The influence of inhibitors on the growth of barium sulfate crystals in suspension: Scale prevention (II)

The inhibiting influence of four organic bisphosphonates with different substituents on the growth rate of barium sulfate crystals, suspended in a supersaturated solution, has been investigated. The growth process has been studied conductometrically. Plots of both the relative supersaturation versus time and the mean linear rate versus the growth affinity have been given. — The results have been interpreted using a hypothesis, stating that growth inhibition occurs due to simultaneous coordination of the cations and hydrogen bonding of the anions at the active growth spots on the crystal surface.     

Studies on epitaxial growth of organic compounds on sucrose by the fourier transform method (I). On crystal growth of the participants

Epitaxial growth of organic compounds on sucrose crystals has been observed. In any case two-dimensional lattice analogies exist. The structural relations are, as a rule, unknown. In the present first part crystal growth of the participants was investigated. Equilibrium and growth forms of host (sucrose) and guest crystals (β-succinic acid, hexachlorobenzene, anthraquinone, isatin) have been determined by the Fourier transform method. The growth polyhedra fully correspond to the experimental observations.     

Growth of the New Infrared Nonlinear Optical Crystal DCNP

This paper reports on the growth of 3-(1,1-dicyanothenyl)-1-phenyl-4,5-dihydro-1 H-pyrazole (DCNP) crystals in dimethylformamide. The effect of different solvents on the growth of DCNP has been investigated. Dimethylformamide was found to be a good solvent, Transparent DCNP single crystals were grown from this solvent. They are a promising infrared nonlinear material.     

Microstructures of gel-grown ammonium hydrogen tartrate single crystals

Single crystals of ammonium hydrogen tartrate (AHT) have been grown in silica gels by employing the controlled reaction between ammonium chloride and tartaric acid. Transparent AHT crystals upto 24 × 4 × 3 mm³ in size have been grown at room temperature. Optical and electron-optical studies have been made on the various surface structures of {010} faces of the grown crystals. A variety of growth striations and growth hillocks have been observed. Growth layers modified by the presence of misaligned microcrystals have been illustrated. It has been suggested that two-dimensional nucleation, spreading and pilling up of growth layers is mainly responsible for the growth of these crystals and the implications are discussed.     

Crystal growth of calcium oxalate induced by the extracts of Semen Plantaginis and Folium Pyrrosiae

The crystallization of calcium oxalate (CaOxa) in aqueous solutions of the extracts of Semen Plantaginis and Folium Pyrrosiae has been investigated, focusing on the inhibition mechanism of some herbs on stone formation. It has been shown that in the presence of extracts of above two herbs, calcium oxalate dihydrate (COD) crystals with typical morphologies of tetragonal bipyramids were obtained. This suggests that the extracts of Semen Plantaginis and Folium Pyrrosiae can promote the formation of thermodynamically unstable COD, and inhibit the formation of calcium oxalate monohydrate (COM), a major component of urinary stone. The formation mechanism of COD crystals induced by Semen Plantaginis and Folium Pyrrosiae is also discussed, indicating that the bioorganic molecules in the extracts of the herbs can induce the nucleation and growth of COD crystals. This study can help us make clear the inhibition mechanism of some herbs on stone formation that is in favor of the prevention and treatment of urolithiasis. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The growth kinetics of barium sulphate crystals in suspension: Scale prevention (I)

The growth process of barium of sulfate crystals suspended in a supersaturated solution has been studied conductometrically. The mean linear rate R̄ has been plotted as a function of the growth affinity — Δμ/RT. A first attempt has been made to fit the experimental growth data in the highest supersaturation range with surface nucleation models.     

Growth of large single crystals of stearic acid from solution

The growing of large single crystals of stearic acid (CH₃(CH₂)₁₆COOH), one of the saturated fatty acids, from organic solutions is reported. There are two parts in this experimental investigation; (1) to clarify the relationship between polymorphism of stearic acid having three modifications, namely, the A-form (orthorhombic), the B- and C-forms (monoclinic) and the growth conditions in the case of solution growth, because this complicated relationship has apparently made it very difficult to obtain large single crystals, (2) to produce large single crystals of stearic acid under the optimum growth conditions according to part (1). As a result large single crystals of stearic acid more than 8 × 8 mm² in area of the B- and C-modifications were successfully obtained. The values of long spacing, the crystal habit and the cleavage plane are also reported.     

A detailed study of gold single crystal growth in a silica gel

Gold single microcrystals have been fabricated by electrochemical growth in a silica gel. Structural characterization of the single crystals by backscatter electron diffraction showed a preferred orientation of Au (1 1 1) and a minor orientation of Au (1 0 0). In addition, the influence of additives on the nucleation and growth of gold microcrystals has been studied. It was found that the inclusion of chemical additives in the growth solutions altered the characteristics of the gold crystals. Possible mechanisms for nucleation and growth of these crystals are discussed.     

Studies on Epitaxial Growth of Organic Compounds on Sucrose by the Fourier Transform Method (II). Iso- and Heteroepitaxy

Iso-epitaxial growth (twinning, parallel growth) of sucrose, β-succinic acid, anthraquinone and isatin can be explained by a good fit of the energetic structures of both partners. The symmetry operations result from the pseudo-symmetries of the reciprocal crystals. In all cases possible planes favoured for the formation of twins or parallel grown individuals can be predicted. Heteroepitaxial growth of β-succinic acid, hexachlorobenzene, anthraquinone and isatin on (100)-oriented sucrose has been observed. It is possible to explain the growth mechanisms by symmetry considerations of the energetic structures.     

Synthesis,growth and characterization of single crystals of pure and thiourea doped L‐glutamic acid hydrochloride

L(+)Glutamic acid hydrochloride [HOOC (CH₂)₂CH(NH₂) COOH·HCl], a monoamino dicarboxylic acid salt of L‐Glutamic acid was synthesized and the synthesis was confirmed by FTIR analysis. Solubility of the material in water was determined. Pure and Thiourea doped L‐Glutamic acid hydrochloride crystals were grown by low temperature solution growth using solvent evaporation technique. XRD, UV‐Vis‐NIR analyses were carried out for both pure and thiourea doped crystals. The crystals were qualitatively analyzed by EDAX analysis and the presence of thiourea was confirmed. The cell parameters of L‐Glutamic acid hydrochloride have been determined as a = 5.151 Å, b = 11.79 Å, c = 13.35 Å by X‐ray diffraction analysis and it crystallizes in orthorhombic space group P2₁2₁2₁. UV‐Vis‐NIR spectra analysis showed good optical transmission in the entire visible region for both pure and doped crystals. Micro hardness of both pure and doped crystals has been determined using Vickers micro hardness tester. The SHG efficiencies of both pure and doped crystals were determined using Kurtz powder test and pure L‐Glutamic acid hydrochloride crystal was found to possess better efficiency than thiourea doped L‐Glutamic acid hydrochloride crystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the incorporation mechanism and distribution mode of impurities in potassium acid phthalate crystals grown from aqueous solutions

Mechanism of impurity structure formation in crystals grown from aqueous solutions has been studied on the example of potassium acid phtalate (abbreviated hereafter as KAP) single crystals. Gold decoration technique at an electronmicroscopic scale has been applied to the study of the distribution of uncontrolled impurities on KAP cleavage face (010) after 10, 20 and 30 days of growth, taking into consideration different growth rates in 〈001〉 and 〈001 〈 directions. A technique for visualization of impurities in water, based on the adsorption of these impurities by the surface of amorphous film of nitrocellulose (parlodion) and the vacuum decoration with gold of these impurities, has been developed. Differences in the impurity structure of KAP regions located in 〈001〉 and 〈001〉 directions from the seed have been established. In 〈001〉 direction after 20 days of growth impurity assemblies 0.1—0.4 μm in size are revealed, and in 〈001〉 direction heterogeneous impurity structure is revealed only after 30 days of growth. The real (impurity) structure of KAP outside impurity assemblies is quite homogeneous and is the same throughout the whole crystal volume, the impurities incorporating mainly into complex active centres. From comparison of the changes in time of the impurity structure of water used for crystallization solutions and the impurity structure of KAP crystals a conclusion is made that the impurity structure of crystals is “programmed” in the impurity structure of crystallization solutions which regularly changes with time, i. e. impurities from different kinds of assemblies which are selectively adsorbed by the growing crystal faces. The role of the adjacent to the growing face interfacial layers which control the growth rate and have a complex impurity structure is stressed.     

