Nanoscience and Nanotechnology Commons^™

Image-Based Nanocrystallography With Online Database Support, Peter Moeck, Ján Zahornadsky, Boris Dusek

Physics Faculty Publications and Presentations

The crystallographic phase and morphology of many materials change with the crystal size so that new needs arise to determine the crystallography of nanocrystals. Direct space high-resolution phase-contrast transmission electron microscopy (HRTEM) and atomic resolution scanning TEM (STEM) when combined with tools for image-based nanocrystallography in two (2D) and three (3D) dimensions possess the capacity to meet these needs. After a concise discussion of lattice-fringe visibility spheres and maps, this paper discusses lattice-fringe fingerprinting in 2D and tilt protocol applications. On-line database developments at Portland State University (PSU) that support image-based nanocrystallography are also mentioned.

Efficient Inverted Polymer Solar Cells, G. Li, C.-W. Chu, V. Shrotriya, Jinsong Huang, Y. Yang

Department of Mechanical and Materials Engineering: Faculty Publications

We investigate the effect of interfacial buffer layers—vanadium oxide (V₂O₅) and cesium carbonate (Cs₂CO₃)—on the performance of polymer solar cells based on regioregular poly-(3-hexylthiophene) and [6,6]-phenyl C₆₀ butyric acid methyl ester blend. The polarity of solar cells can be controlled by the relative positions of these two interfacial layers. Efficient inverted polymer solar cells were fabricated with the structure of indium tin oxide (ITO)/Cs₂CO₃/polymer blend/vanadium oxide (V₂O₅)/aluminum (Al). Short-circuit current of 8.42 mA/cm2, open-circuit voltage of 0.56 V, and power conversion efficiency of …

Improving The Power Efficiency Of White Light-Emitting Diode By Doping Electron Transport Material, Jinsong Huang, Wei-Jen Hou, Juo-Hao Li, Gang Li, Yang Yang

Department of Mechanical and Materials Engineering: Faculty Publications

Highly efficient white light emission was realized via the partial energy transfer from blue host polyfluorene (PF) to orange light emission dopant rubrene. A more balanced charge transport was achieved by adding an electron transport material, 2-(4-biphenylyl)-5-(4-tertbutylphenyl)-1,3,4-oxadiazole (PBD), into the PF-rubrene system to enhance the electron transportation. Efficiency improvement by as much as a factor of 2 has been observed through the addition of PBD. These devices can easily reach high luminance at low driving voltages, thus achieving high power efficiency at high luminance (14.8, 13.5, and 12.0 lm/W at the luminances of 1000, 2000, and 4000 cd/m², …

Piezoelectromagnetic Waves In A Ceramic Plate Between Two Ceramic Half-Spaces, S. N. Jiang, Q. Jiang, X. F. Li, S. H. Guo, H. G. Zhou, J. S. Chang

Department of Mechanical and Materials Engineering: Faculty Publications

We analyze the propagation of piezoelectromagnetic waves guided by a plate of polarized ceramics between two ceramic half-spaces. An exact dispersion relation is obtained, which reduces to a few known elastic, electromagnetic, and quasistatic piezoelectric wave solutions in the literature as special cases. Numerical solutions to the equation that determines the dispersion relation show the existence of guided waves. The results are useful for acoustic wave and microwave devices.

Conduction-Band Electron Effective Mass In Zn0.87Mn0.13Se Measured By Terahertz And Far-Infrared Magnetooptic Ellipsometry, Tino Hofmann, U. Schade, K.C. Agarwal, B. Daniel, C. Klingshirn, M. Hetterich, C.M. Herzinger, Mathias Schubert

Nebraska Center for Materials and Nanoscience: Faculty Publications

We determine the electron effective mass parameter m^*=0.086±0.004 m₀ of thin-film n-type low-chlorine-doped Zn_0.87Mn_0.13Se with free-charge-carrier concentration N=4.5x10¹⁷ cm^-3 and optical mobility ) =300±20 cm² / (V s) using magneto-optic generalized ellipsometry in the terahertz and far-infrared spectral domain for wave numbers from ω =30–650 cm^-1. The room-temperature measurements were carried out with magnetic fields up to 3 T. We employ synchrotron and black-body radiation sources for the terahertz and far-infrared spectral regions, respectively. Comparison with previous experimental results from samples with considerably higher free electron …

Corrosion Barrier Development For Lbe Corrosion Resistance: Quarterly Report (April 2006), Biswajit Das

Transmutation Sciences Materials (TRP)

As reported in the last quarterly report, synthesis of Cr nanowires was found to be problematic in terms of uniform coverage. Hence Ni was identified as the alternative metal to form the nanowires. The purpose of the metal nanowires is to provide structural integrity to the nanoporous alumina, as well as a second defense mechanism against corrosion by oxidizing in case the top alumina layer is compromised. Nickel was selected due to its established electrochemical synthesis procedure. While Ni can provide very good structural integrity to the porous alumina, one potential problem is its higher dissolution rate in LBE. However, …

Development Of Nanostructure Based Corrosion-Barrier Coatings On Steel For Transmutation Applications, Biswajit Das

Transmutation Sciences Materials (TRP)

Advanced transmutation systems require structural materials that are able to withstand high neutron fluxes, high thermal cycling, and high resistance to chemical corrosion. The current candidate materials for such structures are ferritic and ferritic-martensitic steels due to their strong resistance to swelling, good microstructural stability under irradiation, and the retention of adequate ductility at typical reactor operating temperatures.

In parallel, lead bismuth eutectic (LBE) has emerged as a potential spallation target material for efficient production of neutrons, as well as a coolant in the accelerator system. While LBE has excellent properties as a nuclear coolant, it is also highly corrosive …

Lattice Fringe Fingerprinting In Two Dimensions With Database Support, Peter Moeck, B. Seipel, R. Bjorge, P. Fraundorf

Physics Faculty Publications and Presentations

A brief introduction to lattice fringe fingerprinting in two dimensions (2D) with database support is given. The method is employed for the identification of the crystal phase of a small ensemble of nanocrystals. The enhanced viability of this method in aberration-corrected transmission electron microscopes (TEMs) and scanning TEMs (STEMs) is also illustrated.

Simulation Of Phonon-Assisted Band-To Band Tunneling In Carbon Nanotube Field-Effect Transistors, Siyuranga O. Koswatta, Mark S. Lundstrom, M. P. Anantram, Dmitri E. Nikonov

Other Nanotechnology Publications

Electronic transport in a carbon nanotube metal-oxide-semiconductor field effect transistor (MOSFET) is simulated using the nonequilibrium Green’s functions method with the account of electron-phonon scattering. For MOSFETs, ambipolar conduction is explained via phonon-assisted band-to-band (Landau–Zener) tunneling. In comparison to the ballistic case, we show that the phonon scattering shifts the onset of ambipolar conduction to more positive gate voltage (thereby increasing the off current). It is found that the subthreshold swing in ambipolar conduction can be made as steep as 40 mV/decade despite the effect of phonon scattering.

An Investigation On Poly(Vinyl Chloride-Co-Isobutyl Vinyl Ether) Coatings Modified By Rutile Nano-Tio2 Pastes, Xiang Bin, Sheng-Tao Zhang, Yan Li, Bao-Rong Hou

Journal of Electrochemistry

The anti-corrosion coating of Poly(Vinyl Chloride-Co-Isobutyl Vinyl Ether) (PVCCIVE) was modified by rutile nano-TiO₂. The influence of nano-TiO₂ pastes on the coating's corrosion resistance was investigated through electrochemistry impedance spectroscopy (EIS). The results show that the addition of nano-TiO₂ pastes does not have obvious effect on the coating's performance of adhesion, flexility, impact resistance, but improves the coating's UV resistance and the gloss.Meanwhile,with the proper addition of rutile nano-TiO₂ pastes, the anti-corrosion behavior of the coating was advanced.

