Ecological, health and environmental concerns are driving the need for bio-resourced foams for the building industry and for other applications. This is because insulation is one of the most important aspects of the building envelope. Global building insulation is expected to reach USD 27.74 billion in 2022. Conventional insulation materials currently used in buildings are made from nonrenewable products (petroleum, fiber glass). However, they yield increasing unrecyclable eco-unfriendly waste at the end of their lives; styrene and polyurethane generates over 100,000 kg of waste insulation in US alone yearly. This is because they are non-biodegradable and can remain as microplastics in the environment for 1000 years. Polyurethane contains the same amount of energy as coal. Additionally, most of the processing techniques and blowing agents used in this manufacturing of these foams are cancerous and injurious to health when inhaled. Because buildings and their construction together account for 36% of global energy use and 39% of energy-related carbon dioxide emissions annually, there is a need to develop eco-friendly foams that will serve as possible substitutes to the currently used petroleum-based foams. This dissertation examined the development and characterization of eco-friendly foams that were developed using the melt mixing technique of bio-resourced …

This dissertation focuses on studying membrane air dehumidification for a membrane moisture exchanger in a membrane heat pump system. The study has two parts: an optimization of membrane moisture exchanger for air dehumidification in the macroscale, and diffusion of water vapor in polymer nanocomposites membrane for humid air dehumidification in the nanoscale. In the first part of the research, the mass transport of water vapor molecules through hydrophilic silica nanochannel chains in hydrophobic polyurethane matrix was studied by simulations and experiments for different membrane moisture exchanger design configurations. The mass transport across the polymer nanocomposite membrane occurs with the diffusion of moist air water vapor molecules in the membrane moisture exchanger in a membrane heat pump air conditioning system for air dehumidification purposes. The hydrophobic polyurethane matrix containing the hydrophilic silica nanochannel chains membrane is responsible for transporting water vapor molecules from the feed side to the permeate side of the membrane without allowing air molecules to pass through.In the second part of the research, diffusion analysis of the polymer nanocomposite membrane were performed in the nanoscale for the polymer nanocomposite membrane. The diffusion phenomena through the polymer, the polymer nanocomposite without modifying the silica surfaces, and the polymer nanocomposite …

Immersed boundary (IB) methods are attractive due to their ability to simulate flow over complex geometries on a simple Cartesian mesh. Unlike conformal grid formulation, the mesh does not need to conform to the shape and orientation of the boundary. This eliminates the need for complex mesh and/or re-meshing in simulations with moving/morphing boundaries, which can be cumbersome and computationally expensive. However, the imposition of boundary conditions in IB methods is not straightforward and numerous modifications and refinements have been proposed and a number of variants of this approach now exist. In a nutshell, IB methods in the literature often suffer from numerical oscillations, implementation complexity, time-step restriction, burred interface, and lack of generality. This limits their ability to mimic conformal grid results and enforce Neumann boundary conditions. In addition, there is no generic IB capable of solving flow with multiple potentials, closely/loosely packed structures as well as IBs of infinitesimal thickness. This dissertation describes a novel 2$ ^{\text{nd}} $ order direct forcing immersed boundary method designed for simulation of two- and three-dimensional incompressible flow problems with complex immersed boundaries. In this formulation, each cell cut by the IB is reshaped to conform to the shape of the IB. IBs …

While ozone design values have decreased since 2000, the values measured in Denton Airport South (DEN), an exurban region in the northwest tip of the Dallas-Fort Worth (DFW) metroplex, remains above those measured in Dallas Hinton (DAL) and Fort Worth Northwest (FWNW), two extremely urbanized regions; in addition, all three sites remained in nonattainment of National Ambient Air Quality Standards (NAAQS) ozone despite reductions in measured NOx and CO concentrations. The region's inability to achieve ozone attainment is tied to its concentration of total non-methane organic compounds (TNMOC). The mean concentration of TNMOC measured at DAL, FWNW, and DEN between 2000 and 2018 were 67.4 ± 1.51 ppb-C, 89.31 ± 2.12 ppb-C, and 220.69 ± 10.36 ppb-C, respectively. Despite being the least urbanized site of the three, the TNMOC concentration measured at DEN was over twice as large as those measured at the other two sites. A factor-based source apportionment analysis using positive matrix factorization technique showed that natural gas was a major contributing source factor to the measured TNMOC concentrations at all three sites and the dominant source factor at DEN. Natural gas accounted for 32%, 40%, and 69% of the measured TNMOC concentration at DAL, FWNW, and DEN, …

