Effect of Chromium on Magnetic Properties of Y2.9Ce0.1Fe5-xCrxO12 Nanoparticles

Y_2.9Ce_0.1Fe_5-xCr_xO₁₂ (x = 0-0.5) nanoparticles were fabricated by a sol-gel method. Samples with particle size ranging from 60 to 64 nm were obtained and their crystalline structures and magnetic properties were investigated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). Results of VSM show that the saturation magnetization is increased firstly, after decreased with the Cr concentration (x). The saturation magnetization is increased with increasing the particle size.     

Pulsed laser deposition of Y2O3 : Eu thin film phosphors

Thin films of Y₂O₃ : Eu cathodoluminescent (CL) phosphors were deposited using pulsed laser deposition using deposition temperature between 250°C and 800°C, O₂ pressures between residual vacuum (2×10⁻⁵ Torr) and 6 Torr, and post annealing up to 1200° for 1 h in air. The CL efficiency of the best thin film was about one third that of the starting powder. The brightness and efficiency of the thin films improved as the deposition temperature, O₂ pressure and post annealing temperature were increased, except that O₂ pressures above 600 mTorr did not significantly improve the CL properties. At deposition temperatures >600°C, the surface morphology changed from a smooth film to a nodular deposit for O₂ pressures >200 mTorr, with nodule dimensions ≈100 nm. Simultaneously, the CL properties improved dramatically because of enhanced optical scattering out of the thin film. Optical scattering was discussed in terms of anomalous diffraction. The CL properties also improved dramatically with high temperature post annealing. This effect was interpreted in terms of improved crystallinity and activation of the Eu. The low brightness and efficiency of thin films versus powder was affected by depletion of the Eu in the thin films owing to the deposition process.     

Elaboration and characterization of yttrium implanted low manganese steel.

Low manganese steel samples were yttrium implanted using ion implantation technique. Sample compositions and structures were investigated before and after yttrium implantations to determine the yttrium distribution in low manganese steel. Yttrium implantation depth profiles were characterized using conventional techniques such as X-ray photoelectron spectroscopy (XPS), reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), glancing angle X-ray diffraction (GAXRD) and a nuclear analytical method: Rutherford backscattering spectroscopy (RBS). The aim of this study is to show that correlation between composition and structural analyses allows to understand the effect of implanting yttrium in low manganese steel.     

异丙醇钇〔Y(OC_3H7)_3〕合成的研究

本文采用 Ｉ２ 及 Ｈｇ Ｃｌ２ 为催化剂,用金属钇和异丙醇直接反应合成了异丙醇钇,产率可达８３ ％ 以上,而反应时间只需５ 个小时左右,超过了已有文献的报道。     

Effect of Yttrium on Microstructure and Properties of High Temperature Alloys

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Luminescence properties of dysprosium doped YVO4 phosphor

Trivalent dysprosium(Dy~(3+)) activated nanocrystalline yttrium vanadate(YVO_4) phosphor was synthesized via co-precipitation method. The prepared samples were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), optical absorption and photo luminescence(PL) techniques. The XRD patterns reveal the tetragonal crystalline phase. SEM images reveal that Dy doped YVO_4 nanocrystals are agglomerated. EDAX confirms the formation of YVO_4:Dy. FTIR spectrum shows two strong absorption bands at 459 and 761 cm~(-1). Optical absorption spectrum showed the surface defects in the as-prepared samples. The PL emission spectrum shows two characteristic emission bands at 485 and 575 nm. The strong yellow emission peak at 575 nm is assigned to ~4 F_(9/2)→~6 H_(13/2) hyper sensitive transition of Dy~(3+) ions, Study of CIE chromaticity diagram indicates the suitability of the phosphor for the development of yellow-green LEDs.     

Dielectric and microstructural properties of YAG:Dy3+ ceramics

Yttrium aluminium garnet(Y_3 Al_5 O_(12):YAG) singly doped with Dy3+ at different concentrations was prepared by solid state reactions using repeated heating cycles over the temperature range of 1300-1600 ℃. X-ray powder diffraction analysis confirms the presence of a well-crystallized YAG perovskite phase with cubic structure(by Rietveld refinement). The rare earth dopant is successfully integrated into the YAG host lattice without any major changes in the original structure. The temperature dependence,up to 250 ℃, of the conductivity, dielectric constant, dielectric loss, and loss tangent, at various frequencies of up to 5.0 MHz for undoped and doped crystals is compared to understand the electrical and structural characteristics. The experimental results reveal that Dy3+ dopants in YAG crystal significantly influence the conductivity, dielectric constant, and lossy mechanisms, which is probably due to the 3 d-AI ions and 4 f-Dy ions incorporated at different positions of both tetrahedral and octahedral symmetries in YAG:xDy3+ ceramics.     

稀土钇对管线钢耐蚀性和物理化学行为的影响

试验管线钢（/%:0.04~0.05C,0.20~0.24Si,1.80~1.88Mn,0.010~0.012P,0.004~0.005S,0.27~0.30Cr,0.42~0.46Ni,0.24~0.28Mo,0.20Cu,0.005V,0~0.017Y,0.0031~0.0053O）由10 kg感应炉熔炼,并轧成试棒。采用扫描电镜和能谱仪、电化学技术以及热力学计算的方法研究了稀土钇对管线钢在模拟海水溶液（3.5%NaCl）中抗腐蚀性能的影响。结果表明,稀土可以对钢中夹杂产生变质作用,将大尺寸、尖角状的Al₂O₃夹杂变质为小尺寸、球状的稀土复合夹杂,所以有利于形成连续致密的内锈层,减少钢基的点蚀源,从而提高钢的抗腐蚀性能。