Engineering Commons^™

Spray Printing Of Organic Semiconducting Single Crystals, Grigorios-Panagiotis Rigas, Marcia M. Payne, John E. Anthony, Peter N. Horton, Fernando A. Castro, Maxim Shkunov

Chemistry Faculty Publications

Single-crystal semiconductors have been at the forefront of scientific interest for more than 70 years, serving as the backbone of electronic devices. Inorganic single crystals are typically grown from a melt using time-consuming and energy-intensive processes. Organic semiconductor single crystals, however, can be grown using solution-based methods at room temperature in air, opening up the possibility of large-scale production of inexpensive electronics targeting applications ranging from field-effect transistors and light-emitting diodes to medical X-ray detectors. Here we demonstrate a low-cost, scalable spray-printing process to fabricate high-quality organic single crystals, based on various semiconducting small molecules on virtually any substrate by …

Thin Film Concrete Coatings, Bobby W. Meade, Danny Wells, Theodore Hopwood Ii, Sudhir Palle

Kentucky Transportation Center Research Report

KTC researchers obtained eight types of concrete coatings to assess their performance and resistance to chloride penetration. Researchers evaluated eight of the systems in the field and seven in the laboratory. In the field, coatings were applied to a bridge pier that had suffered degradation and chloride contamination. This site will undergo long term monitoring in order to thoroughly evaluate the coating systems. Adhesion of all products in both field and laboratory application was sufficient to provide a durable coating, and ranged from approximately 500 psi to 1,600 psi. Researchers also tested color and gloss changes, which are early indicators …

Enhanced Metallic Properties Of Srruo3 Thin Films Via Kinetically Controlled Pulsed Laser Epitaxy, Justin K. Thompson, J. Nichols, S. Lee, S. Ryee, John H. Gruenewald, John G. Connell, Maryam Souri, J. M. Johnson, J. Hwang, M. J. Han, H. N. Lee, D. -W. Kim, Sung S. Ambrose Seo

Physics and Astronomy Faculty Publications

Metal electrodes are a universal element of all electronic devices. Conducting SrRuO₃ (SRO) epitaxial thin films have been extensively used as electrodes in complex-oxide heterostructures due to good lattice mismatches with perovskite substrates. However, when compared to SRO single crystals, SRO thin films have shown reduced conductivity and Curie temperatures (T_C), which can lead to higher Joule heating and energy loss in the devices. Here, we report that high-quality SRO thin films can be synthesized by controlling the plume dynamics and growth rate of pulsed laser epitaxy (PLE) with real-time optical spectroscopic monitoring. The SRO thin …

Preparation And Microstructure Of Machinable Al2O3/Mica Composite By Ball Milling And Hot-Press Sintering, Qingbo Tian, Deyu Kong, Tongguang Zhai

Chemical and Materials Engineering Faculty Publications

A machinable α-Al₂O₃/mica composite was prepared by hot-press sintering. In this experiment, a mica-contained glass ceramic in the MgO-Al₂O₃-SiO₂-F glassy system was employed and the base glass powders were obtained by traditional melting-quenched method. Then, α-Al₂O₃ milling swarf was introduced by medium α-alumina milling ball to the glass powders. The test results indicate that the composites consist of mica crystal and mullite crystal, which are precipitated in the base glass. The α-Al₂O₃ shows an irregular polygon, which is inlayed in the base material. With …

Fast Diffusion Of Silver In Tio2 Nanotube Arrays, Wanggang Zhang, Yiming Liu, Diaoyu Zhou, Hui Wang, Wei Liang, Fuqian Yang

Chemical and Materials Engineering Faculty Publications

Using magnetron sputtering and heat treatment, Ag@TiO₂ nanotubes are prepared. The effects of heat-treatment temperature and heating time on the evolution of Ag nanofilms on the surface of TiO₂ nanotubes and microstructure of Ag nanofilms are investigated by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Ag atoms migrate mainly on the outmost surface of the TiO₂ nanotubes, and fast diffusion of Ag atoms is observed. The diffusivity for the diffusion of Ag atoms on the outmost surface of the TiO₂ nanotubes at 400 °C is 6.87 × 10⁻¹⁸ m²/s, …

