Galvanic Corrosion of High-Temperature Low-Sag (HTLS) High Voltage Conductors: New Materials - New Challenges

High-Temperature Low-Sag (HTLS) high voltage overhead conductors offer higher operating temperatures, reduced resistance and less sag than conventional designs. With up to twice the current capacity for the same diameter conductor, they may help ease the power shortage in the constantly increasing electricity demand, but there might be some concerns about their corrosion resistance. These new conductors use materials relatively new to the power industry, such as advanced carbon fiber polymer matrix composites and unique metal matrix composites/nano-composites predominantly used in aerospace industries. This study has made an initial assessment of potential galvanic corrosion problems in three very different HTLS designs: ACCC (Aluminum Conductor Composite Core), ACCR (Aluminum Conductor Composite Reinforced) and ACSS (Aluminum Conductor Steel Supported). In particular the ACCC design was evaluated for its resistance to corrosion and compared to the other designs. The study concludes that all three designs can develop galvanic corrosion under certain circumstances. While the results are not sufficient to make service life predictions of any of the tested conductors, they point out the necessity of thorough corrosion testing of all new conductor designs.

The Adsorption of Polyatomic Molecules on Carbon Surfaces

Carbon nanotubes exhibit the structure and chemical properties that make them apt substrates for many adsorption applications. Of particular interest are carbon nanotube bundles, whose unique geometry is conducive to the formation of pseudo-one-dimensional phases of matter, and graphite, whose simple planar structure allows ordered phases to form in the absence of surface effects. Although both of these structures have been the focus of many research studies, knowledge gaps still remain. Much of the work with carbon nanotubes has used simple adsorbates1-43, and there is little kinetic data available. On the other hand, there are many studies of complex molecules adsorbing on graphite; however, there is almost no kinetic data reported for this substrate. We seek to close these knowledge gaps by performing a kinetic study of linear molecules of increasing length adsorbing on carbon nanotube bundles and on graphite. We elucidated the process of adsorption of complex admolecules on carbon nanotube bundles, while at the same time producing some of the first equilibrium results of the films formed by large adsorbates on these structures. We also extended the current knowledge of adsorption on graphite to include the kinetics of adsorption. The kinetic data that we have produced enables a more complete understanding of the process of adsorption of large admolecules on carbon nanotube bundles and graphite. We studied the adsorption of particles on carbon nanotube bundles and graphite using analytical and computational techniques. By employing these methods separately but in parallel, we were able to constantly compare and verify our results. We calculated and simulated the behavior of a given system throughout its evolution and then analyzed our results to determine which system parameters have the greatest effect on the kinetics of adsorption. Our analytical and computational results show good agreement with each other and with the experimental isotherm data provided by our collaborators. As a result of this project, we have gained a better understanding of the kinetics of adsorption. We have learned about the equilibration process of dimers on carbon nanotube bundles, identifying the “filling effect”, which increases the rate of total uptake, and explaining the cause of the transient “overshoot” in the coverage of the surface. We also measured the kinetic effect of particle-particle interactions between neighboring adsorbates on the lattice. For our simulations of monomers adsorbing on graphite, we succeeded in developing an analytical equation to predict the characteristic time as a function of chemical potential and of the adsorption and interaction energies of the system. We were able to further explore the processes of adsorption of dimers and trimers on graphite (again observing the filling effect and the overshoot). Finally, we were able to show that the kinetic behaviors of monomers, dimers, and trimers that have been reported in experimental results also arise organically from our model and simulations.