How to understand expanded graphite?

(How to understand expanded graphite?)

As a new type of functional carbon material, Expanded Graphite (EG) is a loose and porous worm-like substance obtained from natural graphite flakes through intercalation, washing, drying and high temperature expansion. In addition to the excellent properties of natural graphite such as cold and heat resistance, corrosion resistance, and self-lubrication, EG also has softness, compression resilience, adsorption, ecological environment coordination, biocompatibility, and radiation resistance that natural graphite does not have. and other characteristics. As early as the early 1860s, Brodie heated natural graphite with chemical reagents such as sulfuric acid and nitric acid, and discovered expanded graphite, but its application did not begin until a hundred years later. Since then, many countries have successively launched the research and development of expanded graphite, and made major scientific breakthroughs.

Expanded graphite can instantly expand 150~300 times in volume when exposed to high temperature, changing from flake to worm-like, so that the structure is loose, porous and curved, the surface area is enlarged, the surface energy is improved, and the adsorption force of flake graphite is enhanced. combined, which increases its softness, resilience and plasticity.

What are several development directions of expanded graphite?

1. Special purpose expanded graphite

Experiments show that graphite worms have the function of absorbing electromagnetic waves, which makes expanded graphite have high military application value. Both the U.S. military and our military have conducted experimental research in this regard. This expanded graphite must meet the following requirements: (1) The initial expansion temperature is low and the expansion volume is large; (2) The chemical properties are stable, and the expansion rate is basically not attenuated after 5 years of storage; (3) The surface of the expanded graphite is neutral, and Shells are non-corrosive.

2. Granular expanded graphite

Small particle expanded graphite mainly refers to 300 mesh expandable graphite, and its expansion volume is 100ml/g. This product is mainly used for flame retardant coatings, and its demand is very large.

3. Expanded graphite with high initial expansion temperature

The initial expansion temperature of the expanded graphite with high initial expansion temperature is 290-300 ° C, and the expansion volume is ≥ 230 ml/g. This kind of expanded graphite is mainly used for the flame retardant of engineering plastics and rubber. The product has been successfully developed by Hebei Agricultural University and has applied for a national patent.

4. Surface modified graphite

When expanded graphite is used as a flame retardant material, it involves the compatibility of graphite and other components. Due to the high degree of salinity on the surface of graphite, it is neither lipophilic nor hydrophilic. Therefore, the graphite surface must be modified to solve the problem of compatibility between graphite and other components. It has been proposed to whiten the surface of graphite, that is, to cover the surface of graphite with a solid white film. This is a difficult problem to solve. It involves membrane chemistry or surface chemistry. It may be done in the laboratory, but there are difficulties in industrialization. This kind of white expandable graphite is mainly used for flame retardant coatings.

5. Low initial expansion temperature, low temperature expanded graphite

The temperature at which this type of expanded graphite begins to expand is 80-150°C, and the expansion volume reaches 250ml/g at 600°C. The difficulties in preparing expandable graphite that meet this condition lie in: (1) selection of appropriate intercalation agent; (2) control and mastery of drying conditions; (3) determination of moisture; (4) solution of environmental protection problems. At present, the preparation of low-temperature expandable graphite is still in the experimental stage.

High expanded graphite suppliers

Luoyang Moon & Star New Energy Technology Co., LTD, founded on October 17, 2008, is a high-tech enterprise committed to developing, producing, processing, selling, and technical services of lithium-ion battery anode materials. After more than 10 years of development, the company has gradually developed into a diversified product structure with natural graphite, artificial graphite, composite graphite, intermediate phase, and other negative materials (silicon-carbon materials, etc.). The products are widely used in high-end lithium-ion digital power and energy storage batteries.

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(How to understand expanded graphite?)