Combustion of boron particles in products of an air–acetylene flame

Chintersingh, Kerri Lee; Nguyen, Quang Minh; Schoenitz, Mirko; Dreizin, Edward L.

doi:10.1016/j.combustflame.2016.07.014

Cited by 54 publications

(22 citation statements)

References 34 publications

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“…A [ms mm Àn ] n Al [10] 4.55 0.50 B [28] 4.73 0.75 Al · Ca(IO 3 ) 2 6.61 0.52 B · Ca(IO 3 ) 2 10.81 0.27…”

Section: Methodsunclassified

“…In this experiment, powders are aerosolized and fed through tubing into the flame. The setup has been described previously [24][25][26][27][28], and further details are given below. For a meaningful sizeburn time correlation, it was essential to describe the particles after they had passed through the particle feeding system of the burner, accounting for potential particle agglomeration or fragmentation.…”

Section: Particle Morphology and Sizesmentioning

confidence: 99%

“…For each material, SEM images of the same sample were taken at three different magnifications to capture both finer and coarser particles present in the materials. Particle size distributions obtained at different magnification were combined, following the methodology described in detail elsewhere [28]. Thus, particle size dis- tributions representing all particles present in the powder were obtained.…”

Section: Particle Morphology and Sizesmentioning

confidence: 99%

“…Assuming that larger particles burn longer, the distributions of pulse durations were correlated with the respective distributions of particle sizes ( Figure 2). This experimental technique and data processing methodology was extensively discussed in the literature [10,[24][25][26][27][28]32].…”

Section: Ignition and Combustion Experimentsmentioning

confidence: 99%

“…Based on correlation between statistical distribution of pulse durations and particle size distributions shown in Figure 2, particle combustion times as a function of their sizes were obtained and plotted in Figure 6. For comparison, data for pure aluminum [10] and boron particles [28] are also shown. Both reference data sets for pure elements were obtained using the same experimental methodology as in this work.…”

Section: Particle Combustionmentioning

confidence: 99%

See 4 more Smart Citations

Nanocomposite Thermites with Calcium Iodate Oxidizer

Wang

Liu

Schoenitz

et al. 2017

Prop., Explos., Pyrotech.

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Iodine bearing reactive materials and fuel additives are being developed to inactivate harmful aerosolized spores and bacteria by combined thermal and chemical effects. Nanocomposite thermites with aluminum and boron serving as fuels and calcium iodate as an oxidizer were prepared by arrested reactive milling. Both materials contained 80 wt % of calcium iodate. Morphology and particle sizes of the prepared materials were characterized using scanning electron microscopy (SEM). Both powders comprised particles finer than ca. 10 μm with fuel and oxidizer mixed on the submicrometer scale. Powders were exposed to room air to assess their stability. They were ignited as a thin coating on an electrically heated filament. Powders were injected in an air‐acetylene flame to observe combustion of individual particles. Pressed pellets for both prepared materials were prepared and ignited using a CO2 beam. Al ⋅ Ca(IO3)2 oxidizes rapidly in room air, whereas no aging was detected for B ⋅ Ca(IO3)2. Ignition of Al ⋅ Ca(IO3)2 occurs around 1150 K, after both aluminum and calcium iodate melt. Ignition is accompanied by ejection of sintered particles undergoing microexplosions while they are combusting. Ignition of B ⋅ Ca(IO3)2 occurs between 600 and 700 K, before either of the components melt. Combustion is accompanied by the formation of a luminous halo above the material, suggesting a vapor‐phase reaction involving boron suboxides. Longer ignition delays are observed for the pellets of Al ⋅ Ca(IO3)2 heated by the CO2 laser beam compared to similar pellets of B ⋅ Ca(IO3)2. Burn rates of B ⋅ Ca(IO3)2 pellets are nearly twice as fast as those of Al ⋅ Ca(IO3)2, primarily due to the lower ignition temperature for the boron‐based thermite. The flame temperatures obtained from the time‐integrated optical spectra are close to 2140 and 2060 K for Al ⋅ Ca(IO3)2 and B ⋅ Ca(IO3)2, respectively. Individual particles of B ⋅ Ca(IO3)2 injected into an air‐acetylene flame burn slower than similar Al ⋅ Ca(IO3)2 particles. Based on their better stability, lower ignition temperatures, shorter ignition delays, and longer burn times leading to a more gradual release of iodine, B ⋅ Ca(IO3)2 composites are suggested to be better suited as components of energetic formulations aimed to defeat stockpiles of biological weapons.

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“…A [ms mm Àn ] n Al [10] 4.55 0.50 B [28] 4.73 0.75 Al · Ca(IO 3 ) 2 6.61 0.52 B · Ca(IO 3 ) 2 10.81 0.27…”

Section: Methodsunclassified

Section: Particle Morphology and Sizesmentioning

confidence: 99%

Section: Particle Morphology and Sizesmentioning

confidence: 99%

Section: Ignition and Combustion Experimentsmentioning

confidence: 99%

Section: Particle Combustionmentioning

confidence: 99%

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Nanocomposite Thermites with Calcium Iodate Oxidizer

Wang

Liu

Schoenitz

et al. 2017

Prop., Explos., Pyrotech.

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Reactive Structural Materials: Preparation and Characterization

Hastings

Dreizin

2017

Adv Eng Mater

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Reactive structural materials, which can serve both as structural elements as well as a source of chemical energy released upon initiation have emerged as an important class of metal-based composites for use in various energetic systems. Such materials rely on a variety of exothermic reactions, from oxidation to formation of metal-metalloid and intermetallic phases. The rates of these reactions are as important as the energy that may be released, in order for them to occur at the time scales compatible with the requirements of applications. Therefore, chemical composition, scale at which reactive components are mixed, and the structure and morphology of materials are important and can be controlled by the method of preparation and compaction of the composite materials. Methods of preparation of the composite structures are briefly reviewed as well as methods of characterization of their mechanical and energetic properties. In addition to common thermo-analytical and static mechanical property measurements, dynamic tests of mechanical properties as well as ignition and combustion experiments are necessary to understand the fragmentation, initiation, and heat release expected for these materials when they are stimulated by an impact, shock, or rapid heating. Reaction mechanisms are studied presently for the thin layers and small samples of reactive materials initiated in carefully designed experiments. In other experiments, impact and explosive initiation are characterized for larger material compacts in the conditions imitating practical scenarios. Examples of results describing thermal, impact, and explosive initiation of some of the reactive materials are presented.

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Combustion of Magnesium‐Sulfur Composite Particles Ignited by Different Stimuli

Monk

Schoenitz

Dreizin

2018

Propellants Explo Pyrotec

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Composite Mg · S powders were prepared by mechanical milling. Magnesium powders coated with sulfur were prepared by soft milling using glass beads as milling media. Three-dimensional composite powders, in which magnesium and sulfur were mixed on the nanoscale were prepared by milling using steel balls as milling media. Both composite powders were explored in two ignition experiments. In one case, monolayers of the prepared powders were exposed to electrostatic discharge (ESD). In the other case, powder particles were fed through a focused CO 2 laser beam. In both experiments, emission traces produced by burning particles were captured using a filtered photomultiplier tube; the data were processed to recover respective combustion times. Combustion products were col-lected and examined using electron microscopy for the ESD-ignition experiments. It was found that the burn times of the sulfur coated magnesium powders were shorter than those of three-dimensional composites in both experiments. No effect of ignition method on burn times was observed for the sulfur-coated powders. For three-dimensional composite powder, burn times of ESD-ignited particles were shorter than those for particles ignited by passing through the CO 2 laser beam. Analysis of the captured combustion products suggests that magnesium and sulfur are readily separated upon heating for the coated powders, but not for the three-dimensional composites. For the latter case, the reaction is dominated by MgS formation, while for the former case, it is primarily magnesium oxidation in air.

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Combustion of boron particles in products of an air–acetylene flame

Cited by 54 publications

References 34 publications

Nanocomposite Thermites with Calcium Iodate Oxidizer

Nanocomposite Thermites with Calcium Iodate Oxidizer

Reactive Structural Materials: Preparation and Characterization

Combustion of Magnesium‐Sulfur Composite Particles Ignited by Different Stimuli

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