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Abstract: Dy3+-doped NaGdTiO4 phosphors were synthesized by a solid-state reaction method. The crystal structure, spectral properties and fluorescence quenching of the phosphors were systematically studied by means of X-ray diffraction (XRD) and spectroscopy. It was found that the phosphors can be effectively excited by 281nm ultraviolet light, and intense white light emission was observed. The white light was generated by mixing blue (483nm) and yellow (578nm) emissions corresponding to the transitions from 4F9/2 to 6H15/2 and 6H13/2 levels of Dy3+. The electric dipole–dipole interaction between Dy3+ ions was identified as the main mechanism for the concentration dependent fluorescence quenching of 4F9/2 level. The CIE color coordinates of the phosphors were calculated to be (x =0.3345, y =0.3535) in the white region under 281nm excitation, which is very close to the E point (energy equal point, x =0.3333, y =0.3333). In addition, the thermal quenching behavior of 4F9/2 level of Dy3+ was also discussed, and the crossover effect was confirmed to be the dominant physical mechanism responsible for the fluorescence temperature quenching of Dy3+ in NaGdTiO4 host. [Copyright &y& Elsevier]

The β 1 ′and β 2 ′ are important precipitates in Mg-Zn alloys. Two types of precipitates both are composed of MgZn 2 , but the orientation relationships of MgZn 2 with the α-Mg matrix in two precipitates are different. To understand the properties of β 1 ′and β 2 ′, we use the first-principles method to perform a systematical investigation of coherent interfaces of β 1 ′/α-Mg and β 2 ′/α-Mg. Here, we present exhaustive analysis of the structure and stability for these interfaces, and find that the interfacial energy is highly dependent on the average coordination of interfacial structures. Furthermore, we find that the MgZn 2 slab in matrix with [11 2 ¯ 0] MgZn2 //[0001] α , (0001) MgZn2 //(11 2 ¯ 0) α orientation relationship (OR1) is less stable than that with [11 2 ¯ 0] MgZn2 //[10 1 ¯ 0] α , (0001) MgZn2 //(0001) α orientation relationship (OR2), which can explain that the β 2 ′ plate shape precipitates that are frequently observed in Mg-Zn alloys comply with OR2 instead of OR1. [ABSTRACT FROM AUTHOR]

Silicon and its oxides remain the most promising and alternative anode materials for increasing the energy density of Li-ion batteries (LIBs) due to their high theoretical specific capacity and suitable operating voltage. However, the severe volume change effect and rapid capacity attenuation problem make the design and advancement of silicon-based anode materials still challenging for state-of-the-art lithium-ion battery technology. Fortunately, metal-organic frameworks (MOFs) have been widely attracted as emerging materials in energy storage and conversion due to their tunable properties, outstanding morphological and structural advantages. The application of MOF and its derivatives to recast the energy storage properties of silicon and its oxides anode materials is an intriguing approach, where the silicon and its oxide can be embedded into MOF and its derivatives to generate the unique composite anode materials. Besides, the stability of the electrode materials can be significantly improved by adjusting and maintaining the composition and pristine structure of the MOF. However, it is still a great challenge that how to make MOFs better coated on silicon-based materials and what type of MOFs to choose for modification. Concentrating on the above key points, this review paper focuses on the application of MOFs and their derivatives in improving the rational design of silicon and its oxides for Li-ion battery anodes, comparing the advantages and disadvantages of different preparation methods, and discussing the lithium storage mechanism of as-synthesized MOF-modified silicon-based materials, which shows practical significance for the subsequent research in energy storage systems. [ABSTRACT FROM AUTHOR]

This paper reported on the upconversion (UC) spectroscopic properties of Tm 3+ /Yb 3+ codoped Gd 2 (WO 4 ) 3 phosphors synthesized by a traditional co-precipitation method upon excitation of 980 and 808 nm commercial available fiber lasers, respectively. X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to characterize the crystal structure and morphology of the samples. Intense blue emission ( 1 G 4 → 3 H 6 ) and near-infrared (NIR) emission ( 3 H 4 → 3 H 6 ) as well as weak red emission ( 1 G 4 → 3 F 4 ) of Tm 3+ were observed under 980 nm excitation. The concentration quenching processes for blue and NIR emissions were discussed. The blue emission intensity has a cubic dependence on the fiber laser working current, indicating a three-photon process involved in blue UC emission. The blue emission and its concentration quenching process for Tm 3+ /Yb 3+ codoped Gd 2 (WO 4 ) 3 phosphors were also investigated under 808 nm excitation. Weak blue emission ( 1 D 2 → 3 F 4 ) was detected in the UC spectra other than the weak red emissions ( 1 G 4 → 3 F 4 , 3 F 2,3 → 3 H 6 ). The dominant mechanism for blue emission under 808 nm excitation was attributed to the back energy transfer (BET) Tm 3+ → Yb 3+ and the energy transfer (ET) Yb 3+ → Tm 3+ processes. Upon 808 nm excitation, a two-photon process was deduced from the quadratic dependence of blue UC emission intensity on the fiber laser working current. [ABSTRACT FROM AUTHOR]

Sm 3+ doped silicate glasses were synthesized via a conventional melt-quenching and annealing technique. Optical transition properties of Sm 3+ in the studied silicate glass were evaluated in the framework of Judd–Ofelt theory. The radiative transition rates, fluorescence branching ratios and intrinsic lifetime for interested transitions or level were obtained. Concentration quenching, energy transfer and thermal stability were studied by fluorescence spectra and decay curves. It was found that the main reason for concentration quenching was nonradiative energy transfer through cross-relaxation mechanism due to dipole–dipole interaction. The temperature-dependent fluorescence emission was studied in detail, and it was found that crossover mechanism based on the Arrhenius model can well explain the fluorescence temperature quenching behavior of 4 G 5/2 level. [ABSTRACT FROM AUTHOR]

