Nanostructuring of Palladium with Low-Temperature Helium Plasma
<p>Photo of exposure chamber showing MORI (Trikon Technologies, Newport, UK) automated matching network, exposure volume, load lock gate valve, and transfer arm for introducing samples without breaking vacuum.</p> "> Figure 2
<p>Scanning electron microscope (SEM) micrographs of palladium surface (0.5 mm diameter wire sample) after exposure to helium plasma at elevated temperature. The flux to each area is identical, the only changed variable is temperature (noted in the upper left corner of each micrograph both absolute and as a fraction of the melting point of palladium).</p> "> Figure 3
<p>SEM micrographs of palladium surface (0.5 mm plate sample) after exposure to helium plasma at elevated temperature. The flux to each area is identical, the only changed variable is temperature (noted in the upper left corner of each micrograph both absolute and as a fraction of the melting point of palladium). Secondary electron collection performed at a tilt angle of 0° with respect to the surface normal.</p> "> Figure 4
<p>SEM micrographs of palladium surface (0.5 mm plate sample) after exposure to helium plasma at elevated temperature. The flux to each area is identical, the only changed variable is temperature (noted in the upper left corner of each micrograph both absolute and as a fraction of the melting point of palladium). Secondary electron collection performed at a tilt angle of 40° with respect to the surface normal.</p> "> Figure 5
<p>SEM micrograph of palladium surface (0.5 mm diameter wire sample) after exposure to helium plasma at 900 K, only a couple tendrils are visible as the annealing rate of the tendrils begins to exceed the rate of growth.</p> "> Figure 6
<p>SEM micrograph of palladium surface (300 nm thin film deposited on SiO<sub>2</sub>) after exposure to helium plasma at elevated temperature. (<b>A</b>), (<b>B</b>), and (<b>C</b>) are different resolutions of the same location showing growth of tendrils and voids that appear to penetrate down to the SiO<sub>2</sub> substrate. Tendrils approximately the same diameter as those observed on bulk Pd samples are observed. Pits of similar diameter are also observed. (<b>D</b>) shows an area of the palladium film where the helium plasma has eroded through the palladium film to the substrate with very thin tendrils of Pd stretching across.</p> "> Figure 7
<p>SEM micrograph of palladium surface (30 nm thin film deposited on SiO<sub>2</sub>) after exposure to helium plasma at elevated temperature. <a href="#nanomaterials-05-02007-f005" class="html-fig">Figure 5</a>A–D are different resolutions of the same location showing growth no tendril growth, but a significant amount of voids. These voids are of a diameter greater than the pits observed in the bulk and 300 nm film samples. Large wrinkles appear evident in the film. It appears as though formation and growth of bubbles within the 30 nm thick film rupture the film without being able to build upon each other and grow nanostructures.</p> "> Figure 8
<p>A block diagram of the palladium-catalyzed hydrogenation reaction vessel, including the hydrogen gas inlet, the vacuum cylinder outlet, the magnetic stirrer, and the gas bubbler used to qualitatively determine the flow rate of the hydrogen through the reactant volume.</p> "> Figure 9
<p>A plot of the yield measured as the ratio of the concentration of the cylcohexane to cyclohexene. This ratio is based on the ratios of areas under the curve of the cyclohexane 1.4 ppm peak and the mean of the intensities of the three cyclohexene peaks seen at 1.2 ppm, 1.7 ppm, and 2.0 ppm in the NMR scans, which are characteristic for the respective compounds and are normalized to the deuterated chloroform standard. These ratios were also taken as a function of time to, not only observe the effectiveness of each catalyst type, but also how the kinetics of the reaction compare with each catalyst type.</p> ">
Abstract
:1. Introduction
2. Experimental Section
3. Results and Discussion
3.1. Palladium Nanostructuring as a Function of Temperature
3.2. Palladium Nanostructuring versus Palladium Thickness
3.3. Catalysis with Nanostructured Palladium
4. Discussion and Conclusions
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Fiflis, P.; Christenson, M.P.; Connolly, N.; Ruzic, D.N. Nanostructuring of Palladium with Low-Temperature Helium Plasma. Nanomaterials 2015, 5, 2007-2018. https://doi.org/10.3390/nano5042007
Fiflis P, Christenson MP, Connolly N, Ruzic DN. Nanostructuring of Palladium with Low-Temperature Helium Plasma. Nanomaterials. 2015; 5(4):2007-2018. https://doi.org/10.3390/nano5042007
Chicago/Turabian StyleFiflis, P., M.P. Christenson, N. Connolly, and D.N. Ruzic. 2015. "Nanostructuring of Palladium with Low-Temperature Helium Plasma" Nanomaterials 5, no. 4: 2007-2018. https://doi.org/10.3390/nano5042007