Solid-state phase equilibria in the Gd–Co–Al ternary system at 1173 K

A portion of the isothermal section (1173 K) of the phase diagram of the Gd–Co–Al ternary system (up to 33.3 at.% Gd) were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS) techniques. Fourteen single-phase regions (including solid solution regions of the binary compounds), twenty-five two-phase regions and twelve three-phase regions were found to exist at this isothermal section. In the GdCo₂–GdAl₂ system, the existence of the GdCo_0.74Al_1.26 phase is identified and it has a composition range of 30–45 at.% Al, the maximum solid solubility of Al in GdCo₂ is about 15 at.%, and Co in GdAl₂ is about 16 at.%. Besides, the maximum solid solubility of Al in Co, Gd₂Co₁₇ and GdCo₅ is about 6, 17 and 25 at.%, respectively, the maximum solid solubility of Gd in Co, CoAl is below 2 at.% and the solid solubility range is from 47 to 61 at.% Al in CoAl phase. In this work, no new ternary compounds were observed.     

Energy transfer and frequency upconversion in Yb, Er co-doped sodium–lead–germanate glasses

Yb³⁺–Er³⁺ co-doped Na₂O–GeO₂–PbO glass suitable for developing optical fiber lasers and amplifiers has been fabricated. The energy transfer efficiency from Yb³⁺ to Er³⁺ was investigated in the glasses with different Yb³⁺–Er³⁺ concentration ratios and the maximum energy transfer efficiency was found to be 67% at the Yb³⁺–Er³⁺ concentration ratio of 5:1. Subsequently, the studies of upconversion emissions in the visible range were performed. An intense green together with a relatively weak red emission was observed under the excitation of 976 nm diode laser. The quadratic dependence of the green emission on excitation power indicates that a two-photon absorption process occurs under a 976 nm excitation. However, for the red emission the slope of log-log plot of integrated intensity versus pump power declines with increasing Yb³⁺ ions content, indicating it is not resulted from a biphotonic process.     

Thermodynamic analysis and assessment of the Ce–Ni system

An optimised set of thermodynamic parameters for the Ce–Ni system has been obtained using the CALPHAD approach. A thorough thermodynamic analysis of the system has been carried out using different calorimetric techniques and the data have been used in the assessment. The free energy of the liquid phase has been described as a function of temperature and composition using a Redlich–Kister polynomial. Solid compounds have been considered as stoichiometric with the exception of the Laves phases. The phase diagram and thermodynamic quantities calculated from assessed parameters agree well with experimental data.     

一种航空用直线直流步进电机控制系统设计

研究了一种飞机油阀用直线直流步进电机及其控制系统。混合式直线直流步进电机直流驱动替代目前的有刷直流电动机的间接驱动,简化了繁琐的蜗轮蜗杆机构;细分技术使步进电机运行平稳,消除了间接驱动的弊端,提高了飞机油阀驱动控制系统的技术水平。     

稀土永磁无刷直流电动机转矩脉动研究

对方波驱动的稀土永磁无刷直流电动机转矩脉动产生的原因进行了分析,在理论分析的基础上研究了削弱转矩脉动的方法并进行了仿真,结果表明,此方法简单、可靠,能有效抑制电机运行时的转矩脉动。     

稀土湿法生产过程中放射性核素的迁移及对公众所致辐射剂量研究

描述了稀土矿湿法生产过程中放射性核素的迁移规律,并对四川省冕宁稀土矿湿法分离工艺进行分析研究。结果表明,稀土湿法冶炼过程中大部分放射性钍富集在废渣和产品中,仅有1.03%的钍粉尘排入大气,0.27%的放射性钍进入废水。对排入环境中的气载和液载放射性钍的辐射剂量进行了计算,其结果分别为6.02×10-2 mSv·a-1、1.43×10-2 mSv·a-1,该值低于公众个人剂量基本限值(1mSv·a-1),工作人员个人最大有效剂量为7.67×10-2 mSv·a-1     

