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Thixoforming : Semi-solid Metal Processing

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ion energy of approximately 100 eV [53]. It is reasonable to assume that 100 eV ions<br />

bombarding the growing film surface may help diffusion of adsorbed species.<br />

8.5.2.2 Film Morphology and Porosity<br />

The morphology of the films was evaluated by SEM and transmission electron<br />

microscopy (TEM). Three pore populations were observed and are referred to as<br />

micro-, meso- and nanopores. Micropores with a diameter in the sub-micrometre<br />

range are clearly visible in the SEM images presented in Figure 8.31.<br />

Figure 8.31 SEM images of alumina films deposited at<br />

normalized ion fluxes of (a) 50, (b) 70, (c) 100, (d) 140, (e) 270 and<br />

(f) 480 [61].<br />

8.5 Developing Al 2O 3 PECVD Coatings for <strong>Thixoforming</strong> Mouldsj275

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