Magnetic characteristics of Fe4N epitaxial films grown by halide vapor phase deposition under atmospheric pressure

The thin films of Fe₄N, which were prepared by atmospheric pressure halide vapor phase deposition, were epitaxially grown on a MgO(100) substrate and have cubic structure with good crystallinity. The magnetic characteristics of Fe₄N epitaxial film show soft magnetic behavior under various temperatures and various external magnetic field directions. As the temperature is decreased, the saturation magnetization increases. Also, the magnetized behavior is observed when the magnetic field is applied parallel to the film plane. It was found that the magnetic moments of Fe₄N epitaxial film are facing parallel to the film plane.     

强磁场辅助TFA-MOD法制备YBCO厚膜的理论分析

为了实现YBa2Cu3O7-x(YBCO)涂层导体在电力工业中的实际应用，必须有效增加YBCO超导层的厚度。提出一个强磁场辅助TFAMOD法制备YBCO厚膜的新工艺，并从磁热力学和磁性物理出发理论分析其可行性。沿垂直基底平面方向施加强磁场时，磁场将促进c轴取向YBCO晶核的形成，诱导厚膜中非c轴取向晶核转动到c轴平行磁场取向的位置。另外，取向晶粒间磁性相互作用力使晶粒沿磁场方向定向聚合，有利于获得致密的厚膜。因此，强磁场辅助TFA—MOD法有望制备高临界电流密度的YBCO织构厚膜。     

Effect of Film Thickness on the Columnar Packing Structures of Discotic Supramolecules in Thin Films

The effects of film thickness on the columnar packing structure of discotic supramolecules in a thin supported film have been investigated by grazing‐incidence small‐angle X‐ray scattering technique using magnetically aligned cobalt octa(n‐decylthio)porphyrazine (CoS10) films on octadecyltrichlorosilane (OTS)‐functionalized substrates as model systems. Magnetically aligned CoS10 films with a range of film thicknesses (49–845 nm) form uniaxially oriented ‘edge‐on’ columnar superstructures with their columnar directors perpendicular to the applied magnetic field. However, the orientational ordering of the columnar packing in the plane perpendicular to the applied magnetic field is strongly dependent on the film thickness. While being damped by the elasticity of the side chains of CoS10, the strong interfacial interaction at the film‐substrate interface propagates up to 50–100 nm from the substrate, maintaining the orientation of columnar packing in the plane perpendicular to the applied magnetic field. When the distance from the film‐substrate interface becomes larger than about 100 nm, symmetric tilting of columnar layer orientation, which saturates at 11.5°, occurs due to longitudinal edge dislocations induced by accumulated elastic deformation.     

51V NMR of inclusion compounds H2V12O31-y ·n H2O

The parameters of hyperfine interactions on⁵¹V nuclei were determined on films of the inclusion compound H₂V₁₂O_31-y ·n H₂O at different stages of hydration. It was established that the axial symmetry plane of the magnetic interaction tensor coincides with the film plane. The most probable direction (40° of the film plane) and the magnitude of the electric field gradient (EFG) on⁵¹V nuclei (egQ/h = 0.233 MHz) were found for a completely dehydrated sample. An analysis of the line width angular dependences of satellites has shown the existence of a disorientation of the main EFG direction with a distribution width of about 50° in the film plane. The absence of satellites and the presence of an angular dependence of the⁵¹V NMR central signal of hydrated samples allowed the conclusion that the interaction of the V-O layer with molecules of water led to an increase in the disorientation of the film plane.     

间同立构1,2-聚丁二烯的合成和形态结构研究

间同立构 1 ,2 -聚丁二烯自 1 955年问世以来 ,引起人们的广泛关注 ,但绝大多数研究工作集中在聚合物的合成方面[1～ 3] ,对其形态结构方面的研究却很少报道[4 ] ,原因是该聚合物分子侧链含有大量双链 ,在较高温度下 (>1 50℃ )很容易产生热交联 ,这给结构研究造成了很大困难 .间同立构 1 ,2 -聚丁二烯的性能取决于间规度 ,低间规度聚合物呈现弹性体特征 ,而高间规度聚合物则是一种半结晶性塑料 ,其结晶为平面锯齿链正交堆砌 ,Pacm空间群[4 ] .本文采用一种新的催化体系 ,使合成的 1 ,2 -聚丁二烯间规度可以调控 .同时首次报道了结晶性间规…     

溶液法制备的碳纳米管薄膜的结构分析与场致电子发射机理研究

结合紫外光电子能谱和拉曼光谱对溶液法制备的碳纳米管薄膜的场致电子发射性能进行研究。采用溶液滴涂法制备的碳纳米管薄膜的场致电子发射开启电场约为3.33 MV/m,阈值电场约为5.44 MV/m,以福勒-诺得海姆(Fowler-Nordheim,FN)理论对电子发射进行解释,其发射的增强因子接近103。通过对紫外光电子能谱的分析,发现碳纳米管薄膜的低能量截止端在外加电场作用下逐步降低,表明纳米管薄膜的表面有效势垒在外加电场作用下逐步下降,从而使得碳纳米管薄膜的电子更加容易发射进入真空。结合拉曼光谱和电学特性的研究,发现界面过渡层的接触电阻与碳纳米管薄膜中的非晶碳成分均可以增强场致电子发射。     

Thermal effects in low-pressure plane plasma apparatus for thin films applications

Thermal effects in a low-pressure plane plasma discharge were obtained in a novel implementation of triode sputtering method. This plane plasma discharge is formed in a relatively low vapor pressure of 0.03-0.65 Pa. Electron beam temperature and ion beam concentration distribution, as well as their dependence on argon pressure within the plasma, were experimentally studied, using the Langmuir probe technique. The influence of an external magnetic field on the ion beam concentration, and electron beam temperature, were studied too. As a result of these studies, sputtering of various materials was done using the novel plane plasma discharge method. This method enables the deposition of homogeneous thin film coatings. Analysis is done on Cu sputtered layers with plane plasma discharge. This revised version was published online in July 2006 with corrections to the Cover Date.     

Disjoining pressure,contact angles and line tension in free thin liquid films

Three are the main thermodynamic quantities which characterize the physical behaviour of the thin liquid films: the disjoining pressure, the macroscopic contact angle between the film and its adjacent bulk liquid phase, and the line tension of the film contact perimeter. All these quantities manifest the action of the long-range interaction surface forces which take place in any small capillary system. The rigorous introduction of such quantities is closely related to the Gibbs concept of surface of tension. For the case of a thin plane parallel liquid film there exist three surfaces of tension. By making use of them the thickness of the film would also be defined. There are several experimental methods for determining the tension of film, the contact angles. the line tension. Some important details of these methods. some experimental results together with important features of the thermodynamic theory of the thin liquid films are the subject of the present paper.     

单向和双向拉伸聚酯(PET)薄膜取向的光学评价

<正> 通常人们采用X-射线法和红外二向色性法等获得有关高聚物材料的晶区取向和分子链上某些特定基团的取向状况,但存在着设备要求高且操作复杂的弊端。Schael和Samuels等发展了利用改装型阿贝折射仪,可以方便地同时获得高聚物薄膜样品(聚烯烃和羟基丙基纤维素等)三个轴向上的折射率。有关聚酯(PET)的报道则不多见。本工作主要研究了不同拉伸条件(拉伸方式和拉伸速率等)对PET薄膜取向状况(折射率和     

衬底温度对ZnO薄膜生长过程和微结构的影响

从原子尺度上去研究薄膜生长过程中温度对薄膜取向性、缺陷结构以及薄膜完整性的影响和作用规律, 对于解释薄膜生长的物理本质、控制生长条件、提高薄膜制备的质量具有重要意义. 本文应用基于反应力场的分子动力学方法研究了ZnO薄膜(000l)表面作为衬底的薄膜沉积生长过程, 初步讨论了衬底温度(200、500和800 K)变化对沉积较薄ZnO膜质量的影响, 部分结果与实验观察相符. 结果表明, 衬底温度在500 K左右时, 沉积原子结构径向分布函数曲线特征峰尖锐、明显, 有序度较高, 注入和溅射对薄膜完整性影响较小, 沉积形成的薄膜结构稳定而又致密. 在预置衬底表面平坦的情况下薄膜呈现一种链岛状的生长模式, 每原子层均具有两种生长取向, 导致其生长前锋交汇处形成了一种新的有序缺陷.     

Effect of the supporting pattern on the orientation of hexagonal morphology in thin films of diblock copolymers

The model of a thin film sandwiched between two parallel planes the gap between which is filled with the melt of diblock copolymers is revisited. One of the planes (a supporting plane) has a pattern, whereas the other plane (an upper) is uniform. The proposed model is based on mean self-consistent field concepts. The parameters of diblock copolymers are selected so that the melt of diblock copolymers yields a hexagonal morphology in its volume. The upper boundary of the film and support avoid contact with the minor component of the diblock copolymer; as a result, in the film, a hexagonal morphology parallel to the support is formed. When hexagonal and rectangular patterns with preferential interaction with the minor component (the period of patterns coincides with the period of hexagonal symmetry in the volume), the hexagonal morphology changes its orientation from parallel to perpendicular relative to the support. The hexagonal morphology changes its orientation at sufficiently strong interaction between the pattern and minor component. Structural factor is calculated, and characteristic features in the location of peaks for perpendicular and parallel phases of hexagonal morphology are found. The development of additional peaks in the structural factor comes from deformations induced by the interaction between components of the melt of diblock copolymers with the upper boundary, support, and pattern.     

Angular dependence of 1H- and 2H-NMR spectra of H2O and D2O absorbed in cellulose acetate film

¹H- and ²H-NMR spectra of H₂O and D₂O absorbed in cellulose acetate films were observed while changing the angle between the plane of the film and the magnetic field. ¹H-NMR spectra show dipolar splittings that vary depending on the angle. The splitting has a maximum when the surface of the film is perpendicular to the magnetic field. From the angular dependence of the dipolar splitting, it is recognized that the proton-proton dipolar axis of water molecules tends to orient perpendicularly to the surface of the film. ²H-NMR spectra that show quadrupolar splittings also indicate that the quadrupolar axis tends to orient perpendicularly to the film. The so-called bound water and free water in the film can exchange rapidly on the NMR time scale, so that the line width and the splitting of the NMR spectra become smaller as the amount of water in the film increases. From the temperature dependence of line widths, the apparent reorientational activation energy of water molecules in the film is estimated to be 25 kJ/mol from ¹H-NMR and 31 kJ/mol from ²H-NMR.     

Quantum and classical dynamics of wave packets in an electromagnetic plane wave

Dynamics of a charged particle in a plane wave electromagnetic field is analyzed using the relativistic quantum and classical theory. Relativistic quantum dynamics is based on the Klein-Gordon equation. It is shown that the classical theory reproduces quantum results almost exactly.     

高分子乳液的成膜理论研究现状

随着高分子乳液应用的不断拓展,对其成膜理论的研究日益受到重视。本文综述了高分子乳液的成膜过程、成膜过程中乳胶粒子所受的作用力以及乳液的成膜动力理论,分析了目前理论研究的特点以及存在的缺陷,并指出该领域研究的发展趋势。     

Aligned carbon cones in free‐standing UV‐Curable polymer composite

A concept where an alternating electric field (dielectrophoresis) is used to assemble and align carbon nanocone particles (CNCs) into microscopic wires in self‐supporting polymer films is demonstrated. The particle fraction is kept low (one‐tenth of the percolation threshold of isotropic mixture), which allows uniform dispersion and efficient UV curing. The alignment leads to the conductivity enhancement of three to four orders of magnitude (from ～10^?7 to ～10^?3 S/m) in the alignment direction. It does not require passing current so the material can be isolated from the alignment electrodes. This prevents electrodes attaching to the film, if the film is adhesive in nature. The alignment can be done using either in‐plane or out‐of‐plane geometries. It is proposed that this concept could be applied in areas such as electrostatic discharge applications where inexpensive conductive or dissipative materials and macroscopic uniformity are prerequisites. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Chord intercepts in the two-dimensional cell model

The two-dimensional cell model is defined by the following conditions of its formation: athermal nuclei may be randomly (Poisson) distributed in a thin amorphous film. From these nuclei spherulites may start to grow instantaneously, circularly, and at the same rate. Where two spherulites touch growth stops, and all points of contact form a straight intersection between neighboring spherulites. Finally, if the film contains spherulites only, each spherulite (cell) is completely limited by straight intersections, forming an irregular polygon. All irregular polygons of the film together form a planar irregular net of straight intersections. In quantitative microscopy this net is characterized by a “lineal analysis.” A straight line (Rosiwal's line) is arbitrarily put into the plane of the net. The net divides Rosiwal's line into chord intercepts of different lengths. The distribution of these lengths is analytically derived in the present paper by use of the theory of probability.     

The effect of melt processing conditions on the hydrogen-bonded sheet orientation and polarization of nylon 11 films

It is known that melt-quenched, cold-drawn, and then annealed nylon 11 films possess a particular doubly oriented hydrogen-bonded sheet structure: the hydrogen-bonded sheets being in the plane of the film and the molecular chain direction being in the direction of draw. These films have been shown to be ferroelectric. In order to clarify the role of this special double orientation on polarization mechanisms and, in addition, provide insight into the reasons for this unique orientation, a systematic study was undertaken. Nylon 11 was melted at 210°C in a hot press for different melting times (ranging from 30 s to 20 min) prior to quenching into an ice-water bath. The resulting orientation of the hydrogen-bonded sheet structure in these films was examined using wide-angle X-ray diffraction and FTIR spectroscopy. For undrawn, melt-quenched films with short times in the melt, a degree of preferred orientation of the hydrogen-bonded sheets in the plane of the film was observed. As time in the melt increased, this preferred orientation in the plane decreased. This was also observed for films which were cold drawn before annealing. However, following cold drawing and several cycles of polarization using a maximum field of 150 MV/m at room temperature, the uniaxially drawn films with different times in the melt possessed the same remanent polarization and the same final orientation of the hydrogen-bonded sheets in the film thickness direction. © 1996 John Wiley & Sons, Inc.     

Out of shear plane deformations in nematic liquid crystals

The stability of the director field to deformations out of the plane of shear is examined by use of the Taylor expansion method based on catastrophe theory. For simple shear flow of nematics, the coming out of the shear plane is found for suitable surface alignment and not too high twist elastic constant. The role of these parameters is pointed out. Non-flow-aligning nematics are also considered, and results consistent with earlier reports are obtained.     

Droplet shape and reorientation fields in nematic droplet/polymer films

Polymer films containing droplets of nematic liquid crystal form an important class of new electro-optic light valves and displays. While previous work has shown that the nematic droplet size is an important factor in the electro-optic properties of these films, here we report that the droplet shape is equally important in determing the electro-optics of the film. Electron micrographs show that for films using polyvinyl alcohol as the polymeric binder the cavities formed by the polymer matrix are oblate in nature, and aligned with the minor axis perpendicular to the film plane. In oblate cavities the elastic-deformation free energy is minimized when the director field in the droplet is aligned along a major axis of the spheroid; the electric field performs work on the nematic in reorienting the nematic into a higher-energy state, equal to the elastic-free-energy difference between the two configurations. Calculations and experiment are used to estimate the elastic and electric field free-energy-density changes that occur upon reorientation of the nematic droplet. The general agreement between these two values is used to indicate that droplet shape anisotropy is a major factor in determining the electrooptic properties of these films.     

Layer-by-layer electrostatic assembly with a control over orientation of molecules: anisotropy of electrical conductivity and dielectric properties

While forming layer-by-layer (LbL) electrostatic assembly of a magnetic organic molecule, namely, nickel phthalocyanine (NiPc), we apply a magnetic field. The field orients the magnetic moment of the molecules on a monolayer along the direction of magnetic field. Such an orientation of the molecules is then electrostatically immobilized with a monolayer of a polycation. By repeating the dipping cycle, we form LbL films with planar NiPc molecules facing a particular direction. With NiPc's moment perpendicular to the molecular plane, two types of LbL films were formed: (a) NiPc's molecular plane parallel to the substrate (moment is perpendicular) and (b) molecules perpendicular to the substrate and facing one particular direction, the direction of magnetic field. Such films, with the molecules lying either (a) parallel or (b) perpendicular to the substrate, provide unique systems to study anisotropy of optical, dielectric, and electrical characteristics in these planar organic molecules. The latter film responds to the polarization of incident beam in electronic absorption spectroscopy. Here we show methods to obtain an orientation of molecules in LbL films and study anisotropy of dielectric constant and conductivity of the molecules in ultrathin films.