We report the synthesis of a high-performance CO2 methanation catalyst, Ni-Y1/CeO2, comprising Ni nanoparticles and atomically dispersed Y3 + on a ceria support. This precisely designed catalyst achieved an outstanding CO2 conversion of 83 % with 100 % CH4 selectivity at 350 degrees C. XAS unambiguously confirmed the atomic dispersion of Y3+ with the absence of any Y-Y bonds, while STEM-EDS revealed uniform Y distribution with finely dispersed Ni NPs. Enhanced oxygen vacancies and improved basic sites contributed to the superior activity of Ni-Y1/CeO2 even at low temperature (250-300 degrees C) and showed excellent stability over 40 h. Comparative studies with impregnated NiY/CeO2-imp and Ni/CeO2 highlighted the synergistic effect of Y3+ and Ni. These results establish Y3+ single-atom modulation as a powerful approach to tailoring basic sites and enhanced oxygen vacancies, unlocking new design pathways for advanced CO2 methanation catalysts.
A comparative study was conducted using the Johnson-Cook, strain-compensated Arrhenius-type, and modified Zerilli-Armstrong constitutive models to predict the high-temperature flow behaviour of as-cast Zircaloy-4. Multistep temperature hot compression tests were performed using thermo-mechanical simulator in the temperature range of 1173-1023 K and strain rate range of 0.01-1 s-1 to determine the temperature of inhibition of recrystallization. Isothermal hot compression tests were also carried out using thermo-mechanical simulator to determine the material constants required for each constitutive model over a temperature range of 973-1173 K and strain rate range of 0.001-1 s-1. The accuracy and reliability of the models were assessed using the average absolute relative error (AARE) and the correlation coefficient (R). Both the modified Zerilli-Armstrong and strain-compensated Arrhenius models demonstrated good predictive capability for the flow stress behaviour of Zircaloy-4. However, the modified Zerilli-Armstrong model with a temperature compensated material parameter, exhibited superior performance near transition temperature with average prediction error reduced from 20.71 % maximum to 10.79 % maximum as compared to modified Zerilli-Armstrong model. The modified Zerilli-Armstrong model with a temperature compensated material parameteralso achieved better AARE as 7.6 % as compared to the strain-compensated Arrhenius model, which achieved an AARE of 9.79 %. The temperature range associated with inhibition of recrystallization was determined to lie between 1093 and 1103 K for strain rates ranging from 0.01 to 1 s-1.
Ti6Al4V alloys are widely used in engineering applications due to their superior mechanical and chemical properties. This study evaluated the wear performance of additively manufactured (AM) and cast titanium alloys against various hard counter bodies. The percentage change in the coefficient of friction (%Delta COF) was calculated by comparing the COF values of AM and cast samples. The %Delta COF values were + 52.38 % for boron carbide, -11.42 % for silicon carbide, + 32.43 % for tungsten carbide, and + 18.75 % for titanium carbide. Overall, cast titanium alloys exhibited lower COF values than AM alloys, except when contact with silicon carbide. Additionally, the cast titanium alloy exhibited lower specific wear rate against silicon carbide, while the AM titanium alloy showed higher specific wear rate against tungsten carbide.
The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has been continuously providing good quality survey data of the entire sky in the high energy range from 30 MeV to 500 GeV and above since August 2008. A succession of gamma-ray source catalogs is published after a comprehensive analysis of the Fermi–LAT data. The most recent release of data in the fourth Fermi–LAT catalog of gamma-ray sources (4FGL-DR4), based on the first 14 years of observations in the energy band 50 MeV-1 TeV, contains 7195 sources. A large fraction (∼ 33%) of this population has no known counterparts in the lower wave bands. Such high energy gamma-ray sources are referred to as unassociated or unidentified. An appropriate classification of these objects into known type of gamma-ray sources such as the active galactic nuclei or pulsars is essential for population studies and pointed multi-wavelength observations to probe the radiative processes. In this work, we perform a detailed classification of the unassociated sources reported in the 4FGL-DR4 catalog using two supervised machine learning techniques-Random Forest and Extreme Gradient Boosting. We mainly focus on the identification of new gamma-ray pulsar candidates by making use of different observational features derived from the long-term observations with the Fermi–LAT and reported in the incremental 4FGL-DR4 catalog. We also explore the effects of data balancing approach on the classification of the Fermi–LAT unassociated sources.
Structure-luminescence correlation in Dy/Eu doped pyrophosphate materials (A2P2O7; A = Ca, Sr, Ba, Zn) is investigated, unveiling novel strategies for white light generation. The Hubbard corrected density functional theory (DFT+U) calculations reveal that Dy3+ doping reduces the coordination number and metal-oxygen bond lengths. The local lattice distortions enhance the asymmetric crystal field, favoring 4F9/2-6H15/2, 6H13/2 transitions corresponding to blue and yellow emissions following the 4f-5d-4f energy transfer pathway. The luminescence mechanism confirms that Eu2+exhibits stronger hybridization with oxygen, yielding blue-green emission through the f-d transition, while Eu3+contributes red-orange emission via f-f transitions. The Eu doped systems are more resistant to lattice strain than Dy doped ones, and structurally more perturbed due to smaller ionic radii and stronger Coulomb interactions. These findings predict the oxidation state variations based on structural constraints and offer deep insight into the electronic structure and luminescence behavior of pyrophosphate phosphors.
