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Type: Text × Subject: Energy dispersive spectroscopy ×

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Now showing 1 - 4 of 4
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    Plasma-assisted synthesis and high-resolution characterization of anisotropic elemental and bimetallic core-shell magnetic nanoparticles
    (Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2014) Hennes, M.; Lotnyk, A.; Mayr, S.G.
    Magnetically anisotropic as well as magnetic core-shell nanoparticles (CS-NPs) with controllable properties are highly desirable in a broad range of applications. With this background, a setup for the synthesis of heterostructured magnetic core-shell nanoparticles, which relies on (optionally pulsed) DC plasma gas condensation has been developed. We demonstrate the synthesis of elemental nickel nanoparticles with highly tunable sizes and shapes and Ni@Cu CS-NPs with an average shell thickness of 10 nm as determined with scanning electron microscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy measurements. An analytical model that relies on classical kinetic gas theory is used to describe the deposition of Cu shell atoms on top of existing Ni cores. Its predictive power and possible implications for the growth of heterostructured NP in gas condensation processes are discussed.
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    Stabilization of the ζ-Cu10Sn3 Phase by Ni at Soldering-Relevant Temperatures
    (Heidelberg : Springer Verlag, 2020) Wieser, C.; Hügel, W.; Martin, S.; Freudenberger, J.; Leineweber, A.
    A current issue in electrical engineering is the enhancement of the quality of solder joints. This is mainly associated with the ongoing electrification of transportation as well as the miniaturization of (power) electronics. For the reliability of solder joints, intermetallic phases in the microstructure of the solder are of great importance. The formation of the intermetallic phases in the Cu-Sn solder system was investigated for different annealing temperatures between 472 K and 623 K using pure Cu as well as Cu-1at.%Ni and Cu-3at.%Ni substrate materials. These are relevant for lead frame materials in electronic components. The Cu and Cu-Ni alloys were in contact to galvanic plated Sn. This work is focused on the unexpected formation of the hexagonal ζ-(Cu,Ni)10Sn3 phase at annealing temperatures of 523–623 K, which is far below the eutectoid decomposition temperature of binary ζ-Cu10Sn3 of about 855 K. By using scanning electron microscopy, energy dispersive X-ray spectroscopy, electron backscatter diffraction and X-ray diffraction the presence of the ζ phase was confirmed and its structural properties were analyzed.
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    The morphology of silver nanoparticles prepared by enzyme-induced reduction
    (Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2012) Schneidewind, H.; Schüler, T.; Strelau, K.K.; Weber, K.; Cialla, D.; Diegel, M.; Mattheis, R.; Berger, A.; Möller, R.; Popp, J.
    Silver nanoparticles were synthesized by an enzyme-induced growth process on solid substrates. In order to customize the enzymatically grown nanoparticles (EGNP) for analytical applications in biomolecular research, a detailed study was carried out concerning the time evolution of the formation of the silver nanoparticles, their morphology, and their chemical composition. Therefore, silvernanoparticle films of different densities were investigated by using scanning as well as transmission electron microscopy to examine their structure. Cross sections of silver nanoparticles, prepared for analysis by transmission electron microscopy were additionally studied by energy-dispersive X-ray spectroscopy in order to probe their chemical composition. The surface coverage of substrates with silver nanoparticles and the maximum particle height were determined by Rutherford backscattering spectroscopy. Variations in the silver-nanoparticle films depending on the conditions during synthesis were observed. After an initial growth state the silver nanoparticles exhibit the so-called desert-rose or nanoflower-like structure. This complex nanoparticle structure is in clear contrast to the auto-catalytically grown spherical particles, which maintain their overall geometrical appearance while increasing their diameter. It is shown, that the desert-rose-like silver nanoparticles consist of single-crystalline plates of pure silver. The surface-enhanced Raman spectroscopic (SERS) activity of the EGNP structures is promising due to the exceptionally rough surface structure of the silver nanoparticles. SERS measurements of the vitamin riboflavin incubated on the silver nanoparticles are shown as an exemplary application for quantitative analysis.
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    In Situ Transmission Electron Microscopy of Disorder–Order Transition in Epitaxially Stabilized FeGe2
    (Washington, DC : Soc., 2021) Terker, Markus; Nicolai, Lars; Gaucher, Samuel; Herfort, Jens; Trampert, Achim
    Isothermal crystallization of amorphous Ge deposited on a cubic Fe3Si/GaAs(001) substrate is performed by in situ annealing within a transmission electron microscope. It was found that the formation of epitaxially aligned tetragonal FeGe2 is associated with a disorder–order phase transition mainly consisting of a rearrangement of the Fe/vacancy sublattice from a random distribution to alternating filled and empty layers. Additionally, atomically resolved high-angle annular dark-field scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy demonstrated that the vertical lattice spacing of the Ge sublattice reduces across vacancy layers, indicating that strain minimization plays a role in the phase transition process. Crystallization and ordering are both found to proceed layer-by-layer and with square-root-shaped kinetics with a smaller transition rate for the latter.