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The sliding behaviors of two simplified tribofilms with amorphous structure consisting either of SiO₂ molecules or C atoms were simulated by molecular dynamics modeling. The objective was to identify mechanisms explaining the experimentally observed lubricating properties of the two amorphous films. The impacts of layer thickness, normal pressure, temperature and different substrate materials were studied systematically, while the sliding velocity was kept constant at 30 m/s. While the layer thickness was not critical, all the other parameters showed special effects under certain conditions. Normal pressure impeded void formation and could even eliminate voids if applied at high temperature. Stick-slip sliding was changed to smooth sliding at high temperature due to void healing. Considering the carbon film, high friction forces and shearing of the entire film was observed with diamond substrates, whereas interface sliding at low friction forces and an amorphous layer of iron mixed with carbon was observed if the supporting substrates consisted of α-Fe. Both films show a decrease of friction forces and smooth sliding behavior at elevated temperature, corresponding well to the tribological behavior of and advanced nanocomposite sliding against a steel disc under severe stressing conditions when high flash temperatures can be expected.
Designing artificial macromolecules with absolute sequence order represents a considerable challenge. Here we report an advanced light-induced avenue to monodisperse sequencedefined functional linear macromolecules up to decamers via a unique photochemical approach. The versatility of the synthetic strategy—combining sequential and modular concepts—enables the synthesis of perfect macromolecules varying in chemical constitution and topology. Specific functions are placed at arbitrary positions along the chain via the successive addition of monomer units and blocks, leading to a library of functional homopolymers, alternating copolymers and block copolymers. The in-depth characterization of each sequence-defined chain confirms the precision nature of the macromolecules. Decoding of the functional information contained in the molecular structure is achieved via tandem mass spectrometry without recourse to their synthetic history, showing that the sequence information can be read.We submit that the presented photochemical strategy is a viable and advanced concept for coding individual monomer units along a macromolecular chain.
Since decades the evaluation of flaw indications on radiographs from welds or castings are based on well accepted reference film catalogues from organizations like IIW (weldments), ASTM (castings) or DGZfP (D5 recommendation on heavy steel castings). Today, the transformation of classical film radiography to the digital world is in full progress. Some ASTM standards do not permit the evaluation of digital radiographs in reference to film catalogues. Therefore, these reference film catalogues have to be converted into the digital age too. BAM is supporting this transition by high definition film scanning. The result is a corresponding reference image catalogue. The different standard organizations selected different ways to distribute the digital data. ASTM used high definition film scanning at 10 μm pixel size and distribution of a huge amount of high-res data via DVD. The user sub-samples these high-res data during catalogue import to the resolution of his system. The comparison is done by synchronized image viewing on the computer work station. IIW recently decided to distribute their ISO 5817 reference images installed on tablets, which are used for image viewing too. The tablet image has to be compared with the digital image on the system monitor. DGZfP transformed their D5 reference radiographs into a PDF for monitor viewing. This is the simplest and cheapest solution, but still allows the full usage of the catalogue in the digital era. The status of ongoing work in progress will be discussed.
Currently at Deutsche Bahn (DB) ultrasonic inspections in maintenance procedures for wheelset axles with a bore hole are, to the greatest possible extent, carried out using automated ultrasonic inspection system. Although the acceptance levels are in accordance with DIN 27201 part 7, the testing results have shown in recent years that in the case of true indications, the effective defect sizes were far below the level of acceptance. Due to this experience it can be assumed that the automated ultrasonic inspection systems are testing substantially more sensitively than required. This increased sensitivity leads to an increase in false indications, generally resulting in the unnecessary demounting of wheelsets. In Research cooperation between Federal Institute for Materials Research and Testing (BAM) and DB the effective flaw detection sensitivity of existing automated ultrasonic inspection system will be determined and the true/false indication ratio optimised. Through systematic investigations with the Probability of Detection method on the existing automated ultrasonic inspection system the results could be directly applied to the optimisation of existing ultrasonic inspections of wheelset axles with a bore hole in maintenance procedures and the level of reliability can be considerably increased.
Determination of the elastic behavior of silicon nanowires within a scanning electron microscope
(2016)
Three-point bending tests were performed on double-anchored, <110> silicon nanowire samples inside a scanning electron microscope (SEM) via a micromanipulator equipped with a piezo-resistive force sensor. Representing the upper and lower boundaries achievable in a consistent manner, silicon nanowires with widths of 35 nm and 74 nm and a height of 168 nm were fabricated. The nanowires were obtained monolithically along with their 10-m-tall supports through a top-down fabrication approach involving a series of etching processes. Hence, no interface compliance was introduced between supports and nanowires. Exact nanowire dimensions and cross-sectional features were determined by transmission electron microscopy (TEM) following sample preparation through focused ion beam (FIB) machining. Conducting the experiments inside an SEM chamber further raised the opportunity of the direct observation of any deviation from ideal loading conditions such as twisting, which was taken into consideration in simulations. Measured force-displacement behavior was observed to exhibit close resemblance to simulation results obtained by finite element modeling, when the bulk value of 169 GPa was taken as the modulus of elasticity for <110> silicon. Hence, test results show neither any size effect nor evidence of residual stresses for the considered nanoscale objects. The increased effect of the native oxide with reduced nanowire dimensions was captured as well. Thus this very simple in-situ testing method was found to be an alternative to elaborate AFM measurements on geometrically formidable nanostructures. The results demonstrate the applicability of the developed fabrication approach to the incorporation of silicon nanowires in functional micromechanical devices.
An unusually fast and effective synthesis procedure for a host guest system consisting of a metal organic framework (MOF) and a polyoxometalate (POM) is described. The material was synthesised mechanochemically and the evolution of the structure was monitored ex and in situ using synchrotron X-ray diffraction (XRD).
The crystal structures and syntheses of four different copper(II) phenylphosphonates, the monophenylphosphonates α-, β-, and γ-Cu(O3PC6H5)·H2O (α-CuPhPmH (1) β-CuPhPmH (2) and γ-CuPhPmH (3)), and the diphosphonate Cu(HO3PC6H5)2·H2O (CuPhP2mH (4)), are presented. The compounds were synthesized from solution at room temperature, at elevated temperature, under hydrothermal conditions, and mechanochemical conditions. The structures of α-CuPhPmH (1) and CuPhP2mH (4) were solved from powder X-ray diffraction data. The structure of β-CuPhPmH (2) was solved by single crystal X-ray analysis. The structures were validated by extended X-ray absorption fine structure (EXAFS) and DTA analyses. Disorder of the crystal structure was elucidated by electron diffraction. The relationship between the compounds and their reaction pathways were investigated by in situ synchrotron measurements.
We describe a fast and effective synthesis for molecular metal phosphonates. Isomorphic compounds [M(II)(HO₃PPh)₂(H₂O₃PPh)₂(H₂O)₂] (M = Mn (1), Co (2), Ni (3); Ph = C₆H₅) were obtained by grinding. The complexes are mononuclear compounds containing neutral and monodeprotonated phenylphosphonic acid and water as ligands. The crystal structures were determined using powder X-ray diffraction (PXRD) data and validated by extended X-ray absorption fine structure (EXAFS) data. Combined synchrotron XRD measurements and Raman spectroscopy were conducted for investigating the reactions in situ. Based on these data, the intermediates were characterized and the formation mechanism was derived.
The successful mechanochemical syntheses of three cadmium phenylphosphonates indicates that mechanochemistry is ideally suited for synthesizing metal phosphonates. With this powerful synthesis tool it is possible to synthesize rapidly and efficiently both known and novel phosphonates. The Crystal structures of the two new compounds, and, were solved from PXRD data. They contain monodeprotonated phenylphosphonate and neutral phenylphosphonic acid ligands. The synthesis pathways of all three compounds were investigated in situ. A diffusion mechanism is corroborated by our findings.
Intermediates could be detected and identified. The kinetically favored product (3) could always be detected during the syntheses. The thermodynamic stability of the compounds and the stoichiometric ratio of the starting materials are the two directing factors for the synthesis of the final products.
According to several recent studies, an unexpectedly high number of landmark papers seem to be not reproducible by Independent laboratories. Nontherapeutic antibodies used for research, diagnostic, food analytical, environmental, and other purposes play a significant role in this matter. Although some papers have been published offering suggestions to improve the situation, they do not seem to be comprehensive enough to cover the full complexity of this issue. In addition, no obvious improvements could be noticed in the field as yet. This article tries to consolidate the remarkable variety of conclusions and suggested activities into a more coherent conception. It is concluded that funding agencies and journal publishers need to take first and immediate measures to resolve these problems and lead the way to a more sustainable way of bioanalytical research, on which all can rely with confidence.
This author interview is by Dr Michael G. Weller, Head of Division 1.5 Protein Analysis at Federal Institute for Materials Research and Testing (BAM). BAM (www.bam.de/en) is a senior scientific and technical institute with responsibility to the German Federal Ministry for Economic Affairs and Energy. Dr Weller's review paper, Quality issues of research antibodies is available for download in Analytical Chemistry Insights.
For the first time, an ab initio calibration for absolute Mg isotope ratios was carried out, without making any a priori assumptions. All quantities influencing the calibration such as the purity of the enriched isotopes or liquid and solid densities were carefully analysed and their associated uncertainties were considered. A second unique aspect was the preparation of three sets of calibration solutions, which were applied to calibrate three multicollector ICPMS instruments by quantifying the correction factors for instrumental mass discrimination. Those fully calibrated mass spectrometers were then used to determine the absolute Mg isotope ratios in three candidate European Reference Materials (ERM)-AE143, -AE144 and -AE145, with ERM-AE143 becoming the new primary isotopic reference material for absolute isotope ratio and delta measurements. The isotope amount ratios of ERM-AE143 are n(25Mg)/n(24Mg) = 0.126590(20) mol/mol and n(26Mg)/n(24Mg) = 0.139362(43) mol/mol, with the resulting isotope amount fractions of x(24Mg) = 0.789920(46) mol/mol, x(25Mg) = 0.099996(14) mol/ mol and x(26Mg) = 0.110085(28) mol/mol and an atomic weight of Ar(Mg) = 24.305017(73); all uncertainties were stated for k = 2. This isotopic composition is identical within uncertainties to those stated on the NIST SRM 980 certificate. The candidate materials ERM-AE144 and -AE145 are isotopically lighter than ERM-AE143 by 1.6 ‰ and 1.3 ‰, respectively, concerning their n(26Mg)/n(24Mg) ratio. The relative combined standard uncertainties are ≤0.1 ‰ for the isotope ratio n(25Mg)/n(24Mg) and ≤0.15 ‰ for the isotope ratio n(26Mg)/ n(24Mg). In addition to characterizing the new isotopic reference materials, it was demonstrated that commonly used fractionation laws are invalid for correcting Mg isotope ratios in multicollector ICPMS as they result in a bias which is not covered by its associated uncertainty. Depending on their type, fractionation laws create a bias up to several per mil, with the exponential law showing the smallest bias between 0.1 ‰ and 0.7 ‰.
The detection and characterization of surface cracks in steel specimens prior to damage is a technologically and economically highly significant task and is of utmost importance when it comes to safety-relevant structures. In steel production where steel billets at high temperatures have to be inspected while moving a number of well-established NDT methods cannot be applied. Laser thermography however is a promising candidate to serve as a fast, non-contact and remote tool in this case. We present a study that shows that the crack detection capabilities of laser thermography can be extended also to specimens at high temperature. A combination of inductive and laser heating allows to systematically study the contrast formation as well as the optimization of the important measurement parameters. The experiments are accompanied by FEM simulations that provide a better insight of the physical correlations and support the experimental developments. The aim of these studies is to develop a system with high inspection speed and detection performance to be in-line operated under the hostile environment of steel production lines.
