JPH03153511A - Method for finely flaking graphite - Google Patents

Abstract

PURPOSE:To obtain fine flaky particles having superior anisotropy by intercalating a guest substance between the layers of graphite to form an intercalation compd. and crushing this compd. in vacuum. CONSTITUTION:A guest substance such as K, K-NH3, Br, FeCl3 or SbCl5 is intercalated between the layers of graphite to form an intralaminar compd. This compd. is finely flaked by crushing in vacuum or in an atmosphere of an inert gas or dry air optionally after expansion by rapid heating. When the resulting fine flaky graphite is mixed with a solvent, oil, etc., and used to form a graphite coating film, a long service life and high reliability are obtd.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to the fields of electricity, chemistry, metallurgy, rocketry, etc., and more specifically, the present invention relates to the fields of electricity, chemistry, metallurgy, rocketry, etc.
The present invention relates to a method for making graphite into fine flakes, which is characterized by forming an os+-pound (hereinafter referred to as GIC) and pulverizing it in a predetermined atmosphere to make fine flakes.

(Prior Art) Graphite has anisotropy in which properties such as electrical conductivity and thermal conductivity differ in the interlayer direction of a layered structure and in the direction perpendicular to the layer plane, and it is already widely used as an industrial material. Particularly in the field of electronic engineering, graphite coatings are used, for example, as light-absorbing black stripes in color cathode ray tubes and conductive films on the inner surface of funnels. On the other hand, applications such as drawing graphite circuits on insulating substrates and using them in electronic components are also expanding. Such graphite coatings are required to have high reliability, such as being free from uneven coating, detachment, and cracking during the film-forming process, and having a long life. Therefore, it has become an important issue to improve the performance of the membrane, the strength of the membrane, the thinning of the membrane, etc. by making the graphite raw material finer, especially into fine pieces.

Conventionally, wet pulverization was carried out for 24 to 48 hours by adding an appropriate dispersant to water, etc., and the yield was about 1.0 wt%.
Graphite fine flake particles with a size of less than m are obtained.

Also, if fine powder can be produced in a dry state, it can be used in oil,
Since it is possible to use it highly functionally by mixing it with a solvent, etc., a method has actually been reported in which graphite is crushed in a vacuum or in an inert gas such as He [Uehara, Asai, Jimbo, et al.
Tanaka: Collection of chemical engineering papers.

Volume 4, No. 6, p639-645 (1978)).

On the other hand, graphite is made by inserting (intercalating) various substances such as guest substances (INOs-HzSO4 mixed acid, halogens, alkali metals, alkaline earth metals, fluorides, chlorides, etc.) between its layers to form GIC. [Takahashi, Akusawa; Experimental Technology Course,
Carbon, (Yo 1) 1), p171-178 (1982)
), HNO3-[1zSO4 mixed acid CIC is formed, and this is heated to about 800°C, and 1f of the guest substance is formed.
NOi-HgSO4 is rapidly degassed to expand its apparent volume several to several hundred times, and this expanded graphite adsorbs water vapor and organic vapors such as benzene. After freezing with liquid nitrogen, it is frozen and pulverized. A method has been proposed [Osaka Institute of Technology News: No. 12. (1985))
.

(Problem to be solved by the invention) However, since the above-mentioned conventional technology was aimed simply at procuring fine particles, the particle shape was three-dimensional or block-like, and the important property of anisotropy could not be utilized. It was not flaky.

In addition, dry grinding is a difficult method to obtain submicron flakes due to the high lubricity and wettability of layered materials such as graphite.

- After first generating intercalation compounds, there is a method of rapid heating degassing treatment, cooling with liquid nitrogen that adsorbs organic vapors, freezing and crushing, and further desorption of adsorbed vapors, but the size of the obtained fine flakes However, the particle size is limited to about 10-odd micrometers, the aspect ratio (particle diameter/thickness) is limited to about 700, and there are disadvantages in that various complicated steps are required. Furthermore, since the graphite has been expanded several hundred times and has a very large bulk specific gravity, the processing amount (weight) is very small, making industrial scale-up difficult, and the process of manufacturing mixed acid-based expanded graphite. The residual acid remained in the graphite, making it extremely difficult to completely remove it. Therefore, corrosion due to residual acid (strong acid) has become a major problem in the future.

