Fabrication of Translucent Magnesium Aluminum Spinel Ceramics

A precursor for magnesium aluminum spinel powder, composed of crystalline ammonium dawsonite hydrate (NH₄Al(OH)₂CO₃·H₂O) and hydrotalcite (Mg₆Al₂(CO₃)(OH)₁₆·4H₂O) phases, was synthesized via precipitation, using ammonium bicarbonate as the precipitant. The precursor was characterized by differential thermal analysis/thermogravimetry, X-ray diffractometry, and scanning electron microscopy. Reactive spinel powder, which could be densified to translucency under vacuum at 1750°C in 2 h without additives, was obtained by calcining the precursor at 1100°C for 2 h.     

Preparation of Cu(In,Ga)(S,Se)2 thin films by sequential evaporation and annealing in sulfur atmosphere

Cu(In,Ga)(S,Se)₂ thin films with high Ga/III ratio (around 0.8) were prepared by sequential evaporation from CuGaSe₂, CuInSe₂, In₂Se₃ and Ga₂Se₃ compounds and then annealing in H₂S gas atmosphere. The annealing temperature was varied from 400 to 500 °C. These samples were characterized by means of XRF, EPMA, XRD and SEM. The S/(S+Se) mole ratio in the thin films increased with increase in the annealing temperature, keeping the Cu, In and Ga contents nearly constant. The open circuit voltage increased and the short circuit current density decreased with increase in the annealing temperature. The best solar cell using Cu(In,Ga)(S,Se)₂ thin film with Ga/(In+Ga)=0.79 and S/(S+Se)=0.11 annealed at 400 °C demonstrated V_oc=535 mV, I_sc=13.3 mA/cm², FF=0.61 and efficiency=4.34% without AR-coating.     

Novel composite electrolyte membranes consisting of fluorohydrogenate ionic liquid and polymers for the unhumidified intermediate temperature fuel cell

Novel composite electrolyte membranes consisting of [EMIm](FH)_nF (EMIm = 1-ethyl-3-methylimidazolium, n = 1.3 and 2.3) ionic liquids and fluorinated polymers were synthesized and their physical and electrochemical properties were measured under unhumidified conditions for their application to the intermediate temperature fuel cells. The ionic conductivities of composite membrane, P(VdF-co-HFP)/s-DFBP-HFDP/[EMIm](FH)_2.3F (1/0.3/1.75 in weight ratio), were 11.3 and 34.7 mS cm⁻¹ at 25 and 130 °C, respectively. The open circuit voltage (OCV) observed for the single cell using [EMIm](FH)_2.3F composite electrolyte was ∼1.0 V at 130 °C for over 5 h. The maximum power density of 20.2 mW cm⁻² was observed under the current of 60.1 mA cm⁻² at 120 °C. From the high thermal stability and high ionic conductivity, the fluorohydrogenate ionic liquid composite membranes are regarded as promising candidates for the electrolytes of the unhumidified intermediate temperature fuel cells.     

Synthesis and Photoluminescence of Eu2+-Doped α-Silicon Nitride Nanowires Coated with Thin BN Film

A feasible doping strategy is introduced to synthesize Eu²⁺-doped α-Si₃N₄ nanowires coated with a thin BN film. The nanowires were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and a fluorescence spectrophotometer. The Eu²⁺-doped α-Si₃N₄ nanowires emitted strong yellow light, which is related to the 4 f ⁶5 d –4 f ⁷ transition of Eu²⁺, upon a broad excitation wavelength range between 250 and 450 nm. The obtained nanowires provided a potential candidate for application in optical nanodevices, as well as in white LEDs.     

Thermal and Electric Properties in Hot-Pressed ZrB2–MoSi2–SiC Composites

The thermal and electrical properties of MoSi₂ and/or SiC-containing ZrB₂-based composites and the effects of MoSi₂ and SiC contents were examined in hot-pressed ZrB₂–MoSi₂–SiC composites. The thermal conductivity and electrical conductivity of the ZrB₂–MoSi₂–SiC composites were measured at room temperature by a nanoflash technique and a current–voltage method, respectively. The results indicate that the thermal and electrical conductivities of ZrB₂–MoSi₂–SiC composites are dependent on the amount of MoSi₂ and SiC. The thermal conductivities observed for all of the compositions were more than 75 W·(m·K)⁻¹. A maximum conductivity of 97.55 W·(m·K)⁻¹ was measured for the 20 vol% MoSi₂-30 vol% SiC-containing ZrB₂ composite. On the other hand, the electrical conductivities observed for all of the compositions were in the range from 4.07 × 10–8.11 × 10 Ω⁻¹·cm⁻¹.     

