Polishing surface spectroscopy

The obvious application of microfocus Raman spectroscopy is the measurement of individual grains, inclusions, and grain boundary regions in polycrystalline materials. No special surface preparation is needed. Data can be obtained from fresh fracture surfeces, cut and polished surfaces, or natural surfeces. It is also possible to investigate growth zones and phase separated regions if these occur at a scale larger than the 1-2 pm optical focus limitation. 

Microstructures Etching, polishing, reactive ion techniques, ion bombardments, etc. Microscopy, surface spectroscopy... 

Hong et al. examined the effect of nitric acid passivation on type 430 ferritic stainless steel using potentiodynamic polarization, EIS, and Auger electron spectroscopy (AES) (18). Passivation treatments were carried out on wet polished surfaces by immersion for 60 minutes in nitric acid solutions ranging from 1 to 61% at 50°C. Pitting potential and the magnitude of the total impedance were positively correlated with surface Cr concentration. In response to this study,... 

Applications of IR and Raman spectroscopy to the study of clinkers and unhydrated cements have been reviewed (B39,B40). The laser Raman microprobe, with which regions of micrometre dimensions on a polished surface may be examined, has been used to investigate structure and crystallinity, especially of the alite and belite (Cl9). Spectroscopic methods for studying the surface structures and compositions of cements are considered in Section 5.6.2. 

Another technique is the nuclear reaction analysis of Lanford et al. (1976), which was applied to NAMs by Rossman et al. (1988), Skogby et al. (1990), Maldener et al. (2001), and Bell et al. (2003). This technique has the advantage of yielding absolute hydrogen concentrations. It is a near-surface technique in which the hydrogen concentration is measured as a function of depth. The spatial resolution of the technique is at the millimeter level Bell et al. (2003) prepared polished surfaces 5x5 mm in area. Maldener et al. (2001) state that 1 mm diameter samples can be analyzed. This technique has been used to calibrate absorption coefficients for IR spectroscopy (e.g., Maldener et al., 2001 Bell et al., 2003). Bell et al. (2003) applied this technique to hydrogen in olivine, and found some of the previous estimates of hydrogen concentration in olivine need to be revised upward by factors between 2 and 4. Such a correction cannot be applied uniformly to all previous studies, because their new calibrations are specific to polarized spectra. 

Besides these techniques that are applicable to solid electrodes with a smooth or, in the case of IR spectroscopy, carefully polished surface, technologically important rough or porous samples are sometimes of interest. Vibrational spectroscopy at the surfaces of rough or porous samples is possible with photoacoustic and photother-mal spectroscopy (PAS, PTS) [90-94]. 

These spectra were obtained with a smooth, polished surface. Thus no surface enhancement was effective. The molecules under investigation can alternatively be deposited onto roughened surfaces and the obtained spectra show a combination of surface and resonance enhancement. The method is called surface enhanced resonance Raman spectroscopy (SERRS). 

Figure 4.6. Schematic arrangement of conventionai diffuse-reflectance accessory for measuring multiple-transmission spectra of microsamples. (1,2) focusing optical system of accessory (3) sample holder (4) plate under study (5) metallic mirrors, (a) Plate with polished surfaces placed between ground metallic surfaces. (6) Plate with ground surfaces placed between polished mirrors. Reprinted, by permission, from V. P. Tolstoy, Methodsof UV-Vis and IR Spectroscopy of Nanolayers, St. Petersburg University Press, 1998, p. 130, Fig. 4.10. Copyright 1998 St. Petersburg University Press.

Figure 7.13 Complementary functional group maps of a polished surface of a sectional gallstone (a) 875 cm band of CaCOs (b) 1050 cm band of cholesterol [42]. From Wentrup-Byrne, E., Rintoul, L., Smith, J. L. and Fredericks, P. M., Appl. Spectrosc., 49, 1028-1036 (1995), and reproduced by permission of the Society for Applied Spectroscopy.

The microstrnctnres were analysed using scaiming electron microscopy (SEM, Cambridge S360, Cambridge, UK) and energy dispersive spectroscopy (EDS, INCA Energy 300, Oxford Instruments, UK) on fractured and polished surfaces. 

Such effects are observed inter alia when a metal is electrochemically deposited on a foreign substrate (e.g. Pb on graphite), a process which requires an additional nucleation overpotential. Thus, in cyclic voltammetry metal is deposited during the reverse scan on an identical metallic surface at thermodynamically favourable potentials, i.e. at positive values relative to the nucleation overpotential. This generates the typical trace-crossing in the current-voltage curve. Hence, Pletcher et al. also view the trace-crossing as proof of the start of the nucleation process of the polymer film, especially as it appears only in experiments with freshly polished electrodes. But this is about as far as we can go with cyclic voltammetry alone. It must be complemented by other techniques the potential step methods and optical spectroscopy have proved suitable. 

Spherical rollers were machined from AISI 52100 steel, hardened to a Rockwell hardness of Rc 60 and manually polished with diamond paste to RMS surface roughness of 5 nm. Two glass disks with a different thickness of the silica spacer layer are used. For thin film colorimetric interferometry, a spacer layer about 190 nm thick is employed whereas FECO interferometry requires a thicker spacer layer, approximately 500 nm. In both cases, the layer was deposited by the reactive electron beam evaporation process and it covers the entire underside of the glass disk with the exception of a narrow radial strip. The refractive index of the spacer layer was determined by reflection spectroscopy and its value for a wavelength of 550 nm is 1.47. 

X-ray fluorescence is a type of atomic spectroscopy since the energy transitions occur in atoms. However, it is distinguished from other atomic techniques in that it is nondestructive. Samples are not dissolved. They are analyzed as solids or liquids. If the sample is a solid material in the first place, it only needs to be polished well, or pressed into a pellet with a smooth surface. If it is a liquid or a solution, it is often cast on the surface of a solid substrate. If it is a gas, it is drawn through a filter that captures the solid particulates and the filter is then tested. In any case, the solid or liquid material is positioned in the fluorescence spectrometer in such a way that the x-rays impinge on a sample surface and the emissions are measured. The fluorescence occurs on the surface, and emissions originating from this surface are measured. 

The double-layer structure at the electro-chemically polished and chemically treated Cd(OOOl), Cd(lOlO), Cd(1120), Cd(lOh), and Cd(1121) surface electrodes was studied using cyclic voltammetry, impedance spectroscopy, and chronocoulometry [9, 10]. The limits of ideal polarizahility, Epzc, and capacity of the inner layer were established in the aqueous surface inactive solutions. The values of iipzc decrease, and the capacity of the inner layer increases, if the superficial density of atoms decreases. The capacity of metal was established using various theoretical approximations. The effective thickness of the thin metal layer increases in the sequence of planes Cd(1120) < Cd(lOiO) < Cd(OOOl). It was also found that the surface activity of C104 was higher than that of F anions [10]. 

Low tenperature isotropic (LTI) pyrolytic carbon has been studied by X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray analysis. Both silicon-alloyed and unalloyed carbons were studied, in both as-deposited and polished (finished) forms. The polished materials contain significant amounts of surface oxygen. Approximately 1 in 10 of the carbon atoms in the surface volume analyzed by XPS are... 

Fig. 3. Exploded view of the thin film spectroscopy apparatus, showing the relative positions of the optical cooling surface, the interferometer, the optical pathway for measurement and the material source for the film. W, window (polished quartz or sapphire), O, ground surface onto which windows are glued, LED, light emitting diode, PD, photodiode...

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