bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on macrospiral observed in flux‐grown YAG single crystals
Authors: Thirumavalavan M. , Kumar J. , Gnanam F. D. , Ramasamy P. 
Published: January 2007

AbstractPresence of spirals with unit cell dimension step height has been established over a large variety of materials. But often spirals with large step height are also being reported. In this paper such a macrospiral observed over the barium based flux grown YAG crystals is reported. Nature of this depressed spiral and growth conditions are discussed. A possible formation mechanism is suggested for the development of spiral with large step height of giant step, which is termed as macrospiral.
Slope analysis to obtain starting parameters for curve fitting calculations in the special case of the Johnson‐Mehl‐Avrami model function
Authors: Oettel W. , Fabian H.‐G. 
Published: January 2007

AbstractThe attempt was undertaken to describe analytically isothermal resistivity measurement curves of AlZn and AlZnMg alloys by means of the Johnson‐Mehl‐Avrami equation. The paper gives a survey of results obtained based on the application of the Extented Slope Analysis. Comparison was performed to results of fitting calculations (Linear Regression). It can be shown that the intersection behaviour after the Extented Slope Analysis leads to reasonable results if rough evaluation is required in a first stage of an investigation. Furthermore this method leads to reliable starting parameters and starting length of the fitting intervals. Additionally the second process with AlZnMg alloys can be estimated by use of the Extented Slope Analysis.
Kinetic phase diagrams of multicomponent systems
Authors: Chvoj Z. 
Published: January 2007

AbstractIt is derived the method of the calculation of the solidification rate and the concentration of components in the solid phase during the solidification process of the n‐component melt at the given undercooling. The calculations are performed in the framework of the stochastic theory of the kinetic phase diagrams, which were derived in the case of the steady‐state processes. This is the question of the generalization of relations derived for the binary systems.
Influence of mechanical stress on thermal oxidation phenomena of silicon
Authors: Knoll D. , Grabolla T. , Bugiel E. 
Published: January 2007

AbstractSome phenomena of the thermal wet oxidation of polycrystalline silicon structures are discussed in connection with the geometry of this structures and mechanical stress present in the growing oxide layer. A model is presented considering the influence of the stress on the linear and parabolic oxidation rate constants. Basing on this model experimental results concerning the influence of oxidation parameters on the oxidepolysilicon interface structure and on closely related electrical properties can be explained.
The influence of the boundary conditions on the character of the phase transition nematic‐smectic C
Authors: Simova P. , Petrov M. 
Published: January 2007

AbstractThe possibility is investigated for inducing the intermediate smectic A structure in substances with nematic and smectic C phases by the boundary forces. Different geometries are used: homeotropic, homogeneous and tilted under a different angle toward the supporting substrates of the liquid crystal cell. At homeotropic and at tilted orientation where the molecules tilt toward the supporting substrates is different from the molecule tilt in the smectic layer, an intermediate smectic A structure is observed at the transition nematicsmectic C in a narrow temperature interval. In this case the phase transition nematicsmectic C extends and transforms into phase transition of second order. At homogeneous orientation and at tilted orientation of an angle equal to the molecule tilt in the smectic layer, the transition nematic‐smetic C carried out in two stages, as partially it begins on the surface still in the nematic phase and terminates at the temperature of the phase transition N‐Sc. The influence of the boundary forces depends essentially on the energy of the phase transition N‐SC of the substances.
Morphology of SiC epitaxial layers grown by temperature gradient zone melting (II). The dependence of the structural properties of the epitaxial layers on the growth conditions
Authors: Peev N. S. 
Published: January 2007

AbstractIn the present paper the relationships between the structural perfection of the layer, represented by the Tb average integral concentration (which is a criterion for the second phase quantity), the rocking curve half‐width (a criterion for the general structural perfection of the layer) and the layer growth conditions, represented by the quantity, which is the most important characteristic of the growth process, namely the supersaturation are discussed. The considered model allows to conclude, that a optimal value of the supersaturation exists, at which the structural perfection is maximal.
Magnetically induced rhombohedral distortion in the UxTh1−xSe and UxY1−xSe solid solutions
Authors: Palewski T. , Horn J. 
Published: January 2007

AbstractSolid solutions of UxTh1−xSe for x = 1.00 ÷ 0.80 and the solid solutions of UxY1−xSe for x = 1.00 ÷ 0.60 were studied by the X‐ray diffraction over the temperature range 100 ÷ 200 K. In both systems rhombohedral distortions of the cubic rock‐salt crystal structure was observed below the Curie temperatures. The temperature and composition dependences of the rhombohedral angle ω of the rhomboedral cell and the \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{c' - a'}}{{a'}} $\end{document} ratio were determined.
A new technique for measuring thickness of thin solid films
Authors: Desai C. C. 
Published: January 2007

AbstractA new technique has been developed for measuring the thickness parameter for any thin solid films. Various thin films of silver, aluminium and antimony have been prepared by using vacuum evaporation plant at the vacuum of 10−5 torr. The films have been scratched by a fine metal pin. By employing a semi‐silvered cylindrical convex lens, a point contact has been established between a silvered scratch‐film and a cylindrical lens. Multiple beam Fizeau interference fringes have been obtained over the surface of thin films. Across the step of the scratch, because of height difference, the shift in the fringes have been observed. Due to the axis of point contact, no ambiguity in allocation of ringe order has been obtained. The thicknesses of silver, aluminium and antimony thin films have been determined very precisely. The technique gives high resolution with a good degree of reproducibility and implications are discussed.
Infrared lattice vibrations in Cu2GeSe3
Authors: Riede V. , Sharif N. , Neumann H. , Sobotta H. , Omar M. S. , Pamplin B. R. 
Published: January 2007

AbstractInfrared reflectivity spectra of Cu2GeSe3 are measured at room temperature in the wavenumber range from 180 to 4000 cm−1. From an analysis of the spectra the parameters of four vibrational modes are determined. The experimental results are compared with predictions from group theory. From a comparison of the results for Cu2GeSe3 with the vibrational characteristics of other chalcogenides it follows that the force constants of cation‐chalcogen bonds increase with increasing valence of the cation.
Thermal analysis of the microsegregation phenomenon in some alloys from the SbSn system
Authors: Wołczyński Waldemar , Kobylkin Artur N. 
Published: January 2007

AbstractThermal analysis in experimental verification to theoretical prediction of the maximum microsegregation phenomenon in the peritectic alloys solidification has been applied. Satisfactory agreement has been obtained between some results of theoretical calculations and experimental ones. Usibility of the DTA‐5 apparatus (original construction of the Baykov Institute of Metallurgy) to detect quite small amounts of low‐solidifying non‐equilibrium phases has been proved.
Crystallization kinetics of MgSO4 · 7 H2O at higher ranges of the driving force
Authors: König An. , König Ax. , Emons H.‐H. 
Published: January 2007

AbstractBy means of batch crystallization technique the crystallization kinetics of MgSO4 · 7 H2O at 25 °C at higher ranges of the supersaturation from pure aqueous solutions was investigated. It was observed that the growth rate highly depends on the habit of crystals and on their ratio of length to width, respectively. This ratio is a function of the initial supersaturation of each crystal.
Investigation of the acoustic attenuation in lead and tin tellurides obtained by the iodide method
Authors: Assenov R. , Izmailov N. V. , Moshnikov V. A. , Yaroslavtsev N. P. , Yaskov D. A. 
Published: January 2007

AbstractThe products of the reaction for obtaining lead telluride and tin telluride, synthesized by the iodide method, were analyzed by the method of acoustic attenuation (internal friction). The results of the investigations are in agreement with the model, suggested earlier, of self‐alloying of tellurides by metallic component.
Phase transition studies of the liquid crystal 4‐[4‐n‐hexyloxybenzylidene amino] azobenzene thermal microscopy and DSC
Authors: Rao K. R. K. , Rao J. V. , Venkatacharyulu P. , Rao S. V. Chiranjeevi , Baliah V. 
Published: January 2007

