Crystallization Behavior Research Articles

Automated in-situ monitoring of accelerated crystallization processes of nifedipine using terahertz time-domain spectroscopy

We developed and tested an automated measurement platform which can fit multiple samples for their investigation in transmission mode using terahertz time-domain spectroscopy. The temperature inside the platform can be varied to simulate different storage conditions of the samples, in our case, pharmaceuticals. As a proof-of-concept, the setup was successfully tested to monitor the crystallization process of amorphous nifedipine, as a model drug, at 24 °C, 30 °C and 35 °C for over 144 h. To the best of our knowledge, this is the first study to follow the crystallization of nifedipine with quasi-continuous measurements over a time frame of several days. The influence of the storage temperature on the crystallization rate was monitored including the appearance of polymorphic intermediate states of nifedipine throughout the process. The platform developed in combination with terahertz time-domain spectroscopy is a helpful tool for deepening the understanding of the crystallization behavior of amorphous and polymorphic materials and can be, for example, of great importance for the development of novel amorphous pharmaceutical formulations.

Interfacial crystallization behavior and properties of T1100-grade carbon fiber reinforced PEEK composites

As a semi-crystalline resin, the crystallization behavior of Polyether ether ketone at the interface between carbon fiber and resin matrix profoundly affects the interfacial properties of carbon fiber-reinforced PEEK composite. Therefore, the research on the interfacial crystallization behavior of CF/PEEK composite is of great significance. Aiming at Chinese-made T1100-grade carbon fiber and PEEK resin matrix, the effects of cooling rate and sizing agent on the interfacial crystallization behavior of T1100-grade carbon fiber/PEEK were studied by POM and DSC, and the IFSS was tested by microdebond. The experimental results show that the increase of the cooling rate and the removal of the sizing agent can improve the nucleation ability of PEEK and promote the interfacial crystallization of PEEK. PEEK starts to form transcrystallization, when the nucleus density is increased to about 0.07/μm. The interfacial crystallization behavior has an effect on the interfacial properties. The IFSS increases with increasing cooling rate and removal of sizing agent.

Phase transition studies of a fluorinated antiferroelectric liquid crystal probed by temperature dependent Raman spectroscopy

Fluorinated liquid crystals (LCs) have emerged as a valuable option for display technologies, rapid switching applications, and photonic devices. Addition of fluorine atoms in the LCs change the electronic distribution within the molecule, introducing required LC properties for various display techniques. In this study, the structural properties of an antiferroelectric LC, (S)-octan-2-yl 2,3-difluoro-4′’-((6-((2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptanoyl)oxy) hexyl) oxy)-[1,1′,4′,1′’-terphenyl]-4-carboxylate is investigated using Raman spectroscopy. This LC exhibits a unique orthoconic antiferroelectric arrangement along with chiral smectic C (SmC*) and smectic A (SmA*) phases. Raman spectra were recorded over a temperature range of 20 °C to 130 °C, covering the spectral region of 500–3500 cm−1. Additionally, theoretical Raman spectra at room temperature is simulated using density functional theory (DFT) with the B3LYP functional and 6-31G (d, p) basis set, showing good agreement with experimental results. Through meticulous fitting of the spectral features using Lorentzian profiles, precise values for peak positions, linewidths, and integrated intensities of selected Raman bands are obtained. Changes in Raman spectral parameters at the crystalline-SmCA*, SmCA*-SmC*, SmC*-SmA*, and SmA*-isotropic phase transitions are analyzed in terms of molecular alignment and intra/intermolecular interactions. The Raman spectral results provide a detailed understanding of the molecular and structural behaviour of the liquid crystal as it undergoes various phase transitions with increasing temperature.

Changing the Oral Tribology of Emulsions Through Crystallization of the Dispersed Triglyceride Phase.

