An Overview of Energetic
Materials Research at Purdue
University
S.F. Son
School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA
2
2
2
PurdueUniversity
•Landgrantschool
•38,000students(29,000UGs,9000
Grads)
•About600GradstudentsinME
3
3
FaciliFes:ZucrowLabs
•  70yearhistory
–  Solid,hybridandliquid
rockets
–  Jetengines
•  About$9M/yrresearch
expenditures
–  Rocketandair-breathing
propulsion
–  EnergeFcmaterials
–  Energy
•  About90current
students,15faculty
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4
MAURICE ZUCROW LABORATORIES
Chaffee Hall
Advanced Propulsion Lab
(ZL2)
Combustion Lab
(ZL1)
Propulsion Lab
(ZL4)
Storage
Bunker
High Pressure Lab
(ZL3)
5
3
HighPressureLabExpansion
•$8.2MExpansionandremodeling.
•ConstrucFontobeginearly2016.
•FeaturesfiveaddiFonaltestcells.
•Integratedlaserlab
6
AerospaceIndustrialResearchPark
•980-acreaerospaceresearchpark
approved
•Localrelatedsmallbusinessesinclude
INSpace(rocketpropulsion),Adranos(new
EMcompany),En’Urga(diagnosFcs)
•PRFplanstobuilda
44,000-square-foot
facilitywhereRollsRoycewilldevelopand
testjetengines
•AddiFonalspace
availableforothers.
7
OtherFaciliFes
•  BirckNanotechnologyCenter
–  186,000squarefeet,25,000sq.c.Class
1-10-100nanofabricaFoncleanroom
–  OpFcalPhotolithography(resoluFonto
~2µm)
–  Electron-BeamLithography(resoluFon
to~10nm)
–  ReacFveIonEtching(RIE)
–  Plasmaetching
•  HerrickLabs
–
–
–
–
–
NoiseandVibraFonControl
ElectromechanicalSystems
DiagnosFcsandPrognosFcs
EnergeFcmaterialsprinFng
20faculty
•  LaserDiagnosFcsLabs
–  Profs.BobLucht,TerryMeyer(arrived
thissummer),andChrisGoldstein(new
inMarch)
8
EnergeFcMaterialsTeam
•  CapabiliFesinexperiments(fabricaFonanddiagnosFcs),simulaFon(mulFple
scales),explosivesdetecFon,etc.
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
M.Koppes,DirectorofFireProtec:onEngineering-headofcountybombsquad
S.Meyer,ZucrowLabManager,tes:ng
S.Son,combusFonofEMs
hlps://www.purdue.edu/energeFcs/
R.Lucht,laserdiagnosFcsofpropellants
T.Meyer,laserandx-raydiagnosFcsofexplosives
W.Chen,highratemechanicsofEMsandxraydiagnosFcs
A.Varma,CombusFonsynthesis
A.Raman,AFM,dynamicsandvibraFonappliedtoEMs
J.Rhoads,Explosivessensing,thermomechanicsofEMs
G.Chiu,PrinFngofEMs
A.Strachan,atomisFcandmolecularsimulaFonsofEMs
M.Gonzales,mesoscalesimulaFonofEMs
M.Koslowski,mulFscalemodelingofEMs
S.Beaudoin,detecFonofexplosives(adhesionofexplosivesatthenanoscale)
B.Boudouris,advancepolymers
G.Cooks,ExplosivesdetecFon
C.Goldenstein(new),diode-basedlaserdiagnosFcsappliedtoEMs
9
MoleculestoApplicaFon
AFOSR,DHS,ARO,
ONR,DTRA,NASA,
&MDAfunding
Encapsulated
nanocatalysts
WindowedcombusFonvessel
PlusIndustrial
funding
Tailored Al
InsituhighspeedOHPLIF
10 µm
ExplosivesdetecFon
Novelnitrateester(SMX)
Hiringchemist!
Al=blue,F=red,C=green.
Tailoringingredients
&Propellants
Characterizingand
performingunique
dynamic
experiments
RocketmotortesFng
10
SomeCurrentProjects
Hypergolichybrids
Impactini:atedreac:ves
EnergylocalizaFon(hot-spots)inexplosives&detecFon
Coupledacous:candelectromagneFcenergyinsult
CharacterizaFonofenergeFccocrystals
Small-scaleCharacterizaFonofHomemadeExplosives
Core-shellreacFves
IntegraFonofprintedenerge:cmaterialsandMEMs
CharacterizaFonoffuelscontaininginsitugrownaluminum
nanoparFclesforramjets
•  Nanoscalepropellantingredients
•
•
•
•
•
•
•
•
•
–  HighspeedOHPLIF,modifiedmetalfuels,encapsulatedcatalysts
•  Explosivesdetec:on,includingadhesionofexplosives
•  Widecollabora:onswithEnerge:cMaterialsteam!
