Magnetic carbon tube modified TiN0.9 / NC electromagnetic wave absorbent and preparation method thereof

Abstract

The invention relates to a magnetic carbon tube modified TiN0.9 / NC electromagnetic wave absorbent and a preparation method thereof. According to the technical scheme, the preparation method comprises the following steps: carrying out solvothermal reaction on titanate and 2-aminoterephthalic acid to synthesize an NH2-MIL-125 template; adding the NH2-MIL-125 template into an aqueous solution of metal salt and dopamine, and tightly wrapping a continuous metal ion hybridized polydopamine layer on the surface of the disc-shaped template through an oxidative polymerization effect between metal ions and a dopamine monomer; through dicyandiamide-assisted high-temperature carbon thermal reduction treatment, the surface of a product is coated with a large number of multi-walled carbon nanotubes generated through catalysis of magnetic metal nanoparticles, and the magnetic carbon tube modified TiN0.9 / NC electromagnetic wave absorbent is prepared. The preparation method is simple to operate and controllable in morphology and operation process, and the prepared magnetic carbon tube modified TiN0.9 / NC electromagnetic wave absorbent can effectively absorb electromagnetic waves and is high in reflection loss and large in effective absorption bandwidth.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic wave absorbers. Specifically, it relates to a magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber and its preparation method. Background Art

[0002] Electromagnetic wave absorbers have excellent electromagnetic wave absorption performance and are an effective means to solve the increasingly serious electromagnetic pollution problem. Metal organic frameworks (MOFs) have the advantages of adjustable pore size, large specific surface area, controllable morphology and designable chemical composition, and are considered to be very potential candidate templates / precursors in the preparation of carbon-based electromagnetic wave absorbers. Magnetic metal-centered MOF derivatives have attracted the enthusiasm of a large number of researchers due to their good magnetoelectric synergy effect, which can well improve impedance matching and are widely used in the field of electromagnetic wave absorbers.

[0003] Wet grinding is a classic and simple physical method for preparing magnetic carbon-based materials for non-magnetic center MOF. The prior art discloses a simple strategy for introducing metal nickel nanoparticles into a carbon matrix using wet grinding. The prepared Ni / NiO / Cu@C composite material has a minimum reflection loss of -38.1dB when the matching thickness is 3.2mm (L.Huang, C.Chen, X.Huang, S.Ruan, Y.-J.Zeng, Compos.B Eng.164(2019)583–589). However, without surface engineering design, the wet grinding method will cause the sample particles to agglomerate after carbon thermal reduction due to excessive magnetic free ions, as well as uneven distribution of magnetic components, which will destroy the high specific surface area characteristics of MOF-derived carbon-based electromagnetic wave absorbers.

[0004] The in-situ growth method can successfully introduce pre-embedded magnetic nanoparticles into the non-magnetic center MOF, and through the subsequent carbothermal reduction process, various magnetic carbon-based MOF derivatives can be obtained from the prepared precursor. The prior art discloses a method for constructing a magnetic particle precursor by compounding Fe3O4 nanoparticles with MOF-74 using an in-situ growth method (J. Ren, Y. Lyu, Z. Liu, M. Ahmad, Q. Zhang, B. Zhang, ACS Appl. Electr. Mater. 4 (11) (2022) 5221–5233). This method forms a stable magnetic carbon material through a subsequent carbonization process. The minimum reflection loss of the prepared Fe3O4@Ni-C reaches -59.4dB@9.9GHz, and the effective absorption bandwidth of Fe3O4@Co-C reaches 6.8GHz@3.1mm. However, the additional nanoparticles in this process will interfere with the nucleation and growth of MOF, which can easily lead to the collapse and distortion of the morphology of the MOF template.

[0005] In recent years, a series of studies on the construction of magnetic carbon-based electromagnetic wave absorbers based on binary or ternary hybrid MOF-on-MOF precursors have gradually emerged. The prior art discloses a method for constructing two binary hybrid MOF heterostructures through a selective assembly strategy (H. Zhu, Q. Jiao, R. Fu, P. Su, C. Yang, C. Feng, H. Li, D. Shi, Y. Zhao, J. Colloid Interface Sci. 613 (2022) 182–193), and realizes its transformation into a magnetic porous carbon material DUT-52@Co-doped MIL-88 composite material through a simple carbonization process. When the matching thickness is 2 mm, its minimum reflection loss exceeds -65.2 dB, and the effective absorption bandwidth covers 4.8 GHz. However, since epitaxial growth of MOF or selective assembly of external MOF onto internal MOF can only be achieved through precise control of synthesis conditions and elaborate crystal plane lattice matching design, the success rate of constructing magnetic carbon-based electromagnetic wave absorbers using heterogeneous MOF-on-MOF templates is low, making it difficult to achieve efficient absorption of electromagnetic waves.

