Effect of Ni content on the diffusion-controlled growth of the product phases in the Cu(Ni)–Sn system

A strong influence of Ni content on the diffusion-controlled growth of the (Cu,Ni)₃Sn and (Cu,Ni)₆Sn₅ phases by coupling different Cu(Ni) alloys with Sn in the solid state is reported. The continuous increase in the thickness ratio of (Cu,Ni)₆Sn₅ to (Cu,Ni)₃Sn with the Ni content is explained by combined kinetic and thermodynamic arguments as follows: (i) The integrated interdiffusion coefficient does not change for the (Cu,Ni)₃Sn phase up to 2.5 at.% Ni and decreases drastically for 5 at.% Ni. On the other hand, there is a continuous increase in the integrated interdiffusion coefficient for (Cu,Ni)₆Sn₅ as a function of increasing Ni content. (ii) With the increase in Ni content, driving forces for the diffusion of components increase for both components in both phases but at different rates. However, the magnitude of these changes alone is not large enough to explain the high difference in the observed growth rate of the product phases because of Ni addition. (iv) Kirkendall marker experiments indicate that the Cu₆Sn₅ phase grows by diffusion of both Cu and Sn in the binary case. However, when Ni is added, the growth is by diffusion of Sn only. (v) Also, the observed grain refinement in the Cu₆Sn₅ phase with the addition of Ni suggests that the grain boundary diffusion of Sn may have an important role in the observed changes in the growth rate.     

Preparation and characterization of Ag nanoparticle-embedded polymer electrospun nanofibers

Poly (vinyl alcohol) (PVA) and poly (vinyl pyrrolidone) (PVP) nanofibers embedding Ag nanoparticles (5–18 nm) have been prepared successfully by electrospinning at room temperature. Scanning electron microscope (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier transform IR spectra (FTIR), and Raman scattering were used to characterize the structure and properties of Ag nanoparticle-embedded PVA and PVP nanofibers before and after heat treatment at different temperature. The antibacterial activity of Ag nanoparticle-embedded PVP nanofibers after heat treatment was also tested, which indicated that the biological activity of yeast cells was effectively inhibited by these Ag nanoparticle-embedded PVP nanofibers.     

The Structure of Parafermion Vertex Operator Algebras: General Case

The structure of the parafermion vertex operator algebra associated to an integrable highest weight module for any affine Kac-Moody algebra is studied. In particular, a set of generators for this algebra has been determined.     

Density functional theory study of AunMn(n=1-8) clusters

Equilibrium geometries, relative stabilities, and magnetic properties of small Au_nMn (n=1-8) clusters have been investigated using density functional theory at the PW91P86 level. It is found that Mn atoms in the ground state Au_nMn isomers tend to occupy the most highly coordinated position and the lowest energy structure of Au_nMn clusters with even n is similar to that of pure Au_n+1 clusters, except for n=2. The substitution of Au atom in Au_n+1 cluster by a Mn atom improves the stability of the host clusters. Maximum peaks are observed for Au_nMn clusters at n=2, 4 on the size dependence of second-order energy differences and fragmentation energies, implying that the two clusters possess relatively higher stability. The HOMO-LUMO energy gaps of the ground state Au_nMn clusters show a pronounced odd-even oscillation with the number of Au atoms, and the energy gap of Au₂Mn cluster is the biggest among all the clusters. The magnetism calculations indicate that the total magnetic moment of Au_nMn cluster, which has a very large magnetic moment in comparison to the pure Au_n+1 cluster, is mainly localized on Mn atom.     

A revised controlled deterministic secure quantum communication with five-photon entangled state

A revised controlled deterministic secure quantum communication protocol using five-photon entangled state is proposed. It amends the security loopholes pointed by Qin et al. in [S.J. Qin, Q.Y. Wen, L.M. Meng, F.C. Zhu, Opt. Commun. 282 (2009) 2656] in the original protocol proposed by Xiu et al. in [X.M. Xiu, L. Dong, Y.J. Gao, F. Chi, Opt. Commun. 282 (2009) 333]. The security loopholes are solved by using order rearrangement of transmission photons and two-step security test.     

Effects of in situ plasma treatment on optical and electrical properties of index-matched transparent conducting oxide layer

We investigated the effects of in situ plasma-treatment on optical and electrical properties of index-matched indium tin oxide (IMITO) thin film. To render the IMITO-coated surface hydrophilic and study the optical and electrical characteristics, we performed in situ oxygen plasma post-treatment without breaking vacuum. The 94.6% transmittance in the visible wavelength range (400-700 nm) increased on average to 96.4% and the maximum transmittance reached 98% over a broad wavelength range. The surface roughness and sheet resistance improved from 0.9 nm and 200 Ω/sq to 0.0905 nm and 100 Ω/sq, respectively, by in situ plasma post-treatment. We confirmed by contact angle measurement that the hydrophobic IMITO surface was altered to hydrophilic. The improved optical and electrical characteristics of in situ plasma-treated IMITO makes it adequate for high-resolution liquid crystal on silicon displays.     

Electronic structures,magnetic properties and band alignments of 3d transition metal atoms doped monolayer MoS2

Utilizing first-principles calculations, the electronic structures, magnetic properties and band alignments of monolayer MoS₂ doped by 3d transition metal atoms have been investigated. It is found that in V, Cr, Mn, Fe-doped monolayers, the nearest neighboring S atoms (S_NN) are antiferromagnetically polarized with the doped atoms. While in Co, Ni, Cu, Zn-doped systems, the S_NN are ferromagnetically coupled with the doped atoms. Moreover, the nearest neighboring Mo atoms also demonstrate spin polarization. Compared with pristine monolayer MoS₂, little change is found for the band edges' positions in the doped systems. The Fermi level is located in the spin-polarized impurity bands, implying a half-metallic state. These results provide fundamental insights for doped monolayer MoS₂ applying in spintronic, optoelectronic and electronic devices.     

Phase transformations and structural characteristics of AL–Cu–Co(–Si) decagonal phase

The phase transformations and structural characteristics of the Al-Cu-Co-Si alloy have been studied by neutron diffraction and high-resolution electron microscopy. The Al₆₅Cu_17.5Co_17.5 decagonal phase is stable in the temperature range between 973 K and 1350 K. At the low-temperature end, it relaxes to a microcrystalline approximant structure. At the high-temperature end, it melts directly into liquid. Two distinct orthorhombic phases are identified in the Al₆₃Cu_17.5Co_17.5Si₂ microcrystalline structure. They are composed of several structure units that can also construct the Penrose tiling. Because of lack of units, a single orthorhombic phase cannot undergo the transformation towards the high-temperature decagonal phase. An analysis of the orientation relationships between the CsCl and orthorhombic phases leads to the definition of Penrose tiling-like subnetworks inside the orthorhombic unit cells so that these orthorhombic phases can be regarded as the periodic patchworks of quasiperiodic subnetworks.     

Theoretical study of the 5p56s – 5p6 spectra of neutral xenon

Recent high precision measurements on the lifetime of the metastable 6s[3/2]₂ state of atomic xenon display a difference with previous predictions by a factor of 2–3. In the present work, a systematic relaxation and correlation approach, which has been developed on the basis of a widely used multi-configuration Dirac-Fock method, is applied to study the electric dipole allowed E1 and forbidden M1, E2 and M2 transitions between the 5p⁵ 6s and 5p⁶ configurations. We systematically include the correlation effects which arise from all the single and double excitations from the occupied shells into the (n=6–10) active sets and the relaxation effects caused by change of the electron density between the radiative initial- and final-states. This study not only reduces greatly the existing discrepancy in the lifetime of the 6s[3/2]₂ state, but also presents rather consistent results for both the lifetime of the metastable 6s'[1/2]₀ state and the oscillator strength of the 5p⁵ 6s - 5p⁶ E1 resonant transitions.     

激光加工微型光纤折射率传感器的工艺与特性

提出一种由157nm激光制造的新型微型光纤法布里-珀罗折射率传感器的制作方法,传感头由靠近单模光纤端的具有光纤顶端微通道的法布里-珀罗空气腔组成,将单模光纤顶端的微通道作为检测介质的入口.分别在珐珀腔的反射界面镀以薄膜作为反射镜面来确保高的光对比度.试验中获得了1130.887nm/refractive-index的分辨率.和其他的光纤传感器相比,这种传感器具有体积小,结构坚固,高分辨率,线性良好,测量范围宽等优点,能够满足实际应用的要求,特别是对需要小型传感器的场合.