Synthesis of Ammonia in a Strong Electric Field Discharge at Ambient Pressure

The plasma synthesis of ammonia has been studied in a nitrogen–hydrogenplasma using a strong electric field discharge at ambient pressure andtemperature. With this method, N₂ and H₂ molecules are ionized anddissociated and a large number of free atoms, ions, and radicals areformed in a nonequilibrium plasma after inelastic collisions. The finalproduct was mainly ammonia, including a small amount of hydrazine. WhenMgO powder, used as a catalyst, was smeared on the surface of the electrodeplates, the yields of ammonia increased about 1.54–1.75 times andreached 5000 ppm (0.5% v/v). In this way, plasma synthesis of ammonia atambient pressure is realized and a new method is provided for inorganicsynthesis, which consumes little energy and simplifies the process.     

Formation of an Electric Charge in a Dielectric Fluid Above a Rotating Disk

A plane metal disk rotating at a constant angular velocity is considered. Above the disk, there is a dielectric fluid containing a small amount of a foreign electrolyte. The electrolyte contains positive and negative ions and is assumed to be strong. The charging of the fluid is determined by the electrochemical reactions that take place at the disk surface. The effect of an electric field on the charging process is taken into account.     

Melting of Water Molecule Clusters in a Strong Electric Field under the Conditions Modeling Arctic Stratosphere

The melting of (H₂O)₄₀ice microparticles under the conditions of subarctic stratosphere was numerically simulated using the Monte-Carlo method. The melting point of the microparticles was found to be 60 K lower than the melting temperature of bulk ice. The melting was detected by the behavior of the internal energy of microparticles, their heat capacity and electric susceptibility. The melting was accompanied by a qualitative change in the molecular orientation order in a cluster. Abrupt changes in the molecular arrangement in the cluster were not found. An electric field destroys the molecular orientation order in the cluster, and the clear-cut phase transition disappears. An electric field increases the rotational mobility of molecules.     

Dynamics of Drop Formation in an Electric Field

The effect of an electric field on the formation of a drop of an inviscid, perfectly conducting liquid from a capillary which protrudes from the top plate of a parallel-plate capacitor into a surrounding dynamically inactive, insulating gas is studied computationally. This free boundary problem which is comprised of the surface Bernoulli equation for the transient drop shape and the Laplace equation for the velocity potential inside the drop and the electrostatic potential outside the drop is solved by a method of lines incorporating the finite element method for spatial discretization. The finite element algorithm employed relies on judicious use of remeshing and element addition to a two-region adaptive mesh to accommodate large domain deformations, and allows the computations to proceed until the thickness of the neck connecting an about to form drop to the rest of the liquid in the capillary is less than 0.1% of the capillary radius. The accuracy of the computations is demonstrated by showing that in the absence of an electric field predictions made with the new algorithm are in excellent agreement with boundary integral calculations (Schulkes, R. M. S. M. J. Fluid Mech. 278, 83 (1994)) and experimental measurements on water drops (Zhang, X., and Basaran, O. A. Phys. Fluids 7(6), 1184 (1995)). In the presence of an electric field, the algorithm predicts that as the strength of the applied field increases, the mode of drop formation changes from simple dripping to jetting to so-called microdripping, in accordance with experimental observations (Cloupeau, M., and Prunet-Foch, B. J. Aerosol Sci. 25(6), 1021 (1994); Zhang, X., and Basaran, O. A. J. Fluid Mech. 326, 239 (1996)). Computational predictions of the primary drop volume and drop length at breakup are reported over a wide range of values of the ratios of electrical, gravitational, and inertial forces to surface tension force. In contrast to previously mentioned cases where both the flow rate in the tube and the electric field strength are nonzero, situations are also considered in which the flow rate is zero and the dynamics are initiated by impulsively changing the field strength from a certain value to a larger value. When the magnitude of the step change in field strength is small, the results of the new transient calculations accord well with those of an earlier stability analysis (Basaran, O. A., and Scriven, L. E. J. Colloid Interface Sci. 140(1), 10 (1990)) and thereby provide yet another testament to the accuracy of the new algorithm. Copyright 1999 Academic Press.     

Study on Glow Discharge in One-Dimensional Transverse Non-uniform Electric Field and Surface Processing of Aramid Fabric

Using a staggered contact electrode structure, the conditions for and mechanism of uniform discharge in one-dimensional transverse non-uniform electric field and with aramid fiber (AF) as a dielectric barrier material were explored for the first time in this study. An atmospheric pressure glow discharge (APGD) plasma was generated, and the large-area and continuous processing of AF was achieved. Through the electric field simulation as well as scanning electron microscope and X-ray photoelectron spectroscopy tests, it was found that the modification method of pressing the electrode closely to the AF could form the extremely strong electric field region of magnitude 1.444 × 10⁷ V/m under the premise of uniform discharge. The highly active plasma generated could not only effectively increase the surface roughness of the treated material, but also introduce nitrogen functional groups which can’t be introduced through traditional air plasma. As found through the contact angle measurement, the contact angle was greatly decreased (by 52.3%) after being treated with 12.05 W/cm³ of plasma for 10 s, indicating that APGD plasma can achieve a good modification effect and high modification efficiency at low discharge power density.     

