چكيده به لاتين
Porous alumina bodies have recently attentions due to unique properties such as high surface area, low thermal conductivity, high thermal shock resistance, etc, Because of the special properties, The bodies used to produce membranes, filters, substrate catalysts, thermal barrier materials, bioceramics and, etc. Starch –assisted gelcasting, as novel process shaping of porous bodies, due to cheap, non-contaminant, environmentally-friendly, able to produce complex shapes, controlling porosity and pore size by type of selected starch, etc, was used in this research. In this research, suspensions with 60.5, 63 and 65.5 wt% solid loading alumina (7.5, 5 and 2.5 wt% corn starch, respectively) were prepared by starch-assisted gelcasting. Also, the samples containing 5 wt% corn starch were choosed as optimum samples and 2.5, 5 and 7.5 wt% colloidal silica (related to slip weight), were added to suspensions so as improve mechanical properties. After gelation (86oC, 2h), the samples were sinterd in 1400, 1450 and 1500oC during 1h. After sintering, bulk density, total porosity, open porosity (by Archimedes technique following ASTM (C-20)), cold crushing strength (CCS), microstructural examination (by SEM), phase analysis (XRD) and mercury porosimetry were evaluated. Bodies with starch additive, show bulk density 1.41-1.68g.cm-3, total porosity 56.36-63.38%, open porosity 53.92-62.01% and CCS 0.98-3.82MPa. In addition to, Microstructural examination show large pores remain after starch burning out, connected by small throats, which causes interconnecting pores and increasing permeability. Bodies with colloidal silica additive show bulk density 1.55-1.58g.cm-3, total porosity 54.53-55.95%, open porosity 34.40-35.96% and CCS 5.76-12.61 MPa. In addition to, Microstructural examination show mullite particles are in contact with pores which causes bulk density and porosity percent (and permeability) remain constant, improve sinterability and increase strength samples.
