High-performance carbon counter electrode for dye-sensitized solar cells

Here, we reported that a new carbon electrode prepared with an activated carbon was superior to a Pt sputtered electrode as the counter electrode of dye-sensitized solar cells. The photovoltaic performance was largely influenced by the roughness factor of carbon electrode. The open-circuit voltage increased by about 60 mV using the carbon counter electrode compared to the Pt counter electrode because of positive shift of the formal potential for I₃⁻/I⁻ couple.     

Compression molding and melt‐spinning of the blends of poly(lactic acid) and poly(butylene succinate‐co‐adipate)

Poly(lactic acid) (PLA) is a biobased polymer made from biomass having high mechanical properties for engineering materials applications. However, PLA has certain limited properties such as its brittleness and low heat distortion temperature. Thus, the aim of this study is to improve toughness of PLA by blending with poly(butylene succinate‐co‐adipate) (PBSA), the biodegradable polymer having high toughness. Polymer blends of PLA and PBSA were prepared using a twin screw extruder. The melt rheology and the thermal property of the blends were examined. Further the blends were fabricated into compression molded parts and melt‐spun fiber and were subjected to tensile and impact tests. When the PBSA content was low, PBSA phase was finely dispersed in the PLA matrix. On the other hand, when the PBSA content was high, this minor phase dispersed as a large droplet. Mechanical properties of the compression molded parts were affected by the dispersion state of PBSA minor component in PLA matrix. Impact strength of the compression molded parts was also improved by the addition of soft PBSA. The improvement was pronounced when the PBSA phase was finely dispersed in PLA matrix. However, the mechanical property of the blend fibers was affected by the postdrawing condition as well as the PBSA content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41856.     

Photo-electrochemical solar cells with a SnO2-liquid junction sensitized with highly concentrated dyes

The sensitization of a SnO₂-liquid junction cell with highly concentrated dyes was investigated. The dyes used were Crystal Violet, Methyl Violet B, Malachite Green, Pararosaniline, and Rhodamine B. Anomalous or positive photovoltages were obtained in the system when Fe(CN) ₆ ^3– was added. The performance of the photovoltaic cells showed an open-circuit photovoltage,V _oc, of 175 mV, a short-circuit photocurrent,I _sc, of 12 A, and a fill factor of 0.42. The action spectra resembled the absorption spectra of the aggregated dyes. A D-D mechanism is introduced to explain the anomaly of the photovoltage of the SnO₂ electrode sensitized with the dyes. This behaviour is relevant to the practical usage of such photo-electrochemical cells and merits further investigation.     

A Low‐Loss Medium‐Voltage Inverter Applying Series Connected General Purpose 1.2 kV Insulated Gate Bipolar Transistors with Accurate Voltage Balancing Techniques

This paper presents a medium‐voltage inverter applying series connected general‐purpose 1.2 kV insulated gate bipolar transistors (IGBTs) as a switching device to achieve low switching losses compared to inverters applying high‐voltage IGBTs with over 3 kV rating. Gate signal synchronization, which is essential to keep the balance of collector‐emitter voltages across the IGBTs, is achieved by magnetically coupling all gate lines using a simple two‐windings transformer. In order to obtain better voltage balancing, influence of stray capacitance distribution associated with an insulating substrate in a two‐in‐one IGBT module on the voltage sharing is investigated, and an optimized layout of heat sinks for the IGBT modules is proposed. To validate some performances concerning the device losses and the voltage sharing, a 170 kVA inverter based on three 1.2 kV IGBTs connected in series is built and evaluated. The experimental results are shown. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Improvement in photo-alignment efficiency of azobenzene-containing polyimide films

We have investigated the photo-induced in-plane anisotropy of the films of two different polyimides (PIs) containing azobenzene in the backbone structure (Azo-PIs), which were synthesized from the same diamine, 4, 4′-diaminoazobenzene (DAAB), and two different dianhydrides, pyromellitic dianhydride (PMDA) or oxydiphthalic anhydride (ODPA). Under the same photo-alignment condition, the in-plane anisotropy of the ODPA–DAAB PI film was significantly larger than that of the PMDA–DAAB PI film. This result shows that the photo-alignment efficiency of the former is higher than that of the latter; i.e. the photo-alignment efficiency of Azo-PI can be improved by changing the backbone structure. We believe that the observed enhancement in the photo-alignment efficiency is attributed to a lowering of the polymer chain rigidity, which is caused by introducing an ether linkage with free rotation around non-parallel bonds into the dianhydride part.     

The effect of added L-ascorbic acid,and sodium chloride on the change in concentration of some volatiles in pressurised peach homogenate during storage

White peach (Prunus persica L cv Yamane) homogenates with sugar (20%), or with sugar (20%) and/or L -ascorbic acid (0·1%) and/or sodium chloride (0·5%), were packed in plastic bottles, pressurised (400 MPa, 20°C, 10 min), and then stored at 0 and 25°C for various periods. The headspace volatiles which were absorbed on Tenax TA using dynamic headspace sampling were heat desorbed and analysed by capillary gas chromatography mass spectrometry. Enzymatic formation of benzaldehyde during storage was observed in all samples. The homogenate with L -ascorbic acid showed the highest level of benzaldehyde formation. The flavour quality and colour of the pressurised homogenates with ascorbic acid stored at lower temperature were excellent. © 1997 SCI.     

Polyimide photo-alignment layers for inclined homeotropic alignment of liquid crystal molecules

We have succeeded in realizing an inclined homeotropic alignment of liquid crystal (LC) molecules by using photo-aligned films of a polyimide containing azobenzene in the backbone structure. To induce such an LC alignment, a side chain structure was introduced into the backbone structure. The LC pretilt angle, measured from the surface normal, could be controlled up to 1.75° by varying the light exposure in oblique angle irradiation with unpolarized light. Its thermal stability was examined by annealing the LC cell at 100 °C. No change was observed in the pretilt angle even after annealing for 36 h, indicative of its excellent thermal stability. Since photo-alignment has patterning capability, the photo-aligned polyimide film is expected as a promising alignment film for multi-domain vertical alignment mode LC displays.