Shihong LI
,
Shaoyun FU
,
and Benlian ZHOU (Int. Centre for Mater. Phys.
,
Institute of Metal Research
,
Chinese Academy of Science
,
Shenyang
,
110015
,
China)Qiyun ZENG
,
and Xianrong BAO (Institute of Applied Ecology
,
Chinese Academy of Sciences
,
Shenyang
,
11
材料科学技术（英文）
A new technique has been developed for flattening circular natural bamboo culm to plate form for remarkably enhancing its mechanical properties, The enhanced bamboo, cheaper than Al, is then used to reinforce an aluminum alloy for civilian applications. The properties of the composite are greatly enhanced compared to those of the Al alloy. The Al protects bamboo from bioerosion and improves hygroscopicity
关键词:
Journal of Physics and Chemistry of Solids
The layered ternary ceramics Ti3SiC2 and Ti3AlC2 are isostructural and can form Ti3Si1-xAlxC2 solid solutions combining the advanced properties of both compounds [H.B. Zhang, Y.C. Zhou, Y.W. Bao, M.S. Li, Improving the oxidation resistance of Ti3SiC2 by forming a Ti3Si0.90Al0.1C2 solid solution, Acta Mater. 52 (2004) 3631-3637; E.D. Wu, J.Y. Wang, H.B. Zhang, Y.C. Zhou, K. Sun, Y.J. Xue, Neutron diffraction studies of Ti3Si0.9Al0.1C2 compound, Mater. Lett. 59 (2005) 2715-2719; J.Y. Wang, Y.C. Zhou, First-principles study of equilibrium properties and electronic structure of Ti3Si0.75Al0.25C2 solid solution, J. Phys.: Condens. Matter 15 (2003) 5959-5968; Y.C. Zhou, J.X. Chen, J.Y. Wang, Strengthening of Ti3AlC2 by incorporation of Si to form Ti3Al1-xSixC2 solid solutions, Acta. Mater. 54 (2006) 1317-1322]. In the present work, the solid solutions of Ti3Si1-xAlxC2 (x = 0, 0.25, 0.33, 0.5, 0.67, 0.75, 1) are investigated by first-principle calculations based on pseudo-potential plan-wave method within the density functional theory framework. The results show that as Al content increases in the solid solution, all the bonds have weakened to certain extents, which lead to an unstable structure both energetically and geometrically. The calculated results are compared and discussed with the reported data for the Ti3Si1-xAlxC2 solid solutions. (c) 2007 Elsevier Ltd. All rights reserved.
关键词:
ceramics;ab initio calculations;electronic structure;electrical;conductivity;oxidation behavior;mechanical-properties;ti3sic2;temperature;ti3alc2;air;si
Philosophical Magazine
The elastic and plastic anisotropies of three oriented Cu single crystals were determined by a nanoindentation technique with a Berkovich and a cube-corner indenter, respectively. The indentation modulus ( E) of the crystals in the elastic and the plastic regimes were separately extracted using Hertzian elastic analysis and the Oliver-Pharr (O&P) method [J. Mater. Res. 7 1564 ( 1992)]. E values for Cu( 111) and ( 110) are nearly identical, about 20% larger than that of ( 001), as determined using a Berkovich tip in both regimes. E values determined in the plastic regime using a Berkovich tip agree well with theoretical predictions in terms of the Vlassak and Nix [ Phil. Mag. A 67 1065 ( 1993); J. Mech. Phys. Solids 42 1223 ( 1994)] analytical method, but smaller than those determined in the elastic regime. Elastic anisotropies in the plastic regime, however, are not measurable as a cube-corner indenter was used. The hardness ( H) of Cu crystals exhibits an obvious indentation size effect and larger H values are obtained with a sharper indenter.
关键词:
indentation experiments;deformation;mechanisms;hardness
Physica E-Low-Dimensional Systems & Nanostructures
Generally, phase transfer of metal nanoparticles between aqueous phase and organic phase need two reagents at last. One is stabilizer of nanoparticles, the other is phase-transfer agent (Chem. Lett. 21 (1992) 1527; J. Colloid Interface Sci. 161 (1993) 471; J. Phys. Chem B 101 (1997) 9876; Chem. Commun. (1997) 537; Langmuir 14 (1998) 602; J. Phys. Chem B 103 (1999) 7238; Chem. Mater. 13 (2001) 4692; Langmuir 17 (2001) 733; Langmuir 16 (2000) 9775; Langmuir 18 (2002) 3364; J. Am. Chem. Soc. 123 (12001) 11148). In this paper, Ag nanoparticle prepared by tannic acid reduction of AgNO3 in aqueous medium were transferred to chloroform solution via a remarkably simple one-step route under the effect of phase-transfer inducer dimethyldioctadecylammonium chloride (DDAC), where no special stabilizer was required. Monolayer of Ag nanoparticles is obtained on carbon film by self-assembly using chloroform organosol. The effect of the inducer DDAC concentration is checked, and it was found that 5 x 10(-3) mol dm(-3) of DDAC was the optimum concentration for phase transfer of Ag nanoparticles. The organosol, Ag nanoparticle self-assembled monolayer and phase transfer were characterized by UV-vis spectra, TEM, ED and TF-IR. (C) 2004 Elsevier B.V. All rights reserved.
关键词:
silver;nanostructures;UV-Vis spectroscopy;DDAC;organosol;modified gold nanoparticles;shape-controlled synthesis;silver;nanoparticles;colloidal gold;aspect-ratio;nanorods;toluene;nanodisks;platinum;water
Physical Review B
In order to understand the unusually large value of zero-field splitting D for the axial Fe3+ center in a KTaO3 crystal, Zhou made two assumptions in his recent report [Phys. Rev. B 42, 917 (1990)]. In this Comment we will show that his assumption II is qualitatively reasonable, whereas assumption I is unnecessary and doubtful.
关键词:
electric-field;srcl2
Physica Status Solidi B-Basic Research
The perturbation formulae of EPR g-factors g(i) (i = x, y, z) and hyperfine constants Ai for a 3d(7) (Co2+) ion at a rhombic octahedral site in a crystal are established from a cluster approach. In these formulae, the contributions from the covalency effect, the configuration interaction and the rhombic crystal field are considered and the parameters used in the calculation of EPR parameters. except the core polarization constant x in the calculation of Al, can be estimated from the optical spectra and the structure data of the studied system. From these formulae, the EPR parameters g(i) and A(i) for the rhombic Co2+-V-Ag centre in AgCl are reasonably explained by considering suitable rhombic distortion and so the microstructure of this rhombic centre is obtained.
关键词:
superposition model;crystals
Physica Status Solidi B-Basic Research
The EPR g-factors g(\\), g(perpendicular to) and hyperfine structure constants A(\\), A(perpendicular to) for a tetragonal Co2+ centre, i.e.. Co(H2O)(2)Cl-4 centre, in NH4Cl crystal are calculated from the perturbation formulas based on a cluster approach. In these formulas, the parameters related to the contributions from the configuration interaction. the covalency effect and the low-symmetry crystal field can be obtained from the optical spectra and the structural model and data of the studied system. The core polarization constant it in the calculation formulas of hyperfine constants is used as an adjustable parameter. The calculated results are in good agreement with the observed values.
关键词:
superposition model;centers;resonance;ions;cr3+
Physical Review B
The assignment of the absorption spectrum of Y3Fe5O12 (YIG) made by Scott et al. [Phys. Rev. B 10, 971 (1974)] is shown to be incorrect and a new one is made by diagonalizing the complete cubic crystal-field matrices for d5 ions, involving spin-orbit interaction, given by Zhou et al. [Phys. Rev. B 44, 7499 (1991)]. The Racah parameters B and C, the crystal-field parameter Dq, and the spin-orbit coupling coefficient zeta are determined (in units of cm-1) as B = 783.3(530), C = 2928(3220), Dq = 1336(1300), zeta = 395 for octahedral Fe3+, and B = 606.1(705), C = 2696(2730), Dq = -1117.3(560), zeta = 335 for tetrahedral Fe3+, where the numerals in parentheses are the values adopted by Scott et al. Furthermore, the cubic zero-field splitting parameter a of Fe3+ in YIG is calculated to be a(oct) = 156 X 10(-4) cm-1 and a(tet) = 58.6 X 10(-4) cm-1. The value for a(oct) differs from the value of 189 X 10(-4) cm-1 found for Fe3+ in Y3Ga5O12:Fe3+. These results support speculations made by Geschwind [Phys. Rev. 121, 363 (1961)].
关键词:
fe3+;mn2+
Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
关键词:
room-temperature
