bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Nickel and Tungsten species supported on alumina
Authors: Sarbak Z. 
Published: January 2007

AbstractThe effect of thermal activation on NiW/Al2O3 catalyst in their oxide, reduced and sulfided forms has been studied by X‐ray diffraction (XRD), differential thermal analysis (DTA), diffusion reflectance spectroscopy (DTS), infrared spectroscopy (IR), Raman spectroscopy (RS), electron paramagnetic resonance (EPR) and magnetic susceptibility measurements.Thermal activation in oxygen results in production of many species of the mono‐, di‐, and polymeric type. Upon activation in hydrogen they are partially reduced, whereas upon sulfiding number of oxide ions are replaced by sulfide ones. Among others, formation of dithiotungstenates was proved, yet neither the exchange of hydroxyl groups for the thiol ones nor the exchange of bridge oxide ions for sulphur ions was indicated.The simultanous reduction and sulfiding process do not affect the spinel subsurface structure. With respect to the surface species, the catalyst's support takes on a stabilizing function.
Crystal and molecular structure of 7‐[1‐(2‐carbomethoxyanilino)‐1‐(phenyl)‐methyl]‐quinolin‐8‐ol(CMAB‐Oxine) and comparising consideration to CMAP‐Oxine
Authors: Rericha A. , Seidel I. , Röbisch G. 
Published: January 2007

AbstractC24H20N2O3, Pbc21, a = 11.338(4), b = 7.786(3), c = 44.381(6) Å, Dx = 1.29 Mg · m−3, V = 3.82053 · 10−27 m3. There are eight molecules in the unit cell (two molecules, A and B, in the asymmetric unit). The substitution of N (CMAP‐Oxine) by CH(CMAB‐Oxine) in the aldehyde participant of reactants creates differences both in intermolecular contacts and orientation phenomenons of ring planes. A high degree of selectivity of the substitution position for both compounds is given. The reactions to the synthesis of both compounds are difficult to agree upon with the characteristic feature of the Mannichreaction and corresponded more to the character of the electrophilic substitution of aromatics.
Influence of the model parameters on the Monte Carlo simulation of the initial aggregation of point defects in solids
Authors: Schmidt R. , Berg G. 
Published: January 2007

AbstractThe kinetic process to reach the equilibrium state of lattice defects is characterized by an aggregation of these defects. The formation of the precursors of the aggregates, the so called critical nuclei, can be investigated by Monte Carlo simulation. But in many cases the exact interaction potential between the movable defects in the lattice and the nucleus is unknown. Therefore such simulations were carried out for different typical interaction parameters. Conclusions concerning the general behaviour were derived. The calculations allow especially an estimation of the influence of strength of the potential and temperature on the number of defects forming a critical nucleus.
On chemical kinetics of silicon deposition from silane (IV). In‐situ phosphorus doping of LPCVD poly silicon in the temperature range 900–950 K
Authors: Kühne H. , Harnisch H. , Nüske G. 
Published: January 2007

AbstractHighly in‐situ phosphorus‐doped LPCVD poly silicon deposition from mixtures consisting of silane and phosphine has been investigated for limited conditions regarding temperature, silane input, phosphine‐silane ratio and total pressure. Agreeing with the deposition of undoped poly silicon, growth rate linearly decays along the axis of the wafer cage applied for in‐situ doped poly silicon. In consequence layer growth should be controlled by a chemical reaction of 0.5th order. In contrast to undoped poly silicon the slope of axial growth rate decay increases with the distance between wafers increased. This behaviour is a proof for a homogneous chemical reaction mechanism. The silicon forming reaction is characterized by an activation energy of about 25 kcal/mole for PH3/SiH4 = 0.003.
Application of various modes on the growth of magnetoplumbite single crystals from the Na2OBaO flux
Authors: Pollert E. , Durčok S. , Matějková L. , Nevřiva M. 
Published: January 2007

AbstractSeveral growing modes including the bottom growth, the growth on a thermocouple ball and the top seeded growth, were tested to grow BaFe12−2xMgxTixO19 and BaFe12−xGaxO19 magnetoplumbite single crystals from the Na2OBaO flux. Disadvantages of the bottom growth, inhomogeneities, inclusions, difficult separation of the crystals were restricted by using of the top‐seeded growth and by optimization of the ACRT program.
Influence of crystallisation conditions on the microtexture of the directionally solidified eutectic of the MgF2CaF2 system
Authors: Barta Č. , Fendrych F. , Recker K. , Tříska A. , Wallrafen F. 
Published: January 2007

AbstractThe influence of high‐frequency (HF) and resistive (R) heating of a vertical crystallizer furnace on the directional solidification process of the MgF2CaF2 system eutectic has been compared. The turbulent flow induced by HF heating given rise to inhomogeneities in microtexture, which do not occur under R heating conditions. Variations in the growth rate (v) and temperature gradient (ΔT) lead to characteristic changes of the eutectic microstructure: from lamellar to rod‐like. Quantitative analysis of these changes was advantageously performed using a digital image analysis of the area (AR), maximum cross‐section (D‐MAX), direction of the maximum cross‐section (ANGLE D‐MAX) of MgF2 particles of the microtexture. This was recorded on SCAN images of transverse cuts through the given directionally solified samples as well as the analysis of the shape of MgF2 particles.
Role of physical factors in solid – liquid interface formation during oriented eutectic growth
Authors: Wolczyński Waldemar 
Published: January 2007

AbstractThe basic physical factors affecting the eutectic interface shape observed in the microscopic scale have been discussed regarding the theory of completely coupled growth. The analysis considers phenomena like: heterogeneous nucleation and growth, interface undercooling of the both eutectic phases, phase protrusion and eventually horizontal temperature gradient. The contribution of the transition layer to the interface shape formation is emphasised.
To the non‐dislocation model of crystal tensile strength
Authors: Vlasov A. D. 
Published: January 2007

AbstractThe non‐dislocation model of crystal planes slipage has been proposed. The slipage of two planes begins when these planes have diverged to the critical distance by influence of the thermal stress σth that had to be appeared owing to heating of these planes above bulk temperature. This heating is due to the phenomenon supposed by the author, called the effective temperature of crystal surfaces. In such a way the simple expression for load/microscopic strain relation has been proposed. The calculated ratio: tensile strength/Young's modulus (6 · 10−3) is in good agreement with experimental data (of 1 to 2 · 10−3) for a number of metals. The common theories on tensile strength do not take into account the above mentioned thermal stress and this is the reason for theoretical data on strength being of three orders of magnitude above the experimental values.
Influence of O2 in photoluminescence measurements in Zn‐doped Al0.56Ga0.44as layers
Authors: Gracia M. , Hernández L. , Purón E. , De Roux S. 
Published: January 2007

AbstractWe have studied by photoluminescence measurements the influence of O2 in the broad band in Zn‐doped‐Al0.56Ga0.44As grown by LPE technique. The emission peak energy of the band shifts monotonically with temperature. The dependance of the halfwidth with temperature fits the configuration coordinate model. We suggest a ZnGaO2 complex center is responsible for the band. We have determined the ionization energy of Zn and O2.
Temperature Measurement in a THM Solution Zone for the Growth of Hg1−xCdxTe
Authors: Kiessling F. M. , Gille P. 
Published: January 2007

AbstractA combined process for temperature measurements in THM growth systems is described including the preparation of the source material as well as the liquid solution zone in one and the same ampoule. Using starting compositions with an excess of that component to act as the solvent the solution zone is formed during the travelling heater procedure. With thermocouples attached to the slightly modified ampoule axial temperature distributions were recorded under the usual THM growth conditions. The measurements were done in Hg0.8Cd0.2Te growing from Te‐rich solution zones. The procedure described can be applied to all materials for which THM crystal growth can be achieved.
Observations of crack patterns in NaSbF4 and NaSb2F7 single crystals
Authors: Benet Charles J. , Gnanam F. D. 
Published: January 2007

AbstractCrack pattern studies on NaSbF4 and NaSb2F7 single crystals have been carried out using Leitz Wetzler microhardness tester. Attempts have been made to understand the nature of the cracks developed around the microindentation impression. The fracture toughness, index of brittleness and crack resistance have also been calculated.
Growth Velocities and Disappearance of Faces of Crystals
Authors: Szurgot M. , Prywer J. 
Published: January 2007

AbstractThe formulae for critical absolute and relative growth velocities which govern the disappearance of faces have been derived and discussed. A face can disappear in the habit only if its velocity is greater than the critical one. Both the fast‐ and the slow‐growing faces can disappear. It was shown that BORGSTRÖM's formula describes only a special case of disappearance of faces. Apart from the nearest neighbours also those farther ones influence the size and presence of faces. The calculations have been verified by the experimental results for triclinic potassium bichromate (KBC) crystals.
Crystal Growth of 2‐Cyclooctylamino‐5‐Nitropyridine (COANP) and 2‐(N‐(L)‐Prolinol‐5‐Nitropyridine (PNP) from TMS Gels
Authors: Br̆ezina B. , Hulliger J. 
Published: January 2007

