The influence of oxygen pressure on lead oxidation kinetics

1980 ◽  
Vol 33 (3) ◽  
pp. 471 ◽  
Author(s):  
GA Hope
Keyword(s):  
Refractive Index ◽  
Pressure Dependence ◽  
Oxidation Kinetics ◽  
Oxidation Rate ◽  
Abrupt Change ◽  
Oxide Interface ◽  
Positive Dependence ◽  
Different Temperatures ◽  
Lead Films ◽  
Lead Oxidation

The dependence of the oxidation rate of lead films on the pressure of oxygen was investigated by ellipsometric and resistance techniques for oxygen pressures between 200 Pa and 100 kPa and in the temperature range 323-423 K. Measurements of the pressure dependence were obtained by studying the change in oxidation rate following an abrupt change in pressure. The results of all experiments indicated a small positive dependence, though significant variations in the values were observed both with extent of oxidation, and between experiments conducted at different temperatures. During the first few minutes of the reaction an unusual trend was noted in the observed kinetics which could be interpreted as being due to absorption of oxygen, by the metal close to the metal-oxide interface, resulting in changes to the metal conductivity and the refractive index, determined by ellipsometry, of the lead substrate.

Interferometric studies in diffusion. I. Determination of concentration distributions

1950 ◽  
Vol 204 (1078) ◽  
pp. 339-359 ◽  
Keyword(s):  
Refractive Index ◽  
Abrupt Change ◽  
Sudden Change ◽  
Small Range ◽  
Component Systems ◽  
Different Temperatures ◽  
Two Component Systems ◽  
Index Curve ◽  
And Diffusion

An interferometer technique for the quantitative study of swelling and diffusion in transparent high polymers and a method of determining the concentration distribution from the fringe system have been developed. The concentration—distance curves in the system chloroform-stretched cellulose acetate have been determined at two different temperatures with a view to estimating activation energies over a range of concentrations. The curves are found to consist of two almost linear portions with a considerable and abrupt change of gradient taking place over a small range of concentration. A corresponding sudden change of gradient has been observed in other systems. Considerable experimental difficulties were met in determining the refractive index and density curves for the two component systems, which were required by the method. Eventually a refractive index curve was constructed with the help of data obtained by several approaches.

Doping Effect in Nickel Oxide

2009 ◽  
Vol 289-292 ◽  
pp. 775-782 ◽  
Author(s):  
Zbigniew Jurasz ◽  
Krzysztof Adamaszek ◽  
Romuald Janik ◽  
Zbigniew Grzesik ◽  
Stanisław Mrowec
Keyword(s):  
Activation Energy ◽  
Nickel Oxide ◽  
High Temperatures ◽  
Oxygen Pressure ◽  
Pressure Dependence ◽  
Oxidation Rate ◽  
Doping Effect ◽  
Self Diffusion ◽  
Electron Holes ◽  
Influence Of Impurities

Detailed investigations of nonstoichiometry as well as chemical and self-diffusion in nickel oxide have shown that doubly ionised cation vacancies and electron holes are the predominant defects in this material. The present work is an attempt to demonstrate that aliovalent impurities (Cr, Al, Na and Li) may considerably influence the concentration of these defects and, consequently, the oxidation rate of nickel at high temperatures. It has been shown that small amounts of tri-valent impurities (Cr, Al) bring about an increase of the oxidation rate, while mono-valent ones (Li, Na) decrease the rate of oxidation. These phenomena may satisfactorily be explained in terms of a doping effect. All experiments have been carried out as a function of temperature (1373-1673 K) and oxygen pressure (1-105 Pa) and consequently, it was possible to determine the influence of impurities not only on the oxidation rate but also on the activation energy of reaction and its pressure dependence. The results of these investigations could again be elucidated in terms of doping effect.

Study the Effect of Heat Treatment and Pressure on some the Optical Properties of the Pure PVA Nano Polymer

2021 ◽  
Vol 900 ◽  
pp. 16-25
Author(s):  
Tabarak Mohammed Awad ◽  
May A.S. Mohammed
Keyword(s):  
Heat Treatment ◽  
Dielectric Constant ◽  
Refractive Index ◽  
Optical Properties ◽  
Absorption Coefficient ◽  
Polyvinyl Alcohol ◽  
Complex Dielectric Constant ◽  
Different Temperatures ◽  
German Origin ◽  
Increasing Temperature

In this study, some optical properties were studied of the pure vinyl polyvinyl alcohol (PVA) nanopolymer (German origin). Under the influence of different temperatures and pressures of PVA. Where 25 samples were prepared for the purpose of conducting the research. Which studied the study of these samples was done by recording the absorbance and transmittance spectra of the wavelengths (200-900) nm. From them, absorbance, transmittance, reflectivity, absorption coefficient, refractive index, extinction coefficient, complex dielectric constant were calculated. At different temperatures (25,40, 80, 120, 160)°C. And with different pressures within the range (7.5,8,8.5,9,9.5) MPa. The results are that the permeability of the polymer (PVA) at different temperatures for each pressure decreases with increasing temperature, and that all other calculated optical properties increase with increasing temperature.

