K Khinchi A Goyal N Roy and R Nagarajan Dept of Chemical Engineering IIT Madras CAV 2012 Aug 1316 2012 Singapore Sono Synthesis and Dispersion of NanoParticles Experiments amp Simulation ID: 479729
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A. Kesavasami, K. Khinchi, A. Goyal, N. Roy and R. NagarajanDept of Chemical EngineeringIIT MadrasCAV 2012, Aug 13-16, 2012, Singapore
Sono
-Synthesis and Dispersion of Nano-Particles: Experiments & SimulationSlide2
WHAT IS SONO-TECHNOLOGY? Intensification of bulk-fluid and surface/ interfacial processes by combined action of cavitation (bubble implosion) and
acoustic streaming (high-velocity shearing)2
micron-size bubbles
Cavitation Bubble
Acoustic
StreamingSlide3
3Slide4
SONO- FRAGMENTATION(SIZE REDUCTION)4
Particles
BubbleSlide5
5
Particles
Bubble
Bubble Collapse due to Implosion
Particle Fragments due to
Violent Bubble collapse
Inter-particle attrition
SONO- FRAGMENTATION
(SIZE REDUCTION)Slide6
6
Particles
Bubble
Bubble Collapse due to Implosion
Particle Fragments due to
Violent Bubble collapse
Inter-particle attrition
Fragmented Particle
SONO- FRAGMENTATION
(SIZE REDUCTION)Slide7
STATE-OF-THE -ART ULTRASONIC FACILITY7
58 kHz, 500 W power Sonicator( Tank Type)
20 kHz, 1000 W power Sonicator
( Probe Type)Slide8
ANALYZERS USED8Slide9
20 kHz_ 500 W
30 minutes
PARTICLE SIZE BEFORE AND AFTER
SONO-FRAGMENTATION
9
Feed Particle Size (74-80 microns)Slide10
EFFECT OF FREQUENCY ON SONO-FRAGMENTATION10Slide11
EFFECT OF APPLIED ULTRASONIC POWER ON SONO-FRAGMENTATION11
Sonic power plays a key role in intensifying the cavitation bubble movement, bubble collapse, and inter-particle attrition.Slide12
20 kHz, 1000 W, Sono-fragmented WFA
nm dimensions confirmed.
12
HR TEM PICTURESSlide13
Simulation of Sono-FragmentationSlide14Slide15
MODEL VALIDATION WITH MEASURED DATASlide16
16Slide17
DISPERSION OF NANOPARTICLES IN SUSPENSIONCohesive tendency
Hydrophobic particles in water attractHydrophilic particles in water repelHence, surfactant coating of nanoparticles in suspensions helps keep them apart
Dynamic behavior
Mean size increases with time
Total # decreases with time
Population balance modeling required
Dispersion just prior to processing is generally required
17Slide18
COHESIVE FORCE AS A FUNCTION OF INTER-PARTICLE DISTANCE IN A COLLOIDAL SUSPENSION18
From Drelich et al., 2006Slide19
From rti.edu
19Slide20
High-Frequency Sono-Blending of Particles in Suspension: Beaker Decantation Trials20Slide21
30 minutes Sono-fragmented Al(OH)3 (Prior to Blending) 21Slide22
20kHz sono-fragmentedfollowed by 58 kHz Blending22Slide23
20kHz sono-fragmentedfollowed by 132 kHz Blending23Slide24
Optimum Sono-Blending Timeas a function of frequency24Slide25
Effect of pH on Dispersion Stability
Nano-ZnO suspensions in pure water, ascending order of pH: 3, 5, 7, 9, 11, 13 (dispersed using 40 kHz ultrasonication) Slide26
Variation of Absorbance of Supernatant with Time of Centrifuge (4000 rpm)Slide27
ConclusionsSono-fragmentation is a promising top-down method for nano-particle synthesisLow-frequency, high-cavitation fields work bestHigh purity, ease of scale-upCan be simulated via population balance techniquesSono-dispersion is an effective method for preparing nano-particle suspensions
Higher frequencies are optimalSolution chemistry will play a roleLong-term stability to be verifiedSlide28
AcknowledgmentCrest Ultrasonics Corporation (Trenton, NJ, USA) provided the sono-processing equipment used in this study.