Engineering Commons^™

Creating Micro- And Nanostructures On Tubular And Spherical Surfaces, O. Lima, L. Tan, A. Goel, Lmehrdad Negahban, Z. Li

Nebraska Center for Materials and Nanoscience: Faculty Publications

The authors developed a new technique to create micro- and nanometer scale structures on curved free-standing objects by combining embossing/imprinting lithography approaches with mechanical loadings on elastic films. Embossing/imprinting generates small structures and mechanical loading determines shape or geometry of the final object. As a result, a portion of the tubes with a radius between 0.5 and 3.5 mm and a portion of the spheres with a radius between 2.4 and 7.0 mm were fabricated with grating line features (period of 700 nm) and microlens array features (lens radius of 2.5 µm) atop, respectively. It was found that both static …

Fabrication Of Robust Superconducting Granular Aluminium/Palladium Bilayer Microbolometers With Sub-Nanosecond Response, Thomas E. Wilson

Physics Faculty Research

We provide a convenient recipe for fabricating reliable superconducting microbolometers as acoustic phonon detectors with sub-nanosecond response, using imagereversal optical lithography and dc-magnetron sputtering, and our recipe requires no chemical or plasma etching. Our approach solves the traditional problem for granular aluminium bolometers of unreliable (i.e., non-Ohmic) electrical contacts by sequentially sputtering the granular aluminium film and then a palladium capping layer. We use dc calibration data, the method of Danilchenko et al. [1], and direct nanosecond-pulsed photoexcitation to obtain the microbolometer’s characteristic current, thermal conductance, characteristic relaxation time, and heat capacity. We also demonstrate the use of the deconvolution …

Modelagem Da Vida De Fadiga E Do Acúmulo De Deformações Permanentes Em Pavimentos Asfálticos Por Meio De Um Modelo De Dano Contínuo, Victor Ferreira Teixeira, Flavio V. Souza, Jorge Barbosa Soares

Department of Mechanical and Materials Engineering: Faculty Publications

: It is known that the conditions of the Brazilian roadways have an enormous impact over the national economy. In face of this problem, there is a need for new methodologies for pavement analyses and design that can more accurately predict pavement distresses. Among the main methods currently used, one can find purely empirical methods and mechanistic-empirical methods which make use of the pavement structure response. The evolution of numerical methods such as the Finite Element Method (FEM) or the Boundary Element Method (BEM) has made the mechanistic-empirical methods more popular for pavement analysis applications. This work shows a mechanistic …

Study On Electrochemical Impedance Spectroscopy Of Carbon Steel Eroded In Methyldiethanolamine Solution, Dong-Ping Wei, Rong-Zong Hu, Dan-Mei Pan, Wei-Xiong Huang, Rui Dong

Journal of Electrochemistry

Corrosion behavior of carbon steel in methyldiethanolamine(MDEA) solution was investigated by Electrochemical Impedance Spectroscopy(EIS).The results were showed that the corrosion rate of carbon steel in solution containing dissolved oxygen is higher than that in solution removed of dissolved oxygen before cathodic activation.They were reversed after cathodic activation.The corrosion rate is increased at first and then decreased when the concentration of MDEA is increased in the blank solutions.In the simulated solutions containing quantities of!heat-stable salts(HSS),the corrosion rate is decreased monotonously with increase of the MDEA concentration.As anodic polarization potential is increased,the EIS of carbon steel in HSS simulated solution showed characteristics …

Preparation And Investigations On The Tio2nanotube Arrays For Cathodic Protection Of 316l Stainless Steel, Jing Li, Hong Yun, Chang-Jian Lin

Journal of Electrochemistry

A highly ordered TiO2nanotube layer was fabricated by potentiostatic anodization of pure titanium in fluorinated electrolyte solutions.The structure and composition of the as-prepared TiO2 nanotubes were characterized by SEM and XRD.The TiO2 nanotubes show a stronger absorption in the ultraviolet(UV) light range.The performances of photogenerated cathodic protection and the photoelectrochemical response for the TiO2 nanotube layers under illumination and dark conditions were evaluated through the electrochemical measurements.It is found that the open-circuit potentials of 316 SS coupled with the TiO2 nanotubes layers shift negatively under UV light irradiation(λ<380nm).It is indicated that the TiO2 nanotubes arrays are able to function effectively a photogenerated cathodic protection for metals under light illumination and keep the cathodic protection for a long time under dark conditions.

