Search

Forced convective jet applied onto carbon arc plasma has significant effects on the formation of carbon nanoparticles (CNPs) containing multiwalled carbon nanotubes mixed with multishelled nanoparticles produced by the “arc in water” method. There is an optimized flow rate of the convective jet that leads to the highest production yield, largest hydrodynamic diameter of the products, and the reduced crystalline defects. With the convective flow rate of 1.36 dm3/min, the highest yield and production rate of CNPs could be obtained at 48.5% and 9.32 g/h, respectively. These effects of the forced convective jet originate from the enhanced quenching of carbon clusters vaporized from graphite anode. Analysis of convective flow field subjected to the arc plasma zone is conducted to indicate that synthesis of CNPs by the arc in water method can be elaborately controlled. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: Hierarchical micro-/macroporous carbon monoliths are prepared as enzyme carriers for flow-through process. The immobilization of Candida rugosa lipase on micro-/macroporous carbon monoliths is studied. Lipase is immobilized by physical adsorption which lipase solution is circulated through the micro-/macroporous carbon monolith. An accessibility of lipase to the surface inside the micro-/macroporous carbon monolith is enhanced by flow-through method which promotes enzyme–surface interaction and finally leads to rapid enzyme immobilization. After immobilization is conducted for 10min, the maximum protein binding can be measured. In terms of substrate-immobilized lipase reactions, flowing of substrate through lipase immobilized micro-/macroporous carbon monolith promotes high efficiency in both reaction and product withdrawal. Moreover, at high flow rates of lipase solution in immobilization step, the lipase activity increases. Oxygenated surface of micro-/macroporous carbon monoliths support also demonstrates an interesting effect on lipase immobilization and biocatalyst activity. The initial reaction rate of lipase immobilized on oxygenated surface carbon monolith support has higher activity compared with normal surface. [Copyright &y& Elsevier]

Abstract: Carbon-coated silica gel beads could be prepared by immersing porous silica gel beads in a resorcinol–formaldehyde (RF) aqueous solution and then following by drying and pyrolysis in nitrogen atmosphere. With the proposed method, deposition of colloidal nanoparticles formed during the sol–gel polycondensation of the RF solution was successfully prepared on the mesopores of the silica gel beads. Both size and concentration of the colloidal particles could be controlled by the gelation time and the mixing ratio (V EtOH /V RF ) of the RF solution to ethanol. The porous characteristics of the prepared carbon-coated silica gel beads and the amounts of deposited carbon could be controlled by changing V EtOH /V RF. Without any significant decrease in mesoporosity, the maximal carbon contents of carbon-coated silica gel beads could be increased up to 18wt% in the inner part and 53wt% on the outer surface, respectively. [Copyright &y& Elsevier]

Abstract: The utilization of naphthalene as an alternative carbon source for synthesis of carbon nanoparticles by pyrolyzing with ferrocene in a quartz tube reactor was experimentally investigated. Carbon nanoparticles including carbon nanotubes (CNTs) and carbon nanocapsules (CNCs), which contained Fe particles in their carbon shells, were simultaneously fabricated. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses revealed that morphology and size of the carbon nanostructure strongly depended on the pyrolysis temperature. At a higher temperature, formation of CNCs would become more enhanced. Particle size distribution and yield of the synthesized products were also significantly influenced by the pyrolysis temperature. [Copyright &y& Elsevier]

Abstract: Effect of monoolein surfactant which promotes n-hexane to dissolve in water was investigated to enhance the carbon nanoparticle (CNP) synthesis by arc discharge in liquid. The production rate of CNPs consisting of multi-shelled fullerenes and multi-walled carbon nanotubes was increased by the addition of the n-hexane to water with support of monoolein surfactant. An optimal amount of monoolein led to the maximal production rate of CNPs which was ca. two-fold higher than that obtained from a pure water system. This effect is ascribed to the role of n-hexane and monoolein to provide carbon clusters to the arc reactive zone. The hydrodynamic particle sizes of CNPs and their crystallinity were also enhanced by the addition of these organic compounds. As the vapor pressure of the organic component is significantly suppressed, the proposed method is much safer than that using pure organic liquid. [Copyright &y& Elsevier]

Abstract: A two-step direct and simple method for the preparation of a hierarchical porous carbon monolith with micropores, mesopores and macropores is described. The two stages give more flexibility in the preparation of a porous carbon monolith. In step I a macroporous interconnected carbon monolith is prepared by ultrasonic irradiation during sol–gel polycondensation. The effects of sol–gel temperature, catalyst concentration and ultrasonic power on the structure of the monolith are investigated. In step II, mesopores are induced in the monolith by Ca(NO3)2 impregnation followed by CO2 activation. The effect of activation temperature is also studied. A hierarchical interconnected carbon monolith with mean pore size diameter of 1.2μm, BET surface area of 624m2/g, mesopore volume of 0.38cm3/g and micropore volume of 0.22cm3/g has been obtained from Ca(NO3)2 impregnation of the macroporous carbon monolith followed by CO2 activation at 850°C. [Copyright &y& Elsevier]

Abstract: In this work, ultrasonic irradiation (with suitable reactant ratios) during gelation of RF solution is a promising technique for maintaining porous properties of carbon gels prepared by microwave drying. [Copyright &y& Elsevier]

Abstract: A new method in preparation of 3D interconnected macroporous carbon monolith has been introduced. Ultrasonic irradiation (ultrasonic intensity 78W/cm2) and low catalyst concentration (C/W=10mol/m3) of RF solution are used as an interesting and unique preparation method for 3D interconnected macroporous sonogel (gel irradiated by ultrasound at gelation stage) and/or 3D interconnected macroporous carbon monolith without using templates. [Copyright &y& Elsevier]