A magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber and preparation method thereof

Abstract

The present invention relates to a magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber and its preparation method. The technical scheme is: titanate and 2-aminoterephthalic acid are reacted by solvent thermal reaction to synthesize NH2-MIL-125 template; the NH2-MIL-125 template is added to an aqueous solution of metal salt and dopamine, and through the oxidative polymerization between metal ions and dopamine monomers, a continuous metal ion hybrid polydopamine layer is tightly wrapped on the surface of the disc-shaped template; after high-temperature carbon thermal reduction treatment assisted by dicyandiamide, a large number of multi-walled carbon nanotubes generated by catalysis of magnetic metal nanoparticles are coated on the surface of the product to obtain magnetic carbon tube-modified TiN 0.9 / NC electromagnetic wave absorber. The present invention is simple to operate, and the morphology and operation process are controllable. 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.

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 preparation method thereof. Background Art

[0002] Electromagnetic wave absorbers, with their excellent electromagnetic wave absorption properties, are an effective means of addressing the increasingly serious problem of electromagnetic pollution. Metal-organic frameworks (MOFs), with their advantages such as adjustable pore size, large specific surface area, controllable morphology, and customizable chemical composition, are considered promising candidate templates / precursors for the preparation of carbon-based electromagnetic wave absorbers. Magnetic metal-centered MOF derivatives, due to their excellent magnetoelectric synergy, can significantly improve impedance matching, attracting considerable research interest and being widely used in the field of electromagnetic wave absorbers.

[0003] Wet milling is a classic and convenient physical method for preparing magnetic carbon-based materials from non-magnetic core metal ion frameworks (MOFs). Prior art discloses a simple strategy for introducing metallic nickel nanoparticles into a carbon matrix using wet milling. The resulting Ni / NiO / Cu@C composite exhibits a minimum reflection loss of -38.1 dB at a matching thickness of 3.2 mm (L. Huang, C. Chen, X. Huang, S. Ruan, Y.-J. Zeng, Compos. B Eng. 164 (2019) 583–589). However, without surface engineering, wet milling can lead to agglomeration of sample particles after carbothermal reduction due to excessive magnetic free ions and uneven distribution of magnetic components, which can 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 are 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 the 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. 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). This method also achieves its conversion into a magnetic porous carbon material, DUT-52@Co-doped MIL-88 composite, through a simple carbonization process. At a matching thickness of 2 mm, its minimum reflection loss exceeds -65.2 dB, and the effective absorption bandwidth covers 4.8 GHz. However, since epitaxial growth of MOFs or selective assembly of external MOFs onto internal MOFs can only be achieved through precise control of synthesis conditions and sophisticated 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 of 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: N,N-dimethylformamide and methanol are mixed at a volume ratio of (7-17) to methanol to obtain a mixed solvent; then, amino-p-phenylenedimethyl is added to the mixed solvent at a solid-liquid ratio of 1-2 g / L, and ultrasonically stirred for 10-35 minutes to obtain solution A.

[0010] Step 2: Mix the titanate and the solution A at a volume ratio of 1:(55-80) and stir for 0.5-2 hours to obtain a solution B; then place the solution B into a Teflon-lined reactor for a solvent thermal reaction; separate the solid and liquid, wash, and dry to obtain an 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: Dissolve the metal salt in aqueous ammonia at a solid-liquid ratio of 15 to 30 g / L and stir for 10 to 35 minutes to obtain solution D;

[0014] Step 5: mixing the solution D and the solution C at a volume ratio of 1:(10-20) of the solution D:the solution C, stirring at room temperature for 8-12 hours, separating the solid and the liquid, washing, and drying 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 stirring speed in step 4 and step 5 is the same as that 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) The present invention synthesizes NH2-MIL-125 template by solvent thermal reaction of titanate and 2-aminoterephthalic acid, adds the template to an aqueous solution of metal salt and dopamine, and then mixes it with dicyandiamide and undergoes carbothermal reduction reaction to obtain magnetic carbon tube modified TiN0.9 / NC electromagnetic wave absorber, simple to operate. The dopamine hydrochloride used in the present invention has a 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 amino terephthalic acid as organic ligand and titanium as central metal atom, and to obtain NH2-MIL-125 template by the coordination reaction between the organic ligand and metal atom. Magnetic carbon tube modified disc-shaped TiN is 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 magnetic carbon nanotubes and graphitization of carbon matrix resulted in the formation of 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 breaks away from the limitations of most MOFs on reaction conditions. 0.9 The magnetic units dispersed 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 effectively improves the impedance matching of the product, significantly improving the magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber effectively absorbs electromagnetic waves. According to the test: when the matching thickness is 1.9mm, the optimal reflection loss is -39.40dB; when the matching thickness is 1.5mm, the effective bandwidth reaches 4.3GHz.

