Scratched substrate

Scratching substrates with diamond powder or other abrasive materials significantly enhances surface nucleation density and rate compared to untreated substrates.t hi70][i79] different suggestions have been made to account for the mechanisms of the nucleation enhancement by scratching (Fig. 2). The first of these is the seeding effect, i.e., diamond, DLC,... 

Figure 2. Schematic diagram of mechanisms for diamond nucleation enhancement on scratched substrates. l (Reproduced with permission.)...

The gum Arabica biopolymer must be examined microscopically for verifying its morphology and microstructure. Figure 12.2a and 12.2b shows the SEM photograph of the caste surface of the biopolymers on smooth and scratched substrate respectively. The latter surface was a textured one with grown anisotropy due to cast over scratched substrate. It was taken at a magnification of 10,000, and indicates a domain like microstructure, which is precursor of a growing anisotropy in the specimen [21]. 

XPS analysis was also performed on the scratched substrates after 6 h of immersion. The XPS spectra obtained on the coatings filled with Ce02 nanoparticles activated with cerium ions revealed the presence of two forms of cerium Ce(III) and Ce(IV). The latter is mainly due to the presence of the Ce02 nanoparticles, whereas the former confirms the existence of Ce, which may precipitate as Ce(OH)3. For the coating modified with Si02 activated with cerium ions, the Ce3d ionisation displayed... 

Decorative. Titanium nitride has a golden color and is used extensively to coat steel and cemented carbide substrates for watch cases, watch bands, eyeglass frames, etc. It provides exceUent scratch resistance as weU as the desired aesthetic appearance, and it replaces gold coatings used previously. 

Pseudomorphism has less desirable consequences, and usually means are sought to suppress it. If the substrate has been scratched, ground or abrasively polished, or if it has been cold rolled or cold formed, the surface is left in a peculiar state. Cold working reduces the surface grain size, and produces deformed, shattered and partly reoriented metal. It may produce microcrevices between the deformed grains, and, with some processes, non-metallic impurities and oxides are embedded in the surface. The disturbed state of the substrate is copied by a pseudomorphic electrodeposit with several consequences (Fig. 12.7). One is aesthetic it has often been noted that almost invisible abrasion of the substrate develops as more prominent... 

Fig. 12.14 Spread of silver sulphide from discontinuities in gold electrodeposits on silver substrates. The gold was deliberately scratched and the specimen exposed for 24 h to an atmosphere containing 10< o SO2. Immediately after this the sulphide stain extended 0-2 mm. Five years later, the stain extends to about 13 mm, after storage in a normal indoors atmosphere...

A nano scratch tester (CSEM) was employed to carry out the scratch test. A Rockwell diamond tip with a radius of 2 fim was used to draw at a constant speed 3 mm/min across the coating/substrate system under progressive loading of 130 mN maximum at a fixed rate 130 mN/min. The total length of the scratch scar is 3 mm. The critical load (L ) here is defined as the smallest load at which a recognizable failure occurs. The failure can be observed both by the built-in sensors and by the optical microscope. 

Figure 35 shows the optical microscopic images of the first crack point on the sample surface. The scratch scar of monolayer Sample 1 has the feature of brittleness. However, there is an obvious crack along the scratch scar of Sample 2 before the coating delamination. This indicates that mono-layer Sample 2 has the feature of ductility, and the adhesion between the film and the substrate is poor. However, there is no obvious crack before the delamination in the scratch scars of other samples. The feature of multilayer Samples 3 and 4 is different from monolayer Samples 1 and 2. There are no obvious cracks in the scratch scars of Samples 5 and 6, except several small cracks along the edge of the scars. These... 

Figure 5.5. Electron micrographs of different types of diamond film grown on silicon. The white bar shows the scale in micrometres (p.m) (thousandths of a millimetre), (a) The initial stages of diamond growth on a nickel substrate, showing individual diamond crystallites nucleating in scratches and crevices created on the surface by mechanical abrasion, (b) a randomly oriented him,...

Figure 4.12 Fluorescence image of PMMA brush layer (a) and schematic drawing of the brush chain (b). The dark region (a) corresponds to the substrate surface exposed by scratching off the brush layer. The filled and open circles indicate the points where the fluorescence anisotropy decay was acquired.

Knife test (KNF) The test is done by making two intersecting scratches through the paint film to the substrate with a sharp steel knife. Adhesive or cohesive failures are evaluated by peeling the coating from the intersection point and outwards. Common for the three adhesion evaluation methods are that the test is performed on immersed and non- immersed panel-half (referred to as respectively "wet" and "dry" adhesion). The type of rupture is reported, and the severity is judged on a scale from 5 (perfect) to 0 (poor). 

The use of specialty substrates for labels have been driven by the market looking for materials with greater dimensional stability at higher temperature, improved mechanical performance under harsh environments, and resistance to scratching and tearing. Up until now, PET-based labels have been used where conditions are moderate, while polyimide-based labels have been employed in the most extreme environments. PEN films offer a unique performance advantage over PET and a considerable cost saving when compared to polyimide films. 

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