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61.
An interdigital transducer device equipped with a metal catalyst sample that can be used to enhance catalytic activity by acoustic excitation is investigated. It was found that the propagation of 20 MHz surface acoustic waves of the Rayleigh type on Pt thin film single crystals causes drastic changes in surface morphology. The process of film breaking is observed and it is concluded that a phase shift in the acoustic wave induced by folds and cavities in the sample is responsible for the appearance of cracks. The influence of the change in morphology on catalytic activity and the acoustically induced rate enhancement effect is studied, and it is concluded that these changes are not a significant factor in the observed enhancement. 相似文献
62.
N. Minkova A. Terziev G. Tzvetkov D. Todorovsky 《Monatshefte für Chemie / Chemical Monthly》1997,128(6-7):593-598
Summary The changes in the solubility and in the phase composition of yttrium-aluminum garnet (YAG) as a result of its mechanochemical treatment for 2 h in a planetary ball mill together with H3BO3 and Na2CO3 (mole ratio H2BO3/Na2CO3=4) in ratios (H3BO3+Na2CO3)/YAG=2,4, and 9 are studied. At a ratio of 9, the yield of yttrium in the water solution obtained upon treatment of the activated mixture at 90 °C (50 cm3 water/g sample) reaches 85%. Its content in the same solution is above 93% relatively to the sum Y+Al.
Umwandlung von Yttrium-Aluminium-Granat in lösliche Formen durch mechanochemische Behandlung
Zusammenfassung Die Änderungen bezüglich Löslichkeit und Phasenzusammensetzung von Yttrium-Aluminium-Granat (YAG) als Ergebnis einer zweistündigen mechanochemischen Behandlung in einer Kugelmühle zusammen mit H3BO3 und Na2CO3 (Molverhältnis H3BO3/Na2CO3=4) bei (H3BO3+Na2CO3)/YAG-Verhältnissen von 2, 4 und 9 wurden untersucht. Bei einem Verhältnis von 9 erreicht die Ausbeute an Yttrium in der wäßrigen Lösung nach Behandlung der aktivierten Mischung bei 90 °C (50 cm3 H2O pro Gramm) 85%. Relativ zur Summe Y+Al beträgt der Yttriumgehalt 93%.相似文献
63.
Mechanically activated mixtures of some hydroxocarbonates with powder, metallic aluminium caused chemical reactions, which result in alloy formation. The identification of phases formed during milling was successfully achieved by thermal analysis methods supplemented by X-ray diffraction measurement. 相似文献
64.
65.
Daniel M. Baier Carolina Spula Stephen Fanenstich Dr. Sven Grätz Prof. Dr. Lars Borchardt 《Angewandte Chemie (International ed. in English)》2023,62(20):e202218719
Photochemical reactors inherently suffer from the low penetration depth of light and therefore rely on high dilutions to enable chemical reactions. Here we present the first method of UV (ultraviolet) photochemistry in the complete absence of bulk solvents in a ball mill. Triphenylene was synthesized by two routes, the Mallory reaction and the cyclodehydrochlorination (CDHC), resulting in yields of 81 and 92 %, respectively. The reaction was successfully scaled up to the gram scale and the robustness of the method was demonstrated for several different substrates. Finally, the regioselective assembly of nanographenes by mechanochemistry was demonstrated for larger systems. Thus, the mechanochemical approach presented here provides a powerful new tool for the atomically precise construction of nanographenes. 相似文献
66.
Kinetics of hydrogen formation was explored as a new chemical dosimeter allowing probing the sonochemical activity of argon-saturated water in the presence of micro- and nano-sized metal oxide particles exhibiting catalytic properties (ThO2, ZrO2, and TiO2). It was shown that the conventional sonochemical dosimeter based on H2O2 formation is hardly applicable in such systems due to catalytic degradation of H2O2 at oxide surface. The study of H2 generation revealed that at low-frequency ultrasound (20 kHz) the sonochemical water splitting is greatly improved for all studied metal oxides. The highest efficiency is observed for relatively large micrometric particles of ThO2 which is assigned to ultrasonically-driven particle fragmentation accompanied by mechanochemical water molecule splitting. The nanosized metal oxides do not exhibit particle size reduction under ultrasonic treatment but nevertheless yield higher quantities of H2. The enhancement of sonochemical water splitting in this case is most probably resulting from better bubble nucleation in heterogeneous systems. At high-frequency ultrasound (362 kHz), the effect of metal oxide particles results in a combination of nucleation and ultrasound attenuation. In contrast to 20 kHz, micrometric particles slowdown the sonolysis of water at 362 kHz due to stronger attenuation of ultrasonic waves while smaller particles show a relatively weak and various directional effects. 相似文献
67.
Xiaohong Wang Dr. Xuemei Zhang Dr. Li Xue Qingqing Wang Fengzhi You Prof. Dr. Lunzhi Dai Prof. Dr. Jiagang Wu Prof. Dr. Søren Kramer Prof. Dr. Zhong Lian 《Angewandte Chemie (International ed. in English)》2023,62(39):e202307054
Aryl fluorides are important structural motifs in many pharmaceuticals. Although the Balz–Schiemann reaction provides an entry to aryl fluorides from aryldiazonium tetrafluoroborates, it suffers from drawbacks such as long reaction time, high temperature, toxic solvent, toxic gas release, and low functional group tolerance. Here, we describe a general method for the synthesis of aryl fluorides from aryldiazonium tetrafluoroborates using a piezoelectric material as redox catalyst under ball milling conditions in the presence of Selectfluor. This approach effectively addresses the aforementioned limitations. Furthermore, the piezoelectric material can be recycled multiple times. Mechanistic investigations indicate that this fluorination reaction may proceed via a radical pathway, and Selectfluor plays a dual role as both a source of fluorine and a terminal reductant. 相似文献
68.
Maria Carta Leonarda Vugrin Dr. Goran Miletić Dr. Marina Juribašić Kulcsár Prof. Dr. Pier Carlo Ricci Dr. Ivan Halasz Prof. Dr. Francesco Delogu 《Angewandte Chemie (International ed. in English)》2023,62(33):e202308046
Typically induced by the mechanical processing of powders in ball mills, mechanochemical transformations are considered to result from the application of mechanical force to solid reactants. However, the undeniable deep connection between the dynamic compaction of powders during impacts and the overall transformation degree has yet to be disclosed. In the present work, we show that the square planar bis(dibenzoylmethanato)NiII coordination compound undergoes trimerization when its powder experiences even a single ball impact. Based on systematic experiments with individual ball impacts and analysis by Raman spectroscopy, we provide here quantitative mapping of the transformation in the powder compact and deduce bulk reaction kinetics from multiple individual impacts. 相似文献
69.
Claudius Lupfer Sebastian Seitel Oliver Skarsetz Andreas Walther 《Angewandte Chemie (International ed. in English)》2023,62(41):e202309236
Cellular organisms possess intricate mechano-adaptive systems that enable them to sense forces and process them with (bio)chemical circuits for functional adaptation. Inspired by such processes, this study introduces a hydrogel system capable of mechanically activated and chemically transduced self-destruction. Our judiciously designed hydrogels can mechanically generate radicals that are processed and amplified in a self-propagating radical de-crosslinking reaction, ultimately leading to mechanically triggered self-immolation. We put such systems to work in mechano-induced debonding, and in a bilayer actuator, where swelling-induced bending generates sufficient force for selective degradation of one layer, leading to autonomous self-regulation associated with unbending. Our work helps define design criteria for molecularly controlled adaptive and self-regulating materials with embodied mechano-chemical information processing, and showcases their potential for adhesives and soft robotics. 相似文献
70.
Takuma Watabe Prof. Hideyuki Otsuka 《Angewandte Chemie (International ed. in English)》2023,62(9):e202216469
We report a novel and versatile approach to achieving swelling-induced mechanochemistry using a multinetwork (MN) strategy that enables polymer networks to repeatedly swell with monomers and solvents. The isotropic expansion of the first network (FN) provides sufficient force to drive the mechanochemical scission of a radical-based mechanophore, difluorenylsuccinonitrile (DFSN). Although prompt recombination generally occurs in such highly mobile environments, the resulting pink radicals are kinetically stabilized in the gels, probably due to limited diffusion in the extended polymer chains. Moreover, the DFSN embedded in the isotropically strained chain exhibits increased thermal reactivity, which can be reasonably explained by an entropic contribution of the FN to the dissociation. The utility of the MN polymers is demonstrated not only in terms of swelling-force-induced network modification, but also in the context of tunable reactivity of the dissociative unit through proper design of the hierarchical network architecture. 相似文献