Self-Similar Random Process And Chaotic Behavior In Serrated Flow Of High Entropy Alloys, Shuying Chen, Liping Yu, Jingli Ren, Xie Xie, Xueping Li, Ying Xu, Guangfeng Zhao, Peizhen Li, Fuqian Yang, Yang Ren, Peter K. Liaw

Chemical and Materials Engineering Faculty Publications

The statistical and dynamic analyses of the serrated-flow behavior in the nanoindentation of a high-entropy alloy, Al_0.5CoCrCuFeNi, at various holding times and temperatures, are performed to reveal the hidden order associated with the seemingly-irregular intermittent flow. Two distinct types of dynamics are identified in the high-entropy alloy, which are based on the chaotic time-series, approximate entropy, fractal dimension, and Hurst exponent. The dynamic plastic behavior at both room temperature and 200 °C exhibits a positive Lyapunov exponent, suggesting that the underlying dynamics is chaotic. The fractal dimension of the indentation depth increases with the increase of temperature, and …

Green Synthesis Nanocomposite Membranes, Dibakar Bhattacharyya, Vasile Smuleac, Rajender S. Varma, Subhas K. Sikdar

Chemical and Materials Engineering Faculty Patents

A nanocomposite membrane includes a macroporous polymer membrane having a plurality of pores. A plurality of metal nanoparticles are synthesized and immobilized within those plurality of pores. The nanoparticles are reduced and capped with a green reducing and capping agent such as green tea extract.

Simultaneous Metal-Insulator And Antiferromagnetic Transitions In Orthorhombic Perovskite Iridate Sr0.94Ir0.78O2.68 Single Crystals, Hao Zheng, Jsaminka Terzic, Feng Ye, X. G. Wan, D. Wang, Jinchen Wang, Xiaoping Wang, P. Schlottmann, Shujuan Yuan, Gang Cao

Center for Advanced Materials Faculty Publications

The orthorhombic perovskite SrIrO₃ is a semimetal, an intriguing exception in iridates where the strong spin-orbit interaction coupled with electron correlations tends to impose an insulating state. We report results of our investigation of bulk single-crystal S_r0.94Ir_0.78O_2.68 or Ir-deficient, orthorhombic perovskite SrIrO₃. It retains the same crystal structure as stoichiometric SrIrO₃ but exhibits a sharp, simultaneous antiferromagnetic (AFM) and metal-insulator (MI) transition occurring in the basal-plane resistivity at 185 K. Above it, the basal-plane resistivity features an extended regime of almost linear temperature dependence up to 800 K but the strong …

Observation Of Metallic Surface States In The Strongly Correlated Kitaev-Heisenberg Candidate Na2Iro3, Nasser Alidoust, Chang Liu, Su-Yang Xu, Ilya Belopolski, Tongfei Qi, Minggang Zeng, Daniel S. Sanchez, Hao Zheng, Guang Bian, Madhab Neupane, Yu-Tzu Liu, Stephen D. Wilson, Hsin Lin, Arun Bansil, Gang Cao, M. Zahid Hasan

Center for Advanced Materials Faculty Publications

We report high-resolution angle-resolved photoemission spectroscopy measurements on the honeycomb iridate Na₂IrO₃. Our measurements reveal the existence of a metallic surface band feature crossing the Fermi level with nearly linear dispersion and an estimated surface carrier density of 3.2 x 10¹³ cm^-2, which has not been theoretically predicted or experimentally observed, and provides the first evidence for metallic behavior on the boundary of this material, whereas the bulk bands exhibit a robust insulating gap. We further show the lack of theoretically predicted Dirac cones at the M¯ points of the surface Brillouin …

Anisotropic Softening Of Magnetic Excitations In Lightly Electron-Doped Sr2Iro4, X. Liu, M. P. M. Dean, Z. Y. Meng, M. H. Upton, T. Qi, T. Gog, Y. Cao, J. Q. Lin, D. Meyers, H. Ding, Gang Cao, J. P. Hill

