Enhancing ignition and combustion of micron-sized aluminum by adding porous silicon

Micron-sized aluminum (Al), due to its large volumetric energy density, is an important fuel additive for broad propulsion and energetic applications. However, micron-sized Al particles are difficult to ignite and react slowly, leading to problems such as incomplete combustion and product agglomeration. Many pioneering strategies have been investigated to overcome the above challenges, ranging from reducing Al particles to nanoscale, coating them with metallic or polymeric materials, to blending Al with other materials to form composites. On the other hand, porous Si has emerged as a promising energetic material with a volumetric energy density comparable to Al, high reactivity at low temperature, and ultrafast flame propagation speeds. To date, the potential of using porous Si as an additive to enhance ignition and combustion of micron-sized Al has not been explored. Herein, we experimentally investigated the effect of porous Si addition on the ignition and combustion characteristics of micron-sized Al with CuO nanoparticles. We consistently observed that the addition of porous Si facilitates both ignition and combustion of Al/CuO mixtures over a wide range of experimental conditions, ranging from slow heating rate conditions in differential scanning calorimetry, fast heating rate conditions in Xe flash ignition, flame propagation in microchannels, to constant-volume pressure vessel experiments. The enhancement effects are attributed to the easy ignition and fast burning properties of porous Si, which elevate the ambient temperature and/or pressure, and hence enhance the ignition, reaction rate, and combustion efficiency of micron-sized Al particles. This work demonstrates that adding porous Si is another viable strategy toward enhancing the ignition and combustion properties of micron-sized Al particles.