Alcaino, P., Santa-Maria, H., Magna-Verdugo, C., & Lopez, L. (2020). Experimental fast-assessment of post-fire residual strength of reinforced concrete frame buildings based on non-destructive tests. Constr. Build. Mater., 234, 10 pp.
Abstract: Assessment of the residual strength of reinforced concrete buildings subjected to fire is a problem that requires fast and sufficiently reliable resolution, necessary for the action of firefighters, forensic fire investigation, and structural assessment of post-fire condition of the building to take place. In all cases safety and integrity of firefighters and researchers can be at risk, and it is necessary to have rapidly and sufficiently reliable information in order to choose whether to enter freely, to enter with caution, or simply do not enter to the burned structure. This required prompt assessment gives no time or background to develop mathematical models of the structure and damage propagation. This work presents an experimental methodology for a fast assessment of post-fire residual strength of reinforced concrete frame buildings based on the high correlation between the loss of strength and non-destructive test results of frame concrete elements subjected to fire action. (C) 2019 Elsevier Ltd. All rights reserved.
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Antico, F. C., De la Varga, I., Esmaeeli, H. S., Nantung, T. E., Zavattieri, P. D., & Weiss, W. J. (2015). Using accelerated pavement testing to examine traffic opening criteria for concrete pavements. Constr. Build. Mater., 96, 86–95.
Abstract: The risk of cracking in a concrete pavement that is opened to traffic at early ages is related to the maximum tensile stress sigma(I), that develops in the pavement and its relationship to the measured, age dependent, flexural strength of a beam,f(r). The stress that develops in the pavement is due to several factors including traffic loading and restrained volume change caused by thermal or hygral variations. The stress that develops is also dependent on the time-dependent mechanical properties, pavement thickness, and subgrade stiffness. There is a strong incentive to open many pavements to traffic as early as possible to allow construction traffic or traffic from the traveling public to use the pavement. However, if the pavement is opened to traffic too early, cracking may occur that may compromise the service life of the pavement. The purpose of this paper is two-fold: (1) to examine the current opening strength requirements for concrete pavements (typically a flexural strength from beams, f(r)) and (2) to propose a criterion based on the time-dependent changes of sigma(I)/f(r), which accounts for pavement thickness and subgrade stiffness without adding unnecessary risk for premature cracking. An accelerated pavement testing (APT) facility was used to test concrete pavements that are opened to traffic at an early age to provide data that can be compared with an analytical model to determine the effective sigma(I)/f(r), based on the relevant features of the concrete pavement, the subgrade, and the traffic load. It is anticipated that this type of opening criteria can help the decision makers in two ways: (1) it can open pavement sections earlier thereby reducing construction time and (2) it may help to minimize the use of materials with overly accelerated strength gain that are suspected to be more susceptible to develop damage at early ages than materials that gain strength more slowly. (C) 2015 Elsevier Ltd. All rights reserved.
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Antico, F. C., Rojas, P., Briones, F., & Araya-Letelier, G. (2021). Animal fibers as water reservoirs for internal curing of mortars and their limits caused by fiber clustering. Constr. Build. Mater., 267, 120918.
Abstract: We present a bottom-up experimental research to address evidence of internal curing of mortars using randomly distributed pig-hair as water reservoirs. Plain and reinforced mortars with pig hair ranging from 0 to 8 kg of fibers per cubic meter of mortar were prepared. The microstructures of plain and reinforced mortars were scanned using electron microscopy and the microhardnesses were measured within
the bulk cement paste and cement paste near pig fibers. Electrical resistivity, surface absorption, and residual compressive strength of mortars after freeze-thaw cycles were used to test the effects of internal curing caused by pig hair. Natural fibers used to reinforce mortars increase their toughness and provide
part of the necessary water for internal curing, yet internal curing originated by the addition of natural fibers is not proportional to fiber dosage; where the potential to form fiber clusters increases as fiber dosage increases. Results show that there is an optimum fiber dosage that maximizes internal curing
caused by these fibers. This study contributes to the research on reinforced mortars with natural fibers to provide sustainable solutions for construction materials.
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Araya-Letelier, G., Antico, F. C., Burbano-Garcia, C., Concha-Riedeld, J., Norambuena-Contreras, J., Concha, J., et al. (2021). Experimental evaluation of adobe mixtures reinforced with jute fibers. Constr. Build. Mater., 276(2021), 122127.
