Scale up of a Solar Reactor for Fullerene and Nanotube Synthesis

Abstract

Conventional methods for the synthesis of fullerenes and carbon nanotubes such as laser or electric arc ablation have failed when the process is scaled up. Our ultimate goal is to scale a solar process up from 2 to 250 kW; this paper shows that our method for achieving this scale-up is valid because we were able to predict process performance variables at the 50 kW level from preliminary experimental results from 2 kW experiments. The key parameters that characterize this process are the carbon soot mass flow rate and the desired product yield. The carbon soot production rate is a function of the target temperature and this can be predicted in a straightforward way from a heat transfer model of the larger system. The yield is a more complicated function of specific reactor variables such as patterns of fluid flow, residence times at various temperatures, and the reaction chemistry, but we have found that for fullerenes it depends primarily on the concentration of carbon vapor in the carrier gas, the target temperature and the temperature distribution in the cooling zone. Using these parameters, we scaled our process up to 50 kW and compared the predicted results to the measured performance. A graphite target 6 cm in diameter was vaporized in an argon atmosphere and a reduced pressure of 120–240 hPa with a solar flux density in the range 600-920W/cm2. Vaporization rates as high as 50 g/h were measured with a fullerene production rate equal to about 2 g/h, i.e., the expected results.

Energy Requirements of Carbon Nanoparticle Production

“…An electric arc or a laser normally delivers the energy for vaporization, but other techniques are being investigated. One interesting development is the use of solar furnaces to provide the vaporization energy (Guillard et al 2002). As it uses solar energy, the power for such a system is, to a large degree, “free.” Additionally, there are fewer problems scaling the power input to the system.…”

A high irradiance solar furnace for solar cell characterization and nanomaterial synthesis

“…A solar furnace can provide this uncommon combination, the first evidence of which was demonstrated for carbon nanomaterials [3][4][5] . More recently, the purely photothermal production of an assortment of inorganic nanomaterials (e.g., MoS 2 , WS 2 , Cs 2 O, Si and SiO 2 ) by highly concentrated sunlight was achieved in miniature solar fiber-optic mini-dish concentrators [6][7][8] .…”

“…High solar irradiance provides a distinctive probe for subtle and sometimes unanticipated properties of ultra-efficient (usually multi-junction) photovoltaic (PV) cells 1,2 , as well as a tool for producing nanostructures the synthesis of which requires high temperature and strongly non-equilibrium environments [3][4][5][6][7][8] . Conducting experiments under controlled indoor conditions is markedly facilitated by a solar furnace: an optical system that reflects sunlight into the laboratory and concentrates it typically to irradiance levels from thousands to tens of thousands of suns [3][4][5][9][10][11][12] (1 sun 1 mW/mm 2 ).…”

“…Conducting experiments under controlled indoor conditions is markedly facilitated by a solar furnace: an optical system that reflects sunlight into the laboratory and concentrates it typically to irradiance levels from thousands to tens of thousands of suns [3][4][5][9][10][11][12] (1 sun 1 mW/mm 2 ).…”

Reexamination of the feasibility of a world-wide, photovoltaic energy grid

“…Elimination of this energy would significantly reduce the amount of energy needed to produce SWCNTs. Solar ovens have been shown in literature to be able to produce single wall carbon nanotubes through graphite vaporization and chemical vapor deposition techniques [12][13][14][15]. The solar ovens are able to take advantage of the solar activity in the more active regions highlighted in Figs.…”