TY - JOUR
T1 - Microwave Power Absorption Mechanism of Metallic Powders
AU - Zhang, Yi
AU - Agrawal, Dinesh K.
AU - Cheng, Jiping
AU - Slawecki, Tania
N1 - Funding Information:
Manuscript received August 28, 2017; revised November 20, 2017 and January 7, 2018; accepted January 13, 2018. Date of publication February 27, 2018; date of current version May 4, 2018. This work was supported by the Fundamental Research Funds for the Central Universities of China. (Corresponding author: Yi Zhang.) Y. Zhang is with the College of Electronics and Information Engineering, Sichuan University, Chengdu 610065, China, and also with the Materials Research Institute, Pennsylvania State University, University Park, State Collage, PA 16802 USA (e-mail: [email protected]).
Funding Information:
He is currently a Visiting Fellow with the Material Research Institute, Pennsylvania State University, State College, PA, USA, which is supported by the China Scholarship Council. His current research interests include microwave power sources, microwave processing and microwave devices with novel materials.
Publisher Copyright:
© 1963-2012 IEEE.
PY - 2018/5
Y1 - 2018/5
N2 - Microwave processing of metallic powders, both in multimode and single-mode cavity, has attracted wide interest. However, the mechanism of interaction between microwaves and metal powders is not yet very well understood. In this paper, the microwave power absorption mechanism in metallic powders has been systematically studied. For this, mixtures of copper and alumina powders have been processed in a 2.45-GHz microwave single mode cavity in either air or forming gas (N2 + 5 wt% H2). In the nominal pure magnetic field (H-field) region in the single-mode microwave cavity, pure copper powder cannot be heated in the reductive (forming gas) atmosphere while it will heat in air atmosphere. Although neither alumina nor copper separately heat up in forming gas in the H-field, mixtures of copper and alumina powders heat up readily. These behaviors can be explained by the presence of oxide layers found on many metallic particles, which play a vital role in the microwave heating of metal powders. The oxide layers isolate the particles and confine the electric current to the surface of every particle, thereby allowing microwaves to penetrate into the sample. Since the particle size is quite small and the surface area is high, the heat produced by the sum of the surface currents on all of these particles is significant. Concurrently, the oxide layer on each metal particle may act as thermal insulation material to help maintain the temperature as the metal particles heat up since many metal oxides have low thermal conductivity. We propose a new mathematical model and derive the power dissipation equation which provides the fundamental basis for the analysis, calculation, and simulation of heating of metallic powders in microwaves.
AB - Microwave processing of metallic powders, both in multimode and single-mode cavity, has attracted wide interest. However, the mechanism of interaction between microwaves and metal powders is not yet very well understood. In this paper, the microwave power absorption mechanism in metallic powders has been systematically studied. For this, mixtures of copper and alumina powders have been processed in a 2.45-GHz microwave single mode cavity in either air or forming gas (N2 + 5 wt% H2). In the nominal pure magnetic field (H-field) region in the single-mode microwave cavity, pure copper powder cannot be heated in the reductive (forming gas) atmosphere while it will heat in air atmosphere. Although neither alumina nor copper separately heat up in forming gas in the H-field, mixtures of copper and alumina powders heat up readily. These behaviors can be explained by the presence of oxide layers found on many metallic particles, which play a vital role in the microwave heating of metal powders. The oxide layers isolate the particles and confine the electric current to the surface of every particle, thereby allowing microwaves to penetrate into the sample. Since the particle size is quite small and the surface area is high, the heat produced by the sum of the surface currents on all of these particles is significant. Concurrently, the oxide layer on each metal particle may act as thermal insulation material to help maintain the temperature as the metal particles heat up since many metal oxides have low thermal conductivity. We propose a new mathematical model and derive the power dissipation equation which provides the fundamental basis for the analysis, calculation, and simulation of heating of metallic powders in microwaves.
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U2 - 10.1109/TMTT.2018.2804980
DO - 10.1109/TMTT.2018.2804980
M3 - Article
AN - SCOPUS:85042697753
SN - 0018-9480
VL - 66
SP - 2107
EP - 2115
JO - IEEE Transactions on Microwave Theory and Techniques
JF - IEEE Transactions on Microwave Theory and Techniques
IS - 5
ER -