1. Thermite Additive Manufacturing (AM) Feedstocks
UNCLASSIFIED
Thermite Additive Manufacturing (AM) Feedstocks
S. M. La Vars, M. G. Morgan, J. S. Brusnahan
Nov 2019

2. Thermites Reactive mixtures of a metal and metal oxide:
CLASSIFICATION
UNCLASSIFIED
Thermites
Reactive mixtures of a metal and metal oxide:
Al, Mg, Ti
Fe2O3, Fe3O4, CuO, Bi2O3, MoO3, MnO, Cr2O3, PbO, PbO2
Typically loose powder mixtures
Does not require air to burn
Used to produce:
High heat
Solid reaction products
Little to no gas
Inter-metallic alloys
Applications:
Cutting
Perforating
Welding
Incendiaries
Limitations:
Do not press well
Blocks prone to layering/cracking
Typically difficult to ignite

3. Additive Manufacturing (AM)
UNCLASSIFIED
Additive Manufacturing (AM)
High Energy
Low Energy
Directed Energy Deposition
Focused thermal energy is used to fuse materials as they are being deposited
Sheet Lamination
Sheets of material are bonded to form an object
Binder Jetting
Liquid bonding agent is selectively deposited to join powder materials
Vat Photopolymerisation
Liquid photopolymer is selectively cured by light-activated polymerisation
Powder Bed Fusion
Thermal energy selectively fuses regions of a powder bed
Material Extrusion
Material is selectively dispensed through a nozzle or orifice
Material Jetting
Droplets of build material are selectively deposited

4. Potential AM Technologies
UNCLASSIFIED
Potential AM Technologies
Filament Extrusion:
Heated thermoplastic filament with pyrotechnic filler that sets as it cools
Screw:
Heated powder/pelleted mixture of pyrotechnic and binder that sets as it cools or chemically cross-links
Plunger/Syringe:
Melted thermoplastic and pyrotechnic solid mixture that sets as it cools
Solubilised binder/surfactants and pyrotechnic mixture, sets as solvent evaporates or binder chemically cross- links
Ref: Gonzalez-Gutierrez et al, Materials, 2018, 11(840)

5. Advantages of AM for Thermites
UNCLASSIFIED
Advantages of AM for Thermites
AM Benefits:
One formulation for multiple applications
Novel architectures
Low cost
Tailored energy release
Key Requirements:
Produces desired pyrotechnic effect
Good mechanical strength
Chemically compatible
Thermally stable components
Safety:
Reduced sensitiveness to ignition stimuli
No need to press
Remote production a possibility
Potential for in situ mixing of separate feedstocks (not energetic until printed)

6. Experimental Methods Formulation Development:
UNCLASSIFIED
Experimental Methods
Formulation Development:
Ingredient selection
Fuel
Oxidiser
Thermite stoichiometry selection
Thermodynamic Modelling (FactSage)
AM feedstock development
Binder selection
Solvent selection
Solids loading
Formulation Characterisation:
Initial Syringe Extrusion
Chemical Compatibility
Simultaneous Differential Thermal (SDT) analysis
Pressure Vacuum Stability Testing (PVST)
Sensitiveness
Temperature of Ignition (T of I)
Impact (Rotter impact test)
Friction (BAM friction test)
Electrostatic Discharge (ESD)
Ignition Testing

7. Thermite Ingredients Fuel: Oxidisers: Aluminium powder
CLASSIFICATION
UNCLASSIFIED
Thermite Ingredients
Fuel:
Aluminium powder
Average particle size = 11 µm
Oxidisers:
Copper(II) oxide (CuO)
Average particle size = 7 µm
Bismuth(III) oxide (Bi2O3)
Average particle size = 6 µm
Scale bar descriptors in white text behind images. Send images to back if required.
SEM images of Aluminium powder (left), copper(II) oxide (centre), bismuth(III) oxide (right). Scale 20 µm.

