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Tb3+‐doped germanate glass ceramics containing CaF2 nanocrystals were prepared by melt quenching method with subsequent heat treatment. Their microstructures were investigated by XRD and TEM techniques. Their optical properties were studied by the transmittance, the photoluminescence, and the X‐ray excited luminescence (XEL). The luminescence intensity in the glass ceramics under 377 nm light and X‐ray excitations is significantly enhanced. The maximum integrated XEL intensity of the glass ceramics is about 50% of that of the commercial Bi4Ge3O12 (BGO) scintillating crystal. The results indicate that Tb3+‐doped germanate glass ceramic could be a promising scintillating material used in X‐ray detection for slow event. [ABSTRACT FROM AUTHOR]

Transparent Tb 3+ -doped glass ceramics containing BaF 2 nanocrystals were prepared by melt-quenching method with subsequent heat treatment. The XRD and EDS results showed the precipitated crystalline phase in the glass matrix was BaF 2 . Under 376 nm light, Tb 3+ doped oxyfluoride glass ceramics containing BaF 2 nanocrystals showed more intense green emission than the as-made glass, and the emission intensity increased with increasing heat treatment temperature and time. The lifetimes of 541 nm emission of Tb 3+ doped oxyfluoride glass ceramics were longer than that of as-made glass, which are in the range from 3.00 ms to 3.55 ms. Under X-ray excitation, the green emission was enhanced in the glass ceramics compared to the as-made glass. The results indicate Tb 3+ doped oxyfluoride glass ceramics containing BaF 2 nanocrystals could be a material candidate for X-ray glass scintillator for slow event detection. [ABSTRACT FROM AUTHOR]

Cubic-to-hexagonal phase evolution, narrow crystalline size distribution and enhancement of luminescence are simultaneously achieved by modifying the ratio of SiO2/B2O3 content in the Eu3+-doped oxyfluoride borosilicate glass ceramics containing NaGdF4 nanocrystals. The mechanisms of phase evolution of NaGdF4 nanocrystals are discussed on the basis of IR spectra, viscosity, XRD and TEM data. The results indicate that the stresses developed during the thermal treatment process play an important role in the phase evolution, which provides an experimental evidence of pressure-induced disorder-to-order phase evolution during the crystallization process for the first time. It is also found that the excitation and emission spectra as well as the luminescence lifetimes of the Eu3+ ions in the oxyfluoride glass ceramic are sensitive to the crystal lattice of NaGdF4. [ABSTRACT FROM AUTHOR]

In this research, activated carbon fiber heated by microwave (WACF) under nitrogen (N2) atmosphere adsorption of tetracycline antibiotics (TCs) was analyzed. WACF was obtained under the microwave radiation temperature of 600°C and the radiation time of 15 min. The properties of WACF were characterized by a scanning electron microscope (SEM), N2adsorption/desorption isotherms, and X-ray diffraction (XRD) compared with activated carbon fibers (ACF) without any treatment. WACF had lower surface area (1008 m2/g) but higher external surface area (429 m2/g) than ACF (surface area: 1153 m2/g; external surface area: 308 m2/g). Meanwhile, the adsorption efficiencies of TCs (including tetracycline hydrochloride (TC) and oxytetracycline hydrochloride (OTC)) on WACF were both increased by about 4 times. These results indicated that mesoporosity amplification of WACF played a crucial role in the adsorption capacity of the two TCs. The kinetics and equilibrium data were agreed well with the pseudo-second-order kinetics model (R2 > 0.99) and Langmuir isotherm model (R2 > 0.98), respectively. It suggested that the adsorption process was dominated by chemisorption. Batch experiments showed the maximum adsorption capacities for both adsorbates were 339 and 331 mg/g respectively at pH 2. [ABSTRACT FROM AUTHOR]

