Secrets of manufacturing graphite

The various uses of graphite derive directly from its exceptional physical properties.
Graphite is characterized by its resilience to very high temperatures and to corrosion,its thermal and electrical conductivity, its mechanical resilience, its self-lubricatingproperties, its suitability for machining and the length of its service life.
All these qualities make it a vital material for a whole host of industrial applications.
Before we take a closer look at them, we will first recap on the history and secrets ofmanufacturing synthetic graphite.

Three basic ingredients:

cokes, obtained through carbonization(above 1,000C) of tar produced by

distilling oil and coal,

artificial graphite, which derives fromthe recycling of graphite materials

carbon black or natural graphite,and additional ingredients: a derivativeof oil and carbon used to bind the parti-cles together.

After inspections to check their quality, the principal ingredients are ground up. Thecoke, graphite and solid binder are then loaded into a mixer that heats them up.The rise in temperature melts the binder and ultimately moistens the grains, beforethe gradual reduction in temperature serves to enhance the viscosity of the mixuntil it solidifiesAfter further grinding, the mix is placed in a rubber mold to be compressed orshaped and it may be extruded into a die.The volatile materials are then eliminated through baking. This extremely lengthystage (1 to 2 months)takes place at a temperature of 800C to 1,000C.Next comes the graphitization phase,which consists in heat-treating the blocks inan electric kiln at 3,000C for one to three weeks. At a very high temperature, thecarbon atoms realign themselves into hexagonal crystalline structures, which thusform artificial graphite. The substance's properties change. It becomes a goodconductor and its resilience to oxidization improves.The blocks are cut to the final dimensions and then undergo a series of tests(density, resilience, resistance to flexion, hardness, expansion coefficient, etc.)tosafeguard its quality.
The first phase lasts for around four months in all.
Various additional purification and impregnation steps enhance the graphite'squalities and give it additional benefits for a number of industrial processes.