Microelectronic devices are multilayered structures with many different interfaces. Their mechanical reliability is of utmost importance when considering the implementation of new materials. Linear elastic fracture mechanics (LEFM) is a common approach that has been used for interfacial fracture analyses in the microelectronics industry where the energy release rate parameter is considered to be the driving force for delamination and the failure criterion is established by comparing this with the interface toughness. However this approach has been unable to model crack-nucleation, which plays an important part in analyzing the mechanical reliability of chip-package systems. The cohesive interface modeling approach, which is considered here, has the capability to model crack nucleation and growth, provided interfacial parameters such as strength and toughness of the system are available. These parameters are obtained through the extraction of traction-separation relations, which can be obtained through indirect hybrid numerical/experimental methods or direct experimental methods. All methods of extracting traction-separation relations require some local feature of the crack-tip region to be measured. The focus in this doctoral work has been on the comparison of the two methods for a mode-I DCB experiment and on the development of a universal loading device to extract mixed-mode traction-separation relations at different mode-mix values. The techniques that have been adopted for the local measurements are infrared crack opening interferometry (IR-COI) and digital image correlation (DIC). Apart from the global measurements of load-displacement (P-[delta]), local crack-tip parameters were measured using IR-COI or DIC. The combination of global and local measurements gave the relations between the fracture driving force (energy release rate or J-integral, J) and crack opening displacements, which were used to obtain the local tractions. IR-COI is an extremely useful technique to image and measure local crack-tip parameters. However, as IR-COI is restricted to normal measurements, the loading device was configured to accommodate a DIC system in order to make both normal and tangential measurements. In addition to measurements, fracture surface characterization techniques such as atomic force microscopy (AFM), profilometry and X-ray photoelectron spectroscopy were used to observe the fracture mechanisms. / text

Physical scaling limits of microelectronic devices and the need to improve electrical performance have driven significant research and development into 3D architecture. The development of die stacks in first level packaging is one of the more viable short-term options for improved performance. Placement of memory die above or below processors in a traditional flip chip C4 package with through-silicon vias (TSVs) has significant benefits in reducing data and power transmission paths. However, with the electrical performance benefits come great thermal and mechanical challenges. There are two key objectives for this work. The first is understanding of the die-die interface resistance, R[subscript dd], composed of the back end of line (BEOL) layers and micro-C4 interconnects. The interfacial resistance between BEOL material layers, the impact of TSVs and the impact of strain on R[subscript dd] are subtopics. The second key objective is the understanding of package thermal and mechanical behavior under operating conditions, such as local thermal disturbances. To date, these topics have not been adequately addressed in the literature. It is found that R[subscript dd] can be affected by TSVs, and that the interfacial contributions predicted by theoretical sub-continuum models can be significantly different than measurements. Using validated finite element models, the significance of the power distribution and R[subscript dd] on the temporal responses of 2D vs. 3D packages is highlighted. The results suggest local thermal hotspots can greatly exacerbate the thermal penalty due to the R[subscript dd] and that no peaks in stress arise in the transient period from power on to power off. / text

Interfacial partitioning tracer tests (IPTT) are one method available for measuring air-water interfacial area (A(ia)).This study used the standard approach comprising tracer injection under steady unsaturated-flow conditions with a uniform water-saturation distribution within the column. Sodium dodecylbezene sulfonate (SDBS) and pentafluorobenzoic acid (PFBA) were used as the partitioning and nonreactive tracers, respectively. Three types of porous media were used for the study: a sandy soil, a well-sorted sand, and glass beads. Initial water saturations, S(w), were approximately 80%, 80%, and 26 % for the soil, sand, and glass beads, respectively. Water saturation was monitored gravimetrically during the experiments. The maximum interfacial areas (A(ia)/(1-S(w))) calculated from the results of the experiments are compared among the three porous media used in this work, and compared to previous air-water interfacial area studies.

