Theses and dissertations

This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students. 

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Granule Formation, Structure and Content Uniformity from Single Drop Impact on Heterogeneous Powder Beds

Description
Single drop impact of liquid on a static powder bed was studied to investigate the granule formation mechanism, droplet penetration time, the characterization of granules (morphology, surface structure and internal structure), as well as the formation regime map. Water was used as the liquid and two pharmaceutical powders, microcrystalline cellulose…

Single drop impact of liquid on a static powder bed was studied to investigate the granule formation mechanism, droplet penetration time, the characterization of granules (morphology, surface structure and internal structure), as well as the formation regime map. Water was used as the liquid and two pharmaceutical powders, microcrystalline cellulose (MCC) and acetaminophen (APAP), were mixed to make heterogeneous powder beds. The complete drop impact and penetration was recorded by a high-speed camera. Two granule formation mechanisms identified previously occurred: Spreading and Tunneling. Spreading occurred for mixtures of large particle sizes, while Tunneling started to occur when the particle sizes of the mixtures decreased. With an increase of APAP concentration, the overall drop penetration time increased, which was in good agreement with previous literature. The granule morphology, surface structure, and internal structure were characterized by a prism method with image analysis, scanning electron microscope, and X-ray microtomography, respectively. The Spreading mechanism produced flat disks with porous internal structures, while the Tunneling mechanism produced round granules with dense internal structures. Granules that were formed via a hybrid of the mechanisms, Spreading/Tunneling, were hybrid granules, with some dense areas and some porous areas. The results of the granule content uniformity from UV-vis spectrometry revealed that with the increase of APAP proportion, the overall uniformity was compromised for mixtures with fine ingredients, while the content was much more uniform for coarse mixtures. It is believed that the mean particle size of the powder bed is the predominant factor in influencing the formation mechanism, drop penetration time, and granule properties, while the content uniformity is affected by both the particle sizes and the mixture hydrophobicity.
ContributorsGao, Tianxiang (Author) / Emady, Heather N (Thesis advisor) / Chawla, Nikhilesh (Committee member) / Jiao, Yang (Committee member) / Pradhan, Shankali (Committee member) / Oka, Sarang (Committee member) / Arizona State University (Publisher)
Created2020
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Effects of Particle and Environmental Variables on Rheology and Interaction of Granular Materials

Description
Granular materials demonstrate complexity in many physical attributes with various shapes and sizes, varying from several centimeters down to less than a few microns. Some materials are highly cohesive, while others are free-flowing. Despite such complexity in their physical properties, they are extremely important in industries dealing with bulk materials.…

Granular materials demonstrate complexity in many physical attributes with various shapes and sizes, varying from several centimeters down to less than a few microns. Some materials are highly cohesive, while others are free-flowing. Despite such complexity in their physical properties, they are extremely important in industries dealing with bulk materials. Through this research, the factors affecting flowability of particulate solids and their interaction with projectiles were explored. In Part I, a novel set of characterization tools to relate various granular material properties to their flow behavior in confined and unconfined environments was investigated. Through this work, a thorough characterization study to examine the effects of particle size, particle size distribution, and moisture on bulk powder flowability were proposed. Additionally, a mathematical model to predict the flow function coefficient (FFC) was developed, based on the surface mean diameter and moisture level, which can serve as a flowability descriptor. Part II of this research focuses on the impact dynamics of low velocity projectiles on granular media. Interaction of granular media with external foreign bodies occurs in everyday events like a human footprint on the beach. Several studies involving numerical and experimental methods have focused on the study of impact dynamics in both dry and wet granular media. However, most of the studies involving impact dynamics considered spherical projectiles under different conditions, while practical models should involve more complex, realistic shapes. Different impacting geometries with conserved density, volume, and velocity on a granular bed may experience contrasting drag forces upon penetration. This is due to the difference in the surface areas coming into contact with the granular media. In this study, a set of non-spherical geometries comprising cuboids, cylinders, hexagonal prisms and triangular prisms with constant density, volume, and impact velocities, were released onto a loosely packed, non-cohesive, dry granular bed. From these experimental results, a model to determine the penetration depth of projectiles upon impact was developed and how it is influenced by the release height and surface area of the projectiles in contact with the granular media was studied.
ContributorsVajrala, Spandana (Author) / Emady, Heather N (Thesis advisor) / Marvi, Hamidreza (Committee member) / Jiao, Yang (Committee member) / Arizona State University (Publisher)
Created2021