Vielitzer Straße 43
95100 Selb
GERMANY
Linseis Inc.
20 Washington Road
P.O.Box 666
Princeton-Jct. NJ 08550
Tel.:
Fax:
Tel.:
Fax:
0049 9287 8800
0049 9287 70488
Email: info@linseis.de
(609) 799-6282
(609) 799-7739
Email: info@linseis.com
The Company
Since 1957 Linseis Corporation delivers outstanding service, know how and leading
innovative products in the field of thermal analysis and thermal physical properties. We
are driven by innovation and customer satisfaction. Customer orientation, innovation,
flexibility and last but not least highest quality are what Linseis stands for from the very
beginning. Thanks to these fundamentals our company enjoys an exceptional reputation
among the leading scientific and industrial companies.
Claus Linseis
Managing Director
ASTM E 1461 - 01
Standard Test Method for Thermal
Diffusivity by the Flash Method
A small, thin disc specimen is subjected to a high intensity short duration
radiant energy pulse. The energy of the pulse is absorbed on the front
surface of the specimen and the resulting rear face temperature rise
(thermogram) is recorded. The thermal diffusivity value is calculated from
the specimen thickness and the time required for the rear face temperature
rise to reach certain percentages of its maximum value. When the thermal
diffusivity of the sample is to be determined over a temperature range, the
measurement must be repeated at each temperature of interest.
Terminology
• 1 Definitions of Terms Specific to This Standard:
• 1.1 thermal conductivity, l, of a solid material—the time
rate of steady heat flow through unit thickness of an
infinite slab of a homogeneous material in a direction
perpendicular to the surface, induced by unit
temperature difference. The property must be identified
with a specific mean temperature, since it varies with
temperature.
• 1.2 thermal diffusivity, a, of a solid material—the property
given by the thermal conductivity divided by the product
of the density and heat capacity per unit mass.
Classification of some
Thermophysical Properties
Thermophysical Properties
Thermodynamic
Properties
Transport
Properties
Thermal Diffusivity
LFA
Thermal Expansion
Dilatometer
Specific Heat
DSC
Thermal
Conductivity
Mass Diffusion
Coefficient
Electric
Resistivity
Kinematic
Viscosity
Thermal Diffusivity Calculation
Calculation
First determine the baseline and maximum rise to give
the temperature difference, ΔTmax Determine the time
required from the initiation of the pulse for the rear face
temperature to reach ΔT½ . This is the half time, t½.
Calculate the thermal diffusivity, a, from the specimen
thickness, L squared and the half time t½, as follows:
Α = 0.13879 L2/t½
Determination of Thermal Diffusivity
The quantities measured are:
temperature (T), time (t) and voltage
change (ΔV). Note ΔV ~ ΔT.
Sample
Power
source
Experimental Data:
Detector
Sample
Thermocouple
V
Time (s)
Measurement Schematic
Laser Pulse
1us
10.6 um
L
Emitted Light
IR
Detector
Temperature
Rear Surface Temperature
Laser Pulse
ΔTm
Time
Real Measurement vs. Adiabatic
1.0
V
Vmax
1.0
V
Vmax
0.5
0.5
Adiabatic
Real measurement
0
0
1.0
1.0
t1/2
t1/2
The two graphs show a true measurement vs. an ideal case of no heat loss
(i.e. adiabatic):
The difference between the two must be accounted for using the correction
models contained by the software.
Significance and Use
Significance and Use
Thermal diffusivity is an important property, required for such
purposes as design applications under transient heat flow
conditions, determination of safe operating temperature, process
control, and quality assurance.
The flash method is used to measure values of thermal diffusivity, a,
of a wide range of solid materials. It is particularly advantageous
because of simple specimen geometry, small specimen size
requirements, rapidity of measurement and ease of handling, with a
single apparatus, of materials having a wide range of thermal
diffusivity values over a large temperature range.
Thermal Diffusivity
It is a measure of how well a material can transmit heat under transient
conditions. Since a material does not just transmit heat, but must be
warmed by it as well, the thermal diffusivity involves thermal conductivity,
specific heat and density.
Characteristics:
1.
Thermal diffusivity is always a function of temperature and is directional
for anisotropic materials
1.
Thermal diffusivity may increase or decrease as a function of temperature,
e.g.
- graphite and many ceramics decrease with temperature
- many metal alloys increase with temperature
3.
Thermal diffusivity maybe dominated by the electronic or lattice
contributions depending upon the type of material
The System II
The Instrument
Detector
Furnace
Laser / Xenon pulse
source
The Specifications
Modular Design
Different furnaces
Different pulse source
Different Sensors
Sample robot
-125 up to 500°C
RT up to 500°X
RT up to 1250°C
RT up to 1600°C
Xenon or Laser pulse source (exchangeable)
MCT detector (cryogenic application)
InSb detector (standard)
round samples
up to 6 samples 10 mm diameter
up to 6 samples 12,7 mm diameter
up to 3 samples 25,4 mm diameter
square samples
up to 6 samples 10x10 mm
liquid samples
Aluminum / Sapphire / Platinum
XFA 500 Xenon Flash
Detector
Iris
Furnace
Sample Carrier
Xenon
Flash
LFA 1000 Laser Flash
Detector
Iris
Furnace
Laser
Sample
Carrier
Technical Specifications
Sample Holders
Sample Holders II
Sample Holder For Liquids
Sample container
Lid
Sample container
Crucible
Liquid
Sample Preparation
Sample
Graphite coating
Samples are normally coated with a graphite film before
testing. The graphite serves several purposes. When testing
samples that do not naturally have a high value of emissivity or
absorptivity, the graphite increases the energy absorbed on the
laser side (bottom) and increases the temperature signal on the
detector side (top) of the sample. Also, a uniform graphite
coating applied to both sample and reference material helps
maintain similar absorptive and emissive efficiencies among
samples, which is needed for accurate specific heat
measurements.
