Chemical Engineering Commons^™

The Role Of Multi-Charged Responses: Construction And Application Of A Tandem Differential Mobility Analyzer (Tdma), Christopher Ray Oxford

McKelvey School of Engineering Graduate Student Theses & Dissertations

Atmospheric aerosols impact health outcomes, visibility, and the energy balance of the earth. The atmosphere contains a variety of compounds, and the volatility (phase change enthalpy and vapor pressure) of each compound determines its partitioning between the gas phase and the particle phase. The hygroscopicity (an aerosol’s affinity for water) of an atmospheric aerosol particle is determined by the many compounds present in the particle, and thus, the volatility impacts hygroscopicity. Changes in hygroscopicity alter the fraction of the aerosol deposited in the lungs and the fraction of the aerosol activated into cloud droplets. Thus, understanding the volatility and hygroscopicity …

Contemporary Problems In Aerosol Aggregation And Gelation, Pai Liu

McKelvey School of Engineering Graduate Student Theses & Dissertations

Aggregation of nanoparticles in aerosols is a fundamental phenomenon with important implications to diverse fields ranging from material synthesis to pollutant control. The past few decades have witnessed extensive research on investigating the structure and growth mechanism of aerosol aggregates with sizes spanning across several orders of magnitude. This dissertation focuses on some contemporary problems that remain unaddressed in this topical area. Aerosol aggregates in sub-micron regimes, which are formed via the irreversible collision and aggregation of solid nanoparticle monomers, are fractal-like in their morphology. A mathematical description of this seemingly random structure dates to the seminal works by Forest …

Anion Exchange And Bipolar Membranes For Electrochemical Energy Conversion And Storage, Zhongyang Wang

McKelvey School of Engineering Graduate Student Theses & Dissertations

Anion exchange and bipolar membrane fuel cells generate electrical energy directly from chemical fuels and have attracted considerable interests as alternate power sources for large market applications, such as transportation (hydrogen fuel cells) and unmanned vehicles (sodium borohydride fuel cells). Anion exchange membrane (AEM), generally composed of a polymer with covalently tethered ionic groups, is the central component of the fuel cell serving as the electrolyte, conducting hydroxide ions from cathode to anode, where fast ionic conduction is directly related to power output. However, AEMs currently used in fuel cells (H2 fuel cells and sodium borohydride fuel cells) exhibit ion …

Cfd Simulation Investigating The Effects Of Groove Geometry On Heat Transfer For Internally Grooved Tubes, Richard Zaven Saroukhanoff

UNLV Theses, Dissertations, Professional Papers, and Capstones

This numerical study investigates the thermal performance of internally grooved tubes used in heat exchangers. In order to enhance the performance of heat exchangers, turbulence promoters are inserted along the streamwise flow. The use of inserts, grooves, and augmentations along the axial length of the tube creates disturbances that improve the overall heat transfer due to enhanced fluid mixing and greater surface contact boundary walls. However, the implementation of tube wall augmentations creates an increase in pressure drop across the tube which must be compensated for with additional pumping power for the working fluid. Therefore, in order to analyze the …

Coulombic And Non-Coulombic Effects Of Single And Overlapping Electric Double Layers With Surface Charge Regulation, Raviteja Vangara

Chemical and Biological Engineering ETDs

The physical origin of charged interfaces involving electrolyte solutions is in the thermodynamic equilibrium between the surface reactive groups and certain dissolved ionic species in the bulk. This equilibrium is very strongly dependent on the precise local density of these species, also known as potential determining ions in the solution. The latter, however, is determined by the overall solution structure, which is dominated by the large number of solvent molecules relative to all solutes. Hence, the solvent contribution to the molecular structure is a crucial factor that determines the properties of electric double layers. Models that explicitly account for the …

Performance Modeling Of Supercritical Carbon Dioxide Zigzag-Channel Printed Circuit Heat Exchangers, Katrine Birgitte Bennett

