6 Materialchemie
Filtern
Erscheinungsjahr
- 2019 (274) (entfernen)
Dokumenttyp
- Vortrag (164)
- Posterpräsentation (76)
- Zeitschriftenartikel (13)
- Beitrag zu einem Tagungsband (13)
- Forschungsbericht (5)
- Sonstiges (2)
- Sammelband (Herausgeberschaft für den kompletten Band) (1)
Sprache
- Englisch (222)
- Deutsch (51)
- Mehrsprachig (1)
Referierte Publikation
- nein (274) (entfernen)
Schlagworte
- Mikroplastik (21)
- Nanoparticles (19)
- TED-GC-MS (18)
- Microplastics (13)
- Mechanochemistry (12)
- Surface functionalization (12)
- Boehmite (10)
- EPMA (10)
- SAXS (10)
- Laser-induced periodic surface structures (LIPSS) (9)
Organisationseinheit der BAM
- 6 Materialchemie (274)
- 6.6 Physik und chemische Analytik der Polymere (91)
- 6.1 Oberflächen- und Dünnschichtanalyse (65)
- 6.3 Strukturanalytik (57)
- 6.2 Material- und Oberflächentechnologien (34)
- 6.7 Materialsynthese und Design (30)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (18)
- 7 Bauwerkssicherheit (15)
- 1 Analytische Chemie; Referenzmaterialien (9)
- 4 Material und Umwelt (9)
Eingeladener Vortrag
- nein (164)
Polymers at interfaces play a major role in a broad variety of applications ranging from engineering purposes (for instance polymer based nanocomposites) to high tech implications (for instance light emitting diodes).
Here, thin films with thicknesses down to few nanometers are prepared on different substrates as model systems for polymer composites. The thin films are investigated by a combination of surface analytical and volume sensitive methods. As surface analytical methods atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements (CAM) are employed. As volume sensitive broadband dielectric spectroscopy (BDS), specific heat spectroscopy (SHS), and ellipsometry are used. Especially attention is paid to understand the glass transition behavior of thin films because the glass transition is the key phenomenon determines the application of polymers also in thin films.
To understand the glass transition behavior of thin films, which is controversially discussed in literature, a three layer model is discussed. Firstly, a mobile surface layer is assumed at polymer air interface of the film due to missing of segment/segment interactions. Secondly, in the middle of the film a bulk-like layer should be expected. Thirdly, for polymers having non-repulsive interactions with the substrate an irreversibly adsorbed layer is expected to be formed. Due the adsorption the molecular mobility of the segments in this layer is slowed down. What is measured for the glass transition of thin films is a complicated average of all of these effects. The different layers are hardly to address separately. Therefore, in the presentation especially model systems are selected and investigated to verify the layer model.
Mechanochemistry is a fast and efficient method applicable for the synthesis of new organic, metal-organic, and inorganic compounds. The direct monitoring of milling reactions is still challenging. The underlying reaction mechanisms remain often unclear. In the last years, have established a tandem in situ approach for investigating mechanochemical reactions using time-resolved in situ XRD coupled with Raman spectroscopy. Here, we present an in situ coupling of synchrotron XRD, Raman spectroscopy, and thermography allowing the observation of mechanochemical reactions in real time. Information on the crystalline, molecular, and temperature state of the materials during grinding could be collected. The chemical composition of the reaction mixture was found to be directly correlated with changes in the temperature profile of the reaction. Furthermore, the presented setup allows the detection of crystalline, amorphous, eutectic as well as liquid intermediates. The resulting deeper kinetic and thermodynamic understanding of milling processes is the key for future optimization of mechanochemical syntheses.
Worldwide there is a variety of regulatory provisions addressing nanomaterials. The identification as nanomaterial in a regulatory context often has the consequence that specific legal rules apply. In identifying nanomaterials, and to find out whether nanomaterial-specific provisions apply, the external size of particles is globally used as a criterion. For legal certainty, its assessment for regulatory purposes should be based on measurements and methods that are robust, fit for the purpose and ready to be accepted by different stakeholders and authorities. This should help to assure the safety of nanomaterials and at the same time facilitate their international trading. Therefore, we propose a categorisation scheme which is driven by the capabilities of common characterisation techniques for particle size measurement. Categorising materials according to this scheme takes into account the particle properties that are most important for a determination of their size. The categorisation is exemplified for the specific particle number based size metric of the European Commission's recommendation on the definition of nanomaterial, but it is applicable to other metrics as well. Matching the performance profiles of the measurement techniques with the material property profiles (i) allows selecting the most appropriate size determination technique for every type of material considered, (ii) enables proper identification of nanomaterials, and (iii) has the potential to be accepted by regulators, industry and consumers alike. Having such a scheme in place would facilitate the regulatory assessment of nanomaterials in regional legislation as well as in international relations between different regulatory regions assuring the safe trade of nanomaterials.