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1.
Anh‐Tuan Nguyen Jeong‐Ki Kang Guang Jin Choi Woo‐Sik Kim 《Crystal Research and Technology》2011,46(1):53-60
The phase transformation of Guanosine 5′‐Monophousphate (GMP) in drowning‐out crystallization using a batch system was experimentally monitored and mathematically modeled. The solid (amorphous and crystalline GMP hydrate) and liquid phases of the GMP products were simultaneously monitored using a video microscope, FT‐IR, and UV/Vis spectroscopy during the phase transformation. For the modeling, the phase transformation was assumed to occur via the simultaneous dissolution of amorphous GMP and growth of crystalline GMP hydrate in the solution. Based on a comparison of the experimental results and model predictions, both the dissolution and growth of the GMP solids were found to contribute competitively to the phase transformation. When varying the crystallization conditions, in this case the agitation speed and feed concentration, the phase transformation was significantly promoted when increasing the agitation speed, yet independent of the feed concentration. The simple mathematical model used for the GMP phase transformation was quite successful in describing the experimental results. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
2.
I.V. Bodnar A. Eifler Th. Doering W. Schmitz K. Bente V.F. Gremenok I.A. Victorov V. Riede 《Crystal Research and Technology》2000,35(10):1135-1140
The crystal structure as well as the optical properties in the band gap region of (CuInTe2)1‐x(2 ZnTe)x solid solution single crystals grown by directional freezing have been studied. The lattice constants exhibit a linear dependence on crystal composition. The chalcopyrite‐sphalerite phase transition was observed between x = 0.3 and x = 0.4°. The variation of the band gap with respect to crystal composition can be described by a quadratic expression. 相似文献
3.
I. V. Bodnar V. F. Gremenok W. Schmitz K. Bente Th. Doering 《Crystal Research and Technology》2004,39(4):301-307
The (CuInSe2)x(2ZnSe)1‐x and (CuInTe2)x(2ZnTe)1‐x solid solution crystals prepared by Bridgman method and chemical vapor transport have been studied. The nature of the crystalline phases, the local structure homogeneity and composition of these materials have been investigated by X‐ray diffraction (XRD) and Electron Probe Microanalysis (EPMA) methods. The analysis revealed the presence of chalcopyrite‐sphalerite phase transition between 0.6 ≤ X ≤ 0.7. Lattice constants, value of σ position parameter and bond length between atoms were also calculated. It was found that the lattice parameters exhibit a linear dependence versus composition. The transmission spectra of solid solution crystals in the region of the main absorption edge were studied. It was established that the optical band gap of these materials changes non‐linearly with the X composition. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
P. M. Reshmi A. G. Kunjomana K. A. Chandrasekharan 《Crystal Research and Technology》2011,46(2):153-158
Different morphologies of indium telluride (In2Te3) including novel spherulites were crystallized using the physical vapour deposition (PVD) method, by varying the difference in the growth and source zone temperature (ΔT) of a dual zone horizontal furnace assembled indigenously. Whiskers and kinked needles of In2Te3were grown at ΔT = 250 K and 300 K respectively, maintaining the growth zone at 500 °C. At high supersaturation (Δ T = 400 K), spherulitic crystals were obtained. The stoichiometric composition of these crystals has been confirmed using energy dispersive analysis by x‐rays (EDAX). The structure of β‐In2Te3 spherulitic crystals is identified as zinc blende with lattice parameter a = 6.159 Å, from x‐ray diffraction (XRD) studies. The scanning electron microscope (SEM) images revealed the radial structure of the grown spherulites. The growth mechanism for the spherulitic crystallization of β‐In2Te3 crystals has been discussed based on the theoretical models. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