In this study, the feasibility of using non-contact Infrared thermography as a potential tool to monitor the CMT welding process is explored. The presence of internal defects such as porosity, lack of filler material deposition and formation of improper weld bead produce perturbations in the surface temperature which can be identified using an Infrared thermography technique. We present recent results obtained from online monitoring of the the dissimilar joining using CMT weld brazing of Aluminum and Steel using a transmission mode measurement approach. The effect of loss of zinc coating on the weldability of the cold metal transfer joining of aluminum to galvanised steel was investigated. A correlation between measured online thermal indications with the weld anomalies is successfully attempted and the results are compared with the conventional post-weld NDT inspection methods.
In this work, fullerene has been functionalized with cyanuric Chloride at room temperature by a nitrene mediated [2 + 1] cycloaddition reaction. The adduct after functionalization is inherently in the form of azafulleroid and shows broad UV absorption in the wavelength range of 200–800 nm, as well as photothermal conversion and fluorescence with a high quantum yield.
Materials and chemical producers require detailed knowledge of surface chemistry for research into new products. One way to understand a surface without damaging it is to bombard it with an electron beam, causing its atoms to emit characteristic X-rays enabling identification. The measurement of these must be precise as many elements emissions are close in energy – traceable reference materials will ensure instruments using this technique are stable and accurate.
IND15 JRP SurfChem: Traceable quantitative surface chemical analysis for industrial applications
(2016)
The SurfChem project has made a significant contribution to traceable quantitative surface chemical analysis for industrial applications by delivering new certified reference materials and test samples for specific technical applications. Regular performance tests of instruments, metrological methodology for the detection of (bio)organic surface species, ambient and non-destructive surface chemical analysis for in-line process control and new in situ characterisation techniques of catalytically active surfaces have been achieved.
Carbon Fibre Reinforced Plastics (CFRP) are more and more used in modern civil aircrafts. These days the whole fuselage is made of this material (B787; A350). Due to strict certification standards the normal in-service loading gives a low stress level compared to the static and even the fatigue strength of the material. Hence CFRP are assumed to have an infinite life. To evaluate this assumption, fatigue tests on CFRP-specimens were performed up to 108 load cycles and the first inter-fibre failure was evaluated non-destructively by accompanying Xray-refraction topography. A tensile testing machine was integrated in a small angle X-ray scattering (SAXS) setup. X-ray refraction topography was performed while the CFRP samples were tensile loaded. This non-destructive technique enables the detection of micro-cracking and inter-fibre failure especially for CFRP. For Glass Fibre Reinforced Plastic (GFRP) X-ray refraction and in-situ loading has already been successfully used. The increase of inner surfaces due to inter fibre failure was measured as a function of the stress state. Fatigue tests were performed at and below the limit of inter-fibre failure strength. State of the art is to assume the failure of the samples under cyclic loading as the fatigue life. Accompanying non-destructive X-ray refraction measurements reflects the damage state and enables to trace its evolution even if the total failure of the specimens does not occur. This investigation technique is of high interest to give the engineer a design value of infinite life which is practically often reached due to knock down factors of certification standards. Finally the infinite life was found for cyclic fatigue loaded CFRP-samples even under high inter fibre transverse and shear loading investigated up to 108 load cycles.
Multiple anthropogenic stressors cause worldwide amphibian declines. Among several poorly investigated causes is global pollution of aquatic ecosystems with endocrine disrupting compounds (EDCs). These substances interfere with the endocrine system and can affect the sexual development of vertebrates including amphibians. We test the susceptibility to an environmentally relevant contraceptive, the artificial estrogen 17α-ethinylestradiol (EE2), simultaneously in three deeply divergent systematic anuran families, a model-species, Xenopus laevis (Pipidae), and two non-models, Hyla arborea (Hylidae) and Bufo viridis (Bufonidae). Our new approach combines synchronized tadpole exposure to three EE2-concentrations (50, 500, 5,000 ng/L) in a flow-through-system and pioneers genetic and histological sexing of metamorphs in non-model anurans for EDC-studies. This novel methodology reveals striking quantitative differences in genetic-male-to-phenotypic-female sex reversal in non-model vs. model species. Our findings qualify molecular sexing in EDC-analyses as requirement to identify sex reversals and state-of-the-art approaches as mandatory to detect speciesspecific vulnerabilities to EDCs in amphibians.
Single particle ICP-MS (spICP-MS) has gained great influence in the analysis of engineered nanoparticles (NPs) due to its simplicity, speed and ability to obtain a particle number size distribution. Despite its many advantages, the method is hampered by matrix effects affecting the sensitivity of the instruments.
Consequently, over- or underestimated particle sizes might be obtained. To overcome these challenges, we present in this work the detection of both Ag isotopes with a quadrupole mass spectrometer for the application of isotopic dilution analysis (IDA) in combination with spICP-MS. Here, the isotopes are measured sequentially using the conventional spICP-MS integration time of 10 ms. Citrate stabilized Ag NPs of a spherical shape with the nominal diameters of 30, 40, 50 and 80 nm have been investigated.
The experimental concept of adding ¹⁰⁹Ag+ solutions to the NP suspensions resulted in the NP Spikes being only visible in the ¹⁰⁷Ag trace. Therefore, a maximum of 45% of the particles was detected compared to that by conventional spICP-MS. A modified mass flow equation was applied to determine the particle sizes, particle size distributions and particle number concentrations of various Ag NPs. The addition of different spike concentrations between 0.5 and 4 mg L⁻¹ ¹⁰⁹Ag resulted in similar particle diameters, suggesting that the calculated diameter might be independent of the spike concentration.
This would have the advantage that no size information would be needed before the analysis. By analyzing Ag NP suspensions in a simulated seawater matrix, we demonstrate its significant influence on the particle size determination using conventional spICP-MS. A lower transport efficiency of 6.1% was found in the matrix compared to 7.3% without the matrix. In our approach, the addition of the Matrix influenced the NP intensity stronger than the spike signal, resulting in slightly smaller diameters using IDA–spICP-MS with the matrix compared to the results without the matrix. On the other hand, the IDA–spICP-MS approach with the matrix can result in equivalent results for the particle sizes compared with
conventional spICP-MS using suspensions without the matrix. Due to the lower instrument sensitivity in the matrix, a diameter of 30 nm was found to be close to the detection limit of the instrument.
The maximum magnetisation (saturation magnetisation) obtainable for iron oxide nanoparticles can be increased by doping the nanocrystals with non-magnetic elements such as zinc. Herein, we closely study how only slightly different synthesis approaches towards such doped nanoparticles strongly influence the resulting sub-nano/atomic structure. We compare two co-precipitation approaches, where we only vary the base (NaOH versus NH3), and a thermal decomposition route. These methods are the most commonly applied ones for synthesising doped iron oxide nanoparticles. The measurable magnetisation change upon zinc doping is about the same for all systems. However, the sub-nano structure, which we studied with Mössbauer and X-ray absorption near edge spectroscopy, differs tremendously. We found evidence that a much more complex picture has to be drawn regarding what happens upon Zn doping compared to what textbooks tell us about the mechanism. Our work demonstrates that it is crucial to study the obtained structures very precisely when “playing” with the atomic order in iron oxide nanocrystals.
The preparation and characterization of poly(ionic liquid)s (PILs) bearing a polystyrene backbone via reversible addition fragmentation chain transfer (RAFT) polymerization and their photolithographic patterning on silicon wafers is reported. The controlled radical polymerization of the styrenic ionic liquid (IL) monomers ([BVBIM]X, X = Cl− or Tf2N−) by RAFT polymerization is investigated in detail. We provide a general synthetic tool to access this class of PILs with controlled molecular weight and relatively narrow molecular weight distribution (2000 g mol−1 ≤ Mn ≤ 10 000 g mol−1 with dispersities between 1.4 and 1.3 for p([BVBIM]Cl); 2100 g mol−1 ≤ MP ≤ 14 000 g mol−1 for p([BVBIM]Tf2N)). More importantly, we provide an in-depth characterization of the PILs and demonstrate a detailed mass spectrometric analysis via matrix-assisted laser desorption ionization (MALDI) as well as – for the first time for PILs – electrospray ionization mass spectrometry (ESI-MS). Importantly, p([BVBIM]Cl) and p([DMVBIM]Tf2N) were photochemically patterned on silicon wafers. Therefore, a RAFT agent carrying a photoactive group based on ortho-quinodimethane chemistry – more precisely photoenol chemistry – was photochemically linked for subsequent controlled radical polymerization of [BVBIM]Cl and [DMVBIM]Tf2N. The successful spatially-resolved photografting is evidenced by surface-sensitive characterization methods such as X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The presented method allows for the functionalization of diverse surfaces with poly(ionic liquid)s.
Impact of gamma radiation on transmission of a commercial Cytop polymer optical fibre (Lucina, Asahi Glass Company) is investigated. Spectral dependence of radiation induced attenuation in the investigated fibre is measured in the VIS-NIR spectral region. Besides attenuation increase, radiation is found to increase fibre susceptibility to water as well. While pristine Cytop fibre is rather humidity insensitive, strong humidity related absorption in the NIR region is observed after fibre irradiation. Selective irradiation of separate fibre sections is proposed as a way of fibre humidity sensitization and quasi-distributed water detection is demonstrated using optical time domain reflectometry at 1310 nm.
Radiation induced attenuation in perfluorinated polymer optical fibres for dosimetry applications
(2016)
Real-time measurement of radiation-induced attenuation (RIA) in a commercial perfluorinated polymer optical fibre (PF-POF) is performed with regard to on-line Radiation monitoring purposes. Spectral character and dose dependence of fibre’s RIA is measured in 450-900 nm spectral region. Fibre exhibited high radiation sensitivity in the visible region with strong increase towards the UV wavelengths. Good linearity and high sensitivity reaching up to 130 dBm-1/kGy was demonstrated in the VIS region for a low-dose range. This of-the-shelf PF-POF could be therefore interesting for on-line remote dosimetry applications.
Selecting a welding process for a given application is crucial with respect to the sustainability of part manufacturing. Unfortunately, since welding processes are evaluated by a number of criteria, preferences for one or the other process can be contradictory. However, the prevalent procedure of weight assignment for each criterion is subjective and does not provide information about the entire solution space. From the perspective of a decision maker it is important to be able to assess the entire set of possible weightings and answer the question which welding process is optimal for which set of weights. This issue is investigated by means of a weight space partitioning approach. Two welding processes are considered with respect to three criteria that reflect their economic and environmental performance. In order to find the most sustainable welding process the underlying weight space partition is evaluated.
Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent discontinuities.
A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. Otherwise, planar discontinuities like cracks in plastics or delaminated layers in composites can be abstracted as layers located at any angle in relation to the outer sample surface direction. A tomogram from the scanned sample can then be reconstructed in case the interactions of electromagnetic pulses with the existing inherent interfaces are detectable and a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielectric properties.
A short description of both the SAFT – and Optical Layer algorithm for the reconstruction of the inherent structure is initially given. Measurements on representative samples with a variety of artificially produced small and large scale. Reconstructed tomograms are presented to discuss and evaluate the benefits and limits of the two different reconstruction approaches.
Real Time Imaging of Deuterium in a Duplex Stainless Steel Microstructure by Time-of-Flight SIMS
(2016)
For more than one century, hydrogen assisted degradation of metallic microstructures has been identified as origin for severe technical component failures but the mechanisms behind have not yet been completely understood so far. Any in-situ observation of hydrogen transport phenomena in microstructures will provide more details for further elucidation of these degradation mechanisms. A novel experiment is presented which is designed to elucidate the permeation behaviour of deuterium in a microstructure of duplex stainless steel (DSS). A hydrogen permeation cell within a TOF-SIMS instrument enables electrochemical charging with deuterium through the inner surface of the cell made from DSS. The outer surface of the DSS permeation cell exposed to the vacuum has been imaged by TOF-SIMS vs. increasing time of charging with subsequent chemometric treatment of image data. This in-situ experiment showed evidently that deuterium is permeating much faster through the ferrite phase than through the austenite phase. Moreover, a direct proof for deuterium enrichment at the austenite-ferrite interface has been found.
In 2011, the German Association of Engineers (VDI) started working on a set of guidelines dealing with the improvement of resource efficiency. These guidelines represent a framework that defines resource efficiency and outlines proposals for the producing industry. A special guideline for small and medium-sized enterprises (SMEs) is included as well as guidelines on methodologies for evaluating resource use indicators, such as the cumulative raw material demand of products and production systems. The work on resource use indicators is still in progress. The evaluation of raw materials expenditure will include water, soil and land use. The model will include the availability of raw materials (criticality). Improving resource efficiency at the end-of-life stage is illustrated in this paper by the example of materials recovery from waste, here from residues out of municipal solid waste incineration (MSWI). With mechanical treatment valuable materials like ferrous and non-ferrous metals and secondary construction material can be extracted from MSWI bottom ash. The potential contribution on the resource efficiency is discussed.
Grating interferometric set-ups have been established in the last decade. They are promising candidates to obtain enhanced image contrast from weakly absorbing micro and nano structures. They are based on X-ray refraction and near-field diffraction using the Talbot effect.
At the expense of taking multiple images, Talbot-Lau grating interferometry allows separating the absorption, refraction, and scattering contributions by analysing the disturbances of a phase grating interference pattern. Contrary to other refraction enhanced methods, this technique can be applied using conventional X-ray tubes (divergent, polychromatic source). This makes it attractive to solve typical non-destructive testing problems.
We investigated the efficiency of phase gratings, i.e. the visibility (the amplitude of oscillations) upon variation of propagation distance and phase grating rotation around an axis parallel to the grid lines. This grating rotation changes the grating shape (i.e. the distributions of phase shifts). This can yield higher visibilities than derived from rectangular shapes.
Our study includes experimental results obtained from synchrotron radiation, as well as simulations for monochromatic radiation. The advantages of Talbot-Lau interferometry are demonstrated at the example of glass capillaries.
Grating interferometric set-ups have been established in the last decade. They are promising candidates to obtain enhanced image contrast from weakly absorbing micro and nano structures. They are based on X-ray refraction and near-field diffraction using the Talbot effect.
At the expense of taking multiple images, Talbot-Lau grating interferometry allows separating the absorption, refraction, and scattering contributions by analysing the disturbances of a phase grating interference pattern. Contrary to other refraction enhanced methods, this technique can be applied using conventional X-ray tubes (divergent, polychromatic source). This makes it attractive to solve typical non-destructive testing problems.
We investigated the efficiency of phase gratings, i.e. the visibility (the amplitude of oscillations) upon variation of propagation distance and phase grating rotation around an axis parallel to the grid lines. This grating rotation changes the grating shape (i.e. the distributions of phase shifts). This can yield higher visibilities than derived from rectangular shapes.
Our study includes experimental results obtained from synchrotron radiation, as well as simulations for monochromatic radiation. The advantages of Talbot-Lau interferometry are demonstrated at the example of glass capillaries.
Sub-aerial biofilms (SAB) are ubiquitous, self-sufficient microbial ecosystems found on mineral surfaces at all altitudes and latitudes. SABs, which are the principal causes of weathering on exposed terrestrial surfaces, are characterized by patchy growth dominated by associations of algae, cyanobacteria, fungi and heterotrophic bacteria. A recently developed in vitro system to study colonization of rocks exposed to air included two key SAB participants - the rock-inhabiting ascomycete Knufia petricola (CBS 123872) and the phototrophic cyanobacterium Nostoc punctiforme ATCC29133. Both partners are genetically tractable and we used them here to study weathering of granite, K-feldspar and plagioclase. Small fragments of the various rocks or minerals (1–6 mm) were packed into flow-through columns and incubated with 0.1% glucose and 10 μM thiamine-hydrochloride (90 μL min−1) to compare weathering with and without biofilms. Dissolution of the minerals was followed by: (i) analysing the degradation products in the effluent from the columns via Inductively Coupled Plasma Spectroscopy and (ii) by studying polished sections of the incubated mineral fragments/grains using scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analyses. K. petricola/N. punctiforme stimulated release of Ca, Na, Mg and Mn. Analyses of the polished sections confirmed depletion of Ca, Na and K near the surface of the fragments. The abrupt decrease in Ca concentration observed in peripheral areas of plagioclase fragments favored a dissolution-reprecipitation mechanism. Percolation columns in combination with a model biofilm can thus be used to study weathering in closed systems. Columns can easily be filled with different minerals and biofilms, the effluent as well as grains can be collected after long-term exposure under axenic conditions and easily analyzed.
Microstrain distributions were acquired in functional thin films by high-resolution X-ray microdiffraction measurements, using polycrystalline CuInSe2 thin films as a model system. This technique not only provides spatial resolutions at the submicrometre scale but also allows for analysis of thin films buried within a complete solar-cell stack. The microstrain values within individual CuInSe2 grains were determined to be of the order of 10^-4. These values confirmed corresponding microstrain distribution maps obtained on the same CuInSe2 layer by electron backscatter diffraction and Raman microspectroscopy.
A novel photoswitchable rotaxane was synthesised and its switching behaviour in solution was analysed with NMR and UV-Vis. A monolayer of rotaxanes was deposited on glass surfaces and the on-surface photoswitching was investigated. Angle-resolved NEXAFS spectra revealed a preferential orientation that reversibly changes upon switching.
Since a few years the direct detection of X-ray photons into electrical signals is possible by usage of highly absorbing photo conducting materials (e.g. CdTe) as detection layer of an underlying CMOS semiconductor X-ray detector. Even NDT energies up to 400 keV are possible today, as well. The image sharpness and absorption efficiency is improved by the replacement of the unsharp scintillation layer (as used at indirect detecting detectors) by a photo conducting layer of much higher thickness. If the read-out speed is high enough (ca. 50 – 100 ns dead time) single X-ray photons can be counted and their energy measured. Read-out noise and dark image correction can be avoided. By setting energy thresholds selected energy ranges of the X-ray spectrum can be detected or suppressed. This allows material discrimination by dual-energy techniques or the reduction of image contributions of scattered radiation, which results in an enhanced contrast sensitivity. To use these advantages in an effective way, a special calibration procedure has to be developed, which considers also time dependent processes in the detection layer. This contribution presents some of these new properties of direct detecting digital detector arrays (DDAs) and shows first results on testing fiber reinforced composites as well as first approaches to dual energy imaging.
A high-performance fiber Bragg grating-based (FBG) sensor device has been developed for the detection of small magnetic fields. Based on a smart multilayer jacket around the fibre over the physical length of the FBG, magnetic fields generated by rotating machine parts, power generators or power cable can be easily detected, analysed and evaluated. Consequently, this innovative, on-line and non-contact inspection method results in an increase in quality and reliability of high-performing machine parts, devices and cables. The basic physical principle is based on a magnetostrictive multilayer system that strains the high-resolution FBG element in presence of magnetic fields. Subsequently, a fixed relationship between induced magnetic field and wavelength change of the FBG element describes the characteristic sensitivity curve. Intensive tests regarding characterisation of this magnetic field FBG sensor have been carried out and its performance has been evaluated.
We use a dynamic scanning electron microscope (DySEM) to map the spatial distribution of the vibration of a cantilever beam. The DySEM measurements are based on variations of the local secondary electron signal within the imaging electron beam diameter during an oscillation period of the cantilever. For this reason, the surface of a cantilever without topography or material variation does not allow any conclusions about the spatial distribution of vibration due to a lack of dynamic contrast. In order to overcome this limitation, artificial structures were added at defined positions on the cantilever surface using focused ion beam lithography patterning. The DySEM signal of such high-contrast structures is strongly improved, hence information about the surface vibration becomes accessible. Simulations of images of the vibrating cantilever have also been performed. The results of the simulation are in good agreement with the experimental images.
Today’s efforts for lightweight design result in a growing application of high-strength structural steels from 960 MPa. In welded structures of these steels increased demands regarding component safety and a high elastic ratio should be considered. Hence, the prevention of an evolution of high weld-induced tensile residual stresses is required. Recent studies showed that component related restraint conditions of welds are able to elevate welding induced stresses to critical values, depending on material characteristics, the welding process and parameters. This work involves multi-axial welding loads as a consequence of the superposition of local residual stresses, global reaction stresses and moments, varying the welding parameters under different restraint conditions. The global welding loads are measured via GMA-weld tests in a special testing facility and via a DIC(Digital Image Correlation)-system in a slot weld. Local transverse residual stresses were analysed by means of X-ray diffraction. The application of a less amount of weld runs due to a modified welding parameters and welds seam configurations revealed as a beneficial approach to reduce welding loads in high-strength steels.
Bei der Power-to-Gas-Technologie wird überschüssiger Strom aus erneuerbaren Ener-gien durch Elektrolyse von Wasser in Wasserstoff umgewandelt. Dieser Wasserstoff kann als „chemischer Energiespeicher“ dienen und rückverstromt werden oder aber in das Erdgasnetz eingespeist werden. Die BAM hat die Auswirkungen von Wasserstoffzu-sätzen zum Erdgas im Hinblick auf den Explosionsschutz untersucht und sicherheitstechnische Kenngrößen für Erdgas-Wasserstoff-Gemische bestimmt.
Von besonderem Interesse waren dabei die Explosionsgrenzen, die Sauerstoffgrenzkonzentration, die maximalen Explosionsdrücke, die KG-Werte und die Normspaltweiten. Für die Messungen sind zwei Modellgase eingesetzt worden, reines Methan und ein Modell-Erdgas mit Anteilen höherer Kohlenwasserstoffe. Sie repräsentieren die Bandbreite der in Deutschland eingesetzten Erdgase.
Die Untersuchungen ergaben, dass bei einem Zusatz von bis zu 10 Mol-% Wasserstoff keine der untersuchten Kenngrößen signifikant beeinflusst wird. Die Gemische haben nur geringfügig erweiterte Explosionsbereiche und bleiben, wie die reinen Erdgase, in der Explosionsgruppe IIA. Auch die maximalen Explosionsdrücke und die zeitlichen Druckanstiege bei den Gasexplosionen werden nur wenig beeinflusst.
Background: Biocidal products can be sources of active substances in surface waters caused by weathering of treated articles. Marketing and use of biocidal products can be limited according to the European Biocidal Products Regulation if unacceptable risks to the environment are expected. Leaching of active substances from treated articles was observed in field experiments to obtain information on leaching processes and investigate the suitability of a proposed test method.
Results: Leaching under weathering conditions proceeds discontinuously and tends to decrease with duration of exposure. It mainly depends on the availability of water, but is also controlled by transport processes within the materials and stability of the observed substances. Runoff amount proved to be a suitable basis to compare results from different experiments. Concentrations of substances are higher in runoff collected from vertical surfaces compared to horizontal ones, whereas the leached amounts per surface area are higher from horizontal surfaces. Gaps in mass balances indicate that additional processes such as degradation and evaporation may be relevant to the fate of active substances in treated articles. Leached amounts of substances were considerably higher when the materials were exposed to intermittent water contact under laboratory conditions as compared to weathering of vertically exposed surfaces.
Conclusions: Experiences from the field experiments were used to define parameters of a procedure that is now provided to fulfil requirements of the Biocidal Products Regulation. The experiments confirmed that the amount of water which is in contact with exposed surfaces is the crucial parameter determining leaching of substances.
The optical properties of semiconductor nanocrystals (SC NCs) are largely controlled by their size and surface chemistry, i.e., the chemical composition and thickness of inorganic passivation shells and the chemical nature and number of surface ligands as well as the strength of their bonds to surface atoms.
