Crystal Growth Time Research Articles

The effect of nucleating temperature on the crystallization, phase formation and properties of lithium aluminum silicate (LAS) glass-ceramics

To study the influence of the nucleation mechanism in lithium aluminosilicate glass, a composition similar to commercially produced glass was used. The glass-ceramics was obtained as a result of two-stage heat treatment, differing in the nucleation temperature and coinciding in the temperature and time of crystal growth. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to study the formed nanocrystals. It was shown that the change of nucleation temperature in the glass transition interval Tg ±15 °C significantly affects the coefficient of thermal expansion, which is due to the formation of a different number of nanocrystals of the general composition LixAlxSi1-xO2 with x = 0.33 with the size less than 50 nm.

One Pot Synthesis of Calcium Sulfate Hemihydrate from Fishbone-derived Carbon

Calcium Sulfate Hemihydrate (CSH) with uniform morphology and high crystallinity were successfully prepared by a precipitation-hydrolysis method in a concentrated sulfuric acid solution containing fishbone-derived carbon. The CSH was produced by carbonization of fishbone powder at 500 °C for 2 h, followed by sulfonation with concentrated sulfuric acid for 3 h. The solid mixture was washed until the pH of 2, then left at room temperature for 3 days. Physical properties of synthesized CSH were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), wavelength dispersive X-ray fluorescence (WDXRF), Scanning Electron Microscope (SEM), nitrogen adsorption-desorption isotherm, and melting point test. It is concluded that the CSH were formed due to hydrolysis of fishbone-derived carbon in a moderately concentrated sulfuric acid solution of carbon-derived fishbone and crystallization into a fibrous octa calcium phosphate (OCP) form. In this research, effect of crystal growth time, effect of pH during the crystal growth, and effect of volume of the solution were also investigated. Copyright © 2023 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).

Improving the Molecular Packing Order and Vertical Phase Separation of the P3HT:O-IDTBR Blend by Extending the Crystallization Period of O-IDTBR.

The morphology with strong molecular packing order and gradient vertical composition distribution associated with efficient charge transport and collection is critical to achieve high performance in nonfullerene solar cells. However, the rapid solidification process of the active layer upon the fast removal of solvent usually results in a kinetically trapped state with undesired morphology. Herein, we proposed a strategy to extend the crystal growth time of the acceptor via a high-boiling-point additive that selectively dissolved the acceptor. This was enabled by adding dibenzyl ether (DBE) to the poly(3-hexylthiophene) (P3HT):O-IDTBR blend in chlorobenzene (CB) solution. The combination of the kinetic study by time-resolved ultraviolet-visible (UV-vis) absorption spectra and detailed morphological characterization allows us to correlate the crystallization kinetics with the microstructural transition. The results show that the crystal growth time of O-IDTBR increases from 3 to 60 s upon the addition of 0.75% DBE, leading to further evolution of the molecular order of O-IDTBR during the DBE-dominated drying period. Meanwhile, O-IDTBR has more time to migrate toward the substrate owing to the larger surface energy. In addition, the onset of the crystallization process of P3HT is brought forward from 8 to 6 s due to the reduced solvent quality, which favors P3HT to crystallize into a fibril network. As a result, an optimized morphology that features the enhanced molecular packing order of P3HT and O-IDTBR as well as the vertical compositional gradient of O-IDTBR is obtained. Devices based on the optimized blend show more balanced charge transport and suppressed bimolecular recombination, giving rise to an improved power conversion efficiency (PCE) from 4.29 ± 0.04 to 7.30 ± 0.12%.

