► A facile preparation method of phosphors of BaLiF3 doped Tb or/and Ce. ► Their structural characterization. ► Their luminescent properties of the rare-earth ion-doped BaLiF3. ► The discussion of ...energy transfer mechanism from Ce3+ to Tb3+ in the host.
Phase-pure Ce-/Tb-doped and co-doped barium lithium fluoride (BaLiF3) phosphors are synthesized by hydrothermal techniques at 200°C for 5days. The crystal structure, particle size, morphologies, the energy band structure and photoluminescence properties of the as-synthesized products are investigated by X-ray powder diffraction (XRD), environment scanning electron microscopy (ESEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). In the co-doping of Ce3+ and Tb3+ in BaLiF3 phosphors, there is the excitation band of Ce3+ exclusively in the excitation spectrum, while the characteristic emission from 5D4→7FJ (J=6, 5, 4, 3) of Tb3+ can only be observed in the emission spectrum. Especially the emission peak ascribed to Tb3+ ions transition from 5D4→7F5 strengthens greatly due to an effective energy transfer from Ce3+ to Tb3+ in co-doped system of BaLiF3. These results suggest that the phosphors of BaLiF3:Ce3+, Tb3+ would become promising green-emitting fluorescent materials.
Nanocomposites of C–Ta4+ co-doped NaTaO3 and reduced graphene oxide (C-NTO/rGO) with highly efficient photocatalytic activity were fabricated by a one-step solvothermal reaction. The optimum ...composites C-NTO/3rGO (with 3 wt% rGO) exhibited superior photocatalytic activity for the degradation of RhB over a mono-component counterpart under visible light irradiation. The photocatalytic efficiency was found to be as high as 97% for 90 min. Both XRD and XPS characterizations indicated that the doping of carbon into the NaTaO3 lattice leads to the reduction of Ta5+ to Ta4+. Furthermore, the co-doping significantly narrows the band gap (about 2.8 eV). Photo-luminescence (PL), time resolved transient PL decay spectra and photo-current results confirmed that photo-induced hole-electron pairs can be effectively separated resulting from the introduction of rGO. The synergistic effect of a decreased band gap and highly effective separation of photo-generated electrons and holes may be responsible for the enhanced photocatalytic activity of the fabricated nanocomposites. Both h+ and •OH active radicals were found to be the key factors for the photo-decomposition process of RhB over the nanocomposites, while •O2− was also involved to a smaller extent. A possible photo-degradation mechanism for C-NTO/rGO was proposed on the basis of the experiments results.
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•Visible light-active co-doped NaTaO3 and reduced graphene oxide photocatalysts were fabricated.•The photocatalysts exhibited high performance for the degradation of rhodamine B.•The narrowed band gap and effective separation of electron-hole were responsible for the excellent performance.•The photo-degradation mechanism for the enhanced activity was discussed deeply.
Phosphors of BaLiF3 doped with Eu or/and Ce were solvothermally prepared at 200℃ for 5 d and characterized by means of X-ray powder diffraction （XRD） and environment scanning electron microscopy ...（ESEM）. The excitation and emission spectra of the rare earth ions doped BaLiF3 were measured by fluorescence spectroscopy and the effects of Ce3＋ ions on the luminescence of Eu〉 ions were in- vestigated. In the co-doped Eu2＋ and Ce3＋ system, the emission intensity of Eu2＋ ion gradually increased with the Ce3＋ concentration increas- ing, and the enhancement of Eu2＋ fluorescence was due to efficient energy transfer from Ce3＋ to Eu2＋ in the host.
Unstructured clinical medical text, as an important part of the electronic health records, is characterized by large quantities and can store substantial disease-related information of patients. ...Currently, the disease risk assessment model based on the analysis of clinical medical text designs relevant characteristics aiming at certain diseases, and different characteristics are identified from the text using different methods. In this way, changes of disease performance characteristics are difficult to adapt. Furthermore, it is hard to use the risk assessment model in other disease applications. As a result, this paper establishes the universal disease risk assessment model using the data of clinical medical text, conducts the independent study, and extracts disease characteristics from substantial historical data to avoid the limitations designing disease characteristics. First, this paper analyzes the medial clinical text to determine the contents related to the disease characteristics of patients. Second, learn the representation of clinical text with unsupervised learning methods, and study and extract the disease characteristics from the substantial historical data of patients in the convolutional neural network to assess disease risks. Finally, make a contrast experiment of disease risk assessment using the clinical text data of patients with cerebral infarction, patients with pulmonary infection, and patients with coronary atherosclerotic heart disease from the data of a second grade-A hospital in China and related methods. The experiments show that the approach proposed in this paper achieves the disease risk assessment for different diseases with the same structure.
