A probabilistic model to predict the lifetimes of the engineered barrier system proposed for the ... more A probabilistic model to predict the lifetimes of the engineered barrier system proposed for the Yucca Mountain repository is described. The model assumes that the titanium Grade-7 drip shield will fail by hydrogen-induced cracking and the Alloy-22 waste package by a combination of passive and crevice corrosion. The model predicts that crevice corrosion of the waste package can be completely avoided ifthe drip shield deflects seepage drips for between 2000 (realistic behaviour) and 6000 years (conservative behaviour). Sensitivity calculations on the crevice corrosion model suggest that early waste package failure is extremely unlikely providing the drip shield performs its function for a minimum of ~ 300 years.
Models that describe hydrogen permeation through a thin TiO 2 film deposited on Pd have been deve... more Models that describe hydrogen permeation through a thin TiO 2 film deposited on Pd have been developed based on a mass-balance equation consisting of diffusion, reversible hydrogen absorption/desorption, and irreversible hydrogen trapping. These models are solved by the finite element method using COMSOL Multiphsics. By comparing model simulations with experimental permeation curves, values of the parameters associated with permeation, such as diffusion coefficients, absorption and desorption rate constants, trapping rate constants, and saturation concentrations can be evaluated. These values are required to develop models to predict hydrogen-induced cracking in oxide-covered Ti-alloys.
Mg is the lightest structural metal with the highest specific strength. It is therefore considere... more Mg is the lightest structural metal with the highest specific strength. It is therefore considered as a solution for vehicular mass reduction so as to reduce the fuel consumption and greenhouse gas emission. Unfortunately, Mg and its alloys are highly susceptible to corrosion, particularly in salt-spray conditions. This has limited its use in the automotive and aerospace industries, where exposure to harsh service conditions is unavoidable. To improve its corrosion resistance it is viable to apply a desirable engineering coating on the Mg surface.This communication discusses the practical aspects of magnesium surface modification based on our review. A novel immersion coating process is also discussed along with the corrosion behavior of coated and uncoated AZ91 magnesium alloy.
A probabilistic model to predict the lifetimes of the engineered barrier system proposed for the ... more A probabilistic model to predict the lifetimes of the engineered barrier system proposed for the Yucca Mountain repository is described. The model assumes that the titanium Grade-7 drip shield will fail by hydrogen-induced cracking and the Alloy-22 waste package by a combination of passive and crevice corrosion. The model predicts that crevice corrosion of the waste package can be completely avoided ifthe drip shield deflects seepage drips for between 2000 (realistic behaviour) and 6000 years (conservative behaviour). Sensitivity calculations on the crevice corrosion model suggest that early waste package failure is extremely unlikely providing the drip shield performs its function for a minimum of ~ 300 years.
Models that describe hydrogen permeation through a thin TiO 2 film deposited on Pd have been deve... more Models that describe hydrogen permeation through a thin TiO 2 film deposited on Pd have been developed based on a mass-balance equation consisting of diffusion, reversible hydrogen absorption/desorption, and irreversible hydrogen trapping. These models are solved by the finite element method using COMSOL Multiphsics. By comparing model simulations with experimental permeation curves, values of the parameters associated with permeation, such as diffusion coefficients, absorption and desorption rate constants, trapping rate constants, and saturation concentrations can be evaluated. These values are required to develop models to predict hydrogen-induced cracking in oxide-covered Ti-alloys.
Mg is the lightest structural metal with the highest specific strength. It is therefore considere... more Mg is the lightest structural metal with the highest specific strength. It is therefore considered as a solution for vehicular mass reduction so as to reduce the fuel consumption and greenhouse gas emission. Unfortunately, Mg and its alloys are highly susceptible to corrosion, particularly in salt-spray conditions. This has limited its use in the automotive and aerospace industries, where exposure to harsh service conditions is unavoidable. To improve its corrosion resistance it is viable to apply a desirable engineering coating on the Mg surface.This communication discusses the practical aspects of magnesium surface modification based on our review. A novel immersion coating process is also discussed along with the corrosion behavior of coated and uncoated AZ91 magnesium alloy.
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