Crystal Growth Time Research Articles

Step-like crystallization of BEA zeolite: Accumulation of oligomeric species in liquid phase followed by the conversion of solid phase to crystals

In this study, the hydrothermal reactions of the synthesis mixtures of BEA zeolite and the synthesis cakes prepared by the filtration of the synthesis mixtures were investigated. The crystallization curves constructed based on the XRD patterns and the SEM images of the solid phases recovered at different reaction times exhibited step-like curves characterized by very long induction periods (70 h for the synthesis mixtures and 37 h for the synthesis cakes) and a short crystal growth time (4 h for both) at 150 °C. The higher concentration of the reactants in the synthesis cakes than in the synthesis mixture quickly generated more nuclei, consequently forming smaller crystals. In order to elucidate the changes occurring in the course of the hydrothermal reaction, a total of seven additional analysis techniques including 29Si MAS NMR spectra, TEM, IR, and UV–Vis spectra were applied to the solid and liquid phases recovered at various times. No significant changes were observed in the solid phases during the induction period in terms of the crystallinity, chemical environment of silicon atoms, porous properties, capture state of structure-directing agent, and the IR bands of the hydroxyl groups, whereas the contents of oligomeric aluminosilicates increased in the liquid phases. Based on these analyses, the long induction periods were required for sufficient accumulation of the building blocks, and the blocks rapidly assembled to form BEA zeolite crystals in the subsequent growth stage, resulting in the step-like crystallization curves.

Zeolite LTA synthesis: Optimising synthesis conditions by using the modified sequential simplex method

This paper presents research concerning the simultaneous effect of the most influential synthesis variables in the preparation of Zeolite LTA. The simplex method was used for ascertaining optimal synthesis conditions, where the relative crystallinity (regarding a commercial sample) of synthesised zeolite was defined as response function. Crystallinity was measured by X-ray diffraction. Optimum conditions were found after 24 trials, giving 95.4% relative crystallinity and Na2O/SiO2=2.58, SiO2/Al2O3=1.45 and H2O/Na2O=46.92 molar ratios; 11.7 h crystal growth time, 6.1 h crystallisation time (reaction) and 78oC reaction temperature were found to be optimal synthesis conditions. A computer programme for simulating a zeolite phase diagram was designed to verify whether the molar ratios indicated by the optimisation algorithm were leading to the desired zeolite type. The results were compared to those in previous work where the fixed factor method was used.

Comparison of Growth Kinetic of Urinary Crystallites from Patients with Calcium Oxalate Stones with that from Healthy Subjects

The differences of growth kinetic of urinary crystallites from patients with CaOxa stones and healthy subjects were compared. With the increase of crystal growth time (t), the size of urinary crystallites from patients increased constantly from 10±9 μm att=1 h to 50±45 μm att=72 h, but the number of urinary crystallites decreased gradually from 1820±610 ind./mm2att=1 h to 220±98 ind./mm2att=72 h, indicating that the formation process of crystallites in lithogenic urine was ascribed to growth control. In contrast, for healthy subjects, the number of crystallites increased from 1650±850 ind./mm2att=1 h to 1800±830 ind./mm2att=72 h. However, the particle size was slowly increased from 7±5 μm att=1 h to 14±13 μm att=72 h, while the sizes of most urinary crystallites were still less than 20 μm, indicating that the growth process of crystallites in healthy urine was dominated by nucleation control. The differences mentioned above are mainly attributed to that both the concentration and the activity of the inhibitors in healthy urine were higher than those in lithogenic urine, and the inhibitors in healthy urine can inhibit the growth and aggregation of urinary crystallites more effectively. This result can help to elucidate the renal-calculi formation mechanism.