[0026] 4) The general metal-polyphenol network coating strategy adopted in the present invention is to mix NH2-MIL-125 template powder with dopamine hydrochloride aqueous solution, then add metal salt dissolved in ammonia solution, separate solid and liquid, and dry to obtain 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 magnetic particles are used to catalyze the generation of hierarchical carbon nanotubes on the surface of the precursor 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, thereby improving the magnetic carbon tube modified TiN 0.9 / Effective bandwidth of NC electromagnetic wave absorber.

[0027] Therefore, the present invention is simple to operate, and the morphology and operation process are controllable. 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 TiN prepared from the precursor powder shown 0.9 / Transmission electron microscope 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 frequencies of 2 to 18 GHz and thicknesses of 1 to 3 mm. DETAILED DESCRIPTION

[0032] The present invention will be further described and explained below in conjunction with the accompanying drawings and specific embodiments. All the embodiments herein are only used to illustrate the present invention and are not intended to limit the scope of protection 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: N,N-dimethylformamide and methanol are mixed at a volume ratio of (7-17) to methanol to obtain a mixed solvent; then, amino-p-phenylenedimethyl is added to the mixed solvent at a solid-liquid ratio of 1-2 g / L, and ultrasonically stirred for 10-35 minutes to obtain solution A.

[0035] Step 2: Mix the titanate and the solution A at a volume ratio of 1:(55-80) and stir for 0.5-2 hours to obtain a solution B; then place the solution B into a Teflon-lined reactor for a solvent thermal reaction; separate the solid and liquid, wash, and dry to obtain an 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: Dissolve the metal salt in aqueous ammonia at a solid-liquid ratio of 15 to 30 g / L and stir for 10 to 35 minutes to obtain solution D;

[0039] Step 5: mixing the solution D and the solution C at a volume ratio of 1:(10-20) of the solution D:the solution C, stirring at room temperature for 8-12 hours, separating the solid and the liquid, washing, and drying 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] The details 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: N,N-dimethylformamide and methanol are mixed at a volume ratio of 7:1 to obtain a mixed solvent; then, amino-p-phenylenedimethyl is added to the mixed solvent at a solid-liquid ratio of 1.0 g / L, and ultrasonically stirred for 10 minutes to obtain solution A.

[0053] Step 2: Mix the titanate and the solution A at a volume ratio of 1:55, and stir for 0.5 to obtain a solution B; then place the solution B into a Teflon-lined reactor for a solvent thermal reaction; separate the solid and liquid, wash, and dry 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 a 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 aqueous ammonia 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 1:10, stirring at room temperature for 8 hours, separating the solid and 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 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 h.

[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: N,N-dimethylformamide and methanol are mixed at a volume ratio of 9:1 to obtain a mixed solvent; amino-p-phenylenedimethyl is added to the mixed solvent at a solid-liquid ratio of 1.2 g / L, and ultrasonically stirred 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 Teflon-lined reactor for solvent thermal 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, and mixing to obtain 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 minutes to obtain solution D.

[0071] Step 5: mixing the solution D and the solution C at a volume ratio of 1:12, stirring at room temperature for 9 hours, separating the solid and the liquid, washing, and drying 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 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 holding 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: N,N-dimethylformamide and methanol are mixed at a volume ratio of 11:1 to obtain a mixed solvent; then, amino-p-phenylenedimethyl is added to the mixed solvent at a solid-liquid ratio of 1.4 g / L, and ultrasonically stirred 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 Teflon-lined reactor for a 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, and mixing to obtain 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 15-30 g / L and stir for 20 minutes to obtain solution D.

[0085] Step 5: Mix the solution D and the solution C at a volume ratio of 1:14, stir at room temperature for 9.5 hours, separate the solid and 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 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 h.

[0089] The metal salt is cobalt chloride.

