Due to the high intrinsic thermal conductivity of graphitic structures, much interest has developed in incorporating these materials into modern nano-devices for improved thermal abatement. In order to be integrated successfully, thermal energy must be able to transport efficiently through the graphitic materials and into the surrounding structure, most commonly a metal. However, thermal boundary conductance at metal-graphite interfaces is traditionally poor in comparison to non-graphitic substrates, due in large part to the weak van der Waals adhesion force between the metal and underlying carbon structure. To be applicable as thermal abatement materials, an enhanced understanding of the role of the metal-carbon interface is required. This paper reports the changes to phononic thermal transport across the interface between metallic thin films and highly oriented pyrolitic graphite (HOPG) substrates due to changes in interface structure and chemistry. The temperature dependent thermal boundary conductance is measured using transient thermoreflectance from 100 K to 400 K. It is found that the differences in metal-carbon bonding and structure at the interface have a significant impact on the thermal conductance between the metallic thin films and the HOPG substrates.

Liquid water behaviors in the porous gas diffusion layer used for PEMFCs were investigated by high-resolution soft X-ray radiography. We observed water evaporation process from the soaked carbon paper GDL and showed the gradual disappearance of liquid water with spatial inhomogeneity. The visualization of liquid water revealed that thin water film was retained in the GDL. This was also observed in the operating fuel cell. Our soft X-ray observation suggests that this thin water film formed in the carbon paper GDL possibly caused increase in the toutuosity of the GDL, resulting in deterioration of cell performance due to less mass transport in fuel cells.

Reburning of cattle manure-based biomass (CB) with coals is performed to develop environmentally friendly thermo-chemical energy conversion technologies for NO x reductions and Hg captures and removals from existing pulverized coal-fired power plants. A small-scale (30 kWth) down-fired boiler burner facility has been used for burning most types of pulverized solid fuels including coal and biomass. Blends of CB and coals are used as reburn fuels. It has hypothesized that a major fraction of the fuel-N in the CB is released in the form of NH3 or urea. In the reburn process, therefore, it is believed that NOx produced by coal is reduced to molecular nitrogen by NH3 released from the pyrolysis of CB under slightly fuel-rich conditions. The CB also contains larger amounts of chlorine (Cl) than most types of coals. Hence gaseous mercury (Hg) in the flue gas is oxidized by large amounts of Cl species mainly from the CB combustion. Consequently, the results indicate that the CB can serve as a very effective fuel supplementing coals on NOx reductions and Hg captures and removals in pulverized coal-fired boilers. It was also found that the auto-gasification occurred during the pyrolysis due to the oxygen available in the fuel mainly helped for burning fixed carbon.

Carbon nanotubes (CNTs), because of their superior mechanical, electrical, and thermal properties and possible low-cost, large volume production, have been projected as promising nanostructure additives in polymer composites to achieve tunable and enhanced materials properties. Transport properties of CNT-polymer composites have been widely studied over the past decade and it is well-accepted that when the added CNTs exceed the percolation limit, the electrical conductivity of CNT-polymer composites can usually increase by several orders of magnitude. However, thermal conductivity measurements present mixed results and even for positive results, the enhancement is much lower than that expected from traditional theories. For example, Biercuk et al. [1] demonstrated that 1 wt% of single-wall CNTs (SWCNTs) in industrial epoxy could increase the thermal conductivity by 125% at room temperature, three-times higher than that from 1 wt% loading of carbon nanofibers. However, similar studies [2] showed that thermal conductivity only increased marginally for multi-wall CNT (MWCNT)-epoxy composites and more surprisingly, the thermal conductivity for SWCNT-epoxy composites was even lower than that of pure epoxy.

The conversion of renewable energy especially solar energy into versatile fuels is a key technology for an innovative and sustainable energy economy. To finally benefit from solar fuels they have to be produced with high efficiencies and low to no greenhouse gas emissions in large quantities. The final goal will most probably be the carbon free fuel hydrogen. But the main challenge is its market introduction. Therefore a strategy incorporating transition steps has to be developed. Solar thermal processes have the potential to be amongst the most efficient alternatives for large scale solar fuel production in the future. Therefore high temperature solar technologies are under development for the different development steps up to the final goal of carbon free hydrogen. This paper discusses the strategy based on the efficiencies of the chosen solar processes incorporating carbonaceous materials for a fast market introduction and processes based on water splitting for long term solar hydrogen generation. A comparison with the most common industrial processes shall demonstrate which endeavors have to be done to establish solar fuels.

Carbon is not only a major product of the methane decomposition but also a catalyst for the heterogeneous methane decomposition reaction. It is highly desirable that the morphology and surface properties of the product carbon be controlled to maximize their catalytic effects. In this paper, we characterize the physical properties of two activated carbon samples by sizes, and crystallographic structures using scanning electron microscope, x-ray diffraction, particle size analyzer, and surface area measurement. The paper also includes high temperature thermogravimetric experiment results on the carbon–hydrogen reaction to show if the injected carbon particles reacts with the formed hydrogen, which has not been studied in solar thermal hydrocarbon decomposition before. Results show that carbon does not react with hydrogen to form methane or any other intermediate compounds up until 900°C, which explains the favorable effect of carbon laden flow experiments for catalytic methane decomposition at lower temperatures. These results will be used to identify the optimal operating conditions for our solar reactor.

A Lean, Premixed, Prevaporized (LPP) combustion technology has been developed that converts liquid biofuels, such as biodiesel or ethanol, into a substitute for natural gas. This fuel can then be burned with low emissions in virtually any combustion device in place of natural gas, providing users substantial fuel flexibility. A gas turbine utilizing the LPP combustion technology to burn biofuels creates a “dispatchable” (on-demand) renewable power generator with low criteria pollutant emissions and no net carbon emissions. Natural gas, petroleum based fuel oil #1 and #2, biodiesel and ethanol were tested in an atmospheric pressure test rig using actual gas turbine combustor hardware (designed for natural gas) and achieved natural gas level emissions. Both biodiesel and ethanol achieved natural gas level emissions for NO x , CO, SO x and particulate matter (PM). Extended lean operation was observed for all liquid fuels tested due to the wider lean flammability range for these fuels compared to natural gas. Autoignition of the fuels was controlled by the level of diluent (inerting) gas used in the vaporization process. This technology has successfully demonstrated the clean generation of green, dispatchable, renewable power on a 30kW Capstone C30 microturbine. Emissions on the vaporized derived from bio-ethanol are 3 ppm NO(x) and 18 ppm CO, improving on the baseline natural gas emissions of 3 ppm NO(x), 30 ppm CO. Performance calculations have shown that for a typical combined cycle power plant, one can expect to achieve a two percent (2%) improvement in the overall net plant heat rate when burning liquid fuel as LPP Gas™ as compared to burning the same liquid fuel in traditional spray-flame diffusion combustors. This level of heat rate improvement is quite substantial, and represents an annual fuel savings of over five million dollars for base load operation of a GE Frame 7EA combined cycle plant (126 MW). This technology provides a clean and reliable form of renewable energy using liquid biofuels that can be a primary source for power generation or be a back-up source for non-dispatchable renewable energy sources such as wind and solar. The LPP technology allows for the clean use of biofuels in combustion devices without water injection or the use of post-combustion pollution control equipment and can easily be incorporated into both new and existing gas turbine power plants. No changes are required to the DLE gas turbine combustor hardware.

In order to improve the power generation performance of polymer electrolyte fuel cells (PEFC), it is necessary to maintain high current density over the whole area of the membrane electrode assembly (MEA) that includes the additional Pt-carbon particles loaded on the Polymer Electrolyte Membrane (PEM) as an electrocatalyst layer. However, the current density generated at the MEA is distributed unevenly due to a lack of hydrogen, flooding, and so on. Therefore, achieving a higher current density in a PEFC requires monitoring the local current density. The local current density in a PEFC can be measured by the frequency shift of the NMR signal received from planar surface coils inserted into the PEFC as sensors. This method is based on the relationship that the spatial gradient of the frequency shifts in NMR signals along the MEA is proportional to the magnetic field strength induced by local current density. In this study, two kinds of MEA were used. One MEA was with the platinum catalyst applied to an area of 50 mm * 50 mm. The other MEA was with platinum catalyst over half this area. The distributions of the frequency shift of NMR signals in PEFCs using these two MEAs were measured. These measured distributions of the spatial gradients were in agreement with those obtained by the theoretical-analysis of magnetic fields in PEFC. The spatial distributions of current density generated in PEFCs were obtained from the spatial gradients and theoretical result.

The transient thermal flash technique, originally developed for testing low thermal diffusivity micro/nanofibers, was implemented for measuring the thermal conductivity of vapor-grown carbon nanofibers. The present technique uses a microfabricated strip of gold, which acts both as a heater and a temperature sensor. The modifications were validated against commercially available carbon fibers (Pyrograf ® – I from Applied Sciences, Inc. and Mitsubishi K13D2U) and the results obtained were seen to match values previously reported in the literature. The carbon nanofibers reported in this article were also obtained from Applied Sciences, Inc. and are known as PR-25, belonging to the Pyrograf ® – III family of nanofibers. The thermal conductivities calculated based on the experimentally determined values of diffusivity along with the specific heat capacity and density of graphite were around 1100 W/m-K and 1700 W/m-K, respectively for the nanofibers heat treated to 1100 °C and 3000 °C.

Considering the massive-scale synthesis of single-walled carbon nanotube (SWCNT), chemical vapor deposition has become a standard process for synthesizing CNTs. In most of these processes, oxygen and hydrogen atoms were included originally or added later; and they are expected to have important roles such that they helped in the removal of amorphous carbon and prevented SWCNTs from containing metal particles. However, whole perspectives for suitable carbon source or ideal balance among carbon, hydrogen, and oxygen have not been reported. We examined a variety of raw materials in our newly developed round-trip-type vacuum furnace in order to determine whether they could be used to synthesize a carbon nanotube. We used Raman spectroscopy for evaluation, and plotted the component ratios of effective and ineffective materials on a C-H-O ternary diagram. Consequently, it is clear that the growth region should satisfy the equation O < C < (H + O) in molar ratio.

Heat transfer through the gas diffusion layer (GDL) is a key process in the design and operation of a PEM fuel cell. The analysis of this process requires determination of the effective thermal conductivity. This transport property differs significantly in the through-plane and in-plane directions due to the anisotropic micro-structure of the GDL. In the present study, a novel test bed that allows the separation of in-plane effective thermal conductivity and thermal contact resistance in GDLs is described. Measurements are performed using Toray carbon paper TGP-H-120 samples for a range of PTFE content at a mean temperature of 65–70°C. The measurements are complemented by a compact analytical model that achieves good agreement with the experimental data. The in-plane effective thermal conductivity is found to be about 12 times higher than the through-plane conductivity and remains approximately constant, k ≈ 17.5 W/mK, over a wide range of PTFE content.

To prepare homogeneous nanoparticles is a key issue for catalytic reaction because it directly connects to the control of the reaction. Using the sidewall of SWCNT as a catalyst supporter, the size of nanoparticle can be controlled, because the particle size should be affected by the interaction between SWCNT and metal species and its curvature. In this study, we focused on the direct synthesis of SWCNT with highly dispersed platinum group metal species. As a result, adding an adequate amount of platinum group metals into catalysts never disturbs the synthesis of SWCNT. Referring to TGA measurement, the presence of metal attached and/or metal involved SWCNT is suggested. Furthermore, SEM images show many nanoparticles are on SWCNT. When ruthenium catalyst is used, ruthenium nanoparticles are observed on the surface of nano carbon materials, which looks like SWCNT. These results indicate the possibility of direct synthesis of metal-containing SWCNT in CVD technique.

The aim of this study is to estimate the interfacial thermal resistance between a carbon nano-particle and alkali molten salt eutectics using molecular dynamics simulations. Additionally the effect of particle shapes and sizes on the interfacial thermal resistance was investigated using three different shapes of the carbon nanoparticles. Transient heat transfer simulation between a carbon particle and molecules of a molten salt was performed with the lumped capacitance method. A carbonate salt eutectic which consists of lithium carbonate (Li 2 CO 3 ) and potassium carbonate (K 2 CO 3 ) in 62:38 molar ratio was used as a solvent medium for the nanoparticles. Three carbon particles of a single walled carbon nanotube (SWNT), a fullerene (C 60 ), and a graphite sheet were used to represent different shapes of cylinders, a spheres, and disks, respectively. The interfacial thermal resistance was determined by a correlation with a specific heat of the carbon particle, their surface area, and the time constant of decaying particle temperature. The results show the interfacial thermal resistance values are independent of the particle size for SWNT and graphite particles. For three carbon particles with a similar particle size, similar resistances were obtained in our simulations. The purpose of this study is to design and develop novel high-temperature Thermal Energy Storage (TES) materials in order to improve the operational efficiencies for harnessing solar thermal power at cheaper costs for Concentrated Solar Power (CSP) systems.

The purpose of this research is to develop a process to use plasma decomposition of hydrocarbon liquids or clathrate hydrates in a microwave oven to produce fuel gas while simultaneously solidifying the carbon and synthesizing it into useful carbonized materials, such as CNTs or activated charcoal. Hydrogen gas with a purity of 60% to 80% can be extracted using a conventional microwave oven. This means that the energy efficiency of hydrogen production using this method is estimated to be approximately 50% of that by electrolysis of alkaline water and approximately 1% of that by the natural gas steam reforming method. However, this process has the added benefit of producing solid carbon at the same time. This method can be applied to a wide variety of waste liquids, or hydrate. Surplus electrical energy could be used to process waste liquids from homes and factories, and the resulting hydrogen energy could be stored and used.