CN110577820B - A kind of porous structure Ni/NiO-C composite material and its preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of electromagnetic wave absorbing materials, and discloses a porous structure Ni/NiO-C composite material and a preparation method and application thereof. The composite material is composed of carbon balls and Ni/NiO composite particles attached to the surface thereof, and micropores are distributed on the surface of the carbon balls, and the Ni/NiO composite particles are in flower-like configuration. Preparation method: add glucose, water-soluble nickel salt, and urea into water, and stir evenly; the temperature of the obtained solution is controlled at 170-190° C. to stand for hydrothermal reaction for 15-18 h; Wash and dry to obtain the precursor; in an inert or protective atmosphere, the precursor is calcined at a temperature of 400-800 °C for 2-3 h, and the obtained calcined product is a porous structure Ni/NiO-C composite material. The prepared Ni/NiO-C composites have better electromagnetic wave absorption properties, and can be widely used as electromagnetic wave absorption materials in the corresponding electromagnetic protection and microwave stealth fields.

Description

A kind of porous structure Ni/NiO-C composite material and its preparation method and application

technical field

The invention belongs to the technical field of electromagnetic wave absorbing materials, and particularly relates to a porous structure Ni/NiO-C composite material and a preparation method and application thereof.

Background technique

Over the past few decades, the rapid development of telecommunications, digital industry and electronic equipment has resulted in excessive electromagnetic radiation. EMI is classified as the pollution of human living space and becomes an important concern of physical health, biological systems, information security and normal operation of electronic equipment. Therefore, some advanced level and efficient electromagnetic wave absorbing materials must be developed to eliminate electromagnetic hazards and electromagnetic interference problems. The efficiency of electromagnetic absorption mainly depends on the inherent electromagnetic properties of microwave absorbing materials. Among countless microwave absorbing materials, carbonaceous microwave absorbers have shown many advantages, including chemical stability, tunable chemical and physical properties, etc. It has been reported that various nanocarbons, such as carbon fibers, carbon nanotubes, carbon nanocoils, carbon nanowires, carbon spheres, graphene, and reduced graphene oxide, have been successfully prepared, and the corresponding microwave absorption properties have been investigated. However, on the basis of impedance matching, carbon materials with relatively high electrical conductivity and dielectric loss alone are detrimental to impedance matching and usually result in microwave reflection at the surface rather than absorption.

The soft magnetic metal Ni is more attractive for electromagnetic wave absorption due to its relatively high magnetization compared to oxides and is relatively stable compared to the easy oxidation of iron and cobalt. The high saturation magnetization of magnetic metals leads to a high Snoek limit and permeability in the high frequency region, which leads to strong magnetic losses. However, metallic Ni always has a high density and is easily oxidized, which not only increases the weight of the electromagnetic wave absorbing film, but also causes a decrease in magnetization. Therefore, carbon composites with protected magnetic metal Ni are expected to be an effective way to improve impedance matching and oxidation resistance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a porous structure Ni/NiO-C composite material and its preparation method and application.

To achieve the above object, the technical scheme adopted by the present invention is as follows:

A porous structure Ni/NiO-C composite material, the composite material is composed of carbon balls and Ni/NiO composite particles attached to the surface thereof, and the surface of the carbon balls is distributed with micropores, and the Ni/NiO composite particles are flower-like structures. type.

The preparation method includes the following steps:

(1), add glucose, water-soluble nickel salt, urea into water, stir; Wherein, in mole-volume ratio, water-soluble cobalt salt is calculated with the nickel actually provided by it, glucose: water-soluble nickel salt: urea: water =(5~25)mmol:(1~5)mmol:(5~30)mmol:(20~200)mL;

(2), control the temperature of the solution obtained in step (1) at 170-190 ℃ and let it stand for hydrothermal reaction for 15-18 h;

(3) After the hydrothermal reaction is completed, take out the precipitate, wash and dry to obtain the precursor;

(4) In an inert or protective atmosphere, the precursor obtained in step (3) is calcined at a temperature of 400-800 °C for 2-3 h, and the obtained calcined product is a porous structure Ni/NiO-C composite material.

Preferably, in step (1), glucose is first added to water, and then water-soluble nickel salt and urea are added in sequence.

