Pyrolytic deposition rate

The pyrolytic regime is distinguished from the (diffusion-limited) dialytic regime by the effect of the input gas flow rate on the deposition rate. Both transport-controlled regimes occur at high temperatures, where the slopes of the Arrhenius plot decrease (Figure 6.12). In the case of small equilibrium constants, the slope of the Arrhenius plot in the pyrolytic regime equals the reaction heat, as will be shown below. 

The deposition rate in the pyrolytic regime is proportional to the equilibrium constant K for small values of K for large K the reaction rate does not depend on K, but only on the mass flow rate. This will be shown for the case of a simple fictitious pyrolysis equilibrium AB g) A(s) -I- B(gf). The equilibrium constant is... 

Codeposition in CVD means deposition of several solid phases simultaneously from the same precursor gas mixture. Making composite coatings by codeposition requires relatively high temperatures, i.e., working in the pyrolytic regime. The reason is that the deposition rates of the phases must be high and approximately comparable and must not depend on the substrate too much. This last condition is... 

Figure 5 Deposition rate of pyrolytic boron films as a function of B10H14 pressure. The films were...

The models incorporate two microscopic parameters, the site density and the critical nucleus size. A fit of experimental current transients to the models allows conclusions, for example, concerning the effect of additives on nucleation rate. Fabricus et al. found by analysis of current transients that thiourea increases the nucleation density of copper deposited on glassy carbon at low concentration, but decreases it at higher concentration [112], Schmidt et al. found that Gold nucleation on pyrolytic graphite is limited by the availability of nucleation sites [113], Nucleation density and rate were found to depend on applied potential as was the critical nucleus size. Depending on concentration, critical nuclei as small as one atom have been estimated from current transient measurements. Michailova et al. found a critical nucleus of 11 atoms for copper nucleation on platinum [114], These numbers are typical, and they are comparable to the thermodynamic critical radii [86],... 

Influence of Temperature, Residence Time and Heating Rate on Pyrolytic Carbon Deposition in Beech Wood Chars... 

In practice, mass yields of carbonization (low heating rate) are always higher than the theoretical mass yields. The theory of pyrolytic carbon deposition (PCD) explains this phenomenon [6]-[12]. The level of PCD can be estimated by the means of a formula which calculates the PCD as the difference between the mass yield of carbonization... 

Table 2 Determination of the pyrolytic carbon deposition as a function of the final carbonization temperature and of two residence times at final temperature (beech cubes 2 cm side - mean values for the three heating rates 2 - S 10 °C/min).

Pyrolytic BN was deposited on Nicalon NL202 silicon carbide yarns at 1000-1200°C to improve aerodynamic resistance and oxidation behavior of silicon carbide. Yarns were fed into a CVD furnace at a rate of 0.01 m/s. The pBN was made by... 

Chin et al. [16] developed the chemical composition-process relationships in CVD-SiC from H2-CH3SiCl3. The phase relationships given in Fig. 10 indicate that the two parameters of supersaturation and temperature are joined by the mass transport requirements in terms of the rate of deposition of silicon carbide. In this case, the rate is also dependent on the hydrogen concentration as it is required in the reaction to form SiC and is the carrier gas for the reactants. At low hydrogen levels, pyrolytic carbon is formed. 

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