PHOTOACTIVE SUSPENSIONS FOR STEREOLITHOGRAPHY OF CERAMICS

Photoactive suspensions suitable for ceramic stereolithography, which builds up ceramic green shapes directly from Computer Aided Design (CA D) files via a layer by layer process, have been developed by dispersi on of a high volume fraction of alumina powder in acrylate or epoxy ba sed monomer systems with the aid of an effective dispersant. Rheologic al characterization showed shear-thinning behavior and relatively low viscosity at low shear rates. Photo-polymerization of the concentrated suspensions was accomplished under laser irradiation with cure depth up to 250 mu m. The multiple light scattering involved at the interfac e of the particles and surrounding medium of a different refractive in dex reduces the cure depth of the suspension by limiting the depth of light transmission. The optical properties of the suspension as charac terized by the scattering and absorption coefficients were obtained by UV diffuse reflectance and transmittance measurements and subsequent Kubelka-Munk analysis, taking into account external and internal refle ction corrections. Correlation between the computed light transmittanc e and the measured cure depth was shown.