However, it was also shown that the total elongation is considerably reduced in the 48-h-milled NiMo-SiC DPS alloy due to high porosity. The amount of grain boundaries greatly increases the Hall–Petch strengthening, resulting in significantly higher strength in the case of 48-h-milled NiMo-SiC DPS alloys compared with the 8-h-milled alloys. Increased milling time seems to limit the grain growth of the NiMo matrix by producing well-dispersed Mo 2C particles during sintering. It was further shown that the milling time has significant effects on the microstructural characteristics of these alloys. The study showed that uniformly-dispersed SiC particles provide dispersion strengthening, the precipitation of nano-scale Ni 3Si particles provides precipitation strengthening, and the solid-solution of Mo in the Ni matrix provides solid-solution strengthening. Neutron Powder Diffraction (NPD), Electron Back Scattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were employed in the characterization of the microstructural properties of these in-house prepared NiMo-SiC DPS alloys. In the current study, a battery of dispersion and precipitation-strengthened (DPS) NiMo-based alloys containing varying amounts of SiC (0.5–2.5 wt %) were prepared from Ni-Mo-SiC powder mixture via a mechanical alloying (MA) route followed by spark plasma sintering (SPS) and rapid cooling. I also learned to use the CrystalMaker software and took what I learned to normalize and compare the data as described above.A new generation of alloys, which rely on a combination of various strengthening mechanisms, has been developed for application in molten salt nuclear reactors. Ronald I performed all x-ray powder diffractions and was responsible for analyzing all of the data that was produced. Thus, the synthesized crystal samples were found to contain a mixture of crystals composed of source materials, SrZrS3 (n=∞), and Sr2ZrS4, the first known experimental product of the n=1 phase of Srn+1ZrnS3n+1 RP crystals.įunder Acknowledgement(s): We would like to thank the National Science Foundation EFRI REM (EFMA-1433378) for funding this research project.įaculty Advisor: Dr. Having done this, the remaining unidentified peaks match very closely with the Sr2ZrS4 (n=1) phase, with Sr3Zr2S7 (n=2) producing a much lower fidelity match. This data was compared to the original sample compound data, aligning the pattern so that the first two unidentified peaks matched the theoretical pattern. Using the known properties of these crystals, the relationships between lattice parameters when phase and elemental site makeup were changed were obtained and used to predict XRD patterns for Sr2ZrS4 and Sr3Zr2S7. Theoretical diffraction patterns for these phases were calculated with CrystalMaker 10.3 and CrystalDiffract 6.7 software by utilizing space group properties and unit cell lattice parameters of n=1 and n=2 phases of the related RP families: Ban+1ZrnS3n+1, Srn+1ZrnO3n+1, and Ban+1ZrnO3n+1. The objective of this project was to use the unknown peaks to ascertain if the product was a synthesis of an as-of-yet unreported phase of the RP family Srn+1ZrnS3n+1, hypothesized to be either the Sr2ZrS4 (n=1) or Sr3Zr2S7 (n=2) phase. Once the reaction was complete, the compound’s x-ray powder diffraction (XRD) pattern was observed to have several unexpected peaks, in addition to the peaks known to be associated with our source materials and SrZrS3 (n=∞), an expected product. The ampoules containing the source materials were gradually heated to 950☌ over 15 hours, held constant for 15 hours, then raised to 1050☌ over 12 hours. SrS, Zr, and S powders were compounded via a solid-state reaction with I2 carrier gas. In this study, both experimental and theoretical x-ray diffraction (XRD) patterns were used to verify the synthesis of a previously unreported n=1 phase of the Srn+1ZrnS3n+1 family, Sr2ZrS4. Ruddlesden-Popper (RP) layered perovskite crystals of the family Srn+1ZrnS3n+1 (n=0, 1, 2, …∞) are theoretically predicted to have ferroelectric properties making them ideal for applications in photovoltaics, sensing, and visible lighting. Seng Huat Lee, The Pennsylvania State University, University Park, PA Ronald Redwing, The Pennsylvania State University, University Park, PA Dr. Katrina Verlinde - The Pennsylvania State UniversityĬo-Author(s): Dr.
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