Postdoctoral Research Associate
Scientific Interests and Work
Develop ultra-incompressible superhard materials and study the mechanical properties of these materials in diamond anvil cell using in situ X-ray diffraction under high pressure.
The high strength of materials is desired in many applications. Nevertheless, there exists a theoretical limit on the achievable strength of a material. It is difficult to achieve this theoretical strength because of the preexisting defects. One of my research interests is to achieve the ideal strength in pure metals by grain refinement and grain boundary deformation suppression under high pressure. In addition to transition metals, compounds formed by low Z elements such as carbon, nitrogen also show great potential to be superhard. I am also interested in the synthesis and characterization of polymorphs of carbon dioxide with extended structures, aiming to understanding the mechanical properties of these compounds under non-hydrostatic compression.
I started performing high pressure experiments at ALS beamline 12.2.2 (LBNL) in 2011. I have run both axial and radial X-ray diffraction under high pressure to examine volume deformation behavior, lattice strain, strength anisotropy, and texture. My research work during my PhD program at UCLA mainly focuses on the synthesis and characterization for a number of high hardness metal borides including TaxW1-xB, ZrxY1-xB12 solid solutions and nanocrystalline ReB2. I study the mechanical properties of these materials in diamond anvil cell using in situ X-ray diffraction under high pressure with a goal of understanding the microscopic response of a crystal lattice to a large applied non-hydrostatic stress and the operative mechanism of the plastic deformation in these materials.
Ph.D. (Chemistry) 2019, University of California, Los Angeles, CA
M.Sc. (Chemistry) 2015, University of California, Los Angeles, CA
M.Sc. (Computer Science) 2013, Southern University and A&M College, Baton Rouge, LA
B.Sc. (Chemistry) 2010, Sichuan University, Chengdu, China
Honors and Recognition
- Louisiana Optical Network Infrastructure (LONI) Institute Graduate Student Fellowship 2011
- J. Lei, G. Akopov, J. Yan, R. B. Kaner and S. H. Tolbert, Radial x-ray diffraction study of superhard early transition metal dodecaborides under high pressure. Adv. Funct. Mater. 1900293 (2019).
- J. Lei, M. T. Yeung, R. Mohammadi, C. L. Turner, J. Yan, R. B. Kaner and S. H. Tolbert, Understanding the Mechanism of Hardness Enhancement in Tantalum-Substituted Tungsten Monoboride Solid Solutions. J. Appl. Phys. 125, 082529 (2019).
- J. Lei, M. T. Yeung, P. J. Robinson, R. Mohammadi, C. L. Turner, A. Kavner, R. B. Kaner and S. H. Tolbert, Understanding How Bonding Controls Strength Anisotropy in Hard Materials by Comparing the High Pressure Behavior of Orthorhombic and Tetragonal Tungsten Monoboride. J. Phys. Chem. C 122, 5647 (2018).
- J. Lei, B. Chen, S. Guo and S. Yang, Structural and mechanical stability of yttrium doped chromium. Appl. Phys. Lett. 102, 021901 (2013).