Understanding the interaction of thiosulfate with Alloy 800 in aqueous chloride solutions using SECM

Multifrequency dielectric mapping of fixed mice colon tissues in cell culture media via scanning electrochemical microscopy

Alternating current scanning electrochemical microscopy (AC-SECM) is a powerful tool for characterizing the electrochemical reactivity of surfaces. Here, perturbation in the sample is induced by the alternating current and altered local potential is measured by the SECM probe. This technique has been used to investigate many exotic a range of biological interfaces including live cells and tissues, as well as the corrosive degradation of various metallic surfaces, etc. In principle, AC-SECM imaging is derived from electrochemical impedance spectroscopy (EIS) which has been used for a century to describe interfacial and diffusive behaviour of molecules in solution or on a surface. Increasingly bioimpedance centric medical devices have become an important tool to detect evolution of tissue biochemistry. Predictive implications of measuring electrochemical changes within a tissue is one of the core concepts in developing minimally invasive and smart medical devices. In this study, cross sections of mice colon tissue were used for AC-SECM imaging. A 10 micron sized platinum probe was used for two-dimensional (2D) tan δ mapping of histological sections at a frequency of 10 kHz, Thereafter, multifrequency scans were performed at 100 Hz, 10 kHz, 300 kHz, and 900 kHz. Loss tangent (tan δ) mapping of mice colon revealed microscale regions within a tissue possessing a discrete tan δ signature. This tan δ map may be an immediate measure of physiological conditions in biological tissues. Multifrequency scans highlight subtle changes in protein or lipid composition as a function of frequency which was recorded as loss tangent maps. Impedance profile at different frequencies could also be used to identify optimal contrast for imaging and extracting the electrochemical signature specific for a tissue and its electrolyte.

Pitting and General Corrosion Susceptibilities of Materials for High Level Radioactive Waste (HLW) Disposal

The disposal of high-level radioactive waste (HLW) in deep stable geological formations is accepted at an international level to be the most promising option for its long-term management. The supercontainer concept is currently being considered as the Belgian reference design, wherein the waste will be stored in geological stable clay formations. The outer barrier of the supercontainer is the envelope, which should be made of a corrosion-resistant material as it will be in contact with the aggressive species leaching from the host rock (i.e., chloride) and diffusing through the cementitious barriers of the disposal system. Polarization measurements are carried out to study the pitting susceptibility and the uniform corrosion of possible candidate materials in chloride-rich concrete pore solutions, aerated by high-purity oxygen. The tests are carried out at a deep soil-representative temperature of 60 °C. All materials showed high pitting resistance in aerated concrete pore solutions and can withstand chloride concentrations up to 1 M. Regular 316L and LDX2304 stainless steel also showed good corrosion resistance and can serve as a more economical alternative. The pH of the used pore solutions did affect the measured corrosion rate irrespective of the alloying elements inside the steel grades.