Vielitzer Straße 43

95100 Selb

GERMANY

Tel.: 0049 9287 8800

Fax: 0049 9287 70488

Email: info@linseis.de

Linseis Inc.

20 Washington Road

P.O.Box 666

Princeton-Jct. NJ 08550Tel.: (609) 799-6282

Fax: (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 LinseisManaging 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 temperaturerise 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

TransportProperties

Thermal DiffusivityLFA

Specific HeatDSC

Thermal ExpansionDilatometer

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

V

Time (s)

Powersource

Detector

Sample

SampleThermocouple

The quantities measured are: temperature (T), time (t) and voltage change (ΔV). Note ΔV ~ ΔT.

Experimental Data:

Measurement Schematic

L

Te

mp

era

ture

Time

Emitted Light

Laser Pulse

1us

10.6 umIR Detector

Rear Surface Temperature

Laser Pulse

ΔTm

Real Measurement vs. Adiabatic

V

t1/2

1.0

Vmax

0.5

0

1.0

V

t1/2

1.0

Vmax

0.5

0

1.0

Adiabatic

Real measurement

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 DiffusivityIt 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 SpecificationsModular Design

Different furnaces -125 up to 500°CRT up to 500°XRT up to 1250°CRT up to 1600°C

Different pulse source Xenon or Laser pulse source (exchangeable)Different Sensors MCT detector (cryogenic application)

InSb detector (standard)Sample robot round samples

up to 6 samples 10 mm diameter up to 6 samples 12,7 mm diameterup to 3 samples 25,4 mm diametersquare samplesup to 6 samples 10x10 mm liquid samplesAluminum / Sapphire / Platinum

XFA 500 Xenon Flash

Detector

Iris

Furnace

Sample Carrier

Xenon Flash

LFA 1000 Laser FlashDetector

Iris

Furnace Sample Carrier

Laser

Technical Specifications

Sample Holders

Sample Holders II

Sample Holder For Liquids

Sample container

Crucible

Sample container

Lid

Liquid

Sample Preparation

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.

Sample

Graphite coating

Application Areas

0.001 10000.01 1001 100.1

Thermal Conductivity (W/m-K)

GASES

LIQUIDS

INSULATION SYSTEMS

NONMETALLIC SOLIDS

PURE METALS

ALLOYS

Hydrogen

Oils

Carbon dioxide

Water Mercury

FoamsVacuum Isolation Fibers

IcePlastics

Aluminum

Oxides

Nickel

SilverZinc

Application Areas II

Silver

, Cop

per,

Silicon

Car

bide

0.001 10000.010 1001.00 10.00.100

Thermal Conductivity (W/m-K)

Vacuu

m Is

olatio

n

Air, P

olysty

rene

, PUR F

oam

s

Fiber b

oard

s, Fibe

r Ins

ulatio

n

Buildin

g bo

ards

, Oils

Woo

d, P

olym

ers,

Coal

Wat

er

Concr

ete,

Glas

s, Fibe

r

clay Por

ous C

eram

ics,

Refra

ctorie

s

Alumina

Silic

ates

Silicon

nitr

ide

Alumina

, Car

bon

Bricks

Iron,

Ste

el

Silicon

Aluminu

m, G

raph

ite

Diamon

d

Flash (-125 …2400°C)

Hot Wire (RT…1500°C)

Guarded Heat Flow Meter (-150…300°C)

Guarded Hot Plate (-180…650°C)

Heat Flow Meter (-20…100°C)

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, executionand evaluation, just like with other thermo analytical experiments. Due to our specialists and application expertsLINSEIS was able to develop this easy understandable and highly practical software.

Applications

TC vs. Sample ThicknessT

he

rma

l Diff

usi

vity

(cm

2 /s)

High Purity Copper

(398 W/m*K)

Graphite

(88 W/m*K)

1.5

Sample Thickness (mm)

1.0

0.5

0.0

Iron

(76.8 W/m*K)

0.1 10

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 geometrySample 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/sThermal conductivity: 0.01 to 2000 W/m-K