bluuebunny/crossref_metadata_2025_split huggingface dataset:
Periodic precipitation of barium molybdate in silica gel
Authors: Kurien K. V. , Vaidyan V. K. , Ittyachen M. A. 
Published: January 2007

AbstractThe mechanism of formation of the rhythmic pattern of precipitate of barium molybdate in one‐dimensional Liesegang phenomena is investigated quantitatively. They rhythmicity is found to be influenced by the molarity of inner and outer electrolytes and pH of the gel medium. The ‘time‐law’, ‘spacing‐law’ and ‘Δx‐law’ are verified.
(110) Twins of n‐C28H58 crystals: Habit changes and lattice net studies
Authors: Prasad P. B. V. , Raju I. V. K. Bhagavan 
Published: January 2007

AbstractThe (110) twins of normal octacosane crystals with hexagonal shape are observed. Various factors that may lead to a shape change are considered. Effect of growth rate anisotropy on the reentrent faces is studied with the help of growth patterns which are derived from a lattice net.
Phase transformation in a linear polycrystal with a rate law of n‐th order
Authors: Schulze G. E. W. 
Published: January 2007

AbstractA phase transformation in a one component polycrystal starts to grow instantaneously and with a constant rate from the grain boundaries. After the time t there exist regions of the old and of the new phase. The derivation of the statistical quantities characterizing this state at t is unknown yet. Therefore we reduce this complicate three‐dimensional problem to a one‐dimensional model analogously to the linear chain in lattice dynamics or to the one‐dimensional energy band model. A closed analytical treatment of this model is practicable. It is derived in detail for those one‐dimensional systems, which transform according to a rate law of n‐th order (n ≧ 0).
The crystal structure of dodecyltrimethylammoniumbromide
Authors: Szulzewsky K. , Schulz B. , Vollhardt D. 
Published: January 2007

AbstractC15H34BrN, monoclinic, P 21/m,a= 21.603(9),b= 7.261(3),c= 5.636(2) Å, β = 86.85(2)°,Z= 2,V= 882.72 Å3,Dx= 1.160 g/cm3, μ(MoKα) = 2.45 cm−1, λ(MoKα) = 0.71069 Å. The structure of this cationic surfactant was solved with Patterson methods and refined toR= 0.091 for 2057 measured reflections. The dodecyl chains are slightly screwed around their chain axes. The hydrocarbon chains are statistically disordered. The polar regions satisfy the mirror plane which is by remaining parts only statistically fulfilled. In the process of structure refinement statistical disorder has been included by separation of some atom positions. The sublattice of the hydrocarbon chains is nearly O⟂ withas= 5.14,bs= 7.26,cs= 2.52 Å.
Influence of film structure on the electron energy loss spectra of GaAs thin films
Authors: Boudriot H. , Kubier B. , Deus K. , Gründler R. , Kusior E. 
Published: January 2007

AbstractEnergy loss measurements of fast electrons on GaAs yielded values for the plasma oscillation, interband transitions and the dielectric function in the region 5 — 30 ev. The results are discussed in comparison with literature statements. It is dealt especially with the influence of the degree of crystallinity of examined GaAs‐films on the energy loss spectrum and the quantities derived from it.
Study of the complex vibrational spectra of natural mesolite
Authors: Pechar F. 
Published: January 2007

AbstractThe vibrational spectra of the natural zeolite, mesolite (locality Akureyri‐Island) were measured in the infrared (200—400 cm−1) and the far infrared — FIR (40—400 cm−1) regions: the infrared reflectance (200—1400 cm−1) and Raman scattering (50—3600 cm−1) spectra of the polycrystalline material were also measured.The Schimanouchi GCCC, BGLZ, and LSMA programs were used to calculate the force constants and vibrational frequencies of the SiO, AlO, OH, cation‐oxygen, OSiO, OAlO, HOH bonds and libration of H2O and Si(Al)OSi on the basis of the symmetry coordinates. The KKK‐1 program (Petzelt, Kroupa) was used to calculate the dispersion curves of the complex refractive index for both parts of the complex dielectric permittivity in the whole measured wavenumber region. The bands in the spectra were assigned to the vibrations of the individual bonds and structural groups of the mesolite on the basis of theoretical calculations.
New liquid crystalline tetrazine derivatives for guest‐host displays
Authors: Isenberg A. , Krücke B. , Pelzl G. , Zaschke H. , Demus D. 
Published: January 2007

