Crystallization Rate Research Articles

Frost-heaving characteristics and formation mechanism of saturated sandstone under unidirectional freezing conditions

In this study, a series of frost-heaving experiments were conducted on saturated sandstone at varying cooling rates under unidirectional freezing conditions. The frost-heaving strain in the freezing process was examined using a novel laboratory testing methodology. The results showed that the frost-heaving behavior of the saturated sandstone was significantly affected by the freezing direction and rate. Specifically, the rapid freezing of sandstone parallel to the freezing direction resulted in a more pronounced frost-heaving strain than that perpendicular to the freezing direction. The rock freezing rate had a positive correlation with the peak frost-heaving strain parallel to the freezing direction, and a negative correlation with that perpendicular to the freezing direction. A microstructure-based conceptual model is proposed to determine the frost-heaving pressure. The conceptual model showed that the ice pressure, determined by the pore-water pressure and capillary force, resulted from the crystallization of the pore water within the pore structure. A nonlinear relationship was observed between the ice pressure and crystallization rate. Capillary forces were more significant for slow crystallization processes, resulting in a larger difference between ice and water pressures. At high crystallization rates, the hydraulic pressure acted on the pore structure before the capillary forces become significant, leading to a smaller difference between the water and ice pressures. Rapid crystallization processes resulted in the uneven distribution of ice pressure within the pore structure, with subsequent re-equilibration occurring with the migration of unfrozen water. The proposed conceptual model presents a new perspective for obtaining an improved understanding of the microscopic frost-heaving mechanism involved in the freeze-thaw damage of porous rocks. It provides an evaluation method for the behavior of rocks during weathering by frost heave in cold regions.

Non-Isothermal Crystallization Kinetics of Polyamide 6/Graphene Nanoplatelets Nanocomposites Obtained via In Situ Polymerization: Effect of Nanofiller Size.

Thermoplastic resin transfer molding (T-RTM) technology was applied to synthesize graphene nanoplatelets-based nanocomposites via anionic ring-opening polymerization (AROP). Polyamide 6 (PA6) was obtained by AROP and was used as the polymeric matrix of the developed nanocomposites. The non-isothermal crystallization behavior of PA6 and nanocomposites was analyzed by differential scanning calorimetry (DSC). Nanocomposites with 0.5 wt.% of graphene nanoplatelets (GNPs) with two different diameter sizes were prepared. Results have shown that the crystallization temperature shifted to higher values in the presence of GNPs. This behavior is more noticeable for the nanocomposite prepared with smaller GNPs (PA6/GN). The crystallization kinetic behavior of all samples was assessed by Avrami and Liu's models. It was observed that GNPs increased the crystallization rate, thus revealing a nucleating ability, and also validated the reduction of half-time crystallization values. Such tendency was also supported by the lower activation energy values determined by Friedman's method.

Nucleation and crystallization of deeply supercooled benzocaine, a rapidly crystallizing organic compound: A Fast scanning calorimetry investigation

Investigation of nucleation and crystal growth in rapidly crystallizing systems represents a serious experimental challenge. Fast Scanning Calorimetry (FSC) was successfully used to study isothermal nucleation and crystallization in deeply supercooled melts of polymers and metallic glasses, but only limited attention was devoted to small organic molecules. In the present work, we present data on the nucleation and crystallization of the rapidly crystallizing organic compound benzocaine. We demonstrate that benzocaine can nucleate and crystallize far below the glass transition temperature. In deeply supercooled conditions, the nucleation and crystallization of benzocaine can be described using the equations derived from the Classic Nucleation Theory (CNT). However, at moderate supercooling, nucleation is not observed. Since the crystal growth rate is high at such temperatures, crystallization occurs only in prenucleated samples. The transition between the different behaviors is sharp, and the temperature of the transition is sample dependent. The presented results show a venue for the development of theories and models of nucleation, and demonstrate an important precedent of nuclei development far in the glassy state that must be considered for the application of amorphous drugs.

