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Bispidines for dual imaging
(2014)
The efficient transformation of the hexadentate bispidinol 1 into carbamate derivatives yields functional bispidines enabling convenient functionalization for targeted imaging. The BODIPY-substituted bispidine 3 combines a coordination site for metal ions, such as radioactive 64CuII, with a fluorescent unit. Product 3 was thoroughly characterized by standard analytical methods, single crystal X-ray diffraction, radiolabeling, and photophysical analysis. The luminescence of ligand 3 was found to be strongly dependent on metal ion coordination: CuII quenches the BODIPY fluorescence, whereas NiII and ZnII ions do not affect it. It follows that, in imaging applications with the positron emitter 64CuII, residues of its origin from enriched 64Ni and the decay products 64NiII and 64ZnII, efficiently restore the fluorescence of the ligand. This allows for monitoring of the emitted radiation as well as the fluorescence signal. The stability of the 64CuII–3 complex is investigated by transmetalation experiments with ZnII and NiII, using fluorescence and radioactivity detection, and the results confirm the high stability of 64CuII–3. In addition, metal complexes of ligand 3 with the lanthanide ions TbIII, EuIII, and NdIII are shown to exhibit emission of the BODIPY ligand and the lanthanide ion, thus enabling dual emission detection.
Die volle Leistung einer auf Reibung basierenden Bremse wird erst nach einem Einlaufvorgang erreicht. Dieser ist notwendig, um auf Belag und Scheibe eine sogenannte Reibschicht aufzubauen. Da diese Zwischenschicht das Reibungsverhalten des Systems maßgeblich bestimmt, ist es wichtig, sich Klarheit über ihre chemische Zusammensetzung, Mikrostruktur und die daraus resultierenden Eigenschaften zu verschaffen.
Als Basismaterial diente ein phenolharzgebundener Belag Jurid 57-62, der mit verschiedenen Parametern (Flächenpressung und Umdrehungsgeschwindigkeit) gegen eine Stahlscheibe getestet wurde. Es wurden Dauerbremsungen von jeweils einer Stunde bzw. bis zu einem maximalen Belagverschleiß von 1 mm simuliert, wobei die Entwicklung der Reibzahl und die Oberflächentemperatur der Scheibe registriert wurde.
Zur Analyse der Reibschichten auf dem Bremsbelag wurden mehrere Methoden parallel angewandt. So wurden Verschleißpartikel, die aus der Reibschicht stammen, gesammelt bzw. abgekratzt und nach Dispergieren auf Kohlefolien direkt im Transmissionselektronenmikros-kop (TEM) untersucht. Ferner wurden von einigen ausgesuchten Belagproben Mikrotom-schnitte sowie dünne Querschnittsfolien für die TEM-Untersuchung präpariert, um den Verbund Reibschicht-Grundmaterial darstellen zu können. Als Ergänzung wurden ferner oberflächenmorphologische und –analytische Verfahren wie REM/EDX und ESCA eingesetzt.
Die Ergebnisse deuten darauf hin, dass die Reibschicht nanokristallin ist, und dass fast alle anorganischen Bestandteile des Bremsbelags sowie Eisenoxid von der Bremsscheibe in sehr fein verteilter Form vorliegen. Bei Belägen ohne Metallanteil bildet eine Barium-Eisen-Sulfatphase offenbar die Grundstruktur der Reibschicht, während auf eisenhaltigen Belägen Eisenoxid dominierend ist. Die nanokristalline Mikrostruktur entsteht, ähnlich wie beim mechanischen Legieren, durch einen Mahlvorgang von Verschleißpartikeln zwischen den Reibpartnern. Bei Überlastung des Belags tritt Zersetzung der Polymer-Bindephase ein, was zu einem raschen Anstieg der Verschleißrate führt.
A method is described for high-resolution label-free molecular imaging of human bone tissue. To preserve the lipid content and the heterogeneous structure of osseous tissue, 4 μm thick human bone sections were prepared via cryoembedding and tape-assisted cryosectioning, circumventing the application of organic solvents and a decalcification step. A protocol for comparative mass spectrometry imaging (MSI) on the same section was established for initial analysis with time-of-flight secondary ion mass spectrometry (TOF-SIMS) at a lateral resolution of 10 μm to <500 nm, followed by atmospheric pressure scanning microprobe matrix-assisted laser desorption/ionization (AP-SMALDI) Orbitrap MSI at a lateral resolution of 10 μm. This procedure ultimately enabled MSI of lipids, providing the lateral localization of major lipid classes such as glycero-, glycerophospho-, and sphingolipids. Additionally, the applicability of the recently emerged Orbitrap-TOF-SIMS hybrid system was exemplarily examined and compared to the before-mentioned MSI methods.
