Martins, R., Ferreira Fortunato I. E. "
Growth model of gas species produced by the hot-wire and hot-wire plasma-assisted techniques."
Key Engineering Materials. 230-232 (2002): 603-606.
AbstractThe model presented is based on the heat transfer and energy balance equations that rule the set of physical and chemical interactions that take place on the gas phase of a growth process, assuming that the deposition process occurs under laminar dynamic flow conditions (Knudsen number below 1). In these conditions, the chemistry and physics of the process involved in the growth mechanism of silicon thin films produced by the hot wire or the hot-wire plasma assisted technique can be proper derived by balance equations that supply information about how the plasma density, the gas dilution and the gas temperature influence the growth mechanism and the equilibrium of the concentration of species presented on the growth surface. The model developed establishes a relation between the abundance species formed and the parameters initiators of the process such as the filament temperature and the rf power density used.
Moniz, António, and Cláudia Gomes Impactos sociais do desinvestimento[Social Impacts of divestment]. University Library of Munich, Germany, 2002.
AbstractThe resulting economic integration of industrial processes and manufacturing internationalisation lead several authors to argue that world economy is globalised. In this context, the approach to the divestment concept without an social and económical context, does not show a group of associated practices and representations. Choices and options are motivated by exogenous forces that pushes companies to determine strategies that stop capital investment on new equipment goods, or on other imaterial goods. This type of strategy is designated by "divestment". The social level of consequencies are not due to the closing down or de-localization of production units that are divesting, but can be materialised of efects that are irreversible. This means unemployment, de-skilling, labour precarization and even emergence of new forms of social exclusion in former industrialised regions.
Mateo, J., M. C. Lanca, and J. Marat-Mendes. "
Infrared spectroscopy studies of aged polymeric insulators."
Advanced Materials Forum I. Ed. T. Vieira. Vol. 230-2. Key Engineering Materials, 230-2. 2002. 384-387.
AbstractThin films of low density polyethylene (LDPE) and crosslinked polyethylene (XLPE) were aged under an AC electric field while kept in sodium chloride aqueous solution. After aging the samples showed water trees (localized damaged with the appearance of hydrophilic ramified structures whose size ranges from a few microns to I mm). Some of the samples suffered dielectric breakdown showing small channels (1-2 mm. diameter) crossing the film and sometimes also signs of carbonization. In order to identify the oxidation mechanisms contributing to aging, FTIR was used to analyze both unaged and aged specimens. Comparing between unaged and aged LDPE an increase in the FTIR spectrum for bands at 1720 cm(-1), 1640 cm(-1) and 1590 cm(-1) was visible for the aged samples. The first region corresponds to carbonyl groups (C=O bonds) resulting from oxidation (most probably ketones). While the second one is related to carbon double bonds formed due to chain scission. Finally the third one is due to carboxylates. For the XLPE the analysis is more difficult. Besides aging it needs to be taken into account the by-products of crosslinking that will tend also to diffuse out with time. The main effect of aging is an increase in the concentration of 1640 cm(-1) band (C=C bonds). For the water treed regions dry and wet samples were compared. In the wet ones the absorbance is larger for the 3380 cm(-1) exhibiting, as expected, water absorption in the water treed regions (hydrophilic characteristics were increased).
Mateo, J., M. C. Lanca, and J. Marat-Mendes. "
Infrared spectroscopy studies of aged polymeric insulators."
Advanced Materials Forum I. Ed. T. Vieira. Vol. 230-2. Key Engineering Materials, 230-2. 2002. 384-387.
AbstractThin films of low density polyethylene (LDPE) and crosslinked polyethylene (XLPE) were aged under an AC electric field while kept in sodium chloride aqueous solution. After aging the samples showed water trees (localized damaged with the appearance of hydrophilic ramified structures whose size ranges from a few microns to I mm). Some of the samples suffered dielectric breakdown showing small channels (1-2 mm. diameter) crossing the film and sometimes also signs of carbonization. In order to identify the oxidation mechanisms contributing to aging, FTIR was used to analyze both unaged and aged specimens. Comparing between unaged and aged LDPE an increase in the FTIR spectrum for bands at 1720 cm(-1), 1640 cm(-1) and 1590 cm(-1) was visible for the aged samples. The first region corresponds to carbonyl groups (C=O bonds) resulting from oxidation (most probably ketones). While the second one is related to carbon double bonds formed due to chain scission. Finally the third one is due to carboxylates. For the XLPE the analysis is more difficult. Besides aging it needs to be taken into account the by-products of crosslinking that will tend also to diffuse out with time. The main effect of aging is an increase in the concentration of 1640 cm(-1) band (C=C bonds). For the water treed regions dry and wet samples were compared. In the wet ones the absorbance is larger for the 3380 cm(-1) exhibiting, as expected, water absorption in the water treed regions (hydrophilic characteristics were increased).