Study of Gel Growth Cobalt (II) Oxalate Crystals as Precursor of Co3O4 Nano Particles

Crystal growth of cobalt (II) oxalate in silica gel at room temperature as precursor of Co3O4 nano particles has been studied. Specifically, this project is focusing on the use of two different reaction tube types toward crystallization of cobalt (II) oxalate in gel. The gel was prepared at pH 5 by reacting sodium metasilicate solution with dilute nitric acid (for U-tube) and oxalic acid (for straight tube), with gelling time of 4 days and crystal growth time of 8 (for straight tube) and 12 (for U-tube) weeks. Result shows that pink crystalline powder was directly formed using straight tube method. The use of different solvents in straight tube method affects crystallization and could delay direct precipitation of the product. In contrast, bigger and better shape of red block crystal was yielded from U-tube method; however, longer growth time was needed. FTIR studies suggest that both growth method produces identical compound of hydrated cobalt (II) oxalate. © 2013 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Thermal properties of oxide glasses

Glasses with the composition Li2O·2SiO2·nTiO2 and Li2O·2SiO2·nZrO2, where n=0, 0.03, 0.062, 0.1, were prepared and the onset and peak temperatures have been determined by DTA. From these characteristic temperatures, the kinetic parameters describing the nucleation and crystal growth have been obtained by isoconversional methods. The kinetic parameters have been used for the calculation of nucleation and crystal growth times for individual glasses so determining the order of glass stability at reheating. The stability of glasses increases with the content of TiO2 or ZrO2 where the increase is higher for ZrO2. Within the concentration range under study, the increase of both times with the metal oxide concentration is quadratic. It has been discussed that the crystallization kinetics does not obey the Arrhenius law and, therefore, when using the evaluation methods based on this law, the results should not be extrapolated outside the temperature range of the measurements.

Study of Gel Growth Cobalt (II) Oxalate Crystals as Precursor of Co3O4 Nano Particles

Crystal growth of cobalt (II) oxalate in silica gel at room temperature as precursor of Co3O4 nano particles has been studied. Specifically, this project is focusing on the use of two different reaction tube types toward crystallization of cobalt (II) oxalate in gel. The gel was prepared at pH 5 by reacting sodium metasilicate solution with dilute nitric acid (for U-tube) and oxalic acid (for straight tube), with gelling time of 4 days and crystal growth time of 8 (for straight tube) and 12 (for U-tube) weeks. Result shows that pink crystalline powder was directly formed using straight tube method. The use of different solvents in straight tube method affects crystallization and could delay direct precipitation of the product. In contrast, bigger and better shape of red block crystal was yielded from U-tube method; however, longer growth time was needed. FTIR studies suggest that both growth method produces identical compound of hydrated cobalt (II) oxalate. © 2013 BCREC UNDIP. All rights reserved Received: 25th October 2012; Revised: 30th November 2012; Accepted: 5th December 2012 [ How to Cite : Y.P. Prananto, M.M. Khunur, D.T. Wahyuni, R.A. Shobirin, Y.R. Nata, E. Riskah, (2013). Study of Gel Growth Cobalt (II) Oxalate Crystals as Precursor of Co3O4 Nano Particles. Bulletin of Chemical Reaction Engineering & Catalysis , 7 (3): 198-204. (doi:10.9767/bcrec.7.3.4066.198-204)] [ Permalink/DOI : http://dx.doi.org/10.9767/bcrec.7.3.4066.198-204 ] View in |

Energetic Coupling between an Oxidizable Cysteine and the Phosphorylatable N-Terminus of Human Liver Pyruvate Kinase

During our efforts to characterize the regulatory properties of human liver pyruvate kinase (L-PYK), we have noted that the affinity of the protein for phosphoenolpyruvate (PEP) becomes reduced several days after cell lysis. A 1.8 Å crystallographic structure of L-PYK with the S12D mimic of phosphorylation indicates that Cys436 is oxidized, the first potential insight into explaining the effect of "aging". Interestingly, the oxidation is only to sulfenic acid despite the crystal growth time period of 2 weeks. Mutagenesis confirms that the side chain of residue 436 is energetically coupled to PEP binding. Mass spectrometry confirms that the oxidation is present in solution and is not an artifact caused by X-ray exposure. Exposure of the L-PYK mutations to H₂O₂ also confirms that PEP affinity is sensitive to the nature of the side chain at position 436. A 1.95 Å structure of the C436M mutant of L-PYK, the only mutation at position 436 that has been shown to strengthen PEP affinity, revealed that the methionine substitution results in the ordering of several N-terminal residues that have not been ordered in previous structures. This result allowed speculation that oxidation of Cys436 and phosphorylation of the N-terminus at Ser12 may function through a similar mechanism, namely the interruption of an activating interaction between the nonphosphorylated N-terminus with the nonoxidized main body of the protein. Mutant cycles were used to provide evidence that mutations of Cys436 are energetically synergistic with N-terminal modifications, a result that is consistent with phosphorylation of the N-terminus and oxidation of Cys436 functioning through mechanisms with common features. Alanine-scanning mutagenesis was used to confirm that the newly ordered N-terminal residues were important to the regulation of enzyme function by the N-terminus of the enzyme (i.e., not an artifact caused by the introduced methionine substitution) and to further define which residues in the N-terminus are energetically coupled to PEP affinity. Collectively, these studies indicate energetic coupling (and potentially mechanistic similarities) between the oxidation of Cys436 and phosphorylation of Ser12 in the N-terminus of L-PYK.

