How to turn flake graphite into expandable graphite?

Flake graphite is a kind of natural graphite. After being mined and purified, the general shape is fish scale shape, so it is called flake graphite. Expandable graphite is flake graphite that is acid-washed and intercalated, which expands about 300 times compared with the previous graphite, and can be used as coil and flexible graphite raw materials.

The difference between flake graphite and expandable graphite:

Although expandable graphite can be made from flake graphite, there are some differences between them.

1. The use of flake graphite is more extensive than that of expandable graphite

In industrial production, in addition to the function of expandable graphite, flake graphite has much better electrical conductivity, thermal conductivity, smoothness, etc. than expandable graphite. Therefore, it is more widely used in industrial practice.

2. The production process of flake graphite and expandable graphite is different

Graphite flakes are mainly made by mechanical damage and grinding. The expandable graphite is mainly made by processing methods such as chemical acid liquid impregnation, and the production process is more complicated than that of flake graphite.

3. The particle size of flake graphite is smaller than that of expandable graphite

The particle size of flake graphite is generally smaller, and the particle size of expandable graphite is relatively coarse. Because of the expansion function of expandable graphite, the coarse particle size simply promotes the expansion of graphite, so the particle size of expandable graphite is relatively coarse.

Common preparation methods of expandable graphite

The main methods for producing expandable graphite are shown below.

1. Chemical intercalation method: the initial raw material for preparation is high-carbon flake graphite, and other chemical reagents such as concentrated sulfuric acid (above 98%), hydrogen peroxide (above 28%), potassium permanganate, etc. are all industrial-grade reagents The general steps of preparation are as follows: at an appropriate temperature, different proportions of hydrogen peroxide solution, natural flake graphite and concentrated sulfuric acid are added in different procedures, reacted for a certain period under constant stirring, and then washed with water until neutral, centrifuged, After dehydration, it was vacuum-dried at 60 °C.

2. Electrochemical method: Graphite powder is treated in a strong acid electrolyte to make expandable graphite, hydrolyzed, cleaned, and dried. As a strong acid, sulfuric acid or nitric acid is mainly used. The expandable graphite obtained by this method has a low sulfur content.

3. Ultrasonic oxidation method: In the process of preparing expandable graphite, ultrasonic vibration is performed on the anodizing electrolyte. The time of ultrasonic vibration is the same as that of anodization. Because the vibration of ultrasonic waves on the electrolyte is conducive to the polarization of the cathode and anode effect, thereby accelerating the speed of anodizing and shortens the oxidation time.

4. Gas-phase diffusion method: The graphite and the intercalator are placed at the two ends of a vacuum-sealed tube respectively, heated at the end of the intercalator, and the necessary reaction pressure difference is formed by using the temperature difference between the two ends so that the intercalator enters in the state of small molecules. The flake graphite layers are interlayered to obtain expandable graphite. The number of layers of the expandable graphite produced by this method can be controlled, but its production cost is high.

5. Molten salt method: several kinds of inserts are mixed with graphite and heated to form expandable graphite.

Our Franli’s factory manufactures different types of graphite, if you are interested, be free to contact us. Any questions, welcome,