Obscurants for Infrared Countermeasures III

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and ABSTRACT (Maximum 200 words)This report describes recent results in the search for an effective obscurant material. The goal is to identify a material that has an infrared extinction comparable to or greater than that of brass but without its toxicity or negative environmental impact. Eighteen new materials were selected based on their having promising bulk optical properties as well as favorable particle size distributions or packing densities. Laboratory measurements of extinction were carried out for the powders using the NRL apparatus in which the materials are entrained in a flowing gas stream such that the mass loading and infrared transmission are determined simultaneously.Carbon black was found to be the best obscurant material of the possible alternatives to brass investigated in this laboratory. Its volume extinction coefficient is lower than that of brass (by a factor of 2-3), but if the relative toxicities are taken into account, it may be a preferable obscurant material. EXECUTIVE SUMMARYMid-infrared obscurant materials are needed by the Navy as an important component in countermeasures to defend against heat-seeking, antiship missile (ASM) attack. There has been an ongoing effort to identify successful obscuring materials that not only exhibit extinction in the spectral regions of interest, the short (3-5 urn) and long (8-12 um) IR bands, respectively, but that also satisfy other criteria concerning toxicity, environmental impact, deployment capabilities, and availability. Brass exhibits favorable obscuration properties but it is also highly toxic and environmentally detrimental. This work is aimed at finding an infrared obscurant material with extinction comparable or superior to that of brass but without its toxicity and environmental effects.This report describes recent results from this laboratory in the ongoing search for a suitable infrared (IR) obscurant. New candidate materials were selected and then characterized by laboratory extinction measurements. The measurements were performed using the NRL apparatus in which dry powder samples are entrained into a flowing gas stream such that the sample mass loading can be determined and its extinction measured by Fourier transform infrared (FTIR) spectroscopy. Previous results in our effort toward finding a suitable obscurant to replace brass were reported previously in which the candidate obscurant materials boron nitride and boric acid were investigated and...

Infrared Extinction Properties of Nanostructured and Conventional Particles

“…And because of their relatively small packing density (< 0.8 g/cm 3 ), the numerical values of σ v were even smaller than those of σ m . This agrees with the experimental results of Owrutsky et al (2001); measured extinction coefficients of metal oxide particles, including titanium oxide, aluminum oxide and manganese oxide were relatively small. It should be noted, however, that NanoActive® TiO 2 had a relatively high σ m value in the 3-to 5-m waveband.…”

“…The reference particles (i.e., brass flakes, graphite flakes and carbon black) showed nearly constant values of σ m throughout the 3-to 12-μm wavelength range ( Figure 5), a trend similar to those observed in previous studies [Owrutsky et. al.…”

“…Owrutsky et al (2001) (Table 4). NaHCO 3 and ISO fine test dust had larger packing densities and larger σ v values than graphite and carbon black.…”

Tuning Molecular Vibrational Energy Flow within an Aromatic Scaffold via Anharmonic Coupling

“…19,21,24 VER have been studied both theoretically [25][26][27][28][29][30][31][32][33][34] and experimentally, where nonlinear techniques, such as IR pump Raman probe and 2D IR, have provided great insights into the rates of VER, direction of heat flow, and diffusive/ballistic transport. 19,21,[35][36][37][38][39][40][41][42] Despite the vast knowledge acquired from such studies, the overall process of VER still remains challenging to understand. The ambiguity in VER, in particular IVR, arises because the energy transfer occurs from one bright mode to another mode via multiple dark states.…”

Calculation of Infrared Mass Extinction Coefficients of Graphite Spheres and the Effects of Diesel Oil Coating

“…H.R.Carlon [1] showed that diesel oil can be changed into a white cloud that is particularly capable of shielding the visible light. J.C. Owrutsky etc [2] measured mass extinction coefficients of 18 candidates in both 3~5 μm and 8~12 μm bands and graphite is regarded as the best. However, it is difficult to attenuate effectively both visible and infrared radiation by using only one obscurant material.…”