The electron diffraction technique is used to study the structures of the oxides which form on the metals, titanium and zirconium, and on the alloys, 50 Ti-Ni, 70 Ti-Ni, 28 Ti-Cu, 20 Zr-Cu, 60 Zr-Co, and 70 Zr-Ni, in the temperature range 300°to 700°C.The structures found are plotted on existence diagrams as functions of time and temperature. Attempts are made to correlate the structures obtained with thermodynamic data reported by other workers. The oxides occurring on titanium and zirconium are titanium dioxide (rutile) and the monoclinic modi-THE determination of the structures of the surface oxides resulting from a gas-metal reaction is one of the important factors in understanding the mechanism of the reaction. If these determinations are carried out in a consistent and systematic manner in regard to time, temperature, and gas pressure, a good deal of information may be obtained concerning the relative importance of the formation and diffusion of the several metal ions or the formation and diffusion of the oxygen ion, atom, or molecule through the oxide film. In addition, it may be possible to check on the thermodynamic predictions of possible oxide structures formed on the metal or alloy as well as reactions between the oxides in the film.The authors (9, 11) have presented electron diffraction investigations of the oxides which form on iron, cobalt, nickel, chromium, copper, tungsten, and molybdenum. This communication reports a similar study on titanium and zirconium and their alloys with nickel, copper, and cobalt.Titanium and zirconium are reported (13) to react with hydrogen, nitrogen, and oxygen at elevated temperatures. Neither metal forms tarnish films in air and both metals are considered protective up to 500°C. The corrosion resistance of both metals
The oxidation process occurring on metals has been studied b y electron diffraction bnd electron microscopy, using oxide films stripped b y procedures suggested b y Evans and co-workers. The apparatus and techniques are briefly described. The metals studied include chromium, cobalt, copper, iron, molybdenum, nickel, aluminum, columbium, and tungsten. The electron micrographs and electron diffraction patterns are presented and discussed. The oxide films are rhown to consist of small oxide crystals ranging in size from 100 to ~S W A H E physical and chemical structure of the oxide films formed T on metals and alloys is of considerable interest in our understanding of their protective properties. The authors (10, 14) have studied the structure of the oxide films formed on metals and alloys by the reflection method of electron diffraction. These studies show that chemical and physical transformations occur during the formation and heating and cooling of the oxide film. Inasmuch as the reflection method samples only the outer surface of the film, the information obtained is incomplete. The bulk structure and composition may be considerably different from that on the outer surface. In addition, the nature and size of the crystals in the oxide film can only be approximated by the reflection technique.This paper presents electron microscope and electron diffraction evidence concerning the structure of electrochemically and chemically stripped films from a series of nine metals which had been oxidized under known conditions: iron, nickel, cobalt, chromium, molybdenum, tungsten, columbium, aluminum, and copper. ELECTRON MICROSCOPE TECHNIQUEThe use of the electron microscope for the study of the submicroscopic fine structure of matter is well known (1): Commercial instruments are available with a resolving power of less than 40 8. Thus, the shape of particles and the nature of the mosaic structure of a system of crystals may be approximated for particles of 150 8. or larger. The low penetrating power of 60-kv. electrons in matter limits its direct use to oxide films of the order of 500 8. in thickness. The preparation of such films requires the use of clectrochemical or chemical methods for stripping the oxide film from the metal. SURVEY OF THE LITERATURE STRIPPING OF FILM. The presence of a film on passive ironwas proved by Evans ( 4 ) who stripped films too thin to show interference colors from metals.His first method was based on electrochemical action, using the oxidized metal as the anode in order to dissolve the metal underlying the film. This method was applied to oxidized elcctrolytic iron, copper, and aluminum to secure films which were examined with the light microscope. The second method was based on direct chemical attack of the underlying metal by a saturated solution of iodine in 10% potassium iodide.Later Evans and Stockdale (5) extended and modified the electrochemical method to remove oxide films from iron, copper, nickel, carbon steel, and stainless steel. For removal of the film I Present address, Americ...
The secularization thesis is dead. There is no doubt whatever about that. Over years that have begun to stretch into decades, through the work of a diverse array of scholars-from Talal Asad, José Casanova, Saba Mahmood, and Charles Taylor, down to Americanists like Tracy Fessenden, Toni Wall Jaudon, Kathryn Lofton, John Modern, and Michael Warner-the notion that something called "secularization" provides an adequate conceptual framework for the post-Enlightenment movement of bodies and belief, of thought and authority, has come under sustained and multidimensional assault. We have become, as the term goes, postsecular, to the degree we understand those assaults to have been, finally, cumulatively, fatal. It's a fairly noncontroversial position at this point, as stated by Asad way back in 2003: "If anything is agreed upon, it is that a straightforward narrative of progress from the religious to the secular is no longer acceptable" (2003, 1). Disenchantment, a swing from superstition to rationality, credulity to skepticism, eschatological fanaticism to liberal tolerance: ours is a scholarly moment no longer persuaded by the clarities of these stories of modernity, nor by the neat dichotomies nested within them. So the secularization thesis is dead. This must be distinctly understood. To be clear, this sense of the postsecular does not carry with it a particular historical claim, as opposed to the desecularization narrative recently offered by the chastened secularization theorist Peter Berger
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.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.