In the present work, alumina (Al2O3) foam was prepared by the replica method where a polyurethane (PU) foam (30 pores per inch (ppi)) template was impregnated with a 60 wt.% Al2O3 suspension. Sintered Al2O3 foam was used as substrate for the deposition of sol-gel derived titania (TiO2) film using dip coating. For the preparation of TiO2 sol, titanium(IV) isopropoxide (Ti-iPrOH) was used as the precursor. The common problem of qualification and quantification of a crystalline coating on a highly porous 3D substrate with an uneven surface was addressed using a combination of different structural characterization methods. Using Powder X-ray Diffraction (PXRD) and synchrotron Grazing Incidence X-ray Diffraction (GIXRD) on bulk and powdered Al2O3 foam and TiO2-coated Al2O3 foam samples, it was determined Al2O3 foam crystallizes to corundum and coating to anatase, which was also confirmed by Fourier Transformed Infrared Spectroscopy (FTIR). Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM/EDS) revealed the structural and microstructural properties of the substrate and coating. Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA) were used to clarify the evolution of the porous microstructure. The Al2O3-TiO2 composite was evaluated as a photocatalyst candidate for the degradation of the micropollutant medication memantine. The degradation rate was monitored using a light-emitting diode (LED) lamp operating at electromagnetic (EM) wavelength of 365 nm. The photocatalytic activity of sol-gel-derived TiO2 film immobilized on the Al2O3 foam was compared with commercially available TiO2 nanoparticles, P25-Degussa, in the form of a suspension. The levels of memantine were monitored by High-Performance Liquid Chromatography–Tandem Mass Spectrometry (HPLC–MS/MS). The efficiency and rate of the memantine photodegradation by suspended TiO2 nanoparticles is higher than the TiO2-coated Al2O3 foam. But, from the practical point of view, TiO2-coated Al2O3 foam is more appropriate as a valuable photocatalytic composite material.

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Slip casting is a widely used colloidal technique for consolidation of ceramic powders from a suspension. The colloidal approach ensures homogeneous microstructure of a green body, thereby reducing post-sintering machining and production costs. The process consists of several steps. The first step is to mix the ceramic powder with a liquid, usually water, where the stabilization of the new obtained suspension with different dispersants follows. When an optimum dispersion of particles is achieved, resulting in low slip viscosity, ceramic slurry can finally be poured into a porous mould, usually a gypsum one. The influence of different dispersants on rheological properties of highly concentrated alumina (Al 2 O 3) suspensions was investigated. The used dispersants were: ammonium polymethacrylate water solution (Darvan C-N), 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt (Tiron) and citric acid. The amount of dispersants was varied from 0.1-1.25 wt. % in order to determine the optimum. Rheological properties of the prepared suspensions were determined by measuring the apparent viscosity at different shear rates. The obtained optimal amount was 0.75 wt. % for Darvan, 0.1 wt. % for Tiron and 0.3 wt. % for citric acid. The obtained results show that the most effective dispersant is 4,5-dihydroxy-1,3benzenedisulfonic acid disodium salt, given that only 0.1 wt. % was required to stabilize the 70 wt. % Al 2 O 3 suspension.

The volume erosion rate of the slip cast monolithic and composite ceramics was studied using SiO 2 and SiC particles as erodents, under different impact angles (30°, 60°, 90°), at room temperature. Therefore, three groups of samples were prepared: (i) monolithic alumina (Al 2 O 3 ); (ii) composite alumina-zirconia (Al 2 O 3 -ZrO 2 ) containing 99 wt-% Al 2 O 3 and 1 wt-% ZrO 2 and (iii) composite alumina-zirconia (Al 2 O 3 -ZrO 2 ) containing 90 wt-% Al 2 O 3 and 10 wt-% ZrO 2 . Erosion mechanisms of all prepared ceramic samples were evaluated by the volume erosion rate (v, mm 3 •g -1 ). Obtained results were compared with the analytical Wiederhorn and Evans equations. The mechanical properties (hardness and fracture toughness) of prepared ceramic samples were compared with their v under the above-mentioned conditions. It was found that the erosion of monolithic and composite ceramics increased with the increase of the impact angle. Volume erosion rate was highest at an impact angle of 90°and amounts to 115 mm 3 •g -1 with SiC, and 12 mm 3 •g -1 with SiO 2 erodent particles for monolithic alumina ceramics, 77 mm 3 •g -1 with SiC, and 8 mm 3 •g -1 with SiO 2 erodent particles for ceramics with the addition of 1 wt-% of ZrO 2 , and 61 mm 3 •g -1 with SiC, and 7 mm 3 •g -1 with SiO 2 erodent particles for ceramics with the addition of 10 wt-% of ZrO 2 . Therefore, it can be concluded that the erosion resistance of monolithic Al 2 O 3 increases with the increasing amount of ZrO 2 in the composite Al 2 O 3 -ZrO 2 ceramics, thus erosion resistance can be improved with the addition of ZrO 2 .