Zugl.: Magdeburg, Universiẗat, Diss., 2004.

Köln, Universiẗat, Diss., 2001.

Universiẗat, Diss., 1995--Karlsruhe.

In the present study low pressure plasma pretreatment has been investigated as an alternative to chemical primer pretreatment. The mechanical properties of Polypropylene-Cyanoacrylate bonding which were both, plasma and primer pretreated were compared. From the investigations, where the plasma parameters were systematically varied, it can be concluded that a very short exposure to an oxygen plasma and new curing conditions led to the best results. The shear strength after plasma pretreatment became even higher than after primer pretreatment.

Single ion activity coeffients of NaCl, KCl, HCl and CaCl2 in aqueous solution have been estimated by means of ion selective electrode (ISE) potentiometric measurements. Two methods are described for the calibration of the electrodes within the extended Debye-Hückel concentration range, using the Henderson-Bates approximation for the diffusion potential arising at the reference electrode. The consistency of the results indicates that the junction potentials in the examined systems calculated by the Henderson-Bates approximation are of reasonable precision. The published methods and data might be useful to develop single ion parameters for individual ion activity coefficient models.

Organic trace substances including pesticides are becoming more important in the drinking water treatment. Nanofiltration for drinking water treatment is mainly used for softening and the removal of humic substances. Recently nanofiltration is sometimes used also for the removal of organic trace substances. The mechanism of the trace substance transport through Nanofiltration membranes is widely unknown. Therefor it is not possible to predict pesticiderejections. Thus one focus of this thesis is the investigation of the rejection of organic trace substances through nanofiltration membranes. By measuring diffusion constants of several electrical uncharged pesticides it could be shown that the size of the molecules is a contributing factor. Due to attached water molecules it is not possible to calculate this "effective" molecule size by molecule modelling programs. To investigat the steric effects the rejection dependent of pH was investigated because the membrane pore size distribution depends on pH. The oppositional behaviour of the rejection and the permeability underlines the steric influence on rejection as well as a mathematical model. With electric charged organic trace substances the electrostatic interactions between the membrane surface and the organic molecule dominates the transport mechanism.

This thesis deals with the development and characterisation of a portable direct methanol fuel cell stack. In addition, calculations of the transport of methanol and water in the membrane are compared with experimentally determined values. It also includes investigations of the behaviour of single-cells and some of its components, as the anode gas diffusion layer and the anode flow-field. For the addition of methanol to the anode feed loop, a passive concept based on a permeable tube was developed and verified by both experiments and simulations.

Fuel cells are high efficient energy production systems producing heat and electrical power. Especially PEM fuel cells (Polymeric Electrolyte Membrane) require pure hydrogen for operation. Hydrogen is produced e.g. by reforming of hydrocarbons like natural gas or ethanol. During the production of hydrogen carbon monoxide is formed. CO is a harmful poison for the platinum catalsyst of the fuel cell electrodes. Therefore hydrogen has to be purified. The goal of this work was to develop a pressure swing adsorption for small scale fuel cell systems. The hydrogen to be purified is produced by reforming bio-ethanol. The PSA is designed for a quite low adsorption pressure of 7 bar and a small thermal hydrogen power for fuel cell systems in a range of 1 kW electrical. For the design of the PSA a simplified method of calculating the bed height of the adsorbers was developed. Most scientists working in the field of pressure swing adsorption use mathematical models of breakthrough curves for PSA calculations. But these models can only be solved numerically. The results of these simulations are approved by performing test at lab-scale PSA. Main focus on the tests is set to the breakthrough time and the shape of the breakthrough curves. The calculation method developed in this work is also verified by test. But no breakthrough curves were taken up and no breakthrough time of the unwished gas component (CO) was measured. Only the hydrogen quality and the hydrogen recovery rate even after several adsorption cycles were the dominating criteria for the approval of the calculation model. The PSA tests showed that the required hydrogen quality (less than 10 ppmv CO in hydrogen) for PEM-fuel cells was reached even after a 20 adsorption cycles (one cycle lasted 12 minutes with 3 minutes adsorption). The tests were performed on several days in series without changing the adsorbents or purging them for a longer time.

Friction Stir Welding (FSW) offers an attractive alternative to conventional fusion welding processes because of the excellent properties (particularly ductility), reproducibility, robustness, and surface finished obtained with FSW. However, questions have been raised regarding the productivity of FSW against fusion welding methods. TWBs from the aluminum alloys 5754-H22 and 6181-T4 with different gauges (1 to 2 mm) are produced and tested. Welding speeds up to 10 m/min have been systematically investigated. The welds produced have been subjected to microstructural analysis, mechanical testing and formability analysis.

This thesis reports on the influence of an aqueous H2O2 solution on the combustion process and the pollutant emissions of a direct injection naturally aspirated diesel engine. The effect of a H2O2/water addition into a flow reactor, into the exhaust gas and into the combustion chamber of a diesel engine was monitored by the measurement of gaseous (HC, CO, NOx, O2) and solid exhaust gas constituents. The effect on solid exhaust gas constituents was observed by the means of mass-, size- and number-related measurement techniques. Additional experiments with cycle resolved spectroscopy and pressure indication were performed in the case of H2O2/water injection into the combustion chamber. The results show that a significant decrease of gaseous and solid pollutant emissions of a diesel engine is possible with H2O2/water addition. Particularly the strong effect of a H2O2/water injection into the combustion chamber on soot oxidation indicates that OH radicals play an important role in the process of soot oxidation wi in the combustion chamber.