Solid Flame:
Fundamentals and
Applications
Combustion: Definitions
• an act or instance of burning
• a usually rapid chemical process (as oxidation)
that produces heat and usually light;
• also : a slower oxidation (as in the body)
• a chemical process in which a substance
reacts vigorously with oxygen to produce heat
and light, seen as a flame
• the burning of fuel in an engine
to provide power
Combustion or burning is a complex sequence of exothermic chemical reactions
between a fuel and an oxidant accompanied by the production of heat or both heat
and light in the form of either a glow or flames.
A simpler example can be seen in the combustion of hydrogen and oxygen,
which is a commonly used reaction in rocket engines:
2H2 + O2 → 2H2O + heat
The result is simply water vapor.
The Phenomenon of Wave Localization
for Solid State Self-propagating Reactions:
SOLID FLAME
A.G. Merzhanov, V.M. Shkiro, I.P. Borovinskaya, 1967
Combustion
products (solid)
Combustion zone
(solid)
Ta + C  ½ Ta2C + ½ C +Q1  TaC + Q2
Tad = 2730 K, Tm =3100 K
Initial reagents
(solid)
ignition
front propagation
cooling
Tantalum - Graphite System
Physical Properties
Tantalum
Physical Properties
Graphite
Atomic Number
180.95
Atomic Number
12.0
Density
16.6 g/cc
Density
2.27 g/cc
Melting Point
3290 K, 2996°C
Melting Point
4300 K, 4027°C
Boiling Point
5731 K, 6100°C
Boiling Point
4000 K, 3727°C
Thermal Conductivity (20°C)
57.8 Wm-1K -1
Thermal Conductivity (20°C)
1-2 103 Wm-1K -1
Thermal diffusivity
0.2 cm2/s
Thermal diffusivity
0.5-1.3 cm2/s
Heat of fusion
37
Heat of fusion
100 kJmol-1
Heat of vaporization
733 kJmol-1
Heat of vaporization
355kLmol-1
kJmol-1
2-5 mm
0.1-1 mm
Thermodynamic Considerations
Temperature, C
Volume of gas products
Ta
Concentration, at %
C
(liters)
0.0000
Pressure of gas products (atm)
1.0000
Temperature
(K)
2744
Gas products amount
(mol)
6.00E-15
Products heat capacity
(J/K)
74.30
Products entropy
(J/K)
161.2
Products enthalpy
(KJ)
0.677
Ta1C 1
(S)
1.0000
Ta + C = TaC + Q
Q=144 kJ/mol
Tantalum carbide (TaC) is an extremely hard refractory (3880°C; 4153 K) ceramic material,
commercially used in tool bits for cutting tools.
It is a heavy, brown powder usually processed by sintering.
Tantalum carbide-graphite composite material, developed in Los Alamos National Laboratory,
is one of the hardest materials ever synthesized.
“Solid Flame”:
Ta + C - Recent Advances (2011)
Nano-Structure of Composite Ta-C particle
Ta + C
Initial
Comparison of XRD patterns for Ta-C system
before (a) and after (b) HEBM
Reaction Front Propagation in Ta-C
Heterogeneous System
TECHNOLOGY FOR MATERIAL
SYNTHESIS:
Self-propagating High-temperature
Synthesis (SHS)
Or Combustion Synthesis
Gasless Combustion Systems
n
m
(s )
( s ,l )
X

P
 i  j  Q,
i 1
j1
Adiabatic
Comb.
Temp.
Tcad, K
Measured
Comb.
Temp.
Tc, K
Lowest
Melting Point
Phase
Diagram,
K
3290
1690
1690
2550
3070
3000
3295 (Ta)
1921 (eut)
1690 (Si)
Borides
Ta + B
Ti+2B
Ti + B
2728
3193
2460
2700
3190
2500
2365 (B)
1810 (eut)
1810 (eut)
Silicides
Mo + 2Si
Ti + 2Si
5Ti + 3Si
1925
1773
2403
1920
1770
2350
1673 (eut)
1600 (eut)
1600 (eut)
Intermetallics
Ni + Al
3Ni + Al
Ti + Al
Ti + Ni
Ti + Fe
1912
1586
1517
1418
1042
1900
1600
n/a
n/a
n/a
921 (eut)
921 (eut)
933 (Al)
1215 (eut)
1358 (eut)
System
Carbides
Ta + C
Ti + C
Si + C
Ti + C + Ni = TiC + Ni
+ 230 kJ/mol.
Gas-Solid Combustion Systems
n p

i 1
p
X i( s ) 

i 1
m
Yi( g ) 

