Showing papers in "Crystal Research and Technology in 2009"

Linear and nonlinear optical properties of tris thiourea zinc sulphate single crystals

Abstract: Optical absorption of tris thiourea zinc sulphate (ZTS) single crystals has been measured and its direct band gap was found to be 3.6 eV. Theoretical calculations were carried out to determine the linear optical constants such as extinction coefficient and refractive index. Further the optical nonlinearties of ZTS have been investigated by Z-scan technique with He-Ne laser at 632.8 nm. The nonlinear refractive index, absorption coefficient and third order susceptibility is found to be in the order of –5.36 ± 0.26 × 10–12 cm2/W, 4.24 ± 0.21 × 10–4 cm/W, 3.5 ± 0.17 × 10–4 esu respectively. Thus optical characterization of ZTS reveals the various industrial application oriented properties of the material. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Optical properties of ZnO nano fiber thin films grown by spray pyrolysis of zinc acetate precursor

Abstract: Good homogeneous and stoichiometric ZnO nanofiber thin films have been deposited onto cleaned glass substrate by a simple spray pyrolysis technique under atmospheric pressure using zinc acetate precursor at temperature 200 °C. Films of various thicknesses have been obtained by varying the deposition time, while all other deposition parameters such as spray rate, carrier gas pressure and distance between spray nozzle to substrate were kept constant. Surface morphology and optical properties of the as deposited thin films have been studied by Scanning Electron Microscopy (SEM) attached with an EDX and UV visible spectroscopy. From EDX data, atomic weight% of Zinc and Oxygen were found to be 49.22% and 49.62% respectively. The SEM micrograph of the film shows uniform deposition and scattered nano fiber around the nucleation centers. The optical band gap of the ZnO thin films was found to be in the range 3.3 to 3.4 eV and the band gap decreases with thickness of the film. Optical constants such as refractive index, extinction coefficient, real and imaginary parts of dielelectric constants were evaluated from reflectance and absorbance spectra. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Review: Indentation size effect, indentation cracks and microhardness measurement of brittle crystalline solids – some basic concepts and trends

Abstract: Indentation size effect, indentation cracks and microhardness measurement of some brittle crystals are reviewed against the background of the existing concepts of indentation deformation of crystalline solids. Several approaches reported in the literature devoted to relationships between applied indentation test load P and indentation diagonal length d are applied to analyze the experimentally observed normal and reverse indentation size effect (ISE) in brittle compounds. Using typical examples of normal and reverse ISE it is shown that the indentation induced cracking model does not give load-independent hardness and the final expression describing the experimental data for various compounds is essentially another form of the Meyer law. Analysis of experiment data on crack lengths and indentation diagonals for different indentation loads suggests that the origin of ISE is associated with the processes of formation of indentation cracks following the general concepts of fracture mechanics. The load-independent hardness H0 may be determined reliably from plots of P /d against d of the proportional resistance model or of HV against 1/d as predicted by strain gradient plasticity theories. It was found that the load-independent hardness of depends on crystal orientation and state of the indented surface. Finally, some comments on determination of fracture toughness and brittle index of crystals are made. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Synthesis and characterization of nano ZnS doped with Mn

Abstract: Nanocrystalline samples of Zn1-xMnxS (x = 0.0, 0.02, 0.04) were synthesized by chemical precipitation method and characterized for magnetism. EPR studies showed an evidence of ferromagnetism around room temperature. Hysterisis from vibrating sample magnetometer supports the observation. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Growth and characterization of NLO active lithium sulphate monohydrate single crystals

Abstract: Single crystals of the NLO active lithium sulphate monohydrate were grown successfully by slow evaporation technique. The as-grown crystal was clear, transparent and the size of the crystal attained was 14 x 8 x 5 mm3 within a period of 4 weeks. The crystal was subjected to Fourier transform infrared spectroscopy (FTIR), Thermal analysis (TG/DTA), UV-Vis analysis, mechanical and dielectric studies. Theoretical calculations for band gap energy were made. An attempt was made to calculate polarizability by Penn analysis and compare with the traditional method and results are tabulated. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A novel self-consistent Nývlt-like equation for metastable zone width determined by the polythermal method