Center for Advanced Materials Faculty Publications

The magnetic excitations in electron-doped (Sr_1−xLa_x)₂IrO₄ with x = 0.03 were measured using resonant inelastic x-ray scattering at the Ir L₃ edge. Although much broadened, well defined dispersive magnetic excitations were observed. Comparing with the magnetic dispersion from the undoped compound, the evolution of the magnetic excitations upon doping is highly anisotropic. Along the antinodal direction, the dispersion is almost intact. On the other hand, the magnetic excitations along the nodal direction show significant softening. These results establish the presence of strong magnetic correlations in electron-doped (Sr_1−xLa_{x …}

Microstructural Properties And Four-Point Bend Fatigue Behavior Of Ti-6.5al-2zr-1mo-1v Welded Joints By Electron Beam Welding, Peng Liu, Tongguang Zhai, Yuanbin Zhang

Chemical and Materials Engineering Faculty Publications

With the help of a four-point-bend of fatigue rig, high-cycle fatigue tests were carried out on an Ti–6.5Al–2Zr-1Mo-1V titanium alloy at room temperature, 20 Hz and R = 0.1 in ambient air. The test results indicated that the fatigue strength of base metal, 888 MPa, is about 120% of yield strength. The fatigue strength of joints is 814 MPa. It is about 110% of yield strength of base metal. When the loading stress is higher, the fatigue failure region is located in middle weld zone of weld face, which the cracks are propagated along coarse β phase’s grain boundary. When …

Size Effect On The Magnetic Phase In Sr4Ru3O10, Yan Liu, Jiyong Yang, Weike Wang, Haifeng Du, Wei Ning, Langsheng Ling, Wei Tong, Zhe Qu, Zhaorong Yang, Minling Tian, Gang Cao, Yuheng Zhang

Center for Advanced Materials Faculty Publications

High quality Sr₄Ru₃O₁₀ nanoflakes are obtained by the scotch tape-based micro-mechanical exfoliation method. The metamagnetic transition temperature T_m^flake is found to decrease in line with the decrease of thickness, while the ferromagnetic (FM) phase, the ordinary, and anomalous Hall effects (OHE and AHE) are independent on the thickness of the flake. Analysis of the data demonstrates that the AHE reflects the FM nature of Sr₄Ru₃O₁₀, and the decrease of thickness favors the Ru moments aligned in the ab-plane, which induces a decrease of the metamagnetic transition …

Notes On Contributions To The Science Of Rare Earth Element Enrichment In Coal And Coal Combustion Byproducts, James C. Hower, Evan J. Granite, David B. Mayfield, Ari S. Lewis, Robert B. Finkelman

Center for Applied Energy Research Faculty and Staff Publications

Coal and coal combustion byproducts can have significant concentrations of lanthanides (rare earth elements). Rare earths are vital in the production of modern electronics and optics, among other uses. Enrichment in coals may have been a function of a number of processes, with contributions from volcanic ash falls being among the most significant mechanisms. In this paper, we discuss some of the important coal-based deposits in China and the US and critique classification systems used to evaluate the relative value of the rare earth concentrations and the distribution of the elements within the coals and coal combustion byproducts.

X-Ray Absorption Spectroscopy Study Of The Effect Of Rh Doping In Sr2Iro4, C. H. Sohn, Deok-Yong Cho, C. -T. Kuo, L. J. Sandilands, Tongfei Qi, Gang Cao, T. W. Noh

Center for Advanced Materials Faculty Publications

We investigate the effect of Rh doping in Sr₂IrO₄ using X-ray absorption spectroscopy (XAS). We observed appearance of new electron-addition states with increasing Rh concentration (x in Sr₂Ir_1−xRh_xO₄) in accordance with the concept of hole doping. The intensity of the hole-induced state is however weak, suggesting weakness of charge transfer (CT) effect and Mott insulating ground states. Also, Ir J_eff = 1/2 upper Hubbard band shifts to lower energy as x increases up to x = 0.23. Combined with optical spectroscopy, these results suggest a hybridisation-related mechanism, in …

Large-Area Graphene-Based Nanofiltration Membranes By Shear Alignment Of Discotic Nematic Liquid Crystals Of Graphene Oxide, Abozar Akbari, Phillip Sheath, Samuel T. Martin, Dhanraj B. Shinde, Mahdokht Shaibani, Parama Chakraborty Banerjee, Rachel Tkacz, Dibakar Bhattacharyya, Mainak Majumder