Suspoemulsions are used for food, cosmetic and pharmaceutical products, including food such as dairy products and non-dairy alternatives. Product properties, such as flow behavior or sensory perception of non-dairy products differ from those of dairy products and are therefore perceived by consumers as products of inferior quality. One reason for this may be the crystallization behavior of the added triglycerides leading to differences in solid fat content in comparison to cow milk. This is discussed with the solidity of the dispersed phase as a parameter of suspoemulsions. The solidity was varied by using low and high melting triglycerides and measuring at different temperatures. The dispersed phase fraction is φ = 30%. The droplet size distribution showed a x50,3 of 1.2 and 3.66 μm, mimicking the droplet sizes of milk and dairy cream. Rheological frequency sweeps were carried out within a temperature range from 5°C to 50°C. The differences in solidity of the dispersed phase caused no changes in viscosity at each temperature. In contrast, oral tribology distinguished different solidities of the dispersed phase with changes in the friction coefficient. The friction coefficient was determined for increasing rotational speeds (0.01-100 mm/s), to compare the so called Stribeck curves with each other. In general, with increasing solidity of the dispersed phase, the friction coefficient increases. Comparing the Stribeck curves of pure butter fat suspoemulsion with those of plant-based fat suspoemulsions, different plant-based fats can be mixed, to mimic the friction profile of milk products in plant-based alternatives.

Improving the performance of polylactic acid/polypropylene/cotton stalk fiber composites with epoxidized soybean oil as a high efficiency plasticizer.

Polylactic acid (PLA) can serve as a biodegradable alternative to traditional petroleum-based plastics, but its poor impact resistance and high production costs limit its applications. In this study, different contents of epoxidized epoxy soybean oil (ESO) were added as plasticizer to melt blend with polylactic acid (PLA), polypropylene (PP) and cotton stalk fiber (CSF), examining its impact on the mechanical properties, thermal stability, microstructure, and crystallization behavior of the blends. The results indicated that ESO reacted with PLA and CSF to form branched polymers and microgels. With increasing ESO content, the blends exhibited increased initial thermal decomposition temperature, impact strength, and elongation at break, while stiffness, maximum decomposition rate, and crystallinity decreased. When the mass ratio of CSF to ESO was 2:1, the notch impact strength and elongation at break of PLA/PP/CSF/ESO blends were 1.63 times and 1.98 times higher than those of PLA/PP/CSF blends, respectively. Moreover, a reduction in surface grooves of CSF and formation of a gel layer were observed. Importantly, this study opens an effective new pathway for the utilization of waste natural fibers and the widespread application of biodegradable composite materials, contributing to environmental protection, resource conservation, and cost reduction.

Crystallization behavior of smelting slag for recovery of platinum group metals from spent automotive catalysts and preparation of foamed glass-ceramics

Spent automotive catalysts (SAC), as a significant secondary resource for platinum group metals (PGMs), can be recovered on a large scale through high-temperature smelting. Besides, as a byproduct, the glass slag lacks high-value applications. This paper proposes a recyclable method to convert slag, graphite powder (GP), and ferric oxide (Fe2O3) into foamed glass-ceramics through low-temperature sintering, significantly reducing environmental impacts and production costs. Non-isothermal differential thermal analysis was used to explore the transition and crystallization temperature range, transition kinetic, crystallization kinetic, and crystallization behavior of the glass slag. Furthermore, the influence of the foaming agent composition and heat treatment temperature on the physical properties, chemical resistance, and mechanical properties of the foamed glass-ceramics was investigated. Foamed glass-ceramics composed of 60wt% slag-30wt% Fe2O3-10wt% GP exhibited the excellent properties of a geometric density of 1.43 g/cm3, a volumetric water absorption of 26.32%, a compressive strength of 8.08 MPa, and a mass loss of 3.56% in strong acid and 0.08% in strong alkali after low temperature heat treatment at 1160°C. This study provides an insight into transforming low-value waste into high-performance foamed glass-ceramics.

