Growth of CdS thin films and nanowires for flexible photoelectrochemical cells

In this study, cadmium sulfide (CdS) nanocrystal thin films and nanowires have been deposited onto mechanically flexible substrates via dc-electrodeposition, which is a very suitable technique for large area manufacturing. For the first time with this study, flexible CdS nanocrystal thin films were integrated into photoelectrochemical (PEC) cells and their performances were compared with CdS nanowires. It has been demonstrated that PEC performance of both nanocrystal thin films and nanowires were a strong function of production conditions such as deposition time and voltage. The maximum power conversion efficiency of the CdS nanocrystal thin films obtained in this study was 0.3%. On the other hand, higher efficiencies (about 1.4%) were observed for the CdS nanowires. UV-vis analysis confirmed that both transmittance and band gap energies of the CdS nanowires were lower than that of CdS nanocrystal thin films. X-ray diffraction analysis revealed that both nanocrystal thin films and nanowires have a preferred orientation at 26° (2θ), which can be attributed to the CdS (0 0 2) structure.     

Sorption and Preconcentration of Vanadium,Chromium, Manganese,and Lead on Silica Gel Modified with (3‐Mercaptopropyl) Trimethoxysilane

Abstract

3‐mercaptopropyltrimethoxysilane, (CH₃O)₃SiCH₂CH₂CH₂SH, loaded on silica gel was used as a preconcentration sorbent for V, Cr, Mn and Pb prior to their determination by graphite furnace atomic absorption spetrometry (GFAAS). Surface characteristics and surface area of the silica gel before and after chemical modification were determined by elemental analysis. The retention and recovery of the analyte elements were studied by applying batch and column techniques. The experimental parameters, such as the effect of pH of the sample, shaking time in batch technique, flow rate of the eluent, the concentration of acid solution in the column section, and the amount of silica on retention and elution have been investigated. All elements were quantitatively (≥90%) recovered in the batch technique with R.S.D. values of 3.0 for vanadium, 1.8 for chromium, 1.7 for manganese, and 0.4 for lead. The same recoveries were obtained in the column techniques for all elements, while manganese in sea water could not be succesfully recovered. Detection limits of the method for vanadium, chromium, manganese, and lead are 1.1, 1.4, 1.3, and 0.8 ng, respectively.     

Laser cutting of 7050 Al alloy reinforced with Al2O3 and B4C composites

In the present study, laser cutting of 7050 aluminum alloy sheets reinforced with Al₂O₃ and B₄C particles are carried out. The cut geometry is examined using scanning electron microscope and the optical microscope. The lump parameter analysis technique is used to formulate and determine the kerf width size. The predictions for kerf width are compared with experimental data. The percentage kerf width size variation along the cut edges is determined and the influence of the laser power level and duty cycle of the laser pulses on the percentage kerf width size variation is examined. It is found that 7050 aluminum alloy reinforced with 20% Al₂O₃ composite results in relatively large kerf width size as compared to its counter parts that corresponding to 7050 aluminum alloy reinforced with 20% B₄C composite. The kerf width size predicted agreed with the experimental data for both composites.     

Effect of edible coatings on the quality of frozen fish fillets

The objective of this study was to determine the changes in the quality of coated trout fillets after coating with edible materials. Fillets were coated and stored at −18 °C for a period lasting up to 7 months. Coating materials were applied in three different stages (first, second, and last coatings). The coated fillets were fried and analyzed for oil absorption and moisture content throughout the storage period. Sensorial attributes and the physical-biochemical changes were also measured before the frying process in each month. It was observed that it is more advantageous to use gluten as the first coating, xanthan gum as the second coating, and wheat (W) and corn (C) flours in the ratio of 1:1 or 2:1 as the last coating. In terms of the fillet quality, the following results were obtained in the analyses conducted before frying. The lowest pH found was 6.25 in zein-containing samples and 6.30 in guar-containing samples. The effects of the last coatings on pH were unimportant (P > 0.05). The lowest thiobarbituric acid levels found were 2.07 mg kg in the fillets coated with casein mixture, 2.44 mg kg in the fillets coated with xanthan gum, and 2.25 mg kg in the fillets coated with W:C flour mixture in the ratio of 2:1. The lowest total volatile basic nitrogen levels found were18.06 mg 100 g in the fillets coated with casein mixture, 18.62 mg 100 g in the fillets coated with xanthan gum, and 18.47 mg 100 g in the fillets coated with W:C flour mixture at 1:1 ratio. In the sensorial analysis, the coated samples were much more preferred than those not coated. As a result of the effects of all the materials, the coating layers on the meat surface provided more resistance against mass transfer during storage.     

The development of the German energy market until 2030—A critical survey of selected scenarios

Many scenarios have been generated in the last years analysing the international energy market. The variety of these scenarios is manifold, as they are generated by different institutions using different methodological approaches and different framework assumptions. However, these scenarios can roughly be classified into three main groups: “moderate”, “climate protection” and “resource scarcity and high fossil fuel prices”. Analysing the German energy market makes a fourth scenario group necessary, which considers the possible revision of the decided nuclear energy phase out. Most of the existing scenarios developed by different institutions can be allocated into one of these groups. A representative scenario for each group has been selected to illustrate the development of the energy sector until 2030. Contrary to the worldwide primary energy demand (PED), the German PED decreases in each scenario, even though the drop differs strongly throughout the scenarios. On the other hand the structure of the PED in 2030 varies strongly for each scenario, especially regarding the share of fossil energy sources. However, a common robust result can be observed throughout all scenarios, namely the high increase in the share of the renewable energy resources, although the scenario generation processes are not always robust.     

Anaerobic H2 production at elevated temperature (60 °C) by enriched mixed consortia from mesophilic sources

Two different enriched mixed consortia from mesophilic sources were used for H₂ production from glucose at 60 °C. The variables were initial pH, nitrogen source, iron and sulfate. pH had a crucial effect and iron was slightly positive for the biohydrogen production performance of the mixed culture. On the other hand, H₂ production decreased with the increasing of ammonia, peptone and sulfate concentrations. Metabolic pathways of mixed culture were affected in different ways depending on the differences in microbial community. The PCR-DGGE and sequencing based microbial community analysis revealed that two enriched mixed cultures had different microbial diversity and both culture were dominated mainly by Thermoanaerobacterium species.     

An analytical approach for thermodynamic properties of the six-component systems Ni-Cr-Co-Al-Mo-Ti and their subsystems

In the present study, the results of some thermodynamic prediction methods were applied to the Ni-Cr-Co-Al-Mo-Ti system of six components. The Chou’s general solution model and the traditional models of Kohler and Muggianu were included in the calculation for the comparison and discussion. The excess Gibbs energy dependences on composition for two investigated cross sections at 2000 K, were obtained according to the applied models. The comparison between the results of the three models shows good mutual agreement.