Residual Crystallinity Research Articles

Lead iodide secondary growth and π-π stack regulation for sequential perovskite solar cells with 23.62% efficiency

The sequential deposited perovskite solar cells (PSCs) have received widespread attention due to its application potential in large-scale perovskite module and perovskite/silicon tandem solar cells. However, insufficient reaction between organic ammonium salts and PbI2 leads to residual PbI2 and low crystallinity of perovskite films, and the fragile Pb-I bonds easily creates iodine loss and reduces the stability of PbI6 framework. In this work, the 4-fluorobenzylamine (FBA) with C = O and –NH2 is employed in PbI2 precursor solution to regulate the secondary growth process of PbI2 film. Due to the low Gibbs free energy and high crystallinity of porous PbI2 film, sufficient reaction between organic ammonium salts and PbI2 is promoted, which results in large-grain, low-defect perovskite films. At the same time, through hydrogen bonding and π-π stacking interactions, the stability of the PbI6 skeleton is effectively improved, significantly suppressing non-radiative recombination and reducing defect state density. Finally, this strategy increases the power conversion efficiency (PCE) of PSCs from 22.06 % to 23.62 %, and the target PSCs maintain 96 % of their initial PCE after being placed in nitrogen for 1300 h.

TEM Image Analysis and Simulation Physics for Two-Step Recrystallization of Discretely Amorphized C3H5-Molecular-Ion-Implanted Silicon Substrate Surface

In this study, we investigate the initial rapid recrystallization of a discretely amorphized C3H5-molecular-ion-implanted silicon (Si) substrate surface in the subsequent thermal annealing treatment through the analysis of plan-view transmission electron microscopy (TEM) images and technology computer-aided design (TCAD) process simulation. In the approach of the analysis of the plan-view TEM image of the Si substrate surface, we found that initial rapid recrystallization occurs in the intermediate regions between the residual crystalline and discrete amorphous regions formed in the C3H5-molecular-ion-implanted Si substrate surface. In addition, the TCAD process simulation results indicate that the intermediate regions correspond to the amorphous pockets formed around the discrete amorphous regions in the C3H5-molecular-ion-implanted Si substrate surface and are recrystallized preferentially during the short thermal annealing time. These plan-view TEM image analysis and TCAD process simulation results reveal a two-step recrystallization of the discretely amorphized C3H5-molecular-ion-implaned Si substrate surface. After the initial rapid recrystallization of amorphous pockets in the 1st step, the recrystallization of discrete amorphous regions starts in the 2nd step. The incubation period between the 1st and 2nd steps is the time required to recrystallize the amorphous pockets around the discrete amorphous regions completely and redefine the amorphous/crystalline interface.

Orthogonal Analytical Methods to Elucidate How Low Levels of Residual Crystallinity in Posaconazole Amorphous Solid Dispersions Impact Phase Behavior during Release

Orthogonal Analytical Methods to Elucidate How Low Levels of Residual Crystallinity in Posaconazole Amorphous Solid Dispersions Impact Phase Behavior during Release

Overcoming drug impurity challenges in amorphous solid dispersion with rational development of biorelevant dissolution-permeation method

Hot-melt extrusion is often used to prepare amorphous solid dispersion to overcome low drug solubility and enhance bio-performance of the formulation. Due to the uniqueness of each drug – polymer combination and its physico-chemical properties, setting the appropriate HME barrel temperature, feed rate and screw speed ensures drug amorphization, absence of residual crystallinity, absence of water, and a suitable drug release profile. In this research, samples with BCS II/IV model drug and PVP/VA polymer were prepared to evaluate the impact of HME process parameters, incoming drug form (anhydrous vs. hydrate), and drug supplier (i.e., impurity profile), on biorelevant drug release. This study provides a relationship between observed in vitro supersaturation and precipitation behavior of amorphous solid dispersion formulation with in vivo results, on patients, by using the acceptor profile of side-by-side dissolution-permeation apparatus.An in vitro dissolution method, in small volumes, in an apparatus with paddles and dissolution-permeation side-by-side method was developed on the MicroFlux™ apparatus to assess if the differences observed in vitro bears relevance to the bioequivalence outcome in vivo. The former was used to guide the generic drug product development due to high discriminatory strength, while the latter was biorelevant, due to the inclusion of the second compartment assuring absorptive environment to capture the impact of supersaturation and subsequent precipitation on bioavailability. Bio-relevancy of the in vitro method was confirmed with the in vivo dog study and clinical study on patients, and an in vitro – in vivo correlation was established.For the investigated BCS II/IV drug, this research highlights the importance of considering supersaturation and formation of colloidal species during amorphous solid dispersion release testing to assure product quality, safety and efficacy.

