Porous anorthite (CaAl₂Si₂O₈) ceramics, suitable for thermal insulation in buildings, were obtained using waste seashells as a source of CaO, kaolin as a source of Al₂O₃ and SiO₂ and banana peel as a pore former. Changing the volume of banana peel as well as the processing temperature was found to be an effective approach to control the thermo-mechanical properties of the obtained anorthite ceramics. The sintering of powder compacts containing up to 30 wt% banana peel at temperatures ranging from 1100 to 1200 °C resulted in anorthite ceramics possessing up to 45% open porosity, a compressive strength between 13 and 92 MPa, a bulk density between 1.87 and 2.62 g/cm³ and thermal conductivity between 0.097 and 3.5 W/mK. It was shown that waste materials such as seashells and banana peel can be used to obtain cost-effective thermal insulation in buildings.

Engineering materials are often exposed to various extremely harsh environments such as high temperatures and/or high pressure, thermal shocks, aggressive solutions, or cavitation erosion. The phenomenon of cavitation erosion is to be expected with flowing fluids where the parts of equipment include turbine blades, high-speed propellers, or pump parts. Such conditions usually cause surface degradation with defects in the form of pits and fractures, resulting in strength deterioration with a potential risk of failure, as well as shortening the lifespan of the materials requiring additional expenses for failure analysis, repair, and/or replacement of parts. This paper presents the main results of the cavitation erosion resistance study of two different engineering materials, 316L austenitic stainless steel and CuAlNi shape memory alloy (SMA). The cavitation erosion testing was carried out using an ultrasonic vibratory method with a stationary sample. The comparison of the behavior of these two materials under cavitation erosion conditions is shown based on the results of mass loss and analysis of the pits formed over time. Image analysis tools were used to quantify the surface damage levels. Detailed analyses revealed that the CuAlNi shape memory alloy (SMA) exhibited superior in terms of resistance and better behavior compared to stainless steel.

In the present study, andesite basalt originated from the deposit site ?Donje Jarinje?, Serbia, was examined as a potential raw material for high-density ceramics production. The production of high-density ceramics included dry milling, homogenization, cold isostatic pressing and sintering in the air. To determine the optimal processing parameters the sintering was conducted at 1040, 1050, 1060, 1070 and 1080?C, and afterwards the sintering duration was varied from 30 to 240min at the optimal sintering temperature of 1060?C. Characterization of the starting and sintered materials included the estimation of particle size distribution, density, hardness and fracture toughness complemented with X-ray diffraction, optical light microscopy, scanning electron microscopy and energy dispersive spectroscopy analysis. Phase transformations did not occur during processing in the investigated temperature range from 1040 to 1080?C. The obtained research results showed that 99.5% of relative density and the highest hardness and fracture toughness values of 6.7GPa and 2.2MPa?m1/2, respectively, were achieved for the andesite basalt sintered at 1060?C for 60min in the air. The results of the present study confirmed that the sintered andesite basalt can be used as a high-density ceramic material for various industrial applications.

This paper presents the technological process for obtaining basalt-stainless steel composite materials and testing their physical and mechanical properties. The phases of the technological process consist of: milling, homogenization, pressing, and sintering to obtain composite materials with improved fracture toughness. Andesite basalt from the deposit site "Donje Jarinje", Serbia, was used as a matrix in the composites, while commercial austenitic stainless steel 316L in the amount of 0-30 wt.% was used as a reinforcement. Although the increase of 316L amount caused a continuous decrease in the relative density of sintered samples, the relative density of sample containing 30 wt.% of 316L was above 94%. The 316L grains, which possess a larger coefficient of thermal expansion than the basalt matrix, shrinking faster during cooling from sintering temperature resulting in the formation of compressive residual stress in the basalt matrix surrounding the spherical steel grains. The presence of this stress activated toughening mechanisms such as crack deflection and toughening due to compressive residual stress. The addition of 20 wt.% of reinforcing 316L particles increased the fracture toughness of basalt by more than 30%. The relative density of these samples was measured to be 97%, whereas macrohardness was found to be 6.2 GPa.