AbstractA number of new liquid crystalline tetrazine derivatives was synthesized. The electro‐optical studies showed that the 3‐n‐alkyl‐6‐[4‐(4‐n‐alkyl‐cyclohexanoyloxy)phenyl]‐1,2,4,5‐tetrazines are excellent dyes for guest‐host displays with positive colour contrast.
The molecular and crystal structure of 2‐oxo‐1‐pyrrolidine‐acetamide
Authors: Pritzkow W. 
Published: January 2007

AbstractC6H10N2O2, P1, a = 6,607(2) Å, b = 8,538(2) Å, c = 6,392(2) Å, α = 102,43(2)°, β = 91,11(2)°, y = 79,82(2)°, V = 349,1 Å3, Z = 2, Dm = 1,36 g × cm−3, Dx = 1,35 g × × cm−3, MoKα radiation, λ = 1.71069 Å, μ(MoKα) = 1.11 cm−1. The structure was solved by direct methods. The parameters were refined by full matrix least squares technique to a final R = 0.088 for 834 reflections with ∥F0∥ > 4σ(F0). The dihedral angle between the least‐squares plane through the pyrrolidine ring and that through the acetamide group is 90.4°. The NH … O hydrogen bonds connect molecules to form bands parallel to the z axis.
A topological approach to studies of ordered structures of absorbed gases in host lattices (I). The structure of γ‐PdD0.5
Authors: Fritsche H.‐G. , Bonchev D. , Mekenyan O. 
Published: January 2007

AbstractA graph‐theoretical method is proposed which describes the deformation caused in the host lattice by absorbed gas atoms, as well as their ordering. The method predicts correctly the ordered γ‐phase of PdD0,5.
Gas bubble associated mass transport in Bridgman‐Stockbarger melt growth system
Authors: Petrosyan A. G. 
Published: January 2007

AbstractExperimental evidence has been obtained showing that gas bubbles may be responsible for melt stirring in Bridgman‐Stockbarger growth system which results in Pfann type impurity distribution profiles along the crystal length. The hypothesis of the gas bubble associated mass transfer mechanism is supported by the production of Y3Al5O12–Nd3+ single crystals under conditions which eliminate or limit gas bubble nucleation in the melts with Nd3+ distribution profiles similar to those generally observed in melt growth systems where the mass transport in the melts is limited to diffusion.
Needle‐shaped and platelet growth of borax crystals
Authors: Takoo R. K. , Joshi M. S. , Patel B. R. 
Published: January 2007

AbstractNeedle‐shaphed and platelet growth of borax crystals from solutions is reported. Results of microtopographical studies on both the varieties are discussed. It is suggested that a slow rate of evaporation favours needle growth and a faster rate is conducive to the growth of platelets.
The precipitation of calcium hydroxoaluminate hydrate powders from sodium hydroxoaluminate solutions: Precipitate phases and precipitation mechanisms
Authors: Packter A. , Derry A. 
Published: January 2007

AbstractCalcium hydroxoaluminate hydrates were precipitated from different sodium hydroxoaluminate and hydroxoaluminate‐excess hydroxide solutions at ambient temperature (at CAl = 0.1 to 0.3 M and at XS OH/Al = 0 to above 8). The precipitations were monitored by potentiometric (pH) measurements. Precipitate morphologies were examined by optical microscopy and precipitate compositions were determine by chemical analysis, infra‐red spectrophotometry and thermal analysis.Generally at OH/Al ratios of 4 to 4.5 (XS OH/Al = 1 to 1.5), the compound 2 CaO · · Al2O3 · 8 H2O (C2AH8) was precipitated with some aluminium hydroxide; then at OH/Al ratios of 5 to above 11 (XS OH/Al = 2 to above 8), the compound 2 CaO · Al2O3 · 8 H2O was precipitated with increasing amounts of the compound 4 CaO · Al2O3 · 13 H2O (C4AH13).
A thermoluminescence study of Z2‐centres in terbium‐doped NaCl crystals
Authors: Reddy K. Narasimha , Ahmed Md. Iqbal , Pandaraiah N. , Rao U. V. Subba , Babu V. Hari 
Published: January 2007

AbstractThermoluminescence (TL), optical absorption are used to correlate thermal annealing of Z2‐centres with TL peak occurring around 110 °C in Terbium doped NaCl crystals. The TL glow peak occurring around 190 °C it attributed to the thermal annealing of F‐centres. The thermal activation parameters are calculated for both Z2‐ and F‐centre peaks.
Deformation and microhardness studies on KClO4 single crystals
Authors: Bhatt V. P. , Patel R. M. , Desai C. F. 
Published: January 2007

AbstractThe deformation characteristics of KClO4 single crystals have been studied by the methods of static and dynamic indentation on (001) plane. The cracks produced by the dynamic indentation have been interpreted in terms of slip‐twin interactions. Also, the load dependence of Vickers microhardness and its anisotropy in this crystal are reported. The observed hardness anisotropy has been used to confirm the indices of the slip system 〈101〉 〈111〉 operative in this crystal at ordinary temperatures.
The relaxation behaviour of strenght and fracture toughness of amorphous metal‐metalloid alloys
Authors: Wetzig K. , Pompe W. , Fiedler H. , Aljochin V. P. 
Published: January 2007

AbstractThe effect of an annealing treatment on crack and fracture kinetics and on mechanical properties of Fe40Ni40P10B6 and Fe5Co70Si15B10 amorphous ribbons — both pure and with defined impurities — was investigated by in‐situ tensile experiments in SEM. The effect of relaxation processes on tensile strength, microhardness and fracture toughness was analysed. A result of technological interest is the increase of fracture toughness after an annealing treatment in the temperature range Tann. = (0.55 … 0.6) · Tcryst.. This effect will be enhanced by defined chemical impurities, and it can be well interpreted by a model of fracture toughness variation during a temper process. In this model the deformation behaviour cannot be described within the scope of a homogeneous solid, but it is determined by a relationship between closely localized deformation instabilities.
Structure of the grain boundary region in an Al–15 at.% Zn and Al–2.0 at.% Zn–1.3 at.% Mg alloy aged at elevated temperatures
Authors: Syneček V. , Simmerska M. , Bartuška P. , Löffler H. , Gerlach R. 
Published: January 2007

AbstractThe results of TEM investigations are presented of the effects of various solutions and ageing treatments, cooling and quenching rates as well as of tensile stress at elevated temperatures on the microstructure of the grain boundary (GB) region of the examined AlZn and AlZnMg alloys.A pronounced influence was found of partial coherency of GB stable β(Zn) precipitates with the α matrix in the AlZn alloy on the asymmetry of Zn depleted GB region and on the shape of GB precipitates. The role of GB's as sources and sinks of vacancies and the effect of stress gradients in GB regions were emphasized in the establishment of differences in the nucleation and decomposition characteristics within the GB region as compared to those within the grain interior. The existence of a negative stress gradient towards the GB has been suggested to lead to the observed gradual retardation of transformation kinetics within the GB region in AlZn alloys. A rapid quench from annealing to ageing temperature introduced large local stresses close to GB giving rise to “band of precipitates” on subsequent ageing within the former precipitate free region (PFZ) in AlZnMg alloy. Similar enhancement of local stresses accompanied by acceleration of decomposition kinetics was also observed in the aged AlZn sample subjected to a prior tensile creep exposure within the one‐phase region.
The use of an electrode potential in the investigation of a single‐crystal semiconductor matrix (I). On the nature of structural sensitivity of an electrode potential
Authors: Gulidov D. N. , Aidelman B. L. , Kwyatt N. A. , Chistyakov Yu. D. , Sverdlin E. A. 
Published: January 2007

AbstractThe fields of application of electrode potential measurement technique for the evaluation of structural perfection of single‐crystal semiconductor matrix are considered. The dependence of the silicon stationary potential on the value of elastic stresses in etching electrolytes is investigated. The structural sensitivity of the technique is confirmed by the investigation of planar anisotropy of mechanical damages due to the treatment of silicon wafers with (111) orientation and by the investigation of distribution of thermal elastic stresses in silicon — silicon dioxide interface.
Heteroepitaxy of ferrite‐spinel layers by CVD method
Authors: Aleksandrov L. N. , Mitlina L. A. , Molchanov V. V. , Vasilyev A. L. 
Published: January 2007

AbstractThe nucleation mechanism, the substructure, the inner stresses, and the formation of different dislocation structures were studied in the epitaxial ferrospinel layers. Monocrystalline layers of Mg‐Mn‐, Min‐ and Li‐ferrites were grown by the CVD method in a small gap on MgO substrates. The initial growth stage begins with the formation of three‐dimensional nuclei, but after their coalescence the mechanism of layer‐to‐layer growth is realized. X‐ray topographical study shows that the layer structure up to 6 μm thick was formed by slip steps but above 10 μm by cleavage steps. The residual elastic compressive stresses studied by X‐ray tensometry are about 6 × 108 N/m2. The development of dislocation structure of layers depending on their thickness and growth conditions was studied by means of optical and scanning electron microscopy: for synthesis temperatures up to 1200 K only the dislocation sliping was observed, above 1370 K their overcreeping occurred.
About the average bond ionicity in AIBIIIC compounds
Authors: Neumann H. 
Published: January 2007

