Materials Science

Seeing sonic hot spots

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Science  01 May 2015:
Vol. 348, Issue 6234, pp. 537
DOI: 10.1126/science.348.6234.537-d

PTFE coatiing on an NaCl crystal degraded by ultrasonic heating

PHOTO: S. YOU ET AL, NATURE COMMUNICATIONS 6 (2 APRIL 2015) © NATURE PUBLISHING GROUP

Mechanical impact can detonate explosives, but how impact heats these materials to initiate reactions has been unclear. You et al. used mild ultrasound irradiation to study composite materials—small crystals of sucrose or table salt in rubber—while performing thermal imaging. Uncoated particles remained unheated, but particles that had a coating that could delaminate (a polyethylene glycol layer that liquefies or Teflon) heated very rapidly (up to ∼22,000 K per second). Delamination allows the particle to move and friction-heat against the matrix, an effect that authors also saw in samples of polymer-bonded explosive (PBX).

Nat. Commun. 10.1038/ncomms7581 (2015).

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