[0006] At present, the existing technology has the problems of complex operation, uncontrollable morphology of reactants and operation process, low success rate in constructing magnetic carbon-based electromagnetic wave absorbers, and difficulty in achieving efficient absorption of electromagnetic waves. Summary of the invention

[0007] The present invention aims to overcome the defects of the prior art and to provide a magnetic carbon tube modified TiN with simple operation and controllable morphology and operation process. 0.9 Preparation method of / NC electromagnetic wave absorber, magnetic carbon tube modified TiN prepared by the method 0.9 / NC electromagnetic wave absorber can effectively absorb electromagnetic waves, with strong reflection loss and large effective absorption bandwidth.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] Step 1, mixing N,N-dimethylformamide and methanol at a volume ratio of (7-17) to methanol to obtain a mixed solvent; then adding aminoparaphenylenedimethyl to the mixed solvent at a solid-liquid ratio of 1-2 g / L, and ultrasonically stirring for 10-35 min to obtain solution A.

[0010] Step 2, mixing the titanate and the solution A at a volume ratio of 1:(55-80) and stirring for 0.5-2h to obtain solution B; placing the solution B in a Teflon-lined reactor for solvent thermal reaction; solid-liquid separation, washing, and drying to obtain NH2-MIL-125 template powder.

[0011] Step 3: placing the NH2-MIL-125 template powder into the dopamine hydrochloride aqueous solution at a mass ratio of NH2-MIL-125 template powder to dopamine hydrochloride of 1:(1-6), mixing, and obtaining solution C.

[0012] The content of dopamine hydrochloride in the dopamine hydrochloride aqueous solution is 2-12 g / L.

[0013] Step 4, dissolving the metal salt in aqueous ammonia at a solid-liquid ratio of 15 to 30 g / L, stirring for 10 to 35 min to obtain solution D;

[0014] Step 5: Mix the solution D and the solution C at a volume ratio of the solution D to the solution C of 1:(10-20), stir at room temperature for 8-12 hours, separate the solid from the liquid, wash, and dry to obtain a precursor powder.

[0015] Step 6: Mix the precursor powder with dicyandiamide at a mass ratio of 1:(1-6), and perform a carbothermal reduction reaction at 700-900° C. to obtain magnetic carbon tube-modified TiN 0.9 / NC electromagnetic wave absorber.

[0016] The titanate is one of n-butyl titanate, tetraisopropyl titanate and ethyl titanate.

[0017] The average particle size of the NH2-MIL-125 template powder is 0.26-1.89 μm.

[0018] The temperature of the solvent thermal reaction is 100-150° C., and the time of the solvent thermal reaction is 20-24 hours.

[0019] The metal salt is one of cobalt nitrate, cobalt sulfate, cobalt chloride, nickel nitrate, nickel sulfate and nickel chloride.

[0020] The heating rate of the carbon thermal reduction reaction is 5-10°C / min, and the heat preservation time is 1-5h.

[0021] The stirring speed in step 2 is 200-500 rpm, and the speeds in step 4 and step 5 are the same as the speed in step 2.

[0022] Due to the adoption of the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0023] 1) In the present invention, titanate and 2-aminoterephthalic acid are reacted by solvent thermal reaction to synthesize NH2-MIL-125 template, which is added to an aqueous solution of metal salt and dopamine, and then mixed with dicyandiamide and subjected to carbothermal reduction reaction to obtain magnetic carbon tube modified TiN0.9 / NC electromagnetic wave absorber, easy to operate. The dopamine hydrochloride used in the present invention has mild reaction and will not damage the template morphology.

[0024] 2) The present invention provides a magnetic carbon tube modified TiN 0.9 The preparation method of / NC electromagnetic wave absorber is to use aminated terephthalic acid as organic ligand and titanium as central metal atom, and to obtain NH2-MIL-125 template by using the coordination reaction between the organic ligand and metal atom. Magnetic carbon tube modified disc-shaped TiN was prepared by using NH2-MIL-125 (Ti) template composite magnetic metal-polydopamine coating and dicyandiamide assisted carbothermal reduction reaction. 0.9 / NC electromagnetic wave absorber. Higher carbothermal reduction temperature will promote the growth of magnetic carbon tubes and high conductivity TiN 0.9 The formation of carbon matrix and graphitization lead to the magnetic carbon nanotubes modified TiN at different carbothermal reduction temperatures. 0.9 / NC electromagnetic wave absorber effectively absorbs electromagnetic waves.