Abstract: Using a power-law relation between three-dimensional nucleation rate J and dimensionless supersaturation ratio S, and the theory of regular solutions to describe the temperature dependence of solubility, a novel Nývlt-like equation of metastable zone width of solution relating maximum supercooling ΔTmax with cooling rate R is proposed in the form: ln(ΔTmax/T0) = Φ + β lnR, with intercept Φ = {(1–m)/m }ln(ΔHs/RGTlim) + (1/m)ln(f/KT0) and slope β = 1/m. Here T0 is the initial saturation temperature of solution in a cooling experiment, ΔHs is the heat of dissolution, RG is the gas constant, Tlim is the temperature of appearance of first nuclei, m is the nucleation order, and K is a new nucleation constant connected with the factor f defined as the number of particles per unit volume. It was found that the value of the term Φ for a system at saturation temperature T0 is essentially determined by the constant m and the factor f. The value of the factor f for a solute–solvent system at initial saturation temperature T0 is determined by solute concentration c0. Analysis of the experiment data for four different solute-water systems according to the above equation revealed that: (1) the values of Φ and m for a system at a given temperature depend on the method of detection of metstable zone width, and (2) the value of slope β = 1/m for a system is practically a temperature-independent constant characteristic of the system, but the value of Φ increases with an increase in saturation temperature T0, following an Arrhenius-type equation with an activation energy Esat. The results showed, among others, that solubility of a solute is an important factor that determines the value of the nucleation order m and the activation energy Esat for diffusion. In general, the lower the solubility of a solute in a given solvent, the higher is the value of m and lower is the value of Esat. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Low temperature hydrothermal growth and optical properties of ZnO nanorods

Abstract: Well-faceted hexagonal ZnO nanorods have been synthesized by a simple hydrothermal method at relative low temperature (90°C) without any catalysts or templates. Zinc oxide (ZnO) nanorods were grown in an aqueous solution that contained Zinc chloride (ZnCl2, Aldrich, purity 98%) and ammonia (25%). Most of the ZnO nanorods show the perfect hexagonal cross section and well-faceted top and side surfaces. The diameter of ZnO nanorods decreased with the reaction time prolonging. The samples have been characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) measurement. XRD pattern confirmed that the as-prepared ZnO was the single-phase wurtzite structure formation. SEM results showed that the samples were rod textures. The surface-related optical properties have been investigated by photoluminescence (PL) spectrum and Raman spectrum. Photoluminescence measurements showed each spectrum consists of a weak band ultraviolet (UV) band and a relatively broad visible light emission peak for the samples grown at different time. It has been found that the green emission in Raman measurement may be related to surface states. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Vertically aligned and interconnected nickel oxide nanowalls fabricated by hydrothermal route

Abstract: Vertically aligned and well interconnected NiO nanowalls with thin nanodiscs of cubic NiO as the in situ formed building blocks were fabricated via a template-free approach. The alkaline solution of ammonium hydroxide was used as a reductant and Ni foil as both source material and substrate for the nanowall synthesis. Surface morphology analysis confirmed the formation of 15 nm thick and 0.2–1.5 μm wide nanowalls. The nanowalls had the crystal structure of cubic NiO with their growth plane along the [111] direction. An optical band gap of about 3.8 eV for the NiO nanowalls was obtained from the optical absorption measurement. NiO nanowalls exhibited a broad UV emission band centered at around 390 nm. This simple, but efficient synthesis technique can facilitate the growth of well aligned 2D nanostructures with large surface area for possible applications in nanoscale devices. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Ultrasound assisted crystallization for the recovery of lactose in an anti-solvent acetone

Abstract: Continuous worldwide increase in high-scale production of dairy products leads to the constant generation of vast amounts of liquid by-product, whey. Disposal of liquid whey is costly due to its high biological oxygen demand (BOD) and water content. More than 90% of whey BOD is due to lactose. Recovery of lactose from whey solves both the problems of improving economics of whey utilization and pollution reduction as lactose recovery itself can reduce BOD of whey by more then 80%. Commercial effluent treatment techniques focus on degradation rather than recovery of useful by-products like lactose. Also, these techniques are time consuming and hence not effective enough. Sonocrystallization is the use of power ultrasound to control the crystallization process during the nucleation phase. In the present study, the process of lactose crystallization has been studied for the recovery of lactose from reconstituted lactose solutions with the aid of ultrasound, in the presence of ‘acetone’, as an anti-solvent. The crystallization is found to be completed with excellent yields in the range of 80 – 92% within 4 minutes of sonication. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Optical, photocatalytic properties of novel CuS nanoplate‐based architectures synthesised by a solvothermal route

Abstract: CuS architectures were successfully prepared by a simple solvothermal route without any surfactant, in which copper nitrate trihydrate and element sulfur were used as reactants. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The optical properties of CuS architectres were investigated by Raman spectrometer, ultraviolet-visible spectroscopy, and fluorescence spectrophotometer. The results showed that the CuS architectures were hexagonal-structured phase and composed of intersectional nanoplates. UV-Vis absorption peaks of CuS architectures showed large blue shifts and PL spectrum exhibited a strong blue emission and a weak green emission. Photocatalytic activity of the CuS architectures was evaluated by measuring the decomposition rate of methylene blue solution under solar light. The CuS architectures show good photocatalytic activity. The effects of the molar ratio of Cu:S and the growth time on the synthesis of CuS crystalline were discussed and the growth mechanism of CuS nanoplate-based architectures was also proposed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of annealing on the structural, electrical and optical properties of nanostructured TiO2 thin films

Abstract: Nanostructured titanium dioxide thin films were prepared using reactive pulsed laser ablation technique. Effects of annealing on the structural, morphological, electrical and optical properties are discussed. The structural, electrical and optical properties of TiO2 films are found to be sensitive to annealing temperature and are described with GIXRD, SEM, AFM, UV-Visible spectroscopy and electrical studies. X-ray diffraction studies showed that the as-deposited films were amorphous and at first changed to anatase and then to rutile phase with increase of annealing temperature. Optical constants of these films were derived from the transmission spectra and the refractive index dispersion of the films, subjected to annealing at different temperatures, is discussed in terms of the single oscillator-Wemple and Didomenico model. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Controlled synthesis of Cu2O cubic and octahedral nano‐ and microcrystals

Abstract: Cubic and octahedral Cu2O nano- and microcrystals were selectively synthesized via a simple wet chemical reduction route at room temperature, with CuCl2 and NaOH as starting reactants, and ascorbic acid or hydrazine hydrate as the reducer. Hydrazine hydrate could be preferentially adsorbed on different crystal faces of Cu2O, affecting the growth rate along the 〈100〉 to that along the 〈111〉 direction, which resulted in the formation of octahedral Cu2O crystals. When ascorbic acid was used as the reducer, the growth rate along the 〈100〉 to that along the 〈111〉 direction was different, which resulted in the formation of cubic Cu2O crystals. The size of cubic and octahedral Cu2O crystals could be varied by adjusting the molar ratio of OH– to Cu2+. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Optical properties of the germanate melilites Sr2MgGe2O7, Sr2ZnGe2O7 and Ba2ZnGe2O7

Abstract: Refractive indices and their dispersion in the wavelength range from 365 nm to 2325 nm and transmission ranges of the tetragonal melilite-type germanates Sr2MgGe2O7, Sr2ZnGe2O7 and Ba2ZnGe2O7 were determined. The uniaxial positive crystals Sr2MgGe2O7 and Ba2ZnGe2O7 both offer the possibility for phase matched second harmonic generation, a detailed analysis of phase matching conditions is given. The refractive indices of Sr2ZnGe2O7 show an isoindex (isotropic) point at 467 nm. The investigation was performed on Czochralski grown large single crystals. The crystal structure of all three germanates were determined by means of X -ray diffraction. The results corroborate unmodulated melilite-type structures at room temperature. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Structural properties of Zn1–xMgxO nanomaterials prepared by sol‐gel method

Abstract: The mixed oxides Zn1-xMgxO (ZMO) were prepared as nano-polycrystalline powders and thin films by a simple sol–gel process and dip coating method. Thermogravimetric (TG) and differential thermal analysis (DTA) were used to study the thermal chemistry properties of dried gel. Structural and microstructural analysis was carried out applying x-ray diffraction (XRD) and Rietveld method. Analysis showed that for x < 0.25, Mg replaces Zn substitutionally yielding ZMO single phase, while for x ≥ 0.25 two phases are identified ZMO and MgO. Replacing Zn2+ by Mg2+ distorts the cation tetrahedrons and decreases the lattice constants ratio c/a of the wurtzite ZMO which deviate the lattice gradually from the hexagonal structure as Mg+2 increases. These distortions are attributed to the difference in electronic configuration of the two cations which suppress the paraelectric-ferroelectric phase transition in the ZMO wurtzite. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Thermoelectric properties of Tl-doped Bi2Se3 single crystals

Abstract: The single crystals of the ternary system based on Bi2-xTlxSe3 (nominaly x = 0.0-0.1) were prepared using the Bridgman technique. Samples with varying content of Tl were characterized by the measurement of lattice parameters, electrical conductivity σ⊥c, Hall coefficient RH (B∥c), and Seebeck coefficient S (ΔT ⊥c). The measurements indicate that by incorporating Tl in Bi2Se3 one lowers the concentration of free electrons and enhances their mobility. This effect is explained in terms of the point defects in the crystal lattice – formation of substitutional defects thallium on the site of bismuth TlBi and the decrease of concentration of selenium vacancies VSe+2. We also discuss the temperature dependence of the power factor σS2 of the samples. Upon the thallium doping we observe a significant increase of the power factor compare to the parental Bi2Se3. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Precipitation of nesquehonite from homogeneous supersaturated solutions

Abstract: The homogeneous (unseeded) precipitation of nesquehonite (MgCO(3)center dot 3H(2)O) was studied over the temperature range of 10-40 degrees C. Precipitation was triggered by the supersaturation created by mixing MgCl(2) solution (0.5-1.5 M) with Na(2)CO(3) solution in the same concentration range. The Meissner's method was adopted in the calculation of supersaturations during the MgCl(2)-Na(2)CO(3) reaction to monitor the precipitation. Solids were identified using X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) images. In the temperature range of 10-40 degrees C, MgCO(3)center dot 3H(2)O with needle-like or gel-like morphology was precipitated. It was seen that the length, width and surface smoothness of the particles changed with reaction temperature and supersaturation. The supersaturation (S) was in the range of 1.09-58.68 during titration of Na(2)CO(3) solution. The dimension of the crystals increased with longer addition time (or lower initial concentration of reactant) at the same temperature. Slower addition via titration of 2 h followed by 2 h of equilibration at 40 degrees C proved successful in producing well developed needle-like MgCO(3)center dot 3H(2)O crystals of 30-50 mu m long and 3-6 mu m wide. MgCO(3)center dot 3H(2)O obtained were calcined to produce highly pure magnesium oxide (MgO) at 800 degrees C. The morphology of MgO was similar to that of their corresponding precursors. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Synthesis of nano-crystalline zeolite β: Effects of crystallization parameters

Abstract: The effects of variation in Si/Al ratio (25 and 100) and crystallization temperature (80 °C to 180 °C, at an interval of 20 K) on crystal size of zeolite β were studied. Products obtained at different synthesis parameters were characterized by powder X-ray diffraction, IR spectroscopy, thermal analysis, scanning electron microscopy and nitrogen adsorption. Increase in crystal size with crystallization temperature and Si/Al molar ratio was observed. Crystal morphology at 140 °C was spherical whereas at 180 °C it was of irregular shape. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Low‐temperature urea‐assisted hydrothermal synthesis of Bi2S3 nanostructures with different morphologies

Abstract: Different morphologies of single-crystalline orthorhombic phase bismuth sulfide (Bi2S3) nanostructures, including sub-microtubes, nanoflowers and nanorods were synthesized by a urea-assisted hydrothermal method at a low temperature below 120 °C for 12 h. The as-synthesized powders were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis spectrophotometry. The experimental results showed that the sulfur sources had a great effect on the morphology and size of the resulting powders. The formation mechanism of the Bi2S3 nanostructures with different morphologies was discussed. All Bi2S3 nanostructures showed an appearance of blue shift relative to the bulk orthorhombic Bi2S3, which might be ascribed to the quantum size effect of the final products. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Synthesis of Fe-doped chrysotile and characterization of the resulting chrysotile fibers

Abstract: This study describes the formation of Fe-doped chrysotile fibers with partial and total substitution of Mg by Fe. Syntheses were carried out with various starting mixtures (oxides, pure synthetic forsterite) in an externally heated pressure vessel in controlled hydrothermal conditions: temperature, 270 – 400 °C; pressure, 0.5 – 2 kbar; duration of treatment 160 – 480 hours. Pure synthetic forsterite was prepared by the flux growth technique. The starting material and run products were characterized by X-ray powder diffraction (XRPD), scanning and transmission electron microscopies combined with energy-dispersive spectrometry (SEM-EDS and TEM-EDS), differential scanning calorimetry (DSC) and thermogravimetry (TG). Variations observed in abundance and size of Fe-doped chrysotile fibers were attributed to different experimental conditions for their synthesis. However, morphological shape turned out to depend on the starting mixtures used. Since natural samples are often difficult to obtain in a sufficiently pure state, these synthetic and well-characterized Fe-doped chrysotile fibers can be used for better understanding of the mechanisms involved in asbestos toxicity, as well as of the role of Fe in diseases induced by asbestos phases. These synthetic Fe-doped chrysotile fibers, together with non-toxicity testing, may also have potential for exploitation in industrial fields. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Sintering behavior of ZnO:Al ceramics fabricated by sol‐gel derived nanocrystalline powders

Abstract: ZnO:Al ceramics (Zn:Al, 0.95:0.05) were prepared by using sol-gel derived nanocrystalline powders. XRD patterns of the doped ceramics revealed the existence of both zincite (JCPDS 36-1451) and gahnite (JCPDS 5-0669) phases. Gahnite phase (ZnAl2O4) was segregated along the ZnO grain boundaries. At the sintering temperature of 1200 °C, relative density of the undoped and Al doped ceramics were measured as 0.695 and 0.628, respectively. Both grain size and relative density of the ceramics decreased with Al doping. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Addressing difficulties in using XRD intensity for structural study of thin films

Abstract: The problem of structure investigation of thin films using laboratory XRD diffraction intensities was discussed as a matter of debate Is the variation in relative intensities of the diffraction patterns due to crystallographic preferred orientation, lattice defects or both? The answer to this question shows a discrepancy in the literatures The present work is an attempt to propose a possible approach to judge the most probable answer Thin films of SnO2 were prepared by spray pyrolysis technique using solution of different SnCl2 concentrations (molarity); at fixed substrate temperature and deposition time The theoretically calculated integrated intensities together with the experimentally obtained and calculated XRD data (relative intensities, texture coefficients and profile analysis) were considered together in order to get the proper picture of the structure characteristics of the prepared films The complete picture can be assembled by integration and correlation of all the crystallographic information that are extracted from the diffraction pattern including not only the observed intensities but also the size/strain analysis and lattice parameters (© 2009 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim)

