Journal of Sol-Gel Science and Technology

, Volume 86, Issue 2, pp 329–342 | Cite as

Production of monodisperse cerium oxide microspheres with diameters near 100 µm by internal-gelation sol–gel methods

  • Jeffrey A. Katalenich
  • Brian B. Kitchen
  • Bruce D. Pierson
Original Paper: Fundamentals of sol-gel and hybrid materials processing


Internal-gelation sol–gel methods have used a variety of sphere-forming methods in the past to produce metal oxide microspheres, but typically with poor control over the size uniformity at diameters near 100 µm. This work describes efforts to make and measure internal-gelation, sol–gel microspheres with very uniform diameters in the 100–200-µm size range using a two-fluid nozzle. A custom apparatus was used to form aqueous droplets of sol–gel feed solutions in silicone oil and heat them to cause gelation of the spheres. Gelled spheres were washed, dried, and sintered prior to mounting them on glass slides for optical imaging and analysis. Microsphere diameters and shape factors were determined as a function of silicone oil flow rate in a two-fluid nozzle and the size of a needle dispensing the aqueous sol–gel solution. Nine batches of microspheres were analyzed and had diameters ranging from 65.5 ± 2.4 µm for the smallest needle and the fastest silicone oil flow rate to 211 ± 4.7 µm for the largest needle and the slowest silicone oil flow rate. Standard deviations for measured diameters were less than 8% for all samples and most of them were less than 4%. Microspheres had excellent circularity with measured shape factors of 0.9–1. However, processing of optical images was complicated by shadow effects in the photoresist layer on glass slides and by overlapping microspheres. Based on the calculated flow parameters, microspheres were produced in a simple dripping mode in the two-fluid nozzle. Using flow rates consistent with a simple dripping mode in a two-fluid nozzle configuration allows for very uniform oxide microspheres to be produced using the internal-gelation sol–gel method.


Internal gelation Cerium oxide Microsphere Monodisperse Two-fluid nozzle Nuclear fuel 



The authors would like to acknowledge and thank Pilar Herrera-Fierro of the University of Michigan’s Lurie Nanofabrication Facility for her instruction and assistance with optical microscopy. The authors would also like to thank Dr. Gary Was of the University of Michigan Department of Nuclear Engineering and Radiological Sciences for his input on this work. This research was conducted with government support under and awarded by DoD, Air Force Office of Scientific Research, and National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a. This material is based upon work supported by the National Science Foundation Graduate Student Research Fellowship under Grant No. DGE 1256260. Any opinion, findings, and conclusions or recommendations expressed in this material are that of the author and do not necessarily reflect the views of the National Science Foundation. This material is based upon work supported by the Center for Space Nuclear Research (CSNR) under the Universities Space Research Association (USRA) Subcontract 06711-003. The USRA operates the CSNR for the Idaho National Laboratory.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2018

Authors and Affiliations

  1. 1.Department of Nuclear Engineering and Radiological SciencesUniversity of MichiganAnn ArborUSA
  2. 2.Pacific Northwest National LaboratoryRichlandUSA

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