Absorption of gas into a wavy falling film

In this work, we present results of a study of gas absorption into a falling film on a vertical substrate. The film flow is accompanied by the formation of nonlinear waves which strongly influence the diffusion layer that develops from the film surface. As a result, significant enhancement of mass transfer has been observed in experiments. We use recent advances in modelling of the hydrodynamics and solve a two-dimensional convective-diffusion equation for the solute concentration. Numerical solutions for the finite-amplitude wave regimes and associated integral absorption rates are obtained for a range of flow conditions. Our results show clearly the influence of waves on the development of the diffusion layer and, in particular, the enhancement of absorption due to the waves; the existence of optimal conditions for maximizing the absorption rate is also demonstrated.     

界面诱导组装聚苯胺晶态薄膜及其气体响应性能

通过界面模板法合成聚苯胺（PANI）晶态薄膜，并基于单晶硅底材制备了PANI薄膜气体传感器，利用傅里叶变换红外光谱仪（FTIR）、拉曼光谱仪（Raman）、Ｘ射线衍射仪（XRD）、 透射电子显微镜（TEM）和智能气敏分析系统（CGS⁃1TP）对产物的结构与性能进行分析，研究界面模板诱导作用对PANI薄膜结构与气体响应性能的影响。结果表明，两亲性模板剂诱导PANI在气⁃液界面聚合并组装成薄膜，PANI薄膜结晶性受反应时间与膜厚影响，24~48 h反应时间制备的PANI薄膜晶态特征明显，薄膜对25 ppm的NH₃气体响应值在15~60之间，平均响应和恢复时间分别为36 s和51 s，表现出快速响应恢复特性和优异的稳定性。     

Latex film formation: atomic force microscopy and theoretical results

We have critically examined the kinetics of latex film formation using an atomic force microscope to obtain corrugation height data as a function of time, temperature, molecular weight, particle size, etc. The results show that the film forming process obeys viscoelastic time/ temperature superposition principles, thus indicating a direct relationship between the kinetics of film formation and rheological properties. Film formation kinetics are examined under ‘wet’ and ‘dry’ conditions, with film formation occurring almost ten-times faster under wet conditions than dry. This proves for the latex system examined that capillary pressure from the water meniscus is the dominant driving stress for film formation. Past theories for latex film formation are reviewed, and problems and deficiencies are noted. A new theory for film formation from a dry latex system is presented, which is based on the use of the Boltzmann Superposition Principle to relate the changing stress and strain fields as the latex particles deform. The predictions of theory and the experimental data show excellent agreement over nearly four decades of time.     

气膜熄焦在焦化生产中的应用

针对新疆炼焦煤焦炭热态性能较差的现状,开展了气膜熄焦试验,在降低5％主焦煤用量的情况下．仍能保证焦炭的冷热强度。使用气膜熄焦后还可降低焦炭含水量．减少蒸汽排放及改善环境。     

防磁控溅射镀银膜变色新工艺

利用RSFM-4直流磁控溅射机在纯铜片上制备了银膜。采用了电化学纯化、化学纯化、浸涂BTA、涂覆DJB-823以及复合处理等多种防银膜变色工艺方法进行处理。分别在二氧化硫气体、硫化氢气体和硫化钠溶液中进行了加速银膜变色试验。通过对试验结果进行综合评价，表明采用化学纯化 涂覆DJB-823的复合处理工艺处理的银膜在各种环境下都有良好的抗银膜变色能力。     

A study of film thickness and hydrodynamic entrance length in liquid laminar film flow along a vertical tube

The liquid film thickness and hydrodynamic entrance length in a vertical tube was studied experimentally and numerically. Measurements using distilled water, 30 wt % MEA and 40 wt % sugar solutions were carried out to investigate the effects of liquid flow rate on the formation of the liquid film. The experimental results validate the new Navier‐Stokes based equation in cylindrical coordinates (Eq. 16) and the volume of fluid (VOF) model giving a competitively high prediction of the liquid film thickness especially in the low Reynolds number region. In addition, a new empirical model and an improved minimal surface model have been first proposed for calculation of the hydrodynamic entrance length, with a relatively reasonable average absolute relative deviation (AARD) of 3.03% and 6.83%, respectively. Furthermore, the effects of the hydrodynamic entry length on the gas–liquid interfacial area calculated by the improved minimal surface model were comprehensively studied, and can be ignored if the ratio of the liquid film length (y) and the hydrodynamic entrance length (λ_E) is lower than 10. However, it should be noted that the hydrodynamic entrance length cannot be ignored in packed columns in which the liquid flow is very complex due to the packings with different structures and materials. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2078–2088, 2018     