Impact of Sulfate Adsorption on Particle Morphology during the Precipitation of Ni-Rich Hydroxide Precursors for Li-Ion Battery Cathode Active Materials

Nickel-cobalt-manganese-hydroxides (NixCoyMnz(OH)2, with x+y+z = 1) are utilized as precursor for lithium-ion battery cathode active material (CAM). The physical properties and electrochemical performance of CAM are affected by the morphology, crystallinity and impurity content of the associated NixCoyMnz(OH)2 (with x+y+z = 1) employed for the CAM synthesis. To promote the mechanistic understanding of the NixCoyMnz(OH)2 (with x+y+z = 1) formation, the coprecipitation pH23 °C-value was systematically varied from 8.6–12.7 during the synthesis of Ni0.8Co0.1Mn0.1(OH)2, and the obtained powders were characterized by elemental analysis. A dependency of residual sulfur content and crystallinity of the obtained Ni0.8Co0.1Mn0.1(OH)2 on the pH-value in relation to the point-of-zero-charge (pzc) is revealed. This result is rationalized by a pH-dependent sulfate adsorption equilibrium. Furthermore, a suppression of the growth along the (001) plane of the crystallites due to sulfate adsorption is identified. This in turn governs the vertical primary particle size and thus the porosity of the secondary particles, which was verified by substituting the sulfate ion of the metal feed by nitrate or acetate. Adsorption/desorption experiments demonstrate the possibility to decouple secondary particle morphology and residual impurity content. The demonstrated relationships allow formulating design strategies to tailor the NixCoyMnz(OH)2 (with x+y+z = 1) morphology and its impurity content for CAM synthesis.

Comparison of hydration water properties of common and durum wheat brans upon grinding with different loading modes

Wheat bran brings healthy properties in food products. However, its incorporation requires a first milling step during which it is subject to various loading modes which have an influence on its properties. This study investigated the influence of the loading modes (high shear or impact) generated by grinders during the milling on the hydration properties of common and durum wheat brans. An original study at molecular scale to target the distribution and intensity of hydration water bonds was carried out by gravimetric and spectroscopic methods. Results were analyzed in regards to the particle size distribution and shape factors as well as biochemical composition to highlight the process-structure-function relationships at macro and microscales. Impact grinder has a stronger effect on water vapor sorption capacity and FTIR multimer water at 3600 cm−1 of durum wheat bran as well as a red shift in the band at 1030 cm−1 related to a high decrease in residual starch crystallinity degree (about 17%). High shear grinder tends to increase the proportion of water strongly bound. Low field NMR analysis revealed differences in the high mobility water peak and a significant lower relaxation time T2 for native and ground durum wheat bran (up to 1.7 fold less).

An Analytical Model of Light Scattering by Birefringent Polycrystalline Dielectrics Using Perturbation of Maxwell's Equations

AbstractPolycrystalline materials have shown promise in advanced optical applications because of their unique optical and mechanical properties. Most polycrystalline materials have non‐uniform optical properties due to residual porosity, secondary phases, and/or crystalline anisotropies (e.g., birefringence). These optical inhomogeneities manifest as scattering that reduces the transparency of the polycrystal. Even in the case of a single‐phase polycrystal with negligible porosity, birefringence scattering will always be present whenever the crystal is anisotropic (non‐cubic). Multiple models for predicting birefringence scattering have been suggested in the literature that are successful in describing scattering loss in specific material systems. Here a first‐principles model of birefringent scattering that is applicable to any single‐phase, unaligned transparent polycrystal is derived. The model can treat grain size distributions and is not limited to a specific material system. The derivation culminates in an equation that describes birefringence scattering coefficient spectra using the single‐crystal refractive index tensor and chord length distribution (measured from a representative polished surface micrograph). The model should be useful for designing materials and characterization. For example, it can be used to predict transmissions of transparent polycrystals for a range of grain sizes or to characterize the average grain size using a transmission measurement.

