Abstract
Synchrotron radiation computed tomography was applied to investigate Cu–Fe mixture microwave sintering in situ and to examine the magnetic force between reversely magnetized micro-metal particles in microwave sintering. Results revealed that the growth rate of the sintering necks between Cu–Fe particles and Cu–Cu particles around the iron particles distributed in a vertical direction was faster than that of the sintering necks in the horizontal direction. These phenomena were consistent with the possible influence caused by the magnetic force between metal particles, as shown in our simple particle model. The kinetic curves of sintering neck growth along the vertical and horizontal directions quantitatively revealed the difference in growth rates. The contributing factors of magnetic force in microwave sintering were subsequently discussed. The volume of iron particles was proportional to the influence of magnetic force, and their shape elicited a remarkable influence based on demagnetization effects. This study provided a useful basis for microwave sintering mechanisms and anisotropic material preparation.
Highlights
Microwave sintering is a novel material preparation method [1,2,3,4] preferred over conventional sintering because of special advantages, including high heating rate, overall and even heating, and material microstructure improvement
Our results revealed that sintering necks around iron particles exhibited different growth rates at various directions
The microwave electromagnetic field type can be adjusted by using a short piston
Summary
Microwave sintering is a novel material preparation method [1,2,3,4] preferred over conventional sintering because of special advantages, including high heating rate, overall and even heating, and material microstructure improvement. The excellent advantages of microwave sintering are attributed to the unique driving force caused by microwave electromagnetic field [6,7]. Conventional sintering is stimulated by thermal field. Electromagnetic field elicits various non-thermal effects except microwave thermal effect. Janney et al [8] indicated that the activation energy is lower in microwave sintering than in conventional sintering. Electromagnetic field influences mass diffusion during sintering [9,10]
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