(Means for solving the problem) The above problem is solved by the fact that atoms and molecules of guest substances are formed between the layers of graphite.
The present method involves intercalating ions to form an intercalation compound and pulverizing it in vacuum or in an inert gas, or the intercalation compound is rapidly thermally expanded and then in a vacuum, in an inert gas, or in dry air. can be solved by this method of grinding in any atmosphere.

The guest substances include potassium (K), potassium-ammonia (K-MHI), bromine (Br), iron chloride (Fe
Cls), antimony chloride (SbCl,) can be used.

(Function) Graphite has a structure in which hexagonal network planes of carbon atoms are stacked in layers, and has anisotropy in which physical properties differ between the planes of the layered structure and the vertical direction, and atoms and molecules of guest substances are distributed between the layers. , has the property of inserting ions and forming GIC. Intercalated potassium (K), potassium-
GIC intercalated with ammonia (K-N) I:l), bromine (Br), etc. has an expanded interlayer spacing and improves the pulverization efficiency by mechanical force. Since the space between the layers expands several to hundreds of times, the pulverization efficiency is significantly improved. Therefore, by pulverizing GIC or its expanded product in a vacuum, an inert gas atmosphere, or the like, fine particles of a desired size, particularly fine flake particles with excellent anisotropy, can be produced.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

In order to synthesize K-GIC, the particle size is 90μm-125μm.
m of natural graphite is dried in a drying oven at 140°C for 48 hours, and then vacuumed to about 10-” Torr and baked out at 70°C for about 14 hours or more. Figure 1 shows the intercalation compound. FIG. 2 is a schematic diagram of a reaction vessel equipped with a breaker pull seal for synthesizing.

After baking out, potassium metal 1) with a purity of 99.9% and the graphite 12 are sampled in the reaction vessel 10 in an argon gas atmosphere. After opening the cock 13 and evacuating the reaction vessel to a sufficient level (approximately 10 Torr), the reaction tube was sealed off with the cutting part 14 while maintaining the vacuum state, and the entire vessel was heated in an electric furnace to heat the K- Synthesis of GIC proceeded. After about 72 hours at about 300° C., the graphite was found to have transformed into first stage golden KC. Furthermore-
In order to generate NH, -GIC, first, -GIC was synthesized in the same manner as in the above method, and then breaker pull seal 1 was synthesized.
5 to absorb NH gas, react at -44°C (acetonitrile slush bath) for several hours, then at room temperature for several hours, then remove excess NH3 to form KNH3G.
An IC ternary intercalation compound was synthesized. Furthermore, -NH
+ - When GIC was rapidly heated at 750°C for 20 minutes,
Expanded graphite with an expansion rate of about 13 times was obtained. FIG. 2 is a schematic diagram of a vibrating ball mill prototyped for pulverizing the above-mentioned intercalation compound. This crushing container had a structure that allowed the crushing atmosphere to be controlled. A graphite sample 21 and a stainless steel ball 22 (outer diameter 5 m) as a grinding medium are placed in a grinding container 20, and a heater 2 is placed in the grinding container 20.
After removing water and impurities by evacuation while heating in Step 3, the desired gas is filled, the valve 24 is closed, and the motor power is turned on. The rotational motion of the motor 25 is transmitted to the eccentric weight 27 via the camp ring 26, vibrates the base 29 supported by the spring 28, and the graphite sample is crushed by the impact force of the stainless steel balls. Up to 6 grinding containers can be attached at one time. The crushing conditions are vibration frequency 9
94 rpm, amplitude 10 m, apparent filling rate of stainless steel balls as the grinding medium 50%, each pinceae 0.3 g, and each sample was charged and ground under the same conditions. The measurement of particle size distribution was natural, centrifugal sedimentation method. This was done by

Figure 3 shows particles with a particle size of 8.5 cm after vacuum drying so that they can be directly compared with the pulverization results of K-GIC and -NH, -GIC.
8-125 μ- natural graphite in dry air, nitrogen gas,
It is a graph of the results of a crushing experiment conducted in vacuum. In the figure, the vertical axis is the 50% sieve passing diameter X, and the horizontal axis is the crushing time t. In this experiment, in vacuum pulverization, X in about 3 hours.

It can be seen that a minimum value of =0.4 μm is obtained. Almost the same results were obtained for xso milled in Nt. on the other hand,
For grinding in dry air, the product X. The grinding time is 6
It can be seen that within time it is larger than in other cases.

