NDTnet 1998 Aug, Vol.3 No.8

Abstract

The loss of tightness of vessels filled with noxious volatile substances is a potential source of environmental pollution. Hence the need in broadening the spectrum of substances to be analysed and designing selective sensors and leak finding apparatuses.
Analysis of working principles and characteristics of different types of sensors shows that mass-sensitive piezo-resonance sensors have good prospects due to such qualities as high sensitivity, broad linear response range, frequency output, and single principle for detecting a large number of different substances (analyses).
The most difficult tasks in the creation of piezo-resonance sensors for a definite analyte are the search for specific chemical substances to be used as active material for the sensor covering, and reproduction of the covering parameters (chemical reactivity and topology).

We have tried as active covering materials a number of coordination compounds capable to chemosorb definite analyses through the formation of specific mixed-ligand complexes with low binding energy. This attitude have let us find substances (some cobalt(II), nickel(II) and copper(II) complexes with Schiff bases) with selective and reversible reactivity to different analyses (e.g. ammonia, hydrazine, organic amines). Such methods as vacuum sublimation and Langmuir-Blotgett molecular film deposition have been used to make sensor coverings, what have also made it possible to reproduce their properties. Sensors for several N-containing gases and vapors have thus been created and tested.

The sensors have been also used to detect local leakages of dangerous substances from containers. Combination of a sensing element with gas curtain in a leak-finding probe has been found especially successful. Due to aerodynamic peculiarities of interaction of the gas current of the probe with the surface under control it has become possible to protect the sensor from outside interference. It let locate both gross and little flows in one run without preliminary mending of the former.
For the gas-protected sensing probes the sensitivity level of 10^-6 m³ Pa/s has been practically achieved, and, in the authors' opinion, it can be further enhanced.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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