Production of microcrystalline metal oxides

Claim 2

A process for the production of a microcrystalline metal oxide powder which comprises (1) forming a homogeneous solvent solution containing a solute of one or more metalorganic compounds; (2) subjecting the solution to ultrasonic wave energy, while treating the said solution to cause formation of a gelled solution; (3) removing solvent medium from the gelled solution to provide a residual mass of precursor solids; and (4) pyrolyzing the precursor solids in the presence of molecular oxygen to form a metal oxide composition having an average particle size less than about 1000 angstroms.

Claim 3

A process in accordance with claim 1 wherein the solution medium in step (1) comprises an organic solvent.

Claim 4

A process in accordance with claim 1 wherein the solution medium in step (1) additionally includes a surfactant.

Claim 5

A process in accordance with claim 1 wherein the metalorganic compound or compounds in step (1) are metal β-diketonates.

Claim 6

A process in accordance with claim 1 wherein the metalorganic compound or compounds in step (1) are metal carboxylate salts.

Claim 7

A process in accordance with claim 1 wherein the metalorganic compound or compounds in step (1) are metal alkoxides.

Claim 8

A process in accordance with claim 1 wherein the ultrasonic wave energy in step (2) has a frequency in the range between about 40-2000 kilohertz.

Claim 9

A process in accordance with claim 1 wherein the solution treatment for gel formation in step (2) comprises cooling the solution medium.

Claim 10

A process in accordance with claim 1 wherein the solution treatment for gel formation in step (2) comprises concentrating the solution medium by solvent removal.

Claim 11

A process in accordance with claim 1 wherein the solution treatment for gel formation in step (2) comprises adding a gelling agent to the solution medium.

Claim 12

A process in accordance with claim 1 wherein the pyrolysis in step (4) is conducted at a temperature between about 300°-900° C.

Claim 13

A process in accordance with claim 1 wherein the metal oxide composition in step (4) is comprised of microspheric particles.

Claim 14

A process in accordance with claim 1 wherein the metal oxide composition in step (4) is a ferrimagnetic spinel.

Claim 15

A process for the production of a microcrystalline ferrimagnetic spinel which comprises (1) forming a solvent solution containing metalorganic compounds in quantities and with metal valences that subsequently yield a spinel product corresponding to the formula: M.sub.1 Fe.sub.2 O.sub.4 where M is manganese, iron, cobalt, nickel, copper, zinc, cadmium, magnesium, barium, strontium, or any combination thereof; (2) subjecting the solution to ultrasonic wave energy, while treating the solution with ammonia or an organic amine to cause formation of a gelled solution; (3) removing solvent medium from the gelled solution to provide a solid-phase spinel precursor; and (4) pyrolyzing the spinel precursor in the presence of molecular oxygen at a temperature in the range between about 300°-900° C. to form a M 1 Fe 2 O 4 spinel composition having an average particle size less than about 1000 angstroms.

Claim 16

A process for the production of a microcrystalline ferrimagnetic spinel which comprises (1) forming a solvent solution containing metalorganic compounds in quantities and with metal valences that subsequently yield a spinel product corresponding to the formula: M.sub.1 Fe.sub.2 O.sub.4 where M is manganese, iron, cobalt, nickel, copper, zinc, cadmium, magnesium, barium, strontium, or any combination thereof; (2) subjecting the solution to ultrasonic wave energy, while treating the solution with ammonia or an organic amine to cause formation of a gelled solution; (3) removing solvent medium from the gelled solution to provide a solid-phase spinel precursor; and (4) pyrolyzing the spinel precursor in the presence of molecular oxygen at a temperature in the range between about 300°-900° C. to form a M 1 Fe 2 O 4 spinel composition having an average particle size less than about 1000 angstroms.

Claim 17

A process in accordance with claim 14 wherein the solvent medium in step (1) comprises an organic solvent, and the metalorganic compounds are metal β-diketonates.

Claim 18

A process in accordance with claim 14 wherein the solvent medium in step (1) comprises an organic solvent, and the metalorganic compounds are metal alkoxides.

Claim 19

A process in accordance with claim 14 wherein the solvent medium in step (1) comprises an organic solvent, and the metalorganic compounds are metal carboxylate salts.

Claim 20

A process in accordance with claim 14 wherein the ultrasonic energy in step (2) has a frequency in the range between about 40-2000 kilohertz.

Claim 21

A process in accordance with claim 14 wherein the spinel composition in step (4) is comprised of microspheric particles.

Claim 22

A process in accordance with claim 14 wherein the spinel product in step (4) has a Ni 0 .7 Zn 0 .3 Fe 2 O 4 composition.

Claim 23

A process for the production of a microcrystalline ferrimagnetic spinel which comprises (1) forming an aqueous solution containing alpha-hydroxycarboxylate metal salts in quantities and with metal valences that subsequently yield a spinel composition corresponding to the formula: M.sub.1 Fe.sub.2 O.sub.4 where M is manganese, iron, cobalt, nickel, copper, zinc, cadmium, magnesium, barium, strontium, or any combination thereof; (2) subjecting the aqueous solution to ultrasonic wave energy, while treating the said solution to cause formation of a gelled solution; (3) removing the aqueous medium to provide a solid-phase spinel precursor; and (4) pyrolyzing the spinel precursor in the presence of molecular oxygen at a temperature in the range between about 300°-900° C. to form a M 1 Fe 2 O 4 spinel composition having an average particle size less than about 1000 angstroms.

Claim 24

A process for the production of a microcrystalline ferrimagnetic spinel which comprises (1) forming an aqueous solution containing alpha-hydroxycarboxylate metal salts in quantities and with metal valences that subsequently yield a spinel composition corresponding to the formula: M.sub.1 Fe.sub.2 O.sub.4 where M is manganese, iron, cobalt, nickel, copper, zinc, cadmium, magnesium, barium, strontium, or any combination thereof; (2) subjecting the aqueous solution to ultrasonic wave energy, while treating the said solution to cause formation of a gelled solution; (3) removing the aqueous medium to provide a solid-phase spinel precursor; and (4) pyrolyzing the spinel precursor in the presence of molecular oxygen at a temperature in the range between about 300°-900° C. to form a M 1 Fe 2 O 4 spinel composition having an average particle size less than about 1000 angstroms.

Claim 25

A process in accordance with claim 21 wherein the alpha-hydroxycarboxylate in step (1) is citrate.

Claim 26

A process in accordance with claim 21 wherein the alpha-hydroxycarboxylate in step (1) is malate.

Claim 27

A process in accordance with claim 21 wherein the alpha-hydroxycarboxylate in step (1) is tartrate.

Claim 28

A process in accordance with claim 21 wherein the alpha-hydroxycarboxylate in step (1) is lactate.

Claim 29

A process in accordance with claim 21 wherein the alpha-hydroxycarboxylate in step (1) is glycolate.

Claim 30

A process in accordance with claim 21 wherein the aqueous solution in step (1) additionally includes a surfactant.

Claim 31

A process in accordance with claim 21 wherein the ultrasonic wave energy in step (2) has a frequency in the range between about 40-2000 kilohertz.

Claim 32

A process in accordance with claim 21 wherein the spinel composition in step (4) is comprised of microspheric particles.

Claim 33

A process in accordance with claim 21 wherein the spinel product in step (4) has a Ni 0 .7 Zn 0 .3 Fe 2 O 4 composition.