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Proceedings Paper

Sand impact testing of durable coating on FLIR ZnS relevant to theLANTIRN E-O system window
Author(s): Ewan M. Waddell; Desmond R. Gibson; J. Meredith
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Paper Abstract

Measurements of the influence of sand/dust impact erosion on FLIR ZnS, coated with a range of durable coatings, have been made using spectral transmission. This activity has been carried out as part of a program to identify a sand/dust and rain erosion protective coating, for use on the Martin Marietta LANTIRN E-O system front element ZnS/ZnSe laminate window. Assessments have been carried out against MIL STD 810E sand/dust erosion specification, using the Defence Nuclear Agency sand erosion facility. A range of sand particle diameters (< 38 to 177 micrometers ), and velocities 45 to 206 m/s), has been investigated. Three anti- reflective durable coatings have been tested: thorium fluoride, diamond like carbon (DLC -- supplied from three separate vendors), and boron phosphide (BP) overcoated with DLC. BP/DLC showed no significant erosion damage or change in transmission for the range of test conditions, while DLC and ThF4 exhibited significant erosion damage and consequent transmission reduction. A basic theory of solid particle impact is used to model transmission reduction in relation to coating hardness, velocity, and size of impacting sand particles. The concept of `erosion parameter and threshold velocity' is introduced, which provides a means of predicting transmission reduction for a range of sand erosion conditions.

Paper Details

Date Published: 28 September 1994
PDF: 12 pages
Proc. SPIE 2286, Window and Dome Technologies and Materials IV, (28 September 1994); doi: 10.1117/12.187377
Show Author Affiliations
Ewan M. Waddell, Pilkington Optronics (United Kingdom)
Desmond R. Gibson, Pilkington Optronics (United Kingdom)
J. Meredith, Martin Marietta Corp. (United Kingdom)

Published in SPIE Proceedings Vol. 2286:
Window and Dome Technologies and Materials IV
Paul Klocek, Editor(s)

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