Late News Poster Session: Ceramic and Glass Materials
Program Organizers: MS&T Administration, MS&T PCC
Tuesday 9:00 AM
November 3, 2020
Room: Poster Hall
Location: MS&T Virtual
Effect of SiC and CNT on thermal stability of HfB2–ZrB2 Based Ultra High Temperature Composites: Shruti Dubey1; Kantesh Balani1; Ambreen Nisar2; 1Indian Institute of Technology; 2Florida International University
HfB2-ZrB2 based ultra-high temperature ceramics (UHTCs) are used as protective tiles for nose cones and leading edges of the re-entry vehicles facing harsh environmental conditions. The present work assesses, the effect of SiC (20 vol %) and carbon nanotubes (CNT, 6 vol %) incorporation on the room temperature thermal stability of HfB2-ZrB2 based ceramics, consolidated via spark plasma sintering. The dissipation of heat is crucial factor concerning the thermal stability of the component under service in stringent environmental condition where temperature is >2000 °C. The thermal conductivity increased by ~> 12 % on CNT reinforcement in HfB2-ZrB2–SiC composites whereas, the oxidation temperature (Tonset) increases by > 18% with only a marginal weight gain ~0.8 %. It was observed that electrical conductivity increased by ~138 times in CNT reinforced HfB2-ZrB2–SiC composites. Despite higher electrical conductivity of ZrB2-HfB2-SiC-CNT ceramics, the phonon contribution dominated in governing the overall thermal conductivity of these composites.
Single and Multi-dopant Diffusion in YAG Ceramics for Lasers: Thomas Rudzik1; Zachary Seeley1; Nerine Cherepy1; Stephen Payne1; 1Lawrence Livermore National Lab
In this work, the effects of diffusion on Yb, Lu, and Nd doping profiles in Yttrium Aluminum Garnet (YAG) ceramic composites were studied in the context of designing specialized laser waveguides. Inkjet printing and cold pressing were used to create green bodies with multiple layers, each incorporating a different dopant. They were then consolidated using a maximum temperature of 1750°C or 1850°C. Electron probe microscopy demonstrated differences in diffusion rates between the dopants and how these rates changed if another dopant diffused in the opposite direction. The results of this study should enable better prediction of diffusion distances of these dopants in YAG, thereby facilitating the design of composites requiring a specific geometry of these dopants to achieve a desired functionality.This work was sponsored by LLNL LDRD 19-ERD-006 and was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. LLNL-ABS-813963.