Carbon supersaturation

To determine the diamond equilibrium solubility in the metal melts in a range of its thermodynamic stability we also used a special method which was originally developed early. Based on the data obtained we estimated carbon supersaturations in the melts [4,5]. 

For these alloys we determined the equilibrium carbon solubility and calculated carbon supersaturation with respect to diamond. We also grew diamond using the alloys and established the average yield of the diamond transformation. The data are listed in Table 1. 

So, our investigations allow us to establish the correlation between physico-chemical properties of the crystallization media (capillary properties of the diamond-metal melt interface, carbon supersaturation in the melt with respect to diamond) and adsorption-structure and energy proreties of the produced diamond powders. Our findings permit us to extend scientific and technological potentialities for production of diamond grinding and micron powders having unique properties. 

At the silicon melting point, this should result in carbon concentration of 9.1 x 1018cm-3. As carbon solubility in solid silicon is 3.5 x 1017cm 3 at the melting point of Si, the high carbon solubility in the liquid silicon should result in carbon supersaturated solidified silicon or the formation of SiC, either residually in the melt or incorporated in the silicon crystal. 

Enhanced calcification, i. e. fast biomineraUza-tion rates, in foraminifer tests could be a direct consequence of higher carbonate supersaturation (Lohmann 1995 Barker Elderfield 2002 Bijma et al. 2002). Since CO2 is less soluble in warmer waters, calcium carbonate supersaturation increases from the poles to the tropics (Buddemeier Eautin... 

As mentioned above, after fast cooling from > 1000 °C, the austenitic stainless steels are free of carbide precipitates. But since steels with > 0.05 wt% C are already carbon-supersaturated at temperatures below 900 °C, holding the material at temperatures between about 400 and 900 °C will lead to preciptation of chromium carbides (mainly M23C6 type), preferentially at the grain boundaries. This will result in an increased susceptibility to intergranular corrosion due to local chromium depletion. The means to avoid this undesir-... 

J. Qu, P. J Blau and Jolly, B. C. Tribological properties of stainless steel treated by colossal carbon supersaturation, Wear (2007) 263,1-6, 719-726... 

Cao Y, Ernst, E, and Michal, G. M. 2003. Colossal carbon supersaturation in austenitic stainless steels carburized at low temperature. Acta Materialia 51 4171-4181. 

In this example, water is said to be saturated with calcium carbonate when it will neither dissolve nor precipitate calcium carbonate scale. This equilibrium condition is based upon an imdisturbed water at constant temperature which is allowed to remain imdisturbed for an infinite period of time. Water is said to be undersaturated if it can still dissolve calcium carbonate. Supersaturated water wiU precipitate calcium carbonate if allowed to rest. If water is undersaturated with respect to calcium carbonate, the SL value will be less than 1.0. When water is at equilibrium, SL will be 1.0 by definition. Water which is supersaturated with calcium carbonate will have a saturation level greater than 1.0. As the saturation level increases beyond 1.0, the driving force for calcium carbonate crystal formation or crystal growth increases. 

Calcium carbonate, supersaturation due to pressure decrease, heat agitation. 

The discussion in this chapter has unveiled several important characteristics of metal dusting. First of all, it occurs in carbon supersaturated environments and in a temperature range of 450-850°C. Secondly, the corrosion rate, in the case of most alloys, undergoes a maximum around 650°C, thus separating the corrosion process into a lower temperature regime where the rate increases... 

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