Residual stress associated with crystalline phase transformation of 3–6 mol% yttria-stabilized zirconia ceramics induced by mechanical surface treatments

Monolithic dental prostheses made of 3–6 mol% yttria-stabilized zirconia (3–6YSZ) have gained popularity owing to their improved material properties and semi-automated fabrication processes. In this study, we aimed to evaluate the influence of mechanical surface treatments, such as polishing, grinding, and sandblasting, on the residual stress of 3–6YSZ used for monolithic prostheses in association with crystalline phase transformation. Plate specimens were prepared from five dental zirconia blocks: Aadva Zirconia ST (3YSZ), Aadva Zirconia NT (6YSZ), Katana HT (4YSZ), Katana STML (5YSZ), and Katana UTML (6YSZ). The specimens were either polished using 1, 3, or 9 μm diamond suspensions, ground using 15, 35, or 55 μm diamond discs, or sandblasted at 0.2, 0.3, or 0.4 MPa. The residual stress, crystalline phase, and hardness were analyzed using the cosα method, X-ray diffraction (XRD), and Vickers hardness test, respectively. Additionally, we analyzed the residual stress on the surfaces of monolithic zirconia crowns (MZCs) made of 4YSZ, 5YSZ, and 6YSZ, which were processed using clinically relevant procedures, including manual grinding, followed by polishing using a dental electric motor on the external surface, and sandblasting on the internal surface. Residual stress analysis demonstrated that grinding and sandblasting, particularly the latter, resulted in the generation of compressive residual stress on the surfaces of the plate specimens. XRD revealed that the ground and sandblasted specimens contained a larger amount of the rhombohedral phase than that of the polished specimens, which may be a cause of the residual stress. Sandblasting significantly increased the Vickers hardness compared to polishing, which may possibly be due to the generation of compressive residual stress. In the case of MZCs, compressive residual stress was detected not only on the sandblasted surface, but also on the polished surface. The difference in the residual stress between the plate and crown specimens may be related to the force applied during the automated and manual grinding and polishing procedures. Further studies are required to elucidate the effects of the compressive residual stress on the clinical performance of MZCs.

Physicochemical and In Vitro Starch Residual Digestion Structures of Extruded Maize and Sorghum Starches Added with Sodium Stearoyl Lactylate.

This research aimed to characterize the physicochemical, in vitro digestion, and structural features of digestion residues of maize and sorghum starches subjected to thermoplastic extrusion, along with the influence of Sodium Stearoyl Lactylate (SSL), to obtain improved starches for food applications and to understand their behavior when consumed as a food ingredient. The morphology of the extruded materials showed remanent starch granules when SSL was used. A higher amount of medium and large linear glucan chains were found in these particles, influencing higher thermal stability (ΔH ≈ 4 J/g) and a residual crystallinity arrangement varying from 7 to 17% in the extrudates. Such structural features were correlated with their digestibility, where slowly digestible starch (SDS) and resistant starch (RS) fractions ranged widely (from 18.28 to 27.88% and from 0.13 to 21.41%, respectively). By analyzing the data with a Principal component analysis (PCA), we found strong influences of B2 and B3 type chains on the thermal stability of the extrudates. The amylose and smaller glucan chains (A and B1) also significantly affected the emulsifying and foam stability properties. This research contributes to the molecular knowledge of starch in extruded products with broad food applications.

The applications of machine learning to predict the forming of chemically stable amorphous solid dispersions prepared by hot-melt extrusion

