Enhancing surface activity of La0.6Sr0.4CoO3-δ cathode by a simple infiltration process

Nanoscaled La_0.6Sr_0.4CoO_3?δ (LSC) prepared by infiltration has been investigated as an effective catalyst to promote oxygen reduction reaction (ORR) performance for solid-oxide fuel cell. The area specific resistance of original cathode is appreciably reduced by the infiltration of LSC nanoparticles into the porous backbones of LSC cathode. The Arrhenius plots reveal that the reduction is originated from the pre-exponential factor, not the activation energy, suggesting that the rate of ORR has been enhanced by the infiltrated LSC nanoparticles. The infiltrated cell shows a high power density of 800 mW cm^?2 at 700 °C, which is more than two times higher than those measured in the same conditions for a similar cell with pristine LSC cathode. Our results demonstrate that simple infiltration process without further heating at high temperature is a potential way to enhance electrochemical performance and to reduce the operating temperature.     

Formation and distribution of silicon carbide (SiC) precipitates in industrial directional solidification of mc-Si ingots

Abstract

Silicon carbide inclusions in multicrystalline (polycrystalline) silicon ingots affect the cutting process and quality of silicon wafers. The higher density of SiC inclusions relative to the silicon melt suggests that they should sink, but inclusions were observed at the top, middle and bottom of industrial ingots. More inclusions were observed at the top relative to the middle and bottom of the ingot. Small SiC inclusions were found at the bottom and reticular SiC inclusions at the top of the ingot, suggesting that inclusion growth may occur during growth of the ingot. A mechanism to explain the formation and distribution of SiC in industrial silicon directionally solidified ingots, based on the thermodynamics of SiC, is proposed together with strategies to reduce carbon contamination and improve ingot quality.     

Factors leading to low cost dye sensitised solar cells with ‘go faster’ stripes

Abstract

Dye sensitised solar cells are a potential low cost photovoltaic technology because they can be manufactured by roll to roll processing. However, to achieve this, each manufacturing step must be extremely rapid (taking minutes at most). This paper addresses ultrafast dye sensitisation that can now be achieved in <5 min using one or multiple dyes. The use of multiple dyes can effectively give rise to any almost any desired colour in minutes, giving rise to ‘go faster’ stripes. This paper describes key parameters affecting dye uptake using metal containing (N719) and organic dyes (triphenylamine or squaraines) as examples.     

A novel Pt/Cr/Ru/C cathode catalyst for direct methanol fuel cells (DMFC) with simultaneous methanol tolerance and oxygen promotion

New carbon supported electrocatalysts Pt/Cr/Ru with distinct compositions and preparation methods were studied with the help of different electrochemical and spectroscopic techniques. The purposes of obtaining these catalysts lie on their possibilities towards methanol/oxygen fuel cells. In this sense, the oxygen reduction reaction and methanol oxidation reaction were analyzed using stationary and fluid dynamic methodologies. Pt_7.8/Ru_1.3/Cr_0.5 and Pt_8.0/Ru_2.0/Cr_0.1 were the most interesting prepared substrates, on which the first one shows the best catalytic properties towards methanol oxidation and the second the finest performance towards oxygen reduction reaction. Reaction orders with respect to oxygen for the oxygen reduction reaction were obtained being equal to ½ at potentials lower than 0.80 V for both catalysts. Polarization curves run for this reaction depicted two Tafel slopes, i.e. 0.09 V dec⁻¹ above 0.8 V and 0.20 V dec⁻¹ below 0.8 V for both catalysts. An analysis of the most likely mechanism for the oxygen reduction was proposed on the base of those reaction orders and Tafel slopes.     

Ice Cream: Foam Formation and Stabilization—A Review

Ice cream has been studied from ingredients to process conditions, ice crystal formation to ice crystal growth, and ingredient selection to eating quality. One of the key aspects of ice cream is air cells, as formation and acceptance of ice cream rely on foam production and stabilization. Air cells in ice cream provide a unique structure that governs many of this product's keeping and eating qualities. The air cells are dependent upon ice cream mix composition (fat, protein, and surface active ingredients) as well as processing conditions (freezer shear force, hardening time, and storage temperatures). Optical, low-temperature scanning electron microscopy and transmission electron microscopy are applied to observe the morphology and size of air cells in ice cream. Air cells are crucial in forming the product and for eating quality and enjoyment.     

Strategies for stationary and portable fuel cell markets

In the future, hydrogen-based stationary and portable fuel cell systems can help supply some or all of the power demanded with additional advantages of higher reliability, lower emissions, independence from the general grid, and cogeneration capability. In order to understand how to prepare the future for this technology, this paper describes a thorough investigation of past alternative stationary and portable power projects in order for an assessment of the opportunities for stationary and portable fuel cell markets, as well as interactions with transportation hydrogen systems. The lessons learned from the programs are used to establish best practices and recommendations for a hydrogen strategy that addresses opportunities for hydrogen in power generation systems, as well as to make recommendations for market transformation within the hydrogen fuel cell industry.     

Use of chalcopyrite semiconductors CuXSe2 (X=Al,Ga and In) in solar cells: a theoretical study

The energy of sunlight falling on surface of the earth can be directly converted into electricity by means of the solar cells. Among the various materials used for photovoltaics, the chalcopyrite compounds CuXSe₂ (X=Al, Ga, In) are very promising as semiconductors and have received much attention in the recent years. To check the applicability of these materials in solar cells, we have computed the energy bands, density of states, optical dielectric tensors, reflectivity, refraction and absorption coefficients using the full potential linearized augmented plane wave method. It is seen that the energy bandgap reduces from X=Al→In. The dielectric property of these materials is discussed in terms of interband transitions. The absorption coefficients of these materials in the region of solar radiation (0–5 eV energy) are discussed to explore their use in the fabrication of solar cells.     

Impact of hydroquinone on thermal and electrical properties of plasticized [poly(vinyl alcohol)]0.7(LiBr)0.3(H2SO4) solid acid membrane

A novel multi‐component system containing poly(vinyl alcohol), lithium bromide, sulfuric acid, ethylene carbonate and hydroquinone was prepared using a solution‐casting technique. The presence of hydroquinone as a reducing agent in the inorganic–organic membrane structure thus produced was thought to lead to enhanced thermal stability of the membrane. The activation energy for the thermal decomposition of the product samples increased with increasing hydroquinone doping. The ionic conductivities of the films were determined from AC impedance measurements in the temperature range 300–373 K. The maximum conductivity was found to be 1.75 × 10^?3 S cm^?1 for a film doped with 4 wt% hydroquinone. The results give some insight into the potential utility of the membrane as a proton‐conducting solid polymer electrolyte. Copyright © 2011 Society of Chemical Industry     

Polymers with triphenylamine units: Photonic and electroactive materials

Organic hole-transporting materials are intensively investigated as thin-layer electro-optical devices, including organic light-emitting diodes, solar cells, organic field-effect transistors and photo-refractive holographic materials. In this review, we discuss synthetic routes and optical (UV-vis, PL, CV) and electrical (I-V, EL, hole drift mobility) properties of polymers with triphenylamine (TPA) units in the main chain or as pendant groups, such as poly(vinylene)s, poly(amide)s, poly(imide)s, poly(azomethine)s, poly(arylate)s, poly(urethane)s and poly(ester)s. The introduction of vinyl, acetylene, ester, imide, amide or azomethine moieties in TPA leads to new functional materials based on their synergistic effects. The introduction of bulky triphenylamine in macromolecules tends to suppress intermolecular aggregation, reduce the crystallisation propensity and improve the hole-transporting ability of the materials.