11
EXAMPLE:Real-TimeDynamicMeasurementsandCharacteriza:on
ofMesoscaleDeforma:onandTemperatureFieldsinReac:ng
Energe:cMaterialsunderImpactandPeriodicLoading
Research Program Areas
v  Mesostructure identification (Chen): 3-D Xray computed tomography determines initial
sample internal structures at the mesoscale.
v  Deformation field (Chen): Impact experiments
with high-speed X-ray imaging record in-situ
dynamic deformation at the mesoscale.
v  Property distribution (Rhoads/Son): Scanning
laser Doppler vibrometry and infrared
thermography characterize the dynamic
interactions that occur at the crystal/crystal and
crystal/binder interfaces.
v  Temperature distribution (Son/Meyer): Laserinduced phosphorescence methods and infrared
imaging measure the temperature field
evolution.
v  Micro-,Mesoscale modeling (Gonzalez/
Koslowski): A predictive modeling and
simulation capability is developed.
Research Team
Wayne
Chen
Marcial
Gonzalez
Jeff
Rhoads
Steve
Son
Marisol
Koslowski
Terry
Meyer
12
MulFscalepredicFvemodelingandsimulaFons
MarcialGonzalezandMarisolKoslowski
Mesoscalepredic:ngmodelingandsimula:on
•  MesoscalemulF-physicsmodelbased
onaparFclemechanicsapproach.
Themodelindividuallydescribeseachgrainin
•  Informedbyproposedlowerscalemodels.
•  Calibratedandvalidatedwithproposed
in-situexperimentalcapabiliFes.
FY15–Researchplan
•  Developmentof3Delasto-plasFccontact
lawsforgrain/grain,grain/binder,grain/wall,
andbinder/wallinterfaces.
•  StudyofweakshockpropagaFonfordifferent
mixturesfracFons,polydispercity,andimpact
velociFes.
•  Extensionofnonlocalcontactmechanics
formulaFonstoelasto-plasFcgrains.
polycrystalline
plasFcity
dislocaFondynamics
ProjecFlepressureandreacFonatbackandlateralwalls
thespecimenandthemulF-physicsisaccounted
bycomplexcontactmechanicslaws)
SIGEFF
5.5E+08
5.3E+08
5.1E+08
4.9E+08
4.7E+08
4.5E+08
4.3E+08
4.1E+08
3.9E+08
3.7E+08
3.5E+08
40kelasto-plasFcgrains
Phasefield
damagemodel
CrackpropagaFon
inpolymerbinder
Grainswith
largestcontact
forcesand
pressures
VolumeoccupiedbygrainsduringpropagaFonofaweakshock[%}
13
Real-:meDeforma:on,Damage,and
TemperatureMeasurements
Chen/Son/Meyers
v  Need for Real-time Visualization:
Impact deformation, damage evolution,
and temperature measurements are
critical physical quantities at meso-scale
to understand the response of energetic
materials but are currently unavailable.
v  Experimental Approach: We will
conduct impact experiments with highspeed X-ray imaging to record in-situ
dynamic deformation and damage at
mesoscale, and laser-induced
phosphorescence method and IR
imaging to measure the temperature
field evolution.
v  Expected Outcome: Meso-scale
measurements of time evolutions of
deformation field, damage status, and
temperature field.
(B)
(A)
355-nmLaser
Irradiation
ICMOS#2
Dynamic
Loading
EnergeticMaterial
Specimen
Synchrotron
X-ray
ICMOS#1
High-speed
OpticalCamera
X-rayPCIHighspeedCamera
14
Par:cle-ScaleThermomechanicalInterac:onsin
Energe:cMaterials
ProjectOverview:
JeffRhodesandSteveSon
•  Thethermomechanicsunderlyinghot-spotformaFonandgrowtharepoorly
understood.
•  Preliminaryexperimentalresults[1,2]havedemonstratedthathotspotscan
begeneratedlocally,evenbyweakperiodicexcitaFons.
•  ThepresenteffortseekstoaddressthefundamentalquesFonsof“Why?”
and“How?”hot-spotformaFontakesplace,throughajointanalyFcaland
experimentalstudy.
[1]Mares,etal.JournalofAppliedPhysics,2013.[2]Mares,etal.JournalofAppliedPhysics2014.
