Go toArchive
Browse byFacets
Bookbag ( 0 )
'Phase transition' in keywords Facet   Publication Year 2001  [X]
Results  4 Items
Sorted by   
Section
Publication Year
2001[X]
1Author    Albert Würflinger, M. Massalska-Arodż3, S. Urbanb, W. Weissflogc, S. EmstcRequires cookie*
 Title    Thermodynamic Measurements on the Binary System Bis{[2,2-di(w- hexyloxycarbonyl)ethenyl]phenyl} Biphenyl-4,4'-dicarboxylate and 4-w-Octyloxyphenyl 4-/i-Pentyloxybenzoate at Elevated Pressures  
 Abstract    Thermodynamic measurements have been carried out on the binary system of a swallow-tailed liquid crystal A = bis{[2,2-di(n-hexyloxycarbonyl)ethenyl]phenyl} biphenyl-4,4'-dicarboxylate (4DS6) and B = 4-n-octyloxyphenyl 4-rc-pentyloxybenzoate (5 0 /0 8). A filled smectic A phase is induced in the concentration range 0.11 < xA < 0.75. The maximum of the SmA-N transition temperature (365 K) is observed for xA = 0.33. Dilatometric measurements show that the packing density in the filled phases is increased. High-pressure DTA is employed in order to investigate the coexistence range of the liquid crystalline phases and the slopes of the transition lines. The slopes of the melting curves for the mixtures are significantly smaller than those for the pure components. The slopes for the smectic -nematic -isotropic transitions are considerably larger. The coexistence range for the (smectic + nematic) phases does not seem to be pressure-limited, rather it increases with pressure. 
  Reference    Z. Naturforsch. 56a, 658—662 (2001); received July 18 2001 
  Published    2001 
  Keywords    Phase Transitions, DTA, High Pressure, Swallow-tailed Liquid Crystals 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0658.pdf 
 Identifier    ZNA-2001-56a-0658 
 Volume    56 
2Author    M. Ohga, F. M. Ostafa, A. Hmed, A. A. YoussefRequires cookie*
 Title    Dielectric Permittivity and AC Conductivity Investigation for the New Model Lipid Bilayer Material: (CH2)io(NH3)2CdCl4  
 Abstract    Differential thermal scanning of the new lipid-like bilayer material (CH2)io(NH3)2CdCl4 showed two structural phase transitions, with onset temperatures at T2 = (359 ± 2) K and 7, = (415± 1) K. Permittiv­ ity measurements were performed between room temperature and 450 K at 60-100 kHz. A step-like rise in permittivity at T2, associated with an order-disorder transition, is attributed to chain melting. Two anomalies at (413 ± 1) K and (430 ± 3) K, showing thermal hysteresis of -8 and 10 K, respectively, in­ dicate first order transitions which are associated with crystalline phase change. The AC conductivity follows an Arrhenius-type relation with the activation energy A£ varying with the frequency / according to the relation AE = A£0 [1 -exp where AE0,f0 and a are 0.95 eV, 52 Hz and 0.11, respectively. The frequency dependent conductivity follows the power law a= C 7dc + ßcov, with 0.3 <s < 1.5 for hopping conduction of hydrogen and/or chloride ions in the high temperature range, and localized hopping and/or orientational motion predominating temperatures lower than 413 K. Variations of B and s with temperature are discussed. PACS No. 76, 77 
  Reference    Z. Naturforsch. 56a, 568—578 (2001); received April 26 2001 
  Published    2001 
  Keywords    Phase Transitions, AC Dielectric Permittivity, Two-dimensional Materials, Lipid Bilayers 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0568.pdf 
 Identifier    ZNA-2001-56a-0568 
 Volume    56 
3Author    E. Mikuli, A. Migdał-Mikuli, I. Natkanieca, B. GradRequires cookie*
 Title    Phase Transitions and Water Dynamics of [Co(H20 ) 6](C104)2 and [Mn(H20 ) 6](BF4)2 Studied by Neutron Scattering Methods  
 Abstract    Inelastic incoherent neutron scattering (IINS) spectra and neutron powder diffraction (NPD) patterns, registered for [Co(H20) 6](C104)2 at 18 -270 K and for [Mn(H20) 6](BF4)2 at 18 -230 K, provided evidence that these crystals possess three solid phases in these ranges of temperatures. In both compounds the phase transition occurring at T C3 is connected with a change of the crystal structure, and that occurring at T C2 with a change in the rate of the reorientational motions of H20 ligands. 
  Reference    Z. Naturforsch. 56a, 244 (2001); received December 12 2000 
  Published    2001 
  Keywords    Hexaaquacobalt(II) chlorate(VII) and Hexaaquamanganese(II) tetrafluoroborate, Phase Transitions, Structural Changes, Water Reorientation, Neutron Scattering 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0244.pdf 
 Identifier    ZNA-2001-56a-0244 
 Volume    56 
4Author    Albert Würflinger, Denise Mondieig3, Fazil Rajabalee3, MiquelAngel Cuevas-DiartebRequires cookie*
 Title    pVT Measurements and Related Studies on the Binary System /iC16H34 -tiC17H36 and on wC18H38 at High Pressures  
 Abstract    The phase diagram of the binary system nC16H34 -rcC17H36 has been established at ambient pressure using DSC and crystallographic measurements. At low temperatures below the rotator phase RI there exist two crystal forms Op (about jc(C17) = 0.25) and Mdci (about x(C17) = 0.67) which are different from the crystal structures of the pure compounds (Tp for C 16 and Oi for C 17). Furthermore two compositions: (a) C 16/C 17 = 3:1 and (b) = 1:2, which correspond to the coexistence range of Op and Mdci, were chosen for high pressure DTA and pVT measurements, yielding the following findings: The specific volume of the rotator phase of C 17 is distinctly lower than those of the binary systems at the same state point. Assuming the existence of a metastable rotator phase for C 16, an excess volume of A V E/V « 0.01 can be estimated. Due to the very enlarged coexistence range of RI, the mixtures reach their lower transition point at considerably lower temperatures (in isobaric measurements) or higher pressures (in isothermal measurements), where the specific volume is lower than that of C 17 at its transition point. Furthermore, the volume and enthalpy changes of the O ord -RI transition is distinctly smaller for the binary systems than for pure C 17. Thus the specific volumes of the phases Op and Mdci are appreciably larger than t>(spec.) of C 17. Op and Mdci have practically the same specific volume in accordance with the crystallographic results. Enthalpy values are obtained with the aid of the Clausius-Clapeyron equation which agree well with enthalpies derived from the DSC measurements. Furthermore, pVT data have been established for the liquid and solid phases of nC18H38 in the neighbourhood of the melting curve, allowing to determine volume and enthalpy changes of melting as a function of pressure. 
  Reference    Z. Naturforsch. 56a, 626—634 (2001); received July 18 2001 
  Published    2001 
  Keywords    Hexadecane, Heptadecane, Octadecane, pVT, Excess Volume, Phase Transition, High Pressure, X-ray 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0626.pdf 
 Identifier    ZNA-2001-56a-0626 
 Volume    56