Examination of a Thermally Viable Structure for an Unconventional Uni-Leg Mg2Si Thermoelectric Power Generator

We have fabricated an unconventional uni-leg structure thermoelectric generator (TEG) element using quad thermoelectric (TE) chips of Sb-doped n-Mg₂Si, which were prepared by a plasma-activated sintering process. The power curve characteristics, the effect of aging up to 500?h, and the thermal gradients at several points on the module were investigated. The observed maximum output power with the heat source at 975?K and the heat sink at 345?K was 341?mW, from which the ??T for the TE chip was calculated to be about 333?K. In aging testing in air ambient, a remarkable feature of the results was that there was no notable change from the initial resistance of the TEG module for as long as 500?h. The thermal distribution for the fabricated uni-leg TEG element was analyzed by finite-element modeling using ANSYS software. To tune the calculation parameters of ANSYS, such as the thermal conductance properties of the corresponding coupled materials in the module, precise measurements of the temperature at various probe points on the module were made. Then, meticulous verification between the measured temperature values and the results calculated by ANSYS was carried out to optimize the parameters.     

Development of mechanical cryocoolers for the cooling system of the Soft X-ray Spectrometer onboard Astro-H

Astro-H is the Japanese X-ray astronomy satellite planned for launch in 2014. The Soft X-ray Spectrometer (SXS) onboard Astro-H, is a high energy resolution spectrometer utilizing an X-ray micro-calorimeter array, which is operated at 50 mK by the ADR with the 30-L superfluid liquid helium (LHe). The mechanical cryocoolers, 4 K-class Joule Thomson (JT) cooler and 20 K-class double-staged Stirling (2ST) cooler are key components to achieve a LHe lifetime for over 3 years in orbit (5 years as a goal). Based on the existing cryocoolers onboard Akari (2006) and JEM/SMILES (2009), modifications for higher cooling power and reliability had been investigated. In the present development phase, the Engineering Models (EMs) of these upgraded cryocoolers are fabricated to carry out verification tests for cooling performance, mechanical performance and lifetime. Nominal cooling power of 200 mW at 20 K for the 2ST cooler and 40 mW at 4.5 K for the JT cooler were demonstrated with temperature and power margin. Mechanical performance test for the 2ST cooler units proves tolerability for pyro shock and vibration environment of the Astro-H criteria. Continuous running of the 4 K-class JT cooler combined with the 2ST precooler for lifetime test has achieved over 5000 h without any degradation of cooling performance.     

Subnanometric stabilization of plasmon-enhanced optical microscopy

We have demonstrated subnanometric stabilization of tip-enhanced optical microscopy under ambient condition. Time-dependent thermal drift of a plasmonic metallic tip was optically sensed at subnanometer scale, and was compensated in real-time. In addition, mechanically induced displacement of the tip, which usually occurs when the amount of tip-applied force varies, was also compensated in situ. The stabilization of tip-enhanced optical microscopy enables us to perform long-time and robust measurement without any degradation of optical signal, resulting in true nanometric optical imaging with high reproducibility and high precision. The technique presented is applicable for AFM-based nanoindentation with subnanometric precision.     

A Numerical Simulation of Nanostructure Formation Utilizing Electromigration

A numerical method to simulate nanostructure formation due to electromigration in passivated Al specimens is developed based on the governing parameter for electromigration damage, AFD^*_gen. {\hbox{AFD}}^{\ast}_{\rm gen}. The nanostructure formation is influenced by conditions such as the current density and substrate temperature. The results of the simulations are verified through experiments, and good agreement between the simulations and experiments is found for changes in nanostructure volume. The simulation is expected to be useful for identifying effective conditions for nanostructure formation.     

Influence of Si species on intergrowth and anisotropic crystal growth of silicalite-1

Silicalite-1 crystals were hydrothermally synthesized from silica gels prepared under different conditions. The influence of the state of Si species in the silica gels and the concentrations of silicate ions and a template agent in the reaction sols on crystal growth of silicalite-1 was examined. The use of silica gels with a high degree of condensation of Si species resulted in the intergrowth of silicalite-1 crystals, whereas a low degree of condensation of Si species led to coffin-shaped crystals. Thus, the degree of condensation of Si species had significant influence on the intergrowth of silicalite-1 crystals. Moreover, at a low silicate concentration, silicalite-1 crystals elongated along the c-axis were obtained. With increasing silicate concentration in the reaction sols, the aspect ratio of silicalite-1 decreased. Furthermore, with decreasing the amount of N(C₃H₇) ₄ ⁺ used as a template agent, the silicalite-1 crystals became larger isotropically. Thus, the growth direction of silicalite-1 crystals was dependent on silicate ion concentration in the reaction sols, but not on N(C₃H₇) ₄ ⁺ concentration.     

Bronchial artery aneurysm as a cause of atelectasis

A 54-year-old nonsmoker female developed atelectasis of the anterior basal segment of the right lower lobe. A non-pulsating endobronchial tumor was observed bronchoscopically obstructing the right basal bronchus. The tumor was confirmed on arteriography to be a saccular aneurysm of the right bronchial artery. The aneurysm was treated with bronchial artery embolization. Bronchial artery aneurysm, without a predisposing disease, is quite rare, but should be considered as an etiological factor of atelectasis.     

Soft X-ray Absorption Near Edge Structure Analysis on Lithium Manganese Oxide Prepared by Microwave Heating

Microwave heating, which is recognized as a time-saving and an energy-efficient process, was used to synthesize manganese oxide from various starting materials. LiOH and MnO₂ (electrochemically prepared manganese dioxide, EMD) were used as starting materials; ε-MnO₂-type lithium manganese oxide that showed excellent cycle ability was the result of 3 min of microwave heating. A change in electronic structure was investigated using manganese L -edge and oxygen K -edge X-ray absorption spectroscopy (XAS). The XAS results indicated that the oxidation-reduction reaction took place in the manganese 3 d and in the oxygen 2 p orbitals during the charge-discharge process and that Jahn-Teller distortion occurred in the reduced samples.     

Detection of superoxide anion radical in a stratum corneum intercellular lipid model using an electrochemical sensor

A stratum corneum intercellular lipid model was prepared in a quasi-non-aqueous system. It was found that the detection of the superoxide anion radical (O???) generated in the lipid model by ultraviolet (UV) irradiation was possible using an electrochemical O??? sensor. The use of an electron spin resonance-spin trap method confirmed that the reactive oxygen species generated in the lipid model by UV irradiation was O???; the presence of a hydroxyl radical (?OH) was also proven. In addition, a reduction in the electric current in the O??? sensor was observed in lipid models containing added antioxidants such as d-α-tocopherol and β-carotene. Moreover, there was a correlation between the degree of oxidative degradation of the lipid, which was determined by the thiobarbituric acid method, and the electric current due to the O??? detected using the O??? sensor.     

Chemical modification of diamond surface with linoleic acid by using benzoyl peroxide

In this study, the introduction of the C=C bond, which is known to be chemically active, on diamond surface was attempted using a reaction with unsaturated fatty acid. The chemical reactivity of a hydrogenated diamond surface with linoleic acid, which was most effective for introducing of the C=C bond, using benzoyl peroxide was investigated in detail. The diamond surface modified with the C=C bond was used as the substrate for the surface-modified diamond. Different radical source such as NCS, NBS, AIBN, and TEMPO were allowed to react with the diamond surface treated with linoleic acid. After the reaction with NCS, NBS, or AIBN, IR peaks at 3011 cm^− 1, which correspond to the C-H bond on the C=C bond, significantly decreased in size, and XPS spectra showed that the elements that derived from the reacted radical source, that is Cl, Br, or N, existed on the diamond surface. On the other hand, after the reaction with TEMPO no XPS peak of the N atoms appeared although the IR peak at 3011 cm^− 1 slightly decreased. These experimental results indicate that the C=C bond introduced on diamond surface can participate in chemical reaction. The method used in this study could become a very useful technique if the coverage factor of the C=C bond is improved by optimization of the reaction condition.     

Thermoelectric Behavior of Sb- and Al-Doped <Emphasis Type="Italic">n</Emphasis>-Type Mg<Subscript>2</Subscript>Si Device Under Large Temperature Differences

The thermoelectric (TE) characteristics of Sb- and Al-doped n-type Mg₂Si elemental devices fabricated using material produced from molten commercial doped polycrystalline Mg₂Si were examined. The TE devices were prepared using a plasma-activated sintering (PAS) technique. To complete the devices, Ni electrodes were fabricated on each end of them during the sintering process. To realize durable devices for large temperature differences, thermodynamically stable Sb-doped Mg₂Si (Sb-Mg₂Si) was exposed to the higher temperature and Al-doped Mg₂Si (Al-Mg₂Si) was exposed to the cooler temperature. The devices consisted of segments of Sb-Mg₂Si and Al-Mg₂Si with sizes in the following ratios: Sb-Mg₂Si:Al-Mg₂Si = 4:1, 1:1, and 1:4. A device specimen composed solely of Sb-Mg₂Si showed no notable deterioration even after aging for 1000 h, while some segmented specimens, such as those with Sb-Mg₂Si:Al-Mg₂Si = 1:1 and 1:4, suffered from a considerable drop in output current over the large ΔT range. The observed power generated by specimens with Sb-Mg₂Si:Al-Mg₂Si = 1:1 and 1:4 and sizes of 2 mm × 2 mm × 10 mm were 50.7 mW and 49.5 mW, respectively, with higher and lower temperatures of 873 K and 373 K, respectively. For the sample composed solely of Sb-Mg₂Si, a power of 55 mW was demonstrated. An aging test for up to 1000 h for the same ΔT range indicated drops in output power of between ∼3% and 20%.