Lignocellulose is the most abundant biopolymer on earth and offers excellent potential for sustainable manufacturing. Because lignocellulose is structurally complex and resistant to decomposition, innovative degradation strategies are necessary to unlock its value. In this dissertation, a green manufacturing process through enzyme-triggered self-cultured bacteria retting for lignocellulosic fiber was developed and investigated. The mechanism of the lignocellulosic fiber retting at a controlled degradation strategy was studied. This enzymatic degradation strategy utilizes a small amount of enzyme to trigger a large aggregation of specific bacteria to obtain clean fibers. Industrial hemp (Cannabis sativa L.) fiber was successfully retted with this strategy. The degradation of pectin was proved through an environmental scanning electron microscope and reducing sugar analysis. The bacterial successions were identified by 16S rRNA gene metagenomic sequencing. The results showed that Bacillaceae dominated the hemp retting conditions containing 1% pectinase, suggesting that pectinase can manipulate bacterial community succession by changing the nutrients available to bacteria through the degradation of pectin. This degradation strategy has 20-25% less environmental impact than the thermochemical degradation strategy, resulting in better fiber consistency and much shorter processing time (3-5 days) than the traditional water degradation strategy. The study on the degradation of lignin-rich lignocellulose also …

Additively manufactured (AM) 316L and 17-4PH stainless steel parts, concretely made by laser powder bed fusion (L-PBF), are characterized and micro-mechanical properties of those steels are analyzed. This study also explored and extended to proton irradiation and small-scale mechanical testing of those materials, to investigate how irradiation affects microstructural evolution and thus mechanical properties at the surface level, which could be detrimental in the long term in nuclear applications. In-depth anisotropy analysis of L-PBF 316L stainless steel parts with the variations of volumetric energy density, a combined study of nanoindentation with EBSD (electron backscatter diffraction) mapping is shown to be an alternative methodology for enriching qualification protocols. Each grain with a different crystallographic orientation was mapped successfully by proper indentation properties. <122> and <111> oriented grains displayed higher than average indentation modulus and hardness whereas, <001>, <101>, and <210> oriented grains were found to be weaker in terms of indentation properties. Based on an extensive nanoindentation study, L-PBF 17-4 PH stainless steels are found to be very sensitive to high load rates and irradiation further escalates that sensitivity, especially after a 0.25 s-1 strain rate. 3D porosity measurement via X-ray microscope ensures L-PBF stainless steel parts are of more than …

The research focuses on the synthesis and application of multifunctional lignocellulosic biomass bioadsorbent and nanobiocomposites for water purification. A bioadsorbent was prepared from kenaf fiber by self-activation without the use of any toxic chemicals in an innovative method. Silver nanoparticles were synthesized by the green route and then impregnated on the surface of kenaf-based activated carbon (KAC), and hemp fibers by heating and photoirradiation. The formation of hemp-based and kenaf-based silver nanocomposites was confirmed using an environmental scanning electron microscope and energy-dispersive x-ray spectroscopy. Low-cost benign nanoadsorbents demonstrated excellent capabilities for the anionic dye Congo red (CR) and cationic dye brilliant green (BG) degradation, inorganic heavy metals [Cu (II), Pb (II), and Cd (II)] adsorption and antibacterial activities. Antibacterial test via a modified disc diffusion method and minimum inhibitory concentrations was assessed towards the pathogenic strains of bacteria, E. coli and S. aureus. A working portable point-of-use filter was designed and developed, with the filter column encapsulated with nanobiocomposites for the removal of multi-metals and dye. Water samples collected from a wastewater treatment plant in Texas and a mining site in Mexico were used to determine the efficacy of the nanobiocomposites columned in the filter. A comparative analysis was also …

