Preparation and Characterization of Bi2Te3/Sb2Te3 Thermoelectric Thin-Film Devices for Power Generation

A device based on a new double-layer-leg thin-film concept has been successfully fabricated by flip-chip bonding of 242 pairs of n-type Bi₂Te₃ and p-type Sb₂Te₃ thin-film legs electrodeposited on top substrates to those processed on bottom substrates. Based on the output voltage–current curve, the internal resistance of the double-layer-leg thin-film device was measured to be 3.47 kΩ at an apparent temperature difference of 25.9 K across the device. The actual temperature difference across the thin-film legs was estimated to be 3.51 K, which is ～13% of the apparent temperature difference ΔT of 25.9 K applied across the thin-film device. The double-layer-leg thin-film device exhibited an open-circuit voltage of 0.43 V and maximum output power of 13.1 μW at an apparent temperature difference ΔT of 25.9 K.     

Molecular-dynamics simulations of thermal accommodation of helium gas on a nanoparticle

Thermal accommodation of inert He gas atoms colliding on a nanometer-sized Ar or N₂ particle was analyzed using molecular dynamics simulations. The instantaneous values of apparent thermal accommodation coefficient (α_th) showed a distribution close to the normal distribution but with a longer tail toward lower values. The mean and standard deviation of α_th for Ar particle were about 0.39 and 0.54, respectively, and 0.44 and 0.56 for a N₂ particle. Those values were almost independent of gas temperature or pressure, with less than 10% variation over a three- or four-fold variation of the gas conditions. The thermal accommodation coefficient per collision (α₀), which was calculated from the apparent α_th and the average number of collisions on the particle surface, was about 0.18 on the Ar particle and 0.20 on the N₂ particle, both of which are in good agreement with theoretical predictions based on single interactions between free molecules.     

Residence time distributions and basic studies of flow and melting in a modular buss kneader

Experimental studies of residence time distribution, fill factor, temperature, and melting profiles of thermoplastic resins are presented. Residence time distributions were determined as a function of throughput and screw speed. The melting of polypropylene and low density polyethylene in the entrance region was investigated. Fill factor and temperature profiles are reported.     

High-throughput SNP markers for authentication of Korean wheat cultivars based on seven complete plastomes and the nuclear genome

Food Science and Biotechnology - Wheat (Triticum aestivum) has diverse uses in the food industry, and different cultivars have unique properties; therefore, it is important to select the optimal...     

Simulation of linear viscoelastic flow behavior in the Buss Kneader

Viscoelastic flow in a Buss Kneader in which the screw has both rotating and oscillating motions is simulated. Linear viscoelastic responses are considered using both the Maxwell model and the Boltzmann superposition model. Calculations are made first in a basic screw element and subsequently in Kneader screw modules where we consider leakage flows through the interrupted screw flights. Our study includes filled length variation in the crosshead screw extruder, screw characteristics of Kneader screw elements, and pressure profiles along the modular Kneader machine.     

Thermal properties of Y(BH4)3 synthesized via two different methods

Y(BH₄)₃ is one of the candidates for solid-state hydrogen storage, which contains 9.06 wt% of hydrogen. In this study, the thermal properties of Y(BH₄)₃ synthesized via two different methods are extensively examined. One method relies on the solid–solid metathesis reaction between LiBH₄ and YCl₃, and the other method is the gas–solid reaction between B₂H₆ and YH₃. The two samples are studied by differential scanning calorimetry, thermogravimetry, and X-ray diffraction. They exhibit distinctly different polymorphic phase transformation and melting. It turns out that the side product LiCl in the metathesis reaction, which has been regarded as being inert, shifts the melting point and promotes the formation of YB₄ during decomposition. Differential scanning calorimetry and in situ X-ray diffraction data indicate that the addition of LiBH₄ to Y(BH₄)₃ induces co-melting as is found in the cases of LiBH₄–Ca(BH₄)₂ or LiBH₄–Mg(BH₄)₂. Melt infiltration of Y(BH₄)₃ into mesoporous carbon cage confirms such melting behavior.     

Comparison of free amino acid,carbohydrates concentrations in Korean edible and medicinal mushrooms

Ten popular species of both edible and medicinal Korean mushrooms were analysed for their free amino acids and disaccharides. The average total free amino acid concentration was 120.79 mg g⁻¹ in edible mushrooms and 61.47 mg g⁻¹ in medicinal mushrooms, respectively. The average total of free amino acids for all mushrooms, edible mushrooms and medicinal mushrooms was 91.13 mg g⁻¹. Agaricus blazei (227.00 mg g⁻¹) showed the highest concentration of total free amino acids; on the other hand, Inonotus obliquus (2.00 mg g⁻¹) showed the lowest concentration among the 10 species of mushrooms. The average total carbohydrates concentration was 46.67 mg g⁻¹ in the 10 species of mushrooms, where the edible mushrooms contained 66.68 mg g⁻¹ and the medicinal mushrooms contained 26.65 mg g⁻¹. The carbohydrates constituents of the 10 mushroom species were mainly mannose (36.23%), glucose (34.70%), and xylose (16.83%).     

Control of particle size and shape of precursors for ceria using ammonium carbonate as a precipitant

Spherical nanocrystalline precursors of ceria (CeO₂) and CeO₂ powder with different size distributions were prepared by a reflux method using cerium nitrate hexahydrate (CN) as the cerium source and ammonium carbonate (AC) as the precipitant. The crystalline phases of the synthesized CeO₂ precursors were identified as orthorhombic Ce₂O(CO₃)₂·H₂O and hexagonal CeCO₃OH. The particle size and shape could be easily controlled by the CN concentration and the ratio of [AC]/[CN]. The CeO₂ precursors were calcined at 400-700 °C to obtain CeO₂. The particle size distribution and morphology of the synthesized CeO₂ powders were unaffected by the calcination. The specific surface area of the CeO₂ powders was increased by the release of CO₂ and H₂O during the calcination. The calcination temperature is an important factor for the preparation of CeO₂ powder with a high surface area.     

Effects of CeO2 coating uniformity on high temperature cycle life performance of LiMn2O4

CeO₂ is coated using different precipitants on the surface of LiMn₂O₄ in order to investigate the effect of CeO₂ coating uniformity on the cycle life performance at high temperature. CeO₂ is prepared by a precipitation method without the use of a surfactant. Ammonium carbonate or ammonium hydroxide is respectively used as a precipitant in order to control the morphology and particle size of CeO₂. More uniform coating layer composed of well dispersed CeO₂ nanoparticles is obtained with ammonium hydroxide while aggregation lead to non-uniform coating layer when ammonium carbonate is used. The CeO₂-coated LiMn₂O₄ shows better cyclability both at room temperature and 60 °C than the pristine sample but much higher capacity retention rate can be achieved by using ammonium hydroxide. The smaller particle size and uniform coating layer obtained using ammonium hydroxide appear to contribute to the better cycling performance.     

Polyaniline and multi-walled carbon nanotube composite electrode for rechargeable battery

The multi-walled carbon nanotube was introduced into the polymer matrix (PANI) to improve the electric conductivity as well as mechanical properties of the original polymer matrix.PANI/multi-walled carbon nanotube (MWCNT) composites were synthesized via ex-situ and in-situ polymerization to improve their electrical property.And the DC conductivities of PANI/MWCNT according to content and diameter of MWCNT were measured by four-point probe.The highest electric conductivity of PANI/MWCNT composite is 20 S/cm when 0.3% (mass fraction) MWCNTs with 10 nm in diameter and 15 μm in length are added in composite.