材料期刊网

CHARACTERIZATION OF NANOSTRUCTURED MATERIALS BY ANALYTICAL ELECTRON MICROSCOPY

L.D. He , G.Y Zeng , X.Liu H.S. Hu , D.Song and L.Z.Cheng(Electron Microscope Laboratory Northeastern University Shenyang 110006 , ChinaManuscript received 20 July 1995 , in revised form 10 April 1996)

金属学报(英文版)

The analytical electron microscopy has been used to characterize the morphology,structure and composition of the nanostructured material of Sn- Bi alloy prepared by a modified electrohydrodynamic technique. The electron diffraction pattern and the corresponding contrast image for the discrete particles with a diameter smaller than 4 nm have been obtained.It is shown that the nanocrystalline Sn-Bi alloy particles comprise a single crystal of Bi-containing β-Sn solid solution or of Sn-containing Bi solid solution. A direct preparation procedure of the samples during the electrohydrodynamic rapid solidification process has been developed for electron microscopic observation.

关键词: :nanostructured material , null , null , null

Studies of the Local Structure and the g Factors of the Cu(2+) Site in Y(2)BaCuO(5)

Journal of Superconductivity and Novel Magnetism

The local structure and the g factors (g(x), g(y), and g(z)) of the Cu(2+) site in Y(2)BaCuO(5) are theoretically studied using the perturbation formulas of the g factors for a 3d(9) ion in orthorhombically elongated octahedra. The orthorhombic field parameters in these formulas are determined from the superposition model and the local geometry of the system. From the calculations, the oxygen octahedron is found to undergo the local elongation Delta Z (approximate to 0.05 angstrom) along c-axis and the relative bond length variation Delta X (approximate to 0.1 angstrom) along a- and b-axes, respectively. The calculated g factors based on the above local structure are in good agreement with the experimental data. The relationships between the anisotropies of the g factors and the low symmetrical (orthorhombic) distortions of the Cu(2+) site in Y(2)BaCuO(5) are discussed.

关键词: Crystal fields and spin Hamiltonians;Electron paramagnetic resonance;Cu(2+);Y(2)BaCuO(5);crystal

添加0.1mass%Y的K38G高温合金1000℃恒温氧化行为

于萍 , 王亚权

腐蚀科学与防护技术

研究了添加0.1mass%稀土Y的铸造K38G高温合金在1000℃的恒温氧化行为.结果表明,较之不含Y的合金，含Y铸态K38G合金的氧化速率显著降低； 氧化时形成双层的外氧化膜，表层为以Cr2O3和TiO.2为主的混合氧化物层，内层为连续的Al2O3层；没有内氧化和内氮化，没有氧化膜的剥落，加入稀土Y有效地提高了氧化膜的粘附性能.

关键词: 高温氧化 , null , null , null

添加0.1 mass%Y的K38G高温合金1000℃恒温氧化行为

于萍 , 王亚权

腐蚀科学与防护技术 doi:10.3969/j.issn.1002-6495.2007.03.010

研究了添加0.1 mass%稀土Y的铸造K38G高温合金在1000℃的恒温氧化行为.结果表明,较之不含Y的合金,含Y铸态K38G合金的氧化速率显著降低;氧化时形成双层的外氧化膜,表层为以Cr2O3和TiO2为主的混合氧化物层,内层为连续的Al2O3层;没有内氧化和内氮化,没有氧化膜的剥落,加入稀土Y有效地提高了氧化膜的粘附性能.

关键词: 高温氧化 , K38G , 高温合金 , 稀土元素 , Y

Theoretical explanation of the g factor for Cr4+ in Y2SiO5 crystal

Solid State Communications

The g factor of Cr4-- in Y2SiO5 crystal is calculated from a completed high-order perturbation formula, in which not only the conventional contribution to the g-shift Deltag(= g - g(c)) from the crystal-field mechanism, but also the contribution from the charge-transfer mechanism (which is neglected in the crystal-field theory) are considered. The calculated result shows good agreement with the observed value. It is found that the calculated Deltag due to the charge-transfer mechanism is opposite in sign and about 38% in magnitude, compared with that due to the crystal-field mechanism. So, in the studies of the g factor for a 3d(n) ion having high valence state in crystals, the contribution due to the charge-transfer mechanism should be taken into account. (C) 2004 Elsevier Ltd. All rights reserved.

关键词: insulators;points defects;crystal and ligand fields;electronic states;(localized);electron paramagnetic resonance;atomic screening constants;scf functions;cr4+-y2sio5;transition;pressure

稀土元素Y对K38G高温合金800 ℃恒温氧化行为的影响

于萍 , 王亚权 , 王文

腐蚀科学与防护技术

对加入0.05mass%～0.5mass%稀土Y铸造的K38G高温合金800 ℃恒温的氧化行为进行了研究.结果表明,含Y铸态K38G合金的氧化动力学曲线偏离了抛物线规律，接近于立方规律；Y有效抑制了该合金的内氧化；当Y含量达0.5mass%时，该合金中析出富Y相，降低了其氧化抗力.  

关键词: 高温氧化 , null , null

稀土元素Y对K38G高温合金 800℃恒温氧化行为的影响

于萍 , 王亚权 , 王文

腐蚀科学与防护技术 doi:10.3969/j.issn.1002-6495.2006.03.008

对加入0.05mass%～0.5mass%稀土Y铸造的K38G高温合金800℃恒温的氧化行为进行了研究.结果表明,含Y铸态K38G合金的氧化动力学曲线偏离了抛物线规律,接近于立方规律;Y有效抑制了该合金的内氧化;当Y含量达0.5mass%时,该合金中析出富Y相,降低了其氧化抗力.

关键词: 高温氧化 , K38G高温合金 , 稀土元素 , 钇(Y)

Investigations of the anisotropic g-factors for the Er3+ doped YBa2Cu3Oy (6 < y < 7) superconductor

Materials Science and Engineering B-Solid State Materials for Advanced Technology

The anisotropic g factors g(//) and g(perpendicular to) for the tetragonal Er3+ center associated with Er3+ on y(3+) site in YBa2Cu3Oy(6 < y < 7) superconductor are investigated by using the second-order perturbation formulas of g factors for a 4f(11) ion in tetragonal symmetry. In these formulas, the contributions to the g factors from the second-order perturbation and the admixture of different energy levels are considered. The related crystal field parameters are calculated from the superposition model parameters obtained for similar tetragonal [ErOs](13-) clusters in some zircon compounds. The reasonableness of the results is discussed. (C) 2003 Published by Elsevier B.V.

关键词: electron paramagnetic resonance (EPR);high-T-c superconductor;YBCO;crystal- and ligand-field theory;Er3+;superposition-model;spin probes;epr;la2-xsrxcuo4;esr

Studies of the EPR parameters g(i) and A(i) for Co2+ in the octahedral sites of Y3Al5O12 and Y3Ga5O12 crystals

Physica Status Solidi B-Basic Research

The perturbation formulas of EPR g factors g(\\) g(perpendicular to) and hyperfine structure constants A(\\) A(perpendicular to) for the trigonal octahedral 3d(7) cluster are derived considering not only the configuration interaction effect due to the admixture among ground and excited states, but also the covalency effect due to the admixture between the d electrons of the 3d(7) ion and the p electrons of ligands. In these formulas, the parameters related to both effects and the trigonal field parameters are estimated from the optical spectra and the structural parameters of the studied system. According to these formulas, the EPR parameters g(\\), g(perpendicular to), A(\\) and A(perpendicular to) for Co2+ in the octahedral sites of Y3Al5O12 and Y3Ga5O12 garnets are satisfactorily explained from the optical spectra and the structure data. The role of the covalency effect is discussed.

关键词: superposition model;phase-transition;absorption;linbo3;ions

Studies of the g factors and the local structure for Ni3+in LaAl0.9Ni0.1O3, La0.75Y0.25Al0.99Ni0.01O3 and YAl0.9Ni0.1O3

Radiation Effects and Defects in Solids

The electron paramagnetic resonance g factors and the local structure for Ni3+ in LaAl0.9Ni0.1O3 (LAN), La0.75Y0.25Al0.99Ni0.01O3 (LYAN) and YAl0.9Ni0.1O3 (YAN) are theoretically studied from the perturbation formulas of the g factors for a 3d7 ion of low spin (S = 1/2) in tetragonally elongated octahedra. In these formulas, the contributions to the g factors from the tetragonal distortion, characterized by the tetragonal field parameters Ds and Dt are taken into account. According to the calculations, the ligand octahedra around Ni3+ are suggested to suffer 2% relative elongation along the [001] (or C4) axis due to the Jahn-Teller effect.

关键词: defect structures;electron paramagnetic resonance;crystal-fields and;spin Hamiltonians;Ni3+;LaAlO3;LaYAlO3;YAlO3;atomic screening constants;optical-spectra;paramagnetic-resonance;superconducting tapes;lattice-distortions;superposition model;scf;functions;cr3+ ions;crystals;epr