Crystal Formation Process Research Articles

Room temperature solution synthesis of hierarchical bow-like Cu2O with high visible light driven photocatalytic activity

Novel hierarchical bow-like Cu2O crystals were successfully synthesized via a facile room temperature solution reaction using PVP as a structure-directing agent in the presence of NaBH4. The morphology evolution of the hierarchical bow-like Cu2O crystals were observed to be tunable as a function of reaction parameters, such as the reaction time, the quality of PVP and the reaction temperature. The possible growth mechanism of hierarchical bow-like Cu2O crystals was investigated. It involves the formation process of the intermediate octahedra Cu2O crystals and subsequent oxidation–erosion process from octahedra to hierarchical bow-like Cu2O crystals. It was found that the octahedra Cu2O crystals are a necessary intermediate for the formation of the bow-like Cu2O crystals. The prepared hierarchical bow-like Cu2O crystals exhibited a higher photocatalytic activity for photodegradation of rhodamine B aqueous solution under visible light illumination than the other prepared Cu2O crystal samples with different morphologies (nanoparticles and octahedra) because of its large surface area and specific hierarchical bow-like structure.

Morphology evolution studies of boehmite hollow microspheres synthesized under hydrothermal conditions

Boehmite (γ-AlOOH) hollow microspheres were synthesized via a convenient hydrothermal route. To investigate its crystal form and morphology formation process, samples subjected to different reaction durations from 1 to 24h were prepared and characterized by techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscope (SEM). A spontaneous morphology evolution mechanism driven by Ostwald ripening and dissolution–renucleation was proposed based on the experimental facts. We think that systematically understanding and hereby manipulating the morphology evolution process will contribute to fabricate novel morphologies of the materials.

Preparation of Acicular γ-FeOOH by Liquid-Precipitation and Air-Oxidation Method

The acicular γ-FeOOH powders were synthesized by liquid-precipitation and air-oxidation method using FeCl2•4H2O as raw material. The affecting factors, which consist of alkaline ratio (OH-/Fe2+), reaction temperature and dropping speed of alkaline, were discussed. From the results, it was shown that when the ratio of OH-/Fe2+ was controlled in the range of 0.6-1.2 in the crystal seeds formation process, the pure phase of γ-FeOOH can be formed. When the ratio of OH-/Fe2+ was lower than 0.6, the γ-FeOOH crystal seeds could not be formed. While the ratio of OH-/Fe2+ was higher than 1.2, the phase of Fe3O4 appeared. According to the principle of chemical kinetics and chemical thermodynamics, the phases of α-FeOOH and Fe3O4 appeared when temperature was higher than 30°C. In the process of the crystal seeds growth, the suitable reaction temperature was at 50°C.

Effects of pulsed magnetic fields on the light scattering property of the freezing process of aqueous solutions

The purpose of the study is to clarify the effect and mechanism of magnetic fields on freeze processes in aqueous solutions. In the present study, an ice crystal formation process in biological aqueous solutions under pulsed train magnetic fields (PMF) of up to 325 T/s at 6.5 mT was observed. The pulsed magnetic field generators were set in a freezer, which controlled the temperature between 10C and −30 °C. During ice formation in the aqueous solution, disk-like ice crystal domains appeared, and the PMF-exposure exhibited a vibration of floating objects in the induced electric field directions under the cooled condition when the pulsed train frequency was changed between 10 and 17 Hz. In the freezing process of the aqueous solution with NaCl, the scattered light transmission of the ion containing the aqueous solution increased in the early phase of freezing, and then began to decrease during the late phase when the ice coagulation proceeded. The PMF exposure enhanced the light-scattering increase and decrease in the early and late phases, respectively. The results suggested that a fine ice crystal, which strongly scattered the irradiated light, increased in number in the early phase of the supercooled state when the PMF was applied.

