Articoli di riviste: "Ice layer crystallization"

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Osmanbegovic, Nahla, Lina Yuan, Heike Lorenz e Marjatta Louhi-Kultanen. "Freeze Concentration of Aqueous [DBNH][OAc] Ionic Liquid Solution". Crystals 10, n. 3 (26 febbraio 2020): 147. http://dx.doi.org/10.3390/cryst10030147.

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In the present work, freeze crystallization studies, as a novel concentration method for aqueous 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc]) ionic liquid solution, were conducted. In order to find the appropriate temperature and composition range for freeze crystallization, the solid–liquid equilibrium of a binary [DBNH][OAc]–water compound system was investigated with differential scanning calorimetry (DSC). Results of this analysis showed that the melting temperature of the pure ionic liquid was 58 ℃, whereas the eutectic temperature of the binary compound system was found to be −73 ℃. The activity coefficient of water was determined based on the freezing point depression data obtained in this study. In this study, the lowest freezing point was −1.28 ℃ for the aqueous 6 wt.% [DBNH][OAc] solution. Ice crystal yield and distribution coefficient were obtained for two types of aqueous solutions (3 wt.% and 6 wt.% [DBNH][OAc]), and two freezing times (40 min and 60 min) were used as the main parameters to compare the two melt crystallization methods: static layer freeze and suspension freeze crystallization. Single-step suspension freeze crystallization resulted in higher ice crystal yields and higher ice purities when compared with the single-step static layer freeze crystallization. The distribution coefficient values obtained showed that the impurity ratios in ice and in the initial solution for suspension freeze crystallization were between 0.11 and 0.36, whereas for static layer freeze crystallization these were between 0.28 and 0.46. Consequently, suspension freeze crystallization is a more efficient low-energy separation method than layer freeze crystallization for the aqueous-ionic liquid solutions studied and, therefore, this technique can be applied as a concentration method for aqueous-ionic liquid solutions.

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Makhinova, А. F., A. N. Makhinov e Liu Shuguang. "Mechanisms of Crystallization of Chemical Compounds in Amur Ice and The Role of Heavy Metals in River Pollution". Ecology and Industry of Russia 27, n. 3 (14 marzo 2023): 54–59. http://dx.doi.org/10.18412/1816-0395-2023-3-54-59.

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It is shown that cryoprocesses play an important role in the pollution of watercourses during ice formation. The content of heavy metals was determined layer by layer in ice cores. The growth rate of ice crystals, determined by the temperature regime, has been established. The mechanisms of concentration of chemical compounds in supercooled water at the contact with the lower surface of the ice mass and their crystallization are considered. It is revealed that the phase transition of water from a liquid to a solid state and the growth of ice crystals contribute to the supersaturation of water with chemical compounds between ice crystals. The conditions under which the concentrations of crystallizing chemical compounds exceed their average content in under-ice water and play an important role in channel pollution during floods are described.

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Klbik, Ivan, Katarína Čechová, Igor Maťko, Ján Lakota e Ondrej Šauša. "On crystallization of water confined in liposomes and cryoprotective action of DMSO". RSC Advances 12, n. 4 (2022): 2300–2309. http://dx.doi.org/10.1039/d1ra08935h.

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Hasan, M., e M. Louhi-Kultanen. "Ice growth kinetics modeling of air-cooled layer crystallization from sodium sulfate solutions". Chemical Engineering Science 133 (settembre 2015): 44–53. http://dx.doi.org/10.1016/j.ces.2015.01.050.

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Jiang, Panxing, Zhigang Zhan, Di Zhang, Chenlong Wang, Heng Zhang e Mu Pan. "Two-Dimensional Simulation of the Freezing Characteristics in PEMFCs during Cold Start Considering Ice Crystallization Kinetics". Polymers 14, n. 15 (5 agosto 2022): 3203. http://dx.doi.org/10.3390/polym14153203.

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Cold start is one of the major issues that hinders the commercialization of polymer electrolyte membrane fuel cells (PEMFCs). In this study, a 2D transient multi-physics model is developed to simulate the cold start processes in a PEMFC. The phase change between water vapor, liquid water, and ice in the catalyst layers (CLs), micro porous layer (MPLs), and gas diffusion layers (GDLs) is also investigated, particularly the effect of ice crystallization kinetics when supercooled liquid water changes into ice. The factors affecting the different operating conditions and structural features of the membrane electrode assembly (MEA) are investigated. The results show that when the start temperature is −20 °C or higher, ice formation is delayed and the formation rate is decreased, and supercooled liquid water permeates from the CL into the MPL. For an MEA with relatively high hydrophobicity, the water permeation rate is high. These results can enable a PEMFC to start at subzero temperatures. The effect of ice crystallization kinetics is negligible when the fuel cell is started at −30 °C or below.

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Dursch, T. J., G. J. Trigub, R. Lujan, J. F. Liu, R. Mukundan, C. J. Radke e A. Z. Weber. "Ice-Crystallization Kinetics in the Catalyst Layer of a Proton-Exchange-Membrane Fuel Cell". Journal of The Electrochemical Society 161, n. 3 (17 dicembre 2013): F199—F207. http://dx.doi.org/10.1149/2.004403jes.

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Dursch, T. J., M. A. Ciontea, C. J. Radke e A. Z. Weber. "Isothermal Ice Crystallization Kinetics in the Gas-Diffusion Layer of a Proton-Exchange-Membrane Fuel Cell". Langmuir 28, n. 2 (3 gennaio 2012): 1222–34. http://dx.doi.org/10.1021/la2033737.

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Sánchez, J., Y. Ruiz, J. M. Auleda, E. Hernández e M. Raventós. "Review. Freeze Concentration in the Fruit Juices Industry". Food Science and Technology International 15, n. 4 (agosto 2009): 303–15. http://dx.doi.org/10.1177/1082013209344267.

