ABSTRACT McNEISH, DARLENE IVEY, Electrorheological Properties of Lead Titanate and Zeolite Silicone Oil Suspensions. (Under the direction of C. Maurice Balik.) The purpose of this research has been to prepare and accurately evaluate the dielectric and rheological properties of lead titanate/silicone oil and zeolite/silicone oil suspensions. The dielectric characteristics and rheological changes occurring with the application of electric fields to the suspensions were compared and the lead titanate suspensions were examined for potential use as electrorheological (ER) fluids. A dielectric spectrometer was utilized to quantify the particle/fluid dielectric mismatch of the lead titanate suspensions and the particle/fluid conductivity mismatch of the zeolite suspensions. The rheological properties were examined by conducting a series of systematic analyses without an electric field and then subsequently with the application of dc and ac fields of various frequencies. Optical microscopy of the suspensions without and with an applied electric field has been employed to determine the particle movement and structure within the suspensions. Observations of the lead titanate particles in suspension under an applied electric field elicited the electrophoretic nature of the particles, which moved towards the electrodes instead of forming chains of particles bridging the electrodes. The lead titanate suspensions exhibited either a very small positive ER effect or in some cases a slight negative ER effect, which involves a reduction in the yield stress with applied electric field. This leads us to conclude that the lead titanate/silicone oil suspensions examined in this study are ineffective ER fluid materials. The zeolite/silicone oil suspensions exhibited a positive ER effect. ELECTRORHEOLOGICAL PROPERTIES OF LEAD TITANATE AND ZEOLITE SILICONE OIL SUSPENSIONS by DARLENE IVEY McNEISH A thesis submitted to the Graduate Facility of North Carolina State University in partial fulfillment of the requirements for the Degree of Master of Science MATERIALS SCIENCE AND ENGINEERING Raleigh 2004 APPROVED BY: ____________________ ____________________ Dr. C.M. Balik Dr. H. Conrad Chair of Advisory Committee ______________________ ______________________ Dr. R.O. Scattergood Dr. A. E. Tonelli Minor Representative DEDICATED TO God and all my gifts … My sons, Spencer and Trevor, for their smiles, love, and keeping me focused on the truly important things in life, My son to be born later this year, My husband, John, for his love, encouragement, interest, and patience, My parents, for supplying lots of love while building my character and always listening to me, My endurance and inherent character that loves to learn. ii Biography DARLENE IVEY McNEISH graduated magna cum laude from North Carolina State University (Raleigh, North Carolina) in 1990 with a B.S. degree in Biology and Life Sciences and a Minor in Business Management. She was employed by CompuChem Laboratories in 1990 and subsequently employed by Underwriters Laboratories Inc. (UL) in 1992. During her employment with UL she held positions of increasing responsibility and developed her knowledge of materials. She participated on the UL team for Indoor Air Quality Research for Office Equipment with respect to volatile organic compound emissions, developed new categories for Thermoplastic Pipe Fittings for Plumbing Service and Protective Shielding Guards for Plumbing, evaluated component plastics for toxicity in food contact zones, assisted with USCG/UL research of sun degradation on marine fabrics and plastic components, and evaluated industrial laminates and polymeric materials for their flammability, electrical, mechanical, and thermal characteristics. In 1998, while employed by UL, she began graduate studies in Materials Science and Engineering at North Carolina State University. In 2003, she was employed by North Carolina State University to conduct the research encompassed within this study. Currently, she is employed by the Eastern North Carolina Plastics Technology Center (ENCPTC) as a full time instructor for an online introductory course on plastics and a seated class for polymeric materials. iii Acknowledgements The author would like to thank Dr. Balik, Dr. Scattergood, and Dr. Tonelli for being excellent professors as well as serving on her advisory committee. Additionally, many thanks are extended to Dr. Conrad for his valuable insight, guidance, and enthusiasm in the subject matter and to Dr. Balik for his technical direction. Special thanks are also extended to Dr. Jung for his assistance with the test equipment and numerous research related tasks. Appreciation is also extended to Michael Jensen for his support and encouragement for completing her thesis while employed at the Eastern North Carolina Plastics Technology Center. iv TABLE OF CONTENTS Page LIST OF TABLES…………………………………………………………………. vii LIST OF FIGURES…………………………………………………………………viii LIST OF SYMBOLS AND ABBREVIATIONS……………………………………. xi 1. INTRODUCTION……………………………………………………………….