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Martinez, C., Briones, F., Rojas, P., Ordonez, S., Aguilar, C., & Guzman, D. (2017). Microstructure and Mechanical Properties of Copper, Nickel and Ternary Alloys Cu-Ni-Zr Obtained by Mechanical Alloying and Hot Pressing. MRS Adv., 2(50), 2831–2836.
Abstract: Elemental powders of Cu and Ni, binary alloys (Cu-Ni and Cu-Zr) and ternary alloy (Cu-Ni-Zr) obtained by mechanical alloying and uniaxial compaction hot microstructure and mechanical properties were investigated. The alloys studied were: pure Cu, pure Ni, binary alloys (Cu-Ni; Cu-Zr) and ternary alloys (Cu-Ni-Zr) under the same mechanical milling and hot pressing conditions. The samples were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM); the mechanical properties were studied by compression tests and hardness in Vickers scale (HV0.5) on polished surfaces at room temperature. According to XRD results, hot pressing process crystallite size increase and microstrain decreases in the compact samples due to the release of crystalline defects. The compacted samples have porosity of approximately 20%. The milling powder samples have a higher hardness than the unmilled samples, this because during milling crystal defects are incorporated together with the microstructural refinement. Ternary alloy is the one with the highest hardness of all systems studied, reaching 689 HV0.5. In compression tests determined a strain 5 %, Zr-containing samples become more fragile presenting the lowest values of compressive strength. In contrast, samples of Ni and Cu-Ni binary alloy are more resistant to compression.
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Sepulveda, E., Mangalaraja, R. V., Troncoso, L., Jimenez, J., Salvo, C., & Sanhueza, F. (2022). Effect of barium on LSGM electrolyte prepared by fast combustion method for solid oxide fuel cells (SOFC). MRS Adv., Early Access.
Abstract: In this work, La0.85Sr0.15-xBaxGa0.85Mg0.15O3-delta (LSBGM), with 0 <= x <= 0.075, were prepared as electrolytes for solid oxide fuel cells applications. The effect of barium and sintering temperature on the structure and electrical properties was studied. A fast combustion method was used, starting with nitrate salts and citric acid as fuel. The XRD spectra showed two main phases corresponding to LSGM orthorhombic (space group Imma) and LSGM-cubic (space group Pm-3 m). From literature, both structures are reported as high oxygen ion conductive species, but normally, they are not reported to appear together. Major secondary phases were LaSrGaO4, BaLaGaO4, and BaLaGaO7. SEM revealed a material with low porosity, indicating incomplete densification. The sample La0.85Sr0.75Ba0.075Ga0.85Mg0.15O3-delta showed a conductivity of 0.016 and 0.058 S cm(-1) at 600 degrees C and 800 degrees C, respectively. This means an improvement of 34% compared to the non-barium sample La0.85Sr0.15Ga0.85Mg0.15O3-delta at 600 degrees C. Thus, this composition could be used in SOFC.
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Sepúlveda, E., Sanhueza, F., Cobo, R., Jiménez, J., & Mangalaraja, R. V. (2024). Relationship among the powder mass, press charge, and final properties of an LSGM electrolyte for solid oxide cells. MRS Adv., Early Access.
Abstract: In this work, La0.85Sr0.15Ga0.85Mg0.15O3-delta (LSGM) was prepared as an electrolyte for solid oxide cell (SOC) applications. A fast combustion method was used, starting with nitrate salts and citric acid as fuel. Different parameters, such as mass and pressing load, in the pre-sintering step were used to obtain a highly ionic conductive material at intermediate temperatures. The aim is to find optimal processing conditions for energy savings. SEM analysis showed similar grain sizes and distributions for all samples. The XRD spectra showed two main phases corresponding to LSGM orthorhombic (space group Imma) and LSGM cubic (space group Pm-3m). LaSrGaO4 appeared in lighter samples. The EIS revealed that heavier samples present high conductivity, showing a clear relationship between conductivity, sample mass (during the pre-sintering step), and the LSGM phase amount. The effect of pressure was less evident. The highest conductivity was 0.013 and 0.063 S cm-1 at 600 and 800 degrees C, respectively.
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