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- 2012 (6) (entfernen)
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- Englisch (6)
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- Adhesion (1)
- Anti-counterfeiting (1)
- Broadband airborne ultrasound (1)
- Centrifuge test (1)
- Coating (1)
- Dissolution-precipitation (1)
- Ellipsometrie (1)
- Ellipsometry (1)
- Experimental mineralogy (1)
- Fabry-Perot Schichten (1)
Public, hidden, and forensic features either encoded or directly legible are used for authentication. Fabry-Perot layer stacks as information carriers in combination with imaging ellipsometry as optical read-out system provide all-in-one anti-counterfeiting capability that may establish the new security level 'encoded forensic'. Different layer designs are described with regard to all three security levels: public features (e.g. color and tilt effect) perceptible by the human eye, hidden features (e.g. spectroscopic response in the UV or IR), and forensic features (ellipsometric quantities Ψ and Δ as a function of wavelength λ and angle of incidence AOI). Physically uncloneable functions (PUF) could be realized as a result of a multi-material and a multi-parameter deposition approach as well as by means of specific design features of the Fabry-Perot layer stack. Hence, they are not subject to any reverse engineering strategies. Examples of stratified, micro-structured, and laser-modified Fabry-Perot layer systems are considered that may be used at all perception levels (e.g. human eye, bar code reader, and imaging ellipsometry) for authentication against product counterfeiting and related areas. --------------------------------------------------------------------------------------------------------------------
Zur Authentifizierung werden offene, versteckte und forensische Merkmale entweder codiert oder direkt auslesbar verwendet. Mit Fabry-Perot Schichtsystemen als Informationsträger in Kombination mit der abbildenden Ellipsometrie als optischem Auslesesystem steht ein 'all-in-one' Fälschungsschutz-System zur Verfügung, das ein neues Sicherheitsniveau 'kodiert-forensisch' darstellt. Es werden unterschiedliche Schichtdesigns beschrieben, mit denen alle drei Sicherheitsniveaus realisiert werden können: offene Merkmale (z.B. Farbe und Kippeffekt), die mit dem menschlichen Auge wahrnehmbar sind, versteckte Merkmale (z.B. die spektrale Antwort im Sichtbaren oder im IR) sowie forensische Merkmale (ellipsometrische Größen Ψ und Δ als Funktion der Wellenlänge λ und des Einfallswinkels AOI).
Physikalisch nicht klonbare Funktionen (PUF) können im Ergebnis einer Multi-Material- und Multi-Parameter Beschichtungsstrategie sowie durch spezifische Design-Merkmale des Fabry-Perot Schichtsystems realisiert werden. Folglich sind solche Schichtsysteme dem 'reverse engineering' nicht zugänglich. Es werden Beispiele für lateral ausgedehnte, mikrostrukturierte und Laser modifizierte Schichtsysteme auf verschiedenen Ausleseniveaus (menschliches Auge, Barcode-Lesegerät, abbildendes Ellipsometer) vorgestellt, die zur Authentifizierung von Produkten und verwandte Gebiete geeignet sind.
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.
Most of the polymeric materials used are easy to ignite and show extensive flame spread along their surfaces. Apart from extensive heat release rates, their short time to ignition (tig), in particular, is a key fire hazard. Preventing ignition eliminates fire hazards completely. Protection layers that shift tig by more than an order of magnitude are powerful flame retardancy approaches presenting an alternative to the usual flame retardancy concepts.
Coatings are proposed that consist of a three-layer system to ensure adhesion to the substrate, acting as an infrared (IR) mirror and protecting against oxidation. The IR-mirror layer stack is realised by physical vapour deposition in the sub-micrometre (<1 µm) range, reducing heat absorption by up to an order of magnitude. Not only is the ease of ignition diminished (tig is increased by several minutes), the flame spread and fire growth indices are also remarkably reduced to as little as 1/10 of the values of the uncoated polymers open for further optimization. Sub-micrometre thin IR-mirror coatings yielding surface absorptivity <0.1 are proposed as a novel and innovative flame retardancy approach.
Embedding of information on surfaces is state of the art for identification testing in which public, hidden and forensic features are used. In many instances, the legal authentication of a product, a material or a document is required. Among the surface-based encoded labels, bar codes and data matrices are most frequently applied. They are publicly visible. The material itself is irrelevant, only a sufficient optical contrast is required.
However, a strong material dependence of the label can be achieved by means of Fabry-Perot layer stacks. Stack designs are described with regard to all three security levels: public features (e.g. color and tilt effect) perceptible by the human eye, hidden features (e.g. optical response in a given spectral range) detectable by commonly available instruments and forensic features (ellipsometric quantities Ψ and Δ as a function of wavelength λ and angle of incidence AOI) only detectable by sophisticated instruments.
Regarding material-correlated authentication, ellipsometric quantities Ψ and Δ are used as encoded forensic features for the first time. Hence, Fabry-Perot layer stacks as information carriers in combination with imaging ellipsometry as optical read-out system provide all-in-one anti-counterfeiting capabilities.
Standardised conventional adhesion tests are time-consuming single-sample tests. Moreover, except for the pull-off test, all these tests provide only qualitative or semi-quantitative (ranking, respectively measurement of an adhesion-correlated quantity) information on adhesion. Sometimes, adhesion is evaluated even under compressive stress conditions (e.g. cross-cut and scratch test), which itself is a contradiction to adhesive strength as defined in terms of tensile force per area.
For optical coatings it has been shown that the pull-off test in a centrifuge is definitely a promising alternative with respect to the reliable, fast and quantitative determination of adhesive strength in N/mm2. The force-controlled centrifuge test is the only multiple-sample test which provides reliable quantitative information on the adhesive strength in agreement with DIN EN 15870 and DIN EN ISO 4624 on a statistical basis for up to eight samples simultaneously tested under identical testing conditions.
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.