Field dependence of carbon electrotransport in gamma iron

1970 ◽  
Vol 48 (17) ◽  
pp. 1984-1990 ◽  
Author(s):  
E. A. Falquero ◽  
W. V. Youdelis
Keyword(s):  
Effective Charge ◽  
Applied Field ◽  
Kcal Mole ◽  
Temperature Dependent ◽  
Gamma Iron ◽  
Interstitial Carbon ◽  
A Value ◽  
Field Independent ◽  
Interstitial Transport ◽  
Carbon Transport

The effect of field strength at constant temperature on the effective charge of carbon in gamma iron in electrotransport experiments is determined. At 950 °C the total effective charge is 4.5 for a field of 0.106 V cm−1, rising to a value of 13.6 at approximately 0.028 V cm−1, and falling rapidly at lower fields. Similar results are encountered at 920 and 980 °C; the temperature dependence of the total effective charge is not marked. It is proposed that carbon transport occurs by two processes: vacancy transport, which is activated by a field of approximately 0.028 V cm−1 but is field independent at higher fields, and interstitial transport, the rate of which is proportional to the applied field. The rate of vacancy transport is determined by an activation energy of 42 kcal/mole. The effective charge for purely interstitial carbon electrotransport is strongly temperature dependent; charge values of 2.5, 1.5, and 0.6 were obtained at 920, 950, and 980 °C respectively.

scholarly journals Temperature Dependence of G and D’ Phonons in Monolayer to Few-Layer Graphene with Vacancies

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Mingming Yang ◽  
Longlong Wang ◽  
Xiaofen Qiao ◽  
Yi Liu ◽  
Yufan Liu ◽  
...  
Keyword(s):  
Negative Temperature Coefficient ◽  
Negative Temperature ◽  
Intrinsic Properties ◽  
Temperature Dependent ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Layer Graphene ◽  
A Value ◽  
Few Layer Graphene

Abstract The defects into the hexagonal network of a sp2-hybridized carbon atom have been demonstrated to have a significant influence on intrinsic properties of graphene systems. In this paper, we presented a study of temperature-dependent Raman spectra of G peak and D’ band at low temperatures from 78 to 318 K in defective monolayer to few-layer graphene induced by ion C+ bombardment under the determination of vacancy uniformity. Defects lead to the increase of the negative temperature coefficient of G peak, with a value almost identical to that of D’ band. However, the variation of frequency and linewidth of G peak with layer number is contrary to D’ band. It derives from the related electron-phonon interaction in G and D’ phonon in the disorder-induced Raman scattering process. Our results are helpful to understand the mechanism of temperature-dependent phonons in graphene-based materials and provide valuable information on thermal properties of defects for the application of graphene-based devices.

THE REACTION OF METHYL RADICALS WITH FORMALDEHYDE

1959 ◽  
Vol 37 (9) ◽  
pp. 1462-1468 ◽  
Author(s):  
A. R. Blake ◽  
K. O. Kutschke
Keyword(s):  
Activation Energy ◽  
Kinetic Analysis ◽  
Addition Reactions ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
A Value ◽  
Abstraction Reaction ◽  
Butyl Peroxide

The pyrolysis of di-t-butyl peroxide has been reinvestigated and used as a source of methyl radicals to study the abstraction reaction between methyl radicals and formaldehyde. At low [HCHO]/[peroxide] ratios the system was simple enough for kinetic analysis, and a value of 6.6 kcal/mole was obtained for the activation energy. At higher [HCHO]/[peroxide] ratios the system became very complicated, possibly due to the increased importance of addition reactions.