Amorphous solid dispersion (ASD) is one of the most important strategies to improve the solubility and dissolution rate of poorly water-soluble drugs. As a widely used technique to prepare ASDs, hot-melt extrusion (HME) provides various benefits, including a solvent-free process, continuous manufacturing, and efficient mixing compared to solvent-based methods, such as spray drying. Energy input, consisting of thermal and specific mechanical energy, should be carefully controlled during the HME process to prevent chemical degradation and residual crystallinity. However, a conventional ASD development process uses a trial-and-error approach, which is laborious and time-consuming. In this study, we have successfully built multiple machine learning (ML) models to predict the amorphization of crystalline drug formulations and the chemical stability of subsequent ASDs prepared by the HME process. We utilized 760 formulations containing 49 active pharmaceutical ingredients (APIs) and multiple types of excipients. By evaluating the built ML models, we found that ECFP-LightGBM was the best model to predict amorphization with an accuracy of 92.8%. Furthermore, ECFP-XGBoost was the best in estimating chemical stability with an accuracy of 96.0%. In addition, the feature importance analyses based on SHapley Additive exPlanations (SHAP) and information gain (IG) revealed that several processing parameters and material attributes (i.e., drug loading, polymer ratio, drug's Extended-connectivity fingerprints (ECFP) fingerprints, and polymer's properties) are critical for achieving accurate predictions for the selected models. Moreover, important API's substructures related to amorphization and chemical stability were determined, and the results are largely consistent with the literature. In conclusion, we established the ML models to predict formation of chemically stable ASDs and identify the critical attributes during HME processing. Importantly, the developed ML methodology has the potential to facilitate the product development of ASDs manufactured by HME with a much reduced human workload.

Cellulose tosylate as support for α-amylase immobilization

Tremendous potential exists to use cellulose as a support for the immobilization of enzymes. In the current study, cellulose was transformed into cellulose tosylate, and α-Amylase was immobilized using the derivatized polymer. Techniques like Fourier transform infrared, scanning electron microscopy, thermogravimetric analysis, and X-ray diffraction methods were used to characterize the support. The support is a perfect illustration of how both covalent and hydrophobic/ionic types of immobilizations can be experimentally used on support. The support was found to show max degradation at 320.2 °C with 3.2 % residual substance and crystallinity of about 56.6 %. The support presented maximum enzyme loading at the support: enzyme ratio of 1:4. The immobilized enzyme displayed two ideal pH values (about 4.6 and 7) and two ideal temperatures (approximately 60 °C & 40 °C). It was discovered that the immobilized α-amylase could be used easily eight times with 9.9 % residual activity. The findings of this study show that the immobilized cellulose tosylate enzyme has the potential for application in both acidic and neutral pH environments with the best activity for commercial use.

A study on residual solvent, crystallinity and thermal properties of poly(styrene)-poly(methyl methacrylate)-toluene coatings

Drying of poly(styrene)-poly(methyl methacrylate)-toluene coating system has been investigated. The effect of coating composition and initial thickness on the residual solvent, average polymer/solvent concentrations, and coating thickness were studied. The findings revealed that by adjusting the mass fractions of polymers and solvents, the residual solvents and final coating thickness could be reduced to a reasonable level. The residual solvent concentration in poly(styrene)–poly(methyl methacrylate)-toluene coatings did not vary significantly when the concentration of poly(styrene) was altered, but it changed when the concentration of poly(methyl methacrylate) was changed. Additionally, raising the mass percentage of both the polymers had no influence on the glass transition temperature of the coating but significantly limited the diffusion mass transfer. The average concentration of solvent and polymer in these coatings were in agreement with Fickian diffusion over a long period of the total drying time. The findings showed that thick coatings lost the residual solvent at a slower rate for sufficiently long time than the thinner ones. The glass transition temperature of the coatings decreased with the increase in the coating thicknesses. Coating 4 had the highest Tg, i.e., 74.08 °C. No noticeable change was observed in crystallinity of the coatings with the change in the thickness of the coatings. Major crystalline peak with intensity of 100 % in all the coatings were observed in the range 28.8931°–29.3518°. The amorphous nature of the coatings was observed as a broad peak at 20°.

Detecting Crystallinity Using Terahertz Spectroscopy in 3D Printed Amorphous Solid Dispersions

This study demonstrates the applicability of terahertz time-domain spectroscopy (THz-TDS) in evaluating the solid-state of the drug in selective laser sintering-based 3D printed dosage forms. Selective laser sintering is a powder bed-based 3D printing platform, which has recently demonstrated applicability in manufacturing amorphous solid dispersions (ASDs) through a layer-by-layer fusion process. When formulating ASDs, it is critical to confirm the final solid state of the drug as residual crystallinity can alter the performance of the formulation. Moreover, SLS 3D printing does not involve the mixing of the components during the process, which can lead to partially amorphous systems causing reproducibility and storage stability problems along with possibilities of unwanted polymorphism. In this study, a previously investigated SLS 3D printed ASD was characterized using THz-TDS and compared with traditionally used solid-state characterization techniques, including differential scanning calorimetry (DSC) and powder X-ray diffractometry (pXRD). THz-TDS provided deeper insights into the solid state of the dosage forms and their properties. Moreover, THz-TDS was able to detect residual crystallinity in granules prepared using twin-screw granulation for the 3D printing process, which was undetectable by the DSC and XRD. THz-TDS can prove to be a useful tool in gaining deeper insights into the solid-state properties and further aid in predicting the stability of amorphous solid dispersions.

