ZHANG Yaqian, ZHANG Rongshi, WANG Yuezhong, LIU Mengyin, ZHANG Tong
(Tianjin Jinhang Institute of Technical Physics, Tianjin Thin Film Optical Key Laboratory, Tianjin 300308, China)
Abstract: Magnesium aluminum spinel (MgAl2O4) transparent ceramics were prepared by means of gel injection molding and pressure free sintering. Effects of monomer density, ratio of monomer to crosslinking agent, catalyst/initiator, ceramic powder solid content (vol.%) on relative density, microstructure and optical properties of the final ceramics were systematically studied. It was demonstrated that relative density of the green body and transmittance of the ceramics were closely dependent on the mass fraction of monomer. When the monomer content was 15%, the relative density of the green body reaches a maximum of 51.1%, while the transmittance of the ceramics was 83% in visible band and 86% in near infrared band. Also, the influence of the monomer content on the transmittance of the spinel ceramics was mainly present in the visible band, while the transmittance in the infrared band was nearly unchanged. As the ratio of monomer to cross-linking agent (m(AM)/m(MBAM)) was increased, the relative density of green body was first increased and then decreased significantly, where the maximum was reached when m(AM)/m(MBAM) was 20:1. By adjusting the contents of the catalyst and initiator, the initial curing time and the curing time of the cross-linking system could be effectively controlled. However, excessive quantity of them would produce a large amount of heat in a relatively short time, resulting in uneven local curing of the crosslinking system and hence affecting the properties of the billet and materials. The optimal contents of the initiator and catalyst were 1.5vol.% and 1.0vol.%, respectively. The optimal solid content was 45vol.%.
Key words: ultra-fine magnesium aluminate spinel; gel injection molding; relative density; micro-uniformity; optical properties