Papers by Keyword: Rare Earth (RE)

Abstract: This paper studied the effect of Mg-Nd alloys on the ignition-proof performance of AZ91D magnesium alloy. The results showed that 0.5%Nd decreased the ignition point of alloy for about 20°C, but the ignition point could been multiplied with the adding of Nd element. When the content of Nd reached 5%, the ignition point increased about 40°C compared with AZ91D alloy. The ignition point reduced after the addition of 0.5%Nd can be attributed to the decrease of the solidus temperature and liquidus temperature. The further analysis indicated Nd and Al formed Al3Nd first, which consumed the content of Nd, so that the alloy didn’t have enough Nd to form Nd2O3 to protecting the alloy. The EDS analysis indicated when the addition of Nd reached 5%, competent Nd2O3 could be formed and compact oxide film which consisted of Nd2O3, MgO and Al2O3 was formed to prevent alloys from oxidation and combustion.

Abstract: Composite coating is a very important part in new materials because it has special excellent physical and chemical properties, and PTFE composite coating is low friction coefficient, high temperature stability and high chemical resistance. To prepare excellent RE-Ni-Fe-P-PTFE composite coating through electrodeposition, some experiments were completed, and the effect of surfactant conc., PTFE conc., and the conc. of rare earth on PTFE content in the coating was studied. The results show that the optimum electrodeposited conditions are that the conc. of rare earth La is 3 g/L, the conc. of PTFE solution is 50 ml/L, temperature is 55 °C, current density is 10 A/dm2. And that the friction coefficient of the coating is decreased significantly, and the lubricating property is improved.

Abstract: The Fe-based composite coatings with RE oxides were prepared on low-carbon steel substrate by use of the plasma jet surface metallurgy, and the effect of RE on microstructure of coating was investigated. The result shows that the microstructure and properties with a proper amount of RE oxides are better than these of the coatings without RE oxides. In addition, the modifying effect of RE oxide on inclusions in metallurgical coating was studied by means of thermodynamics. The thermodynamics analysis shows that RE oxide (Ce2O3) can be reduced to RE by carbon, then the RE element can react with oxygen and sulfur to form the RE oxide-sulfide in metallurgical pool. As a result, the coating is purified and the solidification crack of coating can be restrained by deoxidization and desulphurization.

Abstract: In this paper, rare earth La modifying ZL101 alloy was studied by using of optical microscope, scanning electron microscopy, universal materials tester and small-load Brinell hardness. The influence of T6 heat treatment of the alloy’s microstructure and properties was also studied. The results show that microstructure and mechanical properties of the alloy have much obvious modification effect at modification temperature (690°C). The microstructure and mechanical properties are improved remarkably when La content is up to 0.15wt%.

Abstract: The corrosion behavior of graphite-like carbon (GLC) coating in sea water was studied and yttrium and cerium were doped into it by using mosaic in the target of magnetron sputtering process to improve its corrosion resistance. The result shows that the GLC coating characterizes typical underfilm electrochemical corrosion in sea water. Yttrium added in chromium interlayer or yttrium and cerium added in the surface layer of the GLC coating can apparently improve the microstructure result in significantly decrease the corrosive current density. As the modifications of Y in interlayer and Y, Ce and Ta in top layer are composed together to form complex GLC coating, the wear resistance and the antifriction is dramatically improved, the corrosive current density is only one-twenty fourth of that of the commercial C/Cr GLC coating.

Abstract: BaO-CeO₂-TiO₂ microwave dielectric ceramics with the different content of TiO₂ were fabricated by a solid-state reaction method using BaCO₃, CeO₂, TiO₂ powders as starting materials in view of the dispute. The sintering characteristics, phase composition, micro-structures and microwave dielectric properties of BaO-CeO₂-nTiO₂ microwave dielectric ceramics with different n values sintered at different temperatures were investigated. The results showed that the sintering temperature of BaO-CeO₂-nTiO₂ microwave dielectric ceramics was lower (< 1300°C), and CeO₂ didn’t tend to form polynary compounds. When n = 3, the sintered ceramics had excellent dielectric properties: ε_r ≈40.3, tanδ ≈1.02×10^-3 (1 MHz); ε_r ≈ 41.2, Q•f =19922GHz (6.865 GHz), τ_f = +22 ppm/°C .

Abstract: Clean heavy rail steel was prepared by the process of vacuum induction furnace smelting, forge work and rolling. Effects of Rare earths (RE) on phase transformation and microstructure of heavy rail steel were investigated by thermal simulation machine, metallographic microscope and scanning electronic microscope. Thermal simulate tests indicate that, RE can move the C curve of pearlite transformation to lower right, prolong the incubation period of pearlite and improve the stability of undercooled austenite. The minimum incubation period of pearlite transformation is increased from 24s to 30s by RE. Furthermore, RE can decrease the critical cooling rate of pearlite transformation from 1°C•s^-1 to 0.5°C•s^-1 and the critical cooling rate of quenching from 15°C•s^-1 to 13°C•s^-1. Additionally, RE can fine the annealing and anormalizing pearlite notably. The pearlite laminae distance of heavy rail steel added RE is decreased by 12.9% (annealing) and 13.3% (normalizing), respectively.

Abstract: Ceramic samples with the nominal composition (1-x) BaTiO₃ + x Ba₃Ti₂YO_8.5 (x = 0 - 0.4) were prepared by the solid-state reaction method. The X-ray diffraction (XRD) analysis and the lattice parameters determination indicate that the samples with x≤ 0.16 exhibit a single phase cubic perovskite structure. When x > 0.16, the system is of biphasic composites, which consist of Ba(Ti_0.911Y_0.089)O₃ and Ba₃Ti₂YO_8.5. The microstructure observation by Scanning Electron Microscopy (SEM) supports the XRD result. For the biphasic composites, the dielectric constant follows the Lichtenecker relation in a wide temperature range.

Abstract: The effect of yttrium addition and heat treatment on the mechanical properties and microstructure of AM60 magnesium alloy have been investigated using X-ray phase analysis, microstructure investigation, tensile test, hardness measurement and fracture surfaces analysis. The results showed that the mechanical properties of the alloys were obviously improved with the addition of yttrium no more than 1.0%. The reinforcement of the alloys resulted from the appearance of Al₂Y phase. After solid-solution treatment (T4), the Mg₁₇Al₁₂ phase almost dissolved in Mg matrix, but the rare earth compounds Al₂Y phase was rather stable. The ultimate tensile strength σb was improved, but the yield strength σ_0.2 and elongation δ were only slightly changed. After solid-solution + aging treatment (T6), the Mg₁₇Al₁₂ phase precipitated again and their morphology was changed. The yield strength σ_0.2 was improved.

Abstract: The self-prepared Cu-RE refining agents were used to refine impure-copper. The influences of RE elements on refinements and structures were studied and the mechanism of RE was discussed. The results show that by adding proper amounts of Cu-RE refining agents into impure-coppers, the refinements of RE on impure-coppers are perfect. Furthermore, the dendrites of the RE-refined ingot are refined and the structure becomes more homogeneous, leading that the electric conduction function and mechanics function of impure-copper have been improved.