Microstructures and mechanical properties of Mg-8Gd-0.6Zr-xNd (x=0, 1, 2 and 3 mass%) alloys

Mg-8Gd-0.6Zr-xNd (x = 0, 1, 2 and 3 mass%) alloys were prepared by metal mould casting method, and the microstructures, age hardening responses and mechanical properties have been investigated. The microhardness of the as-cast alloys is increased with increasing Nd content. The age hardening behavior and mechanical properties are enhanced significantly by adding Nd element. The peak ageing hardness of the Mg-8Gd-0.6Zr-3Nd alloy is 103, it is about 1.3 times more than that of the Mg-8Gd-0.6Zr alloy. The aged Mg-8Gd-0.6Zr-3Nd alloy exhibits maximum ultimate tensile strength and yield strength, and the values are 271 and 205 MPa at room temperature, 205 MPa and 150 MPa at 250 degrees C, respectively. Which are about 2 times higher than those of Mg-8Gd-0.6Zr alloy. The improved hardness and strength are mainly attributed to the fine dispersiveness Of Mg5RE and Mg12RE precipitates in the alloy.

Ti基准晶材料制备和贮氢性能研究进展

Ti基准晶材料具有热力学稳定的正二十面体构造,表现出特殊的传输特性、贮氢特性和力学特性等,相关研究受到广泛关注.近年,作者所在研究组在Ti基准晶的制备和贮氢性能研究方面取得了一些新进展.综合报道了Ti-Zr-Ni-Cu系准晶相及其复合相材料的制备和贮氢性能.

Microstructure and some dynamic performances of Ti0.17Zr0.08V0.34RE0.01Cr0.1Ni0.3 (RE = Ce, Dy) hydrogen storage electrode alloys

Microstructure and some dynamic performances of Ti0.17Zr0.08V0.34RE0.01Cr0.1Ni0.3 (RE=Ce, Dy) hydrogen storage electrode alloys have been investigated using XRD, FESEM-EDS, ICP-MS and EIS measurements. The alloy is composed of V-based solid solution phase with a dendritic shape and a continuous C14 Laves phase with a network shape surrounding the dendrite. Pressure-composition isotherm curves indicate that the alloy with Dy addition has a lower equilibrium hydrogen pressure and a wider plateau region. The alloy electrode with Dy addition has higher discharge capacity, while the alloy electrode with Ce addition has better activation and higher cycle stability. The alloy electrode with Ce addition has better electrochemical activity with higher exchange current density (127.5 mA g(-1)), lower charge transfer resistance (1.37 Omega) and lower apparent activation energy (30.5 kJ mol(-1)). The capacity degradation behavior for the alloy electrode is attributed to two main factors: one is the dissolutions of V and Zr element to KOH solution, and another is the larger charge transfer resistance which increases with increasing cycle number.

Preparation of CeO2-ZrO2 ceramic fibers by electrospinning

Electrospinning was employed to fabricate polymer-ceramic composite fibers from solutions containing poly(vinyl pyrrolidone) (PVP), Ce(NO3)(3)(.)6H(2)O and ZrOCl2-8H(2)O. Upon firing the composite fibers at 1000 degrees C, Ce(0.67)Zr(0.33)O(2)fibers with diameters ranging from 0.4 to 2 mu m were synthesized. These fibers exhibit strong resistance to sintering. They still have specific surface area around 11.8 m(2)/g after being heated at 1000 degrees C for 6 h.

Preparation and chracaterization of novel graft copolymers of LLDPE

A series of novel fluorine surfactants, a, b, c, d, e and their acrylates, A, 13, C, D and E, were synthesized via poly( ethylene oxide) ( PEG) ( 200, 600, 1000, 2000, 5000) and perfluorooctane poly (ethylene oxide) ether as the main starting materials. Their chemical structures were characterized by means of FTIR and H-1 NMR. The surface activity and surface tension( y) of surfactants a, b, c, d and e were evaluated by maximum bubble pressure method. Surfactants A, 13, C, D and E were adopted as the grafting monomers of linear low density polyethere( LLDPE), and grafting reaction was carried out by melt reactive extrusion procedure. Their surface properties were characterized with measuring contact angle and XPS. It was found that the hydrophilic property of the graft copolymers was better than the palin LLDPE. Thermal properties of graft copolymers were studied by DSC. It was found that their crystalline temperatures of graft copolymers were faster than that of the plain LLDPE.