UNLV Theses, Dissertations, Professional Papers, and Capstones

Supercritical carbon dioxide (sCO2) is currently being studied as the working fluid in power producing Brayton cycles due to its excellent physical and thermodynamic properties, especially near the critical point. Printed circuit heat exchangers (PCHEs) are being considered for use as condensers and recuperators for this purpose due to their high strength and compact designs. Many experimental and numerical studies are being conducted to characterize and optimize sCO2 PCHE operation and develop correlations to describe their thermal-hydraulic performance. Additionally, a few experimental and numerical structural assessments of these PCHEs have been conducted, but all have been somewhat limited due to …

Ph-Sensitive Oxygen Release Microspheres To Enhance Cell Survival In Ischemic Condition, Zhongting Liu

McKelvey School of Engineering Graduate Student Theses & Dissertations

Ischemic diseases such as myocardial infarction, stroke and limb ischemia are severe cardiovascular diseases with high rate of death and millions of people suffered from these diseases. Under ischemic environment, cells die due to deficient supply of nutrient and oxygen. To regenerate ischemic tissues, stem cell therapy is a promising approach because stem cells can differentiate into cells necessary for the regeneration. However, stem cell therapy has limitations. For example, few cells can survive under harsh ischemic environment. To enhance stem cells survival, implantation of oxygen release microspheres to sustained supply cells with oxygen represents an effective strategy. Previously, our …

Co2 Hydrogenation To High-Value Products Via Heterogeneous Catalysis, Run-Ping Ye, Jie Ding, Weibo Gong, Morris D. Argyle, Qin Zhong, Yujun Wang, Christopher K. Russell, Zhenghe Xu, Armistead G. Russell, Qiaohong Li, Maohong Fan, Yuan-Gen Yao

Faculty Publications

Recently, carbon dioxide capture and conversion, along with hydrogen from renewable resources, provide an alternative approach to synthesis of useful fuels and chemicals. People are increasingly interested in developing innovative carbon dioxide hydrogenation catalysts, and the pace of progress in this area is accelerating. Accordingly, this perspective presents current state of the art and outlook in synthesis of light olefins, dimethyl ether, liquid fuels, and alcohols through two leading hydrogenation mechanisms: methanol reaction and Fischer-Tropsch based carbon dioxide hydrogenation. The future research directions for developing new heterogeneous catalysts with transformational technologies, including 3D printing and artificial intelligence, are provided.

Formulation Optimization Effects On Mechanical And Rheological Properties Of Filled Polysiloxanes, Kevin Mcnay

Electronic Theses & Dissertations

Polysiloxanes are a class of high-performance polymeric materials that are used in a wide variety of applications, including O-rings, gaskets, sealants, coatings, and adhesives. These materials have high temperature resistances as well as flexibility at low temperatures. This is due to the bond between the oxygen and silicon atom, a bond that requires a high dissociation energy to break. However, their elastomers, which can be obtained by crosslinking linear precursors using various crosslinkers, generally exhibit low strength and have poor mechanical properties unless reinforced. Therefore, fillers, additives, UV-stabilizers, and anti-oxidants are often incorporated in order to improve the resulting properties. …

Effect Of Different Types Of Static Mixer Geometry On Quality Of Microbubble Generation, Tee Wu Yang

Student Works (2020-2029)

This research project is mainly focused on the impact of different types of static mixer on the quality of microbubble generation. The design of the microbubble generation consists of venturi to allow the air intake by using pressure difference and then different static mixer geometry are tested to investigate the effect on bubble rising time and dissolved oxygen (DO). At the first part of study, the work comprises of the relationship of bubble rising time at different pressures and bubble diameter at different pressures. It has proved that higher pressure will induce small bubble diameter and the bubble rising time …

An Investigation Of The Chemistry, Thermodynamics And Catalytic Activity Of Molybdenum Carbides, Shanti Kiran Nayak

Chemical and Biological Engineering ETDs

These studies investigate the chemistry and stability of molybdenum carbides as an electrocatalyst. Due to their unique electronic properties, molybdenum carbides are purposed as electrocatalysts for reaction systems such as hydrogen evolution reaction, bifunctional water splitting and CO oxidation.

