MLZ User Meeting 2021Online only
In order to provide our users with the latest updates on our future plans we like to invite all of you to our annual User Meeting on Dec. 07th-08th!
After the successful virtual MLZ User Meeting 2020 (in combination with the DN2020), the User Meeting this year will be held online as well. Looking at the COVID-19 situation not only in Germany, this will be the safest way for this event.
The first day of this virtual meeting will be dedicated to specialised workshops organised by our Science Groups as usual. On the second day, the MLZ spokesman Prof. Dr. Martin Müller will inform you about the current situation here at Garching. Listen also to the plenary talks of Walter Richtering (RWTH Aachen) and Joao Cabral (Imperial College London) - and don't forget to visit the poster sessions and use the possibility to "Ask the instrument" on both days: Each instrument will be present and open for all your questions.
We are looking forward to interesting talks, well designed posters, and fruitful discussions!
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Convener: Ralph Gilles -
Conveners: Peter Link, Sebastian Busch (MLZ - Hereon)
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Convener: Bastian Märkisch (Physik-Department, TUM)
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Convener: Christoph Hugenschmidt
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Conveners: Robert Georgii, Yixi Su (JCNS-MLZ)
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Conveners: Henrich Frielinghaus (JCNS), Michaela Zamponi (Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum)
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Conveners: Anatoliy Senyshyn, Martin Meven (RWTH Aachen University, Institute of Crystallography - Outstation at MLZ)
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Lithium-Ion Batteries turned out as an indispensable energy supplier in modern society which however suffers from safety concerns due to the flammability of the liquid electrolyte. Solid polymer electrolytes (SPEs) can bypass this obstacle and therefore represent a serious alternative to conventional electrolytes. Especially single-ion conducting polymers (SICPs), which have the anion covalently bonded to the backbone of the polymer and thus exhibit a theoretical transference number of unity, are of great interest in battery research. This property is especially interesting for lithium metal batteries due to the ability of supressing dendritic growth. In addition to that, these polymers show reasonable high ionic conductivities, what makes commercialization possible. Here, the SICP Poly((trifluoromethane)sulfonimide lithium styrene) (PSTFSILi) with Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is used as SPE and capillary battery cells are fabricated and tested. This special cell type allows the observation of the structural evolution of the polymer electrolyte during cycling of the battery with small/wide angle x-ray scattering (SAXS/WAXS).
Speaker: Fabian Alexander Christian Apfelbeck (1 Technische Universität München, Fakultät für Physik, Lehrstuhl für Funktionelle Materialien, James-Franck-Str.1, 85748 Garching, Germany) -
We propose to measure a parity-odd asymmetry A in the forward scattering amplitude for neutrons on the p-wave resonance in 139La at 0.73 eV from the correlation k•I, where k is the neutron momentum and I is the spin of the nucleus. One motivation is to take another step towards a future time reversal (T) violation experiment in polarized neutron transmission through polarized 139La [1]. The search for new sources of time reversal (T) violation is one of the highest intellectual priorities in nuclear/particle/astrophysics. Our long-term plan is to investigate T violation in neutron interactions with heavy nuclei by searching for a parity (P)-odd and T-odd component in the neutron forward scattering amplitude using polarized neutrons and polarized 139La nuclei from some new interaction beyond the Standard Model of particles and interactions. It is important to measure this k•I correlation, which is an important source of systematic error. Second, this measurement can also fix the key spectroscopic parameter that determines the sensitivity of the T violation search, which depends on the fractions ΓpI±1/2/(ΓpI-1/2+ΓpI+1/2) of the total width of the 0.73 eV resonance in the I±1/2 channels [2]. A previous measurement by Alfimenkov et al [3] of A=0.31±0.09 is not accurate enough for this purpose. If we confirm the size of A implied by this previous work, it would represent the largest amplification of a symmetry-violating amplitude in nuclear/particle physics and therefore a scientific result of general interest.
[1] P. Fadeev and V. V. Flambaum, Physical Review C 100, 015504 (2019), [2] V. P. Gudkov and H. M. Shimizu, Physical Review C 97, 065502 (2018), [3] V. P. Alfimenkov et al, Physics of Atomic Nuclei 59, 1861 (1996), [4] T. Okudaira et al, Physical Review C 97, 034622 (2018).
Speaker: William M Snow (University of Indiana) -
The saponin aescin can be extracted from the horse chestnut tree and is known for its anti-inflammatory and anti-oedematous properties. Using small, unilamellar lipid vesicle (SUV) as model membrane, we study the mixing properties of aescin with the phospholipid 1,2-dioleoyl-sn-glycero-3-phospho-(1’-rac-glycerol) (DOPG) by using small-angle neutron scattering (SANS), small- and wide-angle X-ray scattering (WAXS, SAXS). Due to the very low phase transition temperature of DOPG at $T_m$=-18 °C only the fluid like phase of the lipid is accessible. For pure DOPG vesicles SANS, SAXS and WAXS measurements lead to the expected vesicle like form factor. In SANS measurements the interaction of aescin is almost not visible in the form factor whereas in SAXS measurements the interaction leads to a significant change in the form factors. With SANS and SAXS measurements combined the dimension of the lipid bilayer is resolvable. In contrast, the chain-chain correlation in the bilayer is observable with WAXS measurements. The interaction of aescin with DOPG can be differentiated into two regimes which are based on the aescin concentration. For concentrations up to 10 mol% aescin is incorporated into the bilayer statistically. For concentrations from 20-50 mol% a nano-domain formation of aescin can be assumed in the bilayer. The nano-domain formation is observable by a change in the SANS and SAXS form factors as well as the appearance of a second chain-chain distance in the WAXS signal.
Speaker: Friederike Gräbitz-Bräuer -
Perovskite solar cells have been the subject of several studies aimed at increasing their operational stability, but few have looked at the underlying degradation mechanisms. The influence of the environment on the performance of devices during operation has been neglected in previous studies [4]. Using synchrotron radiation-based operando grazing-incidence X-ray scattering techniques, we study the degradation processes of perovskite solar cells operating in vacuum and a nitrogen environment. We discover that light-induced phase segregation, lattice shrinkage, and morphological deformation occur in vacuum, contrary to earlier findings. Only lattice shrinkage occurs during the operation of solar cells under nitrogen, resulting in improved device stability. A higher energy barrier for lattice distortion and phase segregation is related to the different behaviors. Finally, we discovered that the migration of excessive PbI2 in the perovskite layer to the interface between the perovskite and the hole transport layer degrades device performance in both vacuum and nitrogen.
Speaker: Renjun Guo (Physics E13, Technical University in Munich) -
Electrochemical cycling of lithium-ion batteries is supplemented by the active transport of lithium ions and electrons, which are exchanged between the cathode and anode material. Besides material properties, such exchange is facilitated by cell parameters like electrode dimensions and geometry, current density, temperature, pressure, reaction rate etc. Such parameters are neither uniformly distributed nor static in general and, therefore, serve as stabilizing factor of heterogeneous states in Li-ion batteries typically reflected in the lithium concentration distribution in the electrodes [1, 2].
In most studies reported in the literature the lithium distribution was typically probed in the static equilibrium (for example in the fully charged state in the graphite anode), neglecting the evolution of the distribution under real charging conditions, influence of C-rates etc.
In this work, the evolution of the lithium-ion distribution in the graphite anode was studied in operando using spatially-resolved neutron powder diffraction. Neutron data were complemented by diffraction studies using high energy photons; occurrence of lithium inhomogeneities on different length scales and their dynamics was observed and will be presented in current contribution.- Senyshyn, A., et al., Homogeneity of lithium distribution in cylinder-type Li-ion batteries. Scientific Reports, 2015. 5(1): p. 18380.
- Petz, D., et al., Heterogeneity of Graphite Lithiation in State-of-the-Art Cylinder-Type Li-Ion Cells. Batteries & Supercaps, 2021. 4(2): p. 327-335.
Speaker: Dominik Petz -
The solid electrolyte interphase (SEI) is a solid protective barrier that forms at the surface of lithium-ion batteries (LIB) operating outside the stability range of the electrolyte. In particular, that happens at the anode where Li metal reduces the liquid electrolyte forming a solid mixture of inorganic and organic components during the lithiation reaction [1]. A good barrier layer prevents further electrolyte decomposition and prevents the exfoliation of the anode material during cycling. However, if the SEI layer is unstable, it would lead to electrolyte loss, termed ‘drying out’, and increased electrode impedance. Both processes cause reduced efficiency and capacity fading [2]. Silicon has drawn the attention of researchers as one of the most outstanding alternate materials for the next generation of LIB anodes. It possesses a very high theoretical storage capacity (4200 mAh g−1) compared to all other known materials [3]. However, in addition to the large volume change during Li (de)intercalation process [4], the instability of the SEI layer is a dominant disadvantage of Si anode, which leads to capacity decline and poor kinetics [5]. To understand the effect of SEI on the lithium-ion transport rate in Si thin-film anodes, galvanostatic intermittent titration technique (GITT) measurements were performed on RF sputtered amorphous Si films. The main goal was to determine Li diffusivities with LiClO4-based and LiPF6-based liquid electrolytes at room temperature. It was found that lithium diffusion coefficients of Si in LiClO4-based electrolytes are higher during the Li intercalation process. Furthermore, the morphology, composition, and thickness of the SEI layer are found to be different in various electrolytes, which will lead to differences in lithium-ion diffusion coefficients. To further explore the effect of the SEI layer, in situ neutron reflectometry (NR) will be applied in the near future to continuously study the composition and thickness of the SEI layer in Si anodes during the (de)lithiation process.
Speaker: Mr Baolin Wu (RWTH Aachen University; Forschungszentrum Jülich (IEK-9)) -
In order to improve the microstructure and mechanical properties of newly developed Ni-base superalloy VDM® Alloy 780 it is necessary to understand the $\gamma$’ hardening phase precipitation process. Here the precipitation process was studied in-situ by time-of-flight (TOF) neutron diffraction (ND) and small-angle neutron scattering (SANS) experiments at high temperature, which allowed us to characterize the obtained $\gamma$’ precipitates, amount and sizes (by SANS from the very early stages) and the misfit between matrix and precipitates (by ND). Besides, atom probe tomography (APT) and scanning electron microscope (SEM) provided further details on microstructural and chemical composition.
The precipitation of $\gamma$’ phase at 720 °C and its size and volume fraction changes as a function of time was monitored in two differently solution-annealed samples. It appears that the obtained results depend on the heat treatment history of the sample. Two particle size distributions of $\gamma$’ precipitates were detected by SANS after 2 h in the case of the sample with an extra step after solution-annealing. Variation in heating rates of SANS and TOF ND measurements results in different precipitates nucleation and growth kinetics. A final heat treatment at 620 °C does not lead to a similar precipitation or growth process.
