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A hybrid-less Strip Telescope for the DESY II Test Beam Facility
No full textThis talk presents the work of constructing a new beam telescope using a innovative hybrid-less strip sensor at DESY II Test Beam Facility
In-situ strengthening of a high strength low alloy steel during Wire and Arc Additive Manufacturing (WAAM)
No full textIn this work, SiC particles were added to the molten pool during WAAM of a high strength low alloy steel. Theintroduction of these high melting point particles promoted grain refinement, and the precipitation of Fe3C dueto SiC dissociation. The microstructural evolution was studied by optical and electron microscopy techniquesand high energy synchrotron X-ray diffraction. Additionally, mechanical testing and hardness profiles wereobtained for the SiC-containing and SiC-free parts. An improvement in the mechanical strength of the SiC-addedWAAM parts was observed, which was attributed to the refined grain structure and finely dispersed Fe3C
Understanding Sulfur Poisoning of Bimetallic Pd-Pt Methane Oxidation Catalysts and their Regeneration
No full textAmorphous Induced Lattice Distortion for a Low-Cost and Highly-Efficient Electrocatalyst for Overall Water Splitting in Acid
No full textThe development of highly active and durable catalysts for water oxidation under acidic conditions is necessary but challenging for renewable energy conversion. Ir-based catalysts are highly efficient for water oxidation in acid, but their large scale application is hindered by the high cost and scarcity of iridium. Herein, we use an amorphous WO3 induced lattice distortion (AWILD) strategy to reduce the Ir content to only 2 wt% in the final material. The optimized hybrid nitrogen-doped carbon (NC)/WO3/IrO2 can efficiently catalyze water oxidation with a low overpotential of 270 mV at 10 mA cm−2 current density (η10) and a high turnover frequency of over 2 s−1 at 300 mV overpotential in 0.5 M H2SO4, a performance that surpasses that of commercial IrO2 significantly. Introducing the layer of amorphous WO3 between IrO2 nanoparticles and NC can distort the lattice of IrO2, exposing more highly active sites for water oxidation. The AWILD effect compensates for the lower Ir content and dramatically reduces the cost of the catalyst without sacrificing the catalytic activity. Additionally, this catalyst also exhibits high activity in acid for hydrogen evolution with only 65 mV of η10 attributed to the AWILD effect, exhibiting efficient bifunctionality as a Janus catalyst for overall water splitting. The AWILD approach provides a novel and efficient strategy for low-cost and highly efficient electrocatalysts for acidic overall water splitting with an extremely low content of noble metals
Reconnaissance of the uncharted low energy vibrational motions of acenaphthene
No full textThe room-temperature, millimeter-wave rotational spectrum of the small polycyclic aromatic hydrocarbon acenaphthene has been measured between 75 and 110 GHz. Accurate rotational and distortion parameters are presented due to the over 1400 transitions that have been included into a global fit. Besides observing transitions of the ground vibrational state, six vibrationally excited states have been identified: four fundamental modes (), one overtone (2), and one combination band (). This is the first report of four of these excited states observed in the gas phase as two of the fundamental modes are IR inactive and the intensities of the overtone and combination bands are often too weak to be observed. These excited states reside less than 300 cm−1 above the ground state, and an experimental approximation of their band centers is presented. The rotational constants and line lists can be used to facilitate the search for this polycyclic aromatic hydrocarbon in the interstellar medium
A zone melting device for the in situ observation of directional solidification using high-energy synchrotron x rays
No full textDirectional solidification (DS) is an established manufacturing process to produce high-performance components from metallic materialswith optimized properties. Materials for demanding high-temperature applications, for instance in the energy generation and aircraft enginetechnology, can only be successfully produced using methods such as directional solidification. It has been applied on an industrial scalefor a considerable amount of time, but advancing this method beyond the current applications is still challenging and almost exclusivelylimited to post-process characterization of the developed microstructures. For a knowledge-based advancement and a contribution to materialinnovation, in situ studies of the DS process are crucial using realistic sample sizes to ensure scalability of the results to industrial sizes.Therefore, a specially designed Flexible Directional Solidification (FlexiDS) device was developed for use at the P07 High Energy MaterialsScience beamline at PETRA III (Deutsches Elektronen–Synchrotron, Hamburg, Germany). In general, the process conditions of the cruciblefree,inductively heated FlexiDS device can be varied from 6 mm/h to 12 000 mm/h (vertical withdrawal rate) and from 0 rpm to 35 rpm(axial sample rotation). Moreover, different atmospheres such as Ar, N2, and vacuum can be used during operation. The device is designedfor maximum operation temperatures of 2200 ○C. This unique device allows in situ examination of the directional solidification process andsubsequent solid-state reactions by x-ray diffraction in the transmission mode. Within this project, different structural intermetallic alloyswith liquidus temperatures up to 2000 °C were studied in terms of liquid–solid regions, transformations, and decompositions, with varyingprocess conditions
Chapter 5 - X-Ray Diffraction Structure Measurements
No full textThis chapter describes how the structure of molten silicates under high pressures may be measured by synchrotron X-ray diffraction, using either large-volume presses or diamond-anvil cells, the latter combined with resistive-heating or laser-heating techniques. A brief summary of the data obtained so far is given, followed by a description of both energy-dispersive and angle-dispersive techniques, including challenges and how they may be overcome. Three areas of research are then highlighted: (1) structural measurements at extreme pressure conditions up to 100 GPa, (2) tracking the structural environment of minor/trace elements in magmas, and (3) the different ways to obtain the density of melts from X-ray diffraction data. Finally, some future prospects are discussed
Wire and arc additive manufacturing of a Ni-rich NiTi shape memory alloy: Microstructure and mechanical properties
No full textWire and Arc Additive Manufacturing (WAAM) was used for fabrication of NiTi parts using a commercialyavailable Ni-rich NiTi wire as the feedstock material. The as-built parts are near fully austenitic at room temperatureas confirmed by differential scanning calorimetry, X-ray diffraction and superelastic cycling. The asbuiltmicrostructure changed from collumnar, in the first deposited layers, to equiaxed in the last deposited onesas a result of the different thermal cycle conditions. This is the first work where WAAM NiTi parts exhibitsuperelastic behavior under tensile conditions, highlighting the potential use of the technique for the creation ofparts shaped in a complex manner based on this material and process. The potential to use WAAM for depositionof advanced functional materials is demonstrated
Density, excess volume, and structure of Fe–Cr–Ni melts
No full textThe relationship between the excess volume and the structure of Fe–Cr–Ni melts is investigated using containerless levitation and in situ high-energy synchrotron x-ray diffraction techniques. The density of six hypoeutectic Fe–Cr–Ni alloys along the 72 wt. % Fe isopleth was measured in the stable and undercooled regions, and the excess volume was evaluated as a function of Cr concentration. It is found that the 72Fe–Cr–Ni alloys exhibit a positive sign of excess volume and the amount increases with increasing Cr concentration. Analysis of the structure factor and pair distribution function of the alloy family reveals that the short-range order in the melt becomes more pronounced with decreasing Cr concentration; this demonstrates a direct correlation between the excess volume and local liquid structure. A characteristic signature of the icosahedral structure is observed in the structure factor of the melts, and the potential origin of the positive excess volume of the 72Fe–Cr–Ni alloys is qualitatively discussed in relation to the icosahedral structure