College of Engineering, All Events

Back to Listing

Hassel and Marianne Ledbetter MatSE Colloquium

Event Type
Materials Science and Engineering Department
Please contact for the Zoom link.
wifi event
Sep 27, 2021   4:00 pm  
Siu-Wai Chan, Department of Applied Physics & Appl. Mathematics, Department of Earth and Environmental Engineering, Columbia University - New York, NY
Originating Calendar
MatSE Colloquium Calendar

“Surface stress in nanoscale”


To appreciate surface stress in nano-scale, we will start with an overview of the size-dependence lattice-parameter of nano-oxides. Lattice expansion of 0.1 to 0.5% is observed as crystallite-size decreases to ~5nm. Here, a compressive surface stress is experienced in each of the five oxides: MgO, Cu2O, Fe3O4, CeO2 and Co3O4. The finding is different from the tensile surface stress observed in nanoparticles of noble metals notably gold, where surface stress is tensile as lattice-contraction with decreasing crystallite-size. Our investigation is possible because of the mono-dispersed nature of the nano-oxide in each batch We have also studied the pressure and thermal response of the lattice-parameter of nano-ceria and nano-MgO.  Hence, size-dependent bulk modulus and coefficient of lattice thermal expansion were measured. Bulk modulus peaks around 33nm for nano-ceria and 14nm for nano-MgO. In both cases there is a quick decline with further size decreases. The coefficients of lattice thermal expansion in both nano-oxides decrease rapidly below 15nm. The findings have a number of implications for bonding, surface-stress, heat capacity and the amount of elastic energy stored in these nanoparticles.

link for robots only