Molecular complexes of metallo tetraphenyl porphyrins with 2,4,5,7-tetranitro fluorenone

The interactions of mesotetraphenyl porphyrin and its metallo derivatives with 2,4,5,7-tetra nitrofluorenone have been studied using spectroscopic methods. The association constants (K) for 1:1 complexes in Ch2Cl2Cl2 follow the order Pd+2>Co+2> Cu+2>VO+2>Ni+2>Zn+2. The values of K are accounted in terms of stereochemistry of MTPPs and the electronic configuration of the metal ions. The magnitude and direction of the proton NMR shifts of the acceptor and donor in the complexes and their ESR parameter furnish information as to the possible structures of these complexes in solution.

Characterization of dry sliding wear of Al---Si alloys

Controversy exists in the published literature as to the effect of silicon content and pressure on the dry sliding wear of Al---Si alloys. The present paper attempts to clarify the question by reporting a statistical analysis of data obtained from factorially designed experiments conducted on a pinon-disc machine in the pressure range 0.105–1.733 MPa and speed range 0.19–0.94 m s−1. Under these conditions it was found that, in the range 4–24 wt.% Si, wear of binary unmodified alloys does not significantly differ between the alloys. However, it is significantly less than that corresponding to an alloy containing no silicon. The effect of pressure on wear rate was found to be linear and monotonie and, over the narrow range of speeds used, the wear rate was found to be unaffected by speed. The coefficient of friction was found to be insensitive to variations in silicon content, pressure and speed.

Preparation, structure, and magnetic properties of isostructural La3MAlS7 and La3MFeS7 (M = Mg, Mn, Fe, Co, Ni, or Zn)

A series of quaternary metal sulfides of the general formula La3MM′S7 (M = Mn, Fe, Co; M′ = Al and M = Mg, Mn, Fe, Co, Ni; M′ = Fe) consisting of linear chains of face shared MS6 octahedra and isolated M′S4 tetrahedra has been prepared and studied. The aluminium compounds La3MAlS7 (M = Mn, Fe, Co) exhibit linear chain antiferromagnetism. Magnetic behavior of other La3MFeS7 sulfides has been examined in detail. The magnetic susceptibility of La3MgFeS7 shows that tetrahedral site Fe3+ undergoes a transition from Image to S = 2 spin state around 150 K.

Stress-induced martensitic phase transformation in Cu-Zr nanowires

A novel stress-induced martensitic phase transformation in an initial < 100 >/{100} B2-CuZr nanowire is reported for the first time in this letter. Such behavior is observed in a nanowire with cross-sectional dimensions of 19.44 x 19.44 angstrom(2) over a temperature range of 100-400 K and at a strain rate of 1 x 10(9) s(-1) using atomistic simulations. Phase transformation from an initial B2 phase to a BCT (Body-Centered-Tetragonal) phase is observed via nucleation and propagation of {100} twinning plane under high strain rate tensile deformation. (C) 2009 Elsevier B.V. All rights reserved.

Mossbauer-Effect Study Of The Thermal-Decomposition In Hydrogen Of Homogeneously Mixed Ferrous Nickel Oxalates With Different Iron To Nickel Ratios

Mossbauer effect and X-ray measurements are carried out on product samples of the thermogravimetric analysis (TGA) and isothermal decomposition in hydrogen of homogeneously mixed ferrous nickel oxalates with different iron to nickel ratios. The formation of Fe-Ni alloy is obtained at considerably lower temperatures (z 300 "C) in each case. The Fe-Ni alloys obtained shift from iron-rich to nickel-rich composition as the nickel ratio in the mixed metal oxalates is increased. The formation of Pe-Ni Invar from mixed metal oxalate with Fe:Ni = 1:l is indicated in the early stages but not from those with Fe:Ni = 2: 1 or 64:36. An Produktproben von homogen verteilten Eisen-Nickeloxalaten mit unterschiedlichem Eisen- Nickel-Verhaltnis nach thermogravimetrischer Analyse (TGA) und isothermem Zerfall in Wasserst off werden Mollbauereffekt- und Rontgenmessnngen durchgefuhrt. In allen Fiillen wird die Bildung der Fe-Ni-Legierung bei betriichtlich niedrigeren Temperaturen (= 300 "C) erhalten. Die erhaltenen Fe-Ni-Legierungen verschieben sich von der eisenreichen zur nickelreichen Zusrtmmensetzung, wenn das Nickelverhaltnis in dem BIetall-Mischoxalat erhoht wird. Die Bildung der Fe-Ni-lnvar-Legierung aus dem Metall-Mischoxalat mit Fe:Ni = 1 : 1 wird in fruhen Zu Zustanden beobachtet, iedoch nicht aus Oxalaten mit Fe:Ni = 2:1 oder 64:36.