Analysis of the mechanism of the effect of N–H–O impurities on diamond growth under HPHT

In this work, diamond crystals were synthesized with N–H–O impurities by the temperature gradient method (TGM) under high pressure and high temperature (HPHT) conditions using FeNi alloy as the metal solvent (MS). The results indicated that the spontaneous nucleation rate and proportion, growth characteristics, surface growth texture, and the impurity concentration of diamond crystals changed drastically upon changing the impurity content in the system. Mutual diffusion between the MS and carbon source (CS) was also blocked, which seriously inhibited the growth rate of diamond crystals. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses corroborated that the zero-valent iron (Fe0) and nickel (Ni0) contents declined after N–H–O impurities were introduced. The newly formed graphite can be found in the MS, but the ferric carbide disappears. XPS also confirmed shifts in the binding energy of FeNi MS peaks, more iron oxide and nickel oxide were identified in MS, hindering the mass transfer process. CO and NO were absorbed on the surface of MS, which hindered the surface processes of diamond growth. The formation of intermediates (Fe3C) was impeded during diamond growth and blocked the spontaneous nucleation of diamond. All of these phenomena contributed to a poor growth rate and changed the surface growth process of diamond crystals.

Role of Stearic Acid as the Crystal Habit Modifier in Candelilla Wax-Groundnut Oil Oleogels

This study investigated the effects of incorporating stearic acid (SAC) in candelilla wax (CW) and groundnut oil (GO) oleogel with potential health benefits as an alternative to saturated fats in processed foods. Results showed that SAC possesses crystal habit-modifying properties on the oleogels, causing its average crystallite size to increase, as observed through polarized light microscopy and XRD analysis. Additionally, SAC caused an increase in ordering within the crystallite network as a result of the decrease in d-spacing. Interestingly, the firmness of the oleogels remained unaffected, even at a higher fraction of SAC. It is believed to be due to the interference caused by the crystallization of high-melting SAC within the fine crystal network of CW-GO oleogel. However, adding 3 mg of SAC significantly increased the work of the shear of the oleogel (SAC3), which decreased the spreadability. As observed through colorimetric analysis, SAC3 showed a dense and uniform distribution of prominent bright crystals with minimal amorphous regions, leading to a high whiteness index. SAC3 also demonstrated the highest compactness and dislocation density among the oleogels, likely due to the formation of prominent crystals. However, SAC did not affect the overall oleogel crystallization rate. SAC3 had delayed secondary crystallization and thermal equilibrium by having a prolonged crystallization time of CW crystals. In the case of controlled delivery studies, the addition of SAC improved CPCR. On the other hand, CPCR decreased with the increase in SAC amount, where SAC3 showed a moderate curcumin release ability among the oleogels.

Synergistic lattice regulation of additive and interface engineering to realize high efficiency CsPbI2Br perovskite solar cell

The CsPbI2Br material has gained recognition as an exceptional candidate for both single- and multi- junction solar cells due to its remarkable thermal and light stability, along with its suitable band gap. However, despite these inherent advantages, CsPbI2Br perovskite solar cells (PSCs) still encounter significant energy losses, which impede the further enhancement of their efficiency. Although various approaches involving additives and interface engineering techniques improved device performance, the influence of these methods on the perovskite lattice is frequently overlooked. Herein, synergistic lattice regulation through the combination of potassium acetate (KAc) as electron interface layer and methylammonium chloride (MACl) as perovskite additive, was proposed. The MACl dopant effectively increases the crystallinity and grain size of CsPbI2Br film by retarding the crystallization rate of perovskite, resulting in the enhancement in short-circuit current density (Jsc) of PSCs. Unfortunately, unlike the behavior observed in inorganic–organic perovskites, the introduction of Cl‾ from MACl into the interstitial positions leads to lattice expansion in CsPbI2Br, resulting in reduced open-circuit voltage (Voc) and fill factor (FF). However, the incorporation of K+ replacing Cs+ effectively mitigates lattice distortion phenomena. Consequently, the CsPbI2Br PSCs, benefiting from the complementary effects of the MACl additive and KAc interfacial layer, exhibit an outstanding champion power conversion efficiency of 17.11 %. This research offers profound insights into the impact of ions introduced through additive and interface engineering on perovskite lattice stress.