In this research work, an innovative method for measurement of thermal conductivity of a small volume of liquids, microsphere, and the single cancer cell is demonstrated using a micro-pipette thermal sensor (MPTS). The method is based on laser point heating thermometry (LPHT) and transient heat transfer. When a single pulse of a laser beam heats the sensor tip which is in contact with the surrounding liquids or microsphere/cells, the temperature change in the sensor is reliant on the thermal properties of the surrounding sample. We developed a model for numerical analysis of the temperature change using the finite element method (FEM) in COMSOL. Then we used MATLAB to fit the simulation result with experiment data by multi-parameter fitting technique to determine the thermal conductivity. To verify the accuracy in the measurement of the thermal conductivity by the MPTS method, a 10µl sample of de-ionized (DI) water, 50%, and 70% propylene glycol solution were measured with deviation less than 2% from reported data. Also, to demonstrate that the method can be employed to measure microparticles and a single spherical cell, we measured the thermal conductivity of poly-ethylene microspheres with a deviation of less than 1% from published data. We estimated the …

Recent advances in manufacturing and growing concerns on the sustainability of aviation environment have led to a remarkable interest in electrical unmanned aerial systems (UASs) in the past decade. Among various UAS types, the newly designed quadrotor biplane tailsitter class is capable of delivering a wide range of civilian and military tasks, relying on its Vertical Take-Off and Landing (VTOL) capability as well as great maneuverability. Nevertheless, as such UASs employ rotors to generate thrust, and wings to generate lift, and operate at less-understood low to mid-Reynolds flow regime, they experience complicated flight aerodynamics with a noise generation mechanism which is different from common aircrafts. The present work aims at addressing this knowledge gap by studying the aerodynamics and aeroacoustics of a UAS of this type designed by the Army Research Lab. High-fidelity computational fluid dynamics (CFD) simulations are carried out for a wide range of operating conditions to understand the physics involved in the UAS aerodynamics and characterize its performance. Relying on the CFD results, a physics-informed reduced order model (ROM) is developed based on machine learning algorithms, to predict the propellers effects on the wings and calculate the dominant loads. The results of this study indicate that the …

In order to better understand the changes occurring in the internal environment of the pyrolysis process a method of monitoring the internal environment in real time is the key objective of this study. To accomplish this objective four tasks were laid out in order to develop an effective way of monitoring the changes in gases present as pyrolysis is occurring as well as in material activation processing. For all processing the self-activation process was used which combines pyrolysis and thermal activation into a single step process. In the first task 10 hard wood species were activated and the resulting properties were compared to see the impact of wood species on the resulting carbon structures. In order to understand the impact of gas concentration on the resulting carbons the second task developed a gas sensor array which effectiveness was corroborated using GC-MS and then comparisons of the changes in the resulting were made. For the third task the gas sensor array was used to analyze the production of CO2 gas and a triple Gaussian model was developed to model the changes in gas production throughout processing. H2 gas production was modeled in the fourth task using the same Gaussian model as …

Motivated by previous relevant research on phononics including both active and passive phononics, the interest of faster turnability and more functions of the active phononics of further study led to this proposing research topic: magnetic field tunable active functional phononics. The first design of magnetic field tunable reciprocal--non-reciprocal transmission acoustic device was established, material was characterized, and numerical simulation has been performed. The simulation results show clear T-symmetric breaking non-reciprocity due to energy level splitting effect with Doppler effect – an acoustic Zeeman effect. Inspired by this preliminary work, further experiments were planned to demonstrate this effective Zeeman effect in phononics and effectively charged phonons in water based ferro-fluid. The objectives of this work as the next series of tasks were to illustrate acoustic Zeeman effect and acoustic Landau levels in various strength of magnetic field to investigate a design non-reciprocal sound device with magnetic field switching, which could be controlled on the amount of non-reciprocity with the strength of magnetic field. Once this new field first discovered by the proposed study tasks, more active tunable magnetic field phononics devices could be designed and exemplified in terms of both simulations and experiments. Faster and more controllable active phononic devices could …

