Self-propagating exothermic chemical reactions can generate electrical pulses when guided along a conductive conduit such as a carbon nanotube. However, these thermopower waves are not described by an existing theory to explain the origin of power generation or why its magnitude exceeds the predictions of the Seebeck effect. In this work, we present a quantitative theory that describes the electrical dynamics of thermopower waves, showing that they produce an excess thermopower additive to the Seebeck prediction. Using synchronized, high-speed thermal, voltage, and wave velocity measurements, we link the additional power to the chemical potential gradient created by chemical reaction (up to 100 mV for picramide and sodium azide on carbon nanotubes). This theory accounts for the waves' unipolar voltage, their ability to propagate on good thermal conductors, and their high power, which is up to 120% larger than conventional thermopower from a fiber of all-semiconducting SWNTs. These results underscore the potential to exceed conventional figures of merit for thermoelectricity and allow us to bound the maximum power and efficiency attainable for such systems.

Optoelectronic properties of CVD graphene are characterized over a wide frequency range: THz, IR, visible and near-UV. We used Raman spectroscopy to characterize the synthesized graphene films. All graphene layers were deposited on various substrates, some ones transparent or flexible, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), quartz and silicon. Transmission Terahertz time-domain spectroscopy (THz-TDS) method, in the range from 100 GHz to 3 THz, is used to analyze the transmittance, sheet conductivity and attenuation of graphene and the complex refractive index of substrates. From IR, near-UV and visible spectroscopy we obtained the transmittance of the substrate and the sample at those frequency ranges, and we deduced the graphene transmittance on each substrate. We found that it is close to 97% in most cases.

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The non-parametric kinetics (NPK) method was developed for simulation purposes by applying macroscopic kinetics to complex reactions and transformations. This is able to describe a reaction and provide information about its temperature function, such as Arrhenius equation, and the type of reaction involved. To determine whether the method is applicable to reactions involving nanoscale materials, the NPK method is applied to study the oxidation of titanium nitride and carbide and the results are compared with those already obtained. NPK reproduces both reactions without any problems. It provides consistent results in the case of nitride, but in the case of carbide it suggests that more transformations are involved in the reaction, most likely including diffusional control of the reaction. C 2011 Wiley Periodicals, Inc. Int J Chem Kinet 44: [147][148][149][150][151][152][153][154] 2012