Anodic passivation of Type 316L stainless steel in a borate‐boric acid buffer solution was studied using cyclic voltammetry and Auger spectroscopy. Based on a comparison with the results obtained on the metals (iron, chromium, and nickel), the reduction peaks appearing in the voltammograms for the steel were attributed to the reductive dissolution of a ferric oxide and to valence transitions associated with chromium and nickel in the oxide. It is shown that cyclic voltammetry in the buffer solution provides a qualitative and semiquantitative analysis of the passive film growth. Okamoto's model of formation of two types of films, determined by the anodization potential, is found to be applicable; the mechanism of oxide growth is related to selective enrichment of iron or chromium, which is based on solubility relationships predicted by thermodynamic considerations.
The slow dehydration and dehydroxylation of porous Vycor glass was followed by infrared spectroscopic techniques. Two sharp bands at 3748 and 3703 cm-1 and also two shoulders near 3850 and 3650 cm-1 were observed. Dehydroxylation, deuteration, fluoridation, and adsorption experiments showed all absorptions to be due to surface hydroxyl species. The 3748-cm-1 absorption is due to free surface silanol groups. The 3650-cm-1 shoulder is due to OH vibrations perturbed by hydrogen bonding. The 3703-cm-1 band has a half-width of 5 to 14 cm-1 and can only be observed at relatively low surface coverage. Impregnation of silica and porous glass with boric acid produced a band at 3703 cm-1 with the silica and enhanced that found with the glass, leading to the assignment of the 3703-cm-1 band to a B-OH surface structure. The nature of the species responsible for the 3850-cm-1 shoulder is uncertain.CaF2 optics, mention the formation of a 30-cm-1 spaced doublet when porous glass was evacuated for 1 hr at 900°. They state that the nature of the second,(1) T.
Infrared spectra of NH3 sorbed on highly dehydroxylated, deuterated, and fluoridated porous glass were recorded. Two pairs of bands at 3409 and 3320 cm-1 and at 3330 and 3308 cm-1 were attributed to physically adsorbed NH3, hydrogen bonded to the SiOH and BOH groups of the glass surface, respectively. Bands at 3368 and 3282 cm-1 were ascribed to a =B-NH3 complex. Two pairs of bands at 3569 and 3479 cm-1 and at 3543 and 3459 cm-1 were ascribed to =BNH2 and =SiNH2 groups, respectively. A single band at 3455 cm-1 was tentatively assigned to the N-H stretching vibration of a secondary amine, the nitrogen atom being bonded to two surface boron atoms.There have been numerous reports dealing with the sorption of NH3 on porous glass.1-15 A variety of experimental techniques has been used and there seems to be a general agreement about the role of surface silanol groups as sites for a weakly bonded NH3 adsorption. A strong adsorption requiring sites other than silanols has also been reported. Folman and Yates suggested that the strong sites were silicon or oxygen atoms.1 2345However, Cant and Little pointed out that porous glass contained 3% B203 and stated that it was not impossible that strongly bound NH3 was adsorbed on electron-deficient surface boron atoms themselves.12 Chapman and Hair similarly concluded that strong NH3 adsorption occurred on (1) D.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.