Metal complexes of 1,10-phenanthroline derivatives. X. 5T2 ↔ 1A1 transitions in iron(II) complexes of 2-(1,10-Phenanthrolin-2-yl)imidazole derivatives

1975 ◽  
Vol 28 (3) ◽  
pp. 505 ◽  
Author(s):  
DW Mather ◽  
HA Goodwin
Keyword(s):  
Metal Complexes ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Chelating Agents ◽  
Elevated Temperatures ◽  
Magnetic Moments ◽  
Spin Transition ◽  
Benzimidazole Derivative ◽  
Crossover Region ◽  
Experimental Temperature Range

The preparation of the tridentate chelating agents 2-(1,10- phenanthrolin-2-yl)imidazoline and 2-(1,10-phenanthrolin-2- yl)benzimidazole and their bis-ligand complexes with iron(II) and nickel(II) is described. The latter ligand coordinates as either a neutral or anionic tridentate. Data from the spectra of the nickel(II) complexes indicate that the ligands have field strengths in the iron(II) crossover region. The temperature dependence of the magnetism of the imidazoline iron(II) complex reveals a gradual, temperature- induced 5T2 ↔ 1A1 transition which is not complete within the experimental temperature range (83-363 K). Both the cationic and neutral iron(II) complexes of the benzimidazole derivative are essentially low-spin at room temperature but a significant increase in their magnetic moments at elevated temperatures indicates that a spin transition may be occurring in these compounds too.

Metal complexes of 1,10-phenanthroline derivatives. XII. Complexes of 2-Hydrazino-1,10-phenanthroline and related molecules

1981 ◽  
Vol 34 (2) ◽  
pp. 313 ◽  
Author(s):  
AS Abushamleh ◽  
HA Goodwin
Keyword(s):  
Field Strength ◽  
Metal Complexes ◽  
Spectral Data ◽  
Chelating Agents ◽  
Spin Transition ◽  
Crossover Region ◽  
Lower Field ◽  
Derivatives Of

2-Hydrazino- and 2-(N1-methylhydrazino)-1,10-phenanthroline have been prepared from 2-chloro-1,10-phenanthroline and the appropriate hydrazine. These tridentate chelating agents yield bis-(ligand) complexes with nickel(II) and iron(II). Spectral data for the nicke(II) complexes indicate that the field strength of the ligands is near the crossover region for iron(II). Magnetic and M�ssbauereffect data indicate that a 5T2 ↔ 1A1 spin transition occurs in salts of the complex of the methylhydrazine derivative, though a marked anion-dependence for this transition is observed. Benzaldehyde hydrazone derivatives of both hydrazines also yielded six-coordinate nickel (II) and iron (II) complexes, but these were of significantly lower field strength than the parent hydrazines.

Metal complexes of 1,10-phenanthroline derivatives. IX. 5T2 ↔ 1A1 spin transitions in iron(II) complexes of 2-(1,10-phenanthrolin-2-yl)thiazole derivatives

1975 ◽  
Vol 28 (1) ◽  
pp. 33 ◽  
Author(s):  
HA Goodwin ◽  
DW Mather ◽  
FE Smith
Keyword(s):  
Metal Atom ◽  
Chelating Agents ◽  
Spin Transition ◽  
Nickel Complexes ◽  
Close Approach ◽  
Crossover Region ◽  
Thiazole Derivatives ◽  
Pyridyl Group ◽  
Spin Pairing ◽  
Experimental Temperature Range

The preparation of the tridentate chelating agents 2-(1,10- phenanthrolin-2-yl)thiazole, 2-(1,10-phenanthrolin-2-yl)-4-(2- pyridyl)thiazole 2-(1,10-phenanthrolin-2-yl)thiazolidine and 2-(1,10- phenanthrolin-2-yl)benzothiazole is described. Data from the spectra of the bis-ligand nickel complexes indicate that the ligands all have field strengths in the iron(II) crossover region. The temperature dependence of the magnetism of the bis-ligand iron(II) complexes reveals that, except for the complexes of the pyridylthiazole, a smooth, temperature-induced 5T2 ↔ 1A1 transition occurs in these compounds. For no complex is the transition complete within the experimental temperature range (83-363 K). The complex of the pyridylthiazole is high-spin throughout the range, the uncoordinated pyridyl group hindering the close approach of ligand and metal atom necessary for spin-pairing. The ability of the other ligands to induce a spin transition is primarily a consequence of distortions in the environment about the metal atom arising from coordination of the five- membered thiazole or related ring.

