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Title: 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:
 [1];  [2];  [1];  [2]
  1. Oak Ridge, TN
  2. Knoxville, TN
Issue Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
OSTI Identifier:
874932
Patent Number(s):
6492016
Assignee:
UT-Battelle, LLC (Oak Ridge, TN)
Patent Classifications (CPCs):
Y - NEW / CROSS SECTIONAL TECHNOLOGIES Y10 - TECHNICAL SUBJECTS COVERED BY FORMER USPC Y10T - TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
C - CHEMISTRY C01 - INORGANIC CHEMISTRY C01G - COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
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 = {2002},
month = {1}
}

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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


Sorption of Strontium(II) and Radio Strontium Ions on Sodium Titanate
journal, January 1981