Processing study of gel-cast tubular porous NiO/SDC composite materials from gel-combustion synthesized nanopowder

Abstract

In the present research, NiO–SDC (Samarium doped Ceria) nanopowder was synthesized through sol–gel combustion method using citric acid as a reducing agent (fuel) and metal nitrates as an oxidant. The characteristics of the synthesized powder were thoroughly analyzed by DTA/TG, XRD, BET and FESEM/EDX. Tubular gel-casted porous specimens of NiO–SDC (50:50 wt%) composite materials were produced after stabilizing suspensions of composite powder in an aqueous environment by addition of 3 wt% dispersant and 2.5 wt% agar as the gel builder. The effect of Dolapix CE64 as a dispersant, agar as a gel-builder and the amount of solid loadings on the processing and properties of porous ceramics was investigated. Viscosity measurements, zeta potentials of suspensions with and without dispersant and sedimentation measurement were used to determine the optimum dispersant concentration and solid concentration needed to prepare a stable slurry. The phase composition and microstructure of sintered samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Moreover, the distribution and porosity of the samples were determined through mercury porosimetry method. Results confirmed that stable NiO–SDC slurries with high solid loading (60 %) were achieved with Dolapix CE64, which also met the requirements to reach porous tubular samples with up to 60% porosity.