Measuring grain rotation at the nanoscale

Abstract

In this paper, we introduced a method to measure grain rotation of nanomaterials under external stress using a high pressure diamond anvil cell and the Laue microdiffraction technique at a synchrotron facility. We used WC tungsten carbide marker crystals to investigate grain rotation activities of 3 nm and 500 nm nickel media. Our results show that the grain rotation of 3 nm and 500 nm nickel nanocrystals increase with pressure and finally rotation of 500 nm nickel tends to stop at a lower pressure/stress level than 3 nm nickel saturate around 5 GPa and 3 GPa, respectively. 3 nm nickel nanocrystals show a higher rotation magnitude than 500 nm nickel nanocrystals. Our measurements show an effective method to study the grain rotation of nanomaterials especially in ultrafine nanocrystals.

Grain splitting is a mechanism for grain coarsening in colloidal polycrystals

“…For nearly a century, grain coarsening has been described by continuum theories in which the energetic cost of disordered grain boundaries creates a surface tension that drives grain boundary migration [8,9]. More recently, grain rotation has been postulated to play a significant role [10][11][12], particularly in nanocrystalline materials, where each grain contains only hundreds or thousands of atoms [13][14][15][16][17][18][19][20][21][22][23][24][25]. Various causes for grain rotation have been proposed, including shear coupling between neighboring grains [26,27], and a driving torque described by the Read-Shockley equation for the free energetic cost of a grain boundary [28][29][30][31].…”