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Wyszukujesz frazę "Boysen, H." wg kryterium: Autor


Wyświetlanie 1-2 z 2
Tytuł:
Evolution of Disordering in SiC upon Sintering; Phase Analysis of SiC by Rietveld Method with Application of Neutron and X-Ray Diffraction
Autorzy:
Pałosz, B.
Boysen, H.
Schneider, J.
Schulz, H.
Powiązania:
https://bibliotekanauki.pl/articles/1924324.pdf
Data publikacji:
1993-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.10.My
61.12.-q
61.50.Ks
81.20.Lb
Opis:
Neutron and X-ray diffraction patterns of α and β powders as well as of sintered SiC were analysed by a multiphase Rietveld method. It is shown that structural models combined of large period polytypes can be used to approximate the disordering of these polytype structures. The hexagonality of the samples could be terminated with reproducibility 1-2% using different combinations of large-period polytypes. It follows that the usual classification into α and β SiC is an oversimplification. The polytype behaviour of SiC powders and the role of twinning of cubic layer stackings is discussed. Distribution functions of stacking sequences of different length in α and β phases are derived.
Źródło:
Acta Physica Polonica A; 1993, 83, 1; 95-106
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Disorder and Diffusion in Mayenite
Autorzy:
Boysen, H.
Kaiser-Bischoff, I.
Lerch, M.
Berendts, S.
Hoelzel, M.
Senyshyn, A.
Powiązania:
https://bibliotekanauki.pl/articles/1550024.pdf
Data publikacji:
2010-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.43.-j
61.66.-f
61.05.fm
Opis:
Mayenite, $Ca_{12}Al_{14}O_{33}$, has attracted enormous attention for novel technological applications after the discovery of its high oxygen ionic conductivity. The crystal structure consists of a calcium-aluminate framework, comprising 32 of the 33 oxygen anions. The remaining oxygen is distributed over 1/6 of large cages within the framework. The true structure is heavily disordered and usually non-stoichiometric due to the presence of extra anions and is presented for four samples: pure oxygen mayenite (O-mayenite), partly (O/N-mayenite) and fully (N-mayenite) exchanged by nitrogen and doped with iron (Fe-mayenite). All samples were investigated by neutron powder diffraction up to 1050°C. Data were analysed by the Rietveld method and by difference Fourier methods. As prepared O-mayenite contains $O_{2}^{-}$ and $OH^{-}$, N- and O/N-mayenite also $NH_{2}^{-}$, $NH^{2-}$ and $N^{3-}$, while Fe-mayenite was free of extra radicals. In O- and N-mayenite the extra species are lost under vacuum conditions above ca. 700°C, whereas O/N-mayenite retained $NH_{2}^{-}$ up to high temperatures. Diffusion of oxygen proceeds via a jump-like interstitialcy process involving exchange of the "free" oxygen with framework oxygen, coupled to relaxations of Ca ions. In O/N-mayenite $NH_{2}^{-}$ diffuses via interstitial process. In Fe-mayenite encaged oxygen is "invisible" due to extreme delocalisation or loss.
Źródło:
Acta Physica Polonica A; 2010, 117, 1; 38-41
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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