Dynamic microscopy of nanoscale cluster growth at the solid-liquid interface

Dynamic processes at the solid-liquid interface are of key importance across broad areas of science and technology. Electrochemical deposition of copper, for example, is used for metallization in integrated circuits, and a detailed understanding of nucleation, growth and coalescence is essential in optimizing the final microstructure. Our understanding of processes at the solid-vapour interface has advanced tremendously over the past decade due to the routine availability of real-time, high-resolution imaging techniques yielding data that can be compared quantitatively with theory. However, the difficulty of studying the solid-liquid interface leaves our understanding of processes there less complete. Here we analyse dynamic observations--recorded in situ using a novel transmission electron microscopy technique--of the nucleation and growth of nanoscale copper clusters during electrodeposition. We follow in real time the evolution of individual clusters, and compare their development with simulations incorporating the basic physics of electrodeposition during the early stages of growth. The experimental technique developed here is applicable to a broad range of dynamic phenomena at the solid-liquid interface.     

Fingering of the solid-liquid4He interface in two-dimensions

A novel Hele-Shaw experiment is described in which the two fluids are superfluid and solid⁴He. A thin cell in which solid and liquid⁴He initial occupy the lower and upper halves, respectively, is inverted. The growth of solid⁴He by simultaneous melting and freezing of different parts of the interface is monitored. Qualitative results on the shape of the interface and the growth rate are presented.     

Supramolecular porphyrin polymers in solution and at the solid-liquid interface

We have investigated in detail the self-assembly of a chiral porphyrin trimer in different solvents and correlated this behavior to the aggregation of the molecule at a solid-liquid interface. In n-hexane and cyclohexane, CD spectroscopy and dynamic and static light scattering studies showed that the porphyrin trimer self-assembles already at micromolar concentrations into long, chiral supramolecular polymers, which precipitate as fibers when the solution is drop-cast onto a mica surface. In contrast, in chloroform, the compound is molecularly dissolved up to concentrations of 0.2 mM and when micromolar solutions are drop-cast onto mica, no precipitation of large assemblies occurs. Instead, at the moment that the chloroform film becomes subject to spinodal dewetting and the porphyrin trimers within this film start to self-assemble, extended patterns of equidistant lines of single molecule thick columnar stacks are formed.     

粗糙界面法向接触振动响应与能量耗散特性研究

粗糙界面的法向接触振动与能量耗散特性对描述界面动力学机理具有重要的理论和实际意义。本文通过建立粗糙界面法向接触振动的动力学模型,提出了其法向接触振动响应特征量和振动能量耗散量的计算方法。基于粗糙表面的三维分形模型描述,构造了粗糙界面的接触力-变形关系式,并与Hertz接触模型的力-变形关系进行了对比分析;建立了粗糙界面接触振动系统的动力学方程,计算了不同表面形貌粗糙界面系统每周期的振动能量耗散率和累计能量耗散率;分析了粗糙界面法向接触振动的响应特征与能量耗散特性,从理论上对界面法向微动能量耗散的实验结果进行了解释,为描述接触界面的动力学机理提供了理论依据。     

The influence of vibration & shock on the crystal growth during solidification

Based on the single-phase solidification experiment of alloy Al-4.5% with lateral single-phase vibrating & shocking on it, the article studies the influence of vibration & shock on the crystal growth and reveals the phenomenon that the dynamics effects only occur near the solid/liquid interface in crystal growth on the basis of vibration reai-time method to locate the solid/liquid interface.     

Solidons bound to a solid-liquid interface and two-dimensional solidons in liquid He layers

In a nearly solid quantum liquid, a longitudinal phonon can get self-trapped in a solid-like region and form a solidon, analogous to a roton with a large solid-like core. Half a solidon can be bound to a solid-liquid interface. A bound state energy of about 5 K is estimated in liquid ⁴He. Surface solidons are also envisaged in two-dimensional liquid layers. The experimental data on helium films are discussed.Laboratoire associé au CNRS.     

