FROM COLLOIDAL CHEMISTRY TO ADVANCED CERAMIC MATERIALS

摘要

The leading role in the fabrication of advanced ceramics and composites play nowadays colloidal processing which can ensure high homogeneity of green bodies, advantageous microstructure and good mechanical properties of as-obtained elements. The main challenge of colloidal processing lies in achieving time-stable, of low viscosity dispersions having high solid loading of well dispersed particles. The key role in the process plays the selection of suitable polymers or monomers, which are able to provide high mechanical strength of a molded element. The applied monomers must perform a series of conditions: they must be water soluble, non-toxic and high mechanical properties must be achieved by as low as possible concentration of polymer or monomer in a ceramic slurry. There are a few commercially available monomers which can be applied in gelcasting process, but they still have some disadvantages. Above all their toxicity is not low enough. Secondly, they must be used in pair with a cross-linking monomer, otherwise the received green bodies would not be rigid enough. For these reasons the synthesis of new low-toxic monomers is essential. The authors therefore performed research on the synthesis of new water-thinnable polymers with designed amphiphilic properties and new monomers on the basis of monosaccharides. Monosaccharides are non-toxic, soluble in water and due to the presence of many hydroxyl groups in a molecule can be applied in gelcasting without adding any external cross-linking agent. The cross-linked polymer network is created by forming hydrogen bonds between polymeric chains. They could play also the role of defflocculants for nano-and submicro-ceramic powders Ceramic suspensions exhibit wide range of rheological behaviors. The authors will also present research on shear thickening fluids which can find applications in such fields where there is a necessity to dampen and disperse energy. This work was focused on study of shear thickening fluids preparation based on nanosilica and poly(propylene glycol) and their rheological properties. The authors will also present also ceramic - polymer composites with a low permittivity and loss tangent based on the barium-strontium titanate (BST) with various dopants and obtained by tape casting method. Dispersions of polymers with different structures were tested as the binders. For obtained ceramic - polymer composites the relative permittivity and loss tangent were measured up to 0.5 THz frequency. This work has been financially supported by the the National Centre for Research and Development (agreement no PBS1/A5/19/2012 ) and by the National Science Centre ( No. DEC-2011/01/B/ST5/06295), Poland.