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Articles 31 - 60 of 79
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How Surface Stresses Lead To Size-Dependent Mechanics Of Tensile Deformation In Nanowires, M. Ravi Shankar, Alexander H. King
How Surface Stresses Lead To Size-Dependent Mechanics Of Tensile Deformation In Nanowires, M. Ravi Shankar, Alexander H. King
Alexander H. King
It has been proposed that surface and interface stresses can modify the elastic behavior in nanomaterials such as nanowires. The authors show that surface stresses modify the tensile response of nanowires only when nonlinear elastic effects become important leading to cross terms between the applied stress and the surface stress. These effects are only significant when the radius of the nanowire is of the order of a few nanometers. The resulting alteration of tensile stiffness, though effected in part by the nonlinear elastic modulus, is particularly wrought by a modification of the stress state in the deformed nanowire.
Effect Of The Lattice Crystallinity On The Electron−Phonon Relaxation Rates In Gold Nanoparticles, Wenyu Huang, Wei Qian, Mostafa El-Sayed
Effect Of The Lattice Crystallinity On The Electron−Phonon Relaxation Rates In Gold Nanoparticles, Wenyu Huang, Wei Qian, Mostafa El-Sayed
Wenyu Huang
In order to study the importance of surface phonons on the electron−phonon relaxation in plasmonic nanoparticles, the effect of size, shape, and materials have recently been studied. Gold and silver nanoparticles have shown no dependence on size and shape while copper nanoparticles have shown some size dependence. This suggests that the bulk phonons, which are sensitive to the bulk-phase structure, are solely responsible for the relaxation of the hot electron in gold and silver plasmonic nanoparticles. The importance of bulk phonons should depend on the degree of crystallinity. In the present study, we have found that the electron−phonon relaxation rate …
On The Universal Scaling Behavior Of The Distance Decay Of Plasmon Coupling In Metal Nanoparticle Pairs: A Plasmon Ruler Equation, Prashant K. Jain, Wenyu Huang, Mostafa A. El-Sayed
On The Universal Scaling Behavior Of The Distance Decay Of Plasmon Coupling In Metal Nanoparticle Pairs: A Plasmon Ruler Equation, Prashant K. Jain, Wenyu Huang, Mostafa A. El-Sayed
Wenyu Huang
Localized surface plasmon resonances (LSPR) in lithographically fabricated gold (Au) nanodisc pairs are investigated using microabsorption spectroscopy and electrodynamic simulations. In agreement with previous work, we find that the fractional plasmon wavelength shift for polarization along the interparticle axis decays nearly exponentially with the interparticle gap. In addition, we find that the decay length is roughly about 0.2 in units of the particle size for different nanoparticle size, shape, metal type, or medium dielectric constant. The near-exponential distance decay and the interesting “universal” scaling behavior of interparticle plasmon coupling can be qualitatively explained on the basis of a dipolar-coupling model …
The Effect Of Plasmon Field On The Coherent Lattice Phonon Oscillation In Electron-Beam Fabricated Gold Nanoparticle Pairs, Wenyu Huang, Wei Qian, Prashant K. Jain, Mostafa El-Sayed
The Effect Of Plasmon Field On The Coherent Lattice Phonon Oscillation In Electron-Beam Fabricated Gold Nanoparticle Pairs, Wenyu Huang, Wei Qian, Prashant K. Jain, Mostafa El-Sayed
Wenyu Huang
By using electron beam lithography, we fabricated pairs of gold nanoparticles with varying interparticle separation. Double-beam femtosecond transient absorption spectroscopy was used to determine the coherent lattice oscillation frequency as a function of the interparticle separation in the presence of the plasmon field excited by the monitoring probe light. We found that the fractional shift in the coherent lattice phonon oscillation frequency follows an exponential decay with respect to the interparticle gap scaled by the disc diameter with the same decay constant as that previously observed for the fractional shift in the surface plasmon electronic oscillation resonance frequency. This strongly …