Crystallization of CoWB ternary boride in nickel-based metallic glass

The crystallization kinetics of CoWB ternary boride were investigated through non-isothermal differential scanning calorimetry experiments, using a Ni-based metallic glass precursor as the starting material. The effects of isothermal heat treatment temperature on the phase evolutions were also systematically studied. The results showed that the melt crystallization and glass crystallization behaviors of the alloy differ from each other. The continuous heating transformation diagram plotted from non-isothermal analyses is consistent with the results of isothermal heat treatments. A broad ternary boride precipitation zone was demonstrated, involving the gradual precipitation of CoWB crystals. Avrami exponent values for the early crystallization stage showed that the crystallization mechanism of CoWB is governed by the interface-controlled three-dimensional growth mechanism, and nucleation rate is high. As the crystallization progresses, a diffusion-controlled growth occurs and the nucleation rate decreases. This study offers insights into the heat treatment of CoWB-reinforced nickel matrix nanocomposites, benefiting future research and industrial production processes.

Phonon dispersion of nanoscale honeycomb phononic crystal: gigahertz and terahertz spectroscopy comparison

Phonons—quantized vibrational modes in crystalline structures—govern phenomena ranging from thermal and mechanical transport to quantum mechanics. In recent years, a new class of artificial materials called phononic crystals has emerged, aiming to control phononic properties. These materials are created by introducing a superlattice structure on top of an already-existing atomic lattice. Typically, phononic crystals are described using a continuous model, in which effective elastic constants approximate potentials between atoms. This approximation, however, assumes the wavelengths of vibrations to be significantly greater than the interatomic distance. In this work, we experimentally investigate the behavior of a honeycomb silicon phononic crystal in the gigahertz range, where the continuum approximation holds, and in the terahertz range, where the phonon wavelengths are comparable to interatomic distances. Using Brillouin light scattering, we investigate the phonon dispersion of the phononic crystal in the gigahertz range, finding a close match with simulations based on the continuous model. Conversely, Raman spectroscopy reveals no difference between the phononic crystal, an unpatterned membrane, and a bulk silicon structure in the terahertz range, showing that the continuous model no longer holds at these higher frequencies.

Polymorphic crystallization and transformation pathways of 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (PPO) during a liquid–solid-liquid journey

Abstract The polymorphic behavior of triacylglycerol (TAG) crystals formed during the manufacturing process of lipid-based food products relates directly to their textural and melting properties. In this work, we analyzed the polymorphic crystallization and transformation behavior of 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (PPO), a widespread TAG in edible fats and oils, during the application dynamic thermal treatments of cooling and heating. By implementing calorimetric, X-ray diffraction, and microscopy techniques, we mapped the polymorphic occurrence and the polymorphic transformation pathways of PPO as a function of the rate of thermal treatments. The results obtained were later compared to that reported for diverse TAGs in previous studies. Despite the overall crystallization and transformation behavior of PPO following a similar trend to other TAGs close in fatty acid composition, we can highlight the much lower influence of varying cooling and heating conditions on the crystallization properties of this TAG. In more detail, crystalline forms of low stability were generally promoted during crystallization, whereas transformations occurred always through the melt independently of the heating conditions. One may expect this behavior to influence the industrial processing and final properties of food products based on edible fats containing PPO.

Freestanding measurement of the polar/nonpolar adsorption interface for complete hydrophobicity switching in polyethylene nanofibrous membranes by trace poly(acrylic acid)

This study explores the underlying mechanisms of polar/nonpolar adsorption dynamics utilizing ultrathin polyethylene (PE) membranes, presenting an innovative method to directly characterize interfacial phenomena. By modifying the surface of these membranes with trace amounts of poly (acrylic acid) (PAA), we probe the entropy-driven hydrophobic and depletion interactions that dominate the adsorption process. This encapsulation significantly alters the hydrophilicity of PE—from a contact angle of 132.2° to 37.0°—while maintaining the micro-structural integrity at remarkably low PAA loadings. For the first time, this approach allows for the isolation and direct characterization of the interface through methods such as weighing, thermal cycling, and tensile testing. Key findings demonstrate that the adsorbed PAA layer is exceptionally loosely packed, exhibiting a porosity exceeding 90 %. Moreover, the presence of PAA differentially impacts the crystallization behavior of FCC and ECC within PE, hindering FCC crystallization significantly while mildly affecting ECC. Post-adsorption, the modified PE membrane exhibits smart separation capabilities: it behaves amphiphilically in air, allowing simultaneous permeation of water and oil, and selectively separates water/oil mixtures in liquid environments based on the pre-wetting phase. The resulting hydrophilic ultrathin PAA-PE membranes maintain high transparency (over 90 %), robust mechanical strength (309 MPa in tensile maximum stress), and substantial porosity, all within a freestanding, 340 nm-thick form. This work not only elucidates several first-time observations of the intriguing polar/nonpolar adsorption interface but also provides new approaches for thorough and stable physical modification to polymer membranes.

