Nucleation kinetics and growth aspects of semi organic non‐linear optical bis thiourea cadmium acetate single crystals

Nucleation parameters such as metastable zone width, induction period and interfacial energy have been determined for the aqueous solution growth of bis thiourea cadmium acetate (BTCA) single crystals. Solubility of BTCA has been determined for various temperatures. Metastable zone width and induction period values have been estimated in order to optimize the growth parameters. The interfacial tension values derived from experimentally determined induction period are found to be comparable with theoretical values. Bulk crystals of BTCA have been grown using the optimized growth parameters. The grown crystals have been subjected to structural, optical and mechanical property studies. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigations on the Nucleation Kinetics of L-Arginine Phosphate single crystals

The nucleation parameters, such as radius of the critical nucleus and critical free energy change have been evaluated for LAP single crystals. The interfacial tension determined by conducting the induction period measurements has been used for the evaluation of nucleation parameters. The determined interfacial tension is found to be comparable with theoretical literature values.     

Nucleation kinetics,growth, solubility and dielectric studies of L‐proline cadmium chloride monohydrate semi organic nonlinear optical single crystal

Nucleation parameters such as solubility, induction period, interfacial energy and metastable zone width have been investigated for the aqueous solution growth of a semi‐organic nonlinear optical (NLO) material of L‐Proline cadmium chloride monohydrate (L‐PCCM) single crystal. Metastable zone width and induction period values were determined experimentally in order to optimize the growth parameters. The grown crystals are transparent (dimensions: 16 x 8 x 5 mm³) and characterized by powder X‐Ray Diffraction and dielectric studies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigations on nucleation,thermodynamical parameters and growth of Benzimidazole crystals from low temperature solution

Metastable zonewidth and induction period measurements of Benzimidazole (BMZ) are presented. The nucleation parameters such as interfacial tension, radius of the critical nucleus and critical free energy change have been calculated for the solution grown Benzimidazole (BMZ) single crystals at different supersaturation ratios. The grown BMZ crystals were characterized by the differential scanning calorimetric studies for analysis of thermal properties. The dielectric behaviour of the crystal was studied at different temperature and frequency. The laser damage threshold studies show that BMZ crystal has higher laser damage threshold. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigations on the nucleation kinetics of bis glycine sodium nitrate

The nucleation parameters such as, energy per unit volume, radius of critical nucleus, critical free energy barrier, number of molecules in the critical nucleus and nucleation rate have been evaluated for bis glycine sodium nitrate single crystals. The interfacial energy of the solution at various temperatures has been estimated from existing solubility data. The metastable zone width and induction period measurements have been carried out experimentally.     

Studies on growth,induction period,interfacial energy and metastable zonewidth of m‐nitroaniline

Single crystals of m‐Nitroaniline (mNA) were grown by slow cooling solution growth technique. Induction period, interfacial energy and metastable zonewidth have been evaluated. The solubility of mNA has been estimated at different temperatures in acetone and ethanol. Interfacial energy has been estimated using the experimentally determined induction period values. It is observed that the nucleation rate increases with the increase of supersaturation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determination of nucleation kinetics of potassium tetraborate tetrahydrate

In this study, the metastable zone width of potassium tetraborate tetrahydrate was determined for four different temperatures and cooling rates. The induction period of potassium tetraborate tetrahydrate in aqueous solution was examined according to polythermal method by using visual observation. The induction period, which changes inversely proportional to the nucleation rate has been used to determine the interfacial tension between the potassium tetraborate tetrahydrate and aqueous solution. By using interfacial tension, the nucleation parameters such as Gibbs free energy change for the formation of critical nucleus, ΔG*, free energy of formation, ΔG, radius of critical nucleus, r and number of molecules in the critical nucleus, i* has been calculated. The effect of Li⁺ and Ca²⁺ impurities on metastable zone width has been studied. The metastable zone width of aqueous solution of potassium tetraborate tetrahydrate decreases with increasing impurity concentrations. The equilibrium saturation concentration change is high in the presence of Ca²⁺ ions while it is low in the presence of Li⁺ ions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nucleation kinetics and growth aspects of organic nonlinear optical L‐arginine trifluoroacetate single crystals