…1 1.1 Background………………………………………………………..…………. 1 1.1.1 Definition of Electrorheological (ER) Fluids …………………………1 1.1.2 First Discovery of the ER Effect……………………………………… 2 1.1.3 General ER behavior …………………………………………………. 3 1.1.4 Applications………………………………………………………...… 6 1.2 Dielectric Theory and Electrorheological Models…………………..……….10 1.2.1 Polarization………………………………………………...…………10 1.2.2 Dielectric Relaxation and the Loss Tangent……………………….…12 1.2.3 Complex Dielectric Constant, Dielectric Constant, and Loss Factor...14 1.2.4 Frequency Variation of the Dielectric Constant and Loss Factor…… 15 1.2.5 Theories of ER Fluid Behavior……………………………………… 16 1.2.6 General Overview of Applicable ER Models……………………….. 18 1.2.7 Point-Dipole Approximation…………………………………………18 1.2.8 Maxwell-Wagner - Interfacial Polarization ………………………… 19 1.2.9 Ohmic verses Non-ohmic…………………………………………… 22 1.2.10 Conduction Model……………………………………………………23 1.3 Literature Review of Experimental ER Fluids………………………………24 1.4 Purpose of Study……………………………………………………………. 35 1.4.1 Identification of Research Goals…………………………………….. 37 2. EXPERIMENTAL……………………………………………………………….. 39 2.1 Materials Selected ……………………………………………………….….. 39 2.1.1 Silicone Oil.…………………………………………………………. 39 2.1.2 Zeolite…………………………………………………………….… 41 2.1.3 Lead Titanate…………………………………………………………43 2.1.4 Desirable ER Fluid Material Properties……………………………... 46 2.1.5 Advantages/Disadvantages of Materials…………………………….. 48 2.2 Dielectric Spectroscopy………………………………………………………50 2.2.1 Method of Measurement…………………………………………….. 50 2.2.2 Permittivity and Loss Factor……….………………………………... 51 2.2.3 Ionic Conductivity and Complex Permittivity.……………………… 52 2.2.4 Description of Dielectric Analysis Equipment……………………….52 2.2.5 Test Methodology…………………………………………………… 57 v TABLE OF CONTENTS – Continued 2.2.6 Sample Preparation………………………………………………….. 58 2.2.6.1 Silicone Oil……………………………………………………….58 2.2.6.2 Zeolite and Lead Titanate Suspensions………………………….. 58 2.3 Rheology…………………………………………………………………..… 60 2.3.1 Viscosity and Shear Stress ………………………………………….. 60 2.3.2 Description of Rheometer and Additional Test Equipment…………. 61 2.3.3 Method of Measurement…………………………………………….. 61 2.3.4 Sample Preparation………………………………………………….. 63 2.4 Optical Microscopy…………………………………………………………. 64 2.4.1 Optical Microscope Information…………………………………….. 64 2.4.2 Optical Microscope with an Electric Field……..…………………….65 2.4.3 Sample Preparation/Method for Applied Field Samples……………. 65 3. RESULTS………………………………………………………………………… 67 3.1 Dielectric Analysis Data…………………………………………………… 67 3.1.1 Silicone Oil………………………………………………………….67 3.1.2 As Received and Dry 15vol% Zeolite/Silicone Oil Suspensions…...69 3.1.3 As Received and Dry 20vol% Lead Titanate/ Silicone Oil Suspensions.…………………………………………..73 3.2 Rheology Data………………………………………………………………84 3.2.1 Shear Stress verses Shear Rate, Electric Field, Strength, and Frequency…………………………………………… 84 3.2.2 Yield Stress verses Electric Field Strength and Frequency..………104 3.3 Optical Micrographs Without and With an Applied Field.……….………. 107 4. CONCLUSIONS AND RECOMMENDATIONS……………………………… 111 4.1 Conclusions – Experimental Data and Other Research ………………….…111 4.2 Recommendations for Future Testing………………………………………118 5. LIST OF REFERENCES………………………………………………………... 122 APPENDIX A: Physical Data for TICON 95 Lead T.……………………………130 APPENDIX B: Volume Fraction Calculations and Experimental Particle Conductivity Calculations………………………………………………….131 APPENDIX C: DEA Data………………………………………………………… 138 APPENDIX D: Dielectric Analysis Tables and Calculations...……………………156 APPENDIX E: Summary of DEA and Rheology Data at Room Temperature.……172 vi LIST OF TABLES Table Page 2.1 Zeolite Z3125 Product Information…………………………………. 42 2.2 Lead Titanate Product and Supplier Information……………………. 46 2.3 TA Instruments DEA 2970 Dielectric Spectrometer Parameters…….56 2.4 Composition Information for Zeolite and Lead Titanate Suspensions…………………………………………... 59 2.5 Rheology Samples and Tests Conducted……………………………. 64 3.1 Summary of Experimental Particle Conductivity Calculations………79 3.2 15vol% Zeolite/Silicone Oil Experimental Dielectric Data Analysis and Conductivity Ratios……………………………………………... 81 3.3 20vol% Lead Titanate/Silicone Oil Experimental Dielectric Data Analysis and Conductivity Ratios…………………………………... 82 3.4 Summary of the ∆K′suspension Values…………………………………. 83 3.5 Summary of the Experimental Yield Stress Values for the Zeolite Suspensions……………………………………………..102 3.6 Summary of the Experimental Yield Stress Values for the Lead Titanate Suspensions.…………………………………….