Crystal Growth and Ferroelectric Properties of Thiourea Picrate Single Crystal

Ferroelectric hysteresis (P-E) loop study strongly confirmed that Thiourea Picrate (TUP) crystal is a new lead free, prolific ferroelectric material and good switching behavior of the polarization. Curie phase transition at 70OC was observed in the dielectric analysis and AC conductivity study followed the power law with frequency depended. The elemental composition and surface morphology of the TUP crystal were investigated by EDX and SEM analysis. The thermal behavior of the TUP crystal was analyzed using TG/DTA, and found that the melting point of the prepared crystal was 155 ℃. The photoluminescence study shows TUP has a Blue Emission Property.

Synthesis, structure, thermal, spectroscopic and theoretical investigations on novel nonlinear metal-organic hexa-aqua magnesium creatinium sulphate single crystal

A novel Hexa-aqua magnesium creatinium sulphate (HMCS) material was synthesized and grown using slow evaporation method and the crystal is monoclinic with centrosymmetric space group P21/n. Optimized molecular geometry inferred that the overall structure of HMCS comprises a hydrogen bonded network. The optical activity of the grown crystal has been examined by using UV–visible spectral analysis. The most abundant O⋯H interaction (49.5 %) in HMCS influences the stabilization of the packing in the crystal structure. The HOMO LUMO plot was used to determine the molecule's chemical potential, electro-negativity, and chemical hardness. The emission behaviour of HMCS single crystal has been examined by using fluorescence spectral analysis. Thermal stability of the synthesized single crystal was analysed by using TG/DTA analysis. Thirdorder nonlinear optical (NLO) behaviour of HMCS compound was illuminated by the Z-scan method.

Synthesis and Properties of 5,15-Dioxaporphyrin Bearing Various meso-Aryl Substituents.

Herein, a scope ofmeso-substituents for the synthesis of 5,15-dioxaporphyrins (DOPs), a novel antiaromatic porphyrinoid, was investigated. DOPs with various types of aryl substituents were synthesized by nucleophilic aromatic substitution reaction of nickel bis(α,α'-dibromodipyrrin) complexes bearing correspondingmeso-aryl substituents and subsequent intramolecular annulation reaction ofβ-hydroxy-substituted intermediates. Using a copper dipyrrin complex instead of nickel complexes, a copper complex of DOP was synthesized for the first time. Themeso-substituents did not significantly alter the antiaromaticity of DOPs but affected crystal packing diagrams and oxidation behaviors; DOPs with less sterically hinderingpara-substituted phenyl or 2-thienyl substituents formed mutual stacking in the crystal structures, whereas the covalentlyβ-βlinked dimer species was generated during the electrochemical oxidation of those kinds of DOPs.

Preparation, microstructure evolution, and crystallization behavior of eutectic YAG/Al2O3 ceramic coating deposited by atmospheric plasma spraying

In this study, eutectic Y3Al5O12/Al2O3 coatings with alternating YAG and Al2O3 phases are successfully prepared using atmospheric plasma spray (APS) technique. Through subjecting the coatings to heat treatments within temperatures ranging from 1000 °C to 1500 °C, it becomes possible to tailor the microstructures of the coatings, including phase distribution, porosity level, grain sizes, and interphase spacing. Furthermore, an investigation into the crystallization behavior of YAG and Al2O3 phases, as well as the formation mechanism of eutectic-like microstructure in YAG/Al2O3 coatings, reveals that YAG phases undergo primary crystallization from the amorphous phase, followed by secondary crystallization of Al2O3 phases between YAG crystals. This work provides insights into understanding the relationship between heat treatment temperatures and coating morphologies, as well as elucidates the formation mechanism of eutectic-like microstructure, thereby guiding the controlled preparation of YAG/Al2O3 coatings via APS technique.