Determination Of Malathion Based On Carbon Nanotubes Modified Electrode Incorporating Acetylcholinesterase, Lu Zhang, Yao-Dong Zhang, Hong-Lan Qi

Journal of Electrochemistry

A biosensor for determination of organophosphorus pesticide based on the acetylcholinesterase and multi-wall carbon nanotubes modified electrode is fabricated.Under the optimal conditions,the chronoamperometric current at +0.70V(vs.SCE) increased linearly with the concentration of malathion in the range from 6.0×10-10 to 6.0×10-9 mol·L-1 with a detection limit of 1.0×10-10 mol·L-1.The recoveries of malathion in lake water is 97% to 105% determinated by this method.

Simulation Of Phonon Transport Across A Non-Polar Nanowire Junction Using An Atomistic Green's Function Method, W Zhang, N Mingo, Timothy Fisher

Birck and NCN Publications

Phonon transport across a non-polar nanowire situated between two semi-infinite contacts is simulated in this paper using the atomistic Green's function method. Abrupt geometric changes between the nanowire and bulk contacts are handled by self-energy matrices obtained from bare surface Green's functions. Transport properties such as phonon transmission functions and thermal conductances are calculated, and their dependencies on the interatomic potential, length, diameter, shape, and lattice orientation are investigated. The results reveal that the overall thermal conductance of the nanowire-bulk-contact structure increases with nanowire diameter while the normalized thermal conductance approaches an asymptotic value. Thermal conductance decreases significantly with increasing …

Growth-Temperature Optimization For Low Carrier-Density In0.75Ga0.25As-Based High Electron Mobility Transistors On Inp, Paul J. Simmonds, H. E. Beere, D. A. Ritchie, S. N. Holmes

Paul J. Simmonds

Two-dimensional electron gases (2DEGs) were formed in undoped In_0.75Al_0.25As / In_0.75Ga_0.25As / In_0.75Al_0.25As quantum wells. The optimal growth temperature for this structure is 410°C, with peak 2DEG electron mobility and density values of μ = 221000 cm²/V s and n = 1.36 × 10¹¹ cm⁻² at 1.5 K. This electron mobility is equal to the highest previously published for these undoped structures but with a factor of 2 reduction in n. This has been achieved through the use of a significantly thinner InAlAs …

Gold Nanorods Mediate Tumor Cell Death By Compromising Membrane Integrity, Ling Tong, Yan Zhao, Terry B. Huff, Matthew N. Hansen, Alexander Wei, Ji-Xin Cheng

Other Nanotechnology Publications

Folate-conjugated gold nanorods targeted to tumor cell surfaces produced severe membrane damage upon near-infrared irradiation. Photoinduced injury to the plasma membrane resulted in a rapid increase in intracellular calcium (shown in green) with subsequent disruption of the actin network, featured prominently by the formation of membrane blebs.

Quantum Dot Resonant Tunneling Diodes For Telecom Wavelength Single Photon Detection, H. W. Li, Paul J. Simmonds, H. E. Beere, B. E. Kardynał, D. A. Ritchie, A. J. Shields

Paul J. Simmonds

Single photon detection was realized at a telecom wavelength with quantum dot resonant tunneling diodes grown on an InP substrate. The structure contains a AlAs/In_0.53Ga_0.47As/AlAs quantum well with InAs quantum dots grown on the top AlAs barrier. The single photon detection efficiency of the device under 1310 nm illumination was measured to be about 0.35% ± 0.07% with a dark count rate of 1.58×10^-6 ns^-1. This corresponds to an internal efficiency of 6.3%.

