Stability of microwave heating of ceramic materials in a cylindrical cavity

Abstract

Microwave heating of ceramic materials in a cylindrical wave field is analyzed by numerical simulation. The issues of temperature uniformity and stability inside the sample undergoing microwave heating are addressed. The heating regimes leading to development of global and localized thermal instabilities are illustrated. The role of the temperature dependence of the material's microwave dielectric properties in the formation of instabilities is demonstrated. The tuning and matching of a cylindrical cavity containing the sample is analyzed within a simple model for the microwave and millimetre-wave frequency ranges.

Microwave Sintering: Fundamentals and Modeling

“…The electromagnetic field structure in these configurations is more complicated as it depends on the angular coordinates within the body. Other analytically tractable geometries include converging cylindrical waves incident on cylindrical workpieces …”

“…Other analytically tractable geometries include converging cylindrical waves incident on cylindrical workpieces. 44,45 (B) Microwave Heating in Applicators: In most cases of practical importance the material object is positioned in a microwave applicator that comprises a cavity resonator. To estimate the electric field in a cavity with a single oscillation mode excited, one can use the expression for the electromagnetic energy stored therein:…”

“…7). 45,134 (C) Models of Microwave Sintering: The above described simulations of microwave heating result in obtaining the distribution of temperature over the ceramic workpiece and the evolution of this distribution. However, a major end result of the sintering process is the densification of ceramic powder compact.…”

“…For certain microwave heating conditions (higher heating rates, strong temperature dependence of the material's properties, low thermal conductivity), the temperature in the core of the workpiece may grow uncontrollably while the surface temperature follows the prescribed schedule (Fig. ) …”

Microwave Penetration Depth in Materials with Non-zero Magnetic Susceptibility

“…magnetite and other ferrites) under microwave irradiation. [19][20][21][22][23][24] However, since magnetic properties can enhance absorption of microwaves, some research has been conducted to take advantage of this property. 10,[25][26][27][28] A typical example is microwave assisted steelmaking, where magnetite concentrate is used as material.…”