AbstractSingle crystals of 2‐cyclooctylamino‐5‐nitropyridine (COANP) and 2‐(N‐(L)‐prolinol‐5‐nitropyridine (PNP) were grown from tetramethoxysilane gels. Lowering the temperature or seeding of supersaturated water/ethanol gel solutions led to optical quality crystals of several mm in size. In the case of PNP the addition of Nd3+ to the gel solutions decreased the concentration of milky defects. Morphological descriptions for COANP and PNP crystals are given.
On the Synthesis and Characterization of Zeolite ZSM‐20
Authors: Tuan Vu Anh , Fricke R. , Szulzewsky K. , Kosslick H. 
Published: January 2007

AbstractZSM‐20 is a silicon‐rich analog of the faujasite‐structure, the synthesis of which is complicated. Starting from known synthesis recipes its crystallization in the system Na2O · Al2O3 · SiO2 · H2O is investigated in the presence of tetraethylammoniumhydroxyde as templating agent. The aim was to find the critical conditions for its synthesis. The synthesis products obtained are investigated by X‐ray diffraction, thermal analysis and i.r. spectroscopy.
Formation of Concave‐Convex Interface Shape during Oriented Eutectic Growth
Authors: Wołczyński Waldemar 
Published: January 2007

AbstractThe concave‐convex interface shape formation of oriented eutectic has been analysed in microscopic scale. The proposed model has considered some physical phenomenona of eutectic growth, in particular preceding of the wetting phase by the leading one. The mechanism of curvature formation of the leading phase is different from that of the wetting one. The worked out model has been refered to the microscopic observations of the Pb–Cd eutectic interface shape. The sinusoidal approximation to the interface has been used to divide the lead distance into the leading phase protrusion and the wetting phase retraction. The behaviour of the contact angle of the wetting phase as a resultant of different physical factors' interaction during eutectic growth has been underlined.
A study of the Growth‐Temperature‐dependent Surface Morphology in InSb Liquid Phase Epitaxy
Authors: Chang L. B. 
Published: January 2007

AbstractInSb LPE layers were grown on (111) InSb substrates, their phase diagram and growth rates studied. The InSb activity coefficient α(T), determined by fitting the experimental data, had a value of 2556–11.11 · T cal · mole−1. The terraces on the surface were reduced by increasing the temperature to 350 °C. Hall measurements of InSb/CdTe heterostructure failed due to the high Te segregation. The carrier concentration of these InSb epilayers, however, was determined by C‐V measurements with values between 7.5 · 1014 cm−3 and 5 · 1015 cm−3.
The Characteristics of EDTA's Transition Metal Complexes (III) The d‐d Transition Spectrum and Structure Characteristic of [Pb.Ni(HEDTA)H2O] Cl Crystal
Authors: Jianmin Li , Yugeng Zhang 
Published: January 2007

AbstractThe electronic absorption spectrum of crystals of the title compound [Pb.Ni(HEDTA) H2O] Cl was recorded and discussed quantitatively. Using ligand field theory and the radial wave function of bound Ni(II) ion, the d‐d transition energy levels of crystals of [Pb.Ni(HEDTA) H2O] Cl, Ca [Ni(EDTA)] · 4H2O, [Li.Ni(HEDTA) H2O], [NiH2EDTA)H2O] were calculated. The different structure characteristics of EDTA's metal complexes are evidently shown in their d‐d transition spectra.
Evaluation of Grain Surface Area in Heavily Arsenic‐doped Polysilicon
Authors: Kalainathan S. , Dhanasekaran R. , Ramasamy P. 
Published: January 2007

AbstractA kinetic model based on thermodynamical concepts has been investigated to determine the grain size and its surface area in heavily arsenic‐doped polysilicon for various arsenic concentrations, annealing times and annealing temperatures. Computer simulation technique has been used to determine the grain boundary self‐diffusion of silicon atoms. The numerical analysis of our results shows that the grain surface area increases with annealing time and annealing temperature, but decreases with arsenic concentration. Our theoretical predictions have been compared with the available experimental results.
High Frequency Dielectric Relaxation of a Ferroelectric Liquid Crystal
Authors: Kresse H. , Tschierske C. , Joachimi D. , Kremer F. , Vallerien S. 
Published: January 2007

