bluuebunny/crossref_metadata_2025_split huggingface dataset:
The precipitation and hydrothermal crystallisation of alkaline‐earth. Metal aluminosilicate hydrates from aqueous solution: Crystalline phases and precipitation and recrystallisation mechanisms
Authors: Packter A. 
Published: January 2007

AbstractThe preparations, precipitations and recrystallisations of magnesium and calcium aluminosilicate hydrates, from aqueous suspensions of microcrystalline silica, aluminium hydroxide (and oxohydroxide) and magnesium (calcium) hydroxides at ambient temperatures to 400 °C, are surveyed. The phases reported in systems of different Mg(Ca)/(Al + Si) and Al/(Al + Si) composition ratios are tabulated and precipitation and recrystallisation mechanisms are proposed.
Geometrical properties of dislocations in potassium bichromate crystals
Authors: Szurgot M. 
Published: January 2007

AbstractThe geometry of growth dislocations present in potassium bichromate crystals grown from aqueous solution has been studied by etching. Etch topographs composed of dislocation etch grooves and grooves representing sector boundaries and growth bands have been analysed. It was found that most of the dislocation lines are straight and have well‐defined directions in each sector. Refractions of dislocations at growth sector boundaries and at other defects have been observed.
Thermal expansion of microcracks and grain boundaries in crystals (II). Thermal expansion and compression under pressure of intermicrocrystallite gaps in liquids
Authors: Vlasov A. D. 
Published: January 2007

AbstractThe changes of melting points under pressure (melting curves) in terms of the microcrystallite model of liquids has been studied. These curves allowed the estimation of temperature dependencies of the scale factor n (or effective temperature) for microcrystallite surfaces for a representative group of liquids above the melting points. Further, by using the results of the author's previous works, general temperature relationship of the scale factor n for microcracks and gaps over a wide range of bulk temperature has been plotted. This relationship is characterized by the sharp jump at the melting point and is asymmetrical with respect to the melting temperature line. Solid‐liquid transitions from the standpoint of the microcrystallite model have been discussed.
Kinetic investigations within the transition region from polyhedral to skeletal growth mode (IV). Comparison between the kinetic critical size and the observed morphological size of the basal face of zinc single crystals
Authors: Iwanov D. 
Published: January 2007

AbstractThe growth of zinc single crystals in a kinetic and a diffusion regime at argon pressures 5 – 250 Torr has been investigated. The growth of the edge of the basal face has been studied as a function of time at constant supersaturation and temperature of the furnace, simultaneously observing the surface of the {0001} face. It was established that in a kinetic growth mode the single crystals retained their polyhedral shape, whereas in a diffusion regime their form was changed into skeletal. A comparison was made between the critical size at which the transition from a kinetic to a diffusion regime began and the size at which a visible depression appeared on the {0001} face. In fact, the transition from a kinetic to a diffusion regime occurs simultaneously with the loss of the morphological stability of the basal face at kinetic critical sizes ak and Rk.
Crystal growth and dislocation arrangement of Czochralski alexandrite (BeAl2O4:Cr) single crystals
Authors: Qiang Zhang , Peizhen Deng , Fuxi Gan 
Published: January 2007

AbstractThe [001] oriented alexandrite (BeAl2O4:Cr) single crystals have been grown by the Czochralski pulling technique. The X‐ray topographic investigation indicates that the grown‐in dislocations mainly originate from the seed and propagate along the path normal or nearly perpendicular to the growth interface. The dislocation density and arrangement is closely related to the quality of the seed crystal.
Crystal structure of phenyl‐β‐methyl‐pyridyl hydroxyimide, C13H12N2O
Authors: Ahmed Farag I. S. , El‐Shora A. I. , Mostafa M. A. , Rybakov V. B. 
Published: January 2007

AbstractPhenyl‐β‐methyl‐pyridyl hydroxyimide crystallizes in the form of prismatic crystals in the space group P 21 with Z = 4, a = 11.401(4) Å, b = 7.793(3) Å, c = 12.766(4) Å and β = 92.97°. The structure was solved by direct methods and was refined by block diagonal least squares calculation to a final value of 0.05. The pyridyl ring in molecule (II) is slightly distorted, all the other rings as expected are planar.
The structure of rapidly solidified ribbons of Al‐12 at. % Zn alloy
Authors: Bartuška P. , Simerská M. , Syneček V. , Lašek J. , Heyroth W. , Löffler H. 
Published: January 2007

