Negative Differential Resistance in Oxygen-ion Conductor Yttria-stabilized Zirconia for Extreme Environment Electronics.

Oxygen-ion conductors have traditionally been studied in the context of high temperature (≈ 873 to 1773 K) energy conversion and sensor technologies. However, there is growing interest in exploring ion-based electronics for harsh environments (400 to 573 K) that represents an emerging field. Here, we utilize a blocking electrode to modify the interface properties of oxygen-ion conducting yttria-stabilized zirconia (YSZ) thin film electrochemical cells. The modified YSZ cell exhibits negative differential resistance (NDR) in the current-voltage curves at 543 K in the air. A double-sweep method and analysis of the scan-rate dependence of the j-V characteristics clearly suggest that the NDR behavior is formed by the reduction reaction of adsorbed oxygen or platinum oxide at the YSZ/Pt interface. A stable and switchable YSZ NDR device is realized with a high peak-to-valley current ratio of 5.8 at 543 K. Utilizing the NDR effect, we demonstrate a proof-of-concept switchable ternary inverter by interfacing with a silicon transistor. Oxygen-ion conductors and their interfaces offer new directions to design electronics for extreme environments.

Synergy between Galvanic Protection and Self-Healing Paints.

Painting is a cost-effective technique to delay the onset of corrosion in metals. However, the protection is only temporary, as corrosion begins once the coating becomes scratched. Thus, an increasingly common practice is to add microencapsulated chemical agents to paint in order to confer self-healing capabilities. The additive's ability to protect the exposed surface from corrosion depends upon (i) how long the chemical agent takes to spread across the exposed metal; (ii) how long the agent takes to form an effective barrier layer; and (iii) what happens to the metal surface before the first two steps are complete. To understand this process, we first synthesized 23 ± 10 µm polyurea microcapsules filled with octadecyltrimethoxysilane (OTS), a liquid self-healing agent, and added them to a primer rich in zinc, a cathodic protection agent. In response to coating damage, the microcapsules release OTS into the scratch and initiate the self-healing process. By combining electrochemical impedance spectroscopy, chronoamperometry, and linear polarization techniques, we monitored the progress of self-healing. The results demonstrate how on-demand chemical passivation works synergistically with the cathodic protection: zinc preserves the surface long enough for self-healing by OTS to reach completion, and OTS prolongs the lifetime of cathodic protection.