Background: Dislocations[1] are being engineered into various ceramic materials for harvesting functionalities[2]. Yet dislocations, like all other crystalline defects, are subject to change at various temperatures and environment (oxidizing, reducing, etc.). The well-controlled annealing conditions on dislocation engineered ceramics have not been thoroughly investigated.
Core questions: How does annealing (temperature, time, environment, etc.) affect the dislocation density/arrangement and therefore material’s mechanical properties such as plasticity (dislocation nucleation, multiplication and motion), fracture toughness (crack initiation/propagation), and thermal shock resistance? How does the thermal conductivity change accordingly?
Objective: Using single crystal SrTiO3 as a model system in this study, together we aim to:
1. Establish a robust and clear annealing protocol to adjust dislocation density.
2. Unmask the dislocation density and configuration change after annealing at different temperatures (e.g., 300, 600, 900°C) with different annealing times (e.g., 1h, 2h, 10h) in both oxidizing and reducing environments.
3. Quantify correspondingly the plastic and fracture behavior of the materials after annealing in comparison to reference samples.
What you can benefit: We offer systematic training in sample preparation (grinding, polishing, annealing, etc.), sample characterization (atomic force microscopy-AFM, chemical etching, etc.), mechanical testing (nanoindentation, fracture toughness measurement, thermal shock testing, etc.), and a better understanding of dislocation-based mechanical/functional properties.
All these skills aim to prepare you for pursuing a career in academia or job-hunting in industry.
Contact:
Dr. Xufei Fang, Junior group leader
Email: fang@ceramics.tu-…
References:
[1] D. Hull, D.J. Bacon, Introduction to Dislocations, Butterworth-Heinemann, Elsevier, 2011.
[2] A. Nakamura, K. Matsunaga, J. Tohma, T. Yamamoto, Y. Ikuhara, Conducting nanowires in insulating ceramics, Nature Materials 2(7) (2003) 453-6.
Expected starting date: Oct. 15, 2020, but can be flexible
