carbon nanotubes

摘要： Solution processability and flexibility still remain major challenges for many thermoelectric(TE)materials,including bismuth telluride(Bi_(2)Te_(3)),a typical and commercially available TE material.Here,we report a new solutionprocessed method to prepare a flexible film of a Bi_(2)Te_(3)/single-walled carbon nanotube(SWCNT)hybrid,where the dissolved Bi_(2)Te_(3) ion precursors are mixed with dispersed SWCNTs in solution and recrystallized on the SWCNT surfaces to form a“cement-rebar”-like architecture.The hybrid film shows an n-type characteristic,with a stable Seebeck coefficient of^(−1)00.00±1.69μVK^(−1) in air.Furthermore,an extremely low in-plane thermal conductivity of∼0.33Wm^(−1) K^(−1) is achieved at 300 K,and the figure of merit(ZT)reaches 0.47±0.02.In addition,the TE performance is independent of mechanical bending.The unique“cement-rebar”-like architecture is believed to be responsible for the excellent TE performances and the high flexibility.The results provide a new avenue for the fabrication of solution-processable and flexible TE hybrid films and will speed up the applications of flexible electronics and energy conversion.

摘要： A bifunctional electroactive filter was rationally fabricated for simultaneous oxidation and sequestration of toxic trivalent arsentic As(Ⅲ).A novel nanoscale La(OH)_(3) modified electrochemical carbon nanotube(CNT)network filter was prepared by a facile electrodeposition strategy.The As(Ⅲ)decontamination kinetics and adsorption capacity were both found to increase with the flow rate(1.5-6.0 mL/min)and the applied voltage(0-2.5 V).The CNT filter hybridized with La(OH)_(3)(CNT-La(OH)_(3))has demonstrated the ultra-high adsorption capacity of 750.2 mg/g for As(Ⅲ),which is ascribed to the combined role of sufficient adsorption sites,flow-through filtration and electric field.XPS analysis revealed that the As(Ⅲ)decontamination mechanism involved a two-step adsorption-oxidation process.The formation of inner-sphere La-O-As complexes,ligand exchange and electro-adsorption are all parts of the As(Ⅲ)adsorption process.The adsorbed neutrally-charged As(Ⅲ)was further oxidized to negatively-charged As(V)when aided by an electric field,which could be effectively sequestrated by La(OH)_(3).The CNT-La(OH)_(3) filter shows high stability under alkaline conditions and can be regenerated with dilute NaOH solution.In this study,all experiment results have demonstrated a promising and effective CNT-La(OH)_(3) electrochemical filter for As(Ⅲ)pollution minimization.

摘要： Nanotube-based mixed-dimensional or one-dimensional heterostructures have attracted great attention recently because of their unique physical properties and therefore potential for novel devices. Their chemical properties, however, were less explored but can be utilized for energy storage and conversion.In this review, we summarize the recent progress of nanotube-based low dimensional materials for electrochemistry, in particular, lithium storage and hydrogen evolution. First, we describe the atomic structure of low-dimensional heterostructures and briefly touch previous work on planar van der Waals heterostructures(2D+2D) in electrochemistry applications. Then we focus this review on the more recently developed nanotube-based, i.e., 1D+2D and 1D + 1D heterostructures, and discuss their various preparation approaches and electrochemical performances. Finally, we outline the challenges and opportunities in this direction and particularly emphasize the possibility of building high-performance electrodes using a single-walled carbon nanotube-based ultra-thin 1D heterostructure, and the importance of understanding the fundamental mechanism at atomic precision.

摘要： Conductive cementitious composites are innovated materials that have improved electrical conductivity compared to general types of cement,and are expected to be used in a variety of future infrastructures with unique functionalities such as self-heating,electromagnetic shielding,and piezoelectricity.In the present study,machine learning methods that have been recently applied in various fields were proposed for the prediction of piezoelectric characteristics of carbon nanotubes(CNTs)-incorporated cement composites.Data on the resistivity change of CNTs/cement composites according to various water/binder ratios,loading types,and CNT content were considered as training values.These data were applied to numerous machine learning techniques including linear regression,decision tree,support vector machine,deep belief network,Gaussian process regression,genetic algorithm,bagging ensemble,random forest ensemble,boosting ensemble,long short-term memory,and gated recurrent units to estimate the time-independent and-dependent electrical properties of conductive cementitious composites.By comparing and analyzing the computed results of the proposed methods,an optimal algorithm suitable for application to CNTs-embedded cementitious composites was derived.

