Katalytische Methanisierung von Kohlenstoffdioxid

Power‐to‐Methane is a technically feasible process that can store large amounts of electrical energy for a long time period. The produced gas of the process can be fed into the natural gas grid or used as fuel. An essential part of the process chain is the catalytic methanation of carbon dioxide. In the methanation process, carbon dioxide and hydrogen are converted into methane and water vapor. Carbon dioxide can be won from industrial processes, ambient air or biogas plants. In this paper, fundamentals and process developments of methanation of carbon dioxide are described.     

Antibacterial properties of raw and degummed silk with nanosilver in various conditions

This article is concerned with the effects of nanosized silver colloids on the antibacterial properties of silk fibers against two kinds of bacteria: Staphylococcus aureus and Escherichia coli. Different concentrations of silver nanoparticles (Ag NPs; 10, 25, 50, and 100 ppm) were applied to silk fibers by an exhaust method. The effect of medium pH on the Ag NP uptake on the fibers was studied. Also, sodium carbonate and sodium chloride were added to the liquor as auxiliaries. Scanning electron microscopy was used to observe the morphology of the silk fibers. The antibacterial activity was examined by a bacterial counting method. Energy‐dispersive X‐ray spectroscopy was also used to show the elements on the surface of the silk fibers. We observed that the antibacterial activity increased with silver treatment. It also increased with decreasing pH, especially for the raw silk. The use of NaCl improved the uniformity of the Ag NPs on the fiber surface and increased the antibacterial activities. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Functional,thermal and molecular behaviours of ozone-oxidised cocoyam and yam starches

Ozone-oxidised starches were prepared from the native starches isolated from white and red cocoyam, and white and yellow yam cultivars. The native and oxidised starches were evaluated for functional, thermal and molecular properties. The correlations between the amount of reacted ozone and carbonyl and carboxyl contents of the starches were positive, as ozone generation time (OGT) increased. Significant differences were obtained in terms of swelling power, solubility, pasting properties and textural properties of the native starches upon oxidation. The DSC data showed lower transition temperatures and enthalpies for retrograded gels compared to the gelatinized gels of the same starch types. The native starches showed C_B-type XRD patterns while the oxidised starches resembled the C_A-type pattern. As amylose content increased, amylopectin contents of the starches decreased upon oxidation. Similarly, an increase in M_w values were observed with a corresponding decrease in M_n values upon oxidation.     

Preparation of nanoporous nickel phosphate VSB-5 nanorods carbon paste electrode as glucose non-enzymatic sensor

In this paper, nanoporous nickel phosphate VSB-5 nanorods was synthesized with microwave irradiation and hydrothermal treatment and characterized by X-ray diffraction, FT-IR spectroscopy, Filed emission scanning electron microscopy (FESEM) and EDS analysis. FESEM technique exhibited the presence of nickel phosphate nanorods morphology. The BET surface area, total pore volume and average pore diameter of synthesized nickel phosphate were obtained to be 102.5 m² g^?1, 0.14 cm³ g^?1 and 3.6 nm, respectively. Carbon paste electrode (CPE) was modified by VSB-5 nanorods and then Ni²⁺ ions incorporated to this electrode to obtain Ni-VSB-5/CPE. The current intensity of glucose oxidation increases impressively on the surface of Ni-VSB-5/CPE and modified CPE can reduce the overvoltage of glucose oxidation in comparison with Ni-CPE. The values of electron transfer coefficient, diffusion coefficient and mean value of catalytic rate constant for glucose and redox sites of electrode were found to be 0.87, 6.18 × 10^?4 cm² s^?1 and 3.06 × 10⁵ cm³ mol^?1 s^?1, respectively. The good catalytic activity, high sensitivity, good selectivity and stability and ease of preparation rendered the Ni-VSB-5/CPE to be a capable electrode for glucose electro-oxidation.     

预循环氧化对无涂层和有Pt-Al涂层的Rene?80高温合金的高温低循环疲劳寿命的影响

预测金属合金的疲劳寿命是冶金和机械工程领域中最重要的研究之一.在高温下,表面氧化对合金的疲劳强度和延展性有重要影响.本文研究了预循环氧化对无涂层和有Pt-Al涂层的镍基高温合金Rene?80在930°C时的高温低循环疲劳(HTLCF)性能的影响.将有涂层和无涂层的疲劳试样在燃烧器钻机中进行发动机热暴露模拟(1100°C...     

Gamma irradiation induced damage creation on the cation distribution,structural and magnetic properties in Ni–Zn ferrite

Ferrite of system, namely Ni_1?xZn_xFe₂O₄ with x = (0.0, 0.2, 0.4, 0.6, 0.8, 1.0), have been prepared by solid state reaction to investigate the effect of gamma rays irradiations using Co⁶⁰ source on the cation distribution, structural and magnetic properties. The unirradiated and irradiated samples were then subjected to characterization techniques such as X-ray diffraction, magnetization and AC susceptibility. The results of these characterizations are found to be different for irradiated from that of the pristine sample. The modifications in respect of irradiated samples are explained in terms of the ion-induced disorder. The important result of γ-irradiation on the cation distribution, structural and magnetic properties is the change of ratio Fe²⁺/Fe³⁺. Possible reasons on the results are proposed.     

