离子型稀土矿山淋洗及尾水富集试验研究

对浸矿后离子型稀土原地浸矿场采用清水进行淋洗，在184天的清水淋洗过程中，尾水氨氮值从最开始的507mg/L，降低至140mg/L，淋洗尾水pH4.52~3.10。淋洗尾水采用两级反渗透膜分离，既回收有价资源稀土，又能使出水氨氮达标。结果表明，产水氨氮浓度稳定低于15mg/L，对稀土的截留率高于98.25%，浓水中稀土离子平均浓度313.4mg/L，可进一步回收稀土资源。     

CNT-interconnected iron-doped NiP2/Ni2P heterostructural nanoflowers as high-efficiency electrocatalyst for oxygen evolution reaction

Oxygen evolution reaction (OER) plays a decisive role in electrolytic water splitting. However, it is still challengeable to develop low-cost and efficient OER electrocatalysts. Herein, we present a combination strategy via heteroatom doping, hetero-interface engineering and introducing conductive skeleton to synthesize a hybrid OER catalyst of CNT-interconnected iron-doped NiP₂/Ni₂P (Fe-(NiP₂/Ni₂P)@CNT) heterostructural nanoflowers by a simple hydrothermal reaction and subsequent phosphorization process. The optimized Fe-(NiP₂/Ni₂P)@CNT catalyst delivers an ultralow Tafel slope of 46.1 mV dec^?1 and overpotential of 254 mV to obtain 10 mA cm^?2, which are even better than those of commercial OER catalyst RuO₂. The excellent OER performance is mainly attributed to its unique nanoarchitecture and the synergistic effects: the nanoflowers constructed by a 2D-like nanosheets guarantee large specific area and abundant active sites; the highly conductive CNT skeleton and the electronic modulation by the heterostructural NiP₂/Ni₂P interface and the hetero-atom doping can improve the catalytic activity; porous nanostructure benefits electrolyte penetration and gas release; most importantly, the rough surface and rich defects caused by phosphorization process can further enhance the OER performance. This work provides a deep insight to boost catalytic performance by heteroatom doping and interface engineering for water splitting.     

地应力条件下的凿岩爆破数值模拟

为了研究地应力对凿岩爆破的影响,采用DDA方法模拟爆炸应力波作用下考虑地应力条件时的单孔和多孔凿岩爆破破岩过程。模拟发现,随着初始地应力水平的增加,裂纹扩展半径和破岩区域面积减小,裂纹发育主方向趋于地应力的最大主应力方向,初始地应力对裂纹的抑制和引导作用明显;初始地应力水平的增加,对拉伸裂纹的抑制作用更为显著,从而降低了拉伸破坏对爆破破岩的贡献。模拟也表明,在初始地应力存在的条件下,通过对爆破载荷和炮孔布置进行针对性的优化,可以克服地应力带来的影响,并取得预期的爆破效果。本研究对地应力条件下的凿岩爆破工程具有理论和参考意义。     

FeCo alloys in-situ formed in Co/Co2P/N-doped carbon as a durable catalyst for boosting bio-electrons-driven oxygen reduction in microbial fuel cells

Non-noble metal catalyst with high catalytic activity and stability towards oxygen reduction reaction (ORR) is critical for durable bioelectricity generation in air-cathode microbial fuel cells (MFCs). Herein, nitrogen-doped (iron-cobalt alloy)/cobalt/cobalt phosphide/partly-graphitized carbon ((FeCo)/Co/Co₂P/NPGC) catalysts are prepared by using cornstalks via a facile method. Carbonization temperature exerts a great effect on catalyst structure and ORR activity. FeCo alloys are in-situ formed in the catalysts above 900 °C, which are considered as the highly-active component in catalyzing ORR. AC-MFC with FeCo/Co/Co₂P/NPGC (950 °C) cathode shows the highest power density of 997.74 ± 5 mW m^?2, which only declines 8.65% after 90 d operation. The highest Coulombic efficiency (23.3%) and the lowest charge transfer resistance (22.89 Ω) are obtained by FeCo/Co/Co₂P/NPGC (950 °C) cathode, indicating that it has a high bio-electrons recycling rate. Highly porous structure (539.50 m² g^?1) can provide the interconnected channels to facilitate the transport of O₂. FeCo alloys promote charge transfer and catalytic decomposition of H₂O₂ to ?OH and ?O₂^?, which inhibits cathodic biofilm growth to improve ORR durability. Synergies between metallic components (FeCo/Co/Co₂P) and N-doped carbon energetically improve the ORR catalytic activity of (FeCo)/Co/Co₂P/NPGC catalysts, which have the potential to be widely used as catalysts in MFCs.     

In-situ measurement of mineral phase transition and kinetics in roasting process of Bayan Obo mixed rare earth concentrate by sodium carbonate

