Pre-burning Characterization of Nanosized Aluminum in Condensed Energetic Systems

Paravan, Christian; Maggi, F.; Dossi, Stefano; Marra, Gianluigi; Colombo, G.; Galfetti, L.

doi:10.1016/b978-0-12-802710-3.00013-1

Cited by 11 publications

(17 citation statements)

References 47 publications

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“…Air was considered at the stagnation temperature. The reduced active metal content of nanoaluminum was simulated by considering a 10 % mass of aluminum oxide, which is a reasonable assumption according to the literature on nAl characterization [23]. It should be noted that compositions AP50Al (0), AP50Al_base, and AP50Al (12) As expected, the increment of the A/P ratio provides a higher gravimetric specific impulse due to the incremented fraction of air used in the process.…”

Section: Ideal Specific Impulsementioning

confidence: 77%

Combustion of Nanoaluminum and Magnesium in Fuel‐Rich Propellants

Maggi

Zadra

2020

Propellants Explo Pyrotec

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Fuel-rich propellants are used in ducted rocket technology. The reduced content of oxidizer and the use of atmospheric air improve the gravimetric specific impulse far above the level of standard rocket motors, granting longer operating range. Peculiar requirements of ducted rockets favor either high or low-pressure exponent propellants, depending on the pressurization strategy of the gas generator. The introduction of metal additives further improves the volumetric specific impulse and plays in favor of system compactness but combustion is difficult due to the intrinsic lack of oxidizer. Agglomeration of metal and low burning rates are observed. In this paper, the combustion of a set of fuel-rich propellants with nanoaluminum and magnesium is investigated. The reported data set comprises ideal performance, burning rate, incipient agglomeration, and metal content of the agglomerates.

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Section: Ideal Specific Impulsementioning

confidence: 77%

Combustion of Nanoaluminum and Magnesium in Fuel‐Rich Propellants

Maggi

Zadra

2020

Propellants Explo Pyrotec

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“…Conventional Al powders feature micron-sized spherical particles [25]. The µAl is typically air-passivated, thus showing a core-shell particle structure with the metal core surrounded by an amorphous Al 2 O 3 layer [26][27][28].…”

Section: Introductionmentioning

confidence: 99%

“…Thus, special manufacturing procedures are typically implemented to disperse nAl in energetic compositions [41][42][43]. Moreover, the use of nano-sized particles is complicated by their effects on propellant/fuel slurry rheology [25,44], and stricter safety requirements than the micron-sized counterpart. Activated Al powders typically feature reactivity tailoring of the starting material by chemical, mechanical, and mechano-chemical methods [22][23][24].…”

Section: Introductionmentioning

confidence: 99%

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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“…These metal powders manifest en-hanced reactivity, assuring an increment of the SP burning rate [7]. Aluminum powders are naturally coated by a thin layer of oxide that has been evaluated in the range of about 3-5 nm [8][9][10][11]. According to literature evidences, its thickness is repeatedly independent of particle size.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the high specific surface area of nAl can introduce manufacturing issues due to the increment of mixing viscosity. [10,12].…”

Section: Introductionmentioning

confidence: 99%

Ignition of Mechanically Activated Aluminum Powders Doped with Metal Oxides

Dossi

Maggi

2019

Propellants Explo Pyrotec

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Use of mechanical milling to increase micrometric powder reactivity is of interest due to several intrinsic advantages of this technique (e. g. versatility and safety). In this work, 30 μm propulsion‐grade aluminum has been activated with and without metal oxides. The powders so obtained were characterized in terms of particle size distribution, metal content, morphology, and ignition temperature. This last parameter represents a good indicator to rate the reaction properties of powders and the effects of activation parameters on the final product. All the ingredients containing metal oxides feature an enhanced reactivity as a consequence of both additives and modification of particle morphology.

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Pre-burning Characterization of Nanosized Aluminum in Condensed Energetic Systems

Cited by 11 publications

References 47 publications

Combustion of Nanoaluminum and Magnesium in Fuel‐Rich Propellants

Combustion of Nanoaluminum and Magnesium in Fuel‐Rich Propellants

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

Ignition of Mechanically Activated Aluminum Powders Doped with Metal Oxides

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