Controlled Crystallization Process Research Articles

Temperature-dependent kinetic pathways of heterogeneous ice nucleation competing between classical and non-classical nucleation

Ice nucleation on the surface plays a vital role in diverse areas, ranging from physics and cryobiology to atmospheric science. Compared to ice nucleation in the bulk, the water-surface interactions present in heterogeneous ice nucleation complicate the nucleation process, making heterogeneous ice nucleation less comprehended, especially the relationship between the kinetics and the structures of the critical ice nucleus. Here we combine Markov State Models and transition path theory to elucidate the ensemble pathways of heterogeneous ice nucleation. Our Markov State Models reveal that the classical one-step and non-classical two-step nucleation pathways can surprisingly co-exist with comparable fluxes at T = 230 K. Interestingly, we find that the disordered mixing of rhombic and hexagonal ice leads to a favorable configurational entropy that stabilizes the critical nucleus, facilitating the non-classical pathway. In contrast, the favorable energetics promotes the formation of hexagonal ice, resulting in the classical pathway. Furthermore, we discover that, at elevated temperatures, the nucleation process prefers to proceed via the classical pathway, as opposed to the non-classical pathway, since the potential energy contributions override the configurational entropy compensation. This study provides insights into the mechanisms of heterogeneous ice nucleation and sheds light on the rational designs to control crystallization processes.

Improving the performance of lead-acetate-based perovskite solar cells using solvent controlled crystallization process

Lead accetate is an important lead source for preparation of organolead trihalide perovskites. In this work, we improved the performance of lead accetate based perovskite solar cells (PSCs) using a mix-solvent of γ-butyrolactone/dimethyl-sulfoxide (GBL/DMSO). Compared with the use of N,N-dimethylformamide (DMF)/DMSO, using GBL/DMSO efficiently retarded the crystallization of perovskite, which improved the crystallinity of the perovskite films. Consequently, the perovskite films processed from GBL/DMSO showed higher light harvesting, longer carrier lifetime and suppressed charge recombination properties in the PSCs. Power conversion efficiency (PCE) of the PSCs was significantly improved from 16.6 to 17.7% with simultaneous improvement in open-circuit voltage, short-circuit current density and fill factor. The best PSC showed a champion PCE of 18.1%, with a stable power output and negligible hysteresis. Moreover, the flexible PSCs (based on polyethylene naphthalate substrates) with perovskite processed from GBL/DMSO exhibited a high PCE of 13.2%. Our results indicate that using GBL/DMSO as a mix-solvent is a simple and effective way for performance improvement of lead-acetate-based PSCs.

Solution versus Crystal Hydration: The Case of γ-Amino Acid Pregabalin

Understanding the link between solution chemistry and nucleation is essential to control crystallization processes, in particular regarding pharmaceutical compounds. In the present work, the link between the solution hydration state and crystallization of the γ-amino acid pregabalin is presented. Pregabalin is a blockbuster pharmaceutical drug having broad therapeutic effects. Using induction time experiments in combination with the classical nucleation theory, we show that the ease of nucleation increases with solubility and water fraction of the solvent. Water was found to enhance both the kinetic and thermodynamic processes of forming a nuclei. As a result, larger clusters which represent the hydrate form were measured using dynamic light scattering in pure water. Once in the solid state, the hydrate form of pregabalin was found to be physically unstable, as it rapidly converted back into its anhydrate form, as rationalized using in-line Raman spectroscopy. Thus, the hydration and nucleation of pregaba...

