Spin coating impregnation

Figure 4.30. AFM images of rhodium particles deposited by spin-coating impregnation on flat Si02 on a Si(lOO) substrate particle, after reduction in hydrogen. [Adapted from...

In the example of Fig. 7.15 [43j rhodium particles have been deposited by spin coat impregnation of a Si02/Si substrate with an aqueous solution of rhodium trichloride. After drying, the particles were reduced in hydrogen. The images show samples prepared at three different rotation speeds in the spin coating process, but with concentrations adjusted such that each sample contains about the same amount of rhodium atoms. The particles prepared at high rotation speeds are smaller, which... 

The Cr/Si02 catalyst is made by spin-coat impregnation of the flat silica support with a solution of chromic acid in water. Figure 9.25 shows the Cr XPS spectrum of the catalyst after drying. Chromium is present as a hydrated Cr(VI) oxide, with a Cr 2p binding energy characteristic of chromate species, as the reference spectra in the lower half of the figure show. An essential step in the... 

Fig. 7.18 AFM image of a planar model catalyst consisting of copper particles deposited by spin-coat impregnation on a flat Si02 on Si(100) substrate, after reduction in hydrogen. Because the image is a convolution of the shape of the particle and that of the tip, the particles appear larger than they are. The height, however, is correctly reproduced.

The spin coating technique has attracted interest, since it maintains many aspects of technical catalysts prepared by pore volume or incipient wetness impregnation, and simultaneously allows the interpretation and analysis in a similar way as the more well-defined model systems discussed above [30]. Here, a solution of the desired catalyst precursor is dropped onto a wafer covered with an oxide film, which is spun on a rotor to create a liquid layer of uniform thickness in order to mimic traditional wet impregnation preparation of catalysts. Control of the catalyst loading and particle size is to some degree achieved by varying the rotation speed, concentration, and vapor pressure of the solute. Still the method suffers, however, from many of the drawbacks associated with wet-impregnated model catalysts, which imparts detailed mechanistic studies. 

Dispersion metal coatings, coating, pulverization, impregnation, cast (for thin films), fibre spinning. 

In this chapter, we will discuss current applications and research on the use of C02 as a solvent for coatings. The first section deals with spray coating from supercritical C02. Subsequent sections deal with the use of liquid coatings, such as spin and free meniscus coatings, and impregnation coatings. 

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