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  • 1
    Digitale Medien
    Digitale Medien
    CPS K 843 Radiation-induced crosslinking: Effect on structure of polyethylene (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 109-115 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Crosslinking ; radiation ; polyethylene ; density ; crystallinity ; d-spacings ; phase densities ; crosslink locations ; lateral grain boundaries ; crosslink mechanisms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Branched polyethylene irradiated (0–400 Mrad) with a Co60 source at room temperature under vacuum was studied by density, wide- and small-angle X-ray scattering (WAXS and SAXS) measurements. The radiation effects on the structure of bulk, branched polyethylene are quite similar to those observed by others on single crystals or oriented preparations. These effects include changes in bulk densityϱ, crystallinity(w c orv c) and¯d 100 and¯d 200 spacings as a function of irradiation. A decrease in crystallinity is seen to begin at radiation dose ≈100 Mrad whereas lattice expansion indicating onset of an orthorhombic-hexagonal transition can begin as low as 10 Mrads. The decrease in crystallinity can be attributed to additional lattice distortions primarily introduced by the crosslinks occurring at the lateral grain boundaries, while lattice expansion can be associated with the same crosslinking mechanism which begins at the defects both within the crystals as well as those outside the crystals at the lateral grain boundaries. Strong evidence for a primary crosslinking-at-the-defects mechanism has also come fromϱ c andϱ a data obtained in this study as a function of radiation dose. The same data have also led to an excellent correspondence between the measured density crystallinityv c and the measured WAXS crystallinityw c. Without consideration of the effects of crosslinks onϱ c andϱ a one would have obtained a divergence of the two crystallinities, especially at radiation doses greater than 100 Mrads.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01412784
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  • 2
    Digitale Medien
    Digitale Medien
    Trapping and reflection coefficients for3He in Ni at oblique incidence (1983)
    Springer
    Applied physics 31 (1983), S. 37-44 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 79.20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The areal density and the depth distribution of3He trapped in Ni as a function of the bombarding fiuence was measured in the energy range of 1–25 keV and at angles of incidence between 0 and 85° using nuclear reaction analysis. At fluences below saturation a linear relation is found between the areal density and the fiuence. From its slope the trapping and reflection coefficients can be determined. The experimental data for trapping and reflection coefficients and for the depth profiles were compared with computer simulation results from the TRIM program. To reduce uncertainties in the absolute values of the experimental trapping coefficients, they were normalized to the TRIM values at normal incidence. The dependence of the measured reflection coefficient on the angle of incidence between 0 and 80° shows good agreement with the calculated data for incident energies from 3 to 25 keV, but for 1 keV the measured reflection coefficients are higher than the calculated ones.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00617186
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  • 3
    Digitale Medien
    Digitale Medien
    Trapping and reflection coefficients for deuterium in graphite at oblique incidence (1984)
    Springer
    Applied physics 33 (1984), S. 265-268 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 79.20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Trapping and particle reflection coefficients for 0.4–10keVD on graphite have been measured for angles of incidence 0≦α≦85° by determining the areal density of implanted D as a function of the implanted fluence. The experimental data are compared to computer calculations with the TRIM-program. The agreement between measurement and calculation is good.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00614669
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  • 4
    Digitale Medien
    Digitale Medien
    Radiation-induced crosslinking: II. Effect on the crystalline and amorphous densities of polyethylene (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 469-476 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Crosslinking ; radiation ; polyethylene ; density ; crystallinity ; d-spacings ; phase densities ; crosslink locations and mechanisms ; defects ; lateral grain boundaries
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Small-angle x-ray scattering (SAXS) was used to determine the structural changes in polyethylene induced by radiation. The changes in densities of the crystalline and amorphous phases, ρ c and ρ a , were calculated after direct determination of the mean square density fluctuation 〈η2〉. ρ a increases with increasing radiation dose for both linear and branched polyethylene. This accounts for the serious discrepancy between crystallinities determined from wide-angle x-ray scattering and density measurements. This study confirms our previous proposal that crosslinks occur primarily in the noncrystalline phase, most likely at the defects in the lateral grain boundary regions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00655884
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  • 5
    Digitale Medien
    Digitale Medien
    Radiation-induced crosslinking: III. Effect on the crystalline and amorphous density fluctuations of polyethylene (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 353-363 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Crosslinking ; radiation ; polyethylene ; density ; crystallinity ; phasedensities ; densityfluctuation ; phasedensityfluctuations ; Crosslink locations and mechanisms ; defects ; lateral grainboundaries
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Small-angle x-ray scattering (SAXS) was used to determine density fluctuation in radiation-induced crosslinked polyethylene of varying degrees of crystallinity. Density fluctuation FL decreases with increasing crystallinity, while it increases linearly with increasing radiation dose or degree of crosslinking. By means of extrapolation, density fluctuations in the crystalline and the amorphous phasesFL c andFL a were obtained. At a given dose,FL a is greater thanFL c . The increase inFL a with radiation is found to be much greater than that ofFL c compared with the initial values at 0 Mrad,FL c showing only a negligible increase event at 312 Mrad. The present findings suggest that crosslinks are not introduced within the crystalline phase; they take place primarily in the noncrystalline phase, in agreement with the conclusions reached previously on the basis of changes in crystalline and amorphous densities in irradiated polyethylene.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00654582
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