The latter is particularly important for CdTe NCs, which – together with alloyed CdₓHg₁₋ₓTe – are the only SC NCs that can be prepared in water in high quality without the need for an additional inorganic passivation shell. Aiming at a better understanding of the role of stabilizing ligands for the control of the application-relevant fluorescence features of SC NCs, we assessed the influence of two of the most commonly used monodentate thiol ligands, thioglycolic acid (TGA) and mercaptopropionic acid (MPA),
on the colloidal stability, photoluminescence (PL) quantum yield (QY), and PL decay behavior of a set of CdTe NC colloids. As an indirect measure for the strength of the coordinative bond of the ligands to SC NC surface atoms, the influence of the pH (pD) and the concentration on the PL properties of these colloids was examined in water and D₂O and compared to the results from previous dilution studies with a set of thiol-capped Cd₁₋ₓHgₓTe SC NCs in D₂O. As a prerequisite for these studies, the number of surface ligands was determined photometrically at different steps of purification after SC NC synthesis with Ellman’s test.
Our results demonstrate ligand control of the pH-dependent PL of these SC NCs, with MPA-stabilized CdTe NCs being less prone to luminescence quenching than TGA-capped ones. For both types of CdTe colloids, ligand desorption is more pronounced in H₂O compared to D₂O, underlining also the role of hydrogen bonding and solvent molecules.
A great number of Central Asian wall paintings, archeological materials, architectural fragments, and textiles, as well as painting fragments on silk and paper, make up the so called Turfan Collection at the Asian Art Museum in Berlin. The largest part of the collection comes from the Kucha region, a very important cultural center in the third to ninth centuries. Between 1902 and 1914, four German expeditions traveled along the northern Silk Road. During these expeditions, wall paintings were detached from their original settings in Buddhist cave complexes. This paper reports a technical study of a wall painting, existing in eight fragments, from the Buddhist cave no. 40 (Ritterhöhle). Its original painted surface is soot blackened and largely illegible. Grünwedel, leader of the first and third expeditions, described the almost complete destruction of the rediscovered temple complex and evidence of fire damage. The aim of this case study is to identify the materials used for the wall paintings. Furthermore, soot deposits as well as materials from conservation interventions were of interest. Non-invasive analyses were preferred but a limited number of samples were taken to provide more precise information on the painting technique. By employing optical and scanning electron microscopy, energy dispersive X-ray spectroscopy, micro X-ray fluorescence spectroscopy, X-ray diffraction analysis, and Raman spectroscopy, a layer sequence of earthen render, a ground layer made of gypsum, and a paint layer containing a variety of inorganic pigments were identified.
The International Dangerous Goods Regulations prescribe the immersion under water method (“bubble test”) as standard method for the leakproofness test of dangerous goods packagings. But this test procedure acts as a test method for leak localisation, not for quantitative leakage rates measurement. Additionally, the sensitivity in detecting leaks of small diameters is restricted, depending on the test liquid and the test pressure. The bubble test is not suitable for a comparison with quantitative limit leakage rates based on realistic transport conditions. This is especially important when estimating the risk of the formation of an explosive atmosphere during the intercontinental carriage of dangerous goods packagings in freight containers. To compare measured leakage rates with limit leakage rates, a quantitative leak testing procedure is required. Therefore a new approach for dangerous goods packagings is implemented: The pressure technique by accumulation using Helium as a tracer gas. This work presents the test equipment necessary for the quantitative measurement of Helium leakage rates through closures of different kinds of dangerous goods packagings. The essential steps to achieve good repeatable results are: A controlled Helium filling process to reach a defined test pressure in the test sample, a sufficient homogenisation of the Helium-air-mixture inside the test sample and the ensuring of a constant pressure level of the test sample during the test. The Helium loss rate of the accumulation chamber has to be measured separately to receive a correction factor for the measured leakage rates. Different constructional measures are introduced to prevent a disturbing influence of the Helium leakage rate of the filling valves on the measurement results. Methods to estimate the disturbing effect of Helium permeation through permeable parts of the test sample are also presented. As a supporting method for the experimental investigations the Helium sniffer test can be applied. This practical application-oriented advice can enable other users to establish a pressure technique by accumulation for their own technical field.
The International Dangerous Goods Regulations prescribe the immersion under water method (“bubble test”) as standard method for the leakproofness test of dangerous goods packagings. But this test procedure acts as a test method for leak localisation, not for quantitative leakage rates measurement. Additionally, the sensitivity in detecting leaks of small diameters is restricted, depending on the test liquid and the test pressure. The bubble test is not suitable for a comparison with quantitative limit leakage rates based on realistic transport conditions. This is especially important when estimating the risk of the formation of an explosive atmosphere during the intercontinental carriage of dangerous goods packagings in freight containers.
To compare measured leakage rates with limit leakage rates, a quantitative leak testing procedure is required. Therefore a new approach for dangerous goods packagings is implemented: The pressure technique by accumulation using Helium as a tracer gas.
This work presents the test equipment necessary for the quantitative measurement of Helium leakage rates through closures of different kinds of dangerous goods packagings. The essential steps to achieve good repeatable results are: A controlled Helium filling process to reach a defined test pressure in the test sample, a sufficient homogenisation of the Helium-air-mixture inside the test sample and the ensuring of a constant pressure level of the test sample during the test. The Helium loss rate of the accumulation chamber has to be measured separately to receive a correction factor for the measured leakage rates. Different constructional measures are introduced to prevent a disturbing influence of the Helium leakage rate of the filling valves on the measurement results. Methods to estimate the disturbing effect of Helium permeation through permeable parts of the test sample are also presented. As a supporting method for the experimental investigations the Helium sniffer test can be applied. This practical application-oriented advice can enable other users to establish a pressure technique by accumulation for their own technical field.
Distickstoffmonoxid (N2O, Lachgas) und Helium (He) sind gängige Prüfgase für Dichtheitsprüfungen. Die einfachste Leckgeometrie stellt ein ideal zylindrisches Rohr dar. Es wurden Glaskapillaren verschiedener Abmessungen mit Lachgas und Helium durchströmt. Der Überdruck am Kapillareingang lag zwischen 100 mbar und 400 mbar. Es handelte sich um vier annähernd zylindrische Glaskapillaren mit den mittleren Durchmessern: Kapillare 1: ca. 102 μm; Kapillare 2: ca. 71 μm; Kapillare 3B: ca. 49 μm; Kapillare 4: ca. 53 μm. Zudem wurde eine nichtzylindrische Kapillare geprüft (Kapillare 3A). Die Kapillaren 1, 2 und 3B wurden mit beiden Prüfgasen getestet. Kapillare 3A wurde nur mit Lachgas durchströmt, Kapillare 4 nur mit Helium. Für die Messung der Leckageraten kam das Überdruckverfahren mit Ansammlung (Verfahren B3 nach DIN EN 1779: 1999-10) zum Einsatz. Als Detektor für Lachgas diente der Lachgasdetektor Maihak Unor 6 N, für Helium der Leckdetektor T-Guard der Firma Inficon.
Es wurden verschiedene Theorieansätze verglichen. Beim Theorieansatz Ib erfolgte die Umrechnung der Lachgas-Messwerte auf die Helium-Messwerte und umgekehrt anhand der Druck-, Temperatur- und Gasartabhängigkeit der Leckagerate für laminar-viskose Gasströmung (DIN EN 1779: 1999-10; DGZfP-Richtlinie DP2: 2009-12). Beim Theorieansatz II wurde die Berechnung der Leckagerate für die laminar-viskose Rohrströmung unter der Annahme einer ideal zylindrischen Kapillare durchgeführt. Zusätzlich wurde mit „ANSYS Fluent“ eine CFD-Simulation vorgenommen. Bei Kapillare 3A wurde eine Serienschaltung der Strömungsleitwerte von Rohr und Düse angesetzt. Bei Anwendung des Ansatzes Ib werden bei Umrechnung der Helium-Messwerte auf Lachgas die Lachgas-Messwerte überschätzt. Umgekehrt werden bei der Umrechnung der Lachgas-Messwerte auf Helium die Helium-Messwerte unterschätzt. Bei Analyse der Einlauflängen der Rohrdurchströmung ist festzustellen, dass diese für Lachgas stets größer als für Helium sind. Bei Lachgas liegt daher für einige Messwerte noch keine ausgebildete laminare Rohrströmung vor. Einlaufeffekte können somit nicht vernachlässigt werden. Als Fazit ergibt sich, dass bei Verwendung von Helium als Prüfgas und Umrechnung der Helium-Messwerte auf Lachgas die Lachgas-Leckageraten sicherheitstechnisch konservativ abgeschätzt werden.
This article reports a comprehensive investigation of the average and local structure of La5.6WO12-δ, which has excellent mixed proton, electron and oxide ion conduction suitable for device applications. Synchrotron X-ray and neutron powder diffraction show that a cubic fluorite supercell describes the average structure, with highly disordered lanthanum and oxide positions. On average, the tungsten sites are sixfold coordinated and a trace [3.7 (1.3)%] of anti-site disorder is detected. In addition to sharp Bragg reflections, strong diffuse neutron scattering is observed, which hints at short-range order. Plausible local configurations are considered and it is shown that the defect chemistry implies a simple 'chemical exchange' interaction that favours ordered WO6 octahedra. The local model is confirmed by synchrotron X-ray pair distribution function analysis and EXAFS experiments performed at the La K and W L-3 edges. It is shown that ordered domains of similar to 3.5 nm are found, implying that mixed conduction in La5.6WO12-δ is associated with a defective glassy-like anion sublattice. The origins of this ground state are proposed to lie in the nonbipartite nature of the face-centred cubic lattice and the pairwise interactions which link the orientation of neighbouring octahedral WO6 sites. This 'function through frustration' could provide a means of designing new mixed conductors.
Rising importance of composite lightweight structures in aircraft and automobile industries increases the demand on reliable non-destructive testing methods for these structures. Air-coupled ultrasonic testing emerged to suit these requirements as it does not require any liquid coupling medium. In conventional air-coupled ultrasonic transducers, matching layers are used in order to decrease the impedance mismatch between transducer and air. Matching layers can be omitted by using ferroelectrets, which are charged cellular polymers having ferroelectric and piezoelectric properties. Especially a low Young’s modulus, low density and low sound velocity of cellular polypropylene (cPP) are properties being required for well-matched air-coupled ultrasonic transducers.
In our contribution we show recent enhancements of cPP transducers resulting in focused sound fields and thus improved lateral sensitivity. The influence of different transmitter apertures was evaluated using measurements of the emitted sound field. Further we show a transmission of a test specimen of carbon-fiber-reinforced plastic (CFRP) containing artificial damages. Results of focused transducers were compared to planar ferroelectret transducers, as well as to conventional air-coupled transducers.
A round robin test on flash thermography was organized within the scope of a standardization research project. This test gives information on reliability, comparability and efficiency of different testing situations. Data recorded on metal and CFRP test specimens with flat bottom holes (FBH) were analysed by evaluating the detectability and by calculating the signal-to-noise ratio (SNR) of the defect signatures as a function of defect parameters. For the investigation of the influence of material properties on the spatial resolution as well as on penetration depth, test specimens made of steel and copper with crossed notches and a notch ramp were constructed and investigated. Here, the minimum resolvable notch distance and the maximum detectable depth of the ramp were analysed.
Within the scope of a DIN INS project, a flash thermography round robin test that evaluates reliability, comparability and efficiency of different testing situations is organized. The results give information about the detectability of defects e.g. by their size and depth, the evaluation method and by the materials used. Besides, the influence of equipment and parameters used by the participants on the results were analysed. All of the quantitative results as well as the feedback given by the participants will be presented in a DIN committee in order to contribute to a flash thermography standard.