Magnetocaloric effect in Gd(1−y)DyyAl2

In this work we calculate the magnetic properties and the magnetocaloric effect in Gd_1−yDy_yAl₂ (y = 0, 0.25, 0.5, 0.75 and 1). The model Hamiltonian includes contributions from the Zeeman effect, the crystalline electrical field anisotropy and the exchange interactions among Gd–Gd, Gd–Dy and Dy–Dy ions. To obtain a composite with ΔS_T as constant as possible in the temperature range from T = 60 K to 170 K, the appropriate concentrations of the five compounds investigated were calculated using the Smaili and Chahine method. The magnetization and ΔS_T dependences on temperature in the composite were simulated and compared with the partial contributions of the single magnetic component materials. Also, the magnetic field dependence on magnetization was investigated in Gd_0.25Dy_0.75Al₂, where the discontinuous spin reorientation transitions were predicted for magnetic fields lower than 2 T, applied along <110> direction.     

Luminescence at 2.8 μm: Er3+-doped chalcogenide micro-waveguide

This paper reports the fabrication of luminescent optical rib/ridge waveguides made of erbium doped Ga-Ge-Sb-S films deposited by RF magnetron sputtering. Several fluorescence emissions of Er³⁺ ions from the visible to the middle infrared spectral domain were clearly observed within the films. The study of the ⁴I_13/2 level lifetime enabled development of a suitable annealing treatment of the films to reach the value of the bulk counterpart while the variation in surface roughness was limited, thus ensuring reasonable optical losses (0.7–0.9 dB/cm). Amplification experiments were carried out at 1.54 μm leading to complete characterization of the erbium-doped micro-waveguide with ∼3.4 dB/cm on/off gain. A demonstration of mid-IR photoluminescence from Er³⁺-doped chalcogenide micro-waveguide was recorded at ∼2.76 μm. The multi-luminescence from the visible to mid-IR generated using erbium doped chalcogenide waveguiding micro-structures might find easy-to-use applications concerning telecommunication technologies or on-chip optical sensors for which luminescent sources or amplifiers operating at different wavelengths are required.     

Structural,electronic, elastic,mechanical and thermal behavior of RESn3(RE = Y,La and Ce) compounds: A first principles study

The structural, electronic, elastic, mechanical and thermal properties of the isostructural and isoelectronic nonmagnetic RESn₃ (RE = Y, La and Ce) compounds, which crystallize in AuCu₃-type structure, are studied using first principles density functional theory based on full potential linearized augmented plane wave (FP-LAPW) method. The calculations are carried out within PBE-GGA, WC-GGA and PBE-sol GGA for the exchange correlation potential. Our calculated ground state properties such as lattice constant (a₀), bulk modulus (B) and its pressure derivative (B′) are in good agreement with the experimental and other available theoretical results. We first time predict the elastic constants for these compounds using different approximations of GGA. All these RESn₃ compounds are found to be ductile in nature in accordance with Pugh's criteria. The computed electronic band structures and density of states show metallic character of these compounds. The elastic properties including Poisson's ratio (σ), Young's modulus (E), shear modulus (G_H) and anisotropy factor (A) are also determined using the Voigt–Reuss–Hill (VRH) averaging scheme. The average sound velocities (v_m), density (ρ) and Debye temperature (θ_D) of these RESn₃ compounds are also estimated from the elastic constants. We first time report the variation of elastic constants, elastic moduli, Cauchy's pressure, sound velocities and Debye temperatures of these compounds as a function of pressure.     

Fabrication and characterization of large-core Yb/Al-codoped fused silica waveguides using dry etching

A deep inductively coupled plasma etching process was developed as a part of a continuous effort to develop an all-silica on-chip platform for high-power optical devices. Combined F and Cl based etching chemistry was found most suitable since silica matrix and Al doping are generally etched using different chemistries. First large-core (∼20 × 20 μm) Yb/Al-codoped fused silica waveguides on pure silica substrate were successfully fabricated, featuring ∼1 dB/cm optical propagation loss.