Slip Casting

The process and impact of shaping mixed vanadium aluminum (hydr)oxides, VAlOH and VAlO, respectively, and BiMo catalysts by tableting and slip-casting were examined. Graphite (G) was employed as a shaping agent for tableting. Without it tableting was impracticable. Graphite was found to enhance the mechanical resistance of VAlOH-xG and BiMo-xG and changed the surface area by increasing it for the non-porous BiMo and by decreasing it for the mesoporous VAlOH. In addition, graphite modified the catalytic performance despite changing neither the chemical nor the structural state of the base VAlO(H) and BiMo catalysts. A positive effect on the performance of VAlO-xG in propane oxidative dehydrogenation was found. It was proposed that catalytic active sites are formed on graphite during calcination. Conversely, graphite was harmful for non-calcined VAlOH-xG and BiMo-xG. On the other hand, the preparation of chemically and physically stable VAlO(H) suspensions for slip-casting was accomplished. Chemical stability was achieved at pHs near the isoelectric point of these catalysts. For physical stability, the use of a dispersing agent, poly(acrylic acid), combined with a control of the solids concentration was necessary. A simple and reliable method for preparing VAlOH and BiMo pellets by slip-casting was thus developed with the use of colloidal silica as binding agent. The so prepared pellets were mechanically resistant and kept the surface area of the base materials. A decrease in the surface concentration of the active metals due to surface active site masking by silicon for VAlOH-xSi and BiMo-xSi led to an inferior catalytic performance.

The achievement of a high esthetic value in polycrystalline yttria-stabilized tetragonal zirconia (Y-TZP)-based dental restorations is hindered by the low translucency of Y-TZP. Thus, this study investigated the effects of processing method and sintering temperature on the translucency of Y-TZP for dental applications. Wet (slip casting) and dry (cold isostatic pressing) processing methods were used. Y-TZP specimens were fabricated by applying the processing methods and sintering at different temperatures (1450-1650°C). The mechanical, morphological, and optical properties of the Y-TZP specimens were examined and compared. The specimens were benchmarked with a commercial Y-TZP, namely, Cercon ©. Results showed that wet processing produced higher mechanical properties and translucency than dry processing. This finding can be mainly attributed to the higher capability of wet processing than dry processing in alleviating the agglomeration in Y-TZP. Among the several specimens that were tested, the slip-casted Y-TZP that was sintered at 1600°C showed the optimum mechanical properties (99.5% density and 12.7 GPa hardness) and translucency (35% light transmission) for dental applications. Furthermore, the light transmission achieved in this study was approximately three times higher than that of the commercial Y-TZP (13%), thereby indicating a potential alternative to replace the commercial Y-TZP. Highly translucent Y-TZP with excellent mechanical properties was developed in this study through wet processing with a sintering temperature of 1600°C. The developed Y-TZP can be an alternative to commercial products to produce a highly esthetic dental restoration.