Pj( s,l )  Q,
j 1
System
Nitrides†
2Ta + N2
2Nb + N2
2Ti + N2
2Al + N2
3Si + 2N2
2B + N2
Adiabatic
Comb.
Temp.
Tcad, K
3165
3322
3446
3639
2430
3437
Measured
Comb.
Temp.
Tc, K
2500
2800
2700
2300
2250
2600
Lowest
Melting Point
Phase
Diagram,
K
3000 (Ta)
2673 (NbN)
1943 (Ti)
933 (Al)
1690 (Si)
2350 (B)
Ti(s) + 0.5N2(g) = TiN(s) + 335 kJ/mol,
3Si(s) + 2N2(g) = Si3N4(s) + 750 kJ/mol.
Reduction Combustion Systems
nq  r
r
q
m k
k
i 1
i 1
i 1
j1
j1
( s)
( s)
( s)
( s, l )
( s,l )
(
MO
)

Z

X

P

(
ZO
)

 i  i  j  y j  Q,
x i
System
B2O3 + Mg
B2O3 + Mg + C
B2O3 + Mg + N2
SiO2 + Mg
SiO2 + Mg + C
La2O3 + Mg +B2O3
Adiabatic
Comb.
Temp.
Tcad, K
2530
2400
2830
2250
2400
n/a
Measured
Comb.
Temp.
Tc, K
2420
2270
2700
2200
2330
2400
Lowest
Melting Point
Phase
Diagram,
K
1415 (eut)
n/a
n/a
1816 (eut)
n/a
n/a
B2O3(s) + 2Al(s) + Ti(s) = Al2O3(l) + TiB2(s,l) + 700 kJ/mol,
Diamond - Intermetallics
Composites
Gasless Combustion to
Produce Advanced Materials
CS-PRODUCTS: Cermets
Self-Sustained Gasless
Heterogeneous Reactions:
Fundamentals
Characteristic Structure of
Combustion Wave
Dynamic Methods
for Rapid Heterogeneous
High-Temperature Reactions
Quasi-homogeneous Model
c 
c

c

 (D  )   (D  )
x x
x y
y
T

T

T
u

 (a  )   (a  )
x x
x
y
y
u
Product
AB
Product
AB
Y
B A B A
)
y 1(x
l
u
l1 l2
y2 (x
)
AB
A
B
l1
l2
Initial Mixture
y  y1
 l1  y1  0 : c  c1 ,
 l1  y  l 2
y
 c c y1 
  uc1  1
D 
x
 y x x 
y
 T y1 T  Q
 
a


u 1
x
 x x y  c s
y  y2
0  y1  l 2 : c  c 2 ,
y
 c c y 2 
  u (1  c 2 )  2
D 
x
 y x x 
y
 T y 2 T  Q
 
a


u 2
x
 x x y  c s
x   : T  T0 , y1  y 2  0
x   :
X
y1 ( x)  y  y 2 ( x)
y1  l1 ; y1  l 2 ,
Aldushin A.P., Martem’yanova T.M., Merzhanov A.G., Khaikin B.I.,
Shkadinskii K.G. Combustion Explosion Shock Wave, 1972, 8(2), 202
c c

