Condensed phases growth

Geohegan, D.B., Schittenhelm, H., Fan, X., Pennycook, S.J., Puretzky. A.A., Guillorn, M.A., Blom, D.A., and Joy, D.C., 2001. Condensed phase growth of single-wall carbon nanotubes from laser annealed particulates, Appl. Phys. Lett., 78, pp. 3307-3309. 

Chemical vapor deposition processes are complex. Chemical thermodynamics, mass transfer, reaction kinetics and crystal growth all play important roles. Equilibrium thermodynamic analysis is the first step in understanding any CVD process. Thermodynamic calculations are useful in predicting limiting deposition rates and condensed phases in the systems which can deposit under the limiting equilibrium state. These calculations are made for CVD of titanium - - and tantalum diborides, but in dynamic CVD systems equilibrium is rarely achieved and kinetic factors often govern the deposition rate behavior. 

It has been shown by FM that the phase state of the lipid exerted a marked influence on S-layer protein crystallization [138]. When the l,2-dimyristoyl-OT-glycero-3-phospho-ethanolamine (DMPE) surface monolayer was in the phase-separated state between hquid-expanded and ordered, liquid-condensed phase, the S-layer protein of B. coagulans E38/vl was preferentially adsorbed at the boundary line between the two coexisting phases. The adsorption was dominated by hydrophobic and van der Waals interactions. The two-dimensional crystallization proceeded predominately underneath the liquid-condensed phase. Crystal growth was much slower under the liquid-expanded monolayer, and the entire interface was overgrown only after prolonged protein incubation. 

Finally, electrodeposition in general is orthogonal to MBE and CVD, as it involves growth in a condensed phase with potential control instead of thermal. This increases the variable space for producing materials the diversity of conditions under which compounds can be formed. 

Ligand affinity series of more bare metal ions and one-coordinate ions are needed to understand the effect of the electronic structure of the ion on ligand strength. The study of catalytic cycles in the gas phase (especially where they relate to condensed phase catalysis) appears to be a growth area for the future. 

Hering and Friedlander (1982) made similar observations for particle sulfate and attributed the smallest mode (referred to as the condensation mode) to formation from gas-phase S02 oxidation and the larger modes (the droplet mode) to oxidation in the condensed phase. Meng and Seinfeld (1994) have shown that the droplet mode particles cannot arise from growth of the smaller, condensation mode particles and propose that the condensation mode particles are activated to form fog or cloud droplets, followed by chemical reactions and subsequent evaporation to form the droplet particles. 

The Initiation and Growth of Explosion in Condensed Phase , Ibid, pp 499 516 31) C.L. Mader, "Shock and Hot Spot In-... 

As can be seen from the expression for the driving force in terms of the chemical potential differences, which are related to the differences in temperature and concentration, the two transporting processes, heat transfer and mass transfer, are coupled in crystal growth. The degree of contribution from the respective transport process is determined by the degree of condensation of the environmental (ambient) phase. To grow crystals in a diluted ambient phase, a condensation process is required, and so mass transfer plays an essential role. The contribution of heat generated by crystallization in this case is small compared with that of the mass transfer. However, for crystallization in a condensed phase, such as a melt phase, heat transfer plays the essential role, and the contribution from the mass transfer will be very small, because the difference in concentration (density) between the solid and liquid phases is very small, smaller, say, than 1 or 2%. It is therefore necessary to classify the types of ambient phases and to be familiar with their respective characteristics from this standpoint. 

In the condensed phase, mass transfer is not significantly involved, and crystal growth occurs by the rearrangement of the atoms at the solid-liquid interface through the removal of heat. Heat transfer is the driving force required for atomic... 

Somorjai (S8) discusses the surface energy effect in the early growth of a condensed phase, and Skinner and Bankoff (S6) discuss the error in assuming a zero initial radius in bubble growth. 

This model allows one to determine the steady-state concentrations of gas and surface substances, the composition of the condensed phase, and the steady-state film growth rate. 

The droplet current / calculated by nucleation models represents a limit of initial new phase production. The initiation of condensed phase takes place rapidly once a critical supersaturation is achieved in a vapor. The phase change occurs in seconds or less, normally limited only by vapor diffusion to the surface. In many circumstances, we are concerned with the evolution of the particle size distribution well after the formation of new particles or the addition of new condensate to nuclei. When the growth or evaporation of particles is limited by vapor diffusion or molecular transport, the growth law is expressed in terms of vapor flux equation, given by Maxwell s theory, or... 

---