Surface Modified TiO2 Obscurants for Increased Safety and Performance

Abstract : Numerical modeling predicts titanium dioxide (TiO2) based obscurants could produce MECs that exceed 10 m2/g across the visible portion of the spectrum and gFOMs of 25 m2/cm3 if TiO2 particles with a narrow size distribution were fabricated and dispersed in a nonagglomerated format. Goal of this project was to develop a visible obscurant using low toxicity TiO2 particles that improves upon the performance of existing powder based visible obscurant grenades. This goal was achieved by chemically and physically improving the dry powder fill material in a TiO2 grenade and investigating new methods of disseminating TiO2 nanoparticles to reduce agglomeration when aerosolized. Several methods to synthesize TiO2 were developed and evaluated; one yielded discrete 184 nm diameter particles with an 18% CV. A variety of commercial TiO2 powders were also acquired, processed, and functionalized with surface chemistries designed to minimize surface adhesion and to optimize dissemination. A wide variety of surface modified TiO2 powders were packed at precisely controlled pressures into various container geometries. The best performing material was Tiona RCL-9 TiO2 (Cristal Global) coated in solution with cyclic azasilanes, lyophilized to remove the solvent without agglomerating the nanomaterials, compressing into a thin puck using a ram with 500 psi pressure, and pneumatically disseminating with a burst of 1000 psi air. Using this optimized approach, gFOMs of up to 4 m2/cm3 were obtained, compared to 0.6 m2/cm3 for the currently fielded M106 grenade (a factor of 6 improvement). Continued improvement in deagglomerating commercial powders followed by surface functionalization and effective dissemination has the potential to increase performance closer to the theoretical gFOM for TiO2 based smokes. If successful, such improvements would allow for the generation of a rapid, safe, and effective new class of obscuration devices that would exceed HC based obscurant devices in performance.