Effective attainment of a substantial proportion of the PbTiO3 crystalline phase through a non-isothermal crystallization process

The crystallization kinetics studies were performed on a lead–titanium borate glass with a composition 50PbO–25TiO2–25B2O3 (mol %) to well understand the crystallization process by a non-isothermal method in an attempt to obtain a substantial proportion of the lead titanate (PbTiO3) crystalline phase. Based on the DTA result, the glassy material was heat-treated to induce crystallization and then produced a glass-ceramic. The broad hump observed in the XRD patterns of a glassy sample affirmed its amorphous nature. However, XRD studies conducted on a glass-ceramic revealed the evolution of the crystalline phase of PbTiO3 and a minor phase of TiO2. The phase relationship of PbTiO3 resulting from the reaction between PbO and TiO2 during a non-isothermal crystallization process has been examined. The activation energy for the crystallization of PbTiO3 is evaluated to be 135 kJ/mol (at PbO/TiO2 ratio = 2/1 mol %). When the Pb/Ti ratio exceeds 1, the process progresses nearly to completion by the first crystallization peak, and the PbTiO3 phase formation is easier. The fraction of PbTiO3 phase in the present glass is 98.3 % at PbO/TiO2 ratio = 2/1 mol %. In addition, FTIR spectra provided the presence of Ti4+ ions in the glass-ceramic. According to the values of crystal growth and Avrami index, surface crystallization and one-dimensional growth mechanisms are suitable mechanisms for contributing to the crystallization of this glassy sample. The obtained findings provided details on the crystallization behaviour of this glassy sample and excellent insight into obtaining the PbTiO3 crystalline phase in a large proportion, which is of great importance in future technological applications.

Crystallization behavior of amorphous GST films under an ultrafast laser irradiation

The crystallization behaviors of amorphous Ge2Sb2Te5 films induced by an ultrafast laser with a time-shaping Gaussian intensity distribution have been studied. The crystalline regions were characterized using optical microscopy, scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. It is found that the region ablated by a single pulse undergoes recrystallization, with a reflectivity higher than that of the non-ablated crystalline region. While preserving the integrity of the film, the diameter of the region with high and uniform reflectivity induced by burst mode is twice that of a single pulse, and the reflectivity is 3 % higher than the 31 % achieved with a single pulse. Additionally, the energy window for laser-induced crystallization expands with an increasing number of burst pulses; specifically, it increases by approximately 2.4 times when the number of sub-pulses is 4 or 5. The Raman results at low pulse energy show a high peak intensity at the 105 cm−1 in related to the vibrations of Te-rich tetrahedra, indicating that the degree of crystallinity in the burst mode region is superior to that achieved with single pulse irradiation. Furthermore, the blue shift of this Raman peak with increased pulse energy further supports that burst mode provides sufficient time for nucleation growth. This work offers insights into achieving more controllable crystallization, which can enhance its applications in phase change memory and other reconfigurable devices.

Enhancing the Non-Isothermal Crystallization Kinetics of Polylactic Acid by Incorporating a Novel Nucleating Agent.

