Accession Number : ADP007744

Title :   Microwave (Hybrid) Heating of Alumina at 2.45 GHZ: I. Microstructural Uniformity and Homogeneity,

Corporate Author : FLORIDA UNIV GAINESVILLE DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s) : De, Arindam ; Ahmad, Iftikhar ; Whitney, E. Dow ; Clark, David E.

Report Date : 27 APR 1992

Pagination or Media Count : 10

Abstract : Microwave (hybrid) heating (MHH) is a unique combination of microwave (MW)material interaction and conventional radiant/conduction mechanisms that facilitates the attainment of very high heating rates in a 2.45 GHz, multimode MW cavity. Microstructural uniformity and homogeneity of dry-pressed green samples of pure, undoped alumina with (MHH relative to conventional fast firing (CFF) has been studied. The confluence of the two heating mechanisms (with MHH) results in an improved parity in temperatures across specimen cross-sections vis-a-vis CFF and stand-alone MW (SMW) sintering. This enhanced parity in temperatures (with MHH) can be said to be responsible for the better microstructural homogeneity and improved mechanical properties relative to CFF. Sintering of larger (20 gm vs. 6 gm) samples with MHH shows evidence of a definitive mass dependence on the MHH phenomena. Larger masses show a better parity in temperatures between the surface and interior of the sample. Consequently, this results in enhancements in the homogeneity of the microstructure, and improved and more uniform mechanical properties relative to the smaller MHH and CFF samples.

Descriptors :   *SINTERING, *MICROWAVES, *CERAMIC MATERIALS, CAVITIES, CONFLUENCE, CROSS SECTIONS, HEATING, HOMOGENEITY, INTERACTIONS, MASS, MECHANICAL PROPERTIES, MICROSTRUCTURE, MICROWAVES, MULTIMODE, SURFACES, TEMPERATURE, RADIANT HEATING, GRAIN SIZE, POWDER ALLOYS, SYMPOSIA, FIRING(CERAMICS).

Subject Categories : Ceramics, Refractories and Glass
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE