Hot spots in energetic materials generated by infrared and ultrasound, detected by thermal imaging microscopy

Chen, Luyang; You, Sizhu; Suslick, Kenneth S.; Dlott, Dana D.

doi:10.1063/1.4864197

Cited by 48 publications

(41 citation statements)

References 29 publications

(35 reference statements)

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“…In the second, ultrasonic, frequency range, a viscoelastic heating effect is commonly cited, 6 wherein there exists significant correlation between surface temperature and surface velocity patterns within select frequency regimes. A second heating effect, centered upon embedded crystals, has also been observed in prior work by the authors 6,7 and others 8,9 at select ultrasonic frequencies. The latter effect exhibited little correlation between surface velocity and temperature patterns though, suggesting crystallevel frictional or stress concentration effects.…”

Section: Introductionsupporting

confidence: 54%

The impact of crystal morphology on the thermal responses of ultrasonically-excited energetic materials

Miller

Mares

Gunduz

et al. 2016

Journal of Applied Physics

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The ability to detect explosive materials may be significantly enhanced with local increases in vapor pressure caused by an elevation of the materials' temperature. Recently, ultrasonic excitation has been shown to generate heat within plastic-bonded energetic materials. To investigate the impact of crystal morphology on this heating, samples of elastic binder are implanted with single ammonium perchlorate crystals of two distinct shape groups. Contact piezoelectric transducers are then used to excite the samples at ultrasonic frequencies. The thermal responses of the crystals are recorded using infrared thermography, and the rate of heating is estimated. Surface temperature increases up to 15 °C are found to arise after 2 s of excitation, with much higher heating levels expected near the inclusions themselves as demonstrated by the chemical decomposition of some crystals under favorable excitation conditions. The rates of heat generation are compared to various crystal morphology features through 2D estimates of length scale, perimeter and irregularity. It is observed that crystals grown in the lab, featuring sharp geometric facets, exhibit a higher probability of significant heat generation than inclusions with more spherical shapes. However, no statistical link is found between the rates of heat generation and the crystal morphology in those samples that do generate significant heating, likely because variations in surface roughness cannot be entirely eliminated during experimentation. It is hoped that this study will lead to a better understanding of the nature of heat generation in energetic materials from ultrasonic sources.

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Section: Introductionsupporting

confidence: 54%

The impact of crystal morphology on the thermal responses of ultrasonically-excited energetic materials

Miller

Mares

Gunduz

et al. 2016

Journal of Applied Physics

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“…3). We have previously described the MWIR microscope for visualization of heating in solids during laser irradiation 28,29 .…”

Section: Resultsmentioning

confidence: 99%

Ultrasonic hammer produces hot spots in solids

et al. 2015

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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 B22,000 K s À 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.

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“…This explosion of bubbles leads to creation of a very high temperature or hotspots as well as a high pressure in the solution's environment, thereby resulting to intense turbulence in the fluid and the development of sheer force across the adsorbent's surface. This culminates in the development of large pores across the adsorbent surface [32,33].…”

Section: Resultsmentioning

confidence: 99%

Facile preparation of porous activated carbon under ultrasonic assistance for the Methylene blue removal from aqueous environment: characterization, isothermal, kinetic and thermodynamic studies

Eslami

Khosravi

Miri

et al. 2020

Mater. Res. Express

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Powdered Peganum Harmala activated carbon (PPAC) was synthesized by a new activation method using ultrasonic waves (with a frequency of 37 KHz for 1 h) after carbonization and application to remove methylene blue (MB) from aqueous solutions. In this experiment, the characteristics of the PPAC were examined through BET, FESEM, and FTIR spectrum. The effects of the initial pH (2-12), the adsorbent's dose (0.5-4 g L −1 ), reaction time (2-80 min), initial concentration of the dye (50-300 mg l −1 ), mixing rate (0-300 rpm), and the solution's temperature (10°C-50°C) in adsorption process were investigated. The results indicated that ultrasonic waves have the significant effect on the carbon activating process. BET analysis indicated that the specific surface area of PPAC before activation was 0.776 m 2 g −1 and had increased to 442.14 m 2 g −1 following activation by ultrasonic waves. FESEM images showed that significant elevation of the porosity level and development of numerous pores in the activated carbon. FTIR analysis indicates that following the activation, -OH groups have been developed onto the PPAC surfaces. The adsorption isotherms and kinetics were well fitted by the Freundlich and pseudo-second order model. Investigation of thermodynamic parameters indicated that adsorption process of MB by PPAC is spontaneous, endothermic, and physical.final concentration of methylene blue (mg l −1 ) C t MB concentrations at time t of reaction (mg l −1 ) k 1 pseudo-first order rate constant (1 min −1 ) k 2 pseudo-second order rate constant (mg (g min) −1 ) K f Freundlich adsorbent capacity (mg g −1 (l mg −1 )

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Hot spots in energetic materials generated by infrared and ultrasound, detected by thermal imaging microscopy

Cited by 48 publications

References 29 publications

The impact of crystal morphology on the thermal responses of ultrasonically-excited energetic materials

The impact of crystal morphology on the thermal responses of ultrasonically-excited energetic materials

Ultrasonic hammer produces hot spots in solids

Facile preparation of porous activated carbon under ultrasonic assistance for the Methylene blue removal from aqueous environment: characterization, isothermal, kinetic and thermodynamic studies

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