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Positron annihilation in synthetic zeolites (II) magnetic quenching effect (1990)

Ito, Y. ; Hirose, M. ; Tabata, Y.

Springer

Applied physics 50 (1990), S. 39-42

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ISSN: 1432-0630

Keywords: 78.70.D ; 81.90.+c

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Abstract Positron lifetime spectra were re-measured for a series of synthetic zeolites using a large time window of observation. Magnetic quenching experiments were also performed for the zeolites, and it has been confirmed that both the λ4 and the λ3 components are due to o-Ps. The annihilation rate of the third component, λ3, showed a good correlation with the size of the largest voids, which is similar to the correlation reported for other compounds. However the annihilation rate of the longest-lived component, λ4, showed a poor correlation with the void size. The λ3 component has thus been assigned to o-Ps in the regular voids of the zeolites, and the λ4 component to that escaped to inter-particle open spaces.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00323952

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Radiation induced terpolymerization of tetrafluoroethylene with propylene and n-butyl vinyl ether in bulk (1992)

Kostov, G. K. ; Matsuda, O. ; Tabata, Y. ; [et al.]

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1077-1082

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ISSN: 0887-624X

Keywords: fluoroelastomers ; tetrafluoroethylene ; radiation ; terpolymerization ; kinetics ; mechanism ; properties ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Terpolymerization of tetrafluoroethylene (TFE) with propylene (P) and n-butyl vinyl ether (NBVE) induced by γ-rays at room temperature at dose rate 5 × 105 rad/h and P/NBVE molar ratio from 49/1 to 10/40 was carried out. An alternating copolymerization between TFE and two α-olefins was found to take place in this system, so that 50 mole % of TFE containing terpolymer is always formed at various monomer compositions. The terpolymer composition can be explained successfully by the treatment by a complex mechanism. The complex reactivity ratios of rI (TFE-complex) and rII (TFE-NBVE complex) were calculated to be 0.5 and 0.6, respectively, assuming a complex mechanism. The polymerization rate and molecular weight increase with NBVE concentration in the monomer mixture. Colorless transparent rubber-like polymers were obtained at each monomer composition. The glass transition temperature sharply decreases with NBVE concentration in the terpolymer but the thermal and chemical resistances of the terpolymer slightly decrease. Considering these results together with the mechanical properties it has been concluded that the 45/48/7 terpolymer of TFE/P/NBVE molar ratio is good as a practical elastomer useful at relatively low temperatures.

Additional Material: 6 Ill.