The Syntheses And Electrochemical Performance Of Nano-Mno_2 For Supercapacitor, Jun Ma, Ming-Sen Zheng, Quan-Feng Dong

Journal of Electrochemistry

Nano-manganese dioxide were prepared by two different methods which are low temperature solid reaction and chemical deposition.The products were characterized by XRD,SEM,BET and constant current charge-discharge tests.The result shows that there is a close relationship between specific capacitance and BET surface areas.Meanwhile the specific capacitance was impacted little by the structure of the nano-manganese dioxides.However,the product performance of high rates,was influenced by structure,the higher rate can be obtained with the more perfect crystal structure.

Growth Mechanism And Morphology Of Electrodeposited Micro-Nanocrystalline Iron, Qiao-Xin Zhang, Jia-Ming Zhang, Li-Ning Yang

Journal of Electrochemistry

Effects of current density,reaction temperature,electrolyte concentration and surfactant on the electrochemical deposition of micro-nanocrystalline iron were studied.Morphologies and structures of the samples were characterized by SEM and XRD,the results showed that the electrodeposits is slice α-Fe under little current and the density,lower temperature and higher concentration,and the dentritic α-Fe is under opposite conditions,but the influence from surfactant is unconsicously.Moreover,the growth mechanism of the electrodeposits was also analysed here.

Pdms Regularly Superhydrophobic Surfaces Prepared By Icp Etching Silicon Model, Run-Xiang Zhang, Yu-Long Zhang, Hua-Shui Lin

Journal of Electrochemistry

A series of different dimensions regularly micropillar array hydrophobic Poly(dimethylsiloxane)(PDMS) surfaces were obtained by peeling off PDMS which was poured onto the silicon models.The silicon models were prepared by ICP etching technology.The results indicate that the water contact angle(WCA) was increased with the size and the height of the mocropillar,decreased with increasing the distance of the mocropillar when the height of the micropillar was relative small;if the height of the micropillar was relative big,WCA was decreased with increasing the size of micropillar,meanwhile,the distance of the micropillar was a complex factor to WCA,and the height of the micropillar have little influence.The …

Study On The Nano Diamond Stable Water Disperse System And Applying In Composite Chromium Plating, Lai-Xiang Zhang, Hong-Bo Xie, Xue-Kui Ma, Guo-Wu Zhao, En-Cheng Yu, Jia-Zhi Wang

Journal of Electrochemistry

The nano diamond stable water disperse system was studied.The low-bublles sulfonic anion sufcace active agent had been choosed out for this system.The affect of different physics agitation mothed on the water separate system stablity were conpared.The nano diamond stable water separate system had been applied to the composite chromium electroplating on this tests.The depositing speed,hardnees and wearing capacity of plating layer were tested.And the metallography structure of plating layer was charasterized by SEM.The test results and reaction princeple were discussed.

Fabrication And Charaterization Of Nitrogen-Doped Tio_2 Nanotube Array And Its Visible Light Activity, Hui-Fang Zhuang, Yue-Kun Lai, Jing Li, Lan Sun, Chang-Jian Lin

Journal of Electrochemistry

Nitrogen-doped TiO2 nanotube array was fabricated by an electrochemical anodic oxidation followed a wet process.XPS result indicates that the nitrogen atoms were doped into lattice of TiO2 nanotubes.The UV-Vis spectra show that the photoabsorption of N-doped TiO2 nanotube array film is enhanced in the visible light region.Compared with the TiO2 nanotube array film,the N-doped TiO2 nanotubes exhibite a higher photocatalytic activity which is evaluated by the decomposition rate of methyl orange using the tungsten-halogen lamp as light source.

Electrocatalytic Oxidation Of Methanol At The Nano Ni-B Amorphous Alloy Powdermicroelectrode, Yi-Xiong Zheng, Shi-Bing Yao, Shao-Min Zhou

Journal of Electrochemistry

Electrocatalytic oxidation of methanol at the nano Ni-B amorphous alloy powder-microelectrode in alkaline media was studied by using cyclic voltammetry.Compared to the highly preferred orientation(220) nickel electrode,The onset potential of methanol electrooxidation at the nano Ni-B microelectrode is negatively shifted about 0.04V,and the current density is increased approximately by 2 orders of magnitude.Thus,the nano Ni-B microelectrode has very strong electrocatalytic activity for the oxidation of methanol.The kinetic parameters were determined with the steady polarization curves.The results show that the rate constants for both the oxidation of Ni(Ⅱ) to Ni(Ⅲ) and the reduction of Ni(Ⅲ) to Ni(Ⅱ) at the nano Ni-B …

Size Effect In Polymer Nanofibers Under Tension, Xiangfa Wu, Yuris A. Dzenis

Nebraska Center for Materials and Nanoscience: Faculty Publications

This article studies the size effect on the elastic behavior of solid and hollow polymer nanofibers (e.g., electrospun nanofibers) subjected to uniaxial tension. A one-dimensional nonlinear elastic tension model is proposed that takes into account the coupling effect of fiber elastic deformation and surface tension. The fiber axial force-displacement and stress-strain relations are obtained in explicit forms. It is shown that, at nanoscale, fiber radius has appreciable effect on the elastic response of polymer nanofibers. With consideration of the fiber radial effect, it is shown that the actual contribution of surface energy of the solid polymer fibers to the axial …

Novel Method For Mechanical Characterization Of Polymeric Nanofibers, Mohammad Naraghi, Loannis Chasiotis, Harold Kahn, Yongkui Wen, Yuris A. Dzenis

Nebraska Center for Materials and Nanoscience: Faculty Publications

A novel method to perform nanoscale mechanical characterization of highly deformable nanofibers has been developed. A microelectromechanical system (MEMS) test platform with an on-chip leaf-spring load cell that was tuned with the aid of a focused ion beam was built for fiber gripping and force measurement and it was actuated with an external piezoelectric transducer. Submicron scale tensile tests were performed in ambient conditions under an optical microscope. Engineering stresses and strains were obtained directly from images of the MEMS platform, by extracting the relative rigid body displacements of the device components by digital image correlation. The accuracy in determining …

Quantum Dot Resonant Tunneling Diode For Telecommunication Wavelength Single Photon Detection, H. W. Li, B. E. Kardynał, P. See, A. J. Shields, P. Simmonds, H. E. Beere, D. A. Ritchie

Paul J. Simmonds

The authors present a quantum dot (QD) based single photon detector operating at a fiber optic telecommunication wavelength. The detector is based on an AlAs/In_0.53Ga_0.47As/AlAs double-barrier resonant tunneling diode containing a layer of self-assembled InAs QDs grown on an InP substrate. The device shows an internal efficiency of about 6.3% with a dark count rate of 1.58 × 10⁻⁶ ns⁻¹ for 1310 nm photons.

Measurement Of Poisson’S Ratio With Contact-Resonance Atomic Force Microscopy, D.C. Hurley, Joseph A. Turner

Nebraska Center for Materials and Nanoscience: Faculty Publications

We describe contact-resonance atomic force microscopy (AFM) methods to quantitatively measure Poisson’s ratio ν or shear modulus G at the same time as Young’s modulus E. In contact-resonance AFM, the frequencies of the cantilever’s resonant vibrations are measured while the tip is in contact with the sample. Simultaneous measurement of flexural and torsional vibrational modes enables E and ν to be determined separately. Analysis methods are presented to relate the contact-resonance frequencies to the tip-sample contact stiffness, which in turn determines the sample’s nanoscale elastic properties. Experimental results are presented for a glass specimen with fused silica used as …

Brillouin-Zone Unfolding Of Perfect Supercells Having Nonequivalent Primitive Cells Illustrated With A Si/Ge Tight-Binding Parameterization, Timothy B. Boykin, Neerav Kharche, Gerhard Klimeck

