(138e) Nanomaterials and Energy: Interfacial Synergy

With energy at the forefront of the national economy and security, energy sources and its utilization are of particular interest. Not surprisingly, energy and materials are intimately related. Many forms of energy processes, e.g. conversion, storage and generation are dominated by interfacial reactions. Therein nanomaterials as interfacial modifiers will play a critical role in these processes. Although synthesis of a host of organic and inorganic nanomaterials has been demonstrated, their integration into these practical, energy-directed applications remains highly challenging. This talk will provide an overview of nanomaterial synthesis, integration and specific gains in energy conservation, storage, efficiency, transfer, control and generation.

Fields of study and specific applications we have explored include the following:

1) Energy Conservation ? Carbon nanotubes add substantial value to polymer composites by strength and weight. Dispersal is perhaps the largest challenge in utilizing CNTs in PMCs. Using CNTs as directly synthesized upon a pre-defined support structure, purification is negated while dispersal is ensured by the in-situ growth. Moreover CNTs in this configuration have the potential to act as interfacial modifiers for traditional matrix reinforcing elements.

2) Energy Storage ? Nanostructured carbons have high potential to improve Li ion battery power by virtue of short transport distances and capacity by full accessibility of lamella galleries. Carbon nanofibers as anode material demonstrate nearly the double intercalation capacity relative to the theoretical capacity of graphite.

3) Energy Efficiency ? Nanolubricants add value because they are size-matched to the surface asperities. Short CNTs purified under mild conditions yield friction coefficients < 0.1 when tested as pure mateiral. Nano-onions as additives in Krytox have increased the lifetime by 100% while decreasing the friction coefficient by ½ in vacuum. CNTs prove synergistic as an additive in ionic fluids for lubrication.

4) Energy Transfer ? Nanofluids aid heat transfer and increase efficiency. By comparison of CNT and nano-onion additives, establishment of a percolation threshold was identified as the operative mechanism. Surface functionalization serves to increase water layer ordering while assisting with soft-assembly, thereby aiding long-range phonon propagation through an extended lattice.

5) Energy Control ? Sensors, in particular metal oxide semi-conductors are currently used in energy control for both consumer comfort and industrial processing. Toxic gases, combustion exhausts and fuel are but some examples. Biomass gasification, deconstruction and liquid fuel generation will rely upon feedback control from sensors. Response magnitude and rate are illustrated for TiO2, ZnO and CNT materials. The role of crystallinity, long recognized as changing the fundamental conductivity sensing mechanism is defined by comparative tests of single versus polycrystalline SnO2.

6) Energy Generation & Conversion - Nanostructured oxides and metal nanoparticles will play a dominant role in photon conversion and catalysis. Volatile organic compound destruction relies upon catalysts supported upon various oxide materials, such as TiO2. Preferential oxidation of CO is a well-recognized step in hydrocarbon processing for fuel cells. Dye sensitized solar cell performance is critically dependent upon the tradeoffs between solar absorption and electron-hole recombination in the nanostructured metal oxide. Metal nanoparticles can enhance performance in each of these applications and are also the core of fuel cell performance. In all these applications the electron mobility is key to minimize electron-hole pair separation!

Results and highlights in each application will be presented.