Der einfluß von faseroberflächen auf die matrixhärtung bei faserverbundwerkstoffen

The influence of extraction of reinforced fibres on surface properties and the curing reaction of epoxy resin matrix in composites were investigated. With increasing fibre surface polarity, as the result of the extraction, the resin wettability was improved and the reaction rate of curing of the epoxy resin matrix increased. The wettability and the reaction rate oppositely decreased with decreasing fibre surface polarity.     

Thin-film solar cells

The R&D status of cells and modules based on hydrogenated amorphous silicon (a-Si:H) and those based on CdTe and CuInSe₂ is reviewed. The stability of a-Si:H solar cells is still a major concern. Improvements have been achieved on an empirical basis by application of multijunction structures, optimization of interfaces, etc. Stabilized efficiencies of close to 10% have been reported. In parallel, the introduction of the ‘defect-pool model’ led to remarkable progress in understanding; it follows that a-SiGe:H instead of a-Si:H should be used for the i-layer (absorber). Improved cell engineering concepts, however, such as enhancement of the built-in electric field via reduction of the i-layer thickness and/or folded structures, are believed to be more promising. Polycrystalline thin-film cells based on CdTe and CuInSe₂ are not affected by inherent degradation mechanisms. the specific properties of these materials demand heterojunctions, and particular problems arise due to the polycrystallinity of the films and to the lattice mismatch and mismatch of the electronic band structures of the materials involved. These are discussed in conjunction with measures currently applied for optimizing solar cell performance. Both cell types exhibit eficiencies in the range 16-17%. Estimations of production costs and energy payback times of thin-film photovoltaic modules are reviewed (even below 1 US$ W_p⁻¹ and as low as 4 months, respectively) and environmental concerns, especially for Cd-containing cells, are summarized.     

Untersuchung fester Komplexe von Triphenylmethylsalzen mit Donatoren

Investigation of Solid Complexes of Triphenylmethyl Salts with Donors Triphenylmethyl salts form crystalline complexes, which can be characterized by UV-VIS reflexion spectroscopy as well as by thermal methods. The stability of the solid complexes is essentially determined by the size of the substituents in the cation (p-R-C₆H₄)₃C⁺ with R = CH₃, H, Br and by that of the aromate (benzene, toluene, p-xylene, mesitylene). In constrat to the behaviour in solution a change of the anion (SbCl₆⁻, FeCl₄⁻) has a strong influence on the stability. Because of the appearance of a charge-transfer absorption the complexes are described as EDA complexes.