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Cyclic Deformation Behavior Of High-Purity Titanium Single Crystals: Part I. Orientation Dependence Of Stress-Strain Response, Xiaoli Tan, H. Gu, C. Laird, N. D. H. Monroe
Cyclic Deformation Behavior Of High-Purity Titanium Single Crystals: Part I. Orientation Dependence Of Stress-Strain Response, Xiaoli Tan, H. Gu, C. Laird, N. D. H. Monroe
Xiaoli Tan
Randomly oriented single crystals of high-purity titanium were prepared by strain annealing and were subjected to multiple-step fatigue testing under strain-controlled conditions, in order to determine their cyclic stress-strain curves (CSSCs). These were found to fall into three groups, depending on orientation and the extent of slip and twinning. For those crystals oriented for single prismatic slip, a plateau was observed in the CSSCs, persistent slip bands (PSBs) occurred, and the plateau stress was 38 MPa. In a second group, oriented for prismatic slip but for which cross-slip and twinning was favored, the plateau was suppressed and the flow stresses …
Ionic Hydrogen Bonds In Bioenergetics. 3. Proton Transport In Membranes, Modeled By Ketone/Water Clusters, Michael Meot-Ner, Steve Scheiner, Edward Yu
Ionic Hydrogen Bonds In Bioenergetics. 3. Proton Transport In Membranes, Modeled By Ketone/Water Clusters, Michael Meot-Ner, Steve Scheiner, Edward Yu
Edward Yu
Hydrogen bond networks in protonated acetone/water clusters are stabilized by H3O+(Me2CO)2 centers, and the stabilizaton increases with further acetone content. For example, proton transfer from neat water (H2O)6H+ clusters to form mixed (Me2CO)3(H2O)3H+ clusters is exothermic by 80 kJ/mol (19 kcal/mol), due to strong hydrogen bonding of the carbonyl groups; in a series of mixed clusters B3(H2O)3H+, the stability of the hydrogen bond network correlates with the proton affinities PA(B). In diketone models of adjacent peptide links, the proton is stabilized by internal hydrogen bonds between the carbonyl groups. The internal bonds can be significant, for example, 31 kJ/mol (7 …
Segregation Of Bismuth To Triple Junctions In Copper, K.-M. Yin, Alexander H. King, T.E. Hsieh, F.-R. Chen, J.J. Kai, L. Chang
Segregation Of Bismuth To Triple Junctions In Copper, K.-M. Yin, Alexander H. King, T.E. Hsieh, F.-R. Chen, J.J. Kai, L. Chang
Alexander H. King
Bismuth segregation in copper has been studied using energy-dispersive X-ray spectrometry (EDX) in a JEOL 2010F transmission electron microscope. In addition to the expected solute enrichment at grain boundaries, we have observed extremely high concentrations of bismuth at certain triple junctions, with significantly greater enrichment factors than in the adjacent grain boundaries. It is shown here that the triple junction segregation is a function of the parameters of the grain boundaries at the triple line, and existence of this type of segregation implies that the affected triple junctions embody excess free energy. At least one of the observed triple junctions …
The S0 State Of The Oxygen-Evolving Complex In Photosystem Ii Is Paramagnetic: Detection Of An Epr Multiline Signal, Johannes Messinger, John H. Robblee, Edward Yu, Kenneth Sauer, Vittal K. Yachandra, Melvin P. Klein
The S0 State Of The Oxygen-Evolving Complex In Photosystem Ii Is Paramagnetic: Detection Of An Epr Multiline Signal, Johannes Messinger, John H. Robblee, Edward Yu, Kenneth Sauer, Vittal K. Yachandra, Melvin P. Klein
Edward Yu
The photosynthetic oxidation of water to molecular oxygen is energetically driven by light-induced charge separations in the reaction center of photosystem II (PS II). The reaction is catalyzed by a tetranuclear manganese cluster contained in the oxygen-evolving complex (OEC). The OEC cycles through five different redox states termed S0 to S4, with S1 being the darkstable state. Oxygen is released during the S4 f S0 transition.1 The removal of one electron from the OEC on each S state transition leads to the idea that alternate S states should be paramagnetic because of their odd-electron number. The multiline EPR signal, which …
