CN109112341B - Preparation method of hierarchical porous nickel-cobalt alloy-carbon composite bulk material with electromagnetic wave absorption performance - Google Patents

Abstract

The invention discloses a preparation method of a hierarchical porous nickel-cobalt alloy-carbon composite block material with electromagnetic wave absorption performance, which comprises the following steps: uniformly mixing deionized water and glycerol, adding polyacrylic acid, fully stirring until the polyacrylic acid is completely dispersed and dissolved, adding a nickel source and a cobalt source which are used as precursors, hydrolyzing, adding a gel accelerator, and stirring; and sealing the obtained sol, performing gelation treatment, drying the obtained block gel, placing the obtained block xerogel in an inert atmosphere tube furnace, heating to 400-1000 ℃, and preserving the temperature for 100-300 min to obtain the hierarchical porous nickel-cobalt alloy-carbon composite block material. The hierarchical porous nickel-cobalt alloy-carbon composite block material prepared by the method has stable wave-absorbing performance.

Description

Hierarchical porous nickel-cobalt alloy-carbon composite bulk material with electromagnetic wave absorption properties the preparation method of

technical field

The invention relates to a preparation method of a hierarchical porous nickel-cobalt alloy-carbon composite bulk material with electromagnetic wave absorption performance.

Background technique

In the process of human progress and social development, along with the development of electronic information technology and the popularization and application of electronic products, the living standard of human beings has been greatly improved, and the quality of life has been significantly improved. While these electronic products greatly facilitate people's daily life, they also bring a lot of trouble. This is because with the wide application of electronic products and electrical equipment such as mobile phones and computers, we will be radiated by electromagnetic waves of various frequencies and energies in our daily living environment. If the level of electromagnetic radiation is too high, it will exceed the level that the body and the environment can bear, resulting in electromagnetic pollution. Due to its seriousness, electromagnetic pollution has become a major emerging pollution source that threatens human life. A large number of medical cases show that excessive electromagnetic wave radiation will pose a threat to human health and affect the normal operation of people's nervous system, endocrine system, and their own circulatory system. Therefore, the development of electromagnetic wave materials that can absorb the frequency range that is commonly encountered has a wide range of applications in the civil field. Absorbing materials have become the main means of preventing and controlling electromagnetic pollution because they can efficiently absorb electromagnetic radiation and are more efficient and universal than electromagnetic shielding materials.

Nano-nickel-cobalt alloy materials have special surface magnetic and catalytic properties, and are widely used in the fields of high-density magnetic storage materials, high-quality magnetic fluid materials, electromagnetic shielding and wave absorbing materials.

The microwave absorbing properties of nickel-cobalt alloys are closely related to its chemical composition, microstructure, particle size and morphology. The smaller the particle size of the material grains, the larger the specific surface area, and the higher the absorption of electromagnetic waves.

At present, the traditional methods for preparing nickel-cobalt alloys mainly include mechanical alloying method, oxalate pyrolysis method, ultrasonic radiation method, hydrothermal reduction method, electrodeposition and other methods. Many, the morphology is difficult to be stably controlled, and the absorbing stability is difficult to solve.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a preparation method of a hierarchical porous nickel-cobalt alloy-carbon composite bulk material with electromagnetic wave absorption performance, which can be used in the field of wave absorption.

In order to solve the above-mentioned technical problems, the present invention provides a preparation method of a hierarchical porous nickel-cobalt alloy-carbon composite bulk material with electromagnetic wave absorption performance, comprising the following steps:

A), weigh 1.0～4.0mL of deionized water and add it to 1.0～3.0mL of glycerin, stir magnetically until the mixture is uniform;

B), add the polyacrylic acid of 1.0～4.0g to the liquid obtained in step A), fully stir until the polyacrylic acid is completely dispersed and dissolved;

C), add 0.5～3.0g of nickel source as precursor and 0.5～4.0g of cobalt source as precursor to the homogeneous solution obtained in step B), and perform hydrolysis under stirring, and the hydrolysis time is 3～5h (this time , the precursor can be completely hydrolyzed to generate the corresponding hydroxide);

D), add gel accelerator 1.0～2.5ml to the solution (clear and transparent solution) obtained in step C) and stir for 20～30min;

E), seal the sol obtained in step D) and place it at 40～60°C (in an oven) for gelation for 48±2h;

F), place the bulk gel obtained in step E) at 50～60 ℃ (in an oven) and dry for 48±2h;

G), placing the block xerogel obtained in step F) in an inert atmosphere tube furnace, heating up to 400-1000°C at a heating rate of 0.5-5°C/min, and keeping the temperature for 100-300min to obtain hierarchical porous nickel-cobalt Alloy-carbon composite bulk material.

As the improvement of the preparation method of the hierarchical porous nickel-cobalt alloy-carbon composite bulk material of the present invention:

The molecular weight of the polyacrylic acid adopted in step B) is 3000, 5000, 50000, 10000;

The nickel source in step C) is NiCl ₂ ·6H ₂ O, Ni(NO ₃ ) ₂ ·6H ₂ O, and the cobalt source is CoCl ₂ ·6H ₂ O, Co(NO ₃ ) ₂ ·6H ₂ O;

The gel accelerators used in step D) are propylene oxide, propylene oxide and formamide.

