Nanoscience and Nanotechnology Commons^™

Droplet Evaporation On Heated Hydrophobic And Superhydrophobic Surfaces, Susmita Dash, Suresh V. Garimella

Birck and NCN Publications

The evaporation characteristics of sessile water droplets on smooth hydrophobic and structured superhydrophobic heated surfaces are experimentally investigated. Droplets placed on the hierarchical superhydrophobic surface subtend a very high contact angle (similar to 160 degrees) and demonstrate low roll-off angle (similar to 1 degrees), while the hydrophobic substrate supports corresponding values of 120 degrees and similar to 10 degrees. The substrates are heated to different constant temperatures in the range of 40-60 degrees C, which causes the droplet to evaporate much faster than in the case of natural evaporation without heating. The geometric parameters of the droplet, such as contact …

Variable-Cell Method For Stress-Controlled Jamming Of Athermal, Frictionless Grains, Kyle C. Smith, Ishan Srivastava, Timothy Fisher, Meheboob Alam

Birck and NCN Publications

A method is introduced to simulate jamming of polyhedral grains under controlled stress that incorporates global degrees of freedom through the metric tensor of a periodic cell containing grains. Jamming under hydrostatic (isotropic) stress and athermal conditions leads to a precise definition of the ideal jamming point at zero shear stress. The structures of tetrahedra jammed hydrostatically exhibit less translational order and lower jamming-point density than previously described maximally random jammed hard tetrahedra. Under the same conditions, cubes jam with negligible nematic order. Grains with octahedral symmetry having s > 0.5 (where s interpolates from octahedra [s = 0] to cubes …

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. …

Selected Durability Studies Of Geopolymer Concrete With Respect To Carbonation, Elevated Temperature, And Microbial Induced Corrosion, Mohammad Sufian Badar

Doctoral Dissertations

This thesis reports a comprehensive study related to the experimental evaluation of carbonation in reinforced geopolymer concrete, the evaluation of geopolymer concretes at elevated temperature, and the resistance of geopolymer concrete to microbial induced corrosion (MIC).

Carbonation: Reinforced concretes, made of geopolymer, prepared from two class F fly ashes and one class C fly ash, were subjected to accelerated carbonation treatment for a period of 450 days. Electrochemical, microstructure and pore structure examinations were performed to evaluate the effect of corrosion caused due to carbonation. GPC specimens prepared from class F fly ash exhibited lower corrosion rates by a factor …

Particle Deposition On Superhydrophobic Surfaces By Sessile Droplet Evaporation, Mercy G. Dicuangco

Open Access Theses

Prediction and active control of the spatial distribution of particulate deposits obtained from sessile droplet evaporation is essential in ink-jet printing, nanostructure assembly, biotechnology, and other applications that require localized deposits. In recent years, sessile droplet evaporation on bio-inspired superhydrophobic surfaces has become an attractive method for depositing materials on a site-specific, localized region, but is less explored compared to evaporative deposition on hydrophilic surfaces. It is therefore of interest to understand particle deposition during droplet evaporation on superhydrophobic surfaces to enable accurate prediction and tunable control of localized deposits on such surfaces. The purpose of the present work is …

Functionalization Of Carbon Nanotube Yarn By Acid Treatment, Heath E. Misak, Ramazan Asmatulu, Mat O'Malley, Emil Jurak, Shankar Mall

Faculty Publications

Carbon nanotube (CNT) yarn was functionalized using sulfuric and nitric acid solutions in 3:1 volumetric ratio. Successful functionalization of CNT yarn with carboxyl and hydroxyl groups (e.g., COOH, COO–, OH, etc.) was confirmed by attenuated total reflectance spectroscopy. X-ray diffraction revealed no significant change to the atomic in-plane alignment in the CNTs; however, the coherent length along the diameter was significantly reduced during functionalization. A morphology change of wavy extensions protruding from the surface was observed after the functionalization treatment. The force required to fracture the yarn remained the same after the functionalization process; however, the linear density was increased …

