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The momentum exchange between lattice atoms and conduction electrons together with the stress gradient along the metal wire embedded into the rigid confinement are two major driving forces for electromigration-induced evolution of stress and vacancy concentration. The growth of mechanical stress causes an evolution of a variety of defects that are inevitably present in the metal, leading to void formation. It affects the electrical properties of the interconnect. In order to estimate the time to failure caused by voiding, the kinetics of stress evolution should be resolved until the first void is nucleated. Then the analysis of the void size evolution should be performed in order to trace changes in resistances of individual voided lines and vias. In this chapter, we review the major results that have been achieved with the 1D phenomenological EM model. We demonstrate its capability to predict the transient and steady-state distributions of the vacancy concentration and the hydrostatic stress, a void nucleation, and its growth, and also a drift of small voids along a metal wire. Despite its simplified nature, the 1D model is capable of addressing the confinement effect of ILD/IMD dielectric on EM-induced degradation, and also the effect of metal grain structure.
Scaling on-chip Cu wiring dimensions has degraded electromigration (EM) reliability with the same metallization and rapidly increased Cu resistivity. The size effects in EM and resistivity were caused by increased contributions from EM-induced mass flow and electron scattering with interfaces and grain boundaries, respectively. The EM Cu interconnect lifetime had further degraded by the decrease in the void volume required to cause EM failure. The Cu interconnect resistance was further increased by increasing the volume fraction of barrier/liner in metal wires that were required to produce chips with good reliability. In this chapter, we review the Cu microstructure and resistivity for various CMOS technological nodes, the basic physics of the EM phenomenon addressing EM mass transport, lifetime scaling rule, and damage formation in Cu damascene line structures. This is followed with discussions on Blech short length and EM scaling rule. Several techniques developed for improving EM reliability using upper-level dummy vias, impurities, Cu surface treatments, alternated liners, and surface metal coating are discussed together with the effects of Cu microstructure, atomic layer deposition MnOx liner, and Cu/carbon nanotube composite line on EM. Finally, the EM lifetimes, failure mechanisms and activation energies through various technological nodes are presented.
In this study, binary as-cast Al–Cu alloys: Al25Cu (Al–25%Cu) and Al45Cu (Al–45%Cu) (in wt%) were severely plastically deformed by extrusion combined with a reversible torsion (KoBo) method to produce an ultrafine-grained structure (UFG). The binary Al–Cu alloys consist of α-Al and intermetallic Al2Cu phases. The morphology and volume fraction of α-Al and Al2Cu phases depend on the Cu content. The KoBo process was carried out using extrusion ratios of λ = 30 and λ = 98. The effect of phase refinement has been studied by means of scanning electron microscopy with electron backscattering diffraction and scanning transmission electron microscopy. The mechanical properties were assessed using compression tests. Detailed microstructural analysis shows that after the KoBo process, a large number fraction of high-angle boundaries (HABs) and a very fine grain structure (~2–4 μm) in both phases are created. An increase of λ ratio during the KoBo processing leads to a decrease in average grain size of α-Al and Al2Cu phases and an increase in fraction of HABs. UFG microstructure and high fraction of HABs provide the grain boundary sliding mechanism during KoBo deformation. UFG microstructure contributes to the enhanced mechanical properties. Compressive strength (Rc) of Al25Cu alloy increases from 172 to 340 MPa with an increase of λ. Compressive strain (Sc) for Al25Cu alloy increased from 35 to 67% with an increase of λ. High fraction of intermetallic phase in Al45Cu alloy was responsible for room temperature strengthening of alloy and low compressive strain. The deformed Al45Cu alloy with λ = 30 showed that Rc is 194 MPa and Sc is equal to 10%.
This paper presents the comparison of the microstructure of the interface zone formed between titanium (Ti Gr. 1) and steel (P265GH+N) in various processing stages—directly after explosive welding versus the annealing state. Transmission electron microscopy technique served as an excellent tool for studies of the sharp interface in-between the waves. Directly after the welding process in this area, a thin layer of the metastable β-Ti (Fe) solid solution was observed. In the next step, two variants of annealing have been employed: ex situ and in situ in TEM, which revealed the complete information on the interface zone transformation. The results have shown that during the annealing at 600°C for 1.5 h, the diffusion of carbon towards titanium caused the formation of titanium carbides with a layered arrangement. Compared to our previous studies, the carbides found here have a hexagonal structure. Furthermore, changes in the dislocation structure were observed, indicating the occurrence of recovery processes. Possible reasons for differences observed in the microstructure of the interface formed due to ex situ and in situ annealing are also discussed. The microstructure observations are accompanied by the microhardness measurements, which showed that the annealing caused a significant reduction in the microhardness values.