Application Areas
Zinc
Silver
PURE METALS
Nickel
Aluminum
ALLOYS
Plastics
Ice
Oxides
NONMETALLIC SOLIDS
Vacuum
Isolation
Foams
Fibers
INSULATION SYSTEMS
Oils
Water
Mercury
LIQUIDS
Carbon
dioxide
Hydrogen
GASES
0.001
0.01
0.1
1
10
Thermal Conductivity (W/m-K)
100
1000
Application Areas II
Heat Flow Meter (-20…100°C)
Guarded Hot Plate (-180…650°C)
Guarded Heat Flow Meter (-150…300°C)
Hot Wire (RT…1500°C)
Flash (-125 …2400°C)
0.001
0.010
0.100
1.00
10.0
Thermal Conductivity (W/m-K)
100
1000
The Software
Software
All thermo analytical devices of LINSEIS
are PC controlled, the individual software
modules exclusively run under Microsoft ®
Windows® operating systems. The
complete software consists of 3 modules:
temperature control, data acquisition and
data evaluation. The Linseis 32 – bit
software encounters all essential features
for measurement preparation, execution
and evaluation, just like with other thermo
analytical experiments. Due to our
specialists and application experts
LINSEIS was able to develop this easy
understandable and highly practical
software.
Applications
TC vs. Sample Thickness
High Purity Copper
Thermal Diffusivity (cm2/s)
1.5
(398 W/m*K)
Graphite
1.0
(88 W/m*K)
Iron
0.5
(76.8 W/m*K)
0.0
0.1
10
Sample Thickness (mm)
TC vs. Temperature
PTFE
PTFE Applications
Chemical processing and petrochemical sectors: used for vessel linings, seals,
spacers, gaskets, well-drilling parts and washers, since PTFE is chemically inert and
resistant to corrosion
Laboratory applications: Tubing, piping, containers and vessels due to resistance to
chemicals and the absence of contaminants attaching to the surface of PTFE
products
Electrical industry: used as an insulator in the form of spacers, tubing and the like
Virgin PTFE had been approved by the FDA for use in the pharmaceutical, beverage,
food and cosmetics industries in the form of conveyor components, slides, guide
rails, along with other parts used in ovens and other heated systems.
Semiconductor sector: used as an insulator in the production of discrete components
such as capacitors and in the chip manufacturing process.
Thermal Diffusivity
Combined Result
Ceramics
Thermal Diffusivity
Combined Results
Inconel 600
Thermal Diffusivity
Thermal Conductivity
Application Example: Graphite
(Polycrystalline)
Graphite is an excellent material for checking the
performance of a Laser/Xenon Flash Thermal
Analyzer. The analyzed material shows a maximum
thermal diffusivity around room temperature. The
specific heat of the material which can be analyzed by
comparative method or by using a DSC / High
Temperature DSC shows a significant increase at
higher temperatures.
Application Graphite
Application Example: Aluminum &
Copper
The pure metals Copper and Aluminum are used in
this example to demonstrate the performance of the
Linseis Laser Flash device. The measurement
results of the two materials are compared with
literature values. The measured results vary within
2% of the given literature values; this demonstrates
the excellent performance of the instrument.
Application: Aluminum & Copper
Application Example: Isotropic
Graphite (AIST)
This graph shows the Thermal Diffusivity values
measured on a Linseis LFA 1000 compared to the
values measured at AIST* Japan. The literature
values of the used Isotropic Graphite from AIST*
the measured results on the LFA 1000 vary by
less than 2%. *(National Institute of Advanced
Industrial Science and Technology, Japan)
Isotropic Graphite (AIST)
The Best Method
Best method for measuring Thermal Diffusivity
→Thermal Conductivity
The flash method is the most accurate and
fastest way of measuring the thermal diffusivity.
It has bee estimated that world-wide over 80% of
the thermal diffusivity measurements are
conducted using the laser flash system
Advantages of Flash Diffusivity
Measurement
1.
Easy sample preparation because of simple geometry
Sample sizes are typically 12,7 or 25,4 mm Ø or 10mm square and range from 0.1
to 6 mm thick.
2.
Less material is required because of small samples: Some test methods used to
measure thermal conductivity directly require very large samples i.e. 30cm x30cm
x 5cm in some case
3.
Fast measurement time due to small samples:
With small samples steady state is reached quickly. Some thermal conductivity
methods require days to complete a set of measurement.
4.
High accuracy:
Depending upon the material accuracies of +/- 3-4% or better can be usually
achieved
5.
Wide thermal diffusivity / thermal conductivity range:
Thermal diffusivity:
0.001 to 10 cm2/s
Thermal conductivity: 0.01 to 2000 W/m-K