Exploration of process optimization for recovery of sodium and ammonium sulfate crystals from vanadium precipitation wastewater

In this paper, we have studied vanadium precipitation wastewater in two stages of the fractional crystallization process. In order to extract sodium sulfate and ammonium sulfate products with large particle size and uniform particle size distribution from the rear end vanadium precipitation wastewater and to realize the resource reuse of vanadium precipitation wastewater, the effects of various operating parameters (seeding amount, evaporation rate, stirring rate, growing time) on the particle size and particle size distribution of sodium sulfate and ammonium sulfate products were investigated. Better separation and crystallization conditions of sodium sulfate and ammonium sulfate were obtained. The optimized crystallization conditions of sodium sulfate are: the addition amount of ammonium sulfate seeding with a particle size of 40 μm is 1.17 %, the evaporation rate is 100 mL/h, the stirring rate is 80 rpm, the crystal growth time is 60 min, and the main particle size M.S. value of sodium sulfate crystals is 242.23 μm; The optimized crystallization conditions of ammonium sulfate were as follows: the addition amount of sodium sulfate seeding with a particle size of 80 μm was 0.68 %, the evaporation rate was 160 mL/h, the stirring rate was 150 rpm, and the crystal growth time was 30 min. The M.S. value of the final ammonium sulfate crystal was 880 μm.

Evaluation of the properties of dolomitization fluids and diagenetic alterations of mg/Ca ratios in carbonate rocks in the cambrian series-2 to miaolingian strata in Central Uplift Belt, Tarim Basin: Constraints from halogens, REEs and isotope geochemistry

The nature of the dolomitization fluids and the diagenetic alterations on carbonate Mg/Ca ratios in Cambrian series-2 to Miaolingian strata in Central Uplift Belt, Tarim Basin are interpreted on the basis of petrography, geochemistry (trace elements, halogens, REEs, O–C–Sr isotopes) and fluid inclusion microthermometry. Based on petrographic examination, two types of less stoichiometric dolomites: dolomicrites (DM), very fine-to fine-crystalline planar-e(s) dolomite (D1) formed at near-surface to shallow-burial settings, and two types of more stochiometric dolomites (fine-to medium-crystalline planar-e(s) dolomite (D2) and medium-to coarse-crystalline.nonplanar-a dolomite (D3)) formed at deep-burial setting are identified. Medium-to coarse-crystalline, nonplanar-a saddle dolomite cement (DC), and early-stage calcite cement (ESCAL) and later-stage calcite cement (LSCAL) are identified. The DM, D1, D2, and D3 samples display positive Cerium anomalies (δCe) and negative Europium anomalies (δEu), and the DC display positive δCe and positive δEu. They show micritic-bladed and blocky calcite-like REE patterns, suggesting their dolomitizing fluids inherited the seawater or seawater-like REE signatures of their precursor carbonate materials at the time of crystal growth. No correlations exist between δ13C, δ18O, 87Sr/86Sr, Mg/Ca, and Mn/Sr which were tools used to evaluate the diagenetic history of the carbonates, coupled with the high Mg/Ca ratios (0.64–0.85), Mn/Sr ratios, and more depleted δ18O, δ13C values of D2, D3, and DC. This suggests that the dolomites were altered by high-temperatures or their isotopic difference may be the result of equilibrium isotopic fractionation. The increasing trend in Cl/(Ca + Mg), I/(Ca + Mg), and Br/(Ca + Mg) ratios in the D2, D3, and DC with dolomite content >50 wt% can be explained by the presence of evaporite (salt) derived from seawater or sedimentary pore waters as fluid interaction with sedimentary materials in the studied strata. The comparable isotopic (δ18O, δ13C and 87Sr/86Sr) values between DM, D1, D2, D3, DC, and coeval Early Paleozoic seawater value, coupled with the relatively high homogenization temperature (Th) and salinity levels in D2, D3, and DC, indicates that their diagenetic fluids were derived from radiogenic 87Sr-enrich coeval seawater with hypersaline signatures in deep-burial settings. The dolomitization model shows that the precipitation of dolomicrites was by evaporative seepage-reflux dolomitization at near-surface burial settings. Evaporative seawater dolomitization supported by 87Sr/86Sr, δ13C values and calculated water oxygen isotope ratio was probably responsible for the D1 during shallow-burial, and D2 and D3 with irregular overgrowth rims were formed during deep-burial dolomitization. The average range of the Th values of DC is 148.2–193.4 °C; mostly overlapping with the estimated ambient temperature (65 °C–180 °C, at a depth >4000 m) for the studied strata, indicates that the growth of DC in fractures may have resulted from upward and laterally squeezed higher-temperature saline-enriched basinal fluids conveyed by geothermal convective-advective fluid flows or squeegee fluid flows at depth resulting in geothermal dolomitization.

