Preparation Of Dense Zircon Refractory By Gelcasting

In this paper,gelcasting of dense zircon?ZrSiO₄?refractory was studied.Two types of zircon powders with mean particle size of 1.2 and 5.5 ?m were used as raw materials and TiO₂ was used as sintering aid.The widely used acrylamide?AM/MBAM?system and the low toxic,surface spallation-free epoxy resin system were studied,respectively.AN-2000 was selected as the dispersant.The following aspects were investigated for AM/MBAM systems:?1?Effects of zeta potential,pH value,concentration of dispersant,particle size distribution?PSD?and milling process on viscosity of zircon suspension were studied in order to prepare high solid loading suspension with low viscosity.Suspension with a maximum solid loading of 61 vol% and a viscosity of 370 mPa·s?at shear rate of 350 s-1?was obtained when pH=9,dispersant content was 0.2 wt%?for fine powder?,fine powder ratio was 60 wt%,milling rpm=750 r/min and mill time was 6 h.?2?Effects of PSD and solid loading on green properties were studied.When fine powder ratio was 60 wt% and solid loading was 56 vol%,green bodies with a maximum flexural strength of 52.58 MPa and relative density of 65.95% were prepared.?3?Effects of PSD and solid loading on properties of sintered bodies were studied.Sintering was carried out at 1550 oC for 2 h.When fine powder ratio was 80 wt% and solid loading was 56 vol%,sintered bodies with a maximum flexural strength of 174.73 MPa,a relative density of 95.06% and apparent porosity of 0.28% were prepared.The following aspects were investigated for epoxy resin systems:?1?Effects of pH value,concentration of dispersant and content of epoxy resin on viscosity of zircon suspension were studied.Suspension with a maximum solid loading of 57 vol% and a viscosity of 210 mPa·s?at shear rate of 350 s-1?was obtained when pH=9,dispersant concentration was 0.2 wt%,and epoxy resin content was 15 wt%.Powder applied here was the one with mean particle size of 1.2 ?m.?2?Effects of solidification process,which played an important role in gel properties for epoxy resin system,and solid loading on green properties were studied.When hardener content was 0.35 mol/eq and solid loading was 56 vol%,green bodies with a maximum flexural strength of 46.74 MPa and relative density of 65.13% were prepared after the suspension was solidified at 40 oC for about 30 min.The green bodies were all in good shape and no surface spallation was observed.