Carbazolyl Nitrenium Ion: Electron Configuration And Antiaromaticity Assessed By Laser Flash Photolysis, Trapping Rate Constants, Product Analysis, And Computational Studies, Arthur Winter, Harry H. Gibson, Daniel E. Falvey
Carbazolyl Nitrenium Ion: Electron Configuration And Antiaromaticity Assessed By Laser Flash Photolysis, Trapping Rate Constants, Product Analysis, And Computational Studies, Arthur Winter, Harry H. Gibson, Daniel E. Falvey
Arthur Winter
Laser flash photolysis of 1-(carbazol-9-yl)-2,4,6-trimethylpyridinium tetrafluoroborate generates the carbazolyl nitrenium ion (τ = 333 ns, kobs = 3.0 × 106 M-1s-1) having absorption bands at 570 and 620 nm in CH3CN. The nitrenium ion is found to have reactivity comparable to structurally similar closed-shell diarylnitrenium ions, but spectroscopic evidence favors an open-shell singlet diradical assignment for the observed nitrenium ion. The carbazolyl nitrenium ion is also more reactive than diarylnitrenium ions as a likely result of antiaromatic character. Ab initio and hybrid DFT calculations were performed to address the degree of antiaromaticity in this and similar nitrenium ions through analysis …
Benzylic Cations With Triplet Ground States: Computational Studies Of Aryl Carbenium Ions, Silylenium Ions, Nitrenium Ions, And Oxenium Ions Substituted With Meta Π Donors, Arthur Winter, Daniel E. Falvey, Christopher J. Cramer, Benjamin F. Gherman
Benzylic Cations With Triplet Ground States: Computational Studies Of Aryl Carbenium Ions, Silylenium Ions, Nitrenium Ions, And Oxenium Ions Substituted With Meta Π Donors, Arthur Winter, Daniel E. Falvey, Christopher J. Cramer, Benjamin F. Gherman
Arthur Winter
Density functional theory (B3LYP/6-31G(d,p)) was used to predict the effect of meta substitution on aryl cationic (Ar−X+) species, including aryloxenium ions, arylsilylenium ions, arylnitrenium ions, and arylcarbenium ions. Multireference second-order perturbation theory (CASPT2) calculations were used to benchmark the quantitative accuracy of the DFT calculations for representative systems. Substituting the meta positions on these species with π donors stabilizes a π,π* diradical state analogous to the well-known m-xylylene diradical. Notably, the 3,5-bis(N,N-dimethylamino)benzyl cation is predicted to have a triplet ground state by 1.9 kcal/mol by DFT and to have essentially degenerate singlet−triplet states at the CASPT2(10,9) level of theory. Adding …
Posterminaries: After Nabarro, Alexander H. King
Posterminaries: After Nabarro, Alexander H. King
Alexander H. King
With the passing of Frank Nabarro in July of this year, we have lost one of the founding fathers of materials science. His name appears in many of the textbooks from which we train our students today, and also on the spines of several volumes on dislocation theory, including his classic monograph on the subject. He rightly stands among the gods of our field. Ninety years old at his death, he was a sprightly dancer at the frontiers of knowledge, right up to the end.
Posterminaries: The Scales Of Judgement, Alexander H. King
Posterminaries: The Scales Of Judgement, Alexander H. King
Alexander H. King
Materials scientists are generally well-versed in physics, and physics, above all, is a science of measurements. The first instinct of a physicist is to parse a problem in terms of its measurables in the dimensions of mass, length, and time, and it is the shifting of attention down the scale of length that particularly characterizes our present times as the Nano Age.
Posterminaries: Plain Text, Alexander H. King
Posterminaries: Plain Text, Alexander H. King
Alexander H. King
You just can’t win an argument with an English professor.
