Glass surface profiles

Some solid materials are very intractable to analysis by standard methods and cannot be easily vaporized or dissolved in common solvents. Glass, bone, dried paint, and archaeological samples are common examples. These materials would now be examined by laser ablation, a technique that produces an aerosol of particulate matter. The laser can be used in its defocused mode for surface profiling or in its focused mode for depth profiling. Interestingly, lasers can be used to vaporize even thermally labile materials through use of the matrix-assisted laser desorption ionization (MALDI) method variant. 

If the rf source is applied to the analysis of conducting bulk samples its figures of merit are very similar to those of the dc source [4.208]. This is also shown by comparative depth-profile analyses of commercial coatings an steel [4.209, 4.210]. The capability of the rf source is, however, unsurpassed in the analysis of poorly or nonconducting materials, e.g. anodic alumina films [4.211], chemical vapor deposition (CVD)-coated tool steels [4.212], composite materials such as ceramic coated steel [4.213], coated glass surfaces [4.214], and polymer coatings [4.209, 4.215, 4.216]. These coatings are used for automotive body parts and consist of a number of distinct polymer layers on a metallic substrate. The total thickness of the paint layers is typically more than 100 pm. An example of a quantitative depth profile on prepainted metal-coated steel is shown as in Fig. 4.39. 

Thickness Measurement. The thickness of poly(I) at different coverages was obtained using a Tencor alpha-step 100 surface profile measuring system. Electrodes used were glass slides coated with Pt by electron beam evaporation. In order to produce a "step" across which the stylus of the surface profiler was drawn, Apiezon N grease was applied to part of the electrode surface and was removed with CH2CI2 after derivatization with poly(I). 

A surface peak effect has been observed during Rb and Sr diffusion in vitreous silica (13). Such large near-surface concentrations are postulated to result from the exposure at the glass surface of a greater number of interstices or defects over which diffusion can occur. This would lead to steep penetration curves observed in some XPS profiles of glass. 

A technique which can yield hydrogen concentration profiles of a glass surface(19) without the complications of ion milling involves using the resonant nuclear reaction between hydrogen 1H) and (1 N). At precisely 6.385 M V (lab) there is a resonance in the reaction 3N + H = X +... 

The profiles of the unleached glass surface showed essentially no change in intensity of the sodium and potassium ions as a function of depth. However, Si and B ion intensities were found to be consistently lower at the outer surface than within the bulk of the glass. Depth profiles for both ions have a similar shape. This effect is believed to result from surface hydration which alters the yield of ions from the borosilicate network. Unhydrated glass surfaces, introduced into the spectrometer immediately fter fracturing, showed little or no depression of either Si or B signals, and hydrate clusters, such as Si(0H)+ were much reduced in intensity. 

Antibody arrays immobilized on glass surfaces mimic DNA microarrays in format and spot size. The biggest challenge in protein profiling using antibody microarrays is selection of validated antibodies that are useful in the desired sample environment. Many of the initial reports used antibody arrays assayed for cytokines because serum presents a relatively simple sample assay environment compared to tissue and also because there are numerous validated antibodies available for this clinically important set of proteins. Tissue and cell lysates present more complex assay environments with more opportunities for antibody cross-reactivity and other interferences which erode the biological meaningfulness of the data. 

Fig. 11 Calculated surface profiles of the octahedral shear stress at yield assuming a modified Von Mises criterion (a), and of the octahedral shear stress for a glass/epoxy contact under gross sliding condition (b). The grey area delimits the region at the leading edge of the contact where the octahedral shear stress is exceeding the limit octahedral shear stress at yield (a is the radius of the contact area) (from [97])...

In agreement with hydrogen depth profiling and XPS analyses, these results show that the basalt glass surface is depleted in network modifying cations that... 

Figure 6.18 shows the profile of a microchannel machined at 30 V and with a tool travel speed of 30 pm/s at different tool distances from the glass surface. The average depth of the microchannels decreases with higher tool distance. The quality of the machined microchannels does not change significantly for tool distances up to 15 pm. Above 25 pm no acceptable results can be achieved. 

Figure 6.18 Profile of microchannel depths at three different tool-electrode distances from the glass surface (machining voltage is 30 V and tool-electrode speed is 30 pm/s in 30 wt% NaOH). Reprinted from [23] with the permission of the Journal of Micromechanics and Microengineering.

Measured average glass surface temperature profile along the furnace axial centerline in the glass tank. (From Hayes, R. R., Wang, ]., McQuay, M. Q., Webb, B. W, and Huber, A. M., Glass Science Technology, 72, no. 12,367-77,1999.)... 

Measurements in the combustion space indicate that the average glass surface temperature profile rises sharply from a low near 1700 K closest to the batch feeder to about 1850 K at the next downstream location, then continues to rise steadily down the axial length of the furnace along the centerline to a peak of approximately 1910 K in the region of ports 4 and 5. The molten glass surface temperature then drops to near 1800 K at the measured location closest to the furnace working end. 

Initial Fast Reversible Adsorption. The chromatographic profiles indicate that protein is adsorbed almost instantaneously on coated glass surfaces, and at short adsorption times, the contact points of the protein with the surface are limited and the kinetic energy of colliding solvent molecules is sufficient to cause desorption, that is, the desorption rate is a function of the surface adsorbed concentration. 

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