Filamentary growth

The carbon deposits from these reactions were examined with an electron microscope, and they appeared to grow in the form of threadlike filaments. In several other cases of filamentary growth, it was found that the deposit contained appreciable amounts of the catalyst material. For example, in the formation of cuprene by the reaction of acetylene on copper oxide, copper was found in the cuprene at appreciable distances from the oxide surface (34). Similarly, in the deposition of soot on firebrick, iron has been found in the carbon. These facts suggest that the formation of a filamentary deposit may require the superposition of a small amount of the catalyst material on some of the reaction product. This material could then be carried away from the surface as the filament grew. The superposition of catalyst on the reaction product could be accomplished by the rearrangement process. 

Figure 20. Pre-filamentary growth of development centers t is development time and n is the number of silver atoms in the developing center. Note the sharp change in activity when n is about 12 atoms [87],...

Pontius and Willis [107] formulated a rate equation (Eq. (77)) for the early stages of chemical development of a single grain, which describes the growth of the latent image during the induction period and the subsequent filamentary growth ... 

Figure 7. SEM photograph of carbon deposited on an iron foil showing filamentary growth. Magnification is 9,350x ...

Particulate and Filamentary Growth. It is implicit in the mechanism proposed above for carbon mound growth, that the crystalline particulates are nucleated at active sites within the metal. The evidence that further growth causes the particles to be ejected through laminar carbon overlayer is given in Figure 13c. 

Murthy, H. N. S. Sadashiva, B. K. Observation of filamentary growth patterns at the isotropic-SmCPA phase transition in new unsymmetrical compounds composed of bent-core molecules. Liq. Cryst. 2004, 31, 361-370. 

The Bj textures show characteristic helical filamentary growth in cooling from isotropic melt. i- 2 However they denote at least two distinct phases. X-ray measurements clarified that the original By materials, which form freestanding strands, - just like columnar liquid crystals of disc-shape molecules (see Chapter 2), indeed have a columnar phase (hereafter we will label them as Bj j). Other By-type materials (we call them Byu) were foimd to have modulated layer structures. We note that the By and B2 type banana-smectics also form strands of fibers. ... 

The high temperature phase that appears directly below the isotropic phase showing characteristic helical filamentary growth in cooling [25] is denoted as B7. Later measurements showed that similar helical structures may appear in materials with different structures, and they correspond to at least two distinct phases. The exact structures of these phases are still under active debate, which we will detail later. 

A third type of problem, that is often mistakenly confused with dendrite formation, is due to the presence of a reaction-product layer upon the growth interface if the electrode and electrolyte are not stable in the presence of each other. This leads to filamentary or hairy growth, and the deposit often appears to have a spongy character. During a subsequent discharge step the filaments often become disconnected from the underlying metal, so that they cannot participate in the electrochemical reaction, and the rechargeable capacity of the electrode is reduced. 

Metallic rhenium, 21 687 Metallic silver growth of, 19 352 in images, 19 366-369 morphology of, 19 359 optical density of, 19 369 rate of formation of, 19 207 Metallic silver clusters, filamentary, 19 367-368... 

Figure 27. Dependence of specific rate constant for pre-filamentary center growth upon bromide ion concentration, showing conformity with the Butler-Volmer law of electrode kinetics. Developing agent, 10 m ascorbic acid [107].

Carbon fibers formed into filaments provide very compatible biomaterials. Carbon does not corrode in the body, nor does it generate a foreign body respon.se. Further, its high electrical conductivity suggests that a variety of electrode and conductor applications are possible. For example, filamentary carbon cathodes have been used to stimulate the growth of bone and soft tissues [136], when adjusting the level of current can be used to influence the growth. 

The deposits formed on transition metals from hydrocarbons or carbon monoxide exhibit a variety of morphologies including graphitic laminar films, mound (monticular) growths, columnar, particulate, and numerous filamentary types of carbon, (1-4). The... 

The results of this in-situ SEM work suggest that solution-precipitation processes have some part in the development of four of the morphological types discussed, i.e. continuous laminar carbon films, mound growths, and two types of particulate material Although a small amount of filamentary carbon was observed, it does not appear to be a major characteristic of the Fe-CH4 reaction. 

J. T. A. Pollock, Filamentary sapphire - The growth of void-free sapphire filament at rates up to 3.0 cm/min, Journal of Materials Science, 7,786-792 (1972). 

Fig. 16. Chemical reactions involved in the film growth process in filamentary discharge in Ar/C2H2 mixture. Thick arrow indicates high probable reaction.

Edison s light bulb filament is the first knovm example of filamentary carbon, made in 1879. Except for early observations of filamentary carbon growth by CVO, it took another 65 years before significant further developments in carbon fiber technology occurred. 

They have revealed that tree-like structures of low density can extend about 0.5 mm out from the cathode as little as 50 ns after the application of a breakdown field. Several trees can appear simultaneously from the cathode surface and breakdown will ensue from one of them. An alternative sequence leading to breakdown which appears to be initiated by an outward growth of low density regions from the anode which is extremely fast has also been observed. The cathode and anode initiated structures are different in appearance, with the latter being much more filamentary and diffuse. 

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