What are the thermal properties of diamond and graphite?

Diamond and graphite both have high thermal conductivity, but diamond's is significantly higher than graphite's.

Diamond and graphite, both forms of carbon, exhibit different thermal properties due to their distinct structures. Diamond has a three-dimensional network of covalent bonds, which makes it an excellent thermal conductor. This is because the vibrations caused by heat energy can easily be transferred through the strong, interconnected carbon bonds. In fact, diamond has the highest thermal conductivity of any known material, making it extremely useful in applications that require efficient heat dissipation, such as in electronics.

On the other hand, graphite's structure consists of layers of carbon atoms arranged in hexagonal rings. These layers are held together by weak Van der Waals forces, allowing them to slide over each other easily. This gives graphite its characteristic slippery feel. However, these weak interlayer bonds also mean that heat energy cannot be transferred as efficiently between the layers as in diamond. Therefore, while graphite is still a good conductor of heat, its thermal conductivity is much lower than that of diamond.

In addition, the thermal expansion of diamond and graphite is also different. Diamond has a very low coefficient of thermal expansion, meaning it does not expand significantly when heated. This is due to its rigid, tightly-bonded structure. Conversely, graphite has a higher coefficient of thermal expansion due to the flexibility of its layered structure. When heated, the layers of graphite can slide further apart, causing the material to expand.

In summary, while both diamond and graphite are good conductors of heat, diamond's thermal conductivity is far superior due to its strong, interconnected covalent bonds. However, graphite's layered structure allows it to expand more when heated, unlike diamond.