A flexible nanofibrous PVDF-BaTiO3 composite material is prepared for impact sensing and biomechanical energy harvesting applications. Dielectric polyvinylidene fluoride (PVDF) and barium titanate (BaTiO3)-PVDF nanofibrous composites were made using the electrospinning process based on a design of experiments approach. The ultrasonication process was optimized using a 2k factorial DoE approach to disperse BaTiO3 particles in PVDF solution in DMF. Scanning electron microscopy was used to characterize the microstructure of the fabricated mesh. The FT-IR and Raman analysis were carried out to investigate the crystal structure of the prepared mesh. Surface morphology contribution to the adhesive property of the composite was explained through contact angle measurements. The capacitance of the prepared PVDF- BaTiO3 nanofibrous mesh was a more than 40% increase over the pure PVDF nanofibers. A comparative study of dielectric relaxation, thermodynamics properties and impact analysis of electrospun polyvinylidene fluoride (PVDF) and 3% BaTiO3-PVDF nanofibrous composite are presented. The frequency dependent dielectric properties revealed micro structural features of the composite material. The dielectric relaxation behavior is further supported by complex impedance analysis and Nyquist plots. The temperature dependence of electric modulus shows Arrhenius type behavior. The observed non-Debye dielectric relaxation in electric loss modulus follows a thermally activated process which …

Pillared-graphene structure (PGS) is a novel three-dimensional structure consists of parallel graphene sheets that are separated by carbon nanotube (CNT) pillars that is proposed for efficient thermal management of electronics. For microscale simulations, finite element analyses were carried out by imposing a heat flux on several PGS configurations using a Gaussian pulse. The temperature gradient and distribution in the structures was evaluated to determine the optimum design for heat transfer. The microscale simulations also included conducting a mesh-independent study to determine the optimal mesh element size and shape. For nanoscale simulations, Scienomics MAPS software (Materials And Processes Simulator) along with LAMMPS (Large-scale Atomic/ Molecular Massively Parallel Simulator) were used to calculate the thermal conductivity of different configurations and sizes of PGS. The first part of this research included investigating PGS when purely made of carbon atoms using non-equilibrium molecular dynamics (NEMD). The second part included investigating the structure when supported by a copper foil (or substrate); mimicking production of PGS on copper. The micro- and nano-scale simulations show that PGS has a great potential to manage heat in micro and nanoelectronics. The fact that PGS is highly tunable makes it a great candidate for thermal management applications. The simulations were …

In this research thermal properties enhancement of phase change material (PCM) using boron nitride nanomaterials such as nanoparticles and nanotubes is studied through experimental measurements, finite element method (FEM) through COMSOL 5.3 package and molecular dynamics simulations via equilibrium molecular dynamics simulation (EMD) with the Materials and Process Simulations (MAPS 4.3). This study includes two sections: thermal properties enhancement of inorganic salt hydrate (CaCl2∙6H2O) as the phase change material by mixing boron nitride nanoparticles (BNNPs), and thermal properties enhancement of organic phase change material (paraffin wax) as the phase change material via encapsulation into boron nitride nanotubes (BNNTs). The results of the proposed research will contribute to enhance the thermal transport properties of inorganic and organic phase change material applying nanotechnology for increasing energy efficiency of systems including electronic devices, vehicles in cold areas to overcome the cold start problem, thermal interface materials for efficient heat conduction and spacecraft in planetary missions for efficient thermal managements.

The recipes of optical radiative properties manipulation are their materials chemistry, nano/microscale geometry, and transport properties of quasiparticle carriers such as photons, phonons, and electrons. The important technical element in optical properties is the dielectric function of materials, which is different for metals, dielectrics, 2D materials, and phase transition materials. Graphene has a unique electrical conductivity profile which have metallic nature depending on the frequency, but also has a negative thermal expansion coefficient that makes graphene unique. Hence, graphene creates wrinkles when deposited on the substrate as temperature decreases to room temperature from high substrate temperature. We also study phase transition material, particularly vanadium dioxide that transitions from insulating to metallic phase based on temperature change; we investigate its role in far-field thermal radiation. Other transition metal oxides are studied as a thermally and electrically tunable plasmonic gratings: Transition metal oxides include vanadium dioxide, tungsten trioxide, and molybdenum trioxide. The work demonstrates plasmonic phenomena and absorptance/emittance tunability. First, surface plasmon polariton along the graphene (SPPG) when wrinkles are formed above the plasmonic grating is studied. The resonance peak shift is modeled for both magnetic polariton (MP) with inductor-capacitor (LC) circuit and SPPG with Fabry-Perot phase change model. Second, the self-adaptive …