材料期刊网

Commercial Purity Aluminum with a BimodalGrain Size Distribution: Mechanical Properties, Deformation and Fracture Mechanisms

S.Billard , E.Meslin , G.F.Dirras , J.P.Fondère , B.Bacroix

材料科学技术（英文）

Commercial purity Al has been processed by hot isostatic pressing consolidation of nanopowders. The resulting bulk material contained a small fraction of microcrystalline grains (>300 nm) embedded in a matrix of ultrafine grains (150 nm). The mechanical properties under compressive tests at various temperatures and at a strain rate of 2×10－4 s－1 have been investigated. At room temperature a brief hardening was observed followed by a stagnation of the flow stress up to failure. From 150 to 200℃ softening occurred after a short hardening stage. A change in the behavior showed up at 300℃: a quasi perfect plasticity was observed subsequently to a yield point. The major deformation mechanisms include dynamic recovery, grain fragmentation and sliding. Besides, when tested up to rupture at elevated temperature filament formation where observed at the fracture surface. The formation mechanism of the filaments is possibly linked to the presence of a viscous-like phase at grain boundaries.

关键词: Aluminum , null , null , null

G(f)/HA-CS复合材料的制备及性能研究

沈基显 , 黄剑锋 , 曹丽云 , 曾燮榕 , 熊信柏

稀有金属材料与工程

以羟基磷灰石-壳聚糖(HA-CS)为基体,玻璃纤维G(f)为增强相,采用原位杂化法制备短玻璃纤维增强HA-CS基生物复合材料.研究交联剂、羟基磷灰石含量和玻璃纤维含量对复合材料性能的影响.采用红外吸收光谱、扫描电子显微镜和万能材料试验机对材料的结构和性能进行表征.结果表明:原位杂化法能制备性能较好的复合材料;用戊二醛交联改性复合材料可以明显增加其韧性和弯曲强度,使复合材料抗弯曲强度提高16%;当CS/HA=10/1(质量比)和玻璃纤维含量为1.5%时复合材料抗折强度达到极大值84.47 MPa;随玻璃纤维含量的增加,复合材料的断裂面由平整向多层断裂变化,材料的韧性有所提高.

关键词: G(f)/HA-CS复合材料 , 玻璃纤维 , 交联剂 , 弯曲强度

Theoretical studies of g factors and defect structures for cubic, tetragonal, and orthorhombic Fe+ Centers in alkali halides MX (M = Li, Na; X = F, Cl)

Communications in Theoretical Physics

The EPR g factors for cubic, tetragonal and orthorhombic Fe+ centers in alkali halides MX (M = Li, Na; X = F, Cl) are calculated from second-order perturbation formulas of g factors based on cluster approach for 3d(7) ions in three symmetries. From calculations, the g factors of these Fe+ centers in MX crystals are reasonably explained and the defect structural data for the tetragonal and orthorhombic Fe+ centers are estimated. The results are discussed.

关键词: crystal;and ligand-field theory;electron paramagnetic resonance;defect structure;atomic screening constants;spin-orbit interaction;superposition model;resonance-spectra;epr parameters;crystal-field;scf functions;ions;co2+

Investigations of EPR g Factors and Rhombic Distortion for the Rhombic Cu2+ Centers in K2Zn1-x Cu (x) F-4 Crystals at Low Temperature

Applied Magnetic Resonance

The electron paramagnetic resonance g factors g (i) (i = x, y, z) of two rhombic Cu2+ centers, Cu2+(II) and Cu2+(III), in K2Zn1-x Cu (x) F-4 crystals found at low temperature are calculated from the complete diagonalization (of energy matrix) method based on the cluster approach. The calculations show that the ground state wave function of the two rhombically compressed Cu2+ centers is with a small admixture of . The rhombic distortions for both Cu2+ centers are obtained from the calculations. The results are discussed.

关键词: electron-paramagnetic-resonance;atomic screening constants;hyperfine;parameters;gyromagnetic factor;spin resonance;scf functions;field;copper(ii);dependence;spectra

Investigations of the EPR g factors for Er3+ in CaMoO4

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The electron paramagnetic resonance (EPR) g factors g(parallel to) and g(perpendicular to) for Er3+ in CaMoO4 are theo retically investigated by using the perturbation formulas of the g factors for a 4f(11) ion in tetragonal symmetry. In these formulas, the contributions to the g factors arising from the second-order perturbation terms and the admixture of various states are considered. The crystal-field parameters for the tetragonally distorted tetrahedra are determined by using the superposition model and the structural data of the impurity Er3+ on the host Ca2+ site in CaMoO4. The calculated g factors agree with the. observed values. The validity of the results is discussed.

关键词: electron paramagnetic resonance (EPR);crystal- and spin Hamiltonians;Er3+;CaMoO4;electron-paramagnetic-resonance;superposition-model;molybdate;crystals;calcium molybdate;ion;spectroscopy;parameters;tungstate;liyf4

A Novel Topological Index F* and Its Correlation With Standard Formaton Enthalpies of ABn(g) Molecules

武汉理工大学学报-材料科学版(英文版)

关键词:

ANISOTROPY OF THE G-FACTOR FOR NI2+ AND NI3+ IONS IN THE TETRAGONAL PHASE OF SRTIO3

Physica B-Condensed Matter

In this paper, a simple and uniform expression for calculating the anisotropy of the g factor (characterized by DELTAg = g(perpendicular-to) - g(parallel-to)) for 3d(n) ions in the tetragonal phase of the perovskite structure from the spin-lattice coupling coefficients F11 and F12 in the cubic phase has been proposed by introducing a release factor k. From this expression, the values of DELTAg for Ni2+(3d8) and Ni3+ (3d7) ions in the tetragonal phase of a SrTiO3 Crystal are studied. It is found that for SrTiO3:Ni2+, the observed isotropy of the g factor (DELTAg = 0) is due to the too small value of (F11 - F12) and for SrTiO3: Ni3+, the contribution to DELTAg from the elongation of the octahedron around the Ni3+ ion is important in the case of T near the transition temperature T(c).

关键词: lattice coupling-coefficients;cubic symmetry;fij

Investigations of the local structure and the g factors for the tetragonal Er3+ center in KMgF3

Materials Letters

The local structure and the electron paramagnetic resonance (EPR) g factors for the tetragonal Er3+ center in KMgF3 are theoretically studied by using the perturbation formulas of the g factors for a 4f(11) ion in tetragonal symmetry. In these formulas, the contributions to the g factors from the second-order perturbation terms and the admixtures of various states are taken into account. Based on the studies, the impurity Er3+ is expected to occupy the octahedral Mg2+ site, associated with an oxygen ion substituting for one of the nearest F- (i.e., O-F) in the C-4 axis, due to charge compensation. Because of the electrostatic attraction of the compensator O-F, the Er3+ ion is found to take an axial displacement Delta Z (approximate to 0.07 angstrom) towards the compensator along the C-4 axis. The calculated g factors based on the above displacement Delta Z show reasonable agreement with the observed values. (C) 2005 Elsevier B.V. All rights reserved.

关键词: defects;electron paramagnetic resonance (EPR);crystal fields;Er3+;KMgF3;electron-paramagnetic-resonance;superposition-model analysis;ce3+;luminescent centers;crystal-field;perovskite kmgf3;parameters;conversion;fluorides;site;ion

离子色谱法测定电镀液中F-和Cl-

冶金分析

提出了离子色谱法检测电镀液中F-和Cl-的方法.根据高沸点酸置换低沸点酸,用硫酸作为蒸馏剂,在一定的温度下,将F-和Cl-一起蒸馏出进行分离和富集,消除了电镀液中大量共存离子的干扰和对色谱柱的污染.使用IonPacASl4A作为色谱柱,在合适的色谱条件下,F-和Cl-的色谱峰能很好地分离,其检出限分别为0.84 μg/L和0.37 μg/L,相对标准偏差F-小于7.3%,Cl-小于4.2%(n=10),加标回收率F-在91%～107%、Cl-在95%～105%之间(n=10),电镀液中共存离子对F-和Cl-的测定无干扰.方法用于电镀液中F-和Cl-的同时测定,具有很好的可行性和实用性.

关键词: F- , Cl- , 离子色谱 , 蒸馏法 , 电镀液

F-12纤维的吸湿行为

阳建红 , 董进辉 , 李海斌 , 石强 , 郭明映

复合材料学报

在60℃、80℃相对湿度90%环境条件下对F-12纤维进行了湿热老化实验,研究了长时间老化时纤维吸湿规律.通过ATR-FTIR光谱分析了湿热老化后水对F-12纤维化学结构的影响以及水在纤维中可能存在的方式,探讨了吸湿机制,实验研究了纤维单丝拉伸强度的变化,并采用SEM观察了纤维表面及拉伸断口形貌.结果表明:F-12纤维长时间的吸湿属于2阶段吸湿,吸湿初期符合Fick第二定律,后期偏离,吸湿2500 h后仍没达到平衡;水分子对F-12纤维的化学结构没有造成明显的破坏,老化2500 h后F-12纤维表面变得粗糙,出现了一些沟槽,老化后期断口呈现出脆性与原纤化复合的特征;拉伸断裂强度并非持续减小,而是在起伏波动中减小.

关键词: F-12纤维 , 吸湿规律 , ATR-FTIR , SEM , 吸湿机制 , 拉伸强度