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In conventional processes, such as evaporation, higher levels of concentration can be reached compared with freeze concentration or membrane techniques. However, the advantage of the freeze concentration technique is based on the quality of the product obtained due to the low temperatures used in the process, which makes it a very suitable technology for the processing of fruit juices. There are two basic methods for concentrating solutions by freezing: suspension and film freeze concentration. Suspension freeze concentration systems (FCS) already have operating equipment in the food industry, while film FCSs, also called layer crystallization, is still at an experimental stage. This review summarizes the most important studies relating to the suspension and film freeze concentration in fruit juices and sugar solutions, illustrating the different possibilities that freeze concentration has in the fruit juices industry; it also presents trends and suggests improvements for the future development of this technology. It is noted that most recent publications refer to the film FCS. The technology used to design, build and maintain layer crystallization equipment is simple and it can be available to any operator in the food industry, layer systems will be used in the future if their results can be improved in terms of ice purity and degree of fluid concentration.

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Nizovtseva, Irina. "Nonlinear model of the mushy layer in the time-dependent crystallization of sea water in ice cracks". Advanced Studies in Theoretical Physics 7 (2013): 1011–16. http://dx.doi.org/10.12988/astp.2013.39112.

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Dursch, T. J., M. A. Ciontea, G. J. Trigub, C. J. Radke e A. Z. Weber. "Pseudo-isothermal ice-crystallization kinetics in the gas-diffusion layer of a fuel cell from differential scanning calorimetry". International Journal of Heat and Mass Transfer 60 (maggio 2013): 450–58. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2012.12.048.

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Kimura, Hiroshi, Koji Wada, Hiroshi Kobayashi, Hiroki Senshu, Takayuki Hirai, Fumi Yoshida, Masanori Kobayashi et al. "Is water ice an efficient facilitator for dust coagulation?" Monthly Notices of the Royal Astronomical Society 498, n. 2 (17 agosto 2020): 1801–13. http://dx.doi.org/10.1093/mnras/staa2467.

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ABSTRACT Beyond the snow line of protoplanetary discs and inside the dense core of molecular clouds, the temperature of gas is low enough for water vapour to condense into amorphous ices on the surface of pre-existing refractory dust particles. Recent numerical simulations and laboratory experiments suggest that condensation of the vapour promotes dust coagulation in such a cold region. However, in the numerical simulations, cohesion of refractory materials is often underestimated, while in the laboratory experiments, water vapour collides with surfaces at more frequent intervals compared to the real conditions. Therefore, to re-examine the role of water ice in dust coagulation, we carry out systematic investigation of available data on coagulation of water-ice particles by making full use of appropriate theories in contact mechanics and tribology. We find that the majority of experimental data are reasonably well explained by lubrication theories, owing to the presence of a quasi-liquid layer (QLL). Only exceptions are the results of dynamic collisions between particles at low temperatures, which are, instead, consistent with the JKR theory, because QLLs are too thin to dissipate their kinetic energies. By considering the vacuum conditions in protoplanetary discs and molecular clouds, the formation of amorphous water ice on the surface of refractory particles does not necessarily aid their collisional growth as currently expected. While crystallization of water ice around but outside the snow line eases coagulation of ice-coated particles, sublimation of water ice inside the snow line is deemed to facilitate coagulation of bare refractory particles.

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Сушков, Sergey Sushkov, Сергеев e Andrey Sergeev. "THE ALGORITHM OF FORMATION OF CRACKS ON THE LOGGING ROADS SURFACE ARRANGED ON THE SLOPE, OVERLAIN BY CLAYEY SOIL AT THE BASE". Forestry Engineering Journal 7, n. 1 (15 agosto 2017): 118–26. http://dx.doi.org/10.12737/25202.

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In the article the algorithm of formation of cracks on the surface of forest roads arranged on the slope, overlain by clayey soil at the base is defined. The possible causes of the moisture transfer from the physical point of view, the movement of soil moisture in the cooling zone, the conditions of formation of cracks are considered. The principle of migration of moisture in freezing soils is formulated as follows: the migration of water into the freezing wet soils is the process of transfer of moisture, constantly arising from any violation of the equilibrium state of the phases of soil and the measurements of the external influences in the presence of temperature gradients, humidity, pressure, surface energy of mineral particles, mobility of the molecules in the water film. The ratio between the rate of migration and rate of cooling determines the number and power of ice layers in soils, freezing with the inflow of water from outside. The more delayed the temperature of ice formation at this level, the more powerful the ice layer arise here, as enough water have time to catch up with for the growth of ice crystals. Water migration in frozen soils is possible only due to the unfrozen water held by adsorption forces by the surface of the mineral particles of soil and ice, it is subjected to the same laws of motion of film water, which are established for soils having a positive temperature, but has its own characteristics due to the additional action of crystallization forces of ice; however, in this case the migration process of water film will be very slow. Transfer of energy and substances in multicomponent environments in the general case is described using the apparatus of the thermodynamics of irreversible processes. When creating temperature gradient in the dispersion medium the main effect occurs – the heat flow and cross effects, including mass flow. The results of the experiments and the numerical calculations made with the assumption that the termination of the water flow to the ice enabled the authors to assert that the frozen fracture of the porous bodies and of frost heaving of soil is the disjoining pressure of thin layers of unfrozen water and their pyro-crystallization flow.

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Mazzam, A. A., H. A. Hamizlan, I. Z. A. I. Jamal Ikhsan, M. N. F. Bakar, F. H. Ab Hamid e F. H. Ab Hamid. "Influence of process parameters in removing wastewater impurities via progressive freeze crystallization". Archives of Materials Science and Engineering 119, n. 2 (1 febbraio 2023): 56–61. http://dx.doi.org/10.5604/01.3001.0053.4741.

