CN100355699C - Process for making graphite powder with electromagnetic property - Google Patents

Abstract

The invention discloses a preparation method of graphite powder with electromagnetic properties. In the method, graphite solution and Fe ²⁺ /Fe ³⁺ mixed solution are uniformly mixed at first, and then the mixed solution is poured into a three-neck flask placed in a constant temperature water bath , and then add lye to the mixed solution until the reacted solution is alkaline, then move the reacted solution to another higher constant temperature water bath for crystallization for a period of time, and finally wash and dry the sample to obtain Graphite powder with attached magnetic nanoparticles. The preparation process of the method is simple, the production cost is low, and it is suitable for industrial production. The prepared magnetic graphite powder has good electrical conductivity and magnetic conductivity, and is an excellent raw material for electromagnetic shielding materials. There are good application prospects in other fields.

Description

A preparation method of graphite powder with electromagnetic properties

technical field

The invention belongs to the technical field of powder preparation, and more specifically relates to a method for preparing graphite powder used for electromagnetic shielding and having conductivity and magnetic conduction.

Background technique

With the development of the electronics industry and science and technology, the widespread use of various electronic and electrical equipment and electronic products, the electromagnetic energy radiated by electromagnetic waves is gradually increasing at a rate of 7%-14% per year, and the pollution of the electromagnetic environment is becoming more and more serious. Another On the one hand, electronic products and electronic and electrical equipment are developing in the direction of digitalization, high integration, and miniaturization of signal levels. They are more sensitive to the external electromagnetic environment and are prone to malfunction, image distortion, and interference with radio communications due to external electromagnetic interference. etc. have brought serious impact on people's production and life. Electromagnetic shielding is an important means of anti-electromagnetic interference. Traditional electromagnetic shielding materials are mainly surface conductive shielding materials and filled composite shielding materials. Surface conductive shielding materials are prepared by mixing conductive fillers such as metal powder and carbon black with polymer materials. Formation or through physical and chemical methods to obtain a thin conductive metal layer on the surface of the insulating material to achieve the shielding effect. Filled composite shielding material is an electromagnetic shielding material processed by injection or extrusion molding of polymer matrix and conductive filler. Although these traditional shielding materials can achieve the shielding effect, their shielding performance is average, and the shielding frequency band is very narrow, thus limiting the application of these shielding materials. According to the theory of electromagnetic shielding, electromagnetic shielding materials with excellent performance should have high electrical conductivity and magnetic permeability. Moreover, while emphasizing the shielding frequency bandwidth and high shielding performance of new shielding materials, the development of lightweight shielding materials is now the focus of research in this field.

Graphite is an excellent conductive filler, especially the expanded graphite prepared by intercalation of graphite has high electrical conductivity and large surface area, which endows expanded graphite with good electromagnetic shielding performance. DDLChung uses expanded graphite through high-pressure pressed graphite gasket to have good electromagnetic shielding effect, and the material also has excellent thermal stability, chemical stability and low thermal expansion coefficient, but the shielding material thus manufactured is diamagnetic, so , the shielding bandwidth of this material is very limited. In order to improve the deficiencies of graphite-based shielding materials in this respect, many researchers consider adding magnetic substances to graphite to improve the shielding performance of graphite-based shielding materials. Peng Junfang mixed expanded graphite with Fe(OH) ₃ , and then rapidly expanded it at high temperature to prepare a graphite-based composite material containing ferrimagnetic iron oxide. The material has conductivity and ferrimagnetism, and its shielding performance is excellent. In particular, the shielding bandwidth of this material has been greatly improved compared with pure graphite, but because the magnetic particles are ferrimagnetic and the particle size is large, it is difficult to achieve the ideal shielding effect.

Contents of the invention

The object of the present invention is to provide a preparation method of graphite powder with electromagnetic properties. The graphite-based shielding material made of graphite powder made by the method of the present invention has better shielding performance and ideal shielding bandwidth.

The technical scheme of the present invention is such: a kind of preparation method of graphite powder with electromagnetic properties, realizes by following steps:

1. Take a certain amount of graphite and disperse it in the liquid medium to form a graphite dispersion, wherein the weight ratio of graphite to the liquid medium is 1:10-1000;

Two, weigh ferrous salt and ferric salt according to the molar ratio of 2.0:1-5.5:1, and prepare a mixed solution of iron ions with a concentration of 0.2-0.8M;

3. After mixing the above-mentioned graphite dispersion and iron ion mixed solution at a volume ratio of 1:1-6:1, place it in a constant temperature water bath at 29°C-31°C, and stir for 10-20min to make it mix Uniform;

Four, add concentration to the mixed solution of step 3 gained and be the lye of 0.3-0.6M, and keep stirring, until the solution is alkaline;

5. Move the solution obtained in step 4 to a constant temperature water bath at 35°C-50°C for crystallization for 1-3 hours;

6. Wash the crystallized solution until the washing solution is neutral, and finally use magnetic separation technology to separate the precipitate in the solution, dry and pulverize to obtain graphite powder with magnetic Fe ₃ O ₄ nanoparticles attached.