Strength of Crystals of Small Dimensions and their Triboluminescence

Stress-dependence of triboluminescence (TBL) in uranyl nitrate, tartaric acid and other nine crystals has been studied with the help of a new technique of crushing the crystals. As the appearance of TBL needs the creation of new surfaces in a crystal, the minimum stress at which TBL appears has been taken to be the fracture-strength of the crystal. The value of the fracture-strength and stress coefficient of binding energy determined from TBL measurements are found to be of correct order. It has been found that the rate of rise of TBL intensity with stress is higher for those crystals which have less value of the fracture-strength. The fracture strength (σ_f) is found to be higher for those crystals which have less value of stress coefficient of binding energy (β) and the product of σ_f and β is higher for those crystals which have higher melting point. It has been shown that the rate of rise of TBL intensity with stress decreases at higher values of stress due to strain hardening in the crystals.     

Organic inclusion complex strategy for designing nonlinear optical crystals for ultraviolet applications

Based on Molecular Engineering and Crystal Engineering concepts, a new method for designing nonlinear optical (NLO) crystal materials, the Organic Inclusion Complex (OIC) method has been demonstrated. In defining an appropriate optical transparent range with respect to the Molecular Engineering method, small organic molecules containing n-π conjugation were selected as “second order harmonic generation (SHG)-active units”(guests). Together with the Crystal Engineering method, chiral molecules were used as “molecular scaffolding” (hosts) to combine with the “SHG-active units” by hydrogen bonds. The former can provide a nonlinear optical effect. The latter leads to the OIC with a noncentrosymmetric structure and are expected to enhance the macroscopic nonlinearity in a synergistic mode of guest and host by inducing the guest molecular dipole alignment as well as other properties, such as thermal stability, mechanical strength and ease of growth. Here, we report two new inclusion complex crystals, urea-(d)tartaric acid (UDT) and urea-(dl)tartaric acid (UDLT) (here, d means dextral and dl means racemic). UDT and UDLT crystals belong to P2,2,2, and P2, space group, respectively. Bulk size crystals with high optical quality were successfully obtained from aqueous solution by using a temperature-lowering method. The experimental results show that these two crystals demonstrate higher NLO effects and shorter wavelength cutoff.     

Crystallization of the E. coli polyamine-induced protein: a novel procedure based on the concept of ionic strength reducers

Nucleation and growth of macromolecular crystals occur in supersaturated solutions the properties of which depend on numerous parameters that influence macromolecular solubility. Detailed knowledge of the effects of those parameters is essential for crystallization. The concept of the so-called “ionic strength reducers” provides insight into the changes of solubility induced by organic solvents and hydrophilic polymers in aqueous electrolytic solutions. A simple and efficient procedure is presented which exploits the properties of ionic strength reducers in the crystallization of proteins. Using this procedure in the crystallization of the E.coli polyamine-induced protein, superior crystals compared to conventional techniques have been obtained. The procedure combines microseeding with dialysis techniques and is applicable to other proteins, particularly in cases where conditions favoring both for nucleation and growth cannot be found, or in cases where excessive nucleation leads to the growth of a large number of very small crystals.     