Experimental determination of solubility, metastable zonewidth and induction period for an organic nonlinear optical (NLO) L‐arginine trifluoroacetate (LATF) crystal is reported. The interfacial tension for different supersaturation conditions has been estimated for the LATF solution at 45°C. Bulk crystal of dimensions 57x5x3 mm³ has been grown by temperature lowering technique using optimized growth parameters. Powder X‐ray diffraction and FTIR studies confirm the crystalline nature and the functional groups of the grown crystals respectively. Linear optical property of the grown crystal has been studied by UV‐Vis spectrum. Thermal analyses have revealed that the compound is thermally stable upto 212°C. Kurtz powder SHG test confirm the nonlinear optical properties of the as‐grown LATF crystal. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth,thermal and optical studies of L‐histidine tetrafluoroborate: A semiorganic NLO material

L‐histidine tetrafluoroborate (L‐HFB), a semiorganic nonlinear optical (NLO) material has been synthesized and characterized by elemental analysis and FT–NMR spectroscopic studies. Solubility of L‐HFB has been determined in water and ethanol. The single crystals with dimensions 15 x 12 x 3 mm³ were grown by slow evaporation technique under two different pH conditions. The effect of pH on the morphology of the crystals have been studied. The grown crystals of both pH values has been subjected to single crystal X‐ray diffraction to determine the unit cell dimensions and morphology. The thermal stability has been analyzed by TGA and DTA. The microhardness test was carried out in (001) plane and the hardness coefficient was calculated. The birefringence values (Δ_n) were determined in the wavelength region 5540–6460 Å. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nucleation kinetics of the formation of low dimensional calcium sulfate dihydrate crystals in isopropyl alcohol medium

Calcium sulfate dihydrate, constituted as uniform crystals of low dimensions, is a potential biomaterial for clinical applications like bone graft substitution and drug delivery. In this work, isopropyl alcohol has been used as a solvent to obtain low dimensional calcium sulfate dihydrate crystals from calcium nitrate ‐ sulfuric acid system. Reactants in 0.5 molar concentration at ambient conditions generated uniform rod‐shaped crystals of length 3–5 µm. Analysis using X‐ray Diffractometry and Fourier Transform Infrared Spectrometry showed the material to be well crystallized, phase‐pure calcium sulfate dihydrate. The nucleation kinetics has been studied by observing the induction time of phase formation in solutions of millimolar concentrations through turbidimetry at 300 K. The data have been analysed using classical nucleation theory to deduce parameters like interfacial tension (or surface free energy), nucleation rate and critical radius. The surface free energy obtained (5.6 mJ/m²) is comparatively lower than that reported for aqueous precipitation, which could be attributed to the presence of isopropyl alcohol. On escalating the supersaturation ratio, the nucleation rate drastically increased and the critical radius decreased exponentially. Particles formed at supersaturation 1.39 showed a monomodal distribution centered at 8.2 nm in Dynamic Light Scattering analysis. Comparable particle sizes were obtained in Transmission Electron Microscopy.     

Kinetics of precipitation of nickel ammonium sulphate hexahydrate from aqueous solutions

The precipitation of nickel ammonium sulphate [Ni(NH₄)₂(SO₄)₂·6H₂O] prepared by mixing of equimolar aqueous solutions of (NH₄)₂SO₄ and NiSO₄ has been studied at 25 °C. Precipitation induction periods and the number of crystals formed per unit volume have been determined experimentally as functions of supersaturation for values of S_{a, H} < 2.6. The mechanisms of nucleation and crystal growth are assessed by comparing the experimental results with theoretical predictions. In this system, heterogeneous nucleation and crystal growth are assessed by comparing the experimental results with theoretical predictions. In this system, heterogeneous nucleation appears to operate at S_{a, H} < 1.3, whereas at S_{a, H} > 1.6 crystals are generated predominantly by homogeneous nucleation and grow by a polynuclear mechanism. The interfacial tension of nickel ammonium sulphate crystals in contact with their supersaturated solution is estimated to be about 20 mJ/ m².     

