Top layer coating

Figure 30. Microstructure of a Zr(C, N) top-layer coated steel turning hardmetal (WIDIA TN7015).

Gas transport through SPPO-PPO composite membranes, depended on the nature of the solvents for the top layer coating solutions. Permeance was higher when DMA was used as the solvent. This effect was thought to be due to the formation of a thinner coated layer of SPPO when a DMA solution was used. For both kinds of membranes permselectivities of 6-8 for O2/N2 gas mixture and about 100 for CO2/N2 mixture were observed. The ionic character of SPPO was believed to have enhanced the CO2 permeance. 

If an elastic or insufficiently hard primer or paint has been applied under a less elastic top coat, or if the first coat (or set of coats) of oil-base paint has been second-coated before it is completely dry, not only will the paintwork remain soft for an unduly fong period, but cracking will also follow, as the upper layer cannot follow the movement. If the last coat is very thick this fault will frequently manifest itself in the form of alligatoring, i.e. the formation of cracks which do not penetrate all the films down to the substrate, and which may be present in the top layer only. 

Figure 16.23 presents the alumina-coated ceramic membrane. There were opportunities to fabricate a crack-free ceramic membrane coated with y-alumina. The supported zirconia-alumina membrane on the ceramic support shows an irregular surface. The non-uniform surface of ceramic support causes the irregular surface on the top layer of the membrane. Some of the membrane sol was trapped in the porous ceramic support during coating, and caused the irregularity of the membrane surface. 

In the case of ta-C coatings sliding on different materials in humid ambient, the top layer of a ta-C coating in the con-... 

When the photostabilization of a polymer material is to be obtained through such a surface treatment process, it is all important to make sure that the protective effect will last throughout the service life and therefore to ensure a long-term adhesion of the coating onto the substrate. This can be best achieved by promoting a grafting reaction between the two elements (20). For that purpose, the photoinitiator was partly incorporated in the top layer of the PVC plate by a surface treatment with an acetone solution. Upon UV-irradiation of the resin-coated sample, the following reactions are expected to occur ... 

Poly(2-acrylamido-2-methyl-l-propanesulfonic acid and isopropylhexafluor-oalcohol), (IV), was prepared by Khojasteh et al. (4) and used as a top antireflective coating and barrier layer for immersion lithography. 

Historically, wrinkles on PDMS were first observed upon metal evaporation. Martin and coworkers reported wrinkle formation by evaporation of aluminum onto PDMS [39], which was first not followed further. The potential of metal evaporation onto PDMS for structuring purposes was recognized only 17 years later by Bowden [15]. In these experiments, the metal was coated onto thermally expanded PDMS. Returning the sample to room temperature causes thermal shrinkage of the PDMS and consequently wrinkling of the top layer. Chen and coworkers have theoretically shown that the herringbone-type pattern observed under these conditions... 

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