DOE Patents title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Method and device for microwave sintering large ceramic articles

Abstract

A microwave sintering system and method are provided for extremely uniform sintering of large and/or irregular shaped ceramic articles at microwave frequencies of at least 28 GHz in the hundreds of kilowatts power range in an untuned cavity. A 28 GHz, 200 kw gyrotron with variable power output is used as the microwave source connected to an untuned microwave cavity formed of an electrically conductive housing through an overmoded waveguide arrangement which acts in conjunction with a mode promoter within the cavity to achieve unexpected field uniformity. The part to be sintered is placed in the cavity and supported on a removable high temperature table in a central location within the cavity. The part is surrounded by a microwave transparent bulk insulating material to reduce thermal heat loss at the part surfaces and maintain more uniform temperature. The cavity may be operated at a high vacuum to aid in preventing arcing. The system allows controlled increased heating rates of greater than 200.degree. C./min to provide rapid heating of a ceramic part to a selected sintering temperature where it is maintained by regulating the microwave power applied to the part. As a result of rapid heating, the extent of non-isothermal processesmore » such as segregation of impurities to the grain boundaries are minimized and exaggerated grain growth is reduced, thereby strengthening the mechanical properties of the ceramic part being sintered.

Inventors:
 [1]
  1. (Knoxville, TN)
Issue Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
OSTI Identifier:
867563
Patent Number(s):
4963709
Assignee:
United States of America as represented by Department of Energy (Washington, DC)
Patent Classifications (CPCs):
H - ELECTRICITY H05 - ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR H05B - ELECTRIC HEATING
C - CHEMISTRY C04 - CEMENTS C04B - LIME, MAGNESIA
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
method; device; microwave; sintering; ceramic; articles; provided; extremely; uniform; irregular; shaped; frequencies; 28; ghz; hundreds; kilowatts; power; range; untuned; cavity; 200; kw; gyrotron; variable; output; source; connected; formed; electrically; conductive; housing; overmoded; waveguide; arrangement; conjunction; mode; promoter; achieve; unexpected; field; uniformity; sintered; placed; supported; removable; temperature; table; central; location; surrounded; transparent; bulk; insulating; material; reduce; thermal; heat; loss; surfaces; maintain; operated; vacuum; preventing; arcing; allows; controlled; increased; heating; rates; degree; provide; rapid; selected; maintained; regulating; applied; result; extent; non-isothermal; processes; segregation; impurities; grain; boundaries; minimized; exaggerated; growth; reduced; strengthening; mechanical; properties; microwave frequencies; heating rate; microwave source; source connected; heat loss; ceramic article; microwave sintering; power output; grain boundaries; insulating material; electrically conductive; mechanical properties; microwave power; microwave cavity; central location; ceramic articles; grain growth; cavity formed; uniform temperature; microwave transparent; allows controlled; reduce thermal; sintering temperature; variable power; power applied; conductive housing; wave frequencies; thermal heat; increased heat; extremely uniform; shaped ceramic; allows control; wave cavity; irregular shape; /219/264/425/

Citation Formats

Kimrey, Jr., Harold D. Method and device for microwave sintering large ceramic articles. United States: N. p., 1990. Web.
Kimrey, Jr., Harold D. Method and device for microwave sintering large ceramic articles. United States.
Kimrey, Jr., Harold D. Mon . "Method and device for microwave sintering large ceramic articles". United States. https://www.osti.gov/servlets/purl/867563.
@article{osti_867563,
title = {Method and device for microwave sintering large ceramic articles},
author = {Kimrey, Jr., Harold D.},
abstractNote = {A microwave sintering system and method are provided for extremely uniform sintering of large and/or irregular shaped ceramic articles at microwave frequencies of at least 28 GHz in the hundreds of kilowatts power range in an untuned cavity. A 28 GHz, 200 kw gyrotron with variable power output is used as the microwave source connected to an untuned microwave cavity formed of an electrically conductive housing through an overmoded waveguide arrangement which acts in conjunction with a mode promoter within the cavity to achieve unexpected field uniformity. The part to be sintered is placed in the cavity and supported on a removable high temperature table in a central location within the cavity. The part is surrounded by a microwave transparent bulk insulating material to reduce thermal heat loss at the part surfaces and maintain more uniform temperature. The cavity may be operated at a high vacuum to aid in preventing arcing. The system allows controlled increased heating rates of greater than 200.degree. C./min to provide rapid heating of a ceramic part to a selected sintering temperature where it is maintained by regulating the microwave power applied to the part. As a result of rapid heating, the extent of non-isothermal processes such as segregation of impurities to the grain boundaries are minimized and exaggerated grain growth is reduced, thereby strengthening the mechanical properties of the ceramic part being sintered.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1990},
month = {1}
}