Accelerated nonisothermal crystallization and improved material properties of biobased poly(butylene 2,5-furandicarboxylate)/talc composites

Biobased poly(butylene 2,5-furandicarboxylate) (PBF) reflects the much poorer crystallizability than its petroleum-based counterpart poly(butylene terephthalate). By introducing talc platelets into PBF matrix to fabricate composites, the effects of low loadings’ layered filler upon nonisothermal melt crystallization and material properties of PBF/talc composites are investigated for the first time. Obviously accelerated crystallization of the composites relative to pure PBF is first evidenced by the simultaneous increase of crystallization temperature and decline of crystallization half-time, and further supported by both the crystallization rate coefficient and crystallization rate parameter. Nonisothermal crystallization kinetics are analyzed by both the Jeziorny model and Mo equations, and the intensifying effect of talc upon PBF's crystallization is attributed to the coupling of enlarging nucleation activity and lowering crystallization activation energy. Meanwhile, the incorporation of layered talc doesn't modify the crystal structure of PBF. Moreover, both the thermal and mechanical properties of PBF/talc composites are reinforced slightly.

Effects of LPCVD-deposited thin intrinsic silicon films on the performance of boron-doped polycrystalline silicon passivating contacts

Highly efficient n-type tunnelling oxide passivated contact solar cells can be realized by integrating p-type polycrystalline silicon (p+ poly-Si) boron (B) diffusion technology. In this study, the intrinsic silicon (i-Si) film was prepared with varying crystalline states, by precisely controlling the deposition temperature using low-pressure chemical vapor deposition (LPCVD). The i-Si films transitioned from amorphous to polycrystalline when the deposition temperature was increased from 560 °C to 590 °C, with the crystallization rate increasing from 0 % to 81.5 %. An inverse correlation was observed between the electrical properties of B-diffused p+ poly-Si and the crystallization rate of i-Si thin films. The crystal structure of p+ poly-Si contained an amorphous phase, even after high-temperature B diffusion (>900 °C).The defect density and grain boundary potential barriers within the crystal were increased, which resulted in enhanced carrier scattering probability and deteriorated material performance. Amorphous silicon film deposited at lower temperatures can achieve low contact resistivity (ρc = 0.81 mΩ·cm2) and improved passivation performance (Δi-Voc > 10 mV) after B diffusion. These results have significant implications for the development of highly efficient passivated contact solar cells with excellent passivation performance and low contact resistance hole-selective contacts.

LBM-PFM simulation of the effect of non-condensable gas on the directional crystallization of seawater

The present study employs the coupled Lattice Boltzmann Method-Phase Field Method (LBM-PFM) to investigate the impact of non-condensable gas bubbles on directional crystallization of seawater at the pore scale. Firstly, the LBM-PFM coupling model is proposed and experimentally validated. Subsequently, this model is applied to numerically simulate the two-phase (bubble -seawater) flow in directional crystallization. Additionally, the influence of factors such as bubble quantity, radius, and arrangement on ice crystal growth and the distribution, quantity, and area of internal brine pockets are discussed. The findings unequivocally demonstrate that the presence of non-condensable gas bubbles significantly enhances the rate of crystallization, resulting in a twofold increase in the area of freshwater ice. Bubbles with different radius, quantities, and spacing exert either promoting or inhibiting effects on the formation of brine pockets. Increasing bubble radius and quantity result in a larger area of freshwater ice crystals and a reduction in the quantity and area of brine pockets, ultimately resulting in an improved desalination efficiency. While changes in bubble spacing have a minimal impact on the generated ice crystal area, they significantly alter the distribution of brine pockets. Smaller spacing between bubbles leads to a lower number of brine pockets formed, thus inhibiting brine pocket generation.

Silicon‐linked polyethylene glycol‐polyethylene terephthalate (PEG‐PET) nanostructures loaded with Eu3+‐complexes for hybrid luminescent PET materials

AbstractIn this work, innovative hybrid poly(ethylene terephthalate) (PET) materials with strong luminescence were successfully synthesized by doping PET with silicon‐linked poly(ethylene glycol)‐PET copolymer nanostructures either with (Si‐PEG‐PET) or with (ETP@Si‐PEG‐PET) luminescent Eu3+‐complexes. The chemical properties and nanostructures of the hybrid materials were characterized by Fourier‐transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, x‐ray photoelectron spectroscopy, and high‐resolution transmission electron microscopy. PET composites ranging from 0.25 to 4 wt% silicon additive were prepared by the melt blending method. The crystal properties, mechanical properties, and fluorescence properties of the composites were systematically studied by differential scanning calorimetry, x‐ray diffractometry, tensile testing, and fluorescence spectrometry. When the addition of Si‐PEG‐PET or ETP@Si‐PEG‐PET was 0.75 wt%, the relative crystallinity and maximum tensile strength increase substantially. Moreover, the fluorescence intensity of hybrid luminescent PET materials is the strongest at 0.75 wt% loading. ETP@Si‐PEG‐PET not only endows PET polyester with stronger fluorescence properties and mechanical properties but also acts as an effective nucleation additive for PET.Highlights Silicon‐linked poly(ethylene glycol)‐poly(ethylene terephthalate) (PEG‐PET) nanostructures generate hybrid luminescent PET materials. ETP@Si‐PEG‐PET improves the crystallization rate and crystallinity of PET. The composite with 0.75% addition showed the best fluorescence performance. Three‐dimensional‐grid structure of ETP@Si‐PEG‐PET enhances the mechanical property of PET.

Development of PLA/Lignin Bio-Composites Compatibilized by Ethylene Glycol Diglycidyl Ether and Poly (ethylene glycol) Diglycidyl Ether.

Poly (lactic acid) (PLA) is a promising green substitute for conventional petroleum-based plastics in a variety of applications. However, the wide application of PLA is still limited by its disadvantages, such as slow crystallization rate, inadequate gas barrier, thermal degradation, etc. In this study, lignin (1, 3, 5 PHR) was incorporated into PLA to improve the thermal, mechanical, and barrier properties of PLA. Two low-viscosity epoxy resins, ethylene glycol diglycidyl ether (EGDE) and poly (ethylene glycol) diglycidyl ether (PEGDE), were used as compatibilizers to enhance the performance of the composites. The addition of lignin improved the onset degradation temperature of PLA by up to 15 °C, increased PLA crystallinity, improved PLA tensile strength by approximately 15%, and improved PLA oxygen barrier by up to 58.3%. The addition of EGDE and PEGDE both decreased the glass transition, crystallization, and melting temperatures of the PLA/lignin composites, suggesting their compatabilizing and plasticizing effects, which contributed to improved oxygen barrier properties of the PLA/lignin composites. The developed PLA/lignin composites with improved thermal, mechanical, and gas barrier properties can potentially be used for green packaging applications.

Revealing the mechanism of quartz sand seeding in accelerating phosphorus recovery from anaerobic fermentation supernatant through vivianite crystallization

The recovery of phosphorus (P) through vivianite crystallization offers a promising approach for resource utilization in wastewater treatment plants. However, this process encounters challenges in terms of small product size and low purity. The study aimed to assess the feasibility of using quartz sand as a seed material to enhance P recovery and vivianite crystal characteristics from anaerobic fermentation supernatant. Various factors, including seed dosage, seed size, Fe/P ratio, and pH, were systematically tested in batch experiments to assess their influence. Results demonstrated that the effect of seed enhancement on vivianite crystallization was more pronounced under higher seed dosages, smaller seed sizes, and lower pH or Fe/P ratio. The addition of seeds increased P recovery by 4.43% in the actual anaerobic fermentation supernatant and also augmented the average particle size of the recovered product from 19.57 to 39.28 μm. Moreover, introducing quartz sand as a seed material effectively reduced co-precipitation, leading to a notable 12.5% increase in the purity of the recovered vivianite compared to the non-seeded process. The formation of an ion adsorption layer on the surface of quartz sand facilitated crystal attachment and growth, significantly accelerating the vivianite crystallization rate and enhancing P recovery. The economic analysis focused on chemical costs further affirmed the economic viability of using quartz sand as a seed material for P recovery through vivianite crystallization, which provides valuable insights for future research and engineering applications.

Effect of hydrophobic nano‐silica/β‐nucleating agent on the crystallization behavior and mechanical properties of polypropylene random copolymers

AbstractIn this work, hydrophobic nano‐silica (SiO2) and β‐nucleating agent are incorporated into polypropylene random copolymer (PP‐R) matrix by melt blending. The effect of the content of nano‐SiO2/β‐nucleating agent on the crystallization and mechanical behaviors of PP‐R was investigated in detail. For a nano‐SiO2 content of 0.5 wt% and a β‐nucleating agent content of 0.5 wt%, the tensile strength and impact strength of the composite were in a more balanced position. Regarding isothermal and non‐isothermal crystallization experiments, nano‐SiO2/β‐nucleating agent significantly accelerated the nucleation and growth of crystallites with a synergistic nucleation effect. Also, the crystallization kinetics of PP‐R/nano‐SiO2/β‐nucleating agent, PP‐R/nano‐SiO2 and PP‐R/β‐nucleating agent composites were analyzed and compared using the Avrami equation. The results showed that the PP‐R/nano‐SiO2/β‐nucleating agent composites have better crystallization rate and shorter semi‐crystallization time. This study shows far‐reaching theoretical and practical implications for accelerating the development of new high‐performance PP‐R materials. © 2023 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Dual regulation of crystal structure and purity of Ti2SC in the Ti/TiC/FeS2 system via enhancing reactant contact and controlling crystal plane growth rates

Typically, the X-ray diffraction spectrum of a highly oriented structure (HOS) MAX phase displays a prominent (002) characteristic peak. Surprisingly, this principle does not hold true for Ti2SC. Instead, the synthesized Ti2SC consistently exhibits a polyhedral structure (PS). Furthermore, even with hot-pressing sintering, the purity of Ti2SC remains relatively low. The primary factors contributing to anomalous crystal structures and low purity are insufficient crystal growth and limited reactant contact. In this study, we successfully achieved dual regulation of the crystal structure and purity of Ti2SC within the Ti/TiC/FeS2 system, which was accomplished by enhancing reactant contact and controlling the growth rates of crystal planes. Notably, the intermediate products FeS and Fe, existing in a liquid phase at varying temperatures, played a crucial role in both the formation of Ti2SC and the growth of Ti2SC crystals. As a result, PS-Ti2SC and HOS–Ti2SC with purity greater than 99 wt% were successfully prepared. The formation of PS-Ti2SC can be attributed to the inadequate growth of each crystal plane at relatively lower temperatures (1500 °C). While the synthesis of HOS–Ti2SC necessitates the utilization of both a liquid phase and high temperature, as the epitaxial growth mechanism followed by vertical growth has been demonstrated to facilitate the generation of highly oriented crystals. The liquid phase facilitates the swift growth of Ti2SC crystals along the (001) crystal plane, while the (002) crystal plane necessitates a higher temperature (1760 °C) for relatively rapid growth. This work will open a new pathway for the development of the MAX phase from the perspective of crystal structure regulation and high purification preparation.