 0,
x y
T T

0
x y
D
   1

Characteristic Temperature
Profiles
QUASIHOMOGENEOUS
Lhz+ Lrz> Lm
T, K
4000
HETEROGENEOUS
4000
3000
3000
2000
2000
1000
1000
0
0
0
5
10
L/Lm
15
20
Lhz + Lrz~ Lm
0
5
10
L/Lm
15
20
High-Speed Micro Video
Recording
Digital High-Speed Microscopic
Video Recording Technique
Recording rate:
up to 12,000 fr./s
Magnification:
up to 800x
Instantaneous Velocity
Distribution of Instantaneous
Combustion Velocity
Initial density above critical
Fraction, %
30
Quasihomogeneous
mechanism
Initial density below critical
30
20
20
Average macroscopic
velocity
10
10
0
Relay-race mechanism
Average macroscopic
velocity
0
0
5
10
15
Instantaneous velocity, cm/s
0
5
10
15
Instantaneous velocity, cm/s
Thermal Structures of
Heterogeneous Reaction Wave
Super-adiabatic peaks
Structure of Reaction Front
Hot Spot
100 mm
Direction of Combustion Front Propagation
Thermal Conductivity of the
Heterogeneous Media
x0
m
mA 
A ( x ) dx
0
x0
A
B
x0
s
sA 
A ( x ) dx
0
m A ( x)  tan(Q)
x0
A2
A1
Electrical analogy
A3
A4
sA(x)
Q
Aa
A
A
i
i

kc  2k ss A n /(1  Ar / AA )1.5

inert
Ar 
B
Heterogeneous Model
Product
Inert layer
Direction of
the combustion
front propagation
Reactive layer
Inert layer
i-layer
Reactive layer
i 1d  d     id  i 1d
  2 1 


