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An experimental investigation of electromechanical responses in a polyurethane elastomer (1997)

Zhang, Q. M. ; Su, J. ; Kim, Chy Hyung

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 81 (1997), S. 2770-2776

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: The electromechanical response of a polyurethane elastomer was investigated at room temperature and in the temperature range near its glass transition. It was found that the Maxwell stress contribution to the strain response can be significant at temperatures higher than the glass transition temperature. In addition, the material exhibits a very high electrostrictive coefficient Q, about two orders of magnitude higher than that of polyvinylidene fluoride. It was also found that in a polymeric material, the chain segment motions can be divided into those related to the polarization response and those related to the mechanical response and the overlap between the two yields the electromechanical response of the material. In general, the activation energies for different types of motion can be different, resulting in different relaxation times in the dielectric, the elastic compliance, and the electrostrictive data, as observed in the polyurethane elastomer investigated. The experimental results indicate that at the temperatures investigated, the activation energy for the mechanical related segment motions is higher than that of nonmechanical related segment motions. © 1997 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.363981

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Surface Sol–gel Synthesis of Ultrathin Titanium and Tantalum Oxide Films (1999)

Fang, Mingming ; Kim, Chy Hyung ; Martin, Benjamin R. ; [et al.]

Springer

Journal of nanoparticle research 1 (1999), S. 43-49

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ISSN: 1572-896X

Keywords: titanium oxide ; tantalum oxide ; dielectric ; thin film ; sol–gel ; microcontact printing

Source: Springer Online Journal Archives 1860-2000

Topics: Physics , Technology

Notes: Abstract TiO2, Ta2O5, and mixed TiO2/Ta2O5 ultrathin films were grown layer-by-layer using a surface sol–gel deposition technique. The technique allows one to prepare smooth films of mixed composition with ångstrom-level control of thickness. The thickness increases per adsorption/hydrolysis cycle were 4.5, 2.1, and 2.5 Å, respectively, for TiO2, Ta2O5, and mixed TiO2/Ta2O5 (1.6sol;1) films. By combining X-ray diffraction and ellipsometric analysis, it was determined that the as-deposited TiO2 films are less dense than bulk TiO2, and do not adhere persistently to Si/SiO2 or Au/2-mercaptoethanol substrates. These ‘green’ films were annealed at 400°C to produce denser and highly adherent films. Patterning the surface by microcontact printing of siloxane polymer thin films allows one to prepare patterned sol–gel oxide thin films.