摘要: We investigated the effects of Fe3O4 (0~0.1 wt.%) on the thermoelectric properties of Bi1Sb4Te7.5 alloy prepared by mechanical alloying process. The Seebeck coefficient increased with Fe3O4 content, but the power factor decreased with Fe3O4 content because of the decreased electrical conductivity. The thermal conductivity decreased with Fe3O4. The carrier concentration measured
by the Hall effect measurement decreased with Fe3O4. The thermal conductivity of 0.1 wt.% Fe3O4 alloy was 0.814 W/Km, 20%lower than that of Fe3O4 free alloy. As a result, the small addition of Fe3O4 improved the Z value owing to the decreased thermal conductivity by adding Fe3O4. The Z value of 0.01 wt.% Bi1Sb4Te7.5 alloy was 3.1×10-3 /K, the highest value among the prepared alloys.
摘要: We propose an electrical detection method for detecting the various bio-molecules
effectively with microcantilevers. The piezoresistive microcantilevers were fabricated employing surface micromachining technique that has attractive advantages in terms of cost efficiency, simplicity, and ability of fabricating in array. The fluid cell system for injection of bio-molecular solution is fabricated using polydimethylsiloxane (PDMS) and a fused silica glass. The microcantilever is deflected with respect to the difference of the surface stress caused by the
formation of self-assembled bio-molecules on the gold coated side of the microcantilever. We confirmed that the deflections occurred by the bio-molecule adsorption and microcantilever can be widely used to a &-TAS and a lab-on-a-chip as a sensor for the potential detection of various biomolecules.
摘要: Scanning probe microscope (SPM) with a conducting tip was used to electrically probe silicon nanocrystals (Si NCs) embedded in a SiO2 layer. The Si NCs were generated by the laser ablation method with compressed Si powder followed by a sharpening oxidation. The size of Si NCs is in the range of 10-50 nm, and the density is around 1011 /cm2. Using a conducting tip, the charge was injected directly into each Si NC, and the image contrast change and dC/dV curve shift
caused by the trapped charges were monitored. The results were compared with those of the conventional MOS capacitor.
摘要: Iron disulfide (FeS2) is attractive as a positive electrode material in lithium batteries because of its low material cost, environmental non-toxicity, and high specific energy density. Furthermore, natural pyrite is a secondary product of the mining extraction of coal. For these reasons, natural and synthetic pyrites have been proposed as active cathode materials in secondary lithium batteries. We investigated the effect of various solvents on the electrochemical properties of
lithium-FeS2 batteries. The specific discharge capacity of Li/FeS2 cells varied from 500 to 780mAh/g based on FeS2.
摘要: Li(Ni1/3Co1/3Mn1/3)O2 powders were synthesized by using an ultrasonic spray pyrolysis method, and then heat-treated at 900 or 1000°C for 20 h. The morphology of the as-synthesized powder was spherical. The post heat-treatment changed the particle size and morphology of the synthesized powders. Structural characteristics of the heat-treated powders were analyzed using XRD and SEM, and their electrochemical properties were compared. Higher first discharge capacity
was obtained from the powder heat-treated at 1000°C, but its rough and rugged surface might cause a rapid decrease of the capacity retention.
摘要: Lithium sulfur cells were prepared by composing with sulfur cathode, 0.5M LiCF3SO3 in tetra ethylene glycol dimethyl ether (TEGDME) solution and lithium anode. Multiwalled carbon nanotubes (MWNTs) were used to form the high electric network and prevent the dissolution of lithium polysulfides in sulfur cathode. The effects of additive contents were investigated by discharge
test. The morphology of cathode with MWNTs (20wt.%) has rough and submicro porous. The initial discharge capacity of lithium sulfur cell using multiwalled carbon nanotubes (MWNTs) was 1,200mAh/g-sulfur, which was better than those of acetylene black (AB). The cycle performance of lithium sulfur cell was remarkably improved by the the addition of MWNTs.
摘要: Te doping effect on the thermoelectric properties of solid solution was investigated. 2at% Te doping was found to be most effective to improve the dimensionless figure of merit, ZT, of pseudo-binary CoSb3-4mol%Zn4Sb3. Maximum ZT of 0.69 was obtained at 450K in CoSb3- 4mol%Zn4Sb3 doped with 2at% Te. Heavy doping of Te above 3at% caused thermal conductivity to increase very high because of the formation of metallic CoSb2 phases and thus did not improve ZT.
摘要: Ceria-coated copper oxide powders were prepared by the precipitation method using
cerium nitrate hexahydrate and ammonia as a precipitant. Heterogeneous nucleation and growth of ceria took place on the copper oxide surface by dispersing the copper oxide particles in cerium nitrate aqueous solution and subsequently adding ammonia into it. Process conditions such as the pH of the precursor solution and precipitation temperatures were carefully controlled for the homogeneous
precipitation of ceria particles. It was found that copper oxide was homogeneously coated with nano-sized (~20 nm) ceria particles at room temperature. The morphology of ceria and ceria-coated copper oxide powder were examined by field-emission scanning electron microscopy (FE-SEM) as a function of precipitation temperature.
摘要: The microstructure and thermoelectrical properties of the 4wt% Te doped p-type
Bi0.5Sb1.5Te3 compounds, fabricated by using spark plasma sintering in the temperature ranging from 250°C to 350°C, were characterized. The density of the sintered compounds was increased to 99.2% of theoretical density by carrying out the consolidation at 350oC for 2 min. The Seebeck coefficient, thermal conductivity and electrical resistivity were dependent on hydrogen reduction
process and sintering temperature. The Seebeck coefficient increased with reduction process while the electrical resisitivity significantly decreased. Also, the electrical resistivity decreased and thermal conductivity increased with sintering temperature. The results suggest that the carrier density and mobility vary with reduction process and sintering temperature. The highest figure of
merit of 3.5×10-3/K was obtained for the compounds spark plasma sintered at 350°C for 2 min by using the hydrogen-reduced powders.