  2  
d
d

 F  , 

Inert layer
id  i  1d    id  d 
s c
s с

R

 2
 s

 2
с

 I I
s  I
cR  R
R
 I,


 s
R


I
  0,   0 :    0 ,   0
(T  T0 ).
Time-Resolved X-Ray Diffraction
Technique
Time-Resolved X-Ray Diffraction
Technique
Scattering angles range: 2Q~ 36o
Grabbing rate of diffraction patterns:up to 103 1/s
Titanium-Air System
I
II
III
IV
V
VI
VII
50
I+VIII
40
Equilibrium Phase
VII
VIII - solid solution
30
VI
V
0
I/I , relative intensity
60
-  - Ti
-  - Ti
- TiN
- Ti 3O5-xN x
- TiO2-xNx
- TiO 2 - high-temperature phase
- TiO2 - rutile
20
IV
II
III
10
2
4
6
TiN – first phase
formed in the combustion wave
8
10
12
time, s
14
16
18
20
Niobium-Boron System
I/I 0
1
Equilibrium Phase
Nb
NbB
0.00
0
1
2
3
4
NbB2
Nb3B4
5
7
6
8
9
10
NbB2 – first phase
formed in the combustion wave
11
12
13
14
15
t, c
Argonne Laboratory: Advanced
Photon Source
Time resolution: 10-12s
Scale resolution: 1 mm
Collaboration with group leaded
by Dr. Jin Wang
Experimental Facilities Division
Argonne National Laboratory
High-Speed
Electrothermography
Electrothermography (ETM)
Schematic diagram of the
electrothermography setup
Typical response characteristics
of temperature controller
The Concept of ETM
where T—wire temperature, c—heat capacity, —density,
r0—wire radius, L—wire length, p(t)—rate of heat generation
from electric current (Joule heat), h(T)—rate of heat
loss (mainly by radiation), and q=q(t,T, ), the rate of heat
evolution, with  being the degree of conversion.
Since q(t) varies with time as reaction proceeds, the experiment
is conducted by varying the electric power p(t) in order to maintain
constant temperature. Under these conditions, from Eq. (1) with
dT/dt=0, we have:
Molybdenum – Silicon System
(a) Typical surface, and (b– c) cross section of
Mo wire clad by Si
Kinetics of High Temperature Reaction:
Mo-Si System
Reaction Mechanisms
• Diffusion through solid product’s layer ~10-10 cm2/s
• Dissolution-recrystallization ~10-5 cm2/s
• Reaction coalescence ~10-5 cm2/s
Electro Thermal Explosion
ETE-100
Collaboration with
ALOFT Company Berkley, CA
Office of Naval Research ONR BAA 07-001
Project: FUNDAMENTAL MECHANISMS OF REACTIVE MATERIALS
RESPONSE UNDER EXTREME MECHANICAL STIMULATION
Kinetics of Heterogeneous Rapid
High-Temperature Reactions
Time resolution up to 10-2 ms
Space resolution 100 mm
Ni-Al System
Ti-C System
Self-Sustained Gasless
Heterogeneous Reactions:
Additional Technological
Capabilities
Joing of Refractory and
Dissimilar Materials
Collaboration with Honeywell
Aircraft Landing Systems, South Band, IN
Concept of Reactive Joining
TiC
Reactive Layer
Pressure
Ti + x C
10-20mm
C-C Composite
C-C Composite
Chemical interaction between C-C composite and reactive media
VCS-RJ of C-C Composites
• Max. Current: 950 A
• Max Voltage: 44 V
• Max Load: 35,000 N
• Press Response Time: 10 ms
• Max. Sample diameter: 5”
Typical Microstructure
of Joining Layer
2
1
3
4
20
19
18
17
16
5 15 6
14
13
12
11
Direction relative
to joint layer
Along
Normal
7
8
9
10
Position of EDS analysis
Element concentration wt. %; Ti / C
1
2
3
4
5
6
7
8
9
10
76.9 / 23.1 78.5 / 21.5 76.7 / 23.3 80.9 / 19.1 78.5 / 21.5 65.5 / 34.5 73.7 / 26.3 68.2 / 31.8 76.0 / 24.0 76.3 / 23.7
11
9.0 / 91.0
12
13
14
15
16
