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    Carbon nanotubes experiment in microgravity
    (2011-10-03) LA NEVE, A.; BELLODI, M.; MELO, M. A. A.; FERREIRA, M.; CASTRO, R. H. R.; PEREIRA, A. N.; F. S. Ortega
    Carbon Nanotubes (CNTs) nanostructures are an interesting focus of research, due to their unique electrical and mechanical properties, including high specific surface area and electrical conductivity. These characteristics make them potential components for applications in microelectronics, field emitters and catalysts, among others. The purpose of this experiment is to obtain CNT homogeneous films on aluminum substrates both in microgravity and on earth, in order to study the real effect of gravity in the deposits organization. This experiment was carried out in microgravity, during a period of 4 minutes, aboard a VSB-30 Brazilian sounding rocket. To perform the experiment, it was developed an equipment, called CADEN, which consists of 3 sets of 4 reaction chambers, each one containing an aluminum substrate (in a total of 12), in addition to embedded electronics, responsible for the system control, data acquisition and monitoring of electric currents in each chamber. The chambers were loaded with a CNT solution in different concentrations, 0.1 mg/ml and 0.5 mg/ml; in each of them an electrolytic current flew according to the electrical potential applied to the aluminum plates, which acted as anode and cathode. In order to provide for a wide range of possibilities, which might be useful in further analysis, different DC voltages were applied to each pair of chambers, which were loaded with different CNT concentrations. On receiving the microgravity signal, on flight, the control system applies a different bias on each of the three sets. From this moment on, each pair of chambers will be active for 2 or 4 minutes time, accordingly to their programming. While the experiment is running, the electric currents that flow through all chambers, along with temperature and other variables, are periodically read and stored in the internal memory, and are also transmitted by telemetry. The launching and payload rescue were successful, and so was the equipment functioning. Electrodes electrical characterization was performed, focusing on the plates surface resistivity, and it was observed a significant increase in electrical conductivity. Additional analyses include plate surfaces electron microscopy, to verify both CNT deposition morphology and the nanotubes orientation on the surface. The results were compared with data obtained on earth under similar conditions, to identify the influence of microgravity and the role of the other variables in the experiment. The electrical resistance of plates with CNT deposited in microgravity was, in general, lower than that of plates with CNT deposited on Earth. Copyright ©2010 by the International Astonautical Federation. All rights reserved.