title: Ultrasonic hammer produces hot spots in solids.
abstract: Mechanical action can produce dramatic physical and mechanochemical effects when the energy is spatially or temporally concentrated. An important example of such phenomena in solids is the mechanical initiation of explosions, which has long been speculated to result from 'hot spot' generation at localized microstructures in the energetic material. Direct experimental evidence of such hot spots, however, is exceptionally limited; mechanisms for their generation are poorly understood and methods to control their locations remain elusive. Here we report the generation of intense, localized microscale hot spots in solid composites during mild ultrasonic irradiation, directly visualized by a thermal imaging microscope. These ultrasonic hot spots, with heating rates reaching ~22,000 K s(-1), nucleate exclusively at interfacial delamination sites in composite solids. Introducing specific delamination sites by surface modification of embedded components provides precise and reliable control of hot spot locations and permits microcontrol of the initiation of reactions in energetic materials including fuel/oxidizer explosives.
authors.affiliation: Chemical and Life Sciences Laboratory, Department of Chemistry, School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.
authors.forename: Sizhu
authors.initials: S
authors.lastname: You
authors.affiliation: Chemical and Life Sciences Laboratory, Department of Chemistry, School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.
authors.forename: Ming-Wei
authors.initials: MW
authors.lastname: Chen
authors.affiliation: Chemical and Life Sciences Laboratory, Department of Chemistry, School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.
authors.forename: Dana D
authors.initials: DD
authors.lastname: Dlott
authors.affiliation: Chemical and Life Sciences Laboratory, Department of Chemistry, School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Suslick