A transparent Tb3+ and Yb3+ codoped oxyfluoride glass-ceramic containing CaF2nanocrystals was prepared by heat treating the as-made glass. Formation of CaF2 nanocrystals in the glass-ceramic was confirmed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). Ultraviolet (UV) and visible emission spectra of the as-made glass and the glass-ceramic following excitation by a 974 nm diode laser were recorded at room temperature. An intense UV emission at 381 nm was observed in the glass-ceramic. The origin of the enhancement of the emission at 381 nm was investigated using spectroscopy and Judd-Ofelt analysis. The enhancement of the emission at 381 nm could be attributed to the change of the ligand field of Tb3+ ions due to the incorporation of some Tb3+ and Yb3+ ions into the CaF2 nanocrystals in the glass-ceramic. [ABSTRACT FROM AUTHOR]

Abstract: In this study, utilization of leather waste (LW) as precursor for activated carbon preparation by physical (steam) and chemical (pyrophosphoric acid, H4P2O7) activation in different conditions (carbonization temperature, carbonization time and impregnation ratio) is discussed. Thermal gravimetric analysis of LW-H4P2O7 indicated that H4P2O7 as the activator promotes the formation of carbonaceous material. The activated carbons obtained under the best conditions were characterized using N2 adsorption/desorption isotherms, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The preparation principle of activated carbon with different methods was also studied. Batch adsorption studies were performed to evaluate the adsorption properties toward methylene blue (MB). Activated carbon produced by H4P2O7 activation showed higher yield, lower S BET, more functional groups and higher adsorption capacities for MB than the carbons prepared by steam activation. Adsorption experiment indicated that the adsorption data fitted the Langmuir equation better than Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherms, and the capacity of adsorption for AC-H4P2O7 was superior to AC-steam, indicating the mechanisms of π–π electron-donor–acceptor (EDA) interaction, cation exchange and hydrogen bond were involved due to the more functional groups. The adsorption has been confirmed to be a spontaneous and endothermic process. [Copyright &y& Elsevier]

Abstract: Orange emitting Sr2.96−x Ba x SiO5: Eu2+ phosphors have been synthesized by a method using Sr2SiO4 instead of simple oxides and carbonate as precursor. The photoluminescence properties, radiative lifetime and formation process were investigated by PL spectra, lifetime decay and XRD analysis, respectively. X-ray diffraction analysis indicates that the phosphor has a single phase of Sr3SiO5 without residual Sr2SiO4 and BaSi4O9 phases. Under 460nm excitation, the emission band of Sr2.96−x Ba x SiO5: Eu2+ has a red-shift from 580–598nm due to varied Ba2+ concentration. Particularly, the emission intensity of Sr2.56Ba0.4SiO5: 0.02Eu2+ sample increased significantly in comparison with the commercial SSE phosphor. The radiative lifetime τ 0 are estimated to be 1.999, 2.316, 2.716 and 2.932μs for samples of x=0, 0.2, 0.4 and 0.6, respectively. It indicates that Eu2+ ions are in different surroundings and the Sr2+ sites were substituted by Ba2+ completely. Compare with the conventional solid-state reaction method, the Sr2.96−x Ba x SiO5: Eu2+ phosphors synthesized by this method show higher crystallinity and more efficient orange emission. [Copyright &y& Elsevier]

Abstract: A series of Bi2O3–BaO–SiO2–RxOy (designated BiBaSi glass) glass sealants doped with different contents of TiO2 were prepared by conventional melting and annealing technique. The onset of crystallization temperature was determined by differential thermal analysis. The CTEs along with transition temperature (Tg) and softening temperature (Tf) were determined from dilatometric measurement. X-ray diffraction was used to determine the crystal phases. Scanning electron microscopy was used to study the microstructure and an associated energy dispersive X-ray spectroscopy was used to study element distribution. The good matching of thermal properties and the strong adherence to the electrolyte and connector indicate that the composite glass with 7.3mol% TiO2 (BAS3) appeared to be a good candidate for SOFC sealing. [Copyright &y& Elsevier]

