Improving the Performance of Mortars Made from Recycled Aggregates by the Addition of Zeolitised Cineritic Tuff

Metropolitan construction and demolition waste (CDW) is currently an important source of recycled materials that, despite having completed their useful life cycle, can be reincorporated into the circular economy process (CEP); however, the recycling process is very selective, and waste material is not always fully satisfactory due to the intrinsic nature of the waste. This work aims to demonstrate and establish how to increase the effectiveness of the construction and demolition waste in more resistant mortars, by mixing it with zeolitised cinerite tuff (ZCT) at varying normalised proportions. To attain the objectives of this research, a series of tests were done: First, a chemical, physical and mineralogical characterisation of the CDW and the ZCT through XRF, XRD, SEM and granulometric methods. Second, a technological test was made to determine the mechanical strength at 7, 28 and 90 days of specimens made with Portland cement (PC) and mixtures of PC/CDW, PC/ZCT, and PC/CDW-ZCT. The results obtained through the characterisation methods showed that the sample of construction and demolition waste consisted of the main phase made of portlandite and tobermorite, and by a secondary phase consisting of quartz, ettringite and calcite; whereas the ZCT has a main phase of mordenite and a secondary phase of smectite (montmorillonite), amorphous materials consisting of devitrified volcanic glass, quartz and plagioclase. Mechanical strength tests established that specimens made with PC/CDW mixtures have very discreet compressive strength values up to 44 MPa at 90 days, whereas specimens made with PC/ZCT mixtures achieved a remarkably high mechanical strength consisting of 68.5 MPa. However, the most interesting conclusion in this research is the good result obtained in mechanical strength of the specimens made up of mixtures of PC/CDW-ZCT, which increased from 52.5 to 62 MPa at 90 days of curing; this fact establishes the positive influence of ZCT on waste in the mortar mixtures, which permits the authors to establish that the objective of the work has been fulfilled. Finally, it can be argued that the results obtained in this research could contribute to more effective use of construction and demolition waste in metropolitan areas.

Studying auroral activity using the SME index at the magnetic storm main phase during CIR and ICME events

In this paper, we examine the relationship of the SME index with magnetic storm characteristics and interplanetary medium parameters during the main phase of magnetic storms caused by CIR and ICME events. Over the period 1990–2017, 107 magnetic storms driven by (64) CIR and (43) ICME events have been selected. In contrast to AE and Kp, a stronger correlation is shown to exist between the average SME index (SMEaver) and interplanetary medium parameters during the magnetic storm main phase. Close correlation coefficients between SMEaver and the SW electric field (southward IMF Bz) have been obtained for CIR and ICME events. SMEaver has been found to increase with the rate of magnetic storm development and |Dstmin|. For CIR and ICME events, no difference has been revealed between SMEaver and |Dstmin| in linear regression equations.

Comparative Study of Structures and Properties of Detonation Coatings with α-Al2O3 and γ-Al2O3 Main Phases

This study is aimed at obtaining a coating of aluminum oxide containing α-Al2O3 as the main phase by detonation spraying, as well as a comparative study of the structural, tribological and mechanical properties of coatings with the main phases of α-Al2O3 and γ-Al2O3. It was experimentally revealed for the first time that the use of propane as a combustible gas and the optimization of the technological regime of detonation spraying leads to the formation of an aluminum oxide coating containing α-Al2O3 as the main phase. Tribological tests have shown that the coating with the main phase of α-Al2O3 has a low value of wear volume and coefficient of friction in comparison with the coating with the main phase of γ-Al2O3. It was also determined that the microhardness of the coating with the main phase of α-Al2O3 is 25% higher than that of the coatings with the main phase of γ-Al2O3. Erosion resistance tests have shown (evaluated by weight loss) that the coating with α-Al2O3 phase is erosion-resistant compared to the coating with γ-Al2O3 (seen by erosion craters). However, the coating with the main phase of γ-Al2O3 has a high value of adhesion strength, which is 2 times higher than that of the coating with the main phase of α-Al2O3. As the destruction of coatings by the primary phase, α-Al2O3 began at low loads than the coating with the main phase γ-Al2O3. The results obtained provide the prerequisites for the creation of wear-resistant, hard and durable layered coatings, in which the lower layer has the main phase of γ-Al2O3, and the upper layer has the main phase of α-Al2O3.

Studying auroral activity using the SME index at the magnetic storm main phase during CIR and ICME events

. In this paper, we examine the relationship of the SME index with magnetic storm characteristics and interplanetary medium parameters during the main phase of magnetic storms caused by CIR and ICME events. Over the period 1990–2017, 107 magnetic storms driven by (64) CIR and (43) ICME events have been selected. In contrast to AE and Kp, a stronger correlation is shown to exist between the average SME index (SMEaver) and interplanetary medium parameters during the magnetic storm main phase. Close correlation coefficients between SMEaver and the SW electric field (southward IMF Bz) have been obtained for CIR and ICME events. SMEaver has been found to increase with the rate of magnetic storm development and |Dstmin|. For CIR and ICME events, no difference has been revealed between SMEaver and |Dstmin| in linear regression equations.