[0025] 3) In the present invention, a metal-polyphenol network coating strategy for imparting magnetism to non-magnetic metal-centered MOF is proposed. This method is applicable to a variety of reaction environments and is free from the restrictions on reaction conditions imposed by most MOFs. 0.9 The dispersed magnetic units in the NC electromagnetic wave absorber not only increase the magnetic carbon tube-modified TiN 0.9 The magnetic loss mechanism of NC electromagnetic wave absorber not only has strong reflection loss, but also can effectively improve the impedance matching of the product, significantly improving the magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber effectively absorbs electromagnetic waves. After testing: when the matching thickness is 1.9mm, the best reflection loss is -39.40dB; when the matching thickness is 1.5mm, the effective bandwidth reaches 4.3GHz.

[0026] 4) The universal metal-polyphenol network coating strategy adopted in the present invention is to mix the NH2-MIL-125 template powder with the dopamine hydrochloride aqueous solution, add the metal salt dissolved in the ammonia solution, separate the solid and liquid, and dry to obtain the precursor powder; on the one hand, the magnetic component can be effectively introduced to enhance the magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber, on the other hand, the hierarchical carbon nanotubes generated by magnetic particles on the surface of the precursor are used to construct a three-dimensional conductive network to improve the conductivity loss of the material. While introducing a new loss mechanism into the non-magnetic metal-centered MOF derivative, the magnetoelectric synergistic effect is also used to greatly improve its impedance matching and improve the magnetic carbon tube modified TiN 0.9 / Effective bandwidth of NC electromagnetic wave absorber.

[0027] Therefore, the present invention is simple to operate, the morphology and operation process are controllable, and the prepared magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber can effectively absorb electromagnetic waves, with strong reflection loss and large effective absorption bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a scanning electron microscope image of a MIL-125(Ti)@Co-PDA precursor powder prepared in the present invention;

[0029] Figure 2 use Figure 1 Magnetic carbon nanotubes modified with TiN prepared from the precursor powder shown 0.9 / TEM image of NC electromagnetic wave absorber;

[0030] Figure 3 for Figure 2 Magnetic carbon tubes modified TiN 0.9 / X-ray diffraction pattern of NC electromagnetic wave absorber;

[0031] Figure 4 for Figure 1 Magnetic carbon tubes modified TiN 0.9 / Reflection loss diagram of NC electromagnetic wave absorber at frequency 2~18GHz and thickness 1~3mm. DETAILED DESCRIPTION

[0032] The present invention is further described and explained below in conjunction with the accompanying drawings and specific implementation methods. All the embodiments herein are only used to illustrate the present invention and are not intended to limit the protection scope of the present invention.

[0033] A magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber and its preparation method. The preparation method described in this specific embodiment is:

[0034] Step 1, mixing N,N-dimethylformamide and methanol at a volume ratio of (7-17) to methanol to obtain a mixed solvent; then adding aminoparaphenylenedimethyl to the mixed solvent at a solid-liquid ratio of 1-2 g / L, and ultrasonically stirring for 10-35 min to obtain solution A.

[0035] Step 2, mixing the titanate and the solution A at a volume ratio of 1:(55-80) and stirring for 0.5-2h to obtain solution B; placing the solution B in a Teflon-lined reactor for solvent thermal reaction; solid-liquid separation, washing, and drying to obtain NH2-MIL-125 template powder.

[0036] Step 3: placing the NH2-MIL-125 template powder into the dopamine hydrochloride aqueous solution at a mass ratio of NH2-MIL-125 template powder to dopamine hydrochloride of 1:(1-6), mixing, and obtaining solution C.

[0037] The content of dopamine hydrochloride in the dopamine hydrochloride aqueous solution is 2-12 g / L.

[0038] Step 4, dissolving the metal salt in aqueous ammonia at a solid-liquid ratio of 15 to 30 g / L, stirring for 10 to 35 min to obtain solution D;

[0039] Step 5: Mix the solution D and the solution C at a volume ratio of the solution D to the solution C of 1:(10-20), stir at room temperature for 8-12 hours, separate the solid from the liquid, wash, and dry to obtain a precursor powder.

[0040] Step 6: Mix the precursor powder with dicyandiamide at a mass ratio of 1:(1-6), and perform a carbothermal reduction reaction at 700-900° C. to obtain magnetic carbon tube-modified TiN 0.9 / NC electromagnetic wave absorber.

[0041] The titanate is one of n-butyl titanate, tetraisopropyl titanate and ethyl titanate.

