ChemInform Abstract: Spectroscopic Investigations of Porous and Sealed Anodic Alumina Films.

Abstract

ChemInform Abstract A broad range of surface and bulk analytical techniques, as XPS, RBS, SIMS, and XRD, are applied to Al specimens anodized in H2SO4 and similar specimens sealed in Ni-acetate and dichromate baths. All the films are amorphous in nature and contain C, significant amounts of H and 1.5-3 at.% S distributed uniformly throughout the oxide matrix. Surface enrichment of Ni and Cr species is observed for the sealed oxide films. This enrichment is of particular significance in the case of Ni. The uniform bulk concentrations of Ni and Cr are of the order of 0.5 and 1 at.%, respectively. The various species present in the films are identified as sulfate-like, Ni(OH)2, and dichromate-like in nature. As a result of ion beam-induced surface chemistry, incorporated Cr, Ni, S, and C are also present in lower oxidation states.

The effects of sealing on cracking tendency of anodic films on 2024 aluminum alloy after heating up to 300 °C

“…However, when anodic films were sealed in K 2 Cr 2 O 7 solution, the pores in the outer oxide layer stayed open and were filled with Cr 6+ [9], which may be considered as an "opening sealing process", in contrast to boiling water sealing or nickel fluoride sealing where the pores are plugged with oxides and hydroxides. It is generally accepted that the main sealing products formed in the pores are AlOHCrO 4 and AlOHCr 2 O 7 and nearly no boehmite is formed [1,9,14]. Therefore, the above results suggest that an opening sealing mode is beneficial to decrease the cracking tendency of anodic films during sealing and heating processes.…”

“…In dilute NiF 2 solutions the pores were sealed by the effects of both hydration and deposition of Ni 2+ . While in dilute dichromate solutions, there were nearly no hydration and the pores were mainly sealed by depositions of alkaline chromate and dichromate [11,14]. In this paper, the cracking mechanism and the effects of different sealing methods on the cracking behavior of anodic films on 2024 aluminum alloy were studied.…”

The Mechanism of Cathodic Disbonding of Hydroxy‐Terminated Polybutadiene on Steel from Acoustic Microscopy and Surface Energy Analysis

“…In addition to these methods, the simplest and the most convenient method is chemical deposition, which has been used to prepare a large number of semiconductor thin films such as PbS (1)(2)(3)(4)(5), PbSe (6), CdS (7), CdSe (6,8), ZnSe (9), Cdi =Pb=Se (10), Pb~_fl-IgxS (10,11), CdL_=Zn~S (10), and CdI_=Hg=S (11). For epitaxial growth, vapor phase epitaxy (VPE), molecular beam epitaxy (MBE), hot wall epitaxy (HWE), and metallorganic chemical vapor deposition (MOCVD) techniques have been used.…”

“…Wenzel (15) considered the contact angle for a rough surface, 0r, and that for a smooth surface, 0, to relate through an enhanced surface energy due to increased surface area in which case cos 0r = r cos 0 [4] where r is a roughness factor. This method for wetting tension measurement is often referred to as the Wilhelmy plate method and has been reported previously as a viable method for characterizing electrochemically governed wetting (8,9). Alternatively, the advancing contact angle for the rough surface can be modified by adding an angle am which accounts for steepness of the slope of surface features at the periphery of the wetting liquid (16) O r ~-0 -t-a m [5] Significantly, this latter analysis predicts hysteresis in the contact angles for rough surfaces in that the advancing contact angle exceeds the receding contact angle which equals 0 -am.…”