Transcript PowerPoint Presentation - Determination of kinetic

2005 Annual MURI/DURINT Review
Aberdeen Proving Grounds, MD November 16-17, 2005
Kinetic Studies of Ultra-Fast
Condensed- Phase Reactions
Dr. Jan A. Puszynski
Chemical and Biological Engineering Department South Dakota
School of Mines & Technology
501 E. St. Joseph Street
Rapid City, SD 57701
Tel: 605/394-1230
Fax: 605/394-1232
E-mail: [email protected]
T
Research Objectives (9/1/04 – 8/31/05)
• Study of aluminum nanopowder reactivity in liquid water.
• Investigation of combustion front propagation characteristics under confined
conditions.
• Measurement of pressure output of MIC systems under confined conditions.
• Investigation of ignition temperatures and reaction kinetic constants for
different MIC systems using TGA/DSC.
• Mathematical modeling of combustion propagation in partially sealed cylindrical
channels.
Prior Research:
• Investigation of Al-MoO3, Al-Fe2O3, Al-CuO, Al-Bi2O3 systems under unconfined
and confined conditions.
• Dispersion and mixing of nanopowder reactants in organic liquids.
• Development and characterization of protective coatings for aluminum
nanopowders exposed to humid air.
• Mathematical modeling of combustion front propagation in nanothermite
systems.
Mixing of energetic nanopowders in liquid water
Advantages:
• Use of environmentally benign and nonflammable solvent;
• Excellent control of evaporation rate by adjusting relative humidity;
• Better conditions for removing of electrostatic charge during
mixing and evaporation processes;
• Overall safety of the process.
Disadvantages:
•
Reactivity of water with nanopowders;
• Difficulties to complete drying process.
Aluminum nanopowder reactivity in liquid water.
Selection of the hydration reaction inhibitors.
+ 3H2O(l)
Al
Al nanoparticle coated with
phenyltrimethoxysilane.
Al(OH)3(s) + 3/2 H2(g)
T=50oC
extent of reaction
1.0
untreated Al
phenyl-silane
n-octyl-silane
succinic acid
n-octanoic acid
oleic acid
ascorbic acid
0.8
0.6
0.4
0.2
0.0
0
•
2
4
6
8
10
12
time [hr]
14
16
18
20
22
Dibasic acids protect aluminum effectively and form a hydrophilic coating
supporting dispersion of aluminum nanoparticles in water.
• Inhibition of the hydration reaction by use of succinic acid is due to a significant
decrease of a pre-exponential factor in the Arrhenius equation.
• Application of succinic acid as an inhibitor for aluminum hydration allowed for
preparing of Al-Bi2O3 MIC mixtures in water.
Aluminum nanopowder reactivity in liquid water.
Effect of succinic acid concentration on inhibition of hydration reaction.
55
1.0
a b c
d
e
g
f
i
h
50
45
reaction induction time [hr]
0.8
extent of reaction
from the slope of
reaction curve
i
0.6
0.4
0.2
40
g,h
35
30
25
20
f
e
15
d
10
a b
5
0.0
using extent of
reaction = 0.01
c
0
0
5
10
15
20
time [hr]
25
30
35
40
0.0
0.5
1.0
1.5
2.0
concentration of succininc acid [mM]
2.5
Aluminum nanopowder reactivity in liquid water.
Effect of temperature on hydration reaction of Al nanopowders.
Arrhenius plots for the hydration reaction
of aluminum nanopowders
untreated aluminum nanopowder
Eact= 137 kJ/mole
-1
reaction rate [hr ]
10
1
0.1
Eact= 77 kJ/mole
aluminum nanopowder
coated with 5 wt% of succinic acid.
2.90 2.95 3.00 3.05 3.10 3.15 3.20 3.25 3.30 3.35 3.40
-1
1000/T [K ]
Mixing of Aluminum and Oxide Nanopowders in Water
• Many oxide nanopowders e.g. MoO3 or WO3, have a relatively high solubility in
water and should not be exposed to liquid water without the presence of
protective coatings.
• Bismuth trioxide reacts very slowly with water and forms BiO+ ion.