Synthesis And Characterization Of A New Class Of Μ3-Oh-Bridged Trimers That Contain Octahedrally Coordinated Divalent Metal Ions Bridged By Three Acetate Ligands And A Unique Catecholate Ligand. Solid State Molecular Structures Of The [(Py)5mii3(Oac)3(Μ3-Oh)((Cat)] Complexes (M = Mn(Ii), Fe(Ii), Co(Ii), Ni(Ii)), R.A. Reynolds, Edward Yu, W.R. Dunham, D. Coucouvanis
Synthesis And Characterization Of A New Class Of Μ3-Oh-Bridged Trimers That Contain Octahedrally Coordinated Divalent Metal Ions Bridged By Three Acetate Ligands And A Unique Catecholate Ligand. Solid State Molecular Structures Of The [(Py)5mii3(Oac)3(Μ3-Oh)((Cat)] Complexes (M = Mn(Ii), Fe(Ii), Co(Ii), Ni(Ii)), R.A. Reynolds, Edward Yu, W.R. Dunham, D. Coucouvanis
Edward Yu
The synthesis and structural characterization of a new class of “basic” trinuclear acetate clusters with solely divalent metal ions and a central μ3-OH ligand are reported. These molecules with the [(py)5MII3(OAc)3(μ3-OH)(cat)] stoichiometry (M = Mn, Fe, Co, Ni) are X-ray isomorphous and isostructural and contain octahedrally coordinated metal ions. The core consists of an antiferromagnetically coupled M3 unit with the metals arranged in the corners of an isosceles triangle. Two of the M−M distances vary between 2.98 and 3.16 Å, and the longer M−M distance is observed between 3.65 and 3.76 Å. As expected from the relative ionic radius lengths, …
Absolute Integrated Cross Sections For Some O2 Herzberg I Transitions Near 248–249 Nm, Zhen-Chuan Bao, Edward Yu, John R. Baker
Absolute Integrated Cross Sections For Some O2 Herzberg I Transitions Near 248–249 Nm, Zhen-Chuan Bao, Edward Yu, John R. Baker
Edward Yu
A frequency doubled tunable dye laser system with ∼0.4 cm−1 resolution was used to measure the integrated absorption cross sections of more than 20 rotational transitions in the O2 Herzberg I (A 3Σ+ u ←X 3Σ− g ) 8‐0 and 9‐0 vibrational bands near 248 nm and 249 nm. Oxygen pressures from 200 to 800 Torr and path lengths from 5 to 25 m were employed. The measured absorbances were fitted using a nonlinear least squares analysis and Beer’s Law to obtain absolute values for the individual transition integrated cross sections in good agreement with a recent spectral simulation and …
Surface-Induced Ordering In Asymmetric Block Copolymers, Y. Liu, W. Zhao, X. Zheng, Alexander H. King, A. Sing, M. H. Rafailovich, J. Sokolov, K. H. Dai, E. J. Kramer, S. A. Schwarz, O. Gebizlioglu, S. K. Sinha
Surface-Induced Ordering In Asymmetric Block Copolymers, Y. Liu, W. Zhao, X. Zheng, Alexander H. King, A. Sing, M. H. Rafailovich, J. Sokolov, K. H. Dai, E. J. Kramer, S. A. Schwarz, O. Gebizlioglu, S. K. Sinha
Alexander H. King
The surface-induced ordering in thin films of asymmetric deuterated polystyrene (dPS)- poly(viny1pyridine) (PVP) diblock and triblock copolymers of comparable polymerization index and PVP volume fraction - 0.25) was studied using transmission electron microscopy, atomic force microscopy, secondary ion massspectrometry, and neutron reflectivity. The morphology of both di- and triblock copolymer films was found to be cylindrical except for the layer adjacent to the silicon oxide surface, which due to the strong interaction of silica with PVP, was lamellar. The spacing between adjacent cylindrical layers was found to be consistent with mean field theory predictions. In the triblock copolymer films the …
Tables Of Coincidence Orientations For Ordered Tetragonal L Lo Alloys For A Range Of Axial Ratios, Abha Singh, Alexander H. King
Tables Of Coincidence Orientations For Ordered Tetragonal L Lo Alloys For A Range Of Axial Ratios, Abha Singh, Alexander H. King
Alexander H. King
In this paper we develop and apply techniques for computation of CSL, DSCL and step-vector data for grain boundaries in tetragonal materials for a range of axial ratios. This has application to L10 alloys including TiA1, which is a candidate for lightweight high-temperature structural applications. Our results are compared with others and found to be more accurate and complete. We provide data for a wider range of axial ratios than those considered by previous workers. We have also derived equivalent quaternions for tetragonal crystals in tetragonal-crystal coordinates and listed conditions for selecting a unique reduced rotation in tetragonal-crystal coordinates so …
A Geometrical Rationalization Of The Special Properties Of The 14° [001] Grain Boundary In Yba2cu3o7−Δ, Alexander H. King, Abha Singh
