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Organisationseinheit der BAM
Paper des Monats
- ja (1)
Adhesion and other mechanical behaviour of coatings is at present routinely tested in industry and research organisations using the scratch test. The test has been the subject of a European Standard prEN 1071-3:2000 established by the European Standards Committee CEN TC184 WG5. A previous European project on the development and validation of test methods for thin hard coatings—FASTE—revealed that uncertainties in the Rockwell C stylus tip shape represent a major source of error for the scratch-test method. Therefore a follow-up project—REMAST—was started to develop and certify a reference material as a quality control tool for the testing and qualification of scratch-test instruments. In addition, a considerable effort was devoted to improve the scratch stylus manufacturing process. This paper presents the results of the REMAST project. During a feasibility study, two candidate materials—titanium nitride (TiN) and diamond-like carbon (DLC) coatings both on high speed steel substrates—were evaluated. Because of the lower sensitivity to styli tip shape variations and higher data scatter observed for the TiN coating, DLC was chosen as the reference material to be certified. One thousand samples were produced, as well as qualified styli to carry out the certification campaign, including homogeneity and stability testing. Nine independent laboratories were involved in the certification exercise, and the data were statistically analysed to obtain the certified critical load values and their uncertainty ranges. A certified reference material BCR-692 is available for verification purposes. This presents three repeatable failure events at certified critical load intervals and can provide a good indication of overall scratch-test instrument performance, including stylus condition and calibration. It is also useful as a diagnostic tool, providing a means of sensitive monitoring of machine and stylus performance over extended periods. Considerable improvement of the quality of scratch styli was achieved by the strict control of all manufacturing steps.
Aufzählung der wichtigsten wissenschaftlich-technischen und anderer wesentlicher Ergebnisse
• ALD Abscheidungen auf Polymeren (PE, PP, PTFE) unter Atmosphärendruck und im Vakuum mit Ozon als Oxidationsmittel wurden durchgeführt:
- Mit Variation der Schichtdicke
- Mit Variation der Zykluszeit
- Mit und ohne Ozon Vorbehandlung der Oberfläche
• ALD Abscheidungen auf (PE, PP, PTFE) in Vakuum mit O2- und H2-Plasma Vorbehandlung wurden durchgeführt.
- Mit Variation der Schichtdicke
- Mit Variation der Zykluszeit
- Mit und ohne Plasma Vorbehandlung der Oberfläche
• Die ALD Prozesse wurden mit in situ Laserellipsometrie untersucht.
• Die ALD Schichten wurden für die Haftfestigkeit bei der BAM ausgewerte
DNA and locked nucleic acid (LNA) were characterized as single strands, as well as double stranded DNA-DNA duplexes and DNA-LNA hybrids using tandem mass spectrometry with collision-induced dissociation. Additionally, ion mobility spectrometry was carried out on selected species. Oligonucleotide duplexes of different sequences – bearing mismatch positions and abasic sites of complementary DNA 15-mers – were investigated to unravel general trends in their stability in the gas phase. Single stranded LNA oligonucleotides were also investigated with respect to their gas phase behavior and fragmentation upon collision-induced dissociation. In contrast to the collision-induced dissociation of DNA, almost no base loss was observed for LNAs. Here, backbone cleavages were the dominant dissociation pathways. This finding was further underlined by the need for higher activation energies. Base losses from the LNA strand were also absent in fragmentation experiments of the investigated DNA-LNA hybrid duplexes. While DNA-DNA duplexes dissociated easily into single stranded fragments, the high stability of DNA-LNA hybrids resulted in predominant fragmentation of the DNA part rather than the LNA, while base losses were only observed from the DNA single strand of the hybrid.
Decorative hard coatings: interdependence of optical, stoichiometric and structural properties
(1993)
Decorative optical coatings
(1994)
Nanotechnologien werden gegenwärtig als leistungsfähige Oberflächentechniken in erheblichem Umfange industriell genutzt. Dabei spielen dünne Schichten und deren Kenndaten eine wesentliche Rolle, z.B. als Röntgenspiegel oder optische und magnetooptische Datenträger. Die Schichtdicke zählt hierbei zu den technologisch wichtigen Parametern. Abgeleitet von Anwenderinteressen, werden für die Röntgenreflektometrie (XRR bzw. GIXR), Elektronenstrahl-Mikroanalyse (EPMA) und Röntgenfluoreszenzanalyse (XRF) einerseits und die Ellipsometrie andererseits zugeschnittene Schichtdickenmaßverkörperungen (SDM) entwickelt, gefertigt und untersucht. Das Ziel ist die Bereitstellung praxistauglicher, kalibrierter SDM, im weiteren Schichtdickennormale (SDN) genannt. SDN sind Maßverkörperungen, für die der Schichtdickenwert mit einer definierten Messunsicherheit bekannt und auf ein metrologisch anerkanntes Längennormal zurückgeführt ist. Berichtet wird über die Herstellung und messtechnische Charakterisierung der beiden spezifischen Varianten von Maßverkörperungen.
