The process of ozone treatment of high kappa kraft pulp is studied using polarization modulated Fourier transform infrared spectroscopy and atomic force microscopy. The complementary information from the two methods enables a detailed analysis of reaction sites on the fibers, and gives a detailed view of the reaction mechanisms of delignification by ozone treatment. Furthermore we describe a simple method to measure the kappa number of paper sheets that can be used on-line.
A flexible transparent heater is presented, based on an all-sprayed composite architecture of indium-doped zinc oxide (IZO) layers that sandwich a network of silver nanowires, on a polyimide-foil substrate. This architecture could be materialized through the development of a low-temperature (240 °C) spray-pyrolysis process for the IZO layers, which is compatible with the thermal stability of the transparent polyimide substrate and allows for the formation of compact and transparent layers, without precipitates. The IZO layers entirely embed the silver nanowires, offering protection against environmental degradation and decreasing the junction resistance of the nanowire network. The resulting transparent heaters have a high mean transmittance of 0.76 (including the substrate) and sheet resistance of 7.5 Ω/sq. A steady-state temperature of ~130 °C is achieved at an applied bias of 3.5 V, with fast heater response times, with a time constant of ~4 s The heater is mechanically stable, reaching or surpassing 100 °C (at 3.5 V), under tensile, respectively, compressive-bending stress. This work shows that high-performance transparent heaters can be fabricated using all-sprayed oxide/silver-nanowire composite coatings, that are compatible with large-scale and low-cost production.
<div class="section abstract"><div class="htmlview paragraph">If an Unmanned Aerial Systems (UAS) encounters icing conditions during flight, those conditions might result in degraded aerodynamic performance of the overall UAS. If the UAS is not reacting appropriately, safety critical situations can quickly arise. Thereby, the rotors, respectively the propellers of the UAS are especially susceptible due to the increased airflow through their domain and the corresponding higher impingement rate of supercooled water droplets. In many cases, the UAS cannot be properly operated if the rotors are not fully functional, as they are a vital component. The FFG/BMK funded research and development project</div><div class="htmlview paragraph">“All-weather Drone” is investigating the icing phenomenon on UAS rotors for a 25 kg maximum take-off weight (MTOW) multirotor UAS and evaluating the feasibility of possible technical ice detection and anti-/de-icing solutions. This paper presents results from the investigation carried out at the Rail Tec Arsenal (RTA) icing wind tunnel (IWT) in Vienna, Austria, where UAS rotors were exposed to defined icing conditions based on EASA CS-25 Appendix C. The experimental tests featured various rotors which were exposed to icing conditions without any protective measures to better understand the influence of ice accretion on the aerodynamic performance. In addition, possible technical solutions in form of an electrothermal and chemical anti-/de-icing system, as well as an ice-repellent surface coating were investigated. During the tests, the performance (power, thrust, torque) of the UAS rotors was monitored. The final ice accretion was documented by 3D laser scanning and photographs. The objective of this work is to contribute to a better understanding of icing of UAS rotors, while also investigating solutions that might enable the safe operation of multirotor UAS in icing conditions in the future.</div></div>
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