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A. Kesavasami, K. Khinchi, A. Goyal, N. Roy and R. Nagarajan Dept of Chemical Engineering IIT Madras CAV 2012, Aug 13-16, 2012, Singapore Sono-Synthesis.

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Presentation on theme: "A. Kesavasami, K. Khinchi, A. Goyal, N. Roy and R. Nagarajan Dept of Chemical Engineering IIT Madras CAV 2012, Aug 13-16, 2012, Singapore Sono-Synthesis."— Presentation transcript:

1 A. Kesavasami, K. Khinchi, A. Goyal, N. Roy and R. Nagarajan Dept of Chemical Engineering IIT Madras CAV 2012, Aug 13-16, 2012, Singapore Sono-Synthesis and Dispersion of Nano-Particles: Experiments & Simulation

2 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 Streaming

3 3

4 SONO- FRAGMENTATION (SIZE REDUCTION) 4 Particles Bubble

5 5 Particles Bubble Bubble Collapse due to Implosion Particle Fragments due to a)Violent Bubble collapse b)Inter-particle attrition SONO- FRAGMENTATION (SIZE REDUCTION)

6 6 Particles Bubble Bubble Collapse due to Implosion Particle Fragments due to a)Violent Bubble collapse b)Inter-particle attrition Fragmented Particle SONO- FRAGMENTATION (SIZE REDUCTION)

7 STATE-OF-THE -ART ULTRASONIC FACILITY 7 58 kHz, 500 W power Sonicator ( Tank Type) 20 kHz, 1000 W power Sonicator ( Probe Type)

8 ANALYZERS USED 8

9 20 kHz_ 500 W 30 minutes PARTICLE SIZE BEFORE AND AFTER SONO-FRAGMENTATION 9 Feed Particle Size (74-80 microns)

10 EFFECT OF FREQUENCY ON SONO- FRAGMENTATION 10

11 EFFECT OF APPLIED ULTRASONIC POWER ON SONO-FRAGMENTATION 11 Sonic power plays a key role in intensifying the cavitation bubble movement, bubble collapse, and inter-particle attrition.

12 20 kHz, 1000 W, Sono- fragmented WFA nm dimensions confirmed. 12 HR TEM PICTURES

13 Simulation of Sono-Fragmentation

14

15 MODEL VALIDATION WITH MEASURED DATA

16 16

17 DISPERSION OF NANOPARTICLES IN SUSPENSION  Cohesive tendency  Hydrophobic particles in water attract  Hydrophilic particles in water repel  Hence, 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 17

18 COHESIVE FORCE AS A FUNCTION OF INTER- PARTICLE DISTANCE IN A COLLOIDAL SUSPENSION 18 From Drelich et al., 2006

19 From rti.edu 19

20 High-Frequency Sono-Blending of Particles in Suspension: Beaker Decantation Trials 20

21 30 minutes Sono-fragmented Al(OH) 3 (Prior to Blending) 21

22 20kHz sono-fragmented followed by 58 kHz Blending 22

23 20kHz sono-fragmented followed by 132 kHz Blending 23

24 Optimum Sono-Blending Time as a function of frequency 24

25 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)

26 Variation of Absorbance of Supernatant with Time of Centrifuge (4000 rpm)

27 Conclusions Sono-fragmentation is a promising top-down method for nano-particle synthesis – Low-frequency, high-cavitation fields work best – High purity, ease of scale-up – Can be simulated via population balance techniques Sono-dispersion is an effective method for preparing nano-particle suspensions – Higher frequencies are optimal – Solution chemistry will play a role – Long-term stability to be verified

28 Acknowledgment Crest Ultrasonics Corporation (Trenton, NJ, USA) provided the sono-processing equipment used in this study.


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