The phenomenon of a reaction, occurring in inorganic high energy density systems after it is stimulated by a shock wave, has been under investigation for a long time. The first experimental studies on the topic of chemical transformations in the inorganic substance under shock compression dated back to the late 1950s and a lot of work has been accomplished since. In this overview, we primarily consider reactive heterogeneous media that involves a powder mixture of the inorganic solid precursors, which, after mechanical stimulation, resulted in the synthesis of a new material. It is no doubt that such reactions can be initiated by sufficient mechanical impulse, but can they occur in the time scale of the high-pressure shock state? What mechanisms may be responsible for such rapid solid-state transformations? These and related questions are discussed based on the recent experimental findings.

1. Mechanical Stimulation of Gasless Reaction
in Inorganic Systems: overview
Alexander S. Mukasyan
Department of Chemical and Biomolecular Engineering, University of Notre Dame, USA

2. Outline
• Systems under investigation
• Developed Methods and Diagnostics
 High-Energy Ball Milling (HEBM)
 3D reconstructions: S&V/X-ray Tomography
 In-situ TEM Diffusion
 High-Temperature Kinetics (ETA)
• Fundamental Results: Solid Flame
• Discovery system
 Cubic BN
 Reaction Mechanism
 Recent Results
• Fundamental Results: Mechanically induced Reactions
• Conclusions
Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM)
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 Time-resolved X-Ray Diffraction (TRXRD)

3. Types of transformations in the inorganic
substance under shock compression
Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM)
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1. Powder Compaction
2. Decomposition of
inorganic chemical compounds
3. Defects Formation
4. Phase transformation
5. Shock Reaction Synthesis (SRS)

4. Systems Under Investigation
• Class of non-catalytic self-sustaining chemical reactions, which does not require oxygen and any other gas-
phase reactants, so-called gasless reactive systems. It is more important that while significant heat is
released during the reactions in such a system, the main product is a valuable solid-state material.
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Combustion
products (solid)
Combustion
Zone (solid)
Initial
reagents
(solid)
Thermal
Initiation
Mechanical
Stimulation
Solid State, Gasless Exchange Reaction
Adiabatic Combustion Temperature:
Tad = 1895 K
Tad << Tmelting (TiN, B, TiB2, BN)
TiN + 3B → BN + TiB2+ Q (85 kJ/mole)
Examples:
Ni + Al → NiAl + Q (117 kJ/mole)
Gasless Reaction
Adiabatic Combustion Temperature:
Tad = 1911 K
Tad = Tmelting (NiAl)
Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM)

5. Chemical Reactions and Shock Wave:
early studies
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Systems Method Conclusion Publication/Year
Ti + C, W + C, Al+ C Recovery From mixture of Ti and Carbon powders
TiC
Y. Horiguchi, and Y. Nomura, 1963
Bull. Chem. Soc. Jap., 36, 486
Cr + S; Cr + Se; Cr + Te Recovery Fabricated CrS had much lower densities
than the ordinary modification;
S. S. Batsanov, 1967
Inzh.-Fiz. Z., 12, 104-119
Al + Cu (3:1) Analysis of Shock adiabat Possible rapid massexchange in shock
wave
O.N. Breusov, 1977
Proc. IV All-Union Symp. Combust. Explos. 61–72
Al + Ni (1:3.5) Recovery XRD analysis: AlNi3 phase; reaction
initiation at hot regions
Y. Horie, R.A. Graham, I.K. Simonsen, 1985
Mater. Lett. 3 354–359
Sn + S Analysis of Shock adiabat Possible rapid mass exchange in SW due
to the difference in the mass velocities
S.S. Batsanov, et.al., 1986
Comb. Expl. Shock. Wave 22, 765–768
Nb + Liquid N2
Nb + Liquid CO2
Recovery XRD analysis: NbN; NbC G.A. Adadurov, 1986
Russ. Chem. Rev. 55 282–296
Al + Ni; Al + Ti Recovery. Modelling Yield depends on pressure : Ni3Al, NiAl,
sol-sol
R.A. Graham, et. al., 1986
Book: Shock Waves Condens. Matter, Springer. Boston, MA, 693–711
Ti + B; Nb + B Recovery. Modelling XRD and SEM: TiB2; NbB2; NbB H. A. Grebe, A. Advani, N. N. Thadhani, 1991
AIP Conference Proceedings 231, 501
Ti – Si; Nb - Si Recovery XRD: Ti5Si3; NiSI in air NOT in argon B.R. Kruger, A.H. Mutz, T. Vreeland Jr. 1992
Metall. Trans. 23A, 55–58
Al + Ni (1:2.6) Time-pressure profile.
Recovery:
EDS; AlNi3; reaction may occur in the
100 ns wide shock front
L.S. Bennett, et al., 1992
Appl. Phys. Lett. 61, 520–521
Al + Ni (1:3) Recovery. Modelling Influence of particle size and
morphology
N.N. Thadhani, et. al., 1992,
J. Mater. Res. 7, 1063–1075.

