Narrow Crystal Size Distribution Research Articles

Ultrafine powder of barium titanate for production of lead-free ceramic piezomaterials

The paper is aimed to perform and compare the capabilities of the solid state technology and a new method of synthesis in supercritical water for the production of barium titanate powder. This material is of interest for applications such as dense piezoceramics. The new method of synthesis in an aqueous medium allowed obtaining barium titanate of higher phase purity and with a narrow crystal size distribution compared to the solid state method. The ceramics manufactured from the barium titanate powder synthesized in supercritical water possessed a consistently high dielectric constant (2400-2600) and a low loss tangent (∼ 10−2) at low and medium frequencies.

OpenCrys: Open-Source Software for the Multiscale Modeling of Combined Antisolvent and Cooling Crystallization in Turbulent Flow

The open-source software, called openCrys, is provided for the multiscale simulation of antisolvent and combined antisolvent-cooling crystallization. It simulates the macro- and micromixing scales, and the complete energy and population balance equations during crystal nucleation and growth. The model is based on the Reynolds-Averaged-Navier–Stokes equation, coupled with a three-environment presumed probability density function model, and the spatially varying population balance equation semidiscretized using a high resolution finite-volume method. openCrys is implemented in C++ object oriented programming language using the open-source CFD package OpenFOAM. The software is used to compare the performance of dual impinging jet, coaxial, and radial crystallizers. It is shown that improving the micromixing does not necessarily result in a narrower crystal size distribution when temperature effects are taken into account. The complex interplay of crystallizer kinetics and momentum, mass, and heat transfer makes the selection of the best mixer for a particular application to be nonobvious, which motivates the development and application of high-fidelity multiscale simulations for the design of antisolvent crystallizers.

Reactive Crystallization Kinetics of Magnesium Hydroxide in the Mg(NO3)2 –NaOH System

AbstractMagnesium hydroxide (Mg(OH)2) is an important chemical raw material and product. Since narrow crystal size distribution of Mg(OH)2 determines its excellent physical and chemical properties, gaining insight into the reactive crystallization kinetics of Mg(OH)2 to obtain narrow particle size distribution is essential. The reactive crystallization kinetics of Mg(OH)2 for the Mg(NO3)2‐NaOH system is systematically investigated during batch crystallization. The effects of supersaturation and temperature on the reactive crystallization kinetics of Mg(OH)2 are studied. Ion concentration over crystallization time at different temperatures is measured by the conductivity method so that the induction period is well defined. Several kinetic parameters during the nucleation and growth process are determined by using the experimental data of ion concentration over crystallization time at different temperatures. Results show that the induction period decreases with increase of temperature and initial reagent concentration. The specific surface Gibbs energy decreases with the increase of temperature. Crystallization rate increases with increase of temperature and initial reagent concentration, and the nucleation and crystal growth rates can be described as the first order reaction model.

The Effect of Power, Pulse Rate and Treatment Time of Sonication on the Nucleation and Growth of α‐Lactose Monohydrate (α‐LM) Single Crystals from Aqueous Solution

AbstractIn the present study, different kinds of ultrasound variables such as power (P‐75W to 225W), pulse rate (Pr‐10s to 60s) and treatment time (T‐04 min and T‐08 min) are employed on the crystallization of α‐ lactose monohydrate (α‐LM) from aqueous solution. The applied energy density of sonication in aqueous solution shows a profound effect on the nucleation and growth characteristics of α‐LM as regards the principal benefits such as reduction of induction period and supersaturation levels required for nucleation, decrease in crystal size with narrow crystal size distribution (CSD) and increase in nucleation rate than uninsonated solution, but have no effect on crystal morphology. Ultrasound promotes only α‐LM nucleation and no nucleation of either both α and β‐L is observed in all the 36 experiments carried out. The form of grown crystals is confirmed by powder X‐ray diffraction (PXRD) and their thermal behaviour is studied by differential scanning calorimetry (DSC) analyses. The purity of the grown crystals is determined using automatic digital polarimeter.