Reversal pulsing electrodeposition of Ni/polypyrrole composite film

A uniform composite film of Ni/polypyrrole was deposited on a copper substrate, without any preliminary chemical and electrochemical surface treatment of the substrate, by reversal potential pulsing technique. The influence of pulse potential, pulse frequency and electrolysis time on the formation of a uniform composite film was investigated. These films were characterized using SEM, EDX, EPMA, and GD-OES. The composite films produced under the optimized conditions exhibited a strong adherence to the substrate and exhibited the better corrosion resistance in a marine environment than that of the electrodeposited nickel coating without any incorporated polymer.     

Effect of graphene film on laser textured alumina surface characteristics

Laser gas assisted texturing of alumina surface is considered and the effects of graphene film on the properties of the textured surface are examined. Since laser texturing under the high pressure nitrogen gas jet environments results in formation of aluminum nitride compounds, free energy of the textured surface reduces considerably. The mismatch between the surface free energies of the graphene film and the laser textured surface makes it difficult to transfer the graphene film on the textured surface without rippling and edge defects. A graphene oxide film is formed at the textured surface prior to transferring of the graphene film. The characteristics of the laser textured and the graphene transferred surfaces are assessed using the analytical tools including electron and atomic force microscopes, Raman spectroscopy, X-ray diffraction, and UV visible absorbance spectroscopy. Surface hydrophobicity of the graphene transferred and laser textured surfaces is determined incorporating the water droplet contact angle measurement technique. Friction coefficient of the graphene transferred and laser textured surfaces are measured using the scratch tester. It is found that laser texturing results in hydrophobic characteristics because of the micro/nano size pillars formed at the surface and reduced surface energy due to aluminum nitride compounds. Transferring of the graphene film on to the laser textured surface reduces both the water droplet contact angle and the contact angle hysteresis. The presence of the graphene film reduces the friction coefficient and it does not alter notably the absorption characteristics of the laser textured surface.     

Regulation of film thickness, surface roughness and porosity in thin film growth using deposition rate

This work focuses on distributed control of film thickness, surface roughness and porosity in a porous thin film deposition process using the deposition rate as the manipulated input. The deposition process includes adsorption and migration processes and it is modeled via kinetic Monte Carlo simulation on a triangular lattice with vacancies and overhangs allowed to develop inside the film. A distributed parameter (partial differential equation) dynamic model is derived to describe the evolution of the surface height profile of the thin film accounting for the effect of deposition rate. The dynamics of film porosity, evaluated as film site occupancy ratio, are described by an ordinary differential equation. The developed dynamic models are then used as the basis for the design of a model predictive control algorithm that includes penalty on the deviation of film thickness, surface roughness and film porosity from their respective set-point values. Simulation results demonstrate the applicability and effectiveness of the proposed modeling and control approach in the context of the deposition process under consideration.     

一种自适应柱状密封气膜特性分析

提出一种自适应柱状气膜密封,构建气膜-密封环为研究对象,考虑了偏心间隙发散问题,并定义Rayleigh台阶对气膜周期的突变性,建立了气膜雷诺方程和膜厚变化函数关系式的动力润滑数值模型,获得了摩擦副气膜润滑特性,研究结果表明：气膜力随转速和压力升高而增加,泄漏量随压力升高而增加但是随转速增加而下降,说明密封内部压力流占主导地位。随后,利用曲面槽型雕刻技术,结合高速试验台对密封进行测试,结果表明：理论计算模型与试验结果吻合度较高,斜槽区域存在更多擦痕与磨损,说明斜槽浮动性弱于直列槽;但斜槽的切向流动小于直列槽,导致斜槽泄漏量小于直列槽。该研究成果为自适应柱状气膜密封的气体流动规律和应用提供了理论基础。     

The effect of potential bias on the formation of ionic liquid generated surface films on Mg alloys