The Development Of 6.7% Efficient Copper Zinc Indium Selenide Devices From Copper Zinc Indium Sulfide Nanocrystal Inks, Brian Kemp Graeser

Open Access Theses

As solar cell absorber materials, alloys of CuIn(S,Se)2 and Zn(S,Se) provide an opportunity to reduce the usage of indium along with the ability to tune the band gap. Here we report successful synthesis of alloyed (CuInS2 )0.5(ZnS)0.5 nanocrystals by a method that solely uses oleylamine as the liquid medium for synthesis. The reactive sintering of a thin film of these nanocrystals via selenization at 500 °C results in a uniform composition alloy (CuIn(S,Se)2 )0.5 (Zn(S,Se)) 0.5 layer with micron size grains. Due to the large amount of zinc in the film, the sintered grains exhibit the zinc blende structure instead …

Controlling Protein Release Using Biodegradable Microparticles, Benjamin Patrick Kline

Open Access Theses

Research in the field of protein therapeutics has exploded over the past decade and continues to grow in both academia and in industry. Protein drugs have advantages of being highly specific and highly active making them coveted targets for high profile disease states like cancer and multiple sclerosis. Unfortunately, their many advantages are complemented by their obstacles. Because proteins are highly active and highly specific, the window between efficacy and toxicity is very narrow and drug development can be long and arduous. In addition, protein activity is dependent on its specific folding conformation that is easily disrupted by a variety …

Mechanistic Study Of The Hydrothermal Reduction Of Palladium On The Tobacco Mosaic Virus, Oluwamayowa Oluwarotimi Adigun

Open Access Theses

Synthesis of nanorods and nanowires is becoming more and more important due to interest in them in a wide range of disciplines. The genetically engineered tobacco mosaic virus (TMV1Cys) provides a template for synthesis of uniform metal nanorods at mild operating conditions and without the use of any expensive technology compared to conventional synthetic methods. The discovery of the hydrothermal synthetic scheme has allowed the production of higher quality nanorods on the TMV template. However, the mechanism for reduction and growth in this process is still not understood. In this paper, the mechanism of synthesis for producing uniform, controllable palladium …

Size-Dependent Interactions Of Metal Nanoparticles With Fluorophores And Semiconductors, Liyana A. Wajira Ariyadasa

Dissertations

In recent years, nanoscale metallic particles have gained considerable interest due to their potential applications in advanced technology. Despite such interest, synthetic procedures that produce gram-scale, well-defined metallic nanoparticles with controlled size and shape, especially with diameters less than 5 nm remains a challenge. Our work has focused on developing synthetic procedures that produce well-defined platinum and palladium metal nanoparticles in the 1-5 nm size range. Thioether ligands were used as stabilizers and resulted in metal nanoparticles with controlled size. The nanoparticles were characterized using transmission electron microscopy (TEM), x-ray diffraction (XRD), selected area electron diffraction (SAED), x-ray photoelectron spectroscopy …

Tunable Hyperbolic Metamaterials Utilizing Phase Change Heterostructures, Harish N.S. Krishnamoorthy, You Zhou, Shriram Ramanathan, Evgenii Narimanov, Vinod M. Menon

Birck and NCN Publications

We present a metal-free tunable anisotropic metamaterial where the iso-frequency surface is tuned from elliptical to hyperbolic dispersion by exploiting the metal-insulator phase transition in the correlated material vanadium dioxide (VO2). Using VO2-TiO2 heterostructures, we demonstrate the transition in the effective dielectric constant parallel to the layers to undergo a sign change from positive to negative as the VO2 undergoes the phase transition. The possibility to tune the iso-frequency surface in real time using external perturbations such as temperature, voltage, or optical pulses creates new avenues for controlling light-matter interaction. (C) 2014 AIP Publishing LLC.