A Comparative Study of Unbalanced Production Lines Using Simulation Modeling: A Case Study for Solar Silicon Manufacturing

In the solar silicon manufacturing industry, the production time for crystal growth is ten times longer than at other workstations. The pre-processing time at the ingot-cutting station causes work-in-process (WIP) accumulation and an excessively long cycle time. This study aimed to find the most effective production system for reducing WIP accumulation and shortening the cycle time. The proposed approach considered pull production systems, and the response surface methodology was adopted for performance optimization. A simulation-based optimization technique was used for determining the optimal pull production system. The comparison between the results of various simulated pull production systems and those of the existing solar silicon manufacturing system showed that a hybrid production system in which a kanban station was installed before the bottleneck station with a CONWIP system incorporated for the rest of the production line could reduce the WIP volume by 26% and shorten the cycle time by 16% under the same throughput conditions.

Regulating zinc electroplating chemistry to achieve high energy coaxial fiber Zn ion supercapacitor for self-powered textile-based monitoring system

Coaxial fiber-shaped Zn-ion hybrid supercapacitors (CFZHSCs) with high power/energy density, long cycle life, splendid mechanical stability, and high safety are promising electrochemical energy storage devices for flexible and wearable electronics. However, the poor electrochemical performance of Zn anode severely restricts their practical application. To address this challenge, a highly reversible fiber-shaped Zn anode with controlled deposition morphology is developed based on theoretical calculation guided design of highly zincophilic 3D metal-organic-frameworks derived carbon with N- and OH-containing functional groups (N,O-MOFC) scaffold, by regulating electroplating chemistry of the initial nucleation and crystal growth time of zinc metal. Benefitting from fast ion diffusion ability of the hierarchically nanostructured 3D Zn/N,O-MOFC anode on the carbon nanotube fiber (CNTF), the assembled CFZHSCs device achieves a large volumetric specific capacitance of 128.06 F cm−3 and a high volumetric energy density of 57.63 mWh cm−3, surpassing the state-of-the-art FZHSCs device. More impressively, the efficient rechargeable capability of the fiber-shaped Zn anode also enables an adequately stable CFZHSCs device with the capacitance retention of 99.20% after 10,000 charge/discharge cycles and remarkable mechanical flexibility. As a conceptual demonstration of system integration, the as-fabricated CFZHSCs device is integrated with triboelectric nanogenerator (TENG) yarn to achieve the self-powered textile-based monitoring systems to stably detect temperature variation.

Fluid-inclusion petrography in calcite stalagmites: Implications for entrapment processes

ABSTRACT Fluids trapped in speleothems have an enormous potential in frontier fields of paleoclimate and paleohydrological research. This potential is, however, hampered by diverse scientific and technical limitations, among which the lack of a systematic methodology for genetically characterizing fluid inclusions is a major one, as these can have different origins, and thus, the trapped fluid (usually water), different meanings. In this work, we propose a systematic petrological classification of fluid inclusions, based on: 1) the temporal relation between fluid inclusions and the host calcite, 2) the spatial relation between fluid inclusions and the “crystallites” and crystals aggregates, and 3) the phases (water, air) trapped inside fluid inclusions. The first criterion allows dividing fluid inclusions in two main categories: primary and secondary, whose identification is critical in any research based on trapped fluids. The other two criteria allow the definition of eight types of primary and four types of secondary fluid inclusions. Primary fluid inclusions contain the drip water that fed stalagmites at the time of crystal growth, and can be intercrystalline, i.e., located between adjacent crystallites, or intracrystalline, i.e., with the fluid trapped within crystallites. We differentiate six main types among the intercrystalline fluid inclusions (elongate, thorn-shaped, down-arrow, interbranch, macro-elongate, and bucket) and other two among intracrystalline inclusions (pyriform and boudin). In primary inclusions, water is the main phase, while gas is much less abundant. The presence of gas could be related to slow drip rates or degassing in the cave, but also to later leakage due to changes in temperature and humidity often occurring during inadequate handling of speleothem samples. Secondary fluid inclusions were clearly related to younger water inlet through stratigraphic disruptions or unconformities. They are formed after water infiltration, but sealed before the renewed crystal growth. We differentiate four main types of secondary inclusions: interconnected, rounded, triangular, and vertical fluid inclusions. The identification of primary and secondary fluid inclusions in speleothems is a key for interpretation in paleoclimate studies. Integration of petrological results allow establishment of three different genetic scenarios for the formation of fluid inclusions, whose identification can be relevant because of their predictive character.

