Nanostructure and Calorimetry of Amorphous SiCN and SiBCN Ceramics

Zusammenfassung der Projektergebnisse

The project was divided into three parts: i) Synthesis of SiCN, SiOC and SiBCN ceramics and their isotope-enriched analogues; ii) Investigation on the nanodomain structure of SiCN ceramics by means of solid-state NMR, SAXS, Raman spectroscopy and TEM; iii) Determination of the enthalpy of formation of the Si(B)CN materials by means of hightemperature oxide melt calorimetry. The major accomplishments are: (a) We have extensively characterized the microstructure of polymer-derived SiOC, SiCN, and SiBCN ceramics and proposed structural/topological models to describe those. (b) We have experimentally determined their energetics (i.e., enthalpy of formation) via drop solution calorimetry and assessed possible relations between the nano/microstructure of the investigated PDCs and their thermodynamic stability. (c) We have attained information on mixed bonding (Si tetrahedra with both oxygen and carbon, SiOxC4-x, or nitrogen and carbon, SiCxN4-x) and bonding in interdomain areas of silicon oxycarbide and silicon carbonitride ceramics, respectively (d) We have shown that hydrogen plays a structural and thermodynamic role in stabilizing mixed bonding in SiOC- and SiCN-based PDCs. (e) We have demonstrated that the microstructure of the PDC directly correlates with the molecular structure of precursors and their processing.

Projektbezogene Publikationen (Auswahl)

• Polymer-derived ceramics: 40 years of research and innovation in advanced ceramics” (Feature Article), Journal of the American Ceramic Society 2010, 93(7), 1805-1837
  Paolo Colombo, Gabriela Mera, Ralf Riedel, Gian Domenico Soraru
  
• “29Si and 13C solid-state NMR spectroscopic study of nanometerscale structure and mass fractal characteristics of amorphous polymer derived silicon oxycarbide ceramics”, Chemistry of Materials 2010, 22[23], 6221-28
  Scarlett J. Widgeon, Sabyasachi Sen, Gabriela Mera, Emanuel Ionescu, Ralf Riedel and Alexandra Navrotsky
  
• “Nanodomain structure of carbon-rich silicon carbonitride polymer-derived ceramics”, Journal of the American Ceramic Society 2010, 93(4), 1169-1175
  Gabriela Mera, Aitana Tamayo, Hong Nguyen, Sabyasachi Sen, Ralf Riedel
  
• “Nanostructure and Energetics of Carbon-Rich SiCN Ceramics Derived from Polysilylcarbodiimides: Role of Nanodomains Interfaces”, Chemistry of Materials 2012, 24, 1181-1191
  Scarlett Widgeon, Gabriela Mera, Yan Gao, Emil Stoyanov, Sabyasachi Sen, Alexandra Navrotsky, Ralf Riedel
  
• “Processing route dramatically influencing the nanostructure of carbon-rich SiCN and SiBCN polymer-derived ceramics. Part I: Low temperature thermal transformation”, Journal of the European Ceramic Society 2012, 32(9), 1857-1866
  Yan Gao, Gabriela Mera, Hong Nguyen, Koji Morita, Hans-Joachim Kleebe, Ralf Riedel
  
• “Thermal decomposition of carbon-rich polymer-derived silicon carbonitrides leading to ceramics with high specific surface area and tunable micro- and mesoporosity”, Journal of the European Ceramic Society 2012, 32[2], 477-484
  Ravi Mohan Prasad, Gabriela Mera, Koji Morita, Mathis Müller, Hans-Joachim Kleebe, Claudia Fasel, Ralf Riedel
  
• “Effect of Demixing and Coarsening on the Energetics of Poly(boro)silazane-Derived Amorphous Si-(B-)C-N Ceramics”, Scripta Materialia 2013, 69, 347-350
  Yan Gao, Scarlett Widgeon, Tien B. Tran, Amir H. Tavakoli, Gabriela Mera, Sabyasachi Sen, Ralf Riedel, Alexandra Navrotsky
  
• “Effect of Precursor on Speciation and Nanostructure of SiBCN Polymer Derived Ceramics”, J. Am. Ceram. Soc. 2013, 96(5), 1651-1659
  Scarlett Widgeon, Gabriela Mera, Yan Gao, Sabyasachi Sen, Alexandra Navrotsky, Ralf Riedel
  
• “Polymer-Derived SiCN and SiOC Ceramics – Structure and Energetics at the Nanoscale” (Feature article), J. Mater. Chem. A 2013, 1, 3826-3836
  Gabriela Mera, Alexandra Navrotsky, Sabyasachi Sen, Hans-Joachim Kleebe, Ralf Riedel