Crystallization Step Research Articles

Safety assessment of the process General Plastic, based on the Starlinger iV+ technology, used to recycle post-consumer PET into food contact materials.

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of the recycling process General Plastic (EU register number RECYC275), which uses the Starlinger iV+ technology. The input is hot caustic washed and dried poly(ethylene terephthalate) (PET) flakes mainly originating from collected post-consumer PET containers, with no more than 5% PET from non-food consumer applications. The flakes are dried and crystallised in a first reactor, then extruded into pellets. These pellets are crystallised, preheated and treated in a solid-state polycondensation (SSP) reactor. Having examined the challenge test provided, the Panel concluded that the drying and crystallisation (step 2), extrusion and crystallisation (step 3) and SSP (step 4) are critical in determining the decontamination efficiency of the process. The operating parameters to control the performance of these critical steps are temperature, air/PET ratio and residence time for the drying and crystallisation step, and temperature, pressure and residence time for the extrusion and crystallisation step as well as the SSP step. It was demonstrated that this recycling process is able to ensure that the level of migration of potential unknown contaminants into food is below the conservatively modelled migration of 0.1 μg/kg food. Therefore, the Panel concluded that the recycled PET obtained from this process is not of safety concern when used at up to 100% for the manufacture of materials and articles for contact with all types of foodstuffs, including drinking water, for long-term storage at room temperature, with or without hotfill. The final articles made of this recycled PET are not intended to be used in microwave and conventional ovens and such uses are not covered by this evaluation.

Safety assessment of the process Green PET Recycling, based on the Starlinger iV+ technology, used to recycle post-consumer PET into food contact materials.

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of the recycling process Green PET Recycling (EU register number RECYC277), which uses the Starlinger iV+ technology. The input is hot caustic washed and dried poly(ethylene terephthalate) (PET) flakes mainly originating from collected post-consumer PET containers, with no more than 5% PET from non-food consumer applications. The flakes are dried and crystallised in a first reactor, then extruded into pellets. These pellets are crystallised, preheated and treated in a solid-state polycondensation (SSP) reactor. Having examined the challenge test provided, the Panel concluded that the drying and crystallisation (step 2), extrusion and crystallisation (step 3) and SSP (step 4) are critical in determining the decontamination efficiency of the process. The operating parameters to control the performance of these critical steps are temperature, air/PET ratio and residence time for the drying and crystallisation step, and temperature, pressure and residence time for the extrusion and crystallisation step as well as the SSP step. It was demonstrated that this recycling process is able to ensure that the level of migration of potential unknown contaminants into food is below the conservatively modelled migration of 0.1 μg/kg food. Therefore, the Panel concluded that the recycled PET obtained from this process is not of safety concern when used at up to 100% for the manufacture of materials and articles for contact with all types of foodstuffs, including drinking water, for long-term storage at room temperature, with or without hotfill. The final articles made of this recycled PET are not intended to be used in microwave and conventional ovens and such uses are not covered by this evaluation.

Membrane-Based Solvent Exchange Process for Purification of API Crystal Suspensions.

Bottom-up approaches to producing aqueous crystal suspensions of active pharmaceutical ingredients (APIs), such as anti-solvent crystallisation, are gaining interest as they offer better control over surface properties compared to top-down approaches. However, one of the major challenges that needs to be addressed is the removal of organic solvents after the crystallisation step due to strict limitations regarding human exposure. Within this work, we investigated a process concept for the removal of solvent (i.e., ethanol) from the API crystal suspension using membrane-based diafiltration. A four-stage diafiltration process successfully reduced the ethanol concentration in the API (here, naproxen) crystal suspension below 0.5 wt% (the residual solvent limit as per ICH guidelines) with a water consumption of 1.5 g of added water per g of feed. The solvent exchange process had no negative influence on the stability of the crystals in suspension, as their size and polymorphic form remained unchanged. This work is a step towards the bottom-up production of API crystal suspension by applying solvent/anti-solvent crystallisation. It provides the proof of concept for establishing a process of organic solvent removal and offers an experimental framework to serve as the foundation for the design of experiments implementing a solvent exchange in API production processes.