As a further improvement of the preparation method of the hierarchical porous nickel-cobalt alloy-carbon composite bulk material of the present invention: in step D), the gel accelerator is added in the form of dropwise addition, and the temperature of the control system during the dropwise addition process does not exceed 60 ° C .

In the present invention, a phase separation agent (polyacrylic acid), a solvent (deionized water, glycerol), a precursor, a gel accelerator and other raw materials are synthesized to prepare a porous block of nickel-cobalt composite hydroxide; after heat treatment in an inert atmosphere , the organic matter is decomposed into carbon under the action of high temperature, and the hydroxide is reduced to metal by the carbon formed by cracking, and finally a hierarchical porous nickel-cobalt alloy-carbon composite bulk material is obtained.

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

1) The introduction of micron-scale macropores by the phase separation agent can keep the nickel-cobalt alloy in a certain size, which is convenient for storage and transportation; the gel accelerator can slowly increase the pH value of the system and control the formation of the skeleton;

2) Under the premise of ensuring the alloy block, the composition change of any proportion of nickel and cobalt can be realized;

3) Heat treatment at different temperatures in an inert atmosphere, the particle size of the alloy can be reasonably controlled;

4), the micropores and mesopores formed after heat treatment combine with the macroporous structure produced by phase separation, forming a macropore-mesoporous-microporous hierarchical porous nickel-cobalt alloy bulk material;

5) The production process and equipment are simple and easy to industrialize;

6) The production process does not produce harmful substances.

To sum up, in the present invention, the wet chemical method of sol-gel with phase separation is used to ensure the uniformity of the nickel-cobalt alloy material. The size of the nickel-cobalt alloy can be controlled by the temperature of heat treatment. The pore size distribution and specific surface area depend on ratio of starting materials. Therefore, the prepared nickel-cobalt alloy has stable wave-absorbing properties.

Description of drawings

The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

Figure 1 shows the physical appearance (a) and scanning electron microscope images (b-f) of the porous silica bulk aerogel prepared in Example 1; (b)-(f) are the porous nickel-cobalt alloy bulk at 400 The pictures of the scanning electron microscope (at 50000 times) after heat treatment at ℃, 500℃, 600℃, 800℃, and 1000℃, it can be seen that there are continuous large pores (about 1 μm) in the block.

Figure 2 shows the microwave absorbing properties of the porous nickel-cobalt alloy prepared in Example 1, of which the 800-degree heat treatment has the best absorbing properties, the minimum reflection loss is -19dB, and the effective absorption (dB less than -10dB) bandwidth reaches 2GHz.

3 is the nitrogen adsorption and desorption curve (upper image) and the BJH pore size distribution curve (lower image) of the porous nickel-cobalt alloy bulk prepared in Example 2. The BET calculation results show that the specific surface area of the porous nickel-cobalt alloy bulk heat-treated at 600℃ can reach 167m ² ·g ^-1 .

Fig. 4 is the XRD pattern of the porous nickel-cobalt alloy bulk prepared in Example 3. The peak position of the (111) crystal plane of the nickel-cobalt alloy is between pure cobalt and pure nickel, indicating that under 800 ℃ heat treatment, nickel can be formed Cobalt alloy. In the figure, from top to bottom, they are pure Co, Ni-Co, and pure Ni.

Detailed ways

The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

In step D) of the following case, propylene oxide is added in the form of dropwise addition, and the temperature of the control system does not exceed 60°C during the dropwise addition.

Embodiment 1. A method for preparing a hierarchical porous nickel-cobalt alloy-carbon composite bulk material, the following steps are performed in sequence:

A), weigh 1.2mL of deionized water and add it to 2.4mL of glycerol, stir magnetically until the two are completely mixed evenly;

B), add the polyacrylic acid (50000) of 4.0g to the obtained liquid of step A), fully stir until the polyacrylic acid is completely dispersed and dissolved;

C), adding nickel source (NiCl ₂ ·6H ₂ O) 0.713g and cobalt source (CoCl ₂ ·6H ₂ O) 1.426g as precursors to the homogeneous solution obtained in step B), and performing hydrolysis under stirring for 5h, this When the precursor is completely hydrolyzed.

D), add propylene oxide 1.76ml to the clear transparent solution obtained in step C) and stir for 20～30min;

E), seal the sol obtained in step D) and place it in a 40～60 ℃ oven for gelation for 48h;

F), place the bulk gel obtained in step E) in an oven at 50～60°C and dry for 48h;

G), place the block xerogel obtained in step F) in an inert atmosphere tube furnace, and heat up to the following 5 temperature points at a heating rate of 2.5°C/min: 400°C, 500°C, 600°C, 800°C Or 1000 ℃, heat preservation for 100min, so as to obtain 5 kinds of hierarchical porous nickel-cobalt alloy-carbon composite materials correspondingly.