The Electrocatalystic Investigation Of 3,4-Dihydroxybenzoic Acid On The Modified Multiply Wall Carbon Nanotubes, Ming-Qi Li, Duo-Chang Cai, Xiao-Ying He

Journal of Electrochemistry

The electrochemical behavior of 3,4-Dihydroxybenzoic acid(DHBA) on modified multiply wall carbon nanotubes electrode was investigated by cyclic voltammetry(CV) and square wave voltammetry(SWV). Results show that in 0.1 mol/L HCl solutions the modified carbon nanotube electrode has an obvious electrocatalytic effect on the oxidation and deoxidization of DHBA. The oxidation current of DHBA is linear to it's concentration in the range of 4.0×10^-6～1.0×10^-4 mol/L and 2.0×10^-4～8.0×10^-4 1mol/L with correlation coefficient of 0.9995 and 0.9992. The detection limit is 1.0×10^-6 mol/L.

In Vitro And In Vivo Two-Photon Luminescence Imaging Of Single Gold Nanorods, Haifeng Weng, Terry B. Huff, Daniel A. Zweifel, Wei He, Philip S. Low, Alexander Wei, Ji-Xin Cheng

Other Nanotechnology Publications

Gold nanorods excited at 830 nm on a far-field laser-scanning microscope produced strong two-photon luminescence (TPL) intensities, with a cos(4) dependence on the incident polarization. The TPL excitation spectrum can be superimposed onto the longitudinal plasmon band, indicating a plasmon-enhanced two-photon absorption cross section. The TPL signal from a single nanorod is 58 times that of the two-photon fluorescence signal from a single rhodamine molecule. The application of gold nanorods as TPL imaging agents is demonstrated by in vivo imaging of single nanorods flowing in mouse ear blood vessels.

Progress Towards Terahertz Acoustic Phonon Generation In Doping Superlattices, Thomas E. Wilson

Physics Faculty Research

Progress is described in experiments to generate coherent terahertz acoustic phonons in silicon doping superlattices by the resonant absorption of nanosecond-pulsed far-infrared laser radiation. Future experiments are proposed that would use the superlattice as a transducer in a terahertz cryogenic acoustic reflection microscope with sub-nanometer resolution.

Self-Assembly Of Nanoparticles On Live Bacterium: An Avenue To Fabricate Electronic Devices, Vikas Berry, Ravi F. Saraf

Papers in Nanotechnology

Recently, hybrid structures of microorganisms with inorganic nanoscale moieties have received great interest due to their potential in fabricating electronic systems. Electronic properties of metal nanoparticles, due to single electron transport of current[1], make them ideal material for nanodevices. Concomitantly, the nanostructure of microorganisms such as bacteria[2], viruses[3;4] and yeast[5] are attractive scaffolds for nanoparticle templating due to surface charge and biological affinities for specific molecules [2-7]. However, the key challenges in building hybrid devices are patterning nanostructures without destroying the biological construct of the microorganism and achieving active integration of biological response to the electrical transport in nanoparticle device. …

Surface And Sructure Investigations Of Membrane Electrode Assembly In Dmfc Lifetime Testing, Xuan Cheng, Cheng Peng, Meng-Di You, Jing Liu, Ying Zhang

Journal of Electrochemistry

The lifetime and performance of a direct methanol fuel cell (DMFC) were investigatedto understand the correlation between thestructure of catalysts/membrane and cell performanceversus time. The cell polarization and performance curves were obtained during the DMFC operation with the time. The catalysts and Nafion membrane of the membrane electrode assembly (MEA) from the lifetime test were comprehensively examined by XRD, HRTEM, FTIR and Raman spectroscope techniques. The results revealed that there was significant performance degradation during the first 200 hours operation; while the degradation was slowing down between 200 and 704 hours operation. The degradation became worse after 1002 h operation. …

The Research Of Nano-Sized Nio Anode Materials For Lithium Ion Batteries, Jun-Mei Yan, Jing Zhang, Yong Yang

Journal of Electrochemistry

The nano-sized NiO materials were synthesized by solid phase method and sol-gel method. The synthesis conditions were optimized by DSC and TG techniques. The sol-gel method was optimized by changing the solvent and regulating the solution's pH for preparing NiO material. The structure and morphology of the materials were also characterized by means of XRD and TEM techniques, and the electrochemical performances of the materials were studied by the galvanostatically charge and discharge experiments.