Gold Nanoparticles Propulsion From Surface Fueled By Absorption Of Femtosecond Laser Pulse At Their Surface Plasmon Resonance, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
Gold Nanoparticles Propulsion From Surface Fueled By Absorption Of Femtosecond Laser Pulse At Their Surface Plasmon Resonance, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
Wenyu Huang
Femtosecond laser irradiation of assembled nanoprisms on a quartz substrate at their strong absorbing surface plasmon resonance frequency causes their propulsion from the substrate. SEM and AFM show that the particles fly while keeping their prismatic shape, but they decrease in size by an amount that can be calculated assuming atomic sublimation. Several mechanisms are mentioned, but the sublimation mechanism, which rapidly builds up pressure under the particle and propels it away from substrate, is discussed in detail. From the kinetic energy given to the flying nanoparticle, an initial velocity of ∼160 m/s (∼360 miles/h) is calculated. The dependence of …
Thermal Effects On Domain Orientation Of Tetragonal Piezoelectrics Studied By In Situ X-Ray Diffraction, Wonyoung Chang, Alexander H. King, Keith J. Bowman
Thermal Effects On Domain Orientation Of Tetragonal Piezoelectrics Studied By In Situ X-Ray Diffraction, Wonyoung Chang, Alexander H. King, Keith J. Bowman
Alexander H. King
Thermal effects on domain orientation in tetragonal lead zirconate titanate (PZT) and lead titanate (PT) have been investigated by using in situ x-ray diffraction with an area detector. In the case of a soft PZT, it is found that the texture parameter called multiples of a random distribution (MRD) initially increases with temperature up to approximately 100 °C and then falls to unity at temperatures approaching the Curie temperature, whereas the MRD of hard PZT and PT initially undergoes a smaller increase or no change. The relationship between the mechanical strain energy and domain wall mobility with temperature is discussed.
Size-Driven Domain Reorientation In Hydrothermally Derived Lead Titanate Nanoparticles, Zhiyuan Ye, Elliot B. Slamovich, Alexander H. King
Size-Driven Domain Reorientation In Hydrothermally Derived Lead Titanate Nanoparticles, Zhiyuan Ye, Elliot B. Slamovich, Alexander H. King
Alexander H. King
High-resolution transmission electron microscopy studies of hydrothermally derived platelike lead titanate nanoparticles reveal that below a critical size of approximately 70 nm, the single ferroelectric domain polarization axis reorients from perpendicular to parallel to the plate. We suggest that during particle growth, ions in the hydrothermal processing medium compensate for the ferroelectric depolarization energy. When the processing medium is removed by washing and drying, single domain nanoparticles minimize their depolarization energy by c-axis flipping.
Mechanism Of Structural Transformation In Bismuth Titanate, Sudhanshu Mallick, Keith J. Bowman, Alexander H. King
Mechanism Of Structural Transformation In Bismuth Titanate, Sudhanshu Mallick, Keith J. Bowman, Alexander H. King
Alexander H. King
Sodium-doped bismuth titanate undergoes a transformation from Bi4Ti3O12 to Na0.5Bi4.5Ti4O15 on heating in air at temperatures exceeding 800 °C. This transformation proceeds through the intermediate Na0.5Bi8.5Ti7O27 structure which is an intergrowth phase of the two. High-resolution transmission electron microscopy was used to study this transformation. From the Moiré pattern that was obtained, the crystallographic orientation of the transformation front has been determined and a mechanism is proposed for this structural transformation.
