Effects of anomalous permittivity on the microwave heating of zinc oxide
| Autor: | B. Levush, M. Rosen, D. Gershon, L. P. Martin, A. Birman, Kirill I. Rybakov, Yuval Carmel, R. Hutcheon, Jeffrey P. Calame, D. Dadon |
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| Rok vydání: | 1998 |
| Předmět: | |
| Zdroj: | Journal of Applied Physics. 83:432-437 |
| ISSN: | 1089-7550 0021-8979 |
| DOI: | 10.1063/1.366735 |
| Popis: | Highly nonuniform heating has been observed in zinc oxide (ZnO) powder compacts exposed to 2.45 GHz microwaves in oxygen deficient atmospheres such as pure nitrogen or argon. This phenomenon manifests as a localized zone of rapid heating which propagates outward from the sample core, and is documented by real-time surface and core temperature measurements performed during the microwave exposure. Measurements of the complex permittivity, e″, during heating of identical ZnO samples in a conventional furnace and in a nitrogen atmosphere, demonstrated that e″ experiences at least one significant maximum between 200 and 500 °C. Mass spectrometry results indicate that the peaks in e″ correlate well with the rate of desorption of chemisorbed water from the surface of the ZnO powder. It was also noted that the nonuniform heating does not manifest when the microwave exposure is performed in air. Similarly, the anomalous peaks in e″ are almost completely suppressed during heating in air. It is well known that oxyge... |
| Databáze: | OpenAIRE |
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