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Luiz Claudio de Santa Maria Mônica R.M.P. Aguiar Leonardo O. Ferreira 《Materials Letters》2007,61(1):160-164
Porous copolymer networks based on styrene (STY) and divinylbenzene (DVB) containing polar monomer (methacrylamide — MAM, methacrylic acid — MAA or acrylonitrile — ACN) were prepared by suspension polymerization using glycerol as a dispersant medium. Poly(styrene-co-methacrylamide-co-divinylbenzene), poly(styrene-co-methacrylic acid-co-divinylbenzene) and poly(styrene-co-acrylonitrile-co-divinylbenzene) were synthesized using mixtures of toluene with 2-butanone, toluene and 2-butanone and n-heptane with ethylacetate, respectively at different dilutions: 50%, 100% and 120% (v/v). The copolymers were characterized by bulk density, infrared spectrometry (FTIR) and elemental analysis (CHN). Morphological features of the copolymer pearls were evaluated by microscopic analysis and correlations between porous structure and parameters of reaction were found. The copolymers presented high incorporation of polar monomers. The pearl porosities and visual appearances had a strict relation with the monomer type and the dilution degree employed in synthesizing them. 相似文献
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NiO粒子修饰的压缩膨胀石墨(EGNiO)浸以煤焦油沥青,经550℃裂解,继而800℃水蒸气活化,制得Ni/C复合物块体。应用TEM考察了复合物中含Ni纳米粒的微结构排列方式。以N2吸附测定分析了复合物的比表面积和孔隙度。以2,2,3—三甲基戊烷脱氢裂解模型反应评估了复合物的催化活性并与EGNiO常规H2处理获得的参照物的活性做了比较。 相似文献
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锂离子二次电池负极材料的研究综述 总被引:1,自引:0,他引:1
总结了在碳材料、合金材料和复合材料等3个锂离子电池负极材料研发的主导方向上的开发情况和它们各自特点,描述了目前的研究所面临难题,给出了锂离子电池负极材料研发取得重大突破的可能途径和建议. 相似文献
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J. D. Carey R. C. Smith S. R. P. Silva 《Journal of Materials Science: Materials in Electronics》2006,17(6):405-412
The influence of the different types of bonding present in a range of carbon based materials is discussed as a precursor to
describing the field emission characteristics of carbon cold cathode materials. Some of the controlling factors which govern
electron emission from carbon based cathodes are discussed. It is shown that from disordered carbon films the interplay between
the clustered sp2 phase and the insulating sp3 matrix is important. The transition from a ‘back contact’ to ‘front surface’ controlled emission mechanism is described in
terms of the sp2 content and field penetration. A possible reason for high field enhancement factors found in disordered films also is provided.
It is further shown that changes to the sp2 phase by current stressing can improve the field emission characteristics. Emission from carbon nanotubes is also discussed
and the prospects for new types of nanotube – polymer composite based cathodes are also considered. 相似文献
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Potassium-ion batteries (PIBs) have attracted increasing interest as promising alternatives to lithium-ion batteries (LIBs) for application in large-scale electrical energy storage systems (EESSs) owing to a wide earth-abundance, potential price advantages, and low standard redox potential of potassium. Developmental materials for use in PIBs that can yield high specific capacities and durability are widely sought with emerging studies on alloying-type anode materials offering significant prospects to meet this challenge. Here, recent advances on alloying-type anodes and their composites for PIBs are reviewed in detail and in a systematic way to capture key aspects from fundamental working principles through major progress and achievements to future perspectives and challenges. Emphasis is placed on critical aspects such as the alloying mechanism and correlation of electrode design and structural engineering for performance enhancement and the crucial role of electrolyte compatibility, additives and binders. The review in appraising all the important contributions on this topic allows for a critical assessment of the research challenges and provides insights on future research directions that can accelerate the important development of PIBs as a viable battery energy storage system. 相似文献
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ZnO/graphene composites were synthesized using a facile solution-based method. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, and Raman spectra revealed that ZnO nanoparticles with a particle size of around 4 nm were densely and homogeneously deposited on graphene sheets. As the anode material for the lithium ion batteries, the ZnO/graphene composites delivered a stable capacity of 404 mAh/g after 100 cycles at a current rate of 0.5 C, which is much superior to bare ZnO nanoparticles. The battery performance result indicates the presence of graphene sheets in the composites effectively enhance the conductivity and accommodate the volume change. 相似文献
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Hongdong Liu 《Journal of Materials Science: Materials in Electronics》2014,25(8):3353-3357
The carbon nanotubes (CNTs) anchored with SnO2 nanosheets were prepared using a hydrothermal method. The as-prepared products were characterized by X-ray diffraction, fourier transform infrared spectroscopy, thermogravimetric analyses, field emission scanning electron microscope and transmission electron microscope. The electrochemical performances of SnO2 nanosheets/CNTs composite were measured by galvanostatic charge/discharge cycling, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the SnO2 nanosheets/CNTs composite maintains high lithium storage capacity and good cycling stability. The designed structure plays key role in improving electrochemical performance. The CNTs anchored with SnO2 nanosheets will be an ideal candidate of anode material for lithium ion batteries. 相似文献
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A facile one-pot hydrothermal method has been developed for the preparation of carbon-coated MoO(2) nanocrystals. The annealed MoO(2)-C nanocomposite consists of interconnected MoO(2)@C nanocrystals. When evaluated for lithium storage capabilities, these MoO(2)@C nanocrystals exhibit high specific capacities (~640 mA h g(-1) at 200 mA g(-1) and ~575 mA h g(-1) at 400 mA g(-1)) and excellent cycling stability. In view of the excellent lithium storage properties and the ease in large-scale preparation, the as-synthesized MoO(2)-C nanocomposite might be used as promising anode materials for high-performance lithium-ion batteries. 相似文献
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A nanocomposite of multiwalled carbon nanotubes (MWCNTs) anchored with SnS(2) nanosheets (NS) (SnS(2) NS@MWCNTs coaxial nanocables) has been synthesized through a simple solution-based method at room temperature. The synthetic mechanism of these intriguing nanocomposites is proposed as electrostatic attraction between tin ions and MWCNTs, followed by the nucleation and two-dimensional growth of SnS(2). The as-synthesized SnS(2) NS@MWCNTs coaxial nanocables have been applied as anode materials for lithium-ion batteries, which show better lithium storage performance compared to pure SnS(2) nanosheets and MWCNTs. The combination of MWCNTs that can hinder the agglomeration and enhance electronic conductivity of the active materials might be responsible for the enhanced cyclic performance. 相似文献
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Low-density Polyethylene (PE) were synthesized with poly[butyl methacrylate (B)-co-styrene (S)], poly(dodecyl methacrylate(D)-co-styrene] and poly(ethyl hexyl methacrylate (EH)-co-styrene] copolymers in order to obtain IPN-like networks. Different S/methacrylate copolymer molar ratios going from 0/100 up to 60/40, a molar percentage of 1.0% of 1,4-butanedioldimethacrylate (b) and 3 wt% of 2,5-dimethyl-2,5-di-(tert-butyl peroxy) hexane (Luperox 101) were used. The samples were analyzed at RT by WAXS, swelling in CCl4 and mechanical tensile tests. Dynamic-mechanical tests and optical investigations were performed in a temperature range between RT and 180°C. All the IPN types showed optical reversible transitions (transparency-to opacity and vice versa) with varying temperature, due to a refractive index (RI) matching-mismatching of PE and copolymer networks. The copolymer chemical nature as well as its composition affected sensitively most of the analyzed properties. 相似文献
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Cavicchi KA 《ACS applied materials & interfaces》2012,4(2):518-526
Sulfonated polymers have found use as ion-exchange membranes for use in fuel cells, water purification, electroactive devices, and inorganic materials templating and synthesis. Improving the materials for these applications and opening up new applications requires the ability to synthesis targeted or more complex sulfonated polymers, which includes tailoring the chemistry (copolymerization across a wider range of solubility) and/or polymer architecture (block, graft, nanoparticle). This article will summarize the recent work using sulfonated monomers with substituted ammonium counterions as a versatile route for enabling this goal. Two main benefits of these monomers are as follows. First, they are useful for preparing amphiphilic copolymers, which is a challenge using traditional acidic or alkali salt forms of sulfonated monomers. Second, sulfonated polymers with substituted ammonium counterions are useful polymers for obtaining unique material properties, such as organo-gelation of low polarity solvents or obtaining ionic liquid polymers for the fabrication of solid polymer electrolytes. 相似文献
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The properties of Alnicos and elongated single-domain fine-particle materials, both interpreted as due to shape anisotropy of fine particles, are still far short of those predicted by simple theory. The hard ferrites, with properties due to magnetocrystalline anisotropy, come much closer, but are restricted by their low magnetization. The search for a combination of high magnetization and high magnetocrystalline anisotropy has led to the investigation of a variety of intermetallic compounds. Some of them, particularly the cobalt-rare earths, appear quite promising. Mechanical grinding often has an adverse effect on the magnetic properties of crystal anisotropy materials. Chemical stability is also often a problem. Crystal anisotropy materials in general have high values of intrinsic coercive force. This makes them especially suitable for applications involving widely varying dynamic conditions. Their proper evaluation may be best done using criteria other than the usual maximum energy product. 相似文献
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SnO nanoflakes were successfully prepared by a simple hydrothermal process, with the use of hydrazine hydrate as the mineralizer
and polyethylene glycol (PEG) or citric acid as an additive. Hydrazine hydrate serves as both a mineralizer and a protective
agent against the oxidation of the SnO products at the hydrothermal stage. X-ray diffraction, field-emission scanning electron
microscopy (FESEM), and transmission electron microscopy were employed to characterize the products. FESEM images reveal that
the thickness of the SnO nanoflakes prepared by the hydrothermal process with the use of PEG as an additive is around 15 nm.
The first reversible specific capacity of the SnO nanoflakes reaches 856 mA h/g, which is near the theoretical value (876
mA h/g). Hydrazine hydrate, the hydrothermal temperature, and the surfactant/complexing agent are three key factors for the
hydrothermal synthesis of the SnO nanoflakes by the process presented here.
The text was submitted by the authors in English. 相似文献