Enhancing interfacial interaction and crystallization in polylactic acid-based biocomposites via synergistic effect of wood fiber and self-assembly nucleating agent

Incorporation of natural fibers into polylactic acid (PLA) provides a feasible pathway to improve the performance of PLA with a low environmental impact. However, the insufficient interfacial adhesion between fiber and matrix limits the reinforcement efficiency of fiber and final mechanical properties of the biocomposites. Herein we reported an efficient method to simultaneously enhance interfacial interaction, crystallization and mechanical performance of PLA-based biocomposites via combination of wood fiber (WF) and a self-assembly nucleating agent (TMC-300). The interactions between WF and TMC-300 and its influence on PLA, including interfacial crystal morphology, crystallization behavior, and mechanical performance were studied. The results showed that TMC-300 could self-assemble into dendritic-like structure on WF surface driven by hydrogen bonding, inducing the epitaxial crystallization of PLA. This unique interfacial crystallization integrated PLA matrix with WF, resulting in better interfacial adhesion. Under the optimal TMC-300 content (0.5 wt%), the flexural strength and notched impact strength of PLA composites increased by 10 % and 69 % compared with neat PLA, respectively. Additionally, TMC-300 and WF synergistically functioned as effective nucleating agents, which significantly accelerated the crystallization rate and improved the crystallinity of PLA. This work provides a new insight into the enhancement of interfacial bonding in natural fiber/PLA biocomposites.

Revealing the hydrodynamic effects on phosphorus recovery as vivianite in stirring and aeration systems through PIV experiments and theoretical calculations

Hydrodynamic conditions have an essential influence on the precipitation and agglomeration processes of crystals. However, the influence of hydrodynamics under different operating conditions on vivianite crystallization is commonly ignored in the phosphorus recovery process. To this purpose, the effects of hydrodynamics on vivianite properties in stirring and aeration systems were investigated with the aid of particle image velocimetry (PIV). Hydrodynamic parameters of shear rate (G), flow velocity, Kolmogorov microscale (η), turbulent dissipation rate (ε), and turbulent kinetic energy (k) were calculated, and the generated vivianite properties were recorded. The analysis of flow field distribution showed that the mixing state under the stirring system was more homogeneous and formed a smaller hydraulic dead zone, which may be more favorable for the formation and growth of crystals. Compared with the aeration system at the same G, the stirring system has higher hydrodynamic parameters, producing stronger turbulent intensity and higher shear rate. The higher recovery efficiency, as well as larger crystal size in the stirring system, demonstrated that higher shear rates (95–309 s−1) increased the crystallization rate, ultimately improving the crystal size and settling performance. Significant relationships between hydrodynamic parameters and the harvested crystal size showed that the flow velocity, η, ε, and k were suitable hydrodynamic parameters for evaluating the growth of vivianite. This work is expected to provide the theoretical basis and technical support for the design and operation of vivianite recovery reactors.

Process optimization and crystallization kinetics of ammonium sulfate from wet ammonia‐based desulfurization

AbstractThere are some problems in the production of ammonium sulfate, a byproduct of the ammonia desulfurization process, such as small crystal size and uneven distribution. The evaporative crystallization kinetics of ammonium sulfate and the factors affecting the crystallization of ammonium sulfate for improving the quality of ammonium sulfate were studied. The results showed that the largest mean diameter of ammonium sulfate was obtained at a stirring speed of 400 r/min, evaporation temperature of 60 °C, and pH of 5.0. The particle size of the ammonium sulfate increased when the crystal seed was introduced. The metastable region of ammonium sulfate was determined by laser method. The crystallization process of ammonium sulfate was studied using population balance equations and intermittent dynamic method, and the empirical equation of nucleation rate and growth rate of ammonium sulfate crystallization was obtained. This experiment can provide a solution for the problems existing in the production of ammonium sulfate in the process of ammonia desulfurization.

