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Title
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Surface and Environmental Effects on Ceramic Materials
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Description
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Polycrystalline sintered compacts of doped Alucer MC alumina have been deformed in three point beam loading from 1000° to 1350°C. The steady state creep rate of specimens doped with MgO or Mn(CO3)2 from 50ppm to 5000ppm by weight were fit to the expression A exp (-E/kT). The activation energy E was found to be 130 Kcal/Mole independent of added impurity. The constant A was independent of Mn(CO3)2, but decreased by a factor of 3-5 on the addition of MgO. It is suggested that polycrystalline creep is controlled by diffusion of vacancies in the steady state.Creep behavior of Linde corundum 0.1 inch diameter rods (1000°-1250°C) is described. At the lowest temperatures and stresses studied, measureable creep ( .1μ per hour beam deflection) began after about an hour's time delay, and increased at an accelerating rate. One run was successfully continued to reach a "steady state" (7500μ deflection). Activation energies increased as creep proceeded (71-135 Kcal/Mole). No mechanical effect could be attributed to flam polishing the samples.A study is described of the dispersal of impurities from a metal contact over the free surface of corundum at 10-4 mm Hg, by measuring the current flowing between two vacuum deposited films as a function of time, temperature (20-640°C), and applied field (0-12v.). At a given temperature, the current increases linearly with time. Heating to 640°C may increase the room temperature current by 4 orders of magnitude, although the current decreases with decreasing temperature. It is suggested that detaching Ag from the deposited film controls the rate of formation of a "semiconducting bridge" on or just beneath the corundum "free surface."
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Date
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1961
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Index Abstract
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Contrails and DTIC truncated
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Photo Quality
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Incomplete
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Report Number
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ASD TR 61-182
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Creator
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Gibbs, P.
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Baker, G. S.
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Dick, B. Gale
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Beauchamp, E. K.
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Miles, M. H.
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Rogers, W. G.
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Corporate Author
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University of Utah
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Laboratory
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Directorate of Materials and Processes
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Extent
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27
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Identifier
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AD0267247
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AD0267247
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Access Rights
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OTS
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Distribution Classification
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1
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Contract
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AF 33(616)-6832
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DoD Project
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7350
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DoD Task
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73500
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DTIC Record Exists
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Yes
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Distribution Change Authority Correspondence
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None
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Report Availability
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Full text available by request
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Date Issued
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1961-08
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Abstract
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Polycrystalline sintered compacts of doped Alucer MC alumina have been deformed in three point beam loading from 1000° to 1350°C. The steady state creep rate of specimens doped with MgO or Mn(CO3)2 from 50ppm to 5000ppm by weight were fit to the expression A exp (-E/kT). The activation energy E was found to be 130 Kcal/Mole independent of added impurity. The constant A was independent of Mn(CO3)2, but decreased by a factor of 3-5 on the addition of MgO. It is suggested that polycrystalline creep is controlled by diffusion of vacancies in the steady state.Creep behavior of Linde corundum 0.1 inch diameter rods (1000°-1250°C) is described. At the lowest temperatures and stresses studied, measureable creep ( .1μ per hour beam deflection) began after about an hour's time delay, and increased at an accelerating rate. One run was successfully continued to reach a "steady state" (7500μ deflection). Activation energies increased as creep proceeded (71-135 Kcal/Mole). No mechanical effect could be attributed to flam polishing the samples.A study is described of the dispersal of impurities from a metal contact over the free surface of corundum at 10-4 mm Hg, by measuring the current flowing between two vacuum deposited films as a function of time, temperature (20-640°C), and applied field (0-12v.). At a given temperature, the current increases linearly with time. Heating to 640°C may increase the room temperature current by 4 orders of magnitude, although the current decreases with decreasing temperature. It is suggested that detaching Ag from the deposited film controls the rate of formation of a "semiconducting bridge" on or just beneath the corundum "free surface."
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Publisher
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Wright-Patterson Air Force Base, OH : Aeronautical Systems Division, Air Force Systems Command, United States Air Force
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Type
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report
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Provenance
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Lockheed Martin Missiles & Fire Control
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Format
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v, 27 pages : ill. ; 28 cm.
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Subject
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Aluminum Compounds
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Ceramic Materials
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Corundum
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Creep
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Crystals
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Deformation
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Diffusion
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Voltage
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Electrical Conductivity
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Energy
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Failure (Mechanics)
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Films
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Finishes
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Flames
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Oxides
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Plastic Properties
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Silver Compounds
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Single Crystals
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Stresses
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Surface Properties
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Temperature
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Thermodynamics