Carbon Materials Research
The University of Kentucky Center for Applied Energy Research has constructed and operates one of the country's only production lines for spinning experimental carbon fiber. The system is designed for researching many of the several parameters that are involved in carbon fiber production. The carbon materials group is uniquely positioned to partner with industry on the development of new carbon fiber products.
Development of experimental carbon fiber necessitates bench scale spin line characteristics mirroring that of mass production companies. Advancements in bench scale spinning for the production PAN-based precursor fiber are researched; in particular, improvements of spin dope characteristics, die geometry, minimizing die swell ratio, solvent bath coagulation for decreased voids and improved mechanical properties, alignment of molecular chains along the fiber axis through steam stretch, and fiber drying before take up resulting in decreased tensile stress on collected fiber. The addition of an inline filtration system resolves common issues in bench scale spinning stability. This system allows for experimentation with innovative spin dopes for the production of experimental precursor fibers, with the financial benefits of a bench scale spin line.
The University of Kentucky Center for Applied Energy Research (UK/CAER) has been involved with multiwalled carbon nanotube synthesis and research for over a decade. During that time, the carbon materials group researched many of the desirable properties that MWCNTs exhibit, including strength, stiffness, electrical conductivity, and thermal conductivity. Additionally, the group has worked extensively to make multiwall carbon nanotubes more accessible by driving down their cost through continuous production technology.
UK/CAER holds 2 patents for the continuous synthesis of high quality (3% residual catalyst), aligned MWCNTs. The MWCNTs are CVD grown in a "wheat-field" orientation on a substrate, from which they are harvested either as a free-standing array or as a powder. UK/CAER has a production capacity of approximately 1 kg of MWCNT powder per business day. UK/CAER has, on-site, a high-temperature graphitization furnace capable of temperatures up to 2700° C with CNT sample sizes of up to approximately 25 g. The heat treatment of the MWCNTs yields a more graphitic microstructure and removes the residual iron catalyst.
At UK/CAER, the carbon materials group has investigated the role of MWCNTs dispersed in thermoplastic and thermosetting polymers extensively. Our research has covered a broad spectrum of composite materials applications. The group has also investigated several applications for free standing arrays of MWCNTs, including thermal interface materials.
The program is directed toward the development of technologies for producing coal-derived feedstocks for the production of a range of high value carbon materials and specialty chemicals. The program has successfully demonstrated that a broad range of value-added carbon materials such as carbon fibers, activated carbon fibers, binder pitches, and carbon/carbon composites can be produced from coal utilizing mild, non-hydrogenative solvent extraction.
Coal tar pitch, a liquid by-product from coke oven operations, is a feedstock for manufacturing a wide range of carbon materials such as anode binders, coke, graphite and different types of carbon fiber. However, the amount of pitch and other coal liquids available from this source is essentially determined by the demand for metallurgical coke, which has decreased due to a decline in the demand for steel and technological improvements in steel making. Furthermore, coke oven operations continue to close due to their failure to meet increasingly stringent environmental regulations and the need for capital investment to rebuild and maintain existing coke ovens. CAER seeks to address these issues by altering the "Liquefaction Concepts" developed in an earlier program, towards economically attractive processes for producing high value chemicals and carbon materials from coal. These processes include low-severity, non-hydrogenative solvent extraction of coal and mild thermal co-processing of coal and solid municipal waste.
The low severity non-hydrogenative solvent extraction process produces a coal-derived pitch. This pitch has been successfully used to produce general-purpose carbon fibers, activated carbon fibers and binders. In all cases, the materials produced were comparable in performance with those commercially available. Mild thermal co-processing of coal with solid municipal waste produces high value oxygenates which can be used as feedstocks for specialty chemical applications. In conjunction with other projects in the Carbon Materials Group, the Coal-Derived Pitch project provides feedstocks to be assessed for use in producing other carbon materials and composites. Recently, coal derived pitch has been used to produce pitch / multiwall carbon nanotube (MWNT) fiber composites. The production pitch/MWNT composites, continues to be developed by the group.
In continuing the development of the low severity, non-hydrogenative extraction process, a new process concept has been developed: an integrated extraction process. This integrated process, designed to minimize processing and solvent costs will produce high value chemicals, carbon products and fuel. Extraction processes currently under development suffer from solvent depletion due to adduction, thermal cracking or chemical reaction with the feed coal. As a result, these processes require a significant amount of expensive solvent makeup and/or solvent treatment. The integrated extraction process solves this problem by generating its own indigenous, coal-derived solvent while simultaneously producing high value chemicals, such as phenols and cresols. Conceptually, the integrated extraction process could be part of a larger co-production power plant where the solid and gas by-products of the process would be utilized as fuel for the power generation plant.