PCA Analysis of In Situ X-ray Powder Diffraction and Imaging Data Shedding New Light on Solid-State Transformations: The Crystallization of Low Temperature Eutectic Mixtures

Eutectic mixtures are usually studied by differential scanning calorimetry (DSC), able to identify the transition temperatures, possible hysteresis, and investigate the energetic features of transformations. However, DSC is not able to give compositional, structural, or morphological information. A new approach is proposed exploiting powder X-ray diffraction (XRPD) and imaging to overcome the issues posed to diffraction by the presence of an amorphous liquid phase. Principal component analysis (PCA) is applied blindly to in situ XRPD data from both solid and liquid phases in an approach called differential scanning diffraction (DSD), with PCA scores being the reaction coordinate of melting or crystallization steps. PCA was used in a similar way to analyze the imaging data in what was named differential scanning imaging (DSI). Exploiting this approach, the structural and morphological changes during phase transitions can be characterized by XRPD and imaging respectively, complementarily to the energetic effects probed by DSC. Melting and crystallization points can be identified together with the hysteresis between downward and upward temperature ramps, by the structural and morphological viewpoints. A three-component mixture (NaBr, KCl, and water), with wide industrial applications, was studied to describe the behavior around the eutectic composition and examine how small mixture changes can affect the transition temperature and the freezing/melting behaviors. The phase composition at the solid state was elucidated and a new phase of NaBr was identified and its lattice parameters were obtained by XRPD. DSD and DSI resulted complementary to traditional DSC data with many potential applications in solid state chemistry and materials science.

Process modelling of protein crystallisation: A case study of lysozyme

With the rise in interest of protein crystallisation as a purification step in downstream processing, there is significant interest in the process modelling of these crystallisation steps. Herein, we demonstrate and compare the applicability of “traditional” nucleation and growth models, commonly used to model small molecule crystallisation, for the successful population balance modelling of lysozyme crystallisation at the 100 mL and 1 L scales. Results show that both empirical power-law and first-principles models for nucleation and growth provide good fits to experimental data. Results from parameter estimation highlight a high degree of model sensitivity to initial guesses and stress the importance of providing particle size estimates in order to extract sensible data from the models. Estimates obtained for the 100 mL scale provided suitable initial guesses for the 1 L scale, despite significant differences in the final values obtained at each scale. For future work, further investigation into model validation upon scale-up is recommended. The work performed demonstrates the effectiveness of population balance modelling in the prediction of protein crystallisation behaviour, regardless of the underlying physical phenomena.

Rapid crystallization of Li1.5Al0.5Ge1.5(PO4)3 glass ceramics via ultra‐fast high‐temperature sintering (UHS)

AbstractLithium aluminum germanium phosphate solid electrolyte is a promising candidate for all‐solid‐state batteries. The currently available processing techniques based on melting‐quenching require a rather lengthy crystallization step lasting up to 8 hours. In this work, the newly emerged ultra‐fast high‐temperature sintering (UHS) was proposed to achieve in a single step reactive consolidation of powder mixture (GeO2, Al(PO3)3, LiPO3) and crystallization of the electrolyte within 16 minutes. Samples produced using UHS had a better phase purity, reduced Li loss, and improved ionic conductivity when compared to the counterparts prepared using conventional crystallization at 850°C for 6 h. In fact, specimens prepared by UHS achieved a crystallinity of 90% and ionic conductivity as high as 1.31 × 10−4 S cm−1.

A Microfluidic Approach to Investigate the Contact Force Needed for Successful Contact-Mediated Nucleation

Emulsions with crystalline dispersed phase fractions are becoming increasingly important in the pharmaceutical, chemical, and life science industries. They can be produced by using two-stage melt emulsification processes. The completeness of the crystallization step is of particular importance as it influences the properties, quality, and shelf life of the products. Subcooled, liquid droplets in agitated vessels may contact an already crystallized particle, leading to so-called contact-mediated nucleation (CMN). Energetically, CMN is a more favorable mechanism than spontaneous nucleation. The CMN happens regularly because melt emulsions are stirred during production and storage. It is assumed that three main factors influence the efficiency of CNM, those being collision frequency, contact time, and contact force. Not all contacts lead to successful nucleation of the liquid droplet, therefore, we used microfluidic experiments with inline measurements of the differential pressure to investigate the minimum contact force needed for successful nucleation. Numerical simulations were performed to support the experimental data obtained. We were able to show that the minimum contact force needed for CMN increases with increasing surfactant concentration in the aqueous phase.