基于魏格纳分布的鼓泡流化床中结焦早期诊断

An experimental verification is reported on the early predicting index of agglomeration in bubbling fluidized bed. Coarse quartz sand, which has the same density but larger diameter than the bed material, was used to simulate the initial agglomerated particle. Wigner distribution was used to analyze the pressure fuctuation of the tested bed, and the average amplitude of local domain frequency （LDF） and local peak weighted average frequency （LPWA） under different operating conditions were measured and compared. The results showed that the LDF is sensitive to the agglomeration phenomena and had quick response to the incipient agglomeration in fluidized beds. It can be concluded from the results that these two parameters could be taken as the characteristic indexes to the agglomeration in fuidized beds.     

High thermal conductivity of spark plasma sintered silicon carbide ceramics with yttria and scandia

A fully dense SiC ceramic with a room‐temperature thermal conductivity of 262 W·(m·K)^?1 was obtained via spark plasma sintering β‐SiC powder containing 0.79 vol% Y₂O₃‐Sc₂O₃. High‐resolution transmission electron microscopy revealed two different SiC‐SiC boundaries, that is, amorphous and clean boundaries, in addition to a fully crystallized junction phase. A high thermal conductivity was attributed to a low lattice oxygen content and the presence of clean SiC‐SiC boundaries.     

Antimicrobial susceptibilities of Salmonella isolates obtained from layer chicken houses on a commercial egg-producing farm in Japan, 1997 to 2002

Susceptibility to antimicrobial agents was examined for 325 isolates of Salmonella enterica serotypes Cerro, Infantis, Livingstone, and Montevideo isolated from layer houses on a commercial egg-production farm in the western region of Japan between 1997 and 2002. No antimicrobials were used for therapeutic purposes on the farm during this period. From 1.8 to 3.1% of the isolates were resistant to ampicillin, chloramphenicol, and tetracycline. Resistance to streptomycin and sulfisoxazole was found in 52.9 and 65.5%, respectively, of Salmonella Montevideo isolates and in 0 to 13.2% of the isolates of the other serotypes. All the streptomycin-resistant isolates of Salmonella Montevideo also exhibited resistance to sulfisoxazole. Salmonella Montevideo isolates were first isolated in 1998, and 80.0% of the isolates obtained in this year were resistant to streptomycin and sulfisoxazole. The results suggest that Salmonella Montevideo isolates that had already acquired resistance may have been introduced into the layer houses, although the route and vehicle of transmission were uncertain. The proportion of Salmonella Montevideo isolates resistant to streptomycin and sulfisoxazole significantly decreased (P < 0.01) from 79.5% for 1998 through 1999 to 37.3% for 2000 through 2002. This decrease probably was due to the fact that no antimicrobials were used on the farm. Among 10 isolates from different serotypes obtained from 1997 to 2002 that were resistant to ampicillin, two and five isolates harbored 42- and 63-kb R plasmids and identical DraI restriction enzyme digest patterns, respectively, and carried the blaTEM gene. The results suggest that the ampicillin resistance determinants were transferred among different serotypes of Salmonella in the layer houses.     

A Two-dimensional Stress Analysis and Strength of Single-lap Adhesive Joints of Dissimilar Adherends Subjected to External Bending Moments

The stress distributions of single-lap adhesive joints of dissimilar adherends subjected to external bending moments are analyzed as a three-body contact problem by using a two-dimensional theory of elasticity (plane strain). In the analysis, dissimilar adherends and an adhesive are replaced by finite strips. In the numerical calculations, the effects of the ratio of Young's moduli of adherends, the adherend thickness ratio and the adherend length ratio between dissimilar adherends on the stress distributions at the interfaces are examined. The results show that the stress singularity occurs at the ends of the interfaces, and its intensity is greater at the interface of the adherend with smaller Young's modulus. It is also noted that the singular stress is greater at the interface of the thinner adherend. It is found that the effect of the adherend length ratio on the stress singularity at the interfaces is very small. Joint strength is predicted by using the interface stress and it was measured by experiments. From the analysis and the experiments, it is found that the joint strength increases as Young's modulus of adherends and the adherend thickness increase while the effect of the adherend lengths on the joint strength is small. For verification of the analysis, a finite element analysis (FEA) is carried out. A fairly good agreement of the interface stress distribution is seen between the analytical and the FEA results.     

Mixing speed-controlled gold nanoparticle synthesis with pulsed mixing microfluidic system

Gold nanoparticles with diameters of a few tens of nanometer and a narrow size distribution were synthesized using a pulsed mixing method with a microfluidic system which consists of a Y-shaped mixing microchannel and two piezoelectric valveless micropumps. This mixing method enables control of the mixing speed of gold salts and reducing agent by changing the switching frequency of the micropumps, which was our focus to improve the particle size distribution, which is an essential parameter in gold nanoparticle synthesis. In the proposed method, the mixing time was inversely proportional to the switching frequency and the minimum mixing time was 95 ms at a switching frequency of 200 Hz. During synthesis experiments, the mean diameter of the synthesized gold nanoparticles was found to increase, and the coefficient of variation of particle size was found to decrease with decreasing mixing time. We successfully improved the coefficient of variation to less than 10% for a mean diameter of around 40 nm.