Effect of swelling response of the support particles on ethylene polymerization

Macroporous and modified macroporous poly(styrene-co-methyl methacrylate-co-divinylbenzene) particles (m-PS and mm-PS) supported Cp2ZrCl2 were prepared and applied to ethylene polymerization using methylaluminoxane (MAO) as cocatalyst. The influences of the swelling response of the support particles on the catalyst loading capabilities of the supports as well as on the activities of the supported catalysts were studied. It was shown that the Zr loadings of the supports and the activities of the supported catalysts increased with the swelling extent of the support particles. The m-PS or mm-PS supported catalysts exhibited very high activities when the support particles were well swollen, whereas those catalysts devoid of swelling treatment gave much lower activities. Investigation on the distribution of the supports in the polyethylene by TEM indicated that the swelling of the support particles allowed the fragmentation of the catalyst particles. In contrast, the fragmentation of the support particles with poor swelling was hindered during ethylene polymerization.

Structural stability and electronic state of transition metal trimers

Ground state geometries were searched for transition metal trimers Sc-3, Y-3, La-3, Lu-3, Ti-3, Zr-3, and Hf-3 by density functional methods. For all the studied trimers, our calculation indicates that the ground state geometries are either equilateral triangle (Zr-3 and Hf-3) or near equilateral triangle (Ti-3, Sc-3, Y-3, La-3, and Lu-3). For rare earth trimers Sc-3, Y-3, La-3, and Lu-3, isosceles triangle (near equilateral triangle) at quartet state is the ground state. Isosceles triangle at doublet state is the competitive candidate for the ground state. For Zr-3 and Hf-3, equilateral triangle at singlet state is the most stable. For Ti-3, isosceles triangle (near equilateral triangle) at quintet state gives the ground state. For Sc-3, Zr-3, and Hf-3, where experimental results are available, the predicted geometries are in agreement with experiment in which the ground state is equilateral triangle (Zr-3) or fluxional (Sc-3 and Hf-3). For Y-3, the calculated geometry is in agreement with experimental observation and previous theoretical study that Y-3 is a bent molecule for the ground state.

Synthesis and photoluminescence properties of erbium-doped BaF2 nanoparticles

Erbium-doped BaF2 nanoparticles were prepared from the microemulsion of cetyl trimethyl ammonium bromide (CTAB), n-butanol, n-octane and water. The X-ray diffraction (XRD) patterns were indexed to a pure BaF2 cubic phase. Transmission electron microscopy (TEM) images showed that BaF2 products were monodispersed with 15-20 nm in size at the dopant concentration of 0.06 mol%. At higher dopant concentration, there was no significant increase in particle size, but more polydispersed. Photoluminescence (PL) properties of the final products were examined. We can observe fluorescence of Er3+ around 1540 nm and with the increase of dopant concentration, the fluorescent intensity increases.

Surprising arching sheet-like dendrites growing from BaF2 nanocubes

BaF2 nanocubes were prepared from quaternary reverse micelles of cetyl trimethyl ammonium bromide (CTAB), n-butanol, n-octane, and water. Interestingly, there are arching sheet-like dendrites growing between two neighbouring sides of these cubes. X-ray powder diffraction (XRD) analysis showed that the products were BaF2 single phase. Scanning electron microscopy (SEM) or transition electron microscopy (TEM) was used to estimate the size of the final products. The results showed that the shape and size of particles were strongly dependent on the reaction conditions, such as the temperature and reaction time. When the reaction temperature was 25 degreesC, we obtained cuboid-like particles with 'clean' surfaces (no dendrites growing on them), and when the temperature was 35 degreesC, we obtained nanocubes with dendrites growing from them between the neighbouring sides. The influence of reaction time at a temperature of 35 degreesC is also discussed.

Pink light emitting long-lasting phosphorescence in Sm3+-doped CdSiO3

Novel pink light emitting long-lasting afterglow CdSiO3:SM3+ phosphors are prepared by the conventional high-temperature solid-state method and their luminescent properties are investigated. XRD and photolurflinescence (PL) spectra are used to characterize the synthesized phosphors. The phosphors are well crystallized by calcinations at 1050degreesC for 5 h. These phosphors emit pink light and show long-lasting phosphorescence after they are excited with 254 nm ultraviolet light. The phosphorescence lasts for nearly 5 h in the light perception of the dark-adapted human eye (0.32mcd/m(2)). The phosphorescence mechanism is also investigated. All the results indicate that these phosphors have promising potential practical applications.

Spectra and long-lasting properties of Sm3+-doped yttrium oxysulfide phosphor

We reported, for the first time to the best of our knowledge, the Sm3+ -doped yttriurn oxysulfide phosphors has reddish orange long-lasting phosphorescence. The phosphor show prominent luminescence in reddish orange due to the electronic transitions of (4)G(5/2) --> H-6(J) (J = 5/2, 7/2, 9/2), the afterglow color of this type of phosphors is a mixture of the three above mentioned electronic transition emissions and have a little different when the concentration of the Sm3+ dopant changes. Synthesis procedure of the Sm3+-yttrium oxysulfide reddish orange phosphor through the flux fusion method with binary flux compositions was presented. The synthesized phosphors were analyzed using X-ray diffraction (XRD) to interpret the structural characterization. The XRD analysis result reveal that the Y2O2S:Sm3+ phosphor synthesized with a binary flux composition containing (S and Na2CO3 at a ratio of 1: 1 at 30 wt.% of total raw material) at 1050degreesC for 3 h was in single-phase. Luminescence properties of the Y2O2S:Sm3+ long-lasting phosphor was analyzed by measuring the excitation spectra, emission spectra and afterglow decay curve. The mechanism of the strong afterglow from Y2O2S:Sm3+ was also discussed in this paper.

Synthesis and fluorescence of europium-doped barium fluoride cubic nanocolumns

Europium-doped barium fluoride cubic nanocolumns were synthesized from the quaternary water in oil reverse microemulsions In this process, the aqueous cores of water/cetyl trimethyl ammonium bromide (CTAB)/n-butanol/n-octane reverse microemulsions were used as microreactors for the precipitation of europium doped barium fluoride. XRD analysis shows that under the dopant concentration of 0.06% (molar fraction), the products are single phase. The result products are cubic column-like with about 30 similar to 50 nm edge length of cross section, and about 200 nm of length obtained from the transmission electron microscopy (TEM), and atomic force microscopy (AFM). Under the 0.06 % (molar fraction) of dopant concentration I the fluorescence of Eu2+ and Eu3+ under the 589 of excitation wavelength is observed.

Long-lasting properties of rare earth-doped Y2O2S phosphors

The aim of this presentation is to report a new result of afterglow materials. The Y2OS: Ln(3+) (Ln = Sm, Tm) phosphors show bright reddish orange and orange-yellow colors when excited by UV or visible light. The main spectroscopic characterizations of Sin(3+) and Tin(3+) in yttrium oxysulfide and their long-lasting phosphorescence were measured and discussed in this presentation. Their long-lasting phosphorescence can be seen by the naked eyes clearly for about one hour in the dark room after the Irradiation light sources were removed. XRD and photoluminescence (PL) spectra as well as the luminance decay were used to characterize these long-lasting phosphorescence phosphors. The results of XRD indicate that the products synthesized through the flux fusion method tinder 1050 degreesC, for 6 It have a good crystallization without any detectable amount of impurity phase. Both the PL spectra and luminance decay results reveal that these phosphors have efficient luminescent and good long-lasting properties. We believe that the experimental data gathered in our present work will be. useful in finding some new long-lasting phosphors with different colors.

Luminescence properties of rare earth ions in cadmium metasilicate

The luminescence properties of CdSio(3):RE3+ phosphors doped with various rare earth ions are reported. The series of rare earth ions doped CdSiO3 phosphors are prepared by the conventional high-temperature solid-state method, and characterized by XRD and photoluminescence (PL) spectra. The results of XRD measurement indicate that the products fired under 1050 degreesC for 3 h have a good crystallization without any detectable amount of impure phase. The PL spectra measurement results show that CdSiO3 is a novel self-activated luminescent matrix. When rare earth ions such as Y3+, La3+, Gds(3+), Lus(3+), Ce3+, Nd3+, Ho3+, Era(3+), Tm3+ and Yb3+ are introduced into the CdSi03 host, one broadband centered at about 420 nm resulted from traps can be observed. In the case of other earth ions which show emissions at the visible spectrum region, such as Pr3+, Sm3+, Eu3+, Tb3+ and Dy3+, the mixture of their characteristic line emissions with the similar to 420 nm strong broadband luminescence results in various emitting colors. As a consequence, different emitting colors can be attairied via introducing certain appropriate active ions into the CdSiO3 matrix. In additional, this kind of phosphors shows good long-lasting properties when excited by UV light. All the results show that CdSiO3 is a potential luminance matrix.

A novel white light emitting long-lasting phosphor

A novel white light emitting long-lasting phosphor Cd1-xDyxSiO3 is reported in this letter. The Dy3+ doped CdSiO3 phosphor emits white light. The phosphorescence can be seen with the naked eye in the dark clearly even after the 254 nm UV irradiation have been removed for about 30 min. In the emission spectrum of 5% Dy3+ doped CdSiO3 phosphor, there are two emission peaks of Dy3+, 580 mn (F-4(9/2)-->H-6(13/2)) and 486 nm (F-4(9/2)-->H-6(15/2)), as well as a broad band emission located at about 410 nm. All the three emissions form a white light with CIE chromaticity coordinates x=0.3874, y=0.3760 and the color temperature is 4000 K under 254 mn excitation. It indicated that this phosphor is a promising new luminescent material for practice application.