How is the acid resistance of Expanded Graphite processed?
Expanded Graphite is an important non-metallic mineral resources, because of its excellent characteristics and rich in nature reserves, so the expansion of graphite in the electrochemical commonly used, often used as electrode materials. But in the electrolyte, even if the strong corrosion resistance of the expansion of graphite will be corrosion, seriously affecting the life of the electrode; in the battery also makes the battery discharge is not resolute.
Expanded Graphite processing of raw materials than the use of natural scale Expanded Graphite as raw material to prepare oxidative expansion of the degree of oxidation of graphite. The XRD pattern of the product with high oxidation degree shows a very clear characteristic peak near 2θ of 10 °. At the same time, the experimental results show that the amount of reactants, the amount of potassium permanganate and the time of low temperature response are important factors influencing the oxidation degree of Expanded Graphite. From the polarization curve, the corrosion resistance of oxidized Expanded Graphite is better than that of expandable graphite, and the corrosion resistance of expansive graphite is better than that of natural expansive graphite. The higher purity is the corrosion resistance of naturally expanding graphite The better the corrosion resistance of oxidized Expanded Graphite prepared by the natural expansion of graphite with the larger diameter of the Expanded Graphite with different Expanded Graphite particles.
Expanded Graphite material is chemically stable and therefore is a corrosion resistant material. But under certain conditions, the carbon and other substances will play a role in its main reaction: at high temperatures and oxidizing atmosphere or strong oxidizing acid oxidation; melting at high temperatures in the metal and generate carbides; Graphite intercalation compounds.
At room temperature, carbon and various gases do not occur in the chemical reaction at about 350 ℃, amorphous carbon that is the beginning of the oxidation reaction, expansion of graphite at 450 ℃ or so began to oxidation reaction. The higher the degree of expansion and graphitization, the more complete the crystal structure of the Expanded Graphite, the reaction activation energy is large, the oxidation resistance is good, the temperature of the same oxidation velocity is reached within 800 ~ C, the Expanded Graphite material is about 50 ~ 100 ℃ in the same material, the binder carbon has a tendency to give priority to oxidation, so the oxidation reaction to a certain extent, the aggregate particles will fall off. At lower temperatures, such as sufficient air supply, carbon and Expanded Graphite materials are mainly the following reactions: C + O 2 - CO 2 at higher temperatures, carbon and Expanded Graphite materials began to attack the following reactions: C + 1 / ZO 2 -CO corrosive charcoal and Expanded Graphite material with water vapor about 700 ° C to start reaction: C + H 2 O - CO + H 2C + 2 H 2 O - C 0 2+ 2 H 2 red hot carbon And Expanded Graphite materials with CO. Of the oxidation reaction at a higher temperature can be carried out: C + CO 2 - 2 C 0 carbon and gas should be between the reflection of gas-solid reaction, oxidation reaction rate and the size of the reaction area in advance, the material porosity and gas pressure Factor, the speed of response depends not only on the surface of the chemical reaction speed, but also with the gas molecules to the material diffusion. Expanded Graphite material containing impurities on the oxidation of the catalytic role, so high-purity graphite and ordinary expansion of graphite oxidation has the potential. Difference.
The chemical composition of diamond and Expanded Graphite is carbon (C), called "allotrope". From this title can know that they have the opposite "quality", but "shape" or "sex" is different, and there are very different, diamond is the hardest material, and expansion of graphite is one of the most soft material.
The difference in hardness between Expanded Graphite and diamond is so great, but people still want to use artificial decomposition method to obtain diamonds, because the natural expansion of graphite (carbon) is very rich. But it is not so easy to make the carbon in the Expanded Graphite turn into carbon as a diamond. Expanded Graphite in the 5-6 million atmospheric pressure ((5-6) × 103MPa) and 1000 to 2000 degrees Celsius high temperature, and then metal iron, cobalt, nickel and other catalysts, can be Expanded Graphite into diamond powder.