Filtern
Erscheinungsjahr
- 2012 (694) (entfernen)
Dokumenttyp
- Zeitschriftenartikel (404)
- Beitrag zu einem Tagungsband (221)
- Beitrag zu einem Sammelband (20)
- Buchkapitel (19)
- Dissertation (8)
- Vortrag (6)
- Sonstiges (4)
- Forschungsbericht (4)
- Monografie (2)
- Sammelband (Herausgeberschaft für den kompletten Band) (2)
Sprache
- Englisch (694) (entfernen)
Schlagworte
- Concrete (16)
- Simulation (11)
- Fluorescence (10)
- Corrosion (9)
- Flame retardancy (9)
- Steel (8)
- Computed tomography (7)
- Non-destructive testing (7)
- Radiography (7)
- SAXS (7)
Eingeladener Vortrag
- nein (6)
The ground vibrations, which are generated by trains on different slab tracks, have been calculated by finite-element boundary-element models. The slab track is modelled in detail by the finite element method.
The infinite soil is modelled by the boundary element method as a homogeneous half-space. The track-soil system is coupled with a simple rigid mass model of the vehicle so that the vehicle-track interaction is completely included. Transfer functions are calculated in frequency domain without and with vehicle-track interaction, the compliance of the track and the mobilities of the soil at different distances from the track.
Finally, the ratios between the ground vibration amplitudes with and without mitigation measure are calculated to quantify the effectiveness of the mitigation measure.
Tracks with under sleeper pads have been investigated in a parameter study. The main parameter that influences the reduction of ground vibration is the stiffness of the under sleeper pad. The softest sleeper pad yields the best reduction of the ground vibration.
The influence of other parameters has been examined. The stiffness of the rail pads, the stiffness of the slab material, the stiffness of the sleeper material, and the distance of the sleepers. All these parameters show no or only a minor influence on the mitigation effect.
As the standard isolated track, a track with an under sleeper pad of a stiffness of kS = 5 107 N/m has been chosen, which can also be expressed as a stiffness per area of kS ’’ = 3.7 107 N/m3 = 0.037 N/mm3.
The resonance frequency for this pad stiffness is observed between 32 and 40 Hz. The reduction of the ground vibration is about vi,I /vi,U = 0.1 at 100 Hz.
Downsizing (power-to-weight ratio) and higher speeds lead to a rise in Hertzian contact pressures in combination with an increase in surface or oil temperatures. Under such conditions, commonly used bearing steels, such as 100Cr6, reach their limits, creating a demand for alternative slip-rolling resistant steel alloys. The present work therefore compares the slip-rolling performance of various steel types with Maraging- and PM-type steel alloys such as e.g. CSS-42L™, ASP2012, BIMAX42+, in the Hertzian contact pressure range up to P0max of 4 GPa. Through-hardened 100Cr6H (AISI 52100), case-hardened 20MnCr5 (AISI 5120H) and nitrogen alloyed Croni-dur30 (AMS 5898) still compete in terms of slip-rolling and wear resistance and load carrying capacity, whereas Maraging- and PM-type steel alloys offer superior strength and toughness properties.
So test therefore
(2012)
Coatings, adhesive-bonded joints and composites have to be tested for their adhesive, bonding and tensile strength. Until now, these tests have been time-consuming single-sample tests in a tensile testing machine. By means of centrifuge technology, tests are much easier now as centrifugal force serves as testing force. Scientists at BAM have developed the test principle, the implementation of this new technology in a testing device was realized by LUM GmbH. In recognition of innovative hard and software solutions, the Berlin-Brandenburg Innovation Award 2012 was given to LUM GmbH.
Nebulizing of polymer solutions, in a high-voltage field under atmospheric conditions by electrospray ionization (ESI), is a comfortable way to deposit ultra-thin layers of polar or ionic polymers onto any conductive substrate materials. The substrate is grounded and the polymer solution is sprayed through a powered capillary. The formed charged droplets shrink by solvent evaporation during their way to the grounded substrate, the charges close ranks and the droplets collapse consecutively by charge repulsion, thus forming finally charged single macromolecules. After their discharging at the grounded substrate, an ultrathin ‘quasi-monomolecular’ polymer layer is formed. It could be shown by imaging of scratches through the polymer layer by atomic force microscopy that the deposited polymer layers are dense at a thickness of about 10 nm. Carbon fibre bundles were coated with poly (allylamine) (PAAm) or poly(acrylic acid) (PAA) as potential adhesion-promoting layers in fibre–polymer composites. The polymer deposition is self-inhibiting after formation of a continuous coverage of about 200 nm for PAAm and 30 nm for PAA as result of surface charging. Continuous deposition onto such isolating layers or polymers without charging can be achieved by using current of alternating polarity. The film formation is self-healing because of the electrophoretic effect, i.e. the ion discharging occurs preferentially at noncoated areas. This electrophoretic effect of ESI was demonstrated by completely enwrapping all the carbon fibres of the roving within a distance of about 100 μm far from its outside and also at the backside of the fibre bundle with about 80% of the topside coverage, as measured by X-ray photoelectron spectroscopy and visualized using scanning electron microscopy.
Globally, cement and concrete experts are at the cutting-edge to sustainable, green, healthy but nonetheless high-performance concrete. Today concrete is not yet well established in Africa, which offers the unique opportunity to build up a cement and concrete market based on the highest available state of technology. As this industry needs high level expertise, a central issue in implementation of skilled technology is crosslinking research institutions and laboratories. It should not be neglected that concrete is a product with low transport ranges. This means that an improved concrete market mainly supports the local economy without exceeding financial drains to the international market. Thus it fosters the fight against poverty, which is an urgent need in most African countries. The project aims to cross-link experts with industry and policy making bodies, aiming to establish sustainable cement and concrete construction in Africa.
A facile and versatile synthetic route for controlling the size and surface potential of organic–inorganic hybrid silica nanoparticles (NPs) is introduced in this paper. For polymer-grafted NPs, the density of polymer chains on the surface is strongly affected by the concentration of precursor. Nevertheless, for condensed NPs, the precursor concentration determines the particle size but not the density of polymer chains on the surface or the adsorption of bovine serum albumin (BSA). Results presented here may have Major implications in biomedical and colloidal chemistry since interfacial and colloidal properties are known to drive several processes associated with nanoparticles in biological media.
Automotive brake pads consist of many components but it is still not entirely clear which role each of the elements of this complex composition plays to provide the specified regimes of sliding. This is due to the mutual interaction of multiscale mechanisms, realized during the friction.
In this work we have attempted to partly answer this question using computer simulations. Since the simulation allows us to consider various combinations of the structure of the system being simulated ceteris paribus, it becomes possible to understand the role of each constituent sequentially. The main attention is paid to the structure and composition of the thin film that forms on the surface of both bodies as a result of compaction of the wear product, its chemical composition and oxidation. This layer, also named a third body or friction film, differs in composition and microstructure from the two first bodies. We considered a single contact for the steady state sliding when the structure and composition of friction films already are formed. As a modelling tool we used the method of movable cellular automata, which has well proven itself in solving of such tasks. We investigated the influence of modification of the structure and composition of the third body on the features of system behaviour at friction. To assess the adequacy of the numerical model, experimental studies with an artificial third body were also carried out. The Simulation results are in good agreement with experimental data.