6. Experimental Configurations for SRS
6Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM)
Schematic diagram of the compression of a
substance in a cylindrical tube; 1)
metallic tube; 2) test substance; 3) and 4)
regions of single compression behind the
front of the incident and head SW; 5)
region of double compression behind the
front of the incident and reflected SW. The
dashed lines indicate the initial positions of
the explosive, the tube, and the specimen.
Schematic of the
Asay shear impact test
Standard shock synthesis equipment with plane
wave apparatus and the combination of different
steels for the sample recovery capsule which
avoids shock wave reflections from the top of the
sample holder piston along the release path.

7. Diagnostics
Hugoniot curves for various substances and
the corresponding shock-wave profiles
1) without transformations (Tr); 2) Tr with
increase in volume; 3) Tr with decrease in
volume; a) pressure profile in the shock wave
in the absence of Tr; b) Tr with increase in
volume; c) Tr with decrease in volume; d) Tr
with decrease in volume at sufficiently high
pressures.
Rankine - Hugoniot
Relationships
Schematic illustrating (a) P-V and (b) P-
Up Hugoniot curves for solid and porous
materials. Curves O'BA' and O'CA' are
for typical metal and ceramic powders
and Curve OA is for solid density
material.
Recover Capsule
Followed by product structural
characterization: XRD, SEM, TEM, EDS etc
Detecting:
(a) Phase transformation: evidence of
the reaction initiation by SW
(b) Synthesis of non-equilibrium phase:
evidence of the reaction occurring in SW
Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM) 7

8. Diagnostics
High-Speed
Micro Video Recording
Time-resolved
Temperature
Measurements
X-ray scattering (SAXS) and
Time-Resolved X-Ray diffraction
of synchrotron radiation
Time resolution 1 ns
Time resolution 1 msTime resolution 1 GHz
Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM) 8

9. Diagnostics
Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM) 8
Dana D. Dlott, Cite as: AIP Conference Proceedings 1793, 020001 (2017)
Shock Compression Dynamics Under a Microscope

10. Conceptual Mechanistic Model
The schematics of the conceptual model showing
the progress of the synthesis in three stages; the
initial configuration, the transition zone, and the
final compressed configuration, where the critical
region in the synthesis event takes place in the
transition zone
Graham
Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM) 9
CONMAH: CONfiguration change, Mixing, Activation, and Heating).

11. SRS Mechanisms
Roller Mechanism:
Shear Stress Plastic Flow
Two layers of the substance are displaced relative to
one another, the nuclei of phase A, located between
them, can be regarded as a kind of roller about which
oscillations are executed. Atoms which are passing in
the immediate vicinity of the nucleus have sufficient
time to combine with the latter forming the new
phase. Thus in contrast to the usual diffusional
growth of crystallization centers, in which each atom
must find its way to the new phase, pushing apart its
neighbors by virtue of the energy of thermal motion,
the formation of the new phase during shock
compression occurs by transport of the entire mass of
the initial phase, by plastic flow.
Supersonic martensitic (MT)
type of reaction waves
MT is a specific variant of the realization of
a polymorphic transformation associated
with a cooperative mechanism of atomic
displacements MT transition occurs upon
a significant deviation from the point of
equilibrium of the phases in an active
medium capable of liberating energy.
Nanoscale mechanisms of phase
Nucleation at plastic-strain-induced
defects.
Mechanically induced
Thermal Explosion
. The shock wave provides an ignition
source at localization centers (for
example, pore collapse). Such
phenomenon has been described as a
virtual combustion wave and is typical
of thermal explosions. The actions of
the stress wave on the material,
through pore collapse and plastic
deformation, heat and mix the material
until the requirements for reaction
initiation are met.
Ultra-fast Force
diffusion
The fluid-dynamic model of
ultrafast (forced) diffusion caused
by a difference in the particle
velocity of the components
in shock-compressed matter
Complete intermixing of particles
is achieved owing to penetration
of rapidly moving particles into
slowly moving particles.
Dremin, Breusov Batsanov Jette, Goroshin, ReevesAl'tshuler
Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM) 10

12. Chemical Reactions and Shock Wave: Ni-Al System
Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM) 5
Systems Method Conclusion Publication/Year
Al + Ni (1:3.5) Recovery XRD analysis: AlNi3 phase; reaction
initiation at hot regions
Horie Y., R. Graham, I.Simonsen, 1985
Mater. Lett. 3 354–359
Al + Ni (3:1) Analysis of Shock adiabat Influence of particle morphology Song, I. and N. Thadhani, 1992
Met. Trans. A, 23(1), 41-48
Al + Ni (3:1; 1:1;1:3) Recovery the chemical reactions in this system
are promoted by increased volume of Ni
Dunbar, E., N. Thadhani, R. Graham, 1993
Mater. Sci., 28, 2903-2914.
Al + Ni (1:2.6) Monitoring pressure The excess pressure is best explained as
an indicator of a fast exothermic
reaction during the shock loading.
Bennett, L., F. Sorrell, et al. 1992
Appl. Phys. Lett., 61(5), 520-521
Al + Ni (1:2.6) Monitoring pressure The excess pressure is best explained as
an indicator of a fast exothermic
reaction during the shock loading
Yang Y. et al. 1997
Appl. Phys. Lett., 70(25), 3365-3367
Al + Ni (1:1 volume) The Hugoniot
measurement
Influence of morphology; melting and
dissolution for spherical Ni; Shock
induced for Ni-flakes
Eakins, D.; Thadhani, N, 2006
J. Appl. Phys., 100, 113521
Al + Ni (1:1 volume) Recovery. Modelling Shock densification for different
morphologies
Eakins, D.; Thadhani, N., 2008
Appl. Phys. Lett. 2008, 92, 111903.
Al + Ni laminate Recovery Laser Shock Compression Wei C. et al., 2009
AIP Conference Proceedings 1195, 305
Al + Ni (1:1)
HEBM
High-speed video
recording, recovery
Asay Shaer impact test Reeves R. et al., 2010
J. Phys. Chem. C 2010, 114, 14772–14780

13. Chemical Reactions and Shock Wave: Ni-Al System
Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM) 5
Systems Method Conclusion Publication/Year
Al + Ni (1:1) Time-pressure profile.
Recovery:
Laser Shock Compression
Melting-dissolution mechanism
Wei C. et al., 2011
Acta Materialia 59 (2011) 5276–5287
Al + Ni (1:1) Recovery. Modelling Configuration effect Specht P., N. Thadhani, T. Weihs, 2012
JJOURNAL OF APPLIED PHYSICS 111, 073527
Al + Ni (1:1) Time-pressure profile.
Recovery:
Laser Shock Compression
Ni/Al laminates
Wei C. et al., 2012
Acta Materialia 60 3929–3942
Al + Ni (1:1)
HEBM
High-speed video
recording, recovery
Asay Shear impact test
Mechanically induced Explosion
Reeves R. et al., 2013
Propellants Explos. Pyrotech. 38, 611 – 621
Al + Ni (1:1) Pressure-time analysis Influence of additives, Cu, PTRE Wei. X et al., 2015
Journal of Alloys and Compounds 648, 540-549
Al + Ni (1:1) The Hugoniot
measurement and
modelling
Multilayered nano foils Kelly S. Thadhani, N, 2016
JOURNAL OF APPLIED PHYSICS 119, 095903
Al + Ni
laminate
The Hugoniot
measurement and
modelling
Shock densification for different
morphologies
Specht P., et,al 2017
JOURNAL OF APPLIED PHYSICS 121, 015110
Al + Ni (1:1) High-speed video
recording, recovery
Asay Shear impact test, role of fracture Beason M. , et al., 2017
Acta Materialia 133, 247-257
Al + Ni (2:1)
HEBM and nano foils
Time-pressure profile.
Recovery, modelling
Asay type of experiment
Influence of additives: oxides
Kerong R. et al., 2019
Metals 2019, 9, 499

14. SSR in Gasless Reaction in Ni + Al System:
Real time Studies
Schematic of Asay shear impact test. Figure (A)
shows the windowed sample holder Fig. (B) shows
the plunger and sample with the retaining plates
removed.
Gas gun constructed at Purdue University.
This gun has a 25.4 mm bore, 4.6 m barrel,
and has accelerated a 26 g projectile to 1 km/s

15. Shock Initiated Reaction: Ni + Al System
Sequence of images high speed video images from shear impact test
in nano-mixture exhibiting reaction
(impact velocity ~250m/s average combustion front velocity ~10cm/s).

16. Shock Induced Thermal Explosion Ni + Al System
Sequence of images high speed video images from shear impact test in nano-mixture
(the impact velocity ~1070 m/s average combustion front velocity ~1000 m/s)

17. Shock Induced Reaction in TiN- B System
XRD results for thermally and
mechanically initiated reactions
Mechanical InitiationThermal Initiation
(a)
(b) (c)
(a)Mechanically-induced
composite TiN/B (dark
phase – B; light phase TiN)
(b)Product of thermal initiation
of TiN/B (dark phase – BN;
light phase TiB2/TiN)
(c)Product of mechanical
initiation of TiN/B (dark
phase – B; light phase –
TiB2/TiN)
Initial Composite
Thermal Initiation Mechanical Initiation
1

