A Comparison of Microstructure and Uniaxial Compressive Response of Ice-Templated Porous Alumina Scaffolds Fabricated from Two Different Particle Sizes

Development of bio-inspired highly porous (\u3e50 vol.%) cellular ceramics is crucial to meet the demand of high-performance lightweight and damage-tolerant materials for a number of cutting-edge applications including impact energy absorption, biomedical implants, and energy storage. A key design feature that is observed in many natural materials (e.g., nacre, bamboo, wood, etc.) is the presence of hierarchical microstructure that results in an excellent synergy of various material properties, which are otherwise considered as mutually exclusive in current paradigm of materials design. To this end, development of multilayered, interconnected and anisotropic cellular ceramics could benefit the aforementioned applications. However, mimicking natural design principles to develop robust cellular materials is of paramount challenge because most of the available processing techniques are limited to the fabrication of simple materials microstructures. In contrast, freeze casting is one emerging technique that has shown great promise to develop nature-inspired hierarchical cellular ceramics. While a large number of recent studies focused on the development of process-structure correlations of freeze-cast ceramics, understanding of the structure-property relationships has been extremely limited. Therefore, this thesis develops a custom-made unidirectional freeze casting device to investigate the effects of the variation of the particle size (0.3 μm vs. 0.9 μm) on the microstructure and uniaxial compressive response of ice-templated sintered alumina scaffolds as a function of solids loading and freezing front velocity (FFV). For comparable solids loading and FFV, particle size effects on the microstructure of the scaffolds are observed to be significant. Moreover, transition of the pore morphology with the increasing solids loading and FFV is observed to be more drastic for the scaffolds processed from the 0.9 μm particles compared to the 0.3 μm particles. Similarly, particle size variations also significantly influenced the relative density and porosity of the scaffolds. However, in spite of the observed differences of the microstructure, relative density and porosity, uniaxial compressive stress-strain measurements revealed marginal particle size effects on the compressive strength. The apparent marginal particle size effects on the compressive strength are rationalized based on the relative variation of the relative density, pore aspect ratio, and interlamellae bridge density in between the sintered alumina scaffolds processed from 0.3 μm and 0.9 μm particle sizes. This study also suggests that particle size variation within a range of submicrometer to few micrometers (typical particle size range used in ceramic processing) can be uniquely employed to systematically modify the microstructure of the ice-templated sintered ceramic scaffolds, without significantly altering their uniaxial compressive response; which can be useful to optimize the structure-property relationships of the ice-templated scaffolds for the structural, biomedical and functional applications

Microscale experiments in chemistry - the need of the new millenium 2. Experiments which bring theory closer to laboratories

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Comparitive Study of Plain Foundations with Shell Foundations

The spread footing for columns transmitting heavy load to weak Soils tends to be massive, if rafts are provided. Shell foundation can serve as better replacement to plain foundation as economic alternative where heavy super structural loads are to be transmitted to weaker soils. The substitution of shell foundations for spread footings and rafts can therefore lead to considerable saving in concrete and reinforcing steel.The sector of spherical dome, in inverted positions can serve as rafts for structures such as water tanks

Microscale experiments in chemistry - the need of the new millenium 5. Organic qualitative analysis and mixture separation on microscale

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Facile method for trimethylsilylation of alcohols using hexamethyldisilazane and ammonium thiocyanate under neutral conditions

A highly efficient method for trimethylsilylation of primary, secondary, tertiary, allylic, and a variety of sugar-derived alcohols using hexamethyldisilazane in the presence of a catalytic amount of ammonium thiocyanate under neutral conditions is reported

Microscale experiments in chemistry-the need of the new millennium. Part 1. Newer ways of teaching laboratory courses with new apparatus

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Password based Doorlock Security System using 8051

Many times we forgot to carry the key of our home. Or sometimes we come out of our home and door latch closes by mistake. In these cases it is really difficult to get inside the house. This project is designed to solve this purpose. Main concept behind this project is of a door-latch opening using a password entered through keypad. As well as turning on the Buzzer when password is entered wrong for multiple times. User can change this password anytime he/she wish using a keypad