Ni Ring Research Articles

ON NCI RINGS

We in this note introduce the concept of NCI rings which is a generalization of NI rings. We study the basic structure of NCI rings, concentrating rings of bounded index of nilpotency and von Neumann regular rings. We also construct suitable examples to the situations raised naturally in the process.

Isolated Heterometallic Cr7Ni Rings Grafted on Au(111) Surface

A study of the deposition of heterometallic antiferromagnetically coupled rings onto gold surfaces is reported. Two new {Cr7Ni} rings, [NH2nPr2][Cr7NiF8(3-tpc)16] (1) (where 3-tpc=3-thiophenecarboxylate) and [nBuNH2CH2CH2SH] [Cr7NiF8(O2CtBu)16] (2) have been made and structurally characterized. They have been deposited from the liquid phase on Au(111) and the adsorbed molecules compared by means of scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS). In both cases a two-dimensional distribution of individually accessible {Cr7Ni} heterometallic rings on the gold surface has been obtained, exploiting the direct grafting of sulfur-functionalized clusters. There is a competition between the chemisorption of the {Cr7Ni} clusters and a thiolic self-assembled monolayer (SAM) formed by free ligands. In 2, the presence of a single sulfur ligand should force the molecule to graft with the ring axis normal to the surface. The cluster stability in the STM images and the S-2p energy positions demonstrate, for both functionalizations, the strength of the grafting with the gold surface.

Ni5Sb17]4‐ Transition‐Metal Zintl Ion Complex: Crossing the Zintl Border in Molecular Intermetalloid Clusters.

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Rings Whose Nilpotent Elements form a Levitzki Radical Ring

It is shown that a locally 2-primal ring, but not 2-primal, can be always constructed from any given a 2-primal ring. Locally 2-primal rings are NI but we show that there are NI rings which are not locally 2-primal. We prove that every minimal noncommutative (locally) 2-primal ring is isomorphic to the 2 by 2 upper triangular matrix ring over GF(2). By Smoktunowicz (2000), a nil ring R need not be locally 2-primal, but we show that it is the case if and only if R is a Levitzki radical ring. We also prove that the local 2-primalness is inherited by polynomial rings, but not by power series rings. However in the case of rings of bounded index of nilpotency, a ring is locally 2-primal if and only if so is its power series ring.

Ni5Sb17]4- Transition-Metal Zintl Ion Complex: Crossing the Zintl Border in Molecular Intermetalloid Clusters

K3Sb7 and Ni(COD)2 react in the presence of 2,2,2-cryptand in ethylenediamine solutions ( approximately 1:8 Ni/Sb molar ratio) to give dark-brown crystals of the paramagnetic cluster anion [Ni5Sb17]4- as the [K(2,2,2-crypt)]+ salt. The cluster has a Ni(cyclo-Ni4Sb4) ring unit that sits inside a Sb13 bowl. The structure is similar to that of the previously reported [Pd7As16]4- ion containing a Pd(cyclo-Pd4As4) ring unit that sits inside a Pd2As12 bowl. Density functional theory and bond valence analyses suggest delocalized charge distributions and intermetallic-like properties.

Structure and topological conditions of NI rings

We first construct an NI ring but not 2-primal from given any 2-primal ring, in a simpler way than well-known examples. We study the structure of NI rings relating to strongly prime ideals and show that minimal strongly prime ideals can be lifted in NI rings. A ring is called (respectively weakly) pm if every (respectively strongly) prime ideal is contained in a unique maximal ideal in it. For a 2-primal ring R Sun proved that R is pm if and only if Max ( R ) is a retract of Spec ( R ) if and only if Spec ( R ) is normal. In the present note we prove for an NI ring R that R is weakly pm if and only if Max ( R ) is a retract of SSpec ( R ) if and only if SSpec ( R ) is normal, where SSpec ( R ) is the space of strongly prime ideals of R. We also prove that R is weakly pm if and only if R is pm when R is a symmetric ring. We lastly consider several kinds of extensions of NI rings.

Aromaticity in Stable Tiara Nickel Thiolates: Computational and Structural Analysis

Quantum chemical calculations as well as crystallographic analyses show that the Ni(n) rings in the tiara Ni thiolates, [NiS2]n and [Ni(SR)2]n (n = 3-6), have highly symmetric polygonal structures. We find that such structural features primarily arise from the effective delocalization of the d-orbital electrons across the Ni(n) rings leading to bond length equalization and thereby aromaticity. We introduce the d-orbital aromaticity for the first time to explain the experimentally observed polygonal structures of these cyclic metal rings bridged by thiol linkages.