Abstract: Due to their sustainability as well as physical and mechanical performance, different natural fibers, both vegetal and animal fibers, have been successfully used in adobe mixtures (AMs) to enhance properties such as cracking control, flexural toughness and water erosion resistance, among others. However, the use of jute fibers (JFs), one of the most largely produced vegetal fiber worldwide, has not been extensively studied on AMs. Consequently, this study evaluates the effects of the incorporation of varying dosages (0.5 and 2.0 wt%) and lengths (7, 15, and 30 mm) of JFs on the physical/thermal/mechanical/fracture and durability performance of AMs, a specific type of earth-based construction material widely used globally. Experimental results showed that the incorporation of 2.0 wt% dosages of JFs increased the capillary water absorption of AMs, which might affect AM durability. The latter result could be explained by the additional porosity generated by the spaces left between the JFs and the matrix of adobe, as well as the inherent water absorption of the JFs. The incorporation of JFs significantly improved the behavior of AMs in terms of thermal conductivity, drying shrinkage cracking control, flexural toughness and water erosion performance, without affecting their compressive and flexural strength. For example, flexural toughness indices were increased by 297% and crack density ratio as well as water erosion depth values were reduced by 93% and 62%, respectively, when 2.0 wt%-15 mm length JFs were incorporated into AM. Since the latter combination of JF dosage and length provided the overall best results among AMs, it is recommended by this study as JF-reinforcement scheme for AMs for construction applications such as adobe masonry and earth plasters.
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Araya-Letelier, G., Antico, F. C., Carrasco, M., Rojas, P., & Garcia-Herrera, C. M. (2017). Effectiveness of new natural fibers on damage-mechanical performance of mortar. Constr. Build. Mater., 152, 672–682.
Abstract: Addition of fibers to cement-based materials improve tensile and flexural strength, fracture toughness, abrasion resistance, delay cracking, and reduce crack widths. Natural fibers have recently become more popular in the construction materials community. This investigation addresses the characterization of a new animal fiber (pig hair), a massive food-industry waste worldwide, and its use in mortars. Morphological, physical and mechanical properties of pig hair are determined in order to be used as reinforcement in mortars. A sensitivity analysis on the volumes of fiber in mortars is developed. The results from this investigation showed that reinforced mortars significantly improve impact strength, abrasion resistance, plastic shrinkage cracking, age at cracking, and crack widths as fiber volume increases. Other properties such as compressive and flexural strength, density, porosity and modulus of elasticity of reinforced mortars are not significantly affected by the addition of pig hair. (C) 2017 Elsevier Ltd. All rights reserved.
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Araya-Letelier, G., Concha-Riedel, J., Antico, F. C., & Sandoval, C. (2019). Experimental mechanical-damage assessment of earthen mixes reinforced with micro polypropylene fibers. Constr. Build. Mater., 198, 762–776.
Abstract: The addition of engineered polypropylene fibers to earthen materials offers new opportunities to control their damage evolution and mechanical properties that altogether provides more reliability and extends the life span of these materials. The latter is of special interest considering that earthen materials are still widely used in the form of adobe blocks for earthen masonry, cob, rammed earth or even earthen mortars for new construction and conservation of historic buildings. In this work, the effect of dosage of micro polypropylene fibers (MPPF) in the damage-mechanical performance of earthen mixes is studied experimentally. Part of the experiments includes two different tests to assess distributed and localized cracking of reinforced earth subject to restrained drying shrinkage. In addition, the experimental results showed that the incorporation of MPPF increases up to 83 times the impact strength and 11 times the flexural toughness of earthen mixes. Other mechanical properties such as compressive and flexural strength are not statistically affected by the incorporation of MPPF. (C) 2018 Elsevier Ltd. All rights reserved.
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Araya-Letelier, G., Concha-Riedel, J., Antico, F. C., Valdes, C., & Caceres, G. (2018). Influence of natural fiber dosage and length on adobe mixes damage-mechanical behavior. Constr. Build. Mater., 174, 645–655.
