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Single crystals of isomeric 1,2,3‐tribromobenzene (123TBB), 1,2,4‐tribromobenzene (124TBB) and 1,3,5‐tribromobenzene (135TBB) have been grown from different solvents and their structures determined by X‐ray diffraction at 100, 200 and 270 K. The melting‐point differences of ca 40 K between 135TBB, 123TBB and 124TBB have been correlated with the molecular symmetry and packing preferences in the crystal, as well as with the main types of intermolecular halogen interactions, i.e. Br...Br, Br...C (Br...π) and Br...H. The relationship between symmetry and melting point in Carnelley's rule has been extended to the accessibility of terminal atoms for the formation of intermolecular interactions, their occurrences and distribution, and the close packing. The electrostatic potential mapped on molecular surfaces demonstrates that in more symmetric molecules the more evenly distributed substituents are more accessible and form more optimum intermolecular interactions. [ABSTRACT FROM AUTHOR]

Trends in the melting points of analogous halogenated benzene isomers are rationalized in terms of molecular symmetry, crystal structure and interactions. [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]

At ambient conditions two liquids, bromoethane, C2H5Br (MBE, m.p. 154.6 K) and iodoethane, C2H5I (MIE, m.p. 162.1 K), have been crystallized under both isobaric and isochoric conditions using in situ low‐temperature and high‐pressure techniques. The single‐crystal X‐ray diffraction studies, supported by the isothermal compressibility and isobaric differential scanning calorimetry measurements, allowed the monitoring and analysis at low temperature and high pressure of the effects of externally induced changes in MBE and MIE. The monoclinic MBE and MIE crystals are found to be isostructural. They are stable, in the investigated regimes, i.e. down to 100 K/0.1 MPa and up to ∼295 K/3.7 GPa, without undergoing any symmetry or phase change. Both the contraction and compression is mainly noted for the intermolecular separation distances. The Hirshfeld surface analysis of intermolecular contacts clearly shows the nature of occurrence and hierarchy of interactions pointing out the role played by Br/I...Br/I contacts, in particular at ambient temperature and high‐pressure conditions. The preferences for the formation of intermolecular contacts in MIE are more pronounced and do not require such extreme conditions as in the case of MBE. It is notable that the Br/I...Br/I and Br/I...H contacts could be basically classified as type‐I interactions. [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]

Ti(C 0.5 ,N 0.5)-reinforced alumina matrix composites with an addition of 2 wt% ZrO 2 were tested to determine residual stresses of Al 2 O 3 and Ti(C 0.5 ,N 0.5) phases. The advanced sintering technique (spark plasma sintering ―SPS) at various temperatures of 1600°C and 1700°C was used. Vickers hardness HV1, Young's modulus E, apparent density ρ and indentation fracture toughness K IC(HV) were evaluated. An indirectly residual stress measurement by the XRD method using the sin2 ψ technique was applied. Compressive residual stresses in both phases: α-Al 2 O 3 and Ti(C 0.5 ,N 0.5) were observed. Residual stresses of α-Al 2 O 3(226) are in the range between −204 ± 20 MPa and −120 ± 20 MPa (for 1600 °C and 1700 °C respectively) are lower compared to Ti(C 0.5 ,N 0.5) (420), for which the stresses are in the range of between −292 ± 20 MPa and −256 ± 20 MPa (for 1600 °C and 1700 °C respectively). The results exhibit the influence of the sintering temperature on the residual stresses of the tested phases. The residual stresses revealed at 1700°C are lower by about 40% for α-Al 2 O 3(226) and much less for Ti(C 0.5 ,N 0.5) (420) , by only about 15%. Microstructure studies using scanning electron microscopy, X-ray and electron diffraction phase analysis were used. [ABSTRACT FROM AUTHOR]

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]

• A novel composite ablator based on silicone resin and B 4 C ceramics is shown. • Methylpolysiloxane ablation rates significantly reduced by formed B 2 O 3 on surface. • Methylpolysiloxane pyrolyses to SiOC and SiO 2. • The presence of B 4 C promotes β-SiC crystallisation during pyrolysis and ablation. Before siloxane resin matrix composites could be successfully used as ablative materials, their mechanism of high-temperature degradation must be investigated in depth. In this study, degradation mechanism, ablation resistance and degradation kinetics of both methylpolysiloxane and the methylpolysiloxane - B 4 C (10 wt%) composite were investigated.. The presence of B 4 C resulted in a higher final sample mass in thermogravimetric tests in synthetic air up to 1500C (85% vs 81%), while during ablation tests it reduced linear and mass ablation rates by 45% and 54%, respectively. The XRD and SEM/EDS studies provided an estimate of the phase contributions formed as a result of exposure to corrosive conditions. The effect of the presence of powders on the amount of SiO 2 glassy phase, β-SiC crystalline phase and free carbon precipitates formed is apparent. [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]

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]

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]