1. Laboratory for High Performance Ceramics, EMPA, Swiss Federal Laboratories for Materials Testing & Research, CH-8600 Dübendorf, Switzerland, Laboratory for Advanced Fibers, EMPA, Swiss Federal Laboratories for Materials Testing & Research, CH-9014 St. Gallen, Switzerland, Department of Materials, Nonmetallic Inorganic Materials, ETH Zurich, Swiss Federal Institute of Technology, CH-8093 Zurich, Switzerland, and Technische Universität Bergakademie Freiberg, D-09596 Freiberg, Germany