In Situ Scanning Electron Microscopy Analysis of the Interfacial Failure of Oxide Scales on Stainless Steels and Its Effect on Sticking during Hot Rolling.

Despite various strategies to address sticking failure in stainless steels (STSs), difficulties in understanding its fundamental mechanisms hinder precise solutions during STS fabrication. This study investigated the effect of chromium (Cr) content on the microstructures and failure modes of oxide scales under a tensile load, simulating the hot-rolling process. The dynamic, real-time behavior of crack initiation, propagation, and interfacial delamination in the oxide scales under tension was analyzed using an in situ scanning electron microscopy (SEM) tensile test. With a high Cr content, iron (Fe) oxide and chromium(III) oxide (Cr2O3) form a layered structure, which is delaminated along the interfaces between the thin Cr2O3 layer and the bulk after perpendicular cracking. The saturated crack densities obtained from in situ SEM provide interfacial strength, while the elastic modulus and hardness obtained from nanoindentation provide vertical fracture strength. In combination with an ex situ elemental image analysis, the in situ SEM results reveal three different failure modes of the four different STSs. The results confirm that sticking failure is more likely to occur as the Cr content increases.

Silver nanowire network transparent electrodes with highly enhanced flexibility by welding for application in flexible organic light-emitting diodes.

We present highly flexible Ag nanowire (AgNW) networks welded with transparent conductive oxide (TCO) for use in electrical interconnects in flexible and wearable electronic devices. The hybrid transparent conductive electrodes (TCEs) produced on polymer substrates consist of AgNW networks and TCO that is deposited atop the AgNWs. The TCO firmly welds the AgNWs together at the junctions and the AgNWs to the polymer substrates. Transmission electron microscopy (TEM) analysis show that TCO atop and near AgNWs grows as crystalline because AgNWs act as crystalline seeds, but the crystallinity of the matrix TCO can be controlled by sputtering conditions. The sheet resistances (Rs) of hybrid TCEs are less than the AgNW networks because junction resistance is significantly reduced due to welding by TCO. The effect of welding on decreasing Rs is enhanced with increasing matrix crystallinity, as the adhesion between AgNWs and TCO is improved. Furthermore, the bending stability of the hybrid TCEs are almost equivalent to and better than AgNW networks in static and cyclic bending tests, respectively. Flexible organic light-emitting diodes (f-OLEDs) are successfully fabricated on the hybrid TCEs without top-coats and the performances of f-OLEDs on hybrid TCEs are almost equivalent to those on commercial TCO, which supports replacing indium tin oxide (ITO) with the hybrid TCEs in flexible electronics applications.