Energetic Coupling between an Oxidizable Cysteine and the Phosphorylatable N-Terminus of Human Liver Pyruvate Kinase

During our efforts to characterize the regulatory properties of human liver pyruvate kinase (L-PYK), we have noted that the affinity of the protein for phosphoenolpyruvate (PEP) becomes reduced several days after cell lysis. A 1.8 Å crystallographic structure of L-PYK with the S12D mimic of phosphorylation indicates that Cys436 is oxidized, the first potential insight into explaining the effect of "aging". Interestingly, the oxidation is only to sulfenic acid despite the crystal growth time period of 2 weeks. Mutagenesis confirms that the side chain of residue 436 is energetically coupled to PEP binding. Mass spectrometry confirms that the oxidation is present in solution and is not an artifact caused by X-ray exposure. Exposure of the L-PYK mutations to H₂O₂ also confirms that PEP affinity is sensitive to the nature of the side chain at position 436. A 1.95 Å structure of the C436M mutant of L-PYK, the only mutation at position 436 that has been shown to strengthen PEP affinity, revealed that the methionine substitution results in the ordering of several N-terminal residues that have not been ordered in previous structures. This result allowed speculation that oxidation of Cys436 and phosphorylation of the N-terminus at Ser12 may function through a similar mechanism, namely the interruption of an activating interaction between the nonphosphorylated N-terminus with the nonoxidized main body of the protein. Mutant cycles were used to provide evidence that mutations of Cys436 are energetically synergistic with N-terminal modifications, a result that is consistent with phosphorylation of the N-terminus and oxidation of Cys436 functioning through mechanisms with common features. Alanine-scanning mutagenesis was used to confirm that the newly ordered N-terminal residues were important to the regulation of enzyme function by the N-terminus of the enzyme (i.e., not an artifact caused by the introduced methionine substitution) and to further define which residues in the N-terminus are energetically coupled to PEP affinity. Collectively, these studies indicate energetic coupling (and potentially mechanistic similarities) between the oxidation of Cys436 and phosphorylation of Ser12 in the N-terminus of L-PYK.

Structural Scheme of Information System for Defect Engineering of Dislocation-free Silicon Single Crystals

The article is devoted to solving the problem of automation of the calculations and analysis of the defect structure of dislocation-free silicon single crystals. As a result, of development of information system kinetics of interaction of point defects at any time of crystal growth or heat treatments can be investigated. The solution to this problem will allow to simulate and to grow crystals with a predetermined defect structure, as well as manage it in the processes in subsequent technological treatments. The article presents the main aspects of information system for defect engineering of the dislocation-free silicon single crystals. The software structure and technology implementation has been considered. Structural scheme<b> </b>of information system was presented. It is assumed that with the help of this information system will be possible to control the defect structure at various stages of manufacture of devices based on silicon.

