1)Introduction of expandable graphite
Expandable graphite, also known as flexible graphite or worm graphite, is a new type of carbon material. Expanded graphite has many advantages, such as large specific surce area, high surface activity, good chemical stability and high temperature resistance. The common preparation process of expanded graphite is to take natural flake graphite as the material, first generate expandable graphite through oxidation process, and then expand it into expanded graphite. In case of high temperature, the expanded graphite material can instantly expand 150 ~ 300 times in volume, and change from flake to worm like, so that the structure is loose, porous and curved, the surface area is expanded, the surface energy is improved, the adsorption force of flake graphite is enhanced, and the worm like graphite can be embedded by itself, so that the material has the functions of flame retardant, sealing and adsorption, and is widely used in the fields of life, military, environmental protection, chemical industry and so on.
2)Preparation method of expanded graphite
Chemical oxidation and electrochemical oxidation are mostly used for expanded graphite. The traditional chemical oxidation method has simple process and stable quality, but there are some problems such as waste of acid and high sulfur content of products. The electrochemical method does not use oxidants, the acid solution can be recycled for many times, with low environmental pollution and low cost, but the yield is low and the requirements for electrode materials are high. At present, it is only limited to laboratory research. In addition to different oxidation methods, the two methods have the same post-treatment such as deacidification, water washing and drying. Chemical oxidation method is the most widely used method so far. The process is mature and has been widely popularized and applied in industry.
3)Difference between expanded graphite and graphene
Graphene and expanded graphite have different performances in both material structure and application field. Expanded graphite can be used as raw material for graphene production. For example, the Hummers method can be used to obtain graphene oxide by ultrasonic expansion of graphite oxide. When the expanded graphite is stripped into a single piece, it becomes graphene. If it is stripped into several layers, it is a few layers of graphene. Graphene nanosheets can be prepared from more than ten to 30 layers.
4)Practical application fields of expanded graphite
1. Application of medical materials
The medical dressing made of expanded graphite can replace most of the traditional gauze because of its many excellent properties.
2. Application of military materials
The expanded graphite is crushed into fine powder, which has strong scattering and absorption characteristics to infrared wave. Making its fine powder into excellent infrared shielding material plays an important role in photoelectric countermeasure in modern war.
3. Application of environmental protection materials
Expanded graphite is widely used in the field of environmental protection because of its low density, non-toxic, pollution-free, easy treatment and excellent adsorption.
4. Biomedical materials
Carbon material has excellent compatibility with human body and is a good biomedical material. As a new type of carbon material, expanded graphite material has excellent adsorption characteristics for organic and biological macromolecules. It has good biocompatibility, non-toxic, tasteless and no side effects. It has a wide application prospect in biomedical materials.
Post time: May-17-2022