Chemical and Materials Engineering Faculty Publications

Graphene-based membranes demonstrating ultrafast water transport, precise molecular sieving of gas and solvated molecules shows great promise as novel separation platforms; however, scale-up of these membranes to large-areas remains an unresolved problem. Here we demonstrate that the discotic nematic phase of graphene oxide (GO) can be shear aligned to form highly ordered, continuous, thin films of multi-layered GO on a support membrane by an industrially adaptable method to produce large-area membranes (13 × 14 cm²) in < 5 s. Pressure driven transport data demonstrate high retention (> 90%) for charged and uncharged organic probe molecules with a hydrated radius above 5 Å as well as modest (30–40%) retention of …

Biopolymeric Mucin And Synthetic Polymer Analogs: Their Structure, Function And Role In Biomedical Applications, Sundar Prasanth Authimoolam, Thomas D. Dziubla

Chemical and Materials Engineering Faculty Publications

Mucin networks are viscoelastic fibrillar aggregates formed through the complex self-association of biopolymeric glycoprotein chains. The networks form a lubricious, hydrated protective shield along epithelial regions within the human body. The critical role played by mucin networks in impacting the transport properties of biofunctional molecules (e.g., biogenic molecules, probes, nanoparticles), and its effect on bioavailability are well described in the literature. An alternate perspective is provided in this paper, presenting mucin’s complex network structure, and its interdependent functional characteristics in human physiology. We highlight the recent advances that were achieved through the use of mucin in diverse areas of bioengineering …

Graphene Oxide Quantum Dots Covalently Functionalized Pvdf Membrane With Significantly-Enhanced Bactericidal And Antibiofouling Performances, Zhiping Zeng, Dingshan Yu, Ziming He, Jing Liu, Fang-Xing Xiao, Yan Zhang, Rong Wang, Dibakar Bhattacharyya, Timothy Thatt Yang Tan

Chemical and Materials Engineering Faculty Publications

Covalent bonding of graphene oxide quantum dots (GOQDs) onto amino modified polyvinylidene fluoride (PVDF) membrane has generated a new type of nano-carbon functionalized membrane with significantly enhanced antibacterial and antibiofouling properties. A continuous filtration test using E. coli containing feedwater shows that the relative flux drop over GOQDs modified PVDF is 23%, which is significantly lower than those over pristine PVDF (86%) and GO-sheet modified PVDF (62%) after 10 h of filtration. The presence of GOQD coating layer effectively inactivates E. coli and S. aureus cells, and prevents the biofilm formation on the membrane surface, producing excellent antimicrobial activity and …

Strain Effects On The Work Function Of An Organic Semiconductor, Yanfei Wu, Annabel R. Chew, Geoffrey A. Rojas, Gjergji Sini, Greg Haugstad, Alex Belianinov, Sergei V. Kalinin, Hong Li, Chad Risko, Jean-Luc Brédas, Alberto Salleo, C. Daniel Frisbie

Chemistry Faculty Publications

Establishing fundamental relationships between strain and work function (WF) in organic semiconductors is important not only for understanding electrical properties of organic thin films, which are subject to both intrinsic and extrinsic strains, but also for developing flexible electronic devices. Here we investigate tensile and compressive strain effects on the WF of rubrene single crystals. Mechanical strain induced by thermal expansion mismatch between the substrate and rubrene is quantified by X-ray diffraction. The corresponding WF change is measured by scanning Kelvin probe microscopy. The WF of rubrene increases (decreases) significantly with in-plane tensile (compressive) strain, which agrees qualitatively with density …

Development Of Pvdf Membrane Nanocomposites Via Various Functionalization Approaches For Environmental Applications, Douglas M. Davenport, Minghui Gui, Lindell E. Ormsbee, Dibakar Bhattacharyya

Chemical and Materials Engineering Faculty Publications

Membranes are finding wide applications in various fields spanning biological, water, and energy areas. Synthesis of membranes to provide tunable flux, metal sorption, and catalysis has been done through pore functionalization of microfiltration (MF) type membranes with responsive behavior. This methodology provides an opportunity to improve synthetic membrane performance via polymer fabrication and surface modification. By optimizing the polymer coagulation conditions in phase inversion fabrication, spongy polyvinylidene fluoride (PVDF) membranes with high porosity and large internal pore volume were created in lab and full scale. This robust membrane shows a promising mechanical strength as well as high capacity for loading …

