Study On Gelcasting Forming Process Of Alumina

The forming process of gel-casting of alumina was provided, wherein, slurry of ceramic powder in good dispersion was casted in a mould with the organic system,which could be caused the polymerization and made the slurry in-situ formation. This process can promise the uniformity of the powder dispersion and improve the reliability of ceramic materials,which also gave the green body in high strength and little shrinkage for machining process. Further, the process is optimized by decreasing the amount of organic substances so that a large amount of time was saving for giving away the organics.For the requirement of in-situ forming and machining process, the solid content of slurry more than 50 %( by volume) is needed. Otherwise, the critical point is to obtain thick suspension in good fluidity. The effect of solid content,dispersant,pH and the ball milling time to the fluidity were discussed in the present thesis. The study showed that alumina slurry of 55%( by volume) in solid content with viscosity 100mPa.s was obtained by adding the dispersant of ammonium poly-acrylate with pH9, which gave the green body with good performance by casting, for example, the three point bending strength was more than 20MPa and the linear shrinkage was less than 2%. By scanning on the broken surface,the SEM picture showed that the inner of the green body was well dispersed without co-aggregation. The effects of catalyst, initiator and temperature on the gelation time were also discussed in the present study. The experiment showed after adding catalyst with 0.04%～0.5%(by volume) and initiator 0.4%～0.6%( by volume), there was 5～30 min remained for slurry casting without gelation. The study also included the process of dryness and degumming, discussing how to reduce time and remove shortage.The present study also included the effect of variable solid content on the performance of the green body and the structure, it showed that high solid content (>50Vol %) was prior to control the microstructure of the green body and less shrinkage which has well uniformity and high consistency for application. Machining test showed adding lubricant...