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201.
Ionic liquid crystals (ILCs) are a class of materials that present a large and varied form of applicability and whose properties can change dramatically with small modifications in their molecular structure. It is, therefore, of great importance to improve the knowledge about the property–molecular structure relationship. In this study, we present the synthesis and characterisation of 7 new rod- and wedge-shaped ILCs, whose liquid crystalline behaviour variation is related to the variations in the number of alkoxy chains and/or in the spacer chain length. All compounds have a rigid core constituted by a tolane group and a 1,2,3-triazole heterocycle, which is connected to a pendant 1-methylimidazolium through a alkyl spacer chain. The mesomorphic properties were studied by DSC, thermogravimetric analysis, polarising optical microscopy, wide angle X-ray diffraction and SAXS with synchrotron radiation. The increase in the number of long alkoxy chains changed the molecular self-assembly from bilayered SmA2 and SmC2 to hexagonal columnar, passing through oblique columnar, bicontinuous cubic and hexagonal close-packed mesophase. On the other hand, the increase in the alkyl spacer chain length has an especially significant effect for the compounds with two terminal alkoxy chains, where a Colo/Colh – Cubv – HCP phase sequences were observed. 相似文献
202.
Pia Aßmann Aldo Saul Gago Pawel Gazdzicki Kaspar Andreas Friedrich Michael Wark 《Current Opinion in Electrochemistry》2020
Proton exchange membrane water electrolysis is technically the most suitable technology for the production of green hydrogen on a large scale. Although it is still more expensive than hydrogen produced from fossil sources, it has already been commercialized. Novel components with cost-effective materials and efficient manufacturing processes are being rapidly developed. However, these components must endure durability tests that can guarantee a lifetime of at least 50,000 operation hours. Consequently, there is an urgent need to develop accelerated stress test protocols based on a deep understanding of degradation mechanisms of stack components. Recent reports show that the main degradation mechanisms are associated to anode catalyst dissolution, membrane chemical decomposition, and formation of semiconducting oxides on the metal components. These mechanisms can be accelerated by stressors such as high current density, dynamic operation, and shutdown modes. On the basis of these reports and knowledge of the operational requirements for large-scale proton exchange membrane water electrolysis, we propose an accelerated stress test protocol for the fast evaluation of newly developed cost efficient and durable components. 相似文献
203.
204.
AEROSPATIALE has, for more than 20 years, developed and perfected a device intended to simulate the atmospheric re-entry conditions: the plasma torch. This technology, developed for the needs of space industry, is also applicable in other industrial fields like metallurgy or waste disposal. For most residues, as, for instance, for polymer residues (in particular for composite materials), incineration is the best solution to be considered. Although the organic molecule may be a real danger for man and his environment, it is possible to split it into elementary molecules easy to eliminate without risks by the simultaneous application of heat and a specific chemical environment. The use of additives in the polymers makes it necessary in most cases to use temperatures as high as possible; these high temperatures have the additional advantage of preventing harmful recombinations in the reaction chamber. Only plasma processes give the possibility to ensure high temperatures in large capacity chambers in a controlled atmosphere. 相似文献