AbstractThe structure of melt spun rapidly solidified ribbons of the Al‐12 at.% Zn alloy has been investigated by scanning electron microscopy and by X‐ray diffraction. Four solidification processes differing in the extent of associated segregation of zinc have been found to be operative during the solidification of the ribbon. These successive processes beginning from above the sites of good contact of the melt with the rotating plane of the copper substrate are as follows: massive planar growth of grains, arrayed dendritic growth, unaligned growth of dendrites, and star‐like dendritic growth out from fragments of dendrites. Smaller grains resulting from the last two mentioned processes have been also found within the regions located above the sites of poor contact of the melt with the substrate (lift‐off regions). All indicated successive growth modes starting with the epitaxial regrowth of grains have been also found to proceed during the solidification of the melt flowed over the already solidified alloy ribbon.Grain boundary precipitation of equilibrium β (≈︁ Zn) phase has been detected in all stages of solidification. High density of lattice defects built‐up during solidification is leading to the immediate intragranular heterogeneous precipitation of β phase at elevated temperatures within the two‐phase region without the formation of intermediate metastable precipitates.
Debye characteristic temperatures from X‐ray diffraction data and some thermal properties for AgGa1−xInxS2 solid solutions
Authors: Orlova N. S. , Bodnar I. V. , Kochkarik O. E. , Janovich V. D. 
Published: January 2007

AbstractInvestigations of the Debye characteristic temperature for the AgGa1−xInxSe2 solid solutions, calculation of some thermodynamic properties and analysis of its variation during substitution of Ga by In showed the increase of the molar volume, density, heat capacity, enthalpy, and decrease of the melting temperature, microhardness, thermal expansion coefficients, intrinsic energy with zero‐point energy, this giving evidence for a decrease of the forces of the interatomic interaction.
Crystal structure of 4‐(2‐hydroxyethyl)‐4‐aza‐5α‐androstan‐17β‐ol “HS‐478”
Authors: El‐shora A. I. , Gabala G. A. , Palmer R. A. 
Published: January 2007

AbstractThe crystal structure of HS‐478 (aqueous solvate) has been determined by direct method and refined by block diagonal least squares to R0 = 0.043. The intensity was measured in a four‐circle diffractometer in the ω/2θ scanning mode, CuKα radiation. The crystals are triclinic P1, a = 6.721(3), b = 66.532(3), c = 12.188(5) Å, α = 96.86(2)°, β = 82.82(2)°, and γ = 114.68(2)°. Rings A, B, C are chair whereas ring D is envelope. Rings A/B and B/C are trans fused, whereas rings C/D are quasi trans. The hydroxyethyl side chain connected to N(4) has conformation of (−t, t).
Crystal structure of n‐phenyl‐2,4,6‐triphenyl perchlorate, C29H22ClO4
Authors: Farag I. S. Ahmed , El‐Shora A. I. , Rybakov V. B. 
Published: January 2007

AbstractThe crystal structure of n‐phenyl‐2,4,6‐triphenyl perchlorate has been determined using the direct methods technique and refined to Ro = 0.055 and Rw = 0.056 for 1321 unique reflections measured on four‐circle diffractometer in the w scanning mode MoKα radiation. The crystals are orthorhombic, Pbca, a = 16.611(9), b = 16.625(6), c = 17.554(5) Å and Z = 8.All rings are planar as expected within the experimental errors. Rings B, C, D, and E are twisted about the formal single bond by 72, 19, 95, and 78°, respectively, out of the plane of the central ring.
Structural characterization of alumina‐supported nickel molybdena catalysts
Authors: Sarbak Z. 
Published: January 2007

AbstractThe object of our studies was a NiMo/Al2O3 catalyst thermally activated in oxygen, hydrogen, and in a mixture of hydrogen and hydrogen sulfide. On the surface of the oxide form of the catalyst there are different species, among them dimeric and polymeric octahedrally coordinated Mo6+ ions containing oxygen bridges are found. The presence of structures resembling α‐ and β‐NiMoO4 and 6‐heteropolymolybdenates was determined. Reduction with hydrogen leads to formation of two nuclear structures with single and double bridges of [Mo25+ O3] and [Mo5+ O4] type, respectively, and partially reduced 6‐heteropolymolybdenates. On the other hand, when the reduction and sulfiding take place at the same time, then terminal oxide ions are partially replaced by sulfide ones. The presence of [MoO2S2]2− species has been observed, however, there is no evidence of the exchange —OH groups for —SH ones and exchange of oxygen bridged ions for sulfur ions. It has been also noted that the subsurface structures remained intact after reduction and sulfiding.
Thermochemical analysis of native point defects and substitutional carbon and boron in GaAs crystal growth
Authors: Wenzl H. , Mika K. , Henkel D. 
Published: January 2007