Three effects have been observed in wet-thermally grown structures under bombardement with energetic 15N ions: (1) Out-diffusion of H from the SiO2/Si system through the surface, (2) Accumulation of H at the SiO2/Si interface, (3) Changes in the optical fingerprint spectra of Ψ and Δ in dependence on λ (wavelength) obtained by ellipsometric measurements.
Flexible electrochromic devices (ECDs) based on Fe(II)-metallo-supramolecular polyelectrolytes (Fe-MEPE) and vanadium oxide are studied in operando by means of x-ray absorption fine structure (XAFS) spectroscopy. The ECDs are blue-purple in the colored state at 0.0 V and become light yellow when a voltage of 1.6 V is applied. The XAFS studies at the K-edge of Fe(II) reveals that the absorption edge is shifted toward higher energies by 1.8 eV in the transparent state. Comparison of two different ECDs and different charge cycles demonstrates the reversibility and repeatability of the process. We attribute the shift to a charge transfer and a change of oxidation state of the ions from Fe2+ to Fe3+. The transition is not accompanied by a noticeable structural change of the octahedral coordination geometry as confirmed by analysis of the extended x-ray absorption fine structure (EXAFS) data. (C) 2015 Elsevier B.V. All rights reserved.
The composition of acoustically levitated droplets was probed by a novel combination of mid-IR laser evaporation and subsequent postionization via secondary electrospray ionization. The combination of microliter samples and subnanoliter sampling provided time-resolved interrogation of droplets and allowed for a kinetic investigation of the laser-induced release of the analyte, which was found to strongly depend on the analytes. The observed substancespecific delayed release of the analytes permitted baseline-separated discrimination of the analytes, ideal for the study of complex samples.
The additionally applied postionization scheme was found to enable efficient detection of small volatile compounds as well as peptides. The detection of small molecules and peptides occurred under very different sampling geometries, pointing to two distinct underlying ionization mechanisms. Overall, our results suggest that the experimental setup presented in this study can serve as a widely applicable platform to study chemical reactions in acoustically levitated droplets as model reactors.
Ancient mariners knew that dust whipped up from deserts by strong winds travelled long distances, including over oceans. Satellite remote sensing revealed major dust sources across the Sahara. Indeed, the Bodélé Depression in the Republic of Chad has been called the dustiest place on earth. We analysed desert sand from various locations in Chad and dust that had blown to the Cape Verde Islands. High throughput sequencing techniques combined with classical microbiological methods showed that the samples contained a large variety of microbes well adapted to the harsh desert conditions. The most abundant bacterial groupings in four different phyla included: (a) Firmicutes—Bacillaceae, (b) Actinobacteria—Geodermatophilaceae, Nocardiodaceae and Solirubrobacteraceae, (c) Proteobacteria—Oxalobacteraceae, Rhizobiales and Sphingomonadaceae, and (d) Bacteroidetes—Cytophagaceae. Ascomycota was the overwhelmingly dominant fungal group followed by Basidiomycota and traces of Chytridiomycota, Microsporidia and Glomeromycota. Two freshwater algae (Trebouxiophyceae) were isolated. Most predominant taxa are widely distributed land inhabitants that are common in soil and on the surfaces of plants. Examples include Bradyrhizobium spp. that nodulate and fix nitrogen in Acacia species, the predominant trees of the Sahara as well as Herbaspirillum (Oxalobacteraceae), a group of chemoorganotrophic free-living soil inhabitants that fix nitrogen in association with Gramineae roots. Few pathogenic strains were found, suggesting that African dust is not a large threat to public health.
Microbiological studies on the intercontinental transport of dust are confounded by the difficulty of obtaining sufficient material for analysis. Axenic samples of dust collected at high altitudes or historic specimens in museums are often so small and precious that the material can only be sacrificed when positive results are assured. With this in mind, we evaluated current methods and developed new ones in an attempt to catalogue all microbes present in small dust or sand samples. The methods used included classical microbiological approaches in which sand extracts were plated out on a variety of different media, polymerase chain reaction (PCR)-based amplification of 16S/18S rRNA sequences followed by construction of clone libraries, PCR amplification of 16S rRNA sequences followed by high-throughput sequencing (HtS) of the products and direct HtS of DNA extracted from the sand. A representative sand sample collected at Bahaï Wadi in the desert of the Republic of Chad was used. HtS with or without amplification showed the most promise and can be performed on ≤100 ng DNA. Since living microbes are often required, current best practices would involve geochemical and microscopic characterisation of the sample, followed by DNA isolation and direct HtS. Once the microbial content of the sample has been deciphered, growth conditions (including media) can be tailored to isolate the micro-organisms of interest.