Meteorites are a unique and inspiring material for microstructural studies because if their very specific genesis. Iron meteorites have been formed under unimaginable cooling rates of a few ten Kelvins per million years so that the observable transformation of the formerly huge Fe-Ni single crystals of taenite occurred under nearly-equilibrium conditions. Octahedrites (meteorites having a Ni content between 6...15%) are characterized by ribbons of the low-temperature Fe-Ni phase kamacite separated by rims of residual taenite. This very specific feature is known as Widmanstaetten structure and has been investigated by synchrotron radiation in order to cover a higher volume fraction for a statistically relevant description of orientation relationships. However, plessite – a microstructure mainly consisting of the same phases – reflects the orientation relationship between kamacite and taenite as well. For their characterization, a scanning electron microscope is very suitable in order to investigate crystal orientations or identify phases. Despite the apparently ideal formation circumstances of iron meteorites, Ni concentration profiles prove non-equilibrium conditions. Combined EDS (energy dispersive spectroscopy) and EBSD (electron backscatter diffraction) measurements at a selected plessitic region of the Cape York iron shows that a correlation exists between Ni-concentration and the locally detected orientation relationship.
Ionic Liquids (ILs) are employed in various fields, for example, reaction engineering (reactions with gases, such as hydroformylation (CO, H2), hydrogenation (H2), oxidation (O2)) or separation technology (separations of gases, reactants, and high-volatility reaction products). For the basic engineering of such processes, knowledge of phase equilibria, particularly of mixtures, over a broad (p,T) range is mandatory. This contribution reports on recent experimental results from our laboratory: – for the simultaneous solubility of a binary gas mixture in a pure ionic liquid – for the solubility of a single gas in a binary liquid solvent mixture.
Declining European natural gas resources and increasing legislation mean that diversification towards ‘non-conventional gases’ is essential. Accurate and traceable measurements of the composition of non- conventional gases are required to ensure gases can be transported in existing pipeline networks, and used with existing appliances. The EMRP ‘Characterisation of energy gases’ project is successfully developing a metrology infrastructure to underpin these measurements. New standards and methods have been developed for biogas composition, biogas impurities, coal mine gases, refinery gases and environmentally-friendly odorants. The project is set to conclude in 2013 with the challenging analysis of a series of real non-conventional gas samples.
In the last two decades, the solubility of gases in ionic liquids has attracted a lot of attention. While at the beginning most publications dealt with the solubility of a single gas in a pure ionic liquid, recently the interest starts to shift to the – from an application-oriented point of view – more challenging area of the simultaneous solubility of several gases in an ionic liquid and/or the solubility of a single gas in solvent mixtures with ionic liquids. The current state of information on experimental data (and the phenomena encountered) in such systems is summarized and discussed.
A simple and efficient method of preparing composites of carbon nanotubes and titania (CNT-TiO2) is reported via a microwave-assisted synthesis in an ionic liquid, [bmim][BF4]. CNT-TiO2 nanocomposites were formed by the thermal decomposition of titanium (IV) isopropoxide (Ti(OPri)4) in the presence of CNTs under microwave irradiation. The obtained product was characterized by BET surface area, XRD, SEM, and TEM. TiO2 particles with average size of 9 nm were as anatase. The surface area of the Composites increased with an increase of CNT content. Moreover, the catalytic efficiency of the composite was investigated through the photoelectrodegradation of methylene blue.
The risk assessment of total petrol hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAH), two of the most frequent soil and water contaminants, has to include their exposure pathways, especially the soil groundwater pathway. Threshold values have to be aquired for the amendment to the German Federal Soil Protection Contaminated Sites Ordinance. For this purpose, a batch experiment with a liquid to solid ratio (L/S) of 2 L/kg was developed. Aim of this work was to verify the robustness of this leaching procedure for TPH and PAH in different soil types against varying test conditions. Also, stir bar sorptive extraction (SBSE) was tested as alternative sample preparation of eluates for PAH analysis.
This paper presents a numerical and an experimental procedure to obtain the pressure field in single-axis acoustic levitators. Numerically, the pressure field is determined by a matrix method based on the Rayleigh integral that take into account the multiple wave reflections that occur between the transducer and the reflector. The numerical pressure field is compared with the acoustic pressure measured by an earplug microphone, that is connected to a hollow needle. The tip of the needle is moved by a µm translation stage through the field and the signal is recorded using a lock-in amplifier locked to the levitator frequency. The pressure field obtained numerically show good agreement with that obtained experimentally.
Ground vibrations created by running high-speed trains at speeds between 100 and 320 km/h are calculated in detail using transfer functions to model the effects of the moving loads. These transfer functions for layered soils are obtained by integration in the wavenumber domain. The train-induced vibrations in a soil that is considered to consist of single layers of two slightly different soils are analysed for different excitations: for their spectra, attenuation laws and amplitude-speed relations. An important mid-frequency component is shifted through the cut-on region of the layered soil with an increase in the train speed. The cut-on frequency divides the response of the layered soil into a low-frequency low-amplitude range and a high-frequency high-amplitude range. This leads to completely different train speed dependencies for the two soil layers with strongly increasing amplitudes around the cut-on frequency and almost constant amplitudes beyond this frequency. All calculated results closely agree with ground vibration measurements at two corresponding sites, especially if the mid-frequency component is calculated by axle impulses.
Effects of amorphous nano-silica additions on mechanical and durability performance of SCC mixtures
(2012)
In the recent years the application of nanotechnology in building materials has increased
exponentially. One of the most referred and used nano-materials is amorphous silica with
particles size in the nano-range, even though its application and effect in concrete has not been
fully understood yet. It has been reported that nano-silica (nS) addition increases the
compressive strength and reduces the overall permeability of hardened concrete due to the
pozzolanic properties which are resulting in finer hydrated phases (C-S-H gel) and densified
microstructure (nano-filler and anti leaching effects). These effects enhance the durability of
concrete structures such as bridges, quays or off-shore oil facilities in marine environments.
In this study two different types of nano-silica were applied in self-compacting concrete (SCC),
both having similar particle size distributions (PSD) but produced in two different processes
(fumed powder silica and precipitated silica in colloidal suspension). The influence of nanosilica
on SCC was investigated with respect to the properties of concrete in the fresh state
(workability) and hardened state (mechanical properties and durability). Additionally, the
densification of microstructure of the hardened concrete was verified by SEM and EDS analyses.
The obtained results demonstrate that an efficient use of nano-silica in SCC can improve its
mechanical properties and durability. Considering the reactivity of the two nano-silica studied,
colloidal type shown more reactivity at early age, which influenced all the final SCC properties.
The aim of this comparison was to demonstrate the capability of national metrology institutes to measure elemental mass fractions at a level of w(E) ≈ 1 g/kg as found in almost all mono-elemental calibration solutions. These calibration solutions represent an important link in traceability systems in inorganic analysis. Virtually all traceable routine measurements are linked to the SI through these calibration solutions. Every participant was provided with three solutions of each of the three selected elements chromium, cobalt and lead. This comparison was a joint activity of the Inorganic Analysis Working Group (IAWG) and the Electrochemical Analysis Working Group (EAWG) of the CCQM and was piloted by the Physikalisch-Technische Bundesanstalt (PTB, Braunschweig, Germany) with the help of the Bundesanstalt für Materialforschung und -prüfung (BAM, Berlin, Germany), the Centro Nacional de Metrología (CENAM, Querétaro, Mexico) and the National Institute of Standards and Technology (NIST, Gaithersburg, USA).
