Materials Literature
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Simple analytic expressions for all six Leslie viscosities for nematics are obtained from the molecular theory for rigid prolate molecules. The theory relates the viscosities to the second and fourth moments, P 2 and P 4, of the molecular distribution function, the aspect ratio a of the molecules, and an isotropic vis…
The relaxation time, 1047 cm−1, of the Raman-active mode in barium nitrate crystal has been measured as a function of temperature by a time-resolved coherent anti-Stokes probe scattering technique. The temperature dependence is consistent with the combination of two relaxation mechanisms involving four and six phonons…
The previously established mechanism of two-phase nitration has been revised by proposing an additional mode of reaction, viz., interfacial nitration. The interfacial mechanism involves adsorption of the nitronium ion at the interface, followed by its reaction with the aromatic substrate present in the interfacial mon…
The ferroelectric properties were studied for polyamides consisting of m -xylylenediamine (MXD) and aliphatic dicarboxylic acids with the number of carbon atoms n =6 to 11, which were designated as nylon MXD n . Quenched samples of these polyamides exhibited the ferroelectric hysteresis loop with the remanent polariza…
We report observations of a temperature-induced orientational transition in a freely suspended nematic film of the liquid crystal 4-ethyl-2-fluoro-4\ensuremath{'}-[2-(trans-4-n-pentylcyclohexyl)-ethyl]-biphenyl (I52). The transition is from a high-symmetry state, where the molecules are perpendicular to the film bound…
Abstract Previous research and this research indicate that the mechanical melting for poly(vinylidene chloride) copolymers (PVDC) is complex. Mechanical melting is defined as the melting (or devitrification) of a polymer when a significant portion of the thermal energy originates from a mechanical energy dissipative p…
Thermoluminescence studies are carried out on samples in powder form of Li2B4O7 doped with Cu or Eu impurities. Results concerning Li2B4O7:Cu are found in agreement with data in the literature and show that the emitting defects are of intrinsic nature. In Li2B4O7:Eu a further emission is attributed to extrinsic aggreg…
Abstract Processing of microcellular foam was investigated for the feasibility of production of tough and lightweight polyurethanes. To increase the nucleation rate in a gas‐supersaturated resin, ultrasonic excitation was applied to the mixture of polyol(polyether‐based polyol) and isocyanate(diphenyl methane diisocya…
Redetermination of the structure of DL-norleucine (2-aminohexanoic acid), C6H13NO2, has given more accurate geometrical information than the early work of Mathieson [Acta Cryst. (1953), 6, 399-403]. Synchrotron radiation Laue diffraction patterns recorded over a range of temperatures have shown (a) the presence of str…
An excimer UV laser (193 nm) was used for preadhesion surface treatment of PEEK (polyetheretherketone) composite. This method presented an alternative to other limited and polluting conventional surface treatment methods. Experimental results indicated that laser preadhesion treatment significantly improved the shear…
At 1 atm of SiF 4 , mullite and SiF 4 react below 660° 7°C to form A1F 3 and SiO 2 . From 660° to 1056°± 5°C, the product is fluorotopaz. Mullite is stable in the presence of 1 atm of SiF 4 above 1056°C. The transition temperatures at other pressures of SiF 4 can be calculated from log p (atm) = 11.587 – 10811/ T (K)…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNew 58 VSE Clusters from the Oxidation of CpEt2Mo2Co2S4(CO)2: Structural and Magnetic Effects and Catalytic Desulfurization ActivityM. Adnan Mansour, M. David Curtis, and Jeff W. KampfCite this: Organometallics 1995, 14, 12, 5460–5462Publication Date (Print):December 1, 1995…
The results of the study both on short-wavelength luminescence and point defects in the large LiB 3 O 5 crystals grown by the advanced technique are reported. It was revealed that corpuscular or photon radiation with energy exceeding Eg efficiently excites the complex broad luminescence band at 290 nm. Decay kinetics…
A high-speed analog optical phase modulator based on chiral smectic and cholesteric liquid crystals is discussed. The chiral smectic liquid-crystal device functions as a variable-orientation half-wave retarder, whereas the polymer cholesteric liquid-crystal film acts as a polarization-preserving mirror. We use circula…
Abstract The development of the infrared (IR) absorption band at 1640 cm −1 (δH 2 O) is employed to monitor the gain in molecular water of progressively mortar-ground kaolinite. The planimetred area of this band shows a linear correlation with weight loss at 105°C (free moisture) between 2 and 18 h grinding, indicatin…
A mathematical model based on four modes of operation is developed to predict the tensile response of a hybrid circular braid encompassing an elastic core. Model inputs include parameters characterizing the initial geometric configuration and ma terial properties of the hybrid. Output parameters are forces, strains, m…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChemical and Electronic Properties of Bimetallic SurfacesJose A. Rodriguez and D. Wayne GoodmanCite this: Acc. Chem. Res. 1995, 28, 12, 477–478Publication Date (Print):December 1, 1995Publication History Published online1 May 2002Published inissue 1 December 1995https://pubs…
A calibration sample for transmission electron microscopy (TEM) has been developed that performs the three major instrument calibrations for a transmission electron microscope: the image magnification calibration for measurements of images, the camera constant calibration for indexing diffraction patterns, and the ima…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis of Alkyl- and Alkyloxy-Substituted 2,3-NaphthalocyaninesRainer Polley and Michael HanackCite this: J. Org. Chem. 1995, 60, 25, 8278–8282Publication Date (Print):December 1, 1995Publication History Published online1 May 2002Published inissue 1 December 1995https://p…
Both anisotropic ablation and thin film formation of polytetrafluoroethylene (PTFE) were successfully demonstrated using synchrotron radiation (SR) irradiation of PTFE, that is, the SR ablation process. Anisotropic ablation by the SR irradiation was performed at an extremely high rate of 3500 µm/min at a PTFE target t…