Environmentally Benign Nano-mixing by Sonication in Supercritical CO2p 2

Ganesh P. Sanganwar, Ram B. GuptaD t t f Ch i l i iDepartment of Chemical engineering

Auburn University, Auburn, AL

Alexandre Ermoline, James V. Scicolone, Rajesh N. Dave, , jNew Jersey Center for Engineered Particulates New Jersey Institute of Technology, Newark, NJ

Outline

IntroductionApplications of nanoparticles / nanocomposites and importance of nano-mixingA il bl th dAvailable methods

ObjectiveExperimental studyExperimental studyResultsConclusionConclusion

Introduction

Nanoparticles and Nanocomposites/Why nanomixing is important ?important ?

Nanoparticles: particle sizes whose novel properties differentiate from bulk material( normally <100 nm)

ApplicationsCarbon nanotube/carbon fiber based composites and films

Continued….

High strength material consisting of

Titania nanoparticles in asphalt and cement

nano grained Aluminium

1-5 micron drug particle

Available Methods for Nano-particle Mixing

Nano-mixing methods*

Dry mixing Rapid expansion of supercritical suspension Magnetically assisted impact mixing Sti d i iStirred mixing Fluidized bedHybridization system (Nara Machinery of Japan)Mechanofusion (Hosokawa Micron Corp )Mechanofusion (Hosokawa Micron Corp.)

Wet mixingSonication in solvent like n-hexane or tolueneMicros (Nara Machinery of Japan)Micros (Nara Machinery of Japan)

*Wei D., Dave R. and Pfeffer R., 2002. Mixing andcharacterization of nanosized powders: An assessment ofdifferent techniques. J.Nanoparticle Res. 4, 21-41.

*Yang j., Wang Y., Dave R.N., and Pfeffer R., 2003. Mixing ofnano-particles by rapid expansion of high pressuresuspensions. Adv. Powder Tech. 14, 471-93.

Objectivej

Wet mixingSonication in n-hexane or

Proposed mixingSonication in high pressure cotoluene

Material has to wet the liquid Involves additional

pressure co2Material does not have to wet the liquid Recovery by simple d i tisteps of filtration

and dryingUses harmful, flammable and

i l t

depressurizationUses environmentally friendly, non-flammable and cheap solventexpensive solvent

Residual solventssolventNo residual solvents

CO2-Sonication Apparatus

Ultrasonic Horn in Pressure Vessel

Experimental studySelection of materials for studies

(Silica/Titania, Silica/Alumina, MWCNT/Silica, MWCNT/Titania)

y

(S ca/ a a, S ca/ u a, C /S ca, C / a a)

Effect of different process variables

Pressure (21 55 and 90 bar)Pressure (21, 55, and 90 bar) Ultrasound amplitude (10, 30, and 50%)

Characterization of Nano-mixtureTEM (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

S f C /SDay-light illumination Spectrophotometry for MWCNT/Silica and MWCNT/ Titania

Nanomaterials

Alumina Titania

50 nm50 nm

MWCNTSilica MWCNTSilica

50 nm100 nm

Analysis of Composition

Procedure for EDSCompressed into wafersCompressed into wafers (1mm thick and 13mm diameter) with applied load of 5-8 ton for 4 min Carbon coatedmin.Carbon coated before analysis

El t b ltElectron beam voltage of 10 keV

Two representativeTwo representative areas with each including 20 randomly selected points

21 µm

Intensity of Segregation

Intensity of segregation

10002

×=I σy g g

[No mixing: I=1000, Complete mixing: I=0]

1000ba

I

2 2( ) ( )N N

a a b b− −∑ ∑2 1 1

( ) ( )

1 1

i ii i

a a b b

N Nσ = == =

− −

∑ ∑Variance

1a b+ =Mixture composition

Danckwerts P.W., 1952. The definition andmeasurement of some characteristics of mixtures.Appl. Sci. Res. A3, 279-296

Results

TEM of nanomixed silica/titania

Effect of ultrasound amplitude and pressure (Silica/Titania mixture)(Silica/Titania mixture)

Mixing of MWCNT/Silica in 90 bar CO2 andMixing of MWCNT/Silica in 90 bar CO2 and n-hexane at various ultrasound amplitude

Day-light illumination spectrophotometry of MWCNT/Silica

TEM of Nanomixed Silica/Titania in CO2

Silica Titania

10 µm 10 µm

Silica/Titania mixtureSilica/Titania mixture

50 nm

Effect of pressure and ultrasound amplitude on mixing

Silica/Titania

100

120

gatio

n

Mixing in CO2, 21 barMixing in CO2, 55 bar

60

80

f Seg

reg g ,

Mixing in CO2, 90 barMixing in n-hexane

20

40

ensi

ty o

f

0

20

0 10 20 30 40 50 60 70

Inte

Amplitude (%)

Intensity of Segregation versus Power Consumption

Silica/Titania

100

120

atio

n

Mixing in CO2, 21 barMi i i CO2 b

60

80

100

Segr

ega Mixing in CO2, 55 bar

Mixing in CO2, 90 barMixing in n-hexane

40

60

nsity

of

0

20

0 10 20 30 40 50

Inte

n

0 10 20 30 40 50Power (W)

Mixing of CNT/Silica at 10% amplitude

S iti l CO

n-hexane

Supercritical CO2

100 nm

1µm

1 µm

100 nm

100 nm100 nm

Mixing of CNT/Silica at 30% amplitude

Supercritical CO2

1 µm 100 nm

n-hexane

1µm 100 nm

Photographs of MWCNT Mixed with SilicaSupercritical

CO2MWCNT

10% amplitude 50% amplitude

n-hexaneSilica

Day-light illumination spectrophotometry

MWCNT/Silica in CO2 at 90 bar and 45 oC

5

6CNT SiO2 Hand MixedCNT-SiO2 10%

4

ce (

%) CNT-SiO2 30%

CNT-SiO2 50%CNT

2

3

Ref

lect

anc

0

1

R

0400 500 600 700

Wavelength (nm)

Comparison of Nano-mixing Methods

3

2

2.5

3

o A

l/Si

1

1.5

Ato

mic

Rat

io

0

0.5

A

1 h 3 h 2000 psi1300 psi 15 min 60 min 25% 85% 1500 psi 1000 psi

Fluidized Bed

1 hr 3 hr

Stirring

pp

MAIM

15 min 60 min

Sonicator

25% ampl ampl

RESS

p p

J Scicolone G Sanganwar D To R Dave R B Gupta R Pfeffer 2007 “ Deagglomeration and mixing ofJ. Scicolone, G. Sanganwar, D. To, R. Dave, R. B. Gupta, R. Pfeffer, 2007. Deagglomeration and mixing of nanoparticles, Partech 2007, Germany.

Conclusions

Nanomixing in CO2 for studied mixture found to be d i has good as in n-hexane

Deagglomeration and mixing of particles occur d i i i i hi h b di idduring sonication in high pressure carbon dioxide

High ultrasound amplitude (30-50%) gave good ltresults

Mixed powder is free of organic solvent and powder i f ilrecovery is facile.

Acknowledgement

The National Science Foundation

g

NIRT grant DMI-0506722

Myself in a Nanomixed world

Colleagues/Team-mates/Friends from 23 countries !

y