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- 2010 (2230) (entfernen)
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- Vortrag (1024)
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- Radar (14)
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Eingeladener Vortrag
- nein (1024)
A new approach is presented to quantify the so-called "heat affected zone" (HAZ) during
femtosecond laser pulse processing. Ablation of titanium nitride (TiN) thin films (~3 μm
thickness) by multiple femtosecond laser pulses (τ=130 fs, λ=800 nm) in air environment was
studied by means of two different surface analytical methods both being sensitive to chemical
alterations at the surface. Scanning Auger electron microscopy was applied for a visualization of the
spatial distribution of specific elements (Ti, O) within the laser-modified areas. The chemical state
of the irradiated surface was revealed by complementary x-ray photoelectron spectroscopy. Both
methods were used for a depth-profiling chemical analysis (tracking the elements Ti, N, O, and C)
using an Ar-ion beam for surface sputtering. In a narrow laser fluence range slightly below the
ablation threshold of TiN significant superficial oxidation can be observed leading to the formation
of substoichiometric TiO2-x. At fluences above the ablation threshold, an increased titanium
concentration is observed within the entire ablation craters. Following upon sputter removal the
elemental distribution into the depth of the nonablated material, the results allow an estimation of
the heat-affected zone for femtosecond laser ablation in air environment. According to our analyses,
the HAZ extends up to a few hundreds of nanometers into the nonablated material.
Gold nanoparticles (AuNP) were prepared by the homogeneous mixing of continuous flows of an aqueous tetrachloroauric acid solution and a sodium borohydride solution applying a microstructured static mixer. The online characterization and screening of this fast process (~2 s) was enabled by coupling a micromixer operating in continuous-flow mode with a conventional in-house small angle X-ray scattering (SAXS) setup. This online characterization technique enables the time-resolved investigation of the growth process of the nanoparticles from an average radius of ca. 0.8 nm to about 2 nm. To the best of our knowledge, this is the first demonstration of a continuous-flow SAXS setup for time-resolved studies of nanoparticle formation mechanisms that does not require the use of synchrotron facilities. In combination with X-ray absorption near edge structure microscopy, scanning electron microscopy, and UV-vis spectroscopy the obtained data allow the deduction of a two-step mechanism of gold nanoparticle formation. The first step is a rapid conversion of the ionic gold precursor into metallic gold nuclei, followed by particle growth via coalescence of smaller entities. Consequently it could be shown that the studied synthesis serves as a model system for growth driven only by coalescence processes.
Amelogenin nanoparticles in suspension: Deviations from spherical shape and pH-dependent aggregation
(2010)
It is well-known that amelogenin self-assembles to form nanoparticles, usually referred to as amelogenin nanospheres, despite the fact that not much is known about their actual shape in solution. In the current paper, we combine SAXS and DLS to study the three-dimensional shape of the recombinant amelogenins rP172 and rM179. Our results show for the first time that amelogenins build oblate nanoparticles in suspension using experimental approaches that do not require the proteins to be in contact with a support material surface. The SAXS studies give evidence for the existence of isolated amelogenin nano-oblates with aspect ratios in the range of 0.45-0.5 at pH values higher than pH 7.2 and show an aggregation of these nano-oblates at lower pH values. The role of the observed oblate shape in the formation of chain-like structures at physiological conditions is discussed as a key factor in the biomineralization of dental enamel.
In this study the microscopic homogeneity of the newly developed plastic reference materials BAM H001-BAM H010 was investigated. The materials consist of an acrylonitryle-butadien-styrene terpolymer, doped with different amounts of the elements Br, Cd, Cr, Hg and Pb. For the quantitative determination of the degree of homogeneity, a procedure proposed by Kempenaers et al. (Fresenius J. Anal. Chem., 2001, 369, 733-737) was used. On every sample an extensive number of different points were analyzed and standard deviation for every element mentioned above was used to calculate a minimal sampling mass that is necessary to reach a certain level of uncertainty caused by inhomogeneity (mmin,5%). The experiments were taken out with synchrotron µ-XRF (SR µ-XRF) at BESSYII in Berlin and by laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS). The calculated values for mmin,5% of both techniques showed comparable results for all elements. It could be shown that the materials are suitable for calibration of micro analytic techniques if at least 64 µg are used.
