CN105862145B - A kind of nano combined absorbing material of shell core structure and preparation method thereof - Google Patents

Abstract

The invention relates to a shell-core structure nano-composite fiber wave-absorbing material and a preparation method thereof. The chemical formula of the wave-absorbing material is expressed as MFe ₁₂ O ₁₉ /BaTiO ₃ . The preparation method of the wave-absorbing material is: use M nitrate and ferric nitrate, polyvinylpyrrolidone and N,N-dimethylformamide in proportion to prepare a shell spinning solution; use barium acetate and butyl titanate as raw materials , Polyvinylpyrrolidone, ethanol, glacial acetic acid and water are prepared in proportion to the core spinning solution. Coaxial electrospinning of the shell spinning solution and the core spinning solution to obtain composite precursor fibers; calcining at 600-800°C to obtain shell-core structure MFe ₁₂ O ₁₉ /BaTiO ₃ nanocomposite fibers. The material has a minimum reflection loss of -23.64dB in the frequency range of 2-18GHz, and an effective frequency bandwidth of 1.36GHz. The preparation method has simple process, uniform and stable material, and high process controllability.

Description

A shell-core structure nanocomposite wave-absorbing material and its preparation method

technical field

The invention belongs to the field of chemical fiber wave-absorbing materials, and in particular relates to a shell-core structure nano-composite fiber wave-absorbing material and a preparation method thereof.

Background technique

Strontium ferrite (SrFe ₁₂ O ₁₉ ) is a ferromagnetic material, which has the advantages of high coercive force, large saturation magnetization and excellent chemical stability, and is widely used in magnetic recording devices, microwave absorbing materials and other fields.

Barium titanate (BaTiO ₃ ) is a ferroelectric material with high dielectric constant, excellent ferroelectric and piezoelectric properties, good chemical stability and low cost. Barium titanate material can be used to eliminate electromagnetic Pollution hazards, prevention of electromagnetic interference and exposure of electromagnetic information, etc., but they have shortcomings such as narrow absorption frequency band and low absorption intensity.

At present, it is difficult for a single material to meet the needs of different forms, and the development of nanomaterials tends to be diversified. For absorbing materials, ferrite absorbers (strontium ferrite, nickel ferrite, etc.) The combination of wave agents (barium titanate, silicon carbide, silicon nitride, etc.) can make the relative permeability of the composite material approximately equal to the relative permittivity, which can improve the wave-absorbing performance of the material. There are many methods for compounding commonly used materials, mainly including coaxial electrospinning, in-situ compounding, and blending. Among them, coaxial electrospinning technology can produce shell-core fibers, which has the characteristics of wide selection range, high composite efficiency, simple device, low cost, and high process controllability, and has gradually become one of the main ways to prepare nanocomposite fiber materials. one.

Patent CN104987056 mixes nickel-copper-zinc ferrite and secret-type perovskite ferroelectric ceramics by ball milling to obtain iron-ferroelectric composite materials, but the metal oxide particles are prone to self-agglomeration during the ball milling process, and the process is tedious.

Patent CN102093045 adopts uniform co-precipitation heterogeneous coating method to prepare core-shell structure barium titanate-barium ferrite composite powder material, but due to the different precipitation values of each metal, the reaction conditions are harsh.

In the literature Avinash B, Yiu WM, Rattikorn Y, Sujitra U.RSC Adv, 2014, 4:55217-55223, BaTiO ₃ , CoFe ₂ O ₄ composite precursor spinning solution was prepared by blending method, and the composite precursor spinning solution was prepared by electrospinning BaTiO ₃ , CoFe ₂ O ₄ compound, and detect its magnetoelectric properties. However, after characterization, it is found that there are uncertain substances in the composite product, and the purity of the product has a great influence on the final performance.

At present, there is no report on the preparation of shell-core structure ferrite/barium titanate nanocomposite fiber material by coaxial electrospinning and its application in the field of microwave absorption.

Contents of the invention

The object of the present invention is to provide a shell-core structure nanocomposite fiber absorbing material and a preparation method thereof, which is applied in the field of microwave absorbing.

The technical solution of the present invention is to prepare MFe ₁₂ O ₁₉ /BaTiO ₃ composite precursor fiber by coaxial electrospinning technology, and obtain composite nanofiber with shell-core structure through high-temperature calcination. The product prepared by the method is uniform and stable, the process is highly controllable, and no uncertain substance exists.

The shell-core structure nanocomposite fiber absorbing material provided by the present invention can be expressed as MFe ₁₂ O ₁₉ /BaTiO ₃ , where M ²⁺ represents divalent metal ions Sr ²⁺ , Ba ²⁺ , and Pb ²⁺ A: The nanocomposite fiber material has a shell-core structure, the diameter of the outer layer is 160-180nm, the diameter of the inner layer is 40-80nm, the fiber thickness is uniform, and the surface is smooth.

The preparation method of the above-mentioned shell-core structure nanocomposite fiber absorbing material, the specific steps are as follows:

A. At room temperature, mix nitrate, polyvinylpyrrolidone and N,N-dimethylformamide in proportion to prepare a shell solution, wherein the mass ratio of nitrate, polyvinylpyrrolidone and N,N-dimethylformamide is 1:(1-3):(10-15);

The mixed nitrate is a mixture of divalent nitrate M(NO ₃ ) ₂ and iron nitrate, wherein the molar ratio of M ²⁺ to Fe ³⁺ is 1:12, wherein M ²⁺ represents divalent metal ion Sr ²⁺ One of , Ba ²⁺ , Pb ²⁺ ;

B. Mix polyvinylpyrrolidone, ethanol, barium acetate, tetrabutyl titanate, glacial acetic acid and water in proportion to prepare a core layer solution, wherein polyvinylpyrrolidone, ethanol, barium acetate, tetrabutyl titanate, glacial acetic acid, water The mass ratio is 1: (8-12): (2-5): (2-5): (5-8): (1-3); and the molar ratio of barium acetate to tetrabutyl titanate is 1 :1;

The polyvinylpyrrolidone used in the shell solution and the core solution is an organic polymer spinning aid, and its molecular weight is 100000-130000;

C. Put the above shell solution in the coaxial electrospinning outer tube, and the core layer solution in the coaxial electrospinning inner tube as the outer layer and the inner layer of the coaxial electrospinning respectively; the outer tube uses a No. 16 needle, Inner tube No. 8 needle, electrospinning, the process parameters are: voltage 10-20kV, inner and outer layer advancing speed 0.3-2mL/h, receiving distance 10-20cm, rotating speed 200-500rpm, spinning temperature 25-40℃; Obtain composite precursor fiber;

D. Dry the composite precursor fiber obtained in step C at 50-100°C; then raise the temperature to 600-800°C for 1-5h at a heating rate of 1-5°C/min, and calcine at a cooling rate of 1-5°C/min After cooling down to room temperature, MFe ₁₂ O ₁₉ /BaTiO ₃ nanocomposite fibers were obtained.

The basic principle of the present invention is: the solution containing M ²⁺ and Fe ³⁺ and the solution containing Ba, Ti are used coaxial electrospinning technology to obtain MFe ₁₂ O ₁₉ /BaTiO ₃ composite precursor fibers, and then subjected to high temperature After heat treatment, MFe ₁₂ O ₁₉ /BaTiO ₃ composite nanofibers with a shell-core structure are obtained.

Compared with the prior art, the present invention has the following advantages and effects:

1. For the first time, MFe ₁₂ O ₁₉ /BaTiO ₃ nanocomposite fibers were prepared by spinning hair. This method is simple to operate, uniform and stable in material, and highly controllable in process.

2. Comparing the prepared MFe ₁₂ O ₁₉ /BaTiO ₃ nanocomposite fiber with the single SrFe ₁₂ O ₁₉ and BaTiO ₃ materials in absorbing performance, the composite material shows the advantages of "thin thickness, wide frequency band and strong absorption". Its absorbing performance is much better than single SrFe ₁₂ O ₁₉ and BaTiO ₃ materials.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) photograph of embodiment 1 composite fiber sample;

Fig. 2 is the scanning electron microscope (SEM) photo of embodiment 1 composite precursor fiber sample;

Fig. 3 is the transmission electron microscope (TEM) photograph of embodiment 1 composite fiber sample;

Fig. 4 is the scanning electron microscope (SEM) photo of embodiment 2 composite precursor fiber samples;

Fig. 5 is the transmission electron microscope (TEM) photograph of embodiment 3 composite fiber samples;

Fig. 6 is a comparison chart of the reflection loss between the composite fiber and the single SrFe ₁₂ O ₁₉ nanofiber in the comparative example.

specific implementation plan

Example 1

A. Weigh 0.021g of strontium nitrate, 0.484g of ferric nitrate, 0.75g of polyvinylpyrrolidone and 5mL of N,N-dimethylformamide, mix them at room temperature until completely dissolved, and obtain a uniform and stable shell solution;

B. Weigh 0.35g PVP, 3.5mL ethanol, 0.75g barium acetate, 1mL tetrabutyl titanate, 2mL glacial acetic acid and 1mL water, stir at room temperature until completely dissolved, and obtain a uniform and stable core layer solution.

C. Put 5mL of shell solution and 5mL of core solution in the coaxial electrospinning outer tube and inner tube respectively, as the coaxial electrospinning outer layer and inner layer spinning solution, using No. 16 outer spraying needle, No. 8 Inner spray needle, coaxial electrospinning, voltage 10kV, inner and outer layer advancing speed 0.3mL/h, receiving distance 15cm, rotating speed 1000rpm, spinning temperature 30℃, to obtain composite precursor fiber;

D. Put the composite precursor fiber obtained in step C into a drying oven at 100°C for 24 hours. After drying, put it into a muffle furnace with a heating rate of 1°C/min, a constant temperature of 750°C for 1h, and a cooling rate of 1°C/min. The temperature is lowered to 200° C. and cooled at room temperature to obtain SrFe ₁₂ O ₁₉ /BaTiO ₃ nanocomposite fibers.

The product is identified as SrFe ₁₂ O ₁₉ and BaTiO ₃ composite material by X-ray diffraction (Fig. 1), and the fiber diameter of the composite precursor is observed by SEM scanning electron microscope (Fig. 2), which is observed by TEM transmission electron microscope (Fig. 3). The product is shell-core structure, the diameter of the outer layer is 160-180nm, and the diameter of the inner layer is 40-80nm.

Example 2

A. Weigh 0.021g of strontium nitrate, 0.484g of iron nitrate, 1.5g of polyvinylpyrrolidone and 7.5mL of N,N-dimethylformamide, mix them at room temperature until completely dissolved, and obtain a uniform and stable shell solution;

B. Weigh 0.35g PVP, 3.5mL ethanol, 1.0g barium acetate, 1.3mL tetrabutyl titanate, 2.8mL glacial acetic acid and 1.3mL water, stir at room temperature until completely dissolved, and obtain a uniform and stable core layer solution.

C. Put 5mL of the shell solution and 5mL of the core solution in the coaxial electrospinning inner tube as the outer layer and the inner layer of the coaxial electrospinning respectively. Axial electrospinning, voltage 18kV, inner and outer layers advancing speed 1mL/h, receiving distance 10cm, rotating speed 1000rpm, spinning temperature 30℃, to obtain composite precursor fibers;

D. Put the composite precursor fiber obtained in step C into a drying oven at 100°C and dry for 24 hours. After drying, put it into a muffle furnace with a heating rate of 5°C/min, a constant temperature of 800°C for 1 hour, and a cooling rate of 5°C/min. The temperature is lowered to 200° C. and cooled at room temperature to obtain SrFe ₁₂ O ₁₉ /BaTiO ₃ nanocomposite fibers.

The composite precursor fiber diameter is 200nm as observed by the SEM scanning electron microscope (Fig. 4) of the product.

Example 3

A. Weigh 0.021g of strontium nitrate, 0.484g of ferric nitrate, 0.75g of polyvinylpyrrolidone and 5mL of N,N-dimethylformamide, mix them at room temperature until completely dissolved, and obtain a uniform and stable shell solution;

B. Weigh 0.35g PVP, 3.5mL ethanol, 0.75g barium acetate, 1mL tetrabutyl titanate, 2mL glacial acetic acid and 1mL water, stir at room temperature until completely dissolved, and obtain a uniform and stable core layer solution.

C. Put 5mL of the shell solution and 5mL of the core solution in the coaxial electrospinning inner tube as the outer layer and the inner layer of the coaxial electrospinning respectively. Axial electrospinning, voltage 20kV, inner and outer layers advancing speed 2mL/h, receiving distance 20cm, rotating speed 1000rpm, spinning temperature 30℃, to obtain composite precursor fibers;

D. Put the composite precursor fiber obtained in step C into a drying oven at 100°C for 24 hours. After drying, put it into a muffle furnace with a heating rate of 1°C/min, a constant temperature of 650°C for 1 hour, and a cooling rate of 1°C/min. The temperature is lowered to 200° C. and cooled at room temperature to obtain SrFe ₁₂ O ₁₉ /BaTiO ₃ nanocomposite fibers.

The shell-core structure of the product can be observed in the TEM transmission electron microscope image (Fig. 5), the diameter of the outer layer is 180-200nm, and the diameter of the inner layer is 50-90nm.

comparative example

The SrFe ₁₂ O ₁₉ /BaTiO ₃ nanocomposite fiber prepared in Example 1 was tested by a vector network analyzer, and a single SrFe ₁₂ O ₁₉ nanofiber was prepared by electrospinning for reflection loss comparison. Both of them use paraffin as the base material, mix the sample and paraffin according to the mass ratio of 3:2, and prepare the samples by the coaxial ring method, and the frequency band for measurement is 2-18 GHz. The reflection loss comparison between the composite fiber and the single SrFe ₁₂ O ₁₉ nanofiber is shown in Figure 6.

Table 1 lists the microwave absorption performance indicators of SrFe ₁₂ O ₁₉ /BaTiO ₃ nanocomposite fibers, SrFe ₁₂ O ₁₉ nanofibers and BaTiO ₃ materials. It can be seen from Table 1 that the microwave absorption of SrFe ₁₂ O ₁₉ /BaTiO ₃ nanocomposite fibers The performance is much better than that of single SrFe ₁₂ O ₁₉ and BaTiO ₃ materials. It is a high-performance wave-absorbing material with thin thickness, wide frequency band and strong absorption.

Table 1

sample matching thickness Effective Bandwidth Minimum reflection loss SrFe ₁₂ O ₁₉ /BaTiO ₃ nanocomposite fibers 2.2mm 1.36GHz -23.64dB SrFe ₁₂ O ₁₉ nanofibers 3.6mm 0.88GHz -11.69dB *BaTiO ₃ material 2mm 0 No effective absorption

*The data illustrating the BaTiO ₃ material comes from Qing YC, Zhou WC, Luo F, Zhu DM.J.Magn.Magn.Mater., 2011, 323:600-606.

Claims (1)

1. a kind of method of shell-core structure nano-composite fiber absorbing material, is comprised the following steps that：

A. at room temperature, by mixed nitrate, polyvinylpyrrolidone and DMF mixed preparing shell in proportion Solution, wherein nitrate, polyvinylpyrrolidone, DMF mass ratio are 1：1-3：10-15；

The mixed nitrate is divalence nitrate M (NO₃)₂, ferric nitrate mixture, wherein M²⁺With Fe³⁺Mol ratio be 1: 12, wherein M²⁺Represent bivalent metal ion Sr²⁺、Ba²⁺、Pb²⁺In one kind；

B. by polyvinylpyrrolidone, ethanol, barium acetate, butyl titanate, glacial acetic acid and water, mixed preparing sandwich layer is molten in proportion Liquid, wherein polyvinylpyrrolidone, ethanol, barium acetate, butyl titanate, glacial acetic acid, the mass ratio of water are 1：8-12：2-5：2- 5：5-8：1-3；And the mol ratio of barium acetate and butyl titanate is 1:1；

The molecular weight of polyvinylpyrrolidone described in step A and step B is 100000-130000；

C. above-mentioned shell solution is placed in coaxial electrostatic spinning outer tube, sandwich layer solution is placed in coaxial electrostatic spinning inner tube, made respectively For coaxial electrostatic spinning outer layer and internal layer；Outer tube carries out electrostatic spinning, its technological parameter using No. 8 No. 16 syringe needles, inner tube syringe needles For：Voltage 10-20kV, ectonexine fltting speed 0.3-2mL/h, receive distance 10-20cm, rotating speed 200-500rpm, spinning temperature 25-40 DEG C of degree；Obtain composite precursor fiber；

D. by the composite precursor fiber that step C is obtained in 50-100 DEG C of drying；Then risen to 1-5 DEG C/min heating rate 600-800 DEG C of roasting 1-5h, with the near room temperature of 1-5 DEG C/min rate of temperature fall, obtains MFe₁₂O₁₉/BaTiO₃Nano-composite fiber； Wherein M²⁺Represent bivalent metal ion Sr²⁺、Ba²⁺、Pb²⁺In one kind；The nanometer composite fiber material is shell-core structure, The a diameter of 160-180nm of its outer layer, a diameter of 40-80nm of internal layer, fiber thickness is uniform, and surface is smooth.