AbstractDielectric relaxation measurements on a optically active thiadiazole derivative in the frequency range from 1 MHz to 1 GHz gave relaxation frequencies between 100 MHz and 1 GHz in the smectic C* phase. This relaxation which is related to molecular reorientation processes around the long molecular axis is connected with a mean activation energy of 57 kJmol−1. A simple model of the energetic behaviour of this reorientation including the production of the spontaneous polarization is discussed.
Copper Incorporation in ZnO during LP‐MOCVD
Authors: Kaufmann Th. , Webert M. , Fuchs G. , Arnol H. 
Published: January 2007

AbstractThe MOCVD of ZnO layers, at a reduced reactor pressure and using DMZ.2THF and tertiary butanol as zinc and oxygen sources, resp., presents a number of advantages compared with the deposition at normal pressure. This also applies to the copper incorporation by means of cyclopentadienyl‐copper(I)‐triethyl phosphine. For the copper concentration in the ZnO layers, which linearly increases with the flow rate of the organocopper compound, values > 1020 cm−3 can be achieved. Even in case of high concentrations, the desired compensating effect of the copper is, for the time being, comparatively little, but increases considerably after a thermal retreatment of the layers. Some chemical‐defect aspects of ZnO will be discussed for the purpose of interpretation.
Characterization of the Microhardness of Ion‐implanted GaP
Authors: Ascheron C. , Neumann H. , Kühn G. 
Published: January 2007

AbstractImplantation induced changes of the microhardness are studied in GaP single crystals which were bombarded with ions in the range of mass numbers M = 1–40. It is observed that point defects and incorporated hydrogen have a stronger hardening effect. The effect of defect complexes is lower, and amorphized layers are softer than crystalline layers.
The Growth of KDP Crystals and its Mechanism by Splicing Misoriented in Aqueous Solution
Authors: Feng Pan , Jinkui Liang , Genbo Su , Youping He , Rong Huang Bing , Yisen Huang , Qinglan Zhao 
Published: January 2007

AbstractThe growing characteristics of splicing misoriented KDP seeds of both bulk and thin pieces were investigated. The chemical etching method was used to determine the prismatic and Z‐plate surfaces of the crystals grown by splicing bulk KDP seeds. The X‐ray Lang topography method was employed to measure original thin platy crystals grown by splicing thin pieces of KDP seeds. From the results it can be concluded that when the misorientation of two seeds on the Z‐axis direction was about 1.5°, the crystal was grown successfully if the secondary capping was controlled properly. In comparison with the growth of splicing “parallel” seeds, the misorientation of both seeds increases such that the secondary capping becomes difficult, the sub‐grain boundary stretches longer, the stress field around the secondary cap enlarges and the crystals grown crack easily.
Preparation, Characterization and Sintering Behaviour of Complex Titanate Powders
Authors: Pfaff G. 
Published: January 2007

AbstractThree methods were used for the preparation of complex barium titanate powders containing Sr, Ca, Mn and La or Pb, Ca and La, respectively: titanyl oxalate route, peroxide route, conventional solid state reaction. The powders are characterized with respect to their analytic and morphologic properties. The isothermal sintering behaviour is studied at 900, 1200, and 1320 °C. Powders prepared by the wet chemical synthesis show an excellent densification with final densities of about 97–98%. Possible sintering mechanisms are discussed.
Studies of Growth Mechanism and Sulfur Incorporation in VPE of GaAs under Nearly Equilibrium Conditions
Authors: Tempelhoff K. , Schmidt P. M. 
Published: January 2007

AbstractDetailed investigations of growth rate of GaAs VPE‐layers and sulfur incorporation during crystal growth have been carried out under nearly equilibrium conditions at low temperatures (680 °C). The present investigation examines the dependence of growth rate and sulfur incorporation on the initial partial pressures (p°) of GaCl and HCl in the deposition zone. The observed deviation from the 1:1 proportion between GaCl before and HCl after the growth reaction will be discussed in a model of chlorine desorption by GaCl3. The sulfur concentration dependence in the grown layer indicates an identic growth mechanism and supports the idea of sulfur incorporation through an activated complex on the GaAs surface.
Growth of Lithium Niobate Single Crystal Fiber by an Edge–defined, Film‐fed Growth Method
Authors: Zhong H. , Hou Y. , Quan N. , Chen X. , Wang R. 
Published: January 2007