Lava Dome Morphology and Viscosity Inferred From Data-Driven Numerical Modeling of Dome Growth at Volcán de Colima, Mexico During 2007-2009

Magma extrusion, lava dome growth, collapse of domes, and associated pyroclastic flow hazards are among important volcanological studies. In this paper, we analyze the influence of the magma viscosity and discharge rates on the lava dome morphology at Volcán de Colima in Mexico during a long dome-building episode lasting from early 2007 to fall 2009 without explosive dome destruction. Camera images of the lava dome growth together with recorded volumes of the erupted lava have been used to constrain numerical modeling and hence to match the history of the dome growth by nudging model forecasts to observations. Our viscosity model incorporates crystal growth kinetics and depends on the characteristic time of crystal content growth (or CCGT) and the crystal-free magma viscosity. Initially, we analyze how this viscosity, CCGT, and the rate of lava extrusion influence the morphology of the growing dome. Several model scenarios of lava dome growth are then considered depending on the crater geometry, the conduit location, the effective viscosity of dome carapace, and the extrusion rates. These rates are determined either empirically by optimizing the fit between the morphological shape of modeled domes and that of the observed dome or from the recorded lava dome volumes. The maximum height of the modeled lava dome and its horizontal extent are in a good agreement with observations in the case of the empirically-derived extrusion rates. It is shown that the topography of the crater at Volcán de Colima is likely to be inclined toward the west. The viscosity of the modeled lava dome (∼1012 Pa s) is in a good agreement with the effective viscosity estimated experimentally from lavas of Volcán de Colima. Due to the interplay between the lava extrusion and the gravity forces, the dome reaches a height threshold, and after that a horizontal gravity spreading starts to play an essential role in the lava dome evolution. The model forecasts that the dome carapace of higher viscosity (∼1014 Pa s) influences the dome growth and its morphology during long dome-building episodes by retarding horizontal advancement and developing steep-sided eastern edge of the dome at the volcano. The developed model can be used in assessments of future effusive eruptions and lava dome growth at Volcán de Colima or elsewhere. History matching modeling of lava dome growth sheds a light on dynamic processes inside the dome and may assist in assessing stress state in the dome carapace and in forecasting the dome failures.

Highly oriented MAPbI3 crystals for efficient hole-conductor-free printable mesoscopic perovskite solar cells

Highly crystalline perovskite films with large grains and few grain boundaries are conducive for efficient and stable perovskite solar cells. Current methods for preparing perovskite films are mostly based on a fast crystallization process, with rapid nucleation and insufficient growth. In this study, MAPbI3 perovskite with inhibited nucleation and promoted growth in the TiO2/ZrO2/carbon triple mesoscopic scaffold was crystallized by modulating the precursor and the crystallization process. N-methylformamide showed high solubility for both methylammonium iodide and PbI2 and hampered the formation of large colloids in the MAPbI3 precursor solution. Furthermore, methylammonium chloride was added to reduce large colloids, which are a possible source of nucleation sites. During the crystallization of MAPbI3, the solvent was removed at a slow controlled speed, to avoid rapid nucleation and provide sufficient time for crystal growth. As a result, highly oriented MAPbI3 crystals with suppressed non-radiative recombination and promoted charge transport were obtained in the triple mesoscopic layer with disordered pores. The corresponding hole-conductor-free, printable mesoscopic perovskite solar cells exhibited a highest power conversion efficiency of 18.82%. The device also exhibited promising long-term operational stability of 1000 h under continuous illumination at maximum power point at 55 ± 5 °C and damp-heat stability of 1340 h aging at 85 °C as well as 85% relative humidity.