Zn:Tl PHASE DIAGRAM AT VERY LOW THALLIUM CONCENTRATIONS

1961 ◽  
Vol 39 (4) ◽  
pp. 588-595 ◽  
Author(s):  
E. H. McLaren ◽  
F. Weinberg
Keyword(s):  
Phase Diagram ◽  
Freezing Point ◽  
Solubility Limit ◽  
Heat Of Fusion ◽  
Kcal Mole ◽  
Solid Solubility Limit ◽  
Pure Zinc ◽  
Latent Heat Of Fusion ◽  
A Value ◽  
Resistance Thermometry

The Zn:Tl liquidus has been accurately determined from pure Zn (419.505 °C) to the monotectic transition temperature (416.926 °C at 0.42 at.% Tl) using precision resistance thermometry. The upper solidus was determined approximately from measurements of the distribution coefficient (~0.01) and the solid solubility limit (~0.004 at.% Tl) of thallium in zinc. A value 1.53 ± 0.1 kcal/mole for the latent heat of fusion of pure zinc was calculated from the freezing point depressions.

Vibrational energy transfer. Collisional quenching of competitive unimolecular reactions

1968 ◽  
Vol 46 (2) ◽  
pp. 341-343 ◽  
Author(s):  
D. C. Tardy ◽  
C. W. Larson ◽  
B. S. Rabinovitch
Keyword(s):  
Vibrational Energy ◽  
Heat Bath ◽  
Polyatomic Molecules ◽  
Unimolecular Reaction ◽  
Collisional Quenching ◽  
Kcal Mole ◽  
Vibrationally Excited ◽  
Reaction Systems ◽  
A Value ◽  
Collisional Deexcitation

A technique is described for the study of collisional deexcitation of highly vibrationally excited polyatomic molecules by use of externally activated competitive unimolecular reaction systems. This method has some advantages and is illustrated by the decomposition of chemically activated hexyl-3 radicals in the presence of H2 and CF4 as heat bath molecules. The former removes ~1.2 kcal mole−1 per successful collision; while for the latter a value in excess of 4.6 kcal is found so that CF4 behaves operationally like a strong collider.

SPECTROSCOPIC STUDIES OF ALCOHOLS: III. FUNDAMENTAL OH STRETCHING BANDS OF 2,2-DI- AND 2,2,2-TRI-HALOETHANOLS

1964 ◽  
Vol 42 (2) ◽  
pp. 340-346 ◽  
Author(s):  
P. J. Krueger ◽  
H. D. Mettee
Keyword(s):  
Spectroscopic Studies ◽  
Kcal Mole ◽  
Temperature Dependent ◽  
Hydrogen Bond Interaction ◽  
Constrained System ◽  
Trans Conformer ◽  
Bond Polarizability ◽  
Inductive Effects ◽  
Geometrically Constrained ◽  
Bond Polarization

The OH stretching region was examined for the compounds F3CCH2OH, Cl2CHCH2OH, Cl3CCH2OH, and Br3CCH2OH in dilute CCl4 solution. The first two compounds exhibit temperature-dependent band asymmetry which is due to trans–gauche equilibria arising from rotation about the C—O bond, with relatively small populations in the trans forms. Enthalpy differences of 3.3 and 2.4 kcal/mole between the conformers were obtained for these two compounds respectively. Although symmetrical at lower temperatures, the band for Cl3CCH2OH shows the presence of a small amount of the trans conformer at temperatures above 45 °C. These results are discussed in terms of intramolecular OH … X hydrogen bond interaction, inductive effects, non-bonded interactions, O—H bond polarization, C—X bond polarizability, and the size of the halogen atoms in a geometrically constrained system.

Heat stability of milk: interrelationship between assay temperature, pH and agitation

1981 ◽  
Vol 48 (1) ◽  
pp. 123-129 ◽  
Author(s):  
Douglas B. Hyslop ◽  
Patrick F. Fox
Keyword(s):  
Heat Stability ◽  
Kcal Mole ◽  
Temperature Dependent ◽  
Total Solids ◽  
Ph Values ◽  
Assay Procedure ◽  
Concentrated Milk ◽  
The Stability ◽  
Ph Curve ◽  
Maximum Minimum

