Transcript Development of Fluorescent Coatings for High Temperature

Measuring Temperature in
Adverse Environments
Using Phosphors
Q u ic k T im e ™ a n d a
G r a p h ic s d e c o m p r e s s o r
a r e n e e d e d t o s e e t h is p ic t u r e .
Dr. Andy Hollerman
Associate Professor of Physics
University of Louisiana at Lafayette
P.O. Box 44210
Lafayette, LA 70504
(337) 482-5063
[email protected]
Outline
• Fluorescence
Based
Engine
Health
Monitoring:
– Derived from several presentations by
S.W. Allison from Oak Ridge National
Laboratory (ORNL) and W.A. Hollerman.
• LED Excitation of High Temperature
Luminescent Coatings:
– Derived from a presentation by S.W.
Allison from ORNL.
Q u ic k T im e ™ a n d a
G r a p h ic s d e c o m p r e s s o r
a r e n e e d e d t o s e e t h is p ic t u r e .
W. A. Hollerman
UL Lafayette
Summary
Thermometry Method
• Researchers have found a method that relies on
measuring the rate of decay of the fluorescent response
of an inorganic phosphor as a function of temperature.
• Having calibrated the phosphor over the temperature
range of interest, a small surface deposit of phosphor is
excited with a pulsed laser and the fluorescent decay is
measured (typically in less than 1 ms) to calculate the
temperature of the substrate.
• Often temperature measurements are made using
thermocouples or optical pyrometry.
However, in
situations where rapid motion or reciprocating
equipment is present at high temperatures, it is best to
use other techniques.
• The time needed to reduce the light intensity to e-1
(36.8%) of its original value is defined as the prompt
fluorescence decay time and is often a strong function of
temperature.
•
•
•
•
Oven temperature is steadily
increased and monitored using a
Type S thermocouple located near
the phosphor.
At a known temperature, the
fluorescent
decay
signal
is
captured from the oscilloscope.
The lifetime of the response is then
calculated
using
a
National
Instruments LabVIEW program.
The lifetime values are then plotted
(on a log scale) versus the
temperature
to
obtain
the
calibration curve.
The region past the “knee” of the
curve
has
a
nearly
linear
relationship between temperature
and the lifetime and is best for
temperature measurement.
0
Signal (V)
•
0.2
-0.2
-0.4
575 nm
453 nm
480 nm
-0.6
-0.8
-1
-1.2
0
500 1000 1500 2000 2500 3000 3500 4000
Time (µs)
Signal from 453, 480, 575 nm emissions
from YAG:Dy (0.27%) at 1,039 °C
1000
Lifetime (µs)
Phosphor
Calibration
100
480 nm
575 nm
10
1
0
200 400 600 800 1000 1200 1400 1600 1800
Temperature (C)
Fluorescence lifetime of 480 and 575 nm
from YAG:Dy (0.27%) versus temperature
Measurement Challenges
0.2
shutter begins to open
0
Signal (V )
• Relatively small phosphor
light emission
• Additional contribution of
blackbody temperature to
mask the light emission of
the phosphor coating.
• Binder must withstand
challenging environments:
– Vibrations,
– Chemical exposure,
– Radiation, and
– Extreme temperatures.
-0.2
-0.4
-0.6
-0.8
-1
-1.2
0
1000 2000 3000 4000 5000 6000 7000 8000
Time (us)
Signal and background from
453 nm emission in YAG:Dy
(0.27%) at 1,306 °C
Fluorescence Decay Time
ZnS:Mn
ZnS:Mn


• Temperature sensitivity is often determined through the
characterization of the prompt fluorescent decay time (lifetime - ).
• Sensitivity
can range from cryogenic temperatures up to
approximately 2000 K.
• Phosphor thermometry allows temperature measurement through
flames and large black body backgrounds.
Fluorescence Decay Time (ns)
120
YAG:Ce Fluorescence
Decay Time
100
Crystal Slice
80
60
Polycrystalline
Polymer Paint
40
I
 t
e
I0
20
0
0
100
200
300
400
500
Temperature (¡C)
(Hollerman et al., IEEE TNS, August 2003)
600
700
Fluor Paint Grain Size
Measurement
S
Y
Eu
10 µm
•
Si
Ca
•
•
•
•
•
•
Y2O2S:Eu
fluor
and
polysiloxane paint on a
glass slide
2 MeV proton beam
2 x 2 µm beam area
µPIXE images
Y, S, and Eu - fluor
Si and Ca - slide
1.7 MV 5SDH-2 Pelletron
accelerator in Louisiana
Phosphor Characterization
SEM
•
•
•
•
Gold-coated
Y2O2S:Eu
and
polysiloxane paint sample.
Small bright clusters represent
individual yttrium fluor grains.
Fluor grain size less than 10 µm.
Magnification of 3,000.
AFM
•
•
•
Y2O2S:Eu and polysiloxane paint
sample.
30 x 30 µm Atomic Force
Microscope (AFM) image
Fluor grain size is less than 10 µm
in extent.
Evaluating
Temperature
Limits
•
•
•
•
A series of samples were prepared
to evaluate the temperature limits
for
the
various
material
combinations.
The samples were heated to
1200 ºC. A UV lamp was used to
excite the samples after heating to
determine if the phosphor survived
the heating.
The process was repeated at
1300 ºC, 1400 ºC, and 1500 ºC.
It can be seen that with increasing
temperature
fluorescence
decreases, but still produces
enough
light
to
make
a
temperature measurement.
ZYP Coatings
ZAP Binder
Y2O3:Eu
YAG:Cr phosphor paint emitted
fluorescence for a repeated exposure
near a hydrogen flame at 2,200 °C.
