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排序方式: 共有193条查询结果,搜索用时 15 毫秒
1.
Anorgano modifiedMgAl layereddoublehydroxide (OMgAl LDH )wassuccessfullyexfoliatedinthexylenesolutionofpolyethylene grafted maleicanhydride (PE g MA )underre fluxingcondition .APE g MA/MgAl LDHexfoliationnano compositewasformedaftertheprecipitationofPE g MAfromthedispersionsystem .ThestructureandthermalpropertyofthePE g MA/MgAl LDHexfoliationnanocompositewerechar acterizedbyX raydiffraction (XRD ) ,transmissionelectronmicroscopy (TEM ) ,andthermogravimetryanalysis (TGA ) .The… 相似文献
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The difficulty of exposing active sites and easy recombination of photogenerated carriers have always been two critical problems restricting the photocatalytic activity of g-C3N4. Herein, a simple (NH4)2MoO4-induced one-step calcination method was successfully introduced to transform bulk g-C3N4 into g-C3N4/MoO2 composites with a large specific surface area. During the calcination, with the assistance of NH3 and water vapor produced by ammonium molybdate, the pyrolytical oxidation and depolymerization of a g-C3N4 interlayer were accelerated, finally realizing the exfoliation of the g-C3N4. Furthermore, another pyrolytical product of ammonium molybdate was transformed into MoO2 under an NH3 atmosphere, which was in situ loaded on the surface of a g-C3N4 nanosheet. Additionally, the results of photocatalytic hydrogen evolution under visible light show that the optimal g-C3N4/MoO2 composite has a high specific surface area and much improved performance, which is 4.1 times that of pure bulk g-C3N4. Such performance improvement can be attributed to the full exposure of active sites and the formation of abundant heterojunctions. However, with an increasing feed amount of ammonium molybdate, the oxidation degree of g-C3N4 was enhanced, which would widen the band gap of g-C3N4, leading to a weaker response ability to visible light. The present strategy will provide a new idea for the simple realization of exfoliation and constructing a heterojunction for g-C3N4 simultaneously. 相似文献
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Zifeng Wang Zijie Tang Qi Xue Yan Huang Yang Huang Minshen Zhu Zengxia Pei Hongfei Li Hongbo Jiang Chenxi Fu Chunyi Zhi 《Chemical record (New York, N.Y.)》2016,16(3):1204-1215
Nanomaterials with layered structures, with their intriguing properties, are of great research interest nowadays. As one of the primary two‐dimensional nanomaterials, the hexagonal boron nitride nanosheet (BNNS, also called white graphene), which is an analogue of graphene, possesses various attractive properties, such as high intrinsic thermal conductivity, excellent chemical and thermal stability, and electrical insulation properties. After being discovered, it has been one of the most intensively studied two‐dimensional non‐carbon nanomaterials and has been applied in a wide range of applications. To support the exploration of applications of BNNSs, exfoliation, as one of the most promising approaches to realize large‐scale production of BNNSs, has been intensively investigated. In this review, methods to yield BNNSs by exfoliation will be summarized and compared with other potential fabrication methods of BNNSs. In addition, the future prospects of the exfoliation of h‐BN will also be discussed. 相似文献
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《先进技术聚合物》2018,29(1):41-51
An innovative eccentric rotor extruder, which can generate continuous elongation flow, was used to fabricate the poly(L‐lactide) (PLLA)/organo‐modified montmorillonite (OMMT) nanocomposites in different OMMT concentrations. The morphology of the nanocomposites was characterized by thermal gravimetric analyzer, X‐ray diffractometer, and transmission electron microscope. The results showed that the OMMT nanoparticles were uniformly dispersed in the PLLA matrix and mainly existed in intercalation mode. The intercalation and exfoliation process of OMMT in the eccentric rotor extruder may be a double‐side exfoliation, which is more effective than the layer‐by‐layer peeling mechanism based on the shear flow. The influence of OMMT on the rheological behavior of PLLA was investigated by dynamic rheological measurements, showing greater improvement of rheological properties for the nanocomposites. The thermo‐mechanical properties analysis indicated that significant enhancement of E′ can be seen for all the nanocomposites. Presence of intercalated OMMT platelets did not lead to a significant shift of the E″ and tan δ curves compared with that of pure PLLA. The crystallization and melting behavior was studied by differential scanning calorimetry, which indicated that the incorporation of OMMT nanoparticles slightly increased the crystallinity of PLLA matrix. The polarizing microscope was further carried out and showed that the dispersed OMMT nanoparticles acted as a heterogeneous nucleating agent to promote the crystallization of PLLA. 相似文献
7.
