Optimization of a High-Energy Ti–Al–B Nanopowder Fuel

Sonochemically generated reactive metal nanopowders containing Ti, Al, and B represent a new class of high-energy-density nanopowder fuels with superior energy content and air stability as compared to nano-aluminum. In this work, we optimize the energy density of a Ti–Al–B reactive metal nanopowder fuel by varying the Ti:Al:B ratios using a sonochemically mediated decomposition of a complex metal-hydride. After heating the recovered solids under vacuum to temperatures in the range between 150 to 300 °C, the powder's air stability is significantly improved so that it can be handled in air. Variable-temperature vacuum heat treatment was used to produce fuels tuned to be stable with a gravimetric energy density exceeding that of pure bulk Al (>31 kJ/g). The density of the powder was found to be 2.62 g/cm3 by helium pycnometry, which translates to an impressive volumetric energy content of 89 kJ/cm3. In poly(methyl methacrylate)-protected bomb calorimetry tests commercial nano-aluminum (SkySpring Nanomaterials, 20% oxide) only produced 25 kJ/g, while the sonochemically generated Ti–Al–B nanopowders released 24% more energy per unit mass and 19% more energy per unit volume in identical experiments.