Combustion products of plastics as indicators for refuse burning in the atmosphere

Despite all of the economic problems and environmental discussions on the dangers and hazards of plastic materials, plastic production worldwide is growing at a rate of about 5% per year. Increasing techniques for recycling polymeric materials have been developed during the last few years; however, a large fraction of plastics are still being discarded in landfills or subjected to intentional or incidental open-fire burning. To identify specific tracer compounds generated during such open-fire combustion, both smoke particles from burning and plastic materials from shopping bags, roadside trash, and landfill garbage were extracted for gas chromatography-mass spectrometry analyses. Samples were collected in Concón, Chile, an area frequently affected by wildfire incidents and garbage burning, and the United States for comparison. Atmospheric samples from various aerosol sampling programs are also presented as supportive data. The major components of plastic extracts were even-carbon-chain n-alkanes (C16-C40), the plasticizer di-2-ethylhexyl phthalate, and the antioxidants and lubricants/antiadhesives Irganox 1076, Irgafos 168, and its oxidation product tris(2,4-di-tertbutylphenyl) phosphate. Major compounds in smoke from burning plastics include the non-source-specific n-alkanes (mainly even predominance), terephthalic acid, phthalates, and 4-hydroxybenzoic acid, with minor amounts of polycyclic aromatic hydrocarbons (including triphenylbenzenes) and tris(2,4-di-tert-butylphenyl)phosphate. 1,3,5-Triphenylbenzene and tris(2,4-di-tert-butylphenyl)- phosphate were found in detectable amounts in atmospheric samples where plastics and refuse were burned in open fires, and thus we propose these two compounds as specific tracers for the open-burning of plastics.     

冷轧堆染色头梢色差控制的优化

报道了冷轧堆染色中头梢色差的形成。指出了减小该问题发生的几种可能性。描述了控制工艺和防头梢色差程序。     

Measurement of emissions from air pollution sources. 4. C1-C27 organic compounds from cooking with seed oils

The emission rates of gas-phase, semivolatile, and particle-phase organic compounds ranging in carbon number from C1 to C27 were measured from institutional-scale food cooking operations that employ seed oils. Two cooking methods and three types of seed oils were examined: vegetables stir-fried in soybean oil, vegetables stir-fried in canola oil, and potatoes deep fried in hydrogenated soybean oil. The emission rates of 99 organic compounds were quantified, and these include n-alkanes, branched alkanes, alkenes, n-alkanoic acids, n-alkenoic acids, carbonyls, aromatics, polycyclic aromatic hydrocarbons (PAH), and lactones. Carbonyls and fatty acids (n-alkanoic and n-alkenoic acids) make up a significant portion of the organic compounds emitted from all three seed oil cooking procedures. The compositional differences in the organic compound emissions between the different cooking operations are consistent with the differences in the organic composition of the various cooking oils used. The distribution of the n-alkanoic acids between the gas and particle phases was found to be in good agreement with gas/particle partitioning theory. The relative importance of emissions from commercial deep frying operations to the total emissions of C16 and C18 n-alkanoic acids in the Los Angeles urban area was estimated using the available information and is estimated to account for approximately 7% of the total primary emissions of these acids. Additional emissions of these n-alkanoic acids from stir-frying and grill frying operations are expected. Estimates also indicate that seed oil cooking may make up a significant fraction of the emissions of lighter n-alkanoic acids such as nonanoic acid.     

Thermal Exposure Effects on the Strength and Microstructure of a Novel Mullite Fiber

The mechanical behavior of the novel fiber CeraFib75 after various thermal exposures is examined. This fully crystalline mullite fiber was developed to exceed the thermal stability of commercially available oxide fibers. Therefore, heat treatments at temperatures ranging from 1000°C to 1400°C for 25 h were performed and results compared to the well‐established Nextel^? 720 fibers. Mechanical characterization was realized with bundle tensile tests using acoustic emission sensors to determinate the fiber failure distributions. Investigations showed that the initial fiber microstructure of mullite grains with traces of alumina transforms starting at 1200°C. Changes include dissociation of the alumina‐rich mullite phase and grain growth. Thus, strength reduction is measured as a result of these microstructure transformations. Remarkably, at 1400°C, fibers become more fragile and Weibull statistics can no longer describe the failure distribution. A relation between the distribution shape and the load redistribution capability of fibers is suggested. This is more pronounced for Nextel^?720 fibers, which present much bigger grains and retain only 10% of their original strength. However, CeraFib75 fibers are more stable and exhibit a strength retention of 50% at the same conditions, which is attributed to the higher amount of mullite phase.     

Hybrid effects on tensile properties of hybrid short-glass-fiber-and short-carbon-fiber-reinforced polypropylene composites

Hybrid composites of polypropylene reinforced with short glass fibers and short carbon fibers were prepared using extrusion compounding and injection molding techniques. The tensile properties of these composites were investigated taking into account the effect of the hybridization by these two types of short fibers. It was noted that the tensile strength and modulus of the hybrid composites increase while the failure strain of the hybrid composites decreases with increasing the relative carbon fiber volume fraction in the mixture. The hybrid effects for the tensile strength and modulus were studied by the rule of hybrid mixtures (RoHM) using the tensile strength and modulus of single-fiber composites, respectively. It was observed that the strength shows a positive deviation from that predicted by the RoHM and hence exhibits a positive hybrid effect. However, the values of the tensile modulus are close to those predicted by the RoHM and thus the modulus shows no existence of a hybrid effect. Moreover, the failure strains of the hybrid composites were found to be higher than the failure strain of the single carbon fiber-reinforced composite, indicating that a positive hybrid effect exists. Explanations for the hybrid effects on the tensile strength and failure strain were finally presented.     

Recent contributions of the Kaiserslautern research group to thin silicon solar cell R&D applying the HW(Cat)CVD

This article reviews the results obtained in Kaiserslautern for research and development on amorphous (a-Si:H) and microcrystalline (μc-Si:H) silicon based thin film solar cells as well as heterojunction solar cells applying entirely or mainly the HWCVD. The activities of the group cover the development of appropriate intrinsic and doped a-Si:H and μc-Si:H films for the different solar cell structures, the realization of many types of such structures with different deposition sequences and the detailed study of their stability behavior. Also the preparation of an HW solar cell on medium size area is demonstrated. Initial and stabilized conversion efficiencies are presented and discussed for the different cell structures realized within about ten years of activity. Main focus will be on the recent activities dealing with the integration of μc-Si:H films into solar cell structures and the extensive study of their stability behavior. In addition the degradation of the applied Ta catalyzer was intensively investigated. Finally advantages and disadvantages will be discussed concerning the commercial use of the HWCVD for solar cell fabrication.     

FEL beam characterization from measurements of the Wigner distribution function

The Free-Electron-Laser FLASH at DESY has been characterized by a quantitative determination of the Wigner distribution function. The setup, comprising an ellipsodial mirror and a moveable extreme UV sensitive CCD detector, enables the mapping of two-dimensional phase spaces corresponding to the horizontal and vertical coordinate axes, respectively. For separable beams this yields the entire Wigner distribution, offering comprehensive information about spatial coherence properties, wavefront, beam profiles, as well as beam propagation parameters.