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ePaper created 2013-09-24, 11:56:35 | version 1.25.20
42 COMPETENCES INTERFACIAL ENGINEERING AND MATERIALS SCIENCE Interfaces play a key role in many technical areas such as the automotive sector, technical textiles and in medical technol- ogy. For many surfaces, properties are required that are very different from those intrinsic to the bulk of the material con- cerned. Besides these material surfaces, inner interfaces in composite materials are becoming increasingly important. Ex- amples are membranes used in separation technology as well as materials for energy conversion, such as separators in fuel cells or thin films in photovoltaics. Another instance of the growing significance of interfaces is as barriers in packaging materials. Finally, in response to the growing complexity of demand, we combine various technical processes under the aspects of ma- terial and energy efficiency. With regard to technical realiza- tion, we have established a large variety of methods which involve either films being deposited from the gas phase or the precipitation of thin films or particles from the liquid phase. Established preparation methods Deposition of thin films by chemical and physical means, i.e. chemical or physical vapor deposition Deposition of nanoparticles using various polymerization methods Production of separation membranes by sol-gel processes and consecutive annealing Deposition of thin layers by layer-by-layer (LbL) techniques as well as by self-assembly monolayers (SAM) Deposition of thin films via spin-coating Generation of nanofibers by electrospinning To achieve reliable processes, all steps of the process develop- ment have to be controlled. In addition, the products have to be characterized in detail. For this purpose a multitude of ana- lytical tools is available and can partly also be used for in situ monitoring of processes (process diagnostics). Due to the fact that the majority of our products are characterized by nano- meter dimensions (ultra-thin films and nanoparticles), we use several methods to deliver information which is space-resolved on the nanometer scale. Application-relevant properties such as the separation and permeation properties of films (mem- branes, barriers and corrosion protection) as well as the spe- cific separation capabilities of molecularly imprinted nanopar- ticles or the dispersibility of modified carbon nanotubes are examined in customized experimental set-ups. Established characterization and diagnostic processes Determination of interfacial energy with different types of tensiometers Logging of the topography and geometric patterning of surfaces on the nanometer scale using a variety of AFM probe modes as well as scanning electron microscopy Determination of adsorption properties either by means of microcaloric measurements at the liquid phase (measure- ment of adsorption enthalpy) or by means of gas adsorp- tion with simultaneous measurements of specific surface area (BET) Determination of film thicknesses using ellipsometry or mi- croscopic techniques