A Geometrical Rationalization Of The Special Properties Of The 14° [001] Grain Boundary In Yba2cu3o7−Δ, Alexander H. King, Abha Singh
Alexander H. King
14° [001] tilt grain boundaries in YBa2Cu3O7−δ have been found to exhibit anomalously good superconducting critical currents, associated with magnetic flux pinning, although no special interfacial structure has heretofore been associated with this misorientation. We present an analysis of the geometry of the grain boundary in question and show that it can correspond to a special interface, within the definition of constrained lattice coincidence, which may lead to new understanding of the superconducting behavior of grain boundaries. Our analysis shows that the tetragonal‐to‐orthorhombic phase transformation may have important effects upon grain boundary structure and properties, indicating new approaches to producing …
Tem Observations Of The Mechanism Of Delamination Of Chromium Films From Silicon Substrates, D. Goyal, Alexander H. King
Tem Observations Of The Mechanism Of Delamination Of Chromium Films From Silicon Substrates, D. Goyal, Alexander H. King
Alexander H. King
We have observed the complete delamination of polycrystalline chromium films from single crystal silicon substrates during deposition due to the formation of high internal stresses. These intrinsic stresses can give rise to interfacial defects which assist in the separation of the film from the substrate. Stresses in the film are balanced by stresses in the substrate, which cause mechanical failure in the substrate near the interface. Extensive arrays of dislocations and cracking of the substrate have been observed. We find that the delamination of the films from the substrate is initiated by the formation of damage in the substrate, rather …
The Interaction Between Dislocations And Intergranular Cracks, H. Zhang, Alexander H. King, R. Thomson
The Interaction Between Dislocations And Intergranular Cracks, H. Zhang, Alexander H. King, R. Thomson
Alexander H. King
The elastic interactions of dislocations and intergranular cracks in isotropic materials have been studied. In the first part of the paper, a model based on the Rice–Thomson theory is established under which the conditions for dislocation emission and crack propagation can be described in terms of an emission surface, cleavage surface, and loading line in the local k-space associated with a mixed mode intergranular crack. For a given crack, the local k-field changes with the emission of dislocations from the crack tip, which alters the balance of cleavage and emission. In the second part, we present experimental results of in …
Structure And Stability Of Hexacoordinated Sila Dianions, Mark S. Gordon, Marshall T. Carroll, Larry P. Davis, Larry W. Burggraf
Structure And Stability Of Hexacoordinated Sila Dianions, Mark S. Gordon, Marshall T. Carroll, Larry P. Davis, Larry W. Burggraf
Mark S. Gordon
The structures and stabilities of hexacoordinated silicon-containing dianions SiX6 2- have been investigated by using both ab initio (X= H, F) and semiempirical AMI (X= H, F, OH, Me, Cl) calculations. Both methods predict the hexacoordinated structures to be minima on the potential energy surfaces, although the semiempirical barriers for the reactions SiX6 2- -+ Six5- + x- appear to be rather overestimated based on the ab initio results for X = H, F. The positive charge on the central silicon atom actually increases as the number of ligands increases, and the role of d orbitals on that atom appears …
Theoretical Study Of Pseudorotation Of Pentacoordinated Silicon Anions: The Prototypical Sih5-, Mark S. Gordon, Theresa L. Windus, Larry W. Burggraf, Larry P. Davis
Theoretical Study Of Pseudorotation Of Pentacoordinated Silicon Anions: The Prototypical Sih5-, Mark S. Gordon, Theresa L. Windus, Larry W. Burggraf, Larry P. Davis
Mark S. Gordon
Ab initio and semiempirical calculations are used to analyze the minimum energy path for the pseudorotation of SiH5-. Both AMI and MP2/6-31++G(d,p) predict pseudorotation barriers of 2.4 kcal/mol. A decomposition of the projected vibrational frequencies along the path is used to assist in the interpretation of the process.
