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NEEM MURI

Development of Ultra-High Pressure Supercritical Fluid Processing of Nano-sized Energetic Oxidizers

Kenneth K. KuoKenneth K. KuoAndrew C. Cortopassi, Andrew C. Cortopassi, Peter J. Ferrara,Peter J. Ferrara,

and Jonathan T. and Jonathan T. EsselEssel

The Pennsylvania State UniversityThe Pennsylvania State UniversityUniversity Park, PA 16802University Park, PA 16802

Presented atPresented atARO Review of ARO Review of NanoenergeticNanoenergetic Materials InitiativesMaterials Initiatives

MURI/DURINT ReviewMURI/DURINT ReviewAberdeen, MD Aberdeen, MD

November 7, 2006

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NEEM MURIMotivation for Nano-particle Synthesis

• The reduction of oxidizer particle size in solid propellants has shown to decrease the propellant sensitivity for hot-spot initiation by mechanical forces (van der Steen, 1995, Armstrong, 2005).

• This reduced sensitivity is attractive for the development of insensitive munition (IM) solid propellants. IM characteristics are desirable due to their safe storage and handling.

• Thus, it is important produce nano-sized energetic particles (such as RDX) to be used as the oxidizer in the manufacturing of IM solidpropellants.

• Physical grinding or milling to achieve nano-sized particles is:– Challenging to create and control desirable size distribution– Dangerous due to the force applied to fragment crystals of reactive

materialThus, we prefer the RESS process.

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NEEM MURI Principles of RESS Process• RESS stands for the Rapid Expansion of a Supercritical Solution, utilized

initially by Coffey and Krukonis in 1989 for making nano-sized particles in the pharmaceutical field.

• In this process, a solvent is pumped to supercritical temperature and pressure conditions.

• The solvent then dissolves a solute in a saturation vessel, under a controlled thermodynamic state.

• The solution is then expanded through a small nozzle to a lower temperature and pressure condition in the expansion vessel.

• This rapid expansion brings the fluid to a super-saturation condition, which introduces a phenomenon called homogeneous nucleation.

• Homogeneous nucleation causes the solute particles to reform into ultra-fine particles.

• By controlling the expansion pressure ratio, nano-sized particles can be produced.

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NEEM MURI Objectives for Nano-particle Synthesis

• The overall objective of this study is to produce nano-sized energetic particles (such as RDX, Fox-12, and TATB) by means of the rapid expansion of supercritical solutions (RESS) technique.

• The specific objectives are:– Select an adequate solvent and co-solvent for the RESS process– Determine the desirable operating conditions for the RESS system– Design, fabricate, and test an ultra-high pressure RESS system for a

broad range of operating conditions with visual observations of the dissolution and the jet expansion processes

– Demonstrate the effect of nozzle size and expansion ratio for production of nano-sized crystalline particles by RESS process

– Design an efficient way to collect nano-sized energetic particles– Characterize the nano-sized particles obtained from the RESS process

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NEEM MURI

Process Flow Diagram of

PSU’s Ultra-High Pressure RESS

System

SOLVENTSUPPLY

NESLABCOOLING

BATH

HiP 30,000 psi CO-SOLVENTLIQUID PUMP

CO-SOLVENT RESERVOIR

CV2FM1

HYDRO-PAC 30,000 psiSOLVENT

COMPRESSOR

HV1

CV1HV2T1

P1 T2

P2

TAPE HEATER

SATURATION VESSEL

TACV3

JACKET HEATER

TB

CONTROLCOMPUTER

BV1(N.O.)

P4

BV2(N.C.)

SAFETY HEAD 1

EXPANSIONVESSEL

SAFETY HEAD 2P5

T3

T4

EXHAUST

P6

SURGETANK

TC

P7

SV1(N.C.)

HV3

NANO-FILTER 1

NANO-FILTER 2

P3

BORESCOPE

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NEEM MURI Recent Modifications to RESS System

• Incorporated high-speed video camera for filming the jet expansion process (for interaction with modeling group headed by Prof. Vigor Yang).

• Utilization of a borescope with a light source for viewing the dissolution process in the saturation vessel at ultra-high pressure conditions

• Nitrogen purge system added in expansion vessel for: 1. Enhancing the filming of jet expansion process associated with

particle formation by nucleation2. Facilitating particle collection from the RESS process

• Designed and tested different particle collection systems at downstream locations of the expansion jet

• Implemented several safety features for processing energetic particles

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NEEM MURI Ultra-High Pressure RESS System

Expansion Vessel

Particle Collector

Hydro-Pac Compressor (30,000 psi)

Borescope

Surge Tank

Air Supply for Ball Valves

High Pressure Solenoid Valve to Surge Tank

High Pressure Solenoid Valve to Expansion Vessel

Saturation Vessel w/Heater

In-Line Exhaust Filter

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NEEM MURI

High-Pressure Co-Solvent Pump (30 kpsi)

