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Abstract
The use of boron as a high-energy fuel additive is generally compromised by the appearance of a strongly protective liquid oxide layer that covers the boron surface. The paper predicts that for ambient temperatures well below 1820 K this surface layer can be destabilized by the Marangoni effect, due to the peculiarity of boron oxide for which the Marangoni numbers are positive. To show the destabilization, a thin-film model is employed that allows the oxide flow field to be derived in the creeping-flow approximation. Ignition, assisted by a heat flow toward the particle, may then be caused by the Marangoni effect, which is shown to entail the spreading of punctures and ruptures in the oxide layer, leading to layer thinning or even complete layer removal. Since previous models of boron particles ignition insisted on conservation of symmetry, they were forced to expressly exclude the treatment of punctures and ruptures in the layer because their appearance constitutes an act of symmetry breaking.