摘要： The dispersion of nanoparticles plays a key role in enhancing the mechanical performance of polymer nanocomposites.In this work,one hybrid epoxy nanocomposite reinforced by a well dispersed,zinc oxide functionalized,multi-wall carbon nanotube (Zn O-MWCNT) and core-shell rubber (CSR) was prepared,which possesses both high modulus and fracture toughness while maintaining relatively high glass transition temperature (Tg).The improved fracture toughness from 0.82 MPa mfor neat epoxy to 1.46 MPa mfor the ternary epoxy nanocomposites is resulted from a series of synergistic toughening mechanisms,including cavitation of CSR-induced matrix shear banding,along with the fracture of MWCNTs and crack deflection.The implication of the present study for the preparation of high-performance polymer nanocomposites is discussed.

摘要： Molecular dynamics simulations have been performed to explore the underlying synergistic mechanism of pillared graphene or non-covalent connected graphene and carbon nanotubes(CNTs) on the mechanical properties of polyethylene(PE) nanocomposites. By constructing the pillared graphene model and CNTs/graphene model, the effect of the structure, arrangement and dispersion of hybrid fillers on the tensile mechanical properties of PE nanocomposites was studied. The results show that the pillared graphene/PE nanocomposites exhibit higher Young’s modulus, tensile strength and elongation at break than non-covalent connected CNTs/graphene/PE nanocomposites. The pull-out simulations show that pillared graphene by CNTs has both large interfacial load and long displacement due to the mixed modes of shear separation and normal separation. Additionally, pillared graphene can not only inhibit agglomeration but also form a compact effective thickness(stiff layer), consistent with the adsorption behavior and improved interfacial energy between pillared graphene and PE matrix.

摘要： Carbon nanotube(CNT),particularly single-walled CNT,possesses exceptional properties,and can be utilized in many high-end applications including high-performance electronics.However,the atomic arrangement of a CNT determines its band structure,making the atomic-precision fabrication one of most important topics for the development of this material.In this perspective,the author gives a personal summary on the history,current status of the atomic-precision fabrication of CNT and outlines the remaining challenges as well as the possible paths that may lead the production of atomically precise CNTs from‘fabrication’to‘manufacturing’.

摘要： The different carbon nanotube(CNT)particles(^(@)A and^(@)V)were bed materials in the pseudo-2D tapered fluidized bed(TFB)with/without a distributor.A detailed investigation of the motion mechanism of bubbles was carried out.The high-speed photography and image analysis techniques were used to study bubble characteristic and mixing behavior in the tapered angle of TFB without a distributor.The fractal analysis method was used to analyze the degree of particles movement.Results showed that an S-shaped motion trajectory of bubbles was captured in the bed of^(@)V particles.The population of observational bubbles in the bed of^(@)V particles was more than that of^(@)A particles,and the bubble size was smaller in the bed of^(@)V particles than that of^(@)A particles.The motion mechanism of bubbles had been shown to be related to bed materials and initial bed height in terms of analysis and comparison of bubble diameter,bubble aspect ratio and bubble shape factor.Importantly,compared to the TFB with a distributor,the TFB without a distributor had been proved to be beneficial to the CNT fluidization according to the study of bubble characteristic and the degree of the particle movement.Additionally,it was found that the mixing behavior of^(@)V particles was better than^(@)A particles in the tapered angle of TFB without a distributor.