AbstractThe phase transition temperatures of the liquid crystal 4‐[4‐n‐hexyloxybenzylideneamino]‐azobenzene have been investigated by the thermal microscopy and the Differential Scanning Calorimetric (DSC) studies. These studies confirm that this mesogen exhibits nematic, smectic A and smectic B phases. The transition enthalpies, transition entropies and also the textures exhibited by the different phases are presented.
Growth mechanism of sodium‐cadmium formate from aqueous solution
Authors: Staroń B. , Kolasiński W. 
Published: January 2007

AbstractThe data on the growth rates of sodium‐cadmium formate crystal faces as a function of supersaturation in the range 0.003 < σ < 0.130 are presented and discussed. It was found that a compound growth mechanism involving volume diffusion controlled dislocation growth and mononuclear two‐dimensional nucleation can explain the data.
Texture growth and screw dislocations in smectic A phases
Authors: Morawietz K. , Demus D. 
Published: January 2007

AbstractThe formation of the textures of smectic A phases was investigated. In planar oriented samples the A phases grow in the shape of rods without defects. The velocity of growth is strongly anisotropic with its maximum normal to the director orientation. In non oriented samples the smectic A texture is growing in batonnets with defect structure to give focal conic textures. The maximum growth velocity of the batonnets is parallel to the director orientation. Since this would contradict to the Wulff theorem we assume a growth mechanism with a screw dislocation.
Investigation of the effect of temperature on the positron annihilation in solid and liquid tin
Authors: Rudzinska W. , Szymanski Cz. , Chabik S. , Rozenfeld B. 
Published: January 2007

AbstractThe temperature dependence of the counting rate, F(T), has been measured in tin. A sudden increase in the counting rate, connected with the creation of vast defects acting as positron traps, has been observed on passing through the melting point. Both the F(T) and angular correlation curves indicate that the defected areas decay with increasing temperature. The kinetics of this effect has been discussed and the vacancy formation energy, being equal to Eν = 0.50 ± 0.02 eV, has been determined.
Defect recovery after 77 K plastic deformation in bismuth
Authors: Lemahieu I. , Dorikens‐Vanpraet L. , Dorikens M. , Segers D. 
Published: January 2007

AbstractDopplerbroadening measurements were performed in 77 K deformed bismuth in the temperature range between 80 K and 410 K. An important trapping effect was observed. Two recovery stages were found, one at 230 K and the other at 380 K. The measurements were compared with the results obtained from positron annihilation lineshape measurements in as‐received polycrystalline bismuth samples of different purities, and in room temperature deformed bismuth samples. In all samples a recovery stage at 380 K was found, which is ascribed to the annealing of dislocations. Lifetime measurements were performed in the as‐received bismuth samples. For dislocations a lifetime of 289 ps was found.
Positron annihilation in thermally treated metallic glasses
Authors: Liolios An. , Dedoussis Sp. , Chardalas M. , Charalambous Ste F. 
Published: January 2007

AbstractThe positron lifetime dependence on the annealing temperature has been studied for two transition metal‐metalloid glasses (FeNi‐based and Co‐based). Small variations of the lifetime observed after annealing below crystallization temperature are attributed to elimination of the structural defects inherent in the as‐quenched metallic glasses. More abrupt changes at higher temperatures are ascribed to crystallization processes which lead to polycrystalline phases. Differences in positron lifetime between annealed FeNi‐based and Co‐based metallic glasses are discussed.
Positron annihilation in Co alloys containing FCC and HCP phases
Authors: Tshernyashevskii A. V. , Mikhalenkov V. S. 
Published: January 2007

AbstractPositron annihilation is studied in CoCu and CoMn alloys subjected to the heat treatments which result in the structural states with various lattices, phase contents and defects concentrations. The positrons are shown to be insensitive to the hcp layers in fcc lattice which form the stacking faults. Multiple transitions through the interval of martensitic transformation initiate the formation of defects of the higher concentration the larger of the volume effect of transformation.
Study of the reversible martensitic transformation in CuZnAl alloy by positron annihilation
Authors: Panek T. J. , Plotkowski K. 
Published: January 2007

AbstractThe positron lifetime measurement to investigate phase transformations: martensitic phase (MP) ⇔︁ parent phase (PP) in CuZnAl alloy has been used. We have observed the generation of new defects by MP → PP transformation; these defects are liquidated by martensitic transformation. This effect is only observed in case of high concentration vacancies in alloy. In order to explain the nature of these defects we take into consideration the supervacancies idea.
Observation of precipitates in a supersaturated FeCo alloy by muon spin rotation spectroscopy: a step towards understanding embrittlement of reactor pressure vessel steels
Authors: Solt G. , Waeber W. B. , Schenck A. , Gygax F. N. , Barth S. , Frisius F. 
Published: January 2007

AbstractThe technique of μ+SR spectroscopy was applied to detect precipitate formation due to ageing in the binary Fe‐0.8 wt% Cu alloy. As compared to the homogenized specimen, the aged sample gives a μ+SR signal with considerably larger relaxation rate in the temperature interval 180 K <T< 350 K, having a maximum nearT= 250 K with Λ = 14 μs−1.Since precipitation of copper plays possibly an important role in the embrittlement of neutron irradiated ferritic steels, the signal from an irradiated steel specimen has also been investigated.
On the deposition mechanism of boron in silicon CVD epitaxy
Authors: Kühne H. , Malze W. 
Published: January 2007

AbstractThe deposition mechanism of boron doping in CVD silicon epitaxy has been investigated by exposing silicon substrates to B2H6H2 doping gas mixtures at epitaxy temperatures and examining the effect by dopant profile measuring in an afterwards intrinsically in‐situ deposited epitaxial silicon layer. It has been shown that boron is deposited increasing its concentration on the surface linearly with prolonged exposition time and desorbed by purging the surface in pure hydrogen. In the latter case its content decreases linearly proportional to the predeposited concentration. The desorbed boron builds up a secondary doping source which maintains a parasitic boron flow for reincorporation during following layer growth.
Study of radiation damage on proton‐bombarded GaP by PIXE
Authors: Ascheron C. , Flagmeyer R. , Otto G. , Vogt J. , Frey H. U. 
Published: January 2007

AbstractOn GaP single crystals bombarded with 0.3 MeV and 1.0 MeV protons the fluence and depth dependences of radiation damage are studied by means of particle induced X‐ray emission spectrometry under chaneling conditions (PIXE‐C) and the Rutherford backscattering/channeling technique (RBS‐C). It is demonstrated that PIXE‐C is suitable to study depth profiles of damage density by the combination with the bevelling technique.
A research into positron annihilation of the B2F steel rolled out in step‐s with constant stretch
Authors: Liu‐Juan Zou , Cai‐Guo Zhang , Gui‐Lan Wang , Ming‐Zhong Wang 
Published: January 2007

AbstractThe rolling out of step‐s with constant stretch (PV‐E) is a new technology developed for rolling steel in recent years. We studied the B2F steel rolled by the new technology with the aid of the positron annihilation technique. The relationships of the average lifetime of positron annihilation with the rolling pressures, the ratio of rolling speed and the mechanical properties are obtained. The value of the lifetime shows that there are many dislocations and vacancy clusters in B2F steel after being rolled, and which are supported by observations with a transmission electronmicroscope.
Positron annihilation study of defects in martensite transformation of FeMn alloy
Authors: Yang Qian , Ruzhang Ma , Yongshu He , Maorong Huang , Shoudan Liu 
Published: January 2007

AbstractIt has been observed that a small number of repetitions of the transformation by thermal cycling enhanced the formation of ϵ‐Martensite whereas a large number of repetitions of transformation decreased the amount of ϵ‐Martensite formed. PAT analysis and electron microscope show that a few repetitions of the transformation produced less defects, including vacancies and dislocations, whereas a large number of repetitions of transformation produced progressively more defects. The PAT analysis also shows that these accumulated defetcs are mainly dislocations, which form a network of dislocations or a Lomer‐Cottrell dislocation net. A small number of dislocations enhanced the nucleation of ϵ‐Martensite whereas a large number of dislocations prevented the nucleation. So the dislocations‐produced by cycling transformation thermally — has a great effect on the ϵ‐formation.
An investigation on the disordered AlNiCo8 magnetic steel containing the higher Co and higher Ti by means of the positron annihilation
Authors: Juan Zou Liu , Guang‐Qu Zhu , Yuan‐Quo Chen , Cai‐Guo Zhang 
Published: January 2007

AbstractIn this paper, we investigate the coercive force and magnetic properties of the disordered AlNiCo8 magnetic steel containing the higher Co and higher Ti by means of the positron annihilation spectroscopy. We found that the positron annihilation lifetime τ2 is closely related to the manufacturing technique and disorientation of this steel, and which directly affect the coercive force and magnetic behavior of the material. It is also found that the microscopic constructional characteristics in the present sample are finer than the ones of the same kind sample of U.S.A. according to an analysis of the positron average life τ.
Positron lifetime study of helium clustering in Ni and Ni‐1 at.% Ti
Authors: Amarendra G. , Viswanathan B. , Gopinathan K. P. 
Published: January 2007

AbstractHelium clustering and bubble growth have been studied in Ni and Ni‐1 at % Ti through positron lifetime measurements. Helium pressure in the bubble as well as bubble concentration have been estimated and compared for the cases of Ni and Ni‐1 at % Ti. The results seem to indicate enhanced helium trapping due to substitutional Ti impurity in the host Ni.
X‐ray, optical and electrical study of melt‐grown CdI2 single crystals
Authors: Nigli Selina , Jagadish C. , Chadha G. K. 
Published: January 2007

AbstractCdI2 has been purified using the zone‐refining technique by giving 20 passes. Single crystals grown from the starting material showed arcing in the X‐ray oscillation photographs whereas it is absent in the crystals grown from the zone refined material. These crystals are found to be of the 4 H type. DC conductivity studies were made on these crystals at various stages of purification. The surface morphology of these crystals have been studied using an optical microscope.
Solid‐state reactivity and mechanisms in oxide systems (IV) on the sintering behaviour of haematite
Authors: Pfaff G. , Feltz A. , Umpfenbach U. 
Published: January 2007

AbstractThe present contribution reports about the sintering behaviour of three α‐Fe2O3 powders which were synthesized in various ways. The different results of the sintering experiments are the consequence of granulometric properties of the samples and of their content of impurities. Possible sintering mechanisms are discussed.
Nonstoichiometry and point defects in PbTe
Authors: Schenk M. , Berger H. , Klimakow A. , Mühlberg M. , Wienecke M. 
Published: January 2007

AbstractThe nostoichiometry and point‐defect structure of PbTe was investigated by various methods including carrier‐concentration, lattice‐constant, positron‐annihilation and vapour‐density measurements. The results are discussed in comparison with data published by other authors. New aspects are obtained especially from high‐temperature experiments. A model of nonstoichiometry and defect structure in PbTe is proposed. The stability region of PbTe is essentially broader than reported until now. The disorder takes place mainly in the Pb sublattice, i.e., there occur charged Pb vacancies (Te‐rich) and Pb interstitials (Pb‐rich), respectively, as well as probably additional neutral Pb interstitials in Pb‐rich PbTe.
Simulation of the carrier diffusion process for the interpretation of EBIC profiles
Authors: Werner U. , Heydenreich J. 
Published: January 2007

AbstractBased on a Monte Carlo calculation procedure a phenomenological description is developed of the diffusion process of excess minority charge carriers inside a semiconducting target. Using this description and an analytic expression of the generation volume of electron‐hole pairs in Si the electron beam induced current (EBIC) obtained by applying a scanning electron microscope can be simulated under consideration of relatively complicated structures of junction semiconductor devices. This allows a better interpretation of EBIC profiles as to the information about the geometric structure of space charge regions built up in junction semiconductor devices. As an example of such an interpretation the verification of the method of Chi and Gatos is presented.
X‐ray determination of solid solution composition in the melilite system åkermanite (Ak) — gehlenite (Ge) — soda melilite (Sm)
Authors: Schmitz W. , Schreiter P. 
Published: January 2007

AbstractExpressions are given and discussed which allow a determination of the composition of solid solutions in the ternary system AkGeSm. Resulting from X‐ray measurements of the tetragonal melilite constants a0 and c0, the composition can be calculated within the limits of ±3% if the lattice constants are determined with an accuracy of ±0.001 Å.