Bilayer Molecular Assembly at a Solid/Liquid Interface as Triggered by a Mild Electric Field

The construction of a spatially defined assembly of molecular building blocks, especially in the vertical direction, presents a great challenge for surface molecular engineering. Herein, we demonstrate that an electric field applied between an STM tip and a substrate triggered the formation of a bilayer structure at the solid–liquid interface. In contrast to the typical high electric‐field strength (10⁹ V m^?1) used to induce structural transitions in supramolecular assemblies, a mild electric field (10⁵ V m^?1) triggered the formation of a bilayer structure of a polar molecule on top of a nanoporous network of trimesic acid on graphite. The bilayer structure was transformed into a monolayer kagome structure by changing the polarity of the electric field. This tailored formation and large‐scale phase transformation of a molecular assembly in the perpendicular dimension by a mild electric field opens perspectives for the manipulation of surface molecular nanoarchitectures.     

聚醚醚酮酮强电场下的熔融结晶

聚醚醚酮酮 (PEEKK)是在聚醚醚酮 (PEEK)基础上开发成功的一种新型特种工程塑料 ,由于酮基与醚基比例的提高 ,其耐热等级比 PEEK提高了近 2 0℃ . Zimmermann等 [1] 首先报道了 PEEKK的晶体结构 ,同 PEEK类似 ,也为正交晶系 ,Pbcn空间群 .众所周知 ,结晶聚合物材料的产品性能与其结晶条件密切相关 .我们先后对 PEEKK的等温及非等温熔融与冷结晶动力学 [2 ,3] ,晶胞参数及结晶度随结晶温度变化关系 [4 ] ,拉伸诱变多晶型5,6] ,溶剂诱变多晶型进行了研究 [7] .但电场效应对聚合物结晶的影响尚罕见报道 [8] .本文对 PEEKK强电场…     

Long-Range Static and Dynamic Previtreous Effects in Supercooled Squalene—Impact of Strong Electric Field

This article presents evidence for the long-range previtreous changes of two static properties: the dielectric constant (ε) and its strong electric field related counterpart, the nonlinear dielectric effect (NDE). Important evidence is provided for the functional characterizations of ε(T) temperature changes by the ‘Mossotti Catastrophe’ formula, as well as for the NDE vs. T evolution by the relations resembling those developed for critical liquids. The analysis of the dynamic properties, based on the activation energy index, excluded the Vogel–Fulcher–Tammann (VFT) relation as a validated tool for portraying the evolution of the primary relaxation time. This result questions the commonly applied ‘Stickel operator’ routine as the most reliable tool for determining the dynamic crossover temperature. In particular, the strong electric field radically affects the distribution of the relaxation times, the form of the evolution of the primary relaxation time, and the fragility. The results obtained in this paper support the concept of a possible semi-continuous phase transition hidden below T_g. The studies were carried out in supercooled squalene, a material with an extremely low electric conductivity, a strongly elongated molecule, and which is vitally important for biology and medicine related issues.     

Plasma Parameters around a Chain-Like Structure of Dust Particles in an External Electric Field

The formation of a 1D chain-like structure of dust particles in a low-temperature argon plasma was studied. A new numerical model for calculation of the self-consistent spatial distribution of plasma parameters around a chain of dust particles was presented. The model described the motion of positively charged ions in the electric potential of several negatively charged dust particles, taking into account the action of an external electric field. The main advantage of the model was that the charges of the dust particles and the interparticle distances were determined self-consistently. As a result of numerical simulations, the dependencies of the spatial distributions of the plasma parameters (the densities of electrons and ions and the self-consistent electric potential) near the dust particles chain on the strength of the external electric field, an external force acted on the last particle, and the mean free path of the ions was determined. The obtained results made it possible to describe the process of the formation of chain-like structures of dust particles in discharge plasma.     

Inertial Hydrodynamic Effects in Electrophoresis of Particles in an Alternating Electric Field

The influence of the effects associated with the inertia of particles and the surrounding fluid on the electrophoresis in an alternating electric field has been theoretically investigated. From solving the hydrodynamic equations the electrophoretic velocity of a spherical particle was found to depend on the frequency of the external electric field and on the particle-to-fluid-density ratio. It is shown that, due to inertial effects, the liquid flow around particles with a thin electrical double layer (EDL) is no longer potential. A mechanism of the formation of steady-state flow in the vicinity of oscillating particles with a thin EDL is proposed. Using numerical methods, a picture of the fluid streamlines in such a flow is obtained. The spatial distribution of the fluid velocity in the vicinity of a particle is also found. It was established that with an increasing frequency of the electric field the steady-state flow velocity passes through a maximum. The flow direction depends on the ratio between the densities of a particle and the surrounding fluid. The reversal of direction takes place when this ratio is about 0.7. The case of a thick EDL has also been considered, and a comparative analysis of the flow distributions around the particles with a thin and those with a thick EDL has been carried out.     

N2分子在强激光场中的场致电离

研究了在强激光脉冲中各种不同取向的N2分子发生场致电离的电离几率和表观电离效率.用量子化学方法计算了N2+分子离子在各种不同取向上的势能曲线,然后用传递矩阵方法得到了N2分子在不同方向上的电离几率,经过角度平均之后得到了各种取向的所有N2分子的总电离几率,并对计算结果进行了激光时间和空间修正.用800nm和70fs的激光脉冲对N2分子进行了在强激光场中的电离实验,得到了N2分子电离后产生的电子的角度分布图和电离几率随激光功率密度变化的关系曲线.实验结果和理论计算结果符合得很好.     

Oxidation of CO Catalyzed by a Cu Cluster: Influence of an Electric Field

Adsorption ability and reaction rate are two essential parameters that define the efficiency of a catalyst. Herein, we implement density functional theory (DFT) and report that CO can be oxidized by a pyramidal Cu cluster with an associated reaction barrier E_b=1.317 eV. In this case, our transition state calculations reveal that the barrier can be significantly lowered after superimposing a negative electric field. Moreover, when the field intensity corresponds to F=?0.010 au, the magnitude of E_b=0.698 eV is equivalent to—or lower than—those of typical catalysts such as Pt, Rh, and Pd. The superimposition of a positive field is found to enhance the release of the nascent CO₂ molecule. Our study demonstrates that small Cu clusters have better adsorption ability than the corresponding flat surface while the field can be used to enhance the purification of the exhaust gas.     

Excitation of Radial Ion Motion in an rf-Only Multipole Ion Guide Immersed in a Strong Magnetic Field Gradient

Radiofrequency (rf) multipole ion guides are widely used to transfer ions through the strong magnetic field gradient between source and analyzer regions of external source Fourier transform ion cyclotron resonance mass spectrometers. Although ion transfer as determined solely by the electric field in a multipole ion guide has been thoroughly studied, transfer influenced by immersion in a strong magnetic field gradient has not been as well characterized. Recent work has indicated that the added magnetic field can have profound effects on ion transfer, ultimately resulting in loss of ions initially contained within the multipole. Those losses result from radial ejection of ions due to transient cyclotron resonance that occurs when ions traverse a region in which the magnetic field results in an effective cyclotron frequency equal to the multipole rf drive frequency divided by the multipole order (multipole order is equal to one-half the number of poles). In this work, we describe the analytical basis for ion resonance in a rf multipole ion guide with superposed static magnetic field and compare with results of numerical trajectory simulations.     

QMS in the Third Stability Zone with a Transverse Magnetic Field Applied

We report here a study using a quadrupole mass spectrometer (QMS) in which a static magnetic field is applied transversely to the body of the mass filter operating in stability zone 3. Significant improvement in QMS performance was obtained under certain magnetic field conditions, and these have been explained in terms of our theoretical model. The theoretical approach assumed in the model is that the QMS contains hyperbolic rods as electrodes and that the magnetic field acts over the full length of the mass filter assembly. Our latest analysis also predicts for what values of operating parameters an enhancement of the quadrupole resolution is achieved when a transverse magnetic field is applied. The model predicts instrument resolution R > 5000 for Ar with a 100 mm long mass filter and R > 3500 for a HT and D₂ mixture with a 200 mm long mass filter via application of a transverse magnetic field.     

Self‐Consistent Brownian Dynamics Simulation of an Anisotropic Brush Under Shear Flow

Summary: The behavior of an anisotropic polymer brush under a lateral shear flow is considered in the framework of a hybrid method combining a self‐consistent field approach and Brownian dynamics simulation. It is shown that such a flow can induce the compression of an anisotropic brush at shear rates much smaller than those which induce the compression of a conventional isotropic brush. Moreover, a lateral flow can initiate a thermotropic collapse which occurs as an LC phase transition. This collapse takes place at higher temperatures than in the absence of the flow. This can help to find brush compression experimentally. The variation of the internal structure of a brush (density, order parameter, and director orientation profiles, distribution of terminal groups) is also investigated. An anomalous effect of brush densification and ordering near the outer surface is observed. At large shear rates the distribution of chains over their deformation has a bimodal character: one fraction of chains is strongly stretched and another fraction remains unperturbed by the flow. Average characteristics of a brush were compared with predictions of the lattice theory for the box model where the lateral force is applied to chain ends. Satisfactory agreement was observed.

Polymer brush under an influence of lateral flow.