In this study, various synthesis processes were utilized to produce different types of molybdenum carbide with varying properties of particle size, surface area and excess carbon. The samples characterized by XRD accompanied by Whole Profile Fitting, Electron Microscopy, Gas Adsorption (surface area) and XPS.

These synthesis processes were refined using fundamental thermodynamic analyses. These analyses highlight regions of stability of different …

Zirconia-Based Compositions For Use In Passive NoX Adsorber Devices, Deborah Jayne Harris, David Alastair Scapens, John G. Darab, Mark Crocker, Yaying Ji

Chemistry Faculty Patents

A passive NO_x adsorbent includes: palladium, platinum or a mixture thereof and a mixed or composite oxide including the following elements in percentage by weight, expressed in terms of oxide: 10-90% by weight zirconium and 0.1-50% by weight of least one of the following: a transition metal or a lanthanide series element other than Ce.

Although the passive NO_x adsorbent can include Ce in an amount ranging from 0.1 to 20% by weight expressed in terms of oxide, advantages are obtained particularly in the case of low-Ce or a substantially Ce-free passive NO_x adsorbent.

Polyvinylpyrrolidone - Reduced Graphene Oxide - Pd Nanoparticles As An Efficient Nanocomposite For Catalysis Applications In Cross-Coupling Reactions, Hany A. Elazab, Tamer T. El-Idreesy

Chemical Engineering

This paper reported a scientific approach adopting microwave-assisted synthesis as a synthetic route for preparing highly active palladium nanoparticles stabilized by polyvinylpyrrolidone (Pd/PVP) and supported on reduced Gra-phene oxide (rGO) as a highly active catalyst used for Suzuki, Heck, and Sonogashira cross coupling reactions with remarkable turnover number (6500) and turnover frequency of 78000 h-1. Pd/PVP nanoparticles supported on re-duced Graphene oxide nanosheets (Pd-PVP/rGO) showed an outstanding performance through high catalytic activ-ity towards cross coupling reactions. A simple, reproducible, and reliable method was used to prepare this efficient catalyst using microwave irradiation synthetic conditions. The synthesis approach requires simultaneous reduc-tion …

Proactive Energy Optimization In Residential Buildings With Weather And Market Forecasts, Cody Simmons, Joshua Arment, Kody M. Powell, John Hedengren

Faculty Publications

This work explores the development of a home energy management system (HEMS) that uses weather and market forecasts to optimize the usage of home appliances and to manage battery usage and solar power production. A Moving Horizon Estimation (MHE) application is used to find the unknown home model parameters. These parameters are then updated in a Model Predictive Controller (MPC) which optimizes and balances competing comfort and economic objectives. Combining MHE and MPC applications alleviates model complexity commonly seen in HEMS by using a lumped parameter model that is adapted to fit a high-fidelity model. Heating, ventilation, and air conditioning …

Metal-Free Deep Eutectic Solvents: Preparation, Physical Properties, And Significance, Burcu E. Gurkan, Henry Squire

Faculty Scholarship

In the past decade, reports detailing the preparation, characterization, and application of deep eutectic solvents (DESs) have grown in number significantly, showing signs of increased interest and attention. Indeed, these systems provide tunable polar environments attractive for their ease of synthesis and lack of need for purification. DESs are homogeneous systems composed of two or more components having a significantly depressed melting point compared to either constituent material. As interest and application of DESs grow, the need for a common understanding of their preparation and characterization is required. In this Perspective, we discuss metal-free DESs, focusing on their preparation, characterization …

Modeling The Effects Of Distribution System Topology On Water Quality, Chun-Ying Chao

McKelvey School of Engineering Graduate Student Theses & Dissertations

Inadequate treatment of drinking water causes the formation of disinfection by-products and the regrowth of harmful microbial species. Various studies have addressed the problem of water quality monitoring, but very few have employed topological analysis, a valuable mathematical tool widely applied in biological, business, and social research. This thesis examines the relationship between the topological properties of water distribution systems and water-quality models. In particular, the research proposes a novel framework for mapping network topological attributes to water-quality models. This research adopts topological metrics to assess the accuracy of the predictions of chlorine concentrations in dead ends. It examines four …