The combination of acoustically levitated droplets, mid-IR laser evaporation, and subsequent post-ionization by secondary electrospray ionization was applied for monitoring the enzymatic digestion of various proteins. Acoustically levitated droplets are an ideal, wall-free model reactor, readily allowing compartmentalized microfluidic trypsin digestions. Time-resolved interrogation of the droplets yielded real-time information on the progress of the reaction and thus provided insights into reaction kinetics. After 30 min of digestion in the acoustic levitator, the obtained protein sequence coverages were identical to the reference overnight digestions. Importantly, our results clearly demonstrate that the applied experimental setup can be used for the real-time investigation of chemical reactions. Furthermore, the described methodology only uses a fraction of the typically applied amounts of solvent, analyte, and trypsin. Thus, the results exemplify the use of acoustic levitation as a green analytical chemistry alternative to the currently used batch reactions.
The multiple-sample approach by means of centrifugal adhesion testing (CAT-technology) allows the determination of bonding strength of adhesive-bonded joints on a statistical basis of up to eight samples. Therefore, it is obvious to ensure the continuous handling and identical processing of an octet of samples within the entire process chain of wet-chemical cleaning, plasma-chemical pre-treatment, bonding of samples, and testing of bonding strength. Within the multiple-sample bonding set-up (MPKV-technology) a defined bonding pressure can be adjusted regardless the actual number of samples. A comparison of single- and multiple-sample approach is made for bonding strength of selected adhesives, double-sided adhesive tapes and different material combinations [stainless steel (V2A) vs. stainless steel, polyamide (PA), or polypropylene (PP)]. It is shown that both technologies improve reliability of results
High-accuracy film thickness measurements in the range below 100 nm can be made by various complex methods like spectral ellipsometry (SE), scanning force microscopy (SFM), grazing incidence X-ray reflectometry (GIXR), or X-ray fluorescence analysis (XRF). The measurement results achieved with these methods are based on different interactions between the film and the probe. A key question in nanotechnology is how to achieve consistent results on a level of uncertainty below one nanometre with different techniques.
Two different types of thickness standards are realised. Metal film standards for X-ray techniques in the thickness range 10 to 50 nm are calibrated by GIXR with monochromatised synchrotron radiation of 8048 eV. The results obtained at four different facilities show excellent agreement. SiO2 on Si standards for SE and SFM in the thickness range 6 to 1000 nm are calibrated by GIXR with monochromatised synchrotron radiation of 1841 eV and with a metrological SFM. Consistent results within the combined uncertainties are obtained with the two methods. Surfaces and interfaces of both types of standards are additionally investigated by transmission electron microscopy (TEM).
Thermo-mechanical fatigue (TMF) testing plays an increasingly important role in the design, the reliability assessment and the lifecycle management of safety critical components used, for instance, for power generation, in the process industry and in aeronautical and automotive applications, with a view to increasing the fuel efficiency, safety and service intervals, while reducing production (and material) costs. In a European Commission funded research project (acronym: TMF-Standard) of the 5th Framework Programme, 20 European laboratories have undertaken a joint research effort to establish a validated code-of-practice (CoP) for strain-controlled TMF testing. Starting from a survey of the testing protocols and procedures previously used by the partners, a comprehensive pre-normative research activity into various issues has been completed, addressing the dynamic temperature control, the effects of deviations in nominal temperatures and phase angles, the influences of temperature gradients, as well as the practicalities of test interruption and restart procedures. Meaningful allowable tolerances for the various test parameters were identified and practical recommendations as to the test techniques were formulated. From this a preliminary CoP was compiled and used to guide an extensive round robin exercise among the project partners. From the statistical analysis of that exercise, a validated CoP was derived dealing with strain-controlled constant amplitude TMF of nominally homogeneous metallic materials subjected to spatially uniform temperature fields and uniaxial mechanical loading. It is intended to give advice and guidance on the appropriate test setup, testing procedures and the analysis of results, in particular for newcomers in the field of strain-controlled TMF. This paper highlights some of the results of the TMF-Standard project. Moreover, commonalities and differences of the present CoP with respect to the standard documents for strain-controlled TMF, which have been developed at ISO and ASTM levels, are presented in this paper.