Abstract: Eu/Tb codoped transparent oxyfluoride borosilicate glass ceramics containing Sr2GdF7 nanocrystals were fabricated under a reductive atmosphere and the conversion of Eu3+ ions to Eu2+ ions was observed. The Sr2GdF7 nanocrystals with an average size of 32nm were homogeneously precipitated in the oxyfluoride borosilicate glass matrix, which could be evidenced by X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) spectroscopy. The enhancement of photoluminescence emission intensity, reduction of the relative emission intensities between 5D0 → 7F2 and 5D0 → 7F1, and long fluorescence lifetimes of Eu2+, Eu3+, and Tb3+ ions revealed that more rare earth ions were partitioned into the low phonon energy environment Sr2GdF7 nanocrystals. Under ultraviolet excitation, pure and bright white light emission was obtained in the oxyfluoride borosilicate glass ceramic, which may be a potential blue, green and red-emitting phosphor for white LEDs. [Copyright &y& Elsevier]

Abstract: A novel orange-yellow-emitting Ba2LiB5O10:Eu2+ phosphor has been synthesized by traditional high temperature solid state reaction. A monoclinic crystal structure of Barium lithiumborates Ba2LiB5O10 was verified by the investigation of X-ray diffraction (XRD). The compound crystallizes in the space group of P121/m1(11) (Z=2) with the unit cell parameters a=4.414(1)Å, b=14.576(2)Å, c=6.697(2)Å and β=104.26(2)°. Barium and lithium atoms are located in distorted octahedral and tetrahedral oxygen coordinations, respectively. Upon around 365nm excitation, the Eu2+-activated Ba2LiB5O10 phosphors exhibit a single broad emission band with the maximum at about 587nm, due to the 4f65d→4f7(8S7/2) transition of Eu2+. This work investigates the relationship between luminescence properties and structural characterization of the Ba2LiB5O10: Eu2+. This newly developed phosphor shows high potential as a phosphor conversion for white LED applications. [Copyright &y& Elsevier]

Abstract: Transparent Eu3+ doped and Tm3+/Yb3+ codoped oxyfluoride glass ceramics were prepared and spectroscopic properties were investigated. The XRD and TEM results demonstrated the formation of Ba2GdF7 nanocrystals, and the reduction of the ratio β between and transitions of Eu3+ ions evidenced rare-earth ions incorporation into Ba2GdF7 nanocrystals. For Tm3+/Yb3+ codoped glass ceramic, unusual ultraviolet upconversion emissions from transition of Gd3+ at 308nm and , and transitions of Tm3+ at 359nm, 449nm and 476nm were observed under 980nm excitation, respectively. And upconversion mechanism of Tm3+–Yb3–Gd3++ system was analyzed. [Copyright &y& Elsevier]

Abstract: Ce3+ doped La4Ca(SiO4)3O phosphors with silicate oxyapatite structure were synthesized by the sol-gel process. The X-ray diffraction (XRD) patterns showed that a pure phase was formed when sintering temperature was higher than 1300°C. The optical properties of La4Ca(SiO4)3O:Ce3+ phosphors with varying sintering temperature and concentration were investigated by examining their excitation and emission spectroscopy. The phosphors exhibited a broad emission band centered at 550nm which could be attributed to the 5d-4f transition of Ce3+ and a stronger excitation peak around 467nm as well as several shoulder bands, nicely matching with the widely applied blue LED chips. Higher emission intensity was observed when firing temperature above 1300°C, due to increasing crystallinity of the powders. When Ce3+ concentration was equal to 5 at%, the sample exhibited the optimum excitation and emission efficiency. The results indicate that La4Ca(SiO4)3O:Ce3+ is a promising candidate in the application of blue chip excited white light emitting diodes (LEDs). [Copyright &y& Elsevier]

Abstract: (Ca1−x, Srx)Al2Si2O8:0.06Ce3+, M+ (M+ =Li+, Na+, K+) phosphors have been prepared by conventional solid-state reaction method. The structural and optical properties of the phosphors were characterized by X-ray diffraction (XRD) technique and spectrophotometer, respectively. A regular variation was found among the XRD patterns of (Ca1−x, Srx)Al2Si2O8:0.06Ce3+ phosphors based on the changing of Sr content. With the increase of Sr content, the maximum of emission band presented slight blue shifts (~15nm). The luminescence intensity of CaAl2Si2O8:0.06Ce3+ and SrAl2Si2O8:0.06Ce3+ were significantly enhanced when K+ and Li+ were incorporated, respectively. [ABSTRACT FROM AUTHOR]