Journal of Raman Spectroscopy
Raman spectra of (CH3NH3)(2)SnCl6 were recorded in the temperature range 5-300 K. A continuous phase transition occurs at T-c=155 K, The fact that all the E modes of the CH3NH3+ ion and the SnCl62- ion remain degenerate in the low-temperature phase indicate that (CH3NH3)(2)SnCl6 still has a trigonal structure in the low-temperature phase, No soft mode was observed in the low-temperature range. (C) 1998 John Wiley & Sons, Ltd.
关键词:
methylammonium;hexachlorostannate(iv);resonance;halogens;nqr
Chinese Physics Letters
Raman-active phonons in orthorhombic perovskite-like RMnO3 were studied by measuring Raman spectra in various scattering configurations. The experimental Raman line wave numbers and the expected shapes for the phonon modes were compared to those reported for other perovskite-like compounds with the Pnma structure and to the results of lattice dynamical calculations. The observed Raman lines in the spectra of RMnO3 were assigned to definite atomic motions. The remaining spectral weight can be explained by the presence of dynamic John-Teller distortions that lower the symmetry of the cubic perovskite.
关键词:
jahn-teller transition;neutron-diffraction;scattering;phonons;lamno3;manganese;ymno3;spin;ho
Journal of Raman Spectroscopy
The phonon spectra and structural characteristics of the LuFe(2)O(4) system were investigated using X-ray diffraction as well as Raman and infrared (IR) spectroscopic techniques. Two step-like anomalies of the wavenumbers of the E(g)(3) peak in the Raman spectra and the E(u)(3) peak in IR spectra, as well as some weak anomalies of the lattice parameters, were found around the ferrimagnetic and ferroelectric transition temperatures. The substitutions of Lu with Yb and Fe with Mn lead to the corresponding wavenumber shifts in the optical spectra, which can be attributed to the changes in the atomic mass and lattice parameters. Furthermore, the Raman intensity was found to be related to the changes in the local structure and electrical conductivity. These results illustrate that the structural fluctuations could effectively influence the phonon modes, and a possible interplay among the structural, magnetic, and charge-ordering properties exists in this multiferroic system. Copyright (C) 2011 John Wiley & Sons, Ltd.
关键词:
phonon spectra;structure;multiferroic;charge;ferroelectricity
Surface and Interface Analysis
We have examined the optimal interface structure, ideal work of adhesion and bonding character of polar Ti(110)/TiN(111) interfaces by first-principles density-functional plane-wave pseudopotential calculations. Both Ti- and N-terminated interfaces, including six different interface structures, were calculated. The interface structure for each termination, continuing the TiN crystal structure across the interface, has the largest work of adhesion. Although both terminations yield substantial adhesion energies in the range 3-7 J m(-2), the N-terminated interface is similar to4 J m(-2) stronger than the Ti-terminated interface. Analysis of the interfacial electronic structure shows that the Ti-terminated interface is a mixed strong, metallic and weak covalent character, whereas the N-terminated interface is a polar covalent bond similar to the Ti/TiC interface. Further study of the separation of the optimal interface shows that the cleavages will never fracture at the interface due to the strong bonding, which is consistent with the experimental results. Copyright (C) 2003 John Wiley Sons, Ltd.
关键词:
first principles;metal/ceramic interface;adhesion;carbides;nitrides;metal-ceramic interfaces;mechanical-properties;first-principles;adhesion;pressure;tin;substrate;surfaces;mmc
Surface and Interface Analysis
The high-temperature structure of the Sigma = 5 bicrystalline interface of B2 NiAl with a large boundary plane is investigated by molecular dynamics simulations on parallel computers. It is observed that the atoms in the grain boundary region tend to form clusters in a thermal structural disorder transition, which is initiated at a temperature well below the thermodynamic melting point T-m (similar to0.52 T-m). The number and size of the clusters are monitored over a wide temperature range including T-m. Below T-m, the number and size of the clusters increase continuously with increasing temperature. When the temperature is up to T-m, the abrupt growth of the clusters induces melting. Once above Tm, the number and size of the clusters decrease significantly upon raising the temperature. The calculations of the potential energy also indicate that the thermal disorder transition is a continuous process, in contrast to the first-order melting transformation. Copyright (C) 2001 John Wiley & Sons, Ltd.
关键词:
interface;molecular dynamics;cluster;order-disorder effects;phase;transitions;boundary melting transition;grain-boundary;simulation;model
Polymers for Advanced Technologies
A corrosion protection coating from polyimide/polyaniline (PI/PAn) blend was prepared by solution blending and the anti-corrosion property of this coating was studied with electrochemical impedance spectroscopy technique. The results show that PAn can react with PI to form chemical bonds between these two polymers and these bonds keep these two polymers as a miscible system. The corrosion protection property of this coating increases with a growth in the PAn component and an excellent anti-corrosion effect emerges when the PAn content reaches 10-15%. The reason why PAn can improve the anti-corrosion property is that PI/PAn blend can form a dense and non-porous polymer film that would prevent some corrupting components from access to the underlying steel surface. And also, PAn may serve as a corrosion inhibiting agent to scavenge any protons and foster a local basic surface environment. Copyright (C) 2001 John Wiley Sons, Ltd.
关键词:
polyaniline;polyimide;corrosion;EIS
刘伶
,
关昶
,
张乃庆
,
孙克宁
人工晶体学报
采用共沉淀法制备锂离子电池正极材料Li(Ni1/3Co1/3Mn1/3)O2,通过循环伏安法和电化学交流阻抗分析,探讨了锂离子在LiNi1/3Co1/3Mn1/3O2中嵌入和脱出的机制.循环伏安测试结果表明,LiNi1/3 Co1/,Mn1/3O2材料结构中不存在John-teller效应,从而抑制了电极材料和电解液之间的副反应.电化学交流阻抗测试结果表明,随着电压的升高Rct(电荷转移电阻)值逐渐减小,而随着循环次数的增加Rct值逐渐增大.
关键词:
锂离子电池
,
正极材料
,
Li( Ni1/3 Co1/3 Mn1/3) O2
,
电极过程动力学
