Nanopowders and ceramics
Three-dimensional shaping of ceramics via Selective Laser Sintering and Melting
Shaping of complex shaped, high precision and reliable parts as well as the long processing time and cost-intensive post processing is a key challenge in ceramics processing. Selective laser melting could be a solution of these problems. Although it is already a well-engineered technology in metals and polymer processing, some problems have still to resolved for the production of high performance ceramics.
The absence of understanding of the interaction of laser light sources with the ceramics based powders and the slow sintering kinetics of ceramics are reasons why no existing SLS process is available to consolidate ceramic powders in to dense structures with desired materials properties for high tech ceramics.
The starting ceramic nanosized powders are granulated by spray drying to achieve a high flowability, a high powder bed packing density for solid and liquid phase sintering. The variation of the composition and morphology of these composite granules influences the absorption behavior of the pulsed laser, which in addition to minimizing thermal stresses and cracks is a key challenge for the future.
Virus Filtration applying surface modified ceramics and carbon nanotubes
Water purification is necessary to prevent the spread of different diseases, caused by water-borne germs like bacteria, protozoa, and viruses. The germs may be separated from the water by a physical process, where the contaminated water is passing a porous medium like a filter or by adsorption driven separation processes. Our projects are focused on the adsorption based separation of viruses from water applying nanostructured, ceramic based filters as well as modified nanofibers originating from carbon nanotubes CNT and graphene. This is a challenge, as viruses are, according to the following figure, 20-50 times smaller than bacteria.
Size of different types of viruses in comparison to E coli bacterium (schematic view)
Recently we could evaluate the application of surface modified ceramic water filters for virus removal. Virus separation efficiency (MS 2 bacteriophages and PhiX 174 bacteriophages ; size 25 nm, PZC 2 respectively 7) of 99 % to 99.99 % could be achieved, but is limited depending on the pH conditions. Modification of the highly active, porous ceramic surface was achieved by incorporation of nanosized inorganic particles. As an alternative and promising solution for a broad pH spectrum, we apply CNT based fibers, after modification of the nanostructured surface.