材料期刊网

Physical and Dielectric Properties of Some Nonionic Surfactants

I.M.EI-Anwar (National Research Center , Dokki , Cairo , Egypt)S.A.El-Henawii (Faculty of Science , Helwan University Egypt)

材料科学技术（英文）

Fatty acid esters have been prepared by reacting the acid C18 with polyethylene glycols having varying numbers of Oxythylene units (4~88 units) by the direct eSterification reaction method.Surface and interfacial tensions are studied at various experimental conditions, including, concentration, temperature, and chemical constitution of the surfactants. Critical micelle concentrations (CMC), surface excess Г and residual area occupied by each surface active agent molecule A have been calculated using Gibb's equation. CMC values range from 10 to 55x10-5 mole/L for all studied agents, while the residual area occupied by each molecule varies from 0.6 to 1.5 nm2. Variation of CMC of some of these agents with temperature have been also examined and data obtained are used to calculate the heat of micellization △Hm and the entropy change during micellization △Sm. Values of △Hm varies from 14.63 kJ/mole to 2.717 kJ/mole depending on the chemical constitution of the agent under consideration. The apparent dipole moments μ of three surfactants were measured following the Headstrand's method. Values of μ are 3.24, 3.14 and 3.02 D for stearates. oleates. and linoleates adducts with polyethylene glycol (1000).

关键词:

THE CHANGING ROLE OF THE NATIONAL LABORATORIES IN MATERIALS RESEARCH

WADSWORTH Jeffrey and FLUSS Michael(Chemistry and Materials Science Directorate , Lawrence Livermore National Laboratory , Livermore , CA 94551)

金属学报(英文版)

The role of the National Laboratories is summarized from the era of post World War II to the present time. The U.S. federal government policy for the National Laboratories and its influence on their materials science infrastructure is reviewed with respect to .determining overall research strategies, various initiatives to interact with industry (especially in recent years),building facilities that serve the nation, and developing leading edge research in the materials sciences. Despite reductions in support for research in the U.S. in recent years, and uncertainties regarding the specific policies for Research &Development (R&D) in the U.S., there are strong roles for materials research at the National Laboratories. These roles will be centered on the abilities of the National Laboratories to field multidisciplinary teams, the use of unique cutting edge facilities, a focus on areas of strength within each of the labs,increased teaming and partnerships, and the selection of motivated research areas. It is hoped that such teaming opportunities will include new alliances with China, in a manner similar, perhaps, to those recently achieved between the U.S. and other countries.

关键词: : U.S. Materials Science. U.S. National Laboratories and Facilities , null

Studies on the EPR parameters for the interstitial tetragonal Co2+center in NH4I

Radiation Effects and Defects in Solids

The electron paramagnetic resonance (EPR) parameters (g factors g//, g and the hyperfine structure constants) for the interstitial Co2+ center in NH4I are theoretically investigated by the diagonalization of the 66 energy matrix of the 4T1 ground state for a 3d7 ion under tetragonal symmetry. The contributions from the admixtures of various J (=1/2, 3/2, 5/2) states and the ligand orbital and spin-orbit coupling interactions, which were normally ignored in previous works, are taken into account in the present treatments. The contributions to the EPR parameters are discussed, and the discrepancies between the calculated hyperfine structure constants and the experimental data are also analyzed.

关键词: defect structures;electron paramagnetic resonance (EPR);Co2+;NH4I;atomic screening constants;electron-paramagnetic-res;anisotropic;g-factors;single-crystals;divalent cobalt;methionine sulfoxide;ammonium iodide;scf functions;resonance;ions

Spin-Hamiltonian parameters and local lattice structure for Pd(I) center in gamma-irradiated bis(acetylacetonato)palladium(II)

Crystal Research and Technology

This paper reports on a theoretical analysis of spin-Hamiltonian parameters and local lattice structure for Pd(I) center in gamma-irradiated Pd(II)(acac)(2). Through the crystal- and ligand-field theory, the microscopic spin-Hamiltonian parameters and local molecular structure for Pd(I) center in the gamma-irradiated Pd(II)(acac)2 System have been studied by using the high-order perturbation formulas and Newman's superposition model. Based on these calculations, it was found that the distance of the metal-ligand bonds in the square planar complex for Pd(I) center in the gamma-irradiated Pd(II)(acac)(2) system increases by 0.1 angstrom. To understand the detailed physical and chemical properties of the [Pd(I)(acac)(2)](2-) complex, the contributions of the spin-orbit coupling of ligand to spin-Hamiltonian parameters for Pd(I) ion are considered. The theoretical results are in reasonable agreement with the experimental values. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

关键词: crystal-field;ligand-field;spin-Hamiltonian parameters;local lattice;structure;Pd(I) ion;atomic screening constants;scf functions;crystal;resonance;ions

Investigations of zero-field splitting and defect structure for the tetragonal Fe-K(3)+-O-I center in KTaO3 crystal

Journal of Physics and Chemistry of Solids

By using the defect structure data (characterized by the coordinates of impurity center) obtained from the shell model and the density functional theory in the generalized gradient approximation (GGA) corresponding to two supercell sizes, the zero-field splitting D of the tetragonal Fe-K(3+)-O-I center in KTaO3 crystal is calculated from the high-order perturbation formula based on the dominant spin-orbit coupling mechanism. The calculated results suggest that the sign of zero-field splitting D is negative and the defect structure data obtained from GGA method are more reasonable. Compared with that corresponding to the smaller supercell size, the calculated D value based on the GGA coordinates corresponding to the larger supercell size is closer to the observed value, suggesting that the GGA coordinates obtained from the larger supercell size are more accurate. (c) 2006 Elsevier Ltd. All rights reserved.

关键词: inorganic compounds;oxides;crystal fields;defects;electron;paramagnetic resonance (EPR);fe centers;ions;scattering;spectra;sites;model;epr

Tetragonal distortion of the tetragonal V2+-V-M center in KBr : V2+ crystal

Journal of Physics and Chemistry of Solids

The tetragonal distortion for the tetragonal V2+-V-M center in KBr:V2+ crystal is estimated by analyzing its EPR data from two theoretical models, one is the two spin-orbit (S.O.) parameter model where the contributions to EPR parameters from both the S.O. coupling of the central metal ion and that of the ligands are considered and another is the conventional one-S.O.-parameter model where only the contribution from the S.O. coupling of the central metal ion is included. The result from the two-S.O.-parameter model is more than ten times that of the one-S.O.-parameter model. The reasonableness of the former is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.

关键词: inorganic compounds;crystal fields;defects;electron paramagnetic;resonance (EPR);epr parameters;transition;ions

INVESTIGATION ON THE DENSITY UNIFORMITY OF PRESSED PARTS BY LOW-VOLTAGE EI,RCTROMAGNETIC COMPACTION

S.Y.Huang

金属学报(英文版)

Powder metallurgy is an efficient approach to fabricate varieties of high performance structure materials, function materials and special materials working under limited conditions. Research and development of new efficient technology to form high-density,high-performance and net shape parts is a key to widen application and development of powder materials. Recently, the low-voltage electromagnetic compaction (EMC) has been used by present authors to compacted copper, tin, aluminum powders and the products with 99relative density have been acquired. In this work, the research has been extended to investigation on the density uniformity of pressed parts. The analysis results show that the density of the part compacted by low-voltage EMC decreases gradually in press direction as static compaction. But it is higher and more homogeneous. The densit3"" of the top part increases gradually from the center to the outer, which is just reversal of the bottom part. In some extent, the higher the discharging voltage is, the higher the densiO' is and the more homogeneous the distribution is. In addition, repetitive compaction can improve the density of powder parts and the distribution uniformity.

关键词: powder , null , null

Re-interpretation of EPR spin-Hamiltonian parameters b(2)(m) for Gd3+-O2- center in the tetragonal phase of perovskite-type compound Rb1-xKxCaF3 with x=0.05

Physica Status Solidi B-Basic Research

The spin-Hamiltonian parameters b(2)(2), b(2)(-1) and b(2)(0) for Gd3+-O2- center in the tetragonal phase of Rb0.95K0.05CaF3 perovskite-type compound are studied by the superposition model which considers the (GdOF5)(4-) octahedron distortion related to the elongation or release of the metal-ligand bond lengths in the octahedron. The parameters b(2)(m) can be reasonably explained, and information for the local phase transition behaviour is obtained.

关键词: transitions;disorder;crystals;resonance;rbcaf3;rbcdf3

稀土区奇奇核πh11/2(×)νi13/2带B(M1)/B(E2)比值增强特性

陆景彬 , 刘运祚 , 孙亮 , 杨东 , 梁国栋 , 王守宇 , 马英君 , 赵广义 , 李险峰 , 崔兴柱 , 李明非 , 霍俊德 , 曾国模 , 竺礼华 , 吴晓光

原子核物理评论 doi:10.3969/j.issn.1007-4627.2005.02.003

在稀土区奇奇核πh11/2(×)νi13/2转动带中, 系统地观测到随转动频率或角动量增加, B(M1)/B(E2)曲线表现出所谓parabola-like形状, 即在增加到某一转动频率或自旋后, B(M1)/B(E2)比值快速增强. 基于推转模型和粒子转子模型关于奇奇核二准粒子转动带磁偶极约化跃迁几率的描述, 对稀土区双奇核的这一行为进行了讨论. 指出该现象的发生与νi13/2准中子转动顺排特性密切相关. B(M1)/B(E2)比值在接近第二带交叉(即BC准中子对顺排)的较高频率处的增强效果, 可以理解为主要来源于带交叉引起的波函数中混合四准粒子成分的结果. 通过对B(M1)/B(E2)比值的增强效果发生在较低频率处的分析, 对稀土区奇奇核πh11/2(×)νi13/2带角动量耦合图像有了进一步认识.

关键词: 高自旋态 , 奇奇核 , 电磁跃迁特性 , 顺排

Studies on the EPR parameters for the rhombic Co2+ center in magnesium acetate

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The electron paramagnetic resonance (EPR) g factors g(i) (i = x,y,z) and the hyperfine structure constants A(i) for the rhombic Co2+ center in magnesium acetate are theoretically studied from the perturbation formulas of these parameters for a 3d(7) ion under rhombic symmetry. In these formulas, the contributions from the admixture among different states, covalency effect and rhombic crystal-fields are taken into account. The related crystal-field parameters are determined from the superposition model and the local geometrical relationship of the impurity center. The calculated results show reasonable agreement with the observed values. In addition, the nuclear quadrupole interaction constant is analyzed, and its negative sign is verified theoretically.

关键词: electron paramagnetic resonance (EPR);crystal- and ligand-fields;Co2+;magnesium acetate;atomic screening constants;paramagnetic-resonance;superposition model;aqueous-solutions;scf functions;g-tensor;crystal;fields;sites;liyf4