A small majority of participants applied inductively coupled plasma optical emission spectrometry (ICP OES) in combination with a variety of calibration strategies (one-point-calibration, bracketing, calibration curve, each with and without an internal standard). But also IDMS techniques were carried out on quadrupole, high resolution and multicollector ICP-MS machines as well as a TIMS machine. Several participants applied titrimetry. FAAS as well as ICP-MS combined with non-IDMS calibration strategies were used by at least one participant. The key comparison reference values (KCRV) were agreed upon during the IAWG/EAWG meeting in November 2011 held in Sydney as the added element content calculated from the gravimetric sample preparation. Accordingly the degrees of equivalence were calculated. Despite the large variety of methods applied no superior method could be identified. The relative deviation of the median of the participants' results from the gravimetric reference value was equal or smaller than 0.1% (with an average of 0.05%) in the case of all three elements.
European and Germany regulations demand an elaborate waste management to save natural resources, reduce waste volumes deposited at landfills and enhance sustainable development by recycling of various residues. Research into the use of these materials in the construction sector and other fields is a positive step forward in achieving these objectives. BAM shares its latest findings.
Traditional earthen structures of cultural value are often damaged by static or dynamic loads. This is usually manifested by the appearance of cracks. All too often these cracks are insufficiently or inappropriately repaired if at all because of lack of knowledge and/or technology. In particular, the behavior of crack repair by grouting poses a challenge in earthen materials and demands specific requirements for the grouting mortar, such as low water content, good water retention, low shrinkage, etc. If dynamic loads, e.g. induced by earthquakes, are expected, the grouting material requires additional specifications such as a compatible strength and modulus of elasticity as well as good adhesion to the earthen materials. The study presents results from the development of a grouting material based on hydraulic lime mortar suitable for the repair of cracks in a variety of earthen building techniques. The goal was to develop a material also compatible with earthen structures exposed to dynamic load. The grouting mortar was designed to be adaptable in strength properties and at the same time to have sufficient robustness for the use on the construction site. First results show a satisfactory performance of the grout concerning fresh and hardened mortar properties as well as injectability. The study is part of our work in the framework of the ongoing project NIKER, funded by the European Commission dealing with improving imovable Cultural Heritage assets against the risk of earthquakes.
Both in developed and developing countries, modern building materials tend to be preferred to traditional earthen construction. Reasons include low durability, inadequate performance under seismic loading and, in developing countries, a wish to replace what is perceived as 'poor' with what is perceived as 'rich'. In an age when building permissions and construction standards are a must, particularly in seismic areas, even when an owner is willing to build in earth, construction approval needs to be granted: we rely on values and standards to build, but the necessary data on material properties and structural performance of earthen building techniques is scarce if compared to the abundance of data for other materials (clay brick masonry, concrete, steel) available to the engineer. At the same time, traditional builders' skills, knowledge and confidence in earthen building techniques are decreasing if not disappearing. A wallette testing campaign was thus carried out with the aim of filling this knowledge gap. Prior to the wallette campaign, material properties, including composition and physical-mechanical parameters, were determined. Compression and diagonal compression (shear) tests were then performed, and a basic analysis of the mechanical behaviour of structural elements built in cob is provided in relation to earth block (adobe) masonry and rammed earth elements. Cob, shown to have low compressive resistance, has a relatively ductile post-peak behaviour if compared to earth block masonry specimens which, as expected, show a marked brittle behaviour. In terms of shear strength, cob performs relatively well in view of its low compressive strength. The study is part of our work within the framework of the ongoing project NIKER funded by the European Commission dealing with improving the structural performance of Cultural Heritage assets in order to limit earthquake hazards.
Methodological aspects for finite element modelling of lid systems for type B(U) transport packages
(2012)
The regulatory compliance of the containment system is of essential importance for the assessment process of Type B(U) transport packages. The requirements of the International Atomic Energy Agency safety standards for transport conditions imply high loading on the containment system. The integrity of the containment system has to be ensured in mechanical and thermal tests. The containment system of German spent nuclear fuel and high level waste transport packages usually includes bolted lids with metal gaskets. The finite element (FE) method is recommended for the analysis of lid systems according to the guideline BAM-GGR 012 for the assessment of bolted lid and trunnion systems. The FE analyses provide more accurate and detailed information about loading and deformation of such kind of structures. The results allow the strength assessment of the lid and bolts as well as the evaluation of relative displacements between the lid and the cask body in the area of the gasket groove. This paper discusses aspects concerning FE simulation of lid systems for type B(U) packages for the transport of spent nuclear fuel and high level waste. The work is based on the experiences of the BAM Federal Institute for Materials Research and Testing as the German competent authority for the mechanical design assessment of such kind of packages. The issues considered include modelling strategies, analysis techniques and interpretation of results. A particular focus of this paper is on the evaluation of the results with regard to FE accuracy, influence of the FE contact formulation and FE modelling techniques to take the metallic gasket into account.
In Germany, the mechanical and thermal safety assessment of approved packages for the transport of RAM is carried out by BAM as the competent authority according to the International Atomic Energy Agency regulations. BAM was involved in several approval procedures with ductile cast iron containers containing wet intermediate level waste. These contents, which are not dried, only drained, consist of saturated ion exchange resin and a small amount of free water. Compared to the safety assessment of packages with dry content, attention must be paid to some more specific points. The physical and chemical compatibility of the content itself and of the content with materials of the package must be shown. From the mechanical resistance point of view, the package has to withstand the forces resulting from the freezing liquid. The most interesting point, however, is the pressure build-up inside the package due to vapourisation. This could be caused by radiolysis of the liquid and must be taken into account for the storage period. The paper deals primarily with the pressure build-up inside the package caused by the regulatory thermal test (30 min at 800°C) as part of the cumulative test scenario under accident conditions of transport. To determine the pressure, the temperature distribution in the content must be calculated for the whole period from the beginning of the thermal test until cooling down. In this case, calculating the temperature distribution requires, besides the consideration of conduction and heat radiation, consideration of evaporation and condensation including the associated processes of transport.
Numerical simulation of ultrasonic guided waves using the scaled boundary finite element method
(2012)
The formulation of the Scaled Boundary Finite Element Method is applied for the computation of dispersion properties of ultrasonic guided waves. The cross-section of the waveguide is discretized in the Finite Element sense, while the direction of propagation is described analytically. A standard eigenvalue problem is derived to compute the wave numbers of propagating modes. This paper focuses on cylindrical waveguides, where only a straight line has to be discretized. Higher-order elements are utilized for the discretization. As examples, dispersion curves are computed for a homogeneous pipe and a layered cylinder.
Moisture ingress is one of the major deteriorating factors for building materials. Today, the only approved way to assess such damage is the gravimetric Darr method, which is essentially destructive. Substantial progress has been made using the geophysical complex-resistivity method, which can be applied non-destructively and provides spatial information along two-dimensional sections, rather than punctual along one borehole. Considerable advantages of complex resistivity are its sensitivity to textural properties, as well as the pore-fluid chemistry of wet, porous media. In a comprehensive laboratory study, and later in field scale experiments, it could be shown that complex resistivity may even be able to distinguish between salt content and saturation degree in a single measurement. A comparison with complementary nondestructive testing techniques points to the benefit and further research to be explored in multimethodical approaches.
