2010:159 CIV MASTER'S THESIS Oxidation of an ultra high temperature ceramic - zirconium carbide Baptiste Pierrat Luleå University of Technology MSc Programmes in Engineering Chemical Engineering Department of Chemical Engineering and Geosciences Division of Biochemical and Chemical Engineering 2010:159 CIV - ISSN: 1402-1617 - ISRN: LTU-EX--10/159--SE TABLE OF CONTENTS ACKNOWLEDGEMENTS .......................................................................................................................................... 4 A. BACKGROUND ............................................................................................................................................... 5 B. LITERATURE REVIEW ..................................................................................................................................... 9 B.1. GENERAL PROPERTIES OF CARBIDES OF GROUP IV ................................................................................................... 9 B.1.1. Crystallography ....................................................................................................................................... 9 B.1.2. Chemical properties .............................................................................................................................. 10 B.1.3. Other properties ................................................................................................................................... 11 B.2. PROCESSING ULTRA-HIGH TEMPERATURE CERAMICS.............................................................................................. 12 B.2.1. Synthesis of powders ............................................................................................................................ 12 B.2.2. High temperature sintering .................................................................................................................. 14 B.2.3. Spark plasma sintering .......................................................................................................................... 15 B.2.4. Thermo-mechanical properties of ZrC and HfC .................................................................................... 16 B.2.5. Emissivity .............................................................................................................................................. 16 B.2.6. Brittle - ductile transition ...................................................................................................................... 17 B.2.7. Mechanical properties .......................................................................................................................... 19 B.3. OXIDATION OF ZRC AND HFC........................................................................................................................... 20 B.3.1. General observations ............................................................................................................................ 20 B.3.2. Effect of the oxygen partial pressure (OPP) and the temperature ....................................................... 21 B.3.3. Oxidation mechanisms ......................................................................................................................... 22 B.3.4. Modelling the oxidation kinetics .......................................................................................................... 23 B.3.5. Improvement of oxidation behavior ..................................................................................................... 25 B.4. IRRADIATION OF ZRC AND HFC......................................................................................................................... 26 B.4.1. Effect on the structure .......................................................................................................................... 26 B.4.2. Effect on mechanical properties ........................................................................................................... 29 C. THERMOCHEMICAL STUDY OF THE OXIDATION OF ZRC ............................................................................... 31 C.1. THE GEMINI SOFTWARE ................................................................................................................................ 31 C.2. BASIC COMPARISON WITH ANOTHER THERMOCHEMICAL ANALYSIS ........................................................................... 32 C.3. INFLUENCE OF TEMPERATURE AND OXYGEN PARTIAL PRESSURE (OPP) ..................................................................... 33 C.4. INFLUENCE OF THE ATMOSPHERE ...................................................................................................................... 38 C.5. CONCLUSION ABOUT THERMOCHEMICAL CALCULATIONS ........................................................................................ 40 D. EXPERIMENTAL SET-UP ............................................................................................................................... 41 D.1. DESCRIPTION OF THE 6 KW SOLAR FURNACE ....................................................................................................... 41 D.2. EXPERIMENTAL SET-UP ................................................................................................................................... 42 E. EXPERIMENTS .............................................................................................................................................. 44 E.1. TESTED MATERIAL .......................................................................................................................................... 44 E.2. EXPERIMENTS ............................................................................................................................................... 46 E.2.1. First results ........................................................................................................................................... 46 E.2.2. Comparison with silicon carbide ........................................................................................................... 49 E.2.3. Problems encountered ......................................................................................................................... 49 E.3. CHARACTERIZATION ....................................................................................................................................... 50 E.3.1. Oxidation under helium for GFR ........................................................................................................... 50 E.3.2. Oxidation under air for solar receivers ................................................................................................. 52 Page – 2 – E.3.3. Comparison ........................................................................................................................................... 56 E.4. CONCLUSION ................................................................................................................................................ 58 E.5. FUTURE WORK .............................................................................................................................................. 59 F. FINITE ELEMENT MODELING OF THE REACTOR WITH ANSYS/FLUENT®. ....................................................... 61 F.1. OBJECTIVES .................................................................................................................................................. 61 F.2. MODELING ................................................................................................................................................... 61 F.2.1. Meshing ................................................................................................................................................ 61 F.2.2. Models .................................................................................................................................................. 62 F.2.3. Materials and reaction .......................................................................................................................... 64 F.2.4. Boundary conditions and solution methods ......................................................................................... 65 F.2.5. Limitations of the models ..................................................................................................................... 66 F.3. RESULTS AND INTERPRETATION ......................................................................................................................... 67 F.3.1. Residuals and convergence .................................................................................................................. 67 F.3.2. Flow in the reactor................................................................................................................................ 68 F.3.3. Radiation and temperature .................................................................................................................. 69 F.3.4. Chemical reactions and species ............................................................................................................ 71 F.4. CONCLUSION ................................................................................................................................................ 73 G. REFERENCES ...............................................................................................................................................