The air-water interface in variably saturated porous media is recognized to influence interfacial retention of organic and inorganic contaminants, and mediate various mass-transfer processes. The formation and presence of water films commonly solvating the surfaces of soil/sediment grains in unsaturated systems, as well as their impact on flow and retention processes have been of sustained interest. X-ray microtomography was used to measure air-water interfacial area at multiple wetting-phase saturations for natural porous media. First, a study was conducted to evaluate image-processing procedures suitable for characterizing fluids and associated interfaces in natural porous media. A simple method was developed for the analysis of all phases in the system, using global threshold for phase identification and combination of binary files (M1). This method was then compared to a simultaneous multiphase segmentation approach using locally adaptive threshold selection (M2). Both methods were used to process data sets comprised of multiple drainage steps for water-saturated packed columns imaged via synchrotron x-ray microtomography. The results of both methods were evaluated based on comparison of values determined for porosity and specific solid surface area to independently measured porosity and specific solid surface areas. The results show both methods are suitable for determination of total air-water interfacial area, which requires characterization of only the non-wetting phase. Conversely, determination of capillary interfacial area requires characterization of all phases present and thus, is more sensitive to the challenges associated with image processing. The simultaneous multiple-phase segmentation (M2) method provides an integrated and consistent analysis of the phases, and anticipated to improve water-phase detection. Using the advanced segmentation approach, the air-water interfacial area is presented as a result of direct measurement of contact areas between the two fluids. This is in contrast to previously reported data, which were derived indirectly from calculations based on individually measured phase surface areas and conceptualizations of fluid distributions. The effects of these assumptions on the capillary interfacial behavior are evaluated. Results from this study confirmed the initial hypothesis that the behavior of fluid surface areas will affect the theoretical shape of the capillary curve. The results support the understanding of the capillary interfacial area behavior in response to changes in the configuration of fluid surface areas during a drainage cycle. Furthermore, results for the measured air-water interface allows for further identification of fluid domains, such as the relationship between film interfacial area, capillary domains (menisci), and the total-measurable interfacial area. Experiments were also conducted using aqueous-phase interfacial partitioning tracer tests for comparison. Results support the hypothesis that different methods provide characterization of different interfacial domains. Overall, this study provides an imaging-based approach for evaluation of water configuration, and presents a measurement-based framework for further understanding of the role of fluid-fluid interfaces in natural porous media.

In this work the nucleation kinetics of propane gas hydrate has been investigated experimentally using a stirred batch reactor. The experiments have been performed isothermally recording the pressure as a function of time. Experiments were conducted at different stirring rates, but in the same supersaturation region. The experiments showed that the gas dissolution rate rather than the induction time of propane hydrate is influenced by a change in the stirring rate. This was especially valid at high stirring rates when the water surface was severely disturbed. Addition of polyvinylpyrrolidone to the aqueous phase was found to reduce the gas dissolution rate slightly, however the induction times were prolonged quite substantially. The induction time data were correlated using a newly developed induction time model based on crystallization theory also capable of taking into account the presence of additives. In most cases reasonable agreement between the data and the model could be obtained. The results revealed that especially the effective surface energy between propane hydrate and water is likely to change when the stirring rate varies from very high to low. The prolongation of induction times according to the model is likely to be due to a change in the nuclei-substrate contact angle.

No description available.

The nanoindentation technique has been used to identify the interfaces between dissimilar materials and subsequently to evaluate the physical and mechanical properties across the interfaces. The interfaces could represent the interface (transition face) between oxidized and unoxidized polymers, the interface between rigid fiber and polymer matrix, or other similar situations. It is proposed to use a nanoindenter equipped with small spherical tip to indent across the interfaces of dissimilar materials. The proposed method has been validated by conducting a large number of virtual experiments through 3-dimensional finite element simulations, by varying the properties of the two dissimilar materials, including various combinations of modulus (E1/E2), yield strength (σy1/σy2), hardening index (n1/n2), interface sizes (R/T), Poisson’s ratio (ν), etc. The mechanical properties across the interfaces have been obtained, and a quantitative model for predicting the interface sizes has been established.

