Wet deposition technique

Sample sheets of 100 x 50 x 4 millimeter were prepared with the wet deposition technique. Two rectangular TMA samples and one circular TMA sample were machined from these sheets. The rectangular samples, 10 x 7 x 4 mm, were taken in the length (X) direction and in the width (Y) direction of the sample sheet. The circular sample, diameter 5 mm, was used to measure the l.e.c. in the Z direction. The samples, placed in a TMA 7, were measured from -20°C to 120°C with a heating rate of 2°C/minute. Subsequently, the sample was cooled with the same rate and heated again for the real measuring scan. The first heating scan was ment to remove the frozen-in stresses which influence the thermal expansion behaviour (see 3.1.2). 

Aegerter, MA Puetz, J Gasparro, G., and Al-Dahoudi, N. (2004) Versatile wet deposition techniques for functional oxide coatings. Opt. Mater., 26, 155-162. 

Thus, although the analysis of scales and deposits typically is carried out by a combination of wet chemistry techniques and atomic absorption spectroscopy, an identification of the specific nature of the crys-... 

Once the structural support layers have been fabricated by extrusion or EPD for tubular cells or by tape casting or powder pressing for planar cells, the subsequent cell layers must be deposited to complete the cell. A wide variety of fabrication methods have been utilized for this purpose, with the choice of method or methods depending on the cell geometry (tubular or planar, and overall size) materials to be deposited and support layer material, both in terms of compatibility of the process with the layer to be deposited and with the previously deposited layers, and desired microstructure of the layer being deposited. In general, the methods can be classified into two very broad categories wet-ceramic techniques and direct-deposition techniques. 

Both wet-ceramic techniques and direct-deposition techniques require preparation of the feedstock, which can consist of dry powders, suspensions of powders in liquid, or solution precursors for the desired phases, such as nitrates of the cations from which the oxides are formed. Section 6.1.3 presented some processing methods utilized to prepare the powder precursors for use in SOFC fabrication. The component fabrication methods are presented here. An overview of the major wet-ceramic and direct-deposition techniques utilized to deposit the thinner fuel cell components onto the thicker structural support layer are presented below. 

Another important consideration involves the hybridization of porous carbon with hierarchical 3D architectures, such as fibers or arrays. Wet chemical techniques are often useless as the mandatory solvent removal/drying typically results in the at least partial collapse of the nanocarbon pore structure. Gas phase deposition is a... 

Using techniques developed for the sampling and analyses of trace metals in marine precipitation by Tramantano, Scudlark, and Church (Environ. Sci. Technol.. in press), Church et al. (11) and Jickells et al. (12) have also reported on concentration measurements of the trace metals Cd, Cu, Fe, Mn, Ni, Pb, V, and Zn in wet deposition at Lewes, Delaware, and on Bermuda. The purpose of this facet of the WATOX research was to assess the sources of, the transport to, and the wet deposition of trace metals to the western Atlantic Ocean during nonsummer months. At this time of the year, trace metals are likely to be transported by a westerly air-mass flow from North America to the open Atlantic. Church and his colleagues report that the concentrations and wet deposition of trace... 

There is no simple device which enables the measurement of dry deposition in a manner as convenient as for wet deposition. Instead, comparatively less direct methods must be used, none of which is fully proven as yet. For particle exchange, leaf-washing and through-fall techniques (1) can provide measurements of the accumulated deposit on natural surfaces. Likewise, accumulation on snow surfaces can be sampled, and subjected to subsequent chemical analysis. It is evident, however, that such methods only apply in certain circumstances. Budget techniques are sometimes advocated, such as in the case of calibrated watersheds, but these have rarely delivered unequivocal results. The difficulty that arises is that the dry deposition must necessarily be computed as the difference between poorly determined in-flow and out-flow measurements. These, and. a wide variety of other experimental methods, have been reviewed elsewhere (2). 

Field studies of wet deposition processes require the differentiation and determination of many trace reactive species in the several phases (gaseous, aerosol, cloud water and precipitation) present in the atmosphere. The requirements imposed on existing analytical techniques by these studies have been extremely rigorous and, in several cases, have necessitated the development of new approaches to the sampling and determination of critical chemical species. 

The sol-gel process is a wet-chemical technique (chemical solution deposition) widely used recently in the fields of materials science and ceramic engineering. Such methods are used primarily for the fabrication of materials (typically a metal oxide) starting from a chemical solution which acts as the precursor for an integrated network (or gel) of either discrete particles or network polymers. Typical precursors are metal alkoxides and metal chlorides, which undergo various forms of hydrolysis and polycondensation reactions. 

Gels are frequently used for ceramic film formation. Many aspects of the processing of films are common to all the deposition techniques. Schroeder [48] has outlined the conditions necessary for thin film formation. The solution must wet the substrate, it must remain stable with aging, it should have some tendency toward crystallization into a stable high-temperature phase, and for miiltiple layers the previous layers must be either insoluble or heat treated to make them insoluble before subsequent depositions. 

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