This paper focuses on the possibility of adapting the centrifugal slip casting method to obtain zirconia–alumina composite materials in the form of finished tube-shaped products. These types of products, due to their unique properties, can be utilised, for example, in the transport of aggressive substances, even in extreme temperatures or corrosive conditions. The study reports on the two series of zirconia–alumina composites differing in the content of ZrO2—2.5 and 25 vol%. The fabricated and sintered materials were characterised using scanning electron microscopy (SEM), X-ray diffraction (XRD) and stereological analysis. Moreover, a life cycle assessment (LCA) was provided in accordance with the requirements of the ISO 14044 and EN 15805 standards. The obtained data clearly show that the centrifugal slip casting method allows obtaining samples with high density and extremely uniform distribution of the ZrO2 phase in the alumina matrix. The stereological analysis results proved also that the addition of ZrO2 is effective in reducing the growth of Al2O3 grains during the sintering process. The phase analysis carried out by means of XRD showed that during the sintering process, in the case of composites with a lower ZrO2 content (2.5 vol%), the monoclinic to tetragonal transformation of ZrO2 was total, while for samples containing 25 vol% ZrO2, the monoclinic phase remained in a small amount in the final product.
The rheological properties of shear thickening fluids based on silica powder of particles size in range 0.10 – 2.80 μm and poly(propylene glycol) of 425, 1000, 2000 g/mol molar mass were investigated. The effect of particle size and the length of the polymeric chain was considered. The objective of this study was to understand basic trends of physicochemical properties of used materials on the onset and the maximum of shear thickening and dilatant effect. Outcome of the research suggested that an increase in the particle size caused a decrease in dilatant effect and shift towards higher shear rate values. Application of carrier fluid of higher molar mass allowed to increase dilatant effect but it resulted in the increase of the initial viscosity of the fluid.
The paper concerns the synthesis and the characterization of new water-thinnable binder such as poly(acrylic-styrene) with the addition of a new amphiphilic macromonomer and it application in shaping of unmodified and modified (by silanization) Al 2 O 3 by die pressing. The organic additives decomposed thermally to non-toxic gases which is beneficial from ecological point of view. Thus, the careful thermal analysis of synthesized binder was done. To characterize the synthesized binder, the glass transition temperature, wetting angle and diameter of polymer particles size in water were also measured. In the next step of the work, the density, porosity, tensile and bending strength, and microstructure observations have been done for modified and unmodified Al 2 O 3 samples obtained by die pressing. The results confirmed that the synthesized binder is eco-friendly, because it decomposed to non-toxic gases such as carbon dioxide and water vapor during heating up to ca. 527°C. The synthesized binders are characterized by low glass transition temperatures 5.6°C and -0.5°C which are much lower than that of PVA (42°C). It provided the high tensile strength (0.22 ± 0.01 MPa) of green bodies, 57% higher than strength of bodies with commercially available PVA and bending strength around 192 MPa. Density of sintered samples was around 95% of TD. Nevertheless, the best results were obtain for bodies based on modified Al 2 O 3 where tensile strength of green bodies and bending strength of sintered samples were 0.30 ± 0.04 MPa and 237 ± 19 MPa, respectively.
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