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The research aims to investigate the effect of the process parameter of progressive freeze concentration to eliminate tricholorophenol in wastewater.A stainless steel crystallizer was used throughout the experiment. Simulated wastewater containing trichlorophenol (TCP) was used as a sample solution, and ethylene glycol was utilized as a coolant to induce the heat transfer at a very low temperature. Progressive freeze crystallization (PFC) is an approach to purify water by implementing the fundamental concept of difference freezing point. In short, the PFC system produces ice-crystal layer by layer on a cooled surface until it forms a large and single-crystal block, leaving the impurities in the mother liquor.It is established that operating time and initial concentration influence the PFC performance. The findings show that the intermediate operating time gave the highest removal of TCP in wastewater. Meanwhile, for the effect of initial concentration, it was discovered that the lowest initial concentration resulted in the best TCP reduction with high purity of the water was obtained.The results can be complemented by studies of the effect of coolant temperature and solution movement. These two parameters are believed to potentially improve the PFC performance.The findings can be implemented to select the optimal operating condition to treat the wastewater, especially in the industrial area with hazardous TCP.The obtained results testify to the predominant influence of operating time and initial concentration on the PFC performance in eliminating TCP in wastewater.

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Yu, Hongfeng, Qiang Zhang e Wei Zhuang. "Comparative analysis of hydration layer reorientation dynamics of antifreeze protein and protein cytochrome P450". Chinese Journal of Chemical Physics 35, n. 3 (giugno 2022): 509–15. http://dx.doi.org/10.1063/1674-0068/cjcp2203038.

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Antifreeze proteins (AFPs) inhibit ice re-crystallization by a mechanism remaining largely elusive. Dynamics of AFPs’ hydration water and its involvement in the antifreeze activity have not been identified conclusively. We herein, by simulation and theory, examined the water reorientation dynamics in the first hydration layer of an AFP from the spruce budworm, Choristoneura fumiferana, compared with a protein cytochrome P450 (CYP). The increase of potential acceptor water molecules around donor water molecules leads to the acceleration of hydrogen bond exchange between water molecules. Therefore, the jump reorientation of water molecules around the AFP active region is accelerated. Due to the mutual coupling and excitation of hydrogen bond exchange, with the acceleration of hydrogen bond exchange, the rearrangement of the hydrogen bond network and the frame reorientation of water are accelerated. Therefore, the water reorientation dynamics of AFP is faster than that of CYP. The results of this study provide a new physical image of antifreeze protein and a new understanding of the antifreeze mechanism of antifreeze proteins.

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Ryu, B. H., M. J. Jones e J. Ulrich. "Crystallization of Hen Egg White Lysozyme by Solvent Freeze-Out: Effect of Cooling Rate on Protein Inclusion in the Ice Layer". Chemical Engineering & Technology 33, n. 10 (28 settembre 2010): 1695–98. http://dx.doi.org/10.1002/ceat.201000130.

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Manikyam, Hemanth Kumar, Dhanaseelan J e Jayaraj Mani. "Cryoethanolic Extraction, Purification of Allicin from Allium sativum and HPTLC analysis". International Journal of Biochemistry Research & Review 33, n. 6 (18 giugno 2024): 43–51. http://dx.doi.org/10.9734/ijbcrr/2024/v33i6887.

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The significance of this research extends beyond the mere extraction and purification of allicin, encompassing its potential applications across diverse industries. Allicin exhibits a plethora of biological activities, including antimicrobial, antifungal, antiviral, and antiprotozoal properties. Its mechanism of action involves the inhibition of thiol-containing enzymes in microorganisms, rendering it effective against a wide array of pathogens. Moreover, allicin has demonstrated promising anticancer properties, eliciting apoptosis and inhibiting cell proliferation in various cancer cell lines. Additionally, its anti-inflammatory and cardioprotective effects underscore its potential therapeutic utility in mitigating cardiovascular diseases and other inflammatory conditions. This study presents a novel method for extracting and purifying allicin from raw garlic cloves. Dry ice ensures the ethanol to reach its cryo temperature (hilled to sub-zero temperatures ranging from -40°C to -80°C). The process involves the use of ethanol, dry ice and ascorbic acid as solvents, vacuum stirring, and subsequent crystallization. The final product, a hygroscopic powder, was analyzed using High-Performance Thin-Layer Chromatography (HPTLC) to determine allicin content. The extraction yielded 5 grams of whitish hygroscopic powder from 21 grams of crude extract, with an allicin content of 5%. Chromatographic conditions included a mobile phase of acetonitrile: water: Formic acid (30:8:2) and derivatization with ninhydrin, with detection under UV light at 366 nm. This method provides an efficient way to isolate and purify allicin for various applications.

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Novikov, Andrey A., Nikolay I. Grebenshchikov, Irina G. Ershova e Aleksey N. Vasil’ev. "Influence of Microwave Radiation on the Freezing Rate of Water in a Heat Pump Installation". Elektrotekhnologii i elektrooborudovanie v APK 3, n. 44 (settembre 2021): 48–52. http://dx.doi.org/10.22314/2658-4859-2021-68-3-48-52.

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The article presents the data obtained as a result of an experiment to determine the eﬀect of microwave radiation on the freezing rate of water in a heat pump installation are presented. (Research purpose) The research purpose is in experimentally evaluating the eﬀect of microwave radiation on the speed of the water-ice phase transition to increase the eﬃciency of the heat pump unit by increasing the rate of water crystallization. (Materials and methods) The main criterion for conducting the experiment was the speed of the water-ice phase transition of ordinary water and water that passed through microwave radiation. The article presents an experimental installation for conducting experiments, consisting of a 90-liter freezer, a Danfoss TLES4F compressor with a cooling capacity of 91 Watts, a programmable Arduino controller with four connected sealed DS18B20 temperature sensors, a water tank made of food- grade plastic. The article presents the scheme of the experimental installation. The water was treated with microwave radiation for 12 seconds, the thickness of the water layer was 4-5 millimeters, and the power of the magnetron used was 750 Watts. (Results and discussion) There was conducted 20 experiments on obtaining thermal energy using the water-ice phase transition. Ten experiments with ordinary filtered water and ten experiments with water subjected to microwave radiation. (Conclusions) Water subjected to uniform microwave radiation cools to 0 degrees Celsius 23 minutes earlier than water that has passed only filtration, and performs a phase transition to a solid state 74 minutes faster. Microwave radiation can be used to increase the eﬃciency of a heat pump using the energy of the water-ice phase transition by accelerating the production of thermal energy from the heat carrier to the heat supply system.

