Effect of Heat-Treatment Process on Properties of Rare Earth Mg-Based System Hydrogen Storage Alloys with AB_3-Type

The effect of heat-treatment process on the properties of Mm0.8Mg0.2(NiCoAlMn)3.5 hydrogen storage alloy was discussed. The electrochemical properties such as cycling stability, activation property, and the plateau voltage of the alloy which was heat-treated in various temperatures and times had different changes during the cycle process, the optimum heat-treatment conditions of this alloy were determined by this work.

Study on Nanocrystalline Rare Earth Mg-Based System Hydrogen Storage Alloys with AB_3-Type

A sort of rare earth Mg-based system hydrogen storage alloys with AB3-type was prepared by double-roller rapid quenching method. The alloys were nanocrystalline multi-phase structures composed of LaNi3 phase and LaNi5 phase by X-ray diffraction and scanning electron microscopy analyses, and the suitable absorption/desorption plateau was revealed by the measurement of P-C-I curve. Electrochemical studies indicate that the alloys exhibit good electrochemical properties such as high capacity and stable cycle life, and the discharge capacity is 369 mAh·g-1 at 0.2 C (72 mA·g-1), after 460 cycles, the capacity decay was only 19.4% at 2 C (720 mA·g-1).

Effects of Phenyl Content and Molecular Structure on the Refractive Index of Organic Silicon Polymer

The effects of phenyl content and group distribution on the refractive index of phenyl silicone oil were investigated by synthesis and characterization of silicone oils of different molecular structures.A group contribution function model was established to predict the refractive index. The results showed that refractive index of phenyl silicone oil increased as its phenyl content increased. A linear equation had been established to describe the quantitative relationship between the refractive index and phenyl content.Refractive index values from the group contribution function model showed good consistency with experimental results.

Structures and properties of La-Mg-Ni system hydrogen storage alloys

The double-roller rapid quenching technology was successfully used to prepare La-Mg-Ni system hydrogen storage alloys. The effects of magnesium content and heat-treatment process on the alloys properties were studied. When the alloy with 1.09%(mass fraction) Mg is heat treated at 900 ℃ for 4 h,its discharge capacity is more than 380 mA·h/g at 0.2C,and the cyclic life is beyond 500 counts at 2C. By XRD and PCI analyzing,the results show that the alloys are composed of LaNi5 and LaNi3 phase. The hydrogen absorption/desorption pressure of the alloy increases,so does the slope of plateau,and the plateau becomes broad first and narrow again as Mg content increases. This method is simple to be suitable for production on a large scale.

Recovery of yttrium from deep-sea mud

Deep-sea mud rich in rare earth yttrium has received lots of attention from the international community as a new resource for Y. A novel process, which mainly includes acid leaching, solvent extraction, and oxalic acid precipitation-roasting, is proposed for recovery of Y from deep-sea mud. A series of experiments were conducted to inspect the impacts of various factors during the process and the optimum conditions were determined. The results show that the Y of deep-sea mud totally exists in apatite minerals which can be decomposed by hydrochloric acid and sulfuric acid solution. The highest leaching efficiency of Y is 94.53% using hydrochloric acid and 84.38% using sulfuric acid under the conditions of H^＋concentration 2.0 mol/L, leaching time 60 min, liquid-solid ratio 4：1 and room temperature 25 ℃（only in case of sulfuric acid, when using hydrochloric acid, the leaching temperature should be 60 ℃）. Because of the much lower leaching temperature, sulfuric acid leaching is preferred. The counter current extraction and stripping tests were simulated by a cascade centrifugal extraction tank device. Using 10 vol% P204,15 vol% TBP and 75 vol% sulfonated kerosene as extractant, 98.79% Y^3＋ and 42.60% Fe^3＋ are extracted from sulfuric acid leaching liquor（adjusted to pH = 2.0） after seven-stage counter current extraction with O/A ratio of 1：1 at room temperature, while other metals ions such as Al^3＋, Ca^2＋, Mg^2＋and Mn^2＋ are almost not extracted. The Y^3＋ in loaded organic can be selectively stripped using 50 g/L sulfuric acid solution and the stripping efficiency reaches 99.86% after seven-stage counter current stripping with O/A ratio of 10：1 at room temperature, while only 2.26% co-extracted Fe^3＋ is stripped. The Y^3＋ of loaded strip liquor can be precipitated by oxalic acid to further separate Y^3＋ and Fe^3＋. The precipitation efficiency of Y^3＋ in loaded strip liquor can be 98.56% while Fe^3＋ is not precipitated under the conditions of oxalic acid solution concentration 200 g/L, quality ratio of oxalic acid to Y of 2, and precipitation time 0.5 h. And the precipitate was roasted at 850 ℃ for 3 h to obtain the oxide of Y in which the purity of Y_2 O_3/REO is 79.02% and the contents of major non-rare earth impurities are less than 0.21%.Over the whole process included acid leaching, solvent extraction, and oxalic acid precipitation-roasting,the yttrium yield is 82.04%.

Microstructure improvement related coercivity enhancement for sintered NdFeB magnets after optimized additional heat treatment

The micro structure, especially the Nd-rich phase and the grain boundary, in sintered NdFeB magnets plays an important role in magnetic reversal and coercivity mechanism. To better understand the effects of the microstructure on the coercivity, we investigated the microstructure and properties improvements of a commercial sintered NdFeB magnet after optimized additional heat treatment. The coercivity is enhanced from 1399 to 1560 kA/m. This enhancement has been explained in terms of the evolution of the grain boundary structure, and the formation of continuous thin layers of Nd-rich phase is important for high coercivity. The micromagnetic simulation together with the numerical analysis based on the nucleation model suggest that the reversed magnetic domains nucleate mainly at the interface of multijunctions of Nd_2 Fe_（14）B grains with high stray fields during the demagnetization process. Both improved anisotropy fields at grain boundaries and reduced stray fields at multi-junction Nd-rich phases contribute to the coercivity enhancement. This work has importance in understanding the crucial micro structure parameters and enhancing the obtainable properties for sintered NdFeB magnets.

Cathode Design for Proton Exchange Membrane Fuel Cells in Automotive Applications

An advanced cathode design can improve the power performance and durability of proton exchange membrane fuel cells(PEMFCs),thus reducing the stack cost of fuel cell vehicles(FCVs).Recent studies on highly active Pt alloy catalysts,short-side-chain polyfluorinated sulfonic acid(PFSA)ionomer and 3D-ordered electrodes have imparted PEMFCs with boosted power density.To achieve the compacted stack target of 6 kW/L or above for the wide commercialization of FCVs,developing available cathodes for high-power-density operation is critical for the PEMFC.However,current developments still remain extremely challenging with respect to highly active and stable catalysts in practical operation,controlled distribution of ionomer on the catalyst surface for reducing catalyst poisoning and oxygen penetration losses and 3D(three-dimensional)-ordered catalyst layers with low Knudsen diffusion losses of oxygen molecular.This review paper focuses on impacts of the cathode development on automotive fuel cell systems and concludes design directions to provide the greatest benefit.