Structural, mechanical, and electrochemical properties of Ceria doped Scandia stabilized Zirconia

The properties of Ceria doped Scandia Stabilized Zirconia (1Ce10ScSZ) nano-powder produced in Ukraine (Ukr, VMMP) are compared to the properties of commercial ones produced by Daiichi Kigenso Kagaku Kogyo (DKKK, Japan) and Praxair (USA). In comparison to DKKK and Praxair, the Ukr nano-powder demonstrated the smallest size of the particles ranging from 20 to 50 nm. The bending strength of the isostatically pressed samples made of Ukr powder was 100–120 MPa similar to that of Praxair. The bending strength of DKKK was lower (50–100 MPa) depending on the isostatic pressure. The biaxial strength of uniaxially pressed samples was the highest for DKKK (375 MPa) decreasing to 250 MPa for Ukr and 220 MPa for Praxair. Among three tested samples, the highest electric conductivity measured at 700 °C was found for Ukr electrolyte.Вивчено й порівняно властивості нанопорошків двоокису цирконію, стабілізованого двоокисами церію та скандію 1Ce10ScSZ, які виготовлено в Україні на Вільногірському державному гірничо-металургійному комбінаті (ВДГМК), в Японії компанією «Daiichi Kigenso Kagaku Kogyo» (DKKK) та в США компанією «Praxair». Порівняно з порошками виробництва DKKK та «Praxair» порошок виробництва ВДГМК (позначено як «Ukr») має найменший розмір частинок в інтервалі 20-50 нм. Міцність зразків, виготовлених із порошку «Ukr» із використанням ізостатичного пресування, становить 100-120 МПа при згині та є подібною до міцності порошку виробництва «Praxair». Міцність зразків виробництва DKKK менша (50-100 МПа) й залежить від ізостатичного тиску. Міцність одновісно пресованих зразків найвища в порошку DKKK (375 МПа), у зразках «Ukr» і «Praxair» вона становить відповідно 250 МПа та 220 МПа. Із-поміж трьох досліджених серій зразків найвищу електричну провідність при 700 °С мали електроліти, виготовлені з порошку «Ukr».Были изучены и сравнены свойства нанопорошков двуокиси циркония, стабилизированного окислами церия и скандия 1Ce10ScSZ, которые произведены в Украине на Вольногорском государственном горно-металлургическом комбинате (ВГГМК), в Японии компанией «Daiichi Kigenso Kagaku Kogyo» (DKKK) и в США компанией «Praxair». В сравнении с порошками производства DKKK и «Praxair» у порошка производства ВГГМК (обозначен как «Ukr») наименьший размер частиц в интервале 20–50 нм. Прочность образцов, изготовленных из порошка «Ukr» с использованием изостатического прессования, составляет 100–120 МПа при изгибе и подобна прочности образцов из порошка производства «Praxair». Прочность образцов из порошка DKKK меньше (50–100 МПа) и зависит от давления изостатического прессования. Прочность одноосно прессованных образцов наиболее высока (375 МПа) у порошка DKKK, в образцах «Ukr» и «Praxair» она составляет соответственно 250 МПа и 220 МПа. Из трех испытанных серий образцов самая высокая электропроводность при 700 °С была у электролитов, изготовленных из порошка «Ukr»

The disappearances of six supernova progenitors

As part of a larger completed Hubble Space Telescope (HST) Snapshot program, we observed the sites of six nearby core-collapse supernovae (SNe) at high spatial resolution: SN 2012A, SN 2013ej, SN 2016gkg, SN 2017eaw, SN 2018zd, and SN 2018aoq. These observations were all conducted at sufficiently late times in each SN's evolution to demonstrate that the massive-star progenitor candidate identified in each case in pre-explosion imaging data had indeed vanished and was therefore most likely the actual progenitor. However, we have determined for SN 2016gkg that the progenitor candidate was most likely a blend of two objects: the progenitor, which itself has likely vanished, and another closely neighbouring star. We thus provide a revised estimate of that progenitor's properties: a binary system with a hydrogen-stripped primary star at explosion with effective temperature ≈6300-7900 K, bolometric luminosity ≈104.65 L⊙, radius ≈118-154 R⊙, and initial mass 9.5-11 M⊙. Utilizing late-time additional archival HST data nearly contemporaneous with our Snapshots, we also show that SN 2017eaw had a luminous ultraviolet excess, which is best explained as a result of ongoing interaction of the SN shock with pre-existing circumstellar matter. We offer the caveat, particularly in the case of SN 2013ej, that obscuration from SN dust may be compromising our conclusions. This sample adds to the growing list of confirmed or likely core-collapse SN progenitors. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Early-time Ultraviolet Spectroscopy and Optical Follow-up Observations of the Type IIP Supernova 2021yja

We present three epochs of early-time ultraviolet (UV) and optical HST/STIS spectroscopy of the young, nearby Type IIP supernova (SN) 2021yja. We complement the HST data with two earlier epochs of Swift UVOT spectroscopy. The HST and Swift UVOT spectra are consistent with those of other well-studied Type IIP SNe. The UV spectra exhibit rapid cooling at early times, while less dramatic changes are seen in the optical. We also present Lick/KAIT optical photometry up to the late-time tail phase, showing a very long plateau and shallow decline compared with other SNe IIP. Our modeling of the UV spectrum with the TARDIS radiative transfer code produces a good fit for a high-velocity explosion, a low total extinction E(B − V) = 0.07 mag, and a subsolar metallicity. We do not find a significant contribution to the UV flux from an additional heating source, such as interaction with the circumstellar medium, consistent with the observed flat plateau. Furthermore, the velocity width of the Mg ii λ2798 line is comparable to that of the hydrogen Balmer lines, suggesting that the UV emission is confined to a region close to the photosphere. © 2022. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Multi-messenger Observations of a Binary Neutron Star Merger

International audienceOn 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim 1.7\,{\rm{s}}$ with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg(2) at a luminosity distance of ${40}_{-8}^{+8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 $\,{M}_{\odot }$. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim 40\,{\rm{Mpc}}$) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position $\sim 9$ and $\sim 16$ days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta