Metal Oxidation Kinetics and the Transition from Thin to Thick Films

We report an investigation of growth kinetics and transition from thin to thick films during metal oxidation. In the thin film limit (< 20 nm), Cabrera and Mott's theory is usually adopted by explicitly considering ionic drift through the oxide in response to electric fields, where the growth kinetics follow an inverse logarithmic law. It is generally accepted that Wagner's theory, involving self-diffusion, is valid only in the limit of thick film regime and leads to parabolic growth kinetics. Theory presented here unifies the two models and provides a complete description of oxidation including the transition from thin to thick film. The range of validity of Cabrera and Mott's theory and Wagner's theory can be well defined in terms of the Debye-Huckel screening length. The transition from drift-dominated ionic transport for thin film to diffusion-dominated transport for thick film is found to strictly follow the direct logarithmic law that is frequently observed in many experiments

Studies on the Reduction of Radon Plate-Out

The decay of common radioactive gases, such as radon, produces stable isotopes by a sequence of daughter particles with varied half-lives. These daughter particles are a significant source of gamma, neutron, and alpha particle backgrounds that can mimic desired signals in dark matter and neutrinoless double beta decay experiments. In the LUMINA Laboratory at Southern Methodist University (SMU), studies of radon plate-out onto copper samples are conducted using one of XIA's first five UltraLo 1800 alpha counters. We present results from investigations into various mitigation approaches. A custom-built copper holder (in either plastic or metal) has been designed and produced to maximize the copper's exposure to 220Rn. The 220Rn source is a collection of camping lantern mantles. We present the current status of control and experimental methods for addressing radon exposure levels.Comment: 4 pages, 1 figure, Conference Proceedings for Low Radioactivity Techniques 201

CUB Plastic Shipping Bag Recycling Program

We implemented a plastic shipping bag recycling program at Gettysburg College. Recycling bags contribute towards contamination within the college\u27s single-stream recycling or end up directly in the landfill via traditional trash collection. The production of plastic bags relies on the continued production of fossil fuel extraction. Plastic bag recycling can decrease fossil fuel extraction and waste entering landfills. To curb Gettysburg College’s generation of waste, we placed four bins in various locations throughout the Center Union Building (CUB) in order to collect plastic shipping bags over a 4.5-week period. We made three hypotheses: that our bins would collect shipping bags and be used by Gettysburg College students, that different locations of the bins would impact their usage, and that over time contamination would decrease and desired product collected would increase. We collected 215 plastic bags, which represented 9.53% of the total amount of plastic shipping picked-up from the mailroom. Placing bins closer to the mailroom and away from dining areas reduced contamination and increased shipping bag collection. We did not find support that over time contamination would decrease and desired product increase. We hope this project will guide future policies to increase recycling of plastic shipping bags

Worries across time and a ge in Germany: Bringing together open- and close-ended questions

We investigate how worries in Germany change across time and age, drawing on both closed-ended questions (which typically list a number of worry items) and open-ended questions answered in text format. We find that relevant world events influence worries. For example, worries about peace peaked in 2003, the year of the Iraq War, with a considerable number of respondents also referring to the Iraq war in their text responses. Furthermore, we found that - controlling for these historical effects - worries about various topics such as health and the general economic situation increase with age. With increasing age, respondents also became more likely to answer the open-ended question. This suggests that the age increases in worries we found are not merely a result of an age-biased choice of worry items, but instead also hold for worries self-generated by the respondents

Worries across time and age in Germany: Bringing together open and close-ended questions

We investigate how worries in Germany change across time and age, drawing on both closed-ended questions (which typically list a number of worry items) and open-ended questions answered in text format. We find that relevant world events influence worries. For example, worries about peace peaked in 2003, the year of the Iraq War, with a considerable number of respondents also referring to the Iraq war in their text responses. Furthermore, we found that - controlling for these historical effects - worries about various topics such as health and the general economic situation increase with age. With increasing age, respondents also became more likely to answer the open-ended question. This suggests that the age increases in worries we found are not merely a result of an age-biased choice of worry items, but instead also hold for worries self-generated by the respondents

Radiation hardening and radiation-induced chromium depletion effects on intergranular stress corrosion cracking of austenitic stainless steels

Available data on neutron-irradiated materials have been analyzed and correlations developed between fluence, yield strength, grain boundary chromium concentration and cracking susceptibility in high-temperature water environments. Large heat-to-heat differences in critical fluence (0.2 to 2.5 n/cm[sup 2]) for IGSCC are documented.In many cases, this variability is consistent with yield strength differences among irradiated materials. IGSCC correlated better to yield strength than to fluence for most heats suggesting a possible role of the radiation-induced hardening (and microstructure) on cracking. However, isolatedheats reveal a wide range of yield strengths from 450 to 800 MPa necessary to promote IGSCC which cannot be understood by strength effects alone. Grain boundary Cr depletion explain differences in IGSCC susceptibility for irradiated stainless steels. Cr contents versus SCC shows that all materials showing IG cracking have some grain boundary depletion ([ge]2%). Grain boundary Cr concentrations for cracking (below [approximately]16 wt %) are in good agreement with similar SCC tests on unirradiated 304 SS with controlled depletion profiles. Heats that prompt variability in the yield strength correlation, are accounted for bydifferences in their interfacial Cr contents. Certain stainless steels are more resistant to cracking even though they have significant radiation-induced Cr depletion. It is proposed that Cr depletion is required for IASCC, but observed susceptibility is modified by other microchemical and microstructural components