CVII.—The retarding effect of oxygen on the rate of interaction of chlorine and hydrogen

1909 ◽  
Vol 95 (0) ◽  
pp. 959-964 ◽  
Author(s):  
David Leonard Chapman ◽  
Patrick Sarsfield MacMahon
Keyword(s):  
Retarding Effect ◽  
Effect Of Oxygen

The decomposition of nitrous oxide catalysed by palladium-gold alloy wires

1966 ◽  
Vol 294 (1436) ◽  
pp. 1-19 ◽  
Keyword(s):  
Activation Energy ◽  
Nitrous Oxide ◽  
Fermi Level ◽  
Apparent Activation Energy ◽  
Frequency Factor ◽  
Kcal Mole ◽  
Dissociative Chemisorption ◽  
Retarding Effect ◽  
Effect Of Oxygen ◽  
Decomposition Of Nitrous Oxide

The rate of decomposition of nitrous oxide has been examined by pressure measurements, at temperatures between 500 and 900 °C and pressures between 10 -2 and 1 torr. The reaction is first order, but shows retardation by oxygen, but not nitrogen. Over the range of alloys, from Pd to nearly 40 at. % Pd, the velocity at 650 °C falls by a factor of 104, the apparent activation energy falls from 30 to 13 kcal/mole, and the retarding effect of oxygen falls to zero. Over this range of alloys the Fermi level which lies in the d band hardly changes but the concentration of the d band vacancies falls to zero. Over the range of alloys from 40 at. % Pd to Au the velocity at 650 °C remains constant but the apparent activation energy and frequency factor, which show an abrupt increase at 40 at. % Pd, show a continuous fall. The retarding effect of oxygen remains zero. In this range the Fermi level has entered the s band and increases to Au. A steady state treatment of an irreversible dissociative chemisorption of nitrous oxide, together with an oxygen chemisorption equilibrium, yields an equation for the velocity in quantitative agreement with the results found. It is also possible to account for the increase in apparent activation energy with oxygen coverage of the surface. The heat of adsorption of oxygen is derived as 32-2±2 kcal/mole, and the activation energy for chemisorption of nitrous oxide as 12-7 ±0-5 kcal/mole.

Effect of Oxygen Absorbers in Rubber

1936 ◽  
Vol 9 (2) ◽  
pp. 322-338
Author(s):  
A. A. Somerville
Keyword(s):  
Atmospheric Oxygen ◽  
Practical Experience ◽  
Working Hypothesis ◽  
Retarding Effect ◽  
Full Effect ◽  
Rubber Surface ◽  
Effect Of Oxygen ◽  
Cracking Tendency ◽  
Main Factor ◽  
Mechanism Of The Reaction

Abstract In this discussion of flex-cracking, its causes, and a means of controlling it, the theory that oxidation of the rubber is the main factor involved has been used as a foundation. No attempt has been made to prove chemically that oxidation of the rubber actually takes place. This would be difficult, since flex-cracked rubber does not necessarily show the ordinary signs of deterioration, but the work of Neal and Northam (4) has indicated that oxygen plays a part. The facts that oxygen absorbers definitely retard flex-cracking and also that the more strongly they are able to absorb oxygen, the greater is their retarding effect, would be difficult to explain on any other basis. The mechanism of the reaction, however, is obscure and is further complicated by the fact that the oxygen absorbers develop their full effect only in the presence of a catalytic antioxidant. As a working hypothesis it may be assumed that the oxygen absorber removes dissolved or absorbed oxygen within the rubber before and during vulcanization, while the antioxidant protects the rubber surface against atmospheric oxygen during service. It is realized that this hypothesis does not explain every fact connected with the use of oxygen absorbers to complete satisfaction and will doubtless be subject to change or modification as practical experience with these agents accumulates. In the meantime it is believed that a practical commercial means of greatly retarding the flex-cracking tendency of rubber goods has been developed.

A TEM study of the effect of oxygen on nanocavity formation and precipitation in rapid - solidified Fe-16Ni-9Cr stainless steels

1994 ◽  
Vol 52 ◽  
pp. 700-701
Author(s):  
S. Wisutmethangoon ◽  
T. F. Kelly ◽  
J.E. Flinn
Keyword(s):  
Stainless Steels ◽  
High Mobility ◽  
Hot Extrusion ◽  
Extrusion Ratio ◽  
Gas Atomization ◽  
Cavity Formation ◽  
Nucleation Sites ◽  
Heat Treated ◽  
Different Types ◽  
Effect Of Oxygen

Vacancies are introduced into the crystal phase during quenching of rapid solidified materials. Cavity formation occurs because of the coalescence of the vacancies into a cluster. However, because of the high mobility of vacancies at high temperature, most of them will diffuse back into the liquid phase, and some will be lost to defects such as dislocations. Oxygen is known to stabilize cavities by decreasing the surface energy through a chemisorption process. These stabilized cavities, furthermore, act as effective nucleation sites for precipitates to form during aging. Four different types of powders with different oxygen contents were prepared by gas atomization processing. The atomized powders were then consolidated by hot extrusion at 900 °C with an extrusion ratio 10,5:1. After consolidation, specimens were heat treated at 1000 °C for 1 hr followed by water quenching. Finally, the specimens were aged at 600 °C for about 800 hrs. TEM samples were prepared from the gripends of tensile specimens of both unaged and aged alloys.

Application of pure, thermostable, alkali-tolerant xylanase in bleaching of oxygen-delignified pine kraft pulp

TAPPI Journal ◽  
2015 ◽  
Vol 14 (11) ◽  
pp. 689-694
Author(s):  
QINGZHI MA ◽  
QI WANG ◽  
CHU WANG ◽  
NIANJIE FENG ◽  
HUAMIN ZHAI
Keyword(s):  
Intrinsic Viscosity ◽  
Chlorine Dioxide ◽  
High Purity ◽  
Kraft Pulp ◽  
Alkaline Media ◽  
Industrial Scale ◽  
Elemental Chlorine ◽  
Effect Of Oxygen ◽  
Alkaline Tolerant ◽  
Ecf Bleaching

The effect of oxygen (O2)-delignified pine kraft pulp pretreatment by high-purity, thermostable, and alkaline-tolerant xylanases on elemental chlorine free (ECF) bleaching of O2-delignification kraft pulp was studied. The study found that xylanase pretreatment preserved the intrinsic viscosity and yield of O2-delignified pulp while causing about 7% of delignification with high delignification selectivity. The xylanases with high purity, higher thermostability (75°C~80°C) in highly alkaline media (pH 8.0~9.5) could be applied on an industrial scale. Pulp pretreatment by the high-purity, thermostable, and alkaline tolerant xylanases could improve pulp brightness or reduce the chlorine dioxide (ClO2) consumption. In a D0ED1D2 bleaching sequence using the same amount of ClO2, the xylanase-pretreated pulp obtained a higher brightness (88.2% vs. 89.7% ISO) at the enzyme dose of 2 U/g pulp; or for the same brightness as control (88.2% ISO), the ClO2 dosage in the D0 stage was reduced by 27%, which represents a 16% savings in total ClO2 used for bleaching.

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