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The wet chemical deposition of solution processed transparent conducting oxides (TCO) provides an alternative low cost and economical deposition technique to realize large-areas of conducting films. Since the price for the most common TCO Indium Tin Oxide rises enormously, Aluminum Zinc Oxide (AZO) as alternative TCO reaches more and more interest. The optoelectronical properties of nanoparticle coatings strongly depend beneath the porosity of the coating on the shape and size of the used particles. By using bigger or rod-shaped particles it is possible to minimize the amount of grain boundaries resulting in an improvement of the electrical properties, whereas particles bigger than 100 nm should not be used if highly transparent coatings are necessary as these big particles scatter the visible light and lower the transmittance of the coatings. In this work we present a simple method to synthesize AZO particles with different shape and size, but comparable electronical properties. We use a simple, well reproducible polyol method for synthesis and influence the shape and size of the particles by adding different amounts of water to the precursor solution. We can show that the addition of aluminum as dopant strongly hinders the crystal growth but the addition of water counteracts this, so that both, spherical and rod-shaped particles can be obtained.
Es wird eine Möglichkeit zur Quantifizierung der Schädigung von Geweben bei der Martindale-Flachscheuerung vorgestellt, die eine interessante Möglichkeit darstellt, vergleichende Untersuchungen durchzuführen, auch wenn die Gewebe nicht bis zu einem Fadenbruch gescheuert werden. Die Untersuchungen deuten außerdem eine Skalierbarkeit der Scheuerversuche bei unterschiedlichen Anpressdrücken an. Sollte sich diese Beobachtung in weiteren Untersuchungen bestätigen, würde dies eine grundlegende Vereinfachung der Scheuerprüfung für verschiedene Anwendungen bedeuten.
Im Zuge von REACH wurden gängige hocheffektive halogenierte Flammschutzmittel verboten, da diese unter dem Verdach stehen, kanzerogen, mutagen und teratogen zu sein. Zur Zeit fehlen entsprechende Alternativen. Daher werden am DTNW neue umweltfreundliche und halogenfreie Flammschutzmittel auf der Basis von Phosphor- und Stickstoffverbindungen entwickelt, um einen entsprechenden Flammschutz zu gewährleisten. Neue Möglichkeiten werden im Rahmen dieses Artikels vorgestellt.
Energy consumption by air-conditioning is expansive and leads to the emission of millions of tons of CO2 every year. A promising approach to circumvent this problem is the reflection of solar radiation: Rooms that would not heat up by irradiation will not need to be cooled down. Especially, transparent conductive metal oxides exhibit high infrared (IR) reflectivity and are commonly applied as low-emissivity coatings (low-e coatings). Indium tin oxide (ITO) coatings are the state-of-the-art application, though indium is a rare and expensive resource. This work demonstrates that aluminum-doped zinc oxide (AZO) can be a suitable alternative to ITO for IR-reflection applications. AZO synthesized here exhibits better emissivity to be used as roofing membrane coatings for buildings in comparison to commercially available ITO coatings. AZO particles forming the reflective coating are generated via solvothermal synthesis routes and obtain high conductivity and IR reflectivity without the need of any further post-thermal treatment. Different synthesis parameters were studied, and their effects on both conductive and optical properties of the AZO nanoparticles were evaluated. To this end, a series of characterization methods, especially 27Al-nuclear magnetic resonance spectroscopy (27Al-NMR) analysis, have been conducted for a deeper insight into the particles’ structure to understand the differences in conductivity and optical properties. The optimized AZO nanoparticles were coated on flexible transparent textile-based roofing membranes and tested as low-e coatings. The membranes demonstrated higher thermal reflectance compared with commercial ITO materials with an emissivity value lowered by 16%.
Using the damage area as a quantification method for the Martindale test is a promising method to compare textile finishes without the need to test to full destruction. In addition, it could be shown that the results of Martindale tests performed with different pressure loads can be scaled to identical functional shape. If these results can be verified, this method would be a simplification of abrasive testing for different application areas.
Three established test methods employed for evaluating the abrasion or wear resistance of textile materials were compared to gain deeper insight into the specific damaging mechanisms to better understand a possible comparability of the results of the different tests. The knowledge of these mechanisms is necessary for a systematic development of finishing agents improving the wear resistance of textiles. Martindale, Schopper, and Einlehner tests were used to analyze two different fabrics made of natural (cotton) or synthetic (polyethylene terephthalate) fibers, respectively. Samples were investigated by digital microscopy and scanning electron microscopy to visualize the damage. Damage symptoms are compared and discussed with respect to differences in the damaging mechanisms.
Cleanable bag filter : comparisons of different testing methods of ageing of filter materials
(2019)
Cleanable bag filters are used to separate dust and other airborne particulate systems. Due to typical process conditions, they are subject to thermal, chemical and mechanical stress during use. The main objective of the IGF project no. 18307 "Investigation of the chemical and thermal degradation of cleanable filter media and improvement of their resistance by surface modification", was the development of a valid test method which can reproduce degradation caused by high temperatures and aggressive chemical atmospheres in a practice-oriented but time-saving manner. Within the IGF project, 2 accelerated ageing methods were applied, both of which have the decisive advantage of investigating damage in the gas phase. Many resistances of filter materials are otherwise carried out by immersing the materials in a mostly liquid damage medium at a defined temperature. These resistances are difficult to transfer ageing in the gas phase.
Abreinigbare Schlauchfilter kommen zur Abscheidung von Stäuben sowie staubförmigen Substanzen zum Einsatz. Aufgrund typischer Prozessbedingungen unterliegen sie während ihres Einsatzes thermischer, chemischer und mechanischer Beanspruchung. Das IGF-Projekt Nr. 18307 "Untersuchung der chemischen und thermischen Degradation von abreinigbaren Filtermedien und Verbesserung deren Beständigkeit durch Oberflächenmodifikation" hat mehrere Prüfmethoden verglichen.
In the IGF project No. 19617 N, nitrogen and phosphorous substituted alkoxysilanes were prepared and their ability to inhibit fire growth and spread for fabrics was explored. To this end, a series of flame retardants were synthesized using different strategies including click chemistry and nucleophilic substitution of commercial organophosphorus compounds with amino-based trialkoxysilanes and/or cyanuric chloride. The new halogen-free and aldehyde-free flame retardants were applied to different fabrics such as cotton (CO), polyethylene terephthalate (PET), polyamide (PA) and their blends using the well-known pad-dry-cure technique and sol-gel method. The flame-retarding efficiencies were evaluated by EN ISO 15025 test methods (protective clothing-protection against heat and flame method of test for limited flame spread). Good flame retardancy of the hybrid organic-inorganic materials was achieved with the addition of as small amount as 3-5 wt.% for cotton fabrics. Moreover, the water solubility and the washing resistance could be controlled through the functional groups attached to the phosphor atom or through the optimization of the curing temperature. Overall, the research project demonstrated that N-P-silanes are very good permanent flame retardants for textiles.
Im IGF-Projekt Nr. 19617 N wurden stickstoff- und phosphorsubstituierte Alkoxysilane hergestellt und ihre flammhemmenden Eigenschaften für Textilien untersucht. Die Synthesen erfolgten nach unterschiedlichen Strategien wie der Klick-Chemie und der nukleophilen Substitution kommerziell erhältlicher Organophosphorverbindungen mit aminobasierten Trialkoxysilanen und/oder Cyanurchlorid. Diese neuartigen, halogen- und aldehydfreien Flammschutzmittel wurden auf Stoffe aus Baumwolle (BW), Polyethylenterephthalat (PET), Polyamid (PA), sowie Mischgeweben daraus mit der industriell etablierten Pad-Dry-Cure-Technik und mittels Sol-Gel-Verfahren aufgetragen. Die flammhemmenden Eigenschaften wurden mit den Prüfverfahren nach EN ISO 15025 (Schutzkleidung – Schutz gegen Hitze und Flammprüfverfahren für begrenzte Flammenausbreitung= bewertet. Eine gute Schwerentflammbarkeit der hybriden organisch-anorganischen Materialien wurde bei einer geringen Menge von 3-5 Gew.% auf Baumwollgeweben erreicht. Darüber hinaus konnten die Wasserlöslichkeit und die Waschbeständigkeit durch die an das Phosphoratom gebundenen funktionellen Gruppen und durch die Optimierung der Härtungstemperatur kontrolliert werden. Insgesamt zeigte das Forschungsprojekt, dass N-P-Silane sehr gute permanente Flammschutzmittel für Textilien sind.