Surface-Enhanced Raman Spectra Of Cytosine Adsorbed On A Roughened Gold Electrode, Yuan-Fei Wu, Jian-Feng Li, De-Yin Wu, Bin Ren, Zhong-Qun Tian

Journal of Electrochemistry

Cytosine adsorbed on a roughened gold electrode has been investigated by using electrochemical cyclic voltammetry and surface-enhanced Raman spectroscopy (SERS). The results indicate that cytosine was adsorbed on the Au electrode in a perpendicular orientation via the N3 position. As the maximum enhancement of ring breathing mode appears at negative potentials compared with other modes, both the electromagnetic enhancement and the charge transfer mechanism were considered to contribute to the SERS intensity. The binding interaction between cytosine and the gold electrode was weakened when the potential was negatively moved. The result also indicates that the SERS technique can be used …

Investigation, On The Accelerated Dissolution Of Metal Induced By Afm Tip Scratching And Suppressed By Inhibitors, Jun-E Qu, Xing-Peng Guo

Journal of Electrochemistry

The accelerated dissolution behavior of Cu-Ni alloy induced by AFM tip scratching and the inhibition effect of corrosion inhibitors were investigated. The results showedthat, with a tip loading of 750nN, continuous scan for 30 min in a contact mode on 4×4 μm² of copper-nickel alloy in 1.5mol/L NaCl and 0.01mol/L HCl could enhance the dissolution of the sample and produced pits on the scratched area. Adding inorganic inhibitors, sodium chromateand organic inhibitor dodecylamine, to the solution suppressed the dissolution of copper-nickel alloyinduced by tip scratching, respectively, by improving the surface passivationperformance of metal surface and forming adsorption films on …

Electrocatalytic Oxidation And Degration Of Active Red X-3b By Nanotubes Catalytic Electrodes, Yi Wen, Jian-Hui Fang, Wei-Min Cao, Li-Yi Shi

Journal of Electrochemistry

The catalytic splitting decomposition of carbon nanotubes isprocessed by dispersing with dilute nitric acid and thermal oxidation. Then well-proportionedphenolic resin is mixed in the carbon nanotubes. Then, the carbon nanotubesare made into electrodes by hot-press molding after the process of milling with high speed. The surface of the carbon nanotubes electrodes is analyzed by SEM. Active red X-3B simulated waster water is disposed by carbon nanotubes catalyticelectrode (anode) and stainless steel(cathode). The influencing factors of degradation by current density, concentrationof electrolyte, systemtemperature and pH are investigated. The experimental results indicated that acidiccondition is propitious tothe degradationreaction of organicdyestuff and wastewater …

The Application Of Astm C1202-93 On Evaluating The Performance Of Anti-Corrosion Of Concrete, Yuan-Chen Yuan, Tsung-Yueh Tu, Chao-Lung Hwang

Journal of Electrochemistry

The test of chloride ion penetration based on the standards of ASTM C1202-93 is applied to evaluate the anti-corrosion performance of concrete in this research. Concrete specimens were produced according to ACI 318-89 mixture proportioning design and the Desenfied Mixture Design Algorithm (DMDA) and were measured the 6-hour coulombs at the age of 91 days. Results show that w/b is not the factor influencing chloride penetration of ACI concrete, as the ion penetration of ACI specimens is all higher than 2 000 Coulombs and can even be poorer than 10 000 Coulombs. With a proper amount of pozzolanic material, the …

