Materials Literature
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This article summarizes basic principles and recent progress in the field of cascade-branched polymers. Methods for the preparation of macromolecules with hyperbranched structures are presented and compared concerning the extent of control over molecular weights and polydispersity. Step-growth and recently developed c…
A multiplex electronic switch on the molecular level has been realized by using a tetranuclear FeII complex of the [2×2] grid type. The four metal ions can be switched stepwise between their high-spin and low-spin states by temperature, pressure, and light, thus representing a triple level, triple switch system as ill…
Effective stiffness properties ( D ) of nanosized structural elements such as plates and beams differ from those predicted by standard continuum mechanics ( D c ). These differences ( D - D c )/ D c depend on the size of the structural element. A simple model is constructed to predict this size dependence of the effec…
A special model of a thin transmission grating used to couple infrared radiation to electronic excitations in quantum wells is examined. The grating is viewed as a periodic array of two-dimensional (2D) conducting strips separated by completely open apertures. The 2D conductivity across each strip has a semielliptic p…
Experimental solubilities are reported for anthracene dissolved in ternary 1,4-dioxane + 1-propanol + 2,2,4-trimethylpentane, 1,4-dioxane + 2-propanol + 2,2,4-trimethylpentane, 1,4-dioxane + 1-butanol + 2,2,4-trimethylpentane, 1,4-dioxane + 2-butanol + 2,2,4-trimethylpentane, and 1,4-dioxane + 2-methyl-1-propanol + 2,…
To determine crude fibre (CF), NDF, ADF and ADL, the conventional technique (CT), using filter crucibles, was compared with the filter bag technique (FBT). The mean CF content of 56 forages and concentrates was slightly, but significantly lower (PO.001) with FBT than with CT (144 vs 138 g kg" 1 DM). The two techniques…
The influence of capillary condensation of water at the atomic force microscope tip and boron carbide film surface on the friction forces and wear of the films is studied by force microscopy. It is shown that friction and wear are strongly dependent on the humidity. At low humidity no wear at the film surface is verif…
We determine the thermal expansion coefficient of a fluorinated poly(arylene ether) low-k dielectric film using Fourier analysis of x-ray reflectivity data. The approach is similar to that used in Fourier analysis of x-ray absorption fine structure. The analysis compares two similar samples, or the same sample as an e…
Transient trapping/detrapping of electrons at the Si(100)/SiO2 outer surface is studied studied in vacuum or with an O2 ambient (between 10−3 and 30 Torr) following internal electron photoemission from Si. Photoemission-current (produced by a 150 fs, 800 nm laser source) and contact-potential-difference techniques wer…
The formation of many oxides with unpredictable structures can be attributed to a balance between stable and unstable compositions. A surprising number of the members of the Ln 4 Cu 3 MoO 12 and Ln‘ 2 Ln‘ ‘ 2 Cu 3 MoO 12 (Ln = La−Nd, Sm−Lu) families form, all crystallizing in a hexagonal structure similar to that of Y…
In this article we report the development of Fe modified BaTiO3 using sol-gel technique and present results of structural and dielectric studies to establish its suitability for pyroelectric sensor applications. Fine powders of Fe modified BaTiO3 were prepared by sol-gel process using barium acetate, iron isopropoxide…
The hard magnetic properties of nitrided melt-spun R(Fe,M)12 (R=Pr and Nd, M=V and Mo) ribbons have been investigated. Hard magnetic powders were prepared by vacuum annealing of ground ribbons in the temperature range from 700 to 950 °C and subsequent nitrogenation. For NdFe10.5Mo1.5Nx and PrFe10.5Mo1.5Nx powders, coe…
Time-resolved measurements of photoluminescence were carried out on a hydrogenated amorphous silicon nitride film prepared by low-pressure chemical vapor deposition. When excited with 5.0-eV photons, photoluminescence occurs over a broad spectrum ranging from 1.8 to 3.6 eV. The peak energy of this photoluminescence va…
Thin films of Bi2VO5.5 have been prepared epitaxially using a pulsed-laser deposition method on a Si(100) substrate using TiN as a buffer layer and SrTiO3 as a seed layer. The films have smooth surface morphology with atomically flat terraces and steps of 4 Å in height. The ferroelectric characterization shows a spont…
We present a characterization of lateral silicon pn junction arrays fabricated on a Si(001) surface using a synchrotron-based scanning photoelectron microscope (SPEM). The Si 2p images show energy dependent contrast which varies continuously across the space charge region between regions of different doping. Combined…
We propose a transition state for oxygen in silica. This state is produced by the insertion of an oxygen molecule into the Si--O--Si bond, i.e., it consists of producing a Si--O--O--O--Si bond. This state allows molecular oxygen diffusion in silica without breaking the molecular ${\mathrm{O}}_{2}$ bond and it is energ…
By solving a set of differential rate equations the precipitation of AgCl clusters in the glass system 30Na2O–70B2O3/AgCl has been modeled. Using a parallel algorithm on a CRAY T3E it was possible to investigate the process of homogeneous nucleation and growth, which starts after an initial quench of the glass melt in…
The defect formation in epitaxial NaCl films (up to 5.6 nm thick) during low-energy (50--1500 eV) electron bombardment has been studied by a combination of low-energy electron diffraction and energy loss spectroscopy. At temperatures below 200 K two types of color center are generated at the surface, showing distinct…
We propose a phase diagram of quasi-low-dimensional type II superconductors in parallel magnetic fields, when antiferromagnetic fluctuations contribute to the pairing interactions. We point out that pairing interactions mediated by antiferromagnetic fluctuations necessarily include both singlet channels and triplet ch…
Organometallic polycondensation gave zinc porphyrin (Por) polymers (e.g., (−Ar−Por-Ar−) n and (−C⋮C−Por-C⋮C−Ar−) n; Ar = arylene) having arylene or aryleneethynylene groups between the zinc porphyrin units. Polymers having long alkyl substituent(s) in the Ar unit were soluble in THF and chloroform, and gave M n and M…