Ceramic fiber filter constructions are known. One such system is described in Kusuda et al., U.S. Pat. No. 4,652,286, the disclosure of which is incorporated herein by reference. The Kusuda et al. arrangement comprises a porous sintered ceramic fiber composite sheet, coiled into a honeycomb, corrugated, structure. The ceramic fiber composite is produced by a paper-forming method, from a slurry of alumino-silicate fibers and fire clay. After the structure is formed, it is fired and hardened. Such a system is usable as a filter for relatively high temperature gases, at least up to about 1000.degree. C., in a generally efficient and effective manner.
A problem with such fired ceramic fiber filter constructions is that they are relatively brittle. Thus, they exhibit some propensity to fracture or crumble under stresses of certain uses.
Another problem with conventional fired ceramic fiber filter constructions is that they are subject to some problems when used under conditions of substantial thermal gradients. That is, they act as insulators, with formation of substantial thermal gradients across their structures. Since one portion of the arrangement tends to expand under applied thermal stress, more greatly than another, due to the structure's insulating character the relatively rigid construction will have somewhat of a propensity to fracture or fragment under thermal stress.
At least for these reasons, conventional ceramic fiber filter constructions have not been completely satisfactory for certain applications, especially those wherein the filter will be subject to wide temperature variations, and thus expansion and contraction, during use. In addition, they have not been fully acceptable as systems subject to substantial vibration or shock, due to their relatively brittle nature.
In addition, in some systems it is desirable to utilize a pliable, i.e., not completely rigid, filter construction. Conventional ceramic fiber constructions have not have been acceptable for such applications, due to their rigidity.