A Hot-Melt Extrusion Risk Assessment Classification System for Amorphous Solid Dispersion Formulation Development

Several literature publications have described the potential application of active pharmaceutical ingredient (API)–polymer phase diagrams to identify appropriate temperature ranges for processing amorphous solid dispersion (ASD) formulations via the hot-melt extrusion (HME) technique. However, systematic investigations and reliable applications of the phase diagram as a risk assessment tool for HME are non-existent. Accordingly, within AbbVie, an HME risk classification system (HCS) based on API–polymer phase diagrams has been developed as a material-sparing tool for the early risk assessment of especially high melting temperature APIs, which are typically considered unsuitable for HME. The essence of the HCS is to provide an API risk categorization framework for the development of ASDs via the HME process. The proposed classification system is based on the recognition that the manufacture of crystal-free ASD using the HME process fundamentally depends on the ability of the melt temperature to reach the API’s thermodynamic solubility temperature or above. Furthermore, we explored the API–polymer phase diagram as a simple tool for process design space selection pertaining to API or polymer thermal degradation regions and glass transition temperature-related dissolution kinetics limitations. Application of the HCS was demonstrated via HME experiments with two high melting temperature APIs, sulfamerazine and telmisartan, with the polymers Copovidone and Soluplus. Analysis of the resulting ASDs in terms of the residual crystallinity and degradation showed excellent agreement with the preassigned HCS class. Within AbbVie, the HCS concept has been successfully applied to more than 60 different APIs over the last 8 years as a robust validated risk assessment and quality-by-design (QbD) tool for the development of HME ASDs.

Transmission Electron Microscopy Study on the Effect of Thermal and Electrical Stimuli on Ge2Te3 Based Memristor Devices

Memristor devices fabricated using the chalcogenide Ge2Te3 phase change thin films in a metal-insulator-metal structure are characterized using thermal and electrical stimuli in this study. Once the thermal and electrical stimuli are applied, cross-sectional transmission electron microscopy (TEM) and X-ray energy-dispersive spectroscopy (XEDS) analyses are performed to determine structural and compositional changes in the devices. Electrical measurements on these devices showed a need for increasing compliance current between cycles to initiate switching from low resistance state (LRS) to high resistance state (HRS). The measured resistance in HRS also exhibited a steady decrease with increase in the compliance current. High resolution TEM studies on devices in HRS showed the presence of residual crystalline phase at the top-electrode/dielectric interface, which may explain the observed dependence on compliance current. XEDS study revealed diffusion related processes at dielectric-electrode interface characterized, by the separation of Ge2Te3 into Ge- and Te- enriched interfacial layers. This was also accompanied by spikes in O level at these regions. Furthermore, in-situ heating experiments on as-grown thin films revealed a deleterious effect of Ti adhesive layer, wherein the in-diffusion of Ti leads to further degradation of the dielectric layer. This experimental physics-based study shows that the large HRS/LRS ratio below the current compliance limit of 1 mA and the ability to control the HRS and LRS by varying the compliance current are attractive for memristor and neuromorphic computing applications.

Surface Tension and Kinematic Viscosity of Multicomponent FeCuNbSiB Melt

This work investigated the surface tension and kinematic viscosity of the multicomponent Fe73.5Cu1Nb3Si13.5B9 melt. A relationship was found between surface tension and kinematic viscosity, which manifests itself in a synchronous change in these quantities at temperatures of 1600 and 1780 K. In the temperature range 1600–1780 K, there is a sharp increase in surface tension upon heating and the same decrease upon cooling. The increase in surface tension during heating was explained by the appearance of a large number of free Nb atoms as a result of the dissolution of the residual crystalline phase in the mushy zone, and their diffusion to the melt surface. The drop in the surface tension on cooling below 1780 K is associated with the liquid–liquid structure transition (LLST), which stimulates the outflow of Nb atoms from the surface in order to form new stable clusters. The LLST manifests itself in a change in the activation energy of a viscous flow, which is higher in the high-temperature region and corresponds to the motion of larger clusters with a length scale of about 1 nm.

