High Modulus Coatings

Abstract

Mechanisms are explored by which the ultimate fracture strength of ZnS can be increased without degrading it's optical transparency in the bandpass of interest. Relatively thin films of Y203 could be used to strengthen substrates of ZnS. The observed strengthening effect was shown to be related to the intrinsic compressive stresses in the film. The magnitude of the strengthening is relatively independent of film thickness, deposition method (i. e. magnetron vs.ion beam sputtering) and even film composition, depending only on the sign of the film stress. For example, the strengthening effect was not observed in ZnS samples coated with evaporated YF3 films, wherein the intrinsic film stresses were found to be tensile. Ion assisted evaporation of the same material resulted in the creation of new compressive stresses and the substrate strengthening effect was again observed. In all cases the observed effect was found to be a 25-35% increase which is in agreement with a model wherein flaws originally residing at the surface of a brittle material like ZnS are internalized. (jhd)

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Document Details

Document Type
Technical Report
Publication Date
Oct 13, 1989
Accession Number
ADA215448

Entities

People

  • Randal W. Tustison

Organizations

  • RTX

Tags

Communities of Interest

  • Advanced Electronics

DTIC Thesaurus Topics

  • Coatings
  • Contracts
  • Diamond Films
  • Films
  • Ion Beams
  • Ions
  • Materials
  • Mechanical Properties
  • Military Research
  • Modulus Of Elasticity
  • Radio Frequency
  • Scientists
  • Substrates
  • Surface Chemistry
  • Surfaces
  • Test Facilities
  • Thin Films

Readers

  • Materials Science and Engineering.
  • Mechanical Engineering/Mechanics of Materials.
  • Nanofabrication and Microfabrication.