Microwave heating of soda-lime glass by addition of iron powder

Experimental studies were conducted to investigate the microwave (MW) heating behavior of soda-lime glass beads with added iron powder. These studies were intended to obtain fundamental knowledge for vitrification solidification and for the fabrication of metal-reinforced glass-matrix composites. The glass beads (0.2 mm diameter) did not heat very well by themselves at temperatures greater than 200 degrees C within 600 s in a multimode applicator at a power of 0.67 W. The addition of iron powder (average 70 mu m, volume fraction 18%) made it possible to heat the glass beads above 700 degrees C within 60 s. At lower fractions of 3-11 vol%, however, a sudden temperature rise [thermal runaway (TRW)] occurred after the incubation time period. A single-mode MW applicator was used for clarifying the electric (E)-field and magnetic (H)-field contributions to the heating of each material and their mixtures. The results of this study demonstrated that the H-field contributed to the heating of,the iron and then triggered the heating of the glass. The E-field component is necessary for heating the glass to a temperature higher than 800 degrees C. The factors determining the threshold values of the volume fraction causing TRW are discussed.