Modeling of Masked Droplet Deposition for Site-Controlled Ga Droplets.

Site-controlled Ga droplets on AlGaAs substrates are fabricated using area-selective deposition of Ga through apertures in a mask during molecular beam epitaxy (MBE). The Ga droplets can be crystallized into GaAs quantum dots using a crystallization step under As flux. In order to model the complex process, including the masked deposition of the droplets and a reduction of their number during a thermal annealing step, a multiscale kinetic Monte Carlo (mkMC) simulation of self-assembled Ga droplet formation on AlGaAs is expanded for area-selective deposition. The simulation has only two free model parameters: the activation energy for surface diffusion and the activation energy for thermal escape of adatoms from a droplet. Simulated droplet numbers within the opening of the aperture agree quantitatively with the experimental results down to the perfect site-control, with one droplet per aperture. However, the model parameters are different compared to those of the self-assembled droplet growth. We attribute this to the presence of the mask in close proximity to the surface, which modifies the local process temperature and the As background. This approach also explains the dependence of the model parameters on the size of the aperture.

The Self-Reduction during the Thermal Decomposition of an Ammonium Molybdate

In the hydrometallurgical process of molybdenum using ammonia solution, ammonium paramolybdate tetrahydrate (APT: (NH4)6Mo7O24·4H2O) is produced as an intermediate product after a crystallization step. ATP is then thermally decomposed at a high temperature to give MoO3, which is reduced by hydrogen gas in a two-stage process to reduce molybdenum metal powder as the final product. If APT is pre-dried at an appropriately low temperature to remove the crystal water corresponding to 4 mol per mol of APT, it changes into (NH4)4Mo5O17, and the content of residual ammonia, which can be utilized as a reductant, in the ammonium molybdate increases. In this regard, the self-reducing potential of (NH4)4Mo5O17 was examined in this study through the effectiveness analysis of the residual ammonia component as a reductant for the primary hydrogen reduction step. In a series of experimental work on the thermal decomposition of (NH4)4Mo5O17 in an inert atmosphere, a maximum self-reduction degree of 18% was achieved. Based on this result, it can be expected that the metal powder can be manufactured in a more effective way than conventional processes in terms of hydrogen consumption and reaction time.

Hydrogen Evolution Reaction Activities of Room-Temperature Self-Grown Glycerol-Assisted Nickel Chloride Nanostructures

Three-dimensional nanomaterials of desired structural/morphological properties and highly porous with a high specific surface area are important in a variety of applications. In this work, glycerol-mediated self-growth of 3-D dandelion flower-like nickel chloride (NiCl2) from nickel-foam (NiF) is obtained for the first time using a room-temperature (27 °C) processed wet chemical method for electrocatalysis application. Glycerol-mediated self-grown NiCl2 flowers demonstrate an excellent electrocatalytic performance towards the hydrogen evolution reaction (HER), which is much superior to the NiF (303 mV) and NiCl2 electrode prepared without glycerol (208 mV) in the same electrolyte solution. With a Tafel slope of 41 mV dec−1, the NiCl2 flower electrode confirms improved reaction kinetics as compared to the other two electrodes, i.e., NiF (106 mVdec−1) and NiCl2 obtained without glycerol (56 mV dec−1). The stability of the glycerol-based NiCl2 electrode has further been carried out for 2000 cycles with the overpotential diminution of just 8 mV, approving an electrocatalyst potential of glycerol-based NiCl2 electrode towards HER kinetics. This simple and easy growth process involves nucleation, aggregation, and crystal growth steps for producing NiCl2 nanostructures for electrocatalytic water splitting application through the HER process.

