Volume 18 - Friction, Lubrication, and Wear Technology Part 12 ppt

Fig. 27 Time-of-flight data for species composing the 1.9 eV ESDIED peak Fig. 28 Time-of-flight data for species composing the 3.5 eV ESDIED peak It has been shown (Ref 55) that the time-of-flight of an ion is proportional to its mass. The relationship is time-of-flight = 4.2 , where m is the mass of the ion. Hence, flight times of 4.2, 16.4, and 16.9 s are expected for H + , O + , and OH + , respectively. Time-of-flight data for the 3.5 eV ESDIED peak also shows that H + is being desorbed, but that O + and/or OH + are probably not. ESD Applications. The data acquired for the polycrystalline tin oxide sample discussed in the previous section is discussed further here. Consider the ESDIED and time-of-flight data shown in Fig. 29. The data were acquired after annealing for 30 min at 600 °C (1110 °F) and 9.3 × 10 -7 Pa (7.0 × 10 -9 torr). Note that the 1.9 eV ESDIED peak is very small relative to the higher-energy peak around 4.3 eV. The time-of-flight data of Fig. 30 and 31 show that O + and OH + are both desorbed, and the 4.3 eV peak has more O + than OH + , relative to the 1.9 eV peak. Fig. 29 ESDIED spect rum for polycrystalline tin oxide sample following annealing in vacuum for 30 min at 600 °C (1110 °F) Fig. 30 Time-of-flight data for species composing the 1.9 eV ESDIED peak following annealing in vacuum for 30 min at 600 °C (1110 °F). Fig. 31 Time-of- flight data for species composing the 4.3 eV ESDIED peak following annealing in vacuum for 30 min at 600 °C (1110 °F) The ESD data can be explained by the following considerations. First, it is necessary to realize that tin oxide undergoes dehydration for the annealing conditions used. This has been shown by Cox (Ref 57) using valence band ESCA. If it is noted that the O + and OH + desorption signal is very small prior to annealing, but significantly larger following annealing, it is clear that the surface O + and OH + for the clean sample, prior to annealing, are not active with regard to desorption by electron stimulation. However, the O + and OH + that remain after dehydration are amenable to desorption by electron stimulation. Therefore, oxygen and hydrogen not associated with water of hydration have been distinguished because these bonding states are active with respect to ESD, whereas those associated with water of hydration are not. It is possible to test this interpretation by exposing the sample to an oxidizing atmosphere. This was accomplished by annealing the sample in oxygen for 1.5 h at 400 °C (750 °F) at 1.3 × 10 -4 Pa (10 -6 torr.) The ESDIED and time-of-flight data are shown in Fig. 32 33 34. The 1.9 eV ESDIED peak has increased in size relative to that observed for the previous 600 °C (1110 °F) annealing treatment. The relative amounts of O + and OH + being desorbed have also decreased again, compared with data collected following the 600 °C (1110 °F) annealing treatment. Fig. 32 ESDIED spectrum for polycrystalline tin oxide sample following annealing in oxygen for 90 min at 400 °C (750 °F) Fig. 33 Time-of- flight data for species composing the 4.3 eV ESDIED peak following annealing in oxygen for 90 min at 400 °C (750 °F) Fig. 34 Time-of- flight data for species composing the 4.3 eV ESDIED peak following annealing in oxygen for 90 min at 400 °C (750 °F) It is reasonable to expect oxygen supplied to the sample during the oxidation treatment to become associated with vacancies generated during the dehydration process. Therefore, it can be concluded that the 1.9 eV ESDIED peak is associated with water of hydration, and the higher-energy ESDIED peak is associated with other species, such as oxygen bound to tin, in the lattice structure. Thus, oxygen and hydroxyl groups associated with water of hydration are not active with regard to desorption by electron stimulation, relative to oxygen and hydroxyl groups associated with other bonding situations. ESD has been used to distinguish these oxygen and hydrogen types. ESD is a valuable technique because it enables hydrogen detection and it can be used with minimum modifications to existing AES equipment. The major drawback is that data interpretation beyond identification of desorbing species is often difficult. An alternative to ESD is discussed next. Secondary Ion Mass Spectrometry (SIMS) SIMS is an analytical technique that has become very popular over the past few years. Enhanced element sensitivity and hydrogen detection capability (order of ppm) are two advantages of SIMS that AES and XPS techniques do not offer. Its primary disadvantages are that it is inherently a destructive