Cryochemical method of preparing ultrafine particles of high-purity superconducting oxides

Patent · Mon Dec 03 23:00:00 EST 1990

OSTI ID:5158031

Gusman, M I; Johnson, S M

This paper discusses an improved method of preparing fine particles of superconducting ceramic powders. It comprises dissolving the soluble salts of cations in aqueous medium; obtaining a substantially saturated solution of the salts and adjusting the pH to between about 4 and 7; atomizing the solution onto liquid nitrogen at about {minus}196{degrees}C.; removing the liquid nitrogen by evaporation of the nitrogen under reaction conditions such that the ice-salt crystals do not coalesce into larger particles; removing the ice by sublimation at reduced pressure under reaction conditions such that the ice-salt crystals do not melt; heating the solid residue at about 40{degrees}-60{degrees}C. at reduced pressure under the reaction conditions such that the residue does not melt; calcining the solid residue in sufficient oxygen or air at temperature of between about 200{degrees} and 895{degrees}C.; and cooling slowly the solid at a temperature of between about 900{degrees}C. and ambient temperature in sufficient air or oxygen concurrently annealing the particles in flowing oxygen or air between about 200{degrees} and 500{degrees}C. for between about 2 and 30 hrs and recovering the superconducting solid powder having an average diameter of between about 0.1 and 10 microns.

• Assignee: SRI-International, Menlo Park, CA (USA)
• Patent Number(s): US 4975415; A
• Application Number: PPN: US 7-71977
• OSTI ID: 5158031
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
ATOMIZATION
CALCINATION
CERAMICS
CHEMICAL REACTIONS
DECOMPOSITION
DISSOLUTION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
PARTICLES
PARTICULATES
PHYSICAL PROPERTIES
PYROLYSIS
SUPERCONDUCTIVITY
SYNTHESIS
THERMOCHEMICAL PROCESSES