Laser Sintering Of Separated And Uniformly Distributed Multiwall Carbon Nanotubes Integrated Iron Nanocomposites, Dong Lin, Chunghorng Richard Liu, Gary J. Cheng

Birck and NCN Publications

Uniform distribution of carbon nanotubes (CNTs) in metal matrix during additive manufacturing of nanocomposites is always a challenge since the CNTs tend to aggregate in the molten pool. In this study, Multiwall carbon nanotubes (MWNTs) were separated and distributed uniformly into iron matrix by laser sintering process. MWNTs and iron powders were mixed together by magnetic stir, coated on steel 4140 surface, followed by laser sintering. Due to the fast heating and cooling rate, the CNTs are evenly distributed in the metal matrix. The temperature field was calculated by multiphysics simulation considering size effects, including size dependent melting temperature, thermal …

Nu=5/2 Fractional Quantum Hall State In The Presence Of Alloy Disorder, Nianpei Deng, Geoff C. Gardner, Sumit Mondal, Ethan Kleinbaum, Michael J. Manfra, Gabor Csathy

Birck and NCN Publications

We report quantitative measurements of the impact of alloy disorder on the. nu = 5/2 fractional quantum Hall state. Alloy disorder is controlled by the aluminum content x in the AlxGa1-xAs channel of a quantum well. We find that the nu = 5/2 state is suppressed with alloy scattering. To our surprise, in samples with alloy disorder the nu = 5/2 state appears at significantly reduced mobilities when compared to samples in which alloy disorder is not the dominant scattering mechanism. Our results highlight the distinct roles of the different types of disorder present in these samples, such as the …

Electrical And Thermal Conductivities Of Reduced Graphene Oxide/Polystyrene Composites, Wonjung Park, Jiuning Hu, Luis A. Jauregui, Xiulin Ruan, Yong P. Chen

Birck and NCN Publications

The author reports an experimental study of electrical and thermal transport in reduced graphene oxide (RGO)/polystyrene (PS) composites. The electrical conductivity (sigma) of RGO/PS composites with different RGO concentrations at room temperature shows a percolation behavior with the percolation threshold of similar to 0.25 vol. %. Their temperature-dependent electrical conductivity follows Efros-Shklovskii variable range hopping conduction in the temperature range of 30-300K. The thermal conductivity (kappa) of composites is enhanced by similar to 90% as the concentration is increased from 0 to 10 vol. %. The thermal conductivity of composites approximately linearly increases with increasing temperature from 150 to 300 …

Carbon Allotrope Dependence On Temperature And Pressure During Thermal Decomposition Of Silicon Carbide, Munson J. Anderson

Theses and Dissertations

Bulk CNT and graphene films form on SiC using a metal-catalyst-free thermal decomposition approach. In this work, the background vacuum pressure and temperature used in the decomposition process are varied to investigate their impact on the type and quality of carbon allotrope formed on the SiC substrate. The carbon nanostructure growth is performed using two approaches, both of which involve intense heating (1400-1700°C) of SiC under moderate vacuum conditions (0.01 - 0.00001 Torr). The first growth method uses a conventional graphite resistance furnace capable of annealing waferscale samples over 1700°C under vacuum. Using this approach, post-growth characterization is performed using …

Zno Nanosheet Arrays Constructed On Weaved Titanium Wire For Cds-Sensitized Solar Cells, Cuncun Wu, Lin Wei, Yitan Li, Chang Liu, Jun Jiao, Yanxue Chen, Liangmo Mei

Mechanical and Materials Engineering Faculty Publications and Presentations

Ordered ZnO nanosheet arrays were grown on weaved titanium wires by a low-temperature hydrothermal method. CdS nanoparticles were deposited onto the ZnO nanosheet arrays using the successive ionic layer adsorption and reaction method to make a photoanode. Nanoparticle-sensitized solar cells were assembled using these CdS/ZnO nanostructured photoanodes, and their photovoltaic performance was studied systematically. The best light-to-electricity conversion efficiency was obtained to be 2.17% under 100 mW/cm/cm² illumination, and a remarkable shortcircuit photocurrent density of approximately 20.1 mA/cm² was recorded, which could attribute to the relatively direct pathways for transportation of electrons provided by ZnO nanosheet arrays as …

Cds Quantum Dot-Sensitized Solar Cells Based On Nano-Branched Tio2 Arrays, Chang Liu, Yitan Li, Lin Wei, Cuncun Wu, Yanxue Chen, Liangmo Mei, Jun Jiao

Mechanical and Materials Engineering Faculty Publications and Presentations

Nano-branched rutile TiO2 nanorod arrays were grown on F:SnO2 conductive glass (FTO) by a facile, two-step wet chemical synthesis process at low temperature. The length of the nanobranches was tailored by controlling the growth time, after which CdS quantum dots were deposited on the nano-branched TiO2 arrays using the successive ionic layer adsorption and reaction method to make a photoanode for quantum dot-sensitized solar cells (QDSCs). The photovoltaic properties of the CdS-sensitized nano-branched TiO2 solar cells were studied systematically. A short-circuit current intensity of approximately 7 mA/cm2 and a light-to-electricity conversion efficiency of 0.95% were recorded for cells based on …

Gas Mixing System For Imaging Of Nanomaterials Under Dynamic Environments By Environmental Transmission Electron Microscopy, M. Cem Akatay, Yury Zvinevich, Philipp Baumann, Fabio H. Ribeiro, Eric A. Stach

Birck and NCN Publications

A gas mixing manifold system that is capable of delivering a stable pressure stream of a desired composition of gases into an environmental transmission electron microscope has been developed. The system is designed to provide a stable imaging environment upon changes of either the composition of the gas mixture or upon switching from one gas to another. The design of the system is described and the response of the pressure inside the microscope, the sample temperature, and sample drift in response to flow and composition changes of the system are reported. (C) 2014 AIP Publishing LLC.

Passive Biaxial Mechanical Properties And In Vivo Axial Pre-Stretch Of The Diseased Human Femoropopliteal And Tibial Arteries, Alexey Kamenskiy, Iraklis I. Pipinos, Yuris A. Dzenis, Clay Lomneth, Syed A. Jaffar Kazmi, Nicholas Y. Phillips, Jason N. Mactaggart

Department of Mechanical and Materials Engineering: Faculty Publications

Surgical and interventional therapies for atherosclerotic lesions of the infrainguinal arteries are notorious for high rates of failure. Frequently, this leads to expensive reinterventions, return of disabling symptoms, or limb loss. Interaction between the artery and repair material likely plays an important role in reconstruction failure, but data describing the mechanical properties and functional characteristics of human femoropopliteal and tibial arteries are currently not available. Diseased superficial femoral (SFA, n=10), popliteal (PA, n=8), and tibial arteries (TA, n=3) from 10 patients with critical limb ischemia were tested to determine passive mechanical properties using planar biaxial extension. All …

Underpotential Deposition Of Germanium On Au(111) And Pt(111) Surfaces In Ionic Liquids, Xu-Fen Xie, Jia-Wei Yan, Jing-Hong Liang, Ji-Jun Li, Meng Zhang, Bing-Wei Mao

Journal of Electrochemistry

The underpotential deposition (UPD) of germanium (Ge) in BMIPF₆ ionic liquids on Au(111) and Pt(111) surfaces have been investigated by cyclic voltammetry (CV) and in-situ scannin tunneling microscopy (STM). The CV results show that there are two reduction peaks related to the electrodeposition of Ge. The first reduction peak appeared in the CV curve may cover the transformation of Ge⁴⁺ to Ge²⁺ and the UPD of Ge. The second reduction peak corresponds to the bulk deposition of Ge. In-situ STM study suggests that the two UPD layers of Ge are formed on Au(111) and Pt(111) surfaces. The …