17
18
19
26.9 / 73.1 58.7 / 41.3 76.2 / 23.8 79.5 / 20.5 81.3 / 18.7 73.0 / 27.0 41.4 / 58.6 21.3 / 78.7
20
8.2 / 91.8
Scaling Up - Die
Scaling up - Overview
Solution Combustion Synthesis:
Nano Materials
Concept of SCS
Water
Metal Nitrate(s)
Fuel(s)
Men(NO3) n + (n·f) CH2NH2CO2H + n·f1 O2 
MeOn/2(s)+(n·f)CO2(g)+f H2O(g) +nf1/2 N2(g)
Water
Hot Plate
Reactants mixed on the molecular level !!
where Men is a metal with valence n; f is a fuel to
oxidizer ratio, f =1 means that the initial mixture
does not require atmospheric oxygen for complete
oxidation of fuel, while f>1 (<1) implies fuel-rich
(lean) conditions.
Solution Combustion:
Volume Reaction Mode
Self-ignition
Volume reaction
Product
• Reactants mixed on the molecular level
Combustion Temperature, K
1800
VCS mode
• Short reaction time (~seconds)
Tmax
1600
Reaction
with air oxygen
1400
Nano-size particles
1200
•Relatively high temperatures
1000
800
o
600
400
Preheating
Stage
220
230
Tig=130 C
Solution
Reaction
~3 s
240
Time,s
250
260
Well crystalline structure
Avoid calcination !!
VCS: Different Fuels
 – Fe2O3
  Fe2O3
Fe3O4
Deshpande K., Mukasyan A.S. and Varma A., Chem. Mater. 16 (24), 4896-4904 (2004)
Example: Synthesis of Iron
Oxides
Conditions
Phase
Iron nitrate, glycine
and hydrazine
Iron Oxalate,
ammonium nitrate
and hydrazine
Iron nitrate and citric
acid in argon
 Fe2O3
Surface area,
m2/g
60
 Fe2O3
200
Fe3O4
50
Solution Combustion:
Thermal Explosion Mode
Self-ignition
Volume reaction
Product
COMBUSTION PROCESS = BLACK BOX
THERMAL EXPLOSION =DIFFICULT TO CONTROL
Solution Combustion:
Sol-Gel Self-Propagating Mode
Igniter
Sol-Gel media
Direction of reaction front propagation
Product
450
400
1- Self-Propagating Mode
2- Volume Reaction Mode
4.0
2
2
1
300
250
Specific surface area, m /g
o
Temperature, C
350
2 s
 1 s
200
150
100
50
0
150
200
250
300
350
400
Time,s
450
500
550
•Easy to control
•Product quenching effect
• 10-15 nm particles
3.5
3.0
2.5
2.0
1.5
f1
1.0
VCS
600
320
340
360
380
400
Initial Temperature, K
Mukasyan, A., P.Epstein and P.Dinka, Proc. Combustion Institute, 31(2), 1789-1795 (2007)
Solution Combustion:
Impregnated Combustion Mode
Initial
porous support
Solution
impregnation
Combustion
Catalytic
layer
Combustion Product:
supported catalyst
•Very high specific surface
area of active sites
•High mechanical properties
Dinka P. and Mukasyan A., J. Phys. Chem. 109(46), 21627-21633 (2005)
Nano-Reactor Effect !!
BET support
[m2/g]
BET iron
oxide powder
[m2/g]
BET of
supported
catalyst [m2/g]
Al2O3
activ.
149
40
225
 -Al2O3
5.1
4.5
5.8
 - Al2O3
244
37
197
ZrO2
125
22
112
Support
Catalytic
layer
30 mm
Support
Dinka P. and Mukasyan A., J. Phys. Chem. 109(46), 21627-21633 (2005)
Solution Combustion:
Impregnated Paper
Drying
Solution
impregnation
Paper
Impregnated paper
Solution
Reaction front
Combustion
Product
Product: Metal
oxides
1.
2.
3.
High product yield
Reactions in low exothermic systems
Continuous technology
Mukasyan, A.S, Dinka, P. J. Adv. Eng. Mater. 9, 653-657. (2007)
Continuous Technology
for Synthesis of Nanopowders
Continuous Technology
for Synthesis of Nanopowders
• Production capacity: 15 – 500 g/h
• Safe process
• Low energy consumption
Mukasyan A., Dinka, P., US Patent US2006/030486, Filed: August 4, 2006.
