X-Ray Absorption Study of Electrochemically Grown Oxide Films on Al-Cr Sputtered Alloys I. Ex situ Studies

Oxides grown electrochemically in a borate buffer solution on the surface of sputter-deposited AlCr alloy films were studied by x-ray absorption near edge structure (XANES). The measurements were made in air immediately following polarization in solution. The oxides were also examined with x-ray photoelectron spectroscopy (XPS). The effects of alloy composition and thickness as well as applied potential were studied. Cr( VI) was found in the oxides if the applied potential was sufficiently high. The Cr(VI) was enriched at the interface with the electrolyte and the proportion of Cr(VI) in the oxide was higher for alloy films containing more Cr. The Cr(VI) in the oxides could be reversibly reduced to Cr(III) and reoxidized to Cr(VI) by subsequent potentiostatic treatments in solution.Research was carried out in part at the National Synchroton Light Source, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences. A. J. D. and H. S. I. were supported by the U.S. Department of Energy, Division of Materials Sciences, Office of Basic Energy Science under Contract No. DE-AC02-76CH00016

Corrosion and Passivation of Fe and FeN Films

The role of nitrogen in corrosion and passivation of thin Fe-N films was studied. Sputtered films with different levels of nitrogen were characterized for composition, conductivity, stress, and crystallinity. Corrosion and passivation of the films were evaluated by electrochemical measurements combined with in situ ellipsometry and ex situ x-ray photoelectron spectroscopy. The results indicate that in deaerated solutions the primary action of N is to reduce the catalytic activity of the surface for the hydrogen reaction and thereby reduce corrosion. In aerated solutions the corrosion rate increases with N content. Kinetics of the protective oxide formation as a function of potential, percent N, and the presence of borate buffer are discussed in detail. The work is relevant to the behavior of oxide-free Fe-N surfaces in contact with mild, nearly neutral electrolytes, such as could be used in fabrication of magnetic recording heads

Optimal triangulation in the presence of range errors

This paper is essentially a subset of the report NPS-53-84-0008 by I.B. Russak and A. A. Goldstein with modifications made to the proof of the optimal ity of the three dimensional triangulation. The problem of determining the location of a fixed point using range only data occurs in a variety of areas including military applications. An example is outlined below and formed the intcentive for the work herein. The application consisted of precisely locating hydrophones placed on a ship's hull for the purpose of receiving acoustic signals to be used in calculating torpedo positions during a test. In this paper a method is developed which under the assumption of fixed system error input (in range data) produces the smallest possible error in locating the hydrophones.Naval Postgraduate School, Monterey, CAhttp://archive.org/details/optimaltriangula00gol

An algorithm for noisy function minimization for use in determining optimal trajectories

This work concerns a technique to be used in the solution of optimal trajectory problems associated with kinetic energy weapons. In this problem, it is desired to solve for a control function (which might be thrust magnitude and direction of a gimbaled engine) in time in order to minimize time to intercept an enemy missile.Prepared for: Naval Postgraduate School, Monterey, CA.http://archive.org/details/algorithmfornois00russNAApproved for public release; distribution is unlimited