AbstractThe phase extent of GaAs has been analyzed and compared with published phase diagrams as related to total and partial point defect equilibria including charged and uncharged Frenkel, Schottky, antisite defects and substitutional carbon and boron on both sublattices.The well‐known transition between semiconducting and semi‐insulating behaviour at 300 K as a function of melt stoichiometry in LEC crystals can be reproduced in our model in which complete equilibrium exists above, only electronic equilibrium below a freeze‐in temperature of 1100 K.The corresponding model standard enthalpy of formation of neutral Schottky defects is 4.0 eV, of a pair of neutral uncorrelated antisite defects 3.8 eV, of neutral Ga Frenkel defects 4.1 eV and of neutral As Frenkel defects 3.6 eV.Defect reactions in cooling processes after crystal growth are discussed and shown to be quite different for crystals with high or low dislocation density. Semi‐insulating behaviour requires the existence of carbon acceptors if dislocations provide internal sources and sinks for point defects. For ideal crystals carbon would not be necessary.The possible site distribution of C and B is analyzed in its dependence on temperature and chemical potential of As.Constitutional supercooling is negligible in LEC growth. Macrosegregation is severe if the As fraction in the melt deviates more than ±0.02 from the stoichiometric value 0.5.
X‐ray investigation on GaAlAs/GaAs epilayers bending at temperatures 77–750 K
Authors: Leszczynski M. 
Published: January 2007

AbstractThe Bond method of precise lattice constants measurements and double crystal (+, −) (004) reflections were applied to measure lattice constants, lattice mismatch, thickness of the layers and samples bending in temperature 77–750 K. The results enabled to calculate the ratio of GaAs and Ga1−xAlxAs elastic constants as well as thermal expansion coefficients.
Crystal and molecular structures of N‐alkyl‐N, N‐dimethyl‐3‐(heptamethyltrisiloxan‐3‐yl) propylammonium bromides
Authors: Ramm M. , Schulz B. , Sonnek G. , Schmaucks G. 
Published: January 2007

AbstractC16H42NO2Si3Br: Mr = 444.76, monoclinic space group P 21/c, a = 23.300(8), b = 8.918(4), c = 13.403(2) Å, β = 101.69(4)°, V = 2727(1) Å3, Dx = 1.08 Mgm−3, Dexp = 1.06 Mgm−3, Z = 4, F(000) = 932, λ(MoKα) = 0.71069 Å, μ = 16.3 cm−1. The crystal structure was determined by direct methods and refined by least‐squares procedure to the discrepancy factor R = 0.117.C15H40NO2 Si3Br: Mr = 430.34, monoclinic space group P21/c, a = 23.460(4), b = 8.518(2), c = 13.403(2) Å, β = 102.03(2)°, V = 2619(1) Å3, Dx = 1.09 Mgm−3, Dexp = 1.07 Mg−3, Z = 4, F (000) = 920, λ(MoKα) = 0.71069 Å, μ = 33.9 cm−1. The crystal structure was determined by least‐squares refinement of the structure model derived from structure determination of C16H42NO2·Si3Br to the discrepancy factor R = 0.099.C16H42NO2Si3Br: Daten siehe oben.C15H40NO2Si3Br: Daten siehe oben.
Chemistry of organic eutectics: Phenanthrene — benzoic acid and phenanthrene — cinnamic acid systems
Authors: Rai U. S. , Shekhar H. 
Published: January 2007

AbstractSolid‐liquid equilibrium data for binary systems of phenanthrene with benzoic acid and cinnamic acid, expressed in the form of temperature‐composition curves, show the formation of a simple eutectic in each case. Linear velocity of crystallisation (v), studied by capillary method at different undercoolings (ΔT), suggests the applicability of Hillig‐Turnbull equation, v = u(ΔT) n, where u and n are constants depending on the nature of solidification. Data on heats of fusion of pure components and eutectics, determined by the DTA method, infer appreciable interaction among the components in the eutectic melts. To highlight the nature of interactions among the components forming the eutectic melt, the excess thermodynamic functions such as hE, sE, and gE were computed. Microscopic studies reveal that the structure of eutectic is different from those of the parent components. Infrared spectra, recorded in the region, 4000 —625 cm−1, indicate weak interactions among the components in the eutectic.
Study of sintering processes in copper and nickel by positron annihilation
Authors: Krause R. , Schatt W. , Vetter B. , Polity A. 
Published: January 2007