AbstractAverage ionicities of the AIBIIIC2VI compounds are derived from the long‐wavelength electronic susceptibility and from the antisymmetric gap and the total width of the valence band. It is found that the ionicities determined in this manner are slightly larger than the arithmetic and geometric means of the individual bond ionicities are always below the critical ionicity value for the transition from tetrahedral to octrahedral coordination which explains the stability of the chalcopyrite structure in these compounds.
Growth of ammonium hydrogen tartrate single crystals in silica hydrogel
Authors: Desai C. C. , Hanchinal A. N. 
Published: January 2007

AbstractAmmonium Hydrogen Tartrate (AHT) single crystals have been grown for the first time in silica hydrogel. The controlled reaction between tartaric acid and ammonium chloride solutions by diffusion process in gel medium has been employed. The colourless transparent AHT crystals upto 22 × 4 × 2 mm3 in size have been grown at room temperature. A brief description of the material preparation, growth procedure and crystal nucleation, have been given. X‐ray analysis showed that the AHT crystals belong to monoclinic crystal system. The average density of crystals measured pyknometrically and found to be 1.636 g cm−3. The effect of concentration of reactants on the growth and morphology of these crystals has been studied. The observations of the microstructures on the faces of these crystals revealed that they have been grown by layer mechanism. Chemical etching has been used to show the perfection of the crystals and implications are discussed.
Mathematical model of particle size distribution of crystals taking into account the growth dispersion
Authors: Baumann K.‐H. 
Published: January 2007

AbstractThis paper presents a mathematical model to describe the effect which the growth dispersion has on the particle‐size distribution of crystals which are formed in a crystallizer with an ideally mixed suspension and ideal product discharge (MSMPR crystallizer). This model starts from a number density distribution of crystals, which shows dependence on the process duration, the rate of crystal growth and the crystal size. The model differs from the diffusion model. The distribution data calculated are in agreement with distribution data measured and published by a number of other authors. The influence of the two parametersbandrLHon the mathematically determined frequency distributions is being studied.
The coprecipitation of magnesium nickel hydroxide solid solutions from aqueous solution: Precipitate compositions and precipitation mechanisms
Authors: Packter A. , Uppaladinni S. C. 
Published: January 2007

AbstractMagnesium nickel hydroxides (solid solutions) were coprecipitated from different mixed metal cation solutions (overall concentration 0.1 M) and from hydroxide solution (0.1 M). The course of different coprecipitations was monitored by potentiometric (pH) titrations. Final Coprecipitate compositions were determined by chemical analysis, infra‐red spectrophotometry and thermal analysis. The ionic equilibria involved in different coprecipitations and the precipitation mechanisms are discussed.
Contribution of Z1‐centers in radiation hardening of NaCl: Sm2+ crystals — a study
Authors: Narasimha Reddy K. , Iqbal Ahmed Md. , Subba Rao U. V. , Hari Babu V. 
Published: January 2007

AbstractMicrohardness studies on X‐irradiated NaCl and NaCl:Sm crystals are studied with varying times of X‐irradiation in pre‐quenched and quenched crystals. The contribution of Z1‐centers in radiation hardening studies is discussed.
The role of impurity dispersion and hardness anisotropy studies in NaCl:Sm crystals
Authors: Narasimha Reddy K. , Subba Rao U. V. , Hari Babu V. 
Published: January 2007

AbstractThe effect of the distributed impurities and their state of dispersion on hardness of crystal is studied from microhardness measurements on NaCl crystals doped with different concentrations of samarium both in as‐grown state as well as after quenching them from various elevated temperatures. It is found that the small additions of impurity decrease the hardness. This has been explained on the basis of formation and dissolution of precipitates
Ionic conductivity of BaFBr
Authors: Somaiah K. , Hari Babu V. 
Published: January 2007

AbstractThe ionic conductivity of flux grown BaFBr crystals is reported. Measurements were made parallel to the crystallographic C‐axis in the temperature range 300 to 800 K. The ionic conductivity of the BaFBr pellet is found to be more than that of a single crystal. A tentative identification of low and high temperature conduction has been made as extrinsic association and extrinsic dissociation state of defect in the crystal while in pellet extrinsic dissociation and intrinsic regions. The probable mechanism for the conduction process has been discussed on the basis of structural considerations of the unit cell.
Linear growth of two‐phase regions during unmixing of NaCl‐KCl crystals
Authors: Andreev G. A. , Buritskova L. G. 
Published: January 2007

