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This paper analyses the key findings of a study devoted to PET-modified bitumen. The research program was run according to the D-optimal experimental plan based on a factorial design. Five factors, i.e., the type of polymer (source), the type of bitumen (qualitative factors), PET amount, mixing rate, and mixing temperature (quantitative factors), controlled the bitumen–polymer mixing process. The experiment included a series of determinations of bitumen's rheological characteristics obtained by MSCR (Jnr, R) and G*/sin(δ) at 50 °C, 60 °C, and 70 °C. The low-temperature properties of the composite (critical temperature) were evaluated using a BBR test. The findings showed that bitumen modification with PET primarily reduced the creep susceptibility of the bituminous–polymer mixture. The low-temperature characteristics of the modified bitumen played a secondary but essential role. The amount of polymer and the mixing rate interacted with the temperature, significantly reducing the stiffness of the composite, while the type and amount of bitumen had a substantial effect on the results obtained in the BBR test. It is worth noting that when combining bitumen and plastomer, special attention should be paid to ensuring a high level of homogeneity of the mixture by controlling the parameters of the mixing process accordingly. The tests and analyses provided crucial models (GLM), which allowed for the prediction of the plastomer-modified bitumen's low- and high-temperature properties. The resulting relationships between factors and the identification of their impact on the bitumen properties enable a better understanding of the process of bitumen modification with PET. The conclusions presented here serve as a basis for future optimisation of the modified bitumen composition. The performed studies indicate that the use of >3% plastomer in bitumen 70/100 allows for a reduction in its susceptibility (MSCR) to below 0.5 kPa−1, making it suitable for bituminous mixtures for high-traffic roads. No significant increase in critical temperature (BBR) was observed. [ABSTRACT FROM AUTHOR]

The effect of zirconium diboride (ZrB2) and titanium diboride (TiB2) on the microstructure as well as the physical, mechanical, and tribological properties of composites based on 316 L steel is presented. Each reinforcing phase was added to the base alloy in the amount of 5 wt% and 10 wt%. The composites were fabricated by the SPS process (Spark Plasma Sintering). The results show that the weight fraction of the reinforcing phase affects the physical, mechanical, and tribological properties of the sintered composites. The sintered materials were characterized by a very high level of density. The addition of TiB2 has proved to be effective in increasing the hardness and compressive strength of the composites. The hardness of the composites with the addition of 10% TiB2 increased by 100% compared to the hardness of sintered 316L steel. It was found that introducing ZrB2 to the steel matrix significantly improved the wear resistance of the composites. The results showed that compared to 316L steel with the wear rate of 519 × 10−6 mm3/Nm, the wear rate of the composites containing 10% ZrB2 decreased more than twice, i.e., to 243 × 10−6 mm3/Nm. [ABSTRACT FROM AUTHOR]

The deformation of the cold recycled mixture with foamed bitumen in a recycled base with an innovative three-component road binder and foamed bitumen is analysed. Numerical simulation results for the pavement constructed, based on laboratory test results, were verified against the data from the monitoring system installed on the road trial section. In addition, environmental effects, such as air temperature and humidity levels in the pavement structure layers, were considered. Thermal analyses were conducted to identify the thermal properties of the pavement materials under steady heat transfer rate. Determining temperature distribution in the road cross-section in combination with relaxation functions determined for individual pavement layers contributed to the high effectiveness of the numerical simulation of deformation and displacement in the recycled base and the entire pavement. The experimental method of identifying thermal properties allows a fast and satisfactory prediction of temperature distribution in the pavement cross-section. [ABSTRACT FROM AUTHOR]

Titanium diboride (TiB2) is a hard, refractory material, attractive for a number of applications, including wear-resistant machine parts and tools, but it is difficult to densify. The spark plasma sintering (SPS) method allows producing TiB2-based composites of high density with different sintering aids, among them titanium silicides. In this paper, Ti5Si3 is used as a sintering aid for the sintering of TiB2/10 wt % Ti5Si3 and TiB2/20 wt % Ti5Si3 composites at 1600 °C and 1700 °C for 10 min. The phase composition of the initial powders and produced composites was analyzed by the X-ray diffraction method using CuKα radiation. The microstructure was examined using scanning electron microscopy, accompanied by energy-dispersive spectroscopy (EDS). The hardness was determined using a diamond indenter of Vickers geometry loaded at 9.81 N. Friction–wear properties were tested in the dry sliding test in a ball-on-disc configuration, using WC as a counterpart material. The major phases present in the TiB2/Ti5Si3 composites were TiB2 and Ti5Si3. Traces of TiC were also identified. The hardness of the TiB2/Ti5Si3 composites was in the range of 1860–2056 HV1 and decreased with Ti5Si3 content, as well as the specific wear rate Wv. The coefficient of friction for the composites was in the range of 0.5–0.54, almost the same as for TiB2 sinters. The main mechanism of wear was abrasive. [ABSTRACT FROM AUTHOR]