Glass-ceramics synthesis using the collaborative smelting slag of spent automotive catalyst and copper-bearing electroplating sludge

This paper studied the glass-ceramics preparation from the collaborative smelting slag of spent automotive catalyst (SAC) and copper-bearing electroplating sludge (CBES) by the one-step sintering method without additional nucleating agents. The crystallization mechanism, including nucleation and crystal growth steps, was investigated by DSC, XRD and FETEM-EDS. The crystallization process during heat treatment could be summarized as follows: Fe3+ ions will congregate firstly in a small range on the surface and inside of the originally homogeneous amorphous matrix, and then gradually crystallize and transform into stable hematite (Fe2O3) crystal nuclei. Augite and gehlenite as the main two crystalline phases grow around hematite (Fe2O3) epitaxially. Additionally, the surface crystallization dominates the overall process based on the crystallization kinetics calculation. The optimum sintering temperatures of glass-ceramics preparation were researched according to the physicochemical properties analysis. When the sintering temperatures are 850℃−875℃, the density, water absorption, Vickers hardness, flexible strength, acid and alkali resistance of glass-ceramics products are 2.8–2.9 g/cm3, 0.08%–0.09%, 6.5–6.7 GPa, 98–115 MPa, 96.6%–96.9% and 98.5%–99.6%, respectively. Toxicity characteristic leaching procedure (TCLP) test shows that the material can be taken as non-hazardous. This work realizes resource utilization and detoxification of the co-smelting slag of SAC and CBES.

Crystal step edges with alternating rows of growth units: 1D nucleation and step velocity

Crystals with asymmetric growth units present a ubiquitous challenge for modeling crystal growth. We derive the crystal step edge velocity for steps with alternating rows of growth units (i.e., a row of A followed by a row of B growth units). We construct a free energy model for 1D nucleation of this two-tiered row and show that a single anisotropic interaction parameter and the supersaturation characterize the edge stability. A Fokker–Planck model captures the kinetics of nucleation and seamlessly connects the stable and unstable regimes, whereas previous models diverge near the transition between these cases. The 1D nucleation model leads to an expression that predicts the step velocity as a function of supersaturation and edge stability. We show that the model is in excellent agreement with kinetic Monte Carlo simulations.

Understanding the Role of Cesium on Chemical Complexity in Methylammonium‐Free Metal Halide Perovskites

AbstractMixed cesium‐ and formamidinium‐based metal halide perovskites (MHPs) are emerging as ideal photovoltaic materials due to their promising performance and improved stability. While theoretical predictions suggest that a larger composition ratio of Cs (≈30%) aids the formation of a pure photoactive α‐phase, high photovoltaic performances can only be realized in MHPs with moderate Cs ratios. In fact, elemental mixing in a solution can result in chemical complexities with non‐equilibrium phases, causing chemical inhomogeneities localized in the MHPs that are not traceable with global device‐level measurements. Thus, the chemical origin of the complexities and understanding of their effect on stability and functionality remain elusive. Herein, through spatially resolved analyses, the fate of local chemical structures, particularly the evolution pathway of non‐equilibrium phases and the resulting local inhomogeneities in MHPs is comprehensively explored. It is shown that Cs‐rich MHPs have substantial local inhomogeneities at the initial crystallization step, which do not fully convert to the α‐phase and thereby compromise the optoelectronic performance of the materials. These fundamental observations allow the authors to draw a complete chemical landscape of MHPs including nanoscale chemical mechanisms, providing indispensable insights into the realization of a functional materials platform.

Development of Commercial Manufacturing Processes for Acalabrutinib

The development of processes to produce the Bruton tyrosine kinase inhibitor, acalabrutinib 1, has resulted in improvements to the yield, cycle time, and operability, to realize a robust commercial manufacturing process. A highly accelerated clinical program meant that numerous key process challenges had to be resolved in a short timeframe. Issues are discussed, such as the uncontrolled epimerization of a chiral center and the control of the acalabrutinib 1 crystallization step, which was prone to oiling. Specifically, work to understand the complex polymorph landscape of a key intermediate (to facilitate resolution of a filtration issue) is described.