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Barthelat, Francois. "Biomimetics for next generation materials". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, n. 1861 (13 settembre 2007): 2907–19. http://dx.doi.org/10.1098/rsta.2007.0006.

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Billions of years of evolution have produced extremely efficient natural materials, which are increasingly becoming a source of inspiration for engineers. Biomimetics—the science of imitating nature—is a growing multidisciplinary field which is now leading to the fabrication of novel materials with remarkable mechanical properties. This article discusses the mechanics of hard biological materials, and more specifically of nacre and bone. These high-performance natural composites are made up of relatively weak components (brittle minerals and soft proteins) arranged in intricate ways to achieve specific combinations of stiffness, strength and toughness (resistance to cracking). Determining which features control the performance of these materials is the first step in biomimetics. These ‘key features’ can then be implemented into artificial bio-inspired synthetic materials, using innovative techniques such as layer-by-layer assembly or ice-templated crystallization. The most promising approaches, however, are self-assembly and biomineralization because they will enable tight control of structures at the nanoscale. In this ‘bottom-up’ fabrication, also inspired from nature, molecular structures and crystals are assembled with a little or no external intervention. The resulting materials will offer new combinations of low weight, stiffness and toughness, with added functionalities such as self-healing. Only tight collaborations between engineers, chemists, materials scientists and biologists will make these ‘next-generation’ materials a reality.

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Tsutsumi, S., A. Yamazaki, M. Uehara e R. Otsuka. "Preparation and properties of a basic lead carbonate–montmorillonite complex". Clay Minerals 28, n. 1 (marzo 1993): 13–24. http://dx.doi.org/10.1180/claymin.1993.028.1.02.

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AbstractA basic lead carbonate-montmorillonitec omplexw as prepared by treating a natural montmorillonite hydrothermally for 120 h at 250°C with lead powder, dry ice and lead nitrate solution. The product is a non-swelling material showing well-outlined, hexagonal, thin plates <1 µm in size; the symmetry is pseudo-orthorhombic, a = 5·141(7) Å, b = 9·005(5) Å, c = 17·420(4) Å, and Z = 2. The X-ray powder pattern is characterized by a 17·4 Å reflection and an integral series to the 14th order. The TG-DTA curves of this 17 Å-mineral showed one endotherm around 400°C accompanied by weight loss and two exthotherms at about 680 and 780°C By applying hightemperature X-ray diffractometry (XRD) and infrared (IR) spectroscopy, it was found that the endotherm is due to decomposition of carbonate hydroxide in the interlayer, while the two exthotherms are caused by crystallization of a hexagonal phase of PbAl2Si2O8 and by the conversion of this phase into lead feldspar, respectively. The crystal structure of the 17 Å-mineral was determined and refined as a 2:1 dioctahedral smectite interlayered with a hydrocerussite-like layer by a one-dimensional Fourier synthesis method.

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ROGERSON, M. A., e S. S. S. CARDOSO. "Patterns of bubble desorption during the solidification of a multicomponent melt". Journal of Fluid Mechanics 419 (25 settembre 2000): 263–82. http://dx.doi.org/10.1017/s0022112000001208.

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The desorption of bubbles during solidification of a melt occurs in processes as diverse as the making of ice cubes, the formation of igneous rocks and the casting of metals. In both the metal casting and rock formation processes, careful observation of the final solid suggests that the desorbed bubbles often form regular spatial patterns. Understanding and quantifying the mechanisms by which such patterns arise is important. In the geological context, comparison between field measurements and the predictions of a model will allow geologists to estimate in-situ magma properties. In the metal casting context, engineers would like to be able to specify mould geometries and cooling conditions to ensure that the distribution of bubbles will not compromise the strength of critical sections of the casting.In the present study, we develop a detailed mathematical model to predict the distribution of desorbed bubbles in a solidified melt. Our new model builds upon previous knowledge on this phenomenon in the geological context (Toramaru et al. 1996, 1997). We describe desorption of a dissolved gas in a semi-infinite melt, solidified by a one-dimensional heat flux. In the absence of convection, the transfer of heat and solute occurs mainly by a diffusive mechanism and the crystallization proceeds most rapidly near the cooled boundary. The crystals formed contain almost no dissolved gas and hence the concentration of gas dissolved in the melt increases progressively towards the cooled boundary. Diffusion of dissolved gas from the crystallizing zone is slow and, as a result, the local melt becomes supersaturated and gas bubbles desorb. The full equations for this coupled solidification and desorption processes are solved numerically.We find that bubbles desorb forming a sequence of layers parallel to the cooled boundary. The spacing between these bubble layers increases geometrically from the cooled boundary. We give a physical interpretation for this geometric pattern and analyse the effect of physical parameters on the layer spacing. We show that our theoretical model captures the important physical mechanisms involved in the solidification and desorption processes by comparing its predictions with available measurements from a geological formation.

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Ladd-Parada, Marjorie, Katrin Amann-Winkel, Kyung Hwan Kim, Alexander Späh, Fivos Perakis, Harshad Pathak, Cheolhee Yang et al. "Following the Crystallization of Amorphous Ice after Ultrafast Laser Heating". Journal of Physical Chemistry B 126, n. 11 (11 marzo 2022): 2299–307. http://dx.doi.org/10.1021/acs.jpcb.1c10906.