A rotating disk electrode study on the ammonia oxidation

The anodic oxidation of ammonia in alkaline solutions was investigated by using rotating disk electrode (RDE) and rotating ring–disk electrode (RRDE) techniques. The ammonia oxidation current on the rotating platinum disk was confirmed not to increase but to decrease with increasing the rotation rate at 25–60 °C. The in situ ring electrode detector gave two kinds of signals for the electroactive species transported from the disk electrode engaged in ammonia oxidation; one can be again reduced and another can further be oxidized on Pt or Ni ring. These results suggested that at least some of the intermediates involved in ammonia oxidation on Pt may not be strongly adsorbed but be detached from the surface regions.

Planar Hall sensors for micro-Hall magnetometry

In this work we present a new method to fabricate planar Hall sensors from GaAs–AlGaAs heterojunctions, which can be used to examine the local stray field at a specific section of a micron-sized magnet. Instead of mesa etching we implanted oxygen ions with an energy of 1.5 keV which deplete the two-dimensional electron gas underneath the exposed areas but leave the wafer flat. Planar double Hall cross devices were employed to investigate 30 nm thick electroplated Ni rings with outer and inner diameters ranging from 1.2 to 2 μm and from 0.3 to 1.6 μm, respectively. By comparing the signals from both Hall crosses of the sensor, we can distinguish between local stray field variations and changes of the global magnetization pattern. A hysteresis loop measured at a temperature of 110 K suggests that magnetization reversal occurs via a magnetic vortex structure.

Magnetron sputtered CrNiN and TiMoN films: comparison of mechanical properties

This article reports on structure and mechanical properties of CrNiN and TiMoN films with a low (<10 at.%) content of Ni or Mo, respectively. The films were deposited by reactive sputtering using d.c. unbalanced magnetron equipped with a round planar Cr target fixed to the magnetron cathode with a Ni ring or alloyed TiMo (90:10 at.%) target. The investigation of sputtered films showed that: (i) both CrNiN and TiMoN films can form a superhard material with a maximum microhardness H max of approximately 45 GPa; (ii) the films with H max exhibit a single-oriented structure and; (iii) the CrNiN films exhibit a higher resistance to plastic deformation compared to the TiMoN films. The relationships between microhardness, H, reduced Young's modulus, E *= E/(1−ν 2), and elastic recovery, W e, evaluated from loading/unloading curves measured using a computer-controlled microhardness tester Fisherscope H 100, are given; here E and ν are the Young's modulus and Poisson ratio, respectively. The production of a high-temperature (β-Ti,Mo)(110) phase in pure TiMo alloy film sputtered on unheated steel substrate is also reported.

Composition Control of NiTi Shape Memory Alloy Films Formed by Sputter Deposition with a Composite Target

In order to obtain NiTi films by magnetron sputtering, the authors devised a target composed of Ti and Ni rings and a Ti disk. The fabricated films were analyzed by energy-dispersive X-ray analysis (EDX) and Rutherford backscattering spectrometry (RBS). X-ray diffraction measurements (XRD) of the films were also carried out. It was shown that the composition of the film formed with the target was easily controlled with an accuracy of 0.5 at.% by changing the electric current flowing through the solenoid coil of an electromagnet. The composition of the film was affected by the Ar gas pressure. It was also shown that a film with an in-depth composition gradient was easily formed. The obtained films were confirmed by a bending test to show the shape memory effect.

Atomic and electronic structure of decagonal Al-Ni-Co alloys and approximant phases

Detailed investigations of the atomic and electronic structures of decagonal AlNiCo alloys have been performed. Several different models for the decagonal structure have been investigated: A model based on a rhombic-hexagon tiling proposed by Henley and models based on a cluster decoration of the Penrose tiling with large rhombus edge. The topology of the structural models has been refined on the basis of the existing x-ray-diffraction data which, however, do not allow us to specify the chemical decoration uniquely. The chemical order on the decagonal lattice has been optimized via the comparison of the calculated electronic spectra with photoemission and soft-x-ray data and using total-energy calculations. The electronic structure calculations for large periodic approximants with up to 1276 atoms/cell have been performed self-consistently using a real-space tight-binding linear muffin-tin orbital technique. The best agreement with the experimental spectra is achieved for a large-rhombus-tiling model with the innermost ring of the pentagonal columnar clusters occupied by Ni atoms only. This configuration also has the lowest total energy. As in decagonal AlCuCo we find a high density of states at the Fermi level, but the chemical ordering is very different: whereas in d-AlCuCo direct Cu-Cu neighbors are suppressed and there is a slight preference for Co-Co homocoordination, in $d\ensuremath{-}\mathrm{AlNiCo}$ a strong Ni-Ni interaction stabilizes the innermost Ni ring, direct Co-Co neighbors are suppressed and there is a strong Co-Al interaction.