In this study, the Bayan Obo rare earth concentrates mixed with Na₂CO₃ were used for roasting research. The phase change process of each firing stage was analyzed. The kinetic mechanism model of the continuous heating process was calculated. This study aims to recover valuable elements and optimize the production process to provide a certain theoretical basis. Using X-ray diffraction (XRD), Fourier infrared spectroscopy, scanning electron microscopy with energy dispersive spectrometry, the reaction process and the existence of mineral phases were analyzed. The variable temperature XRD and thermogravimetric method were used to calculate the roasting kinetics. The phase transition results show that carbonate-like substances first decompose into fine mineral particles, and CaO, MgO, and SiO₂ react to form silicates, causing hardening. Further, REPO₄ and NaF can directly generate CeF₃ and CeF₄ at high temperatures, and a part of CeF₄ and NaF forms a solid solution substance Na₃CeF₇. Rare earth oxides calcined at a high temperature of 750 °C were separated to produce Ce_0.6Nd_0.4O_1.8, Ce₄O₇, and LaPrO_3+x. Then, BaSO₄, Na₂CO₃, and Fe₂O₃ react to form barium ferrite BaFe₁₂O₁₉; the kinetic calculation results show that during the continuous heating process, the apparent activation energy E reaches the minimum in the entire reaction stage in the temperature range of 440–524 °C, and the reaction order n reaches the maximum, which indicates that the decomposition product REFO significantly impacts the reaction system and reduces the activation energy. The mechanism function is F(α) = [?ln (1?α)]^1/3. The reaction order n reaches the minimum in the temperature range of 680–757 °C, and the apparent activation energy E is large. The difficulty of the reaction increases during the final stage. The reaction mechanism function is F(α) = [1?(1?α)^1/3]². Observing the entire reaction stage, the step of controlling the reaction rate changes from random nucleation to three-dimensional diffusion (spherical symmetry).     

Synthesis,microstructures, and corrosion behaviors of multi-components rare-earth silicates

Multi-components and equimolar rare earth monosilicates, (Y_1/3Dy_1/3Er_1/3)₂SiO₅, (Y_1/3Dy_1/3Lu_1/3)₂SiO₅, (Y_1/4Dy_1/4Ho_1/4Er_1/4)₂SiO₅ and (Yb_1/4Dy_1/4Ho_1/4Er_1/4)₂SiO₅, were prepared by solid-state reactions and the following hot-pressing. Dense microstructures with uniform elemental distributions were obtained for all samples. These investigated multi-components monosilicates exhibit low thermal conductivities and similar coefficients of thermal expansion with SiC. Moreover, they exhibit high corrosion resistances in 1400 °C water vapor, especially, four-components (Y_1/4Dy_1/4Ho_1/4Er_1/4)₂SiO₅ and (Yb_1/4Dy_1/4Ho_1/4Er_1/4)₂SiO₅ experienced almost invariable weights after small weight losses during the initial 0.5 h. All those results indicate that multi-components rare earth monosilicates are promising candidates of environmental barrier coatings for SiC/SiC composites.     

Synthesis and luminescence enhancement of red-emitting Sr9Y(PO4)7:Eu3+ phosphor through Gd3+ co-doping for white light-emitting diodes

A series of Sr₉Y(PO₄)₇:Eu³⁺ and Sr₉Y(PO₄)₇:Eu³⁺, Gd³⁺ red-emitting phosphors were prepared via a high-temperature solid-state method, Gd³⁺ ion was co-doped in Sr₉Y(PO₄)₇:Eu³⁺ as sensitizer to enhance the luminescence property. The X-ray diffraction results verify that the structure of the as-prepared samples is consistent with the standard Sr₉Y(PO₄)₇ phase. All the Sr₉Y(PO₄)₇:Eu³⁺ samples show both characteristic emission peaks at 594 nm and 614 nm under near-ultraviolet excitation of 394 nm. The co-doping of Gd³⁺ significantly improves the luminescence intensity of the Sr₉Y(PO₄)₇:Eu³⁺ phosphors due to the crystal field environment effect and energy transfer of Gd³⁺→Eu³⁺ caused by the introduction of Gd³⁺, especially Sr₉Y(PO₄)₇:0.11Eu³⁺, 0.05Gd³⁺, which emission intensity is higher than that of Sr₉Y(PO₄)₇:0.11Eu³⁺ by 1.21 times. The color purity and lifetime of Sr₉Y(PO₄)₇:0.11Eu³⁺, 0.05Gd³⁺ phosphor are 88.26% and 3.7615 ms, respectively. A w-LED device was packaged via coating the as-prepared phosphor on n-UV chip of 395 nm with commercial phosphors. These results exhibit that the Sr₉Y(PO₄)₇:Eu³⁺, Gd³⁺ red-emitting phosphor can be used as a red component in the w-LEDs application.     

Novel energy-saving window coating based on F doped TiO2 nanocrystals with enhanced NIR shielding performance

To reduce the energy consumption of cooling in the hot summer days, searching for novel NIR shielding materials for buildings is of great value. In this report, monodispersed F doped TiO₂ nanocrystals with an average size of 8.6 nm were synthesized as novel solar shielding materials for energy-saving windows. All the products adopted an anatase TiO₂ structure. After doping of F ions, the morphology of TiO₂ was transformed from an irregular shape to a pseudospherical shape. The Raman shift and XPS depth analysis confirmed the successful doping of F⁻ ions into the lattice oxygen sites in the TiO₂ structure. The introduction of F⁻ ions generated free electrons and bulk Ti³⁺ in TiO₂ crystals, which activated a localized surface plasmon resonance (LSPR) absorption in the NIR region. Correspondingly, the NIR shielding performance of the TiO₂ films improved with increasing F doping amounts. The NIR shielding value of the films increased from 1.3% to 43.2% when the molar ratio of F to Ti increased from 0 to 0.3. The reason can be attributed to the enhanced NIR absorption induced by the increased electron concentration after doping of fluorine ions. The F–TiO₂ films showed superior visible transmittance (90.1–96.7%). Moreover, the F–TiO₂ films lowered the indoor temperature of the heat box by 5.3 °C in the thermal tests. Overall, the prepared F–TiO₂ nanocrystals show a great potential to be used for energy-saving windows.