Admissible limits for activity release from type B(U) packages for spent fuel transport specified in the International Atomic Energy Agency regulations (10-6 A2 h-1 for normal conditions of transport and A2 per week for accidental conditions of transport) have to be kept by an appropriate function of the cask body and its sealing system. Direct measurements of activity release from the transport casks are not feasible. Therefore, the most common method for the specification of leak tightness is to relate the admissible limits of activity release to equivalent standardised leakage rates. Applicable procedure and calculation methods are summarised in the International Standard ISO 12807 and the US standard ANSI N14·5. BAM as the German competent authority for mechanical, thermal and containment assessment of packages liable for approval verifies the activity release compliance with the regulatory limits. Two fundamental aspects in the assessment are the specification of conservative design leakage rates for normal and accidental conditions of transport and the determination of release fractions of radioactive gases, volatiles and particles from spent fuel rods. Design leakage rates identify the efficiency limits of the sealing system under normal and accidental transport conditions and are deduced from tests with real casks, cask models or components. The releasable radioactive content is primarily determined by the fraction of rods developing cladding breaches and the release fractions of radionuclides due to cladding breaches. The influence of higher burn-ups on the failure probability of the rods and on the release fractions are important questions. This paper gives an overview about methodology of activity release calculation and correlated boundary conditions for assessment.
The moisture content of wood is known to have a significant influence on the wood's mechanical properties. Using wood as an energy absorber in impact limiters of packages for the transport of radioactive material, it is of particular importance to ensure the moisture content and thus relevant mechanical properties to be in specified limits. The paper surveys the influence of wood moisture content on the mechanical properties of wood. Different measuring methods are discussed with respect to in situ applicability, accuracy and effort. The results of an experimental analysis of the accuracy of hand held moisture metres using the electrical resistance method are discussed. Conclusions are drawn regarding the measurement of moisture content of wood upon delivery as well as of complete impact limiter assemblies. Requirements for quality surveillance during manufacturing of wood filled impact limiters are derived and it is exemplified how to meet them. Construction, manufacturing and inspection of impact limiter encapsulation with regard to leak tightness are addressed.
A novel approach for the generation of broadband airborne ultrasound by using the thermo-acoustic effect is presented in this contribution. We investigate the applicability of resonance-free thermo-acoustic emitters for generation of very short high pressure airborne ultrasound pulses. A thermoacoustic emitter consisting of a 30 nm thin metallic film on a usual soda-lime glass substrate generates sound pressure values of more than 140 dB at 60 mm distance. The results are compared with conventional piezoelectric airborne ultrasound transducers. Our investigations show the applicability of the thermo-acoustic devices for broadband and high pressure ultrasound emitters using pulse excitation.
For the concept of using structural materials such as carbon fibre reinforced plastics as
energy storage devices, new matrix polymers are required. These polymers must provide ionic
conductivity as well as adequate mechanical strength. In the EU-Project StorAGE this
requirements are fulfilled by adding ionic liquid to commercial polymers. The mechanical
properties of these mixtures materials were characterized by using a 3-point-bending device.
In addition, single fibre pull test were performed in order to get information on the interfacial
shear strength. Adding of ionic liquid has an impact on the mechanical performance of the
materials. A decrease of the flexural strength and modulus of less than 10% of the value of the
reference materials took part. The interfacial shear strength decreased to a value of around
one third compare to the reference material.
Polymer-based electrolytes based on commercially available epoxy resins were prepared through the addition of a liquid electrolyte, a solution of a lithium salt in an ionic liquid. The polymer monoliths were characterized using impedance spectroscopy, 3-point bending test, scanning electron microscopy (SEM) and nitrogen adsorption (BET). The balance of ionic conductivity and flexural modulus is crucially dependent on the relative proportions of epoxy resin to electrolyte. Also the effect of the liquid electrolyte on curing kinetics and processing was assessed by complex viscosity measurements and differential scanning calorimetry (DSC). Only one out of the three resins investigated exhibited a significant acceleration effect.
The applicability of polymer-metal composites is mainly determined by the durability of the adhesive strength between both components. Aluminium (Al) deposited on polypropylene (PP) exemplifies different options of interface design. By deposition of plasma polymers on PP the effect of the type of the functionality was investigated. Spacer insertion was accomplished to position the functional group away from the topmost surface. A further kind of interface design involved a partial condensation of functional groups. Hydroxyl and carboxyl groups were most effective to improve adhesion in Al-PP systems. Approximately 7-10 carboxyl or 25-27 hydroxyl groups per 100 C atoms were necessary to increase the peel strength up to ~700 N/m. In this range, the failure of the composite propagated along the interface Al-tape (no peeling of the metal). Spacer molecules between surface and functional groups provoked the effect that the number of needed functional groups for maximum adhesion was strongly reduced. Linking of the functional groups resulted in non-peelable Al-PP laminates. Two adhesion tests were applied - the peel test and the centrifuge technology. For PP foils modified with chemically bonded and additionally linked silanol groups (no peeling) an adhesive strength of (2.5 ± 0.2) N/mm² was determined by centrifuge technology. XPS inspection of both fracture surfaces indicated a sub-surface failure in the polymer.
In geothermal power plants the materials used in pumps are loaded cyclically and
exposed constantly to the highly corrosive hot thermal water. The lifetime reduction
of AISI 420C (X46Cr13, 1.4034) is demonstrated in in-situ-laboratory experiments
(T=60 °C, geothermal brine: Stuttgart Aquifer flow rate: 9 l/h, CO2). S-N plots,
micrographic-, phase-, fractographic- and surface analysis were applied to obtain
sustainable information on the corrosion fatigue behavior. Maximum number of
cycles (here 12.5 x 106 cycles to failure) is reached at σa =173 MPa. No typical
fatigue strength exists and passive corrosion fatigue may be identified as failure
cause.
In the field of water pipelines, geothermal energy production as well as carbon capture and storage technology (CCS) materials have to provide a high resistance to corrosion and mechanical stress. The combination of cyclic load and corrosive aqueous environment leads to corrosion fatigue of pipes and components (e.g. pumps) and thus inevitably to the reduction of the lifetime of these components. To estimate the reliability of components from adjusted in-situ-laboratory experiments a corrosion chamber was designed and tested with CO2 saturated corrosive aqueous media flowing at a steady rate. Unique feature of this special chamber is its installation directly onto the sample and thus providing flexible usability in almost every testing machine. This allows simultaneous mechanical loading of the sample, operation at temperatures up to 100 °C and exposure to fluid flow of corrosive liquids and gases. The lifetime reduction of AISI 420C (X46Cr13, 1.4034) is demonstrated at T=60 °C, geothermal brine: Stuttgart Aquifer flow rate: 9 l/h, CO2. S-N plots, micrographic-, phase-, fractographic- and surface analysis were applied to obtain sustainable information on the corrosion fatigue behavior. Maximum number of cycles (here 12.5 x 106 cycles to failure) is reached at σa =173 MPa. No typical fatigue strength exists and passive corrosion fatigue may be identified as failure cause.
Carbon capture and storage (CCS) includes processing of supercritical carbon dioxide (scCO2). The carbon dioxide (CO2) stemming from flue gases contains acid forming impurities, especially in the case of coal fired power plants. In the present work, the mobility and reactivity of acids in supercritical scCO2 was investigated. The corrosive attack of low alloyed carbon steel (material 1.0484) by water (H2O) alone in scCO2 was negligible. Nitric acid (HNO3) was very mobile and corrosive towards the carbon steel while sulfuric acid did not migrate through the scCO2 to react with the steel surface. Hydrochloric acid in scCO2 was very mobile and reactive towards both carbon steel and high alloyed test equipment. Gravimetric analyses revealed a severe material loss after corrosion in the presence of HNO3. Thickness measurements showed localized material losses.
Thick-walled components made of duplex stainless steels are used in the semi-finished products as well as in machinery, apparatus and plant construction. Electron beam welding (EBW) of these components may be recommended for economic and quality reasons. To guarantee the necessary mechanical and technological properties and the corrosion resistance, the duplex stainless steels are welded with filler material and afterwards undergo a post-weld heat treatment. The present work shows interim results of investigations concerning the development of an electron beam multi-process technology for welding these steels without filler material and post-weld heat treatment. The studies were performed on standard duplex stainless steel of type 1.4462 (X2CrNiMoN22-5-3). When welding duplex stainless steels, the cooling rate and the chemical composition have a crucial influence on the final result. Based on fundamental investigations relating to the influence of the process parameters on the effusion of nitrogen and the cooling rates, the resulting austenite formation, mechanical properties and the corrosion resistance were taken into account to develop appropriate electron beam multi-process techniques. The ferrite content was measured metallographically and by magnetic induction, the impact toughness was measured at –40 °C and the determination of critical pitting temperatures was performed using electrochemical noise measurements.
The sonic surface wave (or Rayleigh wave) velocity measured on prismatic concrete specimens under uniaxial compression was found to be highly stress-dependent. At low stress levels, the acoustoelastic effect and the closure of existing microcracks results in a gradual increase in surface wave velocities. At higher stress levels, concrete suffers irrecoverable damage: the existing microcracks widen and coalesce and new microcracks form. This progressive damage process leads first to the flattening and eventually the drop in the velocity-stress curves. Measurements on specimens undergoing several loading cycles revealed that the velocities show a stress-memory effect in good agreement with the Kaiser effect. Comparing the velocities measured during loading and unloading, the effects of stress and damage on the measured velocities could be differentiated. Moreover, the stress dependency of surface wave velocity proved to be direction-dependent. The velocity increases and decreases the most when measured parallel and perpendicular to the loading axis, respectively.
CO2-induced corrosion of casing and tubing steels is a relevant safety issue for compressing emission gasses into deep geological layers (CCS, Carbon Capture and Storage). The influence of CO2 and pressure of the surrounding media on steels is demonstrated in laboratory experiments providing a corrosive environment similar to a geological onshore CCS-site in the Northern German Basin (T = 60 °C, p = 1 - 100 bar, Stuttgart Aquifer, CO2-flow rate of 3 l/h, 7008000 h exposure time). Corrosion kinetics and microstructures were characterized using specimens of heat treated 42CrMo4 (1.7225, casing) and soft annealed X46Cr13 (1.4034, tubing).
A new high throughput screening method to characterise alloys used as gate metal of Metal/solid Electrolyte/Insulator/Semiconductor (MEIS) gas-sensors was developed. Samples with continuous gradients in alloy concentration for the system Pd1-x-yNiyCoy were analysed regarding H2 sensitivity. First results showed reduced poisoning effects of H2S for Ni concentrations between 4-11 at-% in Pd.
Dynamical simulation of electron backscatter diffraction (EBSD) patterns of imperfect crystals
(2012)
Steels used within the process chain of carbon capture and storage (CCS) are exposed to conditions that are currently not fully tested. In the present work a number of steels were selected as possible construction materials: Alloyed steels for application in the compression and injection sections and low alloyed carbon steels for use as pipelines. Exposure tests were conducted over 600 hours at ambient pressure in a continuous flow of a simulated gas stream consisting of carbon dioxide with low contents of the relevant flue gas components nitrogen dioxide, sulfur dioxide, carbon monoxide, oxygen and water. Temperatures were adjusted to 5, 60 and 170 centigrade.
IIW-2326
Austenitic and austenitic-ferritic CrMnNi-stainless steels are suitable materials in the transport and automotive industry due to their high corrosion resistance and high strength that allows weight and cost savings. This study focuses on the laser weldability of a commercial lean duplex and an austenitic high manganese stainless steel. The impact of different laser sources, i.e. a 5 kW CO2- and a 4 kW Nd:YAG-laser, and of the main process parameters on the resulting weld quality will be investigated. One important aspect will concern the appearance of weld defects such as pores and hot cracks. The factors causing such internal imperfections will be analysed in order to find effective methods for preventing them. Weld microstructure and the associated corrosion and mechanical properties will be assessed with different techniques and adequate process parameters for high quality welds will be determined. The advantages and limitations of the applied welding processes will be evaluated for future applications.
The selective compression of quick response (QR) and Data Matrix code carriers based on shape memory polymer (SMP) with a freely configurable steel ball type indenter and adjacent thermo-mechanical shape fixing gave notched, room temperature (23 °C) stable, temporary shapes with non-decipherable codes. The microscopic investigation of cryomicrotome sections unveiled indentation-related shape fixities of about 90%. Independent of the selected two-dimensional code, the triggering of the SM effect resulted in sufficient shape recoveries to restore the code readability so that a maximum number of characters including 122 for a QR code (version 7) and 112 in case of a Data Matrix code (version 12) could be read with a scanning and decoding device. Due to the large number of difficult to copy shapes with on demand releasable information, SMPs may serve as viable information carriers for product and brand protection applications.
Here we present a suitable tag prototype with phasesegregated
poly(ester urethane) (PEU) as base material for
effectively switching a quick response (QR) code in its surface
from non-readable to readable. In comparison with recently
introduced tags (different geometry) we minimized the
thickness from plaque (2 mm) to foil size (0.5 mm) and reduced
the lateral QR code length from 15 to 5 mm. Subsequent to
surface-dyeing by means of guest diffusion, the QR code was
laser-engraved. The implementation of thermo-mechanical
functionalization via tensile deformation and cooling resulted in
the formation of stable shapes, which exceeded the barrier of
QR code readability at an elongation of 20%. Once
functionalized, tags were switched on demand by heating. As
such the recovery of the PEU was accomplished and the QR
code could again be read out. QR code carriers based on shape
memory polymer can be used in product and brand protection
applications.
The surface of a shape memory poly(ester urethane)
(PEU) was either black- or blue-colored to obtain switchable
quick response (QR) codes after laser engraving and thermomechanical
functionalization (programming). The investigation
of dye and functional stability against UVA and hydrolytic
aging (at 23 and 60 °C) gave that contrast decline due to dye
decolorization (in case of UVA aging) or distinct dye diffusion
(in case of hydrolytic aging) finally inhibited the QR code
readability. By contrast, PEU as marked base material could be
adequately fixed and recovered even when the Michelson
contrast in the QR code region was falling in course of aging
below a crucial value of 0.1, whereupon the QR code was no
longer readable. Hence, we concluded that under the given
experimental conditions the decisive parameter for tag
applicability was the surface contrast.
