European Virtual Institute for Thermal MetrologyNewsletter WP4.2 22.12.2003

Work Package 4: Thermal Conductivity and Diffusivity

1 I n t r o d u c t i o nThis is the second Newsletter summarising the work carried out during the first year of evitherm. Two meetings were organised in Torino by Gian Carlo Bussolino,and in Paris by Bruno Hay; minutes have been distributed to all members. Important progress could be achieved in the collection of “Written Standards”, development of the “Guide to measurement methods and laboratories”, and of the “Input masks for thermophysical properties data”. A brief description of this work is given in the WP4-summary report, section 4. The latest version of the input masks is also included in this Newsletter and attached as Excel document. It is planned to organise a next meeting in Stuttgart in April 2004. Some actions to be fulfilled until that date are also listed below.

2 Me m b e r s o f W P 4There are some new members (bolt) generously prepared to help us in our work to establish a powerful information tool in thermophysics. The complete list is:

Regular members:

Austrian Research Institute Seibersdorf, Wolfgang Hohenauer

Bavarian Centre for applied Energy Research ZAE, Hans-Peter Ebert

BNM-LNE, Filtz Jean-Rémy, Bruno Hay

CNR - Istituto di Metrologia "G.Colonnetti" IMGC,Gian Carlo Bussolino

Hot Disk AB, (HD) Lars Halldahl

Institut fuer Kernenergetik und Energiesysteme (IKE), Guenther Neuer, Ruediger Brandt

Institute of Physics Slovak Academy of Sciences (IP SAS), Ľudovít Kubičár, Vlastimil Boháč, Viliam Vrenetár

National Physical Laboratory NPL, John Redgrove, Ron Tye, Ray Williams

David Salmon

Institut für Kernenergetik und Energiesysteme IKE D-70550 StuttgartGuenther Neuer Phone:++49-711 6852144guenther.neuer@ike.uni-stuttgart.de Fax: ++49-711 6852110

SP Swedish National testing and Research Institute (SP), Bertil Jonsson

Invited members:

Magnus Rohde, Forschungszentrum Karlsruhe, Institut für Materialforschung I

Francois Lepoutre, Professeur titulaire de la Chaire de physique des capteurs, Conservatoire National des Arts et Metiers

The members shown above are representing the following measurement techniques:

Stationary techniques (NPL, LNE, ZAE),

transient techniques (IPSAS, LNE, ZAE): thermal diffusivity, calculation of thermal conductivity

subsecond techniques (IMGC)

el. resistivity (IKE, IMGC), calculation of thermal conductivity

heat flow (HD)

photo thermal methods for thin film thermal conductivity-measurements (Magnus Rohde)

micro/nano-scale techniques (Francois Lepoutre)

3 S u m m a r y r e p o r t o n t h e p r o p o s e d c o n t r i b u t i o n o f W P 4

Thermal conductivity and thermal diffusivity are complex properties because of the combination of various heat transport mechanisms involved in determining the measured values and because of the effects on these values of the composition and the macro- and microscopic structure of the material in question. It is therefore important to subdivide materials into ‘material groups’ each with specific behaviour related to the individual thermal properties. To take account of these requirements the following material groups have been defined by WP4 :- Elements - Glass ceramics- Metallic alloys (except steels) - Minerals, rocks- Steels - Insulation materials - Oxide ceramics - Polymers- Non-Oxide ceramics - Plants- Glasses - Foods

- Composites

The general aim of the work to be carried out in WP4 is to help the user - independent of his thermal knowledge - to find the best way to the required thermal conductivity/thermal diffusivity values. Depending on his application the user will be guided to an appropriate properties database, an optimum measurement technique and measurement laboratory practising the relevant technique, or to instrument suppliers who can provide appropriate measuring equipment. In order to achieve this, work has been carried out on the following tasks during the first 9 months of the project.

Providing the user with properties data Information on thermal conductivity/thermal diffusivity is available from a variety of sources such as handbooks, conference proceedings, scientific journals, and databases. This choice often makes it difficult for the user to find the right source for any given material or application. The fact that many data sources, especially databases of materials suppliers, are not complete enough to judge whether the given values are valid for the material in question or at the temperature of application leads to additional difficulties for the user. WP4 will address this problem by:

Assisting the user to find the best data source for his application. For this purpose existing data sources will be collected and evaluated. The criteria for this evaluation are: easy accessibility; values available as a function of temperature or at one temperature only; material description available; experimental description available; source of data available. A preliminary list of data sources with a ‘star rating’ corresponding to these criteria has now been produced and this list will be expanded during the remainder of the project. The best qualified data sources will be made easily accessible to the evitherm-user.

Preparing a special template to enable easy input of measured values with a complete description and a qualification statement explaining the correct application of the data. The data can be measurement results from the user’s own laboratory or data taken from publications in scientific journals. Using this template data will be able to be transferred to evitherm via the internet, reviewed by experts and then immediately offered to other users. This is the quickest way of getting measurement values from the laboratory to the user. It also provides an easy and consistent method of giving users access to existing published data and links to associated reports or scientific papers. The vision of the project is that in future,

connections to all key laboratories will be established and evitherm will be used as the primary way of getting thermal data published and disseminated to users.

