Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2018 Experimental and theoretical investigation of organically-capped, nanoscale alkali metal hydride and aluminum particles as solid propellant additives Adam Lawrence Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Mechanical Engineering Commons Recommended Citation Lawrence, Adam, "Experimental and theoretical investigation of organically-capped, nanoscale alkali metal hydride and aluminum particles as solid propellant additives" (2018). Graduate Theses and Dissertations. 16837. https://lib.dr.iastate.edu/etd/16837 This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Experimental and theoretical investigation of organically-capped, nanoscale alkali metal hydride and aluminum particles as solid propellant additives by Adam Lawrence A thesis submitted to the graduate faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Major: Mechanical Engineering Program of Study Committee: Travis Sippel, Major Professor James Michael Jaime Juarez The student author, whose presentation of the scholarship herein was approved by the program of study committee, is solely responsible for the content of this thesis. The Graduate College will ensure this thesis is globally accessible and will not permit alterations after a degree is conferred. Iowa State University Ames, Iowa 2018 Copyright © Adam Lawrence, 2018. All rights reserved. ii DEDICATION To coffee, the greatest energy source I’ve yet encountered. iii TABLE OF CONTENTS Page LIST OF FIGURES ........................................................................................................... iv LIST OF TABLES ............................................................................................................. vi NOMENCLATURE ......................................................................................................... vii ACKNOWLEDGMENTS ............................................................................................... viii ABSTRACT ....................................................................................................................... ix CHAPTER 1. INTRODUCTION ....................................................................................... 1 1.1 Motivation ............................................................................................................... 1 1.2 Objectives ................................................................................................................ 5 CHAPTER 2. EXPERIMENTAL METHODS .................................................................. 6 2.1 nMx Material Characterization ................................................................................ 6 2.2 Composite Propellant Fabrication ........................................................................... 7 2.3 Equilibrium Calculations ......................................................................................... 8 2.4 Propellant Combustion - Agglomeration ................................................................. 9 2.5 Propellant Combustion - Lithium Combustion ..................................................... 10 2.6 Propellant Combustion - Burning Rate ................................................................. 13 CHAPTER 3. RESULTS AND DISCUSSION ................................................................ 15 3.1 nMx Material Characterization .............................................................................. 15 3.2 Equilibrium Calculations ....................................................................................... 17 3.3 Agglomeration and Particle Combustion .............................................................. 21 3.4 Lithium Combustion .............................................................................................. 25 3.5 Propellant Burning Rate ........................................................................................ 27 CHAPTER 4. CONCLUSIONS ....................................................................................... 32 REFERENCES ................................................................................................................. 34 APPENDIX A. EXAMPLES OF EMISSIVE OFF-GAS BEHAVIOR ........................... 39 APPENDIX B. EXAMPLES OF LITHIUM COMBUSTION......................................... 40 APPENDIX C. CALIBRATION CORRECTION FACTOR MATLAB CODE ............. 41 APPENDIX D. LITHIUM/GRAYBODY EMISSION OVERLAY MATLAB CODE ................................................................................................................................ 43 iv LIST OF FIGURES Page Figure 1: Left (a): Schematic of the lithium emission setup, which included two high-speed CMOS cameras with separate bandpass filters connected to a long-distance microscope lens by a beam splitter. Right (b): Bandpass filter transmission compared to propellant flame emission spectra captured from a nMx propellant burn. .......................................................... 11 Figure 2: Schematic of pressurized burn rate apparatus including the pressure vessel, high-speed CMOS camera with an attached long-distance microscope, PID controlled pressure regulation, and variac ignition source. .................. 14 Figure 3: SEM backscattered electron images at 60x (top) and 500x (bottom) magnification. Each column shows a different nMx variant at both magnification levels. ..................................................................................... 16 Figure 4: SEM images at 1500x (top) show an overview with a dashed box showing the field of view of the 5000x detail (bottom) images showing morphology of high metal content and the capping agent. .......................... 17 Figure 5: Left, (a): Theoretical specific impulse values (solid) and adiabatic chamber flame temperatures (6.89 MPa, dashed) for each propellant formulation. Right (b): Mass fraction of condensed phase products (solid) and mole fraction of hydrochloric acid (dashed) for each propellant formulation. ................................................................................. 19 Figure 6: 580 nm band-pass filtered laser backlit images of agglomeration behavior from 7 wt. % single fuel propellant formulations. Arrows denote spherical aluminum agglomerates and Al2O3 tails typically seen in micro-scale aluminized propellants. ............................................................. 23 Figure 7: Emission images of agglomeration for 7 wt. % single fuel propellant formulations. Exposure and aperture settings are identical for all images and the burning surface is outlined for clarity. ................................ 23 Figure 8: Overlaid images of lithium emission signal ratio (SRCORRECTED, red color channel) and graybody emission as monitored at 690 nm (grayscale channel) at the burning surface. .................................................................... 26 Figure 9: Burning surface history as a function of time for dual fuel propellants burned at 6.89 MPa in nitrogen gas. ............................................................. 28 v Figure 10: Average burning rates for all dual fuel propellants (a). Individual comparisons of each nMx propellant are shown to illustrate the differences in slope break location between nMx-12 (b), nMx-16 (c), and nMx-20 (d). ............................................................................................ 29 Figure A-1: Particle off-gassing from nMx-19 propellant, a highly emissive particle releases a jet of gas before lifting from the surface (a). A short time later, another less luminous particle from the same propellant also releases a burst of gas without immediately leaving the burning surface (b). .......................40 Figure B-1: Overlaid image sequence of lithium emission signal ratio (SRCORRECTED, red color channel) and graybody emission as monitored at 690 nm (grayscale channel) at the propellant burning surface. Nanoaluminized propellant images are shown as a comparative baseline without any lithium content. ..41 Figure B-2: Image sequence of an nMx-16 particle reacting at the burning surface and exhibiting a strong lithium emission ‘halo.’ The halo starts as a thin envelope attached to the particle burning surface and thickens as the particle releases from the surface and further heats and agglomerates. Lithium emission signal ratio is shown as the red image color channel and graybody emission (690 nm) is shown as the grayscale channel ..................................41 vi LIST OF TABLES Page Table 1: Propellant formulations - all propellants were manufactured using identical materials and processes, varying only in component percentage. .................. 8 Table 2: Fuel particle parameters used for theoretical performance calculations including empirical formulas, densities, and heats of formation .................... 8 Table 3: Propellant composition, Cheetah-calculated equilibrium performance with 6.89 MPa chamber pressure and an ideal expansion to 1 atm, HCl concentration, and exit plane product phase. ................................................ 21 Table 4: