Materials Program for 1994-1995
- Crystalline Nanoparticles
- Polymerization of C60 (Fullerene) Solids
- Chemical Vapor Deposition
- Synthesization and Evaluation of Si Clathate Solids
- Production of Activated Carbons from Wood and Wood Fractions
- Modification of Properties of Wood-Based Activated Carbons
- Activated Carbon Catalysts from Coal Precursors
- Activation and Characterization of Carbon Fiber Composites
- Synthesis of General Purpose and Activated Carbon Fibers
- Activated Carbons for SO2 Conversion
Past Contact: Peter Eklund - Associate Director, Materials Program
Current Contact: Rodney Andrews Phone: 859-257-0265
Research projects in the Materials Program are principally concerned with the synthesis of carbons and carbon-containing materials. Areas of focus include laser pyrolysis-derived catalysts and materials, novel carbon materials (e.g, fullerenes, nanotubes and intercalation compounds) and activated carbons.
Research into the fundamental limitations of crystalline nanoparticles produced by CO2 laser pyrolysis continues with emphasis on the production of ideal transition metal carbides and sulfides [Fe, Mo, W]. This work is funded by the Consortium for Fossil Fuel Liquefaction Science (CFFLS) and the National Science Foundation (NSF). The CFFLS component focuses on the development of catalyst particles for coal liquefaction and plastic waste, whereas the NSF component concerns the development of particles for battery electrodes (Li:MoS2) and gas sensors (Mo2C, Mo2N). In the former, we have produced oxygen-free nitrides and carbides with high activity for heteroatom removal. Work on bi-functional catalysts for coprocessing coal and plastic also began last year. It was found that Brinsted acid sites play a key role in the conversion of medium density polyethylenes to valuable fuel products.
In research on novel carbons, we are studying the polymerization of C60 (fullerene) solids.Work last year emphasized the effects of temperature up to ~ 600 0C and intermediate pressure (~ 50 atm). Comparison of these polymerized products to the photopolymerized products patented by Eklund in 1994 have shown interesting differences in the inter-fullerene bonding.
Recent funding to investigate the production of thin films of layered carbon-selenium (tellurium) compounds by chemical vapor deposition (CVD) has been awarded by the Advanced Research Projects Agency (ARPA). These intercalation compounds are being investigated for their C-axis thermal and electrical transport properties and for Peltier refrigeration.
WithNSF funding, investigations are being made to synthesize and evaluate Si clathrate solids which exhibit a regular array of hollow Si polyhedra. The polyhedra are co-valently bonded and can be endohedrally doped with electron d onors such as Na and Ba. Possible applications in novel semiconductor devices may emerge: the compounds BaNa Si46 were found to exhibit superconductivity at ~4K.
Past Contact: Marit Jagtoyen
Current Content: Rodney Andrews
The program on activated carbons centers on developing an improved understanding of the mechanisms of pore structure development in activated carbons derived from different precursors, by different process routes. Activated carbons have been produced in the form of powders, extrudates, fibers, and activated composites. The ultimate goals are to produce novel materials with controlled porosity and surface chemistry for use as adsorbents or catalysts.
A project entitled "Production of Activated Carbons from Wood and Wood Fractions",funded by the Department of Agriculture, was recently completed. It involved a collaborative effort with the Virginia Polytechnic Institute and State University (VPI) to examine the formation of activated carbons from wood and wood waste by phosphoric acid activation. Precursor materials were prepared at VPI using steam explosion and solvent extraction to produce wood fractions with different cellulose and lignin contents. The results showed that the pore-size distribution of activated carbons can be altered significantly by precursor pretreatment.
Modification of the Properties of Wood-Based Activated
Arising from basic studies of the phosphoric acid activation of hardwoods, techniques have been developed to selectively alter the pore size distribution and chemical composition of activated carbons, and to produce extruded wood-based carbons with strength and adsorptive properties that are comparable to those of commercial coal-based carbons. A patent application has been submitted.
Collaborative efforts with Dr. Malvina Farcasiu at Pittsburgh Energy Technology Center, have led to the synthesis of highly active Activated Carbon Catalysts from Coal Precursors. The catalysts have been rigorously tested in hydrogenation reactions, and form the basis for a patent application.
Research has continued on the activation and characterization of carbon fiber composites under contract to the Oak Ridge National Laboratory. These rigid, highly permeable materials are being studied for their application to gas separation processes. In addition, internally funded work has focused on the formation of alternative carbon fiber composites using techniques developed at the CAER. These composites have a rather different structure to the Oak Ridge materials, and there is a wider range of possibilities for altering pore size distribution and the type of carbon incorporated. The unique properties of both types of composite are leading to investigations, usually on a collaborative basis, of their potential for a diversity of applications, not all of which require the material to be activated.
The synthesis of general purpose carbon fibers and activated carbon fibers from non-commercial pitch--like sources is the subject of ongoing research. The composition of the precursor pitch has a strong influence on both the ability to form and process fibers, and the properties of the final products. Coal liquids derived from a number of processes and coal origins are also being investigated as fiber precursors.
In research originating from a collaborative arrangement with Professor Mochida, shu University, Japan, and co-sponsored by the CAER, investigations are being made of the use of activated carbons for the low-temperature conversion of SO2 to sulfuric acid. Activated carbon fibers from oil shale have been found to be especially active catalysts.