18. TEM: c-BN Formation
(a) TEM images of typical particles formed in the
Ti-B-N system after shock. Relatively large
TiB2 and h-BN crystallites are dominant within
the field of view. The inset shows a magnified
TEM image of the surface area of the large
TiB2 crystallite (70–100 nm in diameter) that
has a layer of the c-BN phase.
(b) Magnified area of the c-BN crystal phase at
the interface with the TiB2 crystalline particle.
Intensity distribution on the magnified fragment of the HRTEM image of the c-BN phase in vertical (a) and
horizontal (b) directions showing that d-spacing in both directions are close to 0.18 nm.
1
Intensity
Intensity
Y, nm X, nm

19. Proposed Reaction Mechanism
TEM & SEM results revealed the formation of a nano-mixture of B and TiN surrounding unreacted B crystals.
Select Area Diffraction (SAD) patterns, EDS, and High Resolution TEM analysis of structural transformations
allow the suggestion of a simple two-step mechanism for reaction of TiN/3B. First, formation of TiB2 from the
finely mixed regions of TiN/B, followed by production of the BN phase.
1
Initial Quenched Thermally Initiated Shock Initiated
J. Physical Chemistry C, 123 (17) 11273-11283 (2019)
A mechanism for the
structural transformation
occurring at the boundary
between initially unreacted
B and TiN phases is
suggested based on
experimental observations
In the case of thermally
initiated reaction, near-
complete conversion to
product is observed. This
is likely due to prolonged
exposure to high
temperature conditions
For the shock-initiated
reaction, some micron
scale Boron crystals remain
unreacted and surrounded
by TiN. The short time
scales during which
conditions suitable for
reaction persist limit the
degree of conversion
B B
TiN/B
TiN
TiB2
BN
B
TiN/B/TiB2
TiB2
BN

20. Structural Transformations: HEBM TiN/3B
2
TEM TiB2 d-spacing (100) 2.62Å
B
B
Reaction
Layers
1 nm
2.60Å 2.60Å
TiB2
SEM Cross-section
Reaction
Layers
B
B
BN
TiB2
Shock-initiated - TEMQuenched Reaction -
TEM

21. 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90
0
200
400
600
800
1000
1200
1400
Intensity(counts)
2 Theta (degrees)
43.36o
50.53o
Shock-induced Synthesis:
B-GaN System
2

22. Solid Flame
Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM)
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A B
AB
d
D
𝒓 =
𝟏
𝜹
𝑭(𝑻, 𝜼)
𝒊𝒇 𝜹 = 𝟎 ↔ 𝒓 = ∞
𝒓 =
𝟏
𝜹 + 𝜹 𝟎
𝑭(𝑻, 𝜼)
𝒍𝒆𝒕 𝒖𝒔 𝒎𝒂𝒌𝒆 𝚫~𝜹 𝟎
𝒘𝒆 𝒎𝒂𝒚 𝒆𝒙𝒑𝒆𝒄𝒕 𝜼 = 𝟏 𝒕𝒉𝒓𝒐𝒖𝒈𝒉 𝒓𝒂𝒑𝒊𝒅
𝒈𝒓𝒂𝒊𝒏 𝒃𝒐𝒏𝒅𝒂𝒓𝒚 𝒅𝒊𝒇𝒇𝒖𝒔𝒊𝒐𝒏
𝑫𝒍𝒊𝒒𝒖𝒊𝒅 = 𝟏𝟎−𝟓
𝒄𝒎 𝟐
𝒔
𝑫 𝒔𝒐𝒍𝒊𝒅 = 𝟏𝟎−𝟗
𝒄𝒎 𝟐
𝒔
𝑫 𝒈𝒓𝒂𝒊𝒏 𝒃𝒐𝒖𝒏𝒅𝒂𝒓𝒚 = 𝟏𝟎−𝟓 − 𝟏𝟎−𝟔
𝒄𝒎 𝟐
𝒔

23. Conclusions
 Ultra-fast (0.1–5 ms) shock-induced reactions occurred in
the 3B-TiN system
 The results illustrate the possibility of rapid reactions
occurring in the solid state on incredibly short timescales.
 This process may provide a unique route for the discovery
and fabrication of advanced compounds.
 Fundamental questions to be resolved :
 What is the mechanism for ultra fast solid-state reactions under
the shock wave conditions?
 Can other metastable phases be produced under unique CS
conditions?
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24. Final Remarks
A long list of fundamental questions
remain re the physical nature of the
heterogeneous self-sustained reactions
Breakthrough hybrid concepts involving
self-sustained reactions make combustion
synthesis method extremely promising
specifically for fabrication of high
temperature and ultra high temperature
ceramics
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25. ACKNOWLEDGMENTS
 This work was supported by the Department of Energy, National Nuclear Security Administration , under
the Award No. DE- NA0 0 02377 as part of the Predictive Science Academic Alliance Program II.
24Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM)