Carbon Composites (carbon + composite)

Distribution by Scientific Domains


Selected Abstracts


Mesoporous, 2D Hexagonal Carbon Nitride and Titanium Nitride/Carbon Composites

ADVANCED MATERIALS, Issue 42 2009
Young-Si Jun
A multistep templating procedure is used to prepare graphitic carbon nitride (g-C3N4) and titanium nitride/carbon composites with ordered, 2D hexagonal porosity. First, the carbon nitride is prepared by nanocasting using a silica (SBA-15) template. This carbon nitride is then replicated as a metal nitride carbon composite, using a simultaneous templating/conversion scheme ("reactive templating"). [source]


Thermal and Structural Characterizations of Individual Single-, Double-, and Multi-Walled Carbon Nanotubes

ADVANCED FUNCTIONAL MATERIALS, Issue 24 2009
Michael T. Pettes
Abstract Thermal conductance measurements of individual single- (S), double- (D), and multi- (M) walled (W) carbon nanotubes (CNTs) grown using thermal chemical vapor deposition between two suspended microthermometers are reported. The crystal structure of the measured CNT samples is characterized in detail using transmission electron microscopy (TEM). The thermal conductance, diameter, and chirality are all determined on the same individual SWCNT. The thermal contact resistance per unit length is obtained as 78,585,m,K,W,1 for three as-grown 10,14,nm diameter MWCNTs on rough Pt electrodes, and decreases by more than 2 times after the deposition of amorphous platinum,carbon composites at the contacts. The obtained intrinsic thermal conductivity of approximately 42,48, 178,336, and 269,343,W,m,1,K,1 at room-temperature for the three MWCNT samples correlates well with TEM-observed defects spaced approximately 13, 20, and 29,nm apart, respectively; whereas the effective thermal conductivity is found to be limited by the thermal contact resistance to be about 600,W,m,1,K,1 at room temperature for the as-grown DWCNT and SWCNT samples without the contact deposition. [source]


Silicon Inverse-Opal-Based Macroporous Materials as Negative Electrodes for Lithium Ion Batteries

ADVANCED FUNCTIONAL MATERIALS, Issue 12 2009
Alexei Esmanski
Abstract Several types of silicon-based inverse-opal films are synthesized, characterized by a range of experimental techniques, and studied in terms of electrochemical performance. Amorphous silicon inverse opals are fabricated via chemical vapor deposition. Galvanostatic cycling demonstrates that these materials possess high capacities and reasonable capacity retentions. Amorphous silicon inverse opals perform unsatisfactorily at high rates due to the low conductivity of silicon. The conductivity of silicon inverse opals can be improved by their crystallization. Nanocrystalline silicon inverse opals demonstrate much better rate capabilities but the capacities fade to zero after several cycles. Silicon,carbon composite inverse-opal materials are synthesized by depositing a thin layer of carbon via pyrolysis of a sucrose-based precursor onto the silicon inverse opals. The amount of carbon deposited proves to be insufficient to stabilize the structures and silicon,carbon composites demonstrate unsatisfactory electrochemical behavior. Carbon inverse opals are coated with amorphous silicon producing another type of macroporous composite. These electrodes demonstrate significant improvement both in capacity retentions and in rate capabilities. The inner carbon matrix not only increases the material conductivity but also results in lower silicon pulverization during cycling. [source]


Modeling the mass transfers during the elaboration of chitosan-activated carbon composites for medical applications

AICHE JOURNAL, Issue 6 2010
A. Venault
Abstract Hydrogels composites composed of chitosan and activated carbon were prepared for medical applications using the vapor-induced phase separation process. Since the gelation process involves mass exchanges between the polymer solution and the air, the kinetics of mass transfer were investigated through experimental and modeling approaches. Among the formulation and process parameters, gravimetric measurements exhibited that mass transfers were mostly controlled by the initial ammonia partial pressure. A nonisotherm mass-transfer model was developed to predict the nonsolvent and solvent exchange rates, therefore, the water and ammonia concentration profiles within the sample during the process. The numerical results were successively validated with gravimetrical kinetic curves obtained in a chamber where the process parameters were controlled. The model aimed also at predicting the pH moving front along the film thickness. The gelation time could also be predicted for different operating conditions (formulation and process parameters). 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]


Oxidation Behavior of Silicon-Infiltrated Carbon/Carbon Composites in High-Enthalpy Convective Environment

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2001
Toshio Ogasawara
Thermal response and oxidation behavior of commercial metal-silicon-infiltrated carbon/carbon composites (MICMATTM; Si-CC) were evaluated in a high-enthalpy convective environment using an arc jet facility (an arc wind tunnel). Composite specimens were put into a supersonic plasma air stream having a gas enthalpy of 12.7,18.8 MJ/kg for 50,600 s. Cold-wall heat fluxes measured by a Gardon-type calorimeter ranged from 1.0 to 1.8 MW/m2, and the maximum surface temperature reached 1300,1660C. After the arc jet testing, no surface recession was observed in the samples, and the mass loss rate of the composites was far less than that of graphite. The excellent oxidation resistance was caused by formation of a porous SiC layer at the surface of the composite. Oxidation behavior of the composites is discussed based on a simplified airflow blocking model of the porous SiC layer. The composites exhibited excellent oxidation resistance for short-term exposure in high-enthalpy airflow. [source]


Mesoporous, 2D Hexagonal Carbon Nitride and Titanium Nitride/Carbon Composites

ADVANCED MATERIALS, Issue 42 2009
Young-Si Jun
A multistep templating procedure is used to prepare graphitic carbon nitride (g-C3N4) and titanium nitride/carbon composites with ordered, 2D hexagonal porosity. First, the carbon nitride is prepared by nanocasting using a silica (SBA-15) template. This carbon nitride is then replicated as a metal nitride carbon composite, using a simultaneous templating/conversion scheme ("reactive templating"). [source]