Hydrogen production by catalytic methane decomposition over Ni,Co, and Ni-Co/Al2O3 catalyst

Hydrogen is a chief source of energy. Catalytic decomposition produces hydrogen and carbon. In this work, x%M/Al₂O₃ (where M is Ni, Co and combined Ni-Co, and x is 10%, 15%, and 30%) has been successfully employed as a catalyst. The effect of activation temperature and active metal type and loading on catalyst perfomance was investigated. The catalysts were characterized with BET, XRD, TPO, TPR, TEM, XPS, and Raman. The results displayed that the 30%Co/Al₂O₃ catalyst activated at 500°C provided the greatest catalytic performance toward methane conversion. 30%Co/Al₂O₃ catalyst activated at 500°C formed amorphous carbon.     

Hydrogen production by coupling pressurized high temperature electrolyser with solar tower technology

Solar hydrogen production by coupling of pressurized high temperature electrolyser with concentrated solar tower technology is studied. As the high temperature electrolyser requires constant temperature conditions, the focus is made on a molten salt solar tower due to its high storage capacity. A flowsheet was developed and simulations were carried out with Aspen Plus 8.4 software for MW-scale hydrogen production plants. The solar part was laid out with HFLCAL software. Two different scenarios were considered: the first concerns the production of 400 kg/d hydrogen corresponding to mobility use (fuel station). The second scenario deals with the production of 4000 kg/d hydrogen for industrial use. The process was analyzed from a thermodynamic point of view by calculating the overall process efficiency and determining the annual production. It was assumed that a fixed hydrogen demand exists in the two cases and it was assessed to which extent this can be supplied by the solar high temperature electrolysis process including thermal storage as well as hydrogen storage. For time periods with a potential over supply of hydrogen, it was considered that the excess energy is sold as electricity to the grid. For time periods where the hydrogen demand cannot be fully supplied, electricity consumption from the grid was considered. It was assessed which solar multiple is appropriate to achieve low consumption of grid electricity and low excess energy. It is shown that the consumption of grid electricity is reduced for increasing solar multiple but the efficiency is also reduced. At a solar multiple of 3.0 an annual solar-to-H₂ efficiency greater than 14% is achieved at grid electricity production below 5% for the industrial case (4000 kg/d). In a sensitivity study the paramount importance of electrolyser performance, i.e. efficiency and conversion, is shown.     

The economic utilisation of sulphonation process residues in the petroleum industry

Sulphonation process residues in the petroleum industry are not exploited in line with their scientific or economic potential. The traditional routes for disposal of these residues can contribute to pollution, whereas various chemical techniques can be used to produce valuable products with domestic and industrial applications. The present work deals with the utilisation of sulphonation process residues. It is found that economic utilisation of sulphonation process residues from the petroleum industry involves the following:

• 1 A comparative evaluation of the performance of the products obtained with other available products demonstrated their efficiency and value.
• 2 Production of highly paraffinic oils with low aromatic content, with potential for use as spray oils, and the utilisation of their residues in the preparation of oil‐soluble neutral and overbased calcium sulphonates, to be used as detergentdispersant additives for crankcase lubricating oils.
• 3 Regeneration of used lubricating oils and use of their residues in the preparation of water‐soluble sodium sulphonates for use as surfactants.
• 4 Reducing the aromatic and sulphur content of kerosene for eventual employment as a carrier solvent for household in secticide.

     

Effect of copper doping on physical properties of nanocrystallized SnS zinc blend thin films grown by chemical bath deposition

SnS: Cu thin films have been successfully prepared on Pyrex substrates using low cost chemical bath deposition (CBD) technique with different copper doped concentration (y = [Cu]/[Sn] = 5%, 6%, 8%, 9% and 10%). The structure, the surface morphology and the optical properties of the SnS:Cu films were studied by X-ray diffraction (XRD), atomic force microscopy (AFM) and spectrophotometer measurements, respectively. To obtain a thickness of the order of 780 ± 31 nm for absorber material in solar cell devices, a system of multilayer has been prepared. It is found that the physical properties of tin sulphide are affected by Cu-doped concentration. In fact, X-ray diffraction study showed that better cristallinity in zinc blend structure with preferential orientations (111)^ZB and (200)^ZB, was obtained for y equal to 6%. According to the AFM analysis we can remark that low average surface roughness (RMS)value of SnS(ZB) thin film obtained with Cu-doped concentrations equal to y = 6%, is about of 54 nm. Energy dispersive spectroscopy (EDS) showed the existence of Cu in the films. Optical analyses by means of transmission T(λ) and reflection R(λ) measurements show 1.51 eV as a band gap value of SnS:Cu(6%) which is nearly equal to the theoretical optimum value of 1.50 eV for efficient light absorption. On the other hand, Cu-doped tin sulphide exhibits a high absorption coefficient up to 2 × 10⁶ cm⁻¹, indicating that SnS:Cu can be used as an absorber thin layer in photovoltaic structure such as SnS:Cu/ZnS/SnO₂:F and SnS:Cu/In₂S₃/SnO₂:F, where ZnS and In₂S₃ are chemically deposited in a previous studies.     