SummaryAs determined by the standard subjective assay procedure, the minimum in the heat stability–pH curve of milk persisted down to at least 116 °C. However when samples were not agitated during heating the minimum became progressively less pronounced as the assay temperature was lowered and it disappeared at approximately 116 °C. Activation energies (Ea) for unagitated samples were approximately 30 Kcal/mole at pH 6·87 (maximum) and at pH 7·18, throughout the temperature range 116–145 °C and for the pH 6·95 (minimum) sample at 116–125 °C; however Eα for the pH 6.95 sample increased to approximately 100 Kcal/mole in the range 127–135 °C suggesting that some highly temperature-dependent reaction had occurred and caused premature coagulation at certain pH values, i.e. to a heat stability minimum. The stability of concentrated milk (20% total solids) was very low at pH values above 6·9, regardless of whether the samples were agitated or not during heating and the maximum/minimum in the heat stability–pH curve persisted down to at least 90 °C in both agitated and quiescent samples.

The Density of States in a-Si:C:H Revealed by Electrophotography

1993 ◽  
Vol 297 ◽  
Author(s):  
R.A.C.M.M. Van Swaaij ◽  
W.P.M. Willems ◽  
J. Bezemer ◽  
M.B. Von Der Linden ◽  
W.F. Van Der Weg
Keyword(s):  
Conduction Band ◽  
Density Of States ◽  
Carbon Concentration ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Temperature Dependent ◽  
Energy Position ◽  
A Value ◽  
Dark Decay ◽  
Bulk Space

Electrophotographic dark decay measurements have been used to determine the surface density of states (SDOS) of a-Si:C:H. Injection of trapped charge from these deep states into the conduction band governs the dark discharge of a photoconductor, provided bulk generation and bulk space charge are negligible. It is found that the SDOS profiles peak around 0.60 eV below the conduction band for materials with different carbon concentration. This observation implies that the energy position of these states is fixed with respect to the conduction band edge, even though the optical band gap of these materials increases with increasing carbon concentration. The nature of these states may be ascribed to D− states, whose density is strongly enhanced by filling D° states when the material is charged negatively. Furthermore, we observed that the SDOS around 0.60 eV below the conduction band edge is approximately the same for materials with up to 8 at.% carbon. From temperature dependent measurements a value of 2·108 s−1 was obtained for the attempt-to-escape frequency.

Some reactions of 2,4-dimethoxytetrahydropyrans

1969 ◽  
Vol 47 (17) ◽  
pp. 3099-3106 ◽  
Author(s):  
M. J. Baldwin ◽  
R. K. Brown
Keyword(s):  
Room Temperature ◽  
Equilibrium Mixture ◽  
Anomeric Effect ◽  
Temperature Reaction ◽  
Trans Isomers ◽  
Kcal Mole ◽  
A Value ◽  
Cis And Trans Isomers ◽  
Acid Catalyzed ◽  
Cis And Trans

Acid-catalyzed elimination of methanol from 2,4-dimethoxytetrahydropyran (1) produces 2-methoxy-5,6-dihydro-2H-pyran (3) rather than the expected olefin 4-methoxy-3,4-dihydro-2H-pyran (2).The reaction of 1,3-dibromo-5,5-dimethylhydantoin with 3 in ether – methanol gives a 2:1 mixture of the isomers 3β-bromo-2α,4α-dimethoxytetrahydropyran (5a) and 3α-bromo-2α,4β-dimethoxytetrahydropyran (5b) respectively. A rationale is given to explain the preponderance of 5a over 5b and the highly selective attack of the bromine of the hydantoin and the methanol on C-3 and C-4 respectively of the double bond of 3. Reduction of 5ab with zinc in ethanol provides only compound 3.The room temperature reaction of 1 in a mixture of water and 1,2-dimethoxyethane containing Amberlite IR-120, produces 2-hydroxy-4-methoxytetrahydropyran (6) as an equilibrium mixture of cis and trans isomers in the ratio 1:1. This gave a value of 0.9 kcal/mole for the anomeric effect in 6. Pyrolysis of the derivative, 2-acetoxy-4-methoxytetrahydropyran failed to produce the olefin 2 and resulted only in extensive decomposition.

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