Coincidence Orientations Of Crystals In Tetragonal Systems, With Applications To Yba2cu3o7, Abha Singh, N. Chandrasekhar, Alexander H. King
Coincidence Orientations Of Crystals In Tetragonal Systems, With Applications To Yba2cu3o7, Abha Singh, N. Chandrasekhar, Alexander H. King
Alexander H. King
We have developed a method for the characterization of coincidence-site lattices (CSL's) in tetragonal or near-tetragonal orthorhombic structures, by suitable modifications to the method of Grimmer & Warrington [Acta Cryst. (1987), A43, 232-243]. We have applied our method to determine coincidence rotations and the associated information appropriate for forming constrained CSL's in the high-To superconductor YBazCu307-n. The unit cell is orthorhombic with lattice parameters a = 3.82, b = 3"89 and c = 11.67 A for the nominal composition. We present tables of coincidence rotation angles, .Z, CSL, DSCL and associated step vectors up to ,~ = 50. We find …
Slip, Twinning, And Fracture At A Grain Boundary In The L12 Ordered Structure—Aς = 9 Tilt Boundary, Alexander H. King, M. H. Yoo
Slip, Twinning, And Fracture At A Grain Boundary In The L12 Ordered Structure—Aς = 9 Tilt Boundary, Alexander H. King, M. H. Yoo
Alexander H. King
The role of interaction between slip dislocations and a Σ = 9 tilt boundary in localized microplastic deformation, cleavage, or intergranular fracture in the Li2 ordered structure has been analyzed by using the anisotropic elasticity theory of dislocations and fracture. Screw superpartials cross slip easily at the boundary onto the (1$\overline 1$1) and the (001) planes at low and high temperatures, respectively. Transmission of primary slip dislocations onto the conjugate slip system occurs with a certain degree of difficulty, which is eased by localized disordering. When the transmission is impeded, cleavage fracture on the ($\overline 1$11) plane is predicted to …
Gas-Phase And Computational Studies Of Pentacoordinate Silicon, Robert Damrauer, Larry W. Burggraf, Larry P. Davis, Mark S. Gordon
Gas-Phase And Computational Studies Of Pentacoordinate Silicon, Robert Damrauer, Larry W. Burggraf, Larry P. Davis, Mark S. Gordon
Mark S. Gordon
We have demonstrated that a wide variety of pentacoordinate silicon anions (siliconates) should be stable and can be prepared by combining the predictive powers of MNDO and ab initio computational methods and the flowing afterglow (FA) experimental technique. MNDO has been used to compute the anion affinities of 91 siliconates; all but five of these are predicted to be stable with respect to the loss of an anion. Twenty-four siliconates, most of them previously unreported, have been prepared and studied in the FA. The MNDO predictions were, in general, consistent with the experimental results and with trends previously reported by …
The Further Geometry Of Grain Boundaries In Hexagonal Close-Packed Metals, Fu-Rong Chen, Alexander H. King
The Further Geometry Of Grain Boundaries In Hexagonal Close-Packed Metals, Fu-Rong Chen, Alexander H. King
Alexander H. King
A technique is given for finding partial DSC vectors appropriate to crystals with more than one atom per lattice site. The DSC lattice is made up of vectors that represent displacements of one crystal with respect to the other that leave the boundary structure shifted, but not complete. A new, rapid method for finding the step vectors associated with perfect DSC dislocations is described. Partial DSC vectors and step vectors for perfect DSC dislocations in hexagonal close-packed crystals are determined. The availability of reactions between lattice partial dislocations and grain boundaries in hexagonal close-packed crystals is also assessed.
Glass Formation And High Conductivity In The Ternary System Silver Iodide + Silver Arsenate (Ag3aso4) + Silver Metaphosphate (Agpo3): Host To Glassy .Alpha.-Silver Iodide?, Steve W. Martin, Alberto Schiraldi
Glass Formation And High Conductivity In The Ternary System Silver Iodide + Silver Arsenate (Ag3aso4) + Silver Metaphosphate (Agpo3): Host To Glassy .Alpha.-Silver Iodide?, Steve W. Martin, Alberto Schiraldi
Steve W. Martin
Wide regions of glass formation have been found in the ternary system xAgI + yAg,As04 + (1 - x - y)AgPO,. Glasses containing up to 75 mol 7% AgI can be formed in sections greater than 2 cm thick without signs of devitrification. Glass transition temperatures as high as 175 OC for glasses containing - 10 mol % AgI fall to -45 OC at the highest AgI content. An equivalent ratio of Ag1:N is defined and it is found that, for all glass-forming compositions, the electrical data as expressed in the Arrhenius form, u = A exp(-E,,/RT), log (./(a cm)-’), …
The Effects On Grain-Boundary Processes Of The Steps In The Boundary Plane Associated With The Cores Of Grain-Boundary Dislocations, Alexander H. King, D. A. Smith
The Effects On Grain-Boundary Processes Of The Steps In The Boundary Plane Associated With The Cores Of Grain-Boundary Dislocations, Alexander H. King, D. A. Smith
Alexander H. King
The contribution of the associated steps to the properties of grain-boundary dislocations are investigated. Two methods of step-height determination are given and it is shown that the step height, like the Burgers vector, must be conserved during the reactions of grain-boundary dislocations: this is not always automatic and additional coherent steps must take part in some reactions. The energies associated with steps have been estimated and compared with the elastic energies of grain-boundary dislocations; these comparisons suggest that (a) the reduction of elastic energy alone may not be a sufficient criterion for the progress of a reaction and (b) that …