Several nickel phosphate molecular sieves were synthesized by conventional heating (CH) and microwave assisted hydrothermal (MAH). Nickel phosphate VSB‐5 (Versailles Santa Barbara‐5) was synthesized with conventional oven for 72 h or with microwave for 1 h and followed by conventional oven for 48 h in the presence of (2‐hydroxyethyl) trimethylammonium hydroxide as template. The phase transformation is observed by variation of CH time for the synthesis of nickel phosphate molecular sieves. At CH time of 24 h, the VSB‐5 crystal together α‐Ni2P2O7, Ni2P4O12 and unknown phases were produced but the pure VSB‐5 crystal was obtained in the CH time of 48 h or more. At high content of nickel, a mixture of α‐Ni2P2O7, Ni2P4O12 phases and small amount of VSB‐5 crystal, was achieved but pure VSB‐5 crystal was obtained in the lower level of nickel and other phases are vanished. An efficient ultrasonic‐assisted aging was found for the synthesis of nickel phosphate molecular sieve, in which by ultrasonic mixing of 0.5 h followed microwave of 1 h, the CH time is significantly reduced from 48 to 24 h. The morphology of nickel phosphate crystals is highly influenced in the presence of ethylene glycol as co‐solvent. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
M. Moser D. Klimm S. Ganschow A. Kwasniewski K. Jacobs 《Crystal Research and Technology》2008,43(4):350-354
The quasi‐binary phase diagram lithium oxide – molybdenum(VI) oxide was investigated by differential scanning calorimetry and X‐ray diffraction. The four intermediate phases Li4MoO5, Li2MoO4, Li4Mo5O17, and Li2Mo4O13 show incongruent melting. The system has one eutectic point at 50.5 mol% MoO3 and 49.5 mol% LiO0.5 with a eutectic temperature of 524.6°C. At this point the melt is in equilibrium with Li2MoO4 and Li4Mo5O17. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
The structural defects and microhardness of Bi2Te3‐xSex whiskers (x = 0, 0.2 and 0.4 at% Se) grown by physical vapour deposition (PVD) method have been investigated. Concentric pairs of dislocation loops were observed on the as‐grown surfaces of short hexagonal prisms. A systematic study of dislocations in these crystals was carried out by chemical etching technique. The effects of Se doping, annealing and quenching on the mechanical properties have also been studied on the prism faces of Bi2Te3‐xSex whiskers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
Peritectic interaction of Y2BaCuO5 and Y2BaCuO9‐d phases with the Y‐Ba‐Cu‐O system flux melt has been modeled. The sequence of phase transformations in the Y2BaCuO5‐«Ba3Cu5O8» and Y2BaCuO5‐«BaCuO2» systems when forming the YBa2Cu3O7‐d single crystal compound has been established. 相似文献
9.
The crystal structure of 1‐allyl‐5‐(4‐methylbenzoyl)‐4‐(4‐methylphenyl)pyrimidine‐2(1H)‐thione (C22H20N2OS) has been determined from three dimensional single crystal X‐ray diffraction data. The title compound crystallizes in the monoclinic space group P 21/c, with a = 10.6674(13), b = 10.1077(7), c = 17.9467(19) Å, β = 98.460(9)°, V = 1914.0(3) Å3, Dcalc = 1.251 g cm–3, Z = 4. In the title compound, the allyl group shows positional disorder. Molecules are linked by C‐H···O, C‐H···N and C‐H···S intermolecular interactions forming two‐dimensional network. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
Ts.Z. Vitkina L.K. Orlik N.S. Orlova O.E. Andreeva 《Crystal Research and Technology》2000,35(2):229-238
The measurements of magnetic susceptibility of the AgGa(S1‐xSex)2solid solutions with the chalcopyrite structure have been performed and the lattice susceptibility separated into the Langevin diamagnetic and the Van Vleck paramagnetic terms. The obtained data were used to evaluate the character of chemical bond in these alloys. The correlations between the parameters of chemical bond and other physical properties are discussed. It is shown that the investigated solid solutions have preferably ionic character of chemical bond. The Ga‐S(Se) (B‐C) bonds are found to be stronger than the Ag‐S(Se) (A‐C) bonds. 相似文献
11.
By the substitution of one methyl group in Neopentane C(CH3)4 with a methylchlorid group the globular sphere is expanded in 1‐chloro‐2,2‐dimethylpropane (CH3)3C(CH2Cl). With the aid of DSC measurements, X‐ray powder diffraction, 1H NMR and 35Cl NQR measurements two orientationally disordered (plastic) phases were established. The low temperature structure was solved and a structural model of phase II is proposed. A mechanism to describe the reorientation in the different phases is given as well as a connectivity scheme between the phases is discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
12.
Bi2Se3‐xAsx single crystals with the As content of cAs = 0 to 2.0x1019 atoms/cm3 prepared from the elements of 5N purity by means of a modified Bridgman method were characterized by measurements of infrared reflectance and transmittance. Values of the plasma resonance frequency omegap, optical relaxation time tau, and high‐frequency permittivity were determined by fitting the Drude‐Zener formulas to the reflectance spectra. It was found that the substitution of As atoms for Se atoms in the Bi2Se3 crystal lattice leads to a decrease in the omegap values. This effect is accounted for by a model of point defects in the crystal lattice of Bi2Se3‐xAsx. The dependences of the absorption coefficient K on the energy of incident photons were determined from the transmittance spectra. The optical width of the energy gap is found to decrease with increasing As content. The values of the exponent b from the relation of K ∼ lamdab for the long‐wavelength absorption edge range within the interval 2.0 to 2.3, i.e. the dominant scattering mechanism of free current carriers in Bi2Se3‐xAsx crystals is the scattering by acoustic phonons. 相似文献
13.
Thiruramanathan Pandirengan Marikani Arumugam Madhavan Durairaj Gokul Raja Thangaiyanadar Suyambulingam 《Crystal Research and Technology》2016,51(6):366-379
As a first attempt, a series of composite materials of general formula (Bi4Ti3O12)X – (CaCu3Ti4O12)1–X (BTOX – CCTO1–X) (X = 0–1.0) is synthesized by a sol‐gel combustion method. The phase changes, including their formation and evolution during the gradual substitution of BTO into CCTO are analyzed from the X‐ray diffraction pattern. The Jana2006 refinement plotting method proves that formation of an ideal dual‐phase composite system with separate orthorhombic and cubic phases occurs. A surface morphological study revealed that the BTOX – CCTO1–X composites are composed of small CCTO grains embedded in large BTO grains and both coexisted with a bimodal distribution. The possible vibrational modes of interactions between the constituent phases are determined from Raman spectra. Our inexpensive, combustion method for BTO0.2 – CCTO0.8 gives a high dielectric constant (ε′ = 3232) at 100 Hz at room temperature. The nature behind these data is revealed that the BTO‐CCTO composite can be applicable for the fabrication of miniaturized global positioning system (GPS) patch antennas. The fabricated GPS patch antenna shows optimum results of small size (2.37 mm × 1.18 mm), return loss (‐14.419) and wide bandwidth (350 MHz) to be operated at 1.57 GHz. 相似文献
14.
N. M. Gasanly 《Crystal Research and Technology》2010,45(5):525-528
The optical properties of the TlInS2xSe2(1‐x)mixed crystals (0.25 ≤ x ≤ 1) have been investigated through the transmission and reflection measurements in the wavelength range of 400–1100 nm. The optical indirect band gap energies were determined by means of the analysis of the absorption data. It was found that the energy band gaps decrease with the increase of selenium atoms content in the TlInS2xSe2(1‐x)mixed crystals. The transmission measurements carried out in the temperature range of 10–300 K revealed that the rates of change of the indirect band gaps with temperature are γ = –9.2×10–4 eV/K, –6.1×10–4 eV/K, –4.7×10–4 eV/K and –5.6×10–4 eV/K for TlInS2, TlInS1.5Se0.5, TlInSSe and TlInS0.5Se1.5 crystals, respectively. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
T. Maimaitiyili A. Steuwer J. Blomqvist C. Bjerkn M.S. Blackmur O. Zanellato J. Andrieux F. Ribeiro 《Crystal Research and Technology》2016,51(11):663-670
We investigate the formation and dissolution of hydrides in commercially pure zirconium powder in‐situ using high‐energy synchrotron X‐ray radiation. Experimental results showed a continuous phase transition between the δ and ε zirconium hydride phases with indication of a second order phase transformation. 相似文献
16.
