nanostructure

摘要： Biomass-derived residue carbonization has been an important issue for"carbon fixation"and"zero emission",and the carbonized products have multiple application potentials.However,there have been no specific research to study the differences in macro-and micro-morphology,electrical properties and many other aspects of the products obtained from carbonization of pure cellulose,pure lignin or their complex,lignocellulose.In this work,lignocellulose with cellulose to lignin mass ratio of 10:1 is obtained using p-toluenesulfonic acid hydrolysis followed by homogenization process at a controlled condition.Then,carbon heterostructure with fibers and sheets(CH-10)are obtained by pyrolysis at 1500°C.Detailed results imply that the fiber-like carbon structure possesses high crystallinity and low defect density,coming from carbonization of the cellulose content in lignocellulose(LC)nanofibers.Correspondingly,the graphite-like carbon sheet with high defect density and low crystallinity comes from carbonization of the lignin content in LCs.Further investigation indicates CH-10 possesses enhanced polarization and moderate impedance matching which makes it an ideal candidate for electromagnetic wave(EMW)absorption.CH-10 exhibits an excellent EMW absorption performance with a minimum RL value of-50.05 dB and a broadest absorption bandwidth of 4.16 GHz at a coating thickness as thin as 1.3 mm.

摘要： This study presents an overview on graphene synthesis,fabrication and different characterization techniques utilized in the production.Since its discovery in 2004 by Andre Geim and Kostya Novoselov several research articles have been published globally to this effect,owing to graphene’s extraordinary,and exclusive characteristics which include optical transparency,excellent thermal,and mechanical properties.The properties and applications of this two-dimensional carbon crystal composed of single-layered material have created new avenues for the development of high-performance future electronics and technologies in energy storage and conversion for the sustainable energy.However,despite its potential and current status globally the difficulty in the production of monolayer graphene sheet still persists.Therefore,this review highlighted two approaches in the synthesis of graphene,which are the top-down and bottom-up approaches and examined the advantages and failings of the methods involved.In addition,the prospects and failings of these methods are investigated,as they are essential in optimizing the production method of graphene vital for expanding the yield,and producing high-quality graphene.

摘要： Copper nanowires were synthesized by the wet chemical reduction method using copper sulfate as the copper precursor,aliphatic amines(methylamine,ethanediamine,1,2-propanediamine)as the inducing reagents,and hydrazine hydrate as the reductant through the aging and reduction processes.The high-resolution transmission electron microscopy(HRTEM)images reveal that the copper nanowires were synthesized by coalescing extremely small-sized copper nanoparticles with the particle sizes of1–6 nm in copper complex micelles.A longer aging time period favored the coalescing of the copper nanoparticles to form thinner copper nanowires in the following reduction process.The coalescing extent of copper nanoparticles in copper nanowires was highly enhanced by ethanediamine and 1,2-propanediamine as compared with that by methylamine.The copper nanowire-filled polyester films had higher electrical conductivity than the copper nanoparticle-filled ones.

摘要： Montmorillonite(MMT) was modified by ultrasound and castor oil quaternary ammonium salt intercalation method to prepare a new type of organic montmorillonite(OMMT). The surface structure, particle morphology, interlayer distance, and thermal behavior of the samples obtained were characterized. The modified OMMT was then added to chlorinated butyl rubber(CIIR) by mechanical blending, and a composite material with excellent damping properties was obtained. The mechanical experiment results of CIIR nanocomposites showed that the addition of OMMT improved their tensile strength, hardness,and stress relaxation rate. Compared with pure CIIR, when the content of OMMT was 5 phr(part per hundred of rubber), the tensile strength of the nanocomposite was increased by 677% and the elongation at break was also increased by 105.4%. The enhancement of this performance was mainly due to the dispersion of the nanosheets in CIIR rubber and the chemical interaction between the organoclay and the polymer matrix, which was confirmed by morphology and spectral analysis. OMMT also endowed a positive effect on the damping properties of CIIR nanocomposites. After adding 5 phr of OMMT, the nanocomposite owned the best damping performance, and the damping factor, tanδmax, was 37.9% higher than that of pure CIIR. Therefore, the good damping and mechanical properties of these CIIR nanocomposites provided some novel and promising methods for preparing high-damping rubber in a wide temperature range.

摘要： Proton exchange membrane fuel cell and direct methanol fuel cells have gained more attention due to high-energy density,remarkable conversion efficiency,and low emission.However,their widely practical application was hindered by the high usage,limited sources,and high price of Pt catalysts.To achieve more cost-effective catalytic systems,PtCu-based multi-metallic nanoparticles are highly efficient for the oxygen reduction reaction(ORR)and methanol oxidation reaction(MOR).The incorporation of non-noble Cu metal can alter the properties of hybrids by forming new facets,planes,edges to promote the cleavage or formation of chemical bonds in catalytic reaction.This is a rapid growing area with numerous contributions from the interdisciplinary areas of nanocatalysis.This paper has summarized the recent progress in the past two years,in synthesizing PtCu-based alloys with various composition and morphologies,and critically discussed the effect of the catalyst preparation method,metal precursor,surfactant,reductant and heating temperature on nanostructure and electronic configuration.The important role of the composition,size,and morphology of PtCu bimetallic catalysts for electro oxidation reactions has been further established for structure-dependency studies.The challenges and perspectives of nanocatalysts for ORR and MOR discussed in this work is to provide further insights into rational design for cost-effective materials for energy.