2059 AQUEOUS EXTRACT OF COSTUS SPIRALIS ROSCOE INHIBITS CALCIUM OXALATE CRYSTAL GROWTH AND ADHESION TO RENAL EPITHELIAL CELLS

You have accessJournal of UrologyStone Disease: Basic Research1 Apr 20112059 AQUEOUS EXTRACT OF COSTUS SPIRALIS ROSCOE INHIBITS CALCIUM OXALATE CRYSTAL GROWTH AND ADHESION TO RENAL EPITHELIAL CELLS Mitra R. de Cógáin, Michael P. Linnes, Sung-Hoon Kim, and John C. Lieske Mitra R. de CógáinMitra R. de Cógáin Rochester, MN More articles by this author , Michael P. LinnesMichael P. Linnes Rochester, MN More articles by this author , Sung-Hoon KimSung-Hoon Kim Seoul, Korea, Republic of More articles by this author , and John C. LieskeJohn C. Lieske Rochester, MN More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.2290AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Costus spiralis Roscoe (C. spiralis) is a plant used in Brazilian folk medicine to treat urolithiasis; however, its' mechanism(s) of action has yet to be elucidated. The interaction between calcium oxalate (CaOx) crystals and the renal epithelium appears important in calculogenesis, and compounds that modulate this process or other aspects of crystal formation represent candidate therapeutic agents for stone prevention. Therefore, we assessed the inhibitory activity of C. spiralis on CaOx crystallization and the interaction of CaOx crystals with the renal epithelium. METHODS A seeded CaOx monohydrate (COM) crystallization system was used to study the effect of C. spiralis on crystal growth. Madin Darby canine kidney (MDCK) cells were used to study [14C] COM crystal adhesion in the presence and absence of an aqueous extract of C. spiralis. Cytotoxicity was assessed using a tetrazolium (MTS) cell proliferation assay. RESULTS Aqueous C. spiralis extract decreased crystal growth in a concentration-dependent manner. The extract decreased crystal adhesion to MDCK cells in a concentration-dependent fashion (Fig. 1). Precoating crystals was effective, while pretreating cells had no effect. The extract was not cytotoxic in concentrations up to 1000 μg/ml. No crystal growth or adhesion activity was found in hexane, methyl chloride, n-butanol, ethyl acetate or water fractions of an ethanol extract of the herb, suggesting that activity may reside in a polar compound. CONCLUSIONS Our findings suggest that C. spiralis contains a compound(s) that may delay calculogenesis by interacting with CaOx crystal surfaces. As activity was present in an aqueous extract, this agent may be bioavailable when administered orally. Preliminary fractionization trials suggest that the active agent might be a polar compound such as a polysaccharide and further identification and characterization appears warranted. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e824 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Mitra R. de Cógáin Rochester, MN More articles by this author Michael P. Linnes Rochester, MN More articles by this author Sung-Hoon Kim Seoul, Korea, Republic of More articles by this author John C. Lieske Rochester, MN More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

On the Use of Ionic Liquids To Tune Crystallization

The precipitation of barium sulfate (barite) in aqueous solutions of ionic liquids (ILs) has been used as a model system to derive fundamental relationships between crystal nucleation phenomena and some properties of those liquid salts. A systematic dependence between the size of the precipitating crystalline particles and the limiting molar conductivity of ILs has been found. The unraveled correlation has been interpreted in the light of the effect of ILs on water structure dynamics in hydration shells of barite building units and in the bulk solution and respective consequences for crystal nucleation. The response of the crystal formation process to the presence of specific ILs has been used to extract information about some particular properties of ILs (ion association and hydration) that modify the crystal hydration environment.

Effect of solar activity and geophysical disturbance on physical-chemical processes in liquid medium: Preliminary analysis of storm-glass activity

Changes in the state of a solution in storm glasses (Fitzroy retort) have been recorded by measuring the height of the level of crystals. Devices manufactured by a group of Crimean researchers have been used to measure these characteristics daily since 1995. Fragments of an accumulated observation dataset have been processed employing standard meteorological and cosmophysical indices. It is found that, 2–3 days before isolated sharp drops in the atmospheric pressure, crystal formation intensifies synchronously in two devices. A relationship is found between the activity under study and changes in the Ap geomagnetic-disturbance index and the flare-intensity index. There is a set of quasi-stable periods in variations of the activity of storm glasses, of which the 120-, 185-, and 360-day periods are most significant. The obtained results are generally consistent with views that changes in the background electromagnetic low-frequency fields are a physical agent influencing the process of crystal formation.

Acoustic Emission Study of Growth Process of Diamond Crystals under HPHT

The growth process of synthetic diamond single crystals under high-pressure and high-temperature (HPHT) was investigated using acoustic emission (AE) technique. And AE parameters corresponding to growth process were analyzed. However, the AE features of diamond growth are relativelyweak and easily obscured by other AE sources. So the fast Fourier transformation (FFT) was used to calculate the frequency spectra of AE signals for identifying different AE sources. The results showed that the variation of AE counts and energy is in a good agreement with the formation process of synthetic diamond crystals. And the AE signals pronounced from diamond growth are concentrated in the frequency range from 100 to 250 kHz. Thus, AE technique is an effective way to monitor and study the diamond growth, and the frequency analysis can be a useful way to identify different AE sources.