The in-situ SANS measurements at 750 °C of the fully precipitation hardened sample with two particle size distributions of $\gamma$’ precipitates at RT confirms the matrix-diffusion-controlled Ostwald ripening of the precipitates.Speaker: Cecilia Solis -
Non-fullerene organic solar cells have undergone significant improvements via both, synthesis of novel organic synthesis materials and application of easy fabrication methods. However, device degradtion is still a major problem. For example, the peeling-off of the top electrode fabricated by thermal evaporation leads to an intrinsic device degradation, which is one ofamong the main reasons for the performance losses of organic solar cells. Another disadvantage is the inevitable high temperature during the evaporation process, which can be harmful to the organic materials and is energy extensive thereby prolonging the energy payback times significantly. To overcome these challenges, the magnetron sputtering technique appears very promising for top contact deposition.
For understanding the mechanism of the metal cluster growth on the thin films with various morphologies used in organic solar cells, we use apply in-situ grazing-incidence small-angle X-ray scattering (GISAXS) to observe the morphology changes during the sputter depositioning process. In the present study, the active layer of the organic solar cells is composed of the polymer donor PffDT4T-2OD and the small molecule accepter EH-IDTBR. Both materials were dissolved in 1,2,4-trimethylbenzene and chlorobenzene, respectively to obtain different morphologies of the printed PffDT4T-2OD: EH-IDTBR films. Then 10 nm MoO3 was deposited on their surfaceese films, which acts as the electron blocking layer for thein an inverted solar cell devicegeometry. A 20 nm Al layer is sputtered on top of MoO3 acting as top contact. Notably, the formation of the Al electrode on MoO3 is slower than on the active layer without deposition of MoO3. In addition, SEM and AFM measurements indicate that the morphology impacts the Al growth significantly.Speaker: Xinyu Jiang (Technische Universität München Fakultät für Physik) -
The interest in all-solid-state lithium batteries mainly originates from its high safety and energy density compared with conventional Li-ion batteries. Solid polymer electrolytes (SPEs) as an essential component with high durability, long shelf life, high energy density, great flexibility for cell design and low weight are considered as the most promising material for next generation batteries. However, as the most common SPE, poly(ethylene oxide) (PEO) electrolytes have a limited electrochemical window and can react with lithium metal to form a solid electrolyte interphase (SEI), meaning that such SPE is more instable in high-energy-density batteries. Moreover, inhomogeneity at the electrolyte/electrode interface can elicit an irregular lithium plating that leads to dendrite formation, resulting in the cycle life reduction and total cell resistance increase. As a modifying strategy, adding inorganic particles can alter the degree of non-conducting crystalline polymer volume within the electrolyte, promote the dissociation of Li+-TFSI- ion pairs and increase the amount of mobility Li+ ions. Herein, Mg(ClO4)2 is introduced to the electrolyte and a series of SPE-Mgx electrolyte(x ranges from 0.25 to 1) are fabricated to modify the structure of SPE and increase the ionic conductivity. Besides, the additive can also assist in constructing a Li+ conducting SEI at the electrolyte/electrode interface. The formation of SEI layer can be detected during cycling with neutron reflectometry in future measurements.
Speaker: Ms Yuxin Liang (Technische Universität München, Fakultät für Physik, Lehrstuhl für Funktionelle Materialien, James-Franck-Str.1, 85748 Garching, Germany) -
Layer formation and annealing of nanoparticles especially colloidal inks applied to porous materials is very relevant for functional coatings and printing. The goal is to distinguish and quantify the differences in structure formation during annealing of deposited colloidal inks on a porous and a solid material. Therefore, we compare two different substrates: As porous template we use a layer of cellulose nano fibers (CNF) – so-called nanopaper – and as non-porous reference medium silicon. We use novel colloidal inks consisting of poly-butylmethacrylate (PBMA) and poly-sobrerolmethacrylate (PSobMA) in aqueous solution. We studied the deposition and the subsequent structural and morphological changes during annealing of the colloidal layers in real-time. We use grazing incidence small-angle neutron scattering (GISANS) and grazing incidence small-angle X-ray scattering (GISAXS). During deposition part of the liquid enters the CNF layer while part of the solvent and the colloids remain on top of the nanopaper surface, leading to a complex drying process. Our results show that the CNF- and colloidal layer will change if the glass transition temperature of the colloids is exceeded.
Speaker: Constantin Harder (DESY & TUM) -
Multilayers composed of heavy metals and ferromagnets with strong perpendicular anisotropy are potential candidates for magnetic memory applications [1,2]. Magnetic skyrmions in particular may enable ultra-dense storage devices due to their extremely low spin currents [2]. Pt/Co-based multilayers generally exhibit worm domains, which can nucleate into domains of skyrmions through breaking/nucleation processes [3,4]. Recent studies have demonstrated the nucleation of skyrmions by varying external magnetic field, temperature and current in Pt/Co/Ta multilayers prepared by sputtering [4,5].
In this work, [Pt/Co/Ta]10 multilayers with cobalt layer thickness between 5 Å to 21 Å were grown by molecular beam epitaxy. We assessed the dependence of the magnetic domain structure on the cobalt thickness of [Pt/Co/Ta]10 multilayers by means of magnetic force microscopy (MFM). The magnetic domains were manipulated by applying different magnetic fields and measuring either in field or in remanence. The results of the systematic investigation are presented and discussed in detail.References:
[1] A. Fert and V. Sampai, Nat. Nanotechnol. 8 (2013) 152–156
[2] C. Wang et al., J. Phys. D: Appl. Phys. 46 (2013) 285001
[3] M. Ma et al., J. Appl. Phys. 127 (2020) 223901
[4] J. Brandao et al., Appl. Nano Mater. 2 (2019) 7532−7539
[5] S. Zhang et al., Appl. Phys. Lett. 112 (2018) 132405Speaker: Liz Margarita Montanez Huaman -
The myelin basic protein (MBP) is a key player when it comes to the formation of tight membrane wrapping around vertebrate’s nerve cells. In physiological conditions, MBP is acting as a glue that stacks multiple myelin layers to build up an insulating sheath which covers axons. To accomplish this task, MBP undergoes a so-called Liquid-Liquid Phase Separation (LLPS) - a property which has recently attracted wide attention in the biological and biophysical community. In a LLPS, two liquid phases with different protein concentrations and physio-chemical properties coexist. Damaged integrity of human MBP and the consequent lack of LLPS capability often results in neurodegenerative diseases such as, for instance, Multiple Sclerosis.
Although the importance of its ability to perform a LLPS is already known, the kinetics of MBP’s phase separation are not well studied yet. Hence, we focus on investigations that follow the formation of liquid-like MBP droplets which can be observed when suitable conditions are applied. To examine both the nucleation and the growth of those μm-sized condensates, we combine imaging techniques and (neutron) scattering experiments: Confocal microscopy of labelled MBP has confirmed the phase separation and provided information about the droplet size distribution. These finding we compared to Small Angle Neutron Scattering (SANS) experiments in a q-range of $7 \cdot 10^{-5}-6 \cdot 10^{-1}$ Å$^{-1}$. Microfluidic experiments where combined with high-speed camera imaging in order to obtain details about the nucleation kinetics. Complementary, a stopped flow setup was used for Time Resolved (TR-SANS) experiments to support the previous results and to determine the growing droplet size within low second to early minute time-scale in situ. For long term droplet growth, Dynamic Light Scattering (DLS) yielded a t$^{1/3}$-dependent growth which indicates Ostwald ripening as dominating mechanism.Speaker: Igor Graf von Westarp -
High-performance energy storage solutions are a basic prerequisite for efficient portable devices and the electrification of the transport sector, and by this reaching the CO$_{2}$ emission targets. The market and progress demand for advances in electrochemical energy storage and a promising approach towards advanced batteries is the so-called all solid state battery concept, where the liquid electrolyte is replaced by a solid state ion conductor.
In this context, search for new types of lithium-permeating membranes along with detailed investigations of potential solid electrolytes are required. The key target is the understanding of structure-property relationships of solid ion conductors, which is inevitable for a purposeful tailoring of a batch of properties directly relevant for applications.
Material classes such as the family of lithium phosphidotetrelates and -trielates, which contain numerous compounds that combine both a great structural variety and closely related structures, are of particular importance because of their diversity, high lithium conductivity, processability etc.$^{[1-3]}$ Herein, the details of lithium diffusion in a series of structurally related fast ion conducting phosphidotetrelates (e.g., Li$_{14}Tt$P$_6$ and (α-/β-)Li$_8Tt$P$_4$; $Tt$ = Si, Ge, Sn) are analyzed and compared with respect to the corresponding materials properties. Applying electrochemical impedance spectroscopy and temperature-dependent powder neutron diffraction experiments in combination with the maximum entropy method as well as one-particle potential analysis, enables a thorough study of lithium transport in this class of materials.[1] S. Strangmüller, et al., J. Am. Chem. Soc., 2019, 141, 14200-14209.
[2] T. M. F. Restle, et al., Angew. Chem., Int. Ed., 2020, 59, 5665-5674.
[3] S. Strangmüller, et al., J. Mater. Chem. A, 2021, 9, 15254-15268.Speaker: Dr Stefan Strangmüller (Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II)) -
Mesoporous Fe2O3 thin films with large area homogeneity demonstrate tremendous application potential in photovoltaic industry, lithium ion batteries, gas or magnetic sensors. In the present work, the synthesis of morphology‐controlled Fe2O3 thin films is realized with the polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer assisted sol-gel chemistry. The effect of the solvent category and polymer-to-FeCl3 ratio is systematically investigated during the sol-gel synthesis process. Spin coating is used for the thin film deposition and a calcination process in the air condition is used for removing the PS-b-P4VP polymer template. For both DMF and 1,4-dioxane solvent system, nanosluster structures are obtained with low PS-b-P4VP concentration, which is supposed to be the result of the weak phase separation property and thereby the weak template effect of the block polymer. When the concentration of the PS-b-P4VP reaches the critical point of micellization, spherical and wormlike porous structures can be specifically formed in the DMF and 1,4-dioxane solvent system, respectively. The further increase of the polymer-to-FeCl3 ratio leads to the enlargement of the spherical pore size in the DMF system and the shrink of center-to-center distance of the worm like structure in the 1,4-dioxane system. Moreover, DMF/1,4-dioxane solvent mixture with different volume ratios are applied for the sol-gel solution preparation to trace the effect of the solvent selectivity on the thin film morphology. By adjusting the preferential affinity of the solvent mixture to the polymer blocks, a spherical to wormlike pore shape transition is observed near a critical value of 0.77.