Optical and dielectric studies on pure and Ni2+, Co2+ doped single crystals of bis thiourea cadmium chloride

Good quality single crystals of Ni²⁺, Co²⁺ ions doped Bisthiourea Cadmium Chloride (BTCC) are some of the excellent and efficient non‐linear optical materials grown from aqueous solution by slow evaporation method. The lattice parameters of the grown crystals are determined by single crystal X‐ray analysis. UV spectral analyses on these samples reveal the improved transparency of the doped crystals ascertaining the inclusion of metal ion in the lattice. FTIR spectral analysis carried out on the materials confirm the presence of functional groups. Dielectric measurements reveal that the dielectric constant of pure and doped crystals decreases with increase of frequency. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determination of nucleation kinetics of lovastatin in acetone solution

The metastable zone widths of lovastatin in acetone solution were determined at different temperatures, cooling rates and initial concentrations by polythermal method. It decreases with the increase of temperature and initial concentration, increases with the increase of cooling rate. The induction periods of lovastatin in acetone solution were also investigated as a function of supersaturation ratios. The crystal‐liquid interfacial tension, thus the fundermental nucleation parameters including Gibbs free energy change for the formation of critical nucleus, radius of critical nucleus and number of molecules in the critical nucleus have been gotten based on the classical homogeneous nucleation theory. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The mechanism of the formation of enantiotropic polymorphs of carisbamate in solution crystallization

The nucleation kinetics, as a function of supersaturation level, was studied for carisbamate, a polymorphic crystalline compound, in methanol, ethanol, 2-propanol and water. The induction times in nucleation kinetics varied markedly with respect to relative supersaturation in the range 1.3–2.3. At the same relative supersaturation, the induction time for carisbamate in methanol is the shortest, increasing in order from ethanol, 2-propanol, and then water. The interfacial tensions γ between carisbamate and methanol, ethanol, 2-propanol, and water were estimated from their induction times based on nucleation theory and were found to be about 3.6, 4.1, 4.5, and 5.7 mJ/m², respectively. These values were of same order of magnitude as those obtained from solubility data. The equation that displays the influence of interfacial tension, supersaturation and temperature on crystallization kinetics was derived, and found to be consistent with experimental observations. The mechanism of enantiotropic polymorphism for carisbamate in the solvents is illustrated. Using interfacial tension values determined for single solvents, the polymorphic form resulting from crystallization in mixed and pure solvent systems could be predicted with good accuracy.     

γ-氨基丁酸晶体成核动力学、晶体生长及热力学性质研究

本文研究了γ-氨基丁酸的热力学及成核动力学性质.对γ-氨酪酸晶体的热力学性质进行研究,γ-氨基丁酸的差示扫描量热研究表明:γ-氨基丁酸的熔点为190.6 ℃,熔化焓为-343.4 J/g.测定了不同温度下γ-氨基丁酸在水中的溶解度及不同过饱和度下的诱导期.结果表明:γ-氨基丁酸的诱导期随着过饱和度的增加而降低.通过经典成核理论计算了固-液表面张力、成核自由能和临界成核半径.     

Single crystal growth and properties of semiorganic nonlinear optical L‐arginine hydrochloride monohydrate crystals

L‐arginine hydrochloride monohydrate (LAHCl.H₂O) has been synthesized and single crystals have been grown from its aqueous solution by slow evaporation and slow cooling methods. The solubility of the material was measured at various temperatures and bulk crystals of size 26×13×11 mm³ have been grown by optimizing the growth parameters. The grown crystals have been subjected to single crystal XRD studies to confirm the structure and to estimate the lattice parameters. FTIR analysis indicate the mode of vibrations of different molecular groups present in LAHCl and confirm the protonation of guanidyl, amino groups and deprotonation of COO^‐ groups. UV‐Vis transmission spectrum revealed the linear optical properties of the grown crystals with a transparency of 65% over the entire visible range upto 300 nm. Thermal behavior of the grown crystal was investigated from DTA and TGA measurements. Dielectric studies have been carried out on the grown crystals. Kurtz and Perry powder SHG technique confirms the NLO property of the grown crystal. The SHG efficiency of LAHCl was found to be 0.38 with respect to KDP. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and Characterization of a New Nonlinear Optical Crystal: Bis Thiourea Zinc Chloride

