University of New Mexico UNM Digital Repository Civil Engineering ETDs Engineering ETDs 7-11-2013 Understanding the Role of Gravity in the Crystallization Suppression of ZBLAN Glass Anthony Torres Follow this and additional works at: https://digitalrepository.unm.edu/ce_etds Recommended Citation Torres, Anthony. "Understanding the Role of Gravity in the Crystallization Suppression of ZBLAN Glass." (2013). https://digitalrepository.unm.edu/ce_etds/13 This Dissertation is brought to you for free and open access by the Engineering ETDs at UNM Digital Repository. It has been accepted for inclusion in Civil Engineering ETDs by an authorized administrator of UNM Digital Repository. For more information, please contact [email protected]. Anthony Samuel Torres Candidate Civil Engineering Department This dissertation is approved, and it is acceptable in quality and form for publication: Approved by the Dissertation Committee: Dr. Arup K. Maji , Chairperson Dr. Jeff M. Ganley Dr. Mahmoud R. Taha Dr. Yu-Lin Shen i UNDERSTANDING THE ROLE OF GRAVITY IN THE CRYSTALLIZATION SUPPRESSION OF ZBLAN GLASS by ANTHONY SAMUEL TORRES B.S. Civil Engineering, New Mexico State University, 2008 M.S. Civil Engineering, University of New Mexico, 2010 DISSERTATION Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Engineering The University of New Mexico Albuquerque, New Mexico May, 2013 ii DEDICATION This dissertation is dedicated to my wife, Allison, for her unwavering support to pursue my dreams. This dissertation wouldn’t exist without her love and encouragement. iii ACKNOWLEDGEMENTS I would like to express my sincerest gratitude and admiration for my advisors, Dr. Arup Maji and Dr. Jeff Ganley. I couldn’t have asked for better advisors. This research wouldn’t be possible without the efforts of Dr. Ganley and Dr. Maji. They were a great source of inspiration, aid, and friendship. I can only hope to be half as exceptional as these astounding advisors. I would also like to offer my thanks to Dr. Dennis Tucker and Dr. Dmitry Starodubov. Their support, expertise, and guidance were greatly appreciated. Additionally, I would like to thank the following individuals of the SSAIG team for their valuable assistance throughout this entire process: Brian Engberg, John Garnham, Dr. Emily Fossum, Jason Baldwin, Tom Venturino, Jared Clements, Jesse Yates, and Dr. Lauren Hunt. I have the privilege and honor of calling each of them my friend. I would also like to thank my supervisor at Applied Technology Associates, Johnathan Jones. This entire process wouldn’t have operated as smoothly without Johnathan’s efforts. This research was funded by the Air Force Research Laboratory Space Vehicles Directorate (AFRL/RV). I want to thank them for the invaluable contributions and support. Anthony Torres The University of New Mexico April, 2013 iv UNDERSTANDING THE ROLE OF GRAVITY IN THE CRYSTALLIZATION SUPPRESSION OF ZBLAN GLASS By: Anthony Samuel Torres B.S., Civil Engineering, New Mexico State University, 2008 M.S., Civil Engineering, University of New Mexico, 2010 Ph.D., Engineering, University of New Mexico, 2013 ABSTRACT Fluorozirconate glasses, such as ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF), have the potential for optical transmission from 0.3 µm in the UV to 7 µm in the IR region. However, crystallites formed during the fiber drawing process prevent this glass from achieving its low loss-capability. Other researchers have shown that microgravity processing leads to suppressed crystal growth in ZBLAN glass, which can lead to lower transmission loss in the desired mid-IR range. However, the mechanism governing crystal growth suppression has not been thoroughly investigated. In the present research multiple ZBLAN samples were subjected to a heating and quenching test apparatus on a parabolic aircraft under controlled µ-g and hyper-g environments and compared with 1-g ground tests. Optical microscopy (transmission and polarized) along with SEM examination elucidates that crystal growth in ZBLAN is suppressed when processed in a microgravity environment. Hence crystallization occurs at a higher temperature in µ-g v and the working temperature range at which the fiber can be manufactured has been extended. We postulate that the fundamental process of nano-scale mass transfer (lack of buoyancy driven convection) in the viscous glass is the mechanism responsible for crystal growth suppression in microgravity. Suppressing molecular mobility within the semi- molten glass starves nucleating crystallites and prevents any further growth. A COMSOL Multi-Physics model was developed to show the velocity contours due to convection processes in a 1-g, µ-g, and hyper-g environment. Analytical models show that while suppressing convection is relevant at fiber drawing temperatures (360°C), mass transfer due to diffusion dominates at higher temperatures leading to crystal growth at temperatures ≥400°C. ZBLAN fibers are also known for their poor handling ability. Therefore an analysis of the thermal degradation of ZBLAN optical fibers based on fracture mechanics was also conducted. Conditions of crack initiation and stable versus unstable crack growth leading to fiber fracture were analyzed to explain behavior observed from controlled flexure tests of ZBLAN optical fibers exposed to various temperatures. vi TABLE OF CONTENTS LIST OF FIGURES ....................................................................................................................................................... ix LIST OF TABLES ..................................................................................................................................................... xiv CHAPTER 1 – INTRODUCTION ............................................................................................................................. 1 1.1 OUTLINE OF DISSERTATION ........................................................................................................................ 1 1.2 BACKGROUND ................................................................................................................................................. 2 1.3 ZBLAN ............................................................................................................................................................ 5 1.4 MICROGRAVITY .............................................................................................................................................. 6 1.5 OVERVIEW OF RESEARCH ............................................................................................................................. 8 CHAPTER 2 – BACKGROUND INFORMATION AND LITERATURE REVIEW ..................................... 9 2.1 LITERATURE REVIEW ........................................................................................................................................ 9 2.2 MICROGRAVITY EXPERIMENTS ..................................................................................................................... 12 2.3 MICROGRAVITY EXPERIMENTS ON ZBLAN ............................................................................................... 23 2.4 RELATED WORK ON ZBLAN ........................................................................................................................ 34 2.5 CRYSTAL GROWTH PROCESSES .................................................................................................................... 44 2.6 ASSESSMENT OF THERMAL DEGRADATION AND FRACTURE OF ZBLAN FIBERS ............................... 49 2.7 CONCLUSIONS .................................................................................................................................................. 51 CHAPTER 3 – EXPERIMENTAL PROGRAM .................................................................................................. 53 3.1 MICROGRAVITY TESTING ............................................................................................................................... 53 3.2 DESCRIPTION OF QUENCHER AND OPERATION ......................................................................................... 53 3.3 CHARACTERIZATION PROCESS ...................................................................................................................... 55 3.4 PRE-HEAT FURNACE ...................................................................................................................................... 56 3.4 ANNEALING FURNACE .................................................................................................................................... 64 3.5 MATERIALS ....................................................................................................................................................... 71 3.6 MATERIAL CHARACTERIZATION .................................................................................................................. 71 3.7 EXPERIMENTAL PROCEDURE ........................................................................................................................ 76 3.8 SUMMARY ......................................................................................................................................................... 79 CHAPTER 4 – RESULTS AND ANALYSIS ....................................................................................................... 80 4.1 OPTICAL MICROSCOPY ..................................................................................................................................
Details
-
File Typepdf
-
Upload Time-
-
Content LanguagesEnglish
-
Upload UserAnonymous/Not logged-in
-
File Pages204 Page
-
File Size-