First-Principles Studies Of Structure-Property Relationships: Enabling Design Of Functional Materials, Qunfei Zhou

Theses and Dissertations--Chemical and Materials Engineering

First-principles calculations based on quantum mechanics have been proved to be powerful for accurately regenerating experimental results, uncovering underlying myths of experimental phenomena, and accelerating the design of innovative materials. This work has been motivated by the demand to design next-generation thermionic emitting cathodes and techniques to allow for synthesis of photo-responsive polymers on complex surfaces with controlled thickness and patterns. For Os-coated tungsten thermionic dispenser cathodes, we used first-principles methods to explore the bulk and surface properties of W-Os alloys in order to explain the previously observed experimental phenomena that thermionic emission varies significantly with W-Os alloy composition. Meanwhile, …

Cryogenic Processing Of Al 7050-T7451 Alloy For Improved Surface Integrity, Bo Huang

Theses and Dissertations--Mechanical Engineering

Al 7050-T7451 alloy with good combinations of strength, stress corrosion cracking resistance and toughness, is used broadly in the aerospace/aviation industry for fatigue-critical airframe structural components. However, it is also considered as a highly anisotropic alloy as the crack growth behavior along the short transverse direction is very different from the one in the long transverse direction, due to the inhomogeneous microstructure with the elongated grains distributed in the work material used in the sheet/plate applications. Further processes on these materials are needed to improve its mechanical and material properties and broaden its applications.

The material with ultra-fine or nano …

Bioactive Poly(Beta-Amino Ester) Biomaterials For Treatment Of Infection And Oxidative Stress, Andrew L. Lakes

Theses and Dissertations--Chemical and Materials Engineering

Polymers have deep roots as drug delivery tools, and are widely used in clinical to private settings. Currently, however, numerous traditional therapies exist which may be improved through use of polymeric biomaterials. Through our work with infectious and oxidative stress disease prevention and treatment, we aimed to develop application driven, enhanced therapies utilizing new classes of polymers synthesized in-house. Applying biodegradable poly(β-amino ester) (PBAE) polymers, covalent-addition of bioactive substrates to these PBAEs avoided certain pitfalls of free-loaded and non-degradable drug delivery systems. Further, through variation of polymer ingredients and conditions, we were able to tune degradation rates, release profiles, cellular …

Improving The Capacity, Durability And Stability Of Lithium-Ion Batteries By Interphase Engineering, Qinglin Zhang

Theses and Dissertations--Chemical and Materials Engineering

This dissertation is focus on the study of solid-electrolyte interphases (SEIs) on advanced lithium ion battery (LIB) anodes. The purposes of this dissertation are to a) develop a methodology to study the properties of SEIs; and b) provide guidelines for designing engineered SEIs. The general knowledge gained through this research will be beneficial for the entire battery research community.

Synthesis Of Titania Thin Films With Controlled Mesopore Orientation: Nanostructure For Energy Conversion And Storage, Suraj R. Nagpure

Theses and Dissertations--Chemical and Materials Engineering

This dissertation addresses the synthesis mechanism of mesoporous titania thin films with 2D Hexagonal Close Packed (HCP) cylindrical nanopores by an evaporation-induced self-assembly (EISA) method with Pluronic surfactants P123 and F127 as structure directing agents, and their applications in photovoltaics and lithium ion batteries. To provide orthogonal alignment of the pores, surface modification of substrates with crosslinked surfactant has been used to provide a chemically neutral surface. GISAXS studies show not only that aging at 4°C facilitates ordered mesostructure development, but also that aging at this temperature helps to provide orthogonal orientation of the cylindrical micelles which assemble into an …

Lnvestigation Of The Critical Role Of Polymeric Binders For Silicon Negative Electrodes In Lithium-Lon Batteries, Jiagang Xu