AbstractIn the advanced stage of non‐isothermal sintering, vacancy clusters are present as prevailing type of defects. Their concentration considerably decreases at further temperature increase, and it can be concluded that thermally activated conversion of multiple vacancies into climbable dislocations takes place. Hence, in conformity with recent experiments, coincidence of intensive material transport (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document} e‐maximum) and decrease of defect concentration (recovery) can be understood.
Infrared reflectivity of ZnIn2Te4
Authors: Neumann H. , Kissinger W. , Lévy F. , Sobotta H. , Riede V. 
Published: January 2007

AbstractInfrared reflectivity spectra of ZnIn2Te4 single crystals are measured at room temperature in the wavenumber range from 170 to 4000 cm−1. The spectra reveal a single vibrational mode the frequency of which compares well with the frequencies of the high‐energy infrared active modes in HgIn2Te4, CuInTe2 and AgInTe2. It is concluded that these modes are sphalerite‐like in nature and that they are essentially determined by the properties of the In—Te bond.
Mechanical characteristics of the NaCl: Eu2+ crystal system
Authors: Suszyńska M. , Nowak‐Woźny D. 
Published: January 2007

AbstractYield strength of NaCl: Eu2+ monocrystals was studied as function of both the dopant concentration and the annealing parameters. Main attention was paid to the strengthening mechanisms induced by the presence of europium related second phases the structure of which was controlled by means of optical methods.Depending on the nature of the second phases and their crystallographic relations with the matrix, two strengthening phenomena have been evidenced: this related with the presence of penetrable and that related with inprenetrable second phase particles. As far as the former ones can be sheared along with the matrix, the later — are overcomed due to a looping mechanism resembling the behaviour of metal alloys with the fcc — type of structure.
Phase formation at constantly increasing supersaturation: Electrolytic nucleation at galvanostatic conditions
Authors: Dobreva A. , Gutzow I. 
Published: January 2007

AbstractA simple theoretical approach treating the kinetics of phase formation at constantly increasing supersaturation is developed. The process of electrolytic nucleation in galvanostatic regime i.e. at time changing cathodic overpotential is analyzed in terms of this formalism.It is found that the atomistic model of nucleation has to be applied in order to describe quantitatively the process of electrolytic phase formation.
Electrical conductivity and thermoelectric power of lithium‐cadmium ferrites
Authors: Ravinder D. , Rao T. Seshagiri 
Published: January 2007

AbstractThe electrical conductivity (σ) and thermoelectric power (Q) of polycrystalline lithiumcadmium ferrites having the chemical formula Li0.5–x/2CdxFe2.5–x/2O4 where (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) have been investigated as a function of temperature. Lithium‐cadmium ferrite with x = 0.4 is found to possess minimum electrical conductivity and lowest Seebeck coefficient. Plots of log (σT) versus 103T are almost linear and have shown a transition near the Curie temperature except in the case of cadmium ferrite. The Seebeck coefficient is negative for all the compositions showing that these ferrites behave as n‐type semiconductors. The values of charge carrier concentration and mobility have also been computed. The properties of cadmium‐substituted lithium ferrites have been correlated with those of zinc‐substituted lithium ferrites, cadmium and zinc being two non‐magnetic divalent ions occupying essentially tetrahedral A sites when substituted in ferrites.
Equilibrium vapour pressures over NaCl‐AgCl melts
Authors: Lenchev A. , Trifonova E. P. 
Published: January 2007

AbstractThe variation of vapour pressures over NaClAgCl melts with increasing of AgCl mole fractions in the interval (0.00–0.33) has been studied at 1073 K by gas transport experiments. The vapour pressures of the individual species of silver chloride [(AgCl), (Ag3Cl3)] and of sodium chloride [(NaCl), (Na2Cl2)] have been calculated using thermodynamic data. The experimental and calculated results have been used for evaluation of the vapour pressures of the complex species Ag2NaCl3 and AgNa2Cl3 at the upper experimental conditions. The equilibrium constants of the following gas‐phase reactions have been computed: 2 AgCl + NaCl ⇌ Ag2NaCl3, Kp1073K = 2.57 · 106, AgCl + 2 NaCl ⇌ AgNa2Cl3, Kp1073K = 1.19 · 107.
Dislocation studies by chemical etching on solution‐grown NaSbF4 and Na3Sb4F15 single crystals
Authors: Benet Charles J. , Gnanam F. D. 
Published: January 2007

AbstractAn attempt has been made to study the etch pit dislocations of isolated as well as matched pairs of cleavage planes of solution grown NaSbF4 and Na3Sb4F15 single crystals when etched with analar grade methyl alcohol and ethyl alcohol. On etching of cleavage faces the pits nucleate at the intersection sites of dislocations with the cleavage face. On successive etching of a cleavage face, arrays of triangular shape etch pits are observed. After prolonged etching some of the etch pits disappear. These pits are curved and terminated indicating that they are crystallographically non‐oriented. One‐to‐one correspondence with respect to number, shape, position and structure of the pits has been established by etching of a matched cleavage face. The etch pit densities of both NaSbF4 and Na3Sb4F15 crystals are found to be 103 per cm2.
Electrical Conductivity and Thermoelectric Power of LithiumZinc Ferrites
Authors: Ravinder D. , Seshagiri Rao T. 
Published: January 2007

AbstractElectrical conductivity (σ) and thermoelectric (Q) of polycrystalline lithium‐zinc ferrites of different compositions was investigated as a function of composition and temperature. Plots of log (σT) versus 103/T are almost linear and show a transition near the Curie temperature. The activation energy. in the ferrimagnetic region is in general less than that in the paramagnetic region. The carrier concentration and mobility of charge carriers has been discussed as a function of composition and temperature.
The thermodynamic equilibrium of the formation process of High‐Tc superconducting phase YBa2Cu3O7−x
Authors: Huan Le Van , Tuong Le Thi Cat 
Published: January 2007

AbstractAnalysing the equilibrium state of the formation reaction of the high‐Tc superconducting phase 1:2:3 (YBa2Cu3O7−x) on the base of the pressure‐temperature‐oxygen content (P‐T−x) correlation research and using the Van't‐Hoff equation, the Gibbs free energy (ΔGm) of the reaction has been calculated for the first time. It is seen that the absolute value of ΔGm is not large and of the order of 2.5 kcal · mole−1. This leads to an instability of the 1:2:3 phase. Also, from the calculated values of ΔGm relative stability regions of the 1:2:3 phase are determined for different values of x. Combinatively analysing the relation lg P = A−B/T (where A – the x‐dependent constant, and value of B was determined to be equal to 10518 atm. K) and the value of ΔGm, we come to the conclusion that the synthesis of YBa2Cu3O7 − x when x → 0 must be carried out under high oxygen pressure and low temperature for a lasting time, because the reaction rate is limited by slow diffusion in the solid phase.
Growth, structure and properties of thin monocrystalline InSb films grown by recrystallization in a narrow gap
Authors: Sheftal R. N. , Zybtsev S. G. 
Published: January 2007

AbstractThe results of investigation of recrystallization kinetics of (≦ 500 Å) InSb films are described with the aid of a laser refractometer. The thermodynamic process characteristic considered to the gap thickness and substrate material are investigated. It was revealed that the method of producing a protective SiOx coating greatly affects the electric properties of InSb films.
Improving the batch crystallizers operation
Authors: Belcu M. , Pincovschi E. 
Published: January 2007

AbstractUsing a mathematical model, from the literature, for the potassium sulphate crystallization, a computer programme was elaborated, aiming to optimize the operation of batch crystallizers through the minimization of the formed crystals number. Owing to the simplifications imposed by the numerical calculation a semnificative reduction of the crystals number was not obtained, comparatively with the constant supersaturation crystallization process, considered as a standard mode of operation. However, the model pointed out the direction for further process improving. Through systematical search, by generating different continuously diminishing functions for the supersaturation value, operating policies were founded, conducting to the reduction of the number of crystals formed in the process.
Crystal structure of a new chalcone compound prepared from khellinone
Authors: Ahmed Farag I. S. , Abd el‐hafez O. M. , Rybakov V. B. 
Published: January 2007

AbstractClaisen‐Schmidt condensation of Khellinone (4,7‐dimethoxy‐5‐acetyl‐6‐hydroxy)benzofuran with 2 thiophenalyde led to synthesis of the new biologically active 4,7‐dimethoxy‐5[γ(2‐thiophene)‐ß‐propene‐α‐one]‐6‐hydroxy‐benzofuran. The crystal structure of this new chalcone was confirmed using X‐ray structure analysis.The structure data obtained for a single crystal of the new chalcone are: Monoclinic, a = 8.845(3), b = 7.813(3), c = 22.146(8) Å; β = 96.51(2)°, V = 1520.6 Å3, Z = 4; Dx = 1.44 g · cm−3, space group P21/c, R = 0.067, Rw = 0.069.The intensity data were collected on an Enraf Nonius CAD‐4 computer controlled diffractometer using MoKα radiation. The structure was solved by the direct method and refined by full matrix least squares using anisotropic temperature factors of all atoms, except for hydrogen atoms, which were treated isotropically.