Cyclic Voltammetry And Surface Enhanced Raman Spectroscopy Of Dissociative Adsorption Of Ethanol On Pt-Ru Electrodes, Bin Zhang, Hai-Hui Zhou, Zu-Biao Wen, Qi-Ling Zhong, Peng Huang, Xiong-Yuan Yang, Bin Ren, Tian

Journal of Electrochemistry

The behaviors of dissociative adsorption of ethanol on roughened platinum-ruthenium electrode with high activity of SERS were studied by using cyclic voltammetry and in-situ surface enhanced Raman spectroscopy, surface enhanced Raman spectra of dissociative adsorption of ethanol on Pt electrode in acid was obtained for the first time. It is shown that the Pt-Ru could lower the over-potential of CO oxidation when compared to Pt electrode. The results show that the ethanol in acid medium can be self-dissociated at Pt-Ru electrode to produce CO, which discourage the further oxidation of ethanol, some information of Pt-C and Pt-C-Pt stretching vibration from …

Evolutionary Algorithm For The Placement Of Fluid Power Valves On A Valve Stand, Trichy M. Kethara Pasupathy, Ravi Teja Seethamraju, Robert G. Wilhelm

Department of Mechanical and Materials Engineering: Faculty Publications

The choice of placement of fluid power valves on a valve stand and routing by pipes has an impact on operational costs. Choosing the right placement that provides optimum routing configuration or determining the optimum routing for a chosen placement are both computationally hard problems. An evolutionary algorithm (EA), to minimize operational costs while optimizing placement and routing of valves, is developed here. The best practices in the industry are abstracted and implemented in the EA. In this paper, the algorithm and its performance for examples with varying complexities are presented. Our results meet or exceed experienced designers’ solutions.

Magnetization Reversal In Particulate L10 Nanostructures, Jian Zhou, Ralph Skomski, Kory D. Sorge, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

Magnetization processes in particulate L1₀ FePt nanostructures are investigated by model calculations and numerical simulations. The systems considered include anisotropic nanograins embedded in non-magnetic matrix; randomly oriented nanoclusters embedded in a C matrix, and nanocomposites of FePt particles in a semi-hard matrix. The reversal mechanisms depend on both intra- and intergranular features. Quasi-coherent rotation dominates the reversal in weakly-coupled granular magnets, but interface imperfections yield a disproportionately strong coercivity reduction. Strong intergranular exchange leads to a transition to a discrete pinning regime, which is accompanied by a coercivity maximum.

Phase Transformations And Thermodynamic Properties Of Nanocrystalline Fept Powders , J. Lyubina, O. Gutfleisch, Ralph Skomski, K.-H. Müller, L. Schultz

Nebraska Center for Materials and Nanoscience: Faculty Publications

The solid state reactions and structural evolution in nanocrystalline FePt powders during mechanical ball milling at 77 K and subsequent annealing have been investigated. Above 310 °C the formation of L1₀ FePt is observed. As the milling time increases, the enthalpy evolved during the transformations is reduced, whereas the corresponding activation energy increases. For accelerating the ordering process a fine lamellar structure of Fe and Pt is favourable.

Atomic And Micromagnetic Aspects Of L10 Magnetism, Ralph Skomski, Arti Kashyap, Jian Zhou

Nebraska Center for Materials and Nanoscience: Faculty Publications

Atomic and continuum effects in L1₀ magnets are investigated. Emphasis is on the competition between ferromagnetism, antiferromagnetism, and noncollinear order in both perfect and imperfect structures, and on the temperature dependence of the magnetic anisotropy. The applicability of micromagnetic and atomistic approaches depends on the length scales involved, but there is a broad range of phenomena where both can be used.

Theoretical Investigation Of Surface Roughness Scattering In Silicon Nanowire Transistors, Jing Wang, Eric Polizzi, Avik Ghosh, Supriyo Datta, Mark Lundstrom

Other Nanotechnology Publications

Using a full three-dimensional (3D), quantum transport simulator, we theoretically investigate the effects of surface roughness scattering (SRS) on the device characteristics of Si nanowire transistors (SNWTs). The microscopic structure of the Si/SiO2 interface roughness is directly treated by using a 3D finite element technique. The results show that (1) SRS reduces the electron density of states in the channel, which increases the SNWT threshold voltage, and (2) the SRS in SNWTs becomes less effective when fewer propagating modes are occupied, which implies that SRS is less important in small-diameter SNWTs with few modes conducting than in planar metal-oxide-semiconductor field-effect-transistors …

Effective Electromechanical Moduli Of Ferroelectric Ceramics With Fiber Textures, Y.C. Zhou, J. Liu, Jiangyu Li

Nebraska Center for Materials and Nanoscience: Faculty Publications

In this letter, we report the predictions on the effective piezoelectric coefficients and electromechanical coupling factors of ferroelectric ceramics BaTiO ₃ and Pb(Mg _1/3Nb _2/3)O ₃–PbTiO ₃ (PMN-PT) with various fiber textures, including [001], [011], and [111], using a two-scale micromechanical model that accounts for microstructural phenomena at both domain and grain levels. It was observed that for BaTiO ₃ the [011] texture is optimal with highest d ₃₁ and d ₃₃, while for PMN-PT [001] texture is optimal despite the fact that [011]-oriented single-crystalline PMN-PT has higher d ₃₂ than that of [001]-oriented PMN-PT single …

Jecp/Holz — An Interactive Computer Program For Simulation Of Holz Patterns, Xingzhong Li

Nebraska Center for Materials and Nanoscience: Faculty Publications

In the present work, an interactive computer program for simulation of the HOLZ line patterns, JECP/HOLZ, is reported. A feature of this program is the integration of the simulation of the HOLZ reflections and the HOLZ (curved and straight) lines, which is interactive with respect to changes of the lattice parameter, the accelerator voltage, the zone axis, and the beam tilt. The program can be used as a teaching aid for students as well as a tool for scientists working on electron diffraction experiments.

Using Electrodeposition To Fabricate Mould For Polymer Microfluidic Chip, Yi Luo, De-Nan Chu, Zhi-Feng Lou, Chong Liu, Li-Ding Wang

Journal of Electrochemistry

Many researches have been focused on polymer microfluidic chip in recent years and the mould plays an important role in its fabrication process. Using electrodepositingmethod to fabricate a metal mould for polymer microfluidic chip has been presented in this paper. An ultra-thick photoresist SU-8 was coated on a pretreated metal plate, after photolithography, nickel was electrodeposited in the patterned SU-8, then was removed the SU-8 to obtain a final metal mould. This methodreduces workload of electrodeposit largely. Applying counter current before deposit, adding additive to solution and vacuum anneal after demould have been used to improve the binding force between …

Preparation, Characterization And Electrochemical Properties Of Nano Tio2-Cnt-Pt On Ti Substrate Complex Electrode, Dao-Bao Chu, De-Xiang Feng, Jin-Hua Zhang, Xiao-Hua Li

Journal of Electrochemistry

The nanoTiO₂-CNT-Pt on Ti substrate complex electrodes were prepared from precursor of (Ti(OEt)₄) directly hydrolyzed and by cyclic voltammograms electroplating method . The XRD and SEM results showed that the nano TiO₂ (anatase) particle sizes ranged 5~10 nm and the Pt nanoparticle (average size 9nm) dispersed uniformly on nanoTiO₂-CNT film surface. The electrocatalytic activity of Ti/nanoTiO₂-CNT-Pt electrode was investigated by cyclic voltammetry and chronopotentiogram. The results indicated that the Ti/nanoTiO₂-CNT-Pt electrode exhibited very high electrocatalytic activity and stability for the electro-oxidation of methanol at room temperature. When Pt loading …