Abstract: This study addresses the use of a natural fiber (pig hair), a massive food-industry waste, as reinforcement in adobe mixes (a specific type of earthen material). The relevance of this work resides in the fact that earthen materials are still widely used worldwide because of their low cost, availability, and low environmental impact. Results show that adobe mixes' mechanical-damage behavior is sensitive to both (i) fiber dosage and (ii) fiber length. Impact strength and flexural toughness are increased, whereas shrinkage distributed crack width is reduced. Average values of compressive and flexural strengths are reduced as fiber dosage and length increase, as a result of porosity generated by fiber clustering. Based on the results of this work a dosage of 0.5% by weight of dry soil using 7 mm fibers is optimal to improve crack control, flexural toughness and impact strength without statistically affecting flexural and compressive strengths. (C) 2018 Elsevier Ltd. All rights reserved.
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Azeem, M., Guérin, A., Dumais, T., Caminos, L., Goldstein, R. E., Pesci, A. I., et al. (2020). Optimal Design of Multilayer Fog Collectors. ACS Appl. Mater. Interfaces, 12(6), 7736–7743.
Abstract: The growing concerns over desertification have spurred research into technologies aimed at acquiring water from nontraditional sources such as dew, fog, and water vapor. Some of the most promising developments have focused on improving designs to collect water from fog. However, the absence of a shared framework to predict, measure, and compare the water collection efficiencies of new prototypes is becoming a major obstacle to progress in the field. We address this problem by providing a general theory to design efficient fog collectors as well as a concrete experimental protocol to furnish our theory with all the necessary parameters to quantify the effective water collection efficiency. We show in particular that multilayer collectors are required for high fog collection efficiency and that all efficient designs are found within a narrow range of mesh porosity. We support our conclusions with measurements on simple multilayer harp collectors.
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Baier, R. V., Raggio, J. I. C., Arancibia, C. T., Bustamante, M., Perez, L., Burda, I., et al. (2021). Structure-function assessment of 3D-printed porous scaffolds by a low-cost/ open source fused filament fabrication printer. Mater. Sci. Eng. C-Mater. Biol. Appl., 123, 111945.
Abstract: Additive manufacturing encompasses a plethora of techniques to manufacture structures from a computational model. Among them, fused filament fabrication (FFF) relies on heating thermoplastics to their fusion point and extruding the material through a nozzle in a controlled pattern. FFF is a suitable technique for tissue engineering, given that allows the fabrication of 3D-scaffolds, which are utilized for tissue regeneration purposes. The objective of this study is to assess a low-cost/open-source 3D printer (In-House), by manufacturing both solid and porous samples with relevant microarchitecture in the physiological range (100?500 ?m pore size), using an equivalent commercial counterpart for comparison. For this, compressive tests in solid and porous scaffolds manufactured in both printers were performed, comparing the results with finite element analysis (FEA) models. Additionally, a microarchitectural analysis was done in samples from both printers, comparing the measurements of both pore size and porosity to their corresponding computer-aided design (CAD) models. Moreover, a preliminary biological assessment was performed using scaffolds from our In-House printer, measuring cell adhesion efficiency. Finally, Fourier transform infrared spectroscopy ? attenuated total reflectance (FTIR?ATR) was performed to evaluate chemical changes in the material (polylactic acid) after fabrication in each printer. The results show that the In-House printer achieved generally better mechanical behavior and resolution capacity than its commercial counterpart, by comparing with their FEA and CAD models, respectively. Moreover, a preliminary biological assessment indicates the feasibility of the In-House printer to be used in tissue engineering applications. The results also show the influence of pore geometry on mechanical properties of 3D-scaffolds and demonstrate that properties such as the apparent elastic modulus (Eapp) can be controlled in 3D-printed scaffolds.
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Beltran, J. F., Nunez, E., Nunez, F., Silva, I., Bravo, T., & Moffat, R. (2018). Static response of asymmetrically damaged metallic strands: Experimental and numerical approach. Constr. Build. Mater., 192, 538–554.