摘要： Hybrid CuO-Co_(3)O_(4)nanosphere building blocks have been embedded between the layered nanosheets of reduced graphene oxides with a three dimensional(3D)hybrid architecture(CuO-Co_(3)O_(4)-RGO),which are successfully applied as enhanced anodes for lithium-ion batteries(LIBs).The CuO-Co_(3)O_(4)-RGO sandwiched nanostructures exhibit a reversible capacity of~847 mA·h·g^(-1)after 200 cycles’cycling at 100 mA·g^(-1)with a capacity retention of 79%.The CuO-Co_(3)O_(4)-RGO compounds show superior electrochemical properties than the comparative CuO-Co_(3)O_(4),Co_(3)O_(4)and CuO anodes,which may be ascribed to the following reasons:the hybridizing multicomponent can probably give the complementary advantages;the mutual benefit of uniformly distributing nanospheres across the layered RGO nanosheets can avoid the agglomeration of both the RGO nanosheets and the CuO-Co_(3)O_(4) nanospheres;the 3D storage structure as well as the graphene wrapped composite could enhance the electrical conductivity and reduce volume expansion effect associated with the discharge-charge process.

摘要： The wing architecture is an inspiration to fabricate novel materials with exquisite properties.The current study characterizes the structure and biological function of a termite’s wing.The topography of the surface of the wing was studied by electron microscopy,and surface profilometer.The physicochemical property of the surface was analyzed by Fourier transform infrared spectroscopy,X-ray diffraction spectroscopy,energy-dispersive X-ray spectroscopy,and gas chromatography-mass spectrometry analysis of the epicuticle content.Water Contact Angle measurement confirmed the hydrophobicity of the wing surface.When microorganisms come in contact with the surface of the wing,they adhere to the wing surface due to cell surface properties of their own and the surface chemistry of the wing.The current study reported the adhesion behavior of two bacterial species.The bactericidal activity of the wing was confirmed by counting the bacterial cell viability and examination under a confocal laser scanning microscope.Adhesion of bacteria was observed under the electron microscope.Bacterial oxidative stress,the topography of the wing,and the surface chemistry of the wing are the crucial factors that induce bactericidal activity.The nanostructure along with the chemical composition of the wing can be mimicked for the fabrication of novel material with antibacterial properties.

摘要： Lithium ion battery (LIB) is one of the promising power storage devices in today’s world. Lithium ion battery like other types of electrochemical cell has anodic and cathodic electrode in which lithium ion is intercalated and deinterclated during charging and discharging process respectively. The capacity of lithium ion battery is improved by the development of innovative kinds of electrode. Carbon, metal/semiconductor, metal oxides and metal phosphides/ nitrides/sulfides based nanomaterials improve the capability of LIBs due to their high surface area, low diffusion distance, high electrical and ionic conductivity. Nanostructured materials represent a rapidly growing area in the field of Li-ion batteries because of their substantial advantages in terms of mass transport. In this review anode nanomaterials classified based on type of transition metal/semiconductor such as carbon, silicon, titanium and tin based nanomaterials are discussed. Additionally, different electrochemical reactions, comparative influence of anode materials on LIBs and their applications are widely explained.

摘要： As two renewable oxygenated biofuels,2,5-dimethylfuran and 2-methylfuran(DMF and MF)have been considered to be two of the most potential fuels in the future due to the development of the second-generation biosynthetic technologies.The atmosphere pyrolysis experiments with 0%,25%,50%,75%and 100%replacement of ethylene by DMF/MF at 1173 and 1273 K were conducted.Collected soot samples were characterized by high resolution transmission electron microscopy(HRTEM)and thermogravimetric analysis(TGA)to acquire their internal structure and oxidation reactivity.Results showed that soot mass was positively related with DMF addition ratios and the reaction temperature.Soot production was also enhanced when the MF addition ratio gradually increased from 0%to 75%.The influences of DMF addition can promote soot formation more obviously than MF.Temperatures showed a more significant influence on soot morphology than fuel types and DMF/MF addition ratios.For a fixed addition ratio of DMF/MF,soot showed liquid-like substances at 1173 K.At 1273 K,approximately round particles formed and linked together in chains.Moreover,at 1273 K,the aggregates obtained by adding MF contained more single particles,longer carbon chains,and larger projection area compared with the aggregates by adding same MF.For nanostructures,as the addition ratios of DMF/MF increased,as well as the reaction temperature improved,the fringe length of the carbon layer increased,the average fringe tortuosity decreased,and the stacking arrangement of soot became more orderly,the soot oxidation reactivity was lower.Under a same addition ratio and reaction temperature,soot obtained by adding DMF possessed slightly longer fringe length,smaller fringe tortuosity and lower oxidation reactivity than those of the soot obtained by adding MF.High correlation between fringe parameters and soot oxidation reactivity was discovered.The more ordered soot nanostructure,the longer fringe length,and the smaller fringe tortuosity could make the oxidation reactivity of soot get lower.

摘要： Lithium-ion batteries(LIBs)have shown considerable promise as an energy storage system due to their high conversion efficiency,size options(from coin cell to grid storage),and free of gaseous exhaust.For LIBs,power density and energy density are two of the most important parameters for their practical use,and the power density is the key factor for applications such as fast-charging electric vehicles,high-power portable tools,and power grid stabilization.A high rate of performance is also required for devices that store electrical energy from seasonal or irregular energy sources,such as wind energy and wave energy.Significant efforts have been made over the last several years to improve the power density of LIBs through anodes,cathodes,and electrolytes,and much progress has been made.To provide a comprehensive picture of these recent achievements,this review discusses the progress made in high-power LIBs from 2013 to the present,including general and fundamental principles of high-power LIBs,challenges facing LIB development today,and an outlook for future LIB development.