（Y,Zn,Sr）3（P,VO4）：Eu^3＋,Bi^3＋发光性质的研究

合成了组成为（Ｙ，Ｚｎ，Ｓｒ）３（Ｐ，ＶＯ４）：Ｅｕ＾３＋，Ｂｉ＾３＋的荧光材料，经Ｘ射线结构分析确定为Ｚｎ３（ＰＯ４）２结构，属于单斜晶系，空间群为Ｐ２１／ｎ。讨论了基质组成对Ｅｕ＾３＋离子发光性质的影响，用Ｙ＾３＋取代了一部分Ｚｎ＾２＋；用ＶＯ４取代了一部分ＰＯ４由于基质的４３６ｎｍ发射与Ｅｕ＾３＋的激发态能级的能量重叠，Ｅｕ＾３＋产生较强的５９８ｎｍ和６１８ｎｍ发射。另外，掺入少量Ｂｉ＾３＋     

美能达α-3 系出名门,一脉相承

本刊讯 美能达公司推出准专业级的α-7和摄影爱好者最佳柏挡α-5之后,深受广大用户的好评。近期,公司又推出了一款性价比相当高的普及型入门相机美能达α-3,α-3继承了美能达一贯推崇的产品理念,     

Crystal growth,structure, infrared spectroscopy,and luminescent properties of rare-earth gallium borates RGa3(BO3)4, R = Nd,Sm–Er,Y

Crystals of the rare-earth gallium borates RGa₃(BO₃)₄, where R = Nd, Sm–Er, or Y, were grown by the flux method. The crystal structures of RGa₃(BO₃)₄ (R = Eu, Ho) were studied on the basis of single-crystal X-ray diffraction measurements. The hexagonal unit-cell parameters are a = 9.4657(1) Å, c = 7.4667(1) Å and a = 9.4394(2) Å, c = 7.4322(1) Å for EuGa₃(BO₃)₄ and HoGa₃(BO₃)₄, respectively, space group R32. Structure model was determined by “charge flipping” method and refined to R = 1.93% [EuGa₃(BO₃)₄] and R = 1.89% [HoGa₃(BO₃)₄] in anisotropic approximation. All grown gallium borates were investigated by infrared (IR) spectroscopy technique in a middle and far IR region. IR spectra of rare-earth gallium borates correspond to a pure rhombohedral (R32) polytype structure. Small inclusions of a monoclinic phase were detected only in Eu and Nd compounds. Luminescence of Eu and Ho gallium borates was studied at room temperature. The measured decay times for the most intensive emission lines of EuGa₃(BO₃)₄ (∼614 nm) and HoGa₃(BO₃)₄ (434 nm) are 940 μs and 140 μs, respectively. The scheme of crystal-field energy levels of Eu³⁺ in EuGa₃(BO₃)₄ was built on the basis of the temperature-dependent optical transmission measurements combined with the luminescence data. The measured UV absorption edge for RGa₃(BO₃)₄ is at about 300 nm.     

Synthesis, magnetization, and photocatalytic activity of LaFeO3 and LaFe0.9Mn0.1O3−δ

LaFe_0.9Mn_0.1O_3?δ and LaFeO₃ were synthesized and characterized by X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared, XPS techniques, UV–Visible absorption spectra techniques, vibrating sample magnetometer, and room temperature Fe⁵⁷ Mössbauer spectra. They were also evaluated for their photocatalytic activity toward the degradation of methyl orange under the sunlight irradiation. The experimental results show that the catalytic activities of the Mn-doped in LaFeO₃, i.e., LaFe_0.9Mn_0.1O_3?δ were much higher than those of LaFeO₃ due to its higher oxygen vacancies, variable valency Mn ions and the strong absorption in visible light, and it has higher magnetic property than that of LaFeO₃ due to the existence of Mn³⁺/Fe³⁺and Mn³⁺/Mn⁴⁺double exchange interaction in LaFe_0.9Mn_0.1O_3?δ. The LaFe_0.9Mn_0.1O_3?δ is the photocatalyst with intrinsic magnetic property and visible light activity, and it is applicable to the magnetic separation process for its higher saturated magnetization (M _s), lower coercivity (H _c), and remanent magnetization (M _r) as well as the superparamagnetic contribution in the sample, and it can be reusable and maintain relatively high activity.     

Structural,dielectric, and reflection characterization of 0.96 ZnxMg1−xTiO3–0.04 SrTiO3 ceramics

Journal of Materials Science: Materials in Electronics - The impact of Zn substitution on structural, dielectric, and reflection properties of the pure MgTiO3 and 0.96 ZnxMg1?xTiO3–0.04...     

全球领先,3D打印飞机零件

<正>"我们的技术将在先进制造领域掀起新一轮的革命。"日前,华中科技大学机械科学与工程学院教授张海鸥携其研发的"智能微铸锻铣复合制造技术",与法国空客公司举行了技术合作签约仪式,这是法中两国在先进制造领域的一项重要合作。这位年过60岁的老人和夫人王桂兰一起,带领团队用14年的时间,破解了困扰金属3D(三维)打印的世界级技术难题,实现了我     

Polymorphism of Ferroelectric, Ferroelastic, Superionic Crystals K3Nb3B2O12 and K3– x Na x Nb3B2O12

Data are presented on the phase transitions and physical properties of K₃Nb₃B₂O₁₂ (KNB) and K_{3 –} Na _x Nb₃B₂O₁₂ (KNNB) crystals. Detailed measurements of the dielectric permittivity, nonlinear optical properties, and electrical conductivity, as well as examination of the domain structure, demonstrate that KNB and KNNB exhibit a complex polymorphism: both have eight different polymorphs between –100 and 900°C. The introduction of Na into KNB raises the transition temperatures, which makes it possible to investigate the low-temperature phases at room temperature. The high-temperature phase transition is antiferroelectric, whereas the other transitions are of a ferroelectric–ferroelastic nature. Along with complex polymorphism, KNB and KNNB exhibit superionic conductivity.     