When reusing or disposing of contaminated granular waste materials there is a need to evaluate how the contaminants will interact on the pathway soil-groundwater and the effect this interaction will have on the surrounding environment. While column testing can provide a closer approximation to field percolation conditions than batch testing, there is still a need to develop column testing procedures that consider the requirements of practical testing time frames. This study evaluates the effect of different column contact times (2.5, 5, and 16 h) on the release of inorganic constituents from bottom ash and demolition waste, two commonly reused granular materials. Leaching data for representative constituents of concern, such as copper, chromium, sulfate and chloride, as well as pH and electrical conductivity was compared for all different contact times studied.
Results for the materials investigated in this study showed that variations in contact time have no significant effect on the release of the selected constituents and leaching parameters at low liquid to solid ratios. However, after a liquid to solid ratio of 1 L/kg, the effect is more noticeable, and higher contact times show lower pH values as well as a reduction in the release of constituents of concern from bottom ash. In the case of demolition waste, the variation of contact time did not have a strong effect on the leaching behavior.
Bestandsaufnahme und Zustandsanalyse von Brücken und Parkhäusern mit automatisierten Verfahren
(2010)
Die Wettbewerbsfähigkeit der Chemisch-Pharmazeutischen Industrie basiert auf der Sicherung der geforderten Produktqualität bei einer optimalen Nutzung von Anlagen, Rohstoffen und Energie. Eine gute Prozessführung unter Einsatz zuverlässiger Prozessautomation sichert hier den globalen Wettbewerbsvorteil. Initiiert von NAMUR und GMA und unter Mitwirkung der Unternehmen ABB, BASF, BTS, BIS Prozesstechnik, E+H, Siemens und der BAM entstand jetzt die grundlegend aktualisierte und überarbeitete Technologie-Roadmap "Prozess-Sensoren 2015+", die im November 2009 veröffentlicht wurde.
Countdown für Konrad
(2010)
Near-IR femtosecond ( τ = 150 fs, λ = 775 nm, repetition rate 1 kHz) and VUV nanosecond (τ = 20 ns, λ = 157 nm, repetition rate 1 to 5 Hz) laser pulse ablation of single-crystalline TeO2 (c-TeO2, grown by the balance controlled Czochalski growth method) surfaces was performed in air using the direct focusing technique. The multi-method characterization using optical microscopy, atomic force microscopy and scanning electron microscopy revealed the surface morphology of the ablated craters. This allowed us to characterize precisely the lateral and vertical dimensions of the laser-ablated craters for different laser pulse energies and pulse numbers at each spot. Based on the obtained information, we quantitatively determined the ablation threshold fluence for the fs laser irradiation when different pulse numbers were applied to the same spot by using two independent extrapolation techniques. We found that in case of NIR femtosecond laser pulse irradiation, the ablation threshold significantly depends on the number of laser pulses applied to the same spot indicating that incubation effects play an important role in this material. In case of VUV ns laser pulses, the ablation rate is significantly higher due to the high photon energy and the predominantly linear absorption in the material. These results are discussed on the basis of recent models of the interaction of laser pulses with dielectrics.
Application and Case Studies
(2010)
Verfleckungen an Edelstählen
(2010)
The solgel process was applied to enhance properties of pine sapwood. For this purpose wood prisms were soaked in nanoscaled precursor solutions prepared from titanium(IV) n-butoxide and titanium(IV) iso-propoxide, respectively, using vacuum impregnation technique. The wet composites were cured by special program with final heat treatment at 103 °C. Weight percent gains (WPG) of the wood specimen in the range of 19-25% were obtained due to these procedures. SEM investigations show that precursor solutions penetrate into the whole wood body and the titania formed after heat treatment in the composites is deposited in the pores (lumen) and partly in the cell walls of the wooden matrix. The moisture sorption was investigated in long term tests for a period of some months by storage at 20-23 °C in humid air (relative humidity of 99%) and ambient atmosphere (relative humidity 40-60%), respectively. For untreated reference samples the moisture sorption results in increasing of mass and volume according to saturation values of 24 and 13%, respectively, after about 15 days. The incorporation of titania reduces the saturation values of the moisture sorption by up to 12% in mass and by up to 5% in volume at a relative humidity of 99%. Thus, an enhancement of the dimensional stability of about 60% is obtained at best. The results demonstrate that modification of wood with sol-gel derived precursors can enhance its dimensional stability, which prevents the formation of cracks. Because of that reduced moisture sorption biological attacks should be delimited. Additionally, thermal analyses show a retarded combustion of the wood matrix due to titania infiltration.
Für eine gute Vergleichbarkeit der Ergebnisse aus verschiedenen Anlagen sollte dieTreffsicherheit der Extremdrücke nach
Maßgabe einer bestimmten wirksamen Haltezeit ermittelt und bewertet werden.