Achieving long-life Prussian blue analogue cathode for Na-ion batteries via triple-cation lattice substitution and coordinated water capture

Prussian blue and its analogues have attracted tremendous interests as cathode materials for sodium ion batteries because of their low cost and high capacity. However, their commercial applications are hindered by low capacity utilization and insufficient cycle life. Here, we report on a MnCoNi-co-doped Prussian blue analogue with high purity and crystallinity by a citrate-assisted controlled crystallization process. Moreover, a novel strategy of in situ capturing for residual coordinated water during sodiation/desodiation process is proposed to achieve a high cyclability by using the aluminium chloride Lewis acid as electrolyte additive. The reversible cubic-rhombohedral phase transition is revealed by in situ X-ray diffraction, ex situ X-ray absorption spectroscopy and transient electrochemical impedance spectroscopy. The MnCoNi-co-doped composite delivers a capacity of 111 mAh g−1 even at 1C and retains a capacity retention of 78.7% after 1500 cycles for sodium ion batteries. This work provides important insights on eliminating the parasitical coordinated water in lattice and modulating the crystallinity to develop high-performance Prussian blue and its analogues.

Cyano-Bridged Cu-Ni Coordination Polymer Nanoflakes and Their Thermal Conversion to Mixed Cu-Ni Oxides

Herein, we demonstrate the bottom-up synthesis of 2D cyano-bridged Cu-Ni coordination polymer (CP) nanoflakes through a controlled crystallization process and their conversion to Cu-Ni mixed oxides via a thermal treatment in air. The chelating effect of citrate anions effectively prevents the rapid coordination reaction between Cu2+ and K2[Ni(CN)4], resulting in the deceleration of the crystallization process of CPs. Specifically, with addition of trisodium citrate dehydrate, the number of nuclei formed at the early stage of the reaction is decreased. Less nuclei undergo a crystal growth by interacting with [Ni(CN)4]2−, leading to the formation of larger Cu-Ni CP nanoflakes. Following heat treatment in air, the -CN- groups present within the CP nanoflakes are removed and nanoporous Cu-Ni mixed oxide nanoflakes are generated. When tested as an electrode material for supercapacitors using a three-electrode system, the optimum Cu-Ni mixed oxide sample shows a maximum specific capacitance of 158 F g−1 at a current density of 1 A g−1. It is expected that the proposed method will be useful for the preparation of other types of 2D and 3D CPs as precursors for the creation of various nanoporous metal oxides.

Alkali metal tantalum germanate glasses and glass-ceramics formation

• New glass-ceramics obtained from glass with composition 70GeO 2 .20Ta 2 O 5 .10K 2 O. • Our glass-ceramics have good optical quality and are promising as rare-earth hosts. • Appropriate annealing successfully controlled crystallization process.

Glass-ceramics from a zinc-electroplating solid waste: Devitrification promoted further crystallization of parent glass upon heat treatment

A solid waste from a zinc electroplating production line was successfully used as a main raw material for synthesizing glass-ceramics with a fine microstructure. X-ray fluorescence spectroscopy analysis on dried solid waste shows that the waste mainly contains iron and zinc oxides. X-ray diffraction (XRD) analysis identifies Fe3O4 and ZnO phases in calcined waste samples. Based on the above results, silica sand, lime stone and potassium feldspar were proportionally added to make parent glasses by melting the batches at 1450 °C for 2 h. The as-synthesized products show typical DSC and thermal expansion curves with obvious glass transition phenomenon. However, XRD patterns reveal that they had devitrified to form ZnFe2O4 phase during the shaping and cooling of the melts. The devitrification became weaker when more potassium feldspar was added. It is interesting to find that the pre-crystallization of ZnFe2O4 in the devitrified sample was beneficial to its further crystallization during the following heat-treatment. The result implies that the devitrification of parent glasses is not necessarily a detriment to the preparation of glass-ceramics via controlled crystallization process.

Memory effect behavior with respect to the crystal grain size in the organic-inorganic hybrid perovskite nonvolatile resistive random access memory

The crystal grain size of CH3NH3PbI3 (MAPbI3) organic-inorganic hybrid perovskite (OHP) film was controllable in the range from ~60 nm to ~600 nm by non-solvents inter-diffusion controlled crystallization process in dripping crystallization method for the formation of perovskite film. The MAPbI3 OHP non-volatile resistive random access memory with ~60 nm crystal grain size exhibited >0.1 TB/in2 storage capacity, >600 cycles endurance, >104 s data retention time, ~0.7 V set, and ~−0.61 V re-set bias voltage.