Crystallization of amorphous silicon thin-film on glass substrate preheated at 650 °C using Xe arc flash of 400 μs

Experimental and theoretical investigations on flash lamp annealing (FLA) of amorphous silicon (a-Si) film on glass were carried out with a view to practical applications in large-window display industries. A Xe arc flash lamp of 950mm in length and 22mm in bore diameter was applied with nominal input voltage of 7kV and flash duration of 400μs. Prior to the annealing process, the specimen for FLA was preheated at 650°C, which was very close to the service temperature of the glass specimen used in this study. By employing a focusing elliptic reflector, maximum light energy density of up to 8.4J/cm2 could be attained with an active exposure width of 2cm. Crystallization of a-Si could be achieved in solid-phase by applying a flash beam with light density of at least 5J/cm2, and its phase-transition characteristics that varied with energy densities could be explained by theoretically estimated temperature fields. Electron microscopy observations confirmed that solid-phase crystallization preceded melting of a-Si due to relatively long flashing (heating) duration of 400μs, which was comparable to solid-phase crystal-growth times at elevated temperatures.

Synthesis and characterization of the CAT's eye-shaped CoO@SiO2 nanoshell aqueous colloids

The “cat's eye”-shaped CoO(core)@SiO2(shell) nanoshell was prepared by the reverse microemulsion method. The core cobalt oxide nanorods with controlled anisotropy were obtained by thermal decomposition of Co-(oleate)2 precursor. The Co-(oleate)2 precursor was synthesized by a simple complex reaction of cobalt chloride hexahydrate and sodium oleate molecules. The aspect ratio of cobalt oxide nanocrystals was controlled from 1.3 to 10.5 by changing the reaction conditions, such as the heating rate (0.5, 1.0, 2.0 and 4.0°C/min) and crystal growth time (30, 60 and 120min), during the reaction. The SiO2 coating on the surface of the core cobalt oxide nanorods was produced by hydrolysis and a condensation reaction of tetraethyl orthosilicate (TEOS) in the water phase of the reverse microemulsion system. The physicochemical characterizations of the obtained CoO@SiO2 nanoshell material were performed by X-ray diffraction (XRD) measurements, Fourier transform-infrared spectroscopy (FT–IR) and high resolution-transmission electron microscopy (HR–TEM).

Crystal Growth of Diazabicyclo[2.2.2]octane-1,4-diium dichromate

The crystal growth of (C6H14N2)[Cr2O7], consists of a diazabicyclo[2.2.2]octane-1,4-diium cation and a discrete dichromate anion, in solution has been determined under the influence of various factors. Four factors, which influence the crystal size, crystal growth and nucleation, were chosen. These factors are concentration, temperature, type of solvent and method of crystallization. Taguchi design of experiments (DOE) method has been used for to plan a minimum number of experiments and optimization of crystallization processes. Crystallization of diazabicyclo[2.2.2]octane-1,4-diium dichromate with desirable particle size, shape and minimum time of crystal growth as performance characteristics were studied. The changes in the crystal growth habit were observed and could be explained by the differences in the morphology on the various photograph of this compound. Crystallization diazabicyclo[2.2.2]octane-1,4-diium dichromate with desirable particle size, shape and minimum time of crystal growth as performance characteristics were studied. The changes in the crystal growth habit were observed and could be explained by the differences in the morphology on the various photograph of this compound.

Seed loading effects on the mean crystal size of acetylsalicylic acid in a continuous‐flow crystallization device

AbstractThis study investigates the effects of seed loading on the mean crystal size of the model substance, acetylsalicylic acid, crystallized from ethanol in a continuously seeded tubular crystallizer. A hot, highly concentrated ethanolic acetylsalicylic acid solution was mixed with an acetylsalicylic acid‐ethanol seed suspension. Subsequent cooling of the slurry in the tubing promoted supersaturation and hence crystal growth. The tubular shape of the 15 m‐long crystallizer with an inner diameter of 2 mm enabled narrow residence time distributions of the crystals in the pipe and excellent temperature control in the radial direction and along the tubing. Crystals entering the crystallizer had both identical growth conditions in each section and about the same time for crystal growth. Narrow crystal size distributions were achieved with decreasing differences in the volume‐mean‐diameter sizes of the seed and product crystals as seed loadings increased. Decreasing the seed size had a similar effect as increasing the seed loading, since in that case the same amount of seed mass resulted in more individual seed particles. Altering the arrangement of the coiled crystallizer with respect to spatial directions (horizontal, vertical) did not lead to a significantly different outcome. All experiments produced considerably larger product crystals in comparison to the seeds despite relatively short crystallization times of less than 3 min. Moreover, product mass gains of a few hundred percent at a g/min‐scale were achieved. Similarities in product crystal samples taken at different times at the outlet of the crystallizer showed that steady‐state conditions were rapidly reached in the continuous flow crystallization device. (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Preservation of Garnet Growth Zoning and the Duration of Prograde Metamorphism

