Page 31 - Handbook of Adhesion Promoters

24 Mechanisms of Adhesion

Figure 2.23. Focus ion beam-SEM image of the inter-
phase between PEDOT/PSS and IrO x (top), compared
to that of PEDOT/PSS and nanostructured Pt (bot-
tom). A dense integration between the metal (bright
structures) and the polymer (dark shades) can be iden-
tified in both cases. The inset figure in the lower
image shows nanostructured Pt without PEDOT,
which shows Pt structure in a form of brush. [Adapted,
by permission, from Boehler, C; Oberueber, F;
Schlabach, S; Stieglitz, T; Asplund, M, Appl. Mater.
Interfaces, 9, 189-97, 2017.]
Figure 2.22. Polarized optical microscopy showing
morphology of single polyaniline-coated short glass
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fiber embedded in (a) iPP and (b) iPP/PP-maleic anhy- adhesion promoter was added. The devel-
dride-grafted blend. A single uncoated glass fiber opment of transcrystalline zones around
embedded in iPP during crystallization is shown in (c)
for comparison. [Adapted, by permission, from Cruz- polyaniline-coated SGF in composites was
Silva, R; Romero-Garcia, J; Vazquez-Rodriguez, S; observed with and without PP-maleic anhy-
Angulo-Sanchez, JL, J. Appl. Polym. Sci., 105, 2387-95, dride grafted (Figures 2.22a&b), respec-
2007.]
tively. No transcrystallization was induced
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by the bare glass fiber (Figure 2.22c).
Epitaxy refers to the deposition of a crystalline overlayer on a crystalline substrate.
Heteroepitaxy refers to the growth of layers of material that are different from the sub-
strate. The partial heteroepitaxy is considered as one of the possible mechanisms enhanc-
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ing the adhesion between the metallic coatings and the ceramic substrates. Local
heteroepitaxy between cubic aluminum and hexagonal aluminum nitride was a result of
the processes which accompanied the cold gas spraying the aluminum on aluminum
nitride and which improved the adhesion of the cold gas sprayed aluminum coatings on
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aluminum nitride substrates. It is the primary adhesion mechanism if aluminium is cold
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gas sprayed on polished aluminum nitride crystals.
The crystallographic bonding was reported for alumina coating on a low carbon
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steel. The wüstite layer was formed on the surface of steel. A physical bonding
resulted from the strong crystallographic relationships between the different phases pres-
ent, such as epitaxy between inner steel and wüstite, the partial topotactic transformation