Transport and Magnetotransport in the New Quasi-Two-Dimensional Organic Metal (BETS)2ZnBr4(C6H4Cl2) with Different Electron Structure of Neighboring Cation Layers

Intralayer and interlayer transports and Shubnikov – de Haas oscillations are investigated in the new dual-layered organic metal (BETS)₄ZnBr₄(C₆H₄Cl₂). It is shown that: a) the interlayer resistance behavior corresponds to incoherent transport; b) the behavior of quantum oscillations is well described by the model of a coherent network of magnetic breakdown orbits. Both the interlayer transport and quantum oscillations are in a good agreement with the theoretical calculation of the zone structure.     

Growth Properties of Carbon Nanowalls on Nickel and Titanium Interlayers

This research is conducted in order to investigate the structural and electrical characteristics of carbon nanowalls (CNWs) according to the sputtering time of interlayers. The thin films were deposited through RF magnetron sputtering with a 4-inch target (Ni and Ti) on the glass substrates, and the growth times of the deposition were 5, 10, and 30 min. Then, a microwave plasma-enhanced chemical vapor deposition (PECVD) system was used to grow CNWs on the interlayer-coated glass substrates by using a mixture of H₂ and CH₄ gases. The FE-SEM analysis of the cross-sectional and planar images confirmed that the thickness of interlayers linearly increased according to the deposition time. Furthermore, CNWs grown on the Ni interlayer were taller and denser than those grown on the Ti interlayer. Hall measurement applied to measure sheet resistance and conductivity confirmed that the electrical efficiency improved significantly as the Ni or Ti interlayers were used. Additionally, UV-Vis spectroscopy was also used to analyze the variations in light transmittance; CNWs synthesized on Ni-coated glass have lower average transmittance than those synthesized on Ti-coated glass. Based on this experiment, it was found that the direct growth of CNW was possible on the metal layer and the CNWs synthesized on Ni interlayers showed outstanding structural and electrical characterizations than the remaining interlayer type.     

黄河小浪底坝区泥化夹层分布及其抗剪试验方法的分析

在大量地质勘探试验研究资料的基础上 ,分析研究了形成泥化夹层的母岩和地质构造力 ,泥化夹层的类型及其粒度成分以及泥化夹层的分布规律。还分析研究了不同试验方法对泥化夹层抗剪强度的影响 ,并着重分析研究了我院研制的控制膨胀饱和固结慢剪的试验成果。     

Local probe of the interlayer coupling strength of few-layers SnSe by contact-resonance atomic force microscopy

The interlayer bonding in two-dimensional (2D) materials is particularly important because it is not only related to their physical and chemical stability but also affects their mechanical, thermal, electronic, optical, and other properties. To address this issue, we report the direct characterization of the interlayer bonding in 2D SnSe using contact-resonance atomic force microscopy (CR-AFM) in this study. Site-specific CR spectroscopy and CR force spectroscopy measurements are performed on both SnSe and its supporting SiO₂/Si substrate comparatively. Based on the cantilever and contact mechanic models, the contact stiffness and vertical Young’s modulus are evaluated in comparison with SiO₂/Si as a reference material. The interlayer bonding of SnSe is further analyzed in combination with the semi-analytical model and density functional theory calculations. The direct characterization of interlayer interactions using this non-destructive methodology of CR-AFM would facilitate a better understanding of the physical and chemical properties of 2D layered materials, specifically for interlayer intercalation and vertical heterostructures.     

超音速火焰喷涂含铝或锌中间层的YSZ热障涂层

在镁合金基底表面直接制备热障涂层,涂层的耐蚀性较差。采用超音速火焰喷涂法在镁合金基底和热障涂层之间分别制备了Al涂层和Zn涂层。通过XRD,SEM和EDS对涂层进行物相、微观结构和点扫描元素分析,采用电化学工作站对Al涂层试样和Zn涂层试样进行耐腐蚀性分析,同时研究了含Al中间层和含Zn中间层的热障涂层的抗热震性能。结果表明:Al涂层表面粗糙度(10.237±0.527μm)大于Zn涂层表面粗糙度(7.171±0.488μm),且喷涂过程中仅有轻微氧化。Al涂层试样的耐腐蚀性优于Zn涂层试样。含Zn中间层的热障涂层具有更好的抗热震性能。     

Magnon energy gap in a four-layer ferromagnetic superlattice

The magnon energy band in a four-layer ferromagnetic superlattice is studied by using the linear spin-wave approach and Green＇s function technique. It is found that three modulated energy gaps exist in the magnon energy band along Kx direction perpendicular to the superlattice plane. The spin quantum numbers and the interlayer exchange couplings all affect the three energy gaps. The magnon energy gaps of the four-layer ferromagnetic superlattice are different from those of the three-layer one. For the four-layer ferromagnetic superlattice, the disappearance of the magnon energy gaps △ω12, △ω23 and △ω34 all correlates with the symmetry of this system. The zero energy gap △ω23 correlates with the symmetry of interlayer exchange couplings, while the vanishing of the magnon energy gaps △ω12 and △ω34 corresponds to a translational symmetry of x-direction in the lattice. When the parameters of the system deviate from these symmetries, the three energy gaps will increase.     

Effect of the compliant interlayer on the dynamic stress intensity factor in a piecewise-homogeneous solid with a circular crack

The dynamic behavior of a circular crack in an elastic composite consisting of two dissimilar half-spaces connected by a thin compliant interlayer is studied. One half-space contains a defect aligned perpendicular to the interlayer; the defect surfaces are loaded by normal harmonic forces, which ensures the symmetry of the stress-strain state. The thin interlayer is modeled by conditions of a nonideal contact of the half-spaces. The problem is reduced to a boundary integral equation with respect to the function of dynamic opening of the defect. The numerical solution of this equation yields frequency dependences of the mode I stress intensity factor in the vicinity of the crack for different values of interlayer thickness and relations between the moduli of elasticity of the composite components. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 197–207, May–June, 2008.     

橡胶沥青应力吸收层力学与疲劳性能研究

防治反射裂缝是半刚性基层沥青路面新建或改建工程中的难题之一.橡胶沥青应力吸收层是一种较好的反射裂缝防治结构.本文设计了包含应力吸收层复合试件的剪切与疲劳试验,通过室内和现场取芯试件,研究了橡胶沥青应力吸收层及其他封层的力学和疲劳性能.聚酯玻纤布应力吸收层疲劳性能最好,但在较高橡胶沥青洒布量下,橡胶沥青与聚酯玻纤布应力吸收层疲劳性能接近;橡胶沥青应力吸收层的抗剪切变形能力最大,且其抗剪强度也比较高;橡胶沥青洒布量对橡胶沥青应力吸收层的抗剪强度、疲劳能力影响较大.当橡胶沥青洒布量在1.8～3.0kg/m2间增加时,橡胶沥青应力吸收层的抗剪强度、疲劳能力均增加,但不是线性关系增加.     

Unsteady Flow to Wells Partially Penetrating in Two-Layered Aquifers

The unsteady flow of water to well in a layered aquifer with an interlayer flow is examined in this paper. The system studied comprises an aquifer consisting of two productive layers of finite thickness that are in a perfect hydraulic contact and a well which partially penetrates in one of the layers. Each layer is assumed to be homogeneous and isotropic and the water contained in the aquifer is of identical physical properties and small compressibility.The analytical solutions are derived for the case when the system is characterised by equality of hydraulic diffusivity of layers. These solutions give the results accurate enough for practical applications and allow to estimate the effects of partial penetration and contrast in parameters of formation on distribution of the flow potential both at large distances from wells and at the wells.The obtained solutions also provide a basis for predicting the interlayer flow arising from the performance of a pumping well as well as between a pair of wells which have an open interval located in different layers of the aquifer. Two cases have been analysed: (1) a pumping pair of wells which is used to prevent water inflow to the productive well, and (2) a pumping-injection pair of wells providing the demanded mixing of water from adjacent layers. Some examples of flow patterns and specially computed diagrams are given to illustrate the operation of such systems.     

EFFECT OF INTERLAYER THICKNESS ON THE MODE I FRACTURE ENERGY RELEASE RATE OF SANDWICH STRUCTURE$^{\bf 1)}$

三明治结构作为载荷传递和连接元件,广泛应用于航空航天、材料表征、柔性电子等领域. 了解其断裂行为和特点能为三明治结构连接件极限载荷的设计提供理论指导. 基于改良弹性地基理论模型,本文提出了一种计算能量释放率的新理论模型,模型中考虑中间层厚度对三明治结构 I 型断裂能量释放率的影响. 结果表明,中间层厚度对三明治结构 I 型断裂的影响存在两个部分：中间层剪切力的影响及中间层引起结构刚度增大的影响. 当无量纲中间层厚度取最大值 2 时,传统模型与有限元计算结果存在 70% 以上的误差;采用本文的模型可以极大地提高精度,将误差降到 5% 以内. 相比改良弹性地基理论只适用于中间层厚度较小的情况,本理论模型的适用范围更广. 此外,利用本模型,本文选取了两个几何参数 (中间层厚度和裂纹初始长度) 和一个材料参数 (模量比) 进行研究. 讨论了剪切效应对结构几何和材料参数的敏感性. 在定载荷的基础上,讨论了几何和材料参数对能量释放率的影响;并在假定结构断裂韧性不变的基础上,得到了几何和材料参数对三明治结构临界载荷的影响规律.