1. Environmentally Benign Nano-mixing by
Sonication in Supercritical CO2
p
Ganesh P. Sanganwar, Ram B. Gupta
Department of Chemical engineering
D t t f Ch i l i i
Auburn University, Auburn, AL
Alexandre Ermoline, James V. Scicolone, Rajesh N. Dave
, , j
New Jersey Center for Engineered Particulates
New Jersey Institute of Technology, Newark, NJ

2. Outline
Introduction
Applications of nanoparticles / nanocomposites
and importance of nano-mixing
Available
A il bl methods
th d
Objective
Experimental study
Results
Conclusion

3. Introduction
Nanoparticles and Nanocomposites/Why nanomixing is
important ?
Nanoparticles: particle sizes whose novel properties differentiate from bulk
material( normally <100 nm)
Applications
Carbon nanotube/carbon fiber based composites and films

4. Continued….
Titania nanoparticles in asphalt and cement
High strength material consisting of
nano grained Aluminium
1-5 micron drug particle

5. Available Methods for Nano-particle Mixing
Nano-mixing methods*
Dry mixing
Rapid expansion of supercritical suspension
Magnetically assisted impact mixing
Stirred i i
Sti d mixing
Fluidized bed
Hybridization system (Nara Machinery of Japan)
Mechanofusion (Hosokawa Micron Corp )
Corp.)
Wet mixing
Sonication in solvent like n-hexane or toluene
Micros (Nara Machinery of Japan)
*Wei D., Dave R. and Pfeffer R., 2002. Mixing and *Yang j., Wang Y., Dave R.N., and Pfeffer R., 2003. Mixing of
characterization of nanosized powders: An assessment of nano-particles by rapid expansion of high pressure
different techniques. J.Nanoparticle Res. 4, 21-41. suspensions. Adv. Powder Tech. 14, 471-93.

6. Objective
j
Wet mixing Proposed mixing
Sonication in n-hexane or Sonication in high
toluene pressure co2
Material has to wet Material does not have
the liquid to wet the liquid
Involves additional Recovery by simple
steps of filtration depressurization
d i ti
and drying Uses environmentally
Uses harmful, friendly, non-
flammable and flammable and cheap
expensive solvent
i l t solvent
Residual solvents No residual solvents

7. CO2-Sonication Apparatus

8. Ultrasonic Horn in Pressure Vessel

9. Experimental study
y
Selection of materials for studies
(S ca/ a a, Silica/Alumina, MWCNT/Silica, MWCNT/Titania)
(Silica/Titania, S ca/ u a, C /S ca, C / a a)
Effect of different process variables
Pressure (21 55 and 90 bar)
(21, 55,
Ultrasound amplitude (10, 30, and 50%)
Characterization of Nano-mixture
TEM (Transmission Electron Microscopy) for Silica/Titania
EDS (Energy dispersive X-ray spectroscopy) for Silica/Alumina
and Silica/Titania
SEM (Scanning Electron Microscopy) for MWCNT/Silica and
MWCNT/Titania
Day-light illumination S
Spectrophotometry for MWCNT/Silica and
f C /S
MWCNT/ Titania

10. Nanomaterials
Alumina Titania
50 nm 50 nm
Silica MWCNT
50 nm
100 nm

11. Analysis of Composition
Procedure for EDS
Compressed into wafers
(1mm thick and 13mm
diameter) with applied
load of 5-8 ton for 4
min.Carbon
min Carbon coated
before analysis
Electron beam voltage
El t b lt
of 10 keV
Two representative
areas with each
including 20 randomly
selected points
21 µm

12. Intensity of Segregation
σ2
Intensity of segregation
y g g I= × 1000
ab
[No mixing: I=1000, Complete mixing: I=0]
N N
∑ ( ai − a ) 2 ∑ (bi − b ) 2
Variance σ2 = i =1
= i =1
N −1 N −1
Mixture composition a + b = 1
Danckwerts P.W., 1952. The definition and
measurement of some characteristics of mixtures.
Appl. Sci. Res. A3, 279-296

13. Results
TEM of nanomixed silica/titania
Effect of ultrasound amplitude and pressure
(Silica/Titania mixture)
Mixing of MWCNT/Silica in 90 bar CO2 and
n-hexane at various ultrasound amplitude
Day-light illumination spectrophotometry of
MWCNT/Silica

14. TEM of Nanomixed Silica/Titania in CO2
Silica Titania
10 µm 10 µm
Silica/Titania mixture
50 nm

15. Effect of pressure and ultrasound amplitude on mixing
Silica/Titania
120
gation
Mixing in CO2, 21 bar
100 Mixing in CO2, 55 bar
g ,
ensity of Segreg
Mixing in CO2, 90 bar
80 Mixing in n-hexane
60
f
40
20
Inte
0
0 10 20 30 40 50 60 70
Amplitude (%)

16. Intensity of Segregation versus Power Consumption
Silica/Titania
ation
120
Mixing in CO2, 21 bar
nsity of Segrega
100 Mixing i CO2
Mi i in CO2, 55 b bar
Mixing in CO2, 90 bar
80 Mixing in n-hexane
60
40
Inten
20
0
0 10 20 30 40 50
Power (W)

17. Mixing of CNT/Silica at 10% amplitude
n-hexane
Supercritical CO2
S iti l
100 nm
1µm
1 µm
100 nm
100 nm

18. Mixing of CNT/Silica at 30% amplitude
Supercritical
CO2
1 µm 100 nm
n-hexane
1µm 100 nm

19. Photographs of MWCNT Mixed with Silica
Supercritical
MWCNT
CO2
10% amplitude 50% amplitude
n-hexane
Silica

20. Day-light illumination spectrophotometry
MWCNT/Silica in CO2 at 90 bar and 45 oC
6
CNT SiO2 Hand Mixed
5 CNT-SiO2 10%
CNT-SiO2 30%
Reflectanc (%)
4 CNT-SiO2 50%
CNT
ce
3
2
R
1
0
400 500 600 700
Wavelength (nm)

21. Comparison of Nano-mixing Methods
3
2.5
Atomic Ratio Al/Si
2
o
1.5
1
A
0.5
0
1300 psi
p 2000 psi
p 15 min 25% 85% 1500 psi
p 1000 psi
p
1h
hr 3h
hr 60 min
ampl ampl
Fluidized Bed Stirring MAIM Sonicator RESS
J. Scicolone, G. Sanganwar D. To, R Dave R B Gupta R Pfeffer 2007.
J Scicolone G Sanganwar, D To R. Dave, R. B. Gupta, R. Pfeffer, 2007 “ Deagglomeration and mixing of
nanoparticles, Partech 2007, Germany.

22. Conclusions
Nanomixing in CO2 for studied mixture found to be
as good as i n-hexane
d in h
Deagglomeration and mixing of particles occur
during
d i sonication i hi h pressure carbon di id
i i in high b dioxide
High ultrasound amplitude (30-50%) gave good
results
lt
Mixed powder is free of organic solvent and powder
recovery i f il
is facile.

23. Acknowledgement
g
The National Science Foundation
NIRT grant DMI-0506722

24. Myself in a Nanomixed world
y
Colleagues/Team-mates/Friends from 23 countries !