Free carbon content

As reported by others, cyclopentadienyl ligands release CpH at low temperature, but decompose to carbon-containing species in the gas phase at high temperature, which lead to deposition of free carbon. The free carbon content could be lowered by using a reactive gas such as H2 (e.g. films with (tBuCp)2V (19) and H2). Moreover, the /-butyl substituent on the Cp ligand in 19 increased the chemical stability of the molecule in the gas... 

Free carbon content in various rocks of the facies profile of the BIF of the KMA (after Plaksenko)... 

S.3.3.9.3 S1C-B4C In the mid 1980 s pressureless sintering and posthipping were developed by Schwetz et al. [157] to produce 100% dense S1C-B4C composite materials having SiC B4C weight ratios within the range of from 90 10 to 10 90 and a free carbon content of 4-5 weight-%. 

Figure 47. Four-point bending strength vs. sintering temperature and free carbon content (after [210]).

Figure 64. Dependence of the grain size of B4C on free carbon content and sintering temperature (after [207]).

F content of the apatite Carbonate content of the apatite Free carbonate content... 

A. Tazi-Mernkta, R. Pailler and R. Naslain, Continuous SiC-based model -mono-filaments with a tow free carbon content Part I From the pyrolysis of a polycarbosilane precursor under an atmosphere of hydrogen. J. Mater. Sd.. 32.2359-2366 (1997). 

A. Tazi-Hemida, R. Pailler, R. Naslain, J. P. Pillot, M. Birot and J. Dunogues, Continuous SiC-based model monofilaments with a low free carbon content. Part 2 from the pyrolysis of a novel copolymer precursor, J. Mater. Sci., 32,2367-72(1997). 

The only measurement at low temperature was made by Kelley (1940b) using TaC containing 6.26% total carbon. Values of 10.1 +0.1 eu for S 298.i5° and 8.764cal/mole-deg for Cp (extrapolated to 298.15°) were obtained. In view of the uncertain free carbon content, this measurement should be repeated, preferably as a function of composition. 

In the case of SiOC ceramics, the parabohc oxidation rates strongly depend on the content of the segregated carbon present within their microstructure. Thus, ceramics with high free carbon content oxidize consequently faster. However, the activity of the free carbon in SiOC is hkely to be less than unity therefore, passive oxidation in the Si-O-C system is possible even for the case of carbon-rich compositions. This... 

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