Quantifying Nanoparticle Ordering Induced by Polymer Crystallization.

It has recently been established that polymer crystallization can preferentially place nanoparticles (NPs) into the amorphous domains of a lamellar semicrystalline morphology. The phenomenology of this process is clear: when the time for NP diffusion is shorter than the crystal growth time, then the NPs are rejected by the growing crystals and placed in the amorphous domains. However, since there is no quantitative characterization of this ordered NP state, we develop a correlation function analysis for small-angle X-ray scattering data, inspired by classical methods used for enunciating the local morphology of lamellar semicrystalline polymers. We show that when the spherulitic growth rate is slower than NP diffusion, then all the NPs are expelled from the crystals. As we increase the crystallization temperature, Tc, the long period characterizing the periodically repeating crystal-amorphous polymer structure, rcc, increases. This results in a smaller number of amorphous domains per unit volume-the number of NPs per amorphous domain thus increases. While the scattering contrast between the pure silica and the polymer is constant, these arguments predict that the apparent contrast between the NP-rich and the polymer-rich domains scale linearly with rcc, as we confirm from our experiments. These facts allow us to posit that the NPs become more efficiently packed in the interlamellar zone with increasing Tc until they form a fully filled monolayer. Above this temperature, NP multilayers form within each of the NP-rich domains. Our analysis approach, therefore, describes NP ordering that is achieved when driven by polymer crystallization.

A Method for Magma Viscosity Assessment by Lava Dome Morphology

Lava domes form when a highly viscous magma erupts on the surface. Several types of lava dome morphology can be distinguished depending on the flow rate and the rheology of magma: obelisks, lava lobes, and endogenic structures. The viscosity of magma nonlinearly depends on the volume fraction of crystals and temperature. Here we present an approach to magma viscosity estimation based on a comparison of observed and simulated morphological forms of lava domes. We consider a two-dimensional axisymmetric model of magma extrusion on the surface and lava dome evolution, and assume that the lava viscosity depends only on the volume fraction of crystals. The crystallization is associated with a growth of the liquidus temperature due to the volatile loss from the magma, and it is determined by the characteristic time of crystal content growth (CCGT) and the discharge rate. Lava domes are modeled using a finite-volume method implemented in Ansys Fluent software for various CCGTs and volcanic vent sizes. For a selected eruption duration a set of morphological shapes of domes (shapes of the interface between lava dome and air) is obtained. Lava dome shapes modeled this way are compared with the observed shape of the lava dome (synthesized in the study by a random modification of one of the calculated shapes). To estimate magma viscosity, the deviation between the observed dome shape and the simulated dome shapes is assessed by three functionals: the symmetric difference, the peak signal-to-noise ratio, and the structural similarity index measure. These functionals are often used in the computer vision and in image processing. Although each functional allows to determine the best fit between the modeled and observed shapes of lava dome, the functional based on the structural similarity index measure performs it better. The viscosity of the observed dome can be then approximated by the viscosity of the modeled dome, which shape fits best the shape of the observed dome. This approach can be extended to three-dimensional case studies to restore the conditions of natural lava dome growth.

Making Room for Growing Oriented FASnI3 with Large Grains via Cold Precursor Solution

AbstractTin halide perovskites are promising candidates for preparing efficient lead‐free perovskite solar cells due to their ideal band gap and high charge‐carrier mobility. However, the notorious rapid crystallization process results in the inferior power conversion efficiency (PCE) of tin perovskite solar cells (TPSCs). Here, a facile method is employed to manage this crystallization process by using cold precursor solution that raises the critical Gibbs free energy to slow down the nucleation rate, sparing both space and time for crystal growth. In this way, highly oriented FASnI3 films with micrometer‐scale grains are fabricated and an increase of 70 mV in the open‐circuit voltage is obtained for TPSCs. This method is compatible with other existed strategies such as additive engineering or the post‐treatment method. The best‐performing device that combines 0 °C precursor solution and post‐treatment method demonstrates a PCE of 12.11%.

