Reactive and Metastable Nanomaterials Prepared by Mechanical Milling

Dreizin, Edward L.; Schoenitz, Mirko

doi:10.1002/9783527680696.ch10

Cited by 7 publications

(4 citation statements)

References 72 publications

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“…Mechanical, chemical, and mechano-chemical activation processes offer breakthrough opportunities for the development of new energetic composites [22][23][24][36][37][38][39][45][46][47][48]. The use of mechanical and mechano-chemical activation processes enables coupling ingredients featuring relatively low compatibility [24,45].…”

Section: Regression Rate Performance and Metal Additivesmentioning

confidence: 99%

“…The micrometric size, together with the particle morphology and the specific surface area (SSA) <1 m 2 /g, yields µAl high metal content (typically >95 wt.%), relatively low reactivity, and inherent safety (i.e., high ignition temperature, reduced dispersion in air, and limited aging influence) [28][29][30][31]. The reactivity of µAl can be enhanced by reducing the particle size down to the nanoscale [32][33][34][35] and by activation processes [23,24,[36][37][38][39]. Nano-sized Al is characterized by SSA~10 m 2 /g (or higher, depending on the average powder particle size and size distribution).…”

Section: Introductionmentioning

confidence: 99%

“…Activated Al powders typically feature reactivity tailoring of the starting material by chemical, mechanical, and mechano-chemical methods [22][23][24]. Activation techniques modify the powder surface characteristics (such as SSA and/or composition), and/or the particle morphology, size, and composition [22][23][24][36][37][38][45][46][47][48]. In particular, activation processes enable the creation of composite additives such as dual-metal [38,48] or metal-oxidizer compositions [45,48], offering wide possibilities for additive reactivity tailoring.…”

Section: Introductionmentioning

confidence: 99%

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Nano-Sized and Mechanically Activated Composites: Perspectives for Enhanced Mass Burning Rate in Aluminized Solid Fuels for Hybrid Rocket Propulsion

Paravan

2019

Aerospace

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This work provides a lab-scale investigation of the ballistics of solid fuel formulations based on hydroxyl-terminated polybutadiene and loaded with Al-based energetic additives. Tested metal-based fillers span from micron- to nano-sized powders and include oxidizer-containing fuel-rich composites. The latter are obtained by chemical and mechanical processes providing reduced diffusion distance between Al and the oxidizing species source. A thorough pre-burning characterization of the additives is performed. The combustion behaviors of the tested formulations are analyzed considering the solid fuel regression rate and the mass burning rate as the main parameters of interest. A non-metallized formulation is taken as baseline for the relative grading of the tested fuels. Instantaneous and time-average regression rate data are determined by an optical time-resolved technique. The ballistic responses of the fuels are analyzed together with high-speed visualizations of the regressing surface. The fuel formulation loaded with 10 wt.% nano-sized aluminum (ALEX-100) shows a mass burning rate enhancement over the baseline of 55% ± 11% for an oxygen mass flux of 325 ± 20 kg/(m2∙s), but this performance increase nearly disappears as combustion proceeds. Captured high-speed images of the regressing surface show the critical issue of aggregation affecting the ALEX-100-loaded formulation and hindering the metal combustion. The oxidizer-containing composite additives promote metal ignition and (partial) burning in the oxidizer-lean region of the reacting boundary layer. Fuels loaded with 10 wt.% fluoropolymer-coated nano-Al show mass burning rate enhancement over the baseline >40% for oxygen mass flux in the range 325 to 155 kg/(m2∙s). The regression rate data of the fuel composition loaded with nano-sized Al-ammonium perchlorate composite show similar results. In these formulations, the oxidizer content in the fuel grain is <2 wt.%, but it plays a key role in performance enhancement thanks to the reduced metal–oxidizer diffusion distance. Formulations loaded with mechanically activated ALEX-100–polytetrafluoroethylene composites show mass burning rate increases up to 140% ± 20% with metal mass fractions of 30%. This performance is achieved with the fluoropolymer mass fraction in the additive of 45%.

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Section: Regression Rate Performance and Metal Additivesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Nano-Sized and Mechanically Activated Composites: Perspectives for Enhanced Mass Burning Rate in Aluminized Solid Fuels for Hybrid Rocket Propulsion

Paravan

2019

Aerospace

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“…Due to the energetic materials community’s interest in improving energetics technology’s capabilities by increasing rates of reactions, in the past 20 years there has been significant research activity focused on the synthesis and passivation of various reactive metal particles and powders, reaching well into the nanometer-size regime . Research has primarily focused on the study of the combustion properties of either pure elemental powders that are commercially available, or the use of mechanical methods to produce composites in an attempt to improve their combustion properties. , A significant challenge to the usefulness of nanometer-scale reactive metal powder fuels is their generally high oxophilicity, meaning that smaller particle size also produces a greater surface area available to react with air. This in turn means particles of decreasing size are less air stable and require surface passivation.…”

Section: Introductionmentioning

confidence: 99%

Optimization of a High-Energy Ti–Al–B Nanopowder Fuel

et al. 2017

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Sonochemically generated reactive metal nanopowders containing Ti, Al, and B represent a new class of high-energy-density nanopowder fuels with superior energy content and air stability as compared to nano-aluminum. In this work, we optimize the energy density of a Ti–Al–B reactive metal nanopowder fuel by varying the Ti:Al:B ratios using a sonochemically mediated decomposition of a complex metal-hydride. After heating the recovered solids under vacuum to temperatures in the range between 150 to 300 °C, the powder’s air stability is significantly improved so that it can be handled in air. Variable-temperature vacuum heat treatment was used to produce fuels tuned to be stable with a gravimetric energy density exceeding that of pure bulk Al (>31 kJ/g). The density of the powder was found to be 2.62 g/cm3 by helium pycnometry, which translates to an impressive volumetric energy content of 89 kJ/cm3. In poly(methyl methacrylate)-protected bomb calorimetry tests commercial nano-aluminum (SkySpring Nanomaterials, 20% oxide) only produced 25 kJ/g, while the sonochemically generated Ti–Al–B nanopowders released 24% more energy per unit mass and 19% more energy per unit volume in identical experiments.

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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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Reactive and Metastable Nanomaterials Prepared by Mechanical Milling

Cited by 7 publications

References 72 publications

Nano-Sized and Mechanically Activated Composites: Perspectives for Enhanced Mass Burning Rate in Aluminized Solid Fuels for Hybrid Rocket Propulsion

Nano-Sized and Mechanically Activated Composites: Perspectives for Enhanced Mass Burning Rate in Aluminized Solid Fuels for Hybrid Rocket Propulsion

Optimization of a High-Energy Ti–Al–B Nanopowder Fuel

Reactive Structural Materials: Preparation and Characterization

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