RV6Sn6 (R = Sc, Y, or rare earth) is a new family of kagome metals that have a similar vanadium structural motif as AV3Sb5 (A = K, Rb, Cs) compounds. Unlike AV3Sb5, ScV6Sn6 is the only compound among the series of RV6Sn6 that displays a charge density wave (CDW) order at ambient pressure, yet it shows no superconductivity (SC) at low temperatures. Here, we perform a high-pressure transport study on the ScV6Sn6 single crystal to track the evolutions of the CDW transition and to explore possible SC. In contrast to AV3Sb5 compounds, the CDW order of ScV6Sn6 can be suppressed completely by a pressure of about 2.4 GPa, but no SC is detected down to 40 mK at 2.35 GPa and 1.5 K up to 11 GPa. Moreover, we observed that the resistivity anomaly around the CDW transition undergoes an obvious change at ~2.04 GPa before it vanishes completely. The present work highlights a distinct relationship between CDW and SC in ScV6Sn6 in comparison with the well-studied AV3Sb5.
A novel and efficient heterogeneous CuSO 4 nanoparticles (CuSO 4 NPs) immobilized on carboxymethylcellulose/polyaniline (CuSO 4 NPs@CMC/PANI) composites were prepared via one-pot and one-step interfacial oxidative polymerization of aniline with sodium carboxymethylcellulose (CMC) as soft template and CuSO 4 as catalyst. The in situ formed CuSO 4 NPs were dispersed uniformly and firmly on the resultant composites and stabilized by complexation with hydroxyl groups (─OH), carboxylate groups (─COO À ), nitrogen atoms, and delocalized π-π conjugate benzenoid and quinoid moieties of CMC/PANI composites. The morphology, composition, and structure of the as-fabricated composites were systematically characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and derivative thermogravimetry (DTG) techniques. The CuSO 4 NPs@CMC/PANI composites were successfully applied as catalysts in aldehyde-alkyne-amine (A 3 ) coupling reactions, A 3cycloisomerization tandem reactions, and Cu-catalyzed azide-alkyne cycloaddition (CuAAC) reactions. All reactions proceeded smoothly and afforded the desired products in excellent yields. Moreover, no significant decrease in catalytic ability was observed in A 3 model reaction after 15 recycles, indicating CuSO 4 NPs@CMC/PANI composites exhibited easy separability and high reusability. Tolerance of wide scope of substrate, excellent catalytic activity, easy operation, recycling of catalyst, and environmental benign are the salient features of these catalytic process.
Through the esteri cation of cellulose (Cell) with ethylenediaminetetraacetic dianhydride, ethylenediaminetetraacetic acid-functionalized cellulose (Cell-EDTA) was conveniently obtained. Furtherly a novel and e cient Cell-EDTA-supported palladium catalyst (Pd@Cell-EDTA) was easily prepared via coordination of Cell-EDTA with PdCl 2 . The as-prepared Pd@Cell-EDTA was fully characterized by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray photoelectron spectroscopy (XPS), Flourier transform infrared spectra (FTIR), energy-dispersive spectroscopy (EDS), scanning electron microscopy, transmission electron microscopy (SEM), thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG) techniques. Then Pd@Cell-EDTA were successfully exerted as catalysts in Suzuki reactions and Sonogashira reactions. Due to the interactions of carboxylic groups, nitrogen atoms, and hydroxyl groups on cellulose, the Pd complex showed excellent activity towards these carbon-carbon cross-coupling reactions. The catalyst recycling experiment for Suzuki model reaction showed that the catalyst can be reused at least ve times without signi cant losing its catalytic performance. The present cellulose-based Pd@Cell-EDTA catalyst offers the salient features of wide application, excellent catalytic activity, good reusability, tolerance of broad scope of substrate, and environmental benign.
A novel and interesting method for the preparation of carboxymethylcellulose–polyaniline film-supported copper catalyst (CuII/I@CMC-PANI) has been developed via spray-assisted interfacial polymerization. Using copper sulfate as an initiator, spraying technology was introduced to form a unique interface that is perfectly beneficial to the polymerization of aniline monomers onto carboxymethylcellulose macromolecule chains. To further confirm the composition and structure of the as-prepared hybrid film, it was systematically characterized by inductively coupled plasma (ICP), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and thermogravimetric analysis (TGA) techniques. The Cu content in the fresh CuII/I@CMC-PANI film was determined to be 1.805 mmol/g, and spherical nanoparticles with an average size of ca. 10.04 nm could be observed in the hybrid film. The CuII/I@CMC-PANI hybrid film was exerted as a dip catalyst to catalyze the aldehyde–alkyne–amine (A3) coupling reactions. High yields of the products (up to 97%) were obtained in this catalytic system, and the catalyst could be easily picked up from the reaction mixture by tweezers and reused for at least six consecutive runs, without any discernible losses in its activity in the model reaction. The dip catalyst of CuII/I@CMC-PANI, with easy fabrication, convenient deployment, superior catalytic activity, and great reusability, is expected to be very useful in organic synthesis.
AbslracI--Transmission towers are usually represented as inductances or as vertical transmission lines when struck by lightning. Honever, i t is helieved that the best approach to an understanding o f the phenomenon occurring in a transmission system is through field theory.The lightning stroke pluses a positive wave of charge and current that moves vertically upward above the tower. The waves of charge and current produce electric fields along the tower, the ground wire and the conductor. On the basis of the electric field analysis, general principles concerning the performance o f tower, ground wire, and conductor combinations when struck by lightning are established and some equations used for calculation are proposed. The effect of the point to which the potentials are referred and current division are analyzed in this paper. The method, called an improved field-cancellation method, provides an iniprovemenl for computing the lightning performance of transmisdon towers. determined, the potential o f the conductor and the potential of the conductor image are determined respectively. '1 hcreiure, the potential across the insulator string can be calculated.The field-cancellation cniethod has been eillplo)ed in IIIV computation of the lightning perfoi-mance of traiisiiiiiaim towers. However, it still can be improved in the following aspects:
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