Epitaxial match

Biosilica extracts from Equisetum arvense have been found to accelerate the rate of formation of small oligomers of silicic acid, and more silica was produced that exhibited a narrower distribution of particle sizes than for silica formed in the absence of the biomolecule extracts (Figure 37.3), with the particle size distribution closely mirroring that found for the biogenic silica from which the biosilica extract was taken. Layered, crystalline materials were also produced that could have arisen from the epitaxial matching of initially formed oligomers on a p-sheet type material, the silica structure continuing to develop from the initial biopolymer-controlled nucleation event. 

Because of epitaxy matching, carbon nanotubes are good nucleating agent for linear polyethylene. The presence of single-walled carbon nanotube, SWCNT, accelerates the crystallization kinetics of polyethylene not only in the qiriescent conditions but also at the relatively low shear rates. For the low shear (<50/s), the shish-kebab structure that is formed due to the chain orientation is enhanced by the presence of SWCNTs. ... 

The orientation of crystals of low peptides and amino acids when grown on quartz surfaces indicates the epitaxial matching which may have played a role, in prebiotic evolution (284). 

Figure 9.6. Epitaxial matching at the graphite/Ni interfaces on different faces of Ni where carbon precipitates (Yang and Chen, 1989).

Growth of semiconductor nanocrystals under arachidic acid (AA) mono-layers by epitaxial matching of the crystals faces and the headgroups of the... 

Numerous studies have indicated that CNTs can nucleate PSCs, and it was suggested that both isothermal and nonisothermal crystallization behavior can be used as a bellwether of CNT/polymer soft epitaxial matching for templated crystallinity. With the addition of CNT fillers into polymer matrices, some new properties (electrical conductivity, flame resistance) can be imparted, while others (mechanical strength, thermal conductivity) can be enhanced. Again, these properties are dependent on the interplay between CNT and polymer matrix, as well as the organization of the two. 

Preservation of a high density of interactions is ideally achieved when the substrate and deposit have identical periodicities. It is therefore of interest to search for substrates that match known periodicities of the polymer, in a one-dimensional or, better, a two-dimensional relationship. Epitaxy may also exist when the corresponding distances are multiple, for example, one substrate periodicity for two deposit periodicities. Larger multiples (1 for 3, or 2 for 3) appear very unlikely, and have been observed only occasionally in polymer epitaxy. Matching of polymer periodicities with that of the substrate may be rather complex. The simplest case is of course to match an interchain periodicity, as is the case for PE, considered in the next paragraphs. However, in polymers with a helical conformation, the heUx axis is not materialized by a string of atoms. The outer part of the helix interacts more closely with the substrate. In other words, the helical path may be involved in the epitaxy, or more exactly the distance between two successive helical paths, that is between parts of the helix located on its outer part. The orientation of the helix path relative to the helix axis differs for right-handed and left-handed helices (cf Fig. 8.9). Therefore, epitaxial deposition of polymers with helical conformation... 

---