[0042] The temperature of the solvent thermal reaction is 100-150° C., and the time of the solvent thermal reaction is 20-24 hours.

[0043] The metal salt is one of cobalt nitrate, cobalt sulfate, cobalt chloride, nickel nitrate, nickel sulfate and nickel chloride.

[0044] The heating rate of the carbon thermal reduction reaction is 5-10°C / min, and the heat preservation time is 1-5h.

[0045] The stirring speed in step 2 is 200-500 rpm.

[0046] In this specific embodiment:

[0047] The average particle size of the NH2-MIL-125 template powder is 0.26-1.89 μm.

[0048] The rotation speed in step 4 and the rotation speed in step 5 are the same as the rotation speed in step 2.

[0049] This will not be described in detail in the embodiments.

[0050] Example 1

[0051] A magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber and its preparation method. The steps of the preparation method described in this embodiment are:

[0052] Step 1: Mix N,N-dimethylformamide and methanol at a volume ratio of 7:1 to obtain a mixed solvent; then add aminop-phenylenedimethyl to the mixed solvent at a solid-liquid ratio of 1.0 g / L, and stir ultrasonically for 10 minutes to obtain solution A.

[0053] Step 2, mixing the titanate and the solution A at a volume ratio of 1:55, stirring for 0.5, to obtain solution B; placing the solution B in a reactor with a Teflon liner for solvent thermal reaction; solid-liquid separation, washing, and drying to obtain NH2-MIL-125 template powder.

[0054] Step 3: placing the NH2-MIL-125 template powder into the dopamine hydrochloride aqueous solution at a mass ratio of 1:1, mixing, and obtaining solution C.

[0055] The content of dopamine hydrochloride in the dopamine hydrochloride aqueous solution is 2 g / L.

[0056] Step 4, dissolve the metal salt in ammonia water at a solid-liquid ratio of 15 g / L, and stir for 10 min to obtain solution D;

[0057] Step 5: mixing the solution D and the solution C at a volume ratio of the solution D to the solution C of 1:10, stirring at room temperature for 8 hours, separating the solid from the liquid, washing, and drying to obtain a precursor powder.

[0058] Step 6: Mix the precursor powder with dicyandiamide at a mass ratio of 1:1, and perform a carbothermal reduction reaction at 700-900° C. to obtain a magnetic carbon tube-modified TiN 0.9 / NC electromagnetic wave absorber.

[0059] The titanate is n-butyl titanate.

[0060] The temperature of the solvent thermal reaction is 100° C., and the time of the solvent thermal reaction is 20 hours.

[0061] The metal salt is cobalt nitrate.

[0062] The heating rate of the carbon thermal reduction reaction is 5°C / min, and the holding time is 1h;

[0063] The stirring speed in step 2 is 200-500 rpm.

[0064] Example 2

[0065] A magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber and its preparation method. The steps of the preparation method described in this embodiment are:

[0066] Step 1: Mix N,N-dimethylformamide and methanol at a volume ratio of 9:1 to obtain a mixed solvent; then add aminop-phenylenedimethyl to the mixed solvent at a solid-liquid ratio of 1.2 g / L, and stir ultrasonically for 15 minutes to obtain solution A.

[0067] Step 2: Mix the titanate and the solution A at a volume ratio of 1:60, stir for 0.8, and obtain solution B; then place the solution B into a reactor with a Teflon liner for solvothermal reaction; separate the solid and liquid, wash, and dry to obtain NH2-MIL-125 template powder.

[0068] Step 3: placing the NH2-MIL-125 template powder into the dopamine hydrochloride aqueous solution at a mass ratio of 1:2, mixing, and obtaining solution C.

[0069] The content of dopamine hydrochloride in the dopamine hydrochloride aqueous solution is 4 g / L.

[0070] Step 4: Dissolve the metal salt in aqueous ammonia at a solid-liquid ratio of 15 to 30 g / L, and stir for 15 min to obtain solution D.

[0071] Step 5: Mix the solution D and the solution C at a volume ratio of 1:12, stir at room temperature for 9 hours, separate the solid from the liquid, wash, and dry to obtain a precursor powder.

[0072] Step 6: Mix the precursor powder with dicyandiamide at a mass ratio of 1:2, and perform a carbothermal reduction reaction at 700-900° C. to obtain a magnetic carbon tube-modified TiN 0.9 / NC electromagnetic wave absorber.

[0073] The titanate is tetraisopropyl titanate.

[0074] The temperature of the solvent thermal reaction is 110° C., and the time of the solvent thermal reaction is 21 h.

[0075] The metal salt is cobalt sulfate.

