Retsch PM400 ball mill

pump

Nanoparticle preparation

Ball Milling Method

Physically grind micron size feedstock down to the nanoscale regime using planetary ball milling with WC balls

Particles are coated with various ligands/capping agents to promote suspension in a variety of fuels and/or to protect them from unwanted oxidation

Particle Characterization

Chemical composition: XPS, FTIR, TGA

Particle Size: DLS, SEM, TEM

1

Boron Nanoparticle Size distribution

Volume weighted

Number weighted

200 nm SEM image of <100 nm particles

Diameter (nm)

10 100 1000

Rela

tive a

mount

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Volume weighted size distribution

~50 nm particles separated by settling big particles

Unoxidized Boron Nanoparticles

• Elemental B1s peak observed at ~188 eV, B3+ at ~193 eV

• Nanosized boron immediately formed oxide upon exposure to air as the XPS samples were prepared.

• Oleic acid prevented oxidation of the fresh boron surfaces formed during the milling process. B 1s Region Scan

Oleic Acid

CeO2 catalyst

Boron core

STEM

A

B ° C °

CeO2 exists as patch of island on a boron nanoparticle

XPS suggests the presence of a low binding energy boride species (CexBy)

XPS

Catalyst Coated, Unoxidized Boron Nanoparticles

Boron Nanoparticles with Polar Surfactants

www.retsch.com

Boron Powder + ⅛” WC balls 80:1 BPR

3 hrs dry milling

+ Surfactant (Ionic Liquid, Et2NH, Et3N, Ethanolamine) ~10 % total volume

3 hrs milling

+ Solvent (Ethanol)

18 hrs milling

Samples washed with EtOH to remove excess surfactant

4 x 250 ml capacity

Method of Preparation: Ball Milling

Solubility /Dispersibility in Ethanol (polar solvent)

Characterize size of particles using: SEM, DLS

Characterize chemical composition using: EDX-STEM, XPS, FTIR

B-Ionic Liquid Et3N Et2NH Boron in EtOH Wet Milled Boron in EtOH

SEM Image of Boron Nanoparticles on TEM Grid

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

10 15 22 32 48 70 104 154 227 335 495 732

Size weighted

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

10 15 22 32 48 70 104 154 227 335 495 732

Number weighted

79 nm (41%)

209 nm (59%)

78 nm (93%)

201nm (7%)

DLS Measurement of Particle Size

Boron-Ionic Liquid Particle Size

0

500

1000

1500

2000

2500

3000

3500

1801851901952000

500

1000

1500

2000

2500

3000

3500

391393395397399401403405

B-N = 191 eV

B0= 188 eV N-B= 398 eV

400 eV Organic N?

B1s Region XPS of Boron milled with Ionic Liquid in EtOH

N1s Region XPS of Boron milled with Ionic Liquid in EtOH

Boron, Nitrogen Species

0

500

1000

1500

2000

2500

3000

3500

391393395397399401403405

B-N = 191 eV

B0= 188 eV N-B= 398 eV

400 eV Organic N?

N1s Region XPS of Boron milled with Ionic Liquid in EtOH

Boron, Nitrogen Species

0

1000

2000

3000

4000

5000

6000

7000

8000

182187192197

191 eV

188 eV 193 eV

Diethylamine Surfactants

0

0.5

1

11 20 35 63 113 203 365 655

0

0.5

1

11 20 35 63 113 203 365 655

86 nm (57%)

189 nm (43%)

81 nm (93%)

178 nm (7%)

Size Weighted

Number Weighted

0

2000

4000

6000

8000

10000

12000

14000

16000

180185190195

XPS

B-N = 192 eV

B0= 188 eV

B1s Region XPS of Boron milled with Et2NH in EtOH

-200

300

800

1300

1800

2300

2800

390395400405410

Light sputter

Unsputtered

N-B= 398 eV

400 eV Organic N?

N1s Region XPS of Boron milled with Et2NH in EtOH

Triethylamine Surfactants

0

0.5

1

11 20 35 63 113 203 365 655

0

0.5

1

11 20 35 63 113 203 365 655

176 nm (41%)

57 nm (97%)

165 nm (3%)

Size Weighted

Number Weighted

59 nm (59%)

XPS

-1000

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

182187192197

B-N = 192 eV

B0= 188 eV

B1s Region XPS of Boron milled with Et3N in EtOH

-100

100

300

500

700

900

1100

1300

393398403408

N-B= 398 eV

400 eV Organic N?

60 sec sputter

Unsputtered

N1s Region XPS of Boron milled with Et3N in EtOH

Combustion testing in a turbulent flame calorimeter

19

24

29

34

39

44

49

0 100 200 300 400 500 600

Tem

pe

ratr

ue

oC

Time (sec)

~3% Boron Loaded Ethanol vs. Pure Ethanol

run 1

run 2

run 3

Boron run

Boron loaded Etoh ∆T = 27.45 oC Temperature Increase = 1.18 oC A 4.49% increase Increase is consistent with complete combustion of the boron. Burner has difficulties with higher loadings.

0

0.5

1

10 15 22 32 48 70 104 154 227 335 495 732

Particle diameter (nm)

104 nm

Boron nanoparticles functionalized with ionic liquid

Dynamic Light Scattering (DLS) of particles suspended in EtOH

15

Acknowledgment

University of Utah Chemistry Department

Prof. Scott L. Anderson Anderson group:

William Kunkel Matt Kane

David Bell Sloan Roberts

Eric Baxter Mark Wirth

Darby Lewis Ashley Becksted

Dr. Dae Jung Kim Sebastian Proch

Our collaborators: Tommy Hawkins Steven Son Robin Rodgers Michael Berman Stefan Schneider Jerry Boatz

Support: Air Force Office of Scientific Research Grant FA9550-08-1-0400

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