Molecular Chemical Concepts for the Synthesis of Novel Ceramics

Abstract

There is presently much effort in basic science and applied research to work on-novel ceramics with properties far beyond those of the existing materials. Aim and scope of the research in this field is to develop materials with superior thermomechanical, physical and chemical properties. In particular, the synthesis of carbide- and nitride-based ceramic,devices from molecular compounds such as inorganic polymers has attracted increasing attention for the production of dense and porous ceramic composites, fibers or coatings. Another important novel development is the synthesis of hybrid materials using sol-gel techniques. In our studies hybrid organic-inorganic xerogels; of general formula (NCN)(1.5)Si-(CH2)(n)-Si(NCN)(1.5) and (NCN)(1.5)Si-CH2-C6H4-CH2-Si(NCN)(1.5) were prepared. These polymeric carbodiimide-gels represent a novel approach to the field of non-oxidic hybrid materials. All the products were characterized by nitrogen adsorption (BET), SEM, TEM and FTIR spectroscopy. Moreover, novel ceramic compositions such as binary carbon nitrides can be synthesized by the polymer-to-ceramic transformation route. The sp(3)-hybridised carbon nitrides are expected to exhibit ultra high hardness. We prepared ON precursor compounds based on the tri-s-triazine unit. The molecular, oligomeric and polymeric compounds exhibit not only high thermal stability, but also interesting optical properties such as strong photoluminescence. Preliminary experiments indicate that the precursors are promising candidates for high pressure bulk synthesis of ceramic CNx materials.