[0090] The heating rate of the carbon thermal reduction reaction is 7°C / min, and the holding 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: N,N-dimethylformamide and methanol are mixed at a volume ratio of 13:1 to obtain a mixed solvent; amino-p-phenylenedimethyl is added to the mixed solvent at a solid-liquid ratio of 1.6 g / L, and ultrasonically stirred 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 seconds to obtain a solution B; then place the solution B into a Teflon-lined reactor for a solvent thermal reaction; and perform solid-liquid separation, washing, and drying to obtain an 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: mixing the solution D and the solution C at a volume ratio of 1:16, stirring at room temperature for 10 hours, separating the solid from the liquid, washing, and drying 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 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 holding 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: N,N-dimethylformamide and methanol are mixed at a volume ratio of 15:1 to obtain a mixed solvent; amino-p-phenylenedimethyl is added to the mixed solvent at a solid-liquid ratio of 1.8 g / L, and ultrasonic stirring is performed 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 Teflon-lined reactor for a solvent thermal reaction; separate the solid and liquid, wash, and dry to obtain an 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, mixing, and obtaining 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 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 h.

[0117] The metal salt is nickel sulfate.

[0118] The heating rate of the carbon thermal reduction reaction is 9°C / min, and the holding 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: N,N-dimethylformamide and methanol are mixed at a volume ratio of 17:1 to obtain a mixed solvent; then, amino-p-phenylenedimethyl is added to the mixed solvent at a solid-liquid ratio of 2 g / L, and ultrasonically stirred 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 Teflon-lined reactor for a 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 minutes to obtain solution D.

[0127] Step 5: mixing the solution D and the solution C at a volume ratio of 1:20, stirring at room temperature for 12 hours, separating the solid from the liquid, washing, and drying 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 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 holding time is 5h.

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

[0134] Compared with the prior art, this embodiment has the following benefits:

[0135] 1) In this 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 embodiment has a mild reaction and will not damage the template morphology.

[0136] 2) This embodiment provides a magnetic carbon tube modified TiN 0.9 The preparation method of / NC electromagnetic wave absorber is to use amino terephthalic acid as organic ligand and titanium as central metal atom, and to obtain NH2-MIL-125 template by the coordination reaction between the organic ligand and metal atom. Magnetic carbon tube modified disc-shaped TiN is 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 magnetic carbon nanotubes and graphitization of carbon matrix resulted in the formation of 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 breaks away from the limitations of most MOFs on reaction conditions. 0.9 The magnetic units dispersed 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 effectively improves the impedance matching of the product, significantly improving the magnetic carbon tube modified TiN 0.9 / NC electromagnetic wave absorber effectively absorbs electromagnetic waves. According to the test: when the matching thickness is 1.9mm, the optimal reflection loss is -39.40dB; when the matching thickness is 1.5mm, the effective bandwidth reaches 4.3GHz.

[0138] 4) The general metal-polyphenol network coating strategy adopted in this embodiment is to mix the NH2-MIL-125 template powder with the dopamine hydrochloride aqueous solution, then add the metal salt dissolved in ammonia solution, 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 magnetic particles are used to catalyze the generation of hierarchical carbon nanotubes on the surface of the precursor 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, thereby improving 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 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 / Transmission electron microscope 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 frequencies of 2 to 18 GHz and thicknesses of 1 to 3 mm.

[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 cobalt hybrid polydopamine (Co-PDA) layer 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. By relying on the hydrocarbon gas such as ammonia 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 clear core-shell structure, with the core composed of TiN derived from NH2-MIL-125(Ti) 0.9 / NC composition, the shell is composed of nitrogen-doped carbon matrix derived from polydopamine. The lowest brightness part in the figure is 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. This 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 the / 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 a matching thickness of 1.5mm.

[0143] Therefore, the present embodiment is simple to operate, and the morphology and operation process are controllable. 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 1 to obtain a mixed solvent; then adding amino-p-xylylene glycol to the mixed solvent at a solid-liquid ratio of 1-2 g / L, and ultrasonically stirring for 10-35 minutes to obtain solution A; Step 2, mixing the titanate and the solution A at a volume ratio of titanate to solution A of 1:(55-80), stirring for 0.5-2 hours 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 a dopamine hydrochloride aqueous solution at a mass ratio of 1:(1-6) and mixing to obtain a solution C; The content of dopamine hydrochloride in the dopamine hydrochloride aqueous solution is 2 to 12 g / L; Step 4: Dissolve the metal salt in aqueous ammonia at a solid-liquid ratio of 15 to 30 g / L and stir for 10 to 35 minutes to obtain solution D; Step 5, mixing the solution D and the solution C at a volume ratio of 1:(10-20) of the solution D:the solution C, stirring at room temperature for 8-12 hours, separating the solid and 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 stirring speed in step 4 and step 5 is the same as that 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 the 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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