Resistive and Magnetic Susceptibility Transitions in Superconducting (TMTSF)2C104

We report measurements of the ac magnetic susceptibility and dc resistive superconducting transitions in the organic superconductor (TMTSF)₂C10₄. Inductive measurements show complete diamagnetic shielding below a broad transition and initial flux penetration at very low fields [H_c1(0) < 1 Oe]. The resistive transition is also broad, but occurs at a significantly higher temperature than the inductive transition, T_c = 1.0 K and 0.65 K respectively. Resistance measurements also show evidence of a phase transition in the vicinity of 24 K. Magnetic field induced transitions, measured both inductively and resistively, show marked anistropy both in magnitude and in breadth of the transition. Results suggest that (TMTSF)₂C10₄ is a quasi ID or 2D superconductor at high temperatures and high magnetic fields and an anisotropic bulk superconductor at low temperatures and fields. Associated thermoelectric power measurements suggest that spin density waves coexist with the superconducting state.     

On the distribution of growth directions of silver and other F.C.C. single crystals from the melt

Thin single crystals of pure Ag, its dilute alloys, Ni – 10 ˜ 60 wt.% Co and Fe – 35 wt.% Ni alloys were grown by the Bridgman method. A preference of growth directions of these crystals changes from the <111>direction towards <100>with increasing growth rate or alloying effect. These results are discussed from a characteristic of nucleus interfaces.     

The Influence of Surface Modification upon the Angular Distribution of Slip Traces on the Surface of Polycrystalline F.C.C. Metals

Surface modification by ion implantation leads to a smaller portion of grains of a polycrystalline metal showing slip traces as a result of cyclical deformation. The analysis of the azimuthal distribution of the slip traces gives an approach to explain this experience in more detail. Analytical and numerical calculation of the azimuthal distribution of slip traces under consideration of the slip geometry relative to the free surface leads to azimuthal distributions as experimentally determined for polycrystalline nickel after implantation with N⁺-ions and following cyclic fatigue with constant amplitude of plastic strain ϵ_pa = 10⁻⁴.     

Formation of a new F.C.C. τ2 phase in rapidly quenched Al55Cu35V10 alloy

X‐ray diffraction and transmission electron microscopy experiments were carried out to study the structure of rapidly solidified as‐cast and annealed Al₅₅Cu₃₅V₁₀ alloy. The as‐cast Al₅₅Cu₃₅V₁₀ alloy shows the presence of a new f.c.c. τ2 phase (a=0.58nm) along with a b.c.c. (a = 0.89 nm) phase which after subsequent annealing transforms into single f.c.c. phase (a = 0.58 nm). In this paper, it is also reported that these phases are crystalline approximants to an icosahedral phase on the basis of e/a (valence electron per atom) constant line. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Charge Transfer Transitions from Cyclohexadienyl-Type Radicals to Host Molecules in Anthracene Single Crystals

The optical absorption spectra of 1-, 2- and 9-dibenzo-cyclohexadienyl radical in anthracene crystals have been obtained and analyzed. It is shown that the absorption lines consist of vibrational progression and charge-transfer lines for 2- and 9-DBCR. Each line belonging to the former has the same polarization as the most intense 0–0 vibrational line and the latter show polarization character depending on the direction of charge transfer and the transition energy was found to have a coulombic dependence on the distance of charge transfer. It is pointed out that only charge transfer lines were observed for 1-DBCR. The splitting of lines were observed and ascribed either to the resonance transfer interaction between two neighboring molecules situated at an equal distance from the radical or to the site symmetry. It is suggested that the intensity of the charge-transfer lines are borrowed from the intra-radical transition. The result that the charge transfer lines are more intense than the intra-radical lines for 1-DBCR was discussed.     

The structure and electrical resistance of thin scandium films (II). F.C.C.–lattice phase observed in films obtained in a vacuum of 10−8 Torr

Phase composition of the Sc-films up to 200 Å thick obtained in a vacuum of 3 · 10⁻⁸ Torr, condensation rate being ω ⋍ 1 to 6 Å/s and ω ⋍ 40 å/s up to 10⁻⁷ Torr, have been studied by an electron-diffraction examination. A phase with an f.c.c.-lattice and a lattice parameter a = 4.76 to 4.80 ± 0.01 Å 0.01 Å is observed in films d ≲ 60 Å thick, whilst with films having a thickness d ≳ 90 Å a h.c.p.-phase is characteristic for solid specimens. Two-phase composition is observed in an interjacent interval of thicknesses. An analysis performed permitted to conclude that the f.c.c.-phase observed is a ScH_x-hydride forming during the post-condensation delay time on a basis of a poly-morphic modification.     