Experimental study of the salt gradient solar pond stability

Many natural systems such as oceans, lakes, etc.…, are influenced by the effect of double-diffusive convection. This phenomenon, which is a combination of heat and mass transfer, can destroy the stability of system-flows.In the case of solar ponds the middle layer, that is linearly stratified, acts as a thermal and mass insulator for the lower layer. This middle layer, called the Non-Convective Zone (NCZ), needs special care to avoid convection and to maintain its stability. In fact, due to an excess of heat stored, a thermal gradient occurs within the NCZ. A convective movement appears at the bottom of the stratified-layers and then grows to a double-diffusive convection movement. This movement transforms the stratified-layers into a well mixed layer, reducing the storage capacity of the pond.Laboratory small-scale pond and middle-scale outdoor solar ponds were designed and built to provide both quantitative data and to study the dynamic processes in solar ponds, including the behavior of the gradient zone.Particle Image Velocimetry (PIV) visualization-experiments carried out in the mechanical and energetic laboratory in the engineering school of Tunisia and experiments in the field showed that the instability of solar ponds could be limited by using porous media placed in the lower layer of the stratification.     

Functional Relationship to Describe Drains with Entrance Resistance

Numerical flow models usually represent drains as a system dependent boundary condition. If soil is saturated, drains act as the Dirichlet boundary condition with pressure head set equal to zero, and if soil is unsaturated, drains act as the Neumann boundary condition with flow set equal to zero. The underlying assumption is that drains exhibit ideal behavior. In reality, however, this is generally not so, and the flow encounters additional resistances due to pipe slotting and clogging of the envelope material around the drains. To account for the resulting resistance, a Hooghoudt-type boundary condition was developed that prescribes drain flow in relation to the groundwater level at a reference position. The measured drain discharge in an old drainage system was compared with calculated discharge assuming an ideal drain. It was found that the ideal drain assumption led to large errors in simulated discharge. With a correctly formulated and calibrated Hooghoudt boundary condition, however, more accurate drain discharges were obtained.     

Treatment of air polluted with high concentrations of toluene and xylene in a pilot-scale biofilter

Air biofiltration is now under active consideration for the removal of the volatile organic compounds from air polluted streams. In order to investigate the performance of this newly developed technology, a biofiltration pilot unit was operated for a continuous period of 8 months. The biofilter column was packed with commercially conditioned peat. At start-up, the filter bed was inoculated with four species of microorganisms. The resulting biofilter was fed with air contaminated with toluene, xylene or a mixture of toluene and xylene. The maximum elimination capacities attained were 165 g m⁻³ h⁻¹ for toluene, 66 g m⁻³ h⁻¹ for xylene and 115 g m⁻³ h⁻¹ for the mixture of toluene and xylene. These specific performances exceed the values published in the technical and commercial literature for similar processes. Xylene isomers were degraded in decreasing order of reactivity, m-xylene, p-xylene, o-xylene. In the case of air polluted with a toluene and xylene mixture, it was noticed that the metabolism of toluene biodegradation was inhibited by the presence of xylene. Characterization of the biofilm microbial populations after several weeks of operation showed that the dominant strains among the isolated culturable strains from the biofilm, even if different from the initially inoculated strains, had at least one physiological property favoring degradation of aromatic organic rings. The performance of the biofilter was found to be dependent on the temperature of the filter media and the pressure drop through the bed. Finally, a steady state mathematical model was tested in order to theoretically describe the experimental results. This model is used to illustrate the operating diffusion and reaction regimes at steady state for the case of each pollutant. © 1998 Society of Chemical Industry     

Comparative composition of aerial and subterranean potato tubers (Solanum tuberosum L)

The composition of aerial and subterranean tubers of two potato genotypes cvs Desiree (red skin) and Epicure (white skin) was compared immediately after harvest using a range of analytical methods. Irrespective of genotype, aspartic acid, arginine, glycine, glutamic acid, histidine, leucine, serine, threonine and total amino acid concentrations were significantly higher (P<0·05) in aerial compared with subterranean tuber tissue. Significant increases (P<0·05) in valine in aerial tubers, but no significant differences in alanine, tyrosine and iso-leucine, when compared with subterranean tubers of cv Desiree, were found. In cv Epicure, alanine, tyrosine and iso-leucine were significantly higher in aerial tubers (P<0·05); however, no significant differences in valine were recorded. There was no significant increases in lysine and phenylalanine between tuber types. Regardless of genotype α-solanine, α-chaconine, chlorogenic acid, chlorophyll and crude protein concentrations were significantly higher in aerial tubers compared with subterranean ones (P<0·01). No significant increases in total lipids between tuber types were found. In cv Desiree, ascorbic acid content was not significantly different between aerial and subterranean tuber tissue, but in cv Epicure concentrations were significantly higher (P<0·01) in aerial tubers. Starch concentrations were significantly higher in subterranean tubers of both cultivars (P<0·05). Sugar content was significantly higher in aerial tubers of cv Epicure (P<0·01), but not significantly different between aerial and subterranean tubers of cv Desiree. Regardless of genotype, phosphorus, magnesium, potassium, zinc, manganese and sodium concentrations were significantly higher (P<0·05) in aerial tubers. Iron and copper concentrations were significantly higher in aerial tubers of cv Desiree (P<0·01), but significantly less in cv Epicure compared with subterranean tubers (P<0·01, P<0·05). Calcium concentrations were not significantly different between aerial and subterranean tubers of cv Desiree, but significantly higher in aerial tuber tissue of cv Epicure (P<0·01). Total gross energy (mJ kg⁻¹ FW) was higher in aerial tubers of cv Desiree compared with subterranean tubers (P>0·05), but not significantly different between aerial and subterranean tubers of cv Epicure. The potential applications of aerial tubers for industrial purposes are discussed. © 1997 SCI.