Safety assessment of the process Duy Tan Plastic Recycling, based on the Starlinger iV+ technology, used to recycle post-consumer PET into food contact materials.

The EFSA Panelon Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of the recycling process Duy Tan Plastic Recycling (EU register number RECYC264), which uses the Starlinger iV+ technology. The input is hot caustic washed and dried poly(ethylene terephthalate) (PET) flakes mainly originating from collected post-consumer PET containers, with no more than 5% PET from non-food consumer applications. The flakes are dried and crystallised in a first reactor, then extruded into pellets. These pellets are crystallised, preheated and treated in a solid-state polycondensation (SSP) reactor. Having examined the challenge test provided, the Panelconcluded that the drying and crystallisation (step 2), extrusion and crystallisation (step 3) and SSP (step 4) are critical in determining the decontamination efficiency of the process. The operating parameters to control the performance of these critical steps are temperature, air/PET ratio and residence time for the drying and crystallisation step, and temperature, pressure and residence time for the extrusion and crystallisation step as well as the SSP step. It was demonstrated that this recycling process is able to ensure that the level of migration of potential unknown contaminants into food is below the conservatively modelled migration of 0.1μg/kg food. Therefore, the Panelconcluded that the recycled PET obtained from this process is not of safety concern when used at up to 100% for the manufacture of materials and articles for contact with all types of foodstuffs, including drinking water, for long-term storage at room temperature, with or without hotfill. The final articles made of this recycled PET are not intended to be used in microwave and conventional ovens and such uses are not covered by this evaluation.

Safety assessment of the process rPET Aviv Shalam, based on the Starlinger iV+ technology, used to recycle post-consumer PET into food contact materials.

The EFSA Panelon Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of the recycling process rPET Aviv Shalam (EU register number RECYC263), which uses the Starlinger iV+ technology. The input is hot caustic washed and dried poly(ethylene terephthalate) (PET) flakes mainly originating from collected post-consumer PET containers, with no more than 5% PET from non-food consumer applications. The flakes are dried and crystallised in a first reactor, then extruded into pellets. These pellets are crystallised, preheated and treated in a solid-state polycondensation (SSP) reactor. Having examined the challenge test provided, the Panelconcluded that the drying and crystallisation (step 2), extrusion and crystallisation (step 3) and SSP (step 4) are critical in determining the decontamination efficiency of the process. The operating parameters to control the performance of these critical steps are temperature, air/PET ratio and residence time for the drying and crystallisation step, and temperature, pressure and residence time for the extrusion and crystallisation step, as well as the SSP step. It was demonstrated that this recycling process is able to ensure that the level of migration of potential unknown contaminants into food is below the conservatively modelled migration of 0.1μg/kg food. Therefore, the Panelconcluded that the recycled PET obtained from this process is not of safety concern when used at up to 100% for the manufacture of materials and articles for contact with all types of foodstuffs, including drinking water, for long-term storage at room temperature, with or without hotfill. The final articles made of this recycled PET are not intended to be used in microwave and conventional ovens and such uses are not covered by this evaluation.

Safety assessment of the process Alef Recycling, based on the Starlinger iV+ technology, used to recycle post-consumer PET into food contact materials.

The EFSA Panelon Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of the recycling process Alef Recycling (EU register number RECYC265), which uses the Starlinger iV+ technology. The input is hot caustic washed and dried poly(ethylene terephthalate) (PET) flakes mainly originating from collected post-consumer PET containers, with no more than 5% PET from non-food consumer applications. The flakes are dried and crystallised in a first reactor, then extruded into pellets. These pellets are crystallised, preheated and treated in a solid-state polycondensation (SSP) reactor. Having examined the challenge test provided, the Panelconcluded that the drying and crystallisation (step 2), extrusion and crystallisation (step 3) and SSP (step 4) are critical in determining the decontamination efficiency of the process. The operating parameters to control the performance of these critical steps are temperature, air/PET ratio and residence time for the drying and crystallisation step, and temperature, pressure and residence time for the extrusion and crystallisation step as well as the SSP step. It was demonstrated that this recycling process is able to ensure that the level of migration of potential unknown contaminants into food is below the conservatively modelled migration of 0.1μg/kg food. Therefore, the Panelconcluded that the recycled PET obtained from this process is not of safety concern when used at up to 100% for the manufacture of materials and articles for contact with all types of foodstuffs, including drinking water, for long-term storage at room temperature, with or without hotfill. The final articles made of this recycled PET are not intended to be used in microwave and conventional ovens and such uses are not covered by this evaluation.

