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Full-Text Articles in Engineering
Aqueous Fabrication Of Pristine And Oxide Coated Znse Nanoparticles, Nicholas L. Van Zandt
Aqueous Fabrication Of Pristine And Oxide Coated Znse Nanoparticles, Nicholas L. Van Zandt
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Semiconducting nanoparticles have received significant attention due to their unique optoelectronic properties. Quantum dots (QDs), a class of spherical nanoparticles, possess a size-dependent bandgap and photoluminescence at visible wavelengths. QDs have many applications including biological labelling, solar cells, chemical impurity detection, and optical glasses. Doping QDs into optical glasses is highly desirable. High-quality QDs can be synthesized via liquid solution methods. However, solution-synthesized QDs often degrade over time and they cannot survive incorporation into a glass melt without protection. In this work, the aqueous synthesis of ZnSe QDs and coating with nanometer silica and alumina protective shells are investigated. The …
Phase Transformation In The Aluminum/Tungsten System, Ammar Azeez Mahdi Al Yasari
Phase Transformation In The Aluminum/Tungsten System, Ammar Azeez Mahdi Al Yasari
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Formation and growth mechanisms of intermetallic compounds in the aluminum/tungsten system were studied during consolidation and subsequent heat treatment. Three different processes, spark plasma sintering (SPS), laser powder bed fusion (LPBF), and metal inert gas welding (MIG) were used, and each of these processes were followed up with heat treatment at different conditions. Al12W, Al5W and Al4W are the three intermetallics that are stable in the system in room temperature, and they were expected to form at the interface between tungsten and aluminum at different temperature ranges. Contrary to expectations, the Al5W phase was not observed during this study and …
Fabrication And Analysis Of High-Performance Thermochemically Densified Wood, Victor Arulappan Pushparaj
Fabrication And Analysis Of High-Performance Thermochemically Densified Wood, Victor Arulappan Pushparaj
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While wood construction may be as ancient as humanity itself, wood remains one of the most utilized structural materials because of it’s availability, low cost, durability, surprisingly high specific mechanical properties, and renewability. Recent research into wood-based materials has focused on strategies for enhancing the strength and stiffness of as-grown materials. We fabricated densified wood by thermochemically treating raw white oak wood in Na2SO3 and NaOH solutions, followed by compressing the treated wood at 5MPa at high temperature. Treating the raw wood in NaOH and Na2SO3 cleaves the alpha-O-4 ether bond and beta-O-4 ether bonds, thus dissolving most of the …
Functionalizing Ceramic Matrix Composites By The Integration Of A Metallic Substructure With Comparable Feature Size, Elizabeth Pierce Heckman
Functionalizing Ceramic Matrix Composites By The Integration Of A Metallic Substructure With Comparable Feature Size, Elizabeth Pierce Heckman
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A metallic network has been embedded in a silicon carbide fiber– silicon carbide (SiC) matrix ceramic composite (CMC) in order to combine the functional properties of the metal and the structural properties of the CMC. The processing of the composite involves iterative pre-ceramic polymer infiltration and heating to temperatures at 1100°C. The metallic structure embedded in the CMC must retain its unique properties during processing and cannot convert to a silicide or carbide resulting from diffusion of Si and C species from the SiC matrix. To gain an understanding of the diffusion process, a fully processed CMC with tungsten, tantalum, …
Texture-Driven Image Clustering In Laser Powder Bed Fusion, Alexander H. Groeger
Texture-Driven Image Clustering In Laser Powder Bed Fusion, Alexander H. Groeger
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The additive manufacturing (AM) field is striving to identify anomalies in laser powder bed fusion (LPBF) using multi-sensor in-process monitoring paired with machine learning (ML). In-process monitoring can reveal the presence of anomalies but creating a ML classifier requires labeled data. The present work approaches this problem by printing hundreds of Inconel-718 coupons with different processing parameters to capture a wide range of process monitoring imagery with multiple sensor types. Afterwards, the process monitoring images are encoded into feature vectors and clustered to isolate groups in each sensor modality. Four texture representations were learned by training two convolutional neural network …
Texture Evolution In Materials With Layered Crystal Structures, Vamsi Krishna Vempati
Texture Evolution In Materials With Layered Crystal Structures, Vamsi Krishna Vempati
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Materials with a layered structure consist of crystalline layers that are bonded to each other with secondary bonds (van der Waals interactions). The bonding between crystalline layers is relatively weak compared to the interatomic bonding within the crystalline layers. This research hypothesizes that under appropriate conditions, such as elevated temperature, the deformation of layered materials occurs like the classic “deck of cards” with no preferred direction of slip on the slip planes. The motivation for this study is from the experimental texture evolution of one such material, Bismuth Telluride ,(Bi2Te3), commonly used materials for thermoelectric applications in the range of …
