Nanoscience and Nanotechnology | Open Access Articles

Study Of Electrochemical Properties Of Ni(Oh)2/Niooh With Spectroscopic Ellipsometry, Shengtao Zhang, Zongqing Huang

Journal of Electrochemistry

Electrochemical reactions of Ni(OH)₂ /NiOOH system were studied by using in-situ spectroscopic ellipsometry and the conventional electrochemical metheds. By fitting data from ellipsometric measurements, a transformation medel of the surface film was obtained for cathedic and anodic processes. The results indicated that the transformation medel after cobalt implantation almost remained the same as that before cobalt implantation, but the electrochemical properties were affected obviously by implantation of cobalt.

Go to article

The Electrode Process Of Y(Ⅲ) On Copper Electrode And Its Surface Metallizing, Chungen Zhou, Shuzhen Duan

Journal of Electrochemistry

The reduction of yttrium ion on copper electrode in NaCl-KCl-YCl₃ molten saltshas been investigated. The results indicate that the formation of intermetallic compounds is occuredbefore the metallic yttrium to be formed. The formation of intermetallic compounds is controlled bythe process of which yttrium atoms are diffusing into copper electrode. The kinetic characters todiffusion of yttrium atoms were also discussed.

Go to article

Characterization Of Piezoceramic Crosses With Large Range Scanning Capability And Applications For Low Temperature Scanning Tunneling Microscopy, J. A. Helfrich, Shireen Adenwalla, J. B. Ketterson, G. A. Zhitomirsky

Shireen Adenwalla Papers

We have developed a large amplitude piezoceramic scanner which should have numerous applications. Scanning tunneling microscopy (STM) and other scanning probe microscopies predominantly use piezoceramics for the scanning elements. Similarly adaptive optics, high resolution lithography, and micromanipulators are other examples of research which regularly utilize piezoceramic scanners. We present a new geometry for a piezoceramic scanner which allows for both high resolution (~nanometers) and large amplitude (~400 µm) displacements. The cross-shaped geometry makes it possible to produce extremely long pieces with very high tolerances. We have shown its effectiveness by using it as the major component of a low temperature …

Go to article

Nmr And Nqr Study Of The Electronic And Structural Properties Of Al-Cu-Fe And Al-Cu-Ru Quasicrystals, A. Shastri, F. Borsa, D.R. Torgeson, Jeffrey E. Shield, A.I. Goldman

Nebraska Center for Materials and Nanoscience: Faculty Publications

²⁷ Al and ^63.65Cu NMR measurements are reported for powder samples of stable Al-Cu-Fe and Al-Cu-Ru icosahedral quasicrystals and their crystalline approximants, and for an Al-Pd-Mn singlegrain quasicrystal. Furthermore, ²⁷Al NQR spectra at 4.2 K have been observed in the Al-Cu-Fe and Al-Cu-Ru samples. From the quadrupole-perturbed NMR spectra at different magnetic fields, and from the zero-field NQR spectra, a wide distribution of local electric-field gradient (EFG) tensor components and principal-axis-system orientations was found at the Al site. A model EFG calculation based on a 1/1 Al-Cu-Fe approximant was successful in explaining the observed NQR spectra. The average …

Go to article

Resonant Tunneling Through Quantum Dot Arrays, Guanlong Chen, Gerhard Klimeck, Supriyo Datta, Guanhua Chen, William A. Goddard Iii

Birck and NCN Publications

We apply the Hubbard Hamiltonian to describe quantum-dot arrays weakly coupled to two contacts. Exact diagonalization is used to calculate the eigenstates of the arrays containing up to six dots and the linear-response conductance is then calculated as a function of the Fermi energy. In the atomic limit the conductance peaks form two distinct groups separated by the intradot Coulomb repulsion, while in the band limit the peaks occur in pairs. The crossover is studied. A finite interdot repulsion is found to cause interesting rearrangements in the conductance spectrum.

Go to article

Conductance Spectroscopy In Coupled Quantum Dots, Gerhard Klimeck, Guanlong Chen, Supriyo Datta

Birck and NCN Publications

We investigate the linear-response conductance through a pair of coupled quantum dots. The conductance spectrum under ideal conditions is shown to consist of two sets of twin peaks whose locations and amplitudes are determined by the interdot coupling and the intradot charging. We will show that the qualitative features of the spectrum survive against experimental nonidealities such as (1) detuning of the individual dots, (2) interdot charging, (3) inelastic scattering, and (4) multiple lateral states. The effect of higher lateral states depends strongly on the nature of the interaction potential, screening lengths, and exchange terms, but the lowest set of …

