Method of making inorganic fibers

Claim 1

A METHOD OF FORMING FILAMENTS HAVING A RECTANGULAR CROSS SECTION AND THE FOLLOWING DIMENSIONS, LENGTH FROM 2.5 MILLIMETERS TO 6 INCHES, WIDTH FROM 5 TO 25 MICRONS, THICKNESS FROM 0.2 TO 1.5 MICRONS, RATIO OF LENGTH TO WIDTH >100:1 AND RATIO OF LENGTH OF THICKNESS >1000:1, SAID FILAMENTS BEING COMPOSED OF INORGANIC OXIDE; WHICH METHOD COMPRISES: FORMING A RELATIVELY STABLE HIGHLY CONCENTRATED SOL, BY BRINGING TOGETHER IN SOLUTION A METAL SALT OF A STRONG ACID AND AN ALKALI METAL SALT OF A WEAK ACID AND THEREAFTER ADJUSTING THE PH OF THE PRODUCT RESULTING FROM THE DOUBLE DECOMPOSITION REACTION WHICH OCCURS WHEN THE TWO SAID SALTS ARE BROUGHT TOGETHER TO PRODUCE A COMPOSITION WITH A PH BETWEEN 5 AND 9; SPREADING THE RESULTING FILAMENT FORMING COMPOSITION AS A THIN LAYER ON A CHHEMICALLY RESISTANT SOLID SURFACE; HEATING THE THIN LAYER TO A TEMPERATURE SUCH THAT THE SOL OF THE LAYER IS QUICKLY TRANSFORMED TO A GEL, SIMULTANEOUSLY WITH THE RAPID EVAPORATION OF WATER; CONTAINING THE HEATING WHILE FILAMENTS ARE FORMED AS A RESULT OF THE CONTINUED DRYING OF THE GEL; COMPLETING THE DRYING AT ABOUT 150*C. UNTIL ALL FREE WATER HAS BEEN REMOVED; CONVERTING THE DRIED FIBROUS MATERIAL TO METAL OXIDE FILAMENTS BY SLOWING RAISING THE TEMPERATURE OF THE DRIED MATERIAL TO BETWEEN ABOUT 600*C. AND 800*C. IN AN OXIDIZING ATMOSPHERE AND MAINTAINING THE FILAMENTS WITHIN SAID TEMPERATURE RANGE FOR BETWEEN 10 AND 120 MINUTES; COOLING THE METAL OXIDE FILAMENTS TO ROOM TEMPERATURE; THEREAFTER WASHING THE FILAMENTS TO REMOVE ALL RESIDUAL WATER SOLUBLE SALTS; DRLLYING THE RESULTING POROUS INORGANIC OXIDE FILAMENTS; AND THEN IMPREGNATING THE POROUS PRODUCT WITH A SOLUTION OF AN OXIDE FORMING METTAL SALT.

Claim 2

A METHOD OF FORMING FILAMENTS HAVING A RECTANGULAR CROSS SECTION AND THE FOLLOWING DIMENSIONS, LENGTH FROM 2.5 MILLIMETERS TO 6 INCHES, WIDTH FROM 5 TO 25 MICRONS, THICKNESS FROM 0.2 TO 1.5 MICRONS, RATIO OF LENGTH TO WIDTH >100:1 AND RATIO OF LENGTH OF THICKNESS >1000:1, SAID FILAMENTS BEING COMPOSED OF INORGANIC OXIDE; WHICH METHOD COMPRISES: FORMING A RELATIVELY STABLE HIGHLY CONCENTRATED SOL, BY BRINGING TOGETHER IN SOLUTION A METAL SALT OF A STRONG ACID AND AN ALKALI METAL SALT OF A WEAK ACID AND THEREAFTER ADJUSTING THE PH OF THE PRODUCT RESULTING FROM THE DOUBLE DECOMPOSITION REACTION WHICH OCCURS WHEN THE TWO SAID SALTS ARE BROUGHT TOGETHER TO PRODUCE A COMPOSITION WITH A PH BETWEEN 5 AND 9; SPREADING THE RESULTING FILAMENT FORMING COMPOSITION AS A THIN LAYER ON A CHHEMICALLY RESISTANT SOLID SURFACE; HEATING THE THIN LAYER TO A TEMPERATURE SUCH THAT THE SOL OF THE LAYER IS QUICKLY TRANSFORMED TO A GEL, SIMULTANEOUSLY WITH THE RAPID EVAPORATION OF WATER; CONTAINING THE HEATING WHILE FILAMENTS ARE FORMED AS A RESULT OF THE CONTINUED DRYING OF THE GEL; COMPLETING THE DRYING AT ABOUT 150*C. UNTIL ALL FREE WATER HAS BEEN REMOVED; CONVERTING THE DRIED FIBROUS MATERIAL TO METAL OXIDE FILAMENTS BY SLOWING RAISING THE TEMPERATURE OF THE DRIED MATERIAL TO BETWEEN ABOUT 600*C. AND 800*C. IN AN OXIDIZING ATMOSPHERE AND MAINTAINING THE FILAMENTS WITHIN SAID TEMPERATURE RANGE FOR BETWEEN 10 AND 120 MINUTES; COOLING THE METAL OXIDE FILAMENTS TO ROOM TEMPERATURE; THEREAFTER WASHING THE FILAMENTS TO REMOVE ALL RESIDUAL WATER SOLUBLE SALTS; DRLLYING THE RESULTING POROUS INORGANIC OXIDE FILAMENTS; AND THEN IMPREGNATING THE POROUS PRODUCT WITH A SOLUTION OF AN OXIDE FORMING METTAL SALT.