The corrosion resistance of martensitic stainless steels (MSS) depends strongly on the chemical composition and the applied heat treatment. Both determines the distribution of the alloying elements in the microstructure and the resulting material properties. The addition of nitrogen is known to be beneficial for the pitting corrosion resistance of stainless steels. In case of MSS this effect is not only connected to nitrogen itself because nitrogen can be used to substitute carbon which also influences the result of the heat treatment process. This paper shows the effect of nitrogen on the corrosion resistance in relation to the hardening process of MSS. Therefore the effects of austenitization duration, austenitization temperature and cooling rate on microstructure, hardness and corrosion resistance were studied on the MSS X30CrMoN15 1 and X50CrMoV15. The effect of different cooling rates was studied in the range of > 100 K/s down to 1 K/s using the jominy end quench test. The changes in corrosion resistance were detected with electrochemical potentiodynamic reactivation (EPR) and by the determination of critical pitting potentials. Besides this experimental approach thermodynamic calculations with the software thermocalc will be presented and used for the interpretation of the effect of nitrogen on the corrosion resistance of MSS.
The General Guidance in the Swedish regulations state that the safety assessment for a final repository for spent nuclear fuel should be 1 million years after closure. SKB developed the KBS-3 method, according to which the spent nuclear fuel is protected by three barriers. It is encapsulated in canisters with a diameter of 1 metre and a length of 5 metres. The canister consists of a cast iron insert surrounded by a 5 centimetre thick shell of copper. The canisters are disposed in the bedrock at a depth of about 500 meters surrounded by bentonite clay. In order to assess the safety over this extremely long period, an extensive quality control programme is applied to the canisters before deposit. In this programme, the use of
non-destructive testing (NDT) is vital. The safety assessment of the canister in turn places high demands on the coverage, detectability, and reliability of the applied NDT inspections of the canister parts, i.e. cast iron insert, copper base, tube and lid, and the copper friction stir welds (FSW). This paper presents the extensive full-scale inspection development programme that runs at the Canister Laboratory in Oskarshamn (Sweden). In order to fulfil the high demands, phased array ultrasonic inspection techniques are developed using practical trials aided by ultrasonic modelling. The techniques apply, for example, different frequencies, inspection angles, focus depths, and both longitudinal and shear waves. Increased inspection reliability of the FSW is achieved by applying digital X-ray technique using a 9 MeV linear accelerator and a line detector. To complete the coverage, complementary surface inspections methods, i.e. eddy current array, magnetic flux sensor techniques and magnetic particle inspection, are applied. The canister safety assessment was the driving force to include reliability studies during the NDT development. Initially, the technical reliability was considered, resulting in development of advanced POD models (probability of detection). In combination with human factors studies, these models were implemented as tools in the development of the NDT techniques. Human factors studies were also applied to improve the inspection procedures to be more user-friendly enabling reliable inspections.
DNA origami nanostructures are a versatile tool to arrange metal nanostructures and other chemical entities with nanometer precision. In this way gold nanoparticle dimers with defined distance can be constructed, which can be exploited as novel substrates for surface enhanced Raman scattering (SERS). We have optimized the size, composition and arrangement of Au/Ag nanoparticles to create intense SERS hot spots, with Raman enhancement up to 10^10, which is sufficient to detect single molecules by Raman scattering. This is demonstrated using single dye molecules (TAMRA and Cy3) placed into the center of the nanoparticle dimers. In conjunction with the DNA origami nanostructures novel SERS substrates are created, which can in the future be applied to the SERS analysis of more complex biomolecular targets, whose position and conformation within the SERS hot spot can be precisely controlled.
Maintenance, repair and overhaul of components are of increasing interest for parts of high complexity and expensive manufacturing costs. In this paper a production process for laser metal deposition is presented, and used to repair a gas turbine burner of Inconel 718. Different parameters for defined track geometries were determined to attain a near net shape deposition with consistent build-up rate for changing wall thicknesses over the manufacturing process. Spot diameter, powder feed rate, welding velocity and laser power were changed as main parameters for a different track size. An optimal overlap rate for a constant layer height was used to calculate the best track size for a fitting layer width similar to the part dimension. Deviations in width and height over the whole build-up process were detected and customized build-up strategies for the 3D sequences were designed. The results show the possibility of a near net shape repair by using different track geometries with laser metal deposition.
The canister for the permanent storage of spent nuclear fuel used by SKB in Sweden consists of a cast iron insert surrounded by a five centimetre thick shell of copper. It is a safety critical component and in order to secure long-term structural integrity non-destructive methods are used to inspect 100% of the volume of each canister, before it is disposed of in the repository. One of the critical components that requires inspection is a sealing weld, joining the copper tube and the lid. The friction stir weld is inspected using an ultrasonic phased array system. The area of the weld is inspected with several inspection channels with different angles and varying coverage. To make sure that no defects that might occur in the weld are overseen, the reliability of the inspection must be quantified. The reliability of NDT is usually quantified with the probability of detection curves. The influence of the parameters that might influence the POD of the flaws in the weld is investigated analysing the experimental results, as well as with a help of a numerical simulation of the inspection.
Reliability analysis of the ultrasonic inspection system for the inspection of hollow railway axles
(2016)
Axles are safety critical train components that are subjected to significant cyclic loading during operation. If the crack is initiated in the axle, cyclic loading will lead to crack propagation. To maintain structural integrity, axles must be periodically inspected for fatigue cracks in the material. Deutsche Bahn uses mechanized ultrasonic inspection system to inspect hollow railway axles. The inspections are performed from the bore surface, using several conventional transducers with different incident angles, inspecting the axle along the entire length. As with the every safety critical system, the reliability of these inspections must be determined with regard to their flaw detection capabilities. Traditionally this is done according to the relevant standards for railway vehicles. To investigate the capability of the NDT system more thoroughly, we want to evaluate the capability of the inspection system to detect flaws by means of probability of detection (POD) curves. It will be shown that other parameters, beside the size of the crack, for example crack position in the axle, influence the detection of the crack. The influence of these parameters was evaluated using ultrasonic simulation. The evaluation served as an input for the manufacturing of the flaws in the real scale axle. Once these axles are inspected and the data evaluated, using data from both measurement and simulation, we will express the POD of the crack as function of influencing parameters using the multiparameter POD model.
The folding of single-stranded telomeric DNA into guanine (G) quadruplexes is a conformational change that plays a major role in sensing and drug targeting. The telomeric DNA can be placed on DNA origami nanostructures to make the folding process extremely selective for K+ ions even in the presence of high Na+ concentrations. Here, we demonstrate that the K+-selective G-quadruplex formation is reversible when using a cryptand to remove K+ from the G-quadruplex. We present a full characterization of the reversible switching between single-stranded telomeric DNA and G-quadruplex structures using Förster resonance energy transfer (FRET) between the dyes fluorescein (FAM) and cyanine3 (Cy3). When attached to the DNA origami platform, the G-quadruplex switch can be incorporated into more complex photonic networks, which is demonstrated for a three-color and a four-color FRET cascade from FAM over Cy3 and Cy5 to IRDye700 with G-quadruplex-Cy3 acting as a switchable transmitter.
Self-assembling biomolecules provide attractive templates for the preparation of metallic nanostructures. However, the intuitive transfer of the “outer shape” of the assembled macromolecules to the final metallic particle depends on the intermolecular forces among the biomolecules which compete with interactions between template molecules and the metal during metallization. The shape of the bio-template may thus be more dynamic than generally assumed. Here, we have studied the metallization of phospholipid nanodiscs which are discoidal particles of ~10 nm diameter containing a lipid bilayer ~5 nm thick. Using negatively charged lipids, electrostatic adsorption of amine-coated Au nanoparticles was achieved and followed by electroless gold deposition. Whereas Au nanoparticle adsorption preserves the shape of the bio-template, metallization proceeds via invasion of Au into the hydrophobic core of the nanodisc. Thereby, the lipidic phase induces a lateral growth that increases the diameter but not the original thickness of the template. Infrared spectroscopy reveals lipid expansion and suggests the existence of internal gaps in the metallized nanodiscs, which is confirmed by surface-enhanced Raman scattering from the encapsulated lipids. Interference of metallic growth with non-covalent interactions can thus become itself a shape-determining factor in the metallization of particularly soft and structurally anisotropic biomaterials.
Immunoassays are suitable tools for high-throughput screenings. The prerequisite for accurate determinations by these methods is the selection of an excellent antibody. The production and selection of monoclonal antibodies is usually a tedious process. In this study, new strategies for improving antibody production and characterization were applied. This includes the monitoring of the immunization progress in mice through antibodies extracted from feces, which allows a time-resolved and animal-friendly monitoring of the immune response. Additionally, fluorescence polarization immunoassay (FPIA) could be successfully applied for fast and easy examination of cell culture supernatants and the investigation of antibody/antigen interactions including kinetics and fluorescence properties. These methods simplify the selection of the optimal antibody. As a target analyte, carbamazepine was chosen. This is a widely used antiepileptic drug which also frequently occurs in the environment. The new antibody enables CBZ determination in the concentration range 0.66–110 µg L-1 within 10 min using a high-throughput microtiter plate-based FPIA, and between 1.4 and 79 µg L-1 within 5 min applying an automated cuvette-based FPIA instrument, and from 0.05–36 µg L-1 using ELISA. The measurements were performed at a non-equilibrium state which improved the sensitivity and selectivity of the assays. Due to low cross-reactivity especially towards the main CBZ metabolite and other pharmaceuticals (<1%), this antibody gives the opportunity for application in medical and environmental analyses.
Investigation of manuscripts found in sites along the Silk Road shows the history of communication and exchange between Asia and the Mediterranean over the centuries. Different scripts and languages preserved on paper in certain styles provide information about traditions and provenance.
To get an idea of the cultural background of the highly developed painting techniques obvious in some illuminated manuscripts, the material used for writing and painting is analyzed. Singular Sogdian and Tocharian manuscripts from Turfan show text on one side with a colorful painting on the other side of the document. In comparison with other productions of different periods or usages from the site, special features are worked out to characterize cultural roots or influence in the network of relationships. Details analyzed in the most elaborated documents Show various influences led to the colorful masterpieces.
A combined experimental numerical approach is applied to determine the transformation induced plasticity (TRIP)-parameter K for different strength low-alloy steels of grade S355J2+N and S960QL as well as the super martensitic filler CN13-4-IG containing 13 wt% chromium and 4 wt% nickel. The thermo-physical analyses were conducted using a Gleeble® 3500 facility. The thermal histories of the specimens to be tested were extracted from corresponding simulations of a real gas metal arc weldment. In contrast to common TRIP-experiments which are based on complex specimens a simple flat specimen was utilized together with an engineering evaluation method. The evaluation method was validated with literature values for the TRIP-parameter. It could be shown that the proposed approach enables a correct description of the TRIP behavior.
Column percolation tests may be suitable for prediction of chemical leaching from soil and soil materials. However, compared with batch leaching tests, they are time-consuming. It is therefore important to investigate ways to shorten the tests without affecting the quality of results. In this study, we evaluate the feasibility of decreasing testing time by increasing flow rate and decreasing equilibration time compared to the conditions specified in ISO/TS 21268-3, with equilibration periods of 48 h and flow rate of 12 mL/h. We tested three equilibration periods (0, 12–16, and 48 h) and two flow rates (12 and 36 mL/h)on four different soils and compared the inorganic constituent releases. For soils A and D, we observed similar values for all conditions except for the 0 h–36 mL/h case. For soil B, we observed no appreciable differences between the tested conditions, while for soil C there were no consistent trends probably due to the difference in ongoing oxidation reactions between soil samples. These results suggest that column percolation tests can be shortened from 20 to 30 days to 7–9 days by decreasing the equilibration time to 12–16 h and increasing the flow rate to 36 mL/h for inorganic substances.
