are very conservative in changing lining concepts or the grades of the lining material. Challenge is the chemical erosion caused by the interaction between the liquid iron and the carbon material. One improvement in the recent past was the introduction of so‐called microporous linings with mainly pores below 1 μm in diameter. The right selection of anthracite can significantly elongate the lifetime of the furnace cycle. Hence, best chemical resistance and mechanical wear resistance are the goals for development.
So far we have considered coarse‐grained carbon and graphite materials. Specialty graphite is a polygranular material with very fine grain sizes. To achieve a high isotropy, not only the raw material is carefully selected among isotropic cokes, but also the process of forming by isostatic pressure application supports the isotropy. This graphite material is known as iso‐graphite. Its main application is the production of silicon single crystals (Figure 1.16) for the semiconductor industry and the production of polysilicon for the solar industry (Figure 1.17). Other applications are electrical discharge machining, casting of non‐iron metals, and many other applications.
Figure 1.16 Silicon single crystal production.
Figure 1.17 Demand for fine‐grained graphite.
The main production capacities are located in Japan (Figure 1.18). China entered this market recently and strives to become a serious competitor in this field.
Figure 1.18 Fine‐grained graphite producer.
The mechanical strength is the key quality parameter for iso‐graphite. Fundamentally the strength of graphite increases with decreasing grain size. This led to a decrease in grain size during the last decades to nowadays few microns and mechanical strength of up to 100 MPa. The future challenging task is the process technology and automation to produce bigger block sizes at high process yield.
It was shown that traditional carbon and graphite materials have a long‐lasting history. During this history they have improved their quality and reliability. Their consumption in their respective application was reduced. Despite this long history there is still room for improvement and open questions for basic research. The industrial perspectives for these materials are prosperous. The most probably ongoing growth in the BRIC countries will provide a constant grown in the demand for graphite electrodes, cathodes, and furnace linings. Iso‐graphite will benefit from the global expansion of clean solar energy.
1.3 Modern Application of Carbon Materials
Carbon fibers are thin (diameter = 7 μm), light (real density = 1.8 g/cm3), strong (strength up to >6 GPa), and stiff (Young’s modulus up to 900 GPa) (Figure 1.19). These fibers exceed any other fiber material in its specific properties and come close to the theoretically predicted properties of pure graphite. The properties depend on the temperature weakly only. Only the presence of oxygen limits the application at elevated temperatures. Carbon fibers can be made from different fiber precursors. These fiber precursors can be polyacrylonitrile (PAN), pitch, or rayon. During the history of the carbon fiber development, PAN‐based carbon fiber won the race. Reasons had been the relatively easy processing and the wideness of achievable mechanical properties. Mesophase pitch‐based carbon fibers are only competitive in applications with extreme stiffness. Embedded in a polymer matrix (carbon fiber reinforced polymer [CFRP]) or a carbon matrix (carbon fiber reinforced carbon [CFRC]), superior material properties are the outcome. These spectacular properties were soon recognized for military application, an area where functionality overrules cost (Figure 1.20). As the carbon fiber price dropped, application in sport articles followed. Today carbon fibers are common in the civil aviation industry. Weight and thus the reduction of operational cost made the use of CFRPs’ attractive.
Figure 1.19 Mechanical properties of carbon fibers.
Figure 1.20 Carbon fiber fields of application.
Modern planes will contain more than 50% of their constructional parts made from CFRPs. In the area of wind power, the blade length is going to exceed 70 m. To provide the necessary stiffness to these blades, the application of CFRPs is unavoidable. CFRPs are indispensable for the requested energy saving in transportation and the start into e‐mobility. These new markets will cause a heavily increasing demand for carbon fibers (Figure 1.21). Forecast expects a growth in demand from 20 000 t in 2010 to 270 000 t in 2030. The production know‐how (precursor) and production capacities are concentrated in companies based in Japan or the United States (Figure 1.22). Europe started to establish its own independent position in this market.
Figure 1.21 Carbon fiber demand and capacity.
Figure 1.22 Carbon fiber producers and their estimated capacities. Sources: The Global CF and CC Market 2018, Sauer & Kühnel; Annual Report Composites United 2019).
The production cost for CFRPs has to be reduced to become competitive versus the traditional construction materials steel and aluminum. The cost for carbon fibers production is linked to the oil price and energy pricing; the biggest potential today is in the manufacturing process for CFRPs itself. Automation and reasonable lot sizes are the keys to success. The development of matrix systems that will accelerate the manufacturing processes and enable the recycling into new components is necessary. Thermoplastic polymers will partially replace the currently used thermosetting resin systems. The fiber surface has to be modified to provide the required interaction with the respective polymer system. On a long‐term perspective, precursor fibers based on renewable materials and “green” matrices will be the
