Characterization of AlN-based ceramic composites for use as millimeter-wave susceptor materials at high temperature: Dielectric properties of AlN:Mo with 0.25 vol% to 4.0 vol% Mo from 25 to 550 °C

Abstract

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High temperature W-band complex permittivity measurements of thermally cycled ceramic-metal composites: AlN:Mo with 0.25 to 4.0 vol% Mo from 25 °C to 1000 °C in air

“…Section 6 provides results from dielectric property measurements of the thermally cycled AlN:Mo samples. These results are compared to previously published measurement data for the same samples, prior to thermal cycling [8]. Finally, a closing summary is provided in section 7.…”

“…The six AlN:Mo samples, having Mo concentrations of 0.25%, 0.5%, 1.0%, 2.0%, 3.0% and 4.0%, by volume, were the same originally analyzed at lower temperatures (25 • C-550 • C) in [8]. During fabrication, each sample was sintered by hot pressing at 1900 • C in an inert atmosphere, cooling to room temperature, then machining into a disk (0.635 cm thick, 5.08 cm diameter).…”

“…Previous studies of the W-band (75-110 GHz) dielectric properties of the present AlN:Mo system, having Mo concentrations ranging from 0.25 to 4 vol%, were limited to temperatures below 550 • C [8]; however, predicted operating parameters for an envisioned mm-wave heat exchanger experiment involve cycling to substantially higher temperatures (600 • C-1000 • C) for multiple hours in air. To ensure that numerical models used for designing high-temperature mm-wave heat exchanger susceptors [11][12][13] adequately represent the electromagnetic behavior of these materials in expected usage conditions, dielectric property data for the proposed susceptor materials are required for temperatures up to 1000 • C, requiring novel modifications to an existing high-temperature, freespace, permittivity characterization system [14] that extend the original (550 • C) temperature limit of the system.…”

“…AlN ceramics with metal powder additives, such as molybdenum, have been proposed for use as high temperature susceptor materials for millimeter wavelength (mm-wave) radiation [8]. One specific application proposed for these materials is for a millimeter wave radiation-powered heat exchanger for power beaming applications [1,2,8].…”

“…AlN ceramics with metal powder additives, such as molybdenum, have been proposed for use as high temperature susceptor materials for millimeter wavelength (mm-wave) radiation [8]. One specific application proposed for these materials is for a millimeter wave radiation-powered heat exchanger for power beaming applications [1,2,8]. The AlN:Mo material system, having a highly thermally conductive matrix (AlN) [9,10] and tunable mm-wave absorption properties by way of Mo powder loading, has been identified as a promising material system for these types of applications.…”