Liping Liao Bing Wu Dr. Evgeniya Kovalska Dr. Vlastimil Mazánek Dr. Martin Veselý Ivo Marek Lucie Spejchalová Prof. Dr. Zdeněk Sofer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13235-13241
The intercalation of cations into layered-structure electrode materials has long been studied in depth for energy storage applications. In particular, Li+-, Na+-, and K+-based cation transport in energy storage devices such as batteries and electrochemical capacitors is closely related to the capacitance behavior. We have exploited different sizes of cations from aqueous salt electrolytes intercalating into a layered Nb2CTx electrode in a supercapacitor for the first time. As a result, we have demonstrated that capacitive performance was dependent on cation intercalation behavior. The interlayer spacing expansion of the electrode material can be observed in Li2SO4, Na2SO4, and K2SO4 electrolytes with d-spacing. Additionally, our results showed that the Nb2CTx electrode exhibited higher electrochemical performance in the presence of Li2SO4 than in that of Na2SO4 and K2SO4. This is partly because the smaller-sized Li+ transports quickly and intercalates between the layers of Nb2CTx easily. Poor ion transport in the Na2SO4 electrolyte limited the electrode capacitance and presented the lowest electrochemical performance, although the cation radius follows Li+>Na+>K+. Our experimental studies provide direct evidence for the intercalation mechanism of Li+, Na+, and K+ on the 2D layered Nb2CTx electrode, which provides a new path for exploring the relationship between intercalated cations and other MXene electrodes. 相似文献
8.
Vladislav V. Klepov Anna A. Berseneva Kristen A. Pace Vancho Kocevski Mengqi Sun Peng Qiu Hui Wang Fanglin Chen Theodore M. Besmann Hans‐Conrad zur Loye 《Angewandte Chemie (International ed. in English)》2020,59(27):10836-10841
Most ternary sulfides belonging to the MGaS2 structure‐type have been known for many years and are well‐characterized. Surprisingly, there have been no reports of the NaGaS2 composition, which contains Na, a monovalent cation slightly larger in size than Li, found in LiGaS2, a compound known for its non‐linear optical properties. Now it is demonstrated for the first time that the unique reversible water absorption in NaGaS2 has resulted in its absence from previous reports owing to difficulties encountered when characterizing this compound by SC XRD. The layered structure of this compound coupled with uniquely easy migration of water molecules between the layers allows for ion exchange with 3d and 5f metal cations. Some cations, for example, Ni2+, facilitate exfoliation of the layers, providing a facile synthetic route to a new class of 2D chalcogenide materials and furthermore demonstrating that NaGaS2 can readily uptake uranyl species from aqueous solutions. 相似文献
9.
David W. Burke Chao Sun Ioannina Castano Nathan C. Flanders Austin M. Evans Edon Vitaku David C. McLeod Robert H. Lambeth Lin X. Chen Nathan C. Gianneschi William R. Dichtel 《Angewandte Chemie (International ed. in English)》2020,59(13):5165-5171
Covalent organic frameworks (COFs) are highly modular porous crystalline polymers that are of interest for applications such as charge‐storage devices, nanofiltration membranes, and optoelectronic devices. COFs are typically synthesized as microcrystalline powders, which limits their performance in these applications, and their limited solubility precludes large‐scale processing into more useful morphologies and devices. We report a general, scalable method to exfoliate two‐dimensional imine‐linked COF powders by temporarily protonating their linkages. The resulting suspensions were cast into continuous crystalline COF films up to 10 cm in diameter, with thicknesses ranging from 50 nm to 20 μm depending on the suspension composition, concentration, and casting protocol. Furthermore, we demonstrate that the film fabrication process proceeds through a partial depolymerization/repolymerization mechanism, providing mechanically robust films that can be easily separated from their substrates. 相似文献
10.
新环氧树脂纳米复合材料的合成和结构研究 总被引:1,自引:0,他引:1
以具有层状硅酸盐结构的累托石(REC)为主体,以烷基季铵盐为改性剂合成了有机累托石(OREC),以有机累托石和环氧树脂复合,制备出纳米复合材料。累托石含量在0.8wt.% 时,纳米复合材料具有最佳力学和热学性能,冲击强度增加到65.6 kJm-2,断裂伸长率从4.7 %增加到20.2 %,玻璃化转变温度提高到 197.9 ℃。用X-小角衍射法、透射电镜和红外吸收光谱研究了材料的微观结构,XRD 衍射图显示,未经处理REC 的层间距d001 = 2. 2 nm,经有机改性后,累托石片层间距扩大到2.8 nm,与环氧树脂复合后,其层间距扩大到4.2 nm 左右,FT-IR图显示,有机累托石中出现十六胺的特征吸收峰,TEM照片显示该复合材料是一种纳米复合材料。 相似文献