Time：2023.11.10Browse：1
Graphite is one of the substances with the highest melting and boiling points in nature, with a melting point of 3850 ± 50 ℃ and a boiling point of 4500 ℃. However, the boiling points of silicate minerals are all below 2750 ℃ (quartz boiling point), and the boiling point of graphite is much higher than the boiling point of the impurity silicate it contains. This characteristic is the theoretical basis for high-temperature purification of graphite. Fill the graphite powder directly into a graphite crucible and heat it in a purification furnace filled with inert gas and Freon protective gas to 2300-3000 ℃ for a period of time. Impurities in the graphite will overflow, thus achieving the purification of the graphite. The high-temperature method generally uses high carbon graphite containing over 99% carbon purified by flotation or chemical methods as the raw material, which can purify the graphite to 99% 99%. By further improving the process conditions and improving the quality of the crucible, the purity can reach 99% More than 995%.
The high-temperature method can produce over 99.99% ultra-high purity graphite, but it requires the fixed carbon of the raw material to be above 99%. Moreover, the equipment is expensive, the investment is huge, and the production scale is limited. The electric furnace heating technology requires strict isolation of air, otherwise the graphite will start to oxidize when heated to 450 ℃ in hot air. The higher the temperature, the greater the loss of graphite. Only special industries with very high requirements for graphite quality (such as national defense, aerospace, etc.) use high-temperature method to produce high-purity graphite in small batches.
2023-02-09The chloride roasting method is to mix graphite with a certain reducing agent to bake at high temperature in specific equipment and atmosphere. The price in the material is transformed into a metal chloride with gas or condensed phase. Purified process.
The size of a material particle determines its proper name. As you asked, micro-powder is a micron-sized powder. In the graphite industry, micro-powder generally refers to a particle with a median diameter of 10~45 microns, and ultra-micro-powder to a particle with a median diameter of less than 5 microns.
Graphene already exists in nature, but it is difficult to peel off a single layer structure. Graphene is stacked layer by layer to form graphite, with a thickness of 1 millimeter containing approximately 3 million layers of graphene. A pencil lightly scratches on paper, leaving traces that may be several or even just one layer of graphene.The carrier mobility of graphene at room temperature is about 15000 cm2/(V · s), which is more than 10 times that of silicon material and more than twice that of the known material indium antimonide (InSb) with the highest carrier mobility. Under certain specific conditions, such as low temperature, the carrier mobility of graphene can even reach up to 250000 cm2/(V · s). Unlike many materials, the electron mobility of graphene is less affected by temperature changes. At any temperature between 50 and 500K, the electron mobility of single-layer graphene is around 15000 cm2/(V · s).In addition, the semi integer quantum Hall effect of electron carriers2023-03-20Is superfine graphite graphite?
2023-11-01The Electronic Effect of Graphene
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