15
Example 2: Nanoscale Propellants MURI
Solid propellants are commonly used in
space launch vehicles and military missiles
§  The most common oxidizer (ammonium
perchlorate, AP) contains:
ü  54.5 wt.% oxygen
X  30.2 wt.% chlorine
As much as 98% of the chlorine is converted to
HCl (hydrochloric acid)
§  The most common fuel (aluminum) forms large
molten products (two phase flow losses)
§  Also, high surface area catalysts or metals
can lead to rheology and mechanical issues
§  Catalysts in binder accelerate aging too!
HCl Formation Issues
•  Corrodes the launch area
•  Deteriorates the ozone layer
Two-Phase Flow Losses
•  Molten particles agglomerate
•  Up to 10% loss in motor Isp
Image:hlp://commons.wikimedia.org/wiki/File:Peacekeeper_launch.jpg
1616
Approach:TailoredParFcles
•  EncapsulatedCatalysts: •  Alloysand“Inclusion
Fuels”
•  Catalystsocenusedin
solidpropellants
•  Anexampleofan
“inclusionfuel”is
•  Catalystsworkbest
aluminumwith
whenincontactwith
nanoscalefeaturesof
oxidizer
anothercomponent
–  So,let’sfabricate
catalystsINSIDEoxidizer •  AlloyssuchasAl-Liare
crystals!
alsobeingstudied
Wealsoneedimproveddiagnos:cs
17
17
PlanarLaser-InducedFluorescence
532nmpumplaser
Pressurevessel
310nmfluorescencecollected
at5kHz
283.2nmbeam
ExpandedtodiagnosFc
sheet
18
InSituFlameVisualizaFon
•  OHPLIFhas
recentlybeen
appliedinsituto
propellantsinour
group(BobLucht
collaborator)
•  Wecannowimage
theflame
structures!
A:Oxidizerreleasedintoafuel-richgasphase
B:RecessedAPburningfasterthansurrounding
mixture.Resultisliced,overvenFlatedflame. 19
CatalyzedPropellant
20
Metallized Fuels
§  Metals and metalloids have been widely used as neat
elemental fuels
§  Modifying and tuning the combustion characteristics of
these fuels remains challenging
§  Can modify reactivity through particle size reduction or surface
modification/functionalization (drawbacks)
§  Howonecanobtaintheadvantagesofnanoscalefuelswithoutthe
drawbacks?
Major Drawbacks to nanoscale and nanoporous materials
•  High Cost
•  Difficulty of synthesis (e.g., strong acids, scalability)
•  High specific surface area (SSA)
•  Processing issues (unfavorable rheology)
•  Rapid oxidation and aging
2121
Lessons from Liquid Microexplosive Liquids
§  Microexplosive liquid fuels have been
investigated since the early 1960’s
§  Mixtures of high/low volatility
constituents
§  The multicomponent fuels can be either
emulsions (oil/water, left) or missive
(heptane/hexadecane, bottom)
§  Has been shown to:
§  Promote fuel atomization
§  Reduce residence times
§  Increase completeness of
combustion
Images:Wang,C.H.,X.Q.Liu,andC.K.Law,Combus'onandmicroexplosionoffreelyfallingmul'componentdroplets.CombusFonandFlame,
1984.56(2):p.175-197.;Kadota,T.,etal.,MicroexplosionofanemulsiondropletduringLeidenfrostburning.ProceedingsoftheCombusFon
InsFtute,2007.31(2):p.2125-2131.
2222
Analogies to Metallized Microexplosive Fuels
Wehavebeenresearchingmicron-scalemetallizedfuel
par:cles/dropletscanhavesimilarproper:estoliquid
fueldropletsthatmicroexplode
Missive Fuels
•  Mechanical activation
(MA, ball milling) can create
composite particles with
nanometric inclusion
material (e.g., polymer)
•  Metal alloys can yield
particles that have
constituents mixed at the
molecular scale
Emulsion Fuels
Constituents
Nanocomposite Particle
New Phase
Solid Solution
RightImages:hlp://www.spaceflight.esa.int/impress/text/educaFon/Images/SolidificaFon/Intermetallics/Intermetallic%20versus%20alloy.jpg
2323
Mechanical Activation
§  Have been shown to:
§  Modify reactivity
§  Alter combustion products
(e.g., morphology, composition, etc.)
§  Affect the completeness of
combustion
Al
F
§  Micron-scale morphologies
(moderate SSA)
§  Can be tailored to achieve desired
material properties and combustion
characteristics
C
Inclusion materials can be
interacting or non-interacting
Imagesmodifiedfrom:Sippel,T.R.,S.F.Son,andL.J.Groven,ModifyingAluminumReac'vitywithPoly(CarbonMonofluoride)viaMechanical
Ac'va'on.PropellantsExplosivesPyrotechnics,2013.38(3):p.321-326.
2424
MA Powders – Solid Propellant
MA 70/30 Al/PTFE
MA Al/PTFE
Neat Aluminum
Neat Aluminum
Images:Sippel,T.R.,S.F.Son,andL.J.Groven,Aluminumagglomera'onreduc'oninacompositepropellantusingtailoredAl/PTFEpar'cles.
CombusFonandFlame,2013(0).
2525
Theoretical Calculations
Neat Al
80/20 Al-Li Alloy
Al2O3
AND
LiCl
Al2O3
Additive
Neat Al
Neat Li
80/20 Al-Li
Max ISP
[sec]
264.8
263.4
271.9
ΔhChamber-Exit Temperature
[K]
[kJ g-1]
3.4
3614
3.3
3204
3.6
3553
Molecular Weight Cl → HCl
[%]
[kg kmol-1]
27.9
98.3
27.3
1.8
26.2
1.9
2626
Al-Li Alloy: Theoretical Performance
High HPHS
•
•
Ideal: 16.9% Li (at 85% Solids Loading)
20% Li powder is ~stable and commercially available
2727
Alloy Powders – Solid Propellant (1000 fps)
26.80/61.48/11.72 Metal/AP/HTPB
Neat Al
80/20 Al-Li Alloy
Appears to be less coarse product
agglomeration from the Al-Li propellant
2828
Alloy Powders – Propellant Surface (9900 fps)
Neat Al
80/20 Al-Li Alloy
Aluminum sinters and
agglomerates on the
propellant surface
Al-Li forms a surface melt
layer, and the Al-Li droplets
appear to microexplode
2929
Alloy Powders – Shattering Microexplosion
The lithium boils within the molten Al-Li,
shattering the liquid droplets
AP Propellant
CO2 Laser in Air
(213 W cm-2)
3030
MA Powders – Microexplosion Mechanism
3131
MA Powders - Explosive Shock Ignition
Explosive Shock Ignition Experiment – MA 70/30 Al/PTFE
3232
Example3:Thermomechanics
•  Emphasisonpre-reac'onmechanicsinplasFc-
bondedexplosives
Elas:cBinder
Energe:cCrystals
Bulk-scale
(Low-frequency)
Par:cle-scale
(Highfrequency)
33
33
TheTakeaway
•  Atthebulk-scale:
–  Homogenizedmaterialmodelsappeartosuffice
–  Thethermomechanicsappeartobeclassical
–  Aginganddamageappeartodominatetheresponse
•  Atthepar'cle-scale:
–  DetailedparFcle-scalemodelsnecessary
–  Hot-spotthermomechanicsrelevant
–  WeakexcitaFonscanhavedramaFceffectsduetoenergy
concentra'on
34
34
Bulk-ScaleThermomechanics
•  Fabricatedsurrogatematerials
–  HTPB/NH4ClforHTPB/AP
–  VariedvolumefracFons
–  Variedgeometry
•  Excitedstructuralresonances
•  Measured
–  Mechanicalresponse
–  Thermalresponse
•  Correlatedresponses
35
35
ParFcle-ScaleThermomechanics
36
36
ParFcle-ScaleThermomechanics
PBX9501,215R
PBX9501,3400A
37
37
ParFcle-ScaleThermomechanics
PBX9501,215R
TwopotenFalpathwaystoheaFng?
Thehammerandthescalpel
PBX9501,3400A
38
38
ParFcle-ScaleThermomechanics
•  Sylgard184embeddedwithvariousenergeFcand
inertparFcles
–  4.0x6.7x9.0mm
–  ParFcles~1.0mmbeneathsurface
•  Piezoelectricultrasonictransducersepoxiedtoeach
sample
–  RadialexcitaFon
–  215kHzresonance
39
39
ParFcle-ScaleThermomechanics
210.39kHz
983.45kHz
40
40
ParFcle-ScaleThermomechanics
41
41
ParFcle-ScaleThermomechanics
AP(550-700μm)
sampleat10Walsof
suppliedelectrical
powerat215kHz.
TotalFmetoigniFon
~8seconds.