Optimizing the Growth of Endothiapepsin Crystals for Serial Crystallography Experiments.

Here, a protocol is presented to facilitate the creation of large volumes (> 100 µL) of micro-crystalline slurries suitable for serial crystallography experiments at both synchrotrons and XFELs. The method is based upon an understanding of the protein crystal phase diagram, and how that knowledge can be utilized. The method is divided into three stages: (1) optimizing crystal morphology, (2) transitioning to batch, and (3) scaling. Stage 1 involves finding well diffracting, single crystals, hopefully but not necessarily, presenting in a cube-like morphology. In Stage 2, the Stage 1 condition is optimized by crystal growth time. This strategy can transform crystals grown by vapor diffusion to batch. Once crystal growth can occur within approximately 24 h, a morphogram of the protein and precipitant mixture can be plotted and used as the basis for a scaling strategy (Stage 3). When crystals can be grown in batch, scaling can be attempted, and the crystal size and concentration optimized as the volume is increased. Endothiapepsin has been used as a demonstration protein for this protocol. Some of the decisions presented are specific to endothiapepsin. However, it is hoped that the way they have been applied will inspire a way of thinking about this procedure that others can adapt to their own projects.

A near-infrared emitting MOF: controlled encapsulation of a fluorescein sensitizer at the time of crystal growth.

We report here a near-infrared (NIR) emitting lanthanide-based metal-organic framework (MOF) in which Yb3+ are sensitized by fluorescein (FL) as a low energy absorbing chromophore (FL@CD-MOF-161). The unique design of CD-MOF-161 allows for the entrapment of FL molecules in its pores during the synthesis and crystal growth, ensuring the efficient loading and spreading of chromophores within the crystal volume.

Numerical Analysis of Difficulties of Growing Large-Size Bulk β-Ga2O3 Single Crystals with the Czochralski Method

The difficulties in growing large-size bulk β-Ga2O3 single crystals with the Czochralski method were numerically analyzed. The flow and temperature fields for crystals that were four and six inches in diameter were studied. When the crystal diameter is large and the crucible space becomes small, the flow field near the crystal edge becomes poorly controlled, which results in an unreasonable temperature field, which makes the interface velocity very sensitive to the phase boundary shape. The effect of seed rotation with increasing crystal diameter was also studied. With the increase in crystal diameter, the effect of seed rotation causes more uneven temperature distribution. The difficulty of growing large-size bulk β-Ga2O3 single crystals with the Czochralski method is caused by spiral growth. By using dynamic mesh technology to update the crystal growth interface, the calculation results show that the solid–liquid interface of the four-inch crystal is slightly convex and the center is slightly concave. With the increase of crystal growth time, the symmetry of cylindrical crystal will be broken, which will lead to spiral growth. The numerical results of the six-inch crystal show that the whole solid–liquid interface is concave and unstable, which is not conducive to crystal growth.

Thermodynamics and kinetics of CO2 hydrate formation in the presence of cellulose nanocrystals with statistical treatment of data

Carbon dioxide hydrate was formed in aqueous suspensions of cellulose nanocrystals (CNC) and the induction time and rate of hydrate crystal growth was compared to data obtained when CO2 hydrate was formed in pure water (blank). CNC concentrations of 0.13, 0.5 and 0.75 wt% were employed to determine whether CNC could reduce the induction time and enhance hydrate growth rate as it has been reported for carbon nanotubes and other nanoparticle suspensions. Hydrate formation experiments were carried out in two different crystallizers. The first set-up was in semi-batch operation mode while the second set-up was in batch operation mode. The results show that the CNC did not have a statistically significant impact on CO2 hydrate formation. This study also raises questions about the validity of conclusions and claims made in the literature about the effect of carbon nanotubes and other nanoparticles on gas hydrate formation. Those claims were based on very small sample sizes and without statistical data analysis.