[0076] The heating rate of the carbon thermal reduction reaction is 6°C / min and the insulation time is 2.

[0077] The stirring speed in step 2 is 250 rpm.

[0078] Example 3

[0079] A magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber and its preparation method. The steps of the preparation method described in this embodiment are:

[0080] Step 1: Mix N,N-dimethylformamide and methanol at a volume ratio of 11:1 to obtain a mixed solvent; then add aminop-phenylenedimethyl to the mixed solvent at a solid-liquid ratio of 1.4 g / L, and stir ultrasonically for 20 minutes to obtain solution A.

[0081] Step 2: Mix the titanate and the solution A at a volume ratio of 1:65, stir for 1 hour, and obtain solution B; then place the solution B into a reactor with a Teflon liner for solvent thermal reaction; separate the solid and liquid, wash, and dry to obtain NH2-MIL-125 template powder.

[0082] Step 3: placing the NH2-MIL-125 template powder into the dopamine hydrochloride aqueous solution at a mass ratio of 1:3, mixing, and obtaining solution C.

[0083] The content of dopamine hydrochloride in the dopamine hydrochloride aqueous solution is 6 g / L.

[0084] Step 4: Dissolve the metal salt in aqueous ammonia at a solid-liquid ratio of 15 to 30 g / L, and stir for 20 min to obtain solution D.

[0085] Step 5: Mix the solution D and the solution C at a volume ratio of the solution D to the solution C of 1:14, stir at room temperature for 9.5 hours, separate the solid from the liquid, wash, and dry to obtain a precursor powder.

[0086] Step 6: Mix the precursor powder with dicyandiamide at a mass ratio of 1:3, and perform a carbothermal reduction reaction at 780° C. to obtain a magnetic carbon tube-modified TiN 0.9 / NC electromagnetic wave absorber.

[0087] The titanate is ethyl orthotitanate.

[0088] The temperature of the solvent thermal reaction is 120° C., and the time of the solvent thermal reaction is 22 hours.

[0089] The metal salt is cobalt chloride.

[0090] The heating rate of the carbon thermal reduction reaction is 7°C / min, and the insulation time is 3h.

[0091] The stirring speed in step 2 is 300 rpm.

[0092] Example 4

[0093] A magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber and its preparation method. The steps of the preparation method described in this embodiment are:

[0094] Step 1, mixing N,N-dimethylformamide and methanol at a volume ratio of 13:1 to obtain a mixed solvent; then adding aminoparaphenylenedimethyl to the mixed solvent at a solid-liquid ratio of 1.6 g / L, and ultrasonically stirring for 25 minutes to obtain solution A.

[0095] Step 2: Mix the titanate and the solution A at a volume ratio of 1:70, and stir for 1.5 to obtain a solution B; then place the solution B into a reactor with a Teflon liner for a solvothermal reaction; separate the solid and liquid, wash, and dry to obtain NH2-MIL-125 template powder.

[0096] Step 3: placing the NH2-MIL-125 template powder into the dopamine hydrochloride aqueous solution at a mass ratio of 1:4, mixing, and obtaining solution C.

[0097] The content of dopamine hydrochloride in the dopamine hydrochloride aqueous solution is 8 g / L.

[0098] Step 4: Dissolve the metal salt in aqueous ammonia at a solid-liquid ratio of 25 g / L and stir for 25 min to obtain solution D.

[0099] Step 5: Mix the solution D and the solution C at a volume ratio of 1:16, stir at room temperature for 10 hours, separate the solid from the liquid, wash, and dry to obtain a precursor powder.

[0100] Step 6: Mix the precursor powder with dicyandiamide at a mass ratio of 1:4, and perform a carbothermal reduction reaction at 800° C. to obtain a magnetic carbon tube-modified TiN 0.9 / NC electromagnetic wave absorber.

[0101] The titanate is n-butyl titanate.

[0102] The temperature of the solvent thermal reaction is 130° C., and the time of the solvent thermal reaction is 23 h.

[0103] The metal salt is nickel nitrate.

[0104] The heating rate of the carbon thermal reduction reaction is 8°C / min, and the insulation time is 4h.

[0105] The stirring speed in step 2 is 350 rpm.

[0106] Example 5

[0107] A magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber and its preparation method. The steps of the preparation method described in this embodiment are:

[0108] Step 1: Mix N,N-dimethylformamide and methanol at a volume ratio of 15:1 to obtain a mixed solvent; then add aminop-phenylenedimethyl to the mixed solvent at a solid-liquid ratio of 1.8 g / L, and stir ultrasonically for 30 minutes to obtain solution A.

