Other Metals

Surface structure on the atomic level, the change of it by adsorption of ethane and other model molecules, and the techniques to monitor it are presented for Pt and Rh model surfaces in [161].

A copper (110) surface with homo- and heterochiral domains of adsorbed glycine could be distinguished with submolecular resolution via STM [162].

A Co-Cr-Mo (ASTM F-75) alloy and its corrosion were investigated by SECM in NaCl solutions. Corrosion took

Figure 10. SFM image of a titanium substrate coated with Teflon (PTFE) by dip coating [155]. The underlying substrate surface is not visible. The coating flattens all the substrate roughness.

Figure 11. SFM image of a titanium substrate coated with Teflon (PTFE) by a powder method [155]. The Teflon layer forms a strongly structured surface.

Figure 10. SFM image of a titanium substrate coated with Teflon (PTFE) by dip coating [155]. The underlying substrate surface is not visible. The coating flattens all the substrate roughness.

Figure 11. SFM image of a titanium substrate coated with Teflon (PTFE) by a powder method [155]. The Teflon layer forms a strongly structured surface.

place mainly at grain boundaries. Corroded material was additionally characterized by X-ray energy dispersive spec-troscopy (EDX) analysis for chemical composition. Two types of corrosion products were seen as flakes on the surface, one with Co 3%, Cr 72%, Mo 24% and the other with Co 12%, Cr 88%, Mo 0%; on the tip abrasion flakes were determined as Co 11%, Cr 66%, Mo 24% [22].

Stainless steel, copper and alloys, and the corrosion processes induced by bacterial attachment including freshwater bacteria monitored with SFM are described in [163]. The electrostatic forces on the surfaces of stainless steel (316l), gold, and an electropolished Nitinol surface were investigated via force curves with the SFM. Gold and stainless steel exhibit repulsive forces at pH 7, Nitinol a slight attractive force. Nitinol surfaces show a heterogeneity in the distribution of surface charges that is rendered more homogeneous upon oxidative treatment [164].

Although gold has been studied for a long time, it is still an actual field of investigation. Comparison of the cell adhesion properties with other materials is made, for example, by SEM examinations as mentioned earlier [132]. But Au is also useful in other applications. The protein adsorption on gold colloid particles, for example, is widely used in biotechnology for diagnostics and separations, for example, in combined fluorescent and gold immunoprobes for correlative light and electron microscopy [165]. To visualize the protein film on nanosized particles, a TEM approach was applied [166]. These proteins cause a significant scattering absorption contrast in TEM based on the materials' electron density. Thus the film thickness was directly measurable in planar projection and the shape of these films was visualized without negative staining methods.

Alkali- and heat-treated tantalum as implant material has been shown to bond to bone, for example, by SEM [167]. The treated implants showed weak bonding to bone after 8 weeks of implantation and exhibited significantly higher tensile failure loads compared with untreated Ta after 16 weeks. In contrast, the untreated TA implants had a intervening fibrous tissue layer between the bone and the Ta and did not bond to bone after 8 and 16 weeks.

Techniques of SEM and light microscopy deal with retrieval analysis of different implanted biomaterials, for example, cobalt-chromium-molybdenum alloys [168]. Cases included both orthopedic and dental implants, as well as entire mandibles and portions of maxillae obtained at autopsy.

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