1. School
of Materials Science and Engineering, The University of New South Wales, Sydney, New South Wales 2052, Australia
2. Materials Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia
3. State Key Laboratory
of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049, China
4. Electron Microscopy Unit, University of New South Wales, Sydney, New South Wales 2052, Australia