Anomalous magnetism of iron(II) complexes of methyl-substituted pyridylthiazoles

1972 ◽  
Vol 25 (4) ◽  
pp. 715 ◽  
Author(s):  
HA Goodwin ◽  
DW Mather
Keyword(s):  
Magnetic Properties ◽  
Temperature Dependence ◽  
High Spin ◽  
Metal Atom ◽  
Electronic Spectra ◽  
Chelating Agents ◽  
Strong Dependence ◽  
Chelating Agent ◽  
Crossover Region ◽  
Field Strengths

Bis-ligand iron(11) and nickel(11) complexes of the potentially tridentate chelating agents 2-(3-methyl-2-pyridylamino)-4-(2-pyridyl)thiazole and 2-(4-methyl- 2-pyridylamino)-4-(2-pyridyl)thiazole are described. The electronic spectra of the nickel(11) complexes show that the field strengths of the ligands are in the neighbourhood of the Crossover region for iron(11). The magnetic properties of the cationic iron(11) complexes are anomalous and consistent with a spin-equilibrium involving the nearly equi-energetic 5T2 and 1A1 states of the metal atom. The magnetism shows a strong dependence on the associated anion. 2-(6-Methyl-2-pyridylamino)-4- (2-pyridyl)thiazole is also described. In its bis-ligand iron(11) complexes it functions as a bidentate chelating agent and the complexes are high-spin. All three ligands may be deprotonated to yield inner complexes with iron(11) which in some instances have anomalous magnetic properties associated with the presence of a spin-equilibrium. 2-(6-Methyl-2-pyridyl)-4-(2-pyridyl)thiaole and its bis-ligand iron(11) and nickel(11) complexes are also described. The iron(11) complexes are high-spin and show normal temperature dependence of their magnetism.

Metal complexes of 1,10-Phenanthroline derivatives. VII. Complexes of 1,10-Phenanthroline-2-carbaldehyde hydrazones

1974 ◽  
Vol 27 (5) ◽  
pp. 965 ◽  
Author(s):  
HA Goodwin ◽  
DW Mather
Keyword(s):  
Field Strength ◽  
Metal Complexes ◽  
High Spin ◽  
Spin State ◽  
Spin Transition ◽  
Pronounced Change ◽  
Temperature Range ◽  
Spin Pairing ◽  
Bivalent Iron ◽  
Experimental Temperature Range

A series of substituted hydrazones derived from 1,l0-phenanthroline-2-carbaldehyde and their bis-ligand complexes with bivalent iron and nickel are described. The hydrazones show a gradation in field strength and this is reflected in the spin-state of the iron complexes. The methylhydrazone complex is essentially low-spin over the temperature range 83-363 K but the presence of some spin-free species at high temperatures is evident. Within the same range the dimethylhydrazone complex is essentially high-spin but undergoes significant spin-pairing and the phenylhydrazone complex displays a complete 5T2 → 1A1 spin transition. This transition is very sharp, resulting in a pronounced change in the magnetism, and colour, of the complex within a few degrees. Complexes of the 2-pyridylhydrazone, the methylphenylhydrazone and the diphenylhydrazone are high-spin over the entire experimental temperature range.

NdFeB Magnets with Improved Temperature Characteristics

1987 ◽  
Vol 96 ◽  
Author(s):  
B. M. Ma
Keyword(s):  
Magnetic Properties ◽  
Curie Temperature ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Temperature Coefficients ◽  
System A ◽  
Rate Of Increase ◽  
Intrinsic Coercivity ◽  
Molybdenum Addition

ABSTRACTThe temperature dependence of magnetic properties for NdFeCoB alloys were investigated. It is well known that dysprosium substitution for neodymium increases the intrinsic coercivity. Aluminum also improves the intrinsic coercivity, Hci, at room temperature but impairs the Curie temperature and the intrinsic coercivity at elevated temperatures. The rate of increase of the Hci with increasing dysprosium in the NdFeCoB system is less than when dysprosium is added to the NdFeB system. A combination of aluminum and dysprosium is more effective than aluminum alone in raising Hci. Molybdenum addition into the NdDyFeCoB alloy was found to reduce the temperature coefficients of Br and Hci. Temperature coefficients of Br and Hci obtained on a Nd10Dy5Fe67Co10Mo1Al1B6 alloy are -0.07 %/°C and -0.4 %/°C respectively.

Metal complexes of 1,10-phenanthroline derivatives. VI. Complexes of iron, cobalt, nickel, and copper with 1,10-Phenanthroline-2-carbothioamide or N Phenyl-1,10-phenanthroline-2-carbothioamide

1973 ◽  
Vol 26 (12) ◽  
pp. 2623 ◽  
Author(s):  
HA Goodwin ◽  
DW Mather ◽  
FE Smith
Keyword(s):  
Temperature Dependence ◽  
Chelating Agents ◽  
Strong Field ◽  
Spin Transition ◽  
Anomalous Temperature Dependence ◽  
Anomalous Temperature ◽  
Iron Cobalt ◽  
Phenyl Derivative ◽  
Cobalt Nickel ◽  
Thioamide Group

Mono- and bis-ligand complexes of iron, cobalt, nickel and mono-ligand complexes of copper with the tridentate chelating agents 1,10- phenanthroline-2-carbo-thioamide and N-phenyl-1,10-phenanthroline-2- carbothioamide are described. Both ligands produce a strong field with iron(II) and the bis-ligand complexes of cobalt(II) and the former display a temperature-induced spin transition resulting in an anomalous temperature-dependence of their magnetism. In all the mono-ligand complexes the metal atom is believed to be six-coordinate. Both ligands may be deprotonated in their complexes and deprotonation of the N- phenyl derivative occurs spontaneously when it interacts with cobalt(II) or copper(II), the reaction with cobalt being accompanied by oxidation of the metal. Both ligands coordinate through the sulphur atoms of the thioamide group.

