Hot press with flat plate heaters and its application to the fabrication of large varistor slugs

Journal Article · Thu May 01 00:00:00 EDT 1980 · Am. Ceram. Soc. Bull.; (United States)

OSTI ID:5347828

Snow, G S; Cooper, R A

A hot press was designed and constructed for fabricating large ZnO varistor slugs. The electrical properties of ZnO varistors containing CoO, PbO, and Bi/sub 2/O/sub 3/ are very dependent on processing temperature. To fabricate varistors with the desired field (E = 42.5 +- 1.5 kV/cm at 5 A/cm/sup 2/), it was necessary to maintain temperature uniformity within +- 3.5/sup 0/C throughout the slug and from run to run. The slugs were fabricated in the form of disks approx. = 75 mm in diameter with a final thickness of approx. = 14 mm. Ceramics have been hot pressed previously using apparatus in which the heat source was in the form of a cylinder surrounding, and coaxial to, the slug. Unless the heat source is long compared with its diameter, such a heating method results in poor temperature uniformity, which is aggravated by poor thermal coupling with the heat source and by large heat losses through the pushrods. In the design described herein, these problems are avoided by using flat plate heaters above and below the slug.

• Research Organization: Sandia Labs., Albuquerque, NM
• OSTI ID: 5347828
• Journal Information: Am. Ceram. Soc. Bull.; (United States), Vol. 59:5
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
47 OTHER INSTRUMENTATION
FURNACES
DESIGN
ZIRCONIUM OXIDES
HOT PRESSING
FABRICATION
PRESSES
CHALCOGENIDES
MATERIALS WORKING
OXIDES
OXYGEN COMPOUNDS
PRESSING
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
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