What is graphite? Generally speaking, we can understand graphite as a kind of "carbon", which is gray-black, solid and chemically stable. It has the characteristics of corrosion resistance, acid and alkali resistance, high temperature resistance, electrical conductivity, thermal conductivity and lubrication, and can be regarded as an allotrope formed by sp2 hybridization of carbon atoms in the same layer. It is widely used in making crucibles, electrodes, brushes, dry batteries, graphite fibers, heat exchangers, coolers, electric arc furnaces, pencil lead, etc. Even the famous graphene is extracted from graphite.
The structure of graphene is also relatively regular. Six carbon atoms form a hexagonal ring on the same plane, which is interrelated to form a lamellar structure and stacked on each other (generally speaking, it is more complicated, just remember that it is a lamellar structure). If graphite is cut into infinitely thin slices, it will show a multi-layer network structure under the microscope.
What is graphene? The last article generally said that some graphite is made up of carbon atoms. If you cut graphite with special equipment, you will get infinitely thin graphite flakes. If there is only one layer of carbon atoms left, it is called "graphene".
If graphite is an allotrope of carbon, then graphene is a two-dimensional crystal material of carbon, which is flat, not powder or has a multi-layer structure like graphite and graphite flakes. The earliest extraction method of graphene is to stick it on the graphite sheet with adhesive tape, and then tear it off repeatedly, leaving only a single layer of carbon atoms on the adhesive tape, which is the earliest extraction method of graphene. Later, with the deepening of research, people invented mechanical stripping method, redox method, directional epiphysis method and so on. Although the extraction difficulty is still high, it is not as difficult as expected. To be sure, it has already left the laboratory stage.
If explained in a language that everyone can understand, graphene is graphite. As long as graphite can be cut infinitely thin, there is only one layer of carbon atoms left, which is graphite graphene. Graphene-related materials in the market include graphene, graphene flakes, graphite flakes and graphite.
The unit of measurement of graphene Up to now, the unit of measurement of graphite has reached a consensus, which can be measured in tons, kilograms and grams, but graphene has not yet reached a consensus. Although there are related evaluation methods, the purity, conductivity, tap density, chip diameter, ash content, volume resistivity, median particle size, square resistance, mobility, particle size, thickness, diameter and size of graphene should be combined for evaluation.
As mentioned above, the thickness of 3 million layers of graphene is about 1mm, which belongs to one kind of nano-materials. Although the measurement unit and evaluation standard are not uniform, it can be determined that only "two-dimensional carbon crystal sheet composed of single-layer carbon atoms" can be called graphene. How much is graphene? Anke sells high purity graphite powder.
The price difference between graphite and graphene When graphene was first born, due to the limitation of purification technology, the price of graphene was much higher than that of graphite, but it was definitely not a million times. Graphene is not sold in the market at all, even if it is used in heating equipment and mobile phones, at most it is graphene sheets and graphene coatings. Although the price is slightly higher than that of graphite, it is not as exaggerated as expected. Coupled with the continuous maturity of graphene preparation technology, the price has come down.