Green Production of Cellular Ceramics by Emulsification of Sunflower Oil Followed by Gelcasting and Starch Consolidation

Abstract An environmentally friendly process combination for the production of alumina-based cellular ceramics is proposed. Biodegradable, renewable additives and low-energy conditions were applied. A fractional factorial design of 2(4-1) + 3C was used to study the influence of gelatin, starch, and solids concentration, as well as water:oil ratio, on the rheological behavior of the suspension, and microstructural and mechanical features of cellular ceramics. A deflocculation curve was elaborated to define the best deflocculant concentration. The emulsions presented a rheopectic and pseudoplastic behavior. The sample with the highest open porosity was selected and analyzed by computer microtomography. SEM images showed open and closed spherical pores in the range of 7 to 22 μm for samples sintered at 1400 oC; 6 to 17 μm at 1550 oC, with respective open porosity values of 36-59% and 23-58%. Mean pore diameters estimated by μCT varied from 2 to 14 μm, with 78% at 1400 oC and 89% at 1550 oC. Compressive strength measured were 16 to 57 MPa (1400 oC), and 40 to 78 MPa (1550 oC). The combination of the three manufacturing methods was effective in the production of cellular ceramics with low energy, low amounts of gelling agents and low environmental costs.