Wetting, nanoscale

In addition to the environmentally benign attributes and the easily tunable solvent properties, other important characteristics such as low interfacial tension, excellent wetting behavior, and high diffusion coefficients also make SCCO2 a superior medium for the synthesis of nanoscale materials [2]. Previous works on w/c RMs showed that conventional hydrocarbon surfactants such as AOT do not form RMs in scCOi [3] AOT is completely insoluble in CO2 due to the poor miscibility of the alkyl chains with CO2, restricting the utilization of this medium. Recently, we had demonstrated that the commonly used surfactant,... 

Several recent molecular dynamics simulations (e.g. [10] and references therein) have focussed on the wetting of interfaces (Section 6.1) and, for example, the behaviour of very small droplets at the nanoscale. Such simulations are able to relate the atomistic behaviour directly to relevant macroscopic parameters such as the contact angle and are able to show the dramatic effects at this length scale of addition of surfactant molecules or roughening of the surface. 

Many hydrogenation and polymerization reactions in the chemical industry are carried out with liquid-phase reactants. An example is the hydrogenation of aliphatic dinitriles to produce diamines (108,109), which are subsequently converted with adipic acid in solution and polymerized to produce linear polyamides, including nylon 6,6. Recently, the development of wet-environmental transmission electron microscopy (wet-ETEM) for direct nanoscale probing of... 

Zhang and Wang (1997) studied the reaction of zero-valent iron powder and palladium-coated iron particles with trichloroethylene and PCBs. In the batch scale experiments, 50 pL of 200 pg/mL PCB-1254 in methanol was mixed with 1 ml ethanol/water solution (volume ratio = 1/9) and 0.1 g of wet iron or palladium/iron powder in a 2-mL vial. The vial was placed on a rotary shaker (30 rpm) at room temperature for 17 h. Trichloroethylene was completely dechlorinated by the nanoscale palladium/iron powders within the 17-h time period. Only partial dechlorination of PCB-1254 was observed when wet iron powder was used. 

Novel wet-ETEM development for nanoscale studies of liquid-catalyst reactions at operating temperatures... 

For the detailed study of reaction-transport interactions in the porous catalytic layer, the spatially 3D model computer-reconstructed washcoat section can be employed (Koci et al., 2006, 2007a). The structure of porous catalyst support is controlled in the course of washcoat preparation on two levels (i) the level of macropores, influenced by mixing of wet supporting material particles with different sizes followed by specific thermal treatment and (ii) the level of meso-/ micropores, determined by the internal nanostructure of the used materials (e.g. alumina, zeolites) and sizes of noble metal crystallites. Information about the porous structure (pore size distribution, typical sizes of particles, etc.) on the micro- and nanoscale levels can be obtained from scanning electron microscopy (SEM), transmission electron microscopy ( ), or other high-resolution imaging techniques in combination with mercury porosimetry and BET adsorption isotherm data. This information can be used in computer reconstruction of porous catalytic medium. In the reconstructed catalyst, transport (diffusion, permeation, heat conduction) and combined reaction-transport processes can be simulated on detailed level (Kosek et al., 2005). 

The dendrimer droplets were used as a tool to examine surface heterogeneity on the nanoscale [319]. Figure 32 shows two pairs of SFM images of the droplets deposited on mica (a,b) and a copolymer film (c,d), respectively. On mica, the hydroxyl terminated dendrimer showed the autophobic or pseudo-partial wetting behaviour as the droplets sit on a thin film of the same material [312,320]. 

Metallic nanorods are highly interesting materials from many points of view as elements in future nanoscale electronic circuits as sensors as catalysts as optical elements in future nanoscale optical devices. Gold and silver nanorods have distinct visible absorption and scattering spectra that are tunable with aspect ratio. Many workers have developed wet synthetic routes to these nanomaterials, with control of aspect ratio a key improvement compared to the synthesis of simple nanospheres. Another key area for which improvements need to be made is the understanding of the atomic arrangements of the different faces of crystalline... 

The sol-gel process is a wet-chemical technique (Chemical Solution Deposition) for the fabrication of metal oxide starting either from a chemical solution (sol short for solution) or colloidal particles (sol for nanoscale particle) to produce an integrated network (gel). Typical precursors are metal alkoxides and metal chlorides, which undergo hydrolysis and polycondensation reactions to form a colloid [a system composed of solid particles (size... 

Finnie, K. R. Nuzzo, R. G., The phase behavior of multicomponent self-assembled monolayers directs the nanoscale texturing of Si(100) by wet etching, Langmuir 2001, 17, 1250-1254... 

Ceramic coatings on fibers and powders have a variety of uses. For example, porous ceramic coatings on nanoscale metallic or ceramic particles can improve the catalytic properties of a powder. Also, the carbon fibers used as reinforcement in metallic matrices can be coated with a thin ceramic film (such as SiC or TiN) to reduce the rate of interdiffusion that may occur between the matrix materials and the fibers, and enhance the wetting of the fiber surface by metals. ... 

Use wet-chemical synthesis methods to prepare aqueous suspensions of nanoscale ceria-based oxides and to incorporate platinum onto ceria nano-particle surfaces. 

Porous silicon (PS) is one of the nanoscale modifications of silicon. There are various approaches to PS producing that are now in use. The technique most generally employed today is known as wet anodization of a crystalline silicon. With this technique, yield parameters of porous material (porosity, pore size and shape, interpore distance) may be readily varied by anodization regimes. However, it is well known the problem of the PS stability influencing the physical properties of the PS layers. P S instability is c onditioned b y very large specific surface area of the porous material. 

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