Influence Of Build Direction On Interface Regions In Additive Manufacturing Of Multi-Material Refractory Alloys, Cherish Christina Clark Lesko
Influence Of Build Direction On Interface Regions In Additive Manufacturing Of Multi-Material Refractory Alloys, Cherish Christina Clark Lesko
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In the pursuit of optimum performance, materials engineering seeks to design the microstructure and thus the properties of a material through the control of the material composition and processing. Functionally graded materials (FGM) are designed to incorporate location-specific material properties through compositional changes within the part. Moving toward location-specific design of material properties requires the ability to produce material gradients in three dimensions which can be accomplished through the use of additive manufacturing (AM). This research examines the composition-process-structure-property relationship of early iteration titanium (Ti) and tantalum (Ta) graded alloys built in a novel laser powder bed fusion (LPBF) process …
Ab Initio Methylammonium Orientation And Monolayer Effects In Hybrid Perovskite Solar Cells, Jacob M. Artz
Ab Initio Methylammonium Orientation And Monolayer Effects In Hybrid Perovskite Solar Cells, Jacob M. Artz
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Methylammonium lead triiodide (MAPbI3) has garnered attention due to their high solar cell efficiencies and low cost to manufacture, but commercialization is not yet possible owing to poor environmental stability. Thus, researchers seek ways which optimize the performance of the MAPbI3 solar cell by modifying the architecture and through interfacial engineering of the charge transport layers. Difficulties in understanding these devices arise from ion migration, charge separation and recombination, and metastable, thermally active precessions of the methylammonium (MA) moiety in the lead iodide framework. In this work, focus is given to the perovskite and an adsorbed monolayer, 2,3,4,5,6-pentafluorothiophenol (C6F5SH), which …
Texture-Driven Image Clustering In Laser Powder Bed Fusion, Alexander H. Groeger
Texture-Driven Image Clustering In Laser Powder Bed Fusion, Alexander H. Groeger
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The additive manufacturing (AM) field is striving to identify anomalies in laser powder bed fusion (LPBF) using multi-sensor in-process monitoring paired with machine learning (ML). In-process monitoring can reveal the presence of anomalies but creating a ML classifier requires labeled data. The present work approaches this problem by printing hundreds of Inconel-718 coupons with different processing parameters to capture a wide range of process monitoring imagery with multiple sensor types. Afterwards, the process monitoring images are encoded into feature vectors and clustered to isolate groups in each sensor modality. Four texture representations were learned by training two convolutional neural network …
Ab Initio Methylammonium Orientation And Monolayer Effects In Hybrid Perovskite Solar Cells, Jacob M. Artz
Ab Initio Methylammonium Orientation And Monolayer Effects In Hybrid Perovskite Solar Cells, Jacob M. Artz
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Methylammonium lead triiodide (MAPbI3) has garnered attention due to their high solar cell efficiencies and low cost to manufacture, but commercialization is not yet possible owing to poor environmental stability. Thus, researchers seek ways which optimize the performance of the MAPbI3 solar cell by modifying the architecture and through interfacial engineering of the charge transport layers. Difficulties in understanding these devices arise from ion migration, charge separation and recombination, and metastable, thermally active precessions of the methylammonium (MA) moiety in the lead iodide framework. In this work, focus is given to the perovskite and an adsorbed monolayer, 2,3,4,5,6-pentafluorothiophenol (C6F5SH), which …
Influence Of Build Direction On Interface Regions In Additive Manufacturing Of Multi-Material Refractory Alloys, Cherish Christina Clark Lesko
Influence Of Build Direction On Interface Regions In Additive Manufacturing Of Multi-Material Refractory Alloys, Cherish Christina Clark Lesko
Browse all Theses and Dissertations
In the pursuit of optimum performance, materials engineering seeks to design the microstructure and thus the properties of a material through the control of the material composition and processing. Functionally graded materials (FGM) are designed to incorporate location-specific material properties through compositional changes within the part. Moving toward location-specific design of material properties requires the ability to produce material gradients in three dimensions which can be accomplished through the use of additive manufacturing (AM). This research examines the composition-process-structure-property relationship of early iteration titanium (Ti) and tantalum (Ta) graded alloys built in a novel laser powder bed fusion (LPBF) process …