Porous bodies with enhanced pore architecture prepared without a high-temperature burnout material

Abstract

A precursor mixture for producing a porous body, wherein the precursor mixture comprises: (i) at least one milled alpha alumina powder having a particle size of 0.1 to 6 microns, (ii) non-silicate powder that functions as a binder of the alpha alumina powders, and (iii) at least one burnout material having a particle size of 1-10 microns and a decomposition temperature of less than 550° C., with the proviso that a burnout material having a decomposition temperature of 550° C. or greater is excluded from the precursor mixture.

What is claimed is: 
     
         1 . A method for producing a porous body, the method comprising:
 providing a precursor mixture comprising (i) milled alpha alumina powder having a particle size of 0.1 to 6 microns, (ii) non-silicate binder of the alpha alumina powders, and (iii) a burnout material having a particle size of 1-10 microns and a decomposition temperature of less than 550° C., with the proviso that a burnout material having a decomposition temperature of 550° C. or above is excluded;   forming the precursor mixture into a predetermined shape; and   subjecting the shape to a heat treatment step in which the shape is sintered to produce the porous body.   
     
     
         2 . The method of  claim 12 , further comprising unmilled alpha alumina powder having a particle size of 10 to 100 microns in said precursor mixture. 
     
     
         3 . The method of  claim 13 , wherein the weight ratio of milled to unmilled alpha alumina powder is in a range of 0.25:1 to about 5:1. 
     
     
         4 . The method of  claim 12 , wherein unmilled alpha alumina powder is excluded from the precursor mixture. 
     
     
         5 . The precursor mixture of  claim 12 , wherein the non-silicate binder is nano-sized boehmite 
     
     
         6 . The method of  claim 12 , wherein the providing the precursor mixture comprises:
 (i) dispersing said non-silicate binder into water to produce a dispersion of said binder;   (ii) adding said milled alpha alumina powder having a particle size of 0.1 to 6 microns to the dispersion of the non-silicate binder, and mixing until a first homogeneous mixture is obtained, wherein said non-silicate binder functions as a binder of the alpha alumina powder; and   (iii) adding said burnout material having said particle size of 1-10 microns and said decomposition temperature of less than 550° C., and mixing until a second homogeneous mixture is obtained.   
     
     
         7 . The method of  claim 12 , wherein said heat treatment step comprises:
 subjecting the formed shape to a heat treatment step within a temperature in a range of 35° C.-550° C. to remove water and burnout the burnout material to produce a pre-fired porous body; and   subjecting the pre-fired porous body to a sintering step at a temperature within a range of 900° C.-2000° C. to produce said porous body.   
     
     
         8 . The method of  claim 12 , wherein said porous body possesses a porosity derived only from said burnout material having said decomposition temperature of less than 550° C. 
     
     
         9 . The method of  claim 12 , wherein said porous body possesses at least one of a water absorption of at least 30%, average crush strength of at least 30 N, and a BET surface area of at least 0.3 m 2 /g. 
     
     
         10 . The method of  claim 12 , wherein said porous body possesses a pore architecture that provides at least one of a tortuosity of 7 or less, a constriction of 4 or less, and a permeability of 30 mdarcys or greater. 
     
     
         11 . The method of  claim 12 , wherein said burnout material having said decomposition temperature of less than 550° C. comprises a polyolefin powder. 
     
     
         12 . The method of  claim 17 , wherein said step (ii) includes, either simultaneous or subsequent to adding and mixing the milled alpha alumina powder, adding unmilled alpha alumina powder having a particle size in a range of 10-100 microns, and mixing until said first homogeneous mixture is obtained. 
     
     
         13 . The method of claim  23 , wherein the weight ratio of milled to unmilled alpha alumina powder is in a range of 0.25:1 to about 5:1. 
     
     
         14 . The method of  claim 12 , wherein unmilled alpha alumina powder is excluded from the method to produce the porous body. 
     
     
         15 . The method of  claim 12 , wherein a silicon-containing substance is substantially excluded from the method to produce the porous body. 
     
     
         16 . The method of  claim 12 , wherein a sodium-containing substance is substantially excluded from the precursor mixture. 
     
     
         17 . The method of  claim 12 , wherein, after said heat treatment step to form a porous body, said method further comprises depositing silver on and/or in said porous body. 
     
     
         18 . The method of  claim 1 , wherein the non-silicate binder is nanosized having a particle size of less than 50 nm. 
     
     
         19 . The method of  claim 1 , wherein the non-silicate binder is selected from the group consisting of an aluminum hydroxide, an oxide-hydroxide, a transition alumina, and an organic or an inorganic precursor that produces alpha-alumina upon firing. 
     
     
         20 . The method of  claim 1 , wherein the burn material comprises a first burnout material having a first decomposition temperature of less than 550° C. and a second burnout material having a second decomposition of less than 550° C. bur greater than the first decomposition temperature, and wherein the first burnout material is present in the precursor mixture in a greater amount than the second burnout material.