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Dursch, T. J., M. A. Ciontea, G. J. Trigub, C. J. Radke e A. Z. Weber. "Ice-Crystallization Kinetics and Water Movement in Gas-Diffusion and Catalyst Layers". ECS Transactions 50, n. 2 (15 marzo 2013): 429–35. http://dx.doi.org/10.1149/05002.0429ecst.

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Lelaurain, M., J. F. Marêché, E. McRae, O. E. Andersson e B. Sundqvist. "A study of temperature and pressure induced structural and electronic changes in SbCl5 intercalated graphite: Part I. Structural aspects". Journal of Materials Research 7, n. 11 (novembre 1992): 2978–88. http://dx.doi.org/10.1557/jmr.1992.2978.

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We have studied the effects of temperature (10 ≤ T ≤ 295 K) and pressure (0 ≤ p ≤ 0.8 GPa) on the state of intercalate layer crystallization in SbCl5 graphite intercalation compounds of stages 2, 4, and 8. At room temperature (RT), the intercalate layer may in some second stage compounds be fully crystallized and lowering the temperature creates no further modifications. In all other cases, i.e., those in which the intercalate layer has only partial crystallization at RT, lowering T leads to the formation of new in-plane unit cells, the final state depending on the kinetics. Applying pressure to above 0.3–0.5 GPa results in crystallization in all cases, different from that induced simply by lowering of the temperature. We discuss the unit cells observed and the relationships they bear to each other in the light of other works on similar compounds.

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Panhwar, Fazil, Zhongrong Chen e Gang Zhao. "Nir-laser mediated modulation of ice crystallization by 2d-nanosheets for cell cryopreservation". Cryobiology 85 (dicembre 2018): 135–36. http://dx.doi.org/10.1016/j.cryobiol.2018.10.071.

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Márquez Aguilar, Pedro A., Marina Vlasova, Mykola Kakazey e Adalberto Castro Hernández. "Phase Transformation in Zone of Laser Treatment of Y2Ti2O7-Al2O3 Compositional Ceramics". MRS Advances 2, n. 61 (2017): 3831–36. http://dx.doi.org/10.1557/adv.2017.606.

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ABSTRACTThe synthesis of Y2Ti2O7-Al2O3 compositional (multiphase) ceramics from powder mixtures Al2O3-Y2O3-TiO2 was carried out in two stages: 1) under the traditional sintering and then 2) in regime of directed laser heating. It was established that the sintering of mixtures with different content of components and the ratio of TiO2/Y2O3 = 2.34 in ceramic specimens the main phases are Y2Ti2O7 and α-Al2O3. The content of the main phases in ceramic materials also depends upon the oxide content in the initial mixtures. In ceramics the Y3Al5O12 is formed only at sufficiently high content of titanium and yttrium oxides in initial mixtures. In laser remelting, the phase composition is substantially different from that obtained at the traditional sintering, and depends on the mode of laser heating: irradiation power and the moving speed of the laser beam (i.e., heating temperature). Under certain conditions of laser remelting can be obtained superficial ceramic layer with crystallographic directional crystallization of Y2Ti2O7 and Al2O3 crystallites. The size of crystallites and the coefficient texturing also depend on the mode of laser treatment.

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Dobrzycki, Lukasz. "Towards clathrates. 2. The frozen states of hydration of tert-butanol". Zeitschrift für Kristallographie - Crystalline Materials 233, n. 1 (26 gennaio 2018): 41–49. http://dx.doi.org/10.1515/zkri-2017-2074.

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AbstractA new crystal structure oftert-butanol and water crystallizing as the decahydrate is reported. The crystallization of the mixture in the desired molar ratio was performed in a capillary placed directly on a goniometer of a single crystal diffractometer at 200 K and ambient pressure using focused IR laser radiation. The crystals were grown while the melting zone formed by the IR laser was moved along the capillary. Usually the crystallization process should be long enough (hours) in order to obtain a good quality single crystal. However, in the case oftert-butanol decahydrate, such a long process led to separation of the ice and alcohol. Only fast crystallization taking tens of seconds allowed crystallization of the desired crystalline phase. In the decahydratetert-butanol molecules are located in channels formed by water molecules. Hydroxyl groups are anchored to the water framework via hydrogen bonds. All water molecules in the structure have hydrogen atoms disordered equally over two sites; the hydroxyl group is likewise disordered. This effect is observed at both, 200 K and 100 K. Raman spectra recorded for the crystalline phase suggest dynamic disorder at higher temperature, converting to static at lowerT. The decahydrate oftert-butanol, together with already known itsdi- andhepta-hydrates, display similar features to those observed for series oftert-butylamine hydrates. The latter structures behave as frozen steps of amine hydration observed as crystal structures leading, at maximum dilution, to hexagonal ice. Hydrates oftert-butanol nicely follow this tendency completing the relationship found for thetert-butylamine: water system.

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Perrotta, Alberto, Julian Pilz, Roland Resel, Oliver Werzer e Anna Maria Coclite. "Initial Growth and Crystallization Onset of Plasma Enhanced-Atomic Layer Deposited ZnO". Crystals 10, n. 4 (10 aprile 2020): 291. http://dx.doi.org/10.3390/cryst10040291.

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Direct plasma enhanced-atomic layer deposition (PE-ALD) is adopted for the growth of ZnO on c-Si with native oxide at room temperature. The initial stages of growth both in terms of thickness evolution and crystallization onset are followed ex-situ by a combination of spectroscopic ellipsometry and X-ray based techniques (diffraction, reflectivity, and fluorescence). Differently from the growth mode usually reported for thermal ALD ZnO (i.e., substrate-inhibited island growth), the effect of plasma surface activation resulted in a substrate-enhanced island growth. A transient region of accelerated island formation was found within the first 2 nm of deposition, resulting in the growth of amorphous ZnO as witnessed with grazing incidence X-ray diffraction. After the islands coalesced and a continuous layer formed, the first crystallites were found to grow, starting the layer-by-layer growth mode. High-temperature ALD ZnO layers were also investigated in terms of crystallization onset, showing that layers are amorphous up to a thickness of 3 nm, irrespective of the deposition temperature and growth orientation.

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Żaba, Krzysztof, Lechosław Tuz, Piotr Noga, Stanislav Rusz e Rostislav Zabystrzan. "Effect of Multi-Variant Thermal Treatment on Microstructure Evolution and Mechanical Properties of AlSi10Mg Processed by Direct Metal Laser Sintering and Casting". Materials 15, n. 3 (27 gennaio 2022): 974. http://dx.doi.org/10.3390/ma15030974.

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This article presents a study on the influence of temperature and time of multi-variant heat treatment on the structure and properties of materials produced in direct metal laser sintering (DMLS) and casting technology. The materials were manufactured in the form of cuboidal elements with a cross-section of 1.5 mm × 15 mm and a length of 60 mm. The samples prepared in this way had a similar volume, but due to the production technology the metal crystallization took place at different rates and directions. In the cast, the direction of heat transfer was toward the mold, and the DMLS was directed locally layer by layer. The small thickness of the cast material allowed reaching conditions similar to the DMLS cooling process. Both DMLS and cast samples show similar mechanical properties (hardness) achieved after long ageing time, i.e., 16 h at 170 °C. The maximum hardness was observed for 8 h. In the DMLS samples, in contrast to cast samples, no lamellar precipitates of silicon were observed, which indicates their better resistance to cracking

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29

Azadbakht, Zeinab, e David R. Lentz. "High-resolution LA-ICP-MS trace-element mapping of magmatic biotite: A new approach for studying syn- to post-magmatic evolution". Canadian Mineralogist 58, n. 3 (1 maggio 2020): 293–311. http://dx.doi.org/10.3749/canmin.1900101.

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ABSTRACT Biotite grains from 22 felsic intrusions in New Brunswick were mapped in situ using a laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS). We investigated the extent to which biotite can retain its magmatic zoning patterns and, where zoning does exist, how it can be used to elucidate early to late stage, syn-magmatic to post-crystallization processes. Although the major element and halogen contents of the examined biotite phenocrysts are homogeneous, two-thirds of the grains display trace-element zoning for Ba, Rb, and Cs. The results also indicated that zoning is better retained in larger grains (i.e., > 500 × 500 μm) with minimal alteration and mineral inclusions. An exceptionally well-zoned Li-rich siderophyllite from the Pleasant Ridge topaz granite in southwestern New Brunswick shows Ti, Ta, Sn, W, Cs, Rb, and V (without Li or Ba) zoning. Cesium values increase from 200 to 1400 ppm from core to rim. Conversely, Sn and W values decrease toward the rim (50 to 10 and 100 to 10 ppm, respectively). Tantalum and Ti values show fewer variations but drop abruptly close to the rim of the grain (100 to 20 and 2000 to 500 ppm, respectively). These observations may indicate crystallization of mineral phases with high partition coefficients for these highly incompatible elements (except Ti) (e.g., cassiterite and rutile) followed by fractionation of a fluid phase at a later stage of magma crystallization. The preservation of zoning may indicate rapid cooling post-crystallization of the parent magma.

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Palade, Catalin, Adrian Slav, Ovidiu Cojocaru, Valentin Serban Teodorescu, Toma Stoica, Magdalena Lidia Ciurea e Ana-Maria Lepadatu. "SiGeSn Quantum Dots in HfO2 for Floating Gate Memory Capacitors". Coatings 12, n. 3 (7 marzo 2022): 348. http://dx.doi.org/10.3390/coatings12030348.

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Group IV quantum dots (QDs) in HfO2 are attractive for non-volatile memories (NVMs) due to complementary metal-oxide semiconductor (CMOS) compatibility. Besides the role of charge storage centers, SiGeSn QDs have the advantage of a low thermal budget for formation, because Sn presence decreases crystallization temperature, while Si ensures higher thermal stability. In this paper, we prepare MOS capacitors based on 3-layer stacks of gate HfO2/floating gate of SiGeSn QDs in HfO2/tunnel HfO2/p-Si obtained by magnetron sputtering deposition followed by rapid thermal annealing (RTA) for nanocrystallization. Crystalline structure, morphology, and composition studies by cross-section transmission electron microscopy and X-ray diffraction correlated with Raman spectroscopy and C–V measurements are carried out for understanding RTA temperature effects on charge storage behavior. 3-layer morphology and Sn content trends with RTA temperature are explained by the strongly temperature-dependent Sn segregation and diffusion processes. We show that the memory properties measured on Al/3-layer stack/p-Si/Al capacitors are controlled by SiGeSn-related trapping states (deep electronic levels) and low-ordering clusters for RTA at 325–450 °C, and by crystalline SiGeSn QDs for 520 and 530 °C RTA. Specific to the structures annealed at 520 and 530 °C is the formation of two kinds of crystalline SiGeSn QDs, i.e., QDs with low Sn content (2 at.%) that are positioned inside the floating gate, and QDs with high Sn content (up to 12.5 at.%) located at the interface of floating gate with adjacent HfO2 layers. The presence of Sn in the SiGe intermediate layer decreases the SiGe crystallization temperature and induces the easier crystallization of the diamond structure in comparison with 3-layer stacks with Ge-HfO2 intermediate layer. High frequency-independent memory windows of 3–4 V and stored electron densities of 1–2 × 1013 electrons/cm2 are achieved.

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Narazaki, Aiko, Katsuhisa Tanaka e Kazuyuki Hirao. "Optical second-order nonlinearity of transparent glass-ceramics containing BaTiO3 precipitated via surface crystallization". Journal of Materials Research 14, n. 9 (settembre 1999): 3640–46. http://dx.doi.org/10.1557/jmr.1999.0491.

