Fast diffusion of silver in TiO₂ nanotube arrays

Abstract

SummaryUsing magnetron sputtering and heat treatment, Ag@TiO2 nanotubes are prepared. The effects of heat-treatment temperature and heating time on the evolution of Ag nanofilms on the surface of TiO2 nanotubes and microstructure of Ag nanofilms are investigated by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Ag atoms migrate mainly on the outmost surface of the TiO2 nanotubes, and fast diffusion of Ag atoms is observed. The diffusivity for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes at 400 °C is 6.87 × 10−18 m2/s, which is three orders of magnitude larger than the diffusivities for the diffusion of Ag through amorphous TiO2 films. The activation energy for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes in the temperature range of 300 to 500 °C is 157 kJ/mol, which is less than that for the lattice diffusion of Ag and larger than that for the grain boundary diffusion. The diffusion of Ag atoms leads to the formation of Ag nanocrystals on the outmost surface of TiO2 nanotubes. Probably there are hardly any Ag nanocrystals formed inside the TiO2 nanotubes through the migration of Ag.

Directed Assembly of Nanoparticle Threshold‐Selector Arrays

“…In addition to the local potential difference between two neighboring lattice sites, the ions must overcome the activation energy E a to perform a hopping process. This energy is set to E a = 0.61 eV corresponding to experimentally observed diffusion coefficients . The diffusion coefficient in a 3D structure is defined aswith 〈 x 2 〉 being the square of the average hopping distance and t the time elapsed for the transition.…”

AgCl-induced hot salt stress corrosion cracking in a titanium alloy

“…Since the repassivation on crack walls can happen rapidly, Ag is expected to diffuse along the top surface of the oxide film and form islands according to STEM-EDX mapping results in Figure 7(b). The rate of diffusion of Ag on smooth and uniform TiO 2 surfaces has been found to be 10 −18 -10 −21 m 2 /s at 400 °C, based on measurements in previous work [25,51]. However, vapor transport of HCl and Cl 2 to the crack tip is thought to be faster than the solid-state diffusion of Ag, and the presence of Cl has be found to enhance SCC susceptibility.…”

Reliable multilevel memristive neuromorphic devices based on amorphous matrix via quasi-1D filament confinement and buffer layer

“…These data implied that surface diffusion facilitated the migration of Ag ions through a 1D path rather than the bulk diffusion. In other words, the diffusivity of Ag along with the pores was enhanced compared to the bulk diffusivity (25,41,42). After the electroforming step, 90 dc sweeps were executed to compare the temporal variations of the devices.…”