Hierbei können selbst bei Flaschen für 700 bar Betriebsdruck bereits Abweichungen
von wenigen bar unbemerkt zu deutlichen Veränderungen der Lebensdauer-Versuchsergebnisse führen.
Speziell für Prüflinge aus Verbundwerkstoff mit tragenden Schichten aus verschiedenen Fasern oder mit mittragendem Liner kommt eine besondere Abhängigkeit der Ermüdungsfestigkeit von der Temperatur und damit auch von deren Schwankung hinzu. Für die Bewertung der Temperaturregelung ist es vor allem erforderlich, die
Oberflächen- und die Medientemperatur zu protokollieren und in engen Grenzen zu regeln.
So wird empfohlen, insbesondere Anlagen, die zukünftig für Versuche zur Ermittlung probabilistischer Kenngrößen von
Composite-Flaschen herangezogen werden, auf diese Aspekte hin besonders zu ertüchtigen und in Ringversuchen - wie dem gezeigten - auf ihre Eigenschaften (ihren spezifischen "Fingerabdruck") hin zu überprüfen.
Versuchsparameter, können für derartige Versuche folgende Empfehlungen gegeben werden:
1. Der Druckbereich sollte auf den größten und auch kleinsten Maximaldruck, der von den Anlagen in Prüfungen abgefordert werden soll, ausgerichtet sein.
2. Der Prüfling sollte so gewählt sein, dass während des Ringversuchs möglichst nicht ausgetauscht werden muss. Hierbei darf er nicht zu klein oder zu steif sein, damit die Anlage bezüglich des Hub- oder Fördervolumens
auch repräsentativ für die Prüfaufgaben gefordert wird.
3. Das beschriebene Prüfprogramm mit wanderndem Prüfling und Messequipment hat sich im Grundsatz genauso bewährt
wie die zentrale Auswertung der Daten.
4. Es ist nicht einfach, ein harmonisiertes Verständnis über die konkreten Aspekte des Prüfprogramms zu erreichen, entsprechend sollte sowohl das Personal im Vorfeld gut über Hintergründe und Zielsetzung informiert sein als auch die Durchführung von Ringversuchen durch sehr erfahrenes, das Prüfequipment permanent begleitendes Personal betreut werden.
Jeder der Partner hat aus diesem Ringversuch viel Erfahrung und Wissen für sich mitnehmen können, sodass ein wesentlicher Vorteil derartiger Versuche im Erfahrungsgewinn aller Beteiligten zu sehen ist.
Gegebenenfalls sollten derartige Ringversuche mittelfristig auch fester Bestandteil der Audits und Reaudits zur Akkreditierung bzw. Anerkennung als technischer Dienst, insbesondere für die 700-bar-Wasserstofftechnik,
werden.
Im Hinblick auf den Inhalt der Ringversuche und die Relevanz der diskutierten
Analytical and numerical methods are used to estimate the temperature field due to the heat effects of welding. Numerical techniques are more adapted for industrial complex applications where analytical solutions do not exist yet. However, computational time is much lower with analytical models and a combination of both methods is investigated. Therefore, the two approaches are introduced and confronted in this paper. The finite-element software Ansys has been used for numerical simulations and Scilab for analytical simulations. In order to get a similar result quality, both methods have to be analysed and compared with respect to boundary conditions. These configurations are presented in this paper. Before starting any analysis, the analytical and numerical models have to be comparable. For the numerical simulation, every in- or output is given in discrete form and, for the analytical simulation, in continuous form. Thus, an analysis of the energy input distribution in both models is compulsory to ensure that the same amount of energy is applied. After this first study, a comparison of the analytical and numerical temperature field simulation is done from a fix point source in an infinite volume in steady state to a moving point source in a finite dimension in a transient state. A good agreement between the analytical and the numerical simulation results is found. However, some techniques, like a consideration of an image heat source for the analytical model or the selection of boundary conditions for the numerical model, need to be taken into consideration when the degree of complexity of the study (finite dimension or cooling time) increases. The limit of the comparison is reached when the geometry becomes too complex and when the effect of variable thermal properties with temperature cannot be neglected.