The liquid medium in the above step 1 is an organic or inorganic solution that easily dissolves graphite.

In the above step 2, the divalent iron salt and the ferric salt are iron salts that do not contain strong oxidizing acid radicals.

The above-mentioned divalent iron salt is FeCl ₂ or FeSO ₄ .

The above ferric salt is FeCl ₃ or Fe ₂ (SO4) ₃ .

In the above step 4, the lye added to the mixed solution is medium strong lye.

After adopting the above scheme, the graphite powder prepared by the present invention has the characteristics of electric conduction and magnetic conduction, which makes up for the deficiency that the traditional graphite has only electric conductivity but no magnetism; moreover, the preparation process of the present invention is simple and easy for industrial production. Using the graphite powder prepared by the present invention to prepare electromagnetic shielding materials has the characteristics of low density, light weight, and good shielding effect in an ultra-wide frequency range, and can be applied to broadband electromagnetic shielding materials in the fields of electromagnetic interference, electromagnetic pollution, communication and information technology. It has good application prospects in the fields of electronics, electricity, communication, aviation and military.

Description of drawings

Fig. 1 is a scanning electron microscope image of Fe ₃ O ₄ /NG nanocomposite particles prepared by the method of the present invention.

Fig. 2 is an energy spectrum diagram of Fe ₃ O ₄ /NG nanocomposite particles prepared by the method of the present invention.

Fig. 3 is the hysteresis curve of Fe ₃ O ₄ /NG nanocomposite particles prepared by the method of the present invention.

Detailed ways

A kind of preparation method of graphite powder with electromagnetic properties of the present invention can be realized by following several embodiments:

Example 1:

1) Weigh 0.5000g of 2000 mesh graphite to prepare 50ml of graphite alcohol dispersion; weigh 0.8341g of FeSO ₄ .6H ₂ O and 0.1622g of FeCl ₃ .7H ₂ O to prepare 50ml of iron salt mixed solution.

2) Pour the above two solutions into an open three-necked flask, place them in a water bath at 30° C., and stir with a stirrer for 15 minutes to make them evenly mixed.

3) Add dropwise a NaOH solution with a concentration of 0.4 mol/l to the mixed solution obtained in step 2), and continuously stir the solution while adding the NaOH solution until the pH of the solution=12.

4) Transfer the solution obtained in step 3) to a water bath at 50° C. for crystallization for 2 hours, and then wash the precipitate obtained after crystallization with distilled water for several times until the pH of the washing solution is 7.

5) Using magnetic separation technology to separate the precipitate, drying the separated precipitate with a vacuum drying oven, and pulverizing to obtain 2000-mesh graphite powder with Fe ₃ O ₄ magnetic nanoparticles attached.

Example 2:

1) Weigh 0.5000g of 7000 mesh graphite to prepare 50ml of graphite alcohol dispersion, and weigh 0.8341g of FeSO ₄ .6H ₂ O and 0.1622g of FeCl ₃ .7H ₂ O to prepare 50ml of iron salt mixed solution.

2) Pour the above two solutions into an open three-necked flask, place them in a water bath at 30° C., and stir with a stirrer for 15 minutes to make them evenly mixed.

3) Add dropwise NaOH solution with a concentration of 0.5 mol/l to the mixed solution obtained in step 2), and keep stirring the solution while adding dropwise the NaOH solution until the pH of the solution=13.

4) Transfer the solution obtained in step 3) to a water bath at 35° C. for crystallization for 2 hours, and then wash the precipitate obtained after crystallization with distilled water for several times until the pH of the washing solution is 7.

5) Using magnetic separation technology to separate the precipitate, drying the separated precipitate with a vacuum drying oven, and pulverizing to obtain 7000-mesh graphite powder with Fe ₃ O ₄ magnetic nanoparticles attached.

Example 3:

1) Weigh 0.5000g of nano-graphite to prepare 50ml of graphite alcohol dispersion, and weigh 0.8341g of FeSO ₄ .6H ₂ O and 0.1622g of FeCl ₃ .7H ₂ O to prepare 50ml of iron salt mixed solution.

