Al < Sub > 2 < / Sub > O < Sub > 3 < / Sub > Gel Injection Molding Molding And Sintering Of Research

Alumina ceramics exhibits good comprehensive performance and gains successful application in the electronics industry at the present time due to its low cost, high intensity, good hardness, and high chemical and thermal stability, accounting for90%of the ceramic substrate.In this dissertation, gelcasting was applied to produce alumina ceramic and three aspects were investigated:preparation of alumina suspension with low viscosity and good stability; effect of acrylamide（AM） and N, N’-methylenebisacrylamide （MBAM） on the tensile strength and microstructure of green body; affect of sintering additives amount, sintering temperature and duration time on relative density, thermal conductivity and microstructure of alumina ceramics. The main results obtained are as follows:（1） Dispersion and stability behavior of alumina suspension are affected by dispersant amount, pH value, solids loading, milling time and ionic strength. The process factors for suspension with minimum viscosity and sedimentation height are dispersant content0.8%, pH value9.5, solid loading50%, and ball milling time24h. The viscosity of suspension prepared with the above conditions is48.3mPa-s, which can meet with the requirement of gelcasting process.（2） Monomer concentration, AM/MBAM ratio and solid volume fraction have great influence on the bending strength of green body and microstructure. The higher the monomer concentration or the smaller AM/MBAM ratio, the more compact of polymer network structure. With increasing solids loading, the particle density increases and the bending strength of green body decreases for the network polymer accounting for only a small amount of the composition.（3） The relative densities and thermal conductivities of alumina ceramic are greatly affected by sintering additives of CAS,Y2O3and Pr6On, sintering temperature and duration time. Both the relative densities and thermal conductivities increase with the increase of sintering additives amount. Samples with1.5%sintering additives almost take on the highest relative density and the highest thermal conductivity. Both the relative densities and thermal conductivities increase with the increase of sintering temperature whereas the increasing rate of relative densities is slowed down when the sintering temperature is above1600℃. Samples with1.5%CAS take on the highest relative density of93%and the highest thermal conductivity of27.70W-m^-1·K^-1 when the sintering temperature is1680℃. The relative densities and thermal conductivities of all samples increase with extending duration time whereas the increasing rate is slowed down when the holding time is over120min. Samples take on the highest relative density and the highest thermal conductivity when the holding time is180min.（4） The sintering mechanisms of alumina ceramics is determined by sintering additives. The sintering mechanism of alumina ceramics with CAS additives is mainly liquid-phase sintering, otherwise it is mainly solid-phase sintering with additives of Y₂O₃or Pr₆O₁1.