Die zerstörungsfreien Prüfverfahren konnten ihre Fähigkeit bei der Untersuchung von Elementwänden in einzelnen Fallstudien erbringen. Aufbauend auf den Kenntnissen aus der Praxis und auf Testreihen im Rahmen von Laboruntersuchungen wurde ein erster Ringversuch geplant und durchgeführt. Im Rahmen dieses Ringversuchs wurden verschiedene Strukturdefekte und Einbauteile in Elementwände eingebaut. Die Messung der Wände erfolgte anschließend durch mehrere Messteams mit unterschiedlichen zerstörungsfreien Prüfverfahren. Zum Einsatz kamen hierbei das Ultraschall-Echo- und das Impact-Echo-Verfahren sowie das Impuls-Radar-Verfahren. Zur Verbesserung der Vergleichbarkeit zwischen den unterschiedlichen Prüfverfahren wurde auf die Elementwände ein einheitliches Messraster aufgebracht. Für eine möglichst objektive Messung der Wände erhielten die Messteams vor den Messungen keine Details zu den Strukturdefekten oder Einbauteilen. Die Prüfaufgabe bestand darin, die Wände mit dem jeweiligen Prüfverfahren zu untersuchen. Anschließend wurden die Ergebnisse der Messteams zentral gesammelt und ausgewertet. Anhand der zentralen Auswertung sollten Aussagen zu den eingebauten Inhomogenitäten ableitet werden. Hierdurch kann zum einen die Leistungsfähigkeit der Prüfverfahren an unterschiedlichsten Inhomogenitäten getestet werden, zum anderen können die Ergebnisse und somit die Prüfverfahren untereinander verglichen werden. Zu diesen in der Praxis immer häufiger vorkommenden Fragestellungen können grundsätzliche Aussagen zum Einsatz von zerstörungsfreien Prüfungen bei Elementwänden gewonnen werden. Über die Ergebnisse dieses Ringversuches wird nachfolgend berichtet.
We report an appropriate preparation of binary isotope calibration mixtures of the three stable isotopes of magnesium to be used in the ab initio calibration of multicollector mass spectrometers (ICPMS and TIMS). For each of the three possible combinations of binary mixtures ("24Mg" + "25Mg", "24Mg" + "26Mg", and "25Mg" + "26Mg"), three individual setups have been prepared under gravimetric control, each of them with an isotope ratio close to unity, and a total magnesium mass fraction close to 20 mg kg-1. The preparation was designed to occur via an intermediate dilution of a parent solution of a highly purified specimen of the isotopically enriched magnesium materials. For the application as calibration mixtures, a complete uncertainty budget was set up, and is presented and discussed in detail, including the aspects that went into the design of the dilution and mixing approach to minimize uncertainty. The principle parameters for the purpose of the later calibration of the mass spectrometers are the absolute masses of isotopically enriched magnesium materials in the primary calibration mixtures. For the first time relative expanded uncertainties U (k = 2) for these masses of ≤0.005% could be achieved for all mixtures.
Compact nuclear magnetic resonance (NMR) instruments make NMR spectroscopy and relaxometry accessible in industrial and harsh environments for reaction and process control. An increasing number of applications are reported. To build an interdisciplinary bridge between “process control” and “compact NMR”,we give a short overviewon current developments in the field of process Engineering such as modern process design, integrated processes, intensified processes along with requirements to process control, model based control, or soft sensing. Finally, robust field integration of NMR systems into processes environments, facing explosion protection or Integration into process control systems, are briefly discussed.
Biofilm formation on materials leads to high costs in industrial processes, as well as in medical applications. This fact has stimulated interest in the development of new materials with improved surfaces to reduce bacterial colonization. Standardized tests relying on statistical evidence are indispensable to evaluate the quality and safety of these new materials. We describe here a flow chamber system for biofilm cultivation under controlled conditions with a total capacity for testing up to 32 samples in parallel. In order to quantify the surface colonization, bacterial cells were DAPI (4‘,6-diamidino-2-phenylindole)-stained and examined with epifluorescence microscopy. More than 100 images of each sample were automatically taken and the surface coverage was estimated using the free open source software g’mic, followed by a precise statistical evaluation. Overview images of all gathered pictures were generated to dissect the colonization characteristics of the selected model organism Escherichia coli W3310 on different materials (glass and implant steel). With our approach, differences in bacterial colonization on different materials can be quantified in a statistically validated manner. This reliable test procedure will support the design of improved materials for medical, industrial, and environmental (subaquatic or subaerial) applications.
In this study, a new reliable, economic, and environmentally-friendly one-step synthesis is established to obtain carbon nanodots (CNDs) with well-defined and reproducible photoluminescence (PL) properties via the microwave-assisted hydrothermal treatment of starch and Tris-acetate-EDTA (TAE) buffer as carbon sources. Three kinds of CNDs are prepared using different sets of above mentioned starting materials. The as-synthesized CNDs: C-CND (starch only), N-CND 1 (starch in TAE) and N-CND 2 (TAE only) exhibit highly homogenous PL and are ready to use without need for further purification.
The CNDs are stable over a long period of time (>1 year) either in solution or as freeze-dried powder. Depending on starting material, CNDs with PL quantum yield (PLQY) ranging from less than 1% up to 28% are obtained. The influence of the precursor concentration, reaction time and type of additives on the optical properties (UV-Vis absorption, PL emission spectrum and PLQY) is carefully investigated, providing insight into the chemical processes that occur during CND formation. Remarkably, upon freeze-drying the initially brown CND-solution turns into a non-fluorescent white/slightly Brown powder which recovers PL in aqueous solution and can potentially be applied as fluorescent marker in bio-imaging, as a reduction agent or as a photocatalyst.
Emerging infectious diseases (EIDs) have contributed significantly to the current biodiversity crisis, leading to widespread epidemics and population loss. Owing to genetic variation in pathogen virulence, a complete understanding of species decline requires the accurate identification and characterization of EIDs. We explore this issue in the Western honeybee, where increasing mortality of populations in the Northern Hemisphere has caused major concern. Specifically, we investigate the importance of genetic identity of the main suspect in mortality, deformed wing virus (DWV), in driving honeybee loss. Using laboratory experiments and a systematic field survey, we demonstrate that an emerging DWV genotype (DWV-B) is more virulent than the established DWV genotype (DWV-A) and is widespread in the landscape. Furthermore, we show in a simple model that colonies infected with DWV-B collapse sooner than colonies infected with DWV-A. We also identify potential for rapid DWV evolution by revealing extensive genome-wide recombination in vivo. The emergence of DWV-B in naive honeybee populations, including via recombination with DWV-A, could be of significant ecological and economic importance. Our findings emphasize that knowledge of pathogen genetic identity and diversity is critical to understanding drivers of species decline.
Ultrasonic phased array is, currently, the technology which is being applied as the solution to a lot of inspection problems. The perceived benefits are seen to be worth the outlay on equipment and specialised personnel. Yet, there is a source of knowledge, freely available, which can also deliver immediate benefits, through more reliable inspection results, and consequently increased client confidence, but which is largely ignored by the greater part of the NDT community. This talk will review the latest Human Factors knowledge and provide practical illustrations of how companies can use it to improve their competitive edge.
Ultrasonic imaging systems usually require an array of ultrasonic transducers for data acquisition on a wide area on top of an object under investigation. The goal of an imaging algorithm is the use of reflected ultrasound data to form a recognizable image. Conventional algorithms like SAFT are based on an inverse Huygens' principle and need therefore a dense measurement grid. This requires a big effort in data capturing. For simple and inexpensive measurement different strategies of imaging with reduced amount of data and examples with a manual scanning device on concrete elements are presented.
Wedemonstrate that a single-layer graphene replicates the shape ofDNAorigami nanostructures very well. It can be employed as a protective layer for the enhancement of structural stability of DNA origami nanostructures. Using the AFM based manipulation, we show that the normal force required to damage graphene encapsulated DNA origami nanostructures is over an order of magnitude greater
than for the unprotected ones. In addition, we show that graphene encapsulation offers protection to the DNA origami nanostructures against prolonged exposure to deionized water, and multiple immersions. Through these results we demonstrate that graphene encapsulated DNA origami nanostructures are strong enough to sustain various solution phase processing, lithography and
transfer steps, thus extending the limits of DNA-mediated bottom-up fabrication.
In this paper, we identify the strategic motives of German manufacturing companies in the electrical engineering and machinery industry to be involved in standards development organizations. First, we present the general motives for the formation of strategic alliances and relate them to specific standardization motives. Then, we identify pursuing specific company interests, solving technical problems, knowledge seeking, influencing regulation, and facilitating market access as motives to standardize by means of factor analysis. In a second step, we test hypotheses on the relationship between the importance of strategic motives and firm level variables, e.g. R&D intensity, innovation activities, and firm size. The results reveal that firms in electric engineering and machinery have a particularly strong interest in ensuring industry-friendly design of regulations, which can be achieved by standards. Moreover, the results confirm that small firms also from these two sectors are active in standardization alliances to access knowledge from other involved stakeholders.
Forderungen nach höherer Geschwindigkeit und die Komplexität der Fragen geben der analytischen Chemie neue Impulse. So nutzt die Prozessanalytik gepulste Ramanspektrometer, die Elemente Arsen und Quecksilber dominieren die Forschung in der Speziesanalytik, und die Omics-Techniken entwickeln sich zu Multi-Omics-Ansätzen. Ambiente MS-Techniken benötigen keine aufwendige Probenvorbereitung, multidimensionale Trenntechniken werden verstärkt in der Routine eingesetzt, und Chip-basierte Trennungen fallen durch Schnelligkeit auf. Molekülspektroskopie und Massenspektrometrie dominieren die bildgebenden Verfahren, und die Lateralauflösung der ToF-Sekundärionenmassenspektrometrie hat sich bei Oberflächenuntersuchungen verbessert.
Active thermography is well suited for the detection of delaminations and cracks in façade elements like plaster and tiles. Not only artificial heating but also solar heating can be used if the adjustment of the façade and the weather conditions are suitable. Optical methods like laser scanners, photogrammetric methods and crack tracking sensors are providing geometrical 3D data which can be used for a 3D mapping of thermograms and for providing data with higher geometrical resolution. Thus, by the combination and fusion of these data, a comprehensive mapping and monitoring of damages of façade systems is possible.
Amongst various other NDT methods, within the EMRP-project
‘VITCEA’ active thermography is validated for testing of CFRP and
GFRP structures constructed for energy application. In this
contribution, the optical and thermal properties of CFRP and GFRP
reference defect artefact (RDA) and natural defects artefact (NDA)
test specimens are characterized. Different excitation techniques
and techniques for data analysis are compared for optimizing the
number of detected defects.
Rekonstruktion des Bestandsplans im Zuge der Nachrechnung der Brücke über die Leine bei Schwarmstedt
(2016)
Der aktuell im Rahmen der Nachrechnungsrichtlinie geforderte Nachweis von Tragfähigkeit, Gebrauchstauglichkeit und Ermüdung der Brückenbauwerke im Bestand der Länder und des Bundes stellt eine enorme Herausforderung dar. Insbesondere bei unvollständigen oder fehlenden Bestandsplänen der Bauwerke sind Maßnahmen erforderlich, um die erforderlichen Informationen zu beschaffen. Ein wirkungsvolles Instrument können hierfür die zerstörungsfreien Prüfverfahren des Bauwesens sein. In dem präsentierten Forschungsprojekt erfolgte die Rekonstruktion eines Bestandsplanes direkt auf die Anforderungen des mit der Nachrechnung beauftragten Ingenieurbüros. Darüber hinaus wurde der Entwurf eines Leitfadens erstellt, der im Falle von unvollständigen oder fehlenden Bestandsplänen die Grundlagen für die Beauftragung und Durchführung der Nachrechnung schafft.
