Polymer derived ceramics are a new class of lightweight and durable materials able to withstand very high temperatures. They have potential uses in aerospace, energy, electronics, and other industries. Yet what their structures are, how stable they are, and how their structure and stability determine their properties and uses are poorly known. This Materials World Network project brings together experts in synthesis, structure determination, thermodynamics, and theory to address these questions. It also provides educational opportunities for exchange between UC Davis and Darmstadt University in Germany.
Polymer derived ceramics in the Si-C-N-O system have unique mechanical and thermal properties, are lightweight, and persist to above 1400 °C, making them potentially useful for aerospace, energy, electronic, and other applications. The goal of this research is to develop a quantitative atomic-level understanding of their structure and stability through a combination of state-of-the-art synthesis, calorimetry, nuclear magnetic resonance, and vibrational spectroscopy, electron microscopy, and theory. Such understanding will transform the very empirical science related to their synthesis and properties into a much more quantitative and predictive understanding that will enable fine-tuning specific materials properties. Students, postdocs, and faculty will have scientific experience in a number of the techniques listed above and the cultural experience of working in the U.S. and Germany.
This Materials World Network is cofunded by the DMR Ceramics program, the DMR Office for Special Programs, and the OISE Central & Eastern Europe Region.
Polymer derived ceramics are specially prepared materials which contain silicon, oxygen, nitrogen, as well as boron and other elements. They withstand very high temperatures and have desirable mechanical, electrical, and chemical properties, with potential applications ranging from high temperature coatings to spark plugs to batteries. They are structurally complex. Although they are without long range crystalline order, they contain specific bonding environments and nanoscale regions of carbon and of a glassy silicon oxycarbide or oxycarbonitride material. Using spectroscopic and calorimetric techniques, this collaboration between groups in Germany and the U.S. has shown the following: (1) The materials are thermodynamically stable, which explains their persistence at high temperature. (2) The presence of mixed bonding (silicon bonded to oxygen and nitrogen or carbon) is characteristic of the silica-rich regions. (3) The silica-rich and carbon-rich regions are intimately intergrown, each forming a continuous fractal network. (4) The stability of these materials is strongly related to bonding at the interfaces between the carbon-rich and silica-rich domains. (5) In nitrogen-containing systems, residual hydrogen may play an important stabilizing role. (6) Boron detracts from thermodynamic stability though it reduces kinetic reactivity. This collaboration with Germany provided international experience for students on both sides, who spent several months abroad. Several of the main investigators and the two Ph.D. students were women. This fundamental understanding of structure and thermodynamics provides insight for tailoring new materials. These may have technological applications (currently the excitement is in using them in Li-ion batteries). Analogous materials may occur in planetary interiors; this is currently under investigation.