Photothermal Reshaping Of Prismatic Au Nanoparticles In Periodic Monolayer Arrays By Femtosecond Laser Pulses, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
Photothermal Reshaping Of Prismatic Au Nanoparticles In Periodic Monolayer Arrays By Femtosecond Laser Pulses, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
Wenyu Huang
Prismatic goldnanoparticles in the periodic monolayer arrays prepared with nanosphere lithography technique can be reshaped with femtosecond laser pulses at different powers and wavelengths. As the power density of 400 nm femtosecond laser increases, the prismatic particle tips begin to round and the overall particle shape changes from a prism to a sphere with a tripodal intermediate. The formation of the tip-rounded nanoprisms is probably due to the dewetting properties of gold on quartz surface and the low melting temperature at the tips. The formation of the tripodal nanoparticles is attributed to the inhomogeneous heating and lattice rearrangement of the …
The Optically Detected Coherent Lattice Oscillations In Silver And Gold Monolayer Periodic Nanoprism Arrays: The Effect Of Interparticle Coupling, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
The Optically Detected Coherent Lattice Oscillations In Silver And Gold Monolayer Periodic Nanoprism Arrays: The Effect Of Interparticle Coupling, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
Wenyu Huang
Using femtosecond transient spectroscopy, we studied the optically detected laser-induced coherent phonon oscillation of monolayers of periodic arrays of prismatic-shaped silver and gold nanoparticles, assembled by using the technique of nanosphere lithography. In this method, the same size of polystyrene sphere and the same vacuum conditions are used. Under these circumstances, the gold nanoprisms formed are found to have sharper tips than the corresponding silver nanoprisms. For both gold and silver nanoparticles, the surface plasmon absorption maximum is found to depend linearly on size. The coherent lattice oscillation periods are also found to depend linearly on size. However, although the …
Dislocation-Indenter Interaction In Nanoindentation, M. Ravi Shankar, Alexander H. King, Srinivasan Chandrasekar
Dislocation-Indenter Interaction In Nanoindentation, M. Ravi Shankar, Alexander H. King, Srinivasan Chandrasekar
Alexander H. King
A formulation of dislocation-indenter interaction in two-dimensional, isotropic elasticity is presented. A significant dislocation-indenter interaction is predicted when dislocations are nucleated very close to the indenter. This interaction is expected to have an important influence on dislocation motion and multiplication. Upon nucleation close to the indenter, the dislocations are shown to modify the load, load distribution, and moment acting on the indenter. This effect is seen to vary with the indentation contact length. Further away from the indenter, the indenter-dislocation interaction is shown to be negligible.
Coherent Vibrational Oscillation In Gold Prismatic Monolayer Periodic Nanoparticle Arrays, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
Coherent Vibrational Oscillation In Gold Prismatic Monolayer Periodic Nanoparticle Arrays, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
Wenyu Huang
We studied the ultrafast laser-induced coherent phonon oscillation in prismatic shaped gold nanoparticles assembled in monolayer periodic arrays by using the nanosphere lithographic technique. The amplitude and phase of the oscillation observed by ultrafast pump−probe transient spectroscopy is monitored as the wavelength of the dipolar surface plasmon absorption decreases. At a certain wavelength, the oscillation could not be observed. As the monitoring wavelength decreases further, the sign of the amplitude changes. From the wavelength at which the oscillation is not detected, the dependence of the absorption maxima on the size of the nanoparticles, the changes in the nanoparticle size are …
Photochemical Generation Of Nitrenium Ions From Protonated 1,1-Diarylhydrazines, Arthur Winter, Selina I. Thomas, Andrew C. Kung, Daniel E. Falvey
Photochemical Generation Of Nitrenium Ions From Protonated 1,1-Diarylhydrazines, Arthur Winter, Selina I. Thomas, Andrew C. Kung, Daniel E. Falvey
Arthur Winter
Laser flash photolysis experiments, chemical trapping studies, and time-dependent density functional theory calculations demonstrate that photolysis of protonated 1,1-diarylhydrazines generates N,N-diarylnitrenium ions.
Effect Of Meta Electron-Donating Groups On The Electronic Structure Of Substituted Phenyl Nitrenium Ions, Arthur Winter
Effect Of Meta Electron-Donating Groups On The Electronic Structure Of Substituted Phenyl Nitrenium Ions, Arthur Winter
Arthur Winter
Density functional theory (UB3LYP/6-31G(d,p)) was used to determine substituent effects on the singlet−triplet-state energy gap for 21 meta-substituted phenylnitrenium ions. It was found that strongly electron-donating substituents stabilize the triplet state relative to the singlet state. With sufficiently strong meta electron donors (e.g., m,m‘-diaminophenylnitrenium ion) the triplet is predicted to be the ground state. Analysis of equilibrium geometries, Kohn−Sham orbital distributions, and Mulliken spin densities for the triplet states of this series of nitrenium ions leads to the conclusion that there are two spatially distinct types of low-energy triplet states. Simple arylnitrenium ions such as phenylnitrenium ions as well as …
Acrb Multidrug Efflux Pump Of Escherichia Coli: Composite Substrate-Binding Cavity Of Exceptional Flexibility Generates Its Extremely Wide Substrate Specificity, Edward Yu, Julio R. Aires, Hiroshi Nikaido
Acrb Multidrug Efflux Pump Of Escherichia Coli: Composite Substrate-Binding Cavity Of Exceptional Flexibility Generates Its Extremely Wide Substrate Specificity, Edward Yu, Julio R. Aires, Hiroshi Nikaido
Edward Yu
Gram-negative bacteria have, in general, much higher intrinsic levels of resistance to various antibiotics, antiseptics, dyes, and detergents than do gram-positive bacteria. This is, in part, due to the effectiveness of the outer membrane as a barrier. The porin channels exclude large compounds (for example, vancomycin) and drastically slow down the influx of most antibiotics, which are usually much larger than common nutrients. Most antibiotics and chemotherapeutic agents that act on targets in the cytosol must cross the inner, cytoplasmic membrane, usually by spontaneous diffusion, and this necessitates their being at least moderately lipophilic. These compounds can in principle diffuse …
Low-Cost Manufacturing Process For Nanostructured Metals And Alloys, Travis L. Brown, Srinivasan Swaminathan, Srinivasan Chandrasekar, W. Dale Compton, Alexander H. King, Kevin P. Trumble
Low-Cost Manufacturing Process For Nanostructured Metals And Alloys, Travis L. Brown, Srinivasan Swaminathan, Srinivasan Chandrasekar, W. Dale Compton, Alexander H. King, Kevin P. Trumble
Alexander H. King
In spite of their interesting properties, nanostructured materials have found limited uses because of the cost of preparation and the limited range of materials that can be synthesized. It has been shown that most of these limitations can be overcome by subjecting a material to large-scale deformation, as occurs during common machining operations. The chips produced during lathe machining of a variety of pure metals, steels, and other alloys are shown to be nanostructured with grain (crystal) sizes between 100 and 800 nm. The hardness of the chips is found to be significantly greater than that of the bulk material.
Dispersion Of Potassium Nitrate And The Resulting Strong Basicity On Zirconia, Ying Wang, Wenyu Huang, Yuan Chun, Jia Rong Xia, Jian Hua Zhu
Dispersion Of Potassium Nitrate And The Resulting Strong Basicity On Zirconia, Ying Wang, Wenyu Huang, Yuan Chun, Jia Rong Xia, Jian Hua Zhu
Wenyu Huang
A novel solid superbase is derived from zirconia-supported potassium nitrate. Dispersion and decomposition of potassium nitrate on zirconia were investigated and compared with that on alumina to explore the effect of the support on the preparation of solid strong bases. Spontaneous dispersion capacity of KNO3 on ZrO2 was found to be 8.1 K+ nm-2, very close to that of a vacant site on ZrO2. An unusually strong basicity was generated on ZrO2 through decomposition of the loaded KNO3 that began around 613 K, enhancing the catalytic activity of ZrO2 in cis-but-2-ene isomerization at 273 K. Moreover, KNO3/ZrO2 samples, except 34% …
Synthesis And Characterization Of Potassium-Modified Alumina Superbases, Ying Wang, Jian Hua Zhu, Wenyu Huang
Synthesis And Characterization Of Potassium-Modified Alumina Superbases, Ying Wang, Jian Hua Zhu, Wenyu Huang
Wenyu Huang
Novel solid superbases can be prepared by dispersing potassium salts such as K2CO3 and KHCO3 on alumina followed by thermal treatments. The resulting materials show an extremely high activity in the isomerization of cis-but-2-ene at 0°C and possess base strength of at least H− = + 26.5. X-Ray diffraction (XRD) and Raman spectra of K2CO3 or KHCO3 modified alumina reveal the formation of potassium hydroalumina carbonate, which is the precursor of active species. Decomposition of potassium salts on alumina has been studied by use of thermal gravimetric differential thermal analysis (TG-DTA) and temperature programmed decomposition-mass spectrometry (TPDE-MS). Two CO2 evolution …
Propagating Conformational Changes Over Long (And Short) Distances In Proteins, Edward Yu, Daniel E. Koshland Jr.
Propagating Conformational Changes Over Long (And Short) Distances In Proteins, Edward Yu, Daniel E. Koshland Jr.
Edward Yu
The problem of the propagation of conformational changes over long distances or through a closely packed protein is shown to fit a model of a ligand-induced conformational change between two protein states selected by evolution. Moreover, the kinetics of the pathway between these states is also selected so that the energy of ligand binding and the speed of the transition between conformational states are physiologically appropriate. The crystallographic data of a wild-type aspartate receptor that has negative cooperativity and a mutant that has no cooperativity but has native transmembrane signaling are shown to support this model.
Behavior Of Grain Boundary Resistivity In Metals Predicted By A Two-Dimensional Model, Rand Dannenberg, Alexander H. King
Behavior Of Grain Boundary Resistivity In Metals Predicted By A Two-Dimensional Model, Rand Dannenberg, Alexander H. King
Alexander H. King
The behavior of a model for the specific grain boundary resistivity in metallic bamboo conductor lines is developed and compared to other theoretical treatments, and to experiment. The grain boundary is modeled as an array of scatterers on a plane. The scatterers are called “vacancy-ion” complexes, in which the vacancy represents the boundary free volume, and the ion is an atom adjacent to the vacancy. Three cases are investigated, that of noninterfering scatterers, a continuum of interfering scatterers, and discrete interfering scatterers. The approximations used lead to a specific grain boundary resistivity ∼10−16 Ω m2 for aluminum, in agreement with …
Structural Change Of The Mn Cluster During The S2→S3 State Transition Of The Oxygen-Evolving Complex Of Photosystem Ii. Does It Reflect The Onset Of Water/Substrate Oxidation? Determination By Mn X-Ray Absorption Spectroscopy, Wenchuan Liang, Theo A. Toelofs, Roehl M. Cinco, Annette Rompel, Matthew J. Latimer, Edward Yu, Kenneth Sauer, Melvin P. Klein, Vittal K. Yachandra
Structural Change Of The Mn Cluster During The S2→S3 State Transition Of The Oxygen-Evolving Complex Of Photosystem Ii. Does It Reflect The Onset Of Water/Substrate Oxidation? Determination By Mn X-Ray Absorption Spectroscopy, Wenchuan Liang, Theo A. Toelofs, Roehl M. Cinco, Annette Rompel, Matthew J. Latimer, Edward Yu, Kenneth Sauer, Melvin P. Klein, Vittal K. Yachandra
Edward Yu
The oxygen-evolving complex of Photosystem II in plants and cyanobacteria catalyzes the oxidation of two water molecules to one molecule of dioxygen. A tetranuclear Mn complex is believed to cycle through five intermediate states (S0−S4) to couple the four-electron oxidation of water with the one-electron photochemistry occurring at the Photosystem II reaction center. We have used X-ray absorption spectroscopy to study the local structure of the Mn complex and have proposed a model for it, based on studies of the Mn K-edges and the extended X-ray absorption fine structure of the S1 and S2 states. The proposed model consists of …
Novel One-Phase Synthesis Of Thiol-Functionalized Gold, Palladium, And Iridium Nanoparticles Using Superhydride, Chanel K. Yee, Rainer Jordan, Abraham Ulman, Henry White, Alexander H. King, Miriam Rafailovich, Jonathan Sokolov
Novel One-Phase Synthesis Of Thiol-Functionalized Gold, Palladium, And Iridium Nanoparticles Using Superhydride, Chanel K. Yee, Rainer Jordan, Abraham Ulman, Henry White, Alexander H. King, Miriam Rafailovich, Jonathan Sokolov
Alexander H. King
A new, facile, general one-phase synthesis for thiol-functionalized gold, palladium, and iridium nanoparticles, using tetrahydrofuran (THF) as the solvent and lithium triethylborohydride (Superhydride) as the reducing agent, is presented. For octadecanethiol-functionalized gold (Au/ODT) nanoparticles, HRTEM of drop-cast particle-films revealed the formation of spherical particles of d = 4 ± 0.3 nm average size. Electron diffraction shows fcc packing arrangement, similar to that of bulk gold. The crystalline gold cores are surrounded with closely packed n-alkyl chains mainly in an all-trans conformation, adopting orthorhombic packing as confirmed by FTIR spectroscopy. Particles are arranged in a discrete solidlike assembly with a correlation …
Resistivity, Thermopower And The Correlation To Infrared Active Vibrations Of Mn1.56co0.96ni0.48o4 Spinel Films Sputtered In An Oxygen Partial Pressure Series, Rand Dannenberg, S. Baliga, R. J. Gambino, Alexander H. King, A. P. Doctor
Resistivity, Thermopower And The Correlation To Infrared Active Vibrations Of Mn1.56co0.96ni0.48o4 Spinel Films Sputtered In An Oxygen Partial Pressure Series, Rand Dannenberg, S. Baliga, R. J. Gambino, Alexander H. King, A. P. Doctor
Alexander H. King
Mn1.56Co0.96Ni0.48O4 spinel was sputter deposited using a series of oxygen partial pressures. Electrical resistivity versus temperature and thermopower versus temperature measurements at each oxygen partial pressure were made. The variations of the thermopower and resistivity with oxygen partial pressure are consistent with a change in the ratio of Mn3+ to Mn4+ cations, which occurs due to changes of oxygen content of the material. The weak temperature dependence of the thermopower indicates small polaron hopping is the charge transport mechanism. Combining the models of Mott and Schnakenberg to analyze the transport data, we find that the Debye temperature (or frequency) is …
Infrared Optical Properties Of Mn1.56co0.96ni0.48o4 Spinel Films Sputter Deposited In An Oxygen Partial Pressure Series, Rand Dannenberg, S. Baliga, R. J. Gambino, Alexander H. King, A. P. Doctor
Infrared Optical Properties Of Mn1.56co0.96ni0.48o4 Spinel Films Sputter Deposited In An Oxygen Partial Pressure Series, Rand Dannenberg, S. Baliga, R. J. Gambino, Alexander H. King, A. P. Doctor
Alexander H. King
Mn1.56Co0.96Ni0.48O4 spinel films were sputter deposited onto silicon substrates using a series of oxygen partial pressures. Fourier transform infrared transmission and reflectance, and Raman scattering measurements were made. The 1–25 μm wavelength range was examined using these optical techniques. The complex index of refraction was calculated for this entire wavelength range. Infrared active vibrations were analyzed using multiple oscillator analysis, Kramers–Kronig analysis, and derivative reflectance spectroscopy. The Raman and infrared active lattice vibrations were observed to shift with increasing oxygen partial pressure during film deposition, and were consistent with the earlier published shift in Debye frequency calculated from resistivity data. …
Cyclic Deformation Behavior Of High-Purity Titanium Single Crystals: Part Ii. Microstructure And Mechanism, Xiaoli Tan, H. Guo, H. Gu, C. Laird, N. D. H. Monroe
Cyclic Deformation Behavior Of High-Purity Titanium Single Crystals: Part Ii. Microstructure And Mechanism, Xiaoli Tan, H. Guo, H. Gu, C. Laird, N. D. H. Monroe
Xiaoli Tan
Strain-controlled cyclic tests have been conducted on high-purity titanium single crystals with different orientations. The fatigue mechanisms of the titanium crystals were studied by means of a scanning electron microscope (SEM) and a transmission electron microscope (TEM). It was found that single slip lines, wavy slip lines, double slip lines, twins, and associated slip lines occurred in differently oriented single crystals. A new type of fractographic morphology, parallel traces, was observed. Dislocation patterns and cyclic twins, as well as the mechanical response, were analyzed. The dependence of the deformation mechanisms on the orientations of the single crystals is discussed.