Polylactic acid (PLA) is a widely recognized biodegradable polymer. However, the slow crystallization rate of PLA restricts its practical applications. In this study, camphor leaf biochar decorated with multi-walled carbon nanotubes (C@MWCNTs) was prepared using the strong adhesive properties of polydopamine, and PLA/C@MWCNTs composites were fabricated via the casting solution method. The influence of C@MWCNTs as a novel nucleating agent on the melt behavior and non-isothermal crystallization behavior of PLA was investigated using differential scanning calorimetry (DSC). The crystallization kinetic parameters were obtained through the Jeziorny, Ozawa, and Mo methods, and the crystallization activation energy of the PLA/C@MWCNTs composites was calculated by the Kissinger method. The results show that the PLA/C@MWCNTs composites exhibit higher crystallinity and crystallization temperatures than those of PLA. Non-isothermal crystallization kinetic analysis reveals that the Mo method better describes the non-isothermal crystallization kinetics of both PLA and PLA/C@MWCNTs composites. In addition, it was found that C@MWCNTs, despite increasing the crystallization activation energy, can act as an efficient nucleating agent to increase the crystallization rate of PLA. These experimental results provide valuable insights for enhancing the slow crystallization rates associated with PLA.

Non-Isothermal Crystallization Kinetics and Properties of CaO-Al2O3-SiO2 (CAS) Glass-Ceramics from Eggshell Waste, Zeolite, and Pumice.

In this study, the crystallization behavior, microstructure, and mechanical and physical properties of CaO-Al2O3-SiO2 (CAS)-based glass-ceramics prepared from eggshell waste, zeolite, and pumice were investigated using X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM), a nanoindentation tester, and the Archimedes method. XRD analysis revealed that anorthite and wollastonite crystalline phases precipitated in the glass-ceramic samples after sintering at temperatures of 1000 °C and 1100 °C. However, diffraction peaks belonging to the wollastonite phase disappeared after sintering at 1200 °C, while peaks representing the pseudowollastonite phase were detected together with anorthite in the samples. SEM images showed that the crystals become coarser as the sintering temperature increased, with the crystal morphology transitioning from needle-like to rod-like. The crystallization activation energy (Ea) and Avrami parameter (n), both kinetic parameters, were calculated from DTA curves plotted at different heating rates using the Kissinger, Ozawa, and Matusita approaches. The results indicated that the crystallization activation energy of the CASZ glass ranged from 406 to 428 kJ mol-1, while that of the CASP glass varied from 356 to 378 kJ mol-1, depending on the method used. Additionally, the Avrami constant (n) was calculated to be 3.33 for CASZ and 2.89 for CASP. The hardness and bulk density of the glass-ceramic samples were significantly affected by the porosity present in the structure, with the highest hardness and bulk density values achieved for the CASZ glass-ceramic sample at the initial sintering temperature of 1000 °C.

Investigation of thermal, crystal and magnetic behavior of addition of Nd rare earth element effect on CuAlMn shape memory alloy

Investigation of thermal, crystal and magnetic behavior of addition of Nd rare earth element effect on CuAlMn shape memory alloy

Thermal Treatment Induced Crystal Development and Crystal Orientation Change in Electrospun Coaxial Fibers Comprising Dual Crystalline Polymers.

This study investigates the crystallization behavior of electrospun coaxial fibers composed of crystalline poly(ethylene oxide) (PEO) in the core and crystalline poly(L-lactide) (PLLA) in the sheath. The influence of cold crystallization temperature and premelting temperature on the crystallization of PEO and PLLA is investigated. At a cold crystallization temperature of ≤60°C, PLLA remained immobile. PEO crystallization is hard-confined, leading to a low degree of crystallinity. At a cold crystallization temperature of >60°C, PEO melted, whereas PLLA crystallized. An increase in cold crystallization temperature results in an increase in the crystallite size and crystallinity of PLLA. Furthermore, the melt crystallization behavior of PEO in the coaxial fibers is strongly influenced by its premelting temperature and crystallization temperature. A higher premelting temperature leads to enhanced interdiffusion between PEO and PLLA. This increased confinement results in a decrease in PEO's crystallizability. Additionally, premelting relaxes the PEO chains, causing a shift in crystal orientation from parallel to the fiber axis (observed in as-electrospun fibers) to perpendicular to the fiber axis (observed in melt-crystallized fibers). Moreover, at a low melt crystallization temperature, demixing between PEO and PLLA is observed. This, coupled with a higher degree of supercooling, leads to an increase in PEO's crystallizability.