The first draft of the data input template was presented at the second meeting of WP4, which was held in Paris on 16 October 2003. It is planned that this template will also be used for WP 5, 6 and 7 which are addressing the other thermal properties covered by evitherm. It was agreed to use this template in the aforementioned WPs for a test phase during which time improvements and areas requiring change will be identified.

Directing the user to measurement laboratoriesIf the required data is not available in the properties database evitherm will point the user to a laboratory or other organisation that can carry out measurements to provide the information. WP4 is confronted with the problem that a large number of measurement methods are available to either measure the thermal conductivity directly or to measure the thermal diffusivity or the electrical resistivity and to calculate the thermal conductivity. The selection of the optimum method depends on the kind and structure of the material, the sample geometry, the temperature of interest, the physical state of the material at this temperature (solid or liquid), the atmosphere and the required accuracy etc. To resolve this problem the members of WP4 decided to develop a ‘guidance structure’ incorporating questions and help information for the user to enable him to provide the necessary technical information that will allow the most appropriate measurement laboratory or expert to be identified. The help information will give short and easy to understand explanations on important technical points e.g. on the problems with measurements in various material groups, advantages and disadvantages of various measurement methods and guidance on appropriate levels of uncertainty in order to help the user to specify realistic requirements. When completed this search structure will in fact represent a basic online training resource which in its own right will be of benefit to users requiring an understanding of the key technical issues concerning thermal conductivity/diffusivity.

The first draft of this guidance structure was also presented by Bruno Hay at the second meeting of WP4 and discussed with representatives of other properties workpackages. (the Power Point presentation is available at the evitherm website www.evitherm.org entitled: “Directing to Experiments-LNE160993”). The guiding structure has been accepted in principal and will be used as a basis for defining a detailed specification for this facility on the proper evitherm website with the website developer.

Assist the user in making his own thermophysical properties measurements Sometimes the user wants to procure his own measurement equipment. In this case he also first has to select the best measurement method for his application - which involves asking the same questions as described above. However, instead of then searching for the most appropriate measurement laboratory the user will directed to the most appropriate equipment provider(s). Work to collect all relevant information to realise this selection and the definition of a suitable template will be carried out later in the project.

In addition to this service evitherm will assist measurement laboratories by providing information on reference materials and written standards.

Reference materials are samples of materials with well known properties that are used to check the performance of measurement apparatus. WP4 has started to collect information about existing materials. Certified reference materials are however not available for all types of materials or for all ranges of thermal conductivity or thermal diffusivity values. In cases where certified materials are not available evitherm will list available thermal conductivity or thermal diffusivity values which are well defined and proven e. g. by comparison measurements. It will also provide information about existing/live intercomparison projects. This will give laboratories the opportunity to participate in such projects thereby helping them check and improve their own measurement accuracies.

Written standards – if available - are important to verify qualified measurements. WP4 has already listed more than 60 standards for thermal conductivity and thermal diffusivity with information about measurement method, type of material to which it applies, accessibility etc.

4 D a ta t em p l a t e sJohn Redgrove distributed updated data templates which are attached to this Newsletter. There are some remarkable changes taking into account our discussions in Paris. Please have a look and check especially the table “Measurement methods” in order to be sure that all relevant specifications are included. We – all together – should start to write the short descriptions, advantages and disadvantages of the various methods. We also should write the qualification statements of the individual material groups in table “Materials” with respect to the thermal conductivity. Corresponding to section 3 the descriptions of methods could be distributed as follows: Stationary techniques (NPL), transient techniques (ZAE), subsecond techniques (IMGC) el. resistivity (IKE), heat flow (HD), photo thermal methods for thin film thermal conductivity-measurements (Magnus Rohde), micro/nano-scale

techniques (Francois Lepoutre). This is my proposal, please contact me if you disagree.

For writing the qualification statements, I am asking for voluntaries. Please select the material groups with which you have experiences. If you write me your preferences I can prepare a list who will write what in order to prevent that same work will be done twice.

5 I n p u t m a s k sThe input masks have been modified corresponding to valuable contributions –especially by Bertil Jonsson. The upgraded version is attached both as word and excel document. I would urgently ask again all members to fill a few input masks with data from own laboratory. This is the best method to find out which further improvements are needed. Please send filled masks, questions and comments to Ruediger Brandt (brandt@ike.uni-stuttgart.de).

6 A c t i o n s6.1 Prepare qualification statements (s. section 4)

6.2 Check data templates and draft descriptions of measurement methods (s. section 4)

6.3 Fill input masks in order to check completeness and practicability (s.Section 5)

AnnexInput Masks

7 Metadata 8 Ma t e r i a l G r o u p s

Material Description

Material Preparation

Measurement Techniques

Properties Metadata

Measurement Parameters