The surface of many termite gut flagellates is colonized with a dense layer of bacteria, yet little is known about the evolutionary relationships of such ectosymbionts and their hosts. Here we investigated the molecular phylogenies of devescovinid flagellates (Devescovina spp.) and their symbionts from a wide range of dry-wood termites (Kalotermitidae). From species-pure flagellate suspensions isolated with micropipettes, we obtained SSU rRNA gene sequences of symbionts and host. Phylogenetic analysis showed that the Devescovina spp. present in many species of Kalotermitidae form a monophyletic group, which includes also the unique devescovinid flagellate Caduceia versatilis. All members of this group were consistently associated with a distinct lineage of Bacteroidales, whose location on the cell surface was confirmed by fluorescence in situ hybridization. The well-supported congruence of the phylogenies of devescovinids and their ectosymbionts documents a strict cospeciation. In contrast, the endosymbionts of the same flagellates (´Endomicrobia´) were clearly polyphyletic and must have been acquired independently by horizontal transfer from other flagellate lineages. Also the Bacteroidales ectosymbionts of Oxymonas flagellates present in several Kalotermitidae belonged to several distantly related lines of descent, underscoring the general perception that the evolutionary history of flagellate-bacteria symbioses in the termite gut is complex.
The use of electrochemical noise (EN) measurements for the investigation and monitoring of corrosion has allowed many interesting advances in the corrosion science in recent years. A special advantage of EN measurements includes the possibility to detect and study the early stages of localized corrosion. Nevertheless, the understanding of the electrochemical information included in the EN signal is actually very limited. The role of the cathodic process on the EN signals remains uncertain and has not been sufficiently investigated to date. Thus, an accurate understanding of the influence of the cathodic process on the EN signal is still lacking. On the basis of different kinetics of the oxygen reduction it was established that the anodic amplitude of transients arising from pitting corrosion on stainless steel can be decreased by the corresponding electron consumption of the cathodic process. Therefore, the stronger the electron consumption, the weaker the anodic amplitude of the EN signal becomes. EN signals arising from pitting corrosion on stainless steel can be measured because the cathodic process is inhibited by the passive layer. This was confirmed by means of EN measurements under cathodic polarisation. Since the cathodic process plays a decisive role on the form of transients arising from pitting corrosion, its influence must be considered in the evaluation and interpretation of the EN signals.
Eine Fallstudie
(2010)
In this work, the applicability of a new 3D micro X-ray fluorescence (3D Micro-XRF) laboratory spectrometer for the investigation of historical glass objects is demonstrated. The non-destructiveness of the technique and the possibility to measure three-dimensionally resolved fluorescence renders this technique into a suitable tool for the analysis of cultural heritage objects. Although absorption and resolution effects complicate qualitative analysis of the data, layered structures can be distinguished from homogeneous samples without the need for full quantification. Different manufacturing techniques were studied in this work with the help of hand-made reference samples. With the gained knowledge it could be shown for the investigated historical glass object, that black enamel as a stained glass contour colour was used in a cold painting. The object was not fired after the application of the black enamel, but instead the adhesion of the paint was solely provided through organic binding agents and the backing with metal foils. Thus, for the manufacturing of the object, a mixture of cold painting technique with a stained glass color was used. Quantitative measurements with a 3D Micro-XRF setup at the Berlin synchrotron BESSY II confirm the assumptions drawn on the basis of the qualitative investigation with the 3D Micro-XRF spectrometer with X-ray tube excitation.
The frictional behavior at local contacts in an automotive brake system was analysed on the basis of computer simulation by movable cellular automata method. The boundary conditions of the model were adjusted to experimental observations obtained by TEM. The model proved to be adequate for simulating mechanical mixing and velocity accommodation at the pad-disc interface. Dynamics of particle interaction were visualized by showing rotation angles and velocity vectors. The model provided information on the development of plastic deformation for metal-on-metal contacts and on crack formation at graphite lamellae of cast iron disc. Results are in agreement with conventional friction theories.
Zuverlässige Bestimmung von Chloridgehalten bei der Instandsetzung tausalzgeschädigter Bauwerke
(2010)
Betreiber, deren Betriebsbereiche den erweiterten Pflichten der Störfall-Verordnung unterliegen, müssen einen Sicherheitsbericht anfertigen, in dem Szenarien möglicher Störfälle beschrieben sind. Im Rahmen dieser Störfallauswirkungsbetrachtungen sind auch oftmals Szenarien zu untersuchen, bei denen Flüssigkeiten freigesetzt werden. Der Verdunstungsmassenstrom aus der Flüssigkeitslache ist der maßgebliche Eingangsparameter für die Gasausbreitungsberechnung mit der die Gefährdungsradien ermittelt werden. Für die Berechnung des Verdunstungsmassenstroms werden meist empirische Modelle eingesetzt. Anhand von experimentellen Daten aus eigenen Freilandversuchen werden die Leistungsfähigkeit sowie die Grenzen des Anwendungsbereichs diverser bekannter Modelle untersucht.
