Impact of MXene (Ti3C2) addition on ignition and combustion properties of boron particles

Abstract

Boron (B) offers high gravimetric and volumetric energy densities, making it an attractive solid fuel for energetic applications. However, boron is hard to ignite and burns slowly and incompletely due to the presence of surface B₂O₃, which has a low melting point but a high boiling temperature. Recently, a new class of two-dimensional materials known as MXene (Ti₃C₂) has emerged, exhibiting characteristics that could potentially enhance boron combustion, but this potential has not been previously explored. Herein, we experimentally investigate the ignition and combustion performance of boron particles, Ti₃C₂ nanosheets, and an 80 wt. % B/Ti₃C₂ mixture. We find that the addition of Ti₃C₂ nanosheets enhances both the ignition and combustion properties of boron particles. Specifically, Schlieren images of CO₂ laser ignition experiments show that the B/Ti₃C₂ mixture has a similar ignition delay time as Ti₃C₂ but is shorter than boron, and the mixture produces more gaseous products, indicating more oxidation. Bomb calorimetry measurements show that the B/Ti₃C₂ mixture’s heat of combustion is greater than the linear sum of its components, suggesting a favorable interaction between Ti₃C₂ and boron. Similarly, differential scanning calorimetry shows that the mixture releases more heat overall and has lower onset temperatures than pure boron oxidation. Variable-temperature X-ray diffraction analysis of B/Ti₃C₂ mixture shows the formation of anatase and rutile TiO₂, TiF₂, B₂O₃, and various mixed metal oxides at elevated temperatures due to reactions between boron and MXene or its oxidation products. In conclusion, these results demonstrate that Ti₃C₂ nanosheets, and potentially other MXenes, are effective additives for promoting boron combustion, leading to easier ignition and increased combustion efficiency.