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Second-harmonic generation of transparent glass-ceramics containing BaTiO3 crystalline phase was investigated using Maker fringe method. When 15BaO · 15TiO2 · 70TeO2 glass was heat-treated at 415 °C for 0.5–12 h, (101)- or (110)-oriented BaTiO3 crystals precipitated in the near-surface region. The resultant glass-ceramics exhibit second-harmonic generation. Variation of second-harmonic intensity with angle of incidence, i.e., the Maker fringe pattern changes drastically with an increase in heat treatment time and temperature. No second-harmonic signal was detected in glass-ceramics derived from 15SrO · 15TiO2 · 70TeO2 glass. These facts suggest that BaTiO3 crystal is responsible for the second-order nonlinear phenomenon, although its structure is closer to cubic than tetragonal according to x-ray diffraction measurements. In order to estimate second-order nonlinear optical coefficient d(2), Maker fringe patterns of the BaTiO3-containing glass-ceramics were analyzed. For the glass-ceramic after heat treatment for 0.5 h, d33 and thickness of BaTiO3-crystallized layer, L, are 3.65 pm/V and 3.43 μm, respectively. The value of second-order nonlinear optical coefficient is comparable to those of BaTiO3 films prepared via metalorganic chemical vapor deposition and pulsed-laser deposition. On the other hand, the glass-ceramic heat-treated for 12 h exhibits d15 = 0.31 pm/V and L = 300 μm. The thickness of the layer active in second-order nonlinearity evaluated from the Maker fringe pattern is coincident with the observation by scanning electron microscopy.

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32

Wang, Yong, Qiang Wang e Wangzhong Mu. "In Situ Observation of Solidification and Crystallization of Low-Alloy Steels: A Review". Metals 13, n. 3 (3 marzo 2023): 517. http://dx.doi.org/10.3390/met13030517.

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Crystallization during the solidification process of steels is of vital importance for controlling the quality of final products. This paper summarizes the in situ characterization research activities of crystallization behaviors of low-alloy steels during the solidification process. The results obtained using high-temperature confocal laser scanning microscope (HT-CLSM) are critically reviewed, and other relevant methodologies, i.e., either classical method using differential scanning calorimetry (DSC) or large-scale facility (LSF), are also briefly mentioned. The evolution of the crystallization front from a planar to a cellular and further to a dendritic one, and subsequential microstructure evolutions, i.e., delta-ferrite (δ) formation from the liquid, austenite (γ) transformation and decomposition, are mainly discussed. The current review aims to highlight the state-of-the-art research outputs obtained by the novel in situ characterization techniques, and the obtained knowledge aims to shed light on the further development of the quality low-alloy steel products by controlling the processing and structure correlation.

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33

Belviso, Benny Danilo, Rosanna Caliandro, Shabnam Majidi Salehi, Gianluca Di Profio e Rocco Caliandro. "Protein Crystallization in Ionic-Liquid Hydrogel Composite Membranes". Crystals 9, n. 5 (17 maggio 2019): 253. http://dx.doi.org/10.3390/cryst9050253.

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Protein crystallization is a powerful purification tool. It is the first step for crystallographic structural investigations, and can be preparatory for biotechnological applications. However, crystallizing proteins is challenging and methods to control the crystallization process are needed. Ionic-liquid hydrogel composite membranes (IL-HCMs) have been used here as material capable of supporting protein crystallization and hosting grown crystals. We found that IL-HCMs affect the selection mechanism of glucose isomerase (GI) polymorphs and make GI crystals grow completely immersed into the hydrogel layer. X-ray diffraction studies show that IL ions do not bind to the protein, likely because IL molecules are constrained in the polymeric framework. Our GI crystal structures have been compared with many existing GI crystal structures using multivariate analysis tools, allowing a comprehensive overview of factors determining structural similarities, i.e., temperature variations and external stresses exerted during or after crystal growth, such as dehydration or presence of hydrogel of a different nature. GI crystals grown on IL-HCM fit perfectly in this framework, showing typical features induced by external forces. Overall, protein crystallization by IL-HCMs show potential for biotechnological applications, as it could constitute a natural means for containing crystallized enzymes in working conditions.

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34

Faizullin, M. Z., A. V. Vinogradov, A. S. Tomin e V. P. Koverda. "Nonstationary nucleation (explosive crystallization) in layers of amorphous ice prepared by low-temperature condensation of supersonic molecular beams". International Journal of Heat and Mass Transfer 108 (maggio 2017): 1292–96. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.12.109.

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35

Shekoofa, Omid, Jian Wang, Dejie Li e Yi Luo. "Investigation of Microcrystalline Silicon Thin Film Fabricated by Magnetron Sputtering and Copper-Induced Crystallization for Photovoltaic Applications". Applied Sciences 10, n. 18 (10 settembre 2020): 6320. http://dx.doi.org/10.3390/app10186320.

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Microcrystalline silicon, which is widely used in the microelectronics industry, is usually fabricated by chemical vapor deposition techniques. In recent years, magnetron sputtering has been considered as an alternative because it is a simpler, cheaper and more eco-friendly technique. The big drawback of this technique, however, is the need to recrystallize the as-deposited amorphous silicon, which can be done by metal-induced crystallization. Among the different suitable metals, copper has not been extensively investigated for this purpose. Furthermore, the applicability of the microcrystalline film prepared by this method has not been evaluated for photovoltaic device fabrication. Therefore, this paper reports the fabrication of p-type microcrystalline silicon thin film by magnetron sputtering and copper-induced crystallization techniques, and evaluates its appropriateness for solar cell fabrication. In the first step, 60 nm of silicon followed by 10 nm of copper were deposited on n-type silicon wafer and glass substrates, both by the magnetron sputtering technique. Then, the as-deposited samples were annealed at temperatures from 450 °C to 950 °C. The crystal properties of the resulting films were characterized by Raman and X-ray diffraction spectroscopies and optical and secondary emission microscopies, while their electrical characteristics were determined by Hall-effect, J-V curve and external quantum efficiency measurements. These characterizations confirmed the formation of a layer of microcrystalline silicon mostly in the <111> direction with a crystallization ratio of 93% and a largest grain size of 20 nm. The hole concentration and mobility of the fabricated p-type microcrystalline silicon layer were about 1017~1019 cm−3 and 8 cm2/V.s, respectively. By using the fabricated film as the emitter layer of a p-n junction solar cell, a good rectification ratio of 4100 and reverse saturation current density of 85 nA.cm−2 were measured under dark conditions. The highest photovoltaic conversion efficiency, i.e., 2.6%, with an open-circuit voltage of 440 mV and short-circuit current density of 16.7 mA/cm2, were measured under AM1.5G irradiance. These results indicate that microcrystalline silicon created by magnetron sputtering and copper-induced crystallization has considerable potential for photovoltaic device fabrication.