Near‐zero thermal expansion transparent lithium aluminosilicate glass‐ceramic by microwave hybrid heat treatment

AbstractThe material of choice for space applications which demand very high dimensional stability is lithium aluminosilicate (LAS) based Ultra Low thermal Expansion Glass‐Ceramic (ULEGC). Generally, the controlled crystallization process recommended for the processing of transparent ULEGC involves a long soaking duration to achieve the required crystal number density. This paper brings out the process optimization procedure adopted for realizing transparent and nanocrystalline ULEGC from conventionally processed LAS glass using microwave‐assisted (hybrid) crystallization. The experimental strategy involves two stages (i) identification of the optimum crystallization temperature (Tc) under a microwave field (ii) optimization of a microwave‐assisted crystallization process to achieve near zero Coefficient of Thermal Expansion (CTE).. Optimum heat‐treatment schedules for nucleation and crystallization under a microwave environment were found to be 720°C/24 hours and 775°C/0.3 hours, respectively. The optimized heat‐treatment condition revealed the efficacy of the microwave hybrid heating, by producing nanocrystalline (35‐50 nm) and transparent (>82%) ULEGC having a thermal expansion of −0.03 × 10−6 K (0°C to 50°C).

Hydrometallurgical processing of lithium, potassium, and boron for the comprehensive utilization of Da Qaidam lake brine via natural evaporation and freezing

A strategy for the hydrometallurgical processing of potassium, boron, and lithium for the comprehensive utilization of Da Qaidam lake brine based on freezing and natural evaporation was developed. This process involves five major crystallization steps: remove sulfate by crystallizing mirabilite at low temperature, deposit carnallite through natural evaporation, enrich boron and lithium by eliminating magnesium through the addition of mirabilite and further evaporation, crystallize borate by brine dilution, and crystallize lithium sulfate monohydrate through further evaporation. In this study, potassium, boron, and lithium salt deposits with relatively high grades and yields were obtained through the controlled crystallization processes. This process provides a feasible and environmentally-friendly alternative for the comprehensive utilization of the Da Qaidam lake brine.

3D visualization of additive occlusion and tunable full-spectrum fluorescence in calcite.

From biomineralization to synthesis, organic additives provide an effective means of controlling crystallization processes. There is growing evidence that these additives are often occluded within the crystal lattice. This promises an elegant means of creating nanocomposites and tuning physical properties. Here we use the incorporation of sulfonated fluorescent dyes to gain new understanding of additive occlusion in calcite (CaCO3), and to link morphological changes to occlusion mechanisms. We demonstrate that these additives are incorporated within specific zones, as defined by the growth conditions, and show how occlusion can govern changes in crystal shape. Fluorescence spectroscopy and lifetime imaging microscopy also show that the dyes experience unique local environments within different zones. Our strategy is then extended to simultaneously incorporate mixtures of dyes, whose fluorescence cascade creates calcite nanoparticles that fluoresce white. This offers a simple strategy for generating biocompatible and stable fluorescent nanoparticles whose output can be tuned as required.

Research and Development of High Density Spherical Electrode Materials for Lithium Ion Batteries

The spherical electrode materials usually exhibit some outstanding advantages, such as high pile-density, high capacity density, easily modified and excellent manufacturing performance, and so on. Synthesis of spherical materials is expected as an important direction for lithium ion batteries. This paper reviews two approaches to the preparation of active electrode materials by controlled crystallization process and sol-gel process. The powders prepared by these two methods are spherical shape, dispersivity, good fluidity and high tap density. Recent work on the typical spherical materials of LiCoO2, LiNi0.8Co0.2O2, LiMn2O4, LiNixCoyMnzO2, LiMPO4, Li1+xV3O8, Li4Ti5O12 and their modification derivatives for rechargeable batteries is provided. The prospective application of the spherical cathode materials is also reviewed.