Chemically zoned garnet growth and coeval modification of this zoning through diffusion are calculated during prograde metamorphic heating to temperatures of up to 850°C. This permits quantification of how the preservation or elimination of zoning profiles in garnet crystals of a given size is sensitive to the specific burial and heating (P–T) path followed, and the integrated duration spent at high temperature (dT/dt). Slow major element diffusion in garnet at T < 600°C means that centimetre-scale zoning profiles may remain for >30 Myr at amphibolite-grade conditions, but small-scale (tens of micrometres) zoning features will be lost early in the prograde stage unless this is ‘rapid’ (⁠5 Myr for rocks reaching c. 600°C). Calculations indicate that preservation of unmodified growth compositions in even relatively large (up to 3 mm diameter) pelitic garnet crystals requires prograde and exhumational events to be <10 Myr for rocks reaching c. 600°C. This timescale can be 5 Myr for garnet in rocks reaching 650°C or hotter. It is likely, therefore, that most natural prograde-zoned crystals record compositions already partially re-equilibrated between the time of crystal growth and of reaching maximum temperature. However, a large T–t window exists within which crystals begin to lose their growth compositions but retain evidence of crystal-scale zoning trends that may still be useful for thermobarometry purposes. The upper limit of this window for 500 μm diameter crystals can be as much as several tens of millions of years of heating to c. 700°C. Absolute re-equilibration timescales can be significantly different for garnet growing in different rock compositions, with examples of a granodiorite and a pelite given.

Assessing the viability of portable Raman spectroscopy for determining the geological source of obsidian

Obsidian is a naturally occurring volcanic silicate glass produced when highly viscous felsic lava cools rapidly through the glass transition temperature, not allowing sufficient time for crystal growth. Obsidian was a popular raw material in prehistory because its amorphous and isotropic nature means that little force is required to produce conchoidal fractures of predictable shapes and sizes and it is easily flaked or knapped into desired shapes. A class of obsidian artefacts known as ‘stemmed tools’ has been found in locations across lowland Papua New Guinea and has been roughly dated to the early and middle Holocene periods (ca. 10,000–3400 BP). The rarity of obsidian in the natural world, the large size, fragility, brilliance, and distinctive shapes of these objects, as well as their manufacture by craft specialists, suggest that the tools were highly valued in the past. This inter-disciplinary project aims to determine when and how prehistoric obsidian stemmed tools were used to structure social relations and if they defined status differences. This involves studying the history, typology, technology, function, and geological sources of the stemmed tools and comparing this information with other highly worked stone tools from the major obsidian sources of West New Britain and Manus. Raman spectroscopy and multivariate analysis have been previously used by the authors to discriminate between three major Pacific obsidian sources, an important first step in tracking the movement of stemmed tools through social networks. This paper assesses the viability of using a portable Raman spectrometer (EZRaman-i, 785 nm, ∼6 cm −1 spectral resolution) for identification of the geological source of obsidian through the comparison of spectra collected from 65 samples of known provenance using both a portable and laboratory-based instrument (Renishaw inVia, 785 nm, ∼1–2 cm −1 spectral resolution). The paper demonstrates that results achieved with the portable instrument are similar to those obtained with a laboratory-based instrument.

In situ measurement of erythromycin crystal size distribution by focused beam reflective measurement technology

AbstractMany factors such as temperature, solvent and water‐dosing rate have impact on erythromycin solventing‐out process. This article studies the water dosing effect on erythromycin solventing‐out process measured by focused beam reflective measurement technology. Our experiments showed that the overall number of nucleated particles went through an explosive increasing after the metastable zone. Followed by a slight decreasing, it reached a relative constancy for a long time. This suggests that earlier crystal nucleation can be induced with higher water dosing rate, nevertheless, it is the same amount of water dosed when the overall crystal number reached its peak during the explosive emergence of crystals. After the overall particle number climaxed, further extension of crystal growth time would not bring any significant increase in crystal size. Copyright © 2009 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Dispersity and growth kinetics of K2SO4 crystals in drops of an evaporating solution