Speaker: Shanshan yin -
A low-temperature routine to realize inorganic amorphous electron-transport layers (ETLs) is of great importance for the commercialization of perovskite solar cells. The fabrication of ETLs at low temperature is energy saving and compatible with flexible substrates. In this work, titanium thin films are synthesized at low temperature (below 100 ℃) with a polymer template sol-gel method based on the amphiphilic diblock copolymer polystyrene-b-polyethylene oxide (PS-b-PEO), in combination with selective incorporation of the titanium precursor ethylene glycol-modified titanate (EGMT). Morphology tailoring of titanium thin films in the low-temperature process is achieved by managing phase separation of the polymer template. The solvent category for the sol-gel solution is varied to tune the thin film morphologies. Scanning electron microscopy is used to study the structure of the titania films.
Speaker: Guangjiu Pan (Lehrstuhl für Funktionelle Materialien, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany) -
Austempered ductile iron (ADI) is an attractive material with excellent mechanical properties, like high strength, good ductility, wear resistance and fatigue strength. Its mechanical properties are largely determined by the ausferritic microstructure which contains retained high carbon enriched austenite. The retained austenite will become unstable under plastic deformation and will transform to strain-induced martensite. Because of plastic deformation and similar crystal structure of martensite and ferrite, the quantitative phase analysis of the strain-induced martensite in ADI using diffraction techniques has two difficulties, i.e., texture formation and peaks overlapping. These difficulties will influence the accuracy of quantitative phase analysis. By means of different neutron diffraction techniques and methods, like standard Rietveld method using whole diffraction pattern (SPODI + STRESS-SPEC) including the texture effect, texture method from the measured pole figure intensity (STRESS-SPEC) and Bragg edge neutron transmission method (Antares), the difficulties in phase quantification were will be presented in current contribution. Furthermore, the advantages, disadvantages and accuracy of each method will be discussed and summarized.
Speaker: Xiaohu Li (FRM2, Physik, TU München) -
The creation of extreme conditions on the sample by means of high external pressure together with changes in the magnetic field and temperature allows to obtain the comprehensive amount of experimental data for a detailed description of the internal properties of materials.
We investigated the Mn$_{1-x}$Fe$_{x}$Ge compounds, which crystallize into a noncentrosymmetric cubic structure of the B20 type, with Small-angle neutron scattering (SANS) under applied pressure and high magnetic field. In order to perform the corresponding study, the nonmagnetic high-pressure cell was developed that fits the standard sample position and allows to increase the pressure up to 12 kbar with possibility of further improvement up to 25 kbar. The ambient pressure experiment was performed at SANS-1 at FRM-II, while the high-pressure experiment was fulfilled at SANS diffractometer PA20, which was located at LLB, Saclay, France.
On the basis of the obtained experimental data, it becomes possible to estimate the real influence of a change of the cell constant, without taking into account the change in the electron concentration, on the evolution of the field-temperature phase diagram for compounder under investigation.Speaker: Daria Skanchenko (NRC «Kurchatov Institute» - PNPI) -
The Coincidence Doppler-Broadening (CDB) spectrometer at NEPOMUC has recently been upgraded with six additional HPGe Detectors, bringing the total number of detectors to ten. To take full advantage of the even more capable instrument a novel data evaluation software package (STACS) was created.
The software can handle and visualize the data generated by Coincidence Doppler-Broadening Spectroscopy (CDBS) and provides a wide range of tools to analyze such data. Some of the main functions include the extraction of the electron-positron annihilation photo peak from CDB spectra as well as a simple background subtraction algorithm that is able to increase the peak-to-noise ratio of the extracted photo peak further. For the first time it is possible to combine the data from multiple detector pairs, improving measurement statistics. The modular design of the software makes it easy to adapt for future instrument upgrades or even other instruments. Over all the STACS package paired with the upgraded spectrometer is able to perform highly sensitive defect studies or precipitate analysis in solid materials.
Speaker: Leon Chryssos -
Metal halide perovskite light-emitting diodes (PeLEDs) are regarded as alternative candidates for next-generation display technologies due to their high efficiency, superior color purity and tunable bandgap. However, PeLEDs based on isotropic perovskite emitting layers with randomly oriented emissive transition dipole moments (TDMs) remain to be inefficient to get upper limit efficiencies of planar PeLEDs. In general, horizontal emissive TDMs parallel to the device substrate are suitable for light out-coupling, while emitted light from vertical TDMs is mostly trapped in the device. Therefore, an emissive layer with high ratios of horizontal TDMs is expected to enhance the efficiency of PeLEDs. A high proportion of horizontal TDMs can be obtained by adjusting the thickness and crystal orientation of the perovskite film. Here, we mainly use grazing-incidence wide-angle X-ray scattering (GIWAXS) to study a series of additives, and explore the effect of additives on the crystal orientation of the two-dimensional perovskite films.
Speaker: Mr Jungui Zhou (Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, P. R. China; LS Funktionelle Materialien, Physik-Department, TU München, 85748 Garching, Germany) -
The new project CAESAR funded by the Bundesministerium für Wirtschaft und Energie (BMWi) is a cooperation of the Technical University Munich (TUM) including the FRM II and several industrial partners under the leadership of the company Wacker. The aim of this project is the development of Li ion batteries (LIB) with increased specific energy (Wh/kg) and energy density (Wh/l) accompanied by a decrease of the specific cost (€/Wh). To this end, an appropriate combination of high-capacity materials is substantial, in this case Si anodes and Ni-rich layered oxide cathodes. The project encompasses the whole value chain of LIBs from the material development to the validation of prototypes for applications. Thereby, neutron studies at the FRM II will help to analyze failure mechanisms of LIBs and reveal inherent processes to improve their performance. Neutrons are well suited for LIB research since measuring concentrations and distributions of light elements such as Li is feasible. Furthermore, the discriminability of neighboring elements in the periodic system with neutrons is essential here since the cathode materials contain Co, Mn as well as Ni. In this poster, the just-started CAESAR project and the associated neutron experiments will be introduced. Moreover, first neutron depth profiling (NDP) results of differently lithiated Si anodes will be presented. They reveal the distribution of Li throughout the anodes which has a major impact on their cycling stability.
Speaker: Lukas Grossmann -
There are various methods for diffraction pattern calculation of powders, differing in Q-averaging procedures. Three of these were studied in detail: (1) The structure factor formula sums up all the hkl planes for a Q-vectors despite their respective orientations. Only peak intensities are calculated and the peak shape is arbitrary. (2) A Monte Carlo (MC) method of averaging used i.a. by the program SASSENA involves a number of random Q-points over which the computed intensity is averaged. (3) The Debye Formula considers only interatomic distances and the integration is taken with respect to scattering angle and the scattering is weighted as the fraction of the Ewald sphere surface area.
The structure factor intensity has to be normalized on the Ewald sphere surface area in order to yield the same result as the Debye formula – with the drawback that the peak shapes are arbitrary. Only a sample of one million Q-points was enough to reproduce the Debye formula for monoatomic powders by the MC method, but still insufficient for biatomic crystals. The time for the monoatomic compound there exceeded an hour (C++) while the Debye calculation is finished on the minutes time scale (python).
Summing up, the Debye formula appears to be the best and the most time-efficient way for crystalline powder diffraction modeling.Speaker: Anastasiia Kuznetsova (WPN Hereon Garching branch) -
With an increase in renewable energy production, the problem of energy storage becomes more and more significant. One of the most promising ideas is storage in form of hydrogen gas, which involves the production of hydrogen by electrolysis and later its reconversion into electricity in fuel cells. It is of great importance for these processes to be carried out most efficiently with the most readily accessible materials. Therefore, there have been intense studies in the search for catalyst materials for the hydrogen and oxygen evolution reactions.
Molybdenum disulphide, MoS$_2$, has shown promising behaviour as a catalyst in the hydrogen evolution reaction (HER), which is completely in line with its known activity for hydrogenation reactions. In this presentation we will show the results of our study of the diffusion of hydrogen adsorbed inside layered MoS$_2$ crystals, for which we used quasi-elastic neutron scattering, neutron spin-echo spectroscopy, nuclear reaction analysis, and X-ray photoelectron spectroscopy [1]. The neutron measurements demonstrate fast diffusion of hydrogen molecules parallel to the basal planes of MoS$_2$. A much slower hydrogen diffusion was observed perpendicular to the basal planes using nuclear reaction analysis.
1 V. Kuznetsov, W. Lohstroh, D. Rogalla, H-W. Becker, T. Strunskus, A. Nefedov, E. Kovacevic, F. Traeger and P. Fouquet, Physical Chemistry Chemical Physics 23 (2021) 7961 – 7973.Speaker: Vitalii Kuznetsov (Institut Laue Langevin) -
The goal of this project was to include a portable Raman spectrometer into the time-of-flight spectrometer TOFTOF. This setup would allow us to measure neutron and Raman spectra of the sample at the same time, under the same conditions and we would be able to vary the temperature of the sample. As the sample evolves with the change of temperature, so does the Raman spectrum and it is important to take these spectra at the same time and same conditions as the neutron spectrum. The first step of this process is to test the setup in the laboratory conditions. We have managed to install the setup in a laboratory and measure some powder samples at room temperature. We have confirmed that the setup was functional and it can be used with some limitations. The ideas for improving the setup, as well as the challenges will be presented. The materials measured were hydrogen storage materials. Raman spectroscopy, along with neutron spectroscopy is a powerful technique for analyzing the bonding and the intermediate phases that appear in the reactions of these materials.
Speaker: Amina Alic (TUM) -
Due to their application potential for new types of memory devices, the research on multiferroic materials has attracted strong interest during the last decades. A prominent mechanism that drives multiferroic behavior is given by the inverse Dzyaloshinskii-Moriya interaction, which yields the shift of a non-magnetic ligand ion due to a non-collinear magnetic structure. It was shown on a powdered sample of LiFe(WO$_4$)$_2$ that the onset of a spiral spin structure is accompanied by an evolving ferroelectric polarization, whose direction is consistent with the inverse DMI [1]. Here, we report on our single crystal investigations on LiFe(WO$_4$)$_2$, for which we utilized neutron scattering experiments on HEIDI and on KOMPASS [2]. It was possible to determine the magnetic structure of both incommensurate phases at low temperature, which follow the typical sequence of magnetic phases for a type-II multiferroic material. First, in the intermediate phase a spin-density wave forms and subsequently in the multiferroic phase, a chiral spin structure evolves. Furthermore, longitudinal neutron polarization analysis on the cold three-axes spectrometer KOMPASS revealed a partially unbalanced multiferroic domain distribution that develops in the multiferroic phase and even in absence of external fields.
[1] Liu et al., Phys. Rev. B 95, 195134 (2017) [2] Biesenkamp et al., Phys. Rev. B 103, 134412 (2021)Speaker: Sebastian Biesenkamp (II. Physikalisches Institut, Universität zu Köln) -
Layered Fe/MgO/Cr/MgO/Fe nanostructures are an artificial ferromagnetic material in which the exchange interaction of magnetic moments of Fe layers through intermediate dielectric and metal layers can lead to magnetic configurations that are not realized in the well-studied Fe/MgO/Fe and Fe/Cr/Fe systems. The correlation between the structural and magnetic properties of layered Fe(10 nm)/MgO(1.5 nm)/Cr(t)/MgO(1.5 nm)/Fe(7 nm) (t = 0.9 and 1.8 nm) nanoheterostructures was studied. X-ray diffractometry and high-resolution reflectometry data confirmed the formation of an epitaxial crystal structure and revealed its well-defined layered nature with sharp interlayer boundaries. Vibration magnetometry did not reveal significant differences in the hysteresis loops of a characteristic stepped shape. Reflectometry of polarized neutrons made it possible to establish that the processes of magnetization reversal in these samples occured in different ways at the level of individual Fe layers. In the sample with a 0.9 nm thick Cr interlayer, the Fe layers were exchange-coupled through the MgO/Cr/MgO interlayer, and their rotation was correlated with the application of a magnetic field. In the sample with a 1.8 nm thick Cr interlayer, the Fe layers were not exchange-coupled and magnetized independently of each other. It was found that the magnetization reversal of the Fe/MgO/Cr/MgO/Fe systems was characterized by an intermediate state, which could be controlled using a small external field of several tens of oersted and a change in the orientation of the sample, as well as by varying the thickness of the MgO layer.
Speaker: Ms Elena Yakunina (Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences) -
Molybdenum Nitride (MoNx) films are investigated as hole-selective layer of crystal Si solar cells due to having a proper work function (5.62 eV) and high conductivity (2000 S/cm). The hole-selectivity so far is limited by the poor surface passivation, which is highly correlated to the interface structure between Si and MoNx. The open circuit voltage and fill factor of devices with thicker MoNx film (200 nm) are better than those of thinner MoNx films (20 nm), which demonstrates that thicker MoNx films induce a better surface passivation and lower contact resistance at the same time. Moreover, the performance is different from MoOx films. Thick MoOx film (>20 nm) will induce a decreased fill factor due to their poor conductivity. In this work, the interface structure change between MoNx and Si is determined with X-ray reflectivity (XRR) analysis to figure out the passivation origin of MoNx films with different thickness. The phase structures and domain size of MoNx films with different thicknesses, compositions and crystallinity are determined with grazing incidence wide and small angle X-ray scattering (GIWAXS and GISAXS) to give important guidance for improving the hole-selectivity of MoNx further.
Speaker: Dr Yajuan Li (Technical University of Munich) -
Large-scale facilities have gained importance for extended characterization methods in the field of material sciences. In particular, structure analysis by highly brilliant X-ray beams is an ideal technique to investigate drying, crystallization, or degradation processes in-situ. These processes require a high time resolution to capture the reaction dynamics, while developments in detector resolution increase the amount of data that must be processed, ideally in real-time. This has raised the necessity to advance data-processing software tools to help the scientist extracting the essential conclusions from big data sets quickly and efficiently.
In this work, we present a self-contained, python-based tool for the analysis of in-situ grazing-incidence wide-angle X-ray scattering (GIWAXS). The focus lies on the performant and loss-free processing of GIWAXS datasets with high system compatibility for the users. In our software, the IN SItu Giwaxs Heuristic Tool (INSIGHT), we included geometrical transformation and corrections similar to GIXSGUI [1] but extended the functionality to arbitrarily positioned and oriented detectors while maintaining full access to the raw data. This allows for post-processing the original data in q-space without any quality loss.
We apply our tool to an exemplary set of in-situ GIWAXS data following the annealing and crystallization process of a thin film of methylammonium lead iodide based perovskite for the application in solar cells.[1] "GIXSGUI: a MATLAB toolbox for grazing-incidence X-ray scattering data visualization and reduction, and indexing of buried three-dimensional periodic nanostructured films," Z. Jiang, J. Appl. Cryst. 48, pp 917-926 (2015).
Speaker: Lennart Reb (TUM E13) -
Latest research has revealed promising results for silicon (Si) and germanium (Ge) as anode materials for lithium-ion batteries (LIBs). Owing to their high energy capacity these two group 14 semiconductors are considered as auspicious alternatives to graphite anodes in LIBs. In this study, we set the goal of synthesizing a porous silicon-germanium structure over a well-known wet chemical sol-gel approach. Here, the amphiphilic diblock copolymer polystyrene-block-polyethylene oxide (PS-b-PEO) is used as the structuring agent. As the silicon/germanium source, novel soluble 29 atomic Zintl clusters (K12SixGe17-x) are used. In the experiment, we investigate the structural difference that occurs when toluene is used as an additive. Real-space data as SEM and microscopy images will be discussed with reciprocal-space analysis methods as grazing-incidence x-ray scattering in small-angle mode and powder x-ray diffraction data. The study is completed by energy-dispersive X-ray spectroscopy (EDS). As EDS mapping can only probe the surface, we are highly interested in the Si/Ge distribution in bulk. Neutron Scattering in grazing-incidence mode (GISANS) is a key factor in analyzing the inner composition of the thin film.
Speaker: Christian L. Weindl (TU München, Physik-Department, LS Funktionelle Materialien) -
Yuqin Zoua, Shuai Yuanb, Ali Buyrukc, Johanna Eichhornd, Shanshan Yina, Manual A. Scheela, Tianxiao Xiaoa, Shambhavi Pratapa, Suzhe Lianga, Wei Chena, Christian L. Weindla, Cheng Mub, Ian Sharpd, Tayebeh Americ,&, Matthias Schwartzkopfe, Stephan V. Rothe, f, Peter Müller-Buschbaum*a, g
aLehrstuhl für Funktionelle Materialien, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany. E-mail: muellerb@ph.tum.de
bDepartment of Chemistry, Renmin University of China, No. 59 Zhongguancun Street, Beijing 100872, P. R. China
cDepartment of Chemistry, Chair of Physical Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstr. 5-13 (E), 81377 München, Germany
dWalter Schottky Institute and Physics Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
eDeutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22607 Hamburg, Germany
fKTH, Department of Fibre and Polymer Technology, Teknikringen 56-58, SE-100 44 Stockholm, Sweden
gHeinz Maier-Leibnitz-Zentrum (MLZ), Technische Universität München, Lichtenbergstr. 1, 85748 Garching, Germany
Orientations of crystal planes impact on the behavior of photogenerated charge carriers and are vital for developing electronic properties of the corresponding devices. Herein, we propose a facile approach to reveal the effect of crystal stacking on the charge carrier kinetics by doping CsBr to enable the formation of a mix-cations perovskite phase. We use grazing-incidence wide-angle X-ray scattering to probe the crystal structure and crystal orientation of the mixed perovskite thin films revealing the effect of the extrinsic CsBr doping on the stacking of the crystal planes. TPV, TPC and tDOS are also used to detect the recombination of the photo-generated charge carriers and the trap-state density. It is demonstrated that CsBr compositional engineering can effectively tune the crystallization orientation of crystal planes, reduce trap-state density and facilitate photocarriers transport across the absorber and pertaining interface simultaneously. This strategy provides a unique insight into the underlying relationship among the stacking pattern of crystal planes, the photo-generated charge carrier transport and the optoelectronic properties of solar cells.Speaker: yuqin zou -
Nowadays, 2H graphites are the most common anode materials in LIBs. Despite its overall popularity, the performance of LIBs is still limited by the capability of graphite electrodes to store lithium ions in its structure. Graphite builds up a layered hexagonal structure. During charging and discharging lithium ions are reversibly incorporated in the hexagonal structure resulting in the formation of lithiated graphite phases Li$_{x}$C$_{6}$ (0 < x < 1) of different kinds.
Despite the overall popularity there is a clear lack of information about the structural behaviour of LixC6 at compositions of x < 0.25 [1, 2]. Even less information is available about the thermal stability of graphite anodes, which becomes more and more popular in the context of all-solid-state-batteries or fast charging.
In the current contribution, a temperature resolved diffraction study on variously lithiated Li$_{x}$C$_{6}$ samples is presented, where battery graphites were pre-lithiated to a desired lithiation grade in a Li-ion battery and then harvested. The thermal behavior of structural parameters was probed by using powder diffraction studies applying high-energy synchrotron radiation.[1] V. Baran, O. Dolotko, M. J. Mühlbauer, A. Senyshyn, and H. Ehrenberg, J. Electrochem. Soc. 165, 1975-1982 (2018).
[2] A. Senyshyn, O. Dolotko, M. J. Mühlbauer, K. Nikolowski, H. Fuess, and H. Ehrenberg, J. Electrochem. Soc. 160, 3198-3205 (2013).Speaker: Tobias Hölderle -
In the present work authors studied magnetic and structural properties of Fe/Pd/Gd superlattices. The particular system [Fe(35 Å)/Pd(t)/Gd(50 Å)/Pd(t)]x12 was chosen with different layer thicknesses of Pd spacer.
By means of x-ray low-angle diffraction (reflectometry, XRR) and scanning transmission electron microscopy (STEM) with the energy dispersive x-ray (EDX) microanalysis the structural quality of the superlattices was attested.
SQUID and PNR techniques were used to analyze the magnetic properties.It was shown that the insertion of a thin (t=10–14 Å) Pd layer between Fe(35 Å) and Gd(50 Å) layers into multilayer structure allows a considerable reduction the spin-flop transition field.
Study of the structure indicates that in the specified range of thicknesses, Gd and Pd are intermixed into a homogeneous alloy.
