Method of making a titanium dioxide oxygen sensor element with fast transient response

Claim 1

A method of making a titanium dioxide element which can be used as an oxygen sensing element, which method comprises the steps of: selecting at least a pair of electrically conductive leads, said leads being formed of a material which is resistant to thermal degradation at temperatures normally found in exhaust gases from operation of an internal combustion engine; placing said pair of leads in a position generally close to one another with a slurry bridgeable space therebetween; applying to said pair of spaced leads a titanium dioxide containing slurry having the following characteristics: said slurry being formed on a volume basis of 10-50% titanium dioxide, 5-15% of an organic heat decomposable binder, and 85-35% of an organic solvent, and said titanium dioxide in said slurry consisting of particles of substantially rutile phase titanium dioxide having a size range from 0.5-10 micrometers and a surface area of 0.1-3 square meters per gram (m 2 /g), whereby when a measured amount of said slurry is applied to the pair of spaced leads, the surface tension of said slurry draws said slurry into a compact, generally cylindrical shape about the pair of spaced leads; drying said slurry applied to said pair of spaced leads so that said leads and remaining of said slurry attached thereto may be subjected to a heating and sintering operation; heating and sintering said pair of spaced leads and remaining of said slurry attached thereto so that said titanium dioxide particles contained in said slurry sinter together to form a titanium dioxide oxygen sensing element bridging said bridgeable space between said pair of spaced leads, said titanium dioxide sensing elements having a thickness in a range of 20-200 micrometers and a density in a range of 60-80% of the theoretical value of density of titanium dioxide which is 4.26 grams per cubic centimeter, whereby said titanium dioxide oxygen sensing element is characterized as a fast responding element in sensing ambient changes from oxygen-rich to oxygen-lean conditions and vice-versa.

Claim 2

A method of making a titanium dioxide element which can be used as an oxygen sensing element, which method comprises the steps of: selecting at least a pair of electrically conductive leads, said leads being formed of a material which is resistant to thermal degradation at temperatures normally found in exhaust gases from operation of an internal combustion engine; placing said pair of leads in a position generally close to one another with a slurry bridgeable space therebetween; applying to said pair of spaced leads a titanium dioxide containing slurry having the following characteristics: said slurry being formed on a volume basis of 10-50% titanium dioxide, 5-15% of an organic heat decomposable binder, and 85-35% of an organic solvent, and said titanium dioxide in said slurry consisting of particles of substantially rutile phase titanium dioxide having a size range from 0.5-10 micrometers and a surface area of 0.1-3 square meters per gram (m 2 /g), whereby when a measured amount of said slurry is applied to the pair of spaced leads, the surface tension of said slurry draws said slurry into a compact, generally cylindrical shape about the pair of spaced leads; drying said slurry applied to said pair of spaced leads so that said leads and remaining of said slurry attached thereto may be subjected to a heating and sintering operation; heating and sintering said pair of spaced leads and remaining of said slurry attached thereto so that said titanium dioxide particles contained in said slurry sinter together to form a titanium dioxide oxygen sensing element bridging said bridgeable space between said pair of spaced leads, said titanium dioxide sensing elements having a thickness in a range of 20-200 micrometers and a density in a range of 60-80% of the theoretical value of density of titanium dioxide which is 4.26 grams per cubic centimeter, whereby said titanium dioxide oxygen sensing element is characterized as a fast responding element in sensing ambient changes from oxygen-rich to oxygen-lean conditions and vice-versa.