[0109] Step 2: Mix the titanate and the solution A at a volume ratio of 1:75, and stir for 1.8 hours to obtain a solution B; then place the solution B into a reactor with a Teflon liner for a solvothermal reaction; separate the solid and liquid, wash, and dry to obtain NH2-MIL-125 template powder.

[0110] Step 3: placing the NH2-MIL-125 template powder into the dopamine hydrochloride aqueous solution at a mass ratio of 1:5, and mixing to obtain solution C.

[0111] The content of dopamine hydrochloride in the dopamine hydrochloride aqueous solution is 10 g / L.

[0112] Step 4: Dissolve the metal salt in aqueous ammonia at a solid-liquid ratio of 27 g / L and stir for 30 min to obtain solution D.

[0113] Step 5: Mix the solution D and the solution C at a volume ratio of 1:18, stir at room temperature for 11 hours, separate the solid and liquid, wash, and dry to obtain a precursor powder.

[0114] Step 6: Mix the precursor powder with dicyandiamide at a mass ratio of 1:5, and perform a carbothermal reduction reaction at 850° C. to obtain a magnetic carbon tube-modified TiN 0.9 / NC electromagnetic wave absorber.

[0115] The titanate is tetraisopropyl titanate.

[0116] The temperature of the solvent thermal reaction is 140° C., and the time of the solvent thermal reaction is 22 hours.

[0117] The metal salt is nickel sulfate.

[0118] The heating rate of the carbon thermal reduction reaction is 9°C / min, and the insulation time is 4.5h.

[0119] The stirring speed in step 2 is 400 rpm.

[0120] Example 6

[0121] A magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber and its preparation method. The steps of the preparation method described in this embodiment are:

[0122] Step 1: Mix N,N-dimethylformamide and methanol at a volume ratio of 17:1 to obtain a mixed solvent; then add aminop-phenylenedimethyl to the mixed solvent at a solid-liquid ratio of 2 g / L, and stir ultrasonically for 35 minutes to obtain solution A.

[0123] Step 2: Mix the titanate and the solution A at a volume ratio of 1:80, stir for 2 hours, and obtain solution B; then place the solution B into a reactor with a Teflon liner for solvent thermal reaction; separate the solid and liquid, wash, and dry to obtain NH2-MIL-125 template powder.

[0124] Step 3: placing the NH2-MIL-125 template powder into the dopamine hydrochloride aqueous solution at a mass ratio of 1:6, and mixing to obtain solution C.

[0125] The content of dopamine hydrochloride in the dopamine hydrochloride aqueous solution is 12 g / L.

[0126] Step 4: Dissolve the metal salt in aqueous ammonia at a solid-liquid ratio of 30 g / L and stir for 35 min to obtain solution D.

[0127] Step 5: Mix the solution D and the solution C at a volume ratio of 1:20, stir at room temperature for 12 hours, separate the solid from the liquid, wash, and dry to obtain a precursor powder.

[0128] Step 6: Mix the precursor powder with dicyandiamide at a mass ratio of 1:6, and perform a carbothermal reduction reaction at 700-900° C. to obtain a magnetic carbon tube-modified TiN 0.9 / NC electromagnetic wave absorber.

[0129] The titanate is ethyl orthotitanate.

[0130] The temperature of the solvent thermal reaction is 150° C., and the time of the solvent thermal reaction is 24 hours.

[0131] The metal salt is nickel chloride.

[0132] The heating rate of the carbon thermal reduction reaction is 10°C / min, and the insulation time is 5h.

[0133] The stirring speed in step 2 is 500 rpm.

[0134] Compared with the prior art, this specific implementation has the following beneficial effects:

[0135] 1) In this specific embodiment, titanate and 2-aminoterephthalic acid are reacted by solvent thermal reaction to synthesize NH2-MIL-125 template, which is added to an aqueous solution of metal salt and dopamine, and then mixed with dicyandiamide and subjected to carbothermal reduction reaction to obtain magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber, easy to operate. The dopamine hydrochloride used in this specific embodiment has a mild reaction and will not damage the template morphology.

[0136] 2) This specific embodiment provides a magnetic carbon tube modified TiN 0.9 The preparation method of / NC electromagnetic wave absorber is to use aminated terephthalic acid as organic ligand and titanium as central metal atom, and to obtain NH2-MIL-125 template by using the coordination reaction between the organic ligand and metal atom. Magnetic carbon tube modified disc-shaped TiN was prepared by using NH2-MIL-125 (Ti) template composite magnetic metal-polydopamine coating and dicyandiamide assisted carbothermal reduction reaction. 0.9 / NC electromagnetic wave absorber. Higher carbothermal reduction temperature will promote the growth of magnetic carbon tubes and high conductivity TiN 0.9 The formation of carbon matrix and graphitization lead to the magnetic carbon nanotubes modified TiN at different carbothermal reduction temperatures. 0.9 / NC electromagnetic wave absorber effectively absorbs electromagnetic waves.