Fractional-submerged membrane distillation crystallizer (F-SMDC) for treatment of high salinity solution

Membrane distillation with crystallization (MDC) is an attractive process for high saline seawater reverse osmosis (SWRO) brine treatment. MDC produces additional fresh water while simultaneously recovering valuable resources. This study developed a novel approach of fractional-submerged MDC (F-SMDC) process, in which MD and crystallizer are integrated in a feed tank with a submerged membrane. F-SMDC principle is based on the presence of temperature/concentration gradient (TG/CG) in the feed reactor. The operational conditions at the top portion of the feed reactor (higher temperature and lower feed concentration) was well suited for MD operation, while the bottom portion of the reactor (lower temperature and higher concentration) was favourable for crystal growth. F-SMDC performance with direct contact MD to treat brine and produce sodium sulfate (Na2SO4) crystals using TG/CG showed positive results. The TG/CG approach in F-SMDC enabled to achieve higher water recovery for brine treatment with a volume concentration factor (VCF) of over 3.5 compared to VCF of 2.9 with a conventional S-MDC set-up. Further, the high feed concentration and low temperature at the reactor bottom in F-SMDC enabled the formation of Na2SO4 crystals with narrow crystal size distribution.

CFD‐PBE‐PBE simulation of an airlift loop crystallizer

AbstractA complete solver (CFD‐PBE‐PBE) for crystallization processes in an airlift loop crystallizer is developed in OpenFOAM (open‐source field operation and manipulation) in this work. It combines computational fluid dynamics (CFD) with population balance equations (PBE) for both gas bubbles and crystals. Models for gas‐liquid mass transfer and chemical reaction are included as well in the solver. PBE describing bubble coalescence and breakage is solved by the cell average method. Primary nucleation, secondary nucleation, and particle growth are considered in the PBE describing the crystallization process. The solver is validated with the formation of calcium carbonate via the reaction of CO2 with Ca(OH)2 solution in an airlift reactor. Effects of the chemical enhancement factor and crystallization kinetics on predictions are systematically investigated. Variation of predicted pH value, concentration of Ca2+, mean particle size, and crystal size distribution (CSD) with time is in qualitative and semi‐quantitative agreement with the published experimental data, when the appropriate crystallization kinetics are used. Effects of operation parameters such as initial concentration and superficial gas velocity are further numerically examined. The increase in superficial gas velocity results in the increasing consumption rates of OH‐ and Ca2+, while the particle diameter seems unchanged in the present simulation. A higher initial concentration of reactants will lead to a smaller particle diameter and a narrower CSD. The predicted results indicate that the developed solver is feasible, and can be used for the design and scale‐up of airlift loop crystallizers.

Model‐free control of a seeded batch crystallizer

AbstractAs the use of a batch crystallization process in several industrial applications is extensive, finding an effective control strategy is important to improve the product quality, which is typically characterized by a unimodal and narrow crystal size distribution (CSD) with a large mean crystal size. To achieve this requirement, an accurate mathematical model is needed to predict the process comportment and to design an efficient and robust controller. However, due to the highly nonlinear comportment, the difficulties of characterizing several phenomenological effects, the kinetic parameters, uncertainty, and the unknown disturbances, the used model may not describe the real process behaviour, resulting in a poor control strategy. In this work, a model‐free control and its corresponding intelligent PI (iPI), the recently introduced approach, has been proposed to ensure that the desired unimodal CSD with a desired mean size could be reached facing these problems with an easy control structure, choosing the seeded batch crystallizer of adipic acid as a case study. The proposed iPI is compared with the classic PI controller. The simulation results demonstrate the effectiveness and disturbance rejection capability of the iPI controller against the classic PI.

Solubility and Crystallization Process of 2,2,6,6-Tetramethyl-4-piperidinol (TMP)

2,2,6,6-Tetramethyl-4-piperidinol (TMP) crystal is a very important intermediate in organic synthesis. To obtain an improved crystallization yield and desirable crystal-size characteristics, several commonly used organic solvents were investigated to determine the solubility of TMP using a gravimetric method. An ethanol solvent and a cooling crystallization method were chosen to obtain an improved theroretical yield. The cooling crystallization process of TMP in the ethanol solution was further optimized to crystallize larger crystals with a narrow crystal-size distribution using an orthogonal array design. Final TMP crystals with an average diameter of 1110 μm and a diameter span of 0.715 were obtained under laboratory conditions using the optimized process.

Effects of Solution Composition and Polymer Additive on the Crystallization of Struvite

AbstractReject water from a wastewater treatment plant contains a large amount of phosphorus that can be recovered and used as phosphate fertilizer. However, the quality of the final products is affected by the variation of wastewater composition. This work focuses on the effects of the nitrogen/phosphorus (N/P) molar ratio, which is a mutable variable in the reject water, and a polymer additive on the crystallization of struvite from an artificial reject water system. The obtained results suggest that crystallization at a low pH (7.5) resulted in a narrow size distribution, over 93 % P could be recovered. The presence of the polymer Aquaflok 414C led to a slightly narrower crystal size distribution at a lower supersaturation index.

Inductive flash-annealing of bulk metallic glasses

We developed a temperature-controlled inductive flash-annealing device, which heats bulk metallic glasses (BMGs) at defined rates of up to 200 K/s to a given temperature. Subsequent instantaneous quenching in water allows preserving the microstructures obtained at various stages of crystallization. One Zr-based and two CuZr-based BMGs were flash-annealed at the onset of crystallization with different heating rates in order to prepare advanced BMG-matrix composites. The highly reproducible composite microstructures contain uniformly dispersed crystals and a narrow crystal size distribution. In order to assess the limitations of the present process, which mainly originate from non-uniform inductive heating, the skin depth was calculated. It is determined to be about 2.3 mm, which enables flash-annealing of rather bulky samples. The cooling rate was estimated from the interlamellar spacing of eutectic Al-Cu alloys to be on the order of 103 K/s. This ensures that decomposition of the microstructure during quenching is prevented. The present flash-annealing procedure is applicable to a wide variety of glass-forming liquids and has a large potential for tailoring the microstructure and, consequently, the mechanical properties of BMG-matrix composites.

ChemInform Abstract: Bioinspired Synthesis of Magnetite Nanoparticles

AbstractReview: 230 refs.

Investigation of the operating conditions to morphology evolution of β-l-glutamic acid during seeded cooling crystallization

In this paper the effects of operating conditions including cooling rate, initial supersaturation, and seeding temperature were investigated on the morphology evolution of β-l-glutamic acid (β-LGA) during seeded cooling crystallization. Based on the results of in-situ image acquisition of the crystal morphology evolution during the crystallization process, it was found that the crystal products tend to be plate-like or short rod-like under a slow cooling rate, low initial supersaturation, and low seeding temperature. In the opposite, the operating conditions of a faster cooling rate, higher initial supersaturation, and higher seeding temperature tend to produce long rod-like or needle-like crystals, and meanwhile, the length and width of crystal products will be increased together with a wider crystal size distribution (CSD). The aspect ratio of crystals, defined by the crystal length over width measured from in-situ or sample images, was taken as a shape index to analyze the crystal morphologies. Based on comparative analysis of the experimental results, guidelines on these operating conditions were given for obtaining the desired crystal shapes, along with the strategies for obtaining a narrower CSD for better product quality. Experimental verifications were performed to illustrate the proposed guidelines on the operating conditions for seeded cooling crystallization of LGA solution.

Observation and evaluation of crystal growth phenomena of glycine at the template interface with L-leucine

In order to achieve narrow crystal size distribution (CSD), an important key is the absence of the additional nucleation. It is desirable to observe and investigate the template interface because it is assumed that no additional nucleation occurred at the template interface. The objectives of this present study are observation of crystallization phenomena at the template interface and discussion on the possibility of application of them to produce crystals with a narrow CSD. The glycine - water - L-leucine (template compound) system was used.From the observations of the behavior of crystals on the template interface and our previous studies, it was suggested that there was an exclusive zone between neighboring crystals at the template interface and no additional nucleation occurred. Observation results were analyzed based on the assumption that no additional nucleation occurred between neighboring crystals. The spread of crystals was analyzed by the application of Hubble’s law. As the result, it was confirmed that initial crystals were generated at one starting point and spread without additional new crystals forming between crystals on the template interface. From the reasons mentioned above, crystallization phenomena at the template interface can be applied to production of the crystals with a narrow CSD.

