fe 1.9 O4;

[0035] Step 2: Take 0.4g of CNT@ZnNd 0.1 Fe 1.9 O4 was added to 5 mL of tetrahydrofuran and ultrasonically dispersed in a 50°C water bath for 30 minutes. Then, 1.6 g of bisphenol E cyanate monomer was added to the above dispersion and stirred vigorously for 2 hours. The mixed solution was vacuum dried at 80°C for 24 hours to remove the solvent. The paste mixture was then poured into a preheated mold and cured by heating and pressurizing to obtain CNT@ZnNd 0.1 Fe 1.9 The O4 / bisphenol E cyanate resin composite material has a heating process of 80°C for 2 hours, 130°C for 2 hours, 180°C for 1 hour and 210°C for 2 hours.

[0036] Example 3: CoNd 0.3 Fe 1.7 Preparation of O4 modified carbon nanotube / bisphenol E cyanate composite materials:

[0037] Step 1: Take 0.1g of oxidized carbon nanotubes and add them into 20mL of ethanol, then add 0.334g of Co(NO3)2·6H2O, 0.789g of Fe(NO3)3·9H2O and 0.151g of Nd(NO3)3·6H2O. The mixture is dispersed by ultrasound and then transferred to an oven at 80℃ for drying. It is then transferred to a tube furnace and heated to 550℃ in an argon atmosphere for 2h to obtain CNT@CoNd 0.2 Fe 1.8 O4, that is, heterogeneous oxide modified carbon nanotubes. Figure 2 Shows CNT@CoNd 0.3 Fe 1.7 XRD spectrum of O4. It can be seen that the diffraction peaks corresponding to carbon nanotubes, spinel phase CoFe2O4 and perovskite phase NdFeO3. Figure 3 Shows CNT@CoNd 0.3 Fe 1.7 TEM image of O4. It can be seen that the carbon nanotubes are uniformly modified with oxide particles. Figure 4 Shows CNT@CoNd 0.3 Fe 1.7 HRTEM images of O4, the lattice fringes in (a) correspond to carbon nanotubes, (b) to spinel phase CoFe2O4, (c) to perovskite phase NdFeO3, and (d) to amorphous phase.

[0038] Step 2: Take 0.4g of CNT@CoNd 0.3 Fe 1.7 O4 was added as a filler to 5 mL of tetrahydrofuran and ultrasonically dispersed in a 50 °C water bath for 30 minutes. Then, 1.6 g of bisphenol E cyanate monomer was added to the above dispersion and stirred vigorously for 2 hours. The mixed solution was vacuum dried at 80 °C for 24 hours to remove the solvent. The paste mixture was then poured into a preheated mold and CNT@CoNd was obtained through a temperature and pressure curing process. 0.3 Fe 1.7 O4 / cyanate ester composites. Figure 5 Shows CNT@CoNd 0.3 Fe 1.7 Cross-sectional SEM image of O4 / cyanate composite material. It can be seen that CNT@CoNd 0.3 Fe 1.7 O4 is evenly distributed in the resin matrix.

[0039] Example 4: Multiphase Oxide CoLa 0.3 Fe 1.7 Preparation of O4 modified carbon nanotube / bisphenol E cyanate composite materials:

[0040] Step 1: Take 0.1g of oxidized carbon nanotubes and add them into 20mL of ethanol, then add 0.336g of Co(NO3)2·6H2O, 0.752g of Fe(NO3)3·9H2O and 0.311g of La(NO3)3·6H2O. The mixture is dispersed by ultrasound and then transferred to an oven at 80℃ for drying. It is then transferred to a tube furnace and heated to 550℃ in an argon atmosphere for 2h to obtain CNT@CoLa 0.3 Fe 1.7 O4, that is, heterogeneous oxide modified carbon nanotubes.

[0041] Step 2: Take 0.4g of CNT@CoLa 0.3 Fe 1.7O4 was added as a filler to 5 mL of tetrahydrofuran and ultrasonically dispersed in a 50°C water bath for 30 minutes. Then, 1.6 g of bisphenol E cyanate monomer was added to the above dispersion and stirred vigorously for 2 hours. The mixed solution was vacuum dried at 80°C for 24 hours to remove the solvent. The paste mixture was then poured into a preheated mold and a composite material was obtained through a temperature and pressure curing process.

[0042] Comparative Example 1: Preparation of carbon nanotube / bisphenol E cyanate resin absorbing material:

[0043] 0.1 g of carbon nanotubes as filler was added to 5 mL of tetrahydrofuran and ultrasonically dispersed in a 50 ° C water bath for 30 minutes. Then, 1.9 g of bisphenol E cyanate monomer was added to the above dispersion and stirred vigorously for 2 hours. The mixed solution was vacuum dried at 80 ° C for 24 hours to remove the solvent. The paste mixture was then poured into a preheated mold, and a carbon nanotube / bisphenol E cyanate resin composite material was obtained by a temperature and pressure curing process.

