Showing papers by "Weizhong Qian published in 2013"

The Road for Nanomaterials Industry: A Review of Carbon Nanotube Production, Post‐Treatment, and Bulk Applications for Composites and Energy Storage

Abstract: The innovation on the low dimensional nanomaterials brings the rapid growth of nano community. Developing the controllable production and commercial applications of nanomaterials for sustainable society is highly concerned. Herein, carbon nanotubes (CNTs) with sp(2) carbon bonding, excellent mechanical, electrical, thermal, as well as transport properties are selected as model nanomaterials to demonstrate the road of nanomaterials towards industry. The engineering principles of the mass production and recent progress in the area of CNT purification and dispersion are described, as well as its bulk application for nanocomposites and energy storage. The environmental, health, and safety considerations of CNTs, and recent progress in CNT commercialization are also included. With the effort from the CNT industry during the past 10 years, the price of multi-walled CNTs have decreased from 45 000 to 100 $ kg(-1) and the productivity increased to several hundred tons per year for commercial applications in Li ion battery and nanocomposites. When the prices of CNTs decrease to 10 $ kg(-1) , their applications as composites and conductive fillers at a million ton scale can be anticipated, replacing conventional carbon black fillers. Compared with traditional bulk chemicals, the controllable synthesis and applications of CNTs on a million ton scale are still far from being achieved due to the challenges in production, purification, dispersion, and commercial application. The basic knowledge of growth mechanisms, efficient and controllable routes for CNT production, the environmental and safety issues, and the commercialization models are still inadequate. The gap between the basic scientific research and industrial development should be bridged by multidisciplinary research for the rapid growth of CNT nano-industry.

Facile Route for Synthesizing Ordered Mesoporous Ni–Ce–Al Oxide Materials and Their Catalytic Performance for Methane Dry Reforming to Hydrogen and Syngas

Abstract: A series of ordered mesoporous Ni–Ce–Al composite oxides with various cerium contents were synthesized via a one-pot route: evaporation-induced self-assembly (EISA) strategy and tested in methane dry reforming for hydrogen and synthesis gas production. Using this method, the hydrophobic nickel precursor was directly incorporated into the hydrophobic cores of surfactant micelles, and thus, the highly dispersed Ni nanoparticles were stabilized inside the mesopore channels of an alumina matrix. For comparison, Ni-based catalysts were also prepared by a traditional impregnation method. The characterization results confirmed that the ordered mesostructures were well maintained in all of the cerium-incorporated Ni–Al materials (Ce/(Ce + Al) molar ratio ≤ 3%). The catalyst with a Ce/(Ce + Al) ratio of 1% exhibited the highest catalytic activity (with CO2 and CH4 initial conversions being 70% and 68% at 700 °C, respectively) and remained stable in a methane dry reforming reaction. This improved activity can be at...

Growth of half-meter long carbon nanotubes based on Schulz-Flory distribution.

Abstract: The Schulz–Flory distribution is a mathematical function that describes the relative ratios of polymers of different length after a polymerization process, based on their relative probabilities of occurrence. Carbon nanotubes (CNTs) are big carbon molecules which have a very high length-to-diameter ratio, somewhat similar to polymer molecules. Large amounts of ultralong CNTs have not been obtained although they are highly desired. Here, we report that the Schulz–Flory distribution can be applied to describe the relative ratios of CNTs of different lengths produced with a floating chemical vapor deposition process, based on catalyst activity/deactivation probability. With the optimized processing parameters, we successfully synthesized 550-mm-long CNTs, for which the catalyst deactivation probability of a single growth step was ultralow. Our finding bridges the Schulz–Flory distribution and the synthesis of one-dimensional nanomaterials for the first time, and sheds new light on the rational design of proc...

Superlubricity in centimetres-long double-walled carbon nanotubes under ambient conditions

Abstract: Friction and wear are two main causes of mechanical energy dissipation and component failure, especially in micro/nanomechanical systems with large surface-to-volume ratios. In the past decade there has been an increasing level of research interest regarding superlubricity, a phenomenon, also called structural superlubricity, in which friction almost vanishes between two incommensurate solid surfaces. However, all experimental structural superlubricity has been obtained on the microscale or nanoscale, and predominantly under high vacuum. Here, we show that superlubricity can be realized in centimetres-long double-walled carbon nanotubes (DWCNTs) under ambient conditions. Centimetres-long inner shells can be pulled out continuously from such nanotubes, with an intershell friction lower than 1 nN that is independent of nanotube length. The shear strength of the DWCNTs is only several pascals, four orders of magnitude lower than the lowest reported value in CNTs and graphite. The perfect structure of the ultralong DWCNTs used in our experiments is essential for macroscale superlubricity.

Fabrication of c-axis oriented ZSM-5 hollow fibers based on an in situ solid-solid transformation mechanism.

Abstract: We report, for the first time, the preparation of novel c-axis oriented ZSM-5 hollow fibers by a combination of seeding and steam-assisted crystallization method using quartz fibers as the temporary soft substrate and Si source. The growth of such unique structure undergoes the development of a b-axis oriented ZSM-5 cylinder, followed by the growth of c-axis oriented ZSM-5 crystals vertically inside the cylinder and then outside the cylinder, by an in situ solid–solid transformation mechanism. The obtained ZSM-5 hollow fibers are composed of pure hierarchical ZSM-5 crystals with high crystallinity, good structural stability, and high surface area and have potential applications for microreactors, separators, and catalysts. The catalytic performance of ZSM-5 hollow fibers is tested in the methanol to gasoline reaction, as an example of their practical application. They exhibit both higher yield of gasoline and far longer lifetime compared to the conventional ZSM-5 due to the improved mass and heat diffusio...

Highly deformation-tolerant carbon nanotube sponges as supercapacitor electrodes

Abstract: Developing flexible and deformable supercapacitor electrodes based on porous materials is of high interest in energy related fields. Here, we show that carbon nanotube sponges, consisting of highly porous conductive networks, can serve as compressible and deformation-tolerant supercapacitor electrodes in aqueous or organic electrolytes. In aqueous electrolytes, the sponges maintain a similar specific capacitance (>90% of the original value) under a predefined compressive strain of 50% (corresponding to a volume reduction of 50%), and retain more than 70% of the original capacitance under 80% strain while the volume normalized capacitance increases by 3-fold. The sponge electrode maintains a stable performance after 1000 large strain compression cycles. A coin-shaped cell assembled with these sponges shows excellent stability over 15,000 charging cycles with negligible degradation after 500 cycles. Our results indicate that carbon nanotube sponges have the potential to fabricate deformable supercapacitor electrodes with stable performance.

Composite Cathodes Containing SWCNT@S Coaxial Nanocables: Facile Synthesis, Surface Modification, and Enhanced Performance for Li‐Ion Storage

Abstract: The arrangement and construction of 1D carbon nanotubes (CNTs) into frameworks with two or more levels of structures is an essential step to demonstrate their intrinsic properties and promising applications for energy storage. Single-walled CNTs (SWCNTs) are considered to have more excellent properties compared with multiwalled CNTs (MWCNTs), however, how to appropriately use SWCNTs as building blocks for nanocomposite electrodes is not well understood. Here, a composite cathode containing SWCNT@S coaxial nanocables for Li-S battery is fabricated by a facile melt-diffusion strategy. Beneficial from its sp2 carbon nanostructure, higher specific surface area, larger aspect ratio, and interconnected electron pathway, the SWCNT@S cathode have reversible capacities of 676, 441 and 311 mAh g−1 for the first discharging at 0.5 C, 100th discharging at 1.0 C, and discharging at 10.0 C, respectively. These capacities are much higher than the corresponding capacities of the MWCNT@S cathode. By introducing polyethylene glycol (PEG) as a physical barrier to trap the highly polar polysulfide species, the PEG modified SWCNT@S cathode afforded improved reversible capacities. The cycling stability of the reversible capacities is expected to be further improved. The SWCNTs can serve as scaffolds for Li-S battery with much improved energy storage performance.