In this research communication we propose a new approach by portable digital microscopy with a 200× objective to improve the visualization of microparticles of pasteurized milk submitted to the alcohol test. Not only did the method reduce the subjectivity of the readings, but also generated high resolution images of the microparticles, which allows the creation of a specific image pattern for each type of final product. In comparison to a control pasteurized milk treatment, the results confirmed the effect and the specificity of added salts (sodium citrate, disodium phosphate or their combination) on the stability of the milk to the alcohol test. Finally, the mixture of stabilizing salts of citrate/phosphate provided the highest degree of stability to pasteurized milk among the treatments studied.
Caseinomacropeptide (CMP) is derived from the chymosin cleavage of κ-casein during cheese production. This study developed gels from CMPs, which were isolated by different ultrafiltration systems, and whey protein isolate (WPI), and studied their rheological and ultrastructural characteristics. The 30% WPI gel showed high elastic modulus (G′) values and stronger structure than the other samples with CMP. Another gel, with 50% protein, 30% WPI and 20% CMP sample isolated from the 30 kDa retentate, had a weaker structure and lower G′ value. The third gel, with 30% WPI and 20% CMP sample from the 5 kDa retentate derived from the 30 kDa retentate, presented intermediate structural strength. Despite the increase in protein concentration from the addition of CMP, there was a decrease in the strength of the gel network. Different CMP isolation processes also contributed to differences in the microscopic analysis of gel structures with the same protein content.
The presented research focused on the microstructural characteristics of explosively welded three-layered Ti Grade (Gr) 1/Alloy 400/1.4462 steel clads before and after heat treatment being of large practical potential. Scanning electron microscopy (SEM) analyses have shown that both interfaces formed between the plates are continuous and without defects. The in-depth examination was dedicated to the upper Ti Gr 1/Alloy 400 interface, located closer to the explosive material, therefore, subjected to more extreme welding conditions. The presence of cubic phase Ti2Ni, hexagonal phase Ni3Ti, and tetragonal phase (CuxNi1−x)2Ti were confirmed within the melted zones, which slightly widened due to annealing, being an essential step in the manufacturing of these modern materials. Transmission electron microscopy observations in the nano scale confirmed the preliminary chemical composition analyses collected with energy-dispersive X-ray spectroscopy in SEM. They additionally revealed the interface zone microstructure transformation due to the annealing. It was evidenced that initially mixed phases in the form of grains, after heat treatment formed irregular bands arranged in the following sequence: Alloy 400/Ni3Ti/(CuxNi1−x)2Ti/Ti2Ni/Ti Gr 1. A clear segregation of Cu and Ni forming two separate layers was also noticed. These diffusion phenomena may influence the strength of the final product, therefore need further studies regarding the prolonged annealing state.
A wide class of aerogels starts from solution of monomers in which the monomers react, forming oligomers, polymers, particles and eventually a spanning cluster or a solid network embedded in a solution: a wet gel. Meanwhile, the two classical aerogels prepared in this way are the silica and resorcinol-formaldehyde ones. In the first section, silica aerogels, silica being the most often used precursor, are treated: the reaction between them in a solution, hydrolysis and polycondensation, the growth of fractal and compact structures, their gelation and ageing after the gel point has passed. Finally, the chemistry of silica aerogels with lower functional silanes is briefly discussed. In the second section, the chemistry of resorcinol (R) and formaldehyde (F) is presented, as well as the reaction between both molecules under basic and acidic conditions and how polymers develop from monomers. The effect of various process parameters, the ratio of R to F or the concentration of a catalyst, the dilution ratio with water and the influence of temperature on gelation are treated in detail. Finally, some thoughts on the thermodynamics of RF gels are presented.
This longitudinal study investigated the development of oral narrative skills in monolingual Swedish-speaking children (N = 17). The MAIN Cat/Dog stories were administered at four timepoints between age 4 and 9. Different narrative aspects were found to develop differently. In story comprehension, the children performed high already at T1 (4;4) and were at ceiling at T2 (5;10), whereas story structure developed significantly until T4 (9;4). Narrative length and syntactic complexity reached a plateau at T3 (7;4). Referent introduction was not mastered until T4. The results suggest that general conclusions regarding the development of narrative skills depend on the specific aspects studied.
