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Takahashi, Nobuaki; Kanaya, Toshiji*; Nishida, Koji*; Seto, Hideki*; Nagao, Michihiro*; Takeda, Takayoshi*
no journal, ,
We have extensively studied nano-scale structure and dynamics of three types of poly(vinyl alcohol) (PVA) gels by using small-angle neutron scattering (SANS) and neutron spin-echo (NSE) techniques; two physical gels and one chemical gel. The first one was a PVA gel in a mixture of deuterated dimethyl sulfoxide (DMSO-d6) and D2O with volume fraction of DMSO-d6 being 0.6, in which cross-links were made of crystallites. On the basis of NSE results, SANS intensity was divided into static and dynamic fluctuations to find that the former contribution was dominant in the present wave vector (Q) range. The latter, dynamic fluctuations were analyzed in terms of fluctuations of cross-links in the quasi-equilibrium position. The second gel was PVA in aqueous borax solution. The intermediate scattering functions of the gel as well as the sol were well described by Zimm mode and gel mode in Q regions of above and below a critical wave vector (Qc). The last one was the chemically cross-linked PVA gel. The intermediate scattering function was also described by Zimm mode in a short-time region, suggesting that it behaves like polymer solution. However, in a long-time region, the data points deviated from Zimm-scaled master curve, suggesting that it was restricted by the cross-links made of covalent bonds.
fuelSuzudo, Tomoaki; Itakura, Mitsuhiro; Kaburaki, Hideo
no journal, ,
We have developed a model of fission-gas-atom clustering and the bubble formation. The model uses a combination of Monte-Carlo simulation and three -dimensional cellular automaton; cellular automata are suitable for the numerical experiments for complex behaviors such as a clustering of atoms. The result has shown that there is a critical concentration of gas atoms to form a stable bubble. The bubble size distributions, generated by the cellular automaton results, are compared with the experimental data and the theoretical results from the master equation approach.
Nakamura, Mitsutaka; Arai, Masatoshi
no journal, ,
The low-energy dynamics characteristic of glassy materials such as an excess vibrational density of states and unusual thermal properties remain unsolved problems in condensed matter physics, although numerous works have been devoted to this problem. Inelastic neutron scattering measurement in pulsed neutron source is a promising tool for the investigation of space-time correlation of low-energy dynamics. Using the most intense inelastic neutron scattering experiments, were ported that low-energy excitations of vitreous silica which is a typical strong glass former is significantly suppressed by densification. Furthermore, we also found that higher ionic conducting glasses show larger intensity in the low-energy region. It is well known that the network structure of superionic conducting glass is expanded by salt doping. Then, an excess intensity in the low-energy region can be generally explained by the development of free spaces for both typical network glass (vitreous silica) and superionic conducting glass. In this presentation, we will present both the similarity and distinction of low-energy dynamics between vitreoussilica and superionic conducting glass in view of 
-dependences of dynamical structure factor 
. We also discuss the role of low-energy excitations in high ionic conductivity.