The Evolution of Intermetallic Compounds in High-Entropy Alloys: From the Secondary Phase to the Main Phase

High-performance structural materials are critical to the development of transportation, energy, and aerospace. In recent years, newly developed high-entropy alloys with a single-phase solid-solution structure have attracted wide attention from researchers due to their excellent properties. However, this new material also has inevitable shortcomings, such as brittleness at ambient temperature and thermodynamic instability at high temperature. Efforts have been made to introduce a small number of intermetallic compounds into single-phase solid-solution high-entropy alloys as a secondary phase to their enhance properties. Various studies have suggested that the performance of high-entropy alloys can be improved by introducing more intermetallic compounds. At that point, researchers designed an intermetallic compound-strengthened high-entropy alloy, which introduced a massive intermetallic compound as a coherent strengthening phase to further strengthen the matrix of the high-entropy alloy. Inspired from this, Fantao obtained a new alloy—high-entropy intermetallics—by introducing different alloying elements to multi-principalize the material in a previous study. This new alloy treats the intermetallic compound as the main phase and has advantages of both structural and functional materials. It is expected to become a new generation of high-performance amphibious high-entropy materials across the field of structure and function. In this review, we first demonstrate the inevitability of intermetallic compounds in high-entropy alloys and explain the importance of intermetallic compounds in improving the properties of high-entropy alloys. Secondly, we introduce two new high-entropy alloys mainly from the aspects of composition design, structure, underlying mechanism, and performance. Lastly, the high-entropy materials containing intermetallic compound phases are summarized, which lays a theoretical foundation for the development of new advanced materials.

A EFFECT OF CeO2 DOPING ON THE MICROSTRUCTURE AND CORROSION BEHAVIOR OF CoCuNiTi HIGH-ENTROPY ALLOY COATINGS

CoCuNiTi high-entropy alloy coatings with an equal molar ratio were prepared on 45 steel substrates using the laser-cladding method. The effect of CeO2 doping on phase structure, microstructure and corrosion behavior of CoCuNiTi coatings were investigated by X-ray diffraction, optical microscope, scanning electron microscope, and electrochemical workstation. The results show that the phase structure of CoCuNiTi coating doped with 1 w/% CeO2 is transformed from the original dual-phase structure of FCC main phase and BCC phase to the dual-phase structure of BCC main phase and FCC phase, mainly because CeO2 addition helps to improve the temperature gradient and solidification rate during solidification, reduce the nucleation resistance and the diffusion distance of the alloying elements, and provide a liquid environment with longer time, lower viscosity and higher diffusion rate. The microstructure of the two coatings is composed of BCC-phase dendrite and FCC-phase interdendrite. The widths of the primary dendrites of the columnar dendrites in CoCuNiTi cladding layer before and after CeO2 doping are about 8.10 µm and 6.51 µm, respectively. The CoCuNiTi coating doped with 1 w/% CeO2 has the smallest corrosion current density, the largest capacitive reactance arc radius and polarization resistance, and the best corrosion resistance in 3.5 w/% NaCl solution, which is mainly due to making the alloy structure refined and the element distribution uniform after the CeO2 addition.

Evaluation of the Physico-Chemical Properties of Liposomes Assembled from Bioconjugates of Anisic Acid with Phosphatidylcholine

The aim of this work was the evaluation of the physico-chemical properties of a new type of liposomes that are composed of DPPC and bioconjugates of anisic acid with phosphatidylcholine. In particular, the impact of modified anisic acid phospholipids on the thermotropic parameters of liposomes was determined, which is crucial for using them as potential carriers of active substances in cancer therapies. Their properties were determined using three biophysical methods, namely differential scanning calorimetry (DSC), steady-state fluorimetry and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Moreover, temperature studies of liposomes composed of DPPC and bioconjugates of anisic acid with phosphatidylcholine provided information about the phase transition, fluidity regarding chain order, hydration and dynamics. The DSC results show that the main phase transition peak for conjugates of anisic acid with phosphatidylcholine molecules was broadened and shifted to a lower temperature in a concentration- and structure-dependent manner. The ATR-FTIR results and the results of measurements conducted using fluorescent probes located at different regions in the lipid bilayer are in line with DSC. The results show that the new bioconjugates with phosphatidylcholine have a significant impact on the physico-chemical properties of a membrane and cause a decrease in the temperature of the main phase transition. The consequence of this is greater fluidity of the lipid bilayer.