Improved rain erosion protection for multi-spectral ZnS

Shay Joseph; Orna Marcovitch; Ygal Yadin; Avi Steimberg; Hedva Zipin

doi:10.1117/12.603106

18 May 2005 Improved rain erosion protection for multi-spectral ZnS

Shay Joseph, Orna Marcovitch, Ygal Yadin, Avi Steimberg, Hedva Zipin

Proceedings Volume 5786, Window and Dome Technologies and Materials IX; (2005) https://doi.org/10.1117/12.603106
Event: Defense and Security, 2005, Orlando, Florida, United States

Abstract

Multi-spectral (WC)-ZnS has high transparency in a wide spectral range, from 0.4μm to 12μm. However, the relatively low hardness of WC-ZnS components limits their use especially for air-borne military systems where conditions such as particle or rain erosion may occur. In this work, a protective coating for WC-ZnS components was developed. The protective coating reduces damage caused by rain drop impacts without affecting the transparency of the uncoated component. An anti-reflective (AR) coating was evaporated over the protective coating to improve the transmission of the component. The microstructure of the protective coating was found to be of columnar grains, tens of nanometers in diameter. Rain erosion tests of the coated WC-ZnS samples conducted at the University of Dayton Research Institute (UDRI) whirling arm apparatus showed that they fully comply with the commonly accepted OCLI specification #6040012 for rain erosion resistant coating for forward looking infra-red (FLIR) grade ZnS. The damage threshold velocity (DTV), measured at the Cambridge University Multiple Impact Jet Apparatus (MIJA), increased from 120m/sec for an AR coated WC-ZnS sample to 178m/sec for a WC-ZnS sample coated with a 17μm protective coating and an AR coating. In this paper we show that the improved rain erosion protection was achieved without causing any change in the transparency of a WC-ZnS substrate. We also thoroughly discuss how the protective coating thickness and WC-ZnS sample thickness affect the damage caused by rain erosion.

Citation Download Citation

Shay Joseph, Orna Marcovitch, Ygal Yadin, Avi Steimberg, and Hedva Zipin "Improved rain erosion protection for multi-spectral ZnS", Proc. SPIE 5786, Window and Dome Technologies and Materials IX, (18 May 2005); https://doi.org/10.1117/12.603106

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