How Artificial Graphite Powder Is Made
Graphite contains delocalised electrons which allows it to conduct electricity. When light strikes the surface, the electrons scatter, causing it to reflect in a specular manner (graphite is often called slippery or lustrous). This conductive behaviour is augmented by its unique combination of properties, such as high thermal and electrical conductivity, mechanical stability and lubricity. As a result, it is used as a material to make crucibles and other refractory products, pencil leads, lubricants, paints, stove polishes, carbon brushes, batteries and powder metallurgy, among many other applications.
The manufacture of artificial graphite begins with the loading of raw materials such as petroleum coke, coal tar pitch and natural flake graphite into raw material silos. They are ground to a fine particle size using crushers and ball mills. This produces a granulate that is blended with a binder such as coal tar pitch or petroleum coke to produce a paste. The granulate is then compacted into shapes by extrusion, vibro-molding or cold isostatic pressing.
To prevent anode defects, it is important for battery manufacturers to characterize the quality of their graphite. In addition to the usual tests, such as particle size distribution and sphericality, powder shear is an important test. This can be measured with the TA Instruments Discovery HR rheometer, a highly flexible instrument capable of measuring both shear and fluid rheology.
A shear curve reveals the degree of agglomeration and particle dispersal. It also provides valuable information about the material’s behavior under consolidation. This information can help manufacturers optimize manufacturing processes, design hoppers and ensure that the raw material is free from impurities.