This article describes a comprehensive quantitative analysis on effect of columnar grain orientation on ultrasonic plane wave energy reflection and transmission behaviour in acoustically anisotropic austenitic weld materials. The quantitative results are presented for following general interfaces (a) Isotropic-Anisotropic, (b) Anisotropic-Isotropic, (c) Fluid-Anisotropic, (d) Anisotropic-Fluid, (e) Anisotropic-Anisotropic, (f) Anisotropic-Free surface occur during the ultrasonic non destructive evaluation of austenitic weld materials. Explicit analytical expressions are presented for energy reflection and transmission coefficients at an interface between two arbitrarily oriented transversely isotropic materials. By applying explicit analytical expressions for energy reflection and transmission coefficients, numerical results are presented for several columnar grain orientations of the transverse isotropic austenitic weld material including both real and complex domain of the reflected and transmitted normal component of slowness vectors. Valid domains of incident wave vector angles, angular dependency of energy reflection and transmission coefficients and critical angles for reflected and transmitted waves are discussed. The existence of a reflected (or) transmitted second branch of quasi shear vertical waves and its consequence to the ultrasonic non destructive testing of austenitic weld materials are investigated. The presented comprehensive quantitative evaluation provides an overview on the effect of anisotropic properties on energy reflection and transmission coefficients in columnar grained austenitic weld materials.
This paper presents an automated system for the evaluation and visualization of structural vibrations on the surface of solid materials in an ultrasonic frequency range using a single head laser Doppler vibrometer. For this method, the vibrometer performs a continuous scan of the surface driven by a two-axes robotic system. Scan and measurement parameters can be adapted to the requirements of geometry, frequency and resolution. Data processing techniques are employed to improve the signal-to-noise ratio and minimize the effect of inconvenient laser beam reflections caused by speckles.
Sensitive, accurate and fast absolute quantification of intact proteins is reported using metal coded affinity tags (MeCATs) combined with gel electrophoresis (GE) separation, inductively coupled plasma mass spectrometry (ICP-MS) detection and label-specific isotope dilution analysis quantification. Two different approaches were investigated concerning the introduction of the sample into ICP-MS, mineralization of the gel and direct laser ablation (LA) of the spot. Three major advantages are remarkable in the proposed method. First, not only heteroatom-containing proteins but also all labeled proteins in the sample can be absolutely quantified preparing an isotopically enriched tracer. On the other hand, highly sensitive determination in the amol range can be performed, considerably reducing the analysis time due to the straightforward measurements by ICP-MS. Furthermore, the studied method allows accurate quantifications with different sample-to-spike ratios and using stock spikes stored for months. After the first characterization using standard proteins, human serum albumin (HSA) and transferrin (Tf) were determined in human serum to test the applicability of the method to biological samples. The results show satisfactory quantifications for the studied proteins despite the difference in concentration and the similarity in migration distances.
Experimental N K-edge NEXAFS data of surface immobilized azide, 1,2,3-triazole and terpyridyl groups are interpreted with the help of DFT spectrum simulations. Assignments of π* resonances in experimental N K-edge NEXAFS spectra to nitrogen atoms within these functional groups have been made. The azide was immobilized on gold as the head group of a thiol SAM, 1,2,3-triazole was formed on this SAM by click reaction and terpyridyl groups were introduced as substituents of the acetylene used for the click reaction. For azide-terminated molecules, DFT spectrum simulations are found to be useful to find measurement conditions delivering experimental N K-edge NEXAFS data with negligible X-ray damage. The 1,2,3-triazole group is found to be rather stable under X-ray irradiation.
In this paper a numerical approach, based on the Scaled Boundary Finite Element Method (SBFEM), is described to obtain dispersion relations for propagating modes in wave guides. While the formulation is developed for plate structures, it can easily be extended to wave guides with arbitrary cross-section. The cross-section is discretized in the Finite Element sense while all equations remain analytical in the direction of propagation. The wave numbers of all propagating modes are obtained as the solutions of a standard eigenvalue problem. The group velocities can be calculated accurately as the eigenvalue derivatives. The use of higher-order elements drastically increases the efficiency and accuracy of the computation. This approach can be used for wave guides with arbitrary distribution of material parameters.
An unusually fast crystallization of the organic glass former nifedipine has been observed. The crystallization process, starting from an amorphous film to crystalline material, was investigated by time resolved Raman microspectroscopy. The crystallization rates of the initially crystallizing metastable β-form are four orders of magnitude higher than those of previous studies.
The main goal of the presented work was to evolve a multifunctional beam composed out of fiber reinforced plastics (FRP) and an embedded optical fiber with various fiber Bragg grating sensors (FBG). These beams are developed for the use as structural member for bridges or industrial applications. It is now possible to realize large scale cross sections, the embedding is part of a fully automated process and jumpers can be omitted in order to not negatively influence the laminate. The development includes the smart placement and layout of the optical fibers in the cross section, reliable strain transfer, and finally the coupling of the embedded fibers after production. Micromechanical tests and analysis were carried out to evaluate the performance of the sensor. The work was funded by the German ministry of economics and technology (funding scheme ZIM). Next to the authors of this contribution, Melanie Book with Röchling Engineering Plastics KG (Haren/Germany) and Katharina Frey with SAERTEX GmbH & Co. KG (Saerbeck/Germany) were part of the research group.
Structuring over many length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, show how Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecules are embedded. It is postulated that this mesocrystalline structure forms via the crystallization of a dense array of amorphous calcium carbonate (ACC) precursor particles. A residual surface layer of ACC and/or macromolecules remains around the nanoparticle units which creates the mesocrystal structure and contributes to the conchoidal fracture behavior. Natures demonstration of how crystallization of an amorphous precursor phase can create a crystalline material with remarkable properties therefore provides inspiration for a novel approach to the design and synthesis of synthetic composite materials.
We report on a new series of isoreticular frameworks based on zinc and 2-substituted imidazolate-4-amide-5-imidate (IFP-1–4, IFP=imidazolate framework Potsdam) that form one-dimensional, microporous hexagonal channels. Varying R in the 2-substitued linker (R=Me (IFP-1), Cl (IFP-2), Br (IFP-3), Et (IFP-4)) allowed the channel diameter (4.0–1.7 Å), the polarisability and functionality of the channel walls to be tuned. Frameworks IFP-2, IFP-3 and IFP-4 are isostructural to previously reported IFP-1. The structures of IFP-2 and IFP-3 were solved by X-ray crystallographic analyses. The structure of IFP-4 was determined by a combination of PXRD and structure modelling and was confirmed by IR spectroscopy and 1H MAS and 13C CP-MAS NMR spectroscopy. All IFPs showed high thermal stability (345–400°C); IFP-1 and IFP-4 were stable in boiling water for 7 d. A detailed porosity analysis was performed on the basis of adsorption measurements by using various gases. The potential of the materials to undergo specific interactions with CO2 was investigated by measuring the isosteric heats of adsorption. The capacity to adsorb CH4 (at 298 K), CO2 (at 298 K) and H2 (at 77 K) at high pressure were also investigated. In situ IR spectroscopy showed that CO2 is physisorbed on IFP-1–4 under dry conditions and that both CO2 and H2O are physisorbed on IFP-1 under moist conditions.
