Supported catalytically
active liquid metal solutions (SCALMS)
of Pt in Ga (2 at.-% Pt) were studied in the temperature range of
500 to 600 °C for propane dehydrogenation. A facile synthesis
procedure using ultrasonication was implemented and compared to a
previously reported organo-chemical route for gallium deposition.
The procedure was applied to synthesize GaPt-SCALMS catalyst on silica
(SiO
2
), alumina (Al
2
O
3
), and silicon
carbide (SiC) to investigate the effect of the support material on
the catalytic performance. The SiC-based SCALMS catalyst showed the
highest activity, while SiO
2
-based SCALMS showed the highest
stability and lowest cracking tendency at higher temperatures. The
selectivity toward propene for the SiO
2
-based catalyst
remained above 93% at 600 °C. The catalysts were analyzed for
coke content after use by temperature-programmed oxidation (TPO) and
Raman spectroscopy. While the SiC- and SiO
2
-supported SCALMS
systems showed hardly any coke formation, the Al
2
O
3
-supported systems suffered from pronounced coking. SEM-EDX
analyses of the catalysts before and after reaction indicated that
no perceivable morphological changes occur during reaction. The SCALMS
catalysts under investigation are compared with supported Pt and supported
GaPt solid-phase catalyst, and possible deactivation pathways are
discussed.
Atom probe tomography (APT) is a powerful technique to obtain 3D chemical and structural information, however the ‘standard’ atom probe experimental workflow involves transfer of specimens at ambient conditions. The ability to transfer air- or thermally-sensitive samples between instruments while maintaining environmental control is critical to prevent chemical or morphological changes prior to analysis for a variety of interesting sample materials. In this article, we describe a versatile transfer system that enables cryogenic- or room-temperature transfer of specimens in vacuum or atmospheric conditions between sample preparation stations, a focused ion beam system (Zeiss Crossbeam 540) and a widely used commercial atom probe system (CAMECA LEAP 4000X HR). As an example for the use of this transfer system, we present atom probe data of gallium- (Ga)-free grain boundaries in an aluminum (Al) alloy specimen prepared with a Ga-based FIB.
Atom probe tomography (APT) is a single-ion sensitive time-of-flight mass spectrometry method with near-atomic spatial resolution. In principle, it can be used to detect any chemical element, but so far hydrogen in the form of protium (1H) had to be largely excluded. This is owing to the residual H emitted from the stainless-steel chambers and in-vacuum parts commonly used in atom probe instrumentation. This residual H is then picked up in the APT experiment. In this paper, we show that by replacing the stainless-steel chamber and in-vacuum parts with titanium parts, this residual H can largely be removed, thus enabling the direct imaging of H using APT. We show that besides the drastic reduction of H, also other contaminants such as O, OH, and H2O are reduced by employing this instrument. In the current set-up, the instrument is equipped with high-voltage pulsing limiting the application to conductive materials.
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