Method for making porous magnetic glass and crystal-containing structures

A method for making porous bodies of magnetic crystal-containing materials with interconnected pores less than 10,000 A in diameter and having iron-containing, magnetic crystals enveloped therewithin with dimensions of less than about 1000 A which method comprises the steps of:

• (a) melting a batch for a glass which, upon cooling and/or subsequent reheating, separates into at least four phases, viz., iron-containing magnetic crystals other than said iron-containing crystals, and two co-connected, chemically-distinct, vitreous phases of different solubility;
• (b) simultaneously forming the melt into a body and cooling to a temperature at least within the range beginning in the vicinity of the transformation range of the glass but below the miscibility temperature of said two vitreous phases, whereby separation of said two vitreous phases and development of said crystals can be initiated;
• (c) exposing said body to a temperature within the range beginning in the vicinity of the transformation range of the glass but below the miscibility temperature of said two vitreous phases for a period of time sufficient to induce separation of said two vitreous phases and to develop said crystals and/or to coarsen the structure of said vitreous phases, to modify the magnetic properties of said body, and to cause the growth of said crystals other than iron-containing crystals;
• and then
• (d) contacting said body with an etchant for a period of time sufficient to remove one of said vitreous phases and thereby produce a porous body of crystal-containing material with interconnected pores, wherein said crystal-containing material consists essentially of a glassy-crystalline skeleton, said crystal portion thereof consisting essentially of a silica-containing species.

A method for making porous bodies of magnetic glass with interconnected pores less than 10,000 A in diameter and having iron-containing, magnetic crystals enveloped therewithin with dimensions less than about 1000 A which method comprises the steps of:

• (a) melting a batch for a glass which, upon cooling and/or subsequent reheating, separates into at least three phases, viz., iron-containing magnetic crystals and two co-connected, chemically-distinct, vitreous phases of different solubility;
• (b) quenching said melt to at least below the transformation range thereof and forming a glass body therefrom;
• (c) rapidly heating said quenched glass body to a temperature above the miscibility temperature of said two vitreous phases and holding at that temperature for a sufficient length of time to cause the development and/or growth of said iron-containing magnetic crystals within said glass;
• (d) quenching the resultant body to a temperature at least below the miscibility temperature of said two vitreous phases;
• (e) exposing said body to a temperature within the range beginning in the vicinity of the transformation range of the glass but below the miscibility temperature of said two vitreous phases for a period of time sufficient to induce separation of said vitreous phases and/or to coarsen the structure of said vitreous phases and to modify the magnetic properties of said body;
• and then
• (f) contacting said body with an etchant for a period of time sufficient to remove one of said vitreous phases and thereby produce a porous glass body with interconnected pores, wherein said glass consists essentially of a vitreous silica skeleton.

A method for making porous bodies of magnetic crystal-containing materials with interconnected pores less than 10,000 A in diameter and having iron-containing, magnetic crystals enveloped therewithin with dimensions of less than about 1000 A which method comprises the steps of:

• (a) melting a batch for a glass which, upon cooling and/or subsequent reheating, separates into at least four phases, viz., iron-containing magnetic crystals, crystals other than said iron-containing crystals, and two co-connected, chemically-distinct vitreous phases of different solubility;
• (b) quenching said melt below the transformation range thereof and forming a glass body therefrom;
• (c) rapidly heating said quenched glass body to a temperature above the miscibility temperature of said two vitreous phases and holding at that temperature for a sufficient length of time to cause the development and/or growth of said iron-containing magnetic crystals;
• (d) quenching the resultant body to a temperature at least below the miscibility temperature of said two vitreous phases;
• (e) exposing said body to a temperature within the range beginning in the vicinity of the transformation range of the glass but below the miscibility temperature of said two vitreous phases for a period of time sufficient to induce separation of said vitreous phases and/or to coarsen the structure of said vitreous phases, to modify the magnetic properties of said body, and to cause growth of said crystals other than iron-containing crystals;
• and then
• (f) contacting said body with an etchant for a period of time sufficient to remove one of said vitreous phases and thereby produce a porous body of crystal-containing material with interconnected pores, wherein said crystal-containing material consists essentially of a glassy-crystalline skeleton, said crystal portion thereof consisting essentially of a silica-containing species.