Abstract: In this study, the effect of the presence of broken wires (damage) asymmetrically distributed on metallic strands surfaces on their static response is assessed. To this end, a general mechanical model for multi layered strands is presented, in which damaged strands are treated as a 1D nonlinear beam under uncoupled biaxial bending and axial load (NLBM). The NLBM is validated by comparisons with the results obtained from an experimental program especially designed for studying the effect of surface damage distribution on strands response and 3D nonlinear finite element simulations. Analyses are carried out on two strand constructions: 1 x 7 and 1 x 19, in which the damage levels and strand diameters vary from 5% to 40% and from 3.5 mm to 22.2 mm, respectively. Results indicate that the NLBM accurate predicts the static response (residual strength, stiffness, axial strain field, and deformed configuration) of the asymmetrically damaged strands, achieving good computational efficiency and numerical robustness. (C) 2018 Elsevier Ltd. All rights reserved.
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Concha-Riedel, J., Antico, F. C., & Lopez-Querol, S. (2021). Mechanical strength, mass loss and volumetric changes of drying adobe matrices combined with kaolin and fine soil particles. Constr. Build. Mater., 312, 125246.
Abstract: Earthen construction represents almost 30% of the housing in developing countries, partially because of its low cost compared to steel and concrete construction, and also because the raw materials are available almost everywhere. One of the biggest disadvantages of earthen materials is the lack of information and variety on their constitutive materials, specifically their soil type. This work addresses the physical and mechanical properties of adobe matrices containing different concentrations of kaolin, which is a specific type of clay, as well as different proportions of fine particles of the original soil of the adobe matrix. All adobe matrices were manufactured with a SM-SC soil obtained from Santiago, Chile, and had concentrations of 0, 10, 30, and 50% of kaolin and 0, 10, 20, and 30% fines of the original soil content. It is concluded that the compressive strength of the studied earthen mixtures improves when kaolin is added to the mixture. The shrinkage of adobe matrices with kaolin compared to plain adobe matrices was reduced during the first days of age and stayed stable after that. This work shows that the inclusion of fines from the original soil (other than kaolin) did not significantly affect any of the studied properties. It also shows that the Unified Soil Classification System is not sufficient to characterize soils for adobe matrices.
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Cortez, V., Saravia, G., & Vogel, E. E. (2014). Phase diagram and reentrance for the 3D Edwards-Anderson model using information theory. J. Magn. Magn. Mater., 372, 173–180.
Abstract: Data compressor techniques are used to study the phase diagram of the generalized Edwards-Anderson model in three dimensions covering the full range of mixture between ferromagnetic (concentration 1-x) and antiferromagnetic interactions (concentration x). The recently proposed data compressor wlzip is used to recognize criticality by the maximum information content in the files storing the simulation processes. The method allows not only the characterization of the ferromagnetic to paramagnetic (FP) transition (x < 0.22, or x > 0.78) but also it equally well yields the spin-glass to paramagnetic (SP) transition (0.22 < x < 0.78). A reentrance of a ferromagnetic phase into the spin-glass phase is found in the vicinity of the multicritical point. The differences in the ways to apply the new method to FP and SP transitions are reported. A phase diagram for the entire range of x based entirely on the use of compression techniques is obtained and discussed. The advantages and disadvantages of the method of data compression as compared to other methods to deal with magnetic phase transitions are brought out and explained. (C) 2014 Elsevier B.V. All rights reserved.
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Fukushima, K., Kabir, M., Kanda, K., Obara, N., Fukuyama, M., & Otsuki, A. (2022). Equivalent Circuit Models: An Effective Tool to Simulate Electric/Dielectric Properties of Ores-An Example Using Granite. Materials, 15(13), 4549.
Abstract: The equivalent circuit model is widely used in high-voltage (HV) engineering to simulate the behavior of HV applications for insulation/dielectric materials. In this study, equivalent circuit models were prepared in order to represent the electric and dielectric properties of minerals and voids in a granite rock sample. The HV electric-pulse application shows a good possibility of achieving a high energy efficiency with the size reduction and selective liberation of minerals from rocks. The electric and dielectric properties were first measured, and the mineral compositions were also determined by using a micro-X-ray fluorescence spectrometer. Ten patterns of equivalent circuit models were then prepared after considering the mineral distribution in granite. Hard rocks, as well as minerals, are dielectric materials that can be represented as resistors and capacitors in parallel connections. The values of the electric circuit parameters were determined from the known electric and dielectric parameters of the minerals in granite. The average calculated data of the electric properties of granite agreed with the measured data. The conductivity values were 53.5 pS/m (measurement) and 36.2 pS/m (simulation) in this work. Although there were some differences between the measured and calculated data of dielectric loss (tan delta), their trend as a function of frequency agreed. Even though our study specifically dealt with granite, the developed equivalent circuit model can be applied to any other rock.