Rhodium(III) octahedral complexes with amine and chloride ligands are the most common starting compounds for preparing catalytically active rhodium(I) and rhodium(III) species. Despite intensive study during the last 100 years, synthesis and crystal structures of rhodium(III) complexes were described only briefly. Some [RhClx(NH3)6-x] compounds are still unknown. In this study, available information about synthetic protocols and the crystal structures of possible [RhClx(NH3)6−x] octahedral species are summarized and critically analyzed. Unknown crystal structuresof(NH4)2[Rh(NH3)Cl5],trans–[Rh(NH3)4Cl2]Cl·H2O,andcis–[Rh(NH3)4Cl2]Clarereported based on high quality single crystal X-ray diffraction data. The crystal structure of [Rh(NH3)5Cl]Cl2 was redetermined. All available crystal structures with octahedral complexes [RhClx(NH3)6-x] were analyzed in terms of their packings and pseudo-translational sublattices. Pseudo-translation lattices suggest face-centered cubic and hexagonal closed-packed sub-cells, where Rh atoms occupy nearly ideal lattices.
Accurate and reproducible measurement of the structure and properties of high-value nanoparticles is extremely important for their commercialization. A significant proportion of engineered nanoparticle systems consist of some form of nominally core-shell structure, whether by design or unintentionally. Often, these do not form an ideal core-shell structure, with typical deviations including polydispersity of the core or shell, uneven or incomplete shells, noncentral cores, and others. Such systems may be created with or without intent, and in either case an understanding of the conditions for formation of such particles is desirable. Precise determination of the structure, composition, size, and shell thickness of such particles can prove challenging without the use of a suitable range of characterization techniques. Here, the authors present two such polymer core-shell nanoparticle systems, consisting of polytetrafluoroethylene cores coated with a range of thicknesses of either polymethylmethacrylate or polystyrene. By consideration of surface energy, it is shown that these particles are expected to possess distinctly differing coating structures, with the polystyrene coating being incomplete. A comprehensive characterization of these systems is demonstrated, using a selection of complementary techniques including scanning electron microscopy, scanning transmission electron microscopy, thermogravimetric analysis, dynamic light scattering, differential centrifugal sedimentation, and X-ray photoelectron spectroscopy. By combining the results provided by these techniques, it is possible to achieve superior characterization and understanding of the particle structure than could be obtained by considering results separately.
The primary crystallite size of titania powder relates to its properties in a number of applications. Transmission electron microscopy was used in this interlaboratory comparison (ILC) to measure primary crystallite size and shape distributions for a commercial aggregated titania powder. Data of four size descriptors and two shape descriptors were evaluated across nine laboratories. Data repeatability and reproducibility was evaluated by analysis of variance. One-third of the laboratory pairs had similar size descriptor data, but 83% of the pairs had similar aspect ratio data. Scale descriptor distributions were generally unimodal and were well-described by lognormal reference models. Shape descriptor distributions were multi-modal but data visualization plots demonstrated that the Weibull distribution was preferred to the normal distribution. For the equivalent circular diameter size descriptor, measurement uncertainties of the lognormal distribution scale and width parameters were 9.5% and 22%, respectively. For the aspect ratio shape descriptor, the measurement uncertainties of the Weibull distribution scale and width parameters were 7.0% and 26%, respectively. Both measurement uncertainty estimates and data visualizations should be used to analyze size and shape distributions of particles on the nanoscale.
Complex formation and the coordination of zirconium with acetic acid were investigated with Zr K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) and single-crystal diffraction. Zr K-edge EXAFS spectra show that a stepwise increase of acetic acid in aqueous solution with 0.1 M Zr(IV) leads to a structural rearrangement from initial tetranuclear hydrolysis species [Zr4(OH)8(OH2)16]8+ to a hexanuclear acetate species Zr6(O)4(OH)4(CH3COO)12. The solution species Zr6(O)4(OH)4(CH3COO)12 was preserved in crystals by slow evaporation of the aqueous solution. Single-crystal diffraction reveals an uncharged hexanuclear cluster in solid Zr6(μ3-O)4(μ3-OH)4(CH3COO)12·8.5H2O. EXAFS measurements show that the structures of the hexanuclear zirconium acetate cluster in solution and the solid state are identical.
Purine nucleotides such as ATP and ADP are important extracellular signaling molecules in almost all tissues activating various subtypes of purinoreceptors. In the brain, the P2Y1 receptor (P2Y1R) subtype mediates trophic functions like differentiation and proliferation, and modulates fast synaptic transmission, both suggested to be affected in diseases of the central nervous system. Research on P2Y1R is limited because suitable brain-penetrating P2Y1R-selective tracers are not yet available. Here, we describe the first efforts to develop an 18F-labeled PET tracer based on the structure of the highly affine and selective, non-nucleotidic P2Y1R allosteric modulator 1-(2-[2-(tert-butyl)phenoxy]pyridin-3-yl)-3- [4-(trifluoromethoxy)phenyl]urea (7). A small series of fluorinated compounds was developed by systematic modification of the p-(trifluoromethoxy)phenyl, the urea and the 2-pyridyl subunits of the lead compound 7. Additionally, the p-(trifluoromethoxy)phenyl subunit was substituted by carborane, a boron-rich cluster with potential applicability in boron neutron capture therapy (BNCT). By functional assays, the new fluorinated derivative 1-{2-[2-(tert-butyl)phenoxy]pyridin-3-yl}-3-[4-(2-fluoroethyl) phenyl]urea (18) was identified with a high P2Y1R antagonistic potency (IC50 ¼10 nM). Compound [18F] 18 was radiosynthesized by using tetra-n-butyl ammonium [18F]fluoride with high radiochemical purity, radiochemical yield and molar activities. Investigation of brain homogenates using hydrophilic interaction chromatography (HILIC) revealed [18F]fluoride as major radiometabolite. Although [18F]18 showed fast in vivo metabolization, the high potency and unique allosteric binding mode makes this class of compounds interesting for further optimizations and investigation of the theranostic potential as PET tracer and BNCT agent.
The fluorolytic sol–gel synthesis is applied with the intention to obtain two different types of core–shell nanoparticles, namely, SrF2–CaF2 and CaF2–SrF2. In two separate fluorination steps for core and shell formation, the corresponding metal lactates are reacted with anhydrous HF in ethylene glycol. Scanning transmission electron microscopy (STEM) and dynamic light scattering (DLS) confirm the formation of particles with mean dimensions between 6.4 and 11.5 nm. The overall chemical composition of the particles during the different reaction steps is monitored by quantitative Al Kα excitation X-ray photoelectron spectroscopy (XPS). Here, the formation of stoichiometric metal fluorides (MF2) is confirmed, both for the core and the final core–shell particles. Furthermore, an in-depth analysis by synchrotron radiation XPS (SR-XPS) with tunable excitation energy is performed to confirm the core–Shell character of the nanoparticles. Additionally, Ca2p/Sr3d XPS intensity ratio in-Depth profiles are simulated using the software Simulation of Electron Spectra for Surface Analysis (SESSA). In principle, core–shell like particle morphologies are formed but without a sharp interface between calcium and strontium containing phases.
Surprisingly, the in-depth chemical distribution of the two types of nanoparticles is equal within the error of the experiment. Both comprise a SrF2-rich core domain and CaF2-rich shell domain with an intermixing zone between them. Consequently, the internal morphology of the final nanoparticles seems to be independent from the synthesis chronology.
Determination of fatigue crack growth in the near-threshold regime using small-scale specimens
(2022)
A complete description of the experimental procedure for characterizing the intrinsic fatigue crack propagation threshold (ΔKth,eff) as well as the fatigue crack growth rate (FCGR) in the near-threshold regime using small-scale specimens is presented. A comparative study is carried out on the high strength steel S960QL considering different single edge notch bend (SENB) specimen geometries. On one hand, the reference dimensions of 6 mm thickness (B) and 19 mm width (W) are analysed and referred to as conventional specimens. On the other hand, small-scale specimens with B = 3 mm and W = 4 and 6 mm are also considered. Several loading configurations (3-, 4- and 8-point bending) are used and a load ratio R = 0.8 is applied to avoid crack closure effects. The direct current potential drop (DCPD) technique is used to monitor the crack length. The reduced dimensions of the small-scale specimens imply the necessity of implementing a modified testing procedure compared to the recommendations of current standards for the generation of FCGR data. The results show a good agreement between tests conducted on different specimen sizes, which opens new perspectives in the use of small-scale specimens for characterizing the fatigue crack growth properties in metallic materials. Recommendations and limitations of the procedure are provided and discussed.
