Luminescence properties of Ca4Y6(SiO4)6O:RE (RE = Eu, Tb, Dy, Sm and Tm) under vacuum ultraviolet excitation

The vacuum ultraviolet excited luminescent properties of Eu³⁺, Tb³⁺, Dy³⁺, Sm³⁺ and Tm³⁺ in the matrices of Ca₄Y₆(SiO₄)₆O were investigated. The bands at about 173 nm in the vacuum ultraviolet excited spectra were attributed to host lattice absorption of the matrix Ca₄Y₆(SiO₄)₆O. For Eu³⁺-doped samples, the O²⁻ → Eu³⁺ CTB was identified at 258 nm. Typical 4f-5d absorption bands in the region of 195-300 nm were observed in Tb³⁺-doped samples. For Dy³⁺-doped and Sm³⁺-doped samples, the broad excitation bands consisted of host absorptions, CTB and f-d transition. For Tm³⁺-doped samples, the O²⁻ → Tm³⁺ CTB was located at 191 nm. About the color purity and emission intensity, Ca₄Y₆(SiO₄)₆O:Tb³⁺ is an attractive candidate of green light PDP phosphor, and Ca₄Y₆(SiO₄)₆O:Dy³⁺ has potential application in the field of mercury-free lamps.     

Effect of initial substrate and biomass concentrations on anaerobic fermentative hydrogen production in batch reactors

The effects of initial substrate (5 -60 g/L) and biomass concentration (0.5 -3 g/L) on fermentative hydrogen production by mixed cultures were investigated in batch tests using glucose as substrate.The...     

Synthesis and hydrogenation properties of Mg–La–Ni–H system by reactive mechanical alloying

We have synthesized Mg–30 mass%LaNi_2.28 composite material and investigated its hydrogenation behaviour. The reactive mechanical alloying process of the mixture of Mg and LaNi_2.28 was studied. It is found that a composite of _MgH2${\mathrm{MgH}}_2$, _La4H12.9${\mathrm{La}}_4{\mathrm{H}}_{12.9}$ and _Mg2NiH4${\mathrm{Mg}}_2{\mathrm{NiH}}_4$ formed after 80 h ball-milling under 3.0 MPa hydrogen. Scanning electron microscopic analysis indicated that these new phases are distributed homogeneously. This composite shows excellent hydriding properties even at moderate temperature. Under 3.0 MPa hydrogen pressure it absorbed more than 80% of its full capacity in the temperature range of 473–553 K within less than 1 min. The maximum hydrogen absorption capacity at 553 K is 5.4 mass%. The enhanced hydriding properties could be attributed to the fine and uniform particles and a synergeticly catalytic effect generated by mechanical milling.     

Three-dimensional thermal conductive behavior of graphite materials sintered from ribbon mesophase pitch-based fibers

Block graphite prepared from ribbon mesophase pitch-based fibers, which are arranged unidirectionally, exhibits three-dimensional anisotropic thermal conductive behavior. The thermal conductivity (TC) of the graphite along the direction parallel to the fiber axis is 30-40× that of the other two directions. And with increasing graphitization temperature, the TC of the graphite material treated at 3273 K in the direction parallel to the fiber axis increases and reaches 837 W m⁻¹ K⁻¹, while that in other direction decreases to 11 W m⁻¹ K⁻¹ because of regular arrangement of graphite crystallites.     

Subsolidus phase relations in the ZnO-WO3-Bi2O3 system

The subsolidus phase relations of the ternary system ZnO-WO₃-Bi₂O₃ were investigated by means of X-ray diffraction (XRD). Six binary compounds and seven 3-phase regions were determined, and no ternary compounds were found in this ternary system. The phase diagram of pseudobinary system ZnO-Bi₂WO₆ was also constructed through XRD and differential thermal analysis (DTA) methods, which forms eutectic system with eutectic temperature about 945 °C, the corresponding eutectic component is 35 mol% ZnO and 65 mol% Bi₂WO₆.     

Optical properties of Si-N doped BaMgAl10O17:Eu, Mn phosphors for plasma display panels

The photoluminescence properties of Si-N doped BaMgAl₁₀O₁₇:Eu²⁺, Mn²⁺ phosphors were studied. Photoluminescence spectrum, powder X-ray diffraction and decay curves were used. The electronic structure of un-doped BaMgAl₁₀O₁₇ was investigated by using the density functional theory. It reveals that an ideal hexagonal shape and particle size in 3-5 μm are obtained by Si-N doping. Additionally, its photoluminescence and thermal stability are both improved. The energy transfer from Eu²⁺ to Mn²⁺ also enhanced by suitable Si-N doping. These are expected to be potentially applicable to industrial production of the phosphor in plasma display panels.     

Light-weight NaNH2–NaBH4 hydrogen storage material synthesized via liquid phase ball milling

As a light-weight and low-cost hydrogen storage composite, NaNH₂–NaBH₄ (molar ratio of 2:1) was prepared by a liquid phase ball milling (LPBM) method under the co-protection of argon and cyclohexane. The structure evolution and the thermal decomposition performance of the as-prepared sample were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermo gravimetric-differential thermal analysis (TG-DTA), respectively. It is found that the interaction of NaNH₂ with NaBH₄ is enhanced by LPBM, thus causes a preferred orientation for the crystal structure of NaNH₂, and the red-shifts of the N–H stretching vibration and the B–H stretching vibration. In addition, the as-prepared NaNH₂–NaBH₄ (2/1) can achieve a low activation energy of 76.4 kJ mol⁻¹ during the main decomposition stage, which is only 47.9% of that of the one synthesized via a solid state ball milling (SSBM) method, and is very close to that of the Co–B catalyst promoted one. This indicates the LPBM method is an efficient way to get high-performance NaNH₂–NaBH₄, whose thermal decomposition kinetics can be greatly improved without any catalyst.