ABSTRACT
Thermoelectrics directly converts waste heat into electricity and is considered a promising means of sustainable energy generation. While most of the recent advances in the enhancement of the thermoelectric figure of merit (ZT) resulted from a decrease in lattice thermal conductivity by nanostructuring, there have been very few attempts to enhance electrical transport properties, i.e., the power factor. Here we use nanochemistry to stabilize bulk bismuth telluride (Bi2Te3) that violates phase equilibrium, namely, phase-pure n-type K0.06Bi2Te3.18. Incorporated potassium and tellurium in Bi2Te3 far exceed their solubility limit, inducing simultaneous increase in the electrical conductivity and the Seebeck coefficient along with decrease in the thermal conductivity. Consequently, a high power factor of â¼43 µW cm-1 K-2 and a high ZT > 1.1 at 323 K are achieved. Our current synthetic method can be used to produce a new family of materials with novel physical and chemical characteristics for various applications.
ABSTRACT
We demonstrate continuous roll-to-roll production of highly conductive silver network films on a plastic substrate via mechanical and chemical welding processes. This process included three essential steps: (i) solvent spraying, (ii) roll compression, and (iii) salt treatment and washing. The sheet resistance of the resulting AgNW film was 5 Ω sq(-1) at 92% transmittance, which was the lowest sheet resistance and the highest transparency among the values reported previously for solution-processed AgNW electrodes. Moreover, the strong contacts among the AgNWs dramatically enhanced the mechanical stability of the network film. The resulting AgNW film was successfully applied to various organic electronic devices, such as organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs), and organic solar cells (OSCs).
ABSTRACT
The image quality of proton radiography using the method of beam energy modulation was studied to look into its practical uses. Two different depth-dose distributions generated by modulation were applied to investigate their effects on the density and spatial resolutions of the radiographic image. A steeper slope was found to provide higher resolution for the matching thickness of a phantom. The image was taken on a scintillation screen, and the distance between the phantom and the screen was a sensitive parameter on the resolution. For a beam with a range of 1.2 cm in Lucite, high-resolution images were attainable in the whole range. The resolution of proton images for different kinds of phantoms was examined in comparison with x-ray images as well as images simulated by a Monte Carlo code MCNPX. For a longer range of 18 cm, images attained by simulations indicated that density resolution is better maintained compared to spatial resolution, which is deteriorated by multiple Coulomb scattering.
