FORMATION OF ALUMINUM NANOPOWDERS AND THEIR APPLICATION IN

NANOENERGETIC MATERIALS

Dr. Jan A. Puszynski

Chemistry and Chemical Engineering Department

South Dakota School of Mines & Technology

Rapid City, SD 57701

Tel: 605/394-5268 Fax: 605/394-5266

E-mail: Jan.Puszynski@sdsmt.edu

Effect of Operating Pressure onReactive Aluminum Content and Surface Area

20

40

60

80

100

0 4 8 12 16

Pressure (Torr)

Aluminum (%) Surface Area (sq. m/g)

PARAMETRIC STUDIES: FORMATION OF ALUMINUM NANOPOWDERS

100 nm

1.5 nm

0

500

1000

1500

2000

2500

3000

3500

4000

4500

15 20 25 30 35 40 45 50 55 60 65 70 75

Two-theta (degree)

Intensity (cps)

Mathematical Modeling of Aerosol Dynamics

Stages in Particle Formation

Stage1 (T1)

Stage2 (T2)

Stagen-1

(Tn-1)

Stagen (Tn)

Modeling the Aerosol Dynamics• The rate of change of various moments of the aerosol size distribution for the n th cell can be written by :

First Moment, M1

Aerosol Surface Area, A

Aerosol Number Density, N

1

3/1

111*

1 ])1([−

+−+=n

MNBSdIkM τ

1−+= nNIN τ

1111* ])1(2[

3/2

−+−+= nAMSBsIkA τπ

Modeling the Aerosol Dynamics• d1 , s1 , v1 are the monomer diameter, surface area and

volume respectively.

• The saturation ratio S is given by:

• The nucleation rate I is given by:

sc

cS 1=

))2

ln(exp()9

2()

2( *2/12/122/1

11

2 SkS

m

TkscI bs −∑=

ππ

Schematic Representation of Cascade Flow Model

Individualaerosol cells

withconstant

temperature

MoltenAluminumin the boat

Inert gasdistributor

Modeling the Aerosol Dynamics

In the case of several CSTAGs (Continuous Stirred Tank Aerosol Generator) in series, the governing mass balance equation is given by:

( )0

2

1

1

111 =⎟⎟

⎠

⎞⎜⎜⎝

⎛ −+−− ∗

−− Vv

ABSIkCFCF nnnn

2-D Temperature Profiles in the Al Nano-Powder Generator (PHe=5Tr)

2-D Temperature Profiles in the Al Nano-Powder Generator (PAr=5Tr)

Axial Temperature Profiles in the Generator for Helium and Argon

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Position in the generator (axis) in m

Temperature, K

Helium

Argon

Median Particle Diameter vs. Inert Gas Pressure

0

20

40

60

80

100

120

140

160

180

0 2 4 6 8 10 12 14 16

Inert Gas Pressure (Torr)

Median Particle Diameter (nm)

Helium

Argon

Linear (Helium)

Linear (Argon)

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16

Inert gas pressure (Torr)

Surface area ( m

2/g )

Helium

Argon

Characterization of uncoated and coated aluminum nanopowders.

DETERMINATION OF REACTIVE ALUMINUM CONTENT

• Thermogravimetric method (TGA)

• Volumetric method (VM)

• Bomb calorimetry method (BCM)

TGA of Aluminum Nanopowders

95

100

105

110

115

120

Weight (%)

0 200 400 600 800

Temperature (°C)

Sample: al nano m040001Size: 8.3950 mgMethod: RampComment: m040001 at 20 c p min in O2 100ml/m on nov 26

DSC-TGAFile: C:...\Al_m040001_20cpm_100mlpm_ox.001Operator: somRun Date: 27-Nov-02 11:13Instrument: SDT Q600 V3.4 Build 41

Universal V3.5B TA Instruments

20.22 wt % of reactive aluminum

80

100

120

140

160

Weight (%)

0 200 400 600 800 1000 1200 1400 1600

Temperature (°C)

Sample: Al Nano 1030001Size: 2.3620 mgMethod: RampComment: Al Nano 1030001 NSWC/IH Argon and Air atmosphere

