Exhaust gas sensor electrode improvement

Patent · Mon Dec 08 23:00:00 EST 1980

OSTI ID:6504960

Achari, A

An improved exhaust gas sensor is described for use in sensing the partial pressure of oxygen in the exhaust gases from an internal combustion engine. The sensor has a titania ceramic element in which two electrodes are embedded. The electrodes in the past have been made from pure platinum, this precious metal being required to enable the sensor electrodes to survive at temperatures up to about 900/sup 0/C in the hostile gaseous environment. Even with the use of this platinum electrode material, electrode failures have occurred. These now have been found to be caused by the formation of platinum carbide from the chemical reaction of the platinum electrode material with exhaust gas constituents. Also, Pt loss has occurred from oxidation thereof and vaporization of the oxide. It has been found that deterioriation of sensor electrodes may be prevented by forming these electrodes from an alloy consisting essentially of platinum and another material having a lower vapor pressure and lower surface tension than platinum. Specifically, an alloy consisting essentially of platinum and another metal selected from the group consisting of gold and rhodium may be used. An alloy of platinum and gold is preferred. Annealing the titania element electrodes functions, as does the alloy formation, as a means for increasing the magnitude of the energy required for reaction of the Pt with carbon or oxygen.

• Assignee: Ford Motor Co
• Patent Number(s): US 4237722
• OSTI ID: 6504960
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
330100 -- Internal Combustion Engines
330700* -- Advanced Propulsion Systems-- Emission Control
ALLOYS
ELECTRODES
ELEMENTS
ENGINES
EXHAUST GASES
FLUIDS
GASEOUS WASTES
GASES
GOLD ALLOYS
HEAT ENGINES
INTERNAL COMBUSTION ENGINES
MEASURING INSTRUMENTS
METERS
NONMETALS
OXYGEN
OXYGEN METERS
PLATINUM ALLOYS
PLATINUM METAL ALLOYS
RHODIUM ALLOYS
WASTES