Time-optimized 15N quantitative NMR (qNMR) is described for the precise determination of Lewis and Brønsted site concentrations per gram catalyst, enabling a measurement time reduction of more than a factor of 10. The proof-of-principle is demonstrated for amorphous aluminum hydroxide fluorides with their tunable Lewis to Brønsted functionalities and relevance to highly active and selective heterogeneous catalysis using pyridine as a widely accepted probe molecule for Lewis and Brønsted sites. Two different Lewis centers were found, and reliable site concentrations down to the micromole per gram region can be determined. Furthermore, 1H{15N} REDOR NMR for the acid proton at the Brønsted site yields a distance of the 15N atom of bonded pyridine to this acid proton of (0.112 ± 0.002) nm, such that fast motion/diffusion of the Brønsted site-bonded pyridine at the surface can be excluded.
Four hundred and sixteen silver coins stemming from the Ottoman Empire (16th and 17th centuries) were analyzed to confirm the fineness of the coinage as well as to study the provenance of the alloy used for the coins. As most of the coins showed the typical green patina on their surfaces due to corrosion processes that have led to the depletion of copper in the near surface domains of the silver coins in comparison to their core composition, small samples had to be taken, embedded in synthetic resin, and cross sectioned to investigate the true-heart metal composition. µ-synchrotron micro X-ray fluorescence analysis and µ-proton-induced X-ray emission were applied to determine the silver contents as well as the minor and trace elements. The type of the alloy was investigated as well as if coins minted in different locations demonstrated homogeneous traits concerning the predominant impurities (Au and Bi), which could suggest a common ore. Finally, energy-dispersive microanalysis in a scanning electron microscope was applied to study the homogeneity/heterogeneity of the coins and the presence of surface enrichments and to explain differences between the µ-synchrotron micro X-ray fluorescence analysis and µ-proton-induced X-ray emission measurements concerning the main component. In general, the silver content of the analyzed specimen varies between 90 and 95%. These outcomes have not supported the historical interpretations, which predict that during the period studied, a debasement of approximately 44% of the silver content of the coins should have occurred.
This manuscript reviews the most used optical systems for X-ray microprobes and summarizes the experiences in research with synchrotron radiation as well as with X-ray tube generators.
The need for smaller beam spot sizes for various applications and the unique properties of X-rays have induced a remarkable and fast development in X-ray optical systems. These systems are divided into three main categories: diffractive, reflective and refractive. Examples of the three will be covered in this paper, highlighting the properties that allow having spot sizes down to sub-micrometer regime.
However, the extraordinary capabilities of such systems are always relative. Therefore, an overview of the techniques that use such optical systems will be given, emphasizing their applicability on several case studies.
In this work, Pb(Zr,Ti)O3 thin films were used to fabricate well-ordered nanodot arrays by means of nanosphere lithography. This technique is based on a two-step etch process that enables excellent control of the fabrication of ordered nanodisc arrays of defined height, diameter, and pitch. Piezoresponse force microscopy was used to investigate both non-patterned and patterned films. The topography and both the out-of-plane and the in-plane polarization were deduced in this mode. Grains of nanodots with a low aspect ratio form domain structures comparable to domains in non-patterned two-dimensional films. In contrast, nanodots with a higher aspect ratio form particular structures like bi-sectioned domain assemblies, c-shaped domains or multi-domains surrounding a center domain. The patterning of the ferroelectric material was shown to affect the formation of ferroelectric domains. The initial polycrystalline films with random polarization orientation re-orient upon patterning and then show domain structures dependent on the nanodisc diameter and aspect ratio.
The analysis of biomolecules requires highly sensitive and selective detection methods capable of tolerating a complex, biological matrix. First applications of biomolecule detection by ICP-MS relied on the use of heteroelements as a label for quantification. However, the combination of immunoassays and ICP-MS facilitates multiparametric analyses through elemental tagging, and provides a powerful alternative to common bioanalytical methods. This approach extends the detection of biomarkers in clinical diagnosis, and has the potential to provide a deeper understanding of the investigated biological system. The results might lead to the detection of diseases at an early stage, or guide treatment plans. Immunoassays are well accepted and established for diagnostic purposes, albeit ICP-MS is scarcely applied for the detection of immune-based assays. However, the screening of biomarkers demands high throughput and multiplex/multiparametric techniques, considering the variety of analytes to be queried. Finally, quantitative information on the expression level of biomarkers is highly desirable to identify abnormalities in a given organism. Thus, it is the aim of this review to introduce the fundamentals, and to discuss the enormous strength of ICP-MS for the detection of different immunoassays on the basis of selected applications, with a special focus on LA-ICP-MS.
Photoluminescence techniques are amongst the most widely used tools in the material and life sciences, with new and exciting applications continuously emerging. Advantages include their comparative ease of use, unique sensitivity, non-invasive character, and potential for multiplexing, remote sensing, and miniaturization. Increasing applications of fluorescence techniques in the life sciences and emerging medical applications of fluorescence microscopic techniques including 1P and 2P fluorescence microscopy combined with fluorescence lifetime imaging (FLIM) in e.g. in vivo eye diagnostics boosted the demand for robust, easy-to-use, and reliable fluorescence standards to ensure the reliability and comparability of fluorescence data. This includes fluorescence standards for the consideration of instrument-specific spectral and intensity distortions of measured signals and instrument performance validation, fluorescence intensity standards for the quantification of measured intensities and for signal referencing, and lately, also fluorescence lifetime standards.
Fluid-assisted mass transport reactions by dissolution-precipitation, where a precursor mineral reacts with a fluid, play an important role in metamorphism and metasomatism. We investigated titanite growth on rutile in time series experiments between one and 107 days at constant P-T conditions of 600 °C and 400 MPa in the system TiO2-CaO-SiO2-Na2O-HCl-H2O. A two-capsule assemblage allows for transport of Ca and Si from dissolving wollastonite to dissolving rutile, the Ti-source, in a NaCl-bearing aqueous fluid, according to the general reaction CaSiO3 + TiO2 = CaTiSiO5. Complete overgrowth of rutile by titanite occurred after just one day of experiment. Fine-grained lozenge-shaped titanite crystals of short-time runs (up to 14 days) reorganize to larger predominantly prismatic crystals after >14 days.
After investigation by scanning electron microscopy, the titanite overgrowth was removed from the rutile by hydrofluoric acid, to provide a three-dimensional view of the dissolution-reaction front on the rutile surface. The morphology of the rutile surface is dominated by humps or ridges beneath the central region of a titanite crystal and valleys at the grain boundaries between adjacent titanite crystals. The dissolution pattern on the rutile surface mimics the titanite overgrowth and changes with changing grain size and shape of the titanite with longer run times. The preferred dissolution of rutile in the valleys is clearly linked to the position of the titanite grain boundaries, which served as pathways for fluid-assisted element transport. Rutile-titanite and titanite-titanite boundaries show a significant porosity in transmission electron microscopy images of foils prepared by focused ion beam milling. The large-scale dissolution pattern on the rutile surface is independent of the crystallographic orientation of the rutile and entirely dominated by the arrangement of titanite crystals in the overgrowth. Dissolution features on a scale smaller than ~1 µm are dominated by stepwise dissolution and etch-pits following the crystallographic orientation of the rutile. Similar observations were made in experiments with an additional Al-source, although these experiments result in a different overgrowth pattern; i.e., an exposed rutile surface is always present and solitary titanite crystals are accompanied by partial overgrowths. Quantitative characterization of the surface morphology by white-light interference microscopy demonstrates that, with increasing grain size of titanite, dissolution of rutile is strongly enhanced at the titanite grain boundaries.
