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- 2012 (5) (entfernen)
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- Africa (2)
- Cement (2)
- Betonpflastersteine (1)
- Chemical vapor deposition (1)
- Concrete (1)
- Difunctionalized [2.2]paracyclophanes (1)
- Education (1)
- Fe-Ni alloy (1)
- Gorham process (1)
- Key comparison (1)
An international interlaboratory comparison of the measurement capabilities of four National Metrology Institutes (NMIs) and one Designated Institute (DI) in the determination of the chemical composition of thin Fe-Ni alloy films was conducted via a key comparison (K-67) of the Surface Analysis Working Group of the Consultative Committee for Amount of Substance. This comparison was made using XPS (four laboratories) and AES (one laboratory) measurements. The uncertainty budget of the measured chemical composition of a thin alloy film was dominated by the uncertainty of the certified composition of a reference specimen which had been determined by inductively coupled plasma mass spectrometry using the isotope dilution method. Pilot study P-98 showed that the quantification using relative sensitivity factors (RSFs) of Fe and Ni derived from an alloy reference sample results in much more accurate result in comparison to an approach using RSFs derived from pure Fe and Ni films. The individual expanded uncertainties of the participants in the K-67 comparison were found to be between 2.88 and 3.40 atomic %. The uncertainty of the key comparison reference value (KCRV) calculated from individual standard deviations and a coverage factor (k) of 2 was 1.23 atomic %.
The synthesis of a disiloxane-functionalized [2.2]paracyclophane and its polymerization to the corresponding siloxane-substituted poly(p-xylylene) via chemical vapor deposition (CVD) has been described. Because of the enhanced solubility of the siloxane substituted poly(p-xylylene) analysis of the molecular structure by NMR, molecular weight, and polydispersity by gel permeation chromatography (GPC), and processing by film casting as well as nanofiber formation by electrospinning was possible. Structural isomers were found by NMR which was expected due to the isomeric mixture of the precursor. High molecular weights at moderate polydispersities were found by GPC which was unexpected for a vapor phase deposition polymerization. The amorphous morphology in combination with a low glass transition temperature led to high elongation at break for the siloxane substituted poly(p-xylylene). Significant difference for the wetting versus water was found for as-deposited films, solution cast films, and nanofibers obtained by electrospinning with contact angles up to 135° close to superhydrophobic behavior.
Sub-Saharan Africa is populated by more than half a billion people,
and rapid urbanization is creating challenges in the areas of housing,
roads, railways, power supply, dams and water pipelines —
aspects of infrastructure that are critical to the well being of the
population. This situation indicates that cement and concrete will
play a major role in the future construction technology in Africa, despite
the fact that it does not have a long-lasting tradition over most
of the continent. Although the continent is rich in natural resources
for the production of mineral binder systems, many sub-Saharan
African countries exhibit challenging boundary conditions, that have
to be well understood in order to use cement and concrete technologies
in a sustainable and reasonable way.