P. M. Vyas J. D. Akbari Satishkumar D. Tala H. S. Joshi M. J. Joshi 《Crystal Research and Technology》2012,47(7):763-770
The synthesis of pyrazoles and its derivatives remains of great interest due to their wide applications in pharmaceutical and agrochemical industry. The 1‐phenyl‐3‐(propan‐2‐yl)‐1H‐pyrazol‐5‐ol was synthesized. The 1‐phenyl‐3‐(propan‐2‐yl)‐1H‐pyrazol‐5‐ol single crystals were grown by slow solvent evaporation technique using mixture of chloroform and methanol as a solvent. Yellowish and transparent crystals having maximum dimensions of 0.005 m × 0.004 m × 0.002 m were grown. The crystals were characterized by powder XRD, FT–IR, TG–DTA–DSC and dielectric study. The crystals remained stable up to 160 °C and then start decomposing. The DSC suggested both endothermic and exothermic reactions. One broad exothermic peak was observed at 558.1 °C due to complete decomposition of the sample into the gaseous phase and reaction within the products. Thermodynamic and Kinetic parameters of decomposition were calculated by Coats–Redfern formula. The dielectric study was carried out in the frequency range from 50 Hz to 5 MHz at room temperature. The dielectric constant decreased as the frequency of the applied field increased. The variations of dielectric loss, a.c. conductivity and a.c. resistivity also studied with the frequency of the applied field. Jonscher's power law was verified for a.c. conductivity. 相似文献
17.
I. A. dos Santos I. M. Ranieri D. Klimm R. Fornari S. L. Baldochi 《Crystal Research and Technology》2008,43(11):1168-1172
Scheelite type LiGdF4, LiLuF4, and mixtures of both end members were prepared by a hydrofluorination route from the rare earth oxides and commercial LiF. The samples were purified by melting in HF/Ar mixtures, and were investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and energy dispersive X‐ray spectroscopy (EDX) techniques. Both end members show unlimited miscibility in the solid phase. Mixed crystals containing at least 65 mol‐% LiLuF4 melt under direct formation of the liquid phase. The gap between solidus and liquidus is narrow. LiGdF4 and mixed crystals with less then 65 mol‐% LiLuF4 decompose peritectically under formation of (Gd,Lu)F3. Crystal growth is expected to be possible either from Lu‐rich melts with the appropriate scheelite composition or from Gd‐rich melts containing an excess of LiF. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
18.
Single crystals of Ca2FeO3Cl have been obtained as a by product during single crystal growth experiments of calcium ferrates from a CaCl2 flux. The reddish‐brown optically uni‐axial crystals adopt the tetragonal space group P4/nmm with a = 3.8381(4) Å and c = 13.685(2) Å and Z = 2 formula units per cell. The structure has been determined from a single crystal diffraction data set collected at room conditions and refined to final residual R(|F|) = 0.053 for 163 observed independent reflections with I > 2σ(I). Ca2FeO3Cl belongs to the structure family of the Ruddlesden‐Popper series with n = 1, which is also referred to as the K2NiF4‐type. Main building units are layers of perovskite type corner connected FeO5Cl‐octahedra perpendicular to [001]. The two crystallographically independent calcium ions are located between the octahedral layers and are coordinated by nine ligands each: Ca1 (4×O + 5×Cl) and Ca2 (9×O). Following prior studies Ca2FeO3Cl crystallizes in space group P4. However, the present investigation shows clearly that this assignment is incorrect and that the compound has been described in an unnecessarily low symmetry. 相似文献
19.
The crystal structure of 4‐(1‐methyl‐1‐mesitylcyclobutane‐3‐yl)‐2‐aminothiazole (C17H22N2S1) has been determined by X‐ray crystallographic techniques. The compound crystallizes in the triclinic space group P‐1 with Z = 6. The crystal structure was solved by direct methods and refined by full‐matrix least squares to a final R‐value of 0.052 for 2298 observed reflections [I > 2σ ( I ) ]. There are three crystallographically independent molecules, I, II and III. These molecules are held together by intermolecular N‐H...N hydrogen bonds. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim 相似文献
20.
G.M. Kuz'micheva Yu.V. Esaulova A.H.R.M. Alsarraf A.S. Andreenko I.E. Kostyleva E.P. Khlybov T. Palewski 《Crystal Research and Technology》2002,37(6):612-626
Conditions of the synthesis, crystal structures, mechanical properties, electrical resistivities and magnetizations of cuprates with the general formula (Cr,Cu)(Sr,La)2(La,A)Cu2O8‐δ where A=Ca or Sr of 1212‐type and (Cr,Cu)Sr2(Y,Ce)2Cu2O10‐δ of 1222‐type were investigated. The compositions of the cuprates and an amount of the impurity phases in the samples were determined. Rietveld refinement of the structure was carried out. It was found that the formal charges of Cu (FCCu) calculated from the electroneutrality of refined phase compositions do not achieve value optimal for the appearence of superconducting phases. 相似文献