Phase transitions in silicon single crystals resulting from directional plastic deformation

The formation of polytypic modifications is observed in dislocation-free silicon single crystals under directional plastic deformation. It is shown that the deformation-stimulated phase appears on the surface of the sample in the form of small grains ranging from several hundred to several thousand angstroms in size. A twin structure in the individual grains is observed. Fiz. Tverd. Tela (St. Petersburg) 40, 746–749 (April 1998)     

Polarization fluoroimmunoassays for the specific determination of amphetamine and methamphetamine in urine with the abbott TDx-analyzer

Two polarization fluoroimmunoassays for the screening of amphetamine and methamphetamine in urine were adapted for use with the Abbott TD_x-Analyzer running in the automatic mode. The detection limits of amphetamine and methamphetamine in 10 μl of urine were 0.03 and 0.05 mg l^?1, respectively. These assays were specific for the determination of amphetamine (cross-reactivity with methamphetamine 1%) or for the determination of methamphetamine (cross-reactivity with amphetamine 2.5%). No significant cross-reaction was observed with other drugs of abuse (ephedrine, morphine and butabarbital).     

Effect of the anionic composition and pH on the dissolution kinetics of chromium(III) oxide and chromium(III) hydroxide oxide in acids

Based on an experimental investigation of the effects of the pH and anionic composition on the dissolution rate of chromium(III) oxide α-Cr₂O₃ and chromium(III) hydroxide oxide α-CrOOH and subsequent modeling of the process, it is demonstrated that, depending on the pH, the rate-controlling stage of the dissolution is the CrOH²⁺ or CrHSO ₄ ²⁺ sobulization.     

Method for stepped etching of optical glass fibers

A method for stepped etching of optical glass fibers using various compositions of etching agents based on a 40% hydrofluoric acid (HF) and aqueous solutions of ammonium fluoride (NH₄F) has been considered. Compositions, etching rates, the dependence of etching rate on temperature, and tyeh dependence of etching forms on composition have been determined. The potential use of the method for stepped etching of optical glass fibers in the manufacture of microelectronic devices has been demonstrated.     

Heat capacity and thermodynamic properties of bismuth orthovanadate in the temperature range 356–980 K

The molar heat capacity of BiVO₄ has been measured in the range 356–980 K by the differential scanning calorimetry method. There is an extreme point in the C_p = f(T) curve at about T = 532 K, which is caused by the existence of a phase transition. The thermodynamic properties of bismuth orthovanadate have been determined from the experimental data.     

Photoluminescence and structural defects in silicon layers implanted by iron ions

The photoluminescence spectra of silicon samples implanted by ⁵⁶Fe⁺ ions [energy, 170 keV; dose, 1×10¹⁶, (2–4)×10¹⁷ cm^?2] and annealed at temperatures of 800, 900, and 1000°C are measured. The structure of the samples at each stage of treatment is investigated using transmission electron microscopy (TEM). It is found that the phase formation and morphology of crystalline iron disilicide precipitates depend on the dose of iron ions and the annealing temperature. A comparison of the dependences of the intensity and spectral distribution of the photoluminescence on the measurement temperature, annealing temperature, and morphology of the FeSi₂ phase revealed the dislocation nature of photoluminescence.     

Nature of EPR line asymmetry in La<Subscript>0.70</Subscript>Ca<Subscript>0.25</Subscript>Ba<Subscript>0.05</Subscript>MnO<Subscript>3</Subscript>

It was pointed out in some works that asymmetry of an electron paramagnetic resonance (EPR) line is generally caused by both the electrical conduction and the nondiagonal elements of the dynamic susceptibility of a magnetic subsystem. Direct measurements of the temperature dependences of the conductivity and the EPR line shape in a La_0.70Ca_0.25Ba_0.05MnO₃ sample showed that the conduction makes the predominant contribution to the EPR line asymmetry.     

Structure and Chemical Composition of Manganese-Doped GaSb Dislocations

Electron microscopic observations showed that the preparation of magnetic semiconductor GaSb〈Mn〉 by melt quenching is accompanied by discrete manganese precipitation on GaSb dislocations, this precipitation generating inclusions sized from a split micrometer to several micrometers. The chemical composition of microinclusions was determined by electron probe microanalysis. The superposition of the magnetic properties of compounds that are formed in the Mn–Sb system determines the magnetic properties of GaSb〈Mn〉.     

Kinetics of the growth of the oxide layer during anodic oxidation of aluminum

Experimental plots of anode current density against time obtained for various electrolytes over a temperature range from 5 to 60°C have been compared with a theoretical model which describes the kinetics of the growth of the oxide film during anodic oxidation of aluminum. It is concluded from differences in the kinetic parameters for ammonium benzoate and ammonium adipate that the oxidative destruction of the corresponding carboxylate anion is involved in a rate determining step of the process. V. I. Vernadskii Institute of General and Inorganic Chemistry, Ukraine Academy of Sciences, 32/34 Academician Palladin Prosp., 252680 Kiev-142, Ukraine. Translated from Teoreticheskiya i éksperimental’naya Khimii, Vol. 33, No. 1, pp. 58–61, January–February, 1997.