Influence Of Nh4f In Dextran Based Biopolymer Electrolytes: Conductivity And Electrical Analysis, Muhamad Hafiz Hamsan, Mohd Fakhrul Zamani Kadir, Shujahadeen Bakar Aziz, Muhammad Amirul Solihin Azha, Saifful Kamaluddin Muzakir

Makara Journal of Technology

Dextran polymer host was doped with different concentrations of ammonium fluoride (NH4F) via casting technique. In this present work, dextran-NH4F film has been employed to investigate the ionic conductivity using electrochemical impedance spectroscopy from 50 to 5 MHz. The highest room temperature conductivity is achieved at (2.33 ± 0.76) × 10-3 S cm-1 with 40 wt.% NH4F. The electrolyte is found to obey Arrhenius rule at high temperature with activation energy of 0.21 eV. Dielectric analysis has been performed to obtain better understanding on the conductivity pattern. The dielectric parameters e.g. ɛreal, ɛimag, Mreal, and Mimag have been tested as …

Neutron Diffraction Study Of Multiferroic 0.6nife2o4/0.4batio3 Composite, Engkir Sukirman, Yosef Sarwanto, Syahfandi Ahda, Andon Insani

Makara Journal of Technology

Neutron diffraction study on the 0.6NiFe2O4/0.4BaTiO3 multiferroic composite has been carried out. The 0.6NiFe2O4/0.4BaTiO3 multiferroic composites have been synthesized by solid reaction method. In this study, 20 g of BaTiO3 (BTO) and 20 g of NiFe2O4 (NFO) compounds were prepared from the powder raw materials of BaO3 and TiO2 for BTO, and NiO and Fe2O3 for NFO. Furthermore, both BTO and NFO were each crushed for 5 hours using High Energy Milling (HEM). Then the BTO and NFO were calcined in the furnace at 950 °C/5 hours and 900 °C/5 hours, respectively. Both NFO and BTO precursors were manually mixed …

Comprehensive Inspection On The Experimental Ferritic Stainless Steel By Means Of Transmission Electron Microscopy And Neutron Diffraction Techniques, Parikin Parikin, Mohammad Dani, Riza Iskandar, Aziz Khan Jahja, Andon Insani, Joachim Mayer

Makara Journal of Technology

The field of physical metallurgy is one of the primary beacons that guide alloy developments for multipurpose materials such as the in-core structure materials for pressure vessel components and heat exchangers. The surface microstructure of new ferritic steel with significant local constituent materials was characterized by high resolution powder neutron diffractometer (HRPD) and transmission electron microscope (TEM), combined with the energy dispersive X-ray spectroscopy (EDX). The alloy contains73% Fe, 24% Cr, 2% Si, 0.8% Mn, and 0.1% Ni, in %wt. The charge materials were melted by the casting techniques. The neutron diffractograms obtained shows five dominant diffraction peaks at (110), …

A New Synthesized Microalloys Steel Ods Of High Amplitude Ultrasonically Irradiation, Marzuki Silalahi, Hanif Abdurrahman Wicaksana, Ferhat Aziz, Syahfandi Ahda, Mohamad Riza Iskandar

Makara Journal of Technology

Micropowders of oxide-dispersion-strengthened (ODS) steel have been synthesized using the ultrasonic irradiation method with variations in amplitude. The ultrasonic irradiation process is performed for 50 h at a frequency of 20 kHz with 40%, 50%, and 60% amplitudes in toluene solution. The formation of Fe-Cr microalloys in the preparation of Fe- 15Cr-0.5Y2O3 powder was analyzed using SEM-EDS, X-ray diffraction (XRD), and TEM-EDS. The percentage of Fe- Cr phase mass fraction of ODS steel micropowder formed during ultrasonic irradiation with 40%:50%:60% amplitude was 12.2%:34.1%:22.1%, with 25.67:77.02:38.51 nm crystallite size. The crystallite size at 50% amplitude was the largest, and the diffusion …