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Gaikwad, V. M., Dash, B. B., Sahoo, P. K., Shirbhate, S. C., Pabba, D. P., Acharya, S. A., et al. (2023). Polarization induced ferroelectric and magnetic ordering in double-perovskite-based flexible 0-3 composite. J. Mater. Sci. Mater. Electron., 34(8), 720.
Abstract: The novel multiferroic flexible films of Dy2NiMnO6 (DNMO) were prepared by incorporating DNMO particles in Polyvinylidene fluoride-based co-polymeric P(VDF-HFP) system. The structural studies validated the crystalline structure of DNMO remains unaffected by the presence of polymer. The scanning electron microscopic image of the composite sample confirms the uniform distribution of DNMO particles in the polymeric matrix. The enhancement in the ferroelectric parameters was observed for the composite sample in comparison with P(VDF-HFP) polymeric film. The composite sample exhibits a large polarization and coercive field at room temperature with enhanced dielectric behavior with reduced dielectric loss. M-H curves of composite show ferromagnetic nature with small increase in coercivity at 5 K. The field- and temperature-dependent magnetic characteristics of DNMO have remained unaltered even though the engagement of P(VDF-HFP) for achieving flexibility. The simultaneous existence of ferroelectric and magnetic order in the flexible DNMO may discover its application in the field of flexible magnetoelectronics.
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Grigioni, I., Polo, A., Dozzi, M. V., Stamplecoskie, K. G., Jara, D. H., Kamat, P. V., et al. (2022). Enhanced Charge Carrier Separation in WO3/BiVO4 Photoanodes Achieved via Light Absorption in the BiVO4 Layer. ACS Appl. Energy Mater., 5(11), 13142–13148.
Abstract: Photoelectrochemical (PEC) water splitting converts solar light and water into oxygen and energy-rich hydrogen. WO3/BiVO4 heterojunction photoanodes perform much better than the separate oxide components, though internal charge recombination undermines their PEC performance when both oxides absorb light. Here we exploit the BiVO4 layer to sensitize WO3 to visible light and shield it from direct photoexcitation to overcome this efficiency loss. PEC experiments and ultrafast transient absorption spectroscopy performed by frontside (through BiVO4) or backside (through WO3) irradiating photoanodes with different BiVO4 layer thickness demonstrate that irradiation through BiVO4 is beneficial for charge separation. Optimized electrodes irradiated through BiVO4 show 40% higher photocurrent density compared to backside irradiation.
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Kumar, N., Gajraj, V., Rameshbabu, R., Mangalaraja, R. V., Joshi, N. C., & Priyadarshi, N. (2022). Redox additive electrolyte assisted promising pseudocapacitance from strictly 1D and 2D blended structures of MnO2/rGO. Mater. Charact., 189, 111991.
Abstract: A promising sustainable energy storage characteristic is achieved in redox additive electrolyte by developing strict blend of one dimensional (1D) and two dimensional (2D) structures. Hydrothermal reaction is followed to obtain the desired morphology. Two dimensional (2D) reduced graphene oxide (rGO) is added into the redox reaction between potassium permanganate and sodium nitrite to obtain nanocomposite comprising 1D and 2D blended structures of MnO2/rGO. Their structures and morphologies are studied by XRD, Raman and HRTEM analyses, respectively. The pseudocapacitive behaviour is studied in a redox additive electrolyte comprising KOH and K3Fe(CN)(6). The effect of electrolytic concentration was studied by varying the concentration of K3Fe(CN)6. The specific capacity is considerably enhanced up to 1741 F/g, 8.75 A/g with increase in concentration of K3Fe (CN)6. The role of redox couple [Fe(CN)(6)](3)-/[Fe(CN)(6)](4)-played a key role in adding the charge movement across the electrode which tuned well with the manganese ions to obtain one of the most promising pseudo-capacitances from the developed 1D and 2D blended structures of MnO2/rGO. For in-depth analysis of Fe ions movement, a symmetric supercapacitor cell is constructed to achieve a commendable specific capacitance of 216 F/g at 3.75 A/g. Prolong cycling hinted decreasing electrolytic interfacial layers resulting in fast reversible ki-netics of Fe(III) -> Fe(II) ions to achieve astonishing capacity retention of 127% after 3000 cycles.