Diese Doktorarbeit untersucht die verschiedenen dynamischen Prozesse, welche sich an der Tropfenoberfläche abspielen, und der Methoden, die für deren Untersuchung verwendet wurden. Das Ziel dieser Arbeit ist es, die entscheidenden Eigenschaften, die einen Einfluss auf das mechanische Verhalten der Grenzfläche haben, zu identifizieren. Wir verwenden die hydrodynamisch erzwungene Deformation eines Tropfens in einem Mikrokanal, um die mechanischen Eigenschaften der Oberfläche zu untersuchen. Diese Methode wird auf drei verschiedene Fälle angewendet. Als erstes verfolgen wir die zeitliche Entwicklung einer Grenzflächenverformung, um die Dynamik der Tensidadsorption an einer Oberfläche zu untersuchen. Dabei kalibrieren wir die Tropfenverformung als Funktion von Tropfengröße und Oberflächenspannung. Diese Technik wird auf den Fall eines perfluorierten Tensids, welches von industriellem und wissenschaftlichem Interesse ist, angewendet. Wir zeigen die Möglichkeit von Messungen der dynamischen Oberflächenspannung auf Zeitskalen von zehn Millisekunden und gewinnen daraus kinetische Eigenschaften der Moleküle. Wir vergleichen die Dynamik, welche mit der klassischen Pendant-Drop-Methode gemessen werden kann mit denen der Mikrofluidik. Es zeigt sich, dass die Adsorption für den Pendant Drop von der Di usion begrenzt wird, während in der Mikrofluidik die Anbindung an die Oberfläche der langsamere Prozess ist. Der Unterschied entsteht durch das Flussprofil in der Mikrofluidik, welches konvektiven Transport induziert. Danach untersuchen wir die Verformung unter verschiedenen räumlichen Beschränkungen im mikrofluidischen Kanal. Die Tropfenverformung wird mit einer zweidimensionalen numerischen Simulationen und mit einem dreidimensionalen Modell eines Rotationsellipsoids verglichen. In beiden Fällen wird eine qualitative Übereinstimmung festgestellt, jedoch existieren auch spürbare Abweichungen vom Experiment. Die Abweichungen vom zweidimensionalen Modell ist erklärbar mit dem sinkenden Einfluss der viskosen Spannungen mit der Kanalhöhe, hervorgerufen durch Beiträge von Deformationen außerhalb der Beobachtungsebene, welche von dem Modell nicht wiedergegeben werden. Die Abweichungen vom dreidimensionalen Modell kommen von den räumlichen Beschränkungen, welche die Tropfenform von einem Rotationsellipsoid abweichend verformt. Die Untersuchung zeigt die Schwierigkeiten bei der Beschreibung von viskosen Kräfte für Abmessungen, die zu groß sind um als zweidimensional betrachtet zu werden, aber wo die Wechselwirkungen mit den Kanalwänden nicht vernachlässigbar sind. Wir diskutieren ebenfalls den Fall der trägen Relaxation des Tropfens bei Reynoldszahlen von Re 10, für welchen Oszillationen der Tropfenoberfläche beobachtet werden. Wir zeigen, dass die Oszillationen als hydrodynamische Analogie zu einer hookeschen Feder beschrieben werden können, wobei die Oberflächenspannung als Federkonstante fungiert und die Dämpfung durch die Viskosität der Flüssigkeit bestimmt wird. Die Methode liefert korrekte Ergebnisse sowohl für reine Grenzflächen als auch für Grenzflächen mit Tensiden, was zu einer zusätzliche Möglichkeit führt, die Oberflächenspannung aus der Frequenz der Verformungen zu bestimmen. Die viskose Relaxation wurde auch hierbei von den Kanalwänden beeinflusst. Als letztes wenden wir die Methode der mikrofluidischen Tensiometrie auf die Kinetik einer Polymerisationsreaktion auf der Tropfenoberfläche an. Der Einfluss der Reagenzkonzentration auf die Reaktionszeit wird untersucht, ebenso wie der E ekt der Gegenwart von Tensidmolekülen. Erste Ergebnisse dieser Untersuchung zeigen, dass die Deformation einer komplexen Grenzfläche nicht mehr allein durch die Oberflächenspannung beschrieben werden kann. Vielmehr muss die Beschreibung der mechanischen Eigenschaften der Grenzfläche notwendigerweise die Entstehung der Viskoelastizität an der Oberfläche mit in Betracht ziehen. Diese Erkenntnis erö net neue Möglichkeiten, mit Hilfe von Mikrofluidik die mechanischen Eigenschaften von komplexen Grenzflächen, wie zum Beispiel kolloidbesetzte Grenzflächen oder Membranen, zu charakterisieren.

The pendant drop technique was used to characterize the adsorption behavior of n-dodecane-1-thiol and n-hexane-1-thiol capped gold nanoparticles at the hexane-water interface. The adsorption process was studied by analyzing the dynamic interfacial tension versus nanoparticle concentration, both at early times and at later stages (i.e., immediately after the interface between the fluids is made and once equilibrium has been established). Following free diffusion of nanoparticles from the bulk hexane phase, adsorption leads to ordering and rearrangement of the nanoparticles at the interface and formation of a dense layer. With increasing interfacial coverage, the diffusion-controlled adsorption for the nanoparticles at the interface was found to change to an interaction-controlled assembly and the presence of an adsorption barrier was experimentally verified. At the same bulk concentration, different sizes of n-dodecane-1-thiol nanoparticles showed different absorption behavior at the interface, in agreement with the findings of Kutuzov et al. [1]. The experiments additionally demonstrated the important role played by the capping agent. At the same concentration, gold nanoparticles stabilized by n-hexane-1-thiol exhibited greater surface activity than gold nanoparticles of the same size stabilized by n-dodecane-1-thiol. 1.6 nm, 2.8 nm, and 4.4 nm nanoparticles capped with n-dodecane-1-thiol, and 2.9 nm, and 4.3 nm particles capped with n-hexane-1-thiol were used in this study. The physical size of the gold nanoparticles was determined by TEM image analysis. The pendant drop technique was also used to study the adsorption properties of mixtures of gold nanoparticles at the hexane-water interface; and also investigate the effects of different factors (i.e., temperature, pH or ionic strength) on interfacial tension (IFT). The interfacial properties of mixtures of these nanoparticles, having different sizes and capping agents, were then studied. No interaction was found between the unmixed studied nanoparticles. Using the theory of non-ideal interactions for binary mixtures, the interaction parameters for mixtures of nanoparticles at the interface were determined. The results indicate that nanoparticle concentration of the mixtures has a profound effect on the interfacial nanoparticle composition. A repulsive interaction between nanoparticles of different size and cap was found in the mixtures at the interface layer. The interfacial tension for mixtures was found to be higher than the interfacial tension for non-mixed nanoparticle suspensions. The nanoparticle composition at the interface was found to differ from the composition of nanoparticles in the bulk liquid phase. The activity of unmixed nanoparticles proved to be a poor predictor of the activity of mixtures. It was observed that the most active nanoparticles concentrated at the interface. The effects of temperature, pH and ionic strength concentration on the equilibrium and dynamic IFT of 4.4 nm gold nanoparticles capped with n-dodecane-1-thiol at the hydrocarbon-water interface was studied. The pendant drop technique was also used to study the adsorption properties of these nanoparticles at the hexane-water and nonane-water interface. The addition of NaCl was found to cause a decrease of the equilibrium and dynamic IFT greater than that, which accompanies the adsorption of nanoparticles at the interface in the absence of NaCl. Although IFT values for acidic and neutral conditions were found to be similar, a noticeable decrease in the IFT was found for more basic conditions. Increasing the temperature of the system was found to cause an increase in both dynamic and equilibrium IFT values. The adsorption of functionalized gold nanoparticles at liquid-liquid interfaces is a promising method for self-assembly and the creation of useful nanostructures. These findings contribute to the design of useful supra-colloidal structures by the self-assembly of alkane-thiol capped gold nanoparticles at liquid-liquid interfaces.

The objective of this study is to analyze theoretically the laminar film condensation of water vapor flowing on a sphere. For this purpose, the problem was handled by including all of the two-phase boundary layer parameters such as gravity, effect of vapor shear, inertia, energy convection and pressure gradient. For this full two-phase boundary layer system, the boundary layer equations, boundary conditions and the interfacial conditions were first analyzed, and then discretized. A computer program in Mathcad, solving these discretized equations, was written to obtain the velocity and temperature profiles within the condensate, the velocity profiles within the vapor, the condensate film thickness and the local Nusselt number. The effects of pressure gradient, gravity, vapor oncoming velocity and sphere radius on these parameters were examined. By alternating the formulation of the problem, the results for the flow over a horizontal cylinder were obtained. These results were then compared with those for the sphere. Finally, the results for the system with Mercury vapor flowing on a sphere were obtained. All of these results were represented as diagrams and tables, and were discussed at the end of the study.