Papers by Keyword: Rare Earth Element (REE)

Abstract: Rare earth elements (REE) are harmless for human health. REE addition contributes to the improvement of the machinability of the steels. In the present paper, machining characteristics of austenitic stainless steels without lead addition were investigated by adding free-machining elements, such as sulfur, REE and bismuth. The results have shown that large numbers of rounded, globular shaped inclusions were obtained for both steels. The machinability of steel B is better than that of steel A, and the cutting forces of steel B are lower than those of steel A at various cutting speeds. Lead can be substituted by REE and bismuth in free machinable austenitic stainless steels. REE significantly affects machining characteristics of austenitic stainless steels without lead addition. The mechanical properties of both steels were similar, and their fracture exhibited ductile characteristics. Satisfactory machinability and mechanical properties can be obtained for both steels.

Abstract: Addition of some active elements such as yttrium, cerium, lanthanum and other rare earths elements (REE) to austenitic stainless steels helps to improve their high temperature oxidation resistance and tribological properties. The high intensity plasma pulses were used to introduce Ce and La into AISI 316L austenitic stainless steel. The plasma pulses contained both ions/atoms of Ce-La and those of the working gas. The pulse energy densities were sufficient to melt the near surface layer of the steel and introduce those elements into the surface layer. Scanning electron microscopy (SEM) as well as energy dispersion spectroscopy (EDS) was used during each one part of surface characterisation. Obtained results allowed us to make decision about directions of modified material successive investigations.

Abstract: Abstract: By adding rare earth lanthanum oxide on Zunyi area failed comprehensive utilization of manganese slag test, according to a certain proportion to make rare earth ceramics, understanding the effects of rare earth elements on firing, and the influence of the temperature of the compressive, flexural performance and bibulous rate test, the rare earth elements manganese residue to explore the influence of the ceramic certain performance. Sintering temperature from 1220 °C to 1135 °C with the increased amount of rare earth, when the rare earth content is 6% the compressive strength is highest, when the rare earth content is 10% the bending strength is the highest and the bibulous rate is the lowest. It has a guiding significance on the rare earth ceramic materials development in the future, at the same time, providing valuable research material for reducing the manganese slag pile.

Abstract: Dabashan Thrust and Fold Belt is situated in the transfer zone between Qinling Orogen and Sichuan Basin, where multi-generation calcite veins were developed. Two kinds of veins, bedding-parallel and fracture-filled veins, were collected for analyses of rare-earth elements (REE), samarium-neodymium and strontium isotopes. The total REE contents of the calcites from the bedding-parallel vein are much higher than those from fracture-filled veins and are rich in light REE (LREE). The chondrite-normalized patterns of REE curves of the calcites from fracture-filled veins are flatten. The 87Sr/86Sr and 143Nd/144Nd ratios of calcites from bedding-parallel vein are from 0.71068 to 0.71115 and from 0.51192 to 0.512058, respectively. On the 147Sm/143Nd vs 143Nd/144Nd diagram, the six samples from the bedding-parallel vein give a Sm-Nd isochron age of 357±230 Ma (2σ)( MSWD = 24) with an initial 143Nd/144Nd ratio of 0.51168±0.00019. However, the plots of the four samples from fracture-filled veins are rather scatter either on 147Sm/143Nd vs 143Nd/144Nd or on 87Sr/86Sr vs 143Nd/144Nd diagram. The fluids, from which the two kinds of veins precipitated, are different in origin and flowing.

Abstract: The as-cast Mg-14Li-3Al-(0-0.9)RE alloys were prepared with vacuum melting method, then processed by hot extrusion. The microstructure and tensile properties were investigated. The results show that both addition of RE and extrusion deformation can refine the grain size. Al₃La compounds are formed with addition of La-rich misch metal. The as-extruded Mg-14Li-3Al-0.6RE alloy obtains the finest grain size (4.28 μm) and the highest mechanical properties (σ_b =222.75 MPa, δ=23.8%), which is related to the grain refinement and the formation of Al₃La.

Abstract: This study explores a series of optical, physical and structural properties based on P₂O₅-Al₂O₃-ZnO (ZAP) with glass doped 1 mol% Tb₂O₃, which changed the composition ratio between ZnO and P2O5. The structure and optical of glasses were studies by Raman spectra and fluorescence spectra. The Raman spectra with the zinc content increases, the 650-810 cm^-1 at the P-­O­-P bond has no shift, but the intensity of the absorption peak decreased. The fluorescence intensity increases with the ZnO content increases. The glass density and refractive index also increases with the ZnO content increases.

