Wissenschaftliche Artikel der BAM
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- 2016 (64) (entfernen)
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Die Anwendung thermoanalytischer Methoden für die Polymercharakterisierung hat aufgrund der makromolekularen Struktur von Polymere Vorteile. Es wurden zwei neue thermoanalyti-sche Verfahren entwickelt und deren Einsatz anhand von Anendungsbeispielen demons-triert, sowie mit etablierten, thermoanalytischen Methoden verglichen.
Für die thermische- und thermo-oxidative Zersetzungsgasanalytik wurde die Thermogravi-metrie (TGA) gekoppelt mit der Thermodesoptions-Gaschromatographie-Massenspektrometrie (TDS-GC-MS). Die Zersetzungsgase der TGA wurden dafür über ei-nen Festphasenadsorber geleitet, auf dem eine repräsentative Auswahl von polymerspezifi-schen Analyten adsorbiert wurde. Die thermische Extraktion der Analyten erfolgte in der TDS-GC-MS. Dies ermöglichte die Trennung der Analyten sowie die eindeutige Identifizie-rung mittels charakteristischer Massenfragmentmuster. Sie wurde als TED-GC-MS bezeichnet. Es stellte sich heraus, dass sie sich besonders für die Analyse von komplexen Kohlen-wasserstoffgemischen mit Molmassen von mehr als 100 g/mol eignet. In Kombination mit anderen Kopplungstechniken wie beispielsweise die TGA-FTIR/MS, die speziell für die Ana-lyse von kleineren Molekülen verwendet wurde, konnten neue grundlegende Zersetzungs-mechanismen entwickelt werden. Es wurde beispielsweise sichtbar, dass sowohl bei der thermischen als auch bei der thermo-oxidativen Degradation von Polyamid 66 (PA 66) Kon-densationsreaktionen eine wichtige Rolle spielen. Die Methode erwies sich darüber hinaus als besonders geeignet für die Identifizierung und Quantifizierung von Polymeren in Umweltproben. Es entstand dazu eine erste grundlegende Arbeit für die quantitative Bestimmung von Polyethylen (PE) Mikroplastik in Umweltproben.
Im zweiten Teil der Arbeit wurde eine steuerbare beheizbare Zelle eingeführt. Mit ihr war es möglich, mit Hilfe der Nahinfrarotspektroskopie (NIR), sich verändernde Netzwerkstrukturen während der Härtung sichtbar zu machen. Vergleichend dazu wurden etablierte, kalorische Messungen durchgeführt. Somit konnten für verschiedene Epoxidsysteme die Aushärtegrade während der Härtung mit variablen Heizraten bestimmt werden. Dadurch konnten Aushär-tungskinetiken erstellt werden, die durch isotherme und komplexe Aushärtungsszenarien validiert wurden.
Radiation induced attenuation in perfluorinated polymer optical fibres for dosimetry applications
(2016)
Real-time measurement of radiation-induced attenuation (RIA) in a commercial perfluorinated polymer optical fibre (PF-POF) is performed with regard to on-line Radiation monitoring purposes. Spectral character and dose dependence of fibre’s RIA is measured in 450-900 nm spectral region. Fibre exhibited high radiation sensitivity in the visible region with strong increase towards the UV wavelengths. Good linearity and high sensitivity reaching up to 130 dBm-1/kGy was demonstrated in the VIS region for a low-dose range. This of-the-shelf PF-POF could be therefore interesting for on-line remote dosimetry applications.
Impact of gamma radiation on transmission of a commercial Cytop polymer optical fibre (Lucina, Asahi Glass Company) is investigated. Spectral dependence of radiation induced attenuation in the investigated fibre is measured in the VIS-NIR spectral region. Besides attenuation increase, radiation is found to increase fibre susceptibility to water as well. While pristine Cytop fibre is rather humidity insensitive, strong humidity related absorption in the NIR region is observed after fibre irradiation. Selective irradiation of separate fibre sections is proposed as a way of fibre humidity sensitization and quasi-distributed water detection is demonstrated using optical time domain reflectometry at 1310 nm.
This author interview is by Dr Michael G. Weller, Head of Division 1.5 Protein Analysis at Federal Institute for Materials Research and Testing (BAM). BAM (www.bam.de/en) is a senior scientific and technical institute with responsibility to the German Federal Ministry for Economic Affairs and Energy. Dr Weller's review paper, Quality issues of research antibodies is available for download in Analytical Chemistry Insights.
Investigation of manuscripts found in sites along the Silk Road shows the history of communication and exchange between Asia and the Mediterranean over the centuries. Different scripts and languages preserved on paper in certain styles provide information about traditions and provenance.
To get an idea of the cultural background of the highly developed painting techniques obvious in some illuminated manuscripts, the material used for writing and painting is analyzed. Singular Sogdian and Tocharian manuscripts from Turfan show text on one side with a colorful painting on the other side of the document. In comparison with other productions of different periods or usages from the site, special features are worked out to characterize cultural roots or influence in the network of relationships. Details analyzed in the most elaborated documents Show various influences led to the colorful masterpieces.
The content of the paper is the assessment of the performance of (conventional) measurement techniques (MTs)with respect to the classification of disperse materials according to the EC recommendation for a definition of nanomaterial. This performance essentially refers to the accurate assessment of the number weighted median of (the constituent) particles. All data and conclusions are based on the analytical study conducted as real-world performance testing.
It comprised different types of MTs (imaging, counting, fractionating, spectroscopic and integral) as well as different types of materials. Beside reference materials with well-defined size distribution the study also included several commercial powders (variation of particle composition, morphology, coating, size range and polydispersity). In order to ensure comparability of measurement results, the participants were guided to use uniform protocols in sample preparation, conducting measurements, data analysis and in reporting results. Corresponding documents have been made public, in order to support the reviewing process of the paper, respectively to ensure the reproducibility of data by other users under the same conditions.
The scientific paper relies on a comprehensive set of revised measurement data reported in uniform templates, completely describes the experimental procedures and discusses the MTs’ performance for selected materials in detail. Even more, the study is summarised and evaluated, which leads to recommendations for the use of MTs within a tiered approach of NM characterisation. In addition, the paper critically examines the factors that may affect the outcome of such a comparison among different MTs.
The detection and characterization of surface cracks in steel specimens prior to damage is a technologically and economically highly significant task and is of utmost importance when it comes to safety-relevant structures. In steel production where steel billets at high temperatures have to be inspected while moving a number of well-established NDT methods cannot be applied. Laser thermography however is a promising candidate to serve as a fast, non-contact and remote tool in this case. We present a study that shows that the crack detection capabilities of laser thermography can be extended also to specimens at high temperature. A combination of inductive and laser heating allows to systematically study the contrast formation as well as the optimization of the important measurement parameters. The experiments are accompanied by FEM simulations that provide a better insight of the physical correlations and support the experimental developments. The aim of these studies is to develop a system with high inspection speed and detection performance to be in-line operated under the hostile environment of steel production lines.
In this study, the feasibility of using non-contact Infrared thermography as a potential tool to monitor the CMT welding process is explored. The presence of internal defects such as porosity, lack of filler material deposition and formation of improper weld bead produce perturbations in the surface temperature which can be identified using an Infrared thermography technique. We present recent results obtained from online monitoring of the the dissimilar joining using CMT weld brazing of Aluminum and Steel using a transmission mode measurement approach. The effect of loss of zinc coating on the weldability of the cold metal transfer joining of aluminum to galvanised steel was investigated. A correlation between measured online thermal indications with the weld anomalies is successfully attempted and the results are compared with the conventional post-weld NDT inspection methods.
IND15 JRP SurfChem: Traceable quantitative surface chemical analysis for industrial applications
(2016)
The SurfChem project has made a significant contribution to traceable quantitative surface chemical analysis for industrial applications by delivering new certified reference materials and test samples for specific technical applications. Regular performance tests of instruments, metrological methodology for the detection of (bio)organic surface species, ambient and non-destructive surface chemical analysis for in-line process control and new in situ characterisation techniques of catalytically active surfaces have been achieved.
Materials and chemical producers require detailed knowledge of surface chemistry for research into new products. One way to understand a surface without damaging it is to bombard it with an electron beam, causing its atoms to emit characteristic X-rays enabling identification. The measurement of these must be precise as many elements emissions are close in energy – traceable reference materials will ensure instruments using this technique are stable and accurate.