DSC-TGAFile: Al+Al2O3_1030001_al1450_100mlpm_argon...Operator: SomRun Date: 18-Jan-03 11:07Instrument: SDT Q600 V3.4 Build 41

Universal V3.5B TA Instruments

67.78 wt % of reactive aluminum

0

500

1000

1500

2000

2500

3000

3500

4000

4500

15 25 35 45 55 65 75

two theta (degree)

Intensity (cps)

aluminum

alon

alumina

Comparison of TGA, Volumetric, and Bomb Calorimetry Methods

Aluminum Average Particle

Size

TGA Method

wt%

Volumetric Method

wt%

Bomb Calorimetry

wt%

50 nm 69.0 68.0 69.4

80 nm 75.1 79.8 79.5

2 m 91.2 99.5 99.3

Surface Functionalization of Al Nanopowders And Their Reactivity with Moisture

and Liquid Water

• Mixing• Processing • Long-term stability

0

10

20

30

40

50

60

70

80

0 200 400 600 800 1000 1200 1400

Time of Exposure (hours)

Weight % Reactive Aluminum

97 % RH84 % RH75 % RH43 % RH

Effect of Moisture on Aluminum Nanopowders

0

20

40

60

80

100

0 50 100 150 200 250 300 350 400

Time of Exposure (hours)

Weight % Reactive Aluminum

Uncoated5.0% Z61245.0% oleic acid

Effect of Moisture (97% RH) on Coated and Uncoated Aluminum Nanopowders

0

20

40

60

80

0 100 200 300 400 500 600 700

Time of Exposure (hours)

Weight % Reactive Aluminum

1.0 % oleic acid3.0 % oleic acid5.0 % oleic acidUncoated

0

20

40

60

80

0 10 20 30 40 50Time (hours)

Percent Reactive Al

Uncoated 40 CUncoated 30 CUncoated 20 CCoated 40 C

Ageing of Aluminum Nanopowders in Liquid Water

Ageing of Aluminum Nanopowders97% RH and 40oC

Aged 0 hrs, 74 wt% reactive Al Aged 40 hrs, 59 wt% reactive Al

Ageing of Aluminum Nanopowders

Aged 60 hrs (97% RH), 17 wt% reactive Al Aged 80 hrs (97% RH), 0 wt% reactive Al

Aluminum Nanopowder Coated with 4 wt%of Silane

DISPERSION AND MIXING OF

NANO-POWDERS

Sedimentation of AluminumNano-powder in Hexane

Time: 30 sec Time: 50 sec

Without dispersant

Time: 5 min Time: 30 min

J

With dispersant (2 wt% sodium dioctyl sulfosuccinate, SDS)

Characterization of Mixing Quality of Binary Nano-powders (high resolution)

Wet Mixing of Al(red) / TiO2(blue) System (with SDS dispersant):SE/Cameo Image 50,000XSE/BSE/Element Mapping 50,000XSE/Element Line Scan 50,000X

Al-TiO2-mixture prepared in absolute ethanol with sodium dioctyl

sulfosuccinate as surfactant. Sample after three line scans of 10 m at 10000 X.

Dry mixingWet mixing hexane

Wet mixing ethanol(w/disp.)

Wet mixing hexane (w /disp.)

Mixing Index AK,L for different samples

0.945 0.950 0.955 0.536

Mixing Index for the Mixtures of Nanosized PowdersMixing Index for the Mixtures of Nanosized Powders

INVESTIGATION OF COMBUSTION CHARACTERISTICS IN SYSTEMS

CONTAINING ALUMINUM AND METALOXIDES NANOPOWDERS

REACTION Tad [K] [kg/m3]

2Al + MoO3 3,253 4.50

2Al + 3MnO2 2,918 4.01

10Al + 3I2O5 >3,253 4.12

2Al + 3CuO 2,843 5.10

2Al + WO3 3,705 5.45

2Al + Fe2O3 3,100 4.23

2Al + Bi2O3 3,325 5.70

Adiabatic Temperature of EnergeticReacting Systems

Computer

Oscilloscope

High Speed Camera(Photron Ltd.)16,000 fps1/128,000 ShutterSpeed

Piezo ElectricIgniter

Stand

OpticalFibers Photo

Detectors

PerforatedBaffles

ReactantMixture

Oscilloscope

Schematics of the Burn Test Equipment

Reacting System: Nanosize Al (40 nm) and Nanosize Fe2O3 (Nanophase Technologies, Corp.)

