We theoretically studied how the electric filed effect can modify thermoelectric properties of intrinsic bismuth telluride nanowires, which are grown along [110] direction. The electronic structure and wave functions ...
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We theoretically studied how the electric filed effect can modify thermoelectric properties of intrinsic bismuth telluride nanowires, which are grown along [110] direction. The electronic structure and wave functions were calculated by solving the self-consistent system of the Schrodinger and Poisson equations by means of both the Thomas-Fermi approximation and the spectral element method. The thermoelectric parameters were determined using a constant relaxation-time approximation. The external electric field can increase the Seebeck coefficient of a nanowire with 7 – 15 nm lateral dimensions by nearly a factor of two, and enhance the figure of merit by an order of magnitude.
Great efforts are expended by researchers to develop new and better thermal interface materials. In contrast, optimization of the performance of a given material is usually left to more empirical efforts. Unfortunatel...
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ISBN:
(纸本)9781615670826
Great efforts are expended by researchers to develop new and better thermal interface materials. In contrast, optimization of the performance of a given material is usually left to more empirical efforts. Unfortunately, interactions between the many parameters affecting performance make the design of experiments required for empirical optimization impractically large. We are conducting systematic mechanistic studies on the combined effects of materials selection and process parameters such as normal forces, assembly speeds, and thermal profiles on bondline macro/microstructure and thermal performance. The most common type of medium/high-performance thermal interface material is undoubtedly that of polymers filled with conductive particles, most often Ag. However, these materials rarely perform as well in a practical application as predicted based on manufacturer supplied data sheets. This is usually ascribed to defects such as voids, porosity and filler distribution heterogeneity. Such defects can be minimized by process optimization, but we also believe that we can learn to tailor some level of heterogeneity to our advantage. In fact, a thermal resistance two and a half times lower than that predicted based on the data sheet has already been demonstrated for one high-end commercial material. Moreover, this can be compatible with a practical manufacturing process. The present paper offers a discussion of results of systematic process studies on commercial filled polymer materials, including correlations between process parameters, defects and final bondline thickness. Important insights were derived from a new technique allowing the in-situ measurement of bondline electrical resistance during processing. The indication is that the dominant pathways for heat transport are provided by chains of Ag particles in good electrical contact with each other. However, typical thermal conductivities of adhesives with, say, 30% Ag (by volume) are lower than that of pure Ag by a
We investigate the evolution of microstructure and mechanical properties of sputter-deposited Al/Nb multilayers with miscible fcc/bcc type interface and individual layer thickness, h, of 1-200 nm, subjected to helium ...
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We report on the measurement of the thermal conductivity of Si/Si 0.8Ge0.2 multilayers on Si substrates through a variation of the 3ω method. We exploit the frequency dependent variation of the thermal wave, through ...
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To investigate the local environment's effect on the lifetime and quantum yield of extended polymer chains in the absence of intra-and interchain aggregation, short, rodlike polymers of poly(2,5-di-n-octyloxy-1,4-...
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The setting rates of inks on paper influence the printing operation and the quality of the final product. While much work has been reported on the effect of the coating structure on setting rates, much less work has b...
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The setting rates of inks on paper influence the printing operation and the quality of the final product. While much work has been reported on the effect of the coating structure on setting rates, much less work has been done understanding the ink parameters, especially the influence of emulsification. A series of four papers were tested with three inks. The inks were characterized in terms of rheology and their filtration behavior. The filtration rate is used to obtain a permeability value of the ink filtercake. The final print ink density and gloss when printed on paper are reported as well as tack dynamics. The value of the maximum tack was found to depend upon the smoothness of the paper tested and not as much as on the type of ink. The dynamics and magnitude of the tack test depended on the ink viscosity, but viscosity alone does not explain the results. The measured ink filtercake permeabilities are different between the ink types by a factor of two. The setting rate is found to mostly be a function of the viscosity of the oil used in the ink, and not as much a function of the pigment and resin system.
A new and promising approach for the design and fabrication of novel optical devices is the functionalization of individual pores in 2D photonic crystals (PhC). This can be done by infiltrating the pores with polymers...
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Protonated polyaniline (PANI) is directly polymerized on Nafion 117 (N117), forming a composite membrane, to act as a methanol-blocking layer to reduce the methanol crossover in the direct methanol fuel cell (DMFC), w...
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