Читать книгу Materials for Biomedical Engineering - Mohamed N. Rahaman - Страница 186

1 5.1 A dental implant composed of titanium (Ti), approximated as a cylinder of diameter 5.0 mm and length 8.0 mm, has a surface layer of thickness 3 nm composed of titanium dioxide (TiO2). Determine the fractional volume of the TiO2 surface layer, that is, the volume of the TiO2 layer relative to the total volume of the implant.

2 5.2 Distinguish between the terms surface tension and surface energy.

3 5.3 Determine the contact angle of a droplet of deionized water on ultrahigh molecular weight polyethylene (UHMWPE), given that the densities of water and UHMWPE are 1.0 and 0.94 g/cm3, respectively, the surface tension of water is 73.0 mN/m, and the surface energy of UHMWPE is 36 mJ/m2.

4 5.4 The contact angle of a droplet of deionized water on a microrough surface of silicon nitride was observed to decrease from 66° ± 9° to 30° ± 9° in 30 minutes. Suggest an explanation for the decrease in contact angle.

5 5.5 Explain the significance of the critical surface tension in relation to biomaterials.

6 5.6 In an X‐ray photoelectron spectrum of titanium, is the adventitious C 1s peak expected to be at a higher or lower binding energy than the O 1s peak? Is the Ti 2s peak expected to be at a higher or lower binding energy than the Ti 2p peak? Explain.

7 5.7 The composition of the oxide surface layer on silicon nitride (Si3N4) can change with depth. Briefly describe a method for studying the change in surface composition with depth and, in general terms, the expected change in surface composition.

8 5.8 Explain how the following biomaterials develop a surface charge when implanted in the physiological environment: (a) titanium, (b) silicon nitride, and (c) PEEK.

9 5.9 Briefly explain the type of surface topographical features that are expected to influence the response of cells.