稀土(钇)对钨钼原子扩散系数的影响

利用双辉等离子表面冶金技术在Q235钢表面渗稀土(钇)钨钼形成共渗合金层。通过对渗层合金元素的分布进行分析,计算出钨钼原子的扩散系数和扩散激活能来分析稀土(钇)的加入对钨钼原子扩散产生的影响。结果表明:稀土(钇)的加入使钼原子在渗层中的扩散系数平均增大1.89倍。钨原子的扩散系数平均降低了0.89倍。稀土(钇)的加入使钼原子在渗层中离表面12～15,24～25,35～36μm处钼原子扩散激活能分别降低了5737.72,6511.72,7853.38J/mol。钨原子扩散激活能提高了998.5,106.37,2904.56J/mol,稀土(钇)对钼原子具有催渗作用,对钨原子没有明显催渗作用。

Study on the Acute Toxicity of Rare Earth Yttrium to Earthworms under the Stress of Leaching Agent Ammonium Sulfate

This study aimed to investigate the toxicity of rare earth ion yttrium under the stress of leaching agent ammonium sulfate （NH4）2SO4. [Method] By using earthworms as indicator organisms of environmental pol ution, acute toxic ef-fects of rare earth yttrium on earthworms under the stress of ammonium sulfate were investigated with filter paper contact method. [Result] Under single stress of rare earth yttrium, the semi-lethal concentration after 48 and 24 h was LC50=213.41 mg/L and LC50=322.63 mg/L, respectively. ② Under single stress of ammonium sul-fate, the semi-lethal concentration after 48 h and 24 h was LC50=13.89 g/L and LC50=15.05 g/L, respectively. ③ In combined treatment of low concentration （10 g/L） of ammonium sulfate and different doses of rare earth yttrium, the semi-lethal con-centration after 48 and 24 h was LC50=198.65 g/L and LC50=399.85 g/L, respective-ly; in combined treatment of middle concentration （14 g/L） of ammonium sulfate and different doses of rare earth yttrium, the semi-lethal concentration after 48 and 24 h was LC50=167.3 mg/L and LC50=256.73 mg/L, respectively; in combined treatment of high concentration （20 g/L） of ammonium sulfate and different doses of rare earth yttrium, the semi-lethal concentration after 48 h and 24 h was LC50=31.03 mg/L and LC50=127.65 mg/L, respectively. [Conclusion] Low concentration of ammonium sulfate could reduce the toxicity of rare earth yttrium to earthworms and produce certain antagonism against rare earth yttrium; middle concentration ammonium sulfate in-creased the toxicity of rare earth yttrium to earthworms and produced relatively sig-nificant synergistic effects; high concentration ammonium sulfate significantly in-creased the toxicity of rare earth yttrium to earthworms. Compared with ammonium sulfate, dead earthworms exposed to rare earth yttrium were more easily fractured, and living earthworms showed insensitive response to acupuncture.

Effect of Y on age hardening response and mechanical properties of Mg-xY-1.5LPC-0.4Zr alloys

Ageing hardening,microstructure and mechanical properties of Mg-xY-1.5LPC-0.4Zr（x=0,2,4,6）alloys（LPC represents La-based rare earth metal）were investigated.It was found that the age hardening was enhanced,the grains became finer and the tensile strength was improved with the increase of Y content in Mg-Y-1.5LPC-0.4Zr alloy.The results show that the formed precipitates responsible for age hardening change from fine hexagonal-shaped equilibrium Mg12RE phase to metastableβ′phase with orthorhombic-bc crystal structure when Y is added into Mg-1.5LPC-0.4Zr alloy,and the volume fraction of precipitate phases also increases.The cubic-shapedβ-Mg24Y5 precipitate phases were also observed at grain boundaries in Mg-6Y-1.5LPC-0.4Zr alloy. The distribution of prismatic shapedβ′phases and cubic shapedβ-Mg24Y5 precipitate phases in Mg matrix may account for the remarkable enhancement of tensile strength of Mg-Y-LPC-Zr alloy.The Mg-6Y-1.5LPC-0.4Zr alloy exhibits maximum tensile strength at peak-aged hardness,and the values are 250 MPa at room temperature and 210 MPa at 250°C.

Effects of rare-earth Y addition on microstructure and mechanical properties of lead-tin bronze

Piston pump rotor is one of the indispensable parts of hydraulic machinery,whose performance and quality determine the drive efficiency and service life of the piston pump.This paper mainly studies the effect of rare-earth yttrium(Y)on the microstructure and properties of the wear layer in piston pump rotor.The material of the wear layer is composed of lead-tin bronze.By adding different contents of rare earth Y,observe the change of microstructure and properties of lead-tin bronze.Through comparison,the addition of rare-earth Y can improve the tensile strength and elongation of lead-tin bronze,and the organization of lead particle morphology has become much smaller and uniformer than that without rare-earth.However,if the amount of rare-earth is too high,the tensile strength and elongation decrease,and the lead particles in the organization also have the tendency to grow up.Finally,it is concluded that when the amount of rare earth is 0.04%,the comprehensive performance is the best.

A review of rare earth minerals flotation: Monazite and xenotime

This paper reviews rare earth minerals(monazite and xenotime) separation by flotation. A wide range of monazite and xenotime flotation test results are summarized including: reasons of variation in the point of zero charges on these minerals, the effects of various flotation conditions on zeta potential of monazite and xenotime, interactions of collectors and depressants on the surface of these minerals during flotation separation, relationship between surface chemistry of the minerals and different types of collector adsorptions and effects of the conditioning temperature on flotation of rare earth minerals. This review collects various approaches for the selective separation of monazite and xenotime by flotation and gives perspectives for further research in the future.

Defects in Tm^(3+)/Yb^(3+)-doped YVO_4 Crystals

The microscopic defects have been investigated for crystal Tm3+/Yb3+:YVO4. These defects mainly include the inclusions (solid inclusions, bubbles and inclusions of the liquid phase), dendrites and growth stripes. They are caused by in-pure raw materials, unstable growth conditions, super-cooling component and so on. Tm3+/Yb3+:YVO4 crystals of large size and excellent optical quality are grown by improving the growth conditions to eliminate these defects.

Specific Adsorption of Trivalent La, Ce and Y by Soils and Ferro-manganese Oxides and Its Mechanism

In this paper, the adsorption-desorption variations of trivalent La, Ce, Y and mixed rare earths are discussed. The curves of pH-rare earth element adsorption were very well fitted to the equation: InD =a+b pH. The selectivity of RE (rare earth element) ions by the samples decreased in the following order: Ce> RE> La> Y, but the sequences were: La> Ce> Y on kaolinite and Y> La on amorphous iron oxide. Since the trivalent RE ions existed in the form of RE(OH)2+ in the solutions from pH < 5.45 to 7.0, the ratio of H+ displaced to RE3+ adsorbed in micromole was proposed to be about 2. The specific adsorption mechanism for RE was proposed to be that the RE ions complexed with oxide surface and the ion-surface complex of Ce3+ promoted oxidization on Mn hydroxide.