Ceramic nanostructure materials, membranes and composite layers

Synthesis methods to obtain nanoscale materials will be briefly discussed with a focus on sol-gel methods. Three types of nanoscale composites (powders, membranes and ion implanted layers) will be discussed and exemplified with recent original research results. Ceramic membranes with a thickness of 1–10 μm consist of a packing of elementary particles with a size of 3–7 nm. The mean pore size is about 2.5–3 nm. The preparation routes are based on sol and sol-gel technologies. The pores can be modified by liquid as well as by gas deposition techniques. This leads to modification of the chemical character and the effective pore size and gives rise to microstructure elements well below the size of the pores (3 nm). The modification of ceramic surface layers with a thickness of 0.05–0.5 μm by ion implantation and annealing procedures yields amorphous or strongly supersatured metastable solid solutions of e.g. Fe2O3 (or TiO2) in zirconia-yttria solid solutions or of very finely dispersed metal particles in the ceramic surface layers. Particle sizes are of the order of 2–4 nm. Both types of structures have interesting transport, catalytic and mechanical properties.