By measuring neutron spin-flip scattering we have detected the presence of a magnetically noncollinear state at temperatures T < 50 K in magnetic fields of above H > 500 Oe for the samples with 10 Å - t - 14 Å. By using an extended Stoner-Wohlfarth model we were able to describe the observed transition as a competition of Zeeman energy, bilinear interaction of order of 1 erg/cm2, and biquadratic addition of the order of 0.5 erg/cm2. The coupling energies can be tuned by varying the thickness of the spacer between
Speaker: Nikolay Antropov -
With an aim of obtaining high-efficient titania photoanodes, we introduce germanium nanocrystals (GeNCs) into a diblock-copolymer polystyrene-block-polyethylene oxide (PS-b-PEO) template-assisted sol-gel synthesis. The surface and inner morphologies of the TiO2/GeNC films with different GeNC content after thermal annealing are investigated via scanning electron microscopy and grazing incidence small-angle X-ray scattering (GISAXS). GISAXS provides important insights into the influence of GeNC addition on the structure evolution. We probe the crystal phase, chemical state and optical properties of the nanocomposite films via X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and ultraviolet-visible spectroscopy. These measurements show that even with GeNC addition, the nanocomposite films still have good crystallinity and high transparency. We further study the charge-carrier dynamics of the nanocomposite films. Compared to pristine titania photoanodes, the GeNC addition enhances the electron transfer, resulting in an overall improvement in the short-circuit current density (Jsc) of the exemplary perovskite solar cells and thereby an enhanced solar cell efficiency. The findings reveal that an optimal morphology is obtained by adding 2.5 wt% GeNCs, showing the largest pore sizes inside films. The optimized structures obtained in 2.5 wt% GeNCs yields, correspondingly, the best device performance.
Speaker: Nian Li
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Convener: Michael Hofmann
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Conveners: Peter Link, Sebastian Busch (MLZ - Hereon)
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Convener: Bastian Märkisch (Physik-Department, TUM)
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Convener: Christoph Hugenschmidt
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Conveners: Robert Georgii, Yixi Su (JCNS-MLZ)
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Conveners: Henrich Frielinghaus (JCNS), Michaela Zamponi (Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum)
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Conveners: Anatoliy Senyshyn, Martin Meven (RWTH Aachen University, Institute of Crystallography - Outstation at MLZ)
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Convener: Michael Schulz
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Conveners: Peter Link, Sebastian Busch (MLZ - Hereon)
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Convener: Bastian Märkisch (Physik-Department, TUM)
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Convener: Christoph Hugenschmidt
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Conveners: Robert Georgii, Yixi Su (JCNS-MLZ)
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Conveners: Henrich Frielinghaus (JCNS), Michaela Zamponi (Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum)
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Conveners: Anatoliy Senyshyn, Martin Meven (RWTH Aachen University, Institute of Crystallography - Outstation at MLZ)
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Convener: Henrich Frielinghaus (JCNS)
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A modified quenching and deformation dilatometer (TA instruments DIL 805A/
D/T) is now in operation at the Heinz Maier-Leibnitz Zentrum (MLZ, Germany)
neutron center. It is customized for running neutron scattering measurements
during the temperature/deformation treatment of the sample, in particular
neutron diffraction (phase, texture, and lattice strain) and neutron small angle
scattering. The bulk length change of dilatometer specimens is successfully
combined with in situ neutron diffraction patterns for analyzing dynamic processes
in metallic materials. A detailed introduction to the unique dilatometer is
given and examples of recent experiments highlight the use of the added insight
provided by combining diffraction and dilatometry.Speaker: Xiaohu Li (Forschungs-Neutronenquelle FRM II) -
Co-nonsolvency occurs if a mixture of two good solvents causes the collapse or demixing of polymers into a polymer-rich phase in a certain range of compositions of these two solvents. The nonionic thermo-responsive polymer, poly(isopropylmethacrylamide) (PNIPMAM), which features a lower critical solution temperature (LCST) in aqueous solution, has been widely used to investigate its collapse transition behavior in a mixture of two competing good solvents. However, co-nonsolvency response of its block copolymer containing the zwitterionic poly(sulfobetaine)s, especially poly(4-((3-methacrylamidopropyl)dimethyllammonio)butane-1-sulfonate)) (PSBP)，which exhibits an lower upper critical solution temperature (UCST) and shows a strong swelling transition in aqueous media, is newly studied. We focus on the co-nonsolvency behavior of PSBP-b-PNIPMAM thin films in water/acetone-d6 mixed vapors by in situ time-of-flight neutron reflectometry (TOF-NR) and spectral reflectance (SR). Furthermore, Fourier Transform Infra-red (FTIR) spectroscopy is applied to investigate the interactions between the polymer thin film and water/co-solvent, which is closely related to their deuteration level.
Speaker: Peixi Wang (Workgroup Polymer Interfaces, TUM Department of Physics, Technical University of Munich) -
Graphite and materials made of graphite have historically been of huge technological importance due to their manifold interesting properties. High performance lithium-ion batteries (LIBs) typically use graphite-based anode materials. The energy storage is achieved through the reversible reaction of the graphite with lithium ions in an electrochemical intercalation reaction. When the material is completely transformed to the stage-1 compound with maximum lithium content, LiC6 is obtained. The transformation to LiC6 however is complex and between the two terminal points of this reversible reaction, many intermediate stages exist. The profound complexity and peculiarities of this “staging” reaction, especially in the Li-Graphite system however are not yet fully understood. Although a full understanding is imperative in order to control aging and cell performance characteristics of lithium ion batteries.
We have critically reviewed the existing binary stage-1 GIC structures and especially the Li-GIC structures from the ICSD-database. We review fundamental structural aspects like bonding distances and packing arrangements and explore their symmetry relationships applying group-subgroup considerations. Our findings can be used to improve the understanding of the intermediate stages occurring during the electrochemical intercalation of lithium ions in LIBs and to enhance the analysing of measured neutron data.Speaker: Dr Stefan Seidlmayer (Technische Universität München, Heinz Maier-Leibnitz Zentrum (MLZ)) -
Hybrid plasmonic nanostructures have raised great interest for being used in a variety of optoelectronic devices, due to the surface plasmon resonance (SPR). Charge carriers trapped in colloidal quantum dots (QDs) at localized surface defects is a key issue in photodetectors. Self-assembled hybrid metal/quantum dots can couple plasmonics and quantum properties to photodetectors and modify their functionality. Arranged and localized hybrid nanostructures impact on excitons traps and light harvesting. Here, we demonstrate a coupling hybrid structure using self-assembled gold nanoparticles (Au NPs) doped in PbS QDs solid for mapping the interface structures and the motion of excitons. Grazing incidence small angle X-ray scattering (GISAXS) was used to characterize the order of the Au NPs in the hybrid structure. Furthermore, by correlating the sizes of the Au NPs in the hybrid structure with corresponding differences in photodetector performance, we could obtain the interface carriers trapping influences in the coupling structure.
Speaker: Tianfu Guan -
Rechargeable lithium metal batteries have been recognized one of the most promising energy storage devices due to their superior energy density. However, serious safety concern and poor cyclability are featured originating from uncontrolled lithium dendrite growth and unstable solid electrolyte interface (SEI) layer. One strategy to suppress dendrite growth is surface modification with Amphiphilic block copolymers, such as PDMS-b-PAA, which bear some clear advantages including absorbing mechanical stress, conducting lithium ion, controling the lithium dendrite growth process. With scattering techniques using neutrons and in situ scattering studies, the structures of the surface modified lithium metal anodes and structure formation processes can be studied. Moreover, by applying GISANS, the horizontal structures and vertical structures of the polymer films on the lithium metal surfaces can be investigated reflectivity.
Speaker: Zhuijun Xu (Technische Universität München) -
Nickel manganese spinel LiNi0.5Mn1.5O4 is considered one of the most promising cathode materials for lithium-ion batteries. On the one hand, this is because of its high energy density due to its high voltage plateau at 4.7 V, and the high rate capability due to its three dimensional diffusion network in the cubic crystal system. On the other hand, this material is interesting because additional lithium can be incorporated into the crystal system by exploiting the redox chemistry of manganese, rather than using only the nickel. This feature can be used to compensate for losses in the initial cycles or to increase the overall capacity and energy density even further.
However, the extensive lithiation to Li2.5Ni0.5Mn1.5O4 in the complete voltage range from 4.9 V to 1.5 V leads to an aging of the material and capacity fading. In order to tackle this problem it is necessary to provide answers to two questions: Are there intermediate phases that can be identified and where is lithium intercalated to when all octahedral site in the spinel are occupied, at x>2 in LixNi0.5Mn1.5O4.
By applying potentiometric entropymetry and operando XRD, we were able to reveal a simultaneous formation of Li2Ni0.5Mn1.5O4 and Li2.5Ni0.5Mn1.5O4, both with tetragonal I41amd space group, but with large c and small a and b lattice parameters. Via neutron diffraction we where able to locate the additional lithium on octahedral 8a and tetrahedral 4a positions of the distorted tetragonal phase I41amd. Furthermore, the neutron diffraction revealed a partial site exchange of lithium and nickel ions. This observation could be identified as one aging mechanism for the material by perfoming post mortem XRD measurements on aged LiNi0.5Mn1.5O4 based electrodes.Speaker: Nicola Jobst (ZSW) -
Nanoscale assemblies in water of novel thermoresponsive and double hydrophilic poly(N-isopropylacrylamide)-block-poly(oligo ethylene glycol methyl ether acrylate) (PNIPAM-b-POEGA) copolymers have been investigated by synergy of Fourier transform infrared (FTIR) spectroscopy and small angle neutron scattering (SANS) experiments. By focusing on the influence of temperature as external stimulus and block length asymmetry, differences in morphologies and molecular hydration characteristics of two PNIPAM-b-POEGA diblock copolymers were resolved. With increasing temperature, the macromolecular structures undergo block-length dependent transformations from hierarchical assemblies to more well-defined spherical morphologies as evidenced by SANS. Differences in the strength and/or amount of hydrogen bonding and hydrophobic interactions lead to distinct morphological transformations expressed by variations in cluster compactness and hydration. In these assemblies of PNIPAM-b-POEGA with the short PNIPAM block, the methyl side group hydration, as evidenced by FTIR, sensitively depends on the temperature increase at temperatures even beyond the nominal volume phase transition temperature. For both blocks, the evolution of the amide I band reflects that solvent-polymer interactions are still favorable even at the highest temperatures. The understanding of these assemblies provides ground for optimization of these scaffolds for drug encapsulation protocols.
Speaker: Apostolos Vagias (FRM2 / TUM) -
The implementation of decommissioning tasks requires accurate radiological characterization to be accomplished. Often, computational codes are used to complement experimental radiological characterization campaigns. These activation codes need accurate knowledge of elemental composition of non-irradiated materials. Besides determination of most nuclides by the well-established Inductively Coupled Plasma – Mass Spectrometry (ICP-MS), Prompt Gamma Activation Analysis (PGAA) may be helpful in measuring light elements such as B, N, and Cl, that are known to be important precursors for medium (3H) and long-lived (14C and 36Cl) neutron activation radionuclides. In fact, the assessment of N and Cl by ICP-MS is nearly impossible, whenever HNO3 and HCl are employed to dissolve the sample.