8. Thermite Stoichiometry
UNCLASSIFIED
Thermite Stoichiometry
Thermodynamic Modelling:
Can be used to reduce the cost and time of energetic materials development
Can select stoichiometry to maximise:
Reaction temperature
Product phase (solid, molten, gaseous)
Maximised
Output
CuO
Bi2O3
wt%
Temp.
2566 °C 81
2917 °C
89.5
Gas
34 %
81.5
86 %
92.5
Liquid
100 % 90
96 % 98
FactSage plots of CuO/Al and Bi2O3/Al thermites with increasing oxidiser content

9. Binder Selection and Solids Loading
UNCLASSIFIED
Binder Selection and Solids Loading
Polymethyl methacrylate
(PMMA)
Component
wt%
Binder 10
Al* 18
9.3
CuO* 72
Bi2O3*
83.4
Solids loading 90
Polylactic acid
(PLA)
* Stoichiometric thermite wt%
Thermoplastics
Non-Hazardous
Most likely decomposition products are CO2 and H2O
Good mechanical properties m.p. 160 °C OB = %
Commonly used for filament
m.p °C
OB = %

10. Inert Formulations (90 wt% Solids Loading)
UNCLASSIFIED
Inert Formulations (90 wt% Solids Loading)
PMMA
PLA
CuO
Bi2O3 Al

11. Initial Syringe Extrusion
UNCLASSIFIED
Initial Syringe Extrusion
Oxidiser
Binder
Spreading
Substrate Adhesion
Layer Adhesion
Layer Structure
CuO
PLA
2-4 mm
Good
Thick 3D Structure
Bi2O3
Poor
PMMA
3-5 mm
Thin 3D Structure

12. Chemical Compatibility
UNCLASSIFIED
Chemical Compatibility
Pressure Vacuum Stability Test (PVST):
Measures the stability of energetic materials by the volume of gas liberated when heating the sample under vacuum
The volume of gas generated by any reaction between two components of a mixture must be < 5 mL (1 mL/g)
Simultaneous Differential Thermal (SDT) Analysis:
Ingredient thermal profiles
Melting
Sublimation
Decomposition
Chemical Compatibility is determined by the difference in thermal events of mixed ingredients (ΔT)
ΔT < 4 °C = Compatible
4 oC < ΔT < 20 °C = A degree of incompatibility
ΔT > 20 °C = Incompatible

13. PVST of Thermite AM Feedstock Ingredients
UNCLASSIFIED
PVST of Thermite AM Feedstock Ingredients
Evolved Gas
(mL/g) VR
(mL) Al
0.63 -
CuO
0.05
Bi2O3
0.02
PMMA
0.11
PLA
Al/PMMA
1.12
3.78
CuO/PMMA
0.80
3.61
Bi2O3/PMMA
0.76
3.31
Al/PLA
1.38
5.19
CuO/PLA
1.00
4.75
Bi2O3/PLA
0.93
4.32
VR = M – (E + S)
Where:
VR – Volume of gas evolved from reaction between ingredients
M – Gas evolved from 5 g of 1: mixture
E – Gas evolved from 2.5 g of thermite ingredient
S – Gas evolved from 2.5 g of binder

14. SDT of Thermite Ingredients with PMMA
UNCLASSIFIED
SDT of Thermite Ingredients with PMMA
PMMA Thermal Events:
Chain end decomposition (Td): °C
Chain backbone decomposition (T'd): °C
Decomposition product reactions/chain scissions (To): > 400 °C Td
ΔTd
T'd
ΔT'd To
ΔTo
PMMA
288.5
391.0
451.7
PMMA/CuO
247.5
41.1
299.7
91.3
369.0
82.7
PMMA/Bi2O3
297.4
8.8
386.2
4.8
424.3
27.4
PMMA/Al
292.3
3.8
377.9
13.1
424.5
27.2

15. SDT of Thermite Ingredients with PLA
UNCLASSIFIED
SDT of Thermite Ingredients with PLA
PLA Thermal Events:
Melting point (Tm): °C
Decomposition temperature (Td): °C
Decomposition product reactions/chain scissions (To): >400 °C Tm
ΔTm Td
ΔTd To
ΔTo
PLA
145.6 -
345.6
374.6
PLA/CuO
148.7
3.1
340.6
4.9
373.6
1.0
PLA/Bi2O3
148.2
2.6
264.6
81.0
377.4
2.8
PLA/Al
147.4
1.8
344.8
0.8
384.9
10.3

