Optimization of temperature and light intensity for improved photofermentative hydrogen production using Rhodobacter capsulatus DSM 1710

Photofermentative hydrogen production is influenced by several parameters, including feed composition, pH levels, temperature and light intensity. In this study, experimental results obtained from batch cultures of Rhodobacter capsulatus DSM 1710 were analyzed to locate the maximum levels for the rate and yield of hydrogen production with respect to temperature and light intensity. For this purpose, a 3^k general full factorial design was employed, using temperatures of 20, 30 and 38 °C and light intensities of 100, 200 and 340 W/m². ANOVA results confirmed that these two parameters significantly affect hydrogen production. Surface and contour plots of the regression models revealed a maximum hydrogen production rate of 0.566 mmol H₂/L/h at 27.5 °C and 287 W/m² and a maximum hydrogen yield of 0.326 mol H₂/mol substrate at 26.8 °C and 285 W/m². Validation experiments at the calculated optima supported these findings.     

Improved PEM fuel cell performance with hydrophobic catalyst layers

Flooding of catalyst layers is one of the major issues, which effects performance of low temperature proton exchange membrane fuel cells (PEMFC). Rendering catalyst layers hydrophobic one may improve the performance of PEMFC depending on Pt percentage in the catalyst and Polytetrafluoroethylene (PTFE) loading on the electrode. In this study, effect of hydrophobicity in catalyst layers on performance has been investigated by comparing performances of membrane electrode assemblies prepared with 48% Pt/C. Ultrasonic coating technique was used to manufacture highly efficient electrodes. Power density at 0.45 V increased by the addition of PTFE, from 0.95 to 1.01 W/cm² with H₂/O₂ feed; while it slightly increased from 0.52 W/cm² to 0.53 W/cm² with H₂/Air feed. Addition of PTFE to catalyst layers while keeping Pt loading constant, enhanced performance providing improved water management. Kinetic activity increased by decreasing Nafion loading from 0.37 mg/cm² to 0.25 mg/cm² while introducing PTFE (0.12 mg/cm²) to the electrode. Electrochemical impedance spectroscopy (EIS) results proved that charge transfer resistance decreased with hydrophobic catalyst layers for H₂/O₂ feed. This is attributed to enhanced water management due to PTFE presence.     

Synergistic effects and optimization of photo-fermentative hydrogen production of Rhodobacter sphaeroides DSM 158

The synergistic effects and optimization of pH, carbon-to-nitrogen ratio (C/N), and light intensity (I) on the photo-fermentative hydrogen production of Rhodobacter sphaeroides 158 DSM and light conversion efficiency have been investigated under different conditions of pH (6.5–8); C/N (15–35); and light intensity (35–185 W m^?2). Response surface methodology (RSM) and Box-Behnken experimental design (BBD) were used to identify the optimum values of the three key parameters of pH, C/N, and I, based on the impact on hydrogen production potential (HPP), hydrogen production rate (HPR), and light conversion efficiency $\eta$. With desirability value of 0.91, the optimum values of 7.4, 27.5, and 126 W m^?2 were identified for pH, C/N, and I respectively, with HPP, HPR and $\eta$ reaching 960 mL L^?1, 41.74 mL L^?1 h^?1, and 0.31 respectively. Regression analysis indicated a good fit between experimental and model data. The study showed that both C/N ratio and I have crucial and significant effect on the HPP, HPR and $\eta$, followed by pH, the synergistic effect of pH–I and C/NI on the light conversion efficiency ($\eta$) was significant while pH C/N was insignificant. The results and analysis obtained could be very useful for better optimizing the photo-fermentative hydrogen production.     

A mobile renewable house using PV/wind/fuel cell hybrid power system

A photovoltaic/wind/fuel cell hybrid power system for stand-alone applications is proposed and demonstrated with a mobile house. This concept shows that different renewable sources can be used simultaneously to power off-grid applications. The presented mobile house can produce sufficient power to cover the peak load. Photovoltaic and wind energy are used as primary sources and a fuel cell as backup power for the system. The power budgeting of the system is designed based on the local data of solar radiation and wind availability. Further research will focus on the development of the data acquisition system and the implementation of automatic controls for power management.     

Effect of talc on the properties of polypropylene/ethylene/propylene/diene terpolymer blends

In the present study, the effect of talc content on the mechanical, thermal, and microstructural properties of the isotactic polypropylene (i‐PP) and elastomeric ethylene/propylene/diene terpolymer (EPDM) blends were investigated. In the experimental study, five different talc concentrations, 3, 6, 9, 12, and 15 wt %, were added to i‐PP/EPDM (88/12) blends to produce ternary composites. The mechanical properties such as yield and tensile strengths, elongation at break, elasticity modulus, izod impact strength for notch tip radius of 1 mm, and hardness with and without heat treatments and thermal properties, such as melt flow index (MFI), of the ternary composites have been investigated. The annealing heat treatment was carried out at 100°C for holding time of 75 h. From the tensile test results, an increased trend for the yield and tensile strengths and elasticity modulus was seen for lower talc contents, while elongation at break showed a sharp decrease with the addition of talc. In the case of MFI, talc addition decreased the MFI of i‐PP/EPDM blends. It was concluded that, taking into consideration, mechanical properties and annealing heat treatment, heat treatment has much more effect on higher yield and tensile strengths, elongation at break, elasticity modulus, impact strength, and hardness. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3033–3039, 2006     

Chemical vapour deposition of pyrolytic carbon from impinging jets

Pyrolytic carbon coatings were deposited on a graphite substrate by chemical vapour deposition technique from impinging jets of ethylene gas. The growth and structure of the coatings were investigated as a function of gas flow velocity. The deposition rate of the coatings increased linearly with the square root of gas velocity or flow rate of ethylene. This behaviour was explained by a mass-transport theory. The coatings exhibited cone-like morphology at low gas velocities and cauliflower-like morphology at high gas velocities. Textural analyses revealed that all the coatings were preferentially oriented in the 001 direction perpendicular to the substrate.     

Copolymers possessing dithienothiophene and boron for optoelectronic applications

In this work, copolymers of dithienothiophenes (DTT) and DTT‐4,4‐dioxide (DTT‐S,S‐O₂) with mesitylboron were prepared for optoelectronic applications. Optical and electrochemical investigations were performed giving rise to the band gaps of 2.46–3.21 and 2.18–2.88 eV, respectively. Copolymers possessing DTT‐S,S‐O₂ units demonstrated the lower band gaps. Density functional theory investigations of the model compounds revealed the presence of an intramolecular charge transfer transition between the donor DTT units and the boron acceptor atoms. POLYM. ENG. SCI., 56:1390–1398, 2016. © 2016 Society of Plastics Engineers     

Wear behaviour of Al/(Al2O3p+SiCp) hybrid composites

In this study, dry sliding metal–metal and metal–abrasive wear behaviours of the aluminium matrix hybrid composites produced by pressure infiltration technique were investigated. These composites were reinforced with 37 vol% Al₂O₃ and 25 vol% SiC particles and contained up to 8 wt% Mg in their matrixes. While matrix hardness and compression strength increased, amount of porosity and impact toughness decreased with increasing Mg content of the matrix. Metal–metal and metal–abrasive wear tests revealed that wear resistance of the composites increased with increasing Mg addition. On the other hand, abrasive resistance decreased with increasing test temperature, especially above 200 °C.