The aim of this work is to complete the elemental characterization of nuclear grade graphite used as moderator and reflector in L-54M nuclear research reactor operated by Politecnico di Milano and now in deferred dismantling decommissioning. The bulk concentrations measured by PGAA resulted to be in agreement with ICP-MS and literature data, when available. Moreover, for the first time, depth distribution concentration profiles of N and Cl have been demonstrated. All data obtained by this innovative approach will be fed into the formerly developed activation code to accurately calculate radionuclides distribution in real samples and support their characterization before decommissioning.Speaker: Eros Mossini (Politecnico di Milano) -
Molecular dynamics simulations are an important tool in evaluating scattering data. They have a high potential, which is even further increasing with the ever increasing computation power and isn't yet fully exploited. For some systems, reliable simulations are already available that are compatible with measured data. For other systems, however, the agreement between simulation and experiment is not satisfactory yet. In this work, we compare measured and simulated data as well as mathematical models on the example of different liquid water models in order to later optimize the underlying forcefields in the simulation as well as the hitherto used mathematical models of the evaluation.
The water molecular dynamics simulations were performed with the program LAMMPS and the program SASSENA was used to calculate the corresponding scattering signals. The outcomes were compared to already existing experimental data and changes in the underlying force fields where evaluated in terms of their impact on the behaviour of the simulation. The long-term aim is to create a new evaluation tool, adapting the parameters of molecular dynamics simulations to match the scattering experiments.Speaker: Veronika Reich (German Engineering Materials Science Center (GEMS) at Heinz Maier-Leibnitz Zentrum (MLZ), Helmholtz-Zentrum Hereon) -
Fast neutrons offer high penetration capabilities for both light and dense materials due to their comparatively low interaction cross-sections, making them ideal for the imaging of large-scale objects such as as-built plane turbines, for which X-rays or thermal neutrons do not provide sufficient penetration. However, inefficient fast neutron detection limits the widespread application of this technique. Traditional phosphors such as ZnS:Cu embedded in plastics are utilized as scintillators in recoil proton detectors for fast neutron imaging. However, these scintillation plates exhibit significant light scattering due to the plastic–phosphor interface along with long-lived afterglow (on the order of minutes), and therefore alternative solutions are needed to increase the availability of this technique. Here, we utilize colloidal nanocrystals (NCs) in hydrogen-dense solvents for fast neutron imaging. The light yield, spatial resolution, and neutron-vs-gamma sensitivity of several chalcogenide (CdSe and CuInS2)-based and perovskite halide-based NCs are determined, with only a short-lived afterglow (below the order of seconds) observed for all of these NCs. FAPbBr3 NCs exhibit the brightest total light output at 19.3% of the commercial ZnS:Cu(PP) standard, while CsPbBrCl2:Mn NCs offer the best spatial resolution at ∼2.6 mm.
Speaker: Kostiantyn Sakhatskyi (ETH Zurich, Empa) -
Cellulose nanofibrils (CNF), extracted from wood, are sustainable materials par excellence and used to fabricate high-strength materials. A promising route for fabricating porous CNF films on large scale is spray deposition using water-based technologies; the resulting porous CNF templates are excellent candidates to infiltrate conductive polymers and plasmon-active nanoparticles for functionalization. This functionalization is based on adding additional layers or depositing CNF-based dispersions using solvent-based methods; often, the solvent itself is water. With CNF being hygroscopic, it is therefore mandatory to understand the interaction of water with the CNF films. We employ in situ grazing incidence small-angle neutron scattering to study the morphological features within the ultra-smooth CNF thin films under as-prepared conditions as well as their rearrangement under humidification. In a next step, we used poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), widely applied in organic photovoltaics and electronics, to functionalize the CNF template. We studied the infiltration, resulting structural rearrangement within the thin CNF template of, and their behavior under cyclic humidity changes by grazing incidence small-angle neutron scattering. Extending to plasmonic applications, we employ layer-by-layer deposition of laser-ablated silver nanoparticles to install a plasmon-active CNF-template.
Speaker: Stephan Roth (DESY / KTH) -
Interfaces based on metal oxides play a major role in functional materials for energy applications. For example, TiO2 can serve as a photocatalyst in the production of hydrogen or as an anode material in emerging solar cell and battery technologies. In most applications, a designed structure is highly de-sired to fulfill performance conditions on different length scales. Moreover, devices benefit from a high interfacial area between functional layers and hence nanostructured TiO2 of high surface-to-volume ratio is favorable. Designed morphologies can be achieved and fabricated by industrial rele-vant, low-cost solution processing, e.g. spray deposition, with the help of diblock copolymer directed sol-gel synthesis. However, involved organic solvents limit the potential in environmentally friendly processing when it comes to an industrial scale. To overcome this, synthetic copolymers can be re-placed by water-soluble biopolymers. The bovine whey protein forms aggregates of different structures by denaturing at different pH values that can act as a template in water-based TiO2 synthesis. Different biohybrid films are obtained by spray deposition from the solutions at different pH. The films are in-vestigated with bulk and surface-sensitive grazing-incidence small-angle neutron scattering (GISANS) to understand the influence of pH on the morphology. The obtained results are complemented by real-space imaging.
Speaker: Mr Julian E. Heger (TUM Physik E13) -
Developing clean energy lies the heart of sustainable development of human society. Triboelectric nanogenerator (TENG) originating from Maxwell’s displacement current is a new type of energy harvester for harnessing ambient mechanical energy based on the coupling of triboelectrification and electrostatic induction effect. Compared with other counterparts, owing to the light-weight, low-cost, and easily fabricated, TENG has become one of the most promising candidates in replacement of conventional fossil fuels and attracted worldwide attention in the past years. However, to further increase the energy harvesting efficiency and broaden application fields, integrating the TENG with other kinds of energy harvesters in one device is a possible way to meet these needs. In the present work, a TENG based hybrid energy harvester is designed and fabricated on the flexible polyethylene terephthalate (PET) substrate. This hybrid device consists of a single-electrode mode TENG component and a PbS quantum dots (QDs) based solar cell component, which can harness both mechanical and solar energy from ambient environment to directly generate electricity.
Speaker: TIANXIAO XIAO (Physik-Department, Lehrstuhl für Funktionelle Materialien, Technische Universität München) -
The combination of dimethyl sulfoxide (DMSO)-solvent doping and physical-chemical DMSO/salt de-doping in a sequence has been used to improve the thermoelectric (TE) properties of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) films. A high power factor of ca.105.2 µW m-1 K-2 has been achieved for the PEDOT:PSS film after post-treatment with 10 % sodium sulfite (Na2SO3) in the DMSO/salt mixture (v/v), outperforming sodium bicarbonate (NaHCO3). The initial DMSO-doping treatment induces a distinct phase separation by facilitating the aggregation of the PEDOT molecules. At the same time, the subsequent DMSO/salt de-doping post-treatment strengthens the selective removal of the surplus non-conductive PSS chains. Substantial alterations in the oxidation level, chain conformations, PEDOT crystallites and their preferential orientation are observed upon treatment on the molecular level. At the mesoscale level, the purification and densification of PEDOT-rich domains enable the realization of inter-grain coupling by the formation of the electronically well-percolated network. Thereby, both electrical conductivity and Seebeck coefficient are optimized.
Speaker: Suo Tu (Institute of Functional Materials) -
The new VDM® Alloy 780 is a Ni-based superalloy developed for higher service temperatures than the widely used alloy 718, consisting of γ matrix, γ´ hardening phase, and δ & η high-temperature phases. Depending on the respective heat treatment of VDM® Alloy 780, various microstructures with different phase proportions can be obtained, which determine the mechanical properties of the alloy over the entire application temperatures.
Via in-situ x-ray diffraction measurements at elevated temperatures, the dissolution of both the γ´ hardening phase and the high-temperature phases can be directly tracked, enabling to determine their solvus temperatures. Also, directly accessible from the measurements is the lattice misfit, i.e. the relative difference of lattice parameters of γ matrix and γ´ hardening phase, and its evolution with temperature which is decisive for the mechanical properties of the alloy and the morphology of the precipitates.
Due to the higher time resolution at the synchrotron, the obtained solvus temperature values are more accurate as previously published by neutron diffraction. However, neutron measurements have much better particle statistics due to the larger measured volume and an enlarged separation of peaks at high theta angles, corroborating the synergistic effect of combining both techniques. Therefore, the synchrotron diffraction data is analyzed comparatively to the existing neutron data.Speaker: Massimo Fritton -
Thermoresponsive polymer thin films have gained a lot of attention in the past decades due to their attractiveness for a wide range of applications. A variety of polymer showing LCST- or UCST-type behavior are known, and their transition temperatures can be influenced by various factors such as molar mass, end groups, copolymerization, or by the addition of salts. For polymers in aqueous solution, it was found that the folding of the polymer chains can be strongly influenced by the type of salt and this ability follows a trend called the Hofmeister series. While this effect is well known in solution, the influence on the swelling behavior of PNIPMAM thin films has yet to be investigated thoroughly. We aim to elucidate the underlying mechanism by spectral reflectance and time-of-flight neutron reflectometry on a macroscopic scale and by in situ Fourier-transform infrared spectroscopy on a molecular level.
Speaker: Julija Reitenbach -
Colloidal quantum dots (CQDs) have generated great interest in various optoelectronic devices because of their size-tunable bandgap, low-temperature solution processability. Lead sulfide (PbS) CQDs, with a strong absorption coefficient and large Bohr radius, enable solar cells to harvest infrared photons of the solar spectrum beyond the absorption edge of crystalline silicon and perovskites. There have been many strategies to improve device performance, among which interface engineering is a promising method. Excellent interface engineering is designed to form an energy cascade to enable an efficient charge transfer and promote exciton dissociation. Moreover, it can also offer good interfacial contact and improve device air stability by selecting appropriate materials. Here, we sputter the indium zinc oxide (IZO) as the interlayer between PbS QDs absorption layer and ZnO nanoparticle (NP) electron transport layer (ETL), to fabricate PbS QD solar cells and study the trap densities and charge transport process at QDs interfaces. In addition, we also study the dynamics process of how the IZO is sputtered on the ITO glass and ITO/ZnO respectively.
Speaker: Huaying Zhong -
Gold deposition via high power impuls magnetron sputtering (HiPIMS) allows to coat thin metal layers on heat sensitive materials allowing increased adhesion compared to an evaporated gold layer. In addition, this particular technique allows deposition at a lower deposited thermal energy. However, the low temperature nucleation and growth processes of HiPIMS are not sufficiently known. Therefore, we investigate the morphology and structure of thin gold layers on three polymers, namely Polystyrene (PS), Polyvinylalcohol (PVA) and Polyvinyl-4-pyridin (PV4P). The polymers are spincoated onto silicon to obtain ~ 40 nm polymer thin films as substrates. These polymers are of interest as they show different functional moieties and thus are expected to influence the growth of the gold layer. We present first results of our investigations using atomic force microscopy (AFM), scanning electron microscopy (SEM) and grazing incidence small angle X-ray scattering (GISAXS).