[0137] 3) In this embodiment, a metal-polyphenol network coating strategy is proposed to impart magnetism to non-magnetic metal-centered MOFs. This method is applicable to a variety of reaction environments and is free from the restrictions on reaction conditions imposed by most MOFs. 0.9 The dispersed magnetic units in the NC electromagnetic wave absorber not only increase the magnetic carbon tube-modified TiN 0.9The magnetic loss mechanism of NC electromagnetic wave absorber not only has strong reflection loss, but also can effectively improve the impedance matching of the product, significantly improving the magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber effectively absorbs electromagnetic waves. After testing: when the matching thickness is 1.9mm, the best reflection loss is -39.40dB; when the matching thickness is 1.5mm, the effective bandwidth reaches 4.3GHz.

[0138] 4) The universal metal-polyphenol network coating strategy adopted in this specific embodiment is to mix the NH2-MIL-125 template powder with the dopamine hydrochloride aqueous solution, add the metal salt dissolved in ammonia water, separate the solid and liquid, and dry to obtain the precursor powder; on the one hand, it can effectively introduce magnetic components and enhance the magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber, on the other hand, the hierarchical carbon nanotubes generated by magnetic particles on the surface of the precursor are used to construct a three-dimensional conductive network to improve the conductivity loss of the material. While introducing a new loss mechanism into the non-magnetic metal-centered MOF derivative, the magnetoelectric synergistic effect is also used to greatly improve its impedance matching and improve the magnetic carbon tube modified TiN 0.9 / Effective bandwidth of NC electromagnetic wave absorber.

[0139] The MIL-125(Ti)@Co-PDA precursor powder and magnetic carbon tube modified TiN prepared in this specific embodiment 0.9 / NC electromagnetic wave absorber is shown in the attached figure. Figure 1 This is a scanning electron microscope image of the MIL-125(Ti)@Co-PDA precursor powder prepared in Example 1; Figure 2 use Figure 1 Magnetic carbon nanotubes modified with TiN prepared from the precursor powder shown 0.9 / TEM image of NC electromagnetic wave absorber; Figure 3 for Figure 2 Magnetic carbon tubes modified TiN 0.9 / X-ray diffraction pattern of NC electromagnetic wave absorber; Figure 4 for Figure 1 Magnetic carbon tubes modified TiN 0.9 / Reflection loss diagram of NC electromagnetic wave absorber at frequency 2~18GHz and thickness 1~3mm.

[0140] Figure 1 (a) is a scanning electron micrograph of the MIL-125(Ti)@Co-PDA precursor prepared in Example 1. Figure 1 (b) Magnetic carbon tube modified TiN prepared in Example 1 0.9 / NC electromagnetic wave absorber scanning electron microscope image. Figure 1(a) It can be seen that a continuous layer of cobalt hybrid polydopamine (Co-PDA) is conformally coated on the disk-shaped template due to the oxidative polymerization between cobalt ions and dopamine (DA) monomers; Figure 1 (b) It can be seen that the prepared magnetic carbon tubes modified TiN 0.9 The / NC electromagnetic wave absorber inherits the disc-shaped morphology of the NH2-MIL-125(Ti) template. Relying on the ammonia and other hydrocarbon gases released by dicyandiamide, the precursor is converted into magnetic carbon tubes modified TiN 0.9 / NC electromagnetic wave absorber.

[0141] from Figure 2 It can be seen that the prepared magnetic carbon tubes modified TiN 0.9 / NC electromagnetic wave absorber particles are disc-shaped particles decorated with nanotubes, showing a distinct core-shell structure, with the core composed of TiN derived from NH2-MIL-125(Ti) 0.9 / NC composition, and the outer shell is composed of a nitrogen-doped carbon matrix derived from polydopamine. The lowest brightness part in the figure is the cobalt particles, which are mainly distributed in the core and have a small amount of agglomeration; in addition, nano-scale cobalt particles can also be found at the top of the bamboo-like carbon tubes outside the core, which is due to the catalytic effect of metal Co in the dicyandiamide-assisted carbon thermal reaction. The local conductive network formed by the widespread distribution and mutual entanglement of magnetic multi-walled carbon nanotubes is conducive to improving the magnetic carbon tube modified TiN 0.9 / Conduction loss of NC electromagnetic wave absorber.

