Fluctuation Microscopy Studies Of Aluminum Oxides Exposed To CL Ions

Abstract

Fluctuation electron microscopy studies have been performed on several aluminum oxides exposed to different electrochemical conditions. Little is known about amorphous aluminum oxide structures and their relationship with their passivation behaviors. Corrosion studies have shown that exposure of aluminum oxide films to Cl ions in solution reduces the oxide's passivity, and this results in the onset of pitting corrosion. The physical changes that occur in the oxide as a result of Cl exposure have not been previously identified due to the difficulty in investigating the structure of this amorphous material. Fluctuation microscopy is a new electron microscopy technique that is able to detect the presence of medium range order structures in amorphous systems. In this paper, we will report fluctuation microscopy results on amorphous aluminum oxides that have been exposed to Cl ions in solution and compare them with oxides that have seen no electrolyte exposure or that have been exposed to electrolytes that do not contain Cl-,such as SO42- containing electrolytes. We will also compare the Cl-exposed oxides with oxides that have been implanted with Cl ions. The differences in pitting behaviors for these oxidesare consistent with our previous speculation on the effect of medium range order on the passivation behavior of aluminum oxides grown using ozone.

Medium-Range Order in High Al-content Amorphous Alloys Measured by Fluctuation Electron Microscopy

“…Finally, to use this theory to extract Λ requires systematically varying Q done with VR FEM, usually involving a STEM 66,67,80 . The majority of FEM data gathered to date has been VC FEM using a TEM at fixed resolution 40,72,75,77,86,[88][89][90][91] which creates a need for a FEM theory that will extract more information about the sample structure from VC FEM data.…”

“…To date, FEM has shown fundamentally new medium-range structure information in several different amorphous systems. Initially FEM was used to study amorphous semiconductors 72,73,75 , but recently it has been used to study amorphous oxides 76,77 , amorphous carbon films 78 , and amorphous metals 40,79 .…”

Electron beam induced crystallization of amorphous Al-based alloys in the TEM

“…Initially, FEM was used to study amorphous semiconductors [10,15,16], but recently it has been used to study amorphous oxides [17,18], amorphous carbon films [19], and amorphous metals [9,20].…”

Understanding Fluctuation Microscopy - A Statistical Theory

“…There have been several attempts to directly address this question, quantitatively [2] and qualitatively [3]. Reference [2] used the kinematical theory of electron microscopy to link the variance to a pair persistence function and then introduced a special functional form based on a para-crystalline model.…”

“…Reference [2] used the kinematical theory of electron microscopy to link the variance to a pair persistence function and then introduced a special functional form based on a para-crystalline model. Reference [3] linked the peak position in the variance function to presence of subunit clusters. Based on the position, clusters were categorized.…”