This article is an outcome of a workshop on Fatigue of Additive Manufactured Metallic Components jointly organized by the Federal Institute for Materials Research and Testing (BAM) Berlin, Germany and the National Institute of Standards and Technology (NIST) Boulder, CO, U.S.A. The aim of the workshop was a comprehensive discussion of the specific aspects of additively manufactured (AM) components in regard to failure under cyclic loading. Undoubtedly, a better understanding and the further development of approaches for damage tolerant component design of AM parts are among the most significant challenges currently facing the use of these new technologies.
This article presents a thorough overview of the workshop discussions. It aims to provide a review of the parameters affecting the damage tolerance of AM parts with special emphasis on the process parameters intrinsic to the AM technologies, the resulting defects and residual stresses. Based on these aspects, concepts for damage tolerant component design for AM are reviewed and critically discussed.
Our group previously synthesized 99mTc-labeled fatty acids suitable for myocardial metabolism and flow imaging. In this set of experiments, 29 new analogues were synthesized according to the 4 + 1 mixed ligand approach with some specific differences. Conventional 4 + 1 99mTc-fatty acids are built in the sequence: Tc-chelate, alkyl chain, and carboxylic group. We developed compounds following a new design with the sequence: carboxylic group, alkyl chain, Tc-chelate, and lipophilic tail. Therefore, the 99mTc-chelate was transferred to a more central position of the compound, aiming toward an improved myocardial profile and an accelerated liver clearance. In this context, several functional groups incorporated in the lipophilic tail section were tested to evaluate their influence on the compound's character. In addition to biodistribution studies in vivo, the myocardial first-pass extraction of the compounds was tested in an isolated Langendorff rat heart model. A satisfactory myocardial uptake of up to 20% of the injected dose (% ID) in the perfused heart and a fast liver clearance in vivo with only 0.29% ID/g at 60 min postinjection demonstrate that the induced molecular modifications affect the kinetics of 99mTc-radiolabeled fatty acid compounds favorably. From the data set, rules for estimating the biodistribution of fatty acids tracers are deduced.
The German Federal Institute for Materials Research and Testing (BAM) has established a testing guideline to assess the suitability of geosynthetic or geocomposite drain (GCD) elements for final landfill cover systems. In an earlier paper the uniform procedure according to the BAM guideline for determining long-term water flow capacity was described, and the structural stability of drain cores under creep was investigated. The extrapolation of creep curves is permissible only when it can be shown, over the extrapolated period (at least 100 years), that oxidative aging does not invoke any relevant changes in the polyolefin material. This can be shown by measuring antioxidant depletion and mechanical degradation of the drain cores and filter/protection geotextiles in oven aging and water immersion tests. In this paper the results of such aging studies on three different GCD products are reported. Degradation of the tensile strength of HALS-stabilized polypropylene needle-punched nonwoven geotextiles (PP NWGTs) starts right from the beginning of the oven aging. This has to be taken into account for lifetime predictions based on residual tensile strength. The rate of oxidative degradation of NWGTs decreases significantly with increasing mass per area. Therefore the expected service life sets a limit on acceptable geotextile grammage. Antioxidant depletion in the drain cores, which are made of relatively thick PP strands or HDPE ribs, is about an order of magnitude slower than in filter and protection NWGTs, which are made of thin fibers. Service life values in excess of 100 years may be obtained for the products when the geotextiles and drain cores are properly stabilized and designed.
In the paper the method of discrete modeling (movable cellular automata method) and combined discrete-continuous description of the simulated medium are used to analyze processes occurring in the local contact of the automotive brake system. The characteristic size of the considered region is 1.5 ?m. The following contact situation is simulated: steel fiber coated by an iron oxide film as the brake pad and pearlitic steel also coated by an iron oxide layer as the disc. On the assumption of oxide layer wearing we simulate the iron oxide - iron oxide, iron oxide - metal and metal - metal contacts.
The calculation results for the friction coefficient for various contact situations give quite adequate values. For example, for the oxide - oxide system the calculated coefficient is approximately equal to 0.4, while for the metal - metal contact the obtained value varies from 0.7 to 0.9. Analysis of a set of the obtained results allows concluding that oxide is formed more rapidly than the sliding layer, which in turn makes the friction coefficient value stabilized.