Synthesis, structural and optical properties of well dispersed anatase TiO2 nanoparticles by non-hydrothermal method

Abstract: The formation of nanocrystalline TiO2 particles has been investigated via a surfactant-free synthetic non-hydrothermal method. Titanium isopropoxide and toluene were used as the starting materials. At a low temperature of 250 °C for 6 h, the reaction mixture turned in to a white precipitate (TiO2) as a result of the thermal decomposition of metal alkoxide. The obtained product was found to crystallize purely in the anatase phase with well defined morphology. The powder XRD study confirms that the average size of the particle is close to ∼15 nm. The TEM analysis indicates the sizes of the primary and secondary particles in the range between 8-10 nm and 15-20 nm respectively. The quantum size confinement of the crystallites is evident from the blue shift of the absorption edge in the UV-Visible absorption spectrum. The luminescence property of the TiO2 nanoparticles studied by the emission spectrum confirms the presence of defect levels caused by the oxygen vacancies. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Ni1‐xCrx alloy for self controlled magnetic hyperthermia

Abstract: It is known now that an increase in tumor temperature decreases the tumor resistance to chemo- and radiation therapies. Hyperthermia treatment of the tumor cells where damage to the healthy cells can be avoided is viable by using magnetic nanoparticles with controlled Curie temperatures. Nickel-Chromium (Ni1-xCrx) particles with varying compositions have been investigated as thermoseeds for use in localized self controlled hyperthermia treatment of cancer. A series of Ni1-xCrx alloys, have been prepared to find the specific composition which has Curie temperature around 316-317 K. The samples were cast by arc melting technique, and were annealed at 850 oC for 5 hours in sealed quartz tubes. Magnetic properties of the samples were investigated, including Curie temperature, saturation magnetization and hysterisis using Superconducting Quantum Interference Device (SQUID) and Vibrating Sample Magnetometer (VSM). The Curie temperatures of the alloys were found to decrease almost linearly from 401 K to 289 K as the Cr concentration was increased from x = 4.54 wt% to x = 5.90 wt%. The results showed that Ni1-xCrx alloys might be good candidates for self regulating magnetic hyperthermia applications. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Characterization of compensation and trapping in CdTe and CdZnTe: Recent advances

Abstract: Results on the properties of the known impurities, Ge, Sn, V and Bi, and the lattice imperfections, VCd and TeCd are summarized. We discuss their role in compensation, and in buffering the variations in shallow electronic levels in the grown ingot. We demonstrate that (∼2÷3 kT) variations of the Fermi energy increases carrier trapping to the deep levels. Trapping is manifest in a photoconductivity signal that can be studied by photoconductivity methods, thus allowing to monitor the spectroscopic-grade material before fabricating the detectors. Our approach could be important in preventing the after-glow effect and polarization. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Calcium oxalate crystallization in the presence of amino acids, proteins and carboxylic acids

Abstract: Reactive crystallization of calcium oxalate was investigated in the presence of amino acids, proteins and carboxylic acids at different pH and temperatures. Average particle size, filtration rates of calcium oxalate crystals obtained in the absence and presence of additives were determined. The influence of pH, temperatures and additives on crystal morphology of calcium oxalate were also investigated and discussed by SEM analysis. TG-DTA, FT/IR and XRD analysis were carried out for all investigated conditions. Average particle size of calcium oxalate was affected significantly by the additive type and concentration. Variation of crystal morphology depending on type and concentration of the additives affected the filtration characteristics. Majority of calcium oxalate crystals occurred in the form of calcium oxalate monohydrate except those in the presence of tartaric acid. TG-DTA, FT/IR and XRD analysis proved that calcium oxalate monohydrate and calcium oxalate dihydrate mixtures are formed in the presence of tartaric acid. The effect of all additives on scale formation was also investigated. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Growth and characterization of glycine doped bis thiourea cadmium chloride single crystal

Abstract: Single crystal of 2 mol% glycine doped Bis Thiourea Cadmium Chloride, a semi organic nonlinear optical material has been grown by slow evaporation technique. Good quality single crystal with dimension 14 × 12 × 5 mm3 was harvested after 35 days. The influence of amino acid glycine was studied for 1, 2 and 3 mol% glycine doped Bis Thiourea Cadmium Chloride by Kurtz and Perry powder second harmonic generation test and compared with pure Bis Thiourea Cadmium Chloride which confirms the enhancement of second harmonic generation property of glycine doped Bis Thiourea Cadmium Chloride. The large enhancement was found for 2 mol% glycine doping. The grown crystal was characterized by various characterizations viz. single crystal X-ray diffraction, energy dispersive X-ray (EDAX), Fourier Transform Infrared Spectroscopy (FTIR) analysis, UV-visible absorption, thermo gravimetric analysis (TGA). (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Minerals as advanced materials

Abstract: A resume is given on relationships between minerals and materials. It is shown that Nature has many advantages over technology which can be profitably exploited for finding new materials with useful properties. However, Nature has also inherent limitations. Therefore, it seems advisable to use the knowledge of minerals as a treasure which can be tapped for getting inspired on the way to finding new materials. Several examples are given, including those of zorite/ETS-4/ETS-10, boracites, zircon, kesterite, a natural quasicrystal, opals, ultramarine and mayenite.

Studies on multiphased mixed crystals of NaCl, KCl and KI

Abstract: Multiphased mixed crystals of NaCl, KCl and KI were grown by the melt method, for the first time. Densities and refractive indices of all the grown crystals were determined and used for the estimation of the composition in the crystal. Atomic absorption spectroscopic measurements were done to estimate the metal atom contents in the crystal. Lattice parameters and thermal parameters (Debye-Waller factor, mean square amplitude of vibration, Debye temperature and Debye frequency) were determined from the X-ray powder diffraction data. DC and AC electrical measurements were done at various temperatures ranging from 40 to 150°C. Activation energies were also estimated. The observed lattice parameters showed that the system exhibits three phases each nearly corresponds to NaCl, KCl and KI. The thermal and electrical parameters show a highly nonlinear bulk composition dependence. Results are reported. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Growth of spinel crystals in vanadium slag and their characterization

Abstract: Morphology of vanadium slags were investigated by scanning electron microscopy (SEM). The mineralogical phases were characterized by energy disperse X-ray spectrometry (EDS) and powder X-ray diffraction (XRD). The obtained results show that spinels and silicates are the major phases in the vanadium slag, and V is concentrated in FexV3-xO4 and Mgx(V, Ti)3-xO4. Both the spinel grain size and volume fraction in the slag with higher V2O3 content are much larger than that with lower V2O3 content. (Fe, Mn)2SiO4 and (Fe, Mn)SiO3 have a higher proportion in the slag with lower V2O3 and higher SiO2 content. The relation among cooling conditions and grain size and volume fraction of spinels is also discussed. It is found that low cooling rate and long holding time benefit spinel crystal growth, especially for the interval of 1200-1250 °C. Both mean diameter and volume fraction of spinels could achieve or exceed the industry vanadium slag when holding more than 45 min. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Growth of barium oxalate crystals in agar–agar gel and their characterization

Abstract: Single crystals of barium oxalate have been grown by gel method using agar-agar gel as media of growth at ambient temperature The optimum conditions were established by varying various parameters such as concentration of gel, concentration of reactant, gel setting time etc Prismatic platy shaped transparent crystals were obtained The grown crystals were characterized through powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) studies, Thermogravimetric (TGA) and Differential thermal analysis (DTA) The compound crystallizes under monoclinic structure with lattice parameters a = 66562 A, b = 80464 A, c = 28090 A, β= 96832°, and V = 14938 A3 The FT-IR spectrum indicates OH and carbonyl group along with the presence of metal-oxygen bond The TGA indicates 1775% weight loss at 550°C from which the decomposition pattern is formulated (© 2009 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim)