Surface and Environmental Effects on Ceramic Materials

Item

Title
Surface and Environmental Effects on Ceramic Materials
Description
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."
Date
1961
Index Abstract
Contrails and DTIC truncated
Photo Quality
Incomplete
Report Number
ASD TR 61-182
Creator
Gibbs, P.
Baker, G. S.
Dick, B. Gale
Beauchamp, E. K.
Miles, M. H.
Rogers, W. G.
Corporate Author
University of Utah
Laboratory
Directorate of Materials and Processes
Extent
27
Identifier
AD0267247
AD0267247
Access Rights
OTS
Distribution Classification
1
Contract
AF 33(616)-6832
DoD Project
7350
DoD Task
73500
DTIC Record Exists
Yes
Distribution Change Authority Correspondence
None
Report Availability
Full text available by request
Date Issued
1961-08
Abstract
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."
Publisher
Wright-Patterson Air Force Base, OH : Aeronautical Systems Division, Air Force Systems Command, United States Air Force
Type
report
Provenance
Lockheed Martin Missiles & Fire Control
Format
v, 27 pages : ill. ; 28 cm.
Subject
Aluminum Compounds
Ceramic Materials
Corundum
Creep
Crystals
Deformation
Diffusion
Voltage
Electrical Conductivity
Energy
Failure (Mechanics)
Films
Finishes
Flames
Oxides
Plastic Properties
Silver Compounds
Single Crystals
Stresses
Surface Properties
Temperature
Thermodynamics

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