Measuring and testing – Gas analysis – Gas chromatography
Patent
1978-07-24
1979-10-02
Kreitman, Stephen A.
Measuring and testing
Gas analysis
Gas chromatography
G01N 2704
Patent
active
041693698
ABSTRACT:
The concentration of NO.sub.x in a gaseous mixture is measured using a solid state sensor comprising a surface thin film of semiconductive material. In a preferred embodiment, the thin film semiconductor comprises tin oxide having an oxygen to tin atomic ratio of between 1.5 and 1.95, preferably between 1.8 and 1.9, and is formed by reactive sputtering from a tin or tin oxide target in an argon-oxygen atmosphere. The electrical resistance of the tin oxide thin film is highly sensitive to NO.sub.x species, but is essentially unaffected by the presence of other common gases such as CO, H.sub.2, O.sub.2, SO.sub.2, NH.sub.3 and hydrocarbons. Water vapor present in the mixture has a small effect upon the resistance of the film. The thin film tin oxide sensor may be used to measure NO.sub.x in air and, in one particularly advantageous aspect of this invention, is employed to measure NO.sub.x emissions in automotive exhaust gas.
REFERENCES:
patent: 3901067 (1975-08-01), Boardman et al.
patent: 3955929 (1976-05-01), Kawakami et al.
patent: 4030340 (1977-06-01), Chang
Ichinose et al., "Ceramic Oxide Semiconductor Elements for Detecting Gaseous Components," Ceramics 11, (3), pp. 203-211, 1976.
Seiyama et al., "Study on a Detector for Gaseous Components Using Semiconductive Thin Films," Analytical Chemistry, vol. 38, No. 8, pp. 1069-1073, Jul. 1966.
General Motors Corporation
Grove George A.
Kreitman Stephen A.
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