Method for preparing spherical ferrite beads and use thereof
Abstract
The invention allows the fabrication of small, dense, highly polished spherical beads of hexagonal ferrites with selected compositions for use in nonreciprocal microwave and mm-wave devices as well as in microwave absorbent or reflective coatings, composites, and the like. A porous, generally spherical bead of hydrous iron oxide is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead is washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) under conditions of elevated temperature and pressure to convert the bead into a mixed hydrous iron-alkaline earth oxide while retaining the generally spherical shape. This mixed oxide bead is then washed, dried, and calcined to produce the desired (BaFe.sub.12 O.sub.19 or SrFe.sub.12 O.sub.19) crystal structure. The calcined bead is then sintered to form a dense bead of the BaFe.sub.12 O.sub.19 and SrFe.sub.12 O.sub.19 phase suitable for polishing and incorporation into various microwave devices and components.
- Inventors:
-
- Oak Ridge, TN
- Knoxville, TN
- Issue Date:
- Research Org.:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- OSTI Identifier:
- 874932
- Patent Number(s):
- 6492016
- Assignee:
- UT-Battelle, LLC (Oak Ridge, TN)
- Patent Classifications (CPCs):
-
C - CHEMISTRY C01 - INORGANIC CHEMISTRY C01G - COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
C - CHEMISTRY C01 - INORGANIC CHEMISTRY C01P - INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- DOE Contract Number:
- AC05-96OR22464
- Resource Type:
- Patent
- Country of Publication:
- United States
- Language:
- English
- Subject:
- method; preparing; spherical; ferrite; beads; allows; fabrication; dense; highly; polished; hexagonal; ferrites; selected; compositions; nonreciprocal; microwave; mm-wave; devices; absorbent; reflective; coatings; composites; porous; bead; hydrous; iron; oxide; sol-gel; process; form; substantially; rigid; fine; crystallite; size; correspondingly; finely; distributed; internal; porosity; resulting; washed; hydrothermally; reacted; soluble; alkaline; earth; salt; typically; sr; conditions; elevated; temperature; pressure; convert; mixed; iron-alkaline; retaining; shape; dried; calcined; produce; bafesub12; osub19; srfesub12; crystal; structure; sintered; phase; polishing; incorporation; components; elevated temperature; alkaline earth; iron oxide; wave device; /428/419/423/
Citation Formats
Lauf, Robert J, Anderson, Kimberly K, Montgomery, Frederick C, and Collins, Jack L. Method for preparing spherical ferrite beads and use thereof. United States: N. p., 2002.
Web.
Lauf, Robert J, Anderson, Kimberly K, Montgomery, Frederick C, & Collins, Jack L. Method for preparing spherical ferrite beads and use thereof. United States.
Lauf, Robert J, Anderson, Kimberly K, Montgomery, Frederick C, and Collins, Jack L. Tue .
"Method for preparing spherical ferrite beads and use thereof". United States. https://www.osti.gov/servlets/purl/874932.
@article{osti_874932,
title = {Method for preparing spherical ferrite beads and use thereof},
author = {Lauf, Robert J and Anderson, Kimberly K and Montgomery, Frederick C and Collins, Jack L},
abstractNote = {The invention allows the fabrication of small, dense, highly polished spherical beads of hexagonal ferrites with selected compositions for use in nonreciprocal microwave and mm-wave devices as well as in microwave absorbent or reflective coatings, composites, and the like. A porous, generally spherical bead of hydrous iron oxide is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead is washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) under conditions of elevated temperature and pressure to convert the bead into a mixed hydrous iron-alkaline earth oxide while retaining the generally spherical shape. This mixed oxide bead is then washed, dried, and calcined to produce the desired (BaFe.sub.12 O.sub.19 or SrFe.sub.12 O.sub.19) crystal structure. The calcined bead is then sintered to form a dense bead of the BaFe.sub.12 O.sub.19 and SrFe.sub.12 O.sub.19 phase suitable for polishing and incorporation into various microwave devices and components.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jan 01 00:00:00 EST 2002},
month = {Tue Jan 01 00:00:00 EST 2002}
}
Works referenced in this record:
The Basic Chemistry Involved in the Internal-Gelation Method of Precipitating Uranium as Determined by pH Measurements
journal, January 1987
- Collins, J. L.; Lloyd, M. H.; Fellows, R. L.
- Radiochimica Acta, Vol. 42, Issue 3
Sorption of Strontium(II) and Radio Strontium Ions on Sodium Titanate
journal, January 1981
- Heinonen, . J.; Lehto, J.; MiETTlNEN, J. K.
- Radiochimica Acta, Vol. 28, Issue 2