Materials Literature
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Study of the relaxation behaviour of a tri-epoxy compound in the supercooled and glassy state by broadband dielectric spectroscopy, D Pisignano, S Capaccioli, R Casalini, M Lucchesi, P A Rolla, A Justl, E Rössler
Aus vielen kristallinen Festkörpern lassen sich keine hinreichend großen und/oder für die Untersuchung mit Einkristall-Röntgenbeugungsverfahren qualitativ geeigneten Einkristalle erhalten. Darum ist für das Verständnis der strukturellen Eigenschaften solcher Stoffe die Möglichkeit zur Strukturbestimmung aus Pulverbeug…
Low-frequency dielectric measurements are performed on a nonchiral liquid crystal (8CB) for two different cell thicknesses 4.5 µm and 1.6 µm, as functions of temperature at various amplitudes of the probe field. Relaxation peak frequencies are observed at ~10 Hz for the 4.5 µm thick sample and ~100 Hz for the 1.6 µm c…
Gefahrlose und hochselektive H2O2-Produktion gelingt mit einem Membranreaktor mit folgendem Aufbau: Eine H2-permselektive Membran (2), bestehend aus dünnen Filmen einer Pd/Ag-Legierung (2b) und oxidiertem Pd (2c) sowie einer hydrophoben Polymermembran (2d), befindet sich auf einer röhrenförmigen Membran (2a) an der In…
Several members of the new family A(1-x)M(4-x)Bi(11+x)Se21 (A = K, Rb, Cs; M = Sn, Pb) were prepared by direct combination of A2Se, Bi2Se3, Sn (or Pb), and Se at 800 degrees C. The single-crystal structures of K(0.54)Sn(3.54)Bi(11.46)Se21, K(1.46)Pb(3.08)Bi(11.46)Se21, Rb(0.69)Pb(3.69)Bi(11.31)Se21, and Cs(0.65)Pb(3.6…
B-trichloroborazene reacts with bis(trimethylsilyl)carbodiimide to form non-oxide gels (see scheme). The xerogels consist of a polymeric network of borazine rings linked by carbodiimide groups. Pyrolysis at 1200°C provides amorphous ceramics with the composition BC0.23N1.1Si0.05H0.09 ≈ B4CN4. At 2000°C pure B4C is for…
Eine prismenartige Hohlraumstruktur baut sich aus drei pyridylsubstituierten Porphyrin-„Platten“ auf, die durch sechs PdII-Ionen verknüpft werden. Eine drastische Strukturänderung (Symmetrieänderung von D3h nach C2) wird durch die Aufnahme von Pyren ausgelöst.
Esterified B12 icosahedra with totally organoderivatized surfaces are obtained from the reaction of [closo-B12(OH)12]2− with acetic anhydride or benzoyl chloride. The resulting “closomers”, in which each cluster vertex is substituted with an organic ester moiety, can provide camouflaged modules of variable size, shape…
The transient thermoreflectance (TTR) method consists of measuring changes in the reflectivity of a material (thin film) under pulsed laser heating, and relating these changes to the corresponding surface temperature variations. Analytical solutions of the diffusion problem are then used to determine the thermal condu…
The 18 and 19 valence electron (VE) nitrosyl complexes [Fe(NO)('pyS4')]BF4 ([1]BF4) and [Fe(NO)('pyS4')] (2) have been synthesized from [Fe('pyS4')]x ('pyS4'(2-) = 2,6-bis(2-mercaptophenylthiomethyl)pyridine(2-)) and either NOBF4 or NO gas. Complex [1]BF4 was also obtained from [Fe(CO)('pyS4')] and NOBF4. The cation […
The water-exchange reactions of three modified iron(III) porphyrins were studied in acidic medium as a function of temperature and pressure using 17O NMR spectroscopic techniques. The positive activation entropies and activation volumes support a dissociative mechanism (see scheme showing the transition state; L=nucle…
By analyzing the point groups of the (nonsymmorphic) rod-groups of carbon nanotubes we show, for the first time, to the best of our knowledge, that all achiral carbon nanotubes possess only 8 Raman-active and 3 infrared-active phonon modes. This is in contrast to previously predicted 15--16 and 7-8 active modes, respe…
The description of molecular motion by macroscopic hydrodynamics has a long and continuing history. The Stokes−Einstein relation between the diffusion coefficient of a solute and the solvent viscosity predicted using macroscopic continuum hydrodynamics is well satisfied for liquids under ordinary to high-temperature c…
The planar aromatic tridentate ligand 2,6-bis(1-S-neopentylbenzimidazol-2-yl)pyridine (L(11)) reacts with Ln(III) (Ln = La-Lu) in acetonitrile to give the successive complexes [Ln(L(11))(n)](3+) (n = 1-3). However, stability constants determined by spectrophotometry and NMR titrations show that formation of the tris c…
In this work we present a prospective study on the potential capabilities of optical devices based on Fibonacci dielectric multilayers. We perform a detailed analytical comparison of the linear optical response of periodic versus quasiperiodic multilayers. Based on this study we will suggest the use of hybrid-order de…
Sozusagen superamphiphob wurden extrem hydrophobe ausgerichtete Filme aus Kohlenstoffnanoröhren (siehe Elektronenmikroskopiebild), die durch Pyrolyse von Metallophthalocyaninen erhalten wurden, durch Modifizierung mit Fluoralkylsilangruppen. Dadurch erhielten die Filmoberflächen sowohl superhydrophobe als auch superli…
The synthesis of nitronyl and imino nitroxides has been reexamined with the aim of both increasing yields and of offering opportunities for new structures. The conditions for the formation of 2,3-bis(hydroxyamino)-2,3-dimethylbutane, the key intermediate of Ullman's route, have been carefully studied, and a new proced…
Ein enger elektrischer Kontakt besteht zwischen einem substituierten Polymetaphenylenvinylen (PmPV) und einem Bündel von Einzelwand-Nanoröhren (SWNT), wie durch kraftmikroskopische, optische und elektronische Messungen an isolierten SWNT/PmPV-Strukturen (siehe Bild) gezeigt wurde. Mithilfe von PmPV könnten SWNTs mögli…
This paper describes the chemical modification of high surface area, photoluminescent porous silicon (PSi) by reaction at a moderately elevated temperature (<115 °C) with alkenes (RCH CH 2 ) and aldehydes (RCHO) to give organic monolayers covalently bonded to the surface through Si−C and Si−O−C linkages, respectively.…
A prismlike hollow structure was assembled when three pyridyl-substituted porphyrin panels were linked by six PdII ions. A dramatic D3h→C2 structural change of the prism (see scheme) was triggered by complexation of pyrene.