The aim of this study was to carry out the consolidation of zirconium diboride-reinforced composites using the SPS technique. The effect of the adopted method of powder mixture preparation (mixing in Turbula or milling in a planetary mill) and of the reinforcing phase content and sintering temperature on the microstructure, physical properties, strength and tribological properties of sintered composites was investigated. Experimental data showed that the maximum relative density of 94–98% was obtained for the composites sintered at 1100 °C. Milling in a planetary mill was found to contribute to the homogeneous dispersion and reduced clustering of ZrB2 particles in the steel matrix, improving in this way the properties of sintered steel + ZrB2 composites. Morphological and microstructural changes caused by the milling process in a planetary mill increase the value of Young's modulus and improve the hardness, strength and wear resistance of steel + ZrB2 composites. Higher content of ZrB2 in the steel matrix is also responsible for the improvement in Young's modulus, hardness and abrasive wear resistance. [ABSTRACT FROM AUTHOR]

Zr-2.5Cu and Zr-10Cu powder mixtures were consolidated in the extrusion process and using the spark plasma sintering technique. In these studies, material tests were carried out in the fields of phase composition, microstructure, hardness and tensile strength for Zr-Cu materials at room temperature (RT) and 400 °C. Fractography analysis of materials at room temperature and 400 °C was carried out. The research took into account the anisotropy of the materials obtained in the extrusion process. For the nonequilibrium SPS process, ZrCu2 and Cu10Zr7 intermetallic compounds formed in the material at sintering temperature. Extruded materials were composed mainly of α-Zr and ZrCu2. The presence of intermetallic compounds affected the reduction in the strength properties of the tested materials. The highest strength value of 205 MPa was obtained for the extruded Zr-2.5Cu, for which the samples were cut in the direction of extrusion. For materials with 10 wt.% copper, more participation of the intermetallic phase was formed, which lowered the mechanical properties of the obtained materials. In addition to brittle intermetallic phases, the materials were characterized by residual porosity, which also reduced the strength properties. [ABSTRACT FROM AUTHOR]

Materials were obtained from commercial zirconium powders. 1 mass%, 2.5 mass% and 16 mass% of niobium powders were used as the reinforcing phase. The SPS method and the extrusion method classified as the SPD method were used. Relative density materials of up to 98% were obtained. The microstructure of the sintered Zr-xNb materials differs from that of the extruded materials. Due to the flammability of zirconium powders, no mechanical alloying was used; only mixing of zirconium and niobium powders in water and isopropyl alcohol. Niobium was grouped in clusters with an average niobium particle size of about 10 μm up to 20 μm. According to the Zr-Nb phase equilibrium system, the stable phase at RT was the hexagonal α-phase. The tests were carried out for materials without the additional annealing process. The effect of niobium as a β-Zr phase stabilizer is confirmed by XRD. Materials differed in their phase composition, and for both methods the β-Zr phase was present in obtained materials. A very favorable effect of niobium on the increase in corrosion resistance was observed, compared to the material obtained from the powder without the addition of niobium. [ABSTRACT FROM AUTHOR]

Ti(C,N)-reinforced alumina-zirconia composites with different ratios of C to N in titanium carbonitride solid solutions, such as Ti(C0.3,N0.7) (C:N = 30:70) and Ti(C0.5,N0.5) (C:N = 50:50), were tested to improve their mechanical properties. Spark plasma sintering (SPS) with temperatures ranging from 1600 °C to 1675 °C and pressureless sintering (PS) with a higher temperature of 1720 °C were used to compare results. The following mechanical and physical properties were determined: Vickers hardness, Young's modulus, apparent density, wear resistance, and fracture toughness. A composite with the addition of Ti(C0.5,N0.5)n nanopowder exhibited the highest Vickers hardness of over 19.0 GPa, and its fracture toughness was at 5.0 Mpa·m1/2. A composite with the Ti(C0.3,N0.7) phase was found to have lower values of Vickers hardness (by about 10%), friction coefficient, and specific wear rate of disc (Wsd) compared to the composite with the addition of Ti(C0.5,N0.5). The Vickers hardness values slightly decreased (from 5% to 10%) with increasing sintering temperature. The mechanical properties of the samples sintered using PS were lower than those of the samples that were spark plasma sintered. This research on alumina–zirconia composites with different ratios of C to N in titanium carbonitride solid solution Ti(C,N), sintered using an unconventional SPS method, reveals the effect of C/N ratios on improving mechanical properties of tested composites. X-ray analysis of the phase composition and an observation of the microstructure was carried out. [ABSTRACT FROM AUTHOR]