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36

Bursik, Josef, Radomir Kuzel, Karel Knizek e Ivo Drbohlav. "Oriented hexagonal ferrite thin films prepared by chemical solution deposition". Acta Crystallographica Section A Foundations and Advances 70, a1 (5 agosto 2014): C725. http://dx.doi.org/10.1107/s2053273314092742.

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Hexagonal ferrites (M, Y, Z-type) represent a new diverse class of magnetoelectric (ME) multiferroics, where ME effect is driven by complex magnetic order. Integration of ME materials with standard semiconductor technology is important for ultimate realization of ME functionalities. They have the potential to display ME coupling under low magnetic field bias and at temperatures close to room temperature. Methods based on sol–gel transition offer possibility of low cost and efficient way for the evaluation of new material system. The single phase, epitaxial thin films of Y-type hexagonal ferrite has been prepared and studied. Thin films of Ba2Zn2Fe12O22(Y) hexaferrite were prepared through the chemical solution deposition method on SrTiO3(111)(ST) single crystal substrates using epitaxial SrFe12O19(M) hexaferrite thin layer as a seed template layer. The process of crystallization was mainly investigated by means of X-ray diffraction and atomic force microscopy. A detailed inspection revealed that growth of seed layer starts through the break-up of initially continuous film into high density of well-oriented isolated grains with expressive shape anisotropy and hexagonal habit.The vital parameters of the seed layer, i.e. thickness, substrate coverage,crystallization conditions and temperature ramp were optimized with the aim to obtain epitaxially crystallized Y phase. By overcoating this seed layer, Y phase prepared under optimum deposition and heat treatment conditions presents a (001) orientation perpendicular to the substrate. Perfect parallel in-plane alignment of the hexagonal cells of SrTiO3substrate and both hexaferrite phases was proved by fast ω and φ scan measurements on sets of several diffraction planes at asymmetric orientations, and also by pole figures. The soft magnetic character and existence of pronounced magnetic anisotropy in Y films were confirmed by room temperature measurements of magnetization.

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37

Xu, Yuntao, Nikolay G. Petrik, R. Scott Smith, Bruce D. Kay e Greg A. Kimmel. "Growth rate of crystalline ice and the diffusivity of supercooled water from 126 to 262 K". Proceedings of the National Academy of Sciences 113, n. 52 (12 dicembre 2016): 14921–25. http://dx.doi.org/10.1073/pnas.1611395114.

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Understanding deeply supercooled water is key to unraveling many of water’s anomalous properties. However, developing this understanding has proven difficult due to rapid and uncontrolled crystallization. Using a pulsed-laser–heating technique, we measure the growth rate of crystalline ice, G(T), for 180 K < T < 262 K, that is, deep within water’s “no man’s land” in ultrahigh-vacuum conditions. Isothermal measurements of G(T) are also made for 126 K ≤ T ≤ 151 K. The self-diffusion of supercooled liquid water, D(T), is obtained from G(T) using the Wilson–Frenkel model of crystal growth. For T > 237 K and P ∼ 10−8 Pa, G(T) and D(T) have super-Arrhenius (“fragile”) temperature dependences, but both cross over to Arrhenius (“strong”) behavior with a large activation energy in no man’s land. The fact that G(T) and D(T) are smoothly varying rules out the hypothesis that liquid water’s properties have a singularity at or near 228 K at ambient pressures. However, the results are consistent with a previous prediction for D(T) that assumed no thermodynamic transitions occur in no man’s land.

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Gazińska, Małgorzata, Anna Krokos, Bartłomiej Kryszak, Paulina Dzienny, Michał Olejarczyk, Piotr Gruber, Ryszard Kwiatkowski e Arkadiusz Antończak. "Influence of Thermal Annealing on the Sinterability of Different Grades of Polylactide Microspheres Dedicated for Laser Sintering". Materials 14, n. 11 (1 giugno 2021): 2999. http://dx.doi.org/10.3390/ma14112999.

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We present a comparison of the influence of the conditioning temperature of microspheres made of medical grade poly(L-lactide) (PLLA) and polylactide with 4 wt % of D-lactide content (PLA) on the thermal and structural properties. The microspheres were fabricated using the solid-in-oil-in-water method for applications in additive manufacturing. The microspheres were annealed below the glass transition temperature (Tg), above Tg but below the onset of cold crystallization, and at two temperatures selected from the range of cold crystallization corresponding to the crystallization of the α’ and α form of poly(L-lactide), i.e., at 40, 70, 90, and 120 °C, in order to verify the influence of the conditioning temperature on the sinterability of the microspheres set as the sintering window (SW). Based on differential scanning calorimetry measurements, the SWs of the microspheres were evaluated with consideration of the existence of cold crystallization and reorganization of crystal polymorphs. The results indicated that the conditioning temperature influenced the availability and range of the SWs depending on the D-lactide presence. We postulate the need for an individual approach for polylactide powders in determining the SