On the Charge Instability and the Metastable Equilibrium State of a Conducting Droplet during Liquid Electrospraying

Colloid Journal - It is known that highly charged droplets formed in the course of electrospraying disintegrate into a number of smaller droplets. The criteria for the instability and...     

General Equations for the Equilibrium Shape of a Fluid Interface and for Its Angle of Contact with a Solid

Abstract

The classical equations of Young-Laplace (equilibrium shape of a fluid interface in a uniform gravitational field) and Young (angle of contact of the fluid interface with a solid) are generalized to take into account: (i) the presence of externally applied fields of any type; (ii) the variation of the interfacial tensions from point to point; (iii) the variation of the fluid interfacial tension with its orientation in space.

The general equations are deduced simultaneously by a variational method, which allows the determination of the minimum Helmholz energy configuration of a system comprising the two fluids and the solid. An axially symmetric geometry is assumed.

The equations so derived clarify the difficulties that have been found in the application of the classical equations-particularly Young's equation-to actual systems. Both equations, in their general form, contain terms that may be interpreted as representing the interaction between the three interfaces near their line of contact, and such an interaction cannot be ignored in actual systems.     

对双有利反应平衡移动的讨论

对双有利化学反应的平衡移动进行了讨论。并以1/2H2（g）＋1/2Cl2（g）=2HCl（g）为例,用计算数据加以说明。     

Study of the Solid—Liquid Equilibrium in Mixed Alkaline Earth Fluorohalides

We have studied the solid-liquid equilibrium of the system Sr_1–yBa_yFCl_1–xBr_x using DTA and X-ray diffraction techniques. The entire composition range in this system yields solid solutions which crystallize in the PbFCl (Matlockite) structure type. The melting points of the entire composition range have been parametrized (within 5°C rms error) using a biquadratic fit of the available data obtained by experiment and from the literature.This revised version was published online in November 2005 with corrections to the Cover Date.     

Modelling the Vapor–Liquid Equilibrium of Polymer Solutions Using a Cubic Equation of State

This work presents the vapor–liquid equilibrium calculations in an isothermal flash, applied to polymer solutions, using the Peng–Robinson cubic equation of state modified by Stryjek–Vera, and the mixing rule introduced by Wong–Sandler. This rule allows combining the rigid lattice thermodynamic model of Flory–Huggins to the Peng–Robinson–Stryjek–Vera equation of state. As the Gibbs free energy must be minimum in the equilibrium state, a stochastic optimization method, the simulated annealing algorithm, was used to find out the extreme of this thermodynamic potential.     

Polymorphism and Conformational Equilibrium of Nitro-Acetophenone in Solid State and under Matrix Conditions

Conformational and polymorphic states in the nitro-derivative of o-hydroxy acetophenone have been studied by experimental and theoretical methods. The potential energy curves for the rotation of the nitro group and isomerization of the hydroxyl group have been calculated by density functional theory (DFT) to estimate the barriers of the conformational changes. Two polymorphic forms of the studied compound were obtained by the slow and fast evaporation of polar and non-polar solutions, respectively. Both of the polymorphs were investigated by Infrared-Red (IR) and Raman spectroscopy, Incoherent Inelastic Neutron Scattering (IINS), X-ray diffraction, nuclear quadrupole resonance spectroscopy (NQR), differential scanning calorimetry (DSC) and density functional theory (DFT) methods. In one of the polymorphs, the existence of a phase transition was shown. The position of the nitro group and its impact on the crystal cell of the studied compound were analyzed. The conformational equilibrium determined by the reorientation of the hydroxyl group was observed under argon matrix isolation. An analysis of vibrational spectra was achieved for the interpretation of conformational equilibrium. The infrared spectra were measured in a wide temperature range to reveal the spectral bands that were the most sensitive to the phase transition and conformational equilibrium. The results showed the interrelations between intramolecular processes and macroscopic phenomena in the studied compound.     

表面电荷及外电场对液固界面热阻的影响

采用非平衡分子动力学方法模拟了外电场及固体表面电荷对水与固体间界面热阻的影响. 结果表明,外加电场平行于界面时, 其对界面热阻几乎没有影响, 而垂直于界面时, 界面热阻将随着电场强度的增大而减小. 壁面带正电荷或负电荷都将使得界面热阻减小. 界面热阻与表面电荷密度及电场强度均满足二次函数关系. 模拟结果表明施加外电场和表面电荷是控制液固界面热阻的有效方法.     

Thiazole Boron Difluoride Dyes with Large Stokes Shift,Solid State Emission and Room-Temperature Phosphorescence

The small Stokes shift and weak emission in the solid state are two main shortcomings associated with the boron-dipyrromethene (BODIPY) family of dyes. This study presents the design, synthesis and luminescent properties of boron difluoro complexes of 2-aryl-5-alkylamino-4-alkylaminocarbonylthiazoles. These dyes display Stokes shifts (Δλ, 77–101 nm) with quantum yields (ϕ_FL) up to 64.9 and 34.7 % in toluene solution and in solid state, respectively. Some of these compounds exhibit dual fluorescence and room-temperature phosphorescence (RTP) emission properties with modulable phosphorescence quantum yields (ϕ_PL) and lifetime (τ_p up to 251 μs). The presence of intramolecular H-bonds and negligible π-π stacking revealed by X-ray crystal structure might account for the observed large Stokes shift and significant solid-state emission of these fluorophores, while the enhanced spin-orbit coupling (SOC) of iodine and the self-assembly driven by halogen bonding, π-π and C−H^…π interactions could be responsible for the observed RTP of iodine containing phosphors.     

A Generalized Formula to Predict the Direction of an Equilibrium Shift

A generalized formula to predict the direction of an equilibrium shift, , is presented, where ξ is the extent of the reaction, t is the characteristic variable to affect an equilibrium and f is the characteristic function whose partial differential with respect to ξ can be used as an equilibrium criterion. When the stable equilibrium of a thermodynamic system is disturbed on condition that f exhibits a minimum with respect to ξ, the equilibrium will shift in the direction to resist the increase of f if the disturbance make f increase; however, the equilibrium will shift in the direction to accelerate the decrease of f if the disturbance make f decrease to minimize f. On condition that f exhibits a maximum with respect to ξ, the equilibrium will shift in the direction to resist the decrease of f if the disturbance make f decrease; however, the equilibrium will shift in the direction to accelerate the increase of f if the disturbance make f increase to maximize f. On the other hand, Le Chatalier’s Principle is not consistent with the real situations under certain circumstances     

Thermal Conductivity of CuSbSe2 and CuBiSe2 in the Solid and Liquid State

Abstract

Thermal Conductivity of CuSbSe₂ and CuBiSe₂ have been studied in the solid and liquid state in a wide range of temperatures. Measurements of thermal conductivity were carried out using the concentric cylinder method which is based on the flow of heat through a cylindrical wall.     

碳纳米管薄膜晶体管中的接触电阻效应

利用不同功函数的金属作为接触电极,研究了网络状碳纳米管薄膜晶体管(CNT-TFT)的接触电阻效应。研究表明金属Pd与碳纳米管薄膜形成良好的欧姆接触, Au则形成近欧姆接触,这两种接触的器件的开态电流和迁移率较高。Ti和Al都与碳纳米管薄膜形成肖特基接触,且Al接触比Ti接触的势垒更高,接触电阻也更大,相应器件的开态电流和迁移率都较低。该结果表明对于CNT-TFT仍然可以通过接触来调控器件的性能,这对CNT-TFT的实用化进程具有重要的促进作用。     

The Surface Energy and Contact Angles of a Liquid Foam

A liquid foam can be regarded as a single fluid with a characteristic "surface tension". This property is calculated for two- and three-dimensional ordered and disordered foams using a broken bond approach. The contact angle of a foam with a solid or a liquid substrate is also calculated from the energies of the bubbles in contact with the substrate. Experiments were carried out in which the contact angles of foams were measured, with reasonable agreement with the predictions. Copyright 2001 Academic Press.     

刍议化学平衡移动方向的判断

众所周知 ,化学平衡状态是指在一定条件下的对峙反应中 ,正反应速度等于逆反应速度(ｖ正 =ｖ逆 ≠ 0 ) ,反应混合物各组分的含量不随时间的改变而改变的状态。当外界条件 (如浓度、压力或温度 )发生变化时 ,化学平衡状态随之发生移动 ,移动的方向可根据著名的Ｌｅｃｈａｔｅｌｉｅｒ原理进行判断。但目前文献[1～ 7] 中 ,运用Ｌｅｃｈａｔｅｌｉｅｒ原理判断化学平衡移动方向讨论得最多的是恒温恒容体系 ,对于恒温恒压体系平衡移动方向的判断方法报道甚少。能否根据Ｌｅｃｈａｔｅｌｉｅｒ原理对恒温恒压体系平衡移动方向进行判断呢 ?实际上…     

Analytical and Numerical Study of Equilibrium Characteristics of a Droplet with Charged Condensation Nucleus in the External Electric Field

The equilibrium parameters of small dielectric droplet with charged condensation nucleus in the external uniform electric field are studied. Two typical cases are considered: (i) the droplet with charged nucleus suspended by external uniform electric field in the gravitational field and (ii) the droplet moves steadily under the action of external electric field with allowance for the resistance of surrounding vapor–gas medium. It is taken into account that the charged condensation nucleus can be displaced from the mass center of the droplet to new equilibrium position inside the droplet under the action of external electric field and response field. The scheme of the numerical solution of a nonlinear system of differential equations for the droplet equilibrium profile and electric potentials inside the droplet and in the vapor–gas medium at the arbitrary values of droplet size, strength of external field, and the charge of condensation nucleus is formulated and realized. Dependences of an equilibrium profile and the thermodynamic characteristics of a droplet such as the chemical potential of condensate and formation work on the droplet size, mass, and charge of condensation nucleus, the strength of external field and ratio of permittivities of droplet and the vapor–gas medium are plotted. Results of numerical calculations are supplemented by the analytical relations for equilibrium droplet characteristics in the first orders of the perturbation theory for a weak external field.     

The Structure of 2-Methylphenylcyanamide in the Solid State

The structure of 2-methylphenylcyanamide NCNH(C₆H₄Me-2) is established in the solid state using single crystal X-ray diffraction data. The contribution of various intermolecular contacts to the crystal packing is studied using the Hirshfeld surface analysis and quantum chemical calculations within the density functional (DFT) M06-2X/6-311++G(d,p) level of theory.     

On the Degree to which the Contact Angle is Affected by the Adsorption onto a Solid Surface of Vapor Molecules Originating from the Liquid Drop

ABSTRACT

From surface tensions of liquids and Lifshitz-van der Waals (LW) and Lewis acid-base (AB) surface tension components and the AB electron-acceptor γ⁺ and electron-donor γ^˙ parameters determined by contact angle (θ) measurements (using the Young-Dupré equation for polar systems), the interfacial work of salvation (W_st) between various contact angle liquids (L) and a moderately polar solid (S), such as polymethylmethacrylate (PMMA) could be determined. From these W_SL -values the maximum values of the equilibrium association constant, K_a, are obtained for the adsorption of molecules of liquids, L, onto a solid substratum, S. From the K_a-values and the vapor pressures of the various liquids, the maximum number of liquid molecules adsorbed from the gaseous phase onto the solid surface can be determined, at 20^°C and 76cm Hg ambient atmospheric pressure. This yields the maximum value for the fraction, ?, of the surface area of the solid that will be covered by molecules of the liquid, L, emanating from the liquid drop, via the gaseous state. From these ?-values, using Cassie's approach, the maximum amount, Δθ, can be determined by which the observed contact angle is lower than the ideal contact angle, as a consequence of the coverage of the solid substratum by adsorbed molecules originating from the contact angle liquid.

For most of the contact angle liquids used, the maximum deviation, Δθ, is well under 1^°; for water on PMMA it is about 1½^°.     

Solid Contact Nitrate Ion‐Selective Electrode Based on Ionic Liquid with Stable and Reproducible Potential

A simple, fast and cheap method of preparation of solid contact nitrate ion‐selective electrode is proposed. The electrode membrane phase consist of only three components: PVC, plasticizer and ionic liquid (IL).The ionic liquid trihexyltetradecylphosphonium chloride is used in triple function as ionophore, as lipophilic ionic component in order to reduce membrane resistance, and as transducer media in order to stabilize the potential of internal Ag/AgCl electrode. The electrical properties of the membrane were studied by electrochemical impedance spectroscopy and the influence of the interfacial water film was evaluated by potentiometric water layer test.