Vapour-liquid-solid

J. Westwater, D. P. Gosain, and S. Usui, Si nanowires grown via ttie vapour—liquid—solid reaction, Phys. Status Solidi A—Appl. Res. 165, 37-42 (1998). 

There is a distinct region of small aggregates or clusters which falls between the atomic (or molecular) domain and that of condensed matter. These small particles and clusters possess unique properties and have several technological applications. The formation of these particles involves a vapour-solid, a liquid-solid, a solid-solid or a vapour-liquid-solid type of phase change governed by nucleation and it is important that the size of the growing nucleus is controlled (Multani, 1981 Hadjipanyas Siegel, 1994). 

The prediction of the thermal conductivity is not as simple for the composite reinforced with SiC whiskers. In fact, as mentioned earlier, the thermal conductivity of the reinforcement phase plays an important role. However, for SiC whiskers, their chemical composition can vary drastically depending on the manufacturing process, which is not the case for Si3N4 whiskers. In fact, the influence of the manufacturing process is drastic the thermal conductivity of SiC(w) produced by the vapour-solid process is around 20 W/m K as opposed to 100-250 W/m K for whiskers produced by the vapour-liquid-solid process. Using a Si3N4 matrix with a nominal thermal conductivity of... 

Chemical transformation of the vapour-liquid-solid (VLS) phases for growing whiskers (reproduced by permission of Chapman Hall)56. 

Vapour —> liquid —> solid Oxides, carbides via high intensity arc metallic powders via ... 

Si nanowires have been grown in templates using a direct vapour-liquid-solid route [56]. The wires were grown in a 60 pm thick and 200 nm pore diameter alumina membrane. A thin layer (< 1 pm) of Au is electrodeposited to form the catalyst. The growth was carried out using a 5% mixture of SiH4 in H2 in an isothermal low pressure reactor at 500 °G. The nanowire has a defect-free core of Si with a 2-3 nm oxide layer and is capped with Au at both ends. It has a growth direction of [100]. 

A whisker is fabricated according to the vapour-solid or vapour-liquid-solid mechanisms with the aid of certain special catalysts [17], It involves nucleation at preferred locations such as the terrace, ledge and kink on a substrate surface, and defects in crystal structures developed along a special direction of impingement of nuclei. Two-dimensional and three-dimensional microstructures have also been... 

The complex product composition (hundreds of compounds, gases, vapours, liquids, solids, an aqueous phase in addition to the organic phase, and compositional changes during formation of the Fischer-Tropsch regime) has been all the time a difficulty in Fischer Tropsch experimentation. But the order of this multiplicity embodies information about the elemental reactions and the nature of the active sites. It seems there is much to learn about catalysis from Fischer-Tropsch synthesis. 

Apart from the gases mentioned in Table 5, the atmosphere contains water in different forms (vapour, liquid, solid) as well as numerous other chemical compounds, which will be called by the general name atmospheric pollutants. 

Sundmacher K, Scott K (1999) Direct methanol polymer electrolyte fuel cell analysis of charge and mass transfer in the vapour-liquid-solid system. Chem Eng Sci 54 2927-2936... 

In the vapour-liquid-solid process, as described in Figures 4.38a and b, a liquid alloy droplet composed of metal cntalyst component (An, Fe, etc.) and nanowire component (Si, M-V component, E-VI compound, oxide, etc.) is first formed under... 

T. Bellamonte, L. Bonnetain and J. L. Ginoux, Synthesis of silicon carbide whiskers using the vapour-liquid-solid mechanism in a silicon rich droplet. Journal of Materials Science, 31 [9], 2367-2371 (1997). 

There has been eonsiderable interest in the synthesis, characterization and properties of nanowires of various inorganic materials [2, 99, 100]. Nanowires have been prepared using vapour phase methods such as vapour-liquid-solid (VLS) growth, vapour-solid... 

Perea, D.E., Hemesath, E.R., Schwalbach, E.I, Lensch-Falk, J.L., Voorhees, P.W., Lauhon, L.J. (2009) Direct measurement of dopant distribution in an individual vapour-liquid-solid nanowire. Nature Nanotechnology, 4, 315-319. 

Figure 5 Demonstration of the activity of printed particles. In printed arrays, 60-nm Au particles retain both their catalytic and optical activities, a. Silicon nanowires grown through a vapour-liquid-solid process from a printed array of Au particles (inset is tilted), b, AFM topography and the corresponding dark-field image of particles on the printing plate (top row) and an SEM image and the corresponding dark-field micrograph on a silicon substrate (bottom row the images were mirrored for convenience).

It is crucial that printed nanoparticles retain their useful properties during integration. Here, a surface-sensitive application was chosen to demonstmte that the individual gold nanocrystals are still catalytically active. Figure 5a shows silicon nanowires (SiNW) that were grown from an array of 60-nm particles using a vapour— liquid-solid (VLS) process. The particles were printed onto a... 

Gas-phase methods-. Nanorods and wires have been produced by vapour-liquid-solid deposition. The substrate is first coated with a thin layer of a catalyst such as gold. A ZnO/graphite mix is placed close to the substrates in a furnace tube and heated at about 900 °C under an argon flow. Zn and CO vapour are formed, and the Zn forms an alloy with the Au particles. ZnO starts to grow when the alloy becomes saturated with Zn. Epitaxial growth of oriented nanowires on sihcon substrates has been reported.f ... 

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