42
42
ParFcle-ScaleThermomechanicalInteracFons
43
43
Trace ExplosivesDetecFon
ResearchatPurdue
SteveBeaudoin
ProfessorofChemicalEngineering
AcademicDirector,TeachingandLearningTechnology
PurdueUniversity
WestLafayePe,IN47907
sbeaudoi@purdue.edu
44
Overall Goals
•  Measureadhesionbetweenexplosivesresidues
andrepresentaFvesubstrates
•  Modelobservedadhesion
•  QuanFfyeffects
•  ResidueandsubstratemechanicalproperFes
•  Residueandsubstratetopography
•  EnvironmentalcondiFons(humidity)
•  Relateadhesionbehaviortoresidueremoval
duringcontactsampling
•  OpFmizecomposiFonandstructureofswabs
•  OpFmizeswabbingprotocols
•  Developbenignsurrogatesforliveexplosives
45
Historical Model: Composite Deformation
Viscous effects
)*=​,​- ↓* ​.↓32 /​γcos⁠0 Surface effects
Peak flow stress
​"#$↑∗ =​1↓2 ​.↓32 /​γcos⁠0 Surface effects
​"#$↑∗ =​'↓1 +​'↓2 ​)*↑+ Iveson, S. M., & Page, N. W. (2004). Brittle to Plastic Transition in the Dynamic Mechanical Behavior of Partially Saturated Granular
Materials. Journal of Applied Mechanics, 71(4), 470–475.
46
Simulated Explosives
Dimensionless peak flow stress, (-)
106
105
)*=​viscous effects/surface e
104
103
​"#$↑∗ =​peak Alow stress/surfac
102
101
100
1.E-06 1.E-04 1.E-02 1.E+00 1.E+02 1.E+04 1.E+06
Behaviorconsistent
withexisFngtheory
Capillary number (-)
47
Viscosity of Explosives Binders
300
Semtex H
binder
150
0
0
20
40
60
Shear rate (1/s)
C-4 binder
80
100
2500
Viscosity (Pa*s)
Viscosity (Pa*s)
450
2000
1500
1000
500
0
0.0
2.5
5.0
7.5
10.0
Shear rate (1/s)
48
Deformation of Simulated Explosive
Stress(kPa)
7.5
5.0
2.5
0.0
0
0.1
0.2
0.3
0.4
0.5
Strain(-)
Stress-strain curve (with error regions) for silica particles (40-150mesh) in PDMS
(60 Pa·s viscosity) at 10mm/s compression rate. Axial images shown bottom and
left; diametrical are top and right.
49
Comparison to Live C-4
100mm/s
10mm/s
w
1mm/s
Stress-strain curves (with error regions) for live C-4 (left) and silica particles in
simulated C-4 binder (right) at 1mm/s, 10mm/s, and 100mm/s compression rates.
•  Shape of profile for simulant matches that of live material
•  Ongoing work: Vary particle size distribution in simulant to match magnitude of
stress response
50
Explosives Adhesion
AdhesionbetweenRDXandcoated
aluminumsubstrates
AdhesionbetweenTNTandcoated
aluminumsubstrates
51
Novel Swabs for Contact Sampling
10 µm
10 µm
10 µm
SEMimagesofpolypyrrolepillarsofvaryingaspectraFo.Thedimensionsofthe
pillarscanbeeasilytunedbychangingthephotolithographictemplate.
52
Acknowledgements
Circled:
•  Melissa Sweat
•
Dec. 2015
•  Aaron Harrison
•
Dec. 2015
Not pictured:
•  Johanna Smith
•
•
Grad. May 2014
Employed at General Mills
•  Andrew Parker
•
Grad. May 2016
•  Chris Browne
•
Grad. May 2017
•  Alyssa Bass
•
Grad. May 2017
This material is based upon work supported by the U.S. Department of Homeland Security, Science and Technology Directorate, Office of University Programs,
under Grant Award 2013-ST-061-ED0001. The views and conclusions contained in this document are those of the authors and should not be interpreted as
necessarily representing the official policies, either expressed or implied, of the U.S. Department of Homeland Security. [10/2013]
53
TheFuture?
•  Performance
–  Roomforimprovement-NOT
10x,probablynoteven5x
–  That’sOK–afewinchesof
extrareachcandeterminethe
outcomeofaboxingmatch
–  TailoredparFcles,tunability,
microenergeFcs,and
switchabilityalso
•  Sensi:vity
–  IHErequirementswillconFnue
todriveresearch
•  Lifecycle
–  Environmental&toxicitydrivers
–  AddiFvemanufacturing
–  Aging
54
54
AFOSR,DHS,ARO,
ONR,DTRA,NASA,
&MDAfunding
NSF,NDSEG,
SMART,NASA
Fellowships
55
QuesFons?
56
2
56