Method of preparing a low-density porous fused-fiber matrix

Abstract

A method is provided for preparing a low density porous rigid fused-fiber matrix having a density of between about 3.5 and 5.5 pounds/cubic foot and a free volume of between about 90-98 volume percent for use as a cell-culture substrate or implant material, or in chromatographic separation of blood cells. The method is carried out by forming a slurry containing (I) silica, alumina or silica and alumina fibers having thicknesses between about 0.5 and 20 .mu.m and lengths between about 1 and 10 mm, and having a fiber:liquid weight ratio of between about 1:25 to 1:70, (ii) a thickening agent to give the slurry a viscosity between about 1,000 and 25,000 centipoise, (iii) boron nitride particles between about 2-12 percent by weight of the total fiber weight, and (iv) a dispersing agent when the slurry contains silica fibers, allowing the slurry to settle in a mold to produce a fiber block, drying the fiber block, and heating the dried fiber block to at least about 2200.degree. F. for a period sufficient to cause the fibers to form the fused-fiber matrix. Graphite or polymer filler elements may be provided in the mold prior to settling of the slurry to form strands or spacers in the fiber block that vaporize during heating to produce channels or plates separated by voids. Two or more slurries can be formed having different fiber thicknesses, densities or compositions to produce a matrix having a discontinuous gradient of density or layers of different compositions.