Controlled Multiscale Synthesis of Porous Coordination Polymer in Nano/Micro Regimes

A simple and straightforward method combines microwave-assisted solvothermal conditions with the coordination modulation method to achieve the size-controlled formation of the porous coordination polymer (PCP), [Cu3(btc)2] (where btc represents benzene-1,3,5-tricarboxylate) in the nano/micro regimes. The addition of a monocarboxylic acid modulator to the reaction mixture greatly influenced the morphology of the resulting sample, through competitive coordination interactions during the crystal formation process. By adjusting the concentration of dodecanoic acid additive, we could subtly control the nucleation rate of a [Cu3(btc)2] framework and, thus, the resulting crystal size. Homogeneous nanocrystals of the PCP with sizes ranging from few tenths of nanometers up to few micrometers could be successfully obtained in a controlled manner. X-ray diffractions and gas sorption measurements revealed highly crystalline particles with large pore volumes. Moreover, variations in the sorption profiles could be corr...

Brownian dynamics simulation of the crystallization dynamics of charged colloidal particles

Crystal formation process of charged colloidal particles is investigated using Brownian dynamics (BD) simulations. The particles are assumed to interact with the pair-additive repulsive Yukawa potential. The time evolution of crystallization process and the crystal structure during the simulation are characterized by means of the radial distribution functions (RDF) and mean square displacement (MSD). The simulations show that when the interaction is featured with long-range, particles can spontaneously assemble into body-centered-cubic (BCC) arrays at relatively low particle number density. When the interaction is short-ranged, with increasing the number density particles become trapped into a stagnant disordered configuration before the crystallization could be actualized. The simulations further show that as long as the trapped configurations are bypassed, the face-centered-cubic (FCC) structures can be achieved and are actually more stable than BCC structures.

Differential calorimetry study of the initial stage of the sulphurisation process of CuInSe 2 solar cell materials

Sulphurisation of CuInSe 2 solar cell absorber materials is of particular interest for band gap engineering by means of compositional grading. We studied the chalcopyrite formation process of Cu–In–S–Se stacks with varying Se to S ratio from 100% Se (0% S) down to 0% Se (100% S). Differential calorimetry (DSC) was applied as a fundamental characterization tool to track the crystal phase formation process. To verify the evolution of various crystallographic phases, DSC measurements were supplemented by temperature dependent in-situ X-ray diffraction (XRD) experiments of equivalent thin film compositions. For a S content of 25% the system is governed by sulphurisation of Cu and In, with the ternary phase CuIn 5(S,Se) 8 and the binary phase Cu 2(S,Se) playing major roles in the chalcopyrite formation process. It is found that the chalcopyrite formation moves to higher temperatures if the S content is increased.

Tripalmitin and monoacylglycerols as modifiers in the crystallisation of palm oil

An exhaustive analysis of the crystallisation behaviour of palm oil was performed using low-resolution magnetic pulsed nuclear resonance, differential scanning calorimetry, polarised light microscopy and X-ray diffraction. The aim of this study was to characterise the changes induced in the crystallisation of palm oil by the addition of two different levels of tripalmitin and two different types of monoacylglycerols. The addition of monoacylglycerols led to the formation of a large number of crystallisation nuclei without changing the final solids content, accelerating the process of crystal formation, leading to the formation of smaller crystals than those found in the refined palm oil. Higher levels of tripalmitin produced crystals with larger dimensions, reducing the induction period and resulted in a higher level of solids at the end of the crystallisation period. The addition of monoacylglycerols and tripalmitin induced the formation of a polymorphic β-form.

