Sintering of Nano Y-TZP Materials by Hot-pressing

The processing of synthesizing nano Y-TZP materials by hot-pressing was investigated. It was found that there were large crack-like pores in the sintered samples. The reason of this new phenomena was that the soft agglomerate in the powder was not efficiently destroyed. When sintered, the soft agglomerate sintered quickly and turned into hard agglomerate, as a result of the interaction between the hard agglomerate and the matrix, large pores formed. On the other hand, the applied pressure was limited because the low stress tolerance of the graphite die, so no plastic displacement could happen and those large pores could not be squashed , As a result, the density of the samples sintered by hot-pressing was lower than that by pressureless sintering at the same sintering temperature. To overcome this shortage of hot-pressing, sinter-forging was applied and nano Y-TZP materials with grain size of about 85um and relative density of 99% could be obtained when sintered at 1100℃.