Go to article

Rate Equations For The Phonon Peak In Resonant-Tunneling Structures, Roger Lake, Gerhard Klimeck, J. P. Anantram, Supriyo Datta

Birck and NCN Publications

The ratio of the phonon peak current to the main peak current in double-barrier resonant-tunneling structures is significantly enhanced by barrier asymmetry. Previously, using the Keldysh formalism, we derived analytical expressions, valid in the zero-temperature, high-bias regime, which explained this eftect. We now provide analytical expressions valid for finite temperature and bias obtained from (i) an intuitive derivation using a rate equation approach and (ii) a more general derivation using the Keldysh formalism. The results of the two difFerent approaches are shown to be essentially identical for the ex- perimental device parameters. The finite temperature expressions shed light on the …

Go to article

Rate Equations From The Keldysh Formalism Applied To The Phonon Peak In Resonant-Tunneling Diodes, Roger Lake, Gerhard Klimeck, Supriyo Datta

Birck and NCN Publications

Starting from the Keldysh formalism, general analytical expressions are derived for the current and the occupation of the well in the presence of inelastic scattering, both at the main peak and at the pho- non peak. These expressions are then evaluated from a continuous coordinate representation of a double-barrier potential profile and also from a tight-binding model of a weakly coupled central site. The resulting expressions are similar, and the analytical expressions derived from the continuous coordi- nate representation compare well with the results obtained from numerical simulations. The analytical expressions and the numerical results show that unlike the main …

Go to article

Icosahedral Phase Stabilities In Al-Cu-Ru Alloys, Jeffrey E. Shield, C. Hoppe, R.W. Mccallum, A.I. Goldman, K.F. Kelton, P.C. Gibbons

Nebraska Center for Materials and Nanoscience: Faculty Publications

By examining a wide region of the Al-Cu-Ru phase diagram, a thorough analysis of the compositional and thermal stability of the icosahedral phase has been completed. The primary solidification product of rapid solidification was a topologically and chemically disordered icosahedral phase with an extensive compositional region. Crystallization through exothermic events of the as-solidified materials produced crystalline phases, without the formation of the face-centered-icosahedral (FCI) phase. However, the FCI phase does form at higher temperatures through an endothermic reaction, indicating that it is a stable phase of the system, but only at elevated temperatures. Of the alloys studied, the FCI phase …

Go to article

Laser Bandwidth-Induced Fluctuations In The Intensity Transmitted By A Fabry-Perot Interferometer, Gerhard Klimeck, Daniel Elliott, M. Hamilton

Birck and NCN Publications

We have measured the power spectrum of the intensity Auctuations of light transmitted by a Fabry- Perot interferometer when the input field is the real Gaussian field. The real Gaussian field is a field characterized by real, random (Gaussian) amplitude Auctuations. The bandwidth of the real Gaussian field was varied, taking on values less than that of the interferometer, as well as greater. Comparisons of the measured spectra with calculated spectra are quite satisfactory. Of special interest is a feature in the spectra centered at the laser-interferometer detuning frequency.

Go to article

Diffraction Studies On Ni-Co And Ni-Cr Alloy Thin Films, A. R. Sethuraman, R. J. De Angelis, P. J. Reucroft

Nebraska Center for Materials and Nanoscience: Faculty Publications

Alloy films of Ni-Co and Ni-Cr of compositional ratios 1:1, 1:3, and 3:1 deposited by vapor deposition were studied by Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). Results of TEM analysis on the Ni-Co alloy films indicated that the films were face-centered cubic (fee) in structure. XRD results confirmed the TEM observations. TEM analysis of Ni-Cr alloy films showed that the films were bodycentered cubic (bec) in structure. With increase in the Cr content more than 25%, the material contained a higher fraction of an amorphous phase. XRD studies provide limited information owing to the quasi-amorphous structure of the …

Go to article

Automating Tolerance Synthesis: A Framework And Tools, Stephen C.-Y. Lu, Robert G. Wilhelm

Department of Mechanical and Materials Engineering: Faculty Publications

This paper describes CASCADE-T—a new approach to tolerance synthesis that uses a complete representation of the conditional tolerance relations that exist between features of a part under design. Conditional tolerances are automatically determined from functional requirements and shape information. Tolerance primitives based on the virtual boundary requirements approach to tolerance representation are composed to form more complex tolerance relationships. Artificial intelligence techniques, including a constraint network, frame-based system, and dependency tracking are used to support flexible and detailed computation for tolerance analysis and synthesis.

