Elemental boron has one of the highest volumetric heats of combustion known and is therefore of interest as a high energy density fuel. The fact that boron combustion is inherently a heterogeneous process makes rapid efficient combustion difficult. An obvious strategy is to increase the surface area/volume ratio by decreasing the particle size. This approach is limited by the fact that boron forms a ∼0.5 nm thick native oxide layer, which not only inhibits combustion, but also consumes an increasing fraction of the particle mass as the size is decreased. Another strategy might be to coat the boron particles with a material (e.g., catalyst) to enhance combustion of either the boron itself or of a hydrocarbon carrier fuel. We present a simple, scalable, one-step process for generating air-stable boron nanoparticles that are unoxidized, soluble in hydrocarbons, and coated with a combustion catalyst. Ball milling is used to produce ∼50 nm particles, protected against room temperature oxidation by oleic acid functionalization, and optionally coated with catalyst. Scanning and transmission electron microscopy and dynamic light scattering were used to investigate size distributions, with X-ray photoelectron spectroscopy to probe the boron surface chemistry.

Thermal breakdown and oxidation of JP-10 (exo-tetrahydrodicyclopentadiene, C 10 H 16 ), in the presence of nanoparticulate CeO 2 and Fe 2 O 3 , was studied in a small alumina flow-tube reactor on time scales around 1 ms. Decomposition products were analyzed by an in situ mass spectrometer. In the absence of any oxidizer, JP-10 pyrolyzes at temperatures above ∼900 K to a variety of hydrocarbon products. In the absence of O 2 , both CeO 2 and Fe 2 O 3 oxidize JP-10 efficiently, with decomposition onset temperatures up to 300 K lower than in a clean alumina flow tube under identical flow conditions and substantial conversion to products such as water, CO 2 , CO, and formaldehyde. Under such noncatalytic conditions, the CeO 2 or Fe 2 O 3 is reduced and deactivated by the reaction with JP-10. Decomposition of JP-10 in the presence of stoichiometric O 2 was also studied, with and without CeO 2 present. In absence of CeO 2 , some oxidation products are observed; however, the rate-limiting step appears to be pyrolysis of JP-10, and pyrolysis products dominate for temperatures up to 1200 K. When both O 2 and CeO 2 are present, oxidation is clearly catalytic; i.e., oxidation is initiated by the reaction of JP-10 with CeO 2 , which is then reoxidized by O 2 .

We report a study of collision-induced dissociation (CID) of H2CO+, including measurement of the effects of collision energy (Ecol) and five different H2CO+ vibrational modes on the CID integral and differential cross sections. CID was studied for collision with both Xe and Ne, and the Ne results provide a very detailed probe of energy transfer collisions leading to CID. The CID appearance threshold is found to depend only on total energy, but for all energies above threshold, vibrational energy is far more effective at driving CID than Ecol, with some mode-specificity. Results are fit with an impact parameter-based mechanism, and considerable insight is obtained into the origins of the Ecol and vibrational effects. A series of ab initio and RRKM calculations were also performed to help interpret the results.

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Here we describe a simple method to produce boron nanoparticles with control over surface chemistry and dispersiblity in different solvents, with potential applications ranging from high energy density fuels to neutron capture therapy. The methodology should be adaptable to many hard materials; indeed, we have produced hydrocarbon-dispersible silicon nanoparticles using a procedure similar to that described below. The method, based on high-energy milling, with subsequent sedimentation to separate aggregates, produces gram quantities of nanoparticles in a narrow distribution of particle sizes centered around 50 nm, and should be readily scalable to industrial scale production.