The effect of reduction on microstructure evolution and mechanical properties in a near α-Zr alloy (Zr0.5Be, wt%) has been studied in detail during cold rolling. The results indicate that the strength of (002)α texture increases gradually with the increase of reduction, which can be attributed to the activation of base slip of α phase under high stress concentration. In the process of cold rolling reduction from 0% to 70%, deformation mode of the α-laths changes from rigid rotation along the RD direction to plastic strain gradually. Microscopic analysis results show that the dislocation slip dominates the plastic behavior of the alloy and the evolution path of the microstructure can be described as: (I) the stage of increasing dislocation density, (II) the stage of dislocation wall and dislocation cell formation, (III) the stage of subgrain formation, and (IV) the stage of nanocrystalline formation. Also, as the reduction increases from 0% to 70%, the tensile strength increases while the fracture elongation decreases. The sample subjected to 70% reduction can display the highest ultimate tensile strength (~ 930 MPa) and retain a fracture elongation of 8.6%. The combined effects of fine grain strengthening, dislocation strengthening and strain hardening play a leading role in the increase of strength and decrease of fracture elongation. • High stress concentration leads to the enhancement of (002) α texture. • Deformation mode of the α-laths changes from rigid rotation to plastic deformation. • The formation process of nanoscale grains is analyzed in detail. • CR-70% sample has the highest σ b (~ 930 MPa) and good ε f (~ 8.6%). [ABSTRACT FROM AUTHOR]

• Three-primary color up-conversion luminescence are achieved in Yb3+ sensitized La 2 Mo 2 O 9. • Up-conversion luminescence properties and mechanisms of Yb3+ sensitized Tm3+, Er3+, and Ho3+ are investigated. • FIR from thermally coupled and non-thermally coupled energy levels of La 2 Mo 2 O 9 :Yb3+,Er3+/Tm3+/Ho3+ are used for temperature sensing. • Highly-sensitive optical temperature sensing behavior is realized. In this paper, a series of Yb3+,Er3+/Tm3+/Ho3+ co-doped La 2 Mo 2 O 9 with three-primary color up-conversion luminescence are synthesized using the solid state reaction method. The luminescence characteristics and mechanisms of La 2 Mo 2 O 9 :Yb3+,Er3+/Tm3+/Ho3+ phosphors excited by 980 nm are investigated in detail. The increased probability of 5I 6 →5I 7 is an important cause of strong red emission in the Yb3+,Ho3+ co-doped La 2 Mo 2 O 9. Furthermore, the optical temperature sensing performance are evaluated according to the typical thermally coupled and non-thermally coupled levels of Yb3+,Er3+/Tm3+/Ho3+ co-doped systems. The maximum relative sensitivity and absolute sensitivities are 1.15% K−1 and 10.03 × 10−3 K−1 for La 2 Mo 2 O 9 :Yb3+,Er3+; 2.29% K−1 and 0.284 × 10−3 K−1 for La 2 Mo 2 O 9 :Yb3+,Tm3+; and 0.30% K−1 and 20 × 10−3 K−1 for La 2 Mo 2 O 9 :Yb3+,Ho3+, respectively. The multi-color up-conversion luminescence phosphors with high temperature sensing sensitivities present broad application prospects in the fields of anti-counterfeiting, three-dimensional display, and non-contact temperature sensing. [ABSTRACT FROM AUTHOR]

• A series of novel Ti–Zr–Mo alloys for biomedical application were prepared. • A single stable β alloy can be obtained when the Mo content is 15 wt%. • The biocompatibility of the alloy consisting of a single β-phase is better. • The corrosion resistance of the alloy with Mo is stronger than that without Mo. • The strength and plasticity increased obviously with the increase of Mo addition. [Display omitted] In this work, the microstructure, mechanical properties and biocompatibility of a novel Ti-Zr- x Mo (x = 0, 5, 10, 15, 20 wt%) alloys were systematically studied. A single stable β-phase is obtained in this study when the Mo content reaches 15 wt%. And the Ti-Zr-10Mo alloy reaches a maximum strength of about 1100 MPa due to the mechanism of second phase strengthening, solid solution strengthening and fine grain strengthening. However, the plasticity of the alloy is poor due to the precipitation of α' phase near the grain boundaries. Meanwhile, the biocompatibility of the alloy is discussed in this paper through in vitro experimental characterization, and it is found that the biocompatibility of the alloy consisting of a single β-phase is better. [ABSTRACT FROM AUTHOR]

Abstract: This study reports the synthesis of Zn2SnO4 (ZTO) nanowires with various morphologies using thermal evaporation without a metal catalyst. X-ray diffraction patterns show that the structure of the as-synthesized ZTO nanowires is a face-centered cubic spinel phase. Scanning electron microscopy images exhibit that the as-synthesized nanowires have various morphologies, and homogeneously cover the area of interest. High-resolution transmittance electron microscopy reveals that these ZTO nanowires have single crystalline microstructures with four morphologies. The results of low-temperature cathodoluminescence (CL) measurements show the crystal defects of oxygen vacancies and interstitials may contribute to blue-green and yellow-orange emissions, respectively, for the as-synthesized single nanowire. This study also discusses the effects of thermal annealing under oxygen-rich and reducing ambient on the CL properties of the single ZTO nanowire. [Copyright &y& Elsevier]