Depth profile composition studies of thin film CdS: Cu,S solar cells using XPS and AES

Surface composition and depth profile studies of hemiplated thin film CdS:CuzS solar cells have been carried out using x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) techniques. These studies indicate that the junction is fairly diffused in the as-prepared cell. However, heat treatment of the cell at 210°C in air relatively sharpens the junction and improves the cell performance. Using the Cu(2p3p)/S(2p) ratio as well as the Cu(LVV)/(LMM) Auger intensity ratio, it can be inferred that the nominal valency of copper in the layers above the junction is Cut and it is essentially in the CUSS form. Copper signals are observed from layers deep down in the cell. These seem to appear mostly from the grain boundary region. From the observed concentration of Cd, Cu and S in these deeper layers and the Cu(LVV)/(LMM) ratio it appears that the signals from copper essentially originate partly from copper in CuS and partly from Cu2t trapped in the lattice. It is significant to note that the nominal valence state of copper changes rather abruptly from Cut to Cuz+ across the junction.

Donor properties of metallomacrocyclic tetrapyrrole pigments with sym-trinitrobenzene

The interactions of metallo derivatives of macrocyclic tetrapyrrole pigments, pheophytin a (pheo), phthalocyanin (phth), and tetraphenylporphyrin (TPP) with sym-trinitrobenzene (TNB) have been studied with use of spectroscopic methods. These macrocyles form 1:l molecular complexw with the acceptor. The association constants (K) for the interactions follow the decreasing order of binding as pheo > phth > TPP. The divalent metal ions influence the values of K for the various metallo TPP derivatives, and the relative order of stabilities decrease as Co > Cu = VO > Ni > Zn. The stereochemistry of M(TPP) and the electronic configuration of the metal ions are shown to contribute to the magnitudes of K. The acceptor strongly quenches the fluorescence of the metallo macrocycles, and the quenching constant decreases as pheo > phth > TPP. The formation of exciplexes is postulated on the basis of the rate of bimolecular quenching constants and solvent effects.

Complexes Of Imidazoline-2-Thione And Its 1-Methyl Analogue With Cu(Ii), Zn(Ii), Cd(Ii) And Hg(Ii) Salts

The reaction of Cu(II), Zn(II), Cd(II) and Hg(II) chlorides and bromides with imidazoline-2-thione (IZT) and its N-methyl derivative (NMIZT) yields complexes of stoichiometry ML3X2 and ML2X (IZT) and its N-methyl derivative (NMIZT) yields complexes of stoichiometry ML3X2 and ML2X (where M=Cu(I)); copper(II) halides yield Cu(I) complexes. On the basis of infrared and 13C n.m.r.

High-Tc superconductivity in the Er---Ba---Cu---O and related systems

ErBa2Cu3O7 and Er0.5Y0.5Ba2Cu3O7 are both high-Tc superconductors attaining zero resistance above 80 K. Preliminary studies indicate that Yb1−xYxBa2Cu3O7 also exhibits zero resistance above 77 K.

Metal Chelates in Vinyl Polymerization: Kinetics and Mechanism of Acrylonitrile Polymerization Initiated by Cu(I1) Imine Complexes

The free radical polymerization of acrylonitrile (AN) initiated by Cu(I1) 4-anilino 3-pentene 2-one [Cu(II) ANIPO] Cu(II), 4-p-toluedeno 3-pentene 2-one [Cu(II) TPO], and Cu(I1) 4-p-nitroanilino 3-pentene 2-one [Cu(II) NAPO] was studied in benzene at 50 and 60°C and in carbon tetrachloride (CCld), dimethyl sulfoxide (DMSO), and methanol (MeOH) at 60°C. Although the polymerization proceeded in a heterogeneous phase, it followed the kinetics of a homogeneous process. The monomer exponents were 22 at two different temperatures and in different solvents. The square-root dependence of R, on initiator concentration and higher monomer exponents accounted for a 1:2 complex formation between the chelate and monomer. The complex formatign was shown by ultraviolet (UV) study. The activation energies, kinetics, and chain transfer constants were also evaluated.

HIGH-Tc superconductivity in perovskite oxides of the Y-Ba-Cu-O system

Several biphasic compositions of the type Y3-xBa3+xCu6O14 show an onset of superconductivity in the 90-115K range, attaining zero resistance in the 70-85K range. The phase responsible for superconductivity in these compositions is a perovskite oxide of composition YBa2Cu3 O7. This oxide annealed in oxygen shows the onset of superconductivity at 120K and zero resistance at 87K. YBa2,Cu3O7 shows the highest Meissner effect of all oxide superconductors. The superconducting behaviour of the two perovskite oxides, Y0.95Ba1.95,Cu3O7 and Y1.05Ba1.95Cu3O7 show interesting features; a marked decrease in resistivity is observed from room temperature itself in the former oxide with zero resistance at 89K. Electron microscopy and infrared spectra of these oxides are briefly discussed.

Thermodynamics of cobalt-manganese alloys using fluoride and oxide electrolytes

Abstract is not available.

An infrared spectroscopic study of the incommensurate transitions and related phase changes in K2Pb[Cu(NO2)6] and [N(CH3)4]2MX4 (M = Mn, Co, Cu or Zn and X = Cl or Br)

K2Pb[Cu(NO2)6] and [N(CH3)4]2MX4 (M = Mn, Co, Cu or Zn and X = Cl or Br) undergo phase transitions which involve incommensurate phases. The transitions have been investigated by examining the changes in the NO2 and CH3 vibration bands in the i.r. spectra. Splitting and broadening of some of the bands across the incommensurate transitions are discussed in the context of geometrical restrictions in the incommensurate phases. The phase transitions have also been characterized using differential scanning calorimetry.