Obscurants and Signature Management
Obscurants are aerosolized clouds of particles that have been designed to block or pass specific wavelength regimes in the visible and infrared regions of the spectrum. NanoComposix has extensive experience manufacturing, processing, drying, and characterizing the physical, chemical, and optical properties of aerosolized nanomaterials. Obscurant formulations that have large extinction cross sections and spectrally selective characteristics have been fabricated and fielded. In addition, we have developed methods to efficiently lyophilize,nanoparticle suspensions, novel mixing methods to incorporate various flow agents into powders, and optimized aerosol dispersion mechanisms.
Nanoengineering of Obscurant Properties
While many naturally occuring or manufactured aerosols can degrade visibility by scattering or absorbing light, nanoengineered particles are advantageous for obscurant applications due to the level of synthetic control available for tuning optical properties and dispersion. During fabrication, a number of parameters can be controlled, including
- Size: obscurant particles are typically most efficient when the major particle dimension is on the order of 1/3 to 1/2 of the wavelength of light being blocked
- Geometry: rod or disc morphologies are more efficient obscurants than spherical particles
- Surface: the surface energy of the particles can be tuned to prevent sintering and increase dispersion
A significant challenge working with nano- and micron-scale materials is the ability to pack and then separate the particles to form an effective screening cloud. By modifying the surface of the nanoparticles to reduce the surface energy, using a controlled drying process that circumvents capillary wicking, and incorporating flow agents, the dispersion of the obscurant powders can be maximized.
To characterize obscurants and aerosols, nanoComposix has validated a 2.5 cubic meter aerosol test chamber with a unique set of characterization tools including spectrometers, nephelometers, high speed video cameras, and sizing equipment. The chamber has been used to perform environmental studies, to test novel obscurant formulations, to optimize aerosols for drug delivery, and to characterize a wide variety of solid and liquid particles.
Available characterization techniques include
- Spectroscopy: Extinction and scattering measurements from 0.2–20 um using a series of overlapping spectrophotometers
- Particle size measurement: Particle sizes in the range of 10 nm–20 micron are measured using a TSI Particle sizer, an Aerodynamic Particle Sizer, and a Scanning Mobility Particle Sizer
- Aerosol mass concentration: Measurements made using a gravimetric filters
- Video: High speed cameras (1000 fps) can be used to analyze launch dynamics
For more information, please contact John Holecek.