Transcript Effects of Impurities on PETN Crystals

Effects of Impurities, Temperature,
and Laser on PETN Crystals
Gengxin Zhang, Rajasekar Pitchimani and
Brandon Weeks
Chemical Engineering Dept
Texas Tech University
Introduction
 Pentaerythritol tetranitrate (PETN) is primarily used
as an initiator for other explosives. The surface area
and density of PETN will modify the initiation
performance.
 The PETN crystal morphology and surface changes
through the coarsening mechanisms over time or
temperature.
 Internal factors (crystal structure, dislocation and
defects) and external factors (such as temperature,
super saturation and impurities) influence the crystal
growth.
Motivation
 Effects of impurities on the PETN crystal and
high temperature annealing
 Thermal stability of dislocations on the pure and
doped PETN crystals
 Effects of Laser (Nd:YAG 532 nm) damage on the
pure and doped PETN crystals
Experiments
 PETN crystals were prepared by solvent evaporation
method
 For Zn, Fe, Ca and Na doped PETN, by dissolving
the metal nitrate in acetone and dissolve PETN to
obtain 100 ppm impurities concentration
 The AFM images (contact mode) were taken with
Nanoscope IIIa (Veeco multimode AFM) instrument
 The temperature was controlled by NanoScope
Heater Controller (calibrated by standard thermal
couple, the precision is ±0.1C)
Experimental Results
 The effects of impurities on the crystal
morphology
 Temperature effects on crystal surface
 Laser hitting effects on crystal surface
Effects of Impurities on Pure
and Doped PETN
We checked the pure and Zn, Na, Ca, and Fe doped
PETN crystals after 1 h annealing at 80 C, the AFM
images showed before and after annealing.
After introducing the impurities, the roughness of the
crystals surface increased much comparing to the
pure crystal.
(All of the images listed below are the height mode.)
Pure PETN crystal
The step heights are about 15 nm, and
the RMS roughness vary around 0.6 1.5 nm before annealing.
Pure PETN Crystal at RM
RMS roughness became bigger,
around 4 nm, and step height are
around 20-30 nm.
Pure PETN Crystal annealing at 80 oC
Ca2+ doped PETN crystal
The step heights are about 50 nm, and
the RMS roughness vary around 40 nm
before annealing.
Ca doped PETN at RM
RMS roughness became bigger,
around 20 nm.
Ca doped PETN at 80 oC
Na+ doped PETN crystal
The step heights are about 15 nm, and
the RMS roughness vary around 70 nm
before annealing.
Na doped PETN at RM
The step heights and RMS roughness
have no big change. They look similar
to pure PETN.
Na doped PETN at 80 oC
Zn doped PETN crystal
The RMS roughness vary around 5 - 40
nm before annealing. No wide terrace.
Zn doped PETN at RM
The step height and RMS roughness do
not change significantly.
Zn doped PETN at 80C
Fe doped PETN
The step heights are about 6 - 100 nm,
and the RMS roughness vary around 2 9 nm before annealing.
Fe doped PETN at RM
RMS roughness vary between 1 -2 nm
after annealing.
Fe doped PETN at 80 oC
Thermal stability of dislocation
on pure PETN crystal
We used the same methods to prepare the crystals,
but the key point is to get rid of the dirty on surface
(solvent, dust et al), one solution is that putting the
other easier volatile solution (we tried menthol,
ethanol), this method did not give any help; we also
tried to use ethanol washing the surface, which will
spoil the surface morphology. The following images
are collected on one pure PETN crystal.
(All of the images in deflection mode.)
Thermal Stability of Dislocation
t = 0.0 min
t = 72.0 min
t = 24.0 min
t = 96.0 min
t = 48.0 min
t = 120.0 min
Dislocations on the pure PETN crystal surface at 40 oC.
Continue…
We also tried to find one dislocation and analysis the volume change or
the height change, but we still not find the good software. (RM)
0.7 m
t = 0 min
0.7 m
t = 270 min
0.7 m
t = 90 min
0.7 m
t = 360 min
0.7 m
t = 180 min
0.7 m
t = 450 min
Laser on pure and Zn-doped PETN
We used the Nd :YAG 532nm Laser hit the pure and Zndoped PETN, we listed some optical images as below, we
also checked the Au coated pure PETN crystal surface.
Pure PETN crystal hit by laser
2 times
Pure PETN crystal hit by laser
3 times
Continue…
Zn-doped PETN crystal hit by
laser 3 times
Zn doped PETN crystal coated
with Au hit by laser 2 times
Effects of Laser Action
The Gold coating PETN was damaged by Laser (Nd:YAG 532 nm).
The scale bar was labeled.(20 m, 10  m, 4.7  m)
Future work
1. Find the suitable software to analyze the dislocation
images
2. Change the Laser focus size and control the damage
area
3. Compare the crystals changing before and after the
force action (shear, cut or twist)