Thermoelectric Analysis for Helical Power Generation Systems

The performance of a three-dimensional helical thermoelectric generation (TEG) system is examined by exposing it to a temperature difference with hot and cold sources. The helical paths for the two thermal fluids give the TEG device the potential to efficiently convert thermal energy. The characteristic performance of the helical system is numerically analyzed by using the finite-volume method in a compact system. The helical system is compared with a straight system in which all the thermoelectric (TE) elements present equivalent geometry. The difference in the TE performance between the two systems is not significant when the TE surfaces are maintained at constant temperatures. Both the electromotive force and the current in the TEG system increase linearly with the temperature difference ΔT applied at the two module surfaces. The current preferentially flows through a main path determined by the geometry of the TE element. The merits of the helical design are its compactness, space saving, and smooth fluid flow due to gravity, compared with the straight system.     

Macro-scale complexity of nano- to micro-scale architecture of olivine crystals through an iodine vapour transport mechanism

The production of nano- to micro-scale olivine (magnesium and iron silicate) crystals has been achieved at relatively low temperatures through an iodine vapour transport of the metal onto amorphous silicon dioxide. The process occurs down a temperature gradient from 800 to 600 °C yielding high quality crystals with long range crystallinity, highly complex interconnectivity and intricate macroscale architecture. Scanning electron microscopy (SEM) imaging of the substrate before and after the reaction reveals that the amorphous silicon oxide species is mobile, due to the lack of correlation between the silicon oxide layer and the final olivine particles, leading to a vapour–liquid–solid or vapour–solid growth mechanism. This technique demonstrates a facile, low temperature synthetic route towards olivine crystals with nano- to micro-scale dimensions.     

Plasma Oxidation of a Titanium Electrode in dc-Plasma Above the Water Surface

Plasma oxidation of a titanium electrode above liquid water was investigated to reveal the interaction between metallic titanium and plasma above liquid water. Dc-plasma was generated between the titanium and water electrodes. When the titanium electrode was set as anodal, a thick rutile layer was formed on the surface. We had reported previously that the layer showed the preferred orientation along 〈110〉normal to the surface. The degree of the preferred orientation showed a maximum of 0.8 at the electrode temperature of 1073 K. When the titanium electrode was set as cathodal, a plume was generated with the temperature rise because of the bombarding effect of cationic species in the plasma. The collected particles were spherical and were identified as anatase with a small amount of rutile. Optical emission spectroscopy suggested that an oxide layer (TiO₂) firstly formed on the Ti cathode surface, and then vaporization took place with the temperature rise. The spherical anatase particles were formed from the TiO₂ vapor through the rapid cooling.     

Dependence of Quasi-Particle Alignment on Proton Number in N=44 Isotones 82Sr,83Y,84Zr and 85Nb

The g-factors of Ground Rotational Band states of N=44 isotones 82Sr, 83Y, 84Zr and 85Nb have been measured by the transient-magnetic-field ion implantation perturbed angular distribution (TMF-IMPAD) method. The measured g-factors of 82Sr increase with the increase of spin I, indicating a proton alignment only. Positive peaks appear in the variation of g-factors with spin for 83Y and 84Zr at spin 21/2+ and 10+ respectively, indicating a proton alignment followed by a neutron alignment. A negative peak occurs for 85Nb at the spin25/2+ , indicating a neutron alignment followed by a proton alignment.     

Counter-ion effect of merocyanine J aggregates: formation and structural change upon chemical and thermal treatments

The counter-ion effect of the J aggregate of a merocyanine dye having a long alkyl chain was investigated with monomolecular films on water and with Langmuir-Blodgett films. As the counter-ions, various amines as well as Ba²⁺, Ca²⁺ and Co²⁺ were employed. The destruction and restoration of the J aggregate were also discussed in relation to the structure.     

Quenched metastable phases and their transformations on heating in the Bi2O3-WO3 system

A single-roller apparatus was used to quench 16 melts in the Bi₂O₃-WO₃ system. Metastable polycrystalline phases were obtained in all compositions. Quenched specimens and their phase transformations on heating were examined by X-ray diffraction, differential thermal analysis, density measurement, electrical measurement and observation of optical anisotropy. F c c solid solutions of the type, 2WO₃ 2W ^Bi + 30 ^pI +30 _X ^PO occurred in the quenched samples for 18 to 32 mol % WO₃. Quenched phases remained unchanged with only a slight structural relaxation at temperatures lower than the first exotherm. Near the first exotherm, most samples showed an irregular change in the lattice parameter(s).     

Effect of platinum distribution on the hydrogen gas sensor properties in tin oxide thin films

Tin oxide and platinum layers were deposited on oxidized silicon wafers by ion-beam sputtering. The hydrogen gas sensing properties of undoped films and platinum-doped films were examined at 300°C for films annealed at 500°C. It was observed that the surface platinum when annealed together with the tin oxide film increased the sensitivity and reduced the response time compared with those of undoped films. Longer annealing tended to shift the optimum sensor thickness to a thicker side; the optimum thickness changed from 17 to 37 nm as the annealing time increased from 2 to 50 h. The interdiffusivity between the platinum and the tin atoms in the bulk was negligibly small at 300°C.