| The zirconia-toughened-alumina (ZTA) ceramic have many advantages compared with metal materials, such as high hardness, toughness, temperature resistance, corrosion resistance and wear resistance. Compared with other ceramic materials, the raw material of ZTA ceramic is extensive and with low price. It has very tempting application prospect in the aerospace, aviation, metallurgy, wear parts of engine, cutter, biomedical materials and the other fields. Ceramic powder injection molding (CIM) is a kind of advanced near-net-shaping technology, the biggest advantage of which is that it can product the ceramic of complex shape and precise size in a batch, which can save a lot of processing costs.In many influencing factors, the influence of raw materials and characteristics of feed used in injection molding is decisive. Usually feed is composed of powder and polymer binder. Rheological behavior of feeding reflects the stability and uniformity, shearing rate and temperature sensitivity, as well as mold filling and formability in the injection process. It is one of the most important factors which decided the shape and quality of compact. The capillary rheometer was used to measure the shear rate and shear stress of feed, viscosity, non-newtonian index, yield stress, and viscous flow activation energy of feed was calculated by the secondary linear regression analysis.The character of each component of feed also has significant effect on the injection molding process. The studies on the rheological properties of feed respectively from two aspect of powder and binder were carried out to analyze the influence of ZTA powder solid content in feed, character of ZTA powder, surfactant, high polymer to viscosity, power-law index, the viscous flow activation energy and yield stress of feed, and the effect on the sintering performance and mechanical performance of subsequent body.The results showed that, viscosity and non-newtonian index of feed increased accordingly with increasing of solid content of powder, and there had been a remarkable increase in the density of green compact, but the density of sintered body only increases slightly, the highest bending strength of sintered body is the compact whose solid content is 60 vol%, because too high solid content is hard to achieve the uniform feed. The higher the apparent density of powder, the lower the viscosity, non-newtonian index and viscous flow activation energy, which is more suitable the feed for injection molding. However the impact of the apparent density of powder on bending strength of body is not obvious; Instead, the compact who has the minimum particle size and the less agglomeration of powder had the largest sintering shrinkage, sintered density and the highest bending strength.The experimental results of surfactant show that, stearic acid, titanate coupling agent and silane coupling agent are all had chemical reactions with the hydroxyl in the surface of powder; the stearic acid can significantly make the powder refining, titanate coupling agent can properly reduce the particle size of powder. However, the silane coupling agent make powder seriously agglomerate. The rheological property of feed and mechanical property of body which is modified by stearic acid was the best. As to the macromolecule polymer, the compatibility of various components of the feed was very good. The liquidity of feed including ethylene-butyl acrylate copolymer EBA was the best and also with the best bending strength which reached 415 MPa. |
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