Preparation Of ZrB₂Porous Ceramics By Gelcasting

Owing to the unique combination of properties as high melting point, high strength, high electrical and thermal conductivities, and excellent corrosion resistance, ZrB2ceramics are attracting increasing attentions in recent years. However, high density and low thermal shock resistance prove to be their major drawbacks. Designs of porous structures can solve this problem well by decreasing the density and improving the thermal shock resistance. In this thesis, ZrB2Porous ceramics were prepared by gelcasting. The major works and results are summarized as follows:The preparation of ZrB2slurries. The results indicated that PAA and PEI were more suitable for ZrB2. Well-dispersed ZrB2slurries were prepared at pH9, ball milling time above12h by application of2wt%PAA. At the same time, another well-stabilized ZrB2suspensions were prepared at pH5, ball milling time above10h with0.9wt%PEI as the dispersant.The gelcasting of ZrB2and drying methods. The gelation time can be controled at about10min when temperature at40℃and adding AM, initiator and catalyst with4wt%,0.02g/100g slurries and0.03g/100g slurries, respectively. After casting, the wet gelled parts were remoulded and immersed in ethanol for24h, then take it out and dried at room temperature for10h, last let it drying at50℃. In this drying processs, malformations such as warping,bending,cracking and other defects can be minimised. There was a large shrinkage when the solid loading less than35vol%.Pressureless sintering of ZrB2Porous ceramics. The sintering temperature, B4C content, solid loading and holding time had significant effects on the properties of the ceramics.35vol%solid loading ZrB2suspension with6wt%B4C as the sintering aid, after pressureless sintering at2050℃for2h, ZrB2Porous ceramics were obtained, with the porosity and compressive strength were45.9%and400MPa, respectively. Figure48table5reference54...