Microstructure and High Temperature Impression Creep Properties of Mg–3Ca–xZr (x = 0.3, 0.6, 0.9 wt%) Alloys

The current study has investigated the influence of zirconium (Zr) addition to Mg–3Ca–xZr (x = 0.3, 0.6, 0.9 wt%) alloys prepared using argon arc melting on the microstructure and impression properties at 448–498 K under constant stress of 380 MPa. Microstructural analysis of as-cast Mg–3Ca–xZr alloys showed grain refinement with Zr addition. The observed grain refinement was attributed to the growth restriction effect of Zr in hypoperitectic Mg–3Ca–0.3 wt% Zr alloys. Heterogeneous nucleation of α-Mg in properitectic Zr during solidification resulted in grain refinement of hyperperitectic Mg–3Ca–0.6 wt% Zr and Mg–3Ca–0.9 wt% Zr alloys. The hardness of Mg–3Ca–xZr alloys increased as the amount of Zr increased due to grain refinement and solid solution strengthening of α-Mg by Zr. Creep resistance of Mg–3Ca–xZr alloys increased with the addition of Zr due to solid solution strengthening of α-Mg by Zr. The calculated activation energy (Q_a) for Mg–3Ca samples (131.49 kJ/mol) was the highest among all alloy compositions. The Q_a values for 0.3, 0.6 and 0.9 wt% Zr containing Mg–3Ca alloys were 107.22, 118.18 and 115.24 kJ/mol, respectively.     

Optical characterization of vacuum evaporated a-Se80Te20−xCux thin films

Thin films of a-Se₈₀Te_20−xCu_x (where x=2, 6, 8 and 10) were deposited on glass substrates by vacuum evaporation technique. The absorbance, reflectance and transmittance of as-deposited thin films were measured in the wavelength region 400-1000 nm. The optical band gap and optical constants of amorphous thin films have been studied as a function of photon energy. The optical band gap increases on incorporation of copper in Se₈₀Te_20−xCu_x system. The value of refractive index (n) decreases while the value of the extinction coefficient (k) increases with increasing photon energy. The results are interpreted in terms of concentration of localized states.     

Modeling the flow-level performance of hierarchical modulation in?OFDMA-based networks

Hierarchical Modulation (HM) is a means to enhance the spectral efficiency of a system by superposing, in terms of modulation, an additional stream for a given user with good radio conditions on a basic stream of a user with worse radio conditions. This, in turn, increases the throughput of the former user and hence the overall performance of the whole system. We consider, in this work, such a performance at the flow level, for a realistic dynamic setting where users come to the system and leave it after a finite duration corresponding, for instance, to the completion of a file transfer. We specifically model and quantify, both analytically and via simulations, the gain thus achieved and propose two extensions to the basic HM algorithm: a first one in which a user with bad radio conditions is also superposed on one with better radio conditions and a second one in which a user of one type is further superposed on a user of the same type as well.     

Progress in Carbon Fiber and Its Polypropylene- and Polyethylene-Based Composites

Due to their lightweight and excellent toughness, carbon fiber (CF) and its reinforced thermoplastic composites are suitable for high-performance applications such as aerospace, aviation, automotive and sport equipments. In this study, comprehensive detail is provided on the production of carbon fiber, its various forms and geometry and their corresponding effects on the mechanical properties of CF and its reinforced polypropylene (PP) and polyethylene (PE) composites. Here we discuss extensively various methods reported in literature on improving the interfacial fiber-matrix adhesion and dispersion in order to achieve better mechanical properties for such composites.