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- 2023 (42) (entfernen)
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- Forschungsdatensatz (17)
- Vortrag (14)
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- X-ray scattering (26)
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Organisationseinheit der BAM
- 6 Materialchemie (42)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (40)
- 6.6 Physik und chemische Analytik der Polymere (9)
- 6.0 Abteilungsleitung und andere (4)
- VP Vizepräsident (4)
- VP.1 eScience (4)
- 5 Werkstofftechnik (3)
- 5.1 Mikrostruktur Design und Degradation (3)
- 6.3 Strukturanalytik (3)
Eingeladener Vortrag
- nein (14)
This talk highlights a proof-of-concept that demonstrates the ability to calculate high-resolution Fourier transforms. These can be combined with multi-scale modeling to simulate scattering over a wide range, from small-angle scattering to XRD and PDF.
The preprint documenting this is available on the ArXiv here:
https://doi.org/10.48550/arXiv.2303.13435
The Jupyter notebook, VASP calculation details and MOUSE measured scattering patterns are available from this Zenodo repository: https://dx.doi.org/10.5281/zenodo.7764045
We demonstrate a strategy for simulating wide-range X-ray scattering patterns, which spans the small- and wide scattering angles as well as the scattering angles typically used for Pair Distribution Function (PDF) analysis. Such simulated patterns can be used to test holistic analysis models, and, since the diffraction intensity is on the same scale as the scattering intensity, may offer a novel pathway for determining the degree of crystallinity.
The "Ultima Ratio" strategy is demonstrated on a 64-nm Metal Organic Framework (MOF) particle, calculated from Q < 0.01 1/nm up to Q < 150 1/nm, with a resolution of 0.16 Angstrom. The computations exploit a modified 3D Fast Fourier Transform (3D-FFT), whose modifications enable the transformations of matrices at least up to 8000^3 voxels in size. Multiple of these modified 3D-FFTs are combined to improve the low-Q behaviour. The resulting curve is compared to a wide-range scattering pattern measured on a polydisperse MOF powder. While computationally intensive, the approach is expected to be useful for simulating scattering from a wide range of realistic, complex structures, from (poly-)crystalline particles to hierarchical, multicomponent structures such as viruses and catalysts.
2PP-TestArtifact
(2023)
This repository contains a test artifact (TA), also called test structure, designed for two-photon polymerization (also known as Direct Laser Writing (DLW) or Two/Multi-photon lithography (2PA/MPA)). Test artifacts can be used to compare structures, to check options used by the slicer, check the state of the 2PP machine itself or to get a construction guidelines for a certain combination of power, velocity and settings.
The associated paper can be found here: https://dx.doi.org/10.1088/1361-6501/acc47a
General ideas behind the test artifact:
1. optimized for 2PP-DLW
2. should be fast and easy to analyse with optical microscopy or 3. scanning electron microscopy without tilt.
3. short time to fabricate
4. include a reasonable amount of different features
5. bulk and small structures on the substrate
In our (dramatically understaffed) X-ray scattering laboratory, developing a systematic, holistic methodology1 let us provide scattering and diffraction information for more than 2100 samples for 200+ projects led by 120+ collaborators over the last five years. Combined with universal, automat-ed data correction pipelines, as well as our analysis and simulation software, this led to more than 40 papers2 in the last 5 years with just over 2 full-time staff members.
While this approach greatly improved the consistency of the results, the consistency of the samples and sample series provided by the users was less reliable nor necessarily reproducible. To address this issue, we built an EPICS-controlled, modular synthesis platform to add to our laboratory. To date, this has prepared over 1200 additional (Metal-Organic Framework) samples for us to meas-ure, analyse and catalogue. By virtue of the automation, the synthesis of these samples is automat-ically documented in excruciating detail, preparing them for upload and exploitation in large-scale materials databases alongside the morphological results obtained from the automated X-ray scat-tering analysis.
Having developed these proof-of-concepts, we find that the consistency of results are greatly im-proved by virtue of their reproducibility, hopefully adding to the reliability of the scientific findings as well. Additionally, the nature of the experiments has changed greatly, with much more emphasis on preparation and careful planning. This talk will discuss the advantages and disadvantages of this highly integrated approach and will touch upon upcoming developments.
