The mechanisms of the oxidation of nickel aluminium coating alloys

Mechanical Maritime and Materials Engineerin

The oxidation mechanism of Pt20Ni30Al50

Additions of platinum to aluminium oxide forming alloys are known to imporve their high temperature corrosion resistance. This is known as the "precious metal effect". In this study the effect of platinum on the oxidation mechanism was investigated by comparing the oxidation mechanism of β-NiAl and Pt20Ni30Al50. This composition agrees with the average composition of a platinum modified aluminide coating. The alloys were oxidized at temperatures from 1000 to 1200°C. The growth of the oxide scale on the NiAl alloy proceeds both by aluminium and by oxygen diffusion through the scale resulting in growth within the scale. However, on Pt20Ni30Al50 the growth of the scale is limited to the oxide/gas interface due to a predominant aluminium transport through the scale. Therefore the growth stresses are reduced. Another difference is the extensive void formation at the β-NiAl/oxide interface. This was not observed on the Pt20Ni30Al50 samples. The phenomena mentioned above are the two likely reasons for the improved oxide scale adherence

Living on the threshold: The spatial experience of living alone with dementia

The purpose of this qualitative study was to understand the meaning of living alone for older people with dementia. Fourteen audio-taped open-ended interviews were conducted with eight such older women in Ontario, Canada. The data were analyzed using an adaptation of van Manen\u27s method. Heidegger\u27s philosophy informed interpretation of the findings through the theme living on the threshold. The study findings deepen understanding of \u27space\u27 and \u27place\u27 in the experience of living alone with dementia. Participants sought the middle-ground of dialectical tensions within the threshold space and shared insights about their spatial experience of: (a) being here, (b) being there, (c) being out, and (d) keeping out. These older women risked losing their threshold space when admitting to mistakes as their illness progressed. The authors conclude with examples of how this spatial interpretation may inform and improve communication with and care of older people in similar circumstances. © The Author(s), 2009