Adding a New Dimension to the Amorphous Solid Dispersion Phase Diagram: Studying Dissolution Kinetics of Crystalline Drugs in a Polymer Matrix Using Temperature Dependent XRPD and DSC

Hot-melt-extrusion (HME) is an enabling technology used for poorly soluble active pharmaceutical ingredients (APIs) to increase the bioavailability by embedding the drug in a water soluble and often amorphous carrier such as a polymer. Knowledge of the most critical factors impacting the dissolution rate of crystalline API in the polymer during manufacturing will provide useful insight for process improvement. In this study, crystalline APIs (Acetaminophen, APAP and Indomethacin, IMC) were analyzed in a polymeric matrix (Copovidone, PVP-VA64) via X-Ray Powder Diffraction (XRPD) and Differential Scanning Calorimetry (DSC) to follow the dissolution process under various conditions in a down-scaled static laboratory system. The combination of in-situ XRPD measurements and a kinetic model based on DSC data proved to be a suitable tool to investigate the dissolution process and can be applied to various APIs and polymers to avoid residual crystallinity and thermal degradation. Thus, the temperature-composition phase diagram in a thermodynamic equilibrium is augmented by the kinetic component as new dimension. The obtained findings set the foundation for investigating the dissolution kinetics and enable the transition from a static to a dynamic system.

Study on Structural Changes of Starches with Different Amylose Content during Gelatinization Process

AbstractA thorough understanding of structural changes during gelatinization is extremely important for precise control of starch functional properties for food processing and human nutrition. Here five starches with different amylose content between 1.06% and 63.08% are selected to reveal the relationship between the structural changes and amylose content during starch gelatinization by Raman spectroscopy and X‐ray diffraction (XRD) in conjunction with a protocol using the rapid viscosity analyzer (RVA) to generate material for analysis. The results show that the high‐amylose starch has stronger resistance to gelatinization, and its long‐range order structure is more stable which is consistent with the conclusion that certain residual crystallinity remains after gelatinization. Meanwhile, the destruction of short‐range order structure is not significant compared with that in low‐amylose starch when the temperature reaches the pasting temperature. These phenomena are related to the fact that the high‐content amylose promotes the formation of the amylose‐lipid complex during the gelatinization by differential scanning calorimeter (DSC). The presence of the amylose‐lipid complex can restrain the swelling of starch granules and maintain their molecular structure during heating.

Hyperacute stromal and endothelial rejection in therapeutic penetrating keratoplasty with residual intra-stromal crystalline deposits

Stromal rejection is rare and uncommonly seen in its pure form. We report a case of hyperacute stromal rejection followed by endothelial rejection post-therapeutic penetrating keratoplasty (PK) done for fungal keratitis. The rejection episode responded to steroids with a clearing of the graft. Residual mid to deep intra-stromal crystalline deposits remained at the area of stromal rejection, which remained stationary for a follow-up period of 1 year. The patient underwent Anterior segment optical coherence tomography (AS-OCT) to demonstrate the condition objectively.

Simultaneous Biaxial Stretching of Polypropylene Resins of Varying Tacticity

AbstractThe simultaneous biaxial stretching behavior of three Ziegler-Natta-based isotactic polypropylene resins of varying isotacticity was studied using a laboratory film stretcher that simulates closely stretching conditions encountered in the commercial process. The effect of isotacticity on the final morphology and end film properties was associated with the effect of isotacticity on the thermal properties of the resin. The results showed that the degree of undermelting, △Tum= Tm–T, determines the phase composition of the polymer before stretching and the morphology and orientation of the stretched films. The size and orientation of the crystallites in the stretching plane is mostly determined by the degree of undermelting. The elongation at break was correlated with the residual crystallinity of the film before stretching, and the elastic modulus was correlated with the final degree of crystallinity and the density of tie chains.