1. The NETZSCH LFA 457 MicroFlash -125 … 1100°C
A. Lindemann, J. Blumm,
NETZSCH-Gerätebau GmbH
Wittelsbacherstr. 42
95100 Selb/Germany
G. Jacquier
NETZSCH-Gerätebau GmbH
L’Orée d’Ecully – Allée A Chemin de la Forestière Ecully/France

2. NETZSCH LFA 457 MicroFlash - Measurement Principle - Introduced by Parker et al. 1961
The front surface of a plane-parallel sample is heated by a short light or laser pulse.
The temperature rise on the rear surface is measured versus time using an IR detector.

3. NETZSCH LFA 457 MicroFlash - Instrument Design -
Newest development
Table-top unit
Temperature range:
-125 to 1100 °C
(with two furnaces)
Integrated sample changer

4. NETZSCH LFA 457 MicroFlash - Instrument Design -
heating element
radiation shield
mirror
sample t.c.
sample carrier
aperture
detector
dewar
furnace hoist
laser
Vertical system
Robot system for up to three samples (up to 12.7 mm in diameter)
Special sample carrier for large samples (up to 25.4 mm in diameter)
Vacuumtight (1 Pa)

5. NETZSCH LFA 457 MicroFlash - Sample Changer -

6. NETZSCH LFA 457 MicroFlash - Measurement Possibilities -
Thermal Diffusivity a (absolute)
Specific Heat cp (ratio method)
Thermal Conductivity  calculation according to:

7. NETZSCH LFA 457 MicroFlash - Possible Sample Geometries -

8. NETZSCH LFA 457 MicroFlash - Ideal Sample Thicknesses -

9. NETZSCH LFA 457 MicroFlash - Analysis Routines (simple) -

10. Standard Application – Cu and Al

11. The New NETZSCH LFA Proteus Software – Specific Heat Measurement
   For decades the acccuracy of specific heat measurements using the laser flash technique and therefore a direct determination of the thermal conductivity is an ongoing discussion. Nowadays, a comparative technique is generally employed, Comparing the detector signal height of a calibration standard with known specific heat with that one of the unknown sample:  

12. The New NETZSCH LFA Proteus Software – Specific Heat Measurement
Current points of improvement: The heat loss corrected detector signal heights are employed for the calculations. The differences in the laser power between the sample and calibration run are considered in the analysis (LFA 457/LFA 427).  

13. The New NETZSCH LFA Proteus Software – Specific Heat Measurement
+- 5 %

14. Standard Application – POCO AXM 5Q
5 %
- Sample changer
1 heating
2 different samples

15. Standard Application – Stainless Steel
0.40
0.45
0.50
0.55
0.60
0.65
Specific Heat / (J/(g*K)
100
200
300
400
500
600
700
800
Temperature / °C 2 3 4 5 6
Thermal Diffusivity / mm²/s
Thermal Diffusivity
Specific Heat
DSC 404 Test
SRM Stainless Steel

16. Standard Application – Stainless Steel

17. The New NETZSCH LFA Proteus Software – Specific Heat Measurement
Critical points: The emissivities of sample and reference surfaces must be the same (generally a coating is required). The surface structure of sample and standard must be the same. The dimensions of standard and sample should be close to each other. The thermophysical properties of sample and standard should be close to each other.  

18. Application – Carbon-Containing Refractories
The thermal diffusivity/thermal conductivity of refractory materials is generally measured using the hot-wire method. Due to contact reactions between hot wire and sample, this method is critical for Carbon- or SiC-containing refractories. The non-contact laser flash method allows more reliable fast measurements on such samples without major cost for consumables.
                                                
                                                

19. Application – Carbon-Containing Refractories
Large Sample

20. Application – Sintering of a Powder Metal
In the production of powder metals the thermophysical properties prior to, during and after the sintering process are important parameters for optimization of the production process as well as quality control for final products.

21. Application – Sintering of a Powder Metal
Sintering step

22. Application – Filled Rubber
                                                 
Wide Aquachannels® to reduce hydroplaning
                                                                                                            
Increased Tread Depth for more landings
Kevlar® belts for added tread stability
Wingstay® formulation to reduce cracking
Goodyear Aircraft tire
Photo: Bridgestone press release June 11th, 2004

23. Application – Filled Rubber

24. Application – Filled Rubber

25. NETZSCH LFA 457 MicroFlash - Specifications -
Desktop design
Temperature ranges
Furnace 1: to 1100 °C
Furnace 2: -125 to °C (LN2 cooling)
Exchangeable by user (motorized lift)
Step-iso temperature programs
Samples
Handling: automatic sample changer
Sample sizes: 12.7 mm diameter (ASC)
25.4 mm diam. max (single sample mode)
Sample carriers: easily user interchangeable

26. NETZSCH LFA 457 MicroFlash - Specifications (cont.) -
Atmospheres
Vacuum 10-2 mbar (1 Pa)
Gas flow predefined, switching via software
Laser
up to 15 Joule / pulse
Pulse energy variable (software controlled)
Pulse width 330 µs
Detectors
Exchangeable MCT LN2 cooled, refilling intervall 8 or 24 h
Exchangeable InSb LN2 cooled, refilling intervall 8 or 24 h

27. Thermophysical Properties of a Carbon Composite AIRBUS Round Robin Test

28. EXPERIMENTAL PARAMETERS
Sample holder: 12.7 mm (round)
Furnace: °C
Detector: MCT (Mercury Cadmium Telluride)
Measurement:5 shots at each temperature
Reference for Cp: Pyroceram
Correction: Cowan + Pulse x y z

29. Thermophysical properties of the Composite (z-direction)

30. Thermophysical properties of the Composite (y-direction)

31. Thermophysical properties of the Composite (x-direction)

32. Sample Direction
Temp /°C
Thermal Diffusivity /mm²/s
Specific Heat /J/(g K)
Thermal Conductivity /W/(m K) Z
-50
0.538
0.526
0.443 25
0.465
0.990
0.720 90
0.416
1.205
0.785 Y
0.762
0.628
0.640
0.992
0.571
1.077 X
4.160
3.426
3.872
6.002
3.636
6.861

33. CONCLUSIONS T  a , Cp  l Highest conductivity  fiber direction
Standard deviation  less than 2%

34. Thank you!