An electrochemical approach to the formation of a protective surface film on Mg alloys immersed in the ionic liquid (IL), trihexyl(tetradecyl)phosphonium-bis 2,4,4-trimethylpentylphosphinate, was investigated in this work. Initially, cyclic voltammetry was used with the Mg alloy being cycled from OCP to more anodic potentials. EIS data indicate that, under these circumstances, an optimum level of protection was achieved at intermediate potentials (e.g., 0 or 0.25 V versus Ag/AgCl). In the second part of this paper, a small constant bias was applied to the Mg alloy immersed in the IL for extended periods using a novel cell design. This electrochemical cell allowed us to monitor in situ surface film formation on the metal surface as well as the subsequent corrosion behaviour of the metal in a corrosive medium. This apparatus was used to investigate the evolution of the surface film on an AZ31 magnesium alloy under a potential bias (between ±100 mV versus open circuit) applied for over 24 h, and the film evolution was monitored using electrochemical impedance spectroscopy (EIS). A film resistance was determined from the EIS data and it was shown that this increased substantially during the first few hours (independent of the bias potential used) with a subsequent decrease upon longer exposure of the surface to the IL. Preliminary characterization of the film formed on the Mg alloy surface using ToF-SIMS indicates that a multilayer surface exists with a phosphorous rich outer layer and a native oxide/hydroxide film underlying this. The corrosion performance of a treated AZ31 specimen when exposed to 0.1 M NaCl aqueous solution showed considerable improvement, consistent with electrochemical data.     

Electrochromic properties of porous NiO thin film as a counter electrode for NiO/WO3 complementary electrochromic window

Highly porous nickel oxide (NiO) thin films were prepared on ITO glass by chemical bath deposition (CBD) method. SEM results show that the as-deposited NiO film is constructed by many interconnected nanoflakes with a thickness of about 20 nm. The electrochromic properties of the NiO film were investigated in a nonaqueous LiClO₄–PC electrolyte by means of optical transmittance, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The NiO film exhibits a noticeable electrochromic performance with a variation of transmittance up to 38.6% at 550 nm. The CV and EIS measurements reveal that the NiO film has high electrochemical reaction activity and reversibility due to its highly porous structure. The electrochromic (EC) window based on complementary WO₃/NiO structure shows an optical modulation of 83.7% at 550 nm, much higher than that of single WO₃ film (65.5% at 550 nm). The response time of the EC widow is found to be about 1.76 s for coloration and 1.54 s for bleaching, respectively. These advantages such as large optical modulation, fast switch speed and excellent cycle durability make it attractive for a practical application.     

Electrochemical investigation of the effects of hydrogen on the stability of the passive film on iron

The effects of hydrogen on the stability of passive films on iron were investigated by electrochemical methods: open circuit potential decay, cathodic galvanostatic reduction, electrochemical impedance spectroscopy, and breakdown potential measurements. The results show that hydrogen decreases the final static open circuit potential, the cathodic charge for reduction and the charge transfer resistance of the passive film, indicating that hydrogen decreases the stability of the passive film. The charge transfer resistance of the passive film formed on the charged specimen does not change with increasing the film formation potentials, suggesting that increasing film formation potentials under hydrogen charging conditions cannot improve the stability of the passive film. Hydrogen decreases the breakdown potential of the passive film, especially at lower chloride ion concentrations, confirming that hydrogen promotes the susceptibility of the passive film on iron to pitting corrosion. The reasons why hydrogen decreases the stability of the passive film were discussed.     

洗涤冷却管内垂直降膜流动特性

采用双平行电导探针对多喷嘴煤气化过程中洗涤冷却管内垂直降膜的液膜厚度分布进行了实验研究,研究发现,经洗涤冷却水分布环分配后在洗涤冷却管内形成的液膜在进口段200～400 mm处呈明显的不均匀分布,液膜厚度差值高达3 mm。流动方向上的液膜波动变化与平均液膜厚度变化相似,但具有滞后性。研究还表明,在2.4～14 m³·h^-1的进水流量范围内,整体液膜厚度随着流量的增大而增大,由此对洗涤冷却管内液膜充分发展区的平均液膜厚度建立了经验关联式。实验还发现,洗涤冷却水分布环的槽缝宽度对液膜分布影响显著,在本文研究条件下,最佳槽缝宽度为3 mm,槽缝宽度继续增大,液膜的均匀性下降。另外,随着气相表观速度的增大,整体液膜厚度减小,但一定程度上改善了液膜分布的均匀性。     

Effect of counter current gas phase on liquid film

Liquid film flow is very important in many industrial applications. However, there are few reports about its characteristics on structured packings. Therefore, in this paper, liquid film phenomena were investigated experimentally to exploit new approaches for intensifying the performance of the structured packings. All experiments were performed at room temperature. Water and air were the working fluids. The effect of counter current gas phase on the liquid film was taken into consideration. A high speed camera, a non-intrusive measurement technique, was used. It is shown that both liquid and gas phases have strong effects on film characteristics. In the present work, liquid film width increased by 57% because of increasing liquid flow rate, while it decreased by 25% resulting from the counter current gas phase.     

A mechanistic model of the gas film dynamics during the electrochemical discharge phenomenon

A model for the prediction of the current–voltage characteristics of a two electrodes cell incorporating the dynamics of the gas film formed during the electrochemical discharge phenomenon is developed. In its mean-field version, the model presents good qualitative agreement but overestimates the hysteresis effect and predicts too large current densities for the cell operation once the gas film is formed. An improved stochastic model, which assumes gas film departures from the electrode surface according to a Poisson process, addresses these issues and gives significantly better predictions. Two relations are presented which allow estimating the mean gas film detachment time and its variance from the experimental study of the hysteresis in the forward and reverse scan of a two electrode cell operated at high current densities.     

Intercalation of lithium in r.f.-sputtered vanadium oxide film as an electrode material for lithium-ion batteries

Vanadium oxide films were prepared by r.f.-sputtering using an argon sputter gas and a V2O5 target. The films were characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical techniques. The oxide film as deposited is amorphous; they are heat-treated in the range 300–700°C in oxygen atmosphere and are composed of orthorhombic V2O5 crystals. At higher heat-treatment temperatures (600–700°C) the crystallization of the oxide proceeded significantly with ab-direction parallel to the substrate. The oxide film undergoes a reversible lithium intercalation and deintercalation process. The kinetics of the intercalation process of lithium into amorphous V2O5 film was studied using an a.c. impedance method. Furthermore, a rocking-chair type V2O5 film/LixV2O5 film cell could be charge–discharge cycled over 300 times at a current of 10A at 25°C.     

Microstructure and electrochemical properties of electron-beam deposited Sn-Cu thin film anodes for thin film lithium ion batteries

Thin film Sn-Cu anodes with high Cu content were prepared by electron-beam evaporation deposition using Cu substrate as current collector. Annealing, with the condition being determined by DSC, was used to improve the performance of these electrodes. X-ray diffraction (XRD), scanning probe microscopy (SPM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the structure and composition of the Sn-Cu thin film electrodes. Cyclic voltammetry and galvanostatical charge-discharge measurement were carried out to characterize the electrochemical properties of the as-deposited and annealed electrodes. ?-Cu₃Sn intermetallic phase was formed and interface strength between deposited active materials layer and current collector was enhanced by annealing the as-deposited film under suitable condition. The annealed thin film electrode showed good cycleability and had no phase change during cycling. Although large initial capacity loss was found associated with SEI formation due to increase of surface roughness of annealed electrode, a stable discharge capacity near 300 mAh/g with Coulomb efficiency of about 96% was obtained at voltage window of 0.1-2.0 V and a discharge capacity of about 200 mAh/g and Coulomb efficiency of 97% were kept stable up to 30th cycle at a narrower voltage window of 0.2-1.5 V versus Li/Li⁺.     

In situ impedance study of the Y-Ni thin film under electrochemical hydrogenation

A thin film of yttrium Y (150 nm) protected by a 6 nm coating of nickel Ni on a glass substrate was completely hydrogenated in a 1 M NaOH electrolyte at a constant negative current until the transparent Y tri-hydride phase was achieved and hydrogen gas evolution from the electrode began. A series of impedance measurements were performed in situ during the electrochemical experiment to study the properties of the system as dependent on hydrogenation degree and time of relaxation. The equivalent electrical circuit (EEC) simulations were performed with a Randles-like scheme R₀[R₁CPE₁], where R₀ is the thin film electrode resistance, R₁ the charge transfer resistance and CPE₁ is the capacitive constant phase element. The behavior of all the components of the EEC undergoes a clear transition when the hydrogenation degree of the electrode is approximated to its maximum value (H to Y ratio 2.7) and electrochemical process changes from hydrogen uptake to hydrogen evolution.     

正极材料钴酸锂表面固体电解质相界面膜的研究

通过循环伏安和交流阻抗（EIS）分析,对锂离子电池正极材料钴酸锂（LiCoO₂）表面的固体电解质相界面膜（SEI膜）的形成进行了研究。循环伏安测试结果表明,钴酸锂表面的SEI膜主要是在第1次循环过程中形成。EIS测试结果表明,在低倍率条件下和常温条件下充放电循环形成的SEI膜更加致密,阻抗值更小;储存时间的长短对电池的阻抗也有影响,储存7 d的阻抗值要小于储存1 d的阻抗值。