Study On Injection Molding Of Zirconia Ceramic Modified By Coupling Agent

In recent years,the rapid development of 5G technology and wireless charging technology has promoted the transformation of the material of the back panel of smart phones.Ceramic materials,especially zirconia ceramics,have become the best choice for the back of smart phones due to their low thermal conductivity,no signal shielding,biocoMPatibility,abrasion and scratch resistance.Ceramic injection molding(CIM)technology can solve the molding problem of some complex shape ceramic products,so it is widely used.The technical difficulties of CIM are mainly the binder formula and debinding process.In order to solve the coMPatibility problem between zirconia powder and binder,the influence of six coupling agents including KH550,KH560,KH570,A151,A171 and PN841 on the ceramic injection molding of zirconia was studied in terms of feedstock's fluidity,strength of green body,solvent debinding radtio,strength of sintered body,microstructure of green body and sintered body.The results showed that:Among the coupling agents studied,A151 had the best comprehensive performance.When adding 0.75 wt.% A151,the melt index of feedstock was 119 g/10 min,75% higher than that of the raw sample.When adding 0.5 wt.% A151,the bending strengths of green body and sintered body were 13.0 MPa and 468 MPa,respectively,which were improved by 23.8% and 14% coMPared with the unmodified samples.The debinding ratio of 1.0 wt.% A151 was 81.6%,11.3% higher than that of the raw sample.Solvent debinding was difficult to remove the soluble binder completely.There were still residual soluble binder and backbone binder in the green body after solvent debinding,which would be removed before 200-230? and 230-370? respectively.When the thermal debinding was too fast or too slow,the strength of the sintered body decreased.When the total thermal debinding time was 512 min(TH7),the maximum bending strength of the sintered body would be 502 MPa.Among 1500-1650?,with the increase of sintering temperature,the sintered grain grew obviously,and above 1550?,obvious abnormal grain growth occurred.Interestingly,the abnormal growth of grains was characterized by transgranular fracture.The strength of sintered body decreased with the increase of grain length,while the fracture of transgranular was beneficial to the improvement of its bending strength.As a result of the joint action of the two aspects,the bending strength of the sintered body changed complicated with sintering temperature.For the sintered body obtained after SD8h-TH7 debinding process,the maximum bending strength appeared at 1575? and reached 533 MPa.Zirconate coupling agent had little effect on bending strength of the green body and the sintered body,but it was beneficial to improve melting index and solvent debinding ratio of feedstock.CoMPared with the raw sample,the melting index of the coupling system with ethanol as dispersion medium was increased from 68 g/10 min to 140 g/10 min.The solvent debinding ratio increased from 73% to 78% in 8 hours.The coupling agent reduced the hydrophilicity of zirconia powder and made the dispersion performance of zirconia powder in the binder better,which was beneficial to the injection molding of zirconia powder and the solvent debinding process.