technique and quantitation is more difficult, relative to techniques such as AES and XPS. Specific examples of the application of SIMS to studies of wear, lubrication, and friction are somewhat limited, when compared with techniques such as AES. An excellent example of the application of SIMS to study material transfer resulting from abrasive contact between a ceramic and several metals is described in Ref 58. SIMS is particularly suited to such studies if the amounts of material transferred are expected to be very small. SIMS Fundamentals. The SIMS process is performed by bombarding the surface of a solid target material of interest with a beam of energetic ions. The ions composing the bombarding beam are referred to as primary ions. These ions can be delivered to the target surface at energies up to approximately 40 keV. The result of collision processes between primary ions and the target surface of interest is the emission of negative, positive, and neutral species. The term "species" is employed to indicate that ions or agglomerations of atoms bearing a net charge can be emitted from the surface. The species emitted from the surface are analyzed in terms of their mass-to-charge ratios (m/e). Therefore, only charged species can be analyzed. Neutral species that have been sputtered from the surface must first be ionized before analysis is possible. It is important to point out that charged species leaving the target surface as a result of sputtering constitute only a small portion of all sputtered atoms leaving the surface. This typically ranges from a few hundredths of a percent, up to approximately 1%. Discussions of analytical descriptions of secondary ion yield and parameters that influence the overall yield, such as ionization probability, are discussed in Ref 46 and 47. SIMS can be performed in two modes. In one case, the primary ion beam is rastered over the surface covering an area of approximately 50 × 50 m (2 × 2 mils) (Ref 46). This mode of analysis is referred to as static SIMS and is characterized by a relatively slow removal rate of atoms from the surface of the target material. Alternatively, the primary ion beam can be focused on an area of submicron dimension and material removed at very high rates relative to static SIMS. This mode of operation is referred to as dynamic SIMS. Its sampling depth is on the order of 10 3 nm, whereas static SIMS is characterized by sampling depths of only a couple of atomic layers (Ref 46). SIMS is often employed to obtain chemical depth profile information. Dynamic SIMS can achieve practical sputter rates, as well as maximum sensitivity (Ref 46). Therefore, this section focuses on this mode. In most cases, the primary ion beam employed with SIMS is an inert gas. However, primary beam systems should be capable of generating both negatively and positively charged ions of reactive gases. Negatively charged ions, such as O - , can be used as a primary beam source when sample charging is expected to be a problem. With versatility in the primary beam source, electrically insulating materials can be analyzed with a minimum of difficulties. An additional advantage of the ability to implement several types of primary ion beam gases is the effect of secondary ion yield. This is because secondary ion yields are influenced by the charge characteristics at the surface. Ion yields are maximized when neutralization probabilities are low. Therefore, positively charged secondary species are less likely to be neutralized when electronegative atoms are present in surface and near-surface regions of the material from which secondary ions are being sputtered. For this reason, if oxygen is used as a primary beam source, rather than an inert gas, the emission of positively charged secondary ions can be expected to be enhanced. This point is discussed in Ref 47. The SIMS spectrum consists of a representation of the signal intensity, or count rate, as a function of mass-to-charge ratio (m/e). Consider the SIMS data presented in Fig. 35. These data represent a SIMS survey scan for the surface and near-surface regions of a BiO x -Au-glass thin-film system, such as that discussed in the AES section (see Fig. 17). The SIMS data in Fig. 35 contain several elements that do not appear in the film data in Fig. 17 (that is, elements in addition to Bi, O, Au, and Si). These additional elements are the result of trace contamination of the deposition chamber from previous deposition processes. This is an excellent example of the increased sensitivity of SIMS relative to AES. [...]