16. Compatibility Summary
CLASSIFICATION
UNCLASSIFIED
Compatibility Summary
PMMA:
PVST Results:
Compatible with CuO
Compatible with Bi2O3
Compatible with Al
SDT Results:
Incompatible with CuO
A degree of incompatibility with Bi2O3
A degree of incompatibility with Al
PLA:
PVST Results:
Compatible with CuO
Compatible with Bi2O3
A degree of incompatibility with Al
SDT Results:
A degree of incompatibility with CuO
Incompatible with Bi2O3

17. Sensitiveness: Thermite/PMMA Feedstocks
UNCLASSIFIED
Sensitiveness: Thermite/PMMA Feedstocks
CuO/Al
PMMA/CuO/Al
Bi2O3/Al
PMMA/Bi2O3/Al
T of I (°C)
>400
BAM Friction (N)
>360
168
Rotter Impact (F of I) 60 70 40 80
Static Discharge* (J)
0.045
4.5
0.45
* Minimum energy to cause ignition
PMMA/CuO/Al:
No change to T of I (insensitive)
No change to friction sensitiveness (insensitive)
Marginally less impact sensitive
Significantly less ESD sensitive
PMMA/Bi2O3/Al:
No change to T of I (insensitive)
Significantly less friction sensitive
Significantly less impact sensitive
Significantly less ESD sensitive

18. Sensitiveness: Thermite/PLA Feedstocks
UNCLASSIFIED
Sensitiveness: Thermite/PLA Feedstocks
CuO/Al
PLA/CuO/Al
Bi2O3/Al
PLA/Bi2O3/Al
T of I (°C)
>400
BAM Friction (N)
>360
168
Rotter Impact (F of I) 60 70 40
Static Discharge* (J)
0.045
4.5
0.45
* Minimum energy to cause ignition
PLA/CuO/Al:
No change to T of I (insensitive)
No change to friction sensitiveness (insensitive)
Marginally less impact sensitive
Significantly less ESD sensitive
PLA/Bi2O3/Al:
No change to T of I (insensitive)
Significantly less friction sensitive
Significantly less impact sensitive
Significantly less ESD sensitive

19. Thermite AM Feedstock Pyrotechnic Effects
UNCLASSIFIED
Thermite AM Feedstock Pyrotechnic Effects
PMMA/CuO/Al
PMMA/Bi2O3/Al

20. Thermite AM Feedstock Pyrotechnic Effects
UNCLASSIFIED
Thermite AM Feedstock Pyrotechnic Effects
PLA/CuO/Al
PLA/Bi2O3/Al

21. Summary Thermite AM feedstocks were produced at 90 wt% solids loading
UNCLASSIFIED
Summary
Thermite AM feedstocks were produced at 90 wt% solids loading
PMMA/CuO/Al
PMMA/Bi2O3/Al
PLA/CuO/Al
PLA/Bi2O3/Al
All feedstocks readily ignited
All feedstocks were significantly less sensitive to ESD than traditional thermite
Bi2O3/Al thermite AM feedstocks were significantly less sensitive to friction and impact than traditional thermite

22. Conclusions and Future Work
UNCLASSIFIED
Conclusions and Future Work
Conclusions:
There is potential for the preparation of inert feedstocks for point-of- printing energetic material production
The utilisation of pyrotechnic feedstocks for AM technologies may provide significant safety advantages over traditional production methods
Future Work:
Formula optimisation
Investigate potential additives
Feedstock harmonisation with custom 3DP hardware/ software

23. Acknowledgements Sensitiveness testing: Reviewing and Advising:
UNCLASSIFIED
Acknowledgements
Sensitiveness testing:
Craig Wall
Joel Huf
Mark Mitchell
Reviewing and Advising:
Phil Davies
Chad Prior
Andrew Hart

24. Active Aluminium Content
UNCLASSIFIED
Active Aluminium Content
Al particles naturally coated in Al2O3
SDT used to measure % Al available for reactions (Al2O3 inert)
Oxidation occurs in stages:
Mass loss due to water < 200 °C
Al particle core melts
Molten core expands Al2O3 shell
Cracks in shell blocked as Al oxidises
Last core Al slowly oxidises
Active Al content = 66.2 wt%