Lava dome morphology inferred from numerical modelling

SUMMARY Lava domes form when highly viscous magmas erupt on the surface. Several types of lava dome morphology can be distinguished depending on the flow rate and the rheology of magma. Here, we develop a 2-D axisymmetric model of magma extrusion on the surface and lava dome evolution and analyse the dome morphology using a finite-volume method implemented in Ansys Fluent software. The magma/lava viscosity depends on the volume fraction of crystals and temperature. We show that the morphology of domes is influenced by two parameters: the characteristic time of crystal content growth (CCGT) and the discharge rate (DR). At smaller values of the CCGTs, that is, at rapid lava crystallization, obelisk-shaped structures develop at low DRs and pancake-shaped structures at high DRs; at longer CCGTs, lava domes feature lobe- to pancake-shaped structures. A thick carapace of about 70 per cent crystal content evolves at smaller CCGTs. We demonstrate that cooling does not play the essential role during a lava dome emplacement, because the thermal thickness of the evolving carapace remains small in comparison with the dome's height. A transition from the endogenic to exogenic regime of the lava dome growth occurs after a rapid increase in the DR. A strain-rate-dependent lava viscosity leads to a more confined dome, but the influence of this viscosity on the dome morphology is not well pronounced. The model results can be used in assessments of the rates of magma extrusion, the lava viscosity and the morphology of active lava domes..

A new melt crystallization process for efficient purification of chlorobromobenzene

O-chlorobromobenzene and some other impurities are easily introduced during the synthesis of p-chlorobromobenzene, which results in the higher impurity content and lower product purity. What’s more, p-chlorobromobenzene and o-chlorobromobenzene are isomers of each other, which brings the high similarity of their physical and chemical properties, thus the conventional separation methods do not work efficiently. A melt crystallization was carried out in this work to explore the separation and purification process of chlorobromobenzene. The influences of the cooling rate, final crystallization temperature, and crystal growth time were examined systemically based on the following criteria: the distribution coefficient, crystallization yield and purity. At last, the optimal process conditions for the separation of p- and o-chlorobromobenzene were reached at the cooling rate of 0.2 °C/min, the final crystallization temperature of −2 °C, and the crystal growth time of 5 h. The final yield was 62.74%, the purity was 99.15%, and the distribution coefficient was 0.0166, which indicated that the optimal process conditions can effectively separate the mixture of o-chlorobromobenzene and p-chlorobromobenzene. The above results indicated that the melting crystallization process was an efficient separation and purification method for chlorobromobenzene.

Correlating precipitation inhibition efficacy of EUD EPO and PVP K30 on supersaturated solution of atorvastatin calcium with Caco-2 permeability enhancement

Supersaturating drug delivery systems (SDDS) are able to generate higher concentration of drugs in the gastrointestinal lumen much beyond their thermodynamic solubility. However, supersaturated state is metastable in nature and has the tendency to precipitate. This precipitation can be eventually prevented by using precipitation inhibiting excipients like polymers which, even in low concentrations, maintain supersaturated state for suitable time of drug absorption. Understanding the mechanisms of polymer mediated precipitation inhibition would enable a formulation scientist to design stable formulations. The current study aims at molecular level understanding of drug-polymer interactions that play a role in stabilizing the supersaturated state of a BCS class II drug, atorvastatin calcium (ATC). Polymers were screened on the basis of quantitative supersaturation assays which showed differential activity on nucleation and crystal growth of ATC, estimated through impact on induction and crystal growth time, respectively. The precipitates obtained from supersaturation assays were subjected to Fourier Transform-Infrared spectroscopy (FTIR) analysis and 1H Nuclear Magnetic Resonance (NMR) to get insights on drug-polymer interactions leading to supersaturation stabilization. ATC showed stronger interaction with EUD EPO as compared to PVP K30 in proton NMR studies. For nucleation to occur, ATC molecules should overcome these drug-polymer interactions to diffuse and form critical nucleus. The polymer assisted supersaturation of ATC has shown 20-fold increase in the permeability, assessed through Caco-2 study, when compared to saturated solution of ATC. In conclusion, polymer-stabilized ATC supersaturation is successful in maintaining the solubility advantage of ATC along with delivering the transmembrane permeability enhancement.