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Complex Microstructures (complex + microstructure)
Selected AbstractsQuasi-two-dimensional electrodeposition growth of Pb0.5Sn0.5 alloyCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2006Bin Sun Abstract Electrodeposition of Pb0.5Sn0.5 alloy is carried out in a quasi-2D electrochemical cell. As the growth proceeds the morphologies of the deposits transit from cake-like to branched and finally to the compact morphology. We show that these morphological transitions arise from the changes in the transport mechanisms of the ions in the electrolyte cell. In addition, it is found that the current density on the growth interface can vary spontaneously due to the irregular shape of the deposit and the generation of hydrogen gas. It causes the formation of the complex microstructure with non-uniform composition. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Advanced Homogenization Strategies in Material Modeling of Thermally Sprayed TBCs,ADVANCED ENGINEERING MATERIALS, Issue 7 2006K. Bobzin Thermal barrier coatings (TBC), obtained by atmospheric plasma spraying (APS), have a complex microstructure (lamellar, porous, micro-cracked). Process parameters take an influence on this microstructure. Two methods based on the homogenization for periodic structures are presented in this article. The methods are used to calculate the effective material behavior of APS-TBCs made of partially yttria stabilized zirconia (PYSZ) depending on the microstructure. [source] Micromorphology of Cotiga Mound, West VirginiaGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 6 2005D.L. Cremeens Micromorphology samples from Cotiga Mound (ca. 2100 yr B.P.) reveal distinct microstructures associated with mound construction and post-construction pedogenesis of the mound materials. The interface between layers of basketloads displays sharp, irregular contacts with little to no evidence of pedoturbation, suggesting rapid construction. Evidence of clay and iron translocation, along with well-preserved charcoal fragments containing identifiable cell structure, were observed in samples collected from hearth features. Both the prepared surface and associated central burial feature at the base of the mound have a complex microstructure, characterized by charcoal layers and zones of clay accumulation, along with microstratification in the prepared surface. Clay translocation, formation of a complex void network, and ironmanganese accumulation were the dominant pedogenic processes that modified the completed mound. © 2005 Wiley Periodicals, Inc. [source] Elastomeric Molds with Tunable Microtopography,ADVANCED MATERIALS, Issue 23-24 2004M. Hoffman Elastomeric "microtunable" molds (,TMs) whose microtopography can be tuned post-fabrication at certain pre-defined locations have been devised. Their features make them very attractive for the molding of complex microstructures. The Figure shows a scanning electron microscopy image of poly(dimethylsiloxane) double- replicas of a ,TM whose membrane contains a 1.18,mm spiral. [source] Modeling solvent evaporation during the manufacture of controlled drug-release coatings and the impact on release kinetics,,JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Chang-Soo Kim Abstract To improve functionality and performance, controlled drug-release coatings comprised of drug and polymer are integrated with traditional medical devices, e.g., drug eluting stents. Depending on manufacturing conditions, these coatings can exhibit complex microstructures. Previously, a thermodynamically consistent model was developed for microstructure evolution in these systems to establish relationships between process variables, microstructure, and the subsequent release kinetics. Calculations based on the model were, in general, consistent with experimental findings. However, because of assumptions regarding the evaporation of solvent during fabrication, the model was unable to capture variations through the coating thickness that are observed experimentally. Here, a straightforward method is introduced to incorporate solvent evaporation explicitly into the model. Calculations are used to probe the impact of solvent evaporation rate and drug loading on the microstructure that forms during manufacturing and subsequent drug release kinetics. The predicted structures and release kinetics are found to be consistent with experimental observations. Further, the calculations demonstrate that solvent evaporation rate can be as critical to device performance as the amount of drug within the coating. For example, changes of a factor of five in the amount of drug released were observed by modifying the rate of solvent evaporation during manufacturing. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Multi-Scale Study of Sintering: A ReviewJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2006Eugene A. Olevsky An integrated approach, combining the continuum theory of sintering with a kinetic Monte-Carlo (KMC) model-based mesostructure evolution simulation is reviewed. The effective sintering stress and the normalized bulk viscosity are derived from mesoscale simulations. A KMC model is presented to simulate microstructural evolution during sintering of complex microstructures taking into consideration grain growth, pore migration, and densification. The results of these simulations are used to generate sintering stress and normalized bulk viscosity for use in continuum level simulation of sintering. The advantage of these simulations is that they can be employed to generate more accurate constitutive parameters based on most general assumptions regarding mesostructure geometry and transport mechanisms of sintering. These constitutive parameters are used as input data for the continuum simulation of the sintering of powder bilayers. Two types of bilayered structures are considered: layers of the same particle material but with different initial porosity, and layers of two different materials. The simulation results are verified by comparing them with shrinkage and warping during the sintering of bilayer ZnO powder compacts. [source] Production of Long-Chain Branched Polyolefins with Two Single-Site Catalysts: Comparing CSTR and Semi-Batch PerformanceMACROMOLECULAR REACTION ENGINEERING, Issue 6 2008Saeid Mehdiabadi Abstract We developed a mathematical model to describe the solution polymerization of olefins with two single-site catalysts in a series of two CSTRs. The model was used to simulate processes where semi-crystalline macromonomers produced in the first reactor are incorporated as long chain branches onto amorphous (or lower crystallinity) chains in the second reactor (cross-products). The simulation results show that CSTRs are more efficient to make chains with high LCB density and high weight percent of cross-products. The model can also predict the polydispersity index, average chain lengths, and fractions of the different polymer populations, and help the polymer reactor engineer formulate new products with complex microstructures. [source] | ||||||||||