BS ISO 19629:2018 pdf download – Fine ceramics (advanced ceramics, advanced technical ceramics) — Thermophysical properties of ceramic composites — Determination of unidimensional thermal diffusivity by flash method

02-19-2022 comment

BS ISO 19629:2018 pdf download – Fine ceramics (advanced ceramics, advanced technical ceramics) — Thermophysical properties of ceramic composites — Determination of unidimensional thermal diffusivity by flash method
The infrared detector, when used, shall be of a type appropriate to the minimum test piece temperature, for example: a) HgCdTe or PbSnTe cells, liquid nitrogen cooled, for test specimen temperatures within the range 300 K to 800 K; b) PbS or InSb cells for test specimen temperatures above 500 K. Care shall be taken that the signal comes only from the central area of the back face, that is with a tolerance of 5 % of the diameter of the test specimen. When used, thermocouples shall be of the separated junction type, the hot junction being the back face of the test piece. They shall be in accordance with EN 60584-1. Electrically non-conductive material shall be coated on the front face and on the rear face, with a thin coating of high thermal conductivity material in order to ensure accurate measurement of surface temperatures. In order to minimize heat losses, the use of the thermocouples with wires of the smallest possible diameter is recommended. The thermocouple type most often used is chromel-alumel for measurements from room temperature up to 1 100 K. Semi-conducting couples may also be used: Bi 2 Te 3 from 90 K to 400 K and FeSi 2 for temperatures up to 1 100 K. For temperatures over 1 100 K, a non-contact measurement technique is recommended. 5.4 Data acquisition The data acquisition system used may be analogue or digital. It shall be equipped with a means of recording the temperature change versus time (before, during and after the pulse) and the time origin. These means shall be accurate to within 0,02 ms. 6 Test specimens The size of the test specimens shall be fixed to meet the requirements for application of the chosen thermal model (for example like the one described in Annex A). Generally a disc of a diameter between 1 to 8 mm is used.

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