Expandable Graphite
Size
0.50mm or 0.106mm, etc
Package
25 kg small bags into ton bags
Origin
China
Features
Preservative/Electrical and thermal conductivity, etc.
Application
Fireproof sealing element, flame retardant, refractory brick, etc.
Expandable graphite crystal is a typical layered carbon material. Other heterogeneous particles such as atoms, molecules, ions, and even atomic clusters are inserted into the interlayer of crystalline graphite by physical or chemical methods to form a new layered compound, which is called graphite interlayer compound, namely expandable graphite.
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The expanded graphite was prepared by chemical oxidation method—concentrated sulfuric acid and concentrated nitric acid, and the loading of graphite, expansion time, acid ratio, and the influence of ultrasonic on the expansion effect of graphite were compared, which were characterized by bulk density. We are the expanded graphite manufacturer.The expanded graphite was prepared by chemical oxidation method—concentrated sulfuric acid and concentrated nitric acid, and the loading of graphite, expansion time, acid ratio, and the influence of ultrasonic on the expansion effect of graphite were compared, which were characterized by bulk density.
Expanded graphite is a widely used carbon material, because of its low density, large specific surface, oxidation resistance, high-temperature resistance, good acid, alkali resistance, and other characteristics, its application range involves adsorption, catalysis, electronics, aviation, etc. fields. Expanded graphite is made of natural flake graphite. Today, expanded graphite, a new type of multi-functional and multi-purpose carbon material, has been widely used in the chemical industry, machinery, environmental protection, medicine, military, and other fields.
Structure and properties of expanded graphite
Expanded graphite is a loose and porous worm-like substance obtained from natural flake graphite through a series of processes of oxidation, intercalation, water washing, drying, and high temperature expansion. Compared with graphite, the structure of expanded graphite has undergone great changes. The original plane layer of graphite has been significantly cracked, resulting in uneven deformation, and the plane layer is in a curled state.
Under the high temperature of expandable graphite, the intercalated material between the graphite layers gasifies and decomposes, forming an instantaneous high pressure, and the generated thrust overcomes the van der Waals force between the graphite layers, so that the expandable graphite sheet expands dozens to hundreds of times in the direction of the C axis, forming loose particles. Lightweight, black or grey-black expanded graphite. Since the yur-ring structure of the graphite layer is not destroyed during the expansion process for expandable graphite, it belongs to the same yur-square crystal system as graphite in terms of microstructure. It not only retains the excellent properties of natural graphite such as heat resistance, corrosion resistance, radiation resistance, electrical and thermal conductivity, and low friction coefficient, but also has the properties of compressibility, self-adhesion, and adsorption that natural graphite does not have.
FRANLI have found that the excellent characteristics of expanded graphite.
1. Wide temperature range of expanded graphite: can withstand ultra-low temperature of -200℃ to high temperature of 3600℃.
2. Strong corrosion resistance of expanded graphite:The chemical properties of expanded graphite are stable. Except for a few strong oxidants such as aqua regia, concentrated nitric acid, oleum, and dichromate and permanganate at high temperature, it can resist almost all common oxidants. Corrosion by chemical media.
3. Strong radiation resistance: expanded graphite can withstand long-term exposure to radiation such as neutron rays, a-rays, gamma rays, and B-rays, and does not age under long-term radiation.
4. Anisotropy: Expanded graphite has excellent anisotropy in heat transfer, electrical conductivity and thermal expansion. The thermal conductivity in the plane layer direction is 28 times larger than that in the thickness direction, and the electrical conductivity is 500 times larger.
5. Impermeability: Expanded graphite has excellent impermeability to gas and liquid media.
6. Self-lubrication of expanded graphite: Under the action of external force, it is easy to produce relative slip along the plane layer direction, forming self-lubrication and low friction coefficient.
7. Softness of expanded graphite: Due to the existence of many special unit structures, as long as a small tightening pressure is used, a good self-adhesion can be achieved and an effective seal can be formed.
8. Resilience of expanded graphite: All kinds of products of different shapes made by direct pressure of expanded graphite have 10-70% resilience in the thickness direction.
The production process of expanded graphite is relatively complex, and its characteristics are suitable for the chemical process industry of many enterprises. FRANLI research results show that the best synthesis process for preparing expanded graphite under laboratory conditions is – graphite: concentrated nitric acid: concentrated sulfuric acid = 1:2:1, the reaction time is 8h under ultrasonic conditions, and it is placed in an oven for drying at 50 ℃. Finally, it is expanded in a muffle furnace at a temperature of 750 °C to obtain expanded graphite with better expansion effect.
