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The paper presents and discusses questions on structure formation during the sintering process of Cr2O3-based composites using the hot pressing method, when a chemical reaction between the components takes place. The task was difficult because Cr2O3 decomposes when sintered at temperatures above 1300 °C. The proposed novel method allowed for interaction between aluminum and chromia, thus avoiding the decomposition of the latter. Here, ultrafine aluminum powder played the role of the active agent forming a liquid phase and reacting with Cr2O3. The appearance of the solid solutions of (Cr,Al)2O3 with different stoichiometry of Cr and Al depended on the aluminum content in the initial mixture. The solid solution significantly strengthened boundaries between composite phases, resulting in the composite material of high fracture toughness between 5 and 7 MPa m½ and bending strength of ca. 500 MPa. The best mechanical properties exhibited the cermet with 22 wt.% of the restored chromium. [ABSTRACT FROM AUTHOR]

Fabrication of alumina–tungsten carbide nanocomposite was investigated. Characteristics of the densification and sintering were analyzed considering both the nano-size particle starting powders and the processing stages. Different heating rates were generated during densification and consolidation with a maximal load was applied only after a temperature of 1000 °C was reached. Due to the varying dominance of different physical processes affecting the grains, appropriate heating rates and pressure at different stages ensured that a structure with submicron grains was obtained. With directly applied alternating current, it was found that the proportion Al2O3 (50 wt.%)–WC provided the highest fracture toughness, and a sintering temperature above 1600 °C was found to be disadvantageous. High heating rates and a short sintering time enabled the process to be completed in 12 min, saving energy and time. [ABSTRACT FROM AUTHOR]

The paper presents the results of investigations on the glass fiber reinforced composite for the floor panels with quartz powder additions of different percentages in terms of wear resistance, friction coefficient, hardness, and strength. The wear resistance was assessed using the specific wear work parameter determined by the novel tribotester with friction band. It was found that an increase in quartz powder addition to the tested polymer composite does not enhance its mechanical increasingly properties. From the wear tests it can be concluded that only the composite with four layers of glass fibers and 6 wt.% of the quartz powder exhibited improvement of the wear resistance, but its shear strength was lower than that of the two layer specimens with similar powder proportions. On the other hand, the highest friction coefficient's, which is microhardness HV05, shear strength and impact strength were attained for the composite with two layers of glass fibers and 3 wt.% of the quartz powder. Among four layer samples, very close results were obtained for the samples with 10% of powder and insignificantly lower strength were observed for the samples with no powder added. The results revealed that there is no clear trend for the effect of silica filler percentage on the composite performance, which indicates the need for individual purpose-dependent decision making in the design of the glass fiber reinforced composites with quartz powder filler. [ABSTRACT FROM AUTHOR]