Nanoscience and Nanotechnology Commons^™

Nanoparticle Catalytic Enhancement Of Carbon Dioxide Reforming Of Methane For Hydrogen Production, Nicholas Groden

Doctoral Dissertations

The U.S. produces 5559.6 million metric tons of carbon dioxide annually, of which 21% is produced by industrial processes. Steam reforming, an industrial process that accounts for 95% of all hydrogen production in industry, produces 134.5 million metric tons of carbon dioxide or around 11% of the total carbon dioxide produced by industry. This carbon dioxide is then either emitted or goes through a sequestration process that accounts for 75% of the plant's operational costs. An alternative reaction to steam reforming is dry reforming, which utilizes carbon dioxide rather than emitting it and can be used in conjunction with current …

Synthesis, Characterization, And Activity Of Co/Fe Alumina/Silica Supported Ft Catalysts And The Study Of Promoter Effect Of Ruthenium, Sunday Azubike Esumike

Doctoral Dissertations

The alumina and hybrid alumina-silica FT catalyst were prepared by one-step solgel/oil-drop methods using metal-nitrate-solutions (method-I), and nanoparticle-metaloxides (method-2). The nanoparticle-metal-oxides did not participate in solubility equilibria in contrast to metal nitrate in method-1 causing no metal ion seepage; therefore, method-2 yields higher XRF metal loading efficiency than method-1. The thermal analysis confirmed that the metal loading by method-1 and method-2 involved two different pathways. Method-1 involves solubility equilibria in the conversion of metal-nitrate to metal- hydroxide and finally to metal-oxide, while in method-2 nanoparticle-metal-oxide remained intact during sol-gel-oil-drop and calcination steps.

The alumina supported catalysts were dominated by γ-alumina …

Immobilization Of Cellulase For Large Scale Reactors To Reduce Cellulosic Ethanol Cost, Dezhi Zhang

Doctoral Dissertations

Cellulosic ethanol is an alternative renewable energy source. Cellulase used in the production of cellulosic ethanol is very expensive. The difficulty in separating cellulase from the cellulose solution after the hydrolysis process limits the reusability of the cellulase, which highly precludes the scales of this application because of the high cost of the enzyme. Immobilization of cellulase provides a promising approach to allow the enzyme to be recycled, thus reducing the production cost. This research focused on immobilizing cellulase for reuse to reduce the cellulosic ethanol cost.

Four immobilization techniques were explored for the immobilization of cellulase on four different …

Manufacturing Polyacrylonitrile Nanowires And Nanofibers For Sensing And Energy Storage Applications, Juan Chen

Doctoral Dissertations

A novel flow guided assembly approach is presented to well align and accurately position nanowire arrays in pre-defined locations with high throughput and large scale manufacturing capability. In this approach, polyacrylonitrile (PAN)/N, N-dimethylformamide (DMF) solution is first filled in an array of microfluidic channels. Then a gas flow is introduced to blow out most solutions while pushing a little leftover against the channel wall to assemble into polymer nanowires. In this way, highly-ordered nanowires are conveniently aligned in the flow direction and patterned along both sides of the microchannels. In this study, we demonstrated this flow-guided assembly process by producing …

Functional Clay Nanotubes And Composites, Yafei Zhao

Doctoral Dissertations

Tubular nanomaterials and their composites have been extensively studied in recent years in the fields of physics, chemistry, biology, and biomedicine. Carbon nanotube is the most commonly studied tubular nanomaterial; however, toxicity and high cost make it less attractive in industry and thus restricts its applications. Halloysite nanotubes, which are available in abundance in the United States as well as in other countries around the world, is a low-cost, unique and versatile aluminosilicate mineral with a chemical formula of Al4Si4O10(OH)8·nH2O. Basically, the halloysite tube diameter is around 50 nm and the length varies with different locations ranging from 0.4-1.5 μm. …

Computational Study Of Sodium Magnesium Hydride For Hydrogen Storage Applications, Fernando Antonio Soto Valle

