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A rhenium promoted Fischer‐Tropsch (FT) cobalt catalyst supported on γ‐Al2O3 has been investigated by Transmission Electron Microscopy (TEM) and X‐ray Diffraction (XRD), before and after reduction. Electron diffraction, High Resolution TEM and Electron Energy Loss Spectroscopy were used to confirm the oxidation state. Cobalt aggregate, particle and crystallite sizes have been studied in detail and measured by TEM and XRD. A cobalt particle size of 10.0±2.4 nm obtained from bright field TEM images for the reduced material is consistent with the XRD analysis of the calcined catalyst. After reduction dark field TEM imaging gave a volume‐weighted crystallite size of 7.5±2.5 nm, which is close to the value obtained by XRD. The particles had lost the parallel orientation and physical continuity within the alumina pore structure that were present before reduction. The latter was confirmed by electron tomography. Lamellae identified with the presence of Hexagonal Close Packed cobalt were observed in the predominantly Face Centred Cubic particles. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hydrogenation of multicrystalline silicon for solar cell applications is considered to be an effective method of increasing the lifetime by passivating defects and impurities. Hydrogen plasma treated as-cut and chemically etched multicrystalline silicon samples have been studied by electron microscopy in order to investigate hydrogen defect formation at extended bulk defects. In chemically etched samples, the texture of the surface after hydrogen plasma treatment differs between different grains depending on grain orientation. In as-cut samples, hydrogen induced defects are formed on sawing defects that extend up to ∼5 μm below the Si surface. Intragranular defects are also observed in the ∼1 μm subsurface region. The density of defects is higher in as-cut samples than in chemically etched samples and the size of the defects increases with depth. Hydrogen induced structural defects on bulk dislocations and on dislocations in twin grain boundaries and stacking faults are found several microns below the sample surface. It is concluded that (i) the passivation efficiency of multicrystalline silicon substrates after H plasma treatment can be limited by the formation of hydrogen induced structural defects and that (ii) such defects can be used to getter unwanted impurities upon high temperature processing of the Si wafers. [ABSTRACT FROM AUTHOR]

The composition of [beta]- precipitates in an Al-Mg-Si alloy is examined by using atom probe tomography, ab initio density functional calculations and quantitative electron diffraction. Ab initio calculations have shown that replacing the [Si.sub.3]-site by aluminum has led to energetically favorable compositions consistent with the other phases in the precipitation sequence.

A high resolution scanning transmission electron tomography of cobalt-based Fischer-Tropsch catalysts reveals their true three-dimensional morphology. The 3-D measurement data provide insight into the nanoscale differences between catalyst systems that are invisible to bulk property measurements.

The microstructure of LiAID4 with TiCl3.1/3(AlCl3) and VCl3 additives is studied during different steps of the decomposition process using electron energy loss spectroscopy and energy-dispersive X-ray spectroscopy in a scanning transmission electron microscope. The results showed that the distribution of the Al in all the particles anticorrelates with the positions of the additives after ball milling.