© Fraunhofer ICT

Aging of RDX Crystals investigated

by X-ray Diffraction

Michael Herrmann and Manfred A. Bohn

2013 IM & EM Technical Symposium

October 7-10, 2013

San Diego, California, USA

Abstract number 16106

© Fraunhofer ICT

Non-EM phase transitions

crystal growth and morphologic transitions

frequency shifts of oscillator crystals

loss of water (e.g. combined with a significant change in color)

Energetic Materials

release of residual H2O from HMX

phase transitions of ammonium nitrate

significant crystal growth on temperature cycling of AN (Tropicalization)

no significant changes of the shock sensitivity after aging of PBXN-109

formulations when RS-RDX is included, which does not seem to be the case

for standard RDX produced by the Bachmann process

-> Aging must be affecting the RDX itself (Spyckerelle)

-> Microstructure of Crystals

Literature: Aging of Crystals

© Fraunhofer ICT

Crystal structure C3H6N6O6; orthorhombic; Space group: Pbca

a = 13.182 Å; b = 11.574 Å; c = 10.709 Å;

atom positions….,

Size and shape of

crystals

Inclusions of solvents

Impurities, e.g. HMX

Lattice defects

e.g. Dislocations in RDX

RDX

Microstructure of RDX

© Fraunhofer ICT

Gallagher H.G. et al., Phil. Trans. R. Soc. Lond., 1992, A 339, 293-303

Armstrong R. W. et al., Proc. Mat. Res. Soc. Symp., Vol 296, 1993, 227-232

Dislocation Slip Systems

(010)[001],

{021} and {02-1} [100]

(slip plane and Burgers vector)

Microstructure of RDX

© Fraunhofer ICT

• Non-destructive

• For powders and

but also composites as PBX

• Separate information of

ingredients

• Benchmarking at the

Synchrotron ANKA

dhkl= lattice plane distance, θ = diffraction angle, λ = wavelength

X-ray Diffraction (XRD) Techniques for

Microstructure

© Fraunhofer ICT

2θ scans & Rietveld-Analysis (RVA) for fine

powders

Peak positions

-> Lattice parameters

(Elementary Cell)

-> Crystal density

-> Residual strain

Profile (width/shape)

-> Crystallite Size

-> Microstrain

(Double Voigt in RVA)

Intensity

-> Concentration

(Quantitative Analysis)

-> Degree of crystallinity

363432302826242220181614

14,000

12,000

10,000

8,000

6,000

4,000

2,000

0

-2,000

hkl_Phase 0.00 %

Rietveld-Plot

© Fraunhofer ICT

Herrmann, M., Kempa, P.B., Doyle, S., 2007, Z. Kristallogr. Suppl. 26, 557.

Source & Detector fixed in reflection condition

Information on single coarse crystallites

(grain by grain)

fine fraction in underground

Stochastic multi crystallite analysis

-scan for coarse powders (rocking curves)

0.0

0.5

1.0

0.00 0.02 0.04 0.06 0.08 0.10

FWHM(ω)

no

rma

lize

d c

um

ula

tive

fre

qu

en

cy .

RS-RDX

RDX

I-RDX

61.5461.5261.561.4861.4661.4461.4261.461.3861.3661.3461.3261.361.2861.2661.2461.2261.261.1861.1661.1461.1261.161.0861.0661.04

7,500

7,000

6,500

6,000

5,500

5,000

4,500

4,000

3,500

3,000

2,500

2,000

1,500

1,000

500

0

© Fraunhofer ICT

Samples & Experimental

aged in air* aged in Ar*

storage time at 90°C 0d 15d 30d 15d 30d

2θ scans

I-RDX, M3C 2 x 1 x 1 x 1 x 1 x

I-RDX, Class 1 2 x 1 x 1 x 1 x 1 x

S-RDX Typ I, Class 5 2 x 1 x 1 x 1 x 1 x

S-RDX Typ I, Class 1 2 x 1 x 1 x 1 x 1 x

scans

I-RDX, Class 1 1 x 1 x 1 x 1 x 1 x

S-RDX Typ I, Class 1 1 x 1 x 1 x 1 x 1 x

© Fraunhofer ICT

Results: 2θ scans

Smooth profiles and reproducible

intensities with fine powders

Ragged profiles in coarse samples

-> poor orientation statistics

I-RDX, Class 1, 3768S03 - File: I-RDX_3768S03_2.raw - Type: Lock

I-RDX, Class 1, 3768S03 - File: I-RDX_3768S03_1.raw - Type: Lock

Lin

(C

ou

nts

)

0

100000

200000

2-Theta - Scale

25 26 27 28 29 30

I-RDX, M3C, 4795S04 - File: I-RDX_4795S04_2.raw - Type: Locked

I-RDX, M3C, 4795S04 - File: I-RDX_4795S04_1.raw - Type: Locked

Lin

(C

ou

nts

)0

100000

200000

2-Theta - Scale

25 26 27 28 29 30

Fine RDX powders

Coarse RDX powders

© Fraunhofer ICT

No significant crystalline HMX in I-RDX but small amount in S-RDX

Results: Impurities

00-045-1539 (C) - beta-Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine - C4H8N8O8 - Y: 1.7