Doctoral Dissertations

Hydrogen offers considerable potential benefits as an energy carrier. However, safe and convenient storage of hydrogen is one of the biggest challenges to be resolved in the near future. Sodium magnesium hydride (NaMgH 3) has attracted attention as a hydrogen storage material due to its light weight and high volumetric hydrogen density of 88 kg/m3. Despite the advantages, hydrogen release in this material occurs at approximately 670 K, which is well above the operable range for on-board hydrogen storage applications. In this regard, hydrogen release may be facilitated by substitution doping of transition-metals. This dissertation describes first-principles computational methods that …

Study And Development Of Sulfated Zirconia Based Proton Exchange Fuel Cell Membranes, Brittany Wilson Kemp

Doctoral Dissertations

With the increasing consumption of energy, fuel cells are among the most promising alternatives to fossil fuels, provided some technical challenges are overcome. Proton exchange membrane fuel cells (PEMFCs) have been investigated and improvements have been made, but the problem with Nafion®, the main membrane for PEMFCs, has not been solved. Nafion® restricts the membranes from operating at higher temperatures, thus preventing them from working in small electronics. The problem is to develop a novel fuel cell membrane that performs comparably to Nafion® in PEMFCs.

The membranes were fabricated by applying sulfated zirconia, via template wetting, to porous alumina membranes. …

Multi-Scale Characterization Of Nanostructured Sodium Aluminum Hydride, Shathabish Narasegowda

Doctoral Dissertations

Complex metal hydrides are the most promising candidate materials for onboard hydrogen storage. The practicality of this class of materials is counter-poised on three critical attributes: reversible hydrogen storage capacity, high hydrogen uptake/release kinetics, and favorable hydrogen uptake/release thermodynamics. While a majority of modern metallic hydrides that are being considered are those that meet the criteria of high theoretical storage capacity, the challenges lie in addressing poor kinetics, thermodynamics, and reversibility. One emerging strategy to resolve these issues is via nanostructuring or nano-confinement of complex hydrides. By down-sizing and scaffolding them to retain their nano-dimensions, these materials are expected to …

Role Of Ammonia In The Activiation Of Methanol Dehydrogenase/Cytochrome C(L) Enzyme, Ancy Kunjumon

Doctoral Dissertations

Recent advancement in enzyme catalysis has opened ways to design efficient biocatalysts, bio-sensors and bio-fuel cells. An in-depth knowledge about the mechanism of the reaction taking place within the enzymes is of great importance to achieve these goals. In this dissertation, various computation methods are applied to investigate the mechanism behind enzyme catalysis in the presence of compounds called activators.

Methanol dehydrogenase (MDH) is a well-known bio-catalyst that can oxidize excess of methanol from the environment to formaldehyde. The enzyme works well within the bacterial environment, but under in vitro, it loses activity. Ammonia is used as an activator …

Halloysite Clay Nanotubes For Controlled Delivery Of Chemically Active Agents, Elshard Abdullayev

Doctoral Dissertations

In this work we explored the capabilities of halloysite nanotubes as capsules for encapsulation and controlled delivery of the chemically and biologically active substances. Halloysite is a two-layered aluminosilicate which has a predominantly hollow tubular structure in the submicron range and is chemically similar to kaolinite [1, 2].

In the first section of this work, we analyzed the structure of the halloysite nanotubes as well as its capability to encapsulate and deliver biologically and chemically active agents, similarities and differences between release characteristics of different agents and how these differences relate with their chemical structure. Models were used to describe …

Analysis Of Conjugated Polymer Nanotubules Formed By Template Wetting Nanofabrication, Steven D. Bearden Jr.

Doctoral Dissertations

Semiconducting and optoelectric conjugated polymers have potential in micro and nano-electronic applications. Their widely tunable physical conformations and orientations make these polymers ideal material for engineering small scale devices. The polymers have been incorporated into several electronic devices including light-emitting diodes, solar cells, and field-effect transistors. Widespread adoption of these materials will not be a reality until the issues of poor device performance, short lifespans, and device degradation are resolved.

Nanostructures have been demonstrated to have improvements in molecular ordering and electronic transport. In the work presented here, tubular nanostructures of conjugated polymers fabricated by the template wetting nanofabrication process …