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Using fly ash to synthesize zeolite molecular sieves can improve the reuse value of coal fly ash resources, reduce the synthesis cost of the zeolites, and protect the ecology. A novel approach was proposed to prepare zeolite socony mobil‐5 (ZSM‐5) zeolite via one‐pot hydrothermal synthesis. The mesoporous ZSM‐5 synthesized by adjusting the molar ratio of chemical reagents has higher crystallinity, larger specific surface area, and more adsorption sites. An analysis of methylene blue (MB) adsorption on mesoporous ZSM‐5 was conducted at many different adsorption parameters, including solution concentration, temperature, and duration of adsorption. The Langmuir model can objectively describe the adsorption behavior of MB on ZSM‐5, and the adsorption characteristics of MB on ZSM‐5 are better described by the pseudo‐second‐order kinetic model. The thermodynamic model provides the adsorption behavior as an endothermic reaction. [ABSTRACT FROM AUTHOR]

In this work, the mechanical properties and solid particle erosion wear behavior of LaMgAl11O19-Al2O3 ceramics toughened and reinforced with LaMgAl11O19 platelets were investigated. The effects of LaMgAl11O19 additions, impingement angles (30°, 45°, 60°, 75°, and 90°), and erosion temperatures varying from room temperature to 1400°C on the erosion rates and material removal mechanisms of LaMgAl11O19-Al2O3 composites were systematically studied. The results indicated that LaMgAl11O19-Al2O3 ceramics exhibited superior erosive wear resistance compared to monolithic Al2O3 ceramics at room and elevated temperatures due to their enhanced mechanical properties and improved microstructure resulting from the introduction of an appropriate amount of LaMgAl11O19 platelets. Examination of the eroded surfaces of LaMgAl11O19-Al2O3 composites revealed that erosion temperatures and impingement angles play important roles in determining the erosion behavior and mechanisms of the tested materials. For the case of elevated temperature and oblique erosion, plowing and subsurface intergranular fracture are the predominant mechanisms resulting in material removal, whereas at room temperature and normal impact, the erosion process of the targets is primarily dominated by grain ejection and lateral crack intersection. [ABSTRACT FROM AUTHOR]

A case of phosphor is reported where the cooling rate parameter significantly influences the luminescence property. By quenching the sample after the high-temperature solid-state reaction at 1250°C, we successfully prepared the Eu2+-doped α form Ca3( PO4)2 (α- TCP:Eu2+) as a new kind of bright cyan-emitting phosphor. The unusual emission color variation (from cyan to blue) depends on the cooling rate after sintering and Eu2+ doping level as it was observed in the TCP-based phosphors. By the Rietveld analysis, it is revealed that the cyan- and blue-emitting phosphors are two different TCP forms crystallizing in the monoclinic (space group P21/ a, α- TCP) and the rhombohedral structure (space group R3 c, β- TCP), respectively. Upon 365 nm UV light excitation, α- TCP:Eu2+ exhibits an asymmetric broad-band cyan emission peaking at 480 nm, while β- TCP:Eu2+ displays a relatively narrow-band blue emission peaking at 416 nm. The Eu2+-doping in Ca3( PO4)2 shifts the upper temperature limit of the stable structural range of β form from 1125°C to ≥1250°C. Moreover, the crystal structures of α/β- TCP:Eu2+ were compared in the aspects of compactness and cation site sets. The emission thermal stability of α/β- TCP:Eu2+ was comparatively characterized and the difference was related to the specific host structural features. [ABSTRACT FROM AUTHOR]

SrIn2O4, which shows lower phonon energy than CaIn2O4, is not only a good photocatalyst but also can be an excellent up-conversion (UC) host to exhibits UC luminescence. In this work, Yb3+ and/or Er3+ doped SrIn2O4 phosphors were synthesized, and their UC luminescence properties were studied and compared with those in the CaIn2O4 host. The structure of SrIn2O4: 0.01Er3+ and SrIn2O4: 0.1Yb3+/0.01Er3+ samples were refined by the Rietveld method and found to that SrIn2O4: 0.1Yb3+/0.01Er3+ showed increasing unit cell parameters and cell volume, indicating In3+ sites were substituted successfully by Yb3+ and/or Er3+ ions. From the UC luminescence spectra and diffuse reflection spectra, Er3+-doped SrIn2O4 showed very weak luminescence due to ground state absorption of Er3+; Yb3+/Er3+ codoped SrIn2O4 presented strong green (550 nm) and red (663 nm) UC emissions which were assigned to energy transfer from Yb3+ transition 2F7/2→2F5/2 to the Er3+ transition 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2. Comparing with CaIn2O4, Yb3+/Er3+ codoped SrIn2O4 showed obvious advantages with higher UC luminescent intensity. The pumping powers study showed that UC emissions in Yb3+/Er3+ codoped SrIn2O4 were attributed to energy transfer of Yb3+→Er3+ with a two-photon process. The possible UC luminescent mechanism of Yb3+/Er3+-doped SrIn2O4 was discussed. [ABSTRACT FROM AUTHOR]

Novel LaMgAl11O19:Tm3+, Dy3+ phosphors were prepared utilizing a high-temperature solid-state reaction method. The phase formation, luminescence properties, energy-transfer mechanism from the Tm3+ to the Dy3+ ions, the thermal stability, and CIE coordinates were investigated. When excited at 359 nm, the LaMgAl11O19: xTm3+ phosphors exhibit strong blue emission bands at 455 nm. After codoping with Dy3+ and excitation at 359 nm, the LaMgAl11O19:0.03Tm3+, yDy3+ phosphors emitted white light consisting of the characteristic emission peaks of Tm3+ and Dy3+. The Dy3+ emission intensity increased with the Dy3+ concentration due to the energy transfer from Tm3+ to Dy3+, and concentration quenching due to the high Dy3+ doping concentration (y = 0.1 mol) did not occur. The calculation of the CIE coordinates of the LaMgAl11O19: Tm3+, yDy3+ phosphors revealed the tunability of the emission color from blue to bluish-white and to white by changing the excitation wavelength and the doping concentration. An energy transfer from Tm3+ to Dy3+ by dipole-dipole interaction was confirmed by the decay curve, lifetime, and energy-transfer efficiency measurements. When excited at 359 nm, the LaMgAl11O19:Tm3+, Dy3+ phosphor also showed good thermal stability, suggesting that it can be used in white LEDs excited by a GaN-based ultraviolet LED. [ABSTRACT FROM AUTHOR]