Growth models, catalytic synthesis

Growth Mechanisms. Growth mechanisms have been investigated, andsev-eral theories have been proposed. There are two general models that are used to explain catalytic synthesis of nanowires or nanotubes. The first is called tip growth, in which... 

Figure 2.4 Three typical growth models for the catalytic synthesis of nanosilica, (a) VLS = vapor-liquid-solid ...

Diffusive and convective transport processes introduce flexibility in the design of catalyst pellets and in the control of FT synthesis selectivity. Transport restrictions lead to the observed effects of pellet size, site density, bed residence time, and hydrocarbon chain size on chain growth probability and olefin content. The restricted removal of reactive olefins also allows the introduction of other intrapellet catalytic functions that convert olefins to other valuable products by exploiting high intrapellet olefin fugacities. Our proposed model also describes the catalytic behavior of more complex Fe-... 

Iron-containing proteins are essential for photosynthetic and respiratory electron transport. Chlorophyll synthesis is also dependent on iron, and chlorophyll content is diminished under iron limitation. Requirements for iron are also influenced by the nitrogen substrate used to support growth. Both nitrate and nitrite reductases contain iron in their catalytical centres. Iron efficiency models (Raven, 1988) and culture studies (Maldonado Price, 1999) show that cells using nitrate require 60-70% more cellular iron to support a given growth rate than those assimilating ammonia. 

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