Abstract: In recent years, as public awareness on environmental problems increasing, soil pollutions are received more and more attention. Choosing a suburban garden soil as objective, adding exogenous heavy metal cadmium (Cd) and rare-earth element lanthanide (La) in the soil, Cd/La single stress and combined stress on soil urease and catalase were studied. The results showed that under Cd/La single or combined processing, both soil urease and catalase activities decrease while the concentration increases. With the incubation time extending, soil urease activities first increase and then decrease, and soil catalase first reduce then increase. Cd/La single and combined process has obvious inhibition on soil urease and catalase. At the same concentration, the inhibition degree to enzyme activity was Cd>Cd, La combined> La, and the inhibition of soil urease was higher than that of catalase. Soil urease and catalase showed a significantly negative correlation under different treatments. So setting soil urease and catalase as ecological indicators to soil heavy metal and rare earth elements pollution is feasible.

Abstract: Rare earth element (REEs) concentrations were measured for groundwater and wall rock samples from two aquifers (sandstone and limestone aquifers) in Renlou coal mine, northern Anhui Province, China. The results indicate that groundwater from these two aquifers are rich in REEs as expressed by their Nd concentrations (0.012 and 0.008 μg/L). They all show heavy REEs enrichment with low NdRN/YbRN ratios (0.35 and 0.40) when normalized to their aquifer rocks. Y- Ho fractionation are only observed for groundwater from limestone aquifer with high Y/Ho ratio (97 in average), whereas groundwater from sandstone aquifer have low Y/Ho ratios (24 in average). The former is considered to be related to the release of Y and Ho from calcite with different partition coefficient. The similarity of some REEs between groundwater and aquifer rock, as well as the different rock composition of aquifers, provide possibility for discrimination of water sources by using REEs, and Y/Ho ratios and Eu anomalies are expected to be useful in Renlou coal mine.

Abstract: Isothermal oxidation experiments at 1100°C in air were carried out to evaluate the protective capability of a new rare earth oxide coating realized by electrodeposition onto a Ni-base single crystal superalloy. A subsequent heat treatment of the RE_xO_y coating already allowed the establishment of a very thin and discontinuous inwardly grown alumina scale. Under isothermal conditions at 1100°C in air a fully parabolic regime installed from 25h leading to parabolic rate constants of 2.5 10^-7 mg².cm^-4.s^-1 after 200h, similar to those of conventional β-NiAl coatings. The initial, transition and parabolic regimes were ascribed to the major development of NiAl₂O₄/Al₂O₃ mixed oxides by in situ high temperature X-ray diffraction (HT-XRD). No major transient alumina was observed. The α-Al₂O₃ scale intensity increased with increasing oxidation time, in particular with respect the rare earth oxide coating signal. The scanning electron microscopy (SEM) images showed an oxide system consisting on a top NiAl₂O₄ oxide and a bottom α-Al₂O₃ scale underneath the RE_xO_y coating. Alumina grew within the substrate surface. After 500 and 1000h of oxidation, very scarce nodules grew between the alumina and the rare earth oxide deposit. Despite the thermodynamic calculations suggested a REAlO_y perovskite at the alumina-RE_xO_y interface, this was not observed experimentally either by XRD or scanning electron microscopy (SEM).

Abstract: Ni(Ⅱ) was reduced to Ni atom irreversibly by a one-step reaction in acetamide-urea-NaBr melt at 353K. The electron-transfer coefficient, and the diffusion coefficient, D₀ were determined to be 0.21 and 1.15×10^-8 cm².s^-1 on Pt electrode. Although the Ce（Ⅲ）and the Mg（Ⅱ）cannot be reduced to Ce and Mg alone, they can be inductively codeposited with Ni（Ⅱ）to obtain an amorphous Ce-Mg-Ni alloy film by potentiostatic electrolysis. The content of Ce in the alloy increase with the increasing of the molar ratio of Ce（Ⅲ）/Ni（Ⅱ） and reaches to the maximum of 49.70 wt%. The content of Mg in the alloy increase with the increasing of the cathode potential and the maximum was 4.558wt%.