TEM investigations of two alloys isothermally heat treated at 175 C and 260 C show how Cu additions to the Al-Mg-Si system affect precipitation. Both alloys had a solute content Mg þ Si ¼ 1.3 at.%, 0.127 at.% Cu, but with Mg/Si 0.8 and 1.25. Cu-containing Guinier-Preston (GP) zones and three types of Q 0 precursors are identified as most common phases at peak-hardness conditions, whereas 00 accounts for maximum 30% of the total number of precipitates. The precursors have needle (L and S precipitates) or plate (C precipitate) morphologies. They consist of different arrangements of Al, Mg and Cu atoms on a grid defined by triangularly arranged Si planes parallel with and having the same period as {100} Al planes. The Si grid is composed of nearly hexagonal sub-cells of a ¼ b ¼ 4.05 Å , c ¼ 4.05 Å . The Cu arrangement on the grid is often disordered in the needle precursors. The plate precursor is ordered, with a monoclinic unit cell of a ¼ 10.32 Å , b ¼ 8.1 Å , c ¼ 4.05 Å , ¼ 101 .

Scanning transmission electron microscopy (STEM) data with atomic resolution can contain a large amount of information about the structure of a crystalline material. Often, this information is hard to extract, due to the large number of atomic columns and large differences in intensity from sublattices consisting of different elements. In this work, we present a free and open source software tool for analysing both the position and shapes of atomic columns in STEM-images, using 2-D elliptical Gaussian distributions. The software is tested on variants of the perovskite oxide structure. By first fitting the most intense atomic columns and then subtracting them, information on all the projected sublattices can be obtained. From this, we can extract changes in the lattice parameters and shape of A-cation columns from annular dark field images of perovskite oxide heterostructures. Using annular bright field images, shifts in oxygen column positions are also quantified in the same heterostructure. The precision of determining the position of atomic columns is compared between STEM data acquired using standard acquisition, and STEM-images obtained as an image stack averaged after using non-rigid registration.

The composition of β″ precipitates in an Al–Mg–Si alloy has been investigated by atom probe tomography, ab initio density functional calculations, and quantitative electron diffraction. Atom probe analysis of an Al-0.72% Si-0.58% Mg (at. %) alloy heat treated at 175 °C for 36 h shows that the β″ phase contains ∼20 at. % Al and has a Mg/Si-ratio of 1.1, after correcting for a local magnification effect and for the influence of uneven evaporation rates. The composition difference is explained by an exchange of some Si with Al relative to the published β″-Mg5Si6 structure. Ab initio calculations show that replacing the Si3-site by aluminum leads to energetically favorable compositions consistent with the other phases in the precipitation sequence. Quantitative electron nanodiffraction is relatively insensitive to this substitution of Al by Si in the β″-phase.

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To study how changes in solute elements affect precipitation, six Al-Mg-Si alloys aged at 175 °C were investigated by transmission electron microscopy (TEM). In alloys with 1.3 at. pct solute, when the Si/Mg ratio exceeds 5/6, a sharp hardness peak appears after 3 hours that correlates with a high density of fine Guinier-Preston (GP) zones. A second, broader peak correlates with ␤Љ precipitates and U phases. With high Si/Mg ratios, GP zones survive for long aging times. The ␤Љ-Mg 5 Si 6 phase becomes very stable in the alloy with its Si/Mg ratio closest to 6/5. Deviation from this ratio increases fractions of ␤Ј, U-phases and disordered precipitates. In Mg-rich alloys less GP zones form and the first peak is suppressed. A coarse precipitate microstructure of ␤Љ and ␤Ј develops, the volume fraction being much higher than in Si-rich alloys. The Mg-rich alloys overage faster. Reducing the content of solutes causes alloys with high Si/Mg ratios to have a more Mg-rich behavior.

An environmentally friendly aqueous sol-gel process has been developed to fabricate thin films of indium tin oxide (ITO). A stable sol was prepared from indium nitrate and tin acetate precursors together with acetic acid and ethylene glycol. The sol transformed into an amorphous gel during heating, which decomposed and crystallized further to nano-crystalline ITO at $300 C. The nanocrystalline ITO powders prepared from the precursor gel were homogeneous and single phase with particle sizes around 15 nm. The aqueous sol was applied for spin coating of ITO films on glass substrates. The deposited thin films were homogeneous and continuous with no cracks or pin-holes and exhibited very good and reproducible optical transparency and electrical conductivity, with a specific resistance of 4.59 Â 10 À3 U cm, thereby demonstrating the potential of this Pechini related sol-gel process. Experiments to determine the robustness of the process with respect to the concentration of the precursors and substitution of the organic components with other alcohols or acids were also performed, and some important aspects of the chemistry of the sol-gel process are addressed.

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To study how changes in solute elements affect precipitation, six Al-Mg-Si alloys aged at 175 °C were investigated by transmission electron microscopy (TEM). In alloys with 1.3 at. pct solute, when the Si/Mg ratio exceeds 5/6, a sharp hardness peak appears after 3 hours that correlates with a high density of fine Guinier-Preston (GP) zones. A second, broader peak correlates with ␤Љ precipitates and U phases. With high Si/Mg ratios, GP zones survive for long aging times. The ␤Љ-Mg 5 Si 6 phase becomes very stable in the alloy with its Si/Mg ratio closest to 6/5. Deviation from this ratio increases fractions of ␤Ј, U-phases and disordered precipitates. In Mg-rich alloys less GP zones form and the first peak is suppressed. A coarse precipitate microstructure of ␤Љ and ␤Ј develops, the volume fraction being much higher than in Si-rich alloys. The Mg-rich alloys overage faster. Reducing the content of solutes causes alloys with high Si/Mg ratios to have a more Mg-rich behavior.