Figure 4 shows the vacuum pulverization of Ni-GIC and the KNH
3X in vacuum grinding of GIC expanded graphite. The relationship between this and the grinding time was shown. Compared to the results of vacuum pulverization of natural graphite shown in Figure 3, the pulverization speed in vacuum pulverization of K-GIC is lower, but X. The minimum value of (milling time = 12 hours) is approximately equal to xs. It can be seen that =0.4-〇, 5 μm. In addition, in vacuum pulverization of expanded KNH3GIC, pulverization apparently does not proceed if the pulverization time is less than 6 hours, and X,
.

The value of is 0.8 μm.

Next, natural graphite (pulverized in dry air and in vacuum), K-G
IC (vacuum crushing), -NHff -GIC (for expansion)
X, the product obtained by grinding for 3 hours under vacuum grinding).

The particle shapes of each were observed using an electron microscope. The shape of the product obtained by dry air or vacuum pulverization of natural graphite is lumpy and agglomerated.
It was observed that the shape of the vacuum-pulverized product of C was clearly flaky when compared with that of natural graphite.

In the example in which bromine was used as an intercalant, the expansion rate of expanded graphite was about 2.75 times, and the crushing characteristics (in vacuum) were also different from those of -GIC. From this, it was found that the grinding characteristics of GIC vary depending on the intercalant used. Therefore, in addition to the above embodiments, when iron chloride or antimony chloride is used as an intercalant, different grinding characteristics can be obtained, and the possibility of producing fine flake particles is expanded.

(Effects of the Invention) The graphite obtained by the present invention has a size of X when pulverized in vacuum by K-GIC. -0.4μ air,
Furthermore, since it is in the form of fine flakes, the anisotropic properties of graphite can be effectively utilized.

Therefore, by mixing it with oil, solvent, etc. and using it in a graphite coating, a highly functional film can be realized.

Graphite coated films in various application fields have long lifespans and high conversion properties, and have improved film performance and strength, making it possible to create ultra-thin films. In addition, the fine flakes obtained by nature are
Since it is not a conventional mixed acid type GrC, it does not require complicated processes such as removal of residual particles that cause corrosion or freezing, so it has great economic effects. Furthermore, since the m1 piece particles produced by this method contain potassium, they have the advantage of having higher electrical conductivity than natural graphite. FIG. 5 shows the powder electrical tit; tj'i of Ni-GIC and natural graphite obtained according to the present invention.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a reaction vessel with a breaker pull seal for synthesis of intercalation compounds, Figure 2 is a schematic diagram of a vibrating ball mill for crushing, and Figure 3 is
A graph showing the results of a crushing experiment of natural graphite in dry air, nitrogen gas, and vacuum; FIG. 4 is a graph showing the results of a crushing experiment of K-GIC and expanded -NH,-GIC in vacuum; FIG. 5 is a graph showing the powder electrical resistance of K-GIC and natural graphite. (Explanation of symbols) IO...Reaction vessel, 1)...Potassium metal, 12.
... Natural graphite, 13 ... Cock, 14 ... Seal, I5 ... Breaker pull seal, 20 ... Grinding container, 21 ... Graphite sample, 22 ... Stainless steel ball, 23
... Heater 24 ... Valve, 25 ... Motor 26 ... Coupling, 27 ... Eccentric weight, 28
...Spring, 29...Base. Compressed density (g/cm2) Procedural amendment (method) % formula % 1. Indication of the case 1999 Patent Application No. 292673 2) Name of the invention Method for micro-exfoliating graphite 3. Person making the amendment Relationship with the case

Claims (3)

[Claims] (1) Intercalate atoms, molecules, and ions of a guest substance between the layers of graphite to form an intercalation compound, and
A method for finely exfoliating graphite, which is characterized by crushing in either an inert gas or dry air atmosphere. (2) The intercalation compound described in claim (1) is rapidly expanded by thermal expansion, and then pulverized in an atmosphere of vacuum, inert gas, or dry air. A method for micro-exfoliating graphite. (3) The guest substance described in claim (1) is potassium (K), potassium-ammonia (K-NH_3)
, bromine (Br), iron chloride (FeCl_3), and antimony chloride (SbCl_5).