Effect of Rare Earth Fluoride Complex Additives on Properties of Steel

A technique of treating steel with rare earth fluoride complex additives(REFCA),effects and influnce factors have been studied.REFCA play a role on controlling inclusion morphology,purifying the molten steel and improving properties of steel.The optimum composition of REFCA is REF_3 42%;CaO 33%;SiCa 25%,and the amount of REF_3 is 0.5 wt%～0.6 wt% of steel.

Fabrication of Ordered Magnetite-Doped Rare Earth Fluoride Nanotube Arrays by Nanocrystal Self-Assembly

We describe a nanocrystal self-assembly method for the preparation of rare earth fluoride nanotube(ReF-NT)arrays and magnetite-doped rare earth fluoride nanotubes(Fe_(3)O_(4)ReF-NTs)by using porous anodic aluminum oxide(AAO)as a hard template.The ReF-NTs can be simply prepared by the impregnation of-NaYF_(4)nanocrystals doped with Yb and Er into the channels of the porous AAO and show a highly ordered nanotube array and excellent upconversion(UC)fluorescence properties.Similarly,the Fe_(3)O_(4)ReF-NTs are obtained by the self-assembly of a mixture of Fe_(3)O_(4)and Yb/Er doped-NaYF4 nanocrystals in the AAO pore channels and have a uniform dispersion of magnetite nanocrystals on the rare earth fluoride tube matrix and possess multifunctional magnetic/UC properties.The diameter of these nanotubes can be varied from 60 nm to several micrometers depending on the pore size of the AAO template.The wall thickness can be increased from 10 to 35 nm by increasing the concentration of nanocrystals from 0.02 to 0.4 mmol/L,while the morphology of the nanotubes can be varied from small isolated domain structures to percolating domains and eventually to compact domains.A template-directed formation mechanism is proposed and the quantitative predictions of the model for such self-assembled nanocrystal spreading processes are demonstrated.Strong UC fluorescent emissions are realized for the nanotube arrays and multifunctional nanotubes with UC excitation in the near-infrared(NIR)region.A strong magnetic response of the multifunctional nanotubes is observed,which facilitates their easy separation from solution by magnetic decantation using a permanent magnet.

Studies on the Preparation and Properties of AIF_3－based Rare Earth Fluoride Glass

AlF3-REF3-AEF2 (RE: rare earth, AE: alkali earth) system fluoride glasses were prepared by quenching melts. The glass forming region of AlF3NdF3-(Mg0.25Ca0.25Sr0.25Ba0.25) F2 system was determined. Effects of AE and RE fluoride on the glass forming ability and thermal properties of the system have been discussed. The IR cut-off wavelength of AIF3-REF3-AEF3 glass is about 7 μm. This system has many advantages, such as low refractive index, high Abbe number, high Tg and Tc-Tg values, and good chemical durability, etc. This is a kind of new excellent ultra-low loss optical fiber and IR optical material.

Fluoride solid electrolytes containing rare earth elements

Relations between the structure, ionic conductivity and dielectric properties of fluoride systems of different structures containing rare earth elements were presented. Superionic conductivities, by fluoride ions, of fluorite-structured （MF2-REF3, M=Ba, Pb, RE=La-Lu, Sc, Y）, orthorhombic （REF3, RE=Tb-Er, Y）, tysonite-structured （REF3-MF2, RE=La-Nd, M=Sr）, monoclinic （BaRE2Fs, RE=Ho-Yb, Y） fluoride single crystals and eutectic composites （LiF-REF3, RE=La-Gd, Y） were compared. Anisotropy of electrical properties of crystals with a lower symmetry was explained by modeling optimum ionic paths. For explanation of concentration dependences of fast ionic conductivity, models of aggregation of defects into clusters were proposed. In fluorite-structured crystals, the highest ionic conductivity was found for PbF2：7 mol% ScF3 （at 500 K, σ500=0.13 S/cm）. In tysonite-structured crystals, the highest ionic conductivity was found for LaF3：3 mol% SrF2 （σ500=2.4×10^-2 S/cm）. Different types of coordination polyhedrons and their different linking in orthorhombic and tysonite structure explained large differences between conductivities in both structures. Eutectic systems, prepared as directionally solidified composites, enabled to study some orthorhombic fluoride phases （GdF3, SmF3）, which cannot be prepared as single crystals. An influence of the orthorhombic-tysonite phase transition on the ionic conductivity was shown.

FLUORIDE GLASSES CONTAINING RARE EARTH

Fluoride glasses containing rare earths exhibit interesting spectroscopic properties.They have wide transmission range from 0.25μm in the UV to 7μm in the IR,allowing observation,in a vitreous material,of absorption and emission bands in a large optical range.The absorption spectra of fluoride glasses with rare earth substitutions are found to vary with the rare earth ions used.The T_g~'s for these glasses average out at 311℃.Optical properties,such as refractive indices are not obviously influenced by rare earth substitutions.