AbstractLithium Niobate (LiNbO3) single crystal fiber with 0.5 mm in diameter and 160–170mm long have been grown by an edge‐defined, film‐fed growth (EFG) technique. The morphology and microcracks of the fiber are studied. The mechanism of forming a single domain structure in the as‐grown LiNbO3 crystal fiber is discussed on the basis of the thermoelectric field model.
On the Influence of the Crystallization Conditions on the Microstructure of the Directionally Solidified Eutectic of the LiF – LiYF4 System
Authors: Barta Č. , Fendrych F. , Recker K. , Tříska A. , Wallrafen F. 
Published: January 2007

AbstractThis paper particularly deals with the transitions in degree and type of ordering of a given microstructure. As a model system the eutectic of the LiF – LiYF4 system was used for studies of transitions from ‘anomal’ microtextures with non‐cooperative production of seeds of both phases to the fibrous microtexture.It was shown that even if the matrix phase LiYF4 contains a relative high volume ratio (36%) of LiF it is possible to create highly ordered fibrous microtextures with pronounced hexagonal ordering of particular LiF fibres. It was also shown that methods of image processing could be used for sensitive evaluation of small changes in degree of ordering of the microstructure.These procedures make possible a deeper understanding of the influence of the solidification conditions on the microstructure of the directionally solidified eutectic and creates possibilities for optimalisation of the technological process.
Chemical Bond in AIIBV2 Systems from Magnetic Susceptibility Data
Authors: Vitkina Ts. Z. , Trukhan V. M. 
Published: January 2007

AbstractSome peculiarites of chemical bond in AIIBV2 systems from the data on the magnetic susceptibility of the AIIBV2 compounds and their solid solutions are discussed. With this aim in view the magnetic susceptibility has been divided into the Langevin diamagnetic and van Vleck paramagnetic terms. The diamagnetic susceptibility of valence electrons, affecting the chemical bond in a crystal against the covalency parameter along the A – B, A – A, B –B bonds in AIIBV2 compounds, has been analysed. The covalency parameter of the AIIBV2 compounds has been evaluated.Closeness of the covalency parameter values for monoclinic β‐ZnP2 and tetragonal CdP2, CdAs2, is evidently, one of the reasons for the solid solution formation between the above mentioned compounds.
Criteria for an Alternative Proposal for Crystal Growing by the Flux Method
Authors: Papadopoulos Ilias 
Published: January 2007

AbstractCriteria are described for an alternative proposal for growing single crystals in the melt. Considering the solid state reactions between the components of the solved substances and the melting materials, a new heating process is discussed, taking into account the transformation temperatures of the intermediary products and also their reaction kinetics of formation and dissociation. As the most important parameter for the growth velocity is considered not the solubility of the initial components but the dissociation velocity of the by‐products.At the start of crystallization an oscillating nucleation process is proposed with decreasing temperature amplitude. Hence, the number of critical nuclei in the neighbourhood of the supersaturated melt solution will be kept as small as possible. In this way, an optimal output and quality of a small number of single crystals was achieved.These considerations were incorporated in a temperature program for the growth of single crystals by the flux method and they constitute an alternative to the usual application of this method.
Dielectric Properties of Tin Oxide Thin Film Capacitors
Authors: Kumar J. Siva , Rao U. V. Subba 
Published: January 2007

AbstractThin films of several thicknesses in the form of MIM structures are prepared from the powders of tin oxide (SnO2) by thermal evaporation technique in a vacuum of 10−5 Torr. The dielectric properties of tin oxide film capacitors have been studied with temperatures varying from 77 to 400 K and also with frequency. At 77 K the values of capacitance and loss tangent are small for these films. With increasing temperature the values of capacitance and loss tangent increase. The capacitance‐temperature plots show peak values of capacitance at 345 K for 1 kHz, 350 K for 2 kHz, 360 K for 5 kHz and 368 K for 10 kHz. These peak values of capacitance can be eliminated by repeated heating and cooling of the structures. The activation energy for the migration of charge carriers is calculated for tin oxide films and is found to be 0.13 eV. The results obtained on the dielectric properties of tin oxide thin films are presented and discussed.
The Effect of Microstructure on Thermally Stimulated Luminescence of Y–Ba–Cu–O System
Authors: Reddy Katta Narasimha , Prasad T. S. P. L. N. , Rao U. V. Subba 
Published: January 2007

AbstractThermally stimulated luminescence of Y – Ba – Cu – O (YBCO) samples in as‐prepared, quenched and water treated conditions have been studied. The TSL spectrum is observed to be different for these samples. Quenched and water‐treated samples are expected to decompose into a number of insulating phases. Identification of such phases using thermally stimulated luminescence is attempted.