Birck and NCN Publications

Numerical calculations of nanostructure electronic properties are often based on a nonprimitive rectangular unit cell, because the rectangular geometry allows for both highly efficient algorithms and ease of debugging while having no drawback in calculating quantum dot energy levels or the one-dimensional energy bands of nanowires. Since general nanostructure programs can also handle superlattices, it is natural to apply them to these structures as well, but here problems arise due to the fact that the rectangular unit cell is generally not the primitive cell of the superlattice, so that the resulting E(k) relations must be unfolded to obtain the primitive- …

In Vivo Quantitation Of Rare Circulating Tumor Cells By Multiphoton Intravital Flow Cytometry, Wei He, Haifeng Wang, Lynn C. Hartmann, Ji-Xin Cheng, Phillip S. Low

Other Nanotechnology Publications

Quantitation of circulating tumor cells (CTCs) constitutes an emerging tool for the diagnosis and staging of cancer, assessment of response to therapy, and evaluation of residual disease after surgery. Unfortunately, no existing technology has the sensitivity to measure the low numbers of tumor cells (< 1 CTC per ml of whole blood) that characterize minimal levels of disease. We present a method, intravital flow cytometry, that noninvasively counts rare CTCs in vivo as they flow through the peripheral vasculature. The method involves i.v. injection of a tumor-specific fluorescent ligand followed by multiphoton fluorescence imaging of superficial blood vessels to quantitate the flowing CTCs. Studies in mice with metastatic tumors demonstrate that CTCs can be quantitated weeks before metastatic disease is detected by other means. Analysis of whole blood samples from cancer patients further establishes that human CTCs can be selectively labeled and quantitated when present at approximate to 2 CTCs per ml, opening opportunities for earlier assessment of metastatic disease.

Tailed Forisomes Of Canavalia Gladiata: A New Model To Study Ca2+-Driven Protein Contractility, Winfried Peters, Michael Knoblauch, Stephen Warmann, Reinhard Schnetter, Amy Shen, William Pickard

Winfried S. Peters

Effects Of Magnetostatic Coupling On Stripe Domain Structures In Magnetic Multilayers With Perpendicular Anisotropy, K. Janicka, John D. Burton, Evgeny Y. Tsymbal

Nebraska Center for Materials and Nanoscience: Faculty Publications

We investigate the effects of magnetostatic interlayer coupling on the formation of magnetic domains in exchange-coupled ferromagnetic films exhibiting perpendicular magnetic anisotropy. Using simple models for the stripe domain structures we investigate how the magnetostatic interlayer interaction affects the domain size. For antiferromagnetically exchange-coupled multilayers, we show that there is a domain overlap due to the magnetostatic interaction which exists only above a critical thickness and below a critical separation between the ferromagnetic films where it is scaled inversely proportional to the antiferromagnetic exchange coupling constant. We show that the magnetostatic coupling is responsible for the periodic “tiger tail” domain …

Physics Of Ultrathin-Body Silicon-On-Insulator Schottky-Barrier Field-Effect Transistors, Joachim Knoch, M Zhang, Joerg Appenzeller, S Mantl

Other Nanotechnology Publications

In this article we give an overview over the physical mechanisms involved in the electronic transport in ultrathin-body SOI Schottky-barrier MOSFETs. A strong impact of the SOI and gate oxide thickness on the transistor characteristics is found and explained using experimental as well as simulated data. We elaborate on the influence of scattering in the channel and show that for a significant barrier the on-state current is insensitive to scattering once the mean free path for scattering is larger than a characteristic length scale. In addition, recent efforts to lower the Schottky barrier at the source/drain channel interfaces are presented. …

Understanding Coulomb Effects In Nanoscale Schottky-Barrier-Fets, Klaus M. Indlekofer, Joachim Knoch, Joerg Appenzeller

Other Nanotechnology Publications

We employ a novel multiconfigurational self-consistent Green's function approach (MCSCG) for the simulation of nanoscale Schottky-barrier-field-effect transistors (SB-FETs). This approach allows the calculation of electronic transport with a seamless transition from the single-electron regime to room-temperature FET operation. The particular improvement of the MCSCG stems from a self-consistent division of the channel system into a small subsystem of resonantly trapped states for which a many-body Fock space approach becomes numerically feasible and the rest of the system which can be treated adequately on a conventional mean-field level. The Fock space description allows for the calculation of few-electron Coulomb charging effects …