Hydrothermal synthesis of mixed rare earth-alkali metal or ammonium fluorides

The recent results on hydrothermal synthesis of mixed rare earth-alkali or ammonium fluorides were presented. The initial ratios of the starting materials, pH value and reaction temperature were the critical factors for obtaining the single-phase product. Four main types of complex rare earth fluorides, AREF4, A2REF5, ARE2F7 and ARE3F10 (A=Na+, K+, Rb+, NH4+), appeared in the primary hydrothermal reactions. The correlation between cation sizes and the formation of mixed rare earth fluorides under mild hydro...

Reaction behavior between the oxide film of LY12 aluminum alloy and the flux

In this paper, the brazing mechanism of LY12 aluminum alloy at middle range temperature was presented. The CsF-AlF_3 non-corrosive flux was utilized to remove the complex oxide film on the surface of LY12 aluminum alloy. The results revealed that the oxide film was removed by the improved CsF-AlF_3 flux accompanied with the occurrence of reaction as well as dissolution and the compounds CsF played an important role to remove the oxide film. Actually, the high activity of flux, say, the ability to remove the oxide film, was due to the presence of the compounds, such as NH_4F,NH_4AlF_4 and composite molten salt. The production of HF was the key issue to accelerate the reaction and enhance to eliminate the oxide film by dissolution. It was found that the rare earth element La at small percentage was not enriched at the interface. Moreover, the rare earth fluoride enhanced the dissolution behavior.

Ultrasonic synthesis, characterization and formation mechanism of aggregated nanorings of EuF_3

The aggregated nanorings of EuF3 were synthesized via ultrasonic irritation in aqueous solution. The products were characterized by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. XRD pattern proved that the crystalline phase of the EuF3 rings was hexagonal. The SEM and TEM images indicated that the as-prepared EuF3 nanocrystals had ring-like morphology and were aggregated by numerous small crystallites （about 10-15 nm in diameter）; the outer diameter of the rings was in the range of 200--300 nm, while the inner diameter was in the range of 50-80 nm with a thickness of 30-40 nm. Moreover, the time-depend experiments were carried out to disclose the formation mechanism of the as-prepared ring-like nanostructures.

Recent progress on upconversion luminescence enhancement in rare-earth doped transparent glass-ceramics

The upconversion（UC） of the rare earth doped glass-ceramics has been extensively investigated due to their potential applications in many fields, such as color display, high density memories, optical data storage, sensor and energy solar cell, etc. Many series of them, especially the oxyfluorides glasses containing Ba2 LaF 7 nanocrystals were studied in this review work, due to the thermal and mechanical toughness, high optical transmittance from the ultraviolet to the infrared regions, and a low nonlinear refractive index compared to the other commercial laser glasses. Moreover, the energy transfer（ET） between the rare earth ions and transition metals plays an important role in the upconversion process. The cooperative ET has been researched very activly in UC glasses due to applications in the fields of solar cells, such as in the Er/Yb, Tm/Yb, Tb/Yb, Tb/Er/Yb and Tm/Er/Yb couples. The present article reviews on the recent progress made on：（i） upconversion materials with fluoride microcrystals in glasses and the mechanisms involved, including the UC in double and tri-dopant RE ions activated fluoride microcrystal, energy transfer process; and（ii） the effect of the metal Mn and nanoparticles of Au, Ag, Cu on the enhancement of UC emissions. Discussions have also been made on materials, material synthesis, the structural and emission properties of glass-ceramics. Additionally, the conversion efficiency is still a challenge for the spectra conversion materials and application; challenge and future advances have also been demonstrated.

Synthesis of a novel Ce(Ⅲ)-incorporated cross-linked chitosan and its effective removal of fluoride from aqueous solution

A novel Ce（Ⅲ）-incorporated cross-linked chitosan（Ce-CCS） was prepared and used for the removal of fluoride from aqueous solution. The structure and morphology of Ce-CCS were measured by Fourier transform infrared spectroscopy（FTIR）, X-ray diffraction（XRD）, scanning electronic microscopy（SEM） and energy dispersive X-ray analyzer（EDAX） techniques. The factors affecting the fluoride adsorption such as adsorbent dosage, initial fluoride concentration, pH, coexisting anions and contact time were investigated. Increasing adsorbent dosage enhanced the removal towards fluoride while increasing initial fluoride concentration reduced the removal towards fluoride. The optimal pH value for fluoride adsorption was 3 or so. The presence of coexisting anions weakened the adsorption of fluoride, and the decreasing order of the removal towards fluoride was PO_4^（3–）〉CO_3^（2–）〉SO_4^（2–）〉Cl~–. The adsorption data were described by Freundlich isotherm model and the pseudo-second order kinetic model. The incorporation of Ce（Ⅲ） enhanced the adsorption capacity of CCS for fluoride ions, the adsorption capacity at equilibrium（q_e） of Ce-CCS increased by 5.0 mg/g or so as compared with the one of CCS at the same temperature tested. The exhausted Ce-CCS could regenerate with 0.1 mol/L HCl solution.