Materials Literature
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The lattice thermal conductivity of superlattices is shown to depend on a new kind of umklapp scattering process, called a mini-umklapp, associated with the mini-Brillouin zone of the superlattice. Expressions for three-phonon mini-umklapp-scattering matrix elements are obtained for superlattices consisting of lattice…
TiO2 varistors with low resistivity were developed to operate at low voltages and have a reasonably high nonlinearity index. The varistor properties of TiO2 ceramics are due to two different groups of dopants. Pentavalent cation dopants are used to decrease the TiO2 lattice resistivity to ≃10–100 Ω cm at 25°C. Divalen…
The complex dielectric constant of liquid water was measured at 9.61 GHz down to −18 °C by means of a two resonant cavities apparatus. The static dielectric constant of bulk samples was also measured at 27.5 MHz down to −16.5 °C using a resonant circuit technique. From the analysis of the experimental results it follo…
The first-order Raman spectra of $3C$-SiC have been measured as a function of hydrostatic pressure up to 22.5 GPa in a diamond anvil cell. The mode-Gr\"uneisen parameters of the LO and TO phonons at $\ensuremath{\Gamma}$ were determined. We observed an increase of the LO-TO splitting with pressure from which an increa…
We have observed fluorescence line narrowing in the LO-phonon-assisted intrinsic exciton emission of $\mathrm{Cd}{\mathrm{S}}_{x}{\mathrm{Se}}_{1\ensuremath{-}x}$, selectively excited over a range of energies below a critical energy ${E}_{\mathrm{em}}$, on the low-energy side of the exciton absorption line. The sharp…
We have calculated the electronic structure of three-dimensional graphite using the modified first-principles Korringa-Kohn-Rostoker technique developed for and applied to the intercalation compound Li${\mathrm{C}}_{6}$. Whereas previous calculations of the electronic band structure of graphite provide explanations ei…
Of the relaxed, graphitic, buckled, and $\ensuremath{\pi}$-bonded-chain-type models for the diamond (111)-(2 \ifmmode\times\else\texttimes\fi{} 1) surface, only the chain model appears to account for the measured surface-band dispersion. The interaction of dangling orbitals which determines the dispersion is large in…
On the basis of both theoretical and experimental studies, it has been suggested that the low-energy charge-excitations introduced into polyacetylene by light doping are charged solitons. However, these solitons are normally bound to oppositely charged impurities so that soliton conduction is inefficient at room tempe…
We investigate diffusion-controlled processes, where the reacting groups (A and B) are attached to long, flexible, macromolecules in melts or in concentrated solutions. We first give a general discussion of the rate constants, and are led to distinguish two fundamental types of behavior, depending on the rms displacem…
Results are presented on the decay of glow peak V (190 degrees C) in powder as well as single crystal chip samples of LiF. The absence of peak IV (170 degrees C) is confirmed and any contribution from higher temperature glow peaks is accounted for, to ascertain that the decay represents the uncontaminated peak V. It i…
Abstract The reaction of a diisocyanate and an asymmetric aliphatic‐aromatic diacid containing a preformed imide group was studied in order to obtain polyamide‐imides. It is shown in this paper that combined 1 H and 13 C NMR spectrometry will permit the quantitative evaluation of the proportions of head‐tail, head‐hea…
Abstract The 13 C NMR spectra of N ‐acetyl‐ D ‐glucosamine ( 1 ) and chitobiose ( 2 ), monomer and dimer of chitin, were assigned and used to assign the 13 C NMR spectra of chitin in lithium thiocyanate and in LiCl/dimethylacetamide solutions. The dissolution of chitin in formic acid was studied. IR, 13 C and 1 H NMR…
With a molecular-field theory that includes local vibronic dynamics, the phase transition at about 10K in the ferrimagnetic spinel FeCr 2 S 4 is described as a cooperative Jahn-Teller effect caused by antiferrodistortive coupling between (Fe 2+ S 4 2- ) Jahn-Teller complexes, using the same parameters that describe th…
Existing theoretical and empirical scaling rules for cratering phenomena are commonly based upon implicit assumptions regarding the roles of the impactor conditions and the target properties. It is common, for example, to assume that only the kinetic energy of the impactor and the work against gravity in the target go…
Abstract We present measurements of the d.c. electrical resistance of three classes of pure epitaxial gold films in the thickness range 30 to 900 nm. The combination of diverse morphological techniques with temperature-dependent data from 2 to 300 K enables us to apply a new theory based on those of Mayadas and Shatzk…
The dependence of secondary structure on SS content was examined to gain further insight into the role of SS bond formation in chain folding. Lysozyme was reduced to various levels, and the products were studied with respect to remaining native structure. Reductions were carried out in the absence of denaturant. Thus,…
The dynamics of librational motion in N2-type crystals is treated by taking into account both correlation and anharmonic effects. Temperature dependences of the order parameter, heat capacity, mean and free energies of the librational subsystems are calculated. Comparison is made with results of a computer experiment…
The transport properties of highly anisotropic conductors, such as tetrathiafulvalene tetracyanoquinodimethane (TTF-TCNQ) or graphite, are strongly influenced by inclusions, which can be represented as regions of different conductivity. This paper presents a theoretical study of such effects in three dimensions. Both…
Abstract Effect of alloying with rare earth elements RE (La, Pd + Nd, or so called “Mischmetall” containing Ce, Pr, Nd, La and traces of the other RE) on the ability to passivate and susceptibility to chloride breakdown of low alloys steels was investigated. Electron microprobe analysis revealed that the effect of RE…
Abstract Mit einem Gasströmungskalorimeter und der differentiellen Scanning‐Kalorimetrie (DSC) wird die Enthalpieretardation in PVC direkt als Wärmeproduktion beim Tempern gemessen (Temperaturbereich 333 bis 357 K, Zeitbereich 1 min bis 250 h). Außerdem wird der thermische Glasübergang für Kühlgeschwindigkeiten im Ber…