Synthesis of cubic boron nitride using Mg and pure or M′-doped Li3N,Ca3N2 and Mg3N2 with M′=Al,B, Si,Ti

The growth pressure-temperature region of cubic boron nitride (cBN) in the systems Mg-BN and MxNy-BN (MxNy=Li₃N, Ca₃N₂, Mg₃N₂) has been redetermined using well-crystallized hexagonal BN (hBN) with low oxygen content (0.2%) as the starting material. The data on the MxNy-BN systems are compatible with the existence of two growth regions: a high-temperature region where cBN grows from a liquid phase, and a low-temperature region where cBN forms from solid-solid reactions. Previous data are discussed according to this model and possible solid-state reactions are proposed on the basis of thermodynamic considerations. The results for the Mg-BN system confirm the effect of the O₂ content of the starting BN on the cBN growth region. The systems (MxNy + M)-BN (M=Al, B, Si, Ti) have been shown to produce cBN crystals of increased size and improved morphology (more compact and perfect) compared to those obtained with the MxNy-BN systems. Their colour is dark or black and their size reaches 0.6 mm. The effect of the relative proportions of M and MxNy on the growth region and yield has been determined and is discussed on the basis of the chemical reactions likely to occur.     

Butterfly-shaped multiferroic BiFeO3@BaTiO3 core–shell nanotubes: the interesting structural, multiferroic, and optical properties

Highly pure butterfly-shaped BiFeO₃@BaTiO₃ nanotubes have been synthesized through a sol–gel method. An obvious ferromagnetic behavior was obtained at room temperature, with a large coercive field (5,403 Oe) and high Mr/Ms value (0.52). The dielectric permittivity of BiFeO₃@BaTiO₃ nanotubes was found to be 1919, which is much higher than that of pure BFO nanostructure. The dielectric loss of BiFeO₃@BaTiO₃ nanotubes is low in the frequency range from 10 Hz to 1 MHz. The maximum magnetoelectric coefficient of BiFeO₃@BaTiO₃ nanotube is 0.272 μV/cm Oe. Moreover, the BiFeO₃@BaTiO₃ nanotubes have exhibited a better ferroelectric property with a large band gap of 3.2 eV which demonstrates the core–shell nanostructure.     

Structure,Performance, and Application of BiFeO3 Nanomaterials

Multiferroic nanomaterials have attracted great interest due to simultaneous two or more properties such as ferroelectricity,ferromagnetism,and ferroelasticity,which can promise a broad application in multifunctional,lowpower consumption,environmentally friendly devices.Bismuth ferrite(BiFeO3,BFO)exhibits both(anti)ferromagnetic and ferroelectric properties at room temperature.Thus,it has played an increasingly important role in multiferroic system.In this review,we systematically discussed the developments of BFO nanomaterials including morphology,structures,properties,and potential applications in multiferroic devices with novel functions.Even the opportunities and challenges were all analyzed and summarized.We hope this review can act as an updating and encourage more researchers to push on the development of BFO nanomaterials in the future.     

Synthesis,structural studies,electrical conductivity and optical properties of new Sb2−xLnxTe3 (Ln: Lu3+, Er3+ and Ho3+) nanomaterials

Ln-doped Sb₂Te₃ (Ln: Lu³⁺, Er³⁺, Ho³⁺) nanomaterials were synthesised by a co-reduction method in hydrothermal condition. Powder X-ray diffraction (XRD) patterns indicate that the Ln_xSb_2?xTe₃ crystals (Ln = Lu³⁺, x = 0.00–0.06; Er³⁺ and Ho³⁺ x = 0.00–0.04) are isostructural with Sb₂Te₃. The cell parameter a decreases for Ln_xSb_2?xTe₃ compounds upon increasing the dopant content (x), while c increases. Scanning electron microscopy and transmission electron microscopy images show that doping of Lu³⁺ and Ho³⁺ ions in the lattice of Sb₂Te₃ results in spherical nanoparticles while that in Er³⁺ leads to hexagonal nanoplates, respectively. The electrical conductivity of Ln-doped Sb₂Te₃ is higher than that of pure Sb₂Te₃ and increases with temperature. By increasing the concentration of Ln³⁺ ions, the absorption spectrum of Sb₂Te₃ shows red shifts and some intensity changes. In addition to the characteristic red emission peaks of Sb₂Te₃, emission spectra of doped materials show other emission bands originating from f–f transitions of the Ho³⁺ ions.     

X-ray structure determination and analysis of hydrogen interactions in 3, 3′-dimethoxybiphenyl

The crystal structure of 3, 3′-dimethoxybiphenyl has been determined by X-ray diffraction methods with an aim of describing the hydrogen interaction in biphenyl derivatives. The title compound crystallizes in monoclinic space groupP2₁/c with unit cell dimensions,a = 7.706(1),b = 11.745(2),c = 12.721(2) Å, β = 92.31(1)°,Z = 4 and its structure has been refined up to the reliability index of 3.8%. The average torsion angle about the inter-ring C-C bond is 37.5°. The O1 and Ol′ atoms of the methoxy group are deviated by 0.046(1) Å and 0.234(1) Å from the mean planes of respective rings. The crystal cohesion is pronounced due to three-inter-molecular C-H...O hydrogen bonds.