Improving aluminum particle reactivity by annealing and quenching treatments: Synchrotron X-ray diffraction analysis of strain

Abstract

In bulk material processing, annealing and quenching metals such as aluminum (Al) can relieve residual stress and improve mechanical properties. On a single particle level, affecting mechanical properties may also affect Al particle reactivity. This study examines the effect of annealing and quenching on the strain of Al particles and the corresponding reactivity of aluminum and copper oxide (CuO) composites. Micron-sized Al particles were annealed and quenched according to treatments designed to affect Al mechanical properties. Synchrotron X-ray diffraction (XRD) analysis of the particles reveals the thermal treatment increased the dilatational strain of the aluminum-core, alumina-shell particles. Flame propagation experiments also show thermal treatments effect reactivity when combined with CuO. An effective annealing/quenching treatment for increasing aluminum reactivity was identified. These results show that altering the mechanical properties of Al particles affects their reactivity. This manuscript focuses on synchrotron x-ray diffraction analysis of aluminum particles that have been treated to improve their mechanical properties. The aluminum is then examined for its reactivity with a metal oxide to show the relationship between material processing and the mechanical properties of the metal then extend this understanding towards application for energy generation technologies. We felt this combination of in-depth analysis of the material property of strain based on annealing and quenching processing of a metal powder and its application to reactivity were the perfect combination of mechanical and functional behavior appropriate for Acta Materialia. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 AbstractIn bulk material processing, annealing and quenching metals such as aluminum (Al) can relieve residual stress and improve mechanical properties. On a single particle level, affecting mechanical properties may also affect Al particle reactivity. This study examines the effect of annealing and quenching on the strain of Al particles and the corresponding reactivity of aluminum and copper oxide (CuO) composites. Micron-sized Al particles were annealed and quenched according to treatments designed to affect Al mechanical properties. Synchrotron Xray diffraction (XRD) analysis of the particles reveals the thermal treatment increased the dilatational strain of the aluminum-core, alumina-shell particles. Flame propagation experiments also show thermal treatments effect reactivity when combined with CuO. An effective annealing/quenching treatment for increasing aluminum reactivity was identified. These resultsshow that altering the mechanical properties of Al particles affects their reactivity.

A slice of an aluminum particle: Examining grains, strain and reactivity

“…The Al was then combined with CuO after thermal treatment to assess reactivity. They found that energy propagation for the 100 and 200 °C treatments did not significantly differ from the untreated case, but the 300 °C treatment showed an increase in energy propagation by 24% [20]. These findings were coupled with synchrotron X-ray diffraction (XRD) measurements to quantify particle strain.…”

“…To gain a better understanding of the effects of annealing µAl particles separately from annealing composites, McCollum et al subjected µAl to a variety of thermal treatments (100, 200 and 300 °C) with one quench rate [20]. The Al was then combined with CuO after thermal treatment to assess reactivity.…”

Stress relaxation in pre-stressed aluminum core–shell particles: X-ray diffraction study, modeling, and improved reactivity

“…Particle size response to annealing and quenching treatment is characterized in [15,16] showing no significant deviation in average particle diameter with annealing and quenching treatment.…”

“…We have detailed the use of this instrumentation for strain measurements on thermally treated Al particles in our previous work [15,16] but the method is summarized here for completeness. Aluminum powder samples were spread over glass slides and scanned under the x-ray beam (either polychromatic or monochromatic) while a diffraction pattern was collected at each step using a DECTRIS Pilatus 1 M detector.…”

“…Figure 1 illustrates a typical powder filled tube arrangement for measuring flame speed as well as representative still frame images of flame propagation. The apparatus and procedure are described in more detail elsewhere [13,14,16,19] …”