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Changes in the valence bands and core levels of Al-modified Ni and Cu surfaces have been investigated. Interaction of oxygen with such modified surfaces gives rise to Al2O3, leaving the transition metal unaffected.
Optical limiting behaviour of suspensions of single-walled carbon nanotubes in water, ethanol and ethylene glycol is reported. Experiments with 532 nm, 15 ns duration laser pulses show that optical limiting occurs mainly due to nonlinear scattering. The observed host liquid dependence of the optical limiting effect in different suspensions suggests that the scattering originates from microbubbles formed due to absorption-induced heating.
Review: (a review article including topics as glass transition, the structure of amorphous materials, models of the amorphous state,electronic properties, heterogeneous catalysis and noncrystalline state as well as material applications and design.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMolecular orbital study of the configuration protonation, and hydrogen bonding of secondary amidesA. S. N. Murthy, K. Gurudath Rao, and C. N. Ramachandra RaoCite this: J. Am. Chem. Soc. 1970, 92, 12, 3544–3548Publication Date (Print):June 1, 1970Publication History Published online1 May 2002Published inissue 1 June 1970https://pubs.acs.org/doi/10.1021/ja00715a003https://doi.org/10.1021/ja00715a003research-articleACS PublicationsRequest reuse permissionsArticle Views93Altmetric-Citations33LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Superconducting Tl1 –δCaBa2Cu2O7 can be prepared without impurity from the corresponding two Tl–O layer cuprate only when some Tl deficiency is incorporated. The Tl1 –δCaBa2Cu2O7 and Tl1 –δY1 –xCaxBa2Cu2O7 series show maximum Tc at an optimal hole concentration. The Tc maximum occurs at a Cu—O distance of ca. 1.924 Å.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Hybrid framework compounds, including both metal–organic coordination polymers and systems that contain extended inorganic connectivity (extended inorganic hybrids), have recently developed into an important new class of solid-state materials. We examine the diversity of this complex class of materials, propose a simple but systematic classification, and explore the chemical and geometrical factors that influence their formation. We also discuss the growing evidence that many hybrid frameworks tend to form under thermodynamic rather than kinetic control when the synthesis is carried out under hydrothermal conditions. Finally, we explore the potential applications of hybrid frameworks in areas such as gas separations and storage, heterogeneous catalysis, and photoluminescence.
La 2−x Sr x NiO 4 shows a maximum in the c/a ratio around x=0.6 up to which composition the concentration of holes is equal to that expected theoretically. The material becomes a degenerate semiconductor above a certain temperature up to x=0.8, but is metallic at room temperature when x≥1.0. All the compositions with x≥0.05 are paramagnetic in the 15-300K range. Based on these measurements, an electronic phase diagram is tentatively proposed. It is noteworthy that the antiferromagnetic order disappears at low doping levels in both La 2−x Sr x NiO 4 and La 2−x Sr x NiO 4 , but metallicity is seen at 300K only at a much higher x value in the former system.
Open-framework cadmium succinates, [CN(3)H(6)](2)[Cd(2)(C(4)H(4)O(4))(Cl)(2)], I; [CN(3)H(6)](2)[Cd(C(4)H(4)O(4))(2)], II; Cd(2)(C(4)H(4)O(4))(2)(C(4)N(2)H(8))(H(2)O)(3), III; [C(4)N(2)H(12)][Cd(2)(C(4)H(4)O(4))(3)].4H(2)O, IV; Cd(C(4)H(4)O(4))(H(2)O)(2), V; and Cd(3)(C(4)H(4)O(4))(2)(OH)(2)], VI, of different dimensionalities have been synthesized by hydrothermal procedure by employing two different strategies, one involving the reaction of Cd salts with organic-amine succinates and the other involving the hydrothermal reaction of Cd salts with a mixture of succinic acid and the organic amine. While the latter procedure yields structures without any amine in them, the former gives rise to amine templated cadmium succinates with open architectures. By employing guanidinium succinate we have obtained I and II, and with piperazinium succinate we obtained III and IV. Of these I has a one-dimensional chain structure, IV has a layered structure, and II and III have three-dimensional architectures. The two cadmium succinates without incorporation of amine, V and VI, possess layered and three-dimensional structures, respectively. The three-dimensional structures II and III exhibit interpenetration similar to that in diamondoid and alpha-polonium type structures, respectively.
The superconducting transition temperature, T c, of several series of cuprates shows a nonlinear dependence on the hole concentration, n h, determined by chemical titrations. The t c becomes maximum when n h is in the 0.12-0.15 range in cuprates containing a single Cu-O layer and around 0.2 in cuprates containing two Cu-O layers.
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Enthalpy changes of the crystal-plastic and plastic-liquid transitions are related to the temperature range of stability of the plastic phase. Thermodynamics of the plastic state of binary mixtures have been examined. Infrared correlation times, τc, and activation energies have been measured for a few molecules in the plastic state. Molecular tumbling times, τt, have also been measured employing ESR spectra of a spin-probe. Plots of log τc(τt) versus 1/T are continuous through the plastic-liquid transition. Activation energies for molecular motion seem to vary in the same direction as the ΔH of the plastic-crystal transition. Infrared correlation times of solute molecules in binary solutions in the plastic and the liquid states show interesting variations with solute concentration.
Abstract X-ray absorption spectra, X-ray photoelectron spectra and Auger spectra of cuprate superconductors are discussed. The studies establish the absence of Cu3+ for all practical purposes, but point out the importance of oxygen holes. X-ray photoelectron spectra of BaBi0.25Pb0.75O3 and related compounds are also examined. Key Words: High-temperature superconductivityphotoemission, auger spectraX-ray absorption spectraYBa2Cu3O7, La1.85Sr0.15CuO4 Bi2CaSr2Cu2O8, Tl2CaBa2Cu2O8.
While La0.7Ba0.3MnO3 is a ferromagnetic metal (TC = 340 K)with long-range ordering, Nd0.7Ba0.3MnO3 shows a transition around 150 K with a small increase in magnetization, but remains an insulator at all temperatures. Gd0.7Ba0.3MnO3 is non-magnetic and insulating at all temperatures. Low field dc magnetization and ac susceptibility measurements reveal the presence of a transition at around 150 K in Nd0.7Ba0.3MnO3, and a complex behaviour with different ordering/freezing transitions at 62, 46 and 36 K in the case of Gd0.7Ba0.3MnO3, the last one being more prominent. The nature of the field dependence of the magnetization, combined with the slow magnetic relaxation, ageing and memory effects, suggests that Nd0.7Ba0.3MnO3 is a cluster glass below 150 K, a situation similar to that found for La1−xSrxCoO3. Gd0.7Ba0.3MnO3, however, shows non-equilibrium dynamics characteristic of spin glasses, below 36 K. The difference in nature of the glassy behaviour between Gd0.7Ba0.3MnO3 and Nd0.7Ba0.3MnO3 probably arises because of the larger disorder arising from the mismatch between the sizes of the A-site cations in the former. Our results on Nd0.7Ba0.3MnO3 and Gd0.7Ba0.3MnO3 suggest that the magnetic insulating states often reported for rare earth manganates of the type Ln1−xAxMnO3 (Ln = rare earth, A = alkaline earth) are likely to be associated with glassy magnetic behaviour.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