Ionic Liquid Crystals are ionic liquids that exhibit liquid crystalline mesomorphism together with ionic conductivity. As known confined liquid crystal mesophases can show an anomalous dynamics and phase behavior. Investigations considering the factors controlling the macroscopic properties of ILCs in confinement are scare in the literature. This study reports the molecular mobility, and the phase transition behavior of a guanidinium based columnar ILC confined in the nanopores of self-ordered anodic aluminum oxide membranes of various pore diameters (25 – 180 nm) using Broadband Dielectric Spectroscopy (BDS), calorimetry and X-ray scattering. It is aimed to reveal in which way the pore size as well as the pore surface wettability (hydrophobic or hydrophilic) alters the molecular dynamics, and phase transition behavior for this system. These properties are crucial for applications. The DSC investigations reveal: (i) the phase transition temperature for the transition from the plastic crystalline to the crystalline-liquid state has non-monotonic dependence versus the inverse pore diameter and (ii) the transition from the liquid crystalline to the isotropic phase is suppressed for all nanoconfined samples. This transition suppressed in the thermal signal was evidenced by BDS and X-ray scattering. It is discussed as a continuous phase transition taking place in the pores instead of a discontinuous first order transition as observed for the bulk. BDS investigations show different relaxation processes for the bulk and the nanoconfined ILC. Molecular origins for various relaxation processes are discussed and suggested. It is further shown that the self-assembly of this ILC is dynamic in nature which might apply for other ILCs too. The obtained results will have implications for the nanoscale applications of ionic liquid crystals.
In our (dramatically understaffed) X-ray scattering laboratory, developing a systematic, holistic methodology let us provide scattering and diffraction information for more than 2100 samples for 200+ projects led by 120+ collaborators. Combined with automated data correction pipelines, and our analysis and simulation software, this led to more than 40 papers in the last 5 years with just over 2 full-time staff members.
This year, our new, modular synthesis platform has made more than 1000 additional samples for us to analyse and catalogue. By virtue of the automation, the synthesis of these samples is automatically documented in excruciating detail, preparing them for upload and exploitation in large-scale materials databases.
This talk is intended to spark ideas and invite collaborations by providing an overview of: 1) the current improvements in our wide-range X-ray scattering laboratory methodology, and 2) introducing our open, modular robotic platform for systematic sample preparation.
Electric Safety Interlock
(2023)
This interlock is designed to prevent electrical shock from high voltage (>60V) equipment.
While the general safety interlock can be generically applied, this particular example employs an external vacuum-activated switch. It is for safeguarding human operations inside a vacuum sample chamber while the chamber doors are open. The circuit is closed (output is active) when a sufficient level of vacuum is reached, i.e. when all accessible openings are necessarily closed.
The initial application is to interrupt power to a 220V, 250W heating cartridge (itself mounted inside a small sample holder with potentially exposed contacts) when the sample chamber is open.
The external circuit can be modified to use different interlock mechanisms as needed. Note that the external interlock circuit is only a single circuit (with two signal lines) and thus is not protected against external shorts.
To accomodate a range of safety interlocks, the 4-pin M12 connector is wired as follows: Pin 1 (Brown): +24V for power supply, max current 0.6A Pin 2 (White): Safety interlock system signal 1 (0 or 24V) Pin 3 (Blue) : Safety interlock system signal 2 (0 or 24V) Pin 4 (Black): 0V for power supply
The safety is interlocked (output active) when both signal pins are set high (24V), with sufficient current to activate the two relays. Pin 1 and 4 can be used to power safety hardware (such as light curtains or proximity detectors) with 24VDC up to a current of 0.6A. A larger power supply can be installed when higher currents are needed, while staying within the current limits imposed by the wiring cross-section.
This talk for the Swiss Society for Crystallography (SSCr) workshop on SAXS will introduce scattering from various angles, focusing in particular on:
- Information content of X-ray scattering experiments, three entry points…
- An introduction to Fourier Transforms
- Sample criteria, compatibility, and selection
- Key indicators of a measurement – where is the information?
- Key indicators of measurement quality
- Experiment planning, the basics
The second talk for the Swiss Society for Crystallography (SSCr) workshop on SAXS will highlight the data processing challenges, holistic experimental workflow developments, and the pitfalls. In particular, the following items will be addressed:
- The importance of data processing and estimating uncertainty
- A universal correction pipeline – away with the headaches, at least for this step!
- Experiment planning part 2, some tips and advice to improve your corrected data.
- Sample preparation, background selection, some tips and advice to improve your corrected data.
- Automate for your mental well-being; electronic logbooks, measurement catalogs and workflow management software
- Life on the edge: several pitfalls to avoid…