Shock Compression Induced Hot Spots in Energetic Material Detected by Thermal Imaging Microscopy

Ming-Wei Chen, Sizhu You, Kenneth K. Suslick and Dana D. Dlott

6/17/2014

Introduction and Motivation (1)

pres

sure

time

P

“Show Highlights Science Behind Bat and Ball Collisions”, http://www.uml.edu/News/stories/2008-09/batlab_discovery_show.aspx

http://baseball.physics.illinois.edu/courtesy, Champaign News-Gazette and photographer Robin Scholtz, 2003

Introduction and Motivation (2)From a cold hammer to a fireball: How does it happen?

Cold EM

Mechanical Energy(Shock, impact, friction)

Warm EM

WithoutEnergy Concentrationprocess

No

deto

natio

n

WithEnergy Concentrationprocess

Exotherm

ic process

Loca

l hea

ting

http://www.bbc.co.uk/news/science-environment-11485672

Mechanical Energy

Chemical Energy

MWIR / Thermal Imaging

Sensor type: mercury cadmium telluride (MCT, >90% quantum efficiency)

Spectral response range: 3.7-4.8 µm.

Spatial resolution: <20 µm.

Frame speed: up to 120fps.

“Telescope orientation” “Microscope orientation”

High-speed MWIR camera

objective lenses

Object PC

Experimental Apparatus

Objective lens

High-speed MWIR camera

sample

glass

Al film glued on glassspacer

salt window

1064nm laser

8Al·MoO3

500μm

0 1000 2000 3000 4000 5000Bla

ck-b

ody

emis

sion

inte

nsity

(a.

u.)

Wavelength (nm)

Planck’s Law

1

125

2

TBkhc

e

hcTB

Visible NIR SWIR MWIR

Spectral response region of MWIR camera

0 1000 2000 3000 4000 5000Bla

ck-b

ody

emis

sion

inte

nsity

(a.

u.)

Wavelength (nm)

5273K 1273K 773K 673K 573K 473K 373K 273K

Shockwave Initiated Hot Spots in Thermite

IR image before experiment Thermal image taken during 200ns after impact

300K

717K

Salt window only

500μm

300K

729K

Shockwave Initiated Hot Spots in Sucrose

300K

745K

IR image before experiment Thermal image taken during 200ns after impact

300K

734K

500μm

Shockwave Initiated Hot Spots in Sucrose/HTPB

pellet

300K

685K

IR image before experiment Thermal image taken during 500ns after impact

500μmThickness ~100 μm

Shockwave Initiated Hot Spots in Sucrose/HTPB

pellet

300K

685K

IR image before experiment Thermal image taken during 500ns after impact

500μmThickness ~100 μm

Summary and Future Works

Summary Direct detection of hot spot initiated by shock impact appearing at around the

location of energetic particles has been demonstrated. Small explosive simulant (1-2mm dia. cross section) has been produced with

~100μm thickness, and tested with the experimental apparatus. Temperature rising rate is about the order of 109K/s within 200ns after impact.

Future Works Better thin sample preparation and fabrication procedure will be needed. Experiments with different composite materials, such as PBS, PBX. Varying

the size and density of particles to discover the energy localization under shock compression.

Acknowledgement• Dr. Dana D. Dlott• Dr. Kenneth S. Suslick• The Dlott research group• The Suslick research group• Funding:

– Office of Naval Research– Defense Threat Reduction Agency– National Science Foundation