Calcined needle coke is a variety of petroleum coke (see section on petroleum coke for a basic introduction to PC manufacturing). The term needle is used to describe the acicular morphology of the coke since it tends to form oriented needle-like structures that are clearly visible to the naked eye. This unique morphology is a reflection of the high degree of liquid crystal alignment that occurs during the coking process. The formation of highly oriented morphology is consistent with a coke that is manufactured from feedstock that has a high aromatic character.Needle coke is a highly crystalline form of carbon and can be viewed as being similar to certain crystalline polymers. In this case the "polymer" system is the coke "backbone" that consists of layers of sp2 hybridized carbon atoms in hexagonal ring structures. A high level of two-dimensional orientations exists in these structures, but they are not well oriented in the "c" axis direction. If heated to graphitization temperatures, "c" axis orientation is affected resulting in the highest quality synthetic graphite.Calcined needle coke is typically higher in carbon and lower in ash constituents, such as sulfur and metals, than standard calcined petroleum coke. In some respects it may offer unique friction and wear properties due to its well developed layer structure. Applications where higher purity, "softer" calcined petroleum coke is required may benefit from utilization of this material.