Recently, a research team from Institute of Solid State Physics, Hefei Institutes of Physical Science of Chinese Academy of Sciences, discovered the relationship between silver nanowire film plasticity and the shear fracture resistance after the team studied the mechanism of silver nanowire films.
"The better the plasticity of silver nanowire films, the stronger the resistance to shear fracture," said JI Shulin, who led the team.
The results were published in the journal of Nanotechnology recently.
Silver nanowire transparent conductive films show outstanding application advantages touch screens, sensors, solar cells, film heaters and other fields due to their excellent conductivity, optical high definition and good flexibility. However, the property of silver nanowire films, one of important flexible electronic materials under extreme mechanical conditions, is instable.
The investigation of fracture behavior of silver nanowires in thin films under shear stress involved shear test, nano-indentation experiments, stress-strain theoretical simulation and in-depth microstructure analysis. It was found that using different diameters of nanowires and film thicknesses to transfer force in films, the plastic deformation caused by the defect nucleation and movement in the stress concentration area, would lead to the difference of "necking" of nanowires. Therefore, adding an ultra-thin metal buffer layer between the silver nanowire film and the substrate to disperse the stress could improve the shear fracture resistance of the films without affecting the optical properties, and could also enhance the flexural stability of the films.
Aside from shear fracture, film uniformity under repeated bending and anti-scratch property were also studied by the team. They achieved higher uniformity than ITO during thousands times of bending and surface hardness of 3H.
This work provided a new idea for the large-scale industrial application of silver nanowire thin films.
The research is funded by the Youth Innovation Promotion Association of the Chinese Academy of Sciences, and also supported by the National Natural Science Foundation of China, the Anhui Natural Science Foundation and enterprise R & D projects.
Figure 1. Bending resistance and surface scratch resistance of silver nanowire films for folding screens. (Image by WANG Mengjiao)
Figure 2. Load-displacement curves of silver nanowire films with different nanowire diameters and film thicknesses. (Image by WANG Mengjiao)
Figure 3. Stress-strain curves of silver nanowire films with different nanowire diameters and film thicknesses. (Image by WANG Mengjiao)
Figure 4. Microstructural characterization of different parts of a silver nanowire after fracture under film shear stress. (Image by WANG Mengjiao)