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Articles 1 - 13 of 13
Full-Text Articles in Mechanics of Materials
Novel Photothermal Materials And Thermally Engineered Membranes For Solar Desalination, Sisi Cao
Novel Photothermal Materials And Thermally Engineered Membranes For Solar Desalination, Sisi Cao
McKelvey School of Engineering Theses & Dissertations
Although 71% of earth surface is covered with water, more than 97% of it is saltwater, and freshwater is limited to only about 2.5%. The freshwater shortage has been exacerbated due to the environmental pollution, increased agriculture needs, socio-economic development, and population growth. Among various desalination technologies, membrane distillation has gained wide attention due to its ability to treat highly saline water utilizing waste heat from industrial processes. However, the implementation of conventional membrane distillation is hindered in the remote regions and disaster-struck communities where the low-grade thermal energy from industrial plants and electricity are not readily available. To address …
Metal Oxide Nanoparticles Synthesized By Nonthermal Plasma For Electrochemical Applications, Qinyi Chen
Metal Oxide Nanoparticles Synthesized By Nonthermal Plasma For Electrochemical Applications, Qinyi Chen
McKelvey School of Engineering Theses & Dissertations
Metal oxide nanocrystals can be synthesized by colloidal processing and gas-phase processing routes. High-quality nanocrystals produced by colloidal routes typically have surface ligands. Transport of electrons and ions among nanocrystals is hindered by surface ligand, and degrades related electrical performance. Gas-phase processing, for example combustion and thermal plasma, can make free-standing nanocrystals. However, nanocrystals produced by combustion method are heavily agglomerated, which further limits the usage of nanoparticles in electrochemical applications. Nonthermal plasma, as an emerging attractive route, has been initially focused on the synthesis of elemental group IV materials, and extended to include the synthesis of multicomponent materials, such …
Flexible Electronics For Neurological Electronic Skin With Multiple Sensing Modalities, Haochuan Wan
Flexible Electronics For Neurological Electronic Skin With Multiple Sensing Modalities, Haochuan Wan
McKelvey School of Engineering Theses & Dissertations
The evolution of electronic skin (E-skin) technology in the past decade has resulted in a great variety of flexible electronic devices that mimic the physical and chemical sensing properties of skin for applications in advanced robotics, prosthetics, and health monitoring technologies. The further advancement of E-skin technology demands closer imitation of skin receptors' transduction mechanisms, simultaneous detection of multiple information from different sources, and the study of transmission, processing and memory of the signals among the neurons. Motivated by such demands, this thesis focuses on design, fabrication, characterization of novel flexible electronic devices and integration of individual devices to realize …
Nucleation Studies In Barium Silicate Glasses And Soda-Lime Silicate Glass, Xinsheng Xia
Nucleation Studies In Barium Silicate Glasses And Soda-Lime Silicate Glass, Xinsheng Xia
McKelvey School of Engineering Theses & Dissertations
Controlling nucleation is key for the manufacture of glasses and glass-ceramics. It has been observed by different researchers in many silicate glasses that at low temperatures the critical work of cluster formation (i.e. the nucleation barrier) slowly rises rather than decreasing with decreasing temperature. However, this experimental observation is in contradiction with nucleation theories. In this dissertation, crystal nucleation was studied in BaO·2SiO2, 5BaO·8SiO2, and Na2O·2CaO·3SiO2 glasses. The main research topics include measurements of the nucleation rate, the structural evolution of the glass, and the low-temperature nucleation behavior. A special focus is given to the low-temperature nucleation anomaly. In total, …
Computational Design Of Two-Dimensional Transition Metal Dichalcogenide Alloys And Their Applications, John Douglas Cavin
Computational Design Of Two-Dimensional Transition Metal Dichalcogenide Alloys And Their Applications, John Douglas Cavin
Arts & Sciences Electronic Theses and Dissertations
The discovery of bronze as an alloy of copper and tin is arguably the earliest form of material design, dating back thousands of years. In contrast, two-dimensional materials are new to the 21st century. The research presented in this dissertation is at the intersection of alloying and two-dimensional materials. I specifically study a class of two-dimensional materials known as transition metal dichalcogenides (TMDCs). Because of the large number of transition metals, there are many combinations of TMDCs that can be alloyed, making experimental exploration of the phase space of possible alloys unwieldly. Instead, I have applied first-principles methods to study …