00-046-1606 (*) - Cyclotrimethylenetrinitramine - C3H6N6O6 - Y: 24.64 % - d x by: 1. - WL: 1

ST-RDX Typ I, Class 1, DDP04D0028E - File: ST-RDX_DDP04D0028E_1.raw - Type: Locke

I-RDX, Class 1, 3768S03 - File: I-RDX_3768S03_1.raw - Type: Locked Coupled - Start: 5.00

Lin

(C

ou

nts

)

0

10000

20000

30000

40000

50000

60000

70000

2Theta-scan

17 18 19 20 21 22 23

pattern of S-RD PDF-46-1606, RDX

pattern of I-RDX PDF 45-1539, HMX

Reference data of the International Centre for Diffraction Data (ICDD)

© Fraunhofer ICT

Results: Rietveld-Analysis (Double Voigt via TOPAS)

Structure Data from Literature

(Choi et al. 1972)

No size broadening in RDX

(Cry Size L = 10000 = max.)

Microstrain due to dislocations

(ε0 = 0.138)

50484644424038363432302826242220181614

11.000

10.000

9.000

8.000

7.000

6.000

5.000

4.000

3.000

2.000

1.000

0

-1.000

-2.000

-3.000

RDX 100.00 %

I-RDX, fine 15d in air

© Fraunhofer ICT

Results: Size/Strain-Analysis

I-RDX:

Reduced microstrain on aging,

no differences between air and Argon

S-RDX:

Increased strain after 15 d

but reduced strain after 30 d.

Different behavior of I-RDX and

S-RDX; significantly higher starting

values of I-RDX but high strain in

S-RDX after 15 d

Concept of defect healing for

I-RDX and S-RDX beyond 15 d

0.120

0.130

0.140

0.150

0.160

0.170

0d 15d 30d

Str

ain

e0

I-RDX in air

I-RDX in Ar

0.120

0.130

0.140

0.150

0.160

0.170

0d 15d 30d

Str

ain

e0

S-RDX in air

S-RDX in Ar

© Fraunhofer ICT

Evaluation of 7 curves with 340 – 520 peaks per sample

2400 peaks…to provide reliable statistical evaluation

Peak fit of -scans

109,89,69,49,298,88,68,48,287,87,67,47,2

110.000

100.000

90.000

80.000

70.000

60.000

50.000

40.000

30.000

20.000

10.000

0

-10.000

7.221178

7.341334

7.428029

7.504838

7.571907

7.65642

7.771623

7.847199

7.961764

8.116956

8.242875

8.288146

8.394976

8.456857

8.550195

8.657292

8.750241

8.929376

9.001078

9.051417

9.252605

9.384558

9.499652

9.569751

9.662505

9.708764

9.806963

9.960037

Operations: Import [003]

S-RDX grob, 15 d, Lu [003] - File: RC_S-RDX-grob-15d-Lu [003].raw - Type: Rocking Curve - Start: 7.000 ° - End: 17.000 ° - Step: 0.010 ° - Step time: 4. s - Temp.: 25 °C (Room) - Time Started: 8034 s

Lin

(C

ounts

)

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

100000

110000

120000

Theta - Scale

7 8 9 10 11 12 13 14 15 16 17

© Fraunhofer ICT

Shift to right means

poor quality or high

micro strain

Plot separates I-RDX

from S-RDX

Significant shift of the

distribution of

S-RDX on aging

Quantification by

median peak widths

(X50)

Cumulative peak width distribution

0.0

0.5

1.0

0.00 0.05 0.10 0.15 0.20

Peak width [°omega]

Cu

mu

lati

ve n

um

ber

of

peaks

S-RDX 0d

S-RDX 15d

S-RDX 30d

I-RDX 0d

I-RDX 15d

I-RDX 30d

© Fraunhofer ICT

Median peak widths / quantification of crystal quality

(Coarse grades)

0.04

0.045

0.05

0.055

0.06

0.065

0.07

0.075

0 5 10 15 20 25 30 35

Storage time [d]

Med

ian

peak w

idth

[°o

meg

a]

I-RDX

S-RDX

Significant higher

quality of I-RDX

compared to S-RDX

Slight improvement of

I-RDX on aging

(healing process)

Significant damage of

S-RDX on aging!!

Effects pronounced

within the second

aging period

(15 – 30d)

© Fraunhofer ICT

Summary and Outlook

Crystalline HMX impurities in the coarse S-RDX

No size-broadening but microstrain

due to dislocations

Different aging mechanisms in I-RDX and S-RDX

- strain release / defect healing in I-RDX

- enhanced strain / crystal damage in S-RDX

(crystal damage less clear in fine samples)

Evaluation of coarse samples aged in argon to be done

Coarse crystals in the binder should be investigated in

future

Automated evaluation of rocking curves and more

detailed evaluation of peak width distribution and

quantification of microstrain in future