• Combustion Front Velocity: 30 m/s

• Recording Speed: 8000 frames/sec

• Playback Rate: 30 frames/sec

st= 0.1

t= 200

t= 600

t= 800

t= 100

t= 300

t= 500

Reacting System: Nanosize Al (50 nm NSWC/IH) and Micronsize MoO3 (Climax Molybdenum Company)

With Perforated Baffles

t= 0.1

t= 100

t= 170

t= 200

t= 50

t= 150

t= 160

s

0

200

400

600

800

0 2 4 6 8 10 12

Weight % Coating

Propagation Velocity (m/s)

oleic acid

Silane 1-6341

Poly. (oleicacid)Linear (Silane1-6341)

Effect of Coating on Combustion Front VelocityUnder Unconfined Conditions

Wt% of Coating Wt% of Coating

0

50

100

150

200

250

0 2 4 6 8 10 12

Weight % Silane Coating

Ignition Delay (us)

Z6124Oleic acid

Wt% of Coating

Effect of Coating on Ignition Delay Time

Effect of Average Particle Size of Aluminum on Burn Rate in Al-CuO System

0

200

400

600

20 40 60 80 100 120

Aluminum Average Particle Size (nm)

Propagation Velocity (m/s)

Average Particle

Size (nm)

Ignition

Delay (ms)50 8980 84100 88

Gas Tank

Pressure ReliefValve

Vacuum Pump

Pressure Vessel

PressureTransducer

Sensor SignalConditioner

PiezoelectricIgniter

Oscilloscope

Oscilloscope

Schematics of the pressure vessel equipment

Equipment for Burn test of Aluminum under confined conditions

CAMERA

REACTOR

AUTOTRANSFORMER

VACUUM PUMP

VENT

GAS INLET

DATA ACQUISITION SYSTEM

PRESSURE GAUGE

THERMOCOUPLE WIRES

SAFETY

VALVE

FLANGE 1 FLANGE 2

ReactorReactor Alumin Boat

LEADS FROMTHERMOCOUPLE TODATA AQUISITION

MOLYBDENUM

IGNITION WIRE

Aluminum loose powder

Pressure Vessel Experimental Set-up

0

10

20

30

40

50

60

70

80

90

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01

Time [s]

Pressure [psi]

Pressure Responses in Al (uncoated)-CuO System

IDT

Pmax

Wt% of Coating Wt% of Coating

0

50

100

150

200

250

0 2 4 6 8 10 12

Weight % Silane Coating

Ignition Delay (us)

Z6124Oleic acid

Wt% of Coating

Effect of Coating on Ignition Delay Time

0

20

40

60

80

100

120

0 0.005 0.01 0.015 0.02

Time [s]

Pressure [psig]

30 psig Ar

15 psig Ar

0 psig Ar

0

20

40

60

80

100

120

0 0.005 0.01 0.015 0.02

Time [s]

Pressure [psig]

30 psig Ar

15 psig Ar

0 psig Ar

20

40

60

80

100

0.01 0.02

Time [s]

Pressure [psig]

Al/MoO 3

Al/Bi 2O3

Al/CuO

0

20

40

60

80

100

0.01 0.02

Time [s]

Pressure [psig]

Al/MoO 3

Al/Bi 2O3

Al/CuO

0

New experimental technique:

Recoil force measurement during unconfined burn of a nanoenergetic

mixture.

Load cell (force transducer) : Entran Devices, Inc.

Linear range: 0 – 1000 NSensitivity : ~200 mV/1000 N

Average recoil force during combustion of the MICs

0 2 4 6 8 10 120

50

100

150

200

250

300

350

400

Al-MoO3

Al-Bi2O

3

Al-CuO

recoil force [N]

mass of the MIC [mg]