Evaluating the Sintering of Glass Frits Using Hot Stage Microscopy

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New York State College of Ceramics at Alfred University. Inamori School of Engineering.
This study uses the direct observation of the heating of cylindrical powder compacts via hot-stage microscope (HSM), with heating rates from 1.0 to 60 K/min, to establish sintering ranges and activation energies of three glasses. The HSM allows the quick and simple thermo-analytical examination of macroscopic sintering behavior, using small samples (approximately 12.8 mm^3) to minimize heat transfer problems. The use of mechanically pressed compacts with similar initial densities allows for the comparison of densification behavior of samples subjected to different heating rates. The sintering of glass powders, recognized to occur through the bulk transport mechanism of viscous flow, subsumes several caveats when comparing theory to experimental observation. The densification of powder particles as they coalesce into a monolith will occur over a temperature range >100 K during non-isothermal heat treatments. The densification temperature, defined as the peak in the shrinkage curve, increased with increasing heating rates. Heat work, defined as the accumulation of thermal energy with time (K∙s), is proposed to have a dependence on the logarithm of time when calculated from the glass transition temperature to the sintering temperature. Heat work is constant for two of the glasses, but decreases with increasing heating rate for the investigated borosilicate glass. Activation energies were calculated and are similar to published values.
Thesis completed in partial fulfillment of the requirements for the degree of Master of Science in Ceramic Engineering at the Inamori School of Engineering, New York State College of Ceramics at Alfred University
Hot stage microscopes, Glass, Sintering