Investigation into thermographic phosphors

Ranson, R.N., 1999. Investigation into thermographic phosphors. PhD, Nottingham Trent University.

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Accurate temperature measurement of rotating components is problematic, particularly for parts within a hostile environment. Knowledge of the surface temperature of turbine blades within an engine would assist in the analysis and improvement of engine design and efficiency. This thesis presents work carried out during an EPSRC Case studentship, in collaboration with Rolls-Royce Pic., towards the development of phosphor thermography as a remote temperature sensing technique. The sensor is based upon the temperature dependence of the rise- and decay-times of the photoluminescent characteristics which are emitted by a phosphor when excited by pulsed laser radiation. By applying a phosphor coating to the component-under-test, the photoluminescent emission can be collected and analysed remotely resulting in the determination of the surface temperature of the component. Since no physical contact is required, this technique can be utilised for the temperature sensing of both static and rotating components.

This research has concentrated on the characterisation of two phosphors; namely, Europium doped Yttrium Oxide (Y2O3:Eu) and Terbium doped Yttrium Aluminium/Gallium Oxide (YAGaG:Tb). Both phosphors have been optimised for their intensity emission levels and decay constant characteristics through the variation of the dopancy level. The discovery of a rise characteristic within the photoluminescent emission has led to a new, low temperature dependent characteristic. The modelling of the rise and decay characteristics has been performed, based upon the energy level transitions for these phosphors. This rise constant characterisation has extended the temperature sensing capabilities of Y2O3:Eu to a range of 25°C to +1100°C. Previously, this phosphor was useful only between 600°C and +1100°C.

Comparison, between the temperature dependence of the two phosphors, shows both are sensitive for the range of 600°C to +1100°C and therefore are suitable for use within the field of turbine engines. Y2O3:Eu is more sensitive to temperature variation defined by the quenching rate i.e. Y2O3:Eu is 15.4mC-1 and YAGaG:Tb is 12.0mC-1. Results presented show Y2O3:Eu to be a more efficient phosphor. Intensity emission levels of Y2O3:Eu are a factor of ten stronger than the emission levels of YAGaG:Tb.

The fabrication of thin film samples of Y2O3:Eu by RF Magnetron Sputtering, have provided intensity levels equal to those obtained from thermographic paints. Lifetime experimentation has shown thermographic paints to survive for only one hour at 1200°C compared with the thin film samples which lasted for up to ten hours. Thus, a robust thermographic coating has been demonstrated which exhibits the ability for long term use within the hostile environment of a turbine engine to aid in the temperature sensing of turbine blades.

Item Type: Thesis
Creators: Ranson, R.N.
Date: 1999
ISBN: 9781369325430
Divisions: Schools > School of Science and Technology
Record created by: Linda Sullivan
Date Added: 05 Jul 2021 14:38
Last Modified: 20 Mar 2024 15:14

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