... Cox, and G.B Hoflund, Rev Sci Instrum., Vol 53, 1982, p 128 1 57 D.F Cox, G.B Hoflund, and H.A Laitinen, Appl Surf Sci., Vol 20, 1984, p 30 58 K Fujiwara, Wear, Vol 51, 1978, p 127 59 A.W Czanderna, Methods of Surface Analysis, Methods and Phenomena, Their Applications in Science and Technology, Elsevier, Amsterdam, 1975 60 C.A Anderson and J.R Hinthrone, Anal Chem., Vol 45, 1973, p 1421 61 T Sugita and. .. constituents composing a layered BiOx-Al-glass system is discussed This system is analogous to the BiOx-Au-glass thin-film system previously discussed and is used here because the amount of interdiffusion associated with high-temperature oxidation of the BiAl-glass-layered structure is substantial and can be clearly identified Consider the SIMS depth profile data shown in Fig 36 and 37 These data respectively... face- and body-centered cubic materials A common pattern is apparent For cold-work filings, one finds that (Eq 27) For the most part, the dislocation density is high and in the 1011/cm2 range Dislocations are highly correlated, with Rc close to the average diameter of the subgrain for metallic filings and ZrO2 debris Table 1 Results for body-centered cubic materials, face-centered cubic aluminum, and partially... Principles, M Cardona and L Ley, Ed., Springer-Verlag, Berlin, 1978 16 A Azouz and D.M Rowson, A Comparison of Techniques for Surface Analysis of Extreme Pressure Films Formed During Wear Tests, Microscopic Aspects of Adhesion and Lubrication, J.M Georges, Ed., Elsevier, Amsterdam, 1982 17 B.A Baldwin, Lubr Eng., Vol 32, 1976, p 125 18 R.J Bird, Wear, Vol 37, 1976, p 132 19 G.B Hoflund, H.-L Yin, A.L Grogan,... and K Ueda, Wear, Vol 97, 1984 62 B.P Straughan and S Walton, Ed., Spectroscopy, Chapman and Hall, London, 1976 63 N.J Harrick, Internal Reflection Spectroscopy, Interscience, 1967 X-Ray Characterization of Surface Wear C.R Houska, Virginia Polytechnic Institute and State University Introduction X-RAY DIFFRACTION and spectroscopy provide a variable-depth probe of the atomic arrangements and composition... p 5172 41 S.J Tauster, S.C Fung, and R.L Gartner, J Am Chem Soc., Vol 106, 1980, p 170 42 H Niehus and E Bauer, Surf Sci., Vol 47, 1975, p 222 43 S.V Pepper, J Appl Phys., Vol 45, 1974, p 2947 44 N Takahashi and K Okador, Wear, Vol 38, 1976, p 177 45 H.J Mathien and D Landolt, Wear, Vol 66, 1981, p 87 46 D Briggs and M.P Seah, Practical Surface Analysis by Auger and X-Ray Photoelectron Spectroscopy,... mechanical energy, and power (bearings, joints, gears, clutches, cams and tappets, bolts and nuts, fasteners, and brakes) The transportation and control of flow of matter (pipelines, wheel/rail, tire/road, valves, and seals) The forming, machining, and tearing of materials (drawing, pressing, cutting, shaping, quarrying, and dredging) The generation and transmission of information (printing heads and magnetic... Harrison and A Paskin, Acta Cryst., Vol 17, 1964, p 325 4 B Hwang and C.R Houska, J Appl Phys., Vol 63, 1988, p 5346 5 C.J Sparks, Synchrotron Radiation Research, H Winick and S Doniach, Ed., Plenum Publishing, 1980 6 B.E Warren, X-Ray Diffraction, Addison-Wesley, 1969 7 L.H Schwartz and J.B Cohen, Diffraction from Materials, Springer-Verlag, 1987 8 B.D Cullity, Elements of X-Ray Diffraction, Addison-Wesley,... data points and computer simulations (solid lines) for and symmetrical optics with CuK radiation ( - 0.15406 nm), (a) and (b); synchrotron radiation with = 0.24797 nm, (c) and (d); and 3° asymmetric optics with = 0.24797 nm, (e) and (f) To further emphasize the near-surface regions, (111) profiles of both samples were measured with asymmetrical diffraction optics, as shown in Fig 8(e) and 8(f) Asymmetric... not subjected to high-temperature oxidation to a sample that was The capability to detect hydrogen can be very useful in friction, lubrication, and wear studies because such studies often involve systems that contain hydrogen For instance, Sugita and Ueda (Ref 61) studied the wear characteristics of silicon nitride in water with respect to the material produced at the specimen-counterface interface . Takahashi and K. Okador, Wear, Vol 38, 1976, p 177 45. H.J. Mathien and D. Landolt, Wear, Vol 66, 1981, p 87 46. D. Briggs and M.P. Seah, Practical Surface Analysis by Auger and X-Ray Photoelectron. of mass-to-charge ratio (m/e). Consider the SIMS data presented in Fig. 35. These data represent a SIMS survey scan for the surface and near-surface regions of a BiO x -Au-glass thin-film system,. Fujiwara, Wear, Vol 51, 1978, p 127 59. A.W. Czanderna, Methods of Surface Analysis, Methods and Phenomena, Their Applications in Science and Technology, Elsevier, Amsterdam, 1975 60. C.A. Anderson