Oxygen dosing

Fig. VIII-13. LEED and ESDIAD on clean and oxygen-dosed Ni(lll) (a) LEED, elean surface (b) H ESDIAD of NH3 on Ni(Ill), the halo suggesting free rotation of the surface NH3 groups (c) ESDIAD after predosing with oxygen, then heated to 600 K and cooled before dosing with NH3—only well-ordered chemisorbed NH3 is now present. (From Ref. 93.)...

Figure 5.21. Experimental setup (inset) showing the location of the working (WE), counter (CE) and reference (RE) electrodes and of the heating element (HE) thermal desorption spectra after gaseous oxygen dosing at 673 K and an 02 pressure of 4x1 O 6 Torr on Pt deposited on YSZ for various exposure times. Oxygen exposure is expressed in kilo-langmuirs (1 kL=l0 3 Torrs). Desorption was performed with linear heating rate, ()=1 K/s.4 S Reprinted with permission from Academic Press.

Manz VA. 1968. [The behavior of tissue oxidase and the effect of oxygen doses on the animal in experimental hydrogen sulfide intoxication.] Zentralbl Arbeitsmed 18 325-333. (German)... 

The clean surface of a Au(lll) crystal at 100 K and a surface covered with o = 0.12, 0.25, 0.75, and 1.0 was dosed with 10 and 50 L CO2. XPS studies of the C(ls) and 0(ls) regions did not reveal any significant new peaks after CO2 exposure. Appreciable CO2 chemisorption does not occur on the clean or oxygen-dosed Au(lll) surface, nor does a stable surface carbonate form under these conditions. 

Figure 5 HREEL spectra recorded after small O2 doses at E = 0.39 eV on flat Ag(l 0 0) (bottom spectrum), Ag(41 0) (middle) and Ag(2 1 0) (top) at T = 105 K. O2 is dosed at normal incidence for Ag(l 0 0) and close to the normal to the step heights for the stepped surfaces. The losses in the 30-40 meV region are due to adatom surface vibrations, those at 80-84 meV to the internal stretch mode of the O2 admolecules. It is evident that only molecular adsorption takes place on flat Ag(l 00), while adatoms and admolecules coexist on Ag(41 0) and the final adsorption state is purely dissociative for Ag(2 1 0). The residual intensity at 84meV in the upper spectrum is most probably due to imperfections of the (21 0) staircase leading to larger terraces. We remind that the oxygen dose is expressed in ML of surface atoms, which are therefore referred to the corresponding face density.

Fig. 3. Molecular (left) and acetone (right) TPD spectra from 0.5, 2.0, and 4.0 L of 2-propyl iodide adsorbed on Ni(lOO) pretreated with a fixed 3.0 L oxygen dose at 300 K. The results from this figure indicate that acetone production starts at the point where the nickel adsorption sites become saturated, suggesting that the proximity of alkyl and oxygen groups on the surface is a requisite for partial oxidation reactions.

The surface-oxidation behavior of the amorphous precursor alloy was investigated by means of XPS and UPS [4.66, 67], Oxygen doses up to 2000 L were used to study the initial stages of the oxidation of the clean surfaces in the temperature range from room temperature to 570 K. Figure 4.7 compares the XPS Zr 3d spectra of the fresh amorphous Ni64Zr36 alloy, the sample after exposure to 80 L 02, and a Zr02 reference sample. The Zr 3d levels of the alloy... 

Fig, 7.2. Chromatogram of oxidation products obtained for nitrogen, carbon and hydrogen determination with the use of a Carlo Etba instrument. 1 = Start of experiment 2 = injection of oxygen dose 3 = injection of sample 4 = nitrogen 5 = carbon dioxide 6 = water. From ref. 74. 

Finer, N. N., Etches, P. C., Kamstra, B., Tierney, A. J., Peliowski, A., and Ryan, C. A. (1994). Inhaled nitric oxide in infants referred for extracorporeal membrane oxygenation Dose response. J. Pediatr. 124, 302-308. 

Figure 8.2 Auger electron peak intensities for Cr and O as a function of oxygen dose measured under UHV conditions [2].

The determining parameter in these curves is the oxygen dose, defined as the exposure time multiplied by the partial pressure. Its unit is the Langmuir L. One Langmuir represents one second of exposure to a partial pressure of 133 Pa (1 torr) 1... 

This equation describes the variation of coverage as a function of the oxygen dose. The maximum surface coverage is equal to 0o,max = Hct. 

Stages (I) and (II) are only observable for very low oxygen doses. As soon as the partial pressure becomes elevated, for example equivalent to that of the atmospheric pressure, the oxide layer covers the surface instantly and only the stage (III) remains measurable. The rate of oxide growth then determines the reaction kinetics. 

Figure 10.6 Effect of adsorbed oxygen on the friction coefficient between two tungsten surfaces variation of the friciton coefficient as a function of oxygen dose. Pressure = 3 x 10 Pa. Also shown is the variation of the surface coverage as a function of the oxygen dose [1].

Fig. 16. The spin polarization in the region of the gadolinium 4f levels of an 80 A thick film as a function of oxygen dosing. With increasing amounts of chemisorbed oxygen the overall net polarization is seen to decrease.

The influence of the potential on the susceptibility to stress corrosion cracking of sensitised (615 °C/10 h) filler materials made of Alloy 182 (67 Ni, 14.12 Cr, 7.44 Mn, 7.43 Fe, 0.41 Ti, 1.95 Nb) in high purity water with < 0.2 pS/cm, pH 6, at oxygen contents up to 200 mg/1 and 288 °C was examined [168]. Test methods included CERT tests and CBB (creviced bent beam) tests. The potential was adjusted using oxygen dosing, see Figure 27. 

Fig. 19. Influence of residual gases in the spectrometer chamber on the CeNi BIS spectrum. Spectrum (e) corresponds to maximum oxygen dose of 12L (IL = 10 Torr s).

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