Perovskites by SC
B-site: Fe(1-Y)MY*
A-site: La(1-X)SrX
A-site: Ce(1-X)SrX
A-site: La(1-X)CeX
X=0.4
X=0.4
X=0.4
Y=0
La0.6Sr0.4FeO3
Ce0.6Sr0.4FeO3
La0.6Ce0.4FeO3
M: Ni
Y=0.2, 0.4, 0.6
La0.6Sr0.4Fe0.8Ni0.2O3
La0.6Sr0.4Fe0.6Ni0.4O3
La0.6Sr0.4Fe0.4Ni0.6O3
Ce0.6Sr0.4Fe0.8Ni0.2O3
Ce0.6Sr0.4Fe0.6Ni0.4O3
Ce0.6Sr0.4Fe0.4Ni0.6O3
La0.6Ce0.4Fe0.8Ni0.2O3
La0.6Ce0.4Fe0.6Ni0.4O3
La0.6Ce0.4Fe0.4Ni0.6O3
M: Co
Y=0.2, 0.4, 0.6
La0.6Sr0.4Fe0.8Co0.2O3
La0.6Sr0.4Fe0.6Co0.4O3
La0.6Sr0.4Fe0.4Co0.6O3
Ce0.6Sr0.4Fe0.8Co0.2O3
Ce0.6Sr0.4Fe0.6Co0.4O3
Ce0.6Sr0.4Fe0.4Co0.6O3
La0.6Ce0.4Fe0.8Co0.2O3
La0.6Ce0.4Fe0.6Co0.4O3
La0.6Ce0.4Fe0.4Co0.6O3
X=0
X=0
X=0
Y=0
LaFeO3
CeFeO3
M: Ni
Y=0.2, 0.4, 0.6
LaFe0.8Ni0.2O3
LaFe0.6Ni0.4O3
LaFe0.4Ni0.6O3
CeFe0.8Ni0.2O3
CeFe0.6Ni0.4O3
CeFe0.4Ni0.6O3
M: Co
Y=0.2, 0.4, 0.6
LaFe0.8Co0.2O3
LaFe0.6Co0.4O3
LaFe0.4Co0.6O3
CeFe0.8Co0.2O3
CeFe0.6Co0.4O3
CeFe0.4Co0.6O3
High Throughput Apparatus
for Catalytic Activity Evaluation
H2O
1
Fue
l
1
Air
2
4
3
5
1 – Evaporator
2 – Distribution
block
3 – Oven
4 – Reactor set
(8 reactors)
5 – Catalysts
6 – Condenser
6
G
C
Reaction conditions: temperature: 800 C,
GHSV: 130000 h-1, Fuel: JP-8 surrogate, 10
ppm of sulfur, H2O/C = 3, O2/C = 0.35
Dinka P. and Mukasyan A., J. Power Sources, 167, 472-481 (2007)
Auto-thermal Reforming of JP-8 Fuel
to Produce Hydrogen
Product gas composition and fuel conversion
(steam reforming of JP-8 surrogate with
10 ppm of sulfur on ISC-catalyst)
Synthesis
Method
80
Composition (dry basis) [mol %]
Specific surface area and catalytic activity of
La0.6Ce0.4Fe0.68Ni0.2K0.12O3 catalyst synthesized by
different CS methods
BET initial,
m2/g
BET, after
reaction, m2/g
Conversion, %
21.3
27.9
28.6
48.8
4.4
4.9
5.3
38.3
72.3
68.5
77.8
58.7
70
60
50
VC
SGC
IPC
ISC
40
30
20
10
0
0
100
H2
N2
CH4
CO
CO2
H2 yield
200
300
400
500
600
700
Time [min.]
1.
2.
Highest conversion was achieved by IPC-catalyst
Catalytic activity does not directly correlated with
catalyst specific surface area
Polarization Curves for Methanol
Oxidation
500
500
LaRuO3+1 wt.%Pt
SrRuO3+1 wt.% Pt
LaRuO3+5 wt.%Pt
450
400
LaRuO3+10 wt.%Pt
400
350
LaRuO3+15 wt.%
Pt
Pt black
300
Current Density (mA/cm2)
Current Density (mA/cm 2)
450
Pt-Ru
250
200
150
100
50
SrRuO3+5 wt.% Pt
SrRuO3+10 wt.%Pt
SrRuO3+15 wt.%Pt
Pt black
350
Pt-Ru
300
250
200
150
100
50
0
0
0.2
0.4
0.6
Potential vs DHE (V)
0.8
0
0
0.2
0.4
0.6
0.8
Potential vs DHE (V)
8ml/min, 0.5 M, 20 mV/s and 90 C
Lan, A. and Mukasyan, A. ECS Trans. 2, (24) 1 (2007).
It works ! Perovskite+Pt > Perovskite or Pt black
LaRuO3+10 wt.% Pt  Pt-Ru ! (with much lower Pt loading)
Potentiostatic Results
200
E = 0.4 V, 80 C
LaRuO3 + 15% Pt
2
Current Density (mA/cm )
150
Pt-Ru
100
SrRuO3 + 10% Pt
50
0
0
500
1000
1500
2000
2500
3000
3500
3000
3500
20
E = 0.4 V, 80 C
15
10
LaRuO3
SrRuO3
5
Pt black
0
0
500
1000
1500
2000
2500
Time (seconds)
Lan, A. and Mukasyan, A. J. Phys. Chem, 26, 9573 – 9582 (2007).
Conclusion
Solid Flame - phenomenon of rapid reaction
propagation in gasless heterogeneous
exothermic systems, being extremely
interesting from fundamental point of view,
also allows development of a variety of
effective, energy saving technologies for
synthesis of advanced materials.