Development of Ni–Al Catalysts for Hydrogen and Carbon Nanofibre Production by Catalytic Decomposition of Methane. Effect of MgO Addition

Catalytic decomposition of methane is a potential alternative route for the production of hydrogen and nanocarbonaceous materials from natural gas and other hydrocarbon feedstocks. In the present paper, we report the results of characterization and catalytic behaviour during the methane decomposition reaction of a spinel-like Ni–Mg–Al catalyst prepared by coprecipitation. The influence of reaction temperature and feed composition on carbon content, carbon formation rate and carbon morphology has also been studied. The main consequence of MgO addition to the support is the increase in the activity and stability of the Ni–Al catalysts. The better performance of Ni–Mg–Al catalysts is due to the higher interaction generated between Ni particles and the support in this catalyst, which prevents the formation of large metallic particles. The carbonaceous products are carbon nanofibres (diameters ~10–35 nm) and amorphous carbon, which causes the catalyst deactivation by encapsulation. The amount of each type of carbonaceous material depends on the different operating conditions used. The reduction–reaction–regeneration cycles lead to a remarkable sintering of the Ni crystallites due to weakening of the metal-support interaction.     

Modification of technological properties of fish protein concentrates

Fish protein concentrates are mixtures of cross‐linked and aggregated molecules of different muscle proteins. The final conformation of the components of the mixtures is formed as a result of procedures applied to convert the raw material into a product of desirable and stable sensory properties, containing less than 0.1% of lipids. To achieve this end usually extraction with hot organic solvents, mainly isopropyl alcohol and 1,2‐dichloroethane, followed by air drying are employed. These conditions bring about denaturation of many of the proteins followed by aggregation of the molecules due to the interaction of reactive functional groups in extended polypeptide chains. In the final product a large proportion of hydrophobic groups is exposed to the solvent and the proteins exhibit an extremely low water affinity. Such concentrates, although valuable as protein supplements, have only limited suitability as active components of various processed foods, as they have poor technological value. They are insoluble or have a very low water dispersibility and swelling ability, do not form gels after heating, or have any significant fat‐emulsifying capacity. Changing the dissociation or number of ionic groups of the molecules prior to extraction, e.g., by acidifying or acylating, can partially reduce the denaturing effect of heat and organic solvents and thus improve the functional properties of the product. An upgrading of the quality of concentrates produced by hot extraction can be achieved by partial enzymatic or chemical deaggregation, hydrolysis followed by the plastein reaction, or formation of suitable derivatives. The best results have been obtained by partial hydrolysis of acylated proteins or precipitation of the aggregated products using sodium hexametaphosphate. The functional properties of such products are comparable to those of vegetable protein isolates used as meat extenders. Various protein products of high technological value can be also obtained by enzymatic hydrolysis of the raw material, followed by separation of the lipids without organic solvent extraction. Such products, however, have a distinct odor and flavor and must be stabilized because of residual lipids.     

Electrodeposition of Zn–SiC nanocomposite coatings

Zn–SiC composite coatings were obtained on mild steel substrate by electrodeposition technique with high-current efficiency. A slightly acidic chloride bath, containing SiC nanoparticles and gelatine as additive, was used. The electrodeposition was carried out under galvanostatic control with pulsed direct current; the effect of experimental parameters (temperature, average current density and particles concentration) on composition, morphology and structure of the deposit was studied. Coatings were characterized by means of scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffractometry and Vickers microhardness measurements. Zn–SiC electrodeposits with the best characteristics were obtained by performing electrodepositions at 45 °C, with 20 g L^?1 SiC in the bath and with average current density in the range 100–150 mA cm^?2. Under these experimental conditions, homogeneous and compact coatings, with low-grain size and SiC content ranging from 1.7 to 2.1 wt%, were found to be electrodeposited. Microhardness measurements showed for these deposits an increase of about 50 % with respect to those without nanoparticles obtained in the same experimental conditions.     

Application of high mobility transparent conductors to enhance long wavelength transparency of the intermediate solar cell in multi-junction solar cells

High mobility transparent conducting oxide (HMTCO) materials (mobility > 60 cm² V^− 1 s^− 1) have a high transmission over the visible to near infra red wavelength region with resistivity < 2 × 10^− 4 Ω cm. We investigate the application of HMTCO materials as transparent contacts for multi-junction and bifacial solar cells to increase the device NIR transmission. Using the HMTCO materials as front contacts significantly reduces absorption and reflection losses of the solar cells, from 850-1500 nm. The need to develop a low temperature process to prepare HMTCO materials as back contacts in semi-transparent solar cells is also emphasized.     

Physical properties of transparent conducting Cd–Te–In–O thin films: Outlining a thermodynamic system for transparent conducting oxides

Cd–Te–In–O thin films are grown by pulsed laser deposition using a composite target of CdTe powder embedded in an indium matrix. Oxygen pressures range from 2.00 to 6.67 Pa at a substrate temperature of 420 °C. The structure, optical transmission and sheet resistance of the films are measured. Substitutional compounds with In_2 − 2x(Cd,Te)_2xO₃ stoichiometry are found at high oxygen pressures. A ternary phase diagram of the CdO–In₂O₃–TeO₂ system shows the relationship between the structure and the stoichiometry of the films. To evaluate film performance, a figure of merit is proposed based on the relationship between the integral photonic flux and the sheet resistance. The best figure of merit values corresponds to a sample prepared at 3.8 Pa O₂ that consists of (In₂O₃)_0.3(CdTe₂O₅)_0.7 and exhibits an optical band gap of 3.0 eV. This sample is a suitable substrate for electrodeposition due to its good electrochemical stability.     

A limited-streamer tube electron detector with high rejection power against pions

The problem of detecting electrons in the 0.5–4.0 GeV energy range, in the presence of a high pion background, has been studied using a new type of electromagnetic shower detector. Its structural properties and the main parameters are given, together with the basic results in terms of energy resolution and of rejection power against pion background. The optimization of this new instrument gives a pion rejection power of ～ 6 × 10^?4 for energy ? 1.2 GeV.