摘要： Drilling fluids face failure during drilling deep reservoir with high temperature and high salt.The experimental results show that high temperature and salinity reduce the negative charge on the surface of bentonite in the drilling fluid and cause the coalescence of bentonite particles.As a result,the particles coalesce,the grid structure is destroyed,and the rheological properties,rock-carrying capacity and filtration properties are lost.To resolve the foregoing,in this study,0.05-wt%carbon nanotubes are introduced into a 4%bentonite drilling fluid under conditions where the temperature and concentration of added Na Cl reach 180°C and 10 wt%,respectively.The carbon nanotubes adsorb on the bentonite surface and increase the space among bentonite particles.The steric hindrance prevents the coalescence of bentonite in high temperature and high salt environment.Thus bentonite maintains the small size distribution of bentonite and supports the bentonite grid structure in the drilling fluid.As a result,the rock-carrying capacity of the drilling fluid increases by 85.1%.Moreover,the mud cake formed by the accumulation of small-sized bentonite particles is dense;consequently,the filtration of bentonite drilling fluid reduced by 30.2%.

摘要： Bimodal carbon nanotube reinforced 7055Al(CNT/7055Al) composites containing coarse grain bands and ultra-fine grain zones were fabricated by high energy ball milling, vacuum hot pressing followed by hot extrusion. The effect of extrusion temperature varied from 320°C to 420°C on the microstructure evolution and tensile properties were investigated. Microstructure observation indicates that the elongated coarse grain bands aligned along the extrusion direction after extrusion. The width of the coarse grain bands increased, and the length of the coarse grain bands increased firstly and then decreased with the increase of extrusion temperature. The grain size of the ultra-fine grain zones changed little after hot extrusion, but the ultra-fine grains coarsened after subsequent heat treatment, especially for the composite extruded at low temperature of 320°C. By observing the CNT distribution, it was found that the higher temperature extrusion was beneficial to the CNT orientation along the extrusion direction.Furthermore, a precipitated free zone formed at the boundary between the coarse grain band and the ultra-fine grain zone as the composite extruded at high temperature of 420°C. As the result of the comprehensive influence of the above microstructure, the tensile strength of the composite extruded at moderate temperature of 370°C reached the highest of 826 MPa.

摘要： The detailed transmission electron microscopy observations of the immature carbon nanotubes (CNTs),obtained at relatively low temperatures by floating chemical vapor deposition (CVD), indicate that they can be viewed as intermediate objects and record rich and convincible traces about CNT evolution.The results clearly show that the CNT formation in floating CVD follows the particle- wire- tube stepwise evolution mechanism and also provide detailed information about the particle coalescence and structural integration and extension.This new knowledge not only gives a clearer picture for the CNT evolution in floating CVD but also might provide a general method for mechanism studies for other synthesis processes.

摘要： The detailed transmission electron microscopy observations of the immature carbon nanotubes (CNTs),obtained at relatively low temperatures by floating chemical vapor deposition (CVD), indicate that they can be viewed as intermediate objects and record rich and convincible traces about CNT evolution.The results clearly show that the CNT formation in floating CVD follows the particle- wire- tube stepwise evolution mechanism and also provide detailed information about the particle coalescence and structural integration and extension.This new knowledge not only gives a clearer picture for the CNT evolution in floating CVD but also might provide a general method for mechanism studies for other synthesis processes.

摘要： The detailed transmission electron microscopy observations of the immature carbon nanotubes (CNTs),obtained at relatively low temperatures by floating chemical vapor deposition (CVD), indicate that they can be viewed as intermediate objects and record rich and convincible traces about CNT evolution.The results clearly show that the CNT formation in floating CVD follows the particle- wire- tube stepwise evolution mechanism and also provide detailed information about the particle coalescence and structural integration and extension.This new knowledge not only gives a clearer picture for the CNT evolution in floating CVD but also might provide a general method for mechanism studies for other synthesis processes.

摘要： The detailed transmission electron microscopy observations of the immature carbon nanotubes (CNTs),obtained at relatively low temperatures by floating chemical vapor deposition (CVD), indicate that they can be viewed as intermediate objects and record rich and convincible traces about CNT evolution.The results clearly show that the CNT formation in floating CVD follows the particle- wire- tube stepwise evolution mechanism and also provide detailed information about the particle coalescence and structural integration and extension.This new knowledge not only gives a clearer picture for the CNT evolution in floating CVD but also might provide a general method for mechanism studies for other synthesis processes.