CO2 Supply

NESLAB Heat Exchanger

Computer Control

Remote Control Area of Ultra-High Pressure RESS System

N2 Supply

Control Panel

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NEEM MURI Features of Control Panel

• Displays system process flow diagram

• Options for manual control of all components of the RESS system

• Stop button for emergency system shutdown

• Monitoring temperatures at key locations for all temperature controllers

• Co-solvent flowmeter w/digital display

• Directly visible pressure transducer data connection ports

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NEEM MURI Developed LabVIEW Control Program for RESS Process

Data Save Feature

Stop Button

Indicating Lights for Status of Compressor and Ball Valve

Temperature-Time Display

Pressure-Time Display Hydro-PAC Compressor Slider Control

Control Switch for Expansion Jet

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NEEM MURI Superimposed Phase Diagram of Solvent & Co-Solvent Materials for RESS Process

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NEEM MURI Use of C10H8 as a Test Substance for System Checkout Purpose

• Naphthalene (C10H8) was selected since it is not an explosive material.

• Allows the expansion process to be observed and has been used as a solute for conventional RESS system checkout purpose.

0

0.02

0.04

0.06

0.08

0.1

0.12

0 5 10 15 20 25 30

Pressure (MPa)

Sol

ubili

ty (m

ole

frac

tion)

35ºC

55ºC

60ºC

(After McHugh, Mark, Paulaitis, Michael E. “Solid Solubilities of Naphthalene and Biehenyl in Supercritical Carbon Dioxide,” Journal of Chemical Engineering Data, vol. 25, pp. 326-329, 1980.)

Solubility isotherms at different pressures

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NEEM MURI Saturation Vessel w/Heating Jacket

• Saturation vessel heated electrically by a temperature controlled heating jacket

• Temperature controlled by an Omega temperature controller

Borescope

Heater Jacket

Sample Holder

Borescope Camera

Secondary Light Source

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NEEM MURI Saturation Vessel Interior Sketch

Solvent Input

Outlet to Expansion Nozzle

Sample Holder

Saturation Vessel Lid

• 4340 alloy steel• 1000mL HiP Vessel• 3″ID, 6.5″OD and

9″ Inside Depth• Working Pressure

– 30,000 psi

Secondary Light to Solute

Container with 5-μm Porous Plate Bottom

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NEEM MURI Borescope Video of Dissolution Process in Saturation Vessel

• Solute: C10H8• Amount of

Solute: 1g• Solvent: CO2• Compression to

10,000 psi• Video shows

the filling of the saturation vessel by compressed CO2 and the dissolution of Naphthalene (C10H8)

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NEEM MURI Viewing of Solute in Saturation Vessel Using Secondary Light Source

• A secondary light passage was designed and demonstrated to illuminate the solute in the high-pressure saturation vessel using fiber optic light through a side port.

• This borescope video shows the solute sample loaded on a glass plate at the bottom of a wire mesh basket.

• Solute: C10H8• Amount of Solute: 1g• Solvent: CO2• Compression to

15,000 psi

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NEEM MURI Windowed Expansion Vessel• Stainless steel expansion vessel with four Acrylic

windows (10.25”x1.25”) for illumination and filming• Four N2 window purge lines• Phenolic particle collector at the bottom of the vessel

with easy disassembling feature• Stainless steel container located at the bottom of the

collector for primary particle collection and sample slide coating for SEM

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NEEM MURI Expansion Jet Video

• Solvent: CO2• Solute: Naphthalene, C10H8• PSV = 10,000psi• TSV = 40°C• Dnozzle = 1/32″ (~793 μm)• Diameter of Nozzle Protrusion

= 0.79″• Filming Rate = 1500 frames/s• Video displaying event

happening in jet expansion for ~ 0.5 s in real time

• Displaying Speed = 10 frames/s

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NEEM MURI SEM Micrographs of Recovered C10H8

• Small C10H8 particles agglomerate very easily

• Average particle size ~ 50 to 100 nm

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NEEM MURI Characteristics of RDX

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NEEM MURI Solubility of RDX in Supercritical CO2

• Solubility of RDX was studied as a function of pressure and temperature by Dr. Jeff Morris of ARL.

• Generally, the RDX solubility is very low in supercritical CO2. Implying the consideration of co-solvent (such as DMSO, DMF, Acetonitrile) is necessary. 0.00E+00

1.00E-05

2.00E-05

3.00E-05

4.00E-05

5.00E-05

6.00E-05

0 5 10 15 20 25 30 35 40 45 50

Pressure (MPa)

Solu

bilit

y (m

ole

frac

tion)

30ºC

35ºC

50ºC

65ºC

80ºC

(After Morris, J.B., “Solubility of RDX in Dense Carbon Dioxide at Temperatures between 303 K and 353 K”, Journal of Chemical Engineering Data, Vol. 43, pp. 269-273, 1998.) Solubility at different pressures and temperatures

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NEEM MURI Preliminary RDX Study

• Purification of military grade RDX particles was performed using recrystallization process to remove HMX.