High-Temperature Performance of 1200 V, 200 A 4H-SiC Power DMOSFETs

2012 ◽  
Vol 717-720 ◽  
pp. 1065-1068 ◽  
Author(s):  
Lin Cheng ◽  
Sei Hyung Ryu ◽  
Anant K. Agarwal ◽  
Michael J. O'Loughlin ◽  
Albert A. Burk ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Behavior ◽  
Temperature Dependence ◽  
Threshold Voltage ◽  
Room Temperature ◽  
First Generation ◽  
Channel Mobility ◽  
Temperature Performance ◽  
Temperature Regimes ◽  
Experimental Temperature Range

We have investigated the thermal behavior of our recently developed 1200 V, 200 A 4H-SiC power DMOSFETs operating from 20°C up to 300°C. Compared to the first generation SiC DMOSFET that was commercially released early this year, this 4H-SiC power DMOSFET shows a ~ 50% reduction in the total specific on-resistance at room temperature. Temperature dependence of the key parameters of this MOSFET, such as on-resistance, threshold voltage, and the MOS channel mobility, are reported in this paper. The MOSFET showed normally-off characteristics throughout the entire experimental temperature range. Different temperature dependence of the total on-resistance in different temperature regimes has been observed.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Spherulite Structures in a Melt Spun Fe-Ni Austenitic Steel

1985 ◽  
Vol 43 ◽  
pp. 52-53
Author(s):  
G. M. Michal ◽  
T. K. Glasgow ◽  
T. J. Moore
Keyword(s):  
Austenitic Steel ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Large Range ◽  
Amorphous Structure ◽  
Nucleation And Growth ◽  
Ni Alloys ◽  
Melt Spun ◽  
Crystal Fibers ◽  
Rapidly Solidified

Large additions of B to Fe-Ni alloys can lead to the formation of an amorphous structure, if the alloy is rapidly cooled from the liquid state to room temperature. Isothermal aging of such structures at elevated temperatures causes crystallization to occur. Commonly such crystallization pro ceeds by the nucleation and growth of spherulites which are spherical crystalline bodies of radiating crystal fibers. Spherulite features were found in the present study in a rapidly solidified alloy that was fully crysstalline as-cast. This alloy was part of a program to develop an austenitic steel for elevated temperature applications by strengthening it with TiB2. The alloy contained a relatively large percentage of B, not to induce an amorphous structure, but only as a consequence of trying to obtain a large volume fracture of TiB2 in the completely processed alloy. The observation of spherulitic features in this alloy is described herein. Utilization of the large range of useful magnifications obtainable in a modern TEM, when a suitably thinned foil is available, was a key element in this analysis.

ABOUT HEAT CAPACITY OF TITANIUM CARBIDE TiCx

2019 ◽  
pp. 56-66
Author(s):  
I. Khidirov ◽  
V. V. Getmanskiy ◽  
A. S. Parpiev ◽  
Sh. A. Makhmudov
Keyword(s):  
Heat Capacity ◽  
High Temperature ◽  
Titanium Carbide ◽  
Temperature Dependence ◽  
Carbon Concentration ◽  
Room Temperature ◽  
Thermodynamic Characteristics ◽  
Liquid Nitrogen Temperature ◽  
Analysis Data ◽  
Thermal Excitation

This work relates to the field of thermophysical parameters of refractory interstitial alloys. The isochoric heat capacity of cubic titanium carbide TiCx has been calculated within the Debye approximation in the carbon concentration  range x = 0.70–0.97 at room temperature (300 K) and at liquid nitrogen temperature (80 K) through the Debye temperature established on the basis of neutron diffraction analysis data. It has been found out that at room temperature with decrease of carbon concentration the heat capacity significantly increases from 29.40 J/mol·K to 34.20 J/mol·K, and at T = 80 K – from 3.08 J/mol·K to 8.20 J/mol·K. The work analyzes the literature data and gives the results of the evaluation of the high-temperature dependence of the heat capacity СV of the cubic titanium carbide TiC0.97 based on the data of neutron structural analysis. It has been proposed to amend in the Neumann–Kopp formula to describe the high-temperature dependence of the titanium carbide heat capacity. After the amendment, the Neumann–Kopp formula describes the results of well-known experiments on the high-temperature dependence of the heat capacity of the titanium carbide TiCx. The proposed formula takes into account the degree of thermal excitation (a quantized number) that increases in steps with increasing temperature.The results allow us to predict the thermodynamic characteristics of titanium carbide in the temperature range of 300–3000 K and can be useful for materials scientists.

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