On the stability of the solid-liquid interface during solidification under convection

The non-dendritic morphology of solid particles forming during rheocasting has been examined in terms of the stability of the solid-liquid interface under the influence of stirring using a constitutional supercooling approach. The theoretical analysis suggests that stability may be achieved if the effective solute partition ratio is less than $\text{2}\text{3}$, or when the particle's Reynolds number exceeds the value required for the laminar to turbulent transition.     

Solute distribution at the solid-liquid interface during steady-state peritectic solidification

The solute distributions at the solid-liquid interface during steady-state directional solidification of two contrasting peritectic systems were examined in detail by electron probe microanalysis. In the Al-Al₃Ti system the peritectic transformation plays a negligible part in the solidification reaction whereas in the Cd-Cd₃Ag system the peritectic transformation dominates. Knowing this, the solid-liquid interface profile during solidification can be predicted with reasonable accuracy on the assumption of equilibrium at all points on the solid-liquid interface. In the Cd-Cd₃Ag system the composition of the peritectic product is rapidly equilibrated by solid-state diffusion. A diffusion coefficient is estimated.     

Application of fractal theory on the study of solid-liquid interface morphology

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Mobility of the3He solid-liquid interface: Experiment and theory

Two experiments are presented that show that the growth resistance of³He crystals is smaller than expected. In order to explain this result the growth resistance is calculated in two different ways, showing that the experimental results are best understood if the liquid quasiparticles interact with the crystal lattice instead of the interface.     

Effects of3He impurities on the4He solid-liquid interface

Using crystallization waves we have measured the interfacial stiffness, , and the temperature dependence of the growth resistance, (Km)^–1, of the⁴He solid-liquid interface in the presence of³He impurities. For the purest⁴He sample, (Km)^–1 is consistent at the lowest temperatures with the assumption that the growth velocity is limited by the scattering of ballistic phonons from the moving interface. At higher concentrations of³He, we observe that (Km)^–1 increases exponentially with temperature below 0.25 K. We observe that decreases with increasing³He concentration.     

Simulation studies of the hydrodynamics in high-temperature solutions for crystal growth. VI. Temperature fluctuations at the crystal/liquid interface

The temperature fluctuations at the crystal/liquid interface have been studied using model liquids. The character of the fluctuations varied depending on whether in the liquid there was only free convection or both free and forced convections were simultaneously present. It has been established that in the second case the amplitude of fluctuations is determined mainly by the rate of the resultant convection flow and the liquid viscosity. A maximum amplitude of fluctuations is observed at a resultant flow rate w_fl = O when the free and forced convections proceed in opposite directions, and at w_fl = min when both convection flows have the same direction. Larger amplitudes of temperature fluctuations are registered in low-viscosity liquids. The conditions under which a flat crystal/liquid interface showing no temperature fluctuations should be formed have been determined for crystal diameters of 10, 15 and 20 mm, respectively.     

Effects of interface slip and viscoelasticity on the dynamic response of droplet quartz crystal microbalances

In the present paper we first present a derivation based on the time-dependent perturbation theory to develop the dynamical equations which can be applied to model the response of a droplet quartz crystal microbalance (QCM) in contact with a single viscoelastic media. Moreover, the no-slip boundary condition across the device-viscoelastic media interface has been relaxed in the present model by using the Ellis-Hayward slip length approach. The model is then used to illustrate the characteristic changes in the frequency and attenuation of the QCM with and without the boundary slippage due to the changes in viscoelasticity as the coated media varies from Newtonian liquid to solid. To complement the theory, experiments have been conducted with microliter droplets of aqueous glycerol solutions and silicone oils with a viscosity in the range of 50 approximately 10,000 cS. The results have confirmed the Newtonian characteristics of the glycerol solutions. In contrast, the acoustic properties of the silicones oils as reflected in the impedance analysis are different from the glycerol solutions. More importantly, it was found that for the silicone oils the frequency steadily increased for several hours and even exceeded the initial value of the unloaded crystal as reflected in the positive frequency shift. Collaborative effects of interfacial slippage and viscoelasticity have been introduced to qualitatively interpret the measured frequency up-shifts for the silicone oils. The present work shows the potential importance of the combined effects of viscoelasticity and interfacial slippage when using the droplet QCM to investigate the rheological behavior of more complex fluids.     

