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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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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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Sepulveda, E., Mangalaraja, R. V., Udayabhaskar, R., Cobo, R., Berzal, M. E., Jimenez, J., et al. (2022). Preparation of LSGM electrolyte via fast combustion method and analysis of electrical properties for ReSOC. J. Electroceramics, 49(2), 85–93.
Abstract: In this work, we prepared La1 – xSrxGa1-yMgyO3 (LSGM) by the fast combustion method and assessed the electrical properties with respect to the composition and sintering temperature (1200, 1300, and 1400 degrees C by 6 h) as an electrolyte material for the reversible solid oxide cells (ReSOCs). For the preparation of samples, two different fuels, such as tartaric acid (TA) and citric acid (CA), with corresponding nitrate salts as precursors, were adopted for the fast combustion method (at 500 degrees C for 10 min). From the X-ray diffractograms, two main phases corresponding to LSGM orthorhombic (space group Imma) and LSGM-cubic (space group Pm-3 m) were identified. From the literature, both structures are reported as high oxygen ion conductive species, but normally they are not reported to appear together. Additionally, in some cases, an isolating (secondary) phase of LaSrGaO4 in a low concentration < 1.98% was observed. The scanning electron microscopy (SEM) studies on samples sintered at 1200 and 1300 degrees C revealed the smaller grain size and irregular morphology. The SEM micrographs depicted a well-defined superficial morphology with less porosity for the samples sintered at 1400 degrees C. For comparative analysis, the conductivity (S.cm(- 1)) was measured at varying temperatures (300-800 degrees C) for the samples sintered at 1300 and 1400 degrees C. Because of the large number of insulating phases produced by the incomplete sintering process, the samples sintered at 1300 degrees C had lower conductivities. A higher conductivity of 0.125 S.cm(- 1) was observed for La0.80Sr0.20Ga0.80Mg0.20O3 (LSGM), which was obtained using the citric acid (sintered at 1400 degrees C), which is in the range of earlier reported similar studies. The observed variation in the conductivity with respect to different phases of LSGM, the influence of the secondary phase, and the wt% of the constituents of LSGM are discussed.
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