[0142] Depend on Figure 3 It can be seen that there are three characteristic peaks of Co at 44.23°, 51.53° and 75.87° (JCPDS No.89-4307), so the magnetic carbon tubes modified TiN prepared in Examples 1-3 0.9 The presence of metal Co can be confirmed in the NC electromagnetic wave absorber. Figure 4 It can be seen that the prepared magnetic carbon tubes modified TiN 0.9 When the matching thickness of / NC electromagnetic wave absorber is 1.9mm, the strongest reflection loss is -39.40dB, and the maximum effective absorption bandwidth is 4.3GHz (13.7GHz~18GHz) at the matching thickness of 1.5mm.

[0143] Therefore, the specific implementation method is simple to operate, the morphology and operation process are controllable, and the prepared magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber can effectively absorb electromagnetic waves, with strong reflection loss and large effective absorption bandwidth.

Claims

1. A magnetic carbon tube modified TiN 0.9 / The preparation method of NC electromagnetic wave absorber is characterized in that: The steps of the preparation method are: Step 1, mixing N,N-dimethylformamide and methanol at a volume ratio of (7-17) to methanol to obtain a mixed solvent; then adding aminoparaphenylenedimethyl to the mixed solvent at a solid-liquid ratio of 1-2 g / L, and ultrasonically stirring for 10-35 min to obtain a solution A; Step 2, mixing the titanate and the solution A at a volume ratio of 1:(55-80) of titanate to the solution A, stirring for 0.5-2h to obtain solution B; placing the solution B in a Teflon-lined reactor for solvothermal reaction; solid-liquid separation, washing, and drying to obtain NH2-MIL-125 template powder; Step 3, placing the NH2-MIL-125 template powder into the dopamine hydrochloride aqueous solution at a mass ratio of 1:(1-6) of the NH2-MIL-125 template powder to dopamine hydrochloride, mixing, and obtaining a solution C; The content of dopamine hydrochloride in the dopamine hydrochloride aqueous solution is 2 to 12 g / L; Step 4, dissolving the metal salt in aqueous ammonia at a solid-liquid ratio of 15 to 30 g / L, stirring for 10 to 35 min to obtain solution D; Step 5, mixing the solution D and the solution C at a volume ratio of the solution D to the solution C of 1:(10-20), stirring at room temperature for 8-12 hours, separating the solid from the liquid, washing, and drying to obtain a precursor powder; Step 6: Mix the precursor powder with dicyandiamide at a mass ratio of 1:(1-6), and perform a carbothermal reduction reaction at 700-900° C. to obtain magnetic carbon tube-modified TiN 0.9 / NC electromagnetic wave absorber.

2. The magnetic carbon tube modified TiN according to claim 1 0.9 / The preparation method of NC electromagnetic wave absorber is characterized in that: The titanate is one of n-butyl titanate, tetraisopropyl titanate and ethyl titanate.

3. The magnetic carbon tube modified TiN according to claim 1 0.9 / The preparation method of NC electromagnetic wave absorber is characterized in that: The average particle size of the NH2-MIL-125 template powder is 0.26-1.89 μm.

4. The magnetic carbon tube modified TiN according to claim 1 0.9 / The preparation method of NC electromagnetic wave absorber is characterized in that: The temperature of the solvent thermal reaction is 100-150° C., and the time of the solvent thermal reaction is 20-24 hours.

5. The magnetic carbon tube modified TiN according to claim 1 0.9 / The preparation method of NC electromagnetic wave absorber is characterized in that: The metal salt is one of cobalt nitrate, cobalt sulfate, cobalt chloride, nickel nitrate, nickel sulfate and nickel chloride.

6. The magnetic carbon tube modified TiN according to claim 1 0.9 / The preparation method of NC electromagnetic wave absorber is characterized in that: The heating rate of the carbon thermal reduction reaction is 5-10°C / min, and the heat preservation time is 1-5h.

7. The magnetic carbon tube modified TiN according to claim 1 0.9 / The preparation method of NC electromagnetic wave absorber is characterized in that: The stirring speed in step 2 is 200-500 rpm, and the speeds in step 4 and step 5 are the same as the speed in step 2.

8. A magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber, characterized in that The magnetic carbon tube modified TiN 0.9 The NC electromagnetic wave absorber is a magnetic carbon tube modified TiN according to any one of claims 1 to 7. 0.9 Magnetic carbon tube modified TiN prepared by the preparation method of NC electromagnetic wave absorber 0.9 / NC electromagnetic wave absorber.

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