Iridium-based materials are among the most active bifunctional catalysts in heterogeneous catalysis and electrocatalysis. We have investigated the properties of atomically defined Ir/CeO2(111) model systems supported on Cu(111) and Ru(0001) by means of synchrotron radiation photoelectron spectroscopy, resonant photoemission spectroscopy, near ambient pressure X-ray photoelectron spectroscopy (NAP XPS), scanning tunneling microscopy, and temperature programmed desorption. Electronic metal-support interactions in the Ir/CeO2(111) system are accompanied by charge transfer and partial reduction of CeO2(111). The magnitude of the charge transfer depends strongly on the Ir coverage. The Ir/CeO2(111) system is stable against sintering upon annealing to 600 K in ultrahigh vacuum (UHV). Annealing of Ir/CeO2(111) in UHV triggers the reverse oxygen spillover above 450 K. The interaction of hydrogen with Ir/CeO2(111) involves hydrogen spillover and reversible spillover between 100 and 400 K accompanied by the formation of water above 190 K. Formation of water coupled with the strong reduction of CeO2(111) represents the dominant reaction channel upon annealing in H2 above 450 K. The interaction of Ir/CeO2(111) with oxygen has been investigated at moderate and NAP conditions. Additionally, the formation and stability of iridium oxide prepared by deposition of Ir in oxygen atmosphere was investigated upon annealing in UHV and under exposure to H2. The oxidation of Ir nanoparticles under NAP conditions yields stable IrOx nanoparticles. The stability of Ir and IrOx nanoparticles under oxidizing conditions is hampered, however, by encapsulation by cerium oxide above 450 K and additionally by copper and ruthenium oxides under NAP conditions.
Multi-beam micro- and nano-machining of material surfaces has been getting more important because of its great potential to increase production speed of large size laser induced periodic surface structures (LIPSS). Fast and cheap production of engineered surfaces structures can bring unique properties of surfaces like tailored wettability, friction, antibacterial properties, etc., to mass-production with consequence in, for example, energy and costs savings. However, tailoring of long-term stable interference patterns from ultrashort laser pulses requires an extremely stable laser system with nearly diffraction-limited output beams. HiLASE Centre developed such a thin-disk-based Yb:YAG sub-picosecond laser platform, PERLA, providing average output power up to 0.5 kW with 2nd and 4th harmonic generation extensions and demonstrated its potential for direct laser interference patterning (DLIP). In this paper, we focus on details of the thin-disk PERLA laser.
The reinforcement of polypropylene (PP) using wood cellulose has been studied. The strength and stiffness of the composites are improved by a prehydrolytic treatment of the cellulose as well as by the use of maleic anhydride--modified PP (MAPP) as a coupling agent for promoting interfacial adhesion. The embrittlement of the cellulosic component brought about by the hydrolysis facilitates fine dispersion of fibers in the shear field of the compounding extruder. The Ε-modulus of composites based on prehydrolyzed fibers is significantly improved as com pared with untreated fibers and exceeds values calculated theoretically with the Halpin-Tsai equation. Strength values increase with increased fiber content, which is a re markable characteristic for such composites. Significant improvement of the modulus and strength in compos ites with hydrolyzed fibers indicates that such fibers are disintegrated into microfibrils characterized by very high modulus and strength values. Selecting suitable process ing conditions was found to be crucial for the chemical reaction between the MAPP coupling agent and fiber surface, which produces improved adhesion.Natural fibers such as wood, cellulose and jute are renewable materials with very attractive mechanical properties. For instance, cellulose fibers with moduli up to 40 GPa can be separated from wood by a chemical pulping process. A growing awareness of environmental problems and the importance of energy conservation have made such renewable reinforcing materials of great importance. The use of wood fibers as fillers and rein forcements in thermoplastics has been documented in several reports (1, 3-5). However, the limited heat stability of cellulose unfortunately reduces
No abstract
Data regarding the influence of screw geometry on homogeneity and fibre length reduction during single screw extrusion of short glass fibre reinforced PP are presented. Three screw geometries, two grades of PP with different melt flow indices, and four levels of filling (10 to 40 wt.%) were the main variables studied. The fibre breakage mechanism was evaluated with respect to solid and melt conveying and melting mechanisms in the screw channels. The screw with a long compression zone produced a material of poor homogeneity, a stable melting mechanism and a medium level of fibre length reduction. The very short compression zone screw produced unstable melting which considerably improved the homogenization process of the fibres in the polymer matrix. In this way the extrudates remained smooth up to the 30 wt.% filling level. The homogeneity was comparable to that obtained by a process including two steps of compounding: twin screw and single screw extrusion. However, the fibre degradation in the screw with a very short compression zone was substantially lower than in the process including two compounding steps.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.