Method for controlling the conductance of a heated cellular substrate

Claim 3

The method of claim 1, wherein the means for shielding a portion of the substrate comprises the steps of: applying photoresist material on the substrate; applying masking material on the inlet end portion; exposing the structure to light radiation; and dissolving the photoresist material from the unexposed inlet end portion.

Claim 4

The method of claim 2, further comprising the step of forming an intermediate layer of suitable material on the substrate prior to applying the photoresist material.

Claim 5

The method of claim 2, further comprising the step of burning off the exposed photoresist material after the conductive material has been applied to the substrate.

Claim 6

The method of claim 1, wherein the means for shielding a portion of the substrate comprises dipping a portion of the substrate into a masking material to form a protective layer over part of the substrate.

Claim 7

The method of claim 1, further comprising the step of forming an intermediate layer of suitable material on the substrate.

Claim 8

The method of claim 6, wherein the intermediate layer is formed on the inlet end portion of the substrate.

Claim 9

The method of claim 6, wherein the intermediate material is selected from the group comprising glass frit, glass-ceramic frit, and cordierite.

Claim 10

The method of claim 6, wherein the intermediate material is a low expansion material selected from the group comprising low expansion zinc petalite-beta quartz glass-ceramic having a composition in the ZnO-Al 2 O 3 -SiO 2 field; sinterable powdered glass comprising, apart from incidental impurities, MgO, Al 2 O 3 , SiO 2 and at least one modifying oxide selected from the group consisting of BaO, PbO, SrO and CaO and which is thermally crystallizable at sintering temperatures to yield a highly crystalline, low expansion, thermally stable glass-ceramic; and lead titanate-containing crystallizable sealing glass consisting essentially, apart from incidental impurities, in weight percent of 60 to 80% of PbO, up to 20% of at least one divalent metal oxide selected from ZnO and BaO such that the total of divalent oxides and PbO is 60 to 80%, 5 to 18% TiO 2 , at least 1% B 2 O 3 and at least 5% SiO 2 , the total of B 2 O 3 and SiO 2 being 10 to 20%.

Claim 11

The method of claim 6, further comprising the step of sintering the intermediate material to form a high density layer.

Claim 12

The method of claim 1, wherein the substrate is a honeycomb structure having an inlet and an outlet end portion, and having a matrix of walls defining a plurality of cells or passageways extending longitudinally and mutually parallel therethrough, between the inlet and outlet end portions.

Claim 13

The method of claim 1, wherein the means for shielding a portion of the substrate comprises plugging the cells in the portion of the substrate to a predetermined depth.

Claim 14

The method of claim 1, wherein the substrate is a ceramic honeycomb structure.

Claim 15

The method of claim 13, further comprising the steps of (a) applying a layer of pre-cordierite glass to the inlet end portion of the substrate, and (b) sintering the glass to form cordierite, and then providing means for shielding a portion of the substrate, and applying a layer of conductive material over the unshielded portion of the substrate.

Claim 16

The method of claim 1, wherein the honeycomb structure further comprises slots forming ridges of cell walls.