• In the presence of aluminum, BiO+ is reduced to elemental Bi and aluminum is
converted to aluminum hydroxide.
• Aluminum nanopowder can also react fast with water, if not protected.
• Addition of small amount of inhibitors, e.g. NH4H2PO4, reduces significantly
the effect of those reactions over acceptable processing time (several hours
to days depending on temperature)
Bi2O3 + H2O  2BiO+ + 2OHBiO+ + Al  Al(OH)3 + Bi + H+
Al + 3H2O  Al(OH)3 + 1.5H2
Al(OH)3 ↔ Al(OH)4- + H+
BiO+ + H2PO4-  BiPO4 + H2O
Al(OH)4- + H2PO4-  BiPO4 + H2O + 2OH-
Wet mixing of Bi2O3 and Al2O3 nanopowders
in hexane
SEM images
Bi2O3, SSA = 1.62 m2/g, calc. average particle size 416 nm.
Al2O3, SSA = 11.4 m2/g, calc. average particle size 132 nm.
Wet mixing of Bi2O3 and Al2O3 nanopowders in hexane
Choice of places for AES point analysis
Wet mixing of Bi2O3 and Al2O3 nanopowders in hexane
Auger electron spectroscopy at chosen points on the sample surface
(points 1 – 5)
s9nov112.spe: Orange powder: Bi2O3-Al2O3
EAG
2005 Nov 9 15.0 keV 0 FRR
1.2589e+005 max
3.92 min
Sur1/Area1/5 (S9D9)
x 10
5
s9nov112.spe
Point 1
charging
5
O
Al
Photo 110/105
As received
Point 2
charging
4.8
4.6
c/s
Point 3
Bi
C
4.4
Bi
Al
O
Point 4
4.2
Bi
O
C
Bi
Al
Point 5
4
charging
200
O
400
600
Al
800
1000
1200
1400
Kinetic Energy (eV)
1600
1800
2000
2200
2400
Wet mixing of Bi2O3 and Al2O3 nanopowders in hexane
Auger electron spectroscopy at chosen points on the sample surface
(points 6 – 10)
s9nov112.spe: Orange powder: Bi2O3-Al2O3
EAG
2005 Nov 9 15.0 keV 0 FRR
1.9353e+005 max
3.92 min
Sur1/Area1/8 (S9D9)
x 10
5
s9nov112.spe
Photo 110/105
As Received
1.8
Point 6
1.7
Bi
Bi
1.6
O
C
1.5
Bi
Point 7
1.4
c/s
C
1.3
O
Point 8
Al
charging
Al
O
1.2
Point 9
1.1
Point 10
O
C
1
Bi
Al
Bi
Al
Bi
Bi
Bi
0.9
C
Bi
Al
O
Bi
Bi
200
400
600
800
1000
1200
1400
Kinetic Energy (eV)
1600
1800
2000
2200
Bi
2400
Wet mixing of Bi2O3 and Al2O3 nanopowders in hexane
AES elemental maps of bismuth trioxide-alumina mixture
Bi
Al
• 2D elemental maps of Bi and Al are complementary
• e-beam charging effect of the surface can be reduced by different technique of
sample preparation for AES analysis (pressing into In foil).
Closed-Volume Pressure Cell
Experiments
• Systems investigated were Al-CuO, Al-MoO3, AlBi2O3 and Al-Fe2O3 nanopowder mixtures.
• Constant volume of powder mixture was used in
each test.
• For comparison of different systems, all tests were
performed in argon atmosphere to prevent a
simultaneous reaction of aluminum with air.
• Al-CuO system was investigated to determine the
effect of initial pressure of both air and argon
separately on the peak pressure of the reaction and
ignition delay.
Closed-Volume Pressure Cell Setup
P iezoelectric
Igniter
Vacuum
P ump
Sensor Signal
Conditioner
P ressure
Relief Valve
Gas
Tank
P ressure
Vessel
P ressure
Transducer
Oscilloscope
Dynamic Pressure Responses During Ignition
of Different Nanothermite Systems
Pressure [psig]
100
80
Al/MoO3
60
Al/Bi2O3
40
20
Al/CuO
0
0.01
Time [s]
0.02
Pressure Cell Results
• Peak pressures of 52 psig for Al-CuO, 67 psig for AlMoO3, and 92 psig for the Al-Bi2O3 system were
measured.
• Previous studies of combustion front velocity in open
trays correlate with these results.
Effect of Initial Pressure of Argon on Pressure
Output
• Tests were done using the Al-CuO system (~30 mg
used in each test).
• Samples were reacted at 0, 15, and 30 psig initial
pressures.
• Intent was to determine if concentration of gaseous
atmosphere played a significant role in the rate of
energy release or total generated pressure.
Dynamic Pressure Plot of Al-CuO System as a
Function of Initial Pressure of Argon
Al-CuO in Argon
120
100
Pressure (psig)
80
60
40
20
0
0
0.002
0.004
0.006
0.008
-20
Time (s)
30 psig Argon
15 psig Argon
0 psig Argon
0.01
0.012
Pressure Plot of Al-CuO System in Various
Initial Pressures of Air
Al-CuO in Air
120
100
Pressure (psig)
80
60
40
20
0
0
0.002
0.004
0.006
0.008
-20
Time (s)
30 psig Air
15 psig air
0 psig Air
0.01
0.012
Force cell responses of reacting system as
a function of mass of material used
400
Al-Bi2O3
350
recoil force [N]
300
250
200
Al-MoO3
150
100
Al-CuO
50
0
0
2
4
6
8
mass of the MIC [mg]
10
12
Combustion Front Propagation in Small
Diameter Tubes
• Tubes are 1.5 inches long and 1/8
inch inside diameter.
• Tube is inserted into acrylic block
shown left.
• Block fitted with piezoelectric
pressure transducers.
• Setup can be configured to block
either end of the tube shut to
prevent pressure release.
Experiments Performed
• Tests were done using the Al-Fe2O3 and Al-CuO
systems (~100 mg).
• Objective was to monitor the effect of confinement
and pressure release on combustion front
propagation.
• High speed video was used to record the reaction.
• This study investigated two different setups: both
tube ends open, and tube end opposite ignition
blocked shut.
Combustion Front Propagation
Both Tube Ends Open
Video Stills
Frames are taken starting at
t=0 in increments of 0.0125s
Pressure is initially released
in direction of ignition
Front accelerates during
propagation
Material is possibly ejected
from opposite end prior to
ignition due to pressure drop
End Opposite Ignition Closed
Video Stills
Stills start at t=0 and are
incremented by 0.04 s
Pressure is allowed to be
released only in direction of
ignition
Front propagates at
constant velocity
Reaction is much slower
than with both ends left open
Pressure Response of Combustion Front of Al-CuO System in
Small Diameter Tubes
Both tube ends open to
atmosphere.
Al-CuO Pressure Response
1000
Pressure transducers at distances
of ½ inch and 1 inch from point of
ignition.
900
800
Peak pressures of 908 psig and
636 psig for points 1 and 2
respectively.
Pressure (psig)
700
600
500
Total reaction time ~ 0.2 ms
compared to ~ 100 ms for AlFe2O3 system under the same
configuration.
400
300
200
Results show convective,
pressure driven combustion
process.
100
0
0
100
200
300
400
500
600
Time (us)
Pressure 1
Pressure 2
700
800
900
1000
Future tests include monitoring
reaction with faster high-speed
camera than currently available.
Determination of Reaction Kinetic Constants
Using DSC
• ASTM Standard E 474 Method used for the
determination of Arrhenius kinetic constants of
thermally unstable materials
• Samples are heated at varying heat rates and peak
reaction temperatures are recorded for each
different heat rate
• Activation energy is computed by the formula:
E = -2.19R[d logβ/d (1/T) where β is the heat rate in
C/min and T is the peak reaction temperature.
• Pre-exponential factor is calculated by:
Z = βEeE/RT/RT2
Systems Investigated
• The systems initially investigated were Al-Fe2O3 and
Al-Bi2O3.
• Since oxides in both systems behave similarly at
high temperatures, Al-MoO3 was later tested as
MoO3 is known to sublime at elevated temperatures.
• The effect of particle coating on reaction kinetics
was also determined in the Al-Bi2O3 system with
aluminum coated with an organic protective coating.