2) Pour the above two solutions into an open three-necked flask, place them in a 30°C water bath, and stir with a stirrer for 1 minute to make them evenly mixed.

3) Add dropwise a NaOH solution with a concentration of 0.4 mol/l to the mixed solution obtained in step 2), and continuously stir the solution while adding the NaOH solution until the pH of the solution=12.

4) Transfer the solution obtained in step 3) to a water bath at 50° C. for crystallization for 2 hours, and then wash the precipitate obtained after crystallization with distilled water for several times until the pH of the washing solution is 7.

5) Using magnetic separation technology to separate the precipitate, drying the separated precipitate with a vacuum drying oven, and pulverizing to obtain nano-graphite powder with Fe ₃ O ₄ magnetic nanoparticles attached.

Example 4:

1) Weigh 0.5000g of nano-graphite to prepare 50ml of graphite alcohol dispersion, and weigh 0.8341g of FeSO ₄ .6H ₂ O and 0.1622g of FeCl ₃ .7H ₂ O to prepare 50ml of iron salt mixed solution.

2) Pour the above two solutions into an open three-necked flask, place them in a water bath at 30° C., and stir with a stirrer for 15 minutes to make them evenly mixed.

3) Add dropwise NH ₃ .H ₂ O solution with a concentration of 0.5 mol/l to the mixed solution obtained in step 2), and keep stirring the solution while adding dropwise NH ₃ .H ₂ O solution until the pH of the solution is =12.

4) Transfer the solution obtained in step 3) to a water bath at 50° C. for crystallization for 1 hour, and then wash the precipitate obtained after crystallization with distilled water for several times until the pH of the washing solution is 7.

5) Using magnetic separation technology to separate the precipitate, drying the separated precipitate with a vacuum drying oven, and pulverizing to obtain nano-graphite powder with Fe ₃ O ₄ magnetic nanoparticles attached.

A _preparation method of graphite powder with electromagnetic properties of the present invention can be realized through the following several embodiments: the characteristics of the graphite powder attached with _Fe3O4 magnetic nanoparticles are as shown in Figures 1, 2 and 3 As shown, it has the characteristics of electrical conductivity and magnetic conductivity, and the use of it to prepare electromagnetic shielding materials has the characteristics of low density, light weight, and good shielding effect in the ultra-wide frequency range.

Claims (6)

1, a kind of preparation method with powdered graphite of electromagnetic property is characterized in that: realize as follows:

One, take by weighing a certain amount of graphite and be scattered in the liquid medium, form the graphite dispersion liquid, wherein, the weight ratio of graphite and liquid medium is 1: 10-1000;

Two, in molar ratio 2.0: 1-5.5: 1 takes by weighing divalent iron salt, trivalent iron salt, and being mixed with concentration is the iron ion mixing solutions of 0.2-0.8M;

Three, be 1 with above-mentioned graphite dispersion liquid and iron ion mixing solutions with volume ratio: 1-6: after 1 the mixed, be placed in 29 ℃ of-31 ℃ of waters bath with thermostatic control, and stir 10-20min, it is mixed;

Four, adding concentration in the mixing solutions of step 3 gained is the alkali lye of 0.3-0.6M, and the stirring that does not stop is alkalescence until solution;

Five, the solution of step 4 gained is moved in 35 ℃ of-50 ℃ of waters bath with thermostatic control crystallization 1-3 hour;

Six, the solution after the washing crystallization is neutral until washings, adopts magnetic separation technique to isolate throw out in the solution at last, and oven dry, pulverizing have promptly obtained being attached with magnetic Fe ₃O ₄The powdered graphite of nanoparticle.

2, a kind of preparation method with powdered graphite of electromagnetic property according to claim 1 is characterized in that: the liquid medium in the above-mentioned steps one is the organic or inorganic solution that easily dissolves graphite.

3, a kind of preparation method with powdered graphite of electromagnetic property according to claim 1 is characterized in that: in the above-mentioned steps two, divalent iron salt and trivalent iron salt are the molysite that does not contain the strong oxidizing property acid group.

4, a kind of preparation method with powdered graphite of electromagnetic property according to claim 3, it is characterized in that: above-mentioned divalent iron salt is FeCl ₂Or FeSO ₄

5, a kind of preparation method with powdered graphite of electromagnetic property according to claim 3, it is characterized in that: above-mentioned trivalent iron salt is FeCl ₃Or Fe ₂(SO4) ₃

6, a kind of preparation method with powdered graphite of electromagnetic property according to claim 1 is characterized in that: in the above-mentioned steps four, the alkali lye that adds in mixing solutions is middle aqueous alkali.

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