TECHNICAL ARTICLE Experimental and Analytical Techniques for Studying ZBLAN Crystallization in Microgravity A. Torres 1 , J. Ganley 2 , and A. Maji 3 1 Department of Engineering Technology, Texas State University, San Marcos, TX 2 Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, Albuquerque, NM 3 Department of Civil Engineering, University of New Mexico, Albuquerque, NM Keywords ZBLAN, Microgravity, Crystallization Correspondence A. Torres, Department of Engineering Technology, Texas State University, San Marcos, TX 78666, USA Email: ast36@txstate.edu Received: January 6, 2014; accepted: February 18, 2014 Abstract One of the promising new areas of materials research is in the field of microgravity. Microgravity experimentation enables new materials to be developed and traditional materials to be improved, which cannot be completed under terrestrial conditions. Recent experiments on ZBLAN (ZrF 4 –BaF 2 –LaF 3 –AlF 3 –NaF) glass have shown that, when heated, there is a crystallization dependency on gravity. This crystallization dependency limits the optical transmissibility of this material, due to crystallites forming during the fiber drawing process. ZBLAN glass has the theoretical potential for optical transmission in the range of 0.3 –7 μm, which would facilitate much needed mid-infrared (IR) fiber technology. Past researchers have completed ZBLAN crystallization microgravity experiments, with limited details on the experimental technique and analysis methods. This study demonstrates an alternative experimental technique for ZBLAN microgravity testing and postprocessing techniques that reveal crystallinity in the sample. Introduction Microgravity is a term that can be used colloquially to mean the lack of gravity. In a scientific sense, microgravity implies a local acceleration level much less than unit gravity, 9.81 m/s 2 , more specifically in the order of 10 −6 g(μ-g). Microgravity can be achieved in varying ways, such as in an orbiting spacecraft, suborbital rocket (sounding rocket), or a parabolic flight aircraft. Each method provides a varying duration and magnitude of reduced gravity. These methods allow researchers to determine the effect of gravity on certain processes. The material used for this research is a flu- orozirconate glass of the Heavy Metal Fluo- ride Glass (HMFG) family known as ZBLAN (ZrF 4 –BaF 2 –LaF 3 –AlF 3 –NaF). ZBLAN is a fluoride- based optical fiber primarily sought out for its supe- rior infrared transmissibility. The optical transmission spectrum for ZBLAN is from 0.3 μm in the ultravi- olet (UV) to 7 μm in the infrared (IR) region. 1 The main obstacle with ZBLAN glass is the problem of devitrification (crystallization). ZBLAN glass has a narrow working temperature range and the viscos- ity is a strong function of temperature, which makes these glasses unstable and prone to crystallization. 2 Many researchers have conducted studies on crys- tal growth under microgravity. 3 – 8 Whereas these researchers have studied ZBLAN, protein crystals, and semiconductor growth under microgravity, all have noticed that devitrification processes are sup- pressed in microgravity. These studies used sounding rockets, parabolic flight aircraft, and even a drop tower to achieve free fall. The authors also noticed that crystal growth was increased during times of high accelerations. 7 When using the parabolic flight aircraft there are periods of approximately 2-g accel- erations. Varma et al. detected twice as many crystals formed during the period of high acceleration as ter- restrial processed fibers. Most of these experimental programs used an automated glass heating appara- tus and have limited detail to the exact science and build of the experimentation. 3 – 8 It should also be noted that these studies were first completed in 1990 Experimental Techniques (2014)  2014, Society for Experimental Mechanics 1 doi:10 1 / 007 s40799-016-00 - . 52 6