Reinforcement size is an important factor that influences the mechanical and tribological properties of particulate reinforced metal matrix composites (PRMMCs). However, relatively few works have ...been carried out to investigate this issue. There are still many problems to be solved, on the optimum design of PRMMCs of tribological applications. In this work, copper-matrix composites reinforced with SiC particles of mono-size and hybrid-size are fabricated through a powder-metallurgy plus hot-extrusion method. The main purpose is to investigate the effect of reinforcement size hybridization on the dry sliding wear behavior of PRMMCs. The results indicate that finer particles result in a better reinforcing effect and significantly reduce the plastic flow and adhesive transfer of surface and subsurface material. The deeply embedded coarse particles bear the external applied load and resist the plowing effect of the counterpart. The different roles of the particulate components with various sizes promote the exertion of the other’s strengthening function, therefore resulting in higher wear resistance.
Size-tunable β-NaYF4: Yb/Er (50–400 nm) up-converting nanoparticles (UCNPs) with a strong green emission were successfully prepared by a facile thermal decomposition method in a short period of time. ...The effects of the reaction time, the oleic acid (OA) content, and the doped Gd3+ concentration on the crystal structure, the size evolution mechanism and the luminescence mechanism of the β-NaYF4: Yb/Er nanoparticles were discussed in detail. Characterization was completed using X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution (HR-TEM), scanning electron microscopy (SEM), and photoluminescence (PL). The results reveal that the phase transition was completed at 15 min and the morphology of the NaYF4: Yb/Er UCNPs changed from spherical to large hexagonal disks (200–400 nm) in non-doped Gd3+. An appropriate decrease in the volume ratio of oleic acid (OA) to 1-octadecene (ODE) promoted NaF production, resulting in the formation of the hexagonal phase crystals and the subsequent increase of luminous intensity by 30–40 times. More importantly, the size of the β-NaYF4: Yb/Er decreased with Gd3+ doping, and the UCNPs ultimately transformed into small hexagonal prisms (50 nm) with high monodispersity when the doping concentration of Gd3+ was 60 mmoL. The PL spectra confirmed that the luminous intensity of the UCNPs with doped Gd3+ was much higher than that of the undoped UCNPs. The results show that this route for UCNP fabrication with high luminous efficiency and a small size could be extended to other UCNP systems for multifunctional biomedical applications.
•Size-tunable β-NaYF4: Yb/Er nanoparticles (UCNPs) were synthesized by thermal decomposition method in a short time.•The effects of various parameters on the properties of UCNPs was discussed in detail.•Gd3+ doping reduced the size and reaction temperature of UCNPs.•The UCNPs with Gd3+ doping exhibited a strong green emission.
Abstract
Reinforcement size is an important factor that influences the mechanical and tribological properties of particulate reinforced metal matrix composites (PRMMCs). However, relatively few works ...have been carried out to investigate this issue. There are still many problems to be solved, on the optimum design of PRMMCs of tribological applications. In this work, copper-matrix composites reinforced with SiC particles of mono-size and hybrid-size are fabricated through a powder-metallurgy plus hot-extrusion method. The main purpose is to investigate the effect of reinforcement size hybridization on the dry sliding wear behavior of PRMMCs. The results indicate that finer particles result in a better reinforcing effect and significantly reduce the plastic flow and adhesive transfer of surface and subsurface material. The deeply embedded coarse particles bear the external applied load and resist the plowing effect of the counterpart. The different roles of the particulate components with various sizes promote the exertion of the other’s strengthening function, therefore resulting in higher wear resistance.
Reinforcement size is an important factor that influences the mechanical and tribological properties of particulate reinforced metal matrix composites (PRMMCs). However, relatively few works have ...been carried out to investigate this issue. There are still many problems to be solved, on the optimum design of PRMMCs of tribological applications. In this work, copper-matrix composites reinforced with SiC particles of mono-size and hybrid-size are fabricated through a powder-metallurgy plus hot-extrusion method. The main purpose is to investigate the effect of reinforcement size hybridization on the dry sliding wear behavior of PRMMCs. The results indicate that finer particles result in a better reinforcing effect and significantly reduce the plastic flow and adhesive transfer of surface and subsurface material. The deeply embedded coarse particles bear the external applied load and resist the plowing effect of the counterpart. The different roles of the particulate components with various sizes promote the exertion of the other’s strengthening function, therefore resulting in higher wear resistance.
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