Combustion Characteristics of Physically Mixed 40 nm Aluminum/Copper Oxide Nanothermites Using Laser Ignition

Abstract

This paper reports on the ignition and flame propagation characteristics of aluminum/copper oxide (Al/CuO) nanothermite at different packing density, manufactured from 40 nm commercial Al and CuO nanopowders. A 3.5 W continuous wave laser was used to ignite the samples in argon at atmospheric pressure, and a high speed camera captured the flame propagation. The high speed images revealed that the fast laser heating creates significant material ablation, followed by heat transfer along the heated surface. The bulk ignition occurs near the edge of the top surface, followed by the self-sustained burning. Lightly pressed powders (90% porosity) ignited in ~0.1 ms and the burning front propagated at around 200 m/s, while the dense pellets (40–60% porosity) ignited in ~1 ms and the burning front propagated at around 10 m/s. These results indicate that the reaction mechanism changes from mass convection to heat diffusion with increasing the packing density. The ignition and burn speeds of these Al/CuO nanothermites at different equivalence ratios (ERs), along with SEM images of pre- and post-combustion, illustrate that the homogeneity of the mixture is a critical parameter for optimizing the performance. The Al rich mixtures show significantly lower ignition delays and higher burn speeds.

Tunable kinetics of nanoaluminum and microaluminum powders reacting with water to produce hydrogen

“…Detailed physical and thermodynamic properties of the 40‐nm and 1‐μm Al powders can be found in Saceleanu et al and Saceleanu et al Figure A shows the thermogravimetric analysis (TGA)/DSC of the reaction between the 40‐nm Al powder and air at a constant heating rate of 30°C/min, and Figure B shows the particle size distribution of this powder. The Al nanopowder reacts in one exothermic step without melting due to its small particles ranging from 10 to 100 nm.…”

Influence of Heating Modes of Compacted Samples from Nickel Powders with Nanosized Particles on Their Interaction with Air

“…In [15], the features of flame propagation over tablets made from mixtures of Al/CuO nanopowders (the so-called nanothermites) were investigated depending on their density during the laser initiation of combus-…”

Time Delay of Initiation of some Primary Explosives and Initiating Mixtures when Exposed to Continuous IR Laser Radiation

“…There is very little data on the time delays of laser initiation of EM. Studies of the effect of continuous laser radiation on EM have also been conducted for many years using different laser sources [7–19] that generate radiation at different wavelengths: CO 2 lasers (10.6 μm) [14, 17]; Ar lasers (0.514 μm) [11, 15–18]; neodymium double‐frequency lasers (0.532 μm) [9]; semiconductor lasers (0.78 – 1.3 μm) [7, 8, 10, 11, 13, 15, 18, 19], etc. Of practical interest is the effect of continuous laser radiation at near‐IR wavelengths of 0.8–2 μm [7–11, 13, 15, 18, 19], since such laser sources are widely used, compact, have high energy characteristics, and their radiation can be transmitted over long distances via an optical fiber.…”

“…Nanothermites take a special place among EMs. Nanothermites are a new kind of pyrotechnic compositions, in which the metal fuel and oxidizer are mixed at the nanoscale level, which gives them greater burning rate and small critical dimensions of the reaction zone [16, 21, 22, 23]. They are offered as promising initiating mixtures to replace traditional PEs and EMs in various initiating devices.…”

“…They are offered as promising initiating mixtures to replace traditional PEs and EMs in various initiating devices. In [16], the initiation of aluminum/copper oxide (Al/CuO) nanothermite under the exposure of continuous Ar laser radiation (0.514 μm) with a power of 3.5 W at different porosity of samples was investigated. For a slightly compressed sample (90 % porosity), a time delay of 0.1 ms was obtained, and for a compressed sample (40–60 % porosity) –1 ms.…”