Theses and Dissertations--Chemical and Materials Engineering

Silicon is capable of delivering a high theoretical specific capacity of 3579 mAh g^-1, which is about 10 times higher than that of the state-of-the-art graphite-based negative electrodes for lithium-ion batteries (LIBs). However, the poor cycle life of silicon electrodes, caused by the large volumetric strain during cycling, limits the commercialization of silicon electrodes. As one of the essential components, the polymeric binder is critical to the performance and durability of lithium-ion batteries as it keeps the integrity of electrodes, maintains conductive path and must be stable in the electrolyte. The guideline for binder selection of silicon electrodes …

Electron Beam Induced Deposition Of Highly Conductive Copper Nanowires From Bulk Liquids, Amjad M. Syam

Theses and Dissertations--Electrical and Computer Engineering

Electron-beam induced deposition (EBID) is a position-controlled technique that can directly fabricate nanometer-sized structures in functional materials. In the standard process, a gaseous precursor delivers the desired substance to the substrate for deposition. However, the material purity from these precursors is typically poor, which often negatively affects the functional properties of the deposit. Recently, bulk liquid precursors have been investigated as promising reactants for high purity deposition without the need for post-processing. In this work, EBID from bulk liquids is shown to yield highly conductive nanowire deposits. Aqueous solutions containing copper sulfate (CuSO₄) and sulfuric acid (H_{2 …}

Evaluation Of Flocculation, Sedimentation, And Filtration For Dewatering Of Algal Biomass, Nicholas A. Rhea

Theses and Dissertations--Biosystems and Agricultural Engineering

Algae can be used as a feedstock for agricultural fertilizers, livestock/poultry feeds, anaerobic digestion, and biofuel production. Regardless of the end product, water removal is necessary and difficult to do cost effectively. For each product the requirements for moisture content (or solids content) vary, such that a desirable water removal strategy would need to be adaptable to varying levels of water removal. Flocculation, with sedimentation and drying was evaluated as a possible strategy for algae dewatering. Anionic and nonionic flocculants are known to be ineffective at flocculating algal culture, which was confirmed for this case by electro-osmotic flow testing of …

Underwater Explosion Energy Dissipation Near Waterborne Infrastructure, Paul R. Smith

Theses and Dissertations--Civil Engineering

Underwater explosions pose a significant threat to waterborne infrastructure though destructive pressure waves that can travel significant distances through the water. However, the use of bubble screens can attenuate the peak pressure and energy flux created by explosions to safe levels. This study investigates the prediction of pressure wave characteristics based on accumulated data, the damage potential of underwater explosions based on applied loads and effective material strength, and the bubble screen parameters required to prevent damage. The results were compiled to form a procedure for the design and implementation of a bubble screen the protection of waterborne infrastructure.

Three-Dimensional Microstructural Effects On Multi-Site Fatigue Crack Nucleation Behaviors Of High Strength Aluminum Alloys, Yan Jin

Theses and Dissertations--Chemical and Materials Engineering

An experimental method was further developed to quantify the anisotropy of multi-site fatigue crack initiation behaviors in high strength Al alloys by four-point bend fatigue testing under stress control. In this method, fatigue crack initiation sites (fatigue weak-links, FWLs) were measured on the sample surface at different cyclic stress levels. The FWL density in an alloy could be best described using a three-parameter Weibull function of stress, though other types of sigmoidal functions might also be used to quantify the relationship between FWL density and stress. The strength distribution of the FWLs was derived from the Weibull function determined by …

Three-Dimensional Microstructure-Based Models For Fatigue Crack Nucleation And Fatigue Crack Branching In High Strength Al Alloys, Lin Yang

Theses and Dissertations--Chemical and Materials Engineering

This study is concerned with using numerical three-dimensional microstructure-based models to quantify the multi-site fatigue crack initiation behaviors by simulating the effects of pores in a cast aluminum alloy, and to analyze the mechanism of fatigue crack branching in thick aluminum alloy plates. It has been recently recognized the three-dimensional effects of pores on fatigue crack initiation, which provide opportunity to quantitatively identify the fatigue weak-link density and strength distribution in aluminum alloy. The stress and strain fields around a micro-pore in an A713 aluminum alloy (an elasto-plastic media) under cyclic loading were quantified as a function of pore position …