Embodiment 2, a preparation method of a hierarchical porous nickel-cobalt alloy-carbon composite bulk material, the following steps are performed in sequence:

A), weigh 2.4mL of deionized water and add it to 1.2mL of glycerol, stir magnetically until the solution is completely mixed;

B), in step A) gained liquid, add the polyacrylic acid (50000) of 4.0g, fully stir until the polyacrylic acid is completely dispersed and dissolved;

C), adding precursor nickel source (NiCl ₂ ·6H ₂ O) 0.713g, cobalt source (CoCl ₂ ·6H ₂ O) 1.426g to the homogeneous solution obtained in step B), stirring for 5h until the precursor is completely hydrolyzed;

D), add propylene oxide 1.76ml to the clear transparent solution obtained in step C) and stir for 20～30min;

E), seal the sol obtained in step D) and place it in a 40～60 ℃ oven for gelation for 48h;

F), place the bulk gel obtained in step E) in an oven at 50～60°C and dry for 48h;

G), placing the bulk xerogel obtained in step F) in an inert atmosphere tube furnace, and heating up to the following 4 temperature points at a heating rate of 2.5 °C/min: 400 °C, 600 °C, 800 °C or 1000 °C, The temperature was kept for 100 min, and 4 kinds of hierarchical porous nickel-cobalt alloy-carbon composite materials were prepared accordingly.

Embodiment 3, a preparation method of a hierarchical porous nickel-cobalt alloy-carbon composite bulk material, the following steps are performed in sequence:

A), weigh 1.2mL of deionized water and add it to 2.4mL of glycerol, stir magnetically until the solution is completely mixed;

B), in step A) gained liquid, add the polyacrylic acid (50000) of 4.0g, fully stir until the polyacrylic acid is completely dispersed and dissolved;

C), add precursor nickel source (NiCl ₂ ·6H ₂ O) 2.16g, nickel source (NiCl ₂ ·6H ₂ O) 0.713g, cobalt source (CoCl ₂ ·6H ₂ O) to the homogeneous solution obtained in step B) ) 1.426g, cobalt source (CoCl ₂ ·6H ₂ O) 2.16g was stirred for 5h until the precursor was completely hydrolyzed;

D), add propylene oxide 1.76ml to the clear transparent solution obtained in step C) and stir for 20～30min;

E), seal the sol obtained in step D) and place it in a 40～60 ℃ oven for gelation for 48h;

F), place the bulk gel obtained in step E) in an oven at 50～60°C and dry for 48h;

G), the block xerogel obtained in step F) was placed in an inert atmosphere tube furnace, heated to 800°C at a heating rate of 2.5°C/min, and kept for 100min to obtain a hierarchical porous nickel-cobalt alloy-carbon composite material.

Finally, it should also be noted that the above enumeration is only a few specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and many modifications are possible. All deformations that those of ordinary skill in the art can directly derive or associate from the disclosure of the present invention shall be considered as the protection scope of the present invention.

Claims (5)

1. The preparation method of the hierarchical porous nickel-cobalt alloy-carbon composite block material with electromagnetic wave absorption performance is characterized by comprising the following steps:

A) weighing 1.0-4.0 mL of deionized water, adding into 1.0-3.0 mL of glycerol, and magnetically stirring until the mixture is uniformly mixed;

B) adding 1.0-4.0 g of polyacrylic acid into the solution obtained in the step A), and fully stirring until the polyacrylic acid is completely dispersed and dissolved;

C) adding 0.5-3 g of nickel source serving as a precursor and 0.5-4.0 g of cobalt source serving as a precursor into the uniform solution obtained in the step B), and hydrolyzing for 3-5 h under stirring;

D) adding 1.0-2.5 ml of gel accelerator into the solution obtained in the step C), and stirring for 20-30 min;

E) sealing the sol obtained in the step D), and then gelatinizing the sol at the temperature of 40-60 ℃ for 48 +/-2 hours;

F) drying the block gel obtained in the step E) at 50-60 ℃ for 48 +/-2 hours;

G) and F) placing the block xerogel obtained in the step F) in an inert atmosphere tube furnace, heating to 400-1000 ℃ at a heating rate of 0.5-5 ℃/min, and preserving heat for 100-300 min to obtain the hierarchical porous nickel-cobalt alloy-carbon composite block material.

2. The method of making a hierarchical porous nickel-cobalt alloy-carbon composite bulk material of claim 1, wherein: the molecular weight of polyacrylic acid adopted in the step B) is 3000, 5000, 50000 and 10000.

3. The method of making a hierarchical porous nickel-cobalt alloy-carbon composite bulk material of claim 2, wherein: the nickel source of the step C) is NiCl₂·6H₂O、Ni(NO₃)₂·6H₂O, cobalt source is CoCl₂·6H₂O、Co(NO₃)₂·6H₂O。

4. The method of making a hierarchical porous nickel-cobalt alloy-carbon composite bulk material of claim 3, wherein: the gel accelerator used in step D) is propylene oxide, formamide.

5. The method of making a hierarchical porous nickel-cobalt alloy-carbon composite bulk material of claim 4, wherein: in the step D), the gel accelerator is added in a dropwise manner, and the temperature of the system is controlled not to exceed 60 ℃ in the dropwise adding process.

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