QuickTime™ and a
decompressor
are needed to see this picture.
Sample Phosphor Paint Results
Binder
Others
(v ol. % )
Phosphor
Manufacturer
Zyp Coatings,
Oak Ridge,
Tennessee
Cotronics
Corporation,
Brooklyn,
New York
Phosphor Emission at Giv en Cycling Temperatures?
Emission (nm)
Trade
Name
Amount
(v ol. % )
Material
Amount
(v ol. % )
H2O
MgO 2
HPC
80
Y2O3:Eu
20
0
0
HPC
80
Y2O3:Eu
10
0
0
HPC
LK
60
20
Y2O3:Eu
20
0
0
611
No
HPC
LK
40
40
Y2O3:Eu
10
0
0
611
Yes
HPC
LK
40
40
Y2O3:Eu
20
0
0
611
Yes
Yes
HPC
LK
40
40
Y2O3:Eu
10
0
0
611
Yes
No
ZAP
50
Y2O3:Eu
50
0
0
611
Yes
Yes
Yes
Yes
ZAP
70
YAG:Dy
30
0
0
585
Yes
Yes
Yes
Yes
Yes
Yes
1200 ¡C
1300 ¡C
1400 ¡C
1500 ¡C
611
Yes
Yes
611
Yes
Yes
1600 ¡C
Yes
ZAP
70
YAG:Tm
30
0
0
420
480
ZAP
70
YAG:Eu
30
0
0
595
611
Resbond 791
35
Y2O3:Eu
20
35
10
611
Yes
Yes
Yes
No
No
Resbond 791
40
Y2O3:Eu
20
40
0
611
Yes
Yes
Yes
No
No
Resbond 791
70
Y2O3:Eu
20
0
10
611
Yes
Yes
Yes
No
No
Resbond 791
80
Y2O3:Eu
20
0
0
611
Yes
Yes
Yes
No
No
Resbond 792
70
Y2O3:Eu
20
0
10
611
Yes
Yes
Yes
Yes
No
Resbond 792
80
Y2O3:Eu
20
0
0
611
Yes
Yes
Yes
Yes
No
Resbond 793
70
Y2O3:Eu
20
0
10
611
Yes
Yes
No
No
No
Resbond 793
80
Y2O3:Eu
20
0
0
611
Yes
Yes
Yes
Yes
Yes
YAG:Dy and ZAP Results
•
•
•
•
•
YAG:Dy phosphor powder
100% ZAP binder
Applied
to
ceramic
substrate using a standard
airbrush.
The mixture is airbrushed
on to surface.
The painted substrate is
then heated for 1 hour at
900 °C to cure the binder.
1,600 °C
1,500 °C
1,400 °C
Three heated samples excited by UV light.
Three coated samples after heating.
Example Emission Spectra
YAG:Ce
FWHM = 100 nm
lc = 525 nm
Wavelength (nm)
YAG:Eu
Peaks at 592, 610, 631,
697, and 710 nm
Wavelength (nm)
Data Taken for
the NASA Glenn
Research
Center
Fluor paints sprayed on a YSZ substrate and excited by a UV lamp.
LED Excitation of High
Temperature Luminescent
Coatings
S. W. Allison ORNL
A. Heyes Imperial College
A. Hollerman UL Lafayette
Rationale
Light Emitting Diodes (LEDs).
For the high
temperature and difficult environments that
turbine engines present, until recently, an
expensive and unwieldy laser was required for
luminescent
thermometry.
However,
technological developments have recently led to
the availability of high brightness light emitting
diodes (LEDs). This development expands the
opportunities and measurement niches for this
technique.
Advantages
• Inexpensive (~$10 USD ea.)
–Price will drop
• Small and Rugged – fit for tight spaces
• Performance will improve!
Thanks to
Lighting Industry drive to develop greater
efficiency and power
• Custom Designs for higher operating
temperatures and currents are possible.
• Long life
Disadvantages
• Some difficulty in coupling to
optical fiber vs lasers
• Cannot achieve high power in
short bursts as lasers can and
total energy output is less
Demonstrations of LED
Excitation of High-Temperature
Phosphors
• LED Excitation of YAG:Dy Powder in High
Temperature Oven (to 1100 °C)
• Of YAG:Dy coating (ambient)
• Of YSZ:Dy (ambient)
LED light directed into oven via Cu-clad fiber bundle
Fiber bundle
Optics
Window/port
Oven
YAG:Powder signal from Cuclad fiber bundle – 2 LEDs
Setup for Coating Fluorescence Measurements
YAG:Dy
•
YAG:Dy
Lens
LED
Detector (not shown) was close
Comparison of YAG:Dy and TBC
Room temperature
Room temperature
Test Conclusions
• LEDs can excite useful fluorescence at high
temperatures and from coatings of interest to the
US/UK program
Some Keys to LED
Implementation
• High current pulser required
• Multifiber for light delivery and collection (metal
coated for highest temperatures)
• Detector (PMT) able to handle continuous blackbody
emission and still respond linearly
• Attention to filter design for blackbody filtering
• Use pulse width of at least several decay constants
in duration
Some Keys to LED
Implementation Continued
• Determine current limit of LEDs and operate just
below that
• Use more LEDs and more delivery and collection
fibers or use Direct Illumination
• Establish
that
LED
wavelength/power
combination is optimized
Steps to an Effective Sensor
System
• Define desired footprint for sensor
–
–
–
–
Identify EngineTest Vehicle
Identify surface of interest
Establish distance from probe to target
Estimate desirable operating temperature
range
• Produce a sensor design to accomplish it
Questions?
• Contact Dr. Andy Hollerman at:
– [email protected]
– (337) 482-5063
• UL Lafayette is always looking for
good graduate students to continue
this work!