30 Ossipee Road P.O. Box 9101 Newton, MA 06-9101 Phone: 617 969-55 Fax: 617 965-113 www.microfluidicscorp.com De-agglomerattion of CeO Nanoparticles using the Microfluidizer. Prepared by: The Microfluidics Technology Center
Product: Objective: Conclusion: The product was an acidic aqueous suspension of 30% wt. high crystallite cerium dioxide (CeO ) for use in polishing applications. The objective of the testing was to deagglomerate the CeO particles and to try and reduce the particle size to 50 nm. The median particle size was reduced from 09 nm to 81 nm after one pass through the G10Z (87 microns) interaction chamber (IXC) at 30,000 psi using the M-110EH Microfuidizer processor. Recommendations: Process the dispersion with an M-110P, M-110EH, or M-700 Microfluidizer processor. Process with the G10Z (87 µm) IXC at 30,000 psi. Optimize the following processing parameters: o Formulation (dispersant, % wt. solid, surfactant) o Number of passes Analyze the processed materials to determine if it meets the desired specifications. Equipment: Microfluidizer processor M-110EH IXC configurations G10Z (87 µm) Microscope Olympus BH- optical with attachments Diluent De-ionized water (17.1 MegaOhms) Particle Size Analyzer Horiba LA 910 (SLS) Malvern Zetasizer NanoS (DLS) Refractive Index (relative) 1.67 0.10i Procedure: Analysis: Results: Two liters of the aqueous CeO was premade and shipped to Microfluidics for processing. Prior to processing, the unprocessed sample was hand stirred and sonicated for 10 minutes to re-disperse the settled material. All samples were processed at either 0,000 or 30,000 psi using the M-110EH Microfluidizer processor with the G10Z (87 µm) IXC. Analysis involved the use of the optical microscope as well as a static light scattering particle analyzer (Horiba LA 910) and a dynamic light scattering particle analyzer (Malvern Zetasizer NanoS). Images and particle size analysis was done with the unprocessed sample and with the samples at the conclusion of each test. Table 1 lists the processing conditions for the trials and the resulting particle sizes: the mean particle size, the d10, the d50, and the d90 of all the samples analyzed. The particle size distribution graphs can be found in Figure 1-. Microscope images of the samples are shown in Figure 3. 1
30% by wt. CeO in water Table 1: Listed below is the particle size data for the CeO sample. All of the particle size analysis measurements were done on the Horiba LA 910 and the Malvern Zetasizer NanoS. Malvern NanoS (no sonication) Horiba LA 910 (1 min sonication) Mean (nm) Mean (nm) d10 (nm) d50 (nm) d95 (nm) NA NA Unprocessed 38.8 6 137 09 38 G10Z 30,000 1 136.1 9 5 8 166 17.1 87 5 81 151 0,000 1 56.7 119 55 10 53 15.7 111 53 91 7 Formulation Chamber Pressure (psi) Pass Frequency (%) 0 18 16 1 1 10 8 6 0 passes 1 pass unprocessed 0.01 0.1 1 10 Diameter (um) Figure 1: Particle size distribution of the CeO sample processed at 30,000 psi using the M-110EH Microfluidizer processor with the G10Z (87µm) IXC. Frequency (%) 18 16 1 1 10 8 6 passes 1 pass 0 0.01 0.1 1 10 Diameter (um) unprocessed Figure : Particle size distribution of CeO sample processed at 0,000 psi using the M-110EH Microfluidizer processor with the G10Z (87µm) IXC.
Unprocessed 1 pass, 30 kpsi passes, 30 kpsi 1 pass, 0 kpsi passes, 0 kpsi Figure 3: Images of the CeO sample processed using the M-110EH Microfluidizer processor with the G10Z (87 µm) IXC. 3
Comments: The high shear of the G10Z at 30,000 psi has quantitatively reduced the particle size to 8 nm in a single pass. There was not a significant reduction in particle size with additional passes. Therefore, a single pass is the recommended processing cycle. Particles under 100 nm in size tend to have a very high surface area to volume ratio which leads to particle size agglomeration over time. A compatible surfactant is recommended to ensure the particles do not aggregate. ****************************************** Glossary APM: IXC: Pass: Psi: Unprocessed: Auxiliary processing module/ interaction chamber used as either a pre-processing chamber for a solid dispersion application, or as a back pressure module to create a back pressure for Y-chamber applications. Interaction chamber; a cylindrical module with a specific orifice and channel design thru which fluid is conducted at high pressures to control shear rates. One (1) processing cycle. Pounds per square inch. A sample that has not experienced any passes through the Microfluidizer processor.