DSC Plot of Reaction Peaks for the Al-Bi2O3
System
4
2
536.54°C
553.09°C
570.35°C
Heat Flow (W/g)
0
-2
-4
-6
–––––––
––––
––––– ·
-8
400
Exo Up
600
Temperature (°C)
Al-Bi2O3 (5 C/min)
Al-Bi2O3 (10 C/min)
Al-Bi2O3 (20 C/min)
Plot of LOG β versus 1/T
1.4
1.2
LOG Heat Rate (K/min)
1
0.8
E = 221.5 kJ/mol
y = -12157x + 15.717
R2 = 1
0.6
Z = 3.872*1013 min-1
0.4
0.2
0
0.00118
0.00119
0.0012
0.00121
1/T (K)
0.00122
0.00123
0.00124
DSC Plot of Reaction Peaks for the Al-Fe2O3
System
4
565.06°C
576.11°C
2
Heat Flow (W/g)
551.41°C
0
-2
-4
–––––––
––––
––––– ·
-6
400
Exo Up
600
Temperature (°C)
Al-Fe2O3 (5 C/min)
Al-Fe2O3 (10 C/min)
Al-Fe2O3 (15 C/min)
Plot of LOG β versus 1/T
1.4
1.2
LOG Heat Rate (K/min)
1
0.8
E = 247.76 kJ/mol
y = -13598x + 17.203
R2 = 0.9935
0.6
Z = 1.147*1015 min-1
0.4
0.2
0
0.001175
0.00118
0.001185
0.00119
0.001195
1/T (K)
0.0012
0.001205
0.00121
0.001215
DSC Plot of Reaction Peaks for the Al-MoO3
System
8
555.80°C
Heat Flow (W/g)
6
4
547.31°C
538.03°C
2
0
-2
0
Exo Up
200
400
Temperature (°C)
600
800
Plot of LOG β versus 1/T
1.4
1.2
y = -11411x + 15.075
R2 = 0.9957
LOG Heat Rate (K/min)
1
0.8
E = 207.92 kJ/mol
0.6
Z = 9.47*1012 min-1
0.4
0.2
0
0.001205
0.00121
0.001215
0.00122
1/T (K)
0.001225
0.00123
0.001235
Reaction Kinetics Results
• Al-MoO3 – oxide sublimes: E=207 kJ/mol
– Ignition temperature @ 10oC/min heating rate is 538oC
• Al-Bi2O3 – oxide decomposes: E=221 kJ/mol
– Ignition temperature @ 10oC/min heating rate is 553oC
• Al-Fe2O3 – most stable oxide: E=247 kJ/mol
– Ignition temperature @ 10oC/min heating rate is 565oC
Effect of Coating on Kinetic Constants of Nanothermite Systems
4
Al-Bi2O3 system reinvestigated to
determine the effect of particle coating on
kinetic constants.
578.79°C
572.90°C
Heat Flow (W/g)
2
562.98°C
Aluminum coated with 5 wt% oleic acid.
0
-2
400
500
600
Calculated activation energy of 245.05
kJ/mol compared to 221 kJ/mol for the
same mixture using uncoated aluminum
powder.
700
Temperature (°C)
Exo Up
1.4
Peak reaction temperature at heating rate
of 10 C/min is 562.9 oC compared to 553.09
oC for the uncoated material.
1.2
y = -13449x + 17.085
R2 = 0.9972
LOG Heat Rate (K/min)
1
0.8
Pre-exponential factor for the system is
8.17 * 1014 min-1, significantly higher than
3.87 * 1013 min-1 for the uncoated system.
0.6
0.4
0.2
0
0.00117
0.001175
0.00118
0.001185
1/T (K)
0.00119
0.001195
0.0012
Conclusions
• It was determined that processing of nanothermites in
liquid water is feasible over the certain period of time,
which is dependent on system temperature.
• Pressure cell experiments indicate that oxygen in air
has a significant effect on overall energy output.
• Direction of pressure release have a strong effect on
combustion front propagation velocity.
• It was demonstrated that activation energies and preexponential factors of nanothermite reactions can be
determined using DSC technique.