Combustion of sonochemically-generated Ti−Al−B nanopowders in a premixed methane/air dust flame.

Sonochemically-generated Ti−Al−B reactive mixed-metal nanopowders were tested by seeding them into a premixed, fuel-lean (Φ = 0.63), methane/air flame to investigate their combustion characteristics. Tests were conducted on powders with and without cryogenic milling. The attenuation of a diode laser beam was measured to calculate the time-resolved concentration of the powder in the flame. Radiant heat flux was measured with three gauges at different heights (1 cm, 6 cm, and 12 cm) along the axis of the flame. Flame spectra were collected to monitor chemiluminescence of intermediate species, and a multi-wavelength pyrometry method was applied to the spectra to calculate the temperature of the hot particulates in the flame. Commercially available metal powders were tested as a benchmark. These included micron-scale aluminum, nano-scale aluminum, micron-scale boron, and inert nano-scale alumina powders. The spectra from flames seeded with the sonochemically-generated Ti−Al−B powder show strong chemiluminescence from the BO 2 , an indicator of boron oxidation. Peak temperatures measured with flame pyrometry were approximately 2100 K, which is below the vaporization point of B 2 O 3 . The radiant heat flux from the seeded flame increased with concentration faster for the Ti−Al−B material than for any of the commercial powders, suggesting a greater gravimetric power density. Based on these results, the Ti−Al−B powders show promising combustion and heat-release characteristics, and therefore warrant further examination as a high-performance solid fuel. [ABSTRACT FROM AUTHOR]