Study on glass-ceramic prepared by zinc leaching residue and solidification mechanism of heavy metals

Zinc leaching residue is a hazardous solid waste with difficult treatment, high hazard and high yield, and it is a great challenge to treat it efficiently, harmlessly and economically among the various methods available. This paper introduced a micro-crystallization method to process zinc leaching residue into glass-ceramics with excellent performance and high value. The heavy metals in the raw material were well solidified in the glass-ceramics, eliminating the high hazard of heavy metals and other components. The bending strength, compressive strength, and Vickers hardness of the glass-ceramics prepared at the sintering temperature of 950 °C were 69.2 MPa, 434.3 MPa, and 6.66 GPa, respectively, while the water absorption, density, and acid and alkali corrosion resistance were excellent. The relationship between the microstructure and properties of glass-ceramics was investigated using traditional analytical techniques such as XRD, Raman, and SEM, and the mechanism of solidification of heavy metals Pb, Zn and Mn in glass ceramics were innovatively researched by the modified BCR sequential leaching test and XPS analysis. Anorthite and diopside ferrian were the two main crystalline phases in glass-ceramics. The sintering temperature affected the formation and growth of crystals, and determined the crystal size and crystallization rate, thus affecting the properties of glass-ceramics. Part of the heavy metal was solidified in the amorphous phase in the glass-ceramic, and the other major part entered the crystal as an impurity substitution to form a solid solution at a specific location. The zinc leaching residue based glass-ceramic had been studied, which was pioneering and with excellent performance and environmental safety. Thus, the safe and economical treatment of these hazardous wastes promotes the clean, green and efficient development of related industries.

Do Pegmatites Crystallise Fast? A Perspective from Petrologically-Constrained Isotopic Dating

Most recent studies consider the formation of individual pegmatite bodies to be a fast process with estimated crystal growth rates reaching a walloping 10 m/day. This opinion is presumably underpinned by the traditional way of thinking of them as the end products of magmatic fractionation. Indeed, modelling has shown that if a pegmatite-forming substance with a temperature near granitic solidus intrudes into a much colder host rock, as recorded in some outcrops, it must cool rapidly. From here, a conclusion is made that the crystallisation must likewise be rapid. However, this view is challenged by several studies that published isotopic dates supported by petrological characterisation of the analysed materials, which suggested or can be used to suggest that some minerals in pegmatites grew over millions of years. Surprisingly, such in-depth work on the geochronology of individual pegmatite bodies is relatively uncommon, so it is early to make generalisations. Here, I highlight some of the existing evidence with the aim to stimulate further research into the timescales of pegmatite crystallisation, including the use of petrologically constrained isotopic dating.

Composites made of Ginkgo biloba fibers and polylactic acid exhibit non-isothermal crystallization kinetics

Polymer crystallization affects material microstructure and the final product quality, and the crystallization kinetics that govern this process are critical. In this study, alkali-treated Ginkgo biloba fibers (GFs) were melt blended with polylactic acid (PLA) to obtain GF/PLA blends. The non-isothermal crystallization kinetics of the GF/PLA composites were subsequently investigated using the Avrami, Jeziorny, Ozawa, and Liu-Mo methods, and the crystallization activation energies of the systems were calculated by Kissinger and Friedman models. The results showed that the GFs significantly promoted PLA crystallization, accelerated the crystallization rate, and shortened the crystallization time. The Avrami method showed some deviation from the linear relationship due to the effect of secondary crystallization, while the numeric value obtained by the Jeziorny method increased with the cooling rate. The Ozawa method could only be used in a very narrow range of temperatures, while the Liu-Mo method showed a more desirable fit. Crystallization activation energy calculations showed that the GFs promoted an increase in the crystallization capacity of the blend and a decrease in the effective potential barrier. This resulted in more selective biocomposites than pure PLA, offering greater applicability in domains including tissue engineering and 3D printing.