Materials Literature
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Abstract Nanostructured mesoporous silicates displaying hexagonally arranged channels, templated using a liquid crystal mesophase, were investigated using H‐2 and N‐15 NMR spectroscopy. It is shown that N‐15 MAS NMR spectroscopy allows to estimate the surface acidity of mesoporous materials by measuring the N‐H bond l…
The field of atomic and molecular photoionization has undoubtedly been transformed by the use of synchrotron radiation. In the mid-1960's the 180 MeV electron synchrotron at the National Bureau of Standards, Washington, DC, was used to discover many resonances in the photoionization continua of atoms and simple molecu…
We report on the specific heat, $C(T)$, measurements in the temperature ranges 4.5 K $<T<$ 30 K and 130 K $<T<$ 730 K of a one-dimensional carbon crystal phase synthesized by condensation of high-temperature carbon gas. Even at the lowest achieved temperatures, the measured $C(T)$ dependence, to the first…
The temperature induced transformation of single crystalline Ni -31.1% Mn -17.7% Ga (at%) shape memory alloy with Ms -446 K has been studied by means of dynamic mechanical analysis (DMA), calorimetry (DSC).dilatometq.three point bending tests and TEM.Two maxima in internal friction (IF) spectra on cooling and a single…
Based on the Pippard-Buckingham-Fairbank relation, a theory of critical ultrasonics near the isotropic-nematic transition in a liquid crystal is developed. This allows us to demonstrate that the attenuation data at different frequencies do indeed collapse on a single scaling plot in the isotropic phase.
Contamination of structures to be analyzed in an electron microscope is a severe problem for dimensional metrology applications, especially for low voltage electron microscopy. Two methods for contamination reduction which do not use a temperature variation of the sample or its environment have been investigated in th…
Abstract The monomer unit triad sequence distribution and the cis/trans linkage configurations at the cyclic maleic anhydride (MA) units in the copolymers of styrene (ST) and MA prepared in CCl 4 with AIBN at 50°C were quantitatively determined by 13 C DEPT NMR spectroscopy. So much as 61 % of the linkages at the MA u…
Experiments on the kinetics of O 2 depletion in air-saturated (65 ppm O 2 ) Jet-A (POSF-2827) fuel containing 4 ppm Fe 2 O 3 were conducted with a near-isothermal flowing test rig (NIFTR) using passivated heat-exchanger tubing over the range 418−468 K. The kinetic data are consistent with an oxidation mechanism involv…
Germanium and silver atomic surroundings of ${\mathrm{Ag}}_{2}{\mathrm{GeS}}_{3}$ glass have been studied by anomalous wide-angle x-ray scattering. The structural parameters deriving from the simulations of the differential distribution functions, characterizing selectively Ge and Ag environments, show that the medium…
Hydrogen adsorption on a Cu/MgO catalyst is investigated using in situ 1 H NMR. The adsorption is largely homogeneous, demonstrating reasonable agreement with the Langmuir isotherm and only small variations in the frequency shift and spin−lattice relaxation time with increasing coverage. The catalyst is investigated u…
Abstract Cyclic voltammetry was used to characterize the oxidation‐reduction behavior of a series of novel hexacoordinate silicon(IV) porphyrin complexes. Each (Por)SiX 2 [Por = the dianions of the porphyrins: tetrakis( p ‐tolyl)porphyrin (TTP), tetraphenylporphyrin (TPP), tetrakis( p ‐trifluoromethylphenyl)porphyrin…
The mean value of a measurement set with precision σ has an offset relative to an accepted standard. Calibration of an instrument involves subtracting the offset between the mean value and the reference. Unfortunately, imaging characteristics for most types of microscopes are not constant. Slight changes in feature wa…
Small angle time-resolved X-ray diffraction was used to monitor the behaviour of the smectic layers during the electric field induced planar to homeotropic transition in a smectic A cell possessing a chevron layer geometry. The liquid crystal material used was S3, from Merck Ltd, and was sandwiched in a 15 mum paralle…
Cu-Zn alloys have been electrodeposited from a pyrophosphate electrolyte containing Cu 2 P20 7> Zn 2 P 2 0 7 salts and an excess of K4P2O7 and KN0 3 . Current-potential data for both copper and zinc, as well their plating current efficiencies were determined from electrochemical polarisation experiments. Copper deposi…
The vibrational spectra (inelastic neutron scattering, infrared absorption and Raman scattering) of fused silica in the amorphous and in the liquid state are investigated by molecular dynamics simulation in using the TTAM interionic potential (Tsuneyuki et al., Phys. Rev. Lett., 61, 869 (1988)). The simulation predict…
The tacticity of poly(maleic acid) has been resolved by 150-MHz 13 C NMR spectroscopy in 0.1 N HCl solution at 60 °C by using the chemical shifts from the backbone carbon atoms and the carboxyl carbon atoms. The racemic propagation is found to be preferred by a factor 2 over mesomeric propagation. The resonances of th…
In this paper the morphology of 10 seldom reported and insufficiently known diatoms from the old catch-all genus Navicula (excl. Navicula sensu stricto) are described based on LM and, in particular, SEM investigations. For most of them SEM micrographs are presented for the first time. It is shown that some of these di…
Silicon carbide kiln furniture systems are an essential part of modern high-temperature technology. SiC ceramics have exceptional high-temperature stability and thermal shock resistance., They show no plastic deformation (creep) under mechanical load and maintain their geometry after each high-temperature cycle. There…
The twisting power of several chiral dopants in two host phase classes is investigated under the viewpoint of its dependence on chain length and size of the headgroups of the surfactants. The results are explained qualitatively, using a simple model of intramicellar chiral induction, which is sensitive to flexibilitie…
Oriented (Ti,Sn)O 2 thin films with modulated microstructure were successfully synthesized on sapphire substrates by using sol–gel processing combined with spinodal decomposition. The degree of orientation of (Ti 0.5 Sn 0.5 )O 2 thin films increased in the following order: sapphire (0001), (110), and (012). (Ti 0.5 Sn…