Study On Aqueous Gelcasting Forming Process Of MgAlON Transparent Ceramic

Nowadays, MgAlON transparent ceramic has aroused increasingly people’s interest and attention, because of its isotropic optical properties and a wide range of wavelength. In addition, as the polycrystalline ceramics, it can be made components with big size and complex shape more easily than single crystal sapphire. However, the forming process plays a vital role in the whole preparation of transparent ceramics. So, it is critical to find a forming technology with low cost and outstanding properties.In this thesis, the suspensions were prepared by the gelcasting forming process, and then the influences of pH, the amount of disperant and ball-milling time on the fluidity properties were investigated. The result indicated that the viscosity was decrease first and then increase with the rise of pH value, disperant amount and ball-milling time. So the suspension with50vol%solids was achieved using the optimal preparation process parameters that were pH in10, the amount of disperant in0.45wt%and4hours of ball-milling time, in which the viscosity of suspension is99.13mPa· s.In order to optimize the preparation process of suspensions, gelation behavour of the suspensions were studied by the gelling condition that APS is used as initiator and TEMED as catalyst. And then the influences of initiator and catalyst content on gelling time were investigated in this gelling condition. It shows that the gelling time was short with the increase of initiator and catalyst content. Therefore, the optimum gelling conditions were achieved that the content of initiator and catalyst are all0.5vol%respectively.To avoid the phenomenon of uneven weightlessness and shrinkage when the wet greens dry in air, a new type of liquid desiccant drying method was used in this thesis. The green body with either bright and clean surface or complete appearance were achieved through the three-step drying method:the green body was firstly dried using liquid desiccant PEG200, and then puted in air for drying, finally taken into a condition at110℃temperature. After doing that, XRD, SEM, wax sealing and three point bending test were used to analyze the characters of green body and study the influence of orgnic monomer on the composition, micorstructure and property of green body.The result of TG-DSC analysis of green body indicated that the organic matters in the green body had the oxidation reaction at the temperature from300℃to550℃and never loss weight after550℃. Therefore, the optimal degreasing temperature was determined to550℃. At last, the body was sintered in nitrogen atmosphere at1900℃temperature and held for6h.