Safety assessment of the process Ester Industries, based on the recoSTAR PET FG technology, used to recycle post-consumer PET into food contact materials.

The EFSA Panelon Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of the recycling process Ester Industries (EU register number RECYC261) using the recoSTAR PET FG technology. The input is hot washed and dried poly(ethylene terephthalate) (PET) flakes originating from collected post-consumer PET containers, mainly bottles, with no more than 5% PET from non-food consumer applications. The flakes are processed continuously under an inert gas flow. They are dried and crystallised in a first reactor and then further heated in a second reactor before being extruded into pellets. Having examined the challenge test provided, the Panelconcluded that the drying and crystallisation (step 2), and the heating of the crystallised flakes (step 3) are the critical steps that determine the decontamination efficiency of the process. The operating parameters to control the performance of these critical steps are temperature, residence time and gas flow rate. It was demonstrated that this recycling process is able to ensure that the level of migration of potential unknown contaminants into food is below the conservatively modelled migration of 0.1μg/kg food. Therefore, the Panelconcluded that the recycled PET obtained from this process is not of safety concern, when used at up to 100% for the manufacture of materials and articles for contact with all types of foodstuffs for long-term storage at room temperature, with or without hotfill. Trays made of this recycled PET are not intended to be used in microwave and conventional ovens and such use is not covered by this evaluation.

Improvement in the polishing characteristics of titanium-based materials using electrochemical mechanical polishing

Titanium (Ti) and its alloys are widely used in aerospace components and biomaterials. The smoothing of Ti materials is essential for realizing high-quality Ti-based devices and components to enhance their physical and chemical properties, such as fatigue strength and biocompatibility. However, with conventional polishing methods, obtaining sub-nanometer roughness in a large measurement area is difficult because of the generation of crystal grain steps on the polished surface. This paper presents an electrochemical mechanical polishing (ECMP) method that involves electrochemical oxidation and subsequent oxide removal using SiO2 particles to achieve a high material removal rate (MRR) and an ultra-smooth surface of pure Ti and Ti-6Al-4V. Under suitable electrolytic current and mechanical conditions, ECMP provides a higher MRR and smoother pure Ti surface than electroless polishing. X-ray and Raman analyses indicate that the mechanical condition affects the chemical states of polished surfaces; higher mechanical conditions retain less oxide film on the polished surface, resulting in a smoother surface. The highly efficient ECMP provides a defect-free and sub-nanometer roughness for pure Ti and Ti-6Al-4V surfaces without using chemicals. Furthermore, it is an environment-friendly and cost-effective approach to prepare Ti-based components.

Model for the current plateau observed on the (310) plane of a room temperature W field electron source

An unexpected pause is observed in the usual exponential current decay when residual gas adsorption occurs on the (310) plane of a room temperature W field emitter (CFE). For most ultrahigh vacuum environments currently achievable, the primary residual gas is H2. High index crystal planes are known to consist of terraces separated by step walls. For a (310) orientation, the bcc crystal terraces and step walls consist of (100) and (110) orientations, respectively. Evidence is presented that the step wall adsorption sites are the preferential sites for initial H2 adsorption causing the work function (ϕ) to decrease. According to Fowler–Nordheim (FN) theory, which relates the CFE emission current and ϕ, the current should increase. Instead, the decrease in ϕ is accompanied by a concomitant decrease in the FN equation pre-exponential factor, which leads to a relatively constant value of the CFE current until these step-wall sites are saturated, after which the ϕ increases with further H2 adsorption. The latter leads to an exponential decrease in the emission current. This fortuitous balance between the ϕ and FN equation pre-exponential factor upon initial H2 adsorption appears to be unique to the (310) crystal plane of a W CFE.