Palbociclib Commercial Manufacturing Process Development. Part III. Deprotection Followed by Crystallization for API Particle Property Control

A three-step commercial manufacturing route has been developed for palbociclib, a highly selective, reversible inhibitor of CDK 4/6. The third step of the palbociclib process is composed of an acid-catalyzed deprotection reaction telescoped through extractive workup and distillation operations into a controlled crystallization process. The selection of n-butanol and anisole as the cosolvents for this step allowed for the development of a robust process for each unit operation and for tight control of the API particle size.

Acoustic emission during the solvent mediated cooling crystallization of citric acid

The potential of Acoustic Emission (AE) for controlling crystallization processes is investigated. The sensing technology is successfully applied to monitor the batch cooling crystallization of citric acid (CA) in water. The solvent-mediated phase transition between the anhydrous and the monohydrated forms of CA is clearly detected from the recorded acoustic measurements. A tremendous amount of acoustic data is recorded by the equipment, and the analysis of the data is focused on the evaluation of AE as a new sensor for monitoring the basic steps of the crystallization processes (i.e., nucleation, growth, phase transition, etc.) A time- and frequency-domain analysis is presented which shows the wealth of the technique. It is finally concluded that AE allows very early detection of nucleation events, provides a means of monitoring the development of the crystallization process and allows monitoring phase transition phenomena obtained through cooling. It is thus suggested that acoustic emission could be valuable in the development of new crystallization monitoring and control strategies: this is all the more interesting that the acoustic piezo-sensor is non-intrusive and does not require any sampling of the slurry, two features which are of tremendous importance in the field of cooling crystallization processes.

Crystal form control and particle size control of RG3487, a nicotinic α7 receptor partial agonist

This paper describes solid form control and particle size control of RG3487, a nicotinic receptor partial agonist. Four crystal forms were identified by polymorph screen under ∼100 varying conditions. Form A and Form B are anhydrates, while Forms C and D are solvates. Forms A, which is enantiotropically related to Form B, is the more thermodynamically stable form under ambient conditions and the desired form selected for clinical development. The crystal form control of Form A was achieved by crystallization solvent selection which consistently produced the desired form. Several process parameters impacting particle size of Form A in the final crystallization step were identified and investigated through both online and offline particle size measurement. The investigation results were utilized to control crystallization processes which successfully produced Form A with different particle size in 500g scale.

Dielectric Investigation of Ferroelectric Glass-Ceramics Containing Sodium Niobate and Barium Niobium Silicate Crystals

Glass-ceramics in the BaO-Na2O-Nb2O5-SiO2 system were fabricated by a controlled-crystallization process. During the process, different heat treatment conditions were applied. Phase formation, micro-structural arrangement, and dielectric properties of the glass-ceramics were investigated by XRD, SEM, and Dielectric spectroscopy techniques. The results of phase identification revealed that NaNbO3 (NN) with perovskite crystals formed at a treatment temperature close to the crystallization peak (Tcr) which was suggested by DTA study of the parent glass. At a higher treatment temperature, Ba3Nb6Si4O26 (BNS) with layered structure was found as the additional crystalline phase. Both crystalline phases distributed randomly throughout the whole bulk glass-ceramic specimens with no observation of phase clustering. The plots of dielectric constant versus temperature revealed the dielectric response of the ferroelectric NaNbO3 crystals. With the presence of Ba3Nb6Si4O26 phase, there was no pronounced effect on the phase transition of the NaNbO3 but it enhanced the dielectric constant at Tmax. The dielectric spectroscopic investigation revealed that dipolar polarization is responsible for overall dielectric contribution.