In this paper, Al2O3–ZrO2 composites with an addition of 20 wt% TiN and 10 wt% TiC were modified. The addition of zirconia in a range from 2 to 5 wt% of the monoclinic phase and 10 wt% of Y2O3 stabilised ZrO2 affected the mechanical properties of the composites. A new type of sintering technique—the spark plasma sintering (SPS) method—within a temperature range from 1575 °C to 1675 °C, was used. Vickers hardness, apparent density, wear resistance and indentation fracture toughness KIC(HV) were evaluated at room temperature. An increase of the sintering temperature resulted in an improvement of Vickers hardness and an increase of the fracture toughness of the tested composites. The tribological properties of the samples were tested using the ball-on-disc method. The friction coefficient was in a range from 0.31 to 0.55, depending on the sintering temperature. An enhancement of the specific wear rate was dependent on the sintering temperature. The mechanical properties of the samples sintered by pressureless sintering (PS) were compared. X-ray diffraction patterns were presented in order to determine the phase composition. SEM microstructure of the tested composites sintered at different temperatures was observed. [ABSTRACT FROM AUTHOR]

Abstract The wear resistance and tribological characteristics of spark plasma sintered ZrB 2 + B 4 C, ZrB 2 + SiC and ZrB 2 + ZrC composites were investigated under dry sliding conditions at applied loads of 5 N and 50 N in air. The microstructure, deformation and damage characteristics were studied using scanning electron microscopy, confocal electron microscopy, a focused ion beam and atomic force microscopy. The friction coefficient values were very similar for all composites with values ranging from 0.63 to 0.72 and with the lowest value recorded for the ZrB 2 + SiC composite at a 5 N applied load. The ZrB 2 + ZrC composite was the most wear resistant, with wear rates at a 5 N load of 6.15 × 10−6 mm3/(N·m) and at a 50 N of 7.3 × 10−6 mm3/(N·m). None, or a very limited number of grain pull-outs and/or lateral fractures of grains were found during the wear tests. At the 5 N load, abrasive grooves connected with deformations and Hertzian crack formations were the main wear mechanisms in all systems, with limited crack formations in the ZrB 2 + ZrC composite. Tribofilm formations connected with debris origin, oxidation and tribochemical reactions were dominant in all composites, with similar chemical compositions but different sizes and thicknesses at the 50 N load. Highlights • To enhance the oxidation resistance, COF, WR and KIC different additives (SiC, B 4 C and ZrC) have been introduced to ZrB 2. • Detailed understanding of the tribological characteristics of Zirconium Diboride composites. • Description and understanding of tribochemical reactions. [ABSTRACT FROM AUTHOR]

The research concerns the optimisation of sintering zirconium by spark plasma sintering (SPS) and modification of microstructures by introducing the manganese component. The problems of preparing mixtures for sintering were investigated. An additive of 2.5 wt% and 5 wt% manganese micropowders and 1 wt% and 2.5 wt% manganese nanopowders were utilized. An increase in the oxygen content in sintered mixtures made of zirconium and manganese along with an increase in their milling time in water was found. 100 rpm was determined as a safe mixing speed. The introduction of manganese nanopowders into zirconium did not significantly improved the homogeneity of the material. Manganese in larger quantities accumulates at the grain boundaries. The material is very difficult to machining, which is indicated by difficulties in sample preparation. • The conditions of high-speed mixing and sintering by the SPS method did not cause the entire manganese content to react to form ZrMn 2. • Due to the explosiveness of the mixture, 200 rpm was adopted as the optimal speed of homogenization of mixtures. • Mechanical milled Zr–Mn mixtures tend to oxidize. [ABSTRACT FROM AUTHOR]