Powder properties influencing the densification kinetics of hot-pressed Si3N4

The densification curves registered during hot- pressing of silicon nitride are analyzed and put into relation with varying powder properties (granulometric values, oxygen content). Densification within the nonisothermal section can be divided into several stages dominated by various mechanisms, which react differently to processing conditions (temperature-pressure-time) due to altering powder properties. The correlation between powder properties and kinetics of the individual stages can be proven quantifiably. The time- and temperature-dependent densification as well as the densification speed during hot-pressing are very sensitive values for evaluating the influence of powder and raw material properties, a fact not only of sinter-kinetical interest but also of technological importance with respect to process control and quality assurance.