1. Chemical intercalation method: the initial raw material for preparation is high carbon flake graphite. Other chemical reagents, such as concentrated sulfuric acid (over 98%), hydrogen peroxide (over 28%), potassium permanganate, etc., all use industrial grade reagents. The general steps for preparation are as follows: under appropriate temperature, hydrogen peroxide solution, natural flake graphite and concentrated sulfuric acid with different ratios are added in different procedures, reacted for a certain time under constant stirring, and then washed to neutral, Centrifuge, dehydrate and then vacuum dry at 60 ℃.
2. Electrochemical method: the graphite powder is treated in a strong acid electrolyte to make expandable graphite, which is hydrolyzed, cleaned and dried. As a strong acid, sulfuric acid or nitric acid is mainly used. The expandable graphite made by this method has low sulfur content.
3. Ultrasonic oxidation method: In the process of preparing expandable graphite, the anodized electrolyte is subject to ultrasonic vibration. The time of ultrasonic vibration is the same as that of anodic oxidation. Since the ultrasonic vibration of electrolyte is conducive to the polarization of cathode and anode, the speed of anodic oxidation is accelerated and the oxidation time is shortened.
4. Vapor phase diffusion method: the graphite and the intercalation are respectively sent to the two ends of a vacuum sealed tube, heated at the end of the intercalation object, and the temperature difference at the two ends is used to form the necessary reaction differential pressure, so that the intercalation object enters the flake graphite layer in the state of small molecules, so as to produce expandable graphite. The number of layers of expandable graphite produced by this method can be controlled, but its production cost is high.
5. Molten salt method: several inserts are mixed with graphite and heated to form expandable graphite.