Bis Thiourea Zinc Chloride (BTZC) a new semiorganic nonlinear optical material has been synthesized. The solubility studies have been carried out in the temperature range 30°‐ 55°C. Single crystals of BTZC have been grown by slow evaporation of saturated aqueous solution at room temperature. The lattice parameters of the grown crystals have been determined by single crystal X‐ray diffraction technique. The UV‐Vis‐NIR transmittance spectrum has been recorded in the range 200‐2000 nm. The FT‐IR spectrum has been recorded in the range 400‐4000 cm^‐1 and the spectral bands have been compared with similar thiourea complexes.     

Supersaturation Dependence of Induction Period for Three-Dimensional Nucleation of Substances from Aqueous Solutions Revisited

The available experimental data on the supersaturation dependence of induction period for the nucleation of some compounds crystallizing from solutions are analysed from the standpoint of the classical nucleation theory and the mononuclear and polynuclear models in order to obtain values of interfacial tension and pre-exponential factor for homogeneous and heterogeneous nucleation. It was found that the contributions of homogeneous and heterogeneous nucleations to the experimental data can be separated by assuming that the nucleation rates due to the two nucleations are additive and that the polynuclear model in combination with the separated contribution of homogeneous nucleation to the induction period gives a satisfactory agreement between theoretical estimates and experimental values of the interfacial tension and the pre-exponential factor.     

Optical and microhardness studies of semiorganic nonlinear optical material: L‐ histidine tetrafluoroborate

L‐histidine tetrafluoroborate (L‐HFB) a semiorganic nonlinear optical material has been synthesized in aqueous solution at 50°C and characterized by FT‐IR and FT‐Raman spectroscopy studies. The solubility was determined in different solvents such as water, methanol and water mixture of methanol. The single crystals with dimensions 15x12x3 mm³ were grown by slow evaporation method within four weeks with approximate growth rate of 0.25 mm/day. The grown crystals have been subjected to single crystal X‐ray diffraction studies to determine the unit cell dimensions and morphology. The Kurtz powder second harmonic generation test shows that the compound is a potential candidate for frequency conversion. The refractive index has been measured using He‐Ne laser. The microhardness test was carried out and the load dependence hardness was observed. The material has a wide transparency in the entire visible region. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigation of nucleation kinetics and crystal defects of HMX

The nucleation kinetics of HMX (cyclotetramethylene tetranitramine, C₄H₈N₈O₈) in γ‐butyrolactone was studied in cooling process by induction time method. The laser scattering method was used to measure the solubility data and metastable region of HMX in γ‐butyrolactone. The induction time was measured over a range of supersaturation at different temperatures. Then, the nucleation mechanism of HMX in γ‐butyrolactone was investigated by analysis the relationships between induction time and supersaturation. The results indicated homogeneous nucleation dominated at high supersaturation of S >1.35, while the heterogeneous nucleation dominated at low supersaturation of S < 1.35. The values of interfacial tension at different final temperatures were calculated to indicate the ability of HMX to be crystallized. The growth mechanism of HMX was investigated by the data fitting applying different growth mechanism models and identified as two‐dimensional nucleation‐mediated (2D) growth. Finally, the effects of supersaturation and temperature on the crystal defects were analyzed based on the nucleation kinetics. When the temperature is below 303.15K, homogeneous nucleation dominated the nucleation process at higher supersaturation. Fine HMX crystals with more defects were produced. On the contrary, heterogeneous nucleation mechanism dominated at lower supersaturation. large regular HMX crystals with fewer defects were formed when the temperature is above 318.15K.