Hydriding And Dehydriding Properties Of Mg/Mg_(1.8)La_(0.2)Ni Nanocomposites, Hong-Liang Sun, Yan-Yan Zhang, Hai-Chang Zhang, Hua-Bin Yang, Zuo-Xiang Zhou

Journal of Electrochemistry

Mg-x %Mg1.8La0.2Ni(x=10,20 and 30)nanocomposites have been synthesized by high-energy ball milling method.Results of the X-ray diffraction(XRD),transmission electron microscopy(TEM)and selected area electron diffraction(SAED)tests were showed that each composite had a nanocrystalline/amorphous structure,which was beneficial for the improvement of the hydriding and dehydriding properties of Mg.The hydrogen absorption temperature decreased and the hydrogen sorption kinetics were improved.Under the conditions of 423 K and the hydrogen pressure of 2.5MPa,each composite could reach the maximum hydriding capacity within 50 s.

Template Synthesis And Electrochemical Studies Of Ag_(Core)Au_(Shell) Nanowires, Li Ling, Ya-Xian Yuan, Min-Min Xu, Jian-Lin Yao, Ren-Ao Gu

Journal of Electrochemistry

Agcore Aushell nanowires with different thicknesses were prepared by combining template synthesis and chemical reduction method,and characterized by SEM and cyclic voltammetry(CV).The CV results revealed that the AgcoreAushell nanowires with pinhole were transferred to pinhole free structure after several potential scans.By using thiophenol(TP)and p-aminothiophenol(PATP)as probe,the surface enhanced Raman scattering(SERS)effect was investigated on the core-shell nanowires.The results indicated that AgcoreAushell nanowires could be served as a potential SERS substrate,and the difference in the spectral feature of PATP adsorbed onto Au and Ag nanowires enable us to diagnose the pinhole effect of core-shell nanowires by SERS.

Self Assemblying Kinetics Of Sodium Steareate At Castor Oil/Water Interface, Yong-Chun Zhu, Li-Na Tang, Hong-Guo Ji

Journal of Electrochemistry

The self assembly membrane(SAM)formation kinetics of sodium stearate at castor oil/water interface was studied by cyclic voltammetrry.At caster oil coated graphite-epoxy solid electrode surface,the SAM grows according to the Gaussian growth function with a rate constant of km=0.0006292(0.0000294)s-1,and maximum particle size at t0=3127s.The SAM of sodium stearate controls the growth and particle size of the deposited copper nano particles well,and forms a composite membrane of the SAM and copper nano particle.The growth mechanism of copper particle at oiled electrode or SAM modified oiled electrode is spherical growth,while it is the semi-spherical growth at bared graphite-epoxy solid phase electrode.Compared with castor …

Determination Of Ddopamine And Ascorbate On Gold Nanoparticle And 4,4-Bis (Methanethiol) Biphenyl (Mtp) Self-Assembled Monolayer Modified Gold Electrode, Hai-Yan Wang, Peng Liu, Ye Wang, Bao-Kang Jin

Journal of Electrochemistry

A new approach to construct an ampermetric biosensor was described.The 4,4-bis(methanethiol)biphenyl(MTP)is adsorbed on to a bare gold electrode to make self-assembled monolayers(MTP/Au SAMs).Then electrodeposited 2mg/mL HAuCl4 at-200 mV,NG/MTP/Au electrode was prepared.When a differential pulse voltammetric(DPV)technique was used,the peak separation between DA and AA is 155 mV.Hence,the selective determination of dopamine(DA)and ascorbate(AA)in the binary mixture system can be performed.Under the chosen conditions,the peak currents are correspondent linearly to the concentrations of DA and AA in the range of 5.0×10-7~1×10-4 mol·L-1 and 3.5×10-6~1.0×10-3mol·L-1,respectively.The correlation coefficients were 0.998.The detection limit were 1.5×10-7 mol·L-1 and 1.2×10-6 mol·L-1for DA and AA.