Go to article

Nondestructive Detection Of An Undeserable Metallic Phase, T1, During Processing Of Alumnum-L Thumalloys, Otto Buck, David J. Bracci, David C. Jiles, Lisa J.H. Brasche, Jeffrey E. Shield, Leonard S. Chumbley

Department of Mechanical and Materials Engineering: Faculty Publications

A method is disclosed for detecting the T1 phase in aluminum-lithium alloys through simultaneous measurement of conductivity and hardness. In employing eddy current to measure conductivity, when the eddy current decreases with aging of the alloy, while the hardness of the material continues to increase, the presence of the T1 phase may be detected.

Go to article

Microcomputer Based Digital Image Processing System Developed To Count And Size Laser-Generated Small Particle Images, K. D. Ahlers, D. R. Alexander

Department of Mechanical and Materials Engineering: Faculty Publications

A microcomputer-based digital image processing system has been developed to count and size laser-generated small particle images. Processing rates of 5 to 600 frames per minute were achieved by utilizing a real-time digital image processor. Particles from 7 to 700 µm in the plane of focus were counted and sized. A major emphasis in this work was to determine the basic problems and limitations involved with using a digital image processing scheme to accurately size particles. Areas that were investigated include the effect of the threshold level on measured particle size, particle boundary diffraction gray-level gradients, and geometric nonlinearities introduced …

Go to article

Nanoscience and Nanotechnology Commons^™

Full-Text Articles in Nanoscience and Nanotechnology

Study Of Electrochemical Properties Of Ni(Oh)2/Niooh With Spectroscopic Ellipsometry, Shengtao Zhang, Zongqing Huang

Journal of Electrochemistry

The Electrode Process Of Y(Ⅲ) On Copper Electrode And Its Surface Metallizing, Chungen Zhou, Shuzhen Duan

Journal of Electrochemistry

Characterization Of Piezoceramic Crosses With Large Range Scanning Capability And Applications For Low Temperature Scanning Tunneling Microscopy, J. A. Helfrich, Shireen Adenwalla, J. B. Ketterson, G. A. Zhitomirsky

Shireen Adenwalla Papers

Nmr And Nqr Study Of The Electronic And Structural Properties Of Al-Cu-Fe And Al-Cu-Ru Quasicrystals, A. Shastri, F. Borsa, D.R. Torgeson, Jeffrey E. Shield, A.I. Goldman

Nebraska Center for Materials and Nanoscience: Faculty Publications

Resonant Tunneling Through Quantum Dot Arrays, Guanlong Chen, Gerhard Klimeck, Supriyo Datta, Guanhua Chen, William A. Goddard Iii

Birck and NCN Publications

Conductance Spectroscopy In Coupled Quantum Dots, Gerhard Klimeck, Guanlong Chen, Supriyo Datta

Birck and NCN Publications

Rate Equations For The Phonon Peak In Resonant-Tunneling Structures, Roger Lake, Gerhard Klimeck, J. P. Anantram, Supriyo Datta

Birck and NCN Publications

Rate Equations From The Keldysh Formalism Applied To The Phonon Peak In Resonant-Tunneling Diodes, Roger Lake, Gerhard Klimeck, Supriyo Datta

Birck and NCN Publications

Icosahedral Phase Stabilities In Al-Cu-Ru Alloys, Jeffrey E. Shield, C. Hoppe, R.W. Mccallum, A.I. Goldman, K.F. Kelton, P.C. Gibbons

Nebraska Center for Materials and Nanoscience: Faculty Publications

Laser Bandwidth-Induced Fluctuations In The Intensity Transmitted By A Fabry-Perot Interferometer, Gerhard Klimeck, Daniel Elliott, M. Hamilton

Birck and NCN Publications

Diffraction Studies On Ni-Co And Ni-Cr Alloy Thin Films, A. R. Sethuraman, R. J. De Angelis, P. J. Reucroft

Nebraska Center for Materials and Nanoscience: Faculty Publications

Automating Tolerance Synthesis: A Framework And Tools, Stephen C.-Y. Lu, Robert G. Wilhelm

Department of Mechanical and Materials Engineering: Faculty Publications

Nondestructive Detection Of An Undeserable Metallic Phase, T1, During Processing Of Alumnum-L Thumalloys, Otto Buck, David J. Bracci, David C. Jiles, Lisa J.H. Brasche, Jeffrey E. Shield, Leonard S. Chumbley

Department of Mechanical and Materials Engineering: Faculty Publications

Microcomputer Based Digital Image Processing System Developed To Count And Size Laser-Generated Small Particle Images, K. D. Ahlers, D. R. Alexander

Department of Mechanical and Materials Engineering: Faculty Publications