Two in situ `nanoreactors' for high-resolution imaging of catalysts have been designed and applied at the hard X-ray nanoprobe endstation at beamline P06 of the PETRA III synchrotron radiation source. The reactors house samples supported on commercial MEMS chips, and were applied for complementary hard X-ray ptychography (23 nm spatial resolution) and transmission electron microscopy, with additional X-ray fluorescence measurements. The reactors allow pressures of 100 kPa and temperatures of up to 1573 K, offering a wide range of conditions relevant for catalysis. Ptychographic tomography was demonstrated at limited tilting angles of at least ±35° within the reactors and ±65° on the naked sample holders. Two case studies were selected to demonstrate the functionality of the reactors: (i) annealing of hierarchical nanoporous gold up to 923 K under inert He environment and (ii) acquisition of a ptychographic projection series at ±35° of a hierarchically structured macroporous zeolite sample under ambient conditions. The reactors are shown to be a flexible and modular platform for in situ studies in catalysis and materials science which may be adapted for a range of sample and experiment types, opening new characterization pathways in correlative multimodal in situ analysis of functional materials at work. The cells will presently be made available for all interested users of beamline P06 at PETRA III.
The microstructure of the materials constituting a metallic frictional contact strongly influences tribological performance. Being able to tailor friction and wear is challenging due to the complex microstructure evolution associated with tribological loading. Here, we investigate the effect of the strain distribution on these processes. High-purity copper plates were morphologically surface textured with two parallel rectangles—referred to as membranes—over the entire sample length by micro-milling. By keeping the width of these membranes constant and only varying their height, reciprocating tribological loading against sapphire discs resulted in different elastic and plastic strains. Finite element simulations were carried out to evaluate the strain distribution in the membranes. It was found that the maximum elastic strain increases with decreasing membrane stiffness. The coefficient of friction decreases with increasing membrane aspect ratio. By analyzing the microstructure and local crystallographic orientation, we found that both show less change with decreasing membrane stiffness. Graphic abstract
In this work we describe the design process of a grating spectrometer with fast superconducting THz detectors based on Niobiumnitride. The main application is the use as a diagnostic tool for accelerator-based sources of THz radiation like synchrotrons, where interactions of the electron bunches in storage ring lead to fluctuations in spectrum and intensity of the emitted radiation. Guidelines for the design of the two main parts, grating and detector design, are given. Here, a blazed reflection grating for a frequency range of 1 THz to 5 THz has been developed and successfully fabricated in a high-precision milling process out of brass. Also three different planar antenna designs (double-slot, annular slot and log-per spiral) in combination with quasioptical bandpass filters for the THz range have been simulated and evaluated for best spectral resolution and power coupling. Finally, we have verified grating performance for pulsed THz radiation of 1 THz in an experiment conducted at the synchrotron light source of the KIT. Excellent agreement of the grating performance to the simulations has been found.
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