[0044] Comparative Example 2: No Ln 3+ Preparation of Cobalt-doped Ferrite Modified Carbon Nanotube / Bisphenol E Cyanate Resin Absorbing Materials:

[0045] Step 1: Take 0.1g of oxidized carbon nanotubes and add them into 20mL of ethanol, then add 0.372g of Co(NO3)2·6H2O and 1.033g of Fe(NO3)3·9H2O. The mixture is dispersed by ultrasound and transferred to an oven at 80°C for drying, then transferred to a tube furnace and heated to 550°C in an argon atmosphere for 2h to obtain cobalt ferrite modified carbon nanotubes CNT@CoFe2O4.

[0046] Step 2: Take 0.4g of CNT@CoFe2O4 as a filler and add it to 5mL of tetrahydrofuran and ultrasonically disperse it in a 50℃ water bath for 30 minutes. Then, add 1.6g of bisphenol E cyanate monomer to the above dispersion and stir vigorously for 2 hours. The mixed solution was vacuum dried at 80℃ for 24 hours to remove the solvent. The paste mixture was then poured into a preheated mold, and a rare earth-free cobalt ferrite modified carbon nanotube / bisphenol E cyanate composite material was obtained through a temperature and pressure curing process.

[0047] The electromagnetic parameters of the absorbing materials provided in Comparative Example 1, Comparative Example 2, Example 2 and Example 3 were measured using an appropriate network analyzer, and the reflection loss of the electromagnetic waves was calculated using the transmission line theory. Figure 6 a to Figure 6 d corresponds to the reflection loss curves of the absorbing materials in the above examples at different thicknesses. It can be seen that the samples provided by Example 2 and Example 3 have better absorbing performance.

[0048] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A Ln 3+ The method for preparing a CNT / cyanate composite absorbing material modified with induced multiphase oxide is characterized by: The oxidized carbon nanotubes (CNT) are immersed in a specific molar ratio of Ln 3+ , Fe 3+ and divalent transition metal salt solutions, and multiphase oxide nanoparticles with inverse spinel ferrite / perovskite orthoferrite / amorphous phases were modified at the defects of carbon nanotubes by thermal decomposition under an inert gas atmosphere. 3+ It plays a role in regulating the crystal form, defects and interfaces of the oxide, and then it is mixed with a cyanate monomer, and is hot-pressed and cured to obtain a multiphase oxide-modified carbon nanotube / cyanate resin composite absorbing material.

2. The preparation method according to claim 1, characterized in that: The steps include: Step 1: Ln 3+ Preparation of induced heterogeneous oxide-modified carbon nanotubes: The carbon nanotubes with uniformly oxidized walls are added to a polar organic solvent, and then Ln 3+ , Fe 3+ and divalent transition metal ions M 2+ The mixture was dispersed by ultrasound and then transferred to an oven to remove the solvent, followed by calcination under an inert gas atmosphere to obtain Ln 3+ Induced heterogeneous oxide modified carbon nanotubes CNT@MLn x Fe 2-x O4; Step 2: Ln 3+ Preparation of induced heterogeneous oxide modified carbon nanotube / cyanate ester resin composites: The CNT@MLn prepared in step 1 x Fe 2-x O4 is added to a polar organic solvent and ultrasonically dispersed in a water bath at room temperature; then, a cyanate resin monomer is added to the above dispersion and vigorously stirred; the mixed solution is vacuum dried to remove the solvent; then the paste mixture is poured into a preheated mold and Ln is obtained through a step-by-step temperature increase hot press curing process. 3+ Induced heterogeneous oxide modified carbon nanotube / cyanate ester resin composites.

3. The preparation method according to claim 2, characterized in that: In the step 1, Ln 3+ is a combination of one or more; and the divalent transition metal ion is a combination of one or more.

4. The preparation method according to claim 2, characterized in that: In step 1, the salts corresponding to all metal ions include but are not limited to nitrates, phosphates or acetates.

5. The preparation method according to claim 2, characterized in that: In step 1, M 2+ , Ln 3+ and Fe 3+ The molar ratio is 1:0.1-0.4:1.6-1.9, preferably 1:0.3;1.

7.

6. The preparation method according to claim 2, characterized in that: In the step 1, the calcination and pyrolysis temperature is 400-900°C.

7. The preparation method according to claim 2, characterized in that: In the step 1, the mass ratio of carbon nanotubes to multiphase oxides is 1:1-4.

8. The preparation method according to claim 2, characterized in that: In the step 2, the organic solvent is one or more of tetrahydrofuran, N,N-dimethylformamide and acetone.

9. A Ln 3+ The induced multiphase oxide modified CNT / cyanate composite absorbing material is characterized by: The method is prepared by any one of claims 1 to 8.

10. The use of the composite absorbing material according to claim 9, characterized in that: Used in the preparation of absorbing materials.

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