Control of Crystal Size Distribution using Non-Isothermal Taylor Vortex Flow

Using a Couette-Taylor (CT) crystallizer, a non-isothermal technique was developed for effective control of the crystal size distribution (CSD) of the suspension. The proposed technique is based on the internal heating–cooling cycle in a non-isothermal CT crystallizer, consisting of a hot cylinder (Th) and cold cylinder (Tc). Thus, an internal loop of fines destruction of the suspension in the heating boundary layer of the hot cylinder and recrystallization in the cooling boundary layer of the cold cylinder is formed by the periodic circulating flow of the Taylor vortex in the non-isothermal CT crystallizer. The efficiency of the heating–cooling cycle for improving the CSD depends on the non-isothermal mode and non-isothermal parameters. When the inner cylinder temperature is hot and the outer cylinder temperature is cold (Mode-I), this is more efficient for improving the mean crystal size and dispersity of the CSD than when the cylinder temperatures are reversed (Mode-II). In addition, the efficiency of the heating–cooling cycle is optimized using the temperature difference between hot and cold cylinders (ΔT = Th – Tc) and saturated bulk temperature. The Taylor vortex fluid motion is always found to enhance the internal cycle efficiency. Thus, the initially small crystal size and broad CSD of the seed suspension (230 μm of mean crystal size and 81% of coefficient of variation) are improved to a large crystal size and narrow CSD of the product suspension (1020 μm of mean crystal size and 31% of coefficient of variation) at a non-isothermality of 8.7 ± 0.1 °C, saturated bulk temperature of 24.0 °C, and rotation speed of 800 rpm. The variation of the cycle efficiency is explained in terms of the driving forces for heating dissolution and cooling recrystallization.

Application of Rosin–Rammler model for analysis of CSD in sugar crystallization

Crystal‐size distribution (CSD) is one of the most important parameters in sugar production. The objective is to grow crystals of uniform sizes or narrow CSD. CSD appears to be determined by the growth‐rate history of the crystals and the relative supersaturation (SS) of the solution from which crystals growth takes place. Three methods for preparation of nucleation seeds were described and used for industrial crystallization of raw and white sugars; these are wet milling filtered sugar (ML), agitating saturated solution (AS) and powdered sugars (PD). Rosin–Rammler (RR) and mathematical models were adopted to investigate CSD and the uniformity of the produced crystals. Higher uniformity coefficients were reported for the AS seeded crystals than the other two seeding methods. Furthermore, higher crystal contents were obtained for the AS seeded white sugar batches in comparison.

Microfluidic sorting of protein nanocrystals by size for X-ray free-electron laser diffraction.

The advent and application of the X-ray free-electron laser (XFEL) has uncovered the structures of proteins that could not previously be solved using traditional crystallography. While this new technology is powerful, optimization of the process is still needed to improve data quality and analysis efficiency. One area is sample heterogeneity, where variations in crystal size (among other factors) lead to the requirement of large data sets (and thus 10–100 mg of protein) for determining accurate structure factors. To decrease sample dispersity, we developed a high-throughput microfluidic sorter operating on the principle of dielectrophoresis, whereby polydisperse particles can be transported into various fluid streams for size fractionation. Using this microsorter, we isolated several milliliters of photosystem I nanocrystal fractions ranging from 200 to 600 nm in size as characterized by dynamic light scattering, nanoparticle tracking, and electron microscopy. Sorted nanocrystals were delivered in a liquid jet via the gas dynamic virtual nozzle into the path of the XFEL at the Linac Coherent Light Source. We obtained diffraction to ∼4 Å resolution, indicating that the small crystals were not damaged by the sorting process. We also observed the shape transforms of photosystem I nanocrystals, demonstrating that our device can optimize data collection for the shape transform-based phasing method. Using simulations, we show that narrow crystal size distributions can significantly improve merged data quality in serial crystallography. From this proof-of-concept work, we expect that the automated size-sorting of protein crystals will become an important step for sample production by reducing the amount of protein needed for a high quality final structure and the development of novel phasing methods that exploit inter-Bragg reflection intensities or use variations in beam intensity for radiation damage-induced phasing. This method will also permit an analysis of the dependence of crystal quality on crystal size.

Analysis of the crystallization process of a biopharmaceutical compound in the presence of impurities using process analytical technology (PAT) tools

BACKGROUND. The crystallization of biopharmaceuticals can be problematic since, because the biosynthesis of these compounds is very difficult to control, they can contain a significant amount of impurities that have to be eliminated. In fact, impurities can lead to changes in the properties of the drug that can significantly reduce its effectiveness or even put the user in danger. The aim of this work is to exploit process analytical technology (PAT) tools to study the crystallization step of vitamin B12 crude product extracted via fermentation. RESULTS. Linear cooling crystallization experiments were performed using different conditions. The effects of solvent, cooling rate, seeding and purity of the initial material on the final size distribution and purity of the crystals were investigated through the use of UV/Vis spectroscopy, focused beam reflectance measurement (FBRM) and the CryPRINS software (Crystallization Process Informatics System). It was found that impurities strongly inhibit the growth of vitamin B12 crystals, promoting nucleation and leading to poor final crystal size distribution. CONCLUSION. Slow cooling can help to increase the purity of the final product but also generates a broad crystal size distribution because of secondary nucleation. Preparing the solution with material already crystallized once and using purified seeds helped to obtain a narrower crystal size distribution and also to reduce breakage.

High throughput protein nanocrystal fractionation in a microfluidic sorter.

Protein crystallography is transitioning into a new generation with the introduction of the X-ray free electron laser, which can be used to solve the structures of complex proteins via serial femtosecond crystallography. Sample characteristics play a critical role in successful implementation of this new technology, whereby a small, narrow protein crystal size distribution is desired to provide high quality diffraction data. To provide such a sample, we developed a microfluidic device that facilitates dielectrophoretic sorting of heterogeneous particle mixtures into various size fractions. The first generation device demonstrated great potential and success toward this endeavor; thus, in this work, we present a comprehensive optimization study to improve throughput and control over sorting outcomes. First, device geometry was designed considering a variety of criteria, and applied potentials were modeled to determine the scheme achieving the largest sorting efficiency for isolating nanoparticles from microparticles. Further, to investigate sorting efficiency within the nanoparticle regime, critical geometrical dimensions and input parameters were optimized to achieve high sorting efficiencies. Experiments revealed fractionation of nanobeads from microbeads in the optimized device with high sorting efficiencies, and protein crystals were sorted into submicrometer size fractions as desired for future serial femtosecond crystallography experiments.

Manufacture of dense CAU-10-H coatings for application in adsorption driven heat pumps: optimization and characterization

CAU-10-H displays a highly suitable step-wise water adsorption behaviour for application in adsorption driven heat pumps and chillers. For actual application, manufacturing of coatings of this material on thermally conductive surfaces is highly desired. Direct, single-step, crystallization of CAU-10-H on either metallic or anodized aluminium yields a significant amount of by-product(s) and an inhomogeneous substrate coverage. Although adequate pretreatment of the substrates before crystallization improves the quality of obtained coatings, significant improvements are achieved only when crystal nucleation and growth are separated. More specifically, application of a reactive seeding approach with anodized aluminium leads to full coverage of the substrate surface, high MOF loading and high purity of the crystalline phase, homogeneous layer thickness, narrow crystal size distribution, and good stability in repeated water adsorption–desorption cycles.

Ultrasound assisted reactive crystallization of strontium sulfate

SrSO4 is the main source of strontium element and widely used by industries as a raw material with narrow crystal size distribution (CSD) to meet excellent physical and chemical properties. An effort has been made to study the effects of various operating parameters such as concentration, temperature, additive (i.e. ethylene disodium salt dihydrate (EDTA)), and power of ultrasound on induction time, CSD and morphology during the reactive crystallization of strontium sulfate. The results showed that the induction time was decreased with an increase in the concentration of the reactant, temperature, and power of ultrasound, while an increasing trend observed with an increase in the concentration of EDTA. CSD was observed to be narrower with an increase in the concentration of EDTA and power of ultrasound while broader CSD observed with the initial concentration of the reactants. The temperature did not show the significant effect on CSD. The morphologies observed were the mixture of cuboids and hexagonal plate structures in the presence of ultrasound.