Temperature dependence and shape effect in high-temperature microwave heating of nickel oxide powders

Abstract

a b s t r a c tThe temperature dependence of microwave absorption was investigated for Ni 1 À y O particles over the frequency range 2.0-13.5 GHz and temperature range 25-1000°C. Using a coaxial transmission line method with a network analyzer, both the real and imaginary parts of the relative permittivity (ε′ r and ε″ r , respectively) and permeability (μ′ r and μ″ r , respectively) were measured; finding that both are largely dependent on the temperature at all frequencies. Furthermore, permeability loss factors related to shape effects were observed at high frequencies, indicating an increase in the microwave-absorption properties. A modified form of Mie's theory was applied to discuss these effects, wherein a spherical model demonstrating a close fit to the shape effect data suggests a more complex microwave-absorption behavior at increased temperature.

Computational analysis of hybrid heating of a heterogeneous core-shell configuration for improving temperature uniformity

“…Hence, it becomes necessary to determine them experimentally. One way of doing so is through the coaxial transmission line (CTL) or the cavity perturbation methods, using a network analyzer [5], [6]. There is also a dependency regarding variables such as sample geometry, porosity and size, as well as the change in their properties and the presence of volatiles, among others.…”

“…There is also a dependency regarding variables such as sample geometry, porosity and size, as well as the change in their properties and the presence of volatiles, among others. Because of this, it becomes paramount to follow a careful analysis of the experimental data, especially when validating a mathematical model [6] - [9]. It is due to the aforementioned difficulties that hybrid heating represents a handsome alternative.…”