Carbon growth apparatus

The use of conductance as a measure of the solution composition is limited unless some other control of the composition is possible. Figure 6 illustrates a schematic of the apparatus used to follow the crystal growth of calcite from calcium bicarbonate solutions under constant composition conditions. In this case, the carbon dioxide concentration is kept constant by the flow of a water-saturated mixture of carbon dioxide and nitrogen gas. The conductance is monitored using an a.c. bridge with the analog signal... 

This procedure involves the pyrolysis of gas molecules with high content in carbon at elevated temperatures in the presence of catalyst [10, 25]. There are two basic protocols, in one of them, called supported growth process (the most used), the catalyst is prepared and deposited on a support medium, which is inserted into a flow apparatus (a tube at atmospheric pressure in a temperature controlled furnace) and exposed to elevated temperatures, usually 500-1100 °C for a given time. In the other protocol, called floating-catalyst growth, the catalyst and the... 

Fig. 11. Direct light image of a Mercenaria mercenaria bivalve sheU, showing that the carbonate is precipitated in layers each dark/hght band represents one year of growth. These layers can be sampled at sub-annual resolution using laser ablation techniques, or high precision microdrih apparatus. Image courtesy of Mary Elliot (University of Edinburgh).

Standard CVD reactors employing the aforementioned precursors have been employed for the formation of Nb Sn films, whiskers/single-crystals, and powders. In addition, two novel reactor designs have been employed for the fabrication of continuous tapes and small diameter particles. Figure 2-12 shows apparatus for the continuous CVD growth of Nb.iSn films on metallic ribbons and wires developed by researchers at RCA [40]. The system consists of niobium and tin chlorinators, a precursor delivery system for the introduction of the metal chlorides plus reactive HCI and H2 gases, and a deposition chamber. The ends of the reaction chamber are fitted with carbon elec-... 

Reports on man-made diamond obtained by HPHT synthesis were first published in 1955 by General Electric [4]. Usually, metals able to dissolve carbon under HPHT conditions are used as catalysts and increase growth rates. Diamond crystals of several millimeters in size can be obtained in this way, but usually small grains for abrasives are produced. Direct conversion of graphite to diamond without catalyst in HPHT apparatus is possible, but uneconomical for industrial application. Direct transformation can be done by the detonation method and produces nanosized powders of diamond and diamond-like carbon [5]. 

Figure 8.2 An apparatus for growing VGCF at atmospheric pressure. Source Reprinted from Tibbetts GG, Rodda EJ, High temperature limit for the growth of carbon filaments on catalytic iron particles, Mater Res Soc Symp Proc, 111, 49, 1988.

MacKenzie, K.J., Dunens, O.M., and Harris, A.T. (2013) Insights into carbon nanotube growth using an automated gravimetric apparatus. Carbon, 59,... 

Earlier, Olson and co-workers [26] obtained Raman spectra of diamond on a scratched silicon crystal after different times of exposure to sputtered carbon and to atomic hydrogen in a CVD apparatus. Only the first monolayer of carbon deposited with each exposure was utilized, indicating that diamond growth was a surface reaction. Increasing carbon exposure increased the layer thickness but decreased the quality of the deposited film as increasingly strong broad peaks appeared at 1140, 1350, and 1450 cm . 

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