Post Impregnation

It is often desired that parts be hardened by the addition of more colloidal silica to the already formed parts. One such product is a ceramic fireplace log. It is formed from 

Initially the colloidal silica particles are uniformly spread through the structure. 

As the water Is evaporated the particles tend to move to the surface along with the liquid water. 

If the article Is fairly thick, there develops a noticeable harder layer on the outside and a soft center portion. 

FIGURE 12.54 Migration of colloidal silica in fiber bonded parts. 

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Two processes may be used in the manufacture of combustible cases the original post-impregnation process and the more recently and more widely employed beater additive process. The processes differ primarily in the point at which the required resin is added to the composition. A schematic of the beater additive process is shown in Figure 11. 

To carry out this test on a wound machine (post-impregnated) would be pointless as the quality of the... 

In heterogeneous catalysis post-impregnation treatments such as calcination and reduction are usually performed to remove ligands or their residues. In some cases the removal of heteroatoms such as carbon, sulfur or chloride is tedious and can... 

The part may be dried, post-impregnated with colloidal silica and dried again. This can be repeated in order to build a dense, ceramic-like body. 

Uemura, Y, Y. Hatate, and A. Ikari, Formation of nickel concentration profile in nickel/alumina catalyst during post-impregnation drying. J. Chem. Eng. Japan, 20 pp. 117-123, 1987. 

Manutocturers (tomments Low strength and quick-setting at RT. Manufacturers Comments Post impregnating, tow viscosity. Quick- ... 

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