Characterization of Aluminum Powders: II. Aluminum Nanopowders Passivated by Non‐Inert Coatings

Abstract

Results of DTA‐TG investigation and chemical analysis of electro‐exploded aluminum nanopowders, passivated and/or coated with the non‐inert reagents: nitrocellulose (NC), oleic acid (C17H33COOH) and stearic acid (C17H35COOH), which were suspended in kerosene and ethanol, amorphous boron, nickel, fluoropolymer, ethanol and air (for comparison), are discussed. Surface protection of aluminum nanopowders by coatings of different origin results in significant advantages in the energetic properties of the powders. Aluminum nanopowders with a protecting surface show increased stability to oxidation in nitrogen, air and in water during storage period. On the basis of the experimental results, a diagram of the formation and stabilization of the coatings is proposed. The kinetics of the interaction of aluminum nanopowders with nitrogen, air and water is discussed. Recommendations concerning the efficiency of non‐inert reagent passivation are proposed on the basis of comprehensive analysis of the experimental data.

Nanoaluminium: is there any Relationship between Powder Particles’ Size, Non-Isothermal Oxidation Data and Ballistics?

“…The formation of nano γ-Al 2 O 3 by slow non-isothermal oxidation (0.5-20.0 K/min) occurs at low temperatures (T = 673-773 K) for electroexplosive nAl [23]. Furthermore, the different definitions of the intense oxidation onset temperature and other parameters on the DTA/DSC/TGA curves can lead to confusing comparisons Copyright © 2017 Institute of Industrial Organic Chemistry, Poland between different datasets [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]. For certain nAl samples with a specific surface area 12 m 2 /g, the mass fraction of micron-sized particle clusters (1-3 µm) could be 68 wt.%, but the number of clusters was only 2% of the total number of particles [56].…”

“…Immediately after production, the nAl powders require passivation or coating procedures to avoid self-ignition and self-sintering of the particles [23][24][25][26][27]. nAl, obtained in inert gas media (argon, nitrogen or their mixtures) by any of the existing methods, is normally pyrophoric in air, because the amount and the rate of heat release from the oxidation reaction is high enough to heat the nanoparticle to its ignition temperature (~670 K for 100 nm nAl particles).…”

“…The TEM images reported in [23][24][25] show the typical structure of airpassivated nAl, with an Al core surrounded by an Al 2 O 3 shell. Fresh air-passivated nAl particles are usually characterized by Al 2 O 3 shell thicknesses in the range 2 nm to 6 nm, irrespective of particle size.…”

Aspekty nanomateriałów w zastosowaniach cywilnych i militarnych. Część 2. Wykorzystanie i obawy wynikające z ich uwalniania do środowiska przyrodniczego

“…Znajduje to odbicie w istotnym wzroście ich reaktywności chemicznej i temperatury produktów detonacji. Ponadto obserwuje się znaczne przyspieszenie osiągania stanu równowagi dystrybucji produktów ich rozkładu oraz polepszenie właściwości piroforycznych, co prowadzi do istotnego wzrostu efektywność ich działania [9,11,16,19,21,33,39,40,122,153,[156][157][158][159][160][161][162][163][164][165]; -termity (ang. thermites) określane też mianem termitów Goldschmidta lub mieszanin pirotechnicznych składających się z proszku określonego metalu spełniającego rolę reduktora zmieszanego w odpowiedniej proporcji z proszkiem właściwego tlenku metalu pełniącego rolę utleniacza oraz odpowiedniego paliwa, jako inicjatora reakcji.…”

Experimental study of thermal oxidation of nanoscale alloys of aluminium and zinc (nAlZn)

“…It is possible that the particles having similar metal content and/or similar diameters but behave differently in the oxidative environment. Four parameters, namely, the onset temperature (T on ), the temperature at which the maximum oxidation rate is achieved (T 01 ), the degree of oxidation (up to a certain temperature, and the specific heat release (H/m), have been proposed to compare the reactivity of different nanoparticles [32,33]. Table 6 shows an example of the comparison between nAlZn and nAl with an average particle size of ~210 nm.…”