Session: 16-02-01: Poster Session: NSF Research Experience for Undergraduates (REU), NSF Posters

Paper Number: 99663

99663 - Methods for Controlling and Reducing Dendritic Growth of Sodium Azide Crystals 

Sodium azide (NaN3) is a common salt crystal used for Solid-State Gas Generators (SSGG) due to its ability to produce nitrogen gas when heated. The University of Arkansas uses micro NaN3 crystals on Printed Circuit Boards (PCBs) to both adjust the attitude of CubeSats, and to inflate the balloon used to deorbit said CubeSat. A problem with NaN3 is the excessive and often uncontrollable growth of dendrites during the evaporation process. Dendrites are undesirable for CubeSat applications for two main reasons. The first being due to the limited thermal conductivity of sodium azide, any dendrites that are not on the heated pad will not generate nitrogen gas meaning that the dendrites would be ‘dead mass’. Additionally, the NaN3 may interfere with and potentially damage electronic components on the PCB if the dendritic growth remains unchecked. Due to the nature of CubeSats, neither dead mass nor potential future damage to crucial parts are feasible for successful missions.

This study looks at different methods to control and reduce dendritic growth of NaN3 crystals. Tests were conducted to observe the changes of crystallization formation based on different: air temperatures, air humidities, concentrations of NaN3, materials for the thermal pads, and different sizes of the pads that the NaN3 solution evaporates on. The first three tests adjust the evaporation rate of the solution because preliminary investigation suggests that there is a relationship between dendrite formation and evaporation rates. The final two tests attempt to influence where the dendrites travel as the solution evaporates; by providing ‘ideal’ areas for said dendrites to form. The locations are made ideal by being both on points of contact with the thermal pads on the PCB, and by being a hydrophilic area (as opposed to the rest of the area on the PCB which is hydrophobic and thus should repel the NaN3 solution).

The expected results will show that faster evaporation rates result in greater amounts of dendritic growth. Additionally, it is expected that the pad sizes will not have as much of an effect on dendritic growth at the shape of the pad does. Additionally, the more complex pad geometries (such as the triangles and star shapes) will have a greater effect on the dendritic growth than the simple shapes of the circular pads due to providing a controlled location for the dendrites to grow to.

This study was conducted as part of the University of Arkansas Research Experience for Undergraduate (REU) program sponsored by the National Science Foundation (NSF).

Presenting Author: Ismar Chew Trine University

Presenting Author Biography: Undergraduate Student at Trine University. This study was conducted as part of the University of Arkansas Research Experience for Undergraduate (REU) program sponsored by the National Science Foundation (NSF).

Authors:

Ismar Chew Trine University
Colton Bruza John Brown University
Patrick Simpson John Brown University
John Lee John Brown University
Po-hao Huang University Of Arkansas