| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014) | |
| Energy Harvesting & Storage | Wednesday Sessions |
| Session EH-WeE |
| Session: | Characterization of Materials for Energy Applications II |
| Presenter: | Motonori Tamura, The Univesity of Electro-Communications, Japan |
| Correspondent: | Click to Email |
A considerable increase in scientific exploration concerning hydrogen production and storage has occurred within the last ten years. Numerous technologies including blast furnace production, biomass production, high temperature electrolysis, thermochemical cycles, advanced gaseous storage tanks, chemical hydrides, and advanced metal hydrides are being developed to provide competitive alternatives to fossil fuel energy technologies. One issue for successful commercial implementation of these technologies is the ability of structural materials for process vessels and piping, storage containers, and engineered components to resist embrittlement from hydrogen.
Hydrogen embrittlement, hydrogen induced cracking, and hydrogen corrosion cracking have long been studied for a wide variety of materials and operating conditions. Major structural component materials for hydrogen service applications are austenitic stainless steels such as Type 304, 316L, etc. These austenitic stainless steels have been previously shown to have a mild susceptibility to hydrogen embrittlement. However, this susceptibility can vary with changing environmental conditions. And as such these materials are often coated with permeation barriers to minimize the potential impact from hydrogen exposure. Some permeation barrier materials such as Al or Al2O3 have been evaluated. These materials have shown permeation reductions that range from 10 to 10000 times. This variation is due to several factors such as inherent permeation resistance and microstructure or nanostructure of thin films. Previous study showed that fine-grained dense films obtained by physical vapor deposition performed low hydrogen permeability. In this study, effect of nanostructure of thin films on hydrogen permeation is evaluated.
The hydrogen permeation behavior of thin films coated Type 316L stainless steel was investigated. Thin films of TiN, TiC, Al2O3 were deposited by ion plating. Coated samples were examined using optical microscopy and scanning electron microscopy (SEM). The coating chemistry was determined using Energy Electron Probe Micro Analysis (EPMA) and the crystallography was analyzed by X-ray diffraction (XRD). Hydrogen permeation test of samples, 35 mm diameter and 0.1 mm thick, was conducted at 773K. The fine-grained and (111) oriented TiN film whose grain size was under 100 nm reduced hydrogen permeation by three orders of magnitude compared to untreated stainless steel. Grain interface was thought to be effective hydrogen trap sites.