Oriented nucleation

In Refs. [292, 293], the BEN treatment followed by the (100) growth was undertaken to identify the most influential parameter for oriented nucleation in the two-step process. The Si(lOO) substrate was placed on a graphite holder. The film characterization was done using the (220) pole density maxima in the (220)XPF diagram, and the FWHM was selected as an orientational parameter. 

The core of the nucleation model proposed in Refs. [362, 363] is an assumption based on the experimental data that epitaxially oriented nucleation sites are formed in the SiC layer of about 10-nm thickness during the bias treatment. These sites are exposed at the SiC surface, while plasma etching of SiC is occurring during both the BEN treatment and the successive diamond growth process. The model of nucleation process is schematically depicted in Figure 11.57 ... 

Polymer blends and alloys have more complex behavior in the presence of fillers than the binary mixtures of polymer and filler. The same factors, such as filler distribution, filler-matrix interaction, filler-matrix adhesion, particle orientation, nucleation, chemical reactivity, etc. have influence on properties, but this influence is complicated by the fact that there are two or more polymers present which compete for the same filler particles. These complex interactions result in many interesting phenomena discussed below. 

Abstract. Kinetic theory of crystal nucleation is proposed for flexible chain polymers subjected to flow deformation with transient molecular deformation and orientation. Significant transient effects in the kinetics of oriented nucleation are expected in melt processing involving high deformation rates, like in high-speed melt spinning. 

Transient effects in the kinetics of oriented nucleation are considered for melt processing in a wide range of deformation rates using a theory of non-linear chain statistics with transient effects. Inverse Langevin elastic free energy of a polymer chain in a Pade approximation, averaged with transient distribution of the chain end-to-end vectors, as well as Peterlin s approximation for the modulus of nonlinear elasticity are used. The effects of transient orientation distribution of the chain segments is also considered. 

Rotational convection and angular Brownian motion of clusters, as well as ather-mal nucleation resulting from transient free energy of the system are considered. One concludes that the cluster growth mechanism dominates the other mechanisms of oriented nucleation in the systems with transient chain deformation and orientation. Example computations illustrating transient effects in oriented nucleation are presented for the case of uniaxial elongational flow. 

Vf-40-50% densities, shapes, and orientation) Nucleation efficiency -1 Demonstration nucleation inside dispersed nodules ... 

Figure 7.4 shows stepwise mechanism which includes absorption, orientation, nucleation and crystal growth. Absorption can be caused by physical or chemical forces. The most likely, hydrogen bond formation. Feasibility of absorption depends on some of the... 

In addition, crystal growth in the presence of an additive (Mg ions) can be coupled with control over the oriented nucleation achieved by using SAMs as nucleation templates [202]. 

Fig. 21 a Schematic illustration of the new approach for the formation of microperfo-rated single crystals deposition of the ACC mesh from the CaCOs solution, oriented nucleation at the imprinted nucleation site, and the amorphous-to-crystalline transition of the ACC film on the engineered 3D templates. (Reproduced from [247], 2003, American Association for the Advancement of Science)... 

Many biological mineralization processes involve oriented nucleation strictly controlled by organized organic interfaces that interact with the nascent crystals by virtue of structural and stereochemical recognition processes [57,91,92,117],... 

Duvauchelle N., Kesteman E., Oudet F. and Bordes E. (1998). Mosaic Crystals of Vanadyl Pyrophosphate Obtained by Oriented Nucleation and Growth, J. Solid State Chem., 137, pp. 311-324. 

As this process occurs in supersaturated solution, the problem consists of suppressing the kinetics of random homogeneous nucleation in the extrapallial fluid wMle enhancing the kinetics of oriented nucleation on the organic protein surface. 

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