AbstractMicroscopic and flotation density investigations have been performed of unmixing in equimolar single crystals of NaCl‐KCl at elevated temperatures. The surface nucleation is found to be characteristic of the decomposition process. The two‐phase regions formed at the surface grow inward at a constant linear rate. The activation energy for the movement of the decomposition front is 0.9 eV at 180 to 260°C. The decomposition is anisotropic, <111> being the fastest unmixing direction. The decomposition zones nucleated on air bubbles inside the crystal tend to acquire a cube‐like form.
A study of complex glow curves of Quenched NaCl:Ca crystals
Authors: Narasimha Reddy K. , Nageshwer Rao C. , Lakshmipathi Rao M. 
Published: January 2007

AbstractGlow curves of the thermally pretreated NaCl:Ca crystals are recorded and are found to be complex in nature. The complex glow curve is analysed using thermal cleaning technique and the trap parameters are calculated by various methods. The glow peaks have been tentatively attributed to impurity and various types of colour centers.
Crystal and molecular structure of p‐Toluquinone‐monoguanylhydrazone, C8H10N4O
Authors: Reck G. , Kretschmer R.‐G. , Schulze W. 
Published: January 2007

AbstractThe crystal structure of p‐toluquinone‐monoguanylhydrazone is orthorhombic, space group Pna21 with 4 formula units C8H10N4O in the unit cell. The lattice constants are a = 7.589, b = 20.117, and c = 5.699 Å. The structure was refined to the conventional R = 0.05. The configuration and conformation of the molecule as well as the unusual hydrogen bridge system are discussed.
Electron microscope studies of phase transformations in thin films of Tin Diselenide
Authors: Fernandez‐Samuel A. M. , Saxena U. , Srivastava O. N. 
Published: January 2007

AbstractThe present investigations explore the structural characteristics of the thin films of tin diselenide (SnSe2). Unlike bulk, only sparse studies are available on the structural characteristics in the thin form. SnSe2 is known to exhibit almost exclusively the 2H CdI2 type structure in bulk (single crystal) form. Particular emphasis on phase formation and structural transformations obtained in the thin film form has been given. The results reveal that all as‐deposited films are amorphous in nature and undergo an amorphous → crystalline transformation upon pulse annealing (∼200 °C), the crystalline phase exhibiting the 2H bulk structure. Further pulse annealing at higher temperatures (∼300 to 500 °C) results in thermal decomposition of this 2H phase, giving rise to several other phases, namely SnSe (orthorhombic), SnSe (cubic) and Sn2Se3 (tetragonal) phases, the SnSe phases exhibiting variations in lattice parameters. In addition, a new incommensurate phase of SnSe has been obtained. A model is proposed for the formation of this phase from the orthorhombie SnSe phase. The final product of decomposition is found to be tetragonal tin.
Structural defects and their genesis in corundum monocrystals
Authors: Dobrovinskaya E. R. , Litvinov L. A. , Pishchik V. V. 
Published: January 2007

AbstractBesides the formation of dislocations and block boundaries behind the crystallization front, there is much experimental evidence indicating the presence of rather big aggregates in various crystal‐forming media. Experimental facts are given proving them to exist in Al2O3 melt. The perfection of a grown crystal depends on aggregation degree of the melt which can be controlled by both impurity cncentration and supercooling of the melt. E.g. in Verneuil‐grown crystals a change in Cr concentration from 1 ṁ 10=3 to 1% leads to a change in aggregate sizes from 100 to 1000 Å. With Stepanov‐, Czochralski‐, and horizontally directed crystallization methods a variation in supercooling the melt enables to change the size of the aggregates from 150 to 400 Å. High values of the diffusion coefficient are accounted for by a higher concentration of the holes. The main reason increasing the number of holes in the crystals grown by the mentioned methods is the presence of the boundaries between incoherently accreted aggregates.
Influence of lateral branches on the properties of liquid‐crystalline 1,4‐Bis‐[4‐n‐hexylbenzoyloxy]‐2‐subst.‐benzenes (I).: measurement of density, viscosity and optical anisotropy
Authors: Hauser A. , Rettig R. , Selbmann Ch. , Weissflog W. , Wulf J. , Demus D. 
Published: January 2007

Abstract8 compounds of the substance class of the 1,4‐bis‐[4‐n‐hexylbenzoyloxy]‐2‐subset.‐benzenesmagnified imageand additionally 1,4‐bis‐[4‐n‐hexyleyclohexanoyloxy]‐2‐ethylbenzene were sythesized and density, viscosity and optical refractive indices were measured in the nematic and isotropic state. The lateral branching causes decrease of the melting and clearing temperatures, diminishing of the optical anisotropy and order parameter, but increase of the viscosity.