Localization Model description of interfacial dynamics of free-standing nanoparticles and thin films, and nanoparticle on supporting interacting substrate

• Author / Creator

  Mahmud, Gazi A

• Localization model (LM) relates, without any free parameter, slow dynamics of α-relaxation time (τα) to fast dynamics of Debye-Waller Factor (DWF) or ⟨u2⟩, which is the mean square displacement of particles at a caging time on the order of picoseconds. Moreover, localization model can also predict the diffusion coefficient D when combined with the ‘decoupling’ or Fractional Stokes-Einstein (FSE) relation linking τα to D. Recently, this excellent model has been proven to be useful to predict τα and D of Cu-Zr metallic glass with wide range of compositions from ⟨u2⟩ without any free parameter over a wide range of temperature. Later, the same model is tested for crystalline UO2 under superionic conditions. In the present work, we begin with testing LM for free-standing Cu64Zr36 metallic glass thin films (MGTF) of different thicknesses. We tested LM in overall MGTF, in interfacial region of MGTF where particles have higher mobility, and core or inside of MGTF where particles have less mobility. Free surface of crystalline metallic materials has dynamics similar to the amorphous materials. Hence, in addition to MGTF, we tested this model for interfacial regions of free-standing crystalline Cu thin films with different crystallographic orientation of free surface. After successfully testing LM for overall free-standing Cu64Zr36 MGTFs and their interfaces and cores, we continued the usefulness of this model for the interfacial regions, core, and overall of free-standing Cu64Zr36 metallic glass nanoparticles (MGNP) with different sizes and interfacial regions Cu nanoparticles with different sizes. Finally, we tested this model for interfacial regions, both free interface and Cu-C interface region of Cu NP, of Cu nanoparticles supported on interacting graphene substrate with varying interaction strength between Cu atoms of nanoparticle and C atoms of graphene substrate. We found this model to be very useful to estimate slow dynamics of τα and D to the fast dynamics of DWF for all the cases we studied. In addition to the localization model, we conduct detailed study interfacial dynamics of free standing Cu64Zr36 metallic glass thin films and nanoparticles and crystalline Cu thin films and nanoparticles. Especially, we focused on the interfacial dynamics of Cu NP supported on an interactive supporting graphene substrate and the effects of substrate on the overall dynamics of Cu NP. Moreover, we show that Tammann Temperature (TTA), the minimum temperature for free interface to have enhanced mobility of particles, can be obtained from the intersection of extrapolated ⟨u2⟩ curves of core and interface. We found that the supporting graphene substrate lowers both melting temperature and Tammann temperature of supported Cu NP indicating the higher interfacial activities and, as a result, higher catalytic activities of supported Cu NP.

• Subjects / Keywords

  • Localization model
  • Interfacial dynamics
  • Surface dynamics
  • Molecular dynamics
  • Nanoparticle on substrate
  • Thin film
  • catalysis

• Graduation date

  Fall 2022

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-ewv5-9s66

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.