Summer freezing resistance decreased in high-elevation plants exposed to experimental warming in the central Chilean Andes

Alpine habitats have been proposed as particularly sensitive to climate change. Shorter snow cover could expose high-elevation plants to very low temperatures, increasing their risk of suffering damage by freezing, hence decreasing their population viability. In addition, a longer and warmer growing season could affect the hardening process on these species. Thus, understanding the ability of these species to withstand freezing events under warmer conditions is essential for predicting how alpine species may respond to future climate changes. Here we assessed the freezing resistance of 11 species from the central Chilean Andes by determining their low temperature damage (LT(50)) and freezing point (FP) after experimental warming in the field. Plants were exposed during two growing seasons to a passive increase in the air temperature using open top chambers (OTCs). OTCs increased by ca. 3 K the mean air and soil daytime temperatures, but had smaller effects on freezing temperatures. Leaf temperature of the different species was on average 5.5 K warmer inside OTCs at midday. While LT(50) of control plants ranged from -9.9 to -22.4, that of warmed plants ranged from -7.4 to -17.3 degrees C. Overall, high-Andean species growing inside OTCs increased their LT(50) ca. 4 K, indicating that warming decreased their ability to survive severe freezing events. Moreover, plants inside OTCs increased the FP ca. 2 K in some studied species, indicating that warming altered processes of ice crystal formation. Resistance of very low temperatures is a key feature of high-elevation species; our results suggest that current climate warming trends will seriously threaten the survival of high-elevation plants by decreasing their ability to withstand severe freezing events.

Synthesis and characterization of highly uniform Lu2O3:Ln3+ (Ln = Eu, Er, Yb) luminescent hollow microspheres

Uniform Lu2O3 hollow microspheres have been successfully fabricated via a urea-based homogeneous precipitation method with colloidal melamine formaldehyde (MF) microspheres as hard templates followed by a subsequent calcination process. The uniform Lu2O3 hollow microspheres with diameters about 1.8 μm inherit the perfect spherical shape and good dispersion of MF templates. The shell of Lu2O3 hollow spheres is composed of a large amount of uniform nanoparticles, and the thickness is about 100 nm. The crystal structure, elemental analysis, morphology, and formation process of the as-synthesized hollow microspheres were investigated in detail. The rare earth ion Ln3+-doped Lu2O3 (Ln = Eu, Er, and Yb) hollow microspheres show bright down- and up conversion luminescence with different colours coming from different activator ions under ultraviolet or 980 nm light excitation, which may find potential applications in the fields such as light phosphor powders, advanced flat panel displays, drug delivery or biological labelling. Furthermore, this study may open new possibilities to synthesize other hollow spherical materials and extend their applications.

Role of Phosphatidyl-Serine in Bone Repair and Its Technological Exploitation

In the 1970s, morphological evidence collected by electron microscopy linked mineral deposition (“calcification” or “mineralization”) in newly-forming bone to membrane-encapsulated particles of a diameter of approximately 100 nm (50–200 nm) that were called “matrix vesiscles”. As the characterisation of these vesicles progressed towards their biochemical composition, the role of lipids in the biomineralization process appeared to be crucial. In particular, a group of cell-membrane phospholipids were identified as major players in the crystal formation process. Indeed, in the 1980s it became clear that phosphatidylserine, together with proteins of the annexin family, was among the most important molecules in binding calcium ions and that this phospholipid was involved in the regulation of the early stages of mineralization in vivo. During the same period of time, the number of surgical implantations of orthopaedic, dental and maxilo-facial devices requiring full integration with the treated bone prompted the study of new functionalisation molecules able to establish a stable bonding with the mineral phase of the host tissue. In the late 1990s studies started that aimed at exploiting the potential of calcium-binding phospholipids and, in particular, of the phosphatidylserine as functionalisation molecules to improve the osteointegration of artificial implants. Later, papers have been published that show the potential of the phophatidylserine and phosphatidylserine-mimicking coating technology to promote calcification both in vitro and in vivo. The promising results support the future clinical application of these novel osteointegrative biomaterials.

Separation of sericin from fatty acids towards its recovery from silk degumming wastewaters

Sericin is a valuable protein, which is currently discarded as a waste in silk industry. Silk degumming wastewaters (SDW) are abundant sources of sericin, however, they contain impurities such as salts of fatty acids (soap) in conventional degumming processes. In this study, a process consisting of centrifugation (CFG), low temperature crystallization (LTC) and ultrafiltration (UF) was developed to separate sericin from fatty acids towards its recovery from conventional SDW. Complete removal of fatty acids was achieved by CFG + LTC, where CFG possibly accelerated crystal formation and separation processes. In CFG + UF (20 kDa), sericin rejection increased as pH was reduced from alkaline to acidic levels, possibly due to decreased solubility of sericin and increased amounts of undissociated fatty acids. Fatty acids were partly retained, leading to inadequate separation. Despite very high flux declines, cakes formed by the combined foulants were removable at both pH conditions. In CFG + LTC + UF (5 kDa), sericin was rejected by 92%. Although solution pH did not affect rejection performance, flux decline decreased from 85% to 61% at alkaline pH. Different fouling mechanisms were observed for different foulant types. Only cake formation occured with combined foulant (sericin + fatty acids). The cake surfaces were irregular, with denser and more heterogeneous structure at acidic pH. However, smooth cake formation plus pore narrowing occured with sericin alone at alkaline pH. Additional pore clogging occured at acidic pH, possibly due to decreased solubility of sericin. Chemical cleaning was less effective at acidic pH due to adsorption and pore clogging. Sericin recovery from conventional SDW was achieved in a three-stage process; CFG + LTC for complete separation of sericin from fatty acids and UF for recovering sericin.

Multi-Level Simulation Study of Crystal Growth and Defect Formation Processes in SiC

The mechanism of layer growth as well as defect formation in the SiC crystal is fundamentally important to derive its appropriate performance. The purpose of the present study is to investigate competitive adsorption properties of growth species on the various 4H-SiC polytype surfaces. Adsorption structure and binding energy of growth species in the experimentally condition on various SiC surfaces were investigated by density functional theory. For the SiC(000-1) and SiC(0001) surfaces, the adsorption energy by DFT follows the orders C > H > Si > SiC2 > Si2C > C2H2. Furthermore, based on the DFT results, amount of adsorption of each species in the experimental pressure condition were evaluated by grand canonical Monte Carlo method. H and Si are main adsorbed species on SiC(0001) and SiC(000-1) surfaces, respectively. The ratio of amount of adsorption of Si to H was depending on the surface structure that might explain different growth rate of the surfaces.

Multi-level simulation study of crystal growth and defect formation processes in SiC

The mechanism of layer growth as well as defect formation in the SiC crystal is fundamentally important to derive its appropriate performance. The purpose of the present study is to investigate competitive adsorption properties of growth species on the various 4H-SiC polytype surfaces. Adsorption structure and binding energy of growth species in the experimentally condition on various SiC surfaces were investigated by density functional theory. For the SiC(000-1) and SiC(0001) surfaces, the adsorption energy by DFT follows the orders C > H > Si > SiC2 > Si2C > C2H2. Furthermore, based on the DFT results, amount of adsorption of each species in the experimental pressure condition were evaluated by grand canonical Monte Carlo method. H and Si are main adsorbed species on SiC(0001) and SiC(000-1) surfaces, respectively. The ratio of amount of adsorption of Si to H was depending on the surface structure that might explain different growth rate of the surfaces.

Modelling crystal growth between potash particles near contact points during drying processes. Part II: Analysis, results, and comparison with experimental data

AbstractCaking of bulk granular materials is a serious problem that affects many industries including the mineral processing industry. Caking occurs when bulk materials undergo wetting and drying cycles and it has been thought that it occurs due to the formation of new crystal bridges between individual particles. In the first paper in this series a mathematical model is developed for the crystal formation process that occurs at the contact point between two particles. In Part II, numerical simulations of the model are used to determine the effects of changes for several independent parameters in this model: initial moisture content; rate of evaporation of the salt solution from the particle surface; relative size of the contact region compared to the initial film thickness of salt solution; and supersaturation levels near the contact point. Non‐dimensional graphical curves of these simulations are used to compare the effects of each parameter for the deposition of salt crystals near the contact point. These results, when compared to data for cake strength in potash specimens which were obtained for various initial moisture contents, drying rate, and chemical composition of the particle surfaces, show good qualitative agreement even though cake strength and mass recrystallization near a contact point are different physical phenomena. The numerical results show that the mass of crystal deposition near the contact point will increase with increased initial moisture content and decreased evaporation rate. It is also found that variations in the degree of supersaturation near the contact point causes significant variations in the crystal mass deposition near the contact point.

On the formation of calcium carbonate thin films under Langmuir monolayers of stearic acid

In this publication, we describe the growth of thin films of calcium carbonate beneath Langmuir monolayers of stearic acid. The size and shape of the crystalline structures were systematically studied by means of different microscopic techniques including Brewster angle microscopy, atomic force microscopy and scanning electron microscopy. In a series of experiments, we explored the calcium carbonate crystallization process for different lipid monolayers and subphases. The observed phenomena support a crystallization process which is induced by a thin, film-like structure of a precursor phase. The basic processes of crystal and aggregate formation can be represented by a simple model which is based on electrostatic interactions between the surfactant film and the inorganic calcium carbonate structures.