Transitions to the relaxor and dipole-glass states in mixed crystals of the potassium dihydrogen phosphate family

Regularities of the formation of the relaxor and dipole-glass states in the systems of mixed ferroelectric-antiferroelectric crystals of the potassium dihydrogen phosphate family are discussed. The problems related to the crystal structure, lattice dynamics, and relaxation processes in dipole glasses and relaxors implemented in systems of this type are considered.     

Dielectric spectroscopy of low-loss sugar lyophiles: II. Relaxation mechanisms in freeze-dried lactose and lactose monohydrate

This article presents an analysis of the dielectric relaxation mechanisms of the disaccharide lactose, in both the freeze-dried state and the crystalline monohydrate. Complex dielectric permittivity spectra for both forms of lactose were measured over wide ranges of frequency (0.1 Hz to 1 MHz) and temperature (−120 °C to +100 °C). The crystalline monohydrate displays a sharp peak in the temperature domain which was ascribed to the percolation of migrating protons over the surfaces of the crystals. The freeze-dried material displayed three relaxation processes. The first (γ) and second (β) processes were observed at low temperature and present as very broad relaxations with low dielectric strength. The relaxation times for both processes showed Arrhenius temperature-dependencies, with activation energies of 52 kJ/mol and 72 kJ/mol, respectively. The mechanisms of dielectric relaxation were ascribed to the motion of the pendant hydroxymethyl group and the relative motion of the pair of saccharide rings, respectively. Analysis and discussion of the third relaxation process is beyond of the scope of this article.     

Formation of a Banded Texture in Solutions of Liquid Crystalline Polymers: 1. Hydroxypropylcellulose in H2O

Abstract

The formation of a banded texture was investigated for sheared anisotropic solutions of hydroxypropylcellulose (HPC) in H₂O. A cone and plate rheometer made of highly polished glass allowed the exploration of the shear rate (γ) range between 0.1 and 150 sec^?1 and the study of the effect of shear time t_s. Texture, monitored with a video-camera, appeared after a time t_b following cessation of shear. t_b is usually a decreasing function of γ and t_s. In most cases a precursor banded texture precedes the banded texture, and t_b attains zero at high enough γ or t_s. However, when a particularly good orientation of the flowing solution is achieved, the precursor texture is not observed, t_b is finite, and the bands are particularly well formed. We speculate that bands are the normal relaxation mode for well oriented solution. For less oriented solutions flow instability may lead to bands even during flow.     

Correction to “Preparation of monodisperse silica particles: Control of size and mass fraction” by G.H. Bogush,M.A. Tracy and C.F. Zukoski IV,Journal of Non-Crystalline Solids 104 (1988) 95–106

A minor, but critical error in Eq. (1) of the paper by Bogush et al. [G.H. Bogush, M.A. Tracy, C.F. Zukoski IV, J. Non-Cryst. Solids 104 (1988) 95] (referred to as Bogush in the following) leads to erroneous predictions of silica particle sizes for given reaction conditions. The published fit gives a 28% error in size predictions for the conditions used in Fig. 4 in Bogush. Bogush used the correct fitting formula in their work and the figures in their publication.     

Doping of microcrystalline Si:H,Cl films in R.F. glow discharge

The deposition rate of n-doped μc-Si:H,Cl GD films has been found to increase with the gas phase phosphine content, while the opposite behaviour has been observed for p-doped specimens. The optical gap ranges between 1.8 ÷ 2.6 eV and its variation seems related to hydrogen and chlorine contents. The effectiveness of the doping has been tested by electrical conductivity measurements.     

X-Ray Characterization of Guanidine Aluminium Sulfate Hexahydrate Crystals in Relation to their Ferroelectric Properties

Characterization of growth defects by X-ray topography of Guanidine aluminium sulfate hexahydrate crystals allows to set a close correlation between ferroelectric domain and growth sector patterns. The crystalline quality of prismatic sectors is much better than that of basal sectors.