Tribology of Mechanical Systems: A Guide to Present and Future Technologies
16 Surface Analysis and Tools
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Many material properties are actually surface properties: For example, erosion, abrasion, wear, oxidation, corrosion, adhesion, bonding, friction, fatigue and cracking are all affected by surface properties [1, 2, 3]. By modifying surfaces, depositing thin films or producing multiple-layered coatings, the designer can enhance performance, such as resistance to erosion, abrasion, wear, oxidation, corrosion and cracking, as well as biocompatibility or environmental compatibility [4, 5, 6, 7].
In order to understand surface properties, and ultimately to provide better surfaces, it is necessary to study the physical and chemical characteristics of the material surface obtained by a given process. A number of tools are now available for surface analysis of any solid surface [8, 9, 10]. Because the surface plays such a crucial role in many processes, surface analysis and its tools have established their importance in a number of scientific, industrial and commercial fields [11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21]. For example, the editors of Research & Development Magazine surveyed the thin-film research community in August 2001 to determine the level of involvement with thin-film characterization tools and the immediate research concerns . The survey indicated that thin films and coatings are commonly used in components and devices to improve mechanical properties, material performance, durability, strength and resistance in basic industries, such as industrial coatings (21% of researchers' responses), nanotechnology (19%), optical components (19%), plastics (17%), ceramics (15%), biomedical technology (10%), instrumentation (10%), microelectromechanical systems (10%) and disk drives (6%). Further, according to the survey, the most widely used tools for examining thin films and coatings are optical microscopy (60%), scanning electron microscopy (56%), energy-dispersive X-ray spectroscopy (29%), Fourier transform infrared spectroscopy (29%), surface profilometry (29%), X-ray diffraction (27%), Auger electron spectroscopy (25%), ellipsometry (23%), scanning probe microscopy (19%), transmission electron microscopy (19%), thermal analysis (15%), X-ray photoelectron spectroscopy (12%), confocal microscopy (10%) and secondary ion mass spectroscopy (8%).
Surface analysis is important for verifying the success of the surface preparation process, including a coating process or surface treatment for controlling the surface quality as well as for identifying surface contamination that can either enhance or inhibit the surface effects of the material. Selecting the proper analytical tool and method is crucial to obtaining the right information. To select the proper tool, the researcher must know the specimen size, sampling area, sampling depth, spatial resolution, detection sensitivity, whether quantitative or qualitative results and destructive or nondestructive analysis are desired, and many other factors. Each technique has its strengths and weaknesses. Therefore, no single tool can provide the answers to all problems. In many cases, it will be necessary to use multiple tools to reach an answer.