Concentrated sunlight was used as an energy source to produce carbon single-wall nanotubes (SWNTs) by co-evaporation of cobalt and carbon in an argon atmosphere. The 10 kW High-Flux Solar Furnace at the National Renewable Energy Laboratory was used to deliver solar radiation to the reaction chamber. Cobalt-doped graphite targets were fabricated from mechanical mixtures of cobalt and graphite, and from graphite powders doped by infiltration of Co-2(CO)(8). All targets produced SWNTs, with yields being the highest for the targets produced by infiltration methods. The approach of using concentrated sunlight for synthesis may enable the development of cost-effective and high-yield SWNT production.

Numerous approaches have been utilized to produce fullerene-related substances. One of these approaches uses sunlight as an energy source to vaporize selected carbon containing materials. Advantages and constraints of the solar fullerene production approach will be evaluated in light of recent work including solar production of single-walled nanotubes and creation of a second generation solar fullerene reactor.

Highly concentrated radiant energy provides a controllable means of delivering large flux densities (>100 W/cm/sup 2/) to solid surfaces. The resulting thermal energy can cause phase changes, atomic migrations, and chemical reactions on a surface without greatly perturbing the bulk properties, or the photons may directly interact with species on the surface to induce some desirable interaction. In a suitably designed solar furnace this flux can be delivered over large areas or tailored to accommodate particular processing requirements. Furthermore, this occurs without the environmental liability associated with providing power to more conventional light sources. Research to date has demonstrated the possibility of performing several interesting surface modifications, including phase transformation hardening of stools, melting powders or preapplied coatings to form fully dense, well-bonded coatings, initiation of self-propagating high-temperature synthesis reactions, rapid thermal annealing, and chemical vapor deposition. Particularly interestin results have been obtained in the cladding work, and the results of efforts to control the physical properties of the interfacial regions of coatings on steel is discussed in some detail.