随机参数结构最优控制的闭环响应分析

在模态坐标下对结构降阶进行最优控制,用近似离散化的方法得到结构闭环响应的近似解来代替精确解。考虑结构中物理参数和几何参数的随机性,将这些随机参数用随机因子来表示。在此基础上,利用求解随机变量函数矩的方法,导出了在最优控制的作用下,随机结构位移闭环响应的均值和方差的计算表达式。通过算例考察了结构各个参数的随机性对闭环响应的影响,经与Monte Carlo数值模拟法结果比较,验证了文中理论分析和计算方法的正确性。     

Enantioselective interactions at the solid-liquid interface of an HPLC column under working conditions

A technique is presented which allows studying the enantioselective interactions occurring at the solid-liquid interface of a chiral stationary phase (CSP) and a racemate relevant to high performance liquid chromatography (HPLC). A conventional chiral column (Chiralpak AS) was mounted on an attenuated total reflection-infrared (ATR-IR) cell mimicking an HPLC setup equipped with an ATR-IR detector. Racemic pantolactone (PL) was used as the selectand. This setup in combination with modulation excitation spectroscopy (MES) allows for the identification of inter- and intramolecular hydrogen bonds being crucial for enantioseparation under HPLC operation conditions. The method is based on a two step strategy. In a first step, the enantiomers are separated by the chiral column similar to a standard HPLC experiment and upon adsorption on the identical CSP deposited on the internal reflection element (IRE), they are detected by ATR-IR spectroscopy. This experiment provides a retention time for each enantiomer. From the difference in retention, a suitable frequency is calculated which is used in a second experiment where the racemate concentration is varied alternately (modulation) in a way that the pulses of ( R)-PL and ( S)-PL exhibit a phase lag of 90 degrees after elution through the column. This procedure allows one to gain separate information of the enantioselective selectand-CSP interaction after performing a demodulation similar to a phase sensitive detection (PSD). A further benefit of this method is the strong enhancement of the signal-to-noise ratio. The effectiveness of the method is demonstrated by investigating the observed faster decrease in retention time of the later-eluted ( R)-PL, as compared to ( S)-PL, when separating at higher temperatures (from 12 to 36 degrees C). The origin is attributed to a weakening of a specific hydrogen bond between the C=O of ( R)-PL and the N-H of the CSP.     

Formation of solid-liquid interface in ferroelectric particle dispersion and its effect on the dispersion stability

A model has been proposed for the formation of the ferroelectric solid-liquid interface in the non-electrolyte dispersion system. Bulk properties as well as the surface properties of the dispersing solid could be a factor which was associated with various characters of the dispersion state. A qualitative investigation was carried out to see whether the continuum polarization process in solid-liquid interface due to the inhomogeneous field from the polar solid might affect the powder dispersion. The development of the polarized solid-liquid interface might depend on the polarity of solid particle and of liquid medium, shapes, mobility, and solubility of the molecules in the liquid phase, and temperature. Two possible effects of polarized solid-liquid interface on the dispersion stability have been discussed. Lastly, this model was applied to interpreting some experimental results of adhesion.     

PDM对模块化设计中接口参数的管理方法

针对面向大规模定制的产品设计,介绍了模块化设计的基本思路,分析了模块化设计过程中接口参数信息管理的必要性,并结合PDM研究了具体的管理方法以及基于该原理实现产品快速设计的方法。