Growth of K2SO4 crystals is studied in solution drops that have different initial heights and evaporate in different times. The dependences of the crystal size on the crystal growth time are obtained. The following three crystal growth modes are detected: rapid crystal growth in a supersaturated solution, a stop in the growth as a result of complete removal of supersaturation, and slow growth at a quasi-equilibrium solution concentration. The dispersities of the crystals that are retained at the bottom of the drop after complete evaporation of the solvent are calculated. A linear relation between the crystal dispersity and the reciprocal crystal growth time is revealed. The dispersity of K2SO4 crystals and the dispersity of the solid-solution dendrites in aluminum alloys are found to exhibit the same character of their dependences on the reciprocal crystal growth time.

Thermal properties of oxide glasses

Glasses with the composition Li 2 O·2SiO 2 ·nTiO 2 and Li 2 O·2SiO 2 ·nZrO 2 , where n=0, 0.03, 0.062, 0.1, were prepared and the onset and peak temperatures have been determined by DTA. From these characteristic temperatures, the kinetic parameters describing the nucleation and crystal growth have been obtained by isoconversional methods. The kinetic parameters have been used for the calculation of nucleation and crystal growth times for individual glasses so determining the order of glass stability at reheating. The stability of glasses increases with the content of TiO 2 or ZrO 2 where the increase is higher for ZrO 2 . Within the concentration range under study, the increase of both times with the metal oxide concentration is quadratic. It has been discussed that the crystallization kinetics does not obey the Arrhenius law and, therefore, when using the evaluation methods based on this law, the results should not be extrapolated outside the temperature range of the measurements.

The role of stress development and relaxation on crystal growth in glass

The role of internal stresses energy is usually neglected when crystallization kinetics is considered. The common argument is that stress is relaxing too fast to affect the process. In this article we develop a generalized formalism to describe steady-state growth kinetics in viscoelastic media. The residual stress energy results from interplay between the rate of stress development (due to the propagation of a crystal throughout the matrix) and rate of stress dissipation (due to relaxation of the viscous matrix). The degree to which the stress energy can relax depends on the ratio of τc/τr the characteristic time for crystal growth, τc, and the relaxation time, τr. The present results challenge the widespread fallacy that internal stresses relax too fast to affect crystal growth. Our model explains the often observed lack of agreement between the theoretical predictions (without taking into account the stresses energy development) and experimental data.

An Origin for Harrisitic and Granular Olivine in the Rum Layered Suite, NW Scotland: a Crystal Size Distribution Study

Dendritic crystal morphologies occur in a number of igneous rocks and are thought to originate from the rapid growth of crystals, yet many examples of dendritic morphologies are found in plutonic igneous rocks where cooling rates should be low. Results from crystal size distribution (CSD) measurements on harrisitic olivines from Rum, Scotland, combined with estimated olivine growth rates, suggest that the characteristic skeletal hopper and branching olivines of harrisitic cumulates that are up to centimetres long, may have exceptionally short crystal growth times (several hours to several hundreds of days).This, together with very low calculated nucleation densities for harrisitic olivine, supports the interpretation of harrisite being a disequilibrium texture, developed in response to supersaturation of the magma in olivine.We propose that this supersaturation arose through undercooling of thin picrite sheets emplaced along the Rum magma chamber floor, beneath cooler resident magma. It is envisaged that the picrite sheets were largely free of suspended olivine crystals. Coupled with the olivine-enriched composition of the melt and the increasing cooling rate, this allowed homogeneous nucleation of olivine to set in at deeper undercooling and greater olivine supersaturation than if there had been plentiful suspended olivines to act as heterogeneous nuclei. The enhanced supersaturation caused rapid growth of olivine once nucleation began, with skeletal and dendritic shapes. It is suggested that the observed, interlayered sequences of harrisite and cumulus peridotite found throughout the Rum Layered Suite are a result of multiple episodes of harrisite crystallization resulting from picrite emplacement that alternated with periods of crystal growth and accumulation in the main body of magma at lesser degrees of undercooling.