Atomic interfacial mixing

Plasma polymers are generally characterized by an extremely tight and three-dimensional network. In Figure 27 a typical stmcture of an organosilicon plasma polymer network is shown [47], It has been shown that the water permeability of a thin plasma polymer (thickness around 20 nm) can be two or three orders of magnitudes lower than that of polyethylene [91]. Moreover, Yasuda et al. showed that under special conditions of plasma polymerization even atomic interfacial mixing (AIM) occurs providing a water-resistant interfece [46]. 

H.K. Yasuda, A.K. Sharma, E.B. Hale, W.J. James, Atomic interfacial mixing to create water insensitive adhesion, J. Adhesion, 13 (1982) 269. 

Wang Y, Chen X, Hamers RJ (1994) Atomic-resolution study of overlayer formation and interfacial mixing in the interaction of phosphorus with Si(001), Phys. Rev. B 50 4534 1547... 

Because the highest possible interfacial area is desired for the heterogeneous reaction mixture, advances have also been made in the techniques used for mixing the two reaction phases. Several jet impingement reactors have been developed that are especially suited for nitration reactions (14). The process boosts reaction rates and yields. It also reduces the formation of by-products such as mono-, di-, and trinitrophenol by 50%. First Chemical (Pascagoula, Mississippi) uses this process at its plant. Another technique is to atomize the reactant layers by pressure injection through an orifice nozzle into a reaction chamber (15). The technique uses pressures of typically 0.21—0.93 MPa (30—135 psi) and consistendy produces droplets less than 1 p.m in size. The process is economical to build and operate, is safe, and leads to a substantially pure product. 

Both hydrocolloids and emulsifiers increase the water-binding capacity in the mix (increased % of hydrogen atoms with low T2 and decreased T2 values). A synergistic effect is observed when both ingredients are present. From studies described earlier in this chapter, the effect of hydrocolloids is assumed to be due to simple water binding and increased thickness of protein layers around the fat globules, whereas the effect of emulsifiers may be due to the increased hydration of interfacially bound protein as well as increased hydration of polar groups of emulsifier at the oil-water interface. 

Unstable Systems Froths and Hollow Cone Atomizing Nozzles We usually think of interfacial contact as a steady-state system of raining droplets or rising bubbles, but some of the most efficient interfacial contactors take advantage of unstable interfacial geometry. The most common is the distillation tray which operates with a wild mix of bubbles, jets, films, and droplets. The mix is often described as froth. Gas pressure drop provides the energy to create the froth. 

Supercritical conditions above P > Fm) or below P < P ) the mixture critical curve lead to different crystallization and aggregation mechanisms (7,20). In the first case there is no interfacial tension, and mass transfer is determined by the flow-molecular diffusion interactions during mixing, defined here as jet mixing. In the second case, there is interfacial tension between the phases, and the mixing mechanism is based on atomization to small droplets while energy and species are being transferred between the... 

---