Amorphous boron nanoparticles were synthesized by heating a B2O3 + 3 Mg + kNaCl (k is the number of moles of NaCl) exothermic mixture in a laboratory oven at 800 degrees C under argon flow. NaCl was used as inert material to decrease the maximum combustion temperature of the reaction mixture when it was self-ignited after the melting of Mg at 650 degrees C. The size of the boron nanoparticles extracted from the final product by acid leaching ranged between 30 and 300 nm for k values ranging from 1 to 5. Moreover, increasing the value of k from 1 to 5 resulted in an increase in the specific surface area of the nanoparticles from 40 to 74 m(2) g(-1). However, at k = 10, a decrease in the specific surface area to 47.56 m(2) g(-1) was recorded due to incomplete reduction of B2O3. The ignition point of boron nanoparticles in air as estimated using a thermocouple was approximately 300 degrees C. Digital camera recording of the combustion process of boron nanoparticles in air revealed that the burning speed of the nanoparticles increased significantly from 0.3 to 15 cm/s when k increased from 1 to 5. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.