Natural examples of titanite overgrowths on rutile show the same relations between element pathways, arrangement of titanite crystals and 3D dissolution pattern on rutile as in the experimental systems. We conclude that the transport of Ti away from the rutile and of Ca + Si into the reaction rim occurred in a grain boundary fluid, the composition of which must have been strongly different from the composition of the bulk fluid in the experiment, as well as in the natural system. The reaction progress depends on the availability of a fluid, and relicts of rutile in titanite indicate restricted availability of fluid in the natural system (e.g., a fluid pulse that was consumed by the reactions). The reaction examined here can serve as a proxy for other reactions of the conversion of oxide minerals (e.g., spinel or corundum) into silicates.
Material performance testing of wood-plastic composites (WPC) requires adequate and time-efficient evaluation of the resistance against fungal colonisation and decay. This study investigates the effects of weathering on WPCs and subsequent material degradation by fungi. Weathering using UV radiation, water spray and repeated frost incidents caused micro- and macro-cracks. Fourier transform infrared spectroscopy (FTIR) demonstrated delignification of wood particles at the weathered WPC surface. Despite of increased surface area, accessibility for fungal hyphae and moisture content, weathering enhanced mass loss due to fungal decay only subtly but not significantly. These potentially enhancing effects for fungal decay are assumed to be outbalanced by delignification due to photo-oxidation and leaching of degradation products resulting in loss of nutrient sources essential for fungal growth.
Analytical and numerical analysis of imaging mechanism of dynamic scanning electron microscopy
(2012)
The direct observation of small oscillating structures with the help of a scanning electron beam is a new approach to study the vibrational dynamics of cantilevers and microelectromechanical systems. In the scanning electron microscope, the conventional signal of secondary electrons (SE, dc part) is separated from the signal response of the SE detector, which is correlated to the respective excitation frequency for vibration by means of a lock-in amplifier. The dynamic response is separated either into images of amplitude and phase shift or into real and imaginary parts. Spatial resolution is limited to the diameter of the electron beam. The sensitivity limit to vibrational motion is estimated to be sub-nanometer for high integration times. Due to complex imaging mechanisms, a theoretical model was developed for the interpretation of the obtained measurements, relating cantilever shapes to interaction processes consisting of incident electron beam, electron–lever interaction, emitted electrons and detector response. Conclusions drawn from this new model are compared with numerical results based on the Euler–Bernoulli equation.
ESEM-EDX analyses for the characterisation and reproduction of nineteenth-century gold tesserae
(2012)
Environmental scanning electron microscopy with energy dispersive X-ray analysis (ESEM-EDX) is a versatile working tool for the examination of gold tesserae as well as for the selection of suitable materials for their reproduction. In this paper, the ESEM-EDX analyses of original gold tesserae and their damage types are presented. These analytical results form the basis for further calculations of glass properties and experiments. These calculated values enable the determination of the relevant glass properties and allow us to choose the appropriate type of modern glass for further experiments. Subsequent experiments convert this knowledge into practice. By comparing the analytical results from the original glasses and the replicas the accuracy and precision will be shown.
Pool fires and spill fires
(2012)
Study of fatigue behavior for spot welded tensile shear specimens of advanced high strength steels
(2012)
For automotive body-in-white applications the influence of manufacture-related gaps between the steel sheets and also of manufacture-related surface cracks on the fatigue behavior of tensile shear specimens for spot welded TRIP steel was analyzed. It was shown that gaps between the steel sheets reduce the fatigue strength, whereas the fatigue behavior is neither influenced by cracks in the electrode indentation area nor in the heat effected zone.
A novel Gram-positive, aerobic, actinobacterial strain, CF5/5, was isolated from soil in the Sahara desert, Chad. It grew best at 20–35 °C and at pH 6.0–8.0 and with 0–4 % (w/v) NaCl, forming black-colored colonies. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus. The DNA G + C content was 75.9 mol%. The peptidoglycan contained meso-diaminopimelic acid; galactose and xylose were detected as diagnostic sugars. The main phospholipids were diphosphatidylglycerol, phosphatidylcholine, and phosphatidylinositol; MK-9(H4) was the dominant menaquinone. The major cellular fatty acids were: iso-C16:0 and iso-C15:0. The 16S rRNA gene showed 95.6–98.3 % sequence similarity with the other named members of the genus Geodermatophilus. Based on the polyphasic taxonomy data, the isolate is proposed to represent a novel species, Geodermatophilus saharensis with the type strain CF5/5T = DSM 45423 = CCUG 62813 = MTCC 11416.
Fire retardancy effects in single and double layered sol-gel derived TiO2 and SiO2-wood composites
(2012)
Sol–gel derived TiO2 and SiO2-wood inorganic composites are prepared by direct vacuum infiltration of silicon and titanium alkoxide based precursors in pine sapwood in one or two cycles followed by a controlled thermal curing process. The resulting flame retardancy effect is investigated under two different fire scenarios using cone calorimetry and oxygen index (LOI). Heat release rates (HRR) especially the values for the second peak, are reduced moderately for all single layered composites. This effect is more pronounced for double layered composites where HRR was reduced up to 40 % showing flame retardancy potential in developing fires. Beside this, smoke release was lowered up to 72 % indicating that these systems had less fire hazards compared to untreated wood, whereas no meaningful improvement is realized in terms of fire load (total heat evolved) and initial HRR increase. However impressively, the LOI of the composites were increased up to 41 vol% in comparison to 23 vol% for untreated wood displaying a remarkable flame retardancy against reaction to a small flame. An approximate linear interdependence among the fire properties and the material loading as well as fire residue was observed. A residual protection layer mechanism is proposed improving the residue properties for the investigated composites.
Sol-gel preparation of calcium titanium phosphate: viscosity, thermal properties and solubility
(2012)
Calcium titanium phosphate (CTP) was prepared by the sol–gel route in order to prepare suitable coatings. This work addresses the question of how to prepare stable CTP sols. Their rheological properties as a function of process parameters like solid loading and water content are investigated. It was found that an increased solid loading as well as an increased water content lead to an increased initial viscosity as well as a more pronounced ageing induced viscosity rise. In addition, the thermal behavior of the resulting xerogels was analyzed. Furthermore, we studied the ion release behavior of the xerogels when brought in contact with water. Results suggest that calcium titanium phosphate shows a diffusion controlled ion release mode with a preferential release of Ca.
Deoxynivalenol (DON) is one of the most abundant mycotoxins contaminating food and feed worldwide. Upon absorption, the major portion of the toxin is excreted by humans and animal species as glucuronide. However, consistent in vitro data on DON glucuronidation are lacking. In the present study, the metabolism of DON was investigated using liver microsomes from humans and six different animal species. It was shown that all animal and human liver microsomes led to the formation of up to three different mono-O-glucuronides with significant interspecies differences. While the activity of human liver microsomes was low (0.8 to 2.2 pmol·min–1·mg–1), bovine liver and rat liver microsomes conjugated DON with activities of 525 pmol·min–1·mg–1 and 80 pmol·min–1·mg–1, respectively.