• Observed the dissolution process of RDX in PSU’shigh-pressure saturation vessel up to ~20,000 psi and with temperature up to 60°C. Extremely slow rate of dissolution was observed.

• Co-solvent will be used to greatly enhance the solubility of RDX in supercritical solution CO2 and selected co-solvent (Acetonitrile).

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NEEM MURI Considerations of Other Energetic Ingredients

• In order to develop insensitive energetic materials, both Fox-12 and TATB are being considered due to their reduced sensitivity to shock and impact.

H2NC

NC

NH2

H

NH O

* HN

NO2

NO2

Fox-12 (C2H7N7O5)

N-GUANYLUREA-DINITRAMIDE

TATB (C6H6N6O6)

1,3,5-TRIAMINO-2,4,6-TRINITROBENZENE

NO2

NH2

NH2

NO2

O2N

H2N

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NEEM MURI Considerations of Other Energetic Ingredients (cont.)

• Even though TATB can decrease the burning rate of the solid propellant, the existing test data are solely based upon micron-sized particles.

• Acquisition of these materials is underway – Fox-12 @ $1500/kg from Eurenco Bofors– TATB @ $440/kg from Holston Army Ammunition Plant of

BAE systems

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NEEM MURI Summary of Progress

• The ultra-high pressure rapid expansion supercritical solution (RESS) system has been modified and tested successfully for producing nano-sized crystalline particles through remote control operations.

• Designed, fabricated, and tested various particle collection systems with detailed consideration and installation for achieving safe operation.

• Designed and implemented optical observation of the dissolving process of solute in high-pressure (28,000 psi) CO2 solvent under supercritical conditions.

• The expansion process of high-pressure discharging jets have been filmed by high-speed video camera through a windowed test chamber for observing the flow field structure.

• Demonstration of the working ranges of the RESS system for production of nano-sized crystalline particles, such as naphthalene.

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NEEM MURI Future Work• In order to aid in the dissolution process, agitation will be implemented

into the saturation vessel• Improve the collection rate by changing nozzle configuration for

producing dry ice during the expansion process• Perform solubility studies of RDX in supercritical CO2 with co-solvent

under different thermodynamic states• Synthesis of nano-sized RDX particles using both co-solvent and

agitation techniques • Characterization of RESS synthesized samples• Supply samples to Prof. Dana Dlott of UIUC for his work on ultrafast

dynamic measurements of nanoenergetic materials• Work with army labs on the characterization of the mechanical and

impact sensitivities of the newly created nano-sized energetic material• Synthesis of nano-sized Fox-12 and TATB particles and collect samples

for characterization

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NEEM MURI Acknowledgements

• Our thanks to the support of Dr. Ralph A. Anthenien of ARO for this MURI project under the leadership of Prof. Rich Yetter.

• The initial support of Dr. David Mann, and Dr. Kevin McNesby is also greatly appreciated.

• We like to acknowledge the technical input of Dr. Jeff Morris ofARL, Prof. Lev Krasnoperov of NJIT and Mr. Victor Stepanov of ARDEC.

• We would also like to thank Dr. Dick Beyer of ARL for his supplyof sapphire windows for our high-pressure solute dissolution process.

• Thanks for the participation of Mr. Scott Blakeslee at PSU.

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NEEM MURI

Thank you very much for your attention

Any questions?

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NEEM MURI

Spare Slides

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NEEM MURI Superimposed Phase Diagram of Solvent & Co-Solvent Materials for RESS Process

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+01

1.0E+02

-150 -100 -50 0 50 100 150 200 250 300 350 400 450 500 550 600Temperature (°C)

Pres

sure

(MPa

)

Supercritical Region of CO2

RESSTmax= 90°C

Tmelt, RDX= 204.1°C

CO2

Phase

Onset of Decomposition of RDXSolid RDX

DMSO

Acetonitrile

Compression

Expansion

DMF

Solid Naphthalene

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NEEM MURI Characteristics of Naphthalene

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NEEM MURI Characteristics of DMF

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NEEM MURI Characteristics of DMSO

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NEEM MURI Characteristics of Acetonitrile

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NEEM MURI Injection Nozzles

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NEEM MURI Nano Filter System

• Nano-filters for exhaust filtration• Two filters arranged in parallel to

allow greater exhaust mass flow rate

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NEEM MURI Particles Recovered on Collection Surfaces