1564, a black mineral-graphite was discovered in a place called barodale, England. Soon, some local shepherds found that they could mark their sheep with graphite. Inspired by this, people cut graphite blocks into small strips for writing and painting. But graphite strips are easy to get dirty and break.

176 1 year, German chemist Faber solved this problem: he first ground graphite ore into powder, washed it with water to remove impurities, and got pure graphite powder; Then he mixed sulfur, antimony, rosin and other substances into graphite powder; Then this mixture is heated and solidified and pressed into the shape of a pen, which is the earliest prototype of a pencil.

Extended data:

Due to its special structure, graphite has the following special properties:

1. High temperature resistance: the melting point of graphite is 3850 50℃ and the boiling point is 4250℃. Even for ultra-high temperature arc combustion, the weight loss and thermal expansion coefficient are very small. The strength of graphite increases with the increase of temperature. At 2000℃, the strength of graphite doubles.

2. Electrical conductivity and thermal conductivity: The electrical conductivity of graphite is 100 times higher than that of general nonmetallic minerals. Thermal conductivity exceeds that of steel, iron, lead and other metal materials. The thermal conductivity decreases with the increase of temperature, and even at extremely high temperature, graphite becomes an insulator. Graphite can conduct electricity because each carbon atom in graphite only forms trivalent bonds with other carbon atoms, and each carbon atom still retains 1 free electrons to transfer charges.

3. Lubricity: The lubricity of graphite depends on the size of graphite flake. The larger the scale, the smaller the friction coefficient and the better the lubricity.

4. Chemical stability: Graphite has good chemical stability at room temperature, and can resist the corrosion of acid, alkali and organic solvents.

5. Plasticity: Graphite has good toughness and can be ground into very thin slices.

6. Thermal shock resistance: When graphite is used at normal temperature, it can withstand drastic changes in temperature without damage. When the temperature changes suddenly, the volume of graphite changes little and cracks will not occur.

References:

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