1. Department of Aerospace and Mechanical Engineering, Mork Family Department of Chemical Engineering and Materials Science, University of Southern California; Los Angeles CA 90089 USA
2. Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory; Livermore CA USA
3. Institute of Materials Physics and Technology, Hamburg University of Technology, Hamburg, Germany, and Institute of Materials Research, Materials Mechanics; Helmholtz-Zentrum Geesthacht Geesthacht Germany