Preferably, in the step (3), during cleaning, firstly, distilled water is used for several times, and then anhydrous ethanol is used for several times.

Preferably, in step (3), the drying temperature is 50-60 °C, and the drying time is 8-12 h.

Preferably, in step (4), the temperature is raised to the calcination temperature at a heating rate of 5-10 °C/min.

The application of the porous structure Ni/NiO-C composite material as an electromagnetic wave absorbing material.

Beneficial effects:

(1) In the present invention, the precursor is first prepared by simple and clean hydrothermal reaction, and then calcined in an inert atmosphere to obtain a Ni/NiO-C composite material with a porous structure, which avoids the need for multi-step synthesis of the previous nanocomposite materials. At the same time, the porous structure Ni/NiO-C composite material prepared by the present invention has the advantages of strong wave absorbing ability and low density;

(2) The porous structure Ni/NiO-C composite material prepared by the present invention contains more functional groups such as C-O, O-C=O, Ni-O, etc., and a large number of defects, and these functional groups and defects are in the electromagnetic field. As the polarization center, it can effectively lose electromagnetic waves; meanwhile, Ni/NiO nanoparticles have larger specific surface area and more concentrated micropore distribution, which play an important role in improving electromagnetic wave absorption active sites and electron transfer efficiency; In addition, Ni/NiO-C composites contain multiple inhomogeneous interfaces, including C-air, C-Ni, and C-NiO, which will generate strong interfacial polarization, and the prepared Ni/NiO-C composites have better electromagnetic wave absorption It can be widely used as electromagnetic wave absorbing material in corresponding electromagnetic protection and microwave stealth fields.

Description of drawings

Figure 1: XRD pattern of N-800 sample.

Figure 2: SEM image of N-800 sample.

Figure 3: TEM image and line scan results of N-800 sample: (a) TEM image, (b) high-angle annular dark field (HAADF) image, (c) line scan results of the straight line in (b).

Figure 4: XRD pattern of the control sample.

Figure 5: SEM image of the control sample.

Figure 6: Schematic diagram of reflection loss of Ni/NiO-C/PVDF matrix composites with 2 wt % content of four samples when the thickness of the absorber layer is 3.6 mm: N-400 sample, N-500 sample, N-600 Samples and N-800 samples.

Detailed ways

The following examples only illustrate the present invention in further detail, but do not constitute any limitation to the present invention; the materials used in the following examples, unless otherwise specified, are purchased from conventional chemical reagent companies and raw material suppliers.

Example 1

A preparation method of a porous structure Ni/NiO-C composite material, comprising the following steps:

(1) Use an analytical balance to weigh 15 mmol glucose, 2 mmol NiSO ₄ ·6H ₂ O, and 10 mmol urea;

(2) Measure 60 mL of deionized water into a glass beaker;

(3) First, slowly add glucose into the glass beaker, then slowly add NiSO ₄ ·6H ₂ O and urea in sequence, and stir magnetically for 1 h;

(4) Transfer the homogeneously mixed solution from the glass beaker to a polytetrafluoroethylene autoclave, and then react in a drying oven at 190 °C for 15 h;

(5) After the reaction, the black precipitate was taken out from the reactor, and washed three times with distilled water and then with anhydrous ethanol for three times, and then dried in a drying oven at 60 °C for 9 h to obtain the precursor;

(6) Under nitrogen atmosphere in a tube furnace, put the obtained precursor in a small porcelain boat, heat it up to a calcination temperature of 400 °C at a heating rate of 5 °C/min, and keep it for 2 h, and mark the obtained calcined product as For the N-400 sample.

Example 2

The difference from Example 1 is that the calcination temperature in step (6) is changed to 500° C., and the obtained calcined product is designated as N-500 sample;

Example 3

The difference from Example 1 is that the calcination temperature in step (6) is changed to 600° C., and the obtained calcined product is labeled as N-600 sample; the others are the same as in Example 1.

Example 4

The difference from Example 1 is that the calcination temperature in step (6) is changed to 800° C., and the obtained calcined product is labeled as N-800 sample; the others are the same as in Example 1.

Figure 1 is the XRD pattern of the N-800 sample. It can be seen from Fig. 1 that there are only Ni, NiO and C components in the product obtained by the present invention, and no other impurity peaks appear.

Figure 2 is an SEM image of the N-800 sample. Figure 3 shows the TEM image and line scan results of the N-800 sample. It can be seen from Fig. 2 and Fig. 3 that the composite material of the product obtained by the present invention is composed of carbon spheres and Ni/NiO composite particles attached to the surface thereof, and micropores are distributed on the surface of the carbon spheres, and the Ni/NiO composite particles are flower-like structures. The size of carbon spheres is 1-6 microns, the pore size of micropores is 2-12 nm, and the size of Ni/NiO composite particles is 0.2-1.2 microns. The formation of micropores is attributed to the formation of Ni/NiO composite particles and the consumption of carbon materials during carbon heat treatment. Because the resulting product has a porous structure, it is characterized by low density and high specific surface area.

Control example

The difference from Example 4 is that urea is not added, and the others are the same as Example 4.

The XRD pattern and SEM pattern of the product obtained in this comparative example are shown in Fig. 4 and Fig. 5, respectively. The XRD pattern shows that the sample without urea is displayed on the PDF card, which does not match the crystallization peaks of Ni and NiO, indicating that the desired product cannot be obtained without the addition of urea; at the same time, the SEM image shows that the samples have different shapes and sizes, and the agglomeration and melting are serious. The presence of Ni/NiO composite particles was not observed, and the porous structure was not shown.

Electromagnetic absorption characteristic test

According to the mass ratio, sample:PVDF=2:98, respectively weigh the N-400 sample, N-500 sample, N-600 sample and N-800 sample obtained in Example 1-4, dissolve PVDF with DMF, and then mix the sample with After the DMF solution of PVDF was mixed uniformly, it was dried into a solid state to obtain a 2 wt% Ni/NiO-C/PVDF matrix composite. Using Matlab software, the reflection loss of Ni/NiO-C/PVDF matrix composites was calculated. The results are shown in Figure 6. It can be seen that under nitrogen conditions, the sample (N-800) calcined at 800 ℃, when the thickness of the absorbing layer is At 3.6 mm, the minimum RL value is -34.7 dB at 5.8 GHz.

Claims (7)

1. a porous structure Ni/NiO-C composite material, it is characterized in that: described composite material is made up of carbon ball and the Ni/NiO composite particle that is attached to its surface, and carbon ball surface is distributed with micropores, Ni/NiO The composite particles have a flower-like configuration. 2. a preparation method of porous structure Ni/NiO-C composite material, is characterized in that, comprises the following steps: (1), add glucose, water-soluble nickel salt, urea into water, stir; Wherein, in mole-volume ratio, water-soluble nickel salt is calculated with the nickel that it actually provides, glucose: water-soluble nickel salt: urea: water =15 mmol: 2 mmol: 10 mmol: 60 mL; (2), controlling the temperature of the solution obtained in step (1) to stand for hydrothermal reaction at 180 °C for 15 h; (3) After the hydrothermal reaction is completed, take out the precipitate, wash and dry to obtain the precursor; (4) In an inert or protective atmosphere, the precursor obtained in step (3) is calcined at 800 °C for 2 h under temperature control, and the obtained calcined product is a porous Ni/NiO-C composite material. 3 . The method for preparing a porous Ni/NiO-C composite material according to claim 2 , wherein in step (1), glucose is first added to water, and then water-soluble nickel salt and urea are added in sequence. 4 . 4 . The preparation method of the porous structure Ni/NiO-C composite material according to claim 2 , wherein in step (3), during cleaning, first, use distilled water for several times, and then use anhydrous ethanol for several times. 5 . The method for preparing a porous Ni/NiO-C composite material according to claim 2 , wherein in step (3), the drying temperature is 50-60° C. and the drying time is 8-12 h. 6 . 6 . The method for preparing a porous Ni/NiO-C composite material according to claim 2 , wherein in step (4), the temperature is raised to the calcination temperature at a heating rate of 5-10° C./min. 7 . 7. Application of the porous structure Ni/NiO-C composite material as claimed in claim 1 as an electromagnetic wave absorbing material.

Images