Felix A. Reifler

Water Shedding Angle: A New Technique to Evaluate the Water-Repellent Properties of Superhydrophobic Surfaces

A new technique is introduced to evaluate the wetting properties of superhydrophobic textiles which are not accessible by classical contact angle measurement techniques. The principle behind the new water shedding angle technique is the ability of a superhydrophobic surface to repel drops of water upon impact. In this sense it shows a strong reference to application and its results are easily understood in terms of water protection. The procedure is simple and straightforward and the experimental setup can be easily built or adapted to most available contact angle measurement systems. In view of the significant potential of superhydrophobic coatings for textile applications, the water shedding angle provides a reliable and comparable measure to judge the quality of a superhydrophobic textile in terms of water repellency. It constitutes a useful addition to existing techniques and has proven to be better suited to evaluate the wetting properties of superhydrophobic textiles than the contemporary methods presently in use.

The method of neutron imaging as a tool for the study of the dynamics of water movement in wet aramid-based ballistic body armour panels

A new non-destructive method based on neutron imaging (neutron radiography) to determine the exact water content in aramid-based soft body armour panels is presented. While investigating the ballistic resistance of aramid-based body armour panels under a wet condition, it is important to precisely determine their water content and its chronological development. Using the presented method, the influence of water amount and location on impact testing as well as its time dependence was shown. In the ballistic panels used, spreading of water strongly depended on the kind of quilting. Very fast water migration could be observed when the panels were held vertically. Some first results regarding the water distribution in wet panels immediately after the impact are presented. On the basis of the presented results, requirements for a standard for testing the performance of ballistic panels in the wet state are deduced.

Photocatalytic Activity of W-Doped TiO2 Nanopowders

Abstract Polycrystalline tungsten-doped titanium dioxide nanopowders within a dopant concentration of 0-1 at.% were prepared by a one-step flame spray synthesis (FSS). Mixtures of titanium tetra-isopropoxide dissolved in ethanol and tungsten hexacarbonyl solubilized in tetrahydrofuran were used as precursors. The specific surface area (SSA) of the powders was between 40 and 130 m2/g depending on the process parameters, namely the flame combustion stoichiometry and their chemical composition. Irrespective of their composition the powders consisted of spherical particles, as visible by transmission electron microscopy (TEM). They are highly crystallized with anatase as the predominant phase, according to X-ray diffraction (XRD). The band gap energy was determined by spectrophotometric measurement and was between 3.29 eV and 3.34 eV. The photocatalytic performance of the powders was studied by the degradation of methylene blue (MB) and methyl orange (MO) in aqueous suspensions under UV-A (365 nm) as well as visible (400-500 nm) irradiation. The catalytic activity was determined as a function of the tungsten concentration, the specific surface area and the flame combustion stoichiometry. It was found that the TiO2-0.7 at %W particles with high SSA have the highest photoactivity for degradation of MB and MO. This can be explained by the incorporation of the tungsten into the TiO2 crystal lattice as well as modification surface properties.

Quick Screening Method for the Photocatalytic Activity of Textile Fibers and Fabrics

A quantitative photometric screening method for the measurement of the degradation of formaldehyde by photocatalytic fibers and fabrics was developed. For quick screening, formaldehyde was chosen as an analyte because of its environmental relevance in indoor air pollution, its easy handling, common use and clear degradation pathway. The degradation of formaldehyde was measured quantitatively by a sensitive photometric method after irradiation in the presence of fibers or fabrics. This method allows a fast screening of produced fibers and fabrics with respect to their odor reduction capability. It is able to reveal the differences in the formaldehyde degradation capabilities of, for example, fibers with different titers as well as fibers or fabrics with various contents of the photocatalyst, titanium dioxide.

One-dimensional small-angle X-ray scattering tomography of dip-coated polyamide 6 monofilaments

A synchrotron study is presented in which the concept of one-dimensional tomographic reconstruction of small-angle X-ray scattering patterns is applied to investigate polyamide 6 monofilaments, dip-coated with alumina particles. The filaments are scanned with a focused synchrotron beam and the resulting scattering patterns are recorded with a PILATUS 2M detector. The reconstructed sequence of SAXS images reflects the local nanostructure variation along the filament radius. In particular, the influence of coating process parameters on the polyamide 6 is investigated.