Growth micromorphology of stearic acid crystals

Growth and micromorphology of stearic acid crystals grown by solvent evaporation method has been studied. The effect of the solvent and the rate of evaporation of the solvent on the growth micromorphology has been investigated. The formation of spherulitic growth features, rhombic platelets of B- and C forms having growth spirals associated with solution channels and twinned crystals involving B-B, C-C, and B-C forms is observed. The complexity of the twins involving the B- and C forms is discussed.     

Synthesis,bulk growth,polarizability and nonlinear optical properties of γ‐glycine single crystals

The role of sodium acetate, sodium nitrate, sodium hydroxide and malonic acid as additives in assisting the nucleation of γ‐polymorph from solution has been investigated. For the first time large dimensional bulk single crystals of γ‐glycine have been grown at the optimized concentration of the additives by the top seeded slow cooling technique. The bulk growth of single crystals elucidates well the unidirectional growth characteristics and the existence of merohedral twinning in γ‐ glycine. Polarizability, plasmon energy and Fermi energy has been evaluated for the first time for γ‐glycine single crystals based on an analytical approach. Structural affirmation of the nucleated polymorph has been carried out by Powder x‐ray diffraction and the thermal characteristics of the nucleated polymorph are well revealed by Differential Scanning Calorimetry. The non linear optical characteristics of γ‐glycine studied by Kurtz and Perry technique revealed increased SHG efficiency with the highest of about 2.2 in the presence of malonic acid compared to the standard Potassium dihydrogen orthophosphate (KDP).     

Ⅰ类高氘DKDP晶片性能研究

受到晶体尺寸以及非线性光学性能的影响,目前可供选择的非线性晶体非常有限。DKDP晶体作为传统大尺寸光电材料,在光参量啁啾脉冲放大(OPCPA)装置中得到了应用。高氘化的DKDP晶体有更好的光学性能,然而生长出高氘化DKDP晶体对生长环境等有更加严格的要求。本文通过改良的原料合成罐以及生长槽,采用点籽晶快速生长法成功生长出高氘DKDP晶体。按照Ⅰ类(θ=37.23°, φ=45°)切割方式制备样品,并对其氘含量、透过率、光学均匀性以及晶体激光损伤阈值进行测试。实验结果表明,晶体的平均氘含量达到98.49%,在可见-近红外波段下具有较宽的透过波段和较高的透过性能。R-on-1的测试结果显示,在3 ns、527 nm条件下,DKDP晶体的激光损伤阈值达到了19.92 J/cm²。晶体光学均匀性均方根达到了1.833×10^-9,表明晶体具有良好的光学均匀性。     

Investigations of the growth mechanism and morphology of silver crystals grown electrolytically in gels

Gel medium has been used for the electrolytic growth of silver dendrites and single crystals of a variety of morphological features and forms. Microtopographic studies of the crystals have been carried out using optical and scanning electron microscopes. Some unusual growth surface morphologies have been observed. The surfaces of some of the crystals have a high degree of perfection. Sufficient experimental evidences are obtained for the striated growth of crystals and twin plane re-entrant edge (TPRE] mechanism of growth. The formation of tertiary three-dimensional (T3D) dendrites and dendrites with obliquely forward and backward branchings at different stages of growth have been investigated.     

Effects of meniscus on the directional growth of potassium niobate single crystals

The study of meniscus effects on the directional growth of single crystals of potassium niobate (KNbO₃) with a [110]_pc oriented seed by the top-seeded-solution-growth technique has been described. The directional growth of KNbO₃ single crystals has been illustrated for different crystallographic orientations of the crystal. Experimental results show that the shape of the solution flux meniscus, which is determined by a number of growth parameters, has a significant effect on growth rates on different 100_pc, 010_pc and 001_pc type surfaces. Findings based on this work enable one to select a dominant growth direction and hence to engineer the geometrical shaping of resultant KNbO₃ single crystals through careful control of growth parameters. Maximum crystal dimensions for the grown KNbO₃ along [100]_pc and [001]_pc achieved in this work are 34.0 and 31.2 mm, respectively.