Speaker: Yusuf Bulut -
Perovskite solar cells (PSCs) have attracted increasing attention in research and industry due to their high efficiency, low material cost and simple solution-based fabrication process, which allow the manufacture of thin, flexible photovoltaic modules.
In laboratory devices, the efficiency already exceeds 25% and is comparable with c-Si.[1] However, one of the most important steps towards commercialisation is upscaling the production of PSCs to a larger area. Slot-die coating is one of the most promising technology being a fast process with minimum material consumption and waste.[2]Furthermore, the highly tuneable perovskite ink composition strongly determines the final morphology of the film, providing an outstanding opportunity to develop a comprehensive understanding of the kinetic processes during film formation. The focus of the work is the effect of additives, such as methylammonium chloride (CH₃NH₃Cl) and methylammonium bromide (CH₃NH₃Br), on the perovskite layer. A complete study - using spectroscopic and X-ray scattering methods - allowed us to effectively understand the role of the halide atoms in the crystallization process.
The ultimate goal of our work is to investigate suitable ink compositions and the resulting final perovskite thin-film to develop a systematic and reproducible printing technique for printed flexible and high-efficiency PSCs.
Speaker: Mr Andrea Vitaloni (Lehrstuhl für Funktionelle Materialien, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany) -
The sodium superionic conductor (NASICON) materials have been a widely studied class of solid electrolytes for Na-ion based all-solid-state batteries due to their high conductivity and facile synthesis conditions. The aim of this work is to elucidate the reason for extremely high conductivity exhibited by some compositions, specifically by $\text{Na}_{1+x} \text{Zr}_{2} \text{Si}_{x} \text{P}_{3-x} \text{O}_{12} (0 ≤ \text{x} ≤ 3)$. We investigate the role of the monoclinic to rhombohedral phase transition for the material with x=2.4, which occurs at ≈170°C, on the Na-ion occupancy in the crystal structure. Additionally, we study the influence of other dopant elements (Sc and Y) on the $\text{Na}^{+}$ ionic conductivity. Quasi-elastic neutron scattering (QENS) is used to measure spatial and temporal dynamic properties of diffusion of $\text{Na}^{+}$ ions in the crystal lattice. The measurements were performed at the BASIS spectrometer at the Spallation Neutron Source, Oak Ridge National Laboratory in Tennessee, USA. For the evaluation of the QENS data, the DAVE software (NIST Center for Neutron Research) is used. Important information about the $\text{Na}^{+}$ ion diffusion process, such as activation energies, jump distances between the occupation sites and characteristic times of jumps can be extracted from the measured QENS data. The detailed data analysis is still in progress. This worked was performed as a collaboration between TUM (Heinz Maier-Leibnitz Zentrum, FRM II) and Forschungszentrum Jülich (IEK-1) in the frame of the BMBF project ExcellBattMat cluster.
Speaker: Ivana Pivarníková -
Perovskite solar cells (PSCs) are one of the most promising photovoltaic technologies and reached a certified 25.2% efficiency owing to their tuneable bandgap, high carrier mobility, long diffusion length and so on. The long-term operational stability of PSCs, however, has been not investigated. Herein, we probe the structure change with grazing-incidence small-angle scattering techniques (GISAXS) under high humidity. Also, the solar cell parameters are obtained simultaneously during the device operation. We find that PSCs fabricated with and without caesium iodide (CsI) show differences in the device degradation and morphology change in the perovskite layer. The decrease of open-circuit voltage (VOC) can be attributed to the morphology changes and the evolution of crystallize grain size. With the additive of CsI, solar cells show slow decay of VOC, which is correlated to improved morphology of active layer and passivation of trap states. Our work presents a crucial step towards a fundamental understanding of morphology change combined with solar cell parameters during the device operation.
Speaker: Mr Kun Sun -
In the past few years, perovskite solar cells (PSCs) received a lot of awareness in research due to their low manufacturing cost, high efficiency, and high specific power. For industry, PSCs are very interesting because of their easy solution-based fabrication process and comparable efficiencies with the established c-Si-based solar cells.[1] Thus, the fabrication can be upscaled with low waste deposition technologies like printing. Being fast and using minimal material, slot-die coating is a very promising technique.[2]
During our work we optimize printed PSCs on flexible substrates and investigate their suitability for the application in space environment.[3] The objective is the development of PSCs by applying different compositions and measuring techniques like spectroscopy and real-space imaging in combination with X-ray scattering methods.
[1] Green, M., et al. (2021). “Solar cell efficiency tables (version 57)”. Prog. Photovolt. Res. Appl. 29: 3– 15.
[2] Patidar, R., et al. (2020). "Slot-die coating of perovskite solar cells: An overview." Materials Today Communications 22: 100808.
[3] Reb, L., et al. (2020). “Perovskite and organic solar cells on a rocket flight”. Joule 4, 1880–1892.Speaker: Christoph Lindenmeir -
ZnO has received much attention over the past years because it has a wide range of properties, including high transparency, piezoelectricity, wide-bandgap semiconductivity, high electron mobility and low crystallization temperature. To improve the photovoltaic performance of ZnO-based hybrid solar cell devices, an interconnected mesoporous inorganic nanostructure is favorable, which can provide a high surface-to-volume ratio for exciton separation within their lifetime and a good pathway for charge carrier transport. To fabricate the mesoporous inorganic ZnO semiconductors, various methods can be employed, such as chemical vapor deposition, wet chemical method and, hydrothermal synthesis. Among these methods, the diblock copolymer assisted sol-gel synthesis approach has been corroborated by countless reports to be powerful in its morphology tunability.
In the present work, an amphiphilic diblock copolymer is used as the template and suitable printing parameters are selected to fabricate the mesoporous ZnO films with varied morphologies. Grazing-incidence small angle X-ray scattering (GISAXS) is used to probe the inner film morphology without intervening the film formation process or impairing the printed films.Speaker: Ting Tian -
Functional nanocomposites are an important class of smart and adaptive materials. They offer a broad application range from sensors through stretchable electronics to energy conversion and human health. Especially, responsive materials which are able to perform self-assembly in different environments (e.g. magnetic field) are in the center of interest. Further developments in this area would significantly benefit from deeper insights into the self-assembly of the nanoparticles depending on the temperature, external field strength, initial distance between particles etc.
Iron oxide nanoparticles grafted with polymer play the significant role in creating magnetically tunable photonic crystal systems. Self-assembly of these nanocomposites can be controlled by varying the core-polymer shell size and the strength of external field. In our scattering experiments we show that application of the magnetic field to the paramagnetic nanoparticles results in ordered crystal structure formation. Moreover, the crystal structure and lattice parameter changes with the magnetic field strength and demonstrate a phase transition.
We established synthesis of highly monodispersed iron oxide nanoparticles
of different size grafted with polymer and use them to control the self-assembly of nanocomposite varying external parameters: temperature, magnetic field strength and mechanical stress.Speaker: Vladislava Fokina -
supper mirror(SM) arrays to greatly reduce stray magnetic fields by using self compensation. This yoke is a minor modification to the typical existing magnetic yokes used for polarized SM arrays, often consisting of rows of very strong permanent magnets, such as NbFeB, arranged on either side between a cavity made of a pair of thick (> 1 cm) soft iron plates. Such configurations can produce high fields (on the order of 500 G) over the large volume of the SM array, however they also create an external dipole field. One can passively shield such devices with additional magnetic layers or shells of $\mu$-metal, soft iron, or even steel, but this adds extra weight, complexity and size while not completely trapping the stray magnetic flux. Therefore we developed and produced a modification to the existing magnetic yoke to compensate the stray fields at long range. This is done by adding a balanced amount of magnets with opposite magnetization to the original yoke, thus effectively canceling the stray field at distances of relevance to neutron instrumentation. The final device is similar to a simplified cladded magnet structure, and can be produced essentially as a bolt-on addition to existing polarized SM array magnetic yokes. This modification, in addition to eliminating the stray dipole fields at long range, actually increases the magnetic field inside the active area of the yoke.
Speaker: Earl Babcock -
The PERC facility is currently under construction at the MEPHISTO beamline of the FRM II. It will serve as an intense and clean source of electrons and protons from neutron beta decay for precision studies. It aims to improve the measurements of the properties of weak interaction by one order of magnitude and to search for new physics via new effective couplings.
PERC's central component is a 12 m long superconducting magnet system that has recently been delivered. It hosts an 8 m long decay region in a uniform field. An additional high-field region selects the phase space of electrons and protons, which can reach the downstream detector and systematic uncertainties.
The downstream main detector and the two upstream backscattering detectors, will initially be scintillation detectors with (silicon) photomultiplier readout. In a later upgrade, the downstream detector will be replaced by a pixelated silicon detector. We present the current design status of the silicon detector prototype.Speaker: Manuel Lebert (Technical University Munich) -
In this work, we present a combined analysis of small angle neutron scattering (SANS), linear rheology and neutron spin eco (NSE) spectroscopy experiments on the supramolecular association and chain structure of supramolecular polymer blends. These consist of well-defined hydrogenated (H) polymers with a polyethylene oxide (PEO) backbone carrying the directed homocomplementary hydrogen-bonding functional end-group, ureidopyrimidinone (upy), immersed in their own deuterated (D) covalent short linear non-functionalized PEO chains in the melt as solvent. The molar mass (MW) of the functionalized (H) PEO is 2000 gmol-1, and of the non-functionalized (D) PEO chains 500 gmol-1. Their self-assembly and phase behavior in the melt state is investigated as a function of temperature and supramolecular polymer mass fraction in the ideal blend. It is found that on contrary to the bulk structure in the melt [1], the supramolecular polymer in the blend is well described by the Gaussian model. In particular, the conformation of the supramolecular polymer in the blend changed from linear to ring -like with increasing supramolecular polymer mass fraction. These findings are also confirmed by the NSE analysis with the modified Rouse model for ring polymers from which the expected diffusion and segmental friction is obtained [2,3].
A.B. acknowledges DFG for a research grant (BR5303) and Prof. D. Richter for discussions
[1] A. Brás, A. Arizaga, U. Agirre, M. Dorau, J. Houston, A. Radulescu, M. Kruteva, W. Pyckhout-Hintzen, A. M. Schmidt, Polymers 2021, 13, 2235.
[2] A. R. Brás, R. Pasquino T. Koukoulas G. Tsolou, O. Holderer, A. Radulescu, J. Allgaier, V. G. Mavrantzas W. Pyckhout-Hintzen, A. Wischnewski, D. Vlassopoulos, D. Richter Soft Matter, 2011, 7, 11169.
[3] K. Niedzwiedz, A. Wischnewski, W. Pyckhout-Hintzen, J. Allgaier, D. Richter , A Faraone, Macromolecules, 2008, 13, 4866.Speaker: Ana Brás Würschig (Institute of Physical Chemistry, University of Cologne) -
We are investigating the crystal structure and properties of inverse perovskite nitrides with elpasolite-type superstructures. This superstructure is due to a full or partial ordering of nitrogen atoms and defects on the perovskite $B$ site. Since nitrogen scatters neutrons much more strongly than X-rays, neutron diffraction measurements of seven compounds with this superstructure were performed. Beforehand, we had illuminated their crystal structures using X-ray powder diffractometry, but were unable to determine the exact nature and extent of the superstructure.
After neutron diffraction measurements, the superstructures could be modeled much more reliably by simultaneous refinement of X-ray and neutron data, utilizing the advantages of both methods. For (Sr$_3$N$_{0.5}$)Ge, (Ba$_3$N$_{0.5}$)Ge, (Ba$_3$N$_{0.5}$)Sn and (Ba$_3$N$_{0.5}$)Pb, a full ordering of nitrogen and vacancies was confirmed. In contrast, analogous calcium compounds have a higher nitrogen content and show only partial ordering. One of the elpasolite B sites is fully occupied by nitrogen in every case. Most of the crystal structures feature octahedral tilting, which leads to an inverse Na$_3$[AlF$_6$]-type structure for (Ca$_3$N$_{0.69}$)Ge, (Sr$_3$N$_{0.5}$)Ge and (Ba$_3$N$_{0.5}$)Ge. (Ba$_3$N$_{0.5}$)Sn and (Ba$_3$N$_{0.5}$)Pb crystallize in space group $R\overline{3}$ with less pronounced tilting, while the inverse K$_2$(NaAlF$_6$)-type structure of (Ca$_3$N$_{0.65}$)Sn and (Ca$_3$N$_{0.56}$)Pb has no octahedral tilting.Speaker: Lukas Link -
For the mechanical characterization of the adhesive bond of pressure-sensitive adhesives one has to take into account the geometry of the adherents and the kind of stress applied. We present a technique, which is especially adapted for the measurement of tack for assemblies of fibers coated with pressure-sensitive adhesives using customized cylindrical composite stamps [1]. Key element of the method is the proposed technique to achieve monolayers of parallel-aligned fibers as a fiber assembly. With the adapted probe tack test we investigated the tack properties of a polymer blend of poly(vinylpyrrolidone-co-vinylacetate) and polyethylene glycol (PEG) coated on human hair. This composition serves as a simple model system for hair styling products. The influence of different PEG contents and of the humidity on the tack is demonstrated. [1] V. Körstgens et al., ACS Appl. Polym. Mater. 2, 3189-3195 (2020).
Speaker: Volker Körstgens (TU München) -
Au/TiO2 nanohybrid materials have attracted significant attention due to the outstanding optical, photocatalytic and photovoltaic performance. We use customized polymer templating to achieve TiO2 nanostructures with different morphologies. Au/TiO2 hybrid thin films are fabricated by sputter deposition. An in-depth understanding of the Au morphology on the TiO2 templates is achieved with in situ GISAXS during the sputter deposition. The resulting Au nanostructure is largely influenced by the TiO2 template morphology. Based on the detailed understanding of the Au growth process, characteristic distances can be selected to achieve tailored Au nanostructures at different Au loadings. For selected sputter-deposited Au/TiO2 hybrid thin films, the optical response with a tailored localized surface plasmon resonance is demonstrated.
Speaker: Suzhe Liang (Physical Department, TUM) -
Thin film samples for neutron investigation can be fabricated with a Molecular Beam Epitaxy (MBE) setup on site. The MBE setup is part of the additional facilities which can be booked in combination with a neutron instrument proposal at MLZ. Discuss your ideas with the thin film lab staff and then write a proposal. There are two options for access: In remote access the thin film staff fabricates the sample for you and in collaborative access: you fabricate the sample with support by the thin film laboratory staff. First option only works if the growth parameters are well identified.
The MBE setup is equipped with effusion cells, electron guns for electron beam evaporation and a plasma source for use with oxygen or nitrogen. A large variety of deposition materials can be used. Please express your ideas! Compounds may be produced either by codeposition or by shutter modulated growth of individual layers. For in-situ surface structure analysis reflection high and low energy electron diffraction is utilized while Auger electron spectroscopy is applied for in-situ chemical surface analysis.
Recently the MBE setup has been moved into the new laboratory in UYL and a new feature, i. e. the determination of the in situ flux rate of atoms using the principle of atomic absorption spectroscopy is about to be established. This method will enhance the precision in stoichometry drastically.
Thin film samples which are sensitive to ambient conditions are first fabricated in the MBE setup and then measured at the neutron reflectometer MARIA of JCNS utilizing a versatile small ultra high vacuum condition chamber (A. Syed Mohd et al. Rev. Sci. Instrum., 87, (2016) 123909)
In the poster various examples for thin film samples will be presented.
Speaker: Sabine Pütter (Jülich Centre for Neutron Science JCNS, Outstation at MLZ, Forschungszentrum Jülich GmbH) -
Cooperative dehydration is a major driving force for the demixing transition in poly(N-isopropylacrylamide) (PNIPAM), causing the polymer chains to collapse at the cloud point, followed by aggregation in aqueous solution. The motion of the hydration water is slowed down compared to bulk water and it is crucial in the solvation behavior in the presence of a co-solvent such as methanol. QENS measurements were conducted on PNIPAM in a 80% H2O / 20% methanol mixture at variable temperature and pressure with the time-of-flight spectrometer TOFTOF [1]. Hydration water is partially released at the demixing transition. The release and adsorption of solvent by the polymer chains correlate with a change in effective solvent composition as evidenced by the diffusive properties of bulk water. At high pressure the solvent phase is enriched with methanol near the cloud point implying that water is preferentially adsorbed.
[1] B.-J. Niebuur et al., Macromolecules 54, 4387 (2021)Speaker: Alfons Schulte (University of Central Florida) -
Metal alloys as anode material for lithium ion batteries such as LiAl offer a high theoretical capacity in relation to their low cost. Compared to the conventional graphite anode, aluminium has an almost three times higher specific capacity with 993 mAh/g. During lithiation, aluminium first forms a solid solution with lithium called the alpha-LiAl phase until the solubility limit is reached. Subsequently, the alpha-LiAl will transform to the beta-LiAl upon further lithiation near the electrolyte-electrode interface.
Here, phase identification via x-ray diffraction (XRD) measurements was performed in order to help the understanding of the lithiation mechanism. First results have shown that both alpha-LiAl and beta-LiAl are present within the sample. Higher lithiated phases such as Al2Li3 could not be identified. For both SOC 25 and SOC 50 however, LiOH could be determined as an additional phase whereas the percentage was higher for samples charged to SOC 50. Similarly, a higher amount of beta-LiAl was identified while the samples charged to SOC 25 showed an increased percentage of alpha-LiAl. Operando XRD measurements are planned that will minimize the ambient air related formation of LiOH and allow the measurement of alpha- and beta-LiAl nucleation directly under protective conditions.
This work is performed as a collaboration between TUM (Heinz Maier-Leibnitz Zentrum, FRM II) and RWTH Aachen (ISEA) in the frame of the BMBF project ExcellBattMat cluster.
Speaker: Mr Thien An Pham (TU München, Heinz Maier-Leibnitz Zentrum (MLZ)) -
Lately, organic solar cells (OSCs) have gained increasing attention due to their rapidly increas- ing efficiencies as well as the relatively easy scalability in their manufacture. However, their production relies heavily on the use of halogenated solvents, as organic solar cells made with environmentally friendly solvents often suffer from reduced performance, which is associated with the reduced solubility of some OSC materials. This can be partially reversed by raising the temperature of the solvents during formation of the bulk-heterojunction (BHJ), increasing the solubility of the respective material.
We investigate and compare the changes in morphology and performance stability of PTQ10:BTP- 4F OSCs processed from various solvents, utilising operando grazing-incidence small and wide angle X-ray scattering during illumination and solar cell operation. We further show the impact of solvent composition on the charge carrier dynamics in the respective BHJs using time-resolved transient absorption spectroscopy, analysing the connection between thin-film morphology and device performance in polymer:non-fullerene acceptor OSCs.Speaker: Lukas Spanier -
Last years, interest in the Dy/Co system has increased, since it became possible to switch the magnetization of the system without applied magnetic field by means of a femtosecond laser pulses. Important requirements for achieving switchable magnetic films are antiferromagnetic coupling between spins of rare-earth and transition metals and perpendicular magnetic anisotropy (PMA). Therefore, it is crucial to find the correlation between the microstructure of thinner and thicker multilayers and their magnetic properties. The aim of this investigation was to define the influence of Dy thicknesses on the magnetic properties of Dy/Co ultilayers.
A series of [Dy (t Å)/Co (30 Å)]40 (t=4 - 20 Å) multilayers were fabricated by DC magnetron sputtering. Structural characterization of the samples was performed by Magnetic properties were investigated by VSM-magnetometry and polarized neutron reflectometry (PNR) and XMCD.X-ray reflectometry and electron-microscopic studies showed formation of DyCo intermetallic compound and Co nanocrystalline layers during the grown process. Also DyCo intermetallic layers are amorphous. The magnetization DyCo is aligned parallel to normal of sample plane, the Co magnetization is oriented in the direction of applied magnetic field. The superlattices consisting of two layers with uniaxial magnetic anisotropies is considered whose easy axes are oriented perpendicular to each other. By neutron reflectometry we observed strong increase of the intensity of spin-flip scattering which evidences increase of non-collinearity of the system. We found rich phase diagram of Dy/Co heterostructures which arising due to the competition of exchange coupling, magneto crystalline anisotropy and Zeeman energy.Speaker: Marina Makarova
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Convener: Ralph Gilles
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Conveners: Martin Müller (Helmholtz-Zentrum Geesthacht), Peter Müller-Buschbaum (1 Technische Universität München, Fakultät für Physik, Lehrstuhl für Funktionelle Materialien, James-Franck-Str.1, 85748 Garching, Germany 2 Heinz Maier-Leibnitz-Zentrum (MLZ), Technische Universität München, Lichtenbergstr. 1, 85748 Garching, Germany)
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