Annealing of Chemical Radiation Damage in Potassium and Caesium Bromates

Journal of Thermal Analysis

Sahoo

Jena

1989

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The effects of SOl-doping and Y-irradiation on the isothermal (563 K) decomposition of barium bromate have been investigated gasometrically with a vacuum apparatus. Plots of the fraction decomposed a vs. time t for pure, doped and irradiated crystals exhibited characteristic stages: initial gas evolution (initial puff), an induction perioc~, linear reaction, an acceleratory period and decay. The data are considered in the light of various kinetic models, e.g. linea~" rate equation, ProutLTompkins and Avrami-Erofecv. The plausible mechanism of the reaction and the effects on this .of anion vacancies and Y-irradiation are discussed briefly.The thermal decomposition of solids is an important field of solid-state chemistry, with vast technical applications [1,2]. The understanding and control of the chemical reactivity of solids are the main objects in decomposition studies [3]. As ammonium perchlorate (AP) is extensively used as a solid propellant and more generally in pyrotechnic systems [4], a detailed study is needed on the decomposition of inorganic oxyanions such as chlorates, bromates and perchlorates, and on how this is influenced by vacancies (cation and anion) and irradiation. Barium bromate, which decomposes entirely in the solid phase, was chosen for the present study. Although the effects of cation vacancies and Y-irradiation on the decomposition of its crystals have been well studied [5][6][7][8], the available data on the effects of anion vacancies are inadequate. The present investigation relates to the effects of SO~-doping and y-irradiation on the isothermal decomposition of barium bromate. ExperimentalBarium bromate was prepared from AR grade chemicals and was purified by repeated recrystallization. Doped (SO~-, 1.0 mol%) crystals of barium bromate

Section: Role T~f Irradiationmentioning

confidence: 81%

Influence of SO 4 2− doping and Y-irradiation on the thermal decomposition of barium bromate

Journal of Thermal Analysis

Sahoo

Jena

1989

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“…The difference in concentration between total-Ox and Br-Ox, constitutes [5] the concentration of non-Br-Ox, (non-Bromine bearing oxidizing fragments). The evaluation of BrO ~ and BrO 2 yields was accurate to within +1 % but that of non-Br-Ox was reproducible to within +2.5%.…”

Section: Methodsmentioning

confidence: 99%

“…Incorporation of cationic vacancies into the lattice increases the free space. It has been reported [5,6,11,12] that large free space in a crystal not only enhances the radiolysis but also produces appreciable thermal recovery of the damage facilitating migration of mobile entities. It is of interest therefore, to study the role of radiation doses and cation doping on the radiolysis and recovery of radiolytic damage entities in y-irradiated solid for which sodium bromate is chosen for the purpose.…”

Section: Introductionmentioning

confidence: 99%

Radiolysis and Annealing of Damage Entities in γ-Irradiated Pure and Doped NaBrO₃

Sahu

1994

Radiochimica Acta

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Radiolysis of pure as well as doped (Ba 2+ ) sodium bromate has been carried out at different irradiation doses. Annealing of damage BrO", BrOj and non-Br-Ox between 393.0-433.0 Κ is enhanced with increasing temperature, irradiation dose as well as by cation doping. Analysing the data in the light of theories of diffusion controlled mechanisms, it is indicated that for each fragment recovery is a combination of one first order and one second order process. The Ζ vs. φ plots are linear in the initial period of recombination suggesting the validity of Smoluchowski boundary condition (SBC) theory.

“…The entities generated [16] are mainly; Br-, BrO-, BROW, Og, 02 and BrO~ and play an important role both in nucleation and nuclei growth [2,4]. Irradiated crystals when subjected to thermal decomposition, the bromine bearing species undergo decomposition resulting bromide and O2 in the manner discussed earlier [5,6].…”

Section: Role Of Irradiationmentioning

confidence: 99%

Role of γ-irradiation and Ba2+ doping on the isothermal decomposition of caesium bromate

Journal of Thermal Analysis

Padhee

1991

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Role of },-irradiation and Ba 2+ doping on the isothermal decomposition of caesium bromate has been investigated gasometrieally. It is seen that decomposition proceeds in a molten/semi-molten state presumably due to formation of an eutectic between the product bromide and the host material, i.e., bromate. The process exhibits stages: (i) initial gas evolution (initial puff) (ii) short aeceleratoty and (iii) long decay. The data are analysed in the light of theories of different kinetic models like Prout-Tompkins, Avrami-Erofeev and explore that irradiation as well as doping enhance decomposition.