Solvent-freeze-out (SFO) technology: A controlled crystallization process—Case study of jack bean urease

The solvent freeze out (SFO) technique is here the first time introduced and used to purify a realistic and complex protein mixture. Urease crystals were obtained from jack bean meal in the process and the purity of which were evaluated via both specific activity and SDS-PAGE. Compared to a conventional salting out crystallization, the use of SFO technology can provide a better control of the crystallization process. A detailed investigation into the crystallization process is presented by carrying out experiments with different parameters. Results showed that the quality of the ice layer is the key factor for the control of the crystallization process. The SFO technology can be considered a promising alternative in protein crystallization, because the process itself is efficient and reproducible. Even though not fully optimized, a satisfactory product purity and a decent yield of urease crystals were obtained using the SFO technology. The enzymatic activity was also preserved after the SFO process in the here carried out case study.

Crystallization and optical properties of Nd3+ doped ferroelectric glass-ceramics in the barium sodium niobosilicate system

Ferroelectric glass-ceramics of the Na2O–BaO–Nb2O5–SiO2 system were obtained from a controlled crystallization process performed on the parent glass of composition 20Na2O–10BaO–30Nb2O5–40SiO2. Nd2O3 doping content was varied in the range 0, 0.1 and 0.5mol%. Thermal properties of the as-quenched sample were studied by DTA technique and the results of DTA showed a possible crystallization peak at 740°C and this was selected as the treatment temperature. The obtained glass-ceramics were investigated in terms of crystalline phase formation by XRD technique, microstructure by SEM and optical property using UV–visible spectroscopy. Fluorescence spectra of the glass-ceramics were also recorded at RT. The results of XRD revealed that NaNbO3 and Ba2NaNb5O15 were the dominant crystalline phases. The microstructures of the glass-ceramics reveal randomly distributions of small crystallites with the size in the range 0.17–0.19µm. At low Nd3+ content, the glass-ceramics were transparent material. With a yellow light excitation at 580nm, the glass-ceramic shows possible emissions in the ultraviolet, blue and green light region.

Controlled sucrose crystallization at pilot-plant scale

The industrial production of sugar is structured such that the development of process innovations is difficult. The evaluation of ideas directly at full scale is risky and costly. Testing basic feasibility at small scale is hence desirable. To this end a pilot scale crystallizer and adequate processing developed is described here. The evaluation covers next to basic quality parameters also the comparison of computed online data with laboratory analysis on samples drawn. The designed evaporating crystallization appeared to be well controlled. At constant supersaturation approximately 50g/100 g of crystals were produced reliably. It turned out that next to the actual well controlled crystallization process the separation and drying processes are very important to produce relevant data. Centrifugation at high centrifugal forces (G=1450) for 120 s with dosage of plain water (2.5g/100g massecuite) as washing fluid yielded best results. Drying in a fluidized bed at temperatures of 343K for 10min was superior to drying at open air or in climate cabinets, this with respect to formation both of agglomerates and fines. It is shown that the designed process allows to crystallize sucrose in small scale with industrially relevant characteristics of process and product.

Effect of Ultrasonically Induced Nucleation on the Drying Kinetics and Physical Properties of Freeze-Dried Strawberry

Power ultrasound has proved to be very useful in controlling crystallization processes since sonication can enhance both the nucleation rate and crystal growth rate by producing fresh and/or more nucleation sites. Therefore, in this study, power ultrasound was applied to control the freezing step of freeze-dried strawberry. The results showed that when power ultrasound was applied at different temperatures, it increased the nucleation temperature and shortened the characteristic freezing time. The application of power ultrasound in the freezing step increased the drying time in subsequently freeze-dried strawberry samples. This longer drying time was found to be due to increased resistance to moisture diffusion due to the formation of a network of small pores caused by sublimation of small ice crystals induced by the power ultrasound. Scanning electron microscopic images revealed that the freeze-dried sample frozen by ultrasound-assisted freezing (UAFD) had finer cellular structure compared to those frozen in other freezing conditions. UAFD samples had better textural hardness, while the rehydration capacity was lower compared to those of NRFD and NIFD samples.