Pressure dependence of the refractive index in wurtzite and rocksalt indium nitride

2014 ◽  
Vol 105 (23) ◽  
pp. 232111 ◽  
Author(s):  
R. Oliva ◽  
A. Segura ◽  
J. Ibáñez ◽  
T. Yamaguchi ◽  
Y. Nanishi ◽  
...  
Keyword(s):  
Refractive Index ◽  
Pressure Dependence ◽  
Indium Nitride

Modelling of semiconductor rib wave guides by a finite difference method

1991 ◽  
Vol 69 (3-4) ◽  
pp. 512-519 ◽  
Author(s):  
A. Delâge
Keyword(s):  
Refractive Index ◽  
Boundary Conditions ◽  
Abrupt Change ◽  
Multiple Quantum Well ◽  
External Boundary ◽  
Multiple Quantum ◽  
Scalar Wave ◽  
Accurate Evaluation ◽  
Wave Guides ◽  
Mode Characteristics

The method of finite differences is used to solve the scalar wave equation for semiconductor rib wave guides. Boundary conditions derived from continuity relations are applied between regions of different refractive index, allowing more accurate evaluation of the propagation constants for ideal cases of abrupt change in the index. Also appropriate external boundary conditions alleviate the inaccuracy generally introduced by setting the field equal to zero on the external limit of the mesh. Our results agree with various other techniques when applied to typical guiding structures. As an example, we model a multiple-quantum-well structure by using an equivalent layered structure. Mode characteristics and confinement factors obtained by the method are of interest in understanding the behaviour of the lasers and modulators fabricated in our laboratory.

Comparative Analysis of Autoxidation of Haemoglobin

2001 ◽  
Vol 204 (11) ◽  
pp. 2029-2033
Author(s):  
Frank B. Jensen
Keyword(s):  
Temperature Sensitivity ◽  
Oxidation Rate ◽  
Protective Role ◽  
Yellowfin Tuna ◽  
Histidine Residue ◽  
River Lamprey ◽  
Different Temperatures ◽  
Lower Temperature ◽  
The Impact

SUMMARY Autoxidation of oxyhaemoglobin (oxyHb) to methaemoglobin was measured at different temperatures in haemoglobin solutions from Atlantic hagfish, river lamprey, common carp, yellowfin tuna and pig. The aims were to evaluate the impact of the absent distal histidine in hagfish haemoglobin, the importance of oxyHb being either monomeric (hagfish and lamprey) or tetrameric (carp, tuna and pig) and to gain information on the temperature-sensitivity of autoxidation. The rate of autoxidation was lower in hagfish than in carp, yellowfin tuna and lamprey haemoglobins at any given temperature. Substitution of the distal histidine residue (His E7) with glutamine in hagfish haemoglobin was therefore not associated with an accelerated autoxidation, as might be expected on the basis of the normal protective role of His E7. Glutamine may have similar qualities to histidine and be involved in the low susceptibility to autoxidation. The low oxidation rate of hagfish haemoglobin, together with an oxidation rate of lamprey haemoglobin that did not differ from that of carp and yellowfin tuna haemoglobins, also revealed that autoxidation was not accelerated in the monomeric oxyhaemoglobins. Pig haemoglobin was oxidised more slowly than fish haemoglobins, demonstrating that fish haemoglobins are more sensitive to autoxidation than mammalian haemoglobins. The rate of autoxidation of hagfish haemoglobin was, however, only significantly greater than that of pig haemoglobin at high temperatures. Autoxidation was accelerated by rising temperature in all haemoglobins. Arrhenius plots of carp and yellowfin tuna haemoglobin revealed a break at 25°C, reflecting a lower temperature-sensitivity between 5 and 25°C than between 25 and 40°C.

Pressure dependence of the refractive index in InSe

2000 ◽  
Vol 15 (8) ◽  
pp. 806-812 ◽  
Author(s):  
F J Manjón ◽  
Y van der Vijver ◽  
A Segura ◽  
V Muñoz
Keyword(s):  
Refractive Index ◽  
Pressure Dependence

Refractive index of GaP and its pressure dependence

1985 ◽  
Vol 32 (10) ◽  
pp. 6614-6619 ◽  
Author(s):  
K. Strössner ◽  
S. Ves ◽  
M. Cardona
Keyword(s):  
Refractive Index ◽  
Pressure Dependence
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