The mechanism of nanotriangle formation in multivesicular vesicles (MMV) is investigated by using time-dependent SAXS measurements in combination with UV−vis spectroscopy, light, and transmission electron microscopy. In the first time period 6.5 nm sized spherical gold nanoparticles are formed inside of the vesicles, which build up soft nanoparticle aggregates. In situ SAXS experiments show a linear increase of the volume and molar mass of nanotriangles in the second time period. The volume growth rate of the triangles is 16.1 nm3/min, and the growth rate in the vertical direction is only 0.02 nm/min. Therefore, flat nanotriangles with a thickness of 7 nm and a diameter of 23 nm are formed. This process can be described by a diffusionlimited Ostwald ripening growth mechanism. TEM micrographs visualize soft coral-like structures with thin nanoplatelets at the periphery of the aggregates, which disaggregate in the third time period into nanotriangles and spherical particles. The 16 times faster growth of nanotriangles in the lateral than that in the vertical direction is related to the adsorption of symmetry breaking components, i.e., AOT and the polyampholyte PalPhBisCarb, on the {111} facets of the gold nanoplatelets in combination with confinement effects of the vesicular template phase.
Mit dem KorroPad Verfahren ist es dem Anwender möglich den Zustand der Passivschicht nichtrostender Stähle auf sehr einfache und schnelle Weise einschätzen zu können. Das Verfahren eignet sich dazu, den Grad der Passivität in Abhängigkeit der Umgebungsbedingungen und der Zeit nachzuvollziehen. Dies ermöglicht dem Anwender und Verarbeiter von nichtrostenden Stählen, die Lagerungsbedingungen und –zeiten einer frisch bearbeiteten Stahloberfläche zu ermitteln, welche für die Ausbildung einer stabilen Passivschicht notwendig sind, bevor diese risikoarm eingesetzt werden kann. Wie die hier dargestellten Beispiele und auch weitere zahlreiche praktische Anwendungen gezeigt haben, eignet sich das KorroPad ebenfalls für die Identifikation kritischer Prozessparameter bei der Verarbeitung nichtrostender Stähle. Mit dem Verfahren lassen sich viele prozessbedingte Einflussfaktoren auf die Oberflächengüte wie auch auf den Werkstoff charakterisieren. Aufgrund der schnellen und einfachen Auswertung der Prüfergebnisse können positive wie auch negative Veränderungen hinsichtlich der Passivschichtstabilität zügig erkannt werden. Dies ermöglicht es dem Anwender schnell zu reagieren, um kritische Einflüsse zu korrigieren und um eine Optimierung von Inhouse-Prozessen durchzuführen. Weitere Einsatzgebiete sind im Bereich der Wareneingangs- und/oder Warenausgangskontrolle denkbar, überall wo es um die Frage der Passivschichtstabilität einer nichtrostenden Stahloberfläche geht.
The nonlinear analysis became a common tool to precisely assess the load-bearing behavior of steel beam and column members. The failure level is significantly influenced by different types of imperfections, among geometric also structural imperfections (residual stresses). Here are still gaps in the knowledge. Nowadays, 3-D welding simulation developed to a level where it could provide reliable estimation of weld-induced distortion and residual stresses. Nevertheless, modelling and computational effort are still in a less practicable range. In this study a simplified procedure to implement residual welding stresses in continuous large scale members is proposed and the influence on the ultimate limit state of slender members in compression is evaluated for two common structural steel grades. The results showed significant improvements in the utilization of load bearing capacity compared with simplified design methods. The comparatively general approach in this study offers
potential for future optimization.
3D Crack analysis in hydrogen charged lean duplex stainless steel with synchrotron refraction CT
(2016)
Hydrogen in metals can cause a degradation of the mechanical properties, the so-called hydrogen embrittlement. In combination with internal stresses, hydrogen assisted cracking (HAC) can occur. This phenomenon is not completely understood yet. To better characterise the cracking behaviour, it is important to gain information about the evolution of the 3D crack network. For this purpose samples of lean duplex stainless steel were loaded with hydrogen by means of electrochemical charging and investigated by means of synchrotron refraction CT and SEM fractography after uniaxial tensile loading. Synchrotron refraction CT is an analyser-based imaging (ABI) technique. It uses a Si (111) single crystal as analyser, which is placed into the beam path between sample and detector. According to Bragg’s law only incident x-rays within a narrow range around the Bragg-angle are diffracted from the analyser into the detector. Hence, the analyser acts as an angular filter for the transmitted beam. This filtering allows to turn the refraction and scattering of x-rays into image contrast. Refraction occurs at all interfaces, where the density of the material changes and is more sensitive to density changes than the attenuation. Therefore, it is possible to detect smaller cracks than with classical x-ray imaging techniques, like CT, with comparable spacial resolution. It also visualises the 3D structure of the cracks and gains quantitative information about their morphology and distribution. Since cracks introduced by HAC are usually very small and have a small opening displacement, synchrotron refraction CT is expected to be well suited for imaging this cracking mechanism and can be a valuable tool to characterise the formation and the evolution of a 3D crack network.
We report on the development of ultra-small core-shell silver nanoparticles synthesized by an up-scaled modification of the polyol process. It is foreseen to use these thoroughly characterized particles as reference material to compare the catalytic and biological properties of functionalized silver nanoparticles. Small-angle X-ray scattering (SAXS) analysis reveal a narrow size distribution of the silver cores with a mean radius of RC = 3.0 nm and a distribution width of 0.6 nm. Dynamic light scattering (DLS) provides a hydrodynamic radius of RH = 10.0 nm and a PDI of 0.09. The particles’ surface is covered with poly(acrylic acid) (PAA) forming a shell with a thickness of 7.0 nm, which provides colloidal stability lasting for more than six months at ambient conditions. The PAA can be easily exchanged by biomolecules to modify the surface functionality. Replacements of PAA with glutathione (GSH) and bovine serum albumin (BSA) have been performed as examples. We demonstrate that the particles effectively catalyze the reduction of 4-nitrophenol to 4-aminophenol with sodium borohydride. With PAA as stabilizer, the catalytic activity of 436 ± 24 L g⁻¹ s⁻¹ is the highest reported in literature for silver nanoparticles. GSH and BSA passivate the surface substantially resulting in a catalytic activity of 77.6 ± 0.9 and 3.47 ± 0.50 L g⁻¹ s⁻¹, respectively.
The most substantial innovations in radiographic imaging techniques of the last two decades aim at enhanced image contrast of weakly absorbing micro and nano structures by taking advantage of X-ray refraction effects occurring at outer and inner surfaces. The applications range from fibre reinforced plastics to biological tissues. These techniques comprise, among others, X-ray refraction topography, diffraction enhanced imaging, phase contrast imaging, Talbot-Lau grating interferometry, and refraction enhanced imaging. They all make use of selective beam deflections up to a few minutes of arc: the X-ray refraction effect. In contrast to diffraction, this type of interaction has a 100 % scattering cross section, as shown experimentally. Since X-ray refraction is very sensitive to the orientation of interfaces, it is additionally a tool to detect, e.g., fibre or pore orientation. If the detector resolution exceeds the size of (small) individual features, one detects the integral information (of inner surfaces) within the gauge volume. We describe the above-mentioned techniques, and show their experimental implementation in the lab and at a synchrotron source. We also show strategies for data processing and quantitative analysis.
A new cocrystal of pyrazinamide with oxalic acid was prepared mechanochemically and characterized by PXRD, Raman spectroscopy, solid-state NMR spectroscopy, DTA-TG, and SEM. Based on powder X-ray diffraction data the structure was solved. The formation pathway of the reaction was studied in situ using combined synchrotron PXRD and Raman spectroscopy. Using oxalic acid dihydrate the initially neat grinding turned into a rapid self-accelerated liquid-assisted grinding process by the release of crystallization water. Under these conditions, the cocrystal was formed directly within two minutes.
Carbon arc-air gouging is a common technology when repairing defects in welded structures. Often this technique is applied in repeated cycles even on the same location of the joint. Due to the multiple heat input by gouging and subsequent re-welding, the residual stresses are strongly influenced. This can become crucial when microstructure and mechanical properties are adversely affected by multiple weld reparations. Knowledge about the relation of gouging and residual stresses is scarce but important when high strength steels, which are sensitive to residual stresses, are processed. The present study shows the effect of repair welding on a high strength steel structural element. The weld and the heat affected zone were subjected to multiple thermal cycles by gouging and subsequent repair welding. The residual stresses were determined by X-ray diffraction at different positions along the joint. The results showed that the residual stress level has increased by the repair cycles. This is most pronounced for the heat affected zone. Adapted welding procedures may prevent detrimental residual stress distributions.
The permanently increasing number of wind turbines requires suited inspection and monitoring methods to ensure liability and security. Concerning the inspection of ro-tor blades, only manual inspections are state of the art. Thermographic Testing (TT) has the potential to detect typical failures and damages on rotor blades. The paper presents some results of onsite measurements carried out as “passive thermogra-phy”, i.e. without a defined heating procedure. Due the totally contactless meas-urement principle, TT can be applied to rotating blades as well as to resting blades. Both methods will be compared with respect to their possible realization.
In respect of modern approaches in material sciences and highly increased
requirements on materials on safety relevant components, quality management
and non-destructive testing reclaims a steadily increased meaning. The
destructive meaning of measuring the degree of purity is defined in DIN EN 10247
through metallurgical investigations, especially microsections.
For and comparable, but non-destructive testing due ultrasonic testing, the material
the SEP 1927 is a well-defined industry standard. A novel and alternative way
of reference block construction was focused by this work. The proposed amendments,
regarding the manufacturing and machining, are less time and cost consuming.
Verified by measurements the presented reference block fits the same acoustical
characteristics and the requirements of the guideline.
With increased usage of highly demanded, modern materials on safety
relevant parts (e.g. railway wheel sets, generator shafts, turbine disks, medical
implants, etc.) comprehensive analyses regarding the quality of the material are
requested. This gives a focus to non-destructive methods using ultrasound immersion
tank testing for classifying the degree of purity. Two autonomous standards,
ASTM E588 and SEP 1927, have been established for the definition, execution and
evaluation for this high resolution ultrasonic measurements on steel products.
The propagation of ultrasonic waves and the resulting sound field are strongly
dependent on the acoustical properties of the inspected material and the geometry
of probes and specimen. The definition of the measurement setup and the evaluation
methods appear to differ significantly in the given standards. ASTM E588 and
SEP 1927 prescribe the requirement for surface roughness and probe selection, are
using threshold based methods for cleanliness detection, but differ in computation
for the degree of purity. This has been the motivation for a comparison between
both standards with the main focus on amplitude depth dependency and overall spatial
resolution taking the influence of different material characteristics, geometry of
the specimen and sound fields into account.
A performance comparison between the use of non-focusing and focusing probes
respective to the threshold based detection will be presented in this contribution. In
addition, the usage of complex reconstruction algorithms (e.g. SAFT, echo tomography)
is compared with the traditional approaches of inclusion detection and
estimation of the degree of purity
Ein wesentliches Grundbedürfnis ist die Sicherheit, d. h. die Gewissheit, in einer sicheren Umgebung zu leben und zu arbeiten. Die existenzielle Sicherheit ist eine notwendige Voraussetzung zur Befriedigung aller weiteren notwendigen Bedürfnisse. Auch die Technik ist ohne Sicherheit nicht denkbar. Trotz aller Bemühungen kommt es aber immer wieder zu Unfällen, aus welchen Gründen auch immer. Eine Strategie, Unfälle zu verhindern bzw. deren Eintrittswahrscheinlichkeit zu minimieren ist es, zwischen einem Objekt mit einem hohen Gefährdungspotenzial und seiner Nachbarschaft, Barrieren zu errichten, z. B. durch eine schützende Isolierung, Sicherheitsabstände oder durch eine Erdüberdeckung. Die erdgedeckte Verlegung von Pipelines ist Stand der Technik. Über die Überdeckungshöhen scheint es jedoch verschiedene Auffassungen zu geben. Im folgenden Beitrag werden dazu einige Beispiele vorgestellt.
A combined analysis of EXAFS and Raman spectra is applied for the study of
InxGa1-xN alloys with 0.3<x<0.5. Alloying causes relaxation of the selection rules resulting in
Raman spectra that resemble the vibrational density of states. On the other hand, theoretical
simulation of the Raman spectra using the Equation of Motion routine of FEFF8 provides the
vibrational component of the Debye-Waller factor (DWF). The static disorder component of
the DWFs was obtained by fitting the Ga and In K-edge EXAFS spectra. The analysis revealed
that the nearest neighbor distances of the 1st and 2nd shell deviate from the values predicted by
the law of Vegard and the virtual crystal approximation. The static disorder in the first nearest
neighboring shell (In-N and Ga-N) is null whereas in the cation-cation neighboring shells the
static component is generally smaller than the vibrational.
The usefulness and purpose of evaluating nondestructive testing (NDT) systems and their capabilities has changed in the last decade. The conventional method of simply applying a familiar statistical algorithm to say whether the system is usable for the tasks is history.
Nowadays, multiple parameter methods which describe the probabilities of detection (POD) of different systems or real defects need new characteristics and a broader variety of statistical models to describe the true system behaviour. The appraisal of the NDT system involves diverse departments within a company (engineering, NDT-operators, and statisticians), but is, at the same time, more needed and requested than in the past. In this article, an approach is discussed in which professionals from different fields worked well together, accomplishing cost-intensive metallographic studies in correlation with well-understood physical behaviour of NDT-methods as well as deep-discussed mathematical methods to create a holistic evaluation of the technical reliability for a specific radiographic testing (RT) equipment. The first part of the publication will show the comparison between metallographic grinding and the RT indications. An essential innovation over past evaluation methods was the use of a multi-scale smoothing algorithm, which describes physical parameters, which were not used in evaluation like the POD in this way in the past.
In the second part the statistical requirements for the POD take the focus. It can often be hard to make significant statements; especially in the case where only a small amount of data is available. The combination of data and the use of knowledge from simulations are essential. One possible solution will be shown for the RT evaluation. The methodology is used for evaluating the digital RT system for the inspection of electron-beam welds, which was method considered to seal the Finnish copper canisters for the final deposit of spent nuclear fuel.
Immuno imaging by the use of Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS) is a growing research field in life sciences such as biology and biomedicine. Various element labeling strategies for antibodies have been developed for the application of multiplex immunoassays analyzed by the use of LA-ICP-MS. High multiplexing capabilities, a wide linear dynamic range and the possibility of absolute quantification are the main advantages of ICP-MS. But in the context of immuno imaging by the use of LA-ICP-MS, quantification of analytes is limited due to non-controllable antibody labeling chemistry. In the presented proof-of-principle a novel antibody labeling technique has been investigated which results in a controlled labeling degree. A small affinity protein based on the C2 domain of protein G was modified with conventional metal coded tags (MeCAT) after introducing a cysteine into the C-terminus of the protein. The modified C2 domain photo-crosslinks to the Fc or Fab region of the IgG and allows specific and covalent labeling of antibodies for multiplex immunoassay analysis by the use of LA-ICP-MS. In combination with a house-made calibration membrane the amount of labeled antibody–antigen complexes in a multiplex western blot immunoassay was determined by LA-ICP-MS.
In this contribution, we discuss the influence of scattered radiation on materials’ effective attenuation coefficients at higher X-ray energies. The selected X-ray spectra for the dual-energy experiments correspond to 3 MV and 7.5 MV acceleration potential of the used betatron. Experiments were performed on a test phantom containing step wedges of different low- and high-Z materials. We evaluated the ratio between low- and high-energy X-ray attenuation coefficients quantitatively based on simulated poly-energetic high-energy X-ray source spectra and the detector sensitivity using the “analytical Radiographic Testing inspection simulation tool” (aRTist) developed at BAM. Furthermore, the influence of scattered radiation is evaluated using an efficient Monte-Carlo simulation. The simulation results are compared quantitatively with experimental investigations. Finally, important applications of the proposed technique in the context of aviation security are discussed.
X-ray backscatter imaging is a well established NDT technique to inspect complex objects using only a single-sided access. In difference to conventional transmission X-ray radiography, the X-ray backscatter imaging utilizes the scattered radiation caused by the Compton scattering effect. In order to achieve high backscatter intensities from a test object, it is necessary to optimize the backscatter system parameters namely the angle between source and slit camera, the slit collimator system, the shielding between source and scatter camera, and the type of detector. In addition, the scatter phenomena in to the investigated object need to be understood.
In this contribution, we present a Monte Carlo model McRay which considers all relevant single and multiple interactions of photons and electrons. This model can be used to simulate back scatter techniques. It allows not only calculating the scatter image for a given experimental setup but also registering the spectrum of the detected scattered photons. Both aspects are important to understand the imaging process, to interpret the results, and to optimize the backscatter camera investigated here. Additionally experimental results will be presented and compared with simulations.
Injection of poly(methyl methacrylate) cements, one standard Treatment for osteoporotic vertebral body fractures, may lead to critical loads and subsequent fractures in adjacent vertebral bodies. Biodegradable calcium phosphate cements (CPC) with bioinductive growth factors may be an alternative, since they have a Young’s modulus comparable to that of cancellous bone. Non-destructive tests with μCT and quantitative Image evaluation are used to assess new bone growth and material resorption following intravertebral injection of CPC. Immediate deep-freezing of excised bone prevents shrinkage or tissue disintegration and the samples have to be kept frozen for all following steps, including transport, μCT measurements, and subsequent biomechanical tests. Here we will report on a set-up to preserve the frozen state of the material and allow stable long-term serial μCT measurements. In addition, the image processing technique for the evaluation of bone growth and selected results on subsequently carried out compressive strength tests will be presented.
Titanium dioxide (TiO₂) nanoparticles (NPs) are one of the main sources of the nanoparticulate matter to which humans are directly exposed and several studies have demonstrated their potential toxic effects. The in vivo detailed spatial distribution of TiO₂ NPs is investigated herein for the first time, using a 2D chemical imaging analysis based on confocal Raman spectroscopy. The invertebrate nematode C. elegans was employed as a prototypical model of living organisms. Rod, bipyramidal and quasispherical engineered TiO₂ NPs with different primary particle sizes and agglomeration states were prepared, characterized and then administered to nematodes. Exploiting the typical fingerprint of TiO₂ in the Raman spectrum, we monitored the biodistribution of NPs inside the worm using a non-invasive, label-free method. The high spatial resolution chemical imaging and the specificity of the Raman technique in the localization of TiO₂ NPs helped in the design of behavioral C. elegans studies aimed at elucidating the relationship among the size, shape, and agglomeration state of NPs and their ability to induce specific toxic effects. Rod-shaped NPs were the most toxic, greatly impairing pharyngeal function, reproduction and larval growth; this indicates that the rod shape, more than the bipyramidal and spherical shapes, enables NPs to interact with biological systems. These findings indicate that this Raman-nematode combined approach represents a step forward in the field of detection of NPs in living organisms, and being rapid and inexpensive enough, it can be applied as the first screening for the ability of NPs to biodistribute and exert toxicological properties in vivo.
A permanent-magnet synchronous motor (PMSM) servo drive for lightweight robotic platforms that have a high torque demand at low rotational speeds has been developed. First, a current-independent torque controller is derived and cascaded with a speed and position controller, while merely an encoder is used as a sensor device in combination with a speed estimator. Finally, the speed estimator output is compared to gyroscope measurements and the overall functioning is verified on a real system.
Safety assessment of nanoparticles (NPs) requires techniques that are suitable to quantify tissue and cellular uptake of NPs. The most commonly applied techniques for this purpose are based on inductively coupled plasma mass spectrometry (ICP-MS). Here we apply and compare three different ICP-MS methods to investigate the cellular uptake of TiO2 (diameter 7 or 20 nm, respectively) and Ag (diameter 50 or 75 nm, respectively) NPs into differentiated mouse neuroblastoma cells (Neuro-2a cells). Cells were incubated with different amounts of the NPs. Thereafter they were either directly analyzed by laser ablation ICP-MS (LA-ICP-MS) or were lysed and lysates were analyzed by ICP-MS and by single particle ICP-MS (SP-ICP-MS).
Applications of fibre reinforced plastic (FRP) composites in modern industries are increasing due to their considerable advantages such as light weight and excellent mechanical properties. Accordingly, importance of operational safety of modern structures made of advanced composites by ensuring the material quality has led to increasing demands for development of non-destructive evaluation (NDE) systems. In the context of a European project entitled “Validated Inspection Techniques for Composites in Energy Applications” (VITCEA), the aim is to develop and validate traceable procedures for novel NDE techniques with contrasting damage detection capabilities in energy related applications such as wind and marine turbine blades, nacelles, oil and gas flexible risers. Accordingly, VITCEA focuses on optimization of ultrasonic tests (UTs) for quantitative defect detection and quality characterization of FRP structures. In this context, the present study describes the ultrasound field in heterogeneous composite materials. The theoretical predictions are compared with simulation results obtained from CIVA a software package dedicated to NDT simulations based on the asymptotic ray theory.
Analyzing the reliability of non-destructive tests using the modular modell - a practical approach
(2016)
Non-destructive testing is an important tool to guarantee the safety of railway traffic.
The infrastructure with tracks, switches and sleepers is regularly tested, the
locomotives and wagons with their wheels, bogies and axles as well. Many years of experience and some events lead in Germany to a good practice in testing the railway components. Now, European authorities are drafting a system of common requirements and standards for the European Railway Market. The German practice combines an intensive training of the NDT-personnel including sufficient time for practical exercises with organizational measures of the companies, responsible for rolling stock and infrastructure. Through the example of UT-testing of railway axles it will be shown, how training and organizational measures influence the reliability of such testing.
Advances in scanning electron microscopy (SEM) enable the high-resolution imaging of single nanoparticles (NPs) with sizes well below 10 nm. The SEM analysis in transmission mode (T-SEM) of NPs on thin film supports has many benefits when compared to the analysis of NPs on bulk substrates. The enhanced material (mass – thickness) contrast of the T-SEM imaging mode is well suited for in-depth and, particularly valuable, to very accurate, traceable, lateral dimensional measurements of NPs. Compared to samples prepared on bulk substrates, T-SEM with energy dispersive X-ray spectroscopy (EDS) achieves a drastically improved spatial resolution of the emitted X-rays. The poor signal-to-noise ratio of the X-ray spectra emitted by a single nanoparticle (NP) can be improved by the use of high-sensitivity (high collection solid angle) silicon drift (SDD), energy-dispersive X-ray spectrometers (EDS). The EDS spectral imaging of a single NP with a spatial resolution below 10 nm has become possible. This is demonstrated by means of various examples of nanostructures. Advanced data processing of T-SEM/EDS results sets the stage for the automated classification of NPs by feature analysis. This method combines the detection of morphological structures of interest by image processing of T-SEM micrographs with the chemical classification by EDS.
Amino acid analysis is considered to be the gold standard for quantitative peptide and protein analysis. Here, we would like to propose a simple HPLC/UV method based on a reversed-phase separation of the aromatic amino acids tyrosine (Tyr), phenylalanine (Phe), and optionally tryptophan (Trp) without any derivatization. The hydrolysis of the proteins and peptides was performed by an accelerated microwave technique, which needs only 30 minutes. Two internal standard compounds, homotyrosine (HTyr) and 4-fluorophenylalanine (FPhe) were used for calibration. The limit of detection (LOD) was estimated to be 0.05 µM (~10 µg/L) for tyrosine and phenylalanine at 215 nm. The LOD for a protein determination was calculated to be below 16 mg/L (~300 ng BSA absolute). Aromatic amino acid analysis (AAAA) offers excellent accuracy and a precision of about 5% relative standard deviation, including the hydrolysis step. The method was validated with certified reference materials (CRM) of amino acids and of a pure protein (bovine serum albumin, BSA). AAAA can be used for the quantification of aromatic amino acids, isolated peptides or proteins, complex peptide or protein samples, such as serum or milk powder, and peptides or proteins immobilized on solid supports.