Converting Inorganic Rust To Organic Nanostructured Conducting Polymers: Synthesis And Applications, Yifan Diao
Converting Inorganic Rust To Organic Nanostructured Conducting Polymers: Synthesis And Applications, Yifan Diao
McKelvey School of Engineering Theses & Dissertations
Iron rust is a type of corrosion product, coming from the chemical reaction between iron and oxygen in the presence of water that first documented ca. 800 BCE. It is a heterogeneous inorganic solid-state material composed of multiple phases and is ubiquitous throughout the universe. Rust species such as Hematite (α-Fe2O3), Akaganeite (β-FeOOH), and ferrous hydroxide (Fe(OH)2), make up the solid-state chemical family composed of iron oxides, oxyhydroxides, and hydroxides that are typically recognized as chemical waste. Conducting polymer is a type of organic plastic composed of long chains with repeating subunits that bonding with strong interactions between neighboring molecules. …
Aerosol Vapor Synthesis Of Organic Processable Pedot Particles And Measuring Electric Conductivity Using A 3d Printed Probe Station, Yang Lu
McKelvey School of Engineering Theses & Dissertations
Conducting polymers are organic semiconductors characterized by conjugated backbones (alternating single-double bonds) that enable mixed ionic-electronic conductivity. Their polymeric nature, tunable band structure and reversible redox capability have demonstrated fundamental advances in the fields ranging from electrochemical energy storage, sensing, to electro/photo catalysis and neuromorphic engineering. Conjugated backbones, the origin of all the unique physical and chemical properties associated with conducting polymers, prevent their solubility due to high lattice energy which hinders processing. Current solution utilizes a long-chain polymer (PSS) as dopants to render conducting polymer water dispersible (PEDOT:PSS). Nonetheless, PSS is highly acidic and hydrophilic limiting applicability with acid-incompatible …
Plasmonically-Enhanced Ultrasensitive Biodetection Technologies, Zheyu Wang
Plasmonically-Enhanced Ultrasensitive Biodetection Technologies, Zheyu Wang
McKelvey School of Engineering Theses & Dissertations
Detection and quantification of biomolecules within biological fluids and tissues is of fundamental importance to biomedical research and clinical diagnostics. It is impossible to fully characterize complex, non-linear, biochemical systems without being able to accurately and quantitatively determine the component molecules. This problem is ubiquitous across all domains of biomedical research, and it is a major barrier to fully understanding health, ageing, and disease. Such bottlenecks are extremely challenging to be solved, especially for proteins and peptides, which do not have amplification schemes such as polymerase chain reaction for nucleic acids, because relevant concentrations of molecules related to diseases such …
Metal Salt Hydrolysis For Electrochemically Active Conducting Polymer Nanocomposites, Hongmin Wang
Metal Salt Hydrolysis For Electrochemically Active Conducting Polymer Nanocomposites, Hongmin Wang
Arts & Sciences Electronic Theses and Dissertations
The diversity of nanostructures obtained from organic polymerization is limited when compared to the vast amount of inorganic nanostructures. This dissertation will focus on a synergistic mechanism between organic polymerization and in situ inorganic salt hydrolysis for developing electrochemically active organic-inorganic hybrid nanostructures. The degree of polymerization, crystallinity and doping level of the conjugated polymer backbone is controlled using oxidative radical vapor-phase polymerization resulting in organic semiconductors featuring high crystallinity and superior electrical conductivity. An aqueous metal salt solution of iron (III) chloride serves as an oxidant for initiating the polymerization and interestingly, this inorganic salt hydrolyzes in situ producing …
Surface Modification Of Ii-Vi Semiconducting Nanocrystals, Calynn Morrison
Surface Modification Of Ii-Vi Semiconducting Nanocrystals, Calynn Morrison
Arts & Sciences Electronic Theses and Dissertations
This dissertation presents the compositional analysis of semiconductor materials by inductively coupled plasma optical emission spectroscopy (ICP-OES), a novel low-temperature shell growth precursor and installation pathway, and L-type for Z-type ligand exchange experiments conducted with four metal dithiocarbamate ligands. The techniques employed in the compositional analysis of semiconductor materials by inductively coupled plasma optical emission spectroscopy (ICP-OES) have a profound influence on the accuracy and reproducibility of the results. In Chapter 3, we describe methods for sample preparation, calibration, standard selection, and data collection. Specific protocols are suggested for the analysis of II-VI compounds and nanocrystals containing the elements Zn, …
Nanoscale Enhancement Of Photosensitized Radionuclide Stimulated Therapy, Daniel Douglas Lane
Nanoscale Enhancement Of Photosensitized Radionuclide Stimulated Therapy, Daniel Douglas Lane
McKelvey School of Engineering Theses & Dissertations
Photodynamic therapy (PDT) provides efficient tumor killing through the generation of reactive oxygen species (ROS) from the optical excitation of a photosensitizer (PS). Furthermore, this mechanism is highly immune stimulating, providing systemic tumor immunity with a reduction in metastasis. However, these materials had previously been limited by their dependence upon external light sources, allowing treatment of only laser-accessible malignancy. With the recent development of photosensitized radiation stimulated therapy (PRaST) this depth dependence is broken through co-localization of radionuclides and semiconducting photosensitizers. This dissertation focuses on the enhancement of titanium dioxide (TiO2) based PRaST agents through understanding of TiO2 material parameters …
Mechanical Strength Of Germanium Doped Low Oxygen Concentration Czochralski Silicon And The Effect Of Oxygen On Nitrogen Dissociation In Silicon, Junnan Wu
McKelvey School of Engineering Theses & Dissertations
During the Czochralski growth of silicon, it is inevitable for oxygen to be incorporated into the silicon crystal from the quartz crucible. Interstitial oxygen improves the mechanical strength of silicon by pinning and locking dislocations, but also generates thermal donors during device processes, shifting the electrical resistivity. For silicon wafers used in radio frequency (RF) applications, it is important to ensure the high resistivity of the substrates for good RF characteristics. Therefore, the oxygen level in these high resistivity silicon wafers is kept very low (< 2.5 × 1017 atoms/cm3) by carefully controlling the Czochralski growth conditions, in order to reduce the thermal donor concentration to an acceptable level. Silicon on insulator (SOI) substrates made from high resistivity wafers have been widely used for RF applications. SOI manufacturing includes multiple high temperature thermal cycles (1000 – 1100 °C), during which the high resistivity wafers are prone to slip and warpage. Therefore, it is technologically important to recover some of the lost mechanical strength due to the lack of oxygen by introducing electrically inactive impurities to suppress the dislocation generation and mobility in silicon. Germanium (Ge) as an isovalent impurity is 4% larger in size and forms a solid solution with silicon in the entire concentration range. Previous works have shown Ge doping at high concentrations above 6 × 1019 atoms/cm3 increased mechanical strength of silicon with high oxygen concentration (~ 1 × 1018 atoms/cm3). In this work, we explore the effect of Ge doping (7 - 9 × 1019 atoms/cm3) on the mechanical strength of low oxygen concentration (< 2 × 1017 atoms/cm3) silicon, where the oxygen associated dislocation locking and pinning are very low. A mechanical bending test was used to study the average dislocation migration velocity and the critical shear stress of dislocations motion at 600 – 750 °C for Ge doped, nitrogen doped, and undoped low oxygen samples, as well as nitrogen doped float-zone and un-doped high oxygen concentration samples. Next, we fabricated SOI substrates using these high resistivity wafers and compared their slip generation rates and the slip-free epitaxial grow temperature windows after the high temperature thermal cycles (> 1000 °C). Our results indicate at lower temperature Ge doesn’t affect the dislocation mobility …
Multifunctional Polydopamine Nanomaterials For Biomedical And Environmental Applications, Hamed Gholami Derami
Multifunctional Polydopamine Nanomaterials For Biomedical And Environmental Applications, Hamed Gholami Derami
McKelvey School of Engineering Theses & Dissertations
Polydopamine (PDA), a synthetic and organic material, has emerged as a promising materialplatform for various applications in energy, environmental, and biomedical fields. PDA, formed by self-polymerization of dopamine, is rich in catechol and amine groups, which facilitate covalent conjugation and/or other non-covalent interactions with organic and inorganic materials. It is highly biocompatible, biodegradable, has broadband light absorption spectrum and excellent light-to-heat conversion efficiency. Also, it is easy to synthesize and functionalize. The combination of excellent characteristics of polydopamine-based nanomaterials, make them a promising adsorbent agent for environmental wastewater treatment and photothermal agent for biomedical applications. In the first half of …