Rietveld refinement of neutron and x-ray diffraction data of Na0.5Bi0.5TiO3 shows R3c phase stabilization at room temperature. The intermediate antiferroelectric region between 180°C to 280°C exhibits phase ...
Rietveld refinement of neutron and x-ray diffraction data of Na0.5Bi0.5TiO3 shows R3c phase stabilization at room temperature. The intermediate antiferroelectric region between 180°C to 280°C exhibits phase coexistence i.e R3c + Pnma, along with decrease in octahedral tilt angle and increase in unit cell volume. The local structural changes observed from Raman scattering in the A-O, Ti-O and TiO6 phonon modes favor the global structural variation. A possible antiparallel cation displacement due to Pnma phase formation leads to the origin of antiferroelectric ordering in Na0.5Bi0.5TiO3.
One of the most significant challenges of luminescent materials is the thermal quenching (TQ) at high temperature. Understanding the correlation between crystal structure variation and photoluminescence (PL) quenching...
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One of the most significant challenges of luminescent materials is the thermal quenching (TQ) at high temperature. Understanding the correlation between crystal structure variation and photoluminescence (PL) quenching is significant to achieve anti-thermal quenching (anti-TQ) phosphors. Herein, we unveil a universal principle governing switchable TQ and anti-TQ behaviors in zero-dimensional (0D) organic–inorganic hybrid manganese bromides. We observed an abnormal anti-TQ phenomenon when phosphor is excited in the valley of PL excitation (PLE) spectrum (indirect excitation) while TQ phenomenon is observed when excited in the peak and shoulder positions of PLE. Our findings demonstrate that PL intensity is influenced by two variable parameters: the effective Mn-ligand distance and the shortest Mn−Mn distance. These excitation-dependent TQ and anti-TQ behaviors originate from the relative changes in these distances, which modulate the competition between radiative and nonradiative recombination rates, as evidenced at the molecular level by molecular dynamics simulation. X-ray activated radioluminescence (RL) also exhibits anti-TQ behavior, which is analogous to the indirect excitation of PL evolution when excited at PLE valley. These insights bridge the gap between PL and RL properties in 0D manganese halides and offer potential avenues for developing advanced anti-TQ phosphors, efficient LEDs, and high-performance scintillators.
Based on the orthogonal experiment of laser cladding technology on the surface of aluminum alloy, the effect of powder type, laser power, spot diameter and scanning speed on the surface hardness of laser cladding proc...
Based on the orthogonal experiment of laser cladding technology on the surface of aluminum alloy, the effect of powder type, laser power, spot diameter and scanning speed on the surface hardness of laser cladding process on aluminum alloy surface was studied using genetic algorithm back-propagation neural network (GA-BPNN), and the process parameters of the laser cladding process test on the aluminum alloy surface were optimized, and the surface hardness under various process parameters was predicted. The predicted results are in good agreement with the actual test results, and the errors are all less than 1%. The results show that the optimal combination of surface hardness influencing parameters is not unique, and this result is closer to the actual production requirements. In addition, no matter whether it is the optimal or various surface hardness predictions, the proposed optimal prediction method can obtain representative results. This paper provides a new method for the selection of the best process scheme for laser cladding of aluminum alloy surface.
Laser-induced gauge fields in neutral atoms serve as a means of mimicking the effects of a magnetic field, providing researchers with a platform to explore behaviors analogous to those observed in condensed matter sys...
Laser-induced gauge fields in neutral atoms serve as a means of mimicking the effects of a magnetic field, providing researchers with a platform to explore behaviors analogous to those observed in condensed matter systems under real magnetic fields. Here, we propose a method to generate chiral motion in atomic excitations within the neutral atomic ground-state manifolds. This is achieved through the application of polychromatic driving fields coupled to the ground–Rydberg transition, along with unconventional Rydberg pumping. The scheme offers the advantage of arbitrary adjustment of the effective magnetic flux by setting the relative phases between different external laser fields. In addition, the effective interaction strength between the atomic ground states can be maintained at 10 kHz, surpassing the capabilities of the previous approach utilizing Floquet modulation. Notably, the proposed method can be readily extended to implement a hexagonal neutral atom lattice, serving as the fundamental unit in realizing the Haldane model.
The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising pathway to resolve energy and environment problems. An electrocatalyst was designed with single Mo atoms (Mo‐SAs) supported ...
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The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising pathway to resolve energy and environment problems. An electrocatalyst was designed with single Mo atoms (Mo‐SAs) supported on N‐doped carbon having outstanding HER performance. The structure of the catalyst was probed by aberration‐corrected scanning transmission electron microscopy (AC‐STEM) and X‐ray absorption fine structure (XAFS) spectroscopy, indicating the formation of Mo‐SAs anchored with one nitrogen atom and two carbon atoms (Mo 1 N 1 C 2 ). Importantly, the Mo 1 N 1 C 2 catalyst displayed much more excellent activity compared with Mo 2 C and MoN, and better stability than commercial Pt/C. Density functional theory (DFT) calculation revealed that the unique structure of Mo 1 N 1 C 2 moiety played a crucial effect to improve the HER performance. This work opens up new opportunities for the preparation and application of highly active and stable Mo‐based HER catalysts.
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