In-situ nucleation

Figure 3.4. (a) In situ nucleation of CS planes at the operating temperature of 400 °C along [001] in M0O3. (b) The corresponding electron diffraction (ED) image with... 

Of relevance to this section, Reculusa et al. also recently demonstrated that the addition of a small amount (only 1.5 pmole/m ) of a monomethylether mono methylmethacrylate poly(ethylene oxide) macromonomer (structure 9, Table 4.5) allowed the direct self-assembly of nanometric polystyrene latex particles on the surface of submicronic sihca particles through an in-situ nucleation and growth process (Fig. 4.12) [102]. The two sets of particles were assembled in a raspberry-like morphology via the formation of hydrogen bonds at the interface of the inorganic and organic coUoids. The size and shape of the assembly can be easily controlled by varying the sizes and stoichiometries of the colloidal components (Fig. 4.13). 

This investigation s motivation essentially arises from a discovery of an unwanted real-time in situ nucleation and growth of Ag filaments on a-Ag2W04, Ag3P04, and Ag2Mo04 crystals which was driven by an accelerated electron beam from an electronic microscope under high vacuum [161-165]. 

Since the location and density of nucleation sites can be well controlled in the secondary growth method, the nature of the support is less important for membrane formation than in the in-situ crystallization synthesis method. Furthermore, the elimination of the in-situ nucleation... 

Budroni, M.A., Rossi, F. A novel mechanism for in situ nucleation of spirals controlled by the interplay between phase fronts and reaction diffusion waves in an oscillatory medium. J. Phys. Chem. C 119(17), 9411-9417 (2015) Carballido-Landeira, J., Trevelyan, P.M.J., Almarcha, C., De Wit, A. Mixed-mode instability of a miscible interface due to coupling between Rayleigh-Taylor and double-diffusive convective modes. Phys. Fluids 25(2), 024107 (2013)... 

Budroni, M.A., Rossi, F. A novel mechanism for in situ nucleation of spirals controlled by the interplay between phase fronts and reaction diffusion waves in an oscillatory medium. J. Phys. Chem. C 119(17), 9411-9417 (2015)... 

Top view of an MFI supported zeolite membrane prior to calcination. (Reprinted from Microporous and Mesoporous Materials 47, Algieri C, Golemme G, Kallus S, Ramsay J D F, Preparation of thin supported membranes by in situ nucleation and secondary growth, 127-134, Copyright (2001) with permission of Elsevier.)... 

X <4 >X Blooming unless nucleated in situ by another additive... 

In summary, we have shown that metal carbonyls formed in situ by adsorption of CO under ultrahigh vacuum condition can serve as a very sensitive tool for monitoring the nucleation site as well as the environment of the metal atom. It was shown that low coordinated metal atoms, in particular... 

We have reviewed experiments on two classes of systems, namely small metal particles and atoms on oxide surfaces, and Ziegler-Natta model catalysts. We have shown that metal carbonyls prepared in situ by reaction of deposited metal atoms with CO from the gas phase are suitable probes for the environment of the adsorbed metal atoms and thus for the properties of the nucleation site. In addition, examples of the distinct chemical and physical properties of low coordinated metal atoms as compared to regular metal adsorption sites were demonstrated. For the Ziegler-Natta model catalysts it was demonstrated how combination of different surface science methods can help to gain insight into a variety of microscopic properties of surface sites involved in the polymerization reaction. 

Layadi et al. have shown, using in. situ spectroscopic ellipsometry, that both surface and subsurface processes are involved in the formation of /xc-Si [502, 503]. In addition, it was shown that the crystallites nucleate in the highly porous layer below the film surface [502, 504], as a result of energy released by chemical reactions [505, 506] (chemical annealing). In this process four phases can be distinguished incubation, nucleation, growth, and steady state [507]. In the incubation phase, the void fraction increases gradually while the amorphous fraction decreases. Crystallites start to appear when the void fraction reaches a maximum... 

The silica nucleated only on the biomacromolecules. By decreasing the THEOS amount in solution from 3 to 0.03 wt.%, we observed a curtailment of the particle diameter to the macromolecular dimension. This constitutes evidence that most of the silica generated in situ was used to form a shell. 

Poly(oxyethylene)-Si02 ormosils have been prepared as an approach to the preparation of biologically active polymer-apatite composites. For this purpose, Yamamoto et al. [72] obtained these Class II hybrids from triethoxysilyl-terminated poly(oxyethylene) (PEG) and TEOS by using the in situ sol-gel process. After being subjected to the biomimetic process to form the bone-like apatite layer, it was found that a dense apatite layer could be prepared on the hybrid materials, indicating that the silanol groups provide effective sites for CHA nucleation and growth. 

A paper that demonstrates the power of the ellipsometric technique is that of Hamnett and Hillman (1988) which investigated the nucleation and growth of polythiophene on an electrode in situ. The ellipsometer employed by the... 

Cracking tendency, crystallization temperature, in situ atmosphere, active nucleation sites. 

Spectroscopic ellipsometry is a non-destructive, interface sensitive, in situ technique for interface characterization. Time resolved ellipsometric spectroscopy was used to determine the mechanism of electrochemical deposition of photoresists on copper electrodes under potentiostatic, anodic conditions. Nucleation of photoresist deposition occurs randomly. During the early stages of nucleation the semi-spherical particles are separated by about 100 A. The deposits tend to grow like "pillars" up to 50 A. Further growth of the "pillars" lead to coalescence of the photopolymer deposits. 

There have been many recent studies in support of this mechanistic approach. Stepwise reductive formation of Ag3+ and Ag4+ clusters has been followed using spectroscopic methods by Henglein [33], Reduction of copper (II) to colloidal Cu protected by cationic surfactants (NR4+) through the intermediate Cu+ prior to nucleation of the particles [36] as monitored by in situ x-ray absorption spectroscopy is another example. The seed-mediated synthesis also serves as evidence in support of this mechanism [38-41],... 

On a clean surface of an Fci7Cr alloy in a 0.5M NaCl electrolyte, corrosion is accelerated as pitting corrosion when a potential pulse of 1 s duration extending from the passive region and above the pitting potential is applied. Gugler et al. ° showed by in situ AFM that in this case the pitting corrosion was initiated close to an inclusion on the surface (Fig. 8). Such a surface defect may act as a center for pit nucleation, as was... 

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