Chemical vapor deposition derived flexible graphene paper and its application as high performance anodes for lithium rechargeable batteries

Abstract: We present a novel approach to fabricate flexible graphene papers using chemical vapor deposition (CVD) derived graphene. Expanded vermiculite was used as a layered template in the CVD process to produce bulk materials containing graphene sheets of the order of hundreds of microns at a gram scale. Meshes or carbon nanotubes can be introduced into the graphene sheets by template pretreating. Owing to the large sheet size, the as-obtained graphene sheets were easily fabricated into flexible graphene papers with low surface density and good conductivity, which exhibited greatly enhanced reversible capacity (1350 mA h g−1 at 50 mA g−1) and cycling performance as anodes for lithium rechargeable batteries as compared to the graphene papers fabricated using reduced graphene oxide.

Direct synthesis of c-axis oriented ZSM-5 nanoneedles from acid-treated kaolin clay

Abstract: c-Axis oriented ZSM-5 nanoneedles with an average diameter of 30 nm were directly prepared using acid-treated kaolin clay as the Al and Si source, which allowed the quick transfer of reaction molecules inside the micropores and exhibited a far longer lifetime to endure coke deposition when used in the catalytic conversion of methanol to aromatics, compared to the conventional microsized ZSM-5 crystal.

Multi-walled carbon nanotube-based carbon/carbon composites with three-dimensional network structures

Abstract: Multi-walled carbon nanotube (MWCNT)-based carbon/carbon composites were fabricated by the chemical vapor infiltration of pyrolytic carbon into pre-compressed MWCNT blocks. The pyrolytic carbon was deposited on the surface of the MWCNTs and filled the gaps between the MWCNTs, which improved the connection between the MWCNTs and formed a three-dimensional network structure. The mechanical and electrical properties were improved significantly. The values of the maximum compressed deformation, maximum breaking strength, Young's modulus and energy absorption are measured as 10.9%, 148.6 MPa, 1588.6 MPa and 13.8 kJ kg−1, respectively. The conductivity reached about 204.4 S cm−1, more than 10 times larger than that of pre-compressed MWCNT blocks. After annealing at 1800 °C in vacuum, the graphitization improved remarkably. The pyrolytic carbon deposited on the surface of the MWCNTs was rearranged along the walls, and resulted in an increase of the number of walls of the MWCNTs.

Facile manipulation of individual carbon nanotubes assisted by inorganic nanoparticles

Abstract: Carbon nanotubes (CNTs) are promising building blocks for nanodevices owing to their superior electrical, thermal and mechanical properties. One of the key issues for their study and application is the efficient location, transfer and manipulation of individual CNTs. In this contribution, we show that the manipulation of individual suspended CNTs has been carried out on the macroscale under low magnification, using inorganic nanoparticles (NPs) as indicators. Individual ultralong CNTs can be stretched, cut, and transferred to other substrates for further characterization. Complicated CNT structures were fabricated under optical microscopes. The inorganic NPs also facilitate the manipulation and characterization of individual CNTs under a scanning electron microscope with low magnification. Additionally, the irregular NPs deposited on suspended CNTs can also make the outer shell of the suspended CNTs display torsion or rotation around the inner shells when placed in a flow of gas, making the fabrication of CNT–NP-hybrid-based nanodevices feasible. Our results demonstrate the extraordinary capability of this manipulation technique for individual CNTs, enabled by decoration with inorganic NPs.

Growth of Half-Meter Long Carbon Nanotubes Based on SchulzFlory

Abstract: TheSchulzFlorydistributionisamathematicalfunctionthatdescribes the relative ratios of polymers of different length after a polymerization process, based on their relative probabilities of occurrence. Carbon nanotubes (CNTs) are big carbon molecules which have a very high length-to-diameter ratio, somewhat similar to polymer molecules. Large amounts of ultralong CNTs have not been obtained although they are highly desired. Here, we report that the SchulzFlory distribution can be applied to describe the relative ratios of CNTs of different lengths produced with a floating chemical vapor deposition process, based on catalyst activity/deactivation probability. With the optimized processing parameters, we successfully synthesized 550-mm-long CNTs, for which the catalyst deactivation probability of a single growth step was ultralow. Our finding bridges the SchulzFlory distribution and the synthesis of one-dimensional nanomaterials for the first time, and sheds new light on the rational design of process toward controlled production of nanotubes/ nanowires.