Ionic liquids (ILs) have attracted tremendous interest in the recent past for their potential in many chemical fields. The current report explores the effects of a set of ILs based on the 1-ethyl-3-methyl-imidazolium cation and different anions on the formation of gold nanoparticles. X-Ray diffraction finds face-centered cubic gold in all cases, but transmission electron microscopy (TEM) shows that there are distinct differences in particle formation and stabilization with the ethyl sulfate (ES), trifluoromethanesulfonate (TfO) and methanesulfonate (MS) anions. With the MS anion, nanoparticles with diameters between 5 and 7 nm form, which increasingly aggregate at higher reaction temperatures. With TfO, also small 5 to 7 nm particles form, but only at low temperatures. Above ca. 160 °C, large, ill-defined and aggregated particles form. With ES, polydisperse samples form at all temperatures except 160 °C. In this case the nanoparticles appear often surrounded by an IL film, which appears to stabilize individual, ca. 15 to 20 nm particles. Dynamic light scattering and UV/Vis spectroscopy further show that in suspension the particles are, much like seen in the TEM, more strongly aggregated with higher reaction temperatures. In summary, the results suggest that there are very specific IL-gold interactions that are responsible for the formation of gold particles with an IL-specific shape, size, and aggregation behavior.
Zuverlässige Bestimmung von Chloridgehalten bei der Instandsetzung tausalzgeschädigter Bauwerke
(2010)
Optical vs. mivroscopic properties of ECR and RF bias generated amoephous hydrogenated carbon films
(2010)
There is a general lack of information on the effects of full-bore obstacles on combustion in the literature, these obstacles are prevalent in many applications and knowledge of their effects on phenomena including burning rate, flame acceleration and DDT is important for the correct placing of explosion safety devices such as flame arresters and venting devices. In this work methane, propane, ethylene and hydrogen-air explosions were investigated in an 18 m long DN150 closed pipe with a 90 degree bend and various baffle obstacles placed at a short distance from the ignition source. After carrying out multiple experiments with the same configuration it was found that a relatively large variance existed in the measured flame speeds and overpressures, this was attributed to a stochastic element in how flames evolved and also how they caused and interacted with turbulence to produce flame acceleration. This led to several experiments being carried out for one configuration in order to obtain a meaningful average. It was shown that a 90 degree bend in a long tube had the ability to enhance flame speeds and overpressures, and shorten the run-up distance to DDT to a varying degree for a number of gases. In terms of the qualitative effects on these parameters they were comparable to baffle type obstacles with a blockage ratios of between 10 and 20%.
Degradation of material properties significant for lifetime extension of nuclear power plants
(2010)
The discussion about the right energy sources or alternative energy generation goes around the world, mostly in connection with green-house gas reduction. Therefore, some countries have started to consider extending operation of nuclear power plants. This demands an extensive plant life management as well as the knowledge of the degradation in material properties. The Basis Safety Concept (BSC) in Germany observed this circumstance. Still, lifetime extension is not an issue in Germany due to phase out of nuclear energy. Part of the BSC is the application of non-destructive examination (NDE) methods from the beginning, i.e. from component manufacture, to the end of life. The application of a NDE method to detect and size defects in components in nuclear power plants is presented. Some material properties and their degradation during increase of operation time are also in the focus of this paper.
Die unterschiedlichen Stoß- und Vibrationsbelastungen bei der Fahrt auf Straßen oder im freien Gelände dürften den meisten Lesern aus dem täglichen Leben bekannt sein. Je nach Ausführung und Zustand des Feder-/Dämpfungssystems eines Fahrzeuges spürt der menschliche Körper unterschiedliche Belastungen, die die Schmerzgrenze erreichen können. Diese dynamischen Belastungen werden auch auf Ladung, in unserem Fall auf die Gefahrgutumschließungen und auf das Gefahrgut, übertragen. Derartige Belastungen können durch entsprechende Stapelung und Sicherung der Ladung in ihren Auswirkungen gemindert werden. Für andere Belastungen, z. B. Stoß durch einen Auffahrunfall, sind Schutzsysteme am Heck des Fahrzeugs gefordert. Bei Tankfahrzeugen kann eine Beschädigung des Tanks durch einen solchen Auffahrschutz gemindert werden. Im vorliegenden Beitrag werden Ergebnisse von Vibrationsmessungen an Lastkraftwagen mit den Ergebnissen des Vibrationstests an einem Intermediate Bulk Container (IBC) verglichen. Berechnungen zum Auffahrschutz an Tankfahrzeugen werden Messergebnissen gegenübergestellt.
Freistrahlmodelle
(2010)