Evolution and impact of temperature patterns during hydrogen oxidation on a Ni ring

Rotating temperature pulses were observed during hydrogen oxidation on a nickel ring. Changes in the pulse amplitude and width (with angular position) caused oscillations in the global reaction rate. With time, the pulse motion transformed to homogeneous oscillations. However, for several weeks, the pulse motion could be restored by a proper start up. As the time-on-stream increased, domain oscillations prevailed in which pulses alternately formed at few catalyst locations. The average conversion attained when a rotating pulse existed was sometimes significantly higher than that for homogeneous oscillations under the same operating conditions. Increasing the gas-phase mixing in the vessel enhanced the formation and prolonged the life of the rotating pulses, indicating that global interaction stabilized this motion. The time-averaged local temperature rise as a function of angular position was similar for various qualitatively different patterns, indicating an underlying nonuniformity in the system.

Atomic and electronic structure of decagonal Al-Pd-Mn alloys and approximant phases

Detailed investigations of the atomic and electronic structures of decagonal AlNiCo alloys have been performed. Several different models for the decagonal structure have been investigated: A model based on a rhombic-hexagon tiling proposed by Henley and models based on a cluster decoration of the Penrose tiling with large rhombus edge. The topology of the structural models has been refined on the basis of the existing x-ray-diffraction data which, however, do not allow us to specify the chemical decoration uniquely. The chemical order on the decagonal lattice has been optimized via the comparison of the calculated electronic spectra with photoemission and soft-x-ray data and using total-energy calculations. The electronic structure calculations for large periodic approximants with up to 1276 atoms/cell have been performed self-consistently using a real-space tight-binding linear muffin-tin orbital technique. The best agreement with the experimental spectra is achieved for a large-rhombus-tiling model with the innermost ring of the pentagonal columnar clusters occupied by Ni atoms only. This configuration also has the lowest total energy. As in decagonal AlCuCo we find a high density of states at the Fermi level, but the chemical ordering is very different: whereas in d-AlCuCo direct Cu-Cu neighbors are suppressed and there is a slight preference for Co-Co homocoordination, in $d\ensuremath{-}\mathrm{AlNiCo}$ a strong Ni-Ni interaction stabilizes the innermost Ni ring, direct Co-Co neighbors are suppressed and there is a strong Co-Al interaction.

ChemInform Abstract: CRYSTAL AND MOLECULAR STRUCTURE OF BIS(DIMETHYLBIS(PYRAZOL‐1‐YL)GALLATO)‐NICKEL(II)

Crystals of the title compound are monoclinic, a= 8·530(6), b= 17·939(10), c= 7·415(6)A, β= 106·88(7)°, space group P21/c, Z= 2. The structure was determined from diffractometer data by Patterson and Fourier syntheses, and refined by full-matrix least-squares methods to R 0·049 for 1352 observed reflexions. The whole molecule is in a pseudo-chair conformation with the two six-membered Ga–(N–N)2–Ni rings in boat conformations. The nickel atom lies on a crystallographic centre of symmetry in the middle of a planar arrangement of four nitrogen atoms. Mean dimensions are: Ga–N 1·977, Ni–N 1·895, Ga–C 1·944, N–N 1·355, C–N 1·333, C–C 1·377 A; N–Ga–N 91·6, Ga–N–N 120·5, C–Ga–C 126·9, N–Ni–N (chelate angle) 92·4, N–Ni–N (non-chelate angle) 87·6, Ni–N–N, 124°.

Crystal and molecular structure of bis[dimethylbis(pyrazol-1-yl)gallato]nickel(II)

Crystals of the title compound are monoclinic, a= 8·530(6), b= 17·939(10), c= 7·415(6)Å, β= 106·88(7)°, space group P21/c, Z= 2. The structure was determined from diffractometer data by Patterson and Fourier syntheses, and refined by full-matrix least-squares methods to R 0·049 for 1352 observed reflexions. The whole molecule is in a pseudo-chair conformation with the two six-membered Ga–(N–N)2–Ni rings in boat conformations. The nickel atom lies on a crystallographic centre of symmetry in the middle of a planar arrangement of four nitrogen atoms. Mean dimensions are: Ga–N 1·977, Ni–N 1·895, Ga–C 1·944, N–N 1·355, C–N 1·333, C–C 1·377 Å; N–Ga–N 91·6, Ga–N–N 120·5, C–Ga–C 126·9, N–Ni–N (chelate angle) 92·4, N–Ni–N (non-chelate angle) 87·6, Ni–N–N, 124°.