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Larrain, F. A., Fuentes-Hernandez, C., Chang, Y. C. H., Rodriguez-Toro, V. A., Abraham, S., & Kippelen, B. (2021). Increasing Volume in Conjugated Polymers to Facilitate Electrical Doping with Phosphomolybdic Acid. ACS Appl. Mater. Interfaces, 13(19), 23260–23267.
Abstract: Molecular p-type electrical dopants have been proven useful to fine-tune the optoelectronic properties of bulk organic semiconductors and their interfaces. Here, the volume in polymer films and its role in solution-based electrical p-type doping using phosphomolybdic acid (PMA) are studied. The polymer film volume was controlled using two approaches. One is based on heating both the PMA solution and the film prior to immersion. The second is based on coating the polymer film with a liquid blend that contains the PMA solution and a swelling solvent. 31P NMR and FTIR experiments indicate that the Keggin structure appears to be preserved throughout the doping process. Results show that increasing the polymer volume facilitates the infiltration of the PMA Keggin structure, which results in an increased electrical p-type doping level.
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Martinez, C., Briones, F., Aguilar, C., Araya, N., Iturriza, I., Machado, I., et al. (2020). Effect of hot pressing and hot isostatic pressing on the microstructure, hardness, and wear behavior of nickel. Mater. Lett., 273, 127944.
Abstract: Nanocrystalline Ni (Ni-nc) obtained by mechanical milling may present improved mechanical properties paired with high abrasion resistance. Different sintering processes were used to consolidate Nanocrystaline Ni: hot pressed (HP) and hot-isostatic pressed (HIP). The microstructure, mechanical properties, and tribological were evaluated to compare the processes. X-ray diffraction patterns showed that HIP-consolidated specimens had larger crystallite sizes and 37% less microstrain when compared to the HP specimens. The nanohardness of the HIP specimens was also carried out and it was 50% lower than that of HP specimens, whereas its coefficient of friction found was 25% higher. These results show the advantages of the HP process over the HIP since the high pressure. The low sintering temperature of HP inhibited the grain growth, which leads excellent mechanical and tribological properties of Ni. (C) 2020 Elsevier B.V. All rights reserved.
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Martinez, C., Briones, F., Rojas, P., Aguilar, C., Guzman, D., & Ordonez, S. (2017). Microstructural and mechanical characterization of copper, nickel, and Cu-based alloys obtained by mechanical alloying and hot pressing. Mater. Lett., 209, 509–512.
Abstract: Mechanical alloying and uniaxial compaction were used to obtain configurations of: elemental powders of Cu and Ni; binary alloys (Cu-Ni and Cu-Zr); and a ternary alloy (Cu-Ni-Zr) under the same mechanical milling and hot pressing conditions. Microstructure and mechanical properties of these were investigated. According to XRD results, hot pressing process increases crystallite size and decreases microstrain in the compact samples, due to the release of crystalline defects without crystallization of amorphous alloys. The milled powder samples have a higher hardness than the unmilled samples, since crystal defects are incorporated into microstructural refinement during milling. The ternary alloy Cu-40Ni-10Zr had the highest hardness of all systems studied, reaching 689 HV0.5. Compression tests at 5% strain determined that Zr-containing samples (amorphous phase) become more fragile after processing, and have the lowest values of compressive strength. In contrast, Ni samples and Cu-Ni binary alloys are more resistant to compression. (
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Mellado, P. (2022). Topological edge states in dipolar zig-zag stripes. J. Phys. Materials, 5(3), 034007.
Abstract: We study the magnon spectrum of stacked zig-zag chains of point magnetic dipoles with an easy axis. The anisotropy due to the dipolar interactions and the two-point basis of the zig-zag chain unit cell combine to give rise to topologically non-trivial magnon bands in 2D zig-zag lattices. Adjusting the distance between the two sublattice sites in the unit cell causes a band touching, which triggers the exchange of the Chern numbers of volume bands switching the sign of the thermal conductivity and the sense of motion of edges modes in zig-zag stripes. We show that these topological features survive when the range of the dipolar interactions is truncated up to the second nearest neighbors.
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