ADVANCED MATERIALS & PROCESSES | NOVEMBER 2026 19 There is always more to the story, as the saying goes, and there is a fascinating connection of nuclear graphite to carbon arcs. The field of arc lighting and the study of arc radiation led to work on spectroscopy. The expertise that National Carbon Company had with arc spectroscopy helped to identify the impurities in the nuclear graphite. Scientists at National Carbon and the Manhattan Project determined that boron was present and knew that it was a key neutron absorbing impurity. The determination of this fact led to the development of a special graphite grade of very high purity through careful control of raw materials and process, the first “nuclear graphite” materials. Nuclear graphite grades were used for additional experimental reactors, and power generation in the U.S., U.K., and other countries. Today, there remains a high level of interest in high-temperature gas-cooled reactors and molten salt reactors, which rely on new generations of engineered graphite grades that meet nuclear specifications. THE SPACE AGE: GRAPHITE TAKES THE HEAT The space age significantly expanded the loading that advanced materials must withstand. Rocket propulsion, atmospheric re-entry, and hypersonic flight placed unprecedented levels of heat flux, shock, and other aero- thermochemical loads on materials. With the advancements in aerospace and rocketry in WWII, polygranular high-performance graphite had been continuously advancing to new levels of density, strength, and thermal shock. Carbon fibers made from rayon or cotton had been known since Thomas Edison’s time, and had been used for early carbon fiber composites, but the fibers were not high strength. Then, a wonderous finding changed everything. Roger Bacon, a physicist working at Union Carbide, accidentally discovered graphite whiskers in 1958, studying vaporized carbon using carbon arcs (Fig. 10). He tested these whiskers and discovered amazing strength and modulus per unit mass[5]. The 1960s became a monumental time in carbon fibers and composites, with simultaneous work being performed in multiple countries on advanced rayon- based carbon fibers, PAN-based carbon fibers, and pitch-based carbon fibers. These rapid advancements led to a class of high-performance carbon fibers and composites, which were capable of the most demanding aerospace applications such as atmospheric re- entry and famously as the nose cone and leading edge of the Space Shuttle orbiter[6]. Carbon fiber composite brakes became widely available for commercial airplanes in the 1980s[7]. As space-age is becoming commer- cial, demand for advanced materials and reusability means carbon fiber- based composites and graphite materials are only increasing in their importance. THE SEMICONDUCTOR AGE: NO SILICON WITHOUT CARBON It is not immediately intuitive that the so-called “silicon age” is built on carbon. However, for example, the Czochralski method for growing single-crystal silicon is the most widely used for producing silicon for semiconductor applications. But at crystal growing temperatures exceeding 1400°C, only high-purity graphite materials can perform as heaters, crucibles, susceptors, and insulating materials. Graphite materials are also used for chemical vapor epitaxy processes, e.g., as in coated plates and susceptors. Advanced semiconductors are also carbon-bound, for example silicon carbide crystal growth can occur at temperatures above 2000°C, creating an even more demanding environment for furnace materials, and specially engineered graphite is used for many critical components[8]. THE NANOTECHNOLOGY AGE: SMALL BUT SPECTACULAR CARBON The 1980s brought the world firmly into the nanotechnology age, when humankind was directly producing and applying nanomaterials. In 1985, scientists Robert Curl, Sir Harold Kroto, and Richard Smalley created fullerenes, Fig. 9 — Illustration of Chicago Pile 1 (CP-1), Stagg Field West Stand, perspective drawing by Melvin A. Miller, 1946, University of Chicago Photographic Archive, The Hanna Holborn Gray Special Collections Research Center, University of Chicago. Fig. 10 — High-magnification electron micrograph of Roger Bacon’s high-strength high-modulus carbon filaments from U.S. Patent No. 2,957,756 (left). High-magnification polarized light optical micrograph of mesophase pitch carbon fiber, showing high oriented structure from Leonard Signer’s U.S. Patent No. 4,005,183 (right). Mesophase pitch fibers with an oriented structure can have very high modulus and conductivity after high-temperature heat treatment.
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