Electrically heatable honeycomb body extruded from ceramic material

Abstract

A honeycomb body formed of ceramic material includes channels separated from one another by walls, a front or anterior end face, a rear or posterior end face and a lateral surface. A fluid can flow through the honeycomb body in a flow direction from the front or anterior end face to the rear or posterior end face. The honeycomb body is less electrically conductive in at least one first portion than in at least one second portion. The portions lie one after another in the flow direction. A method for producing such a honeycomb body includes extruding poorly electrically conductive ceramic material. The honeycomb body is treated after extrusion in at least one second portion so that the electrical conductivity in the second portion is increased, whereas it remains unchanged in at least one first portion. The portions lie one after another in the flow direction.

1 - 15 . (canceled) 
     
     
         16 . A honeycomb body, comprising:
 a front end face, a rear end face and a lateral surface;   channels being separated from one another by walls of extruded ceramic material for conducting a fluid through the honeycomb body in a flow direction from said front end face to said rear end face;   at least one first portion and at least one second portion lying one after another in said flow direction; and   the honeycomb body being less electrically conductive in said at least one first portion than in said at least one second portion.   
     
     
         17 . The honeycomb body according to  claim 16 , which further comprises:
 at least two connection contacts disposed at least on one of said end faces or on said lateral surface;   said at least one second portion defining at least one electrically conductive current path interconnecting said at least two connection contacts.   
     
     
         18 . The honeycomb body according to  claim 17 , wherein said at least one electrically conductive current path includes a plurality of electrically conductive current paths. 
     
     
         19 . The honeycomb body according to  claim 18 , wherein all of said electrically conductive current paths are disposed in vicinity of one of said end faces. 
     
     
         20 . The honeycomb body according to  claim 16 , wherein said at least one second portion has at least one radially or axially inhomogeneous electrical conductivity. 
     
     
         21 . The honeycomb body according to  claim 16 , wherein the honeycomb body is better electrically conductive in said at least one second portion than in said at least one first portion, and said better electrically conductive at least one second portion includes electrically conductive material added to a finished pre-formed honeycomb body formed of the same material throughout. 
     
     
         22 . The honeycomb body according to  claim 16 , wherein said at least one second portion is formed as a raised region protruding on one of said end faces. 
     
     
         23 . The honeycomb body according to  claim 18 , wherein all of said current paths are formed as raised current paths on one of said end faces. 
     
     
         24 . A method for producing a honeycomb body, the method comprising the following steps:
 extruding poorly electrically conductive ceramic material to produce a honeycomb body having a front end face, a rear end face, a lateral surface and channels separated from one another by walls for conducting a fluid through the honeycomb body in a flow direction from the front end face to the rear end face;   providing the honeycomb body with at least one first portion and at least one second portion lying one after another in the flow direction;   treating the at least one second portion following the extrusion to increase electrical conductivity in the at least one second portion; and   maintaining electrical conductivity unchanged in the at least one first portion.   
     
     
         25 . The method according to  claim 24 , which further comprises performing the treating step by using an immersion method. 
     
     
         26 . The method according to  claim 25 , which further comprises further performing the treating step by immersing one of the end faces of the honeycomb body in an immersion bath up to a predefined height. 
     
     
         27 . The method according to  claim 24 , which further comprises performing the step of increasing the electrical conductivity of the at least one second portion of the honeycomb body by a vapor deposition method or a spraying method. 
     
     
         28 . The method according to  claim 24 , which further comprises selectively treating the at least one second portion by protecting predetermined portions of the honeycomb body by a mask or a protective coating prior to the treating step. 
     
     
         29 . The method according to  claim 24 , which further comprises removing material on one or both of the end faces prior to or following the treating step to form or produce at least one raised electrically conductive current path following the treating step. 
     
     
         30 . The method according to  claim 24 , which further comprises performing the treating step prior to or following a firing of the extruded honeycomb body, and removing material at the end faces prior to or following the firing.