THE CHEMICAL FATE OF RECOIL IODINE ATOMS IN IODINE–METHYL IODIDE SOLUTIONS

1964 ◽  
Vol 42 (12) ◽  
pp. 2684-2694
Author(s):  
N. V. Klassen ◽  
A. P. Baerg
Keyword(s):  
Methyl Iodide ◽  
Mole Fraction ◽  
Neutron Irradiation ◽  
Iodine Concentration ◽  
Thermal Reactions ◽  
Chemical Fate ◽  
Diffusion Controlled ◽  
Organic Products

The organic yield of recoil 126I, produced by the 14 MeV neutron irradiation of iodine–methyl iodide solutions, was examined over iodine concentrations from 0.34 mole fraction iodine to "pure" methyl iodide. By correcting for exchange between I2 and methyl iodide, the initial organic yield at very low iodine concentrations was found to be 57%. The time for one-half of the I2 to exchange with CH3I was found to decrease with decreasing iodine concentration. At all iodine concentrations the organic products containing 126I consisted mainly of CH3I and CH2I2. The formation of products is discussed in terms of thermal reactions, diffusion-controlled reactions in the spurs, and hot reactions.

CHEMICAL EFFECTS OF THE (n,r) ACTIVATION OF BROMINE IN THE ALKYL BROMIDES: THE HALOMETHANES

1961 ◽  
Vol 39 (1) ◽  
pp. 121-130 ◽  
Author(s):  
W. E. Harris
Keyword(s):  
Carbon Tetrachloride ◽  
Neutron Flux ◽  
Neutron Irradiation ◽  
Hot Spot ◽  
Thermal Reactions ◽  
Chemical Effects ◽  
Alkyl Bromides ◽  
Organic Products

Techniques for studying the chemical effects accompanying the neutron irradiation of the halomethanes with a neutron flux of only 108 neutrons per square centimeter per second are described. Results are presented from the irradiation of mixtures of bromine with the four bromomethanes and carbon tetrachloride. The formation of organic products which occur as the result of "hot", "hot-spot diffusive", and "thermal" reactions are discussed. The amounts of products resulting from these three types of reactions are estimated. Observations with respect to the formation of bromoethanes are also discussed.

Methyl iodide thermal reactions when chemisorbed on nickel(100) surfaces

Langmuir ◽  
1992 ◽  
Vol 8 (9) ◽  
pp. 2090-2097 ◽  
Author(s):  
Sariwan Tjandra ◽  
Francisco Zaera
Keyword(s):  
Methyl Iodide ◽  
Thermal Reactions

Exchange reactions in hot atom chemistry. II. Liquid methyl iodide

1976 ◽  
Vol 29 (3) ◽  
pp. 495
Author(s):  
FCR Cattell
Keyword(s):  
Methyl Iodide ◽  
Isotope Exchange ◽  
Radioactive Iodine ◽  
Hot Spot ◽  
Iodine Concentration ◽  
Square Root ◽  
Exchange Reactions ◽  
Isotope Exchange Reaction ◽  
Organic Combination ◽  
Atom Chemistry

When dilute solutions of iodine in methyl iodide are irradiated with neutrons more than 56% of the radioactive iodine-128 appears in organic combination. This increase arises from an isotope exchange reaction with a rate independent of iodine concentration. When more concentratedsolutions are irradiated the organic radioactivity is reduced below 56% and the reduction depends on the square root of iodine concentration. Results are examined in terms of the kinetic theory of hot reactions and also a treatment for distinguishing between 'Rot' and 'hot spot diffusive'reactions.

A study of the Szilard-Chalmers reaction of ethyl iodide at low thermal neutron fluxes

1971 ◽  
Vol 24 (1) ◽  
pp. 25 ◽  
Author(s):  
BJ Brown ◽  
DJ Carswell
Keyword(s):  
Thermal Neutron ◽  
Neutron Irradiation ◽  
Solid Phase ◽  
Chemical Exchange ◽  
Irradiation Time ◽  
Iodine Concentration ◽  
Ethyl Iodide ◽  
Bond Rupture ◽  
Post Irradiation ◽  
Free Iodine

Results reported in this paper show that the simple interpretation of the Szilard-Chalmers reaction in ethyl iodide, viz. bond rupture of the radiohalide and absence of subsequent chemical exchange, is not entirely valid. The results also verify and explain the apparently anomalous radiohalide yield of zero for neutron irradiation of pure ethyl iodide in the absence of a γ flux. ��� At low neutron fluxes free radiohalide yields in the liquid phase have been shown to be a function of irradiation and post-irradiation time, γ pre-irradiation dose, and fast/thermal neutron ratio. These results are consistent with the hypothesis that exchange occurs at a rate which decreases as the free iodine concentration increases. ��� Neutron irradiation of ethyl iodide at 77�K produces radioactive iodine in a metastable free state which does not undergo recombination in the frozen solid phase. The rate of post-irradiation recombination between free iodine-128 and the thawed liquid organic phase is independent of irradiation time and was found to be significantly faster than the rate corresponding to neutron irradiation at room temperature.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

A TEM investigation of a hyper-eutectic lead-tin alloy

1988 ◽  
Vol 46 ◽  
pp. 562-563
Author(s):  
John A. Sutliff
Keyword(s):  
Volume Diffusion ◽  
Eutectic Mixture ◽  
Precipitation Reaction ◽  
Directionally Solidified ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Diffusion Controlled ◽  
Discontinuous Precipitation Reaction ◽  
Controlled Precipitation

Near-eutectic Pb-Sn alloys are important solders used by the electronics industry. In these solders, the eutectic mixture, which solidifies last, is the important microstructural consituent. The orientation relation (OR) between the eutectic phases has previously been determined for directionally solidified (DS) eutectic alloys using x-ray diffraction or electron chanelling techniques. In the present investigation the microstructure of a conventionally cast, hyper-eutectic Pb-Sn alloy was examined by transmission electron microscopy (TEM) and the OR between the eutectic phases was determined by electron diffraction. Precipitates of Sn in Pb were also observed and the OR determined. The same OR was found in both the eutectic and precipitation reacted materials. While the precipitation of Sn in Pb was previously shown to occur by a discontinuous precipitation reaction,3 the present work confirms a recent finding that volume diffusion controlled precipitation can also occur.Samples that are representative of the solder's cast microstructure are difficult to prepare for TEM because the alloy is multiphase and the phases are soft.

Quantitative surface damage studies by H.R.E.M.

1989 ◽  
Vol 47 ◽  
pp. 632-633
Author(s):  
S. R. Singh ◽  
H. J. Fan ◽  
L. D. Marks
Keyword(s):  
Solar Wind ◽  
Quantitative Analysis ◽  
Surface Science ◽  
Surface Damage ◽  
Space Environment ◽  
Oxygen Desorption ◽  
The Past ◽  
Diffusion Controlled ◽  
Original Observation ◽  
Substantial Interest

Since the original observation that the surfaces of materials undergo radiation damage in the electron microscope similar to that observed by more conventional surface science techniques there has been substantial interest in understanding these phenomena in more detail; for a review see. For instance, surface damage in a microscope mimics damage in the space environment due to the solar wind and electron beam lithographic operations.However, purely qualitative experiments that have been done in the past are inadequate. In addition, many experiments performed in conventional microscopes may be inaccurate. What is needed is careful quantitative analysis including comparisons of the behavior in UHV versus that in a conventional microscope. In this paper we will present results of quantitative analysis which clearly demonstrate that the phenomena of importance are diffusion controlled; more detailed presentations of the data have been published elsewhere.As an illustration of the results, Figure 1 shows a plot of the shrinkage of a single, roughly spherical particle of WO3 versus time (dose) driven by oxygen desorption from the surface.

Melatonin reduces high levels of lipid peroxidation induced by potassium iodate in porcine thyroid

2019 ◽  
pp. 1-7 ◽  
Author(s):  
Paulina Iwan ◽  
Jan Stepniak ◽  
Malgorzata Karbownik-Lewinska
Keyword(s):  
Lipid Peroxidation ◽  
Oxidative Damage ◽  
Membrane Lipids ◽  
Chemical Properties ◽  
Iodine Concentration ◽  
Free Radical Scavenger ◽  
Radical Scavenger ◽  
Protective Effects ◽  
Potassium Iodate ◽  
Hormone Synthesis

Abstract. Iodine is essential for thyroid hormone synthesis. Under normal iodine supply, calculated physiological iodine concentration in the thyroid is approx. 9 mM. Either potassium iodide (KI) or potassium iodate (KIO3) are used in iodine prophylaxis. KI is confirmed as absolutely safe. KIO3 possesses chemical properties suggesting its potential toxicity. Melatonin (N-acetyl-5-methoxytryptamine) is an effective antioxidant and free radical scavenger. Study aims: to evaluate potential protective effects of melatonin against oxidative damage to membrane lipids (lipid peroxidation, LPO) induced by KI or KIO3 in porcine thyroid. Homogenates of twenty four (24) thyroids were incubated in presence of either KI or KIO3 without/with melatonin (5 mM). As melatonin was not effective against KI-induced LPO, in the next step only KIO3 was used. Homogenates were incubated in presence of KIO3 (200; 100; 50; 25; 20; 15; 10; 7.5; 5.0; 2.5; 1.25 mM) without/with melatonin or 17ß-estradiol. Five experiments were performed with different concentrations of melatonin (5.0; 2.5; 1.25; 1.0; 0.625 mM) and one with 17ß-estradiol (1.0 mM). Malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA) concentration (LPO index) was measured spectrophotometrically. KIO3 increased LPO with the strongest damaging effect (MDA + 4-HDA level: ≈1.28 nmol/mg protein, p < 0.05) revealed at concentrations of around 15 mM, thus corresponding to physiological iodine concentrations in the thyroid. Melatonin reduced LPO (MDA + 4-HDA levels: from ≈0.97 to ≈0,76 and from ≈0,64 to ≈0,49 nmol/mg protein, p < 0.05) induced by KIO3 at concentrations of 10 mM or 7.5 mM. Conclusion: Melatonin can reduce very strong oxidative damage to membrane lipids caused by KIO3 used in doses resulting in physiological iodine concentrations in the thyroid.

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