Melt-spun Ni70Ga30 and Ni70Sn30 monolithic catalysts, when subjected to prolonged oxidation in air at 770 K, undergo different microstructural changes. Whereas Ni70Ga30 is largely stable and composed of Ni3Ga phase, the Ni70Sn30 develops a two-layer microstructure on the exposed ribbon surface. The two-layer structure consists of a Ni-rich zone, which is founded on a SnO2 sublayer. In the bulk, the Ni70Sn30 ribbon is heterogeneous in phase composition and comprises of Ni3Sn and Ni3Sn2 phases. The development of Ni particulates on the outer ribbon surface, through simple oxidation heat treatment, may thus be a way for improving the catalytic performance of Ni70Sn30 ribbons, resembling that of Ni3Al ribbons spontaneously activated under reaction conditions.
Rapidly solidified alloys with a nominal composition of Al76.5Fe23.5 and Al75.8Co24.2 (in at%), corresponding to the Al13Fe4 and Al13Co4 phases, were produced by a melt spinning technique. The microstructure and phase composition of the as-spun and heat-treated ribbons were examined by X-ray diffraction, scanning and transmission electron microscopy. The as-spun ribbons consisted of columnar grains with an average size of 1–2 μm, which increased by a factor of 2 after applied heat treatment. The Al13Fe4 as-spun ribbon comprised of two phases: grains of the Al13Fe4 phase surrounded by solid solution of Al, transformed into a single monoclinic Al13Fe4 phase after annealing. The as-spun Al13Co4 ribbons had a multiphase structure. A decagonal quasicrystalline D-phase, the monoclinic M-Al13Co4 phase, and the Al9Co2 phase were identified in their microstructure. After the heat treatment, the mixture of the orthorhombic O-Al13Co4 phase and grains of monoclinic Y-Al13Co4 were observed. The investigations of catalytic properties were performed for the phenylacetylene hydrogenation reaction using pulverized ribbons in the initial state and after annealing. The degree of conversion was in the range of 8–27% and increased with the increasing reaction temperature. The highest selectivity to styrene was obtained for the Al13Fe4 alloy in the as-spun state.
This chapter is reserved for issues that surfaced in previous chapters but for some reason or other could not be discussed there in any detail. On the one hand, the chapter looks at the framework outlined in Chapter 2 from a wider perspective. It is argued that the presence of two contrasting mechanisms is suggestive of a dual process model of the kind described in work on discourse analysis, neurolinguistics, and social psychology. On the other hand, the chapter shows that whereas the pathways leading to grammaticalization are highly constrained, those leading to the rise of discourse markers are almost unlimited. Further topics discussed in the chapter concern the structure of constituent anchored discourse markers and the role played by imperative forms in the rise of discourse markers. Finally, the chapter also looks into the role of a more marginal category of discourse-structuring devices, namely that of fillers or "hesitation markers."
Rough volatility is a well-established statistical stylized fact of financial assets. This property has led to the design and analysis of various new rough stochastic volatility models. However, most of these developments have been carried out in the mono-asset case. In this work, we show that some specific multivariate rough volatility models arise naturally from microstructural properties of the joint dynamics of asset prices. To do so, we use Hawkes processes to build microscopic models that accurately reproduce high-frequency cross-asset interactions and investigate their long-term scaling limits. We emphasize the relevance of our approach by providing insights on the role of microscopic features such as momentum and mean-reversion in the multidimensional price formation process. In particular, we recover classical properties of high-dimensional stock correlation matrices.
High-temperature differential scanning calorimetry was used to understand the thermal properties of Si-rich metal–silicon alloys. Insoluble metals (A and B) were found to produce an alloy with discrete ASi2 and BSi2 dispersed phases. In contrast, metals that form a solid solution result in a dispersed phase that has a composition of AxB1−xSi2, where x varies continuously across each inclusion. This complex composition distribution is putatively caused by differences in the solidification temperatures of ASi2 versus BSi2. Though this behavior was observed for several different combinations of metals, we focus here specifically on the Cr/V/Si system. To better understand the range and most probable element concentrations in the dispersed silicide domains, a method was devised to generate histograms of their Cr and V concentrations from energy-dispersive X-ray spectroscopy hyperspectral images. Varying the Cr/V/Si ratio was found to change the shape of the element histograms, indicating that the distribution of silicide compositions that form is controlled by the input composition. Adding aluminum was found to result in dispersed phases that had a single composition rather than a range of Cr and V concentrations. This demonstrates that aluminum can be an effective additive for altering solidification kinetics in silicon alloys.
The mineral composition of eggshells is assumed to be a conserved phylogenetic feature. Avian eggshells are composed of calcite, whereas those of taxa within Chelonia are aragonitic. Yet, the eggshells of a passerine bird were reported to be made of aragonite. Here, we report a new study of the same bird eggshells using a combination of in situ microscopy and chemical techniques. A microstructural analysis finds a similar arrangement to other avian eggshells, despite their very thin and fragile nature. Fourier transform infrared spectrometry (FTIR) and electron backscatter diffraction (EBSD) results also confirm that the eggshells are entirely composed of calcite. Our findings demonstrate that passerine eggshells are not an exception and similar to other birds and reinforce the phylogenetic placement of this bird species.
Softness has a great impact on the properties of colloidal suspensions, especially at high concentrations. Particle deformability due to crowding is responsible for elastic interactions strongly affecting the dynamical properties, which therefore differ from those of hard spheres. The universal aspects of the linear and nonlinear rheological response, based on appropriate scaling, are discussed. Different approaches to determine an effective volume fraction and its role on the low frequency plateau modulus in the glassy and jamming regimes are presented. The flow properties often follow Herschel–Bulkley behavior, with the particle microstructure and interactions affecting the yield stress and causing shear banding or wall slip in some cases. Concentrated suspensions exhibit aging and internal stresses with several common but also distinct features compared to hard sphere glasses. The rich state diagrams of mixtures involving soft colloidal glasses and additives (linear polymers, soft or hard particles) suggest the possibility to tailor their flow properties, often in unprecedented ways, by means of osmotic interactions. This wealth of physical properties in relation to particle interactions can be described by different microstructural, statistical, and phenomenological models which offer a valuable predictive toolbox for understanding the complex and tunable rheology of this class of systems.
The microstructure of colloidal suspensions, both at rest and under flow, is a function of the particle and fluid properties, interparticle potential, and processing or flow history. Indeed, complex, nonlinear rheological phenomena, such as thixotropy and shear thickening, are associated with significant changes in microstructure during flow and processing. A modern understanding of colloidal suspension rheology thus necessitates measurement of colloidal suspension microstructure under flow as well as at rest. Two popular classes of experimental methods for microstructure measurement are introduced and explained, namely confocal microscopy and scattering of light, neutrons, and x-rays.
The chapter begins by defining mixing and then discusses how ocean mixing is studied by a combination of direct observations, process studies, and studies integrated with modeling. The role of mixing in the meridional overturning circulation is examined in detail, including current suggestions termed ‘upside-down’ mixing. The chapter concludes with energy and scalar budgets that determine average mixing levels throughout the ocean.
The stratified ocean mixes episodically in small patches where energy is dissipated and density smoothed over scales of centimeters. The net effect of these countless events effects the shape of the ocean's thermocline, how heat is transported from the sea surface to the interior, and how dense bottom water is lifted into the global overturning circulation. This book explores the primary factors affecting mixing, beginning with the thermodynamics of seawater, how they vary in the ocean and how they depend on the physical properties of seawater. Turbulence and double diffusion are then discussed, which determines how mixing evolves and the different impacts it has on velocity, temperature, and salinity. It reviews insights from both laboratory studies and numerical modelling, emphasising the assumptions and limitations of these methods. This is an excellent reference for researchers and graduate students working to advance our understanding of mixing, including oceanographers, atmospheric scientists and limnologists.
This article presents a review on recent advances in the fatigue behavior of Ti alloys, especially the main commercial compositions for orthopedic applications. In the case of well-known Ti–6Al–4V alloy, the major concern is related to the effect of the surface modification necessary to improve the osseointegration. The introduction of surface discontinuities due to the growth of a porous oxide layer, or the roughness development, may severely affect the fatigue performance depending on the level of alteration. In the case of additive manufactured Ti–6Al–4V, the fatigue response is also influenced by inherent defects of as-built parts. Regarding the recently developed metastable β alloys, information about the fatigue properties is still scarce and mainly related to the effect of second phase precipitates, which are introduced to optimize the mechanical properties. The fatigue behavior of the Ti alloys is complex, as is their microstructure, and should not be neglected when the alloys are being developed or improved to be applied in medical devices.