The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Silicon carbide (SiC) was chemical vapor deposited (CVD) onto a carbon fiber to investigate oxidation protection of the coating. This thin film of SiC was analyzed before and after argon and oxygen ion beam etching with core and valence band X-ray Photoelectron Spectroscopy (XPS). The valence band of SiC could be reasonably interpreted by a spectrum generated by a multiple scatter-wave Xα calculation...
Carbon fibers 6.5 μm in diameter were coated with amorphous SiC films by chemical vapor deposition at temperatures as low as 800-900°C, using triisopropylsilane in hydrogen. The morphology of the films was strongly affected by the reaction conditions. The tensile strength of the coated fibers was decreased by the coating, but was little affected by the coating method if smooth and tight films were...
Thermogravimetric analysis together with scanning electron microscopy observations have been used to study the behavior of vapor-grown carbon fibers towards air oxidation. We show that different peaks are present in the rate of gasification curves and we attribute this result, on the one hand to the presence of traces of iron in the fibers and on the other hand to the triplex structure of these kind...
A black reflective solid containing boron and carbon was produced via chemical vapor deposition (CVD) at 700 o C. The boron concentration in these films was determined to be 17at.%. X-ray diffraction has shown the interlayer spacing of this novel compound to be similar to that of graphite (d 002 =0.3384nm). Identification of 00l and hk0 reflections have also been made using...
Silicon infiltration has been used to form a functionally gradient layer on two-dimensional carbon-carbon (2D-C/C) composites. 2D-C/C composites were infiltrated with silicon at temperatures above the melting point of silicon in a NH 3 -containing atmosphere. Some of silicon-infiltrated C/C composites were then coated with a CVD-SiC coating. Electron probe microscopic analysis, X-ray diffraction...
Catalyst-support interactions are critical in CVD processes for nanotube synthesis. In this article, the relative contributions of the catalyst electronic structure and support chemical composition are evaluated with Cu, Fe and Ni as catalysts and Al 2 O 3 , CaO, SiO 2 and TiO 2 as support media. The impact of the interaction is judged qualitatively based on nanotube...
Capillaries, 1.1 mm in diameter and 17.0 or 32.5 mm in length, were infiltrated at a temperature of 1100 o C and methane pressures from 5 to 30 kPa. Layer thickness and carbon texture were determined at cross-sections of 2, 16 and 32 mm from the open end of the capillaries using polarized light microscopy. Average deposition rates, determined from layer thickness and infiltration time, as...
In this paper we report and interpret the effectiveness of different bulk metal catalyst preparations and of various components within reactive gas mixtures for carbon nanotube (CNT) synthesis. The combined catalyst precursor and supporting material is type 304 stainless steel mesh. The steel mesh keenly illustrates the net effect of different pretreatments upon the catalyst because of its resistance...
Multi-walled carbon nanotubes (MWCNTs) have been successfully synthesized with titanate-modified palygorskite as catalyst and acetylene as carbon source by chemical vapor deposition (CVD) at high temperature. Transmission electron microscopy (TEM) studies showed that there were a lot of carbon nanotubes partially filled with elongated foreign material in their inner cavities. X-ray energy dispersive...
Short multi-wall carbon nanotubes (MWNTs) with open tips were obtained by mechanical ball milling. The microstructure characteristics of MWNTs before and after ball milling were checked by transmission electron microscopy (TEM). The effect of ball milling on the hydrogen adsorption behavior of the MWNTs was studied. The hydrogen adsorption experiments were carried out at room temperature under a pressure...
The morphological changes of Fe-Ni catalyst for the preparation of carbon nanofiber (CNF) were examined at 5 steps; (1) the precipitation of Fe-Ni carbonate from Fe-Ni nitrate solution, (2) the calcination of Fe-Ni carbonate into Fe-Ni oxide, (3) the reduction of Fe-Ni oxide, (4) the second reduction of Fe-Ni metal before the growth of CNF, and (5) the reaction with CO/H 2 for the growth of...
Carbon nanocoils possessing a twisting form were prepared from an Fe-based alloy (SUS410) catalyst, the crystallographic properties of the catalyst surface, which was present on the growth tip, were examined, and a novel growth mechanism of the nanocoils is presented. Single-helix twisted carbon nanocoils with a coil diameter of 300–400nm were obtained at 700–800°C with a yield of 60% and a purity...
In a previous study we showed both the formation of genuine vapor grown carbon fibers (VGCFs) and of new and peculiar carbon nanotube-supported morphologies using a chemical vapor deposition process. Briefly, the latter are an association of beads (or fiber segments) with a more or less rough surface and more or less extended cone-based sub-morphologies with a smooth surface. The investigation of...
A system combining pulse chemical vapor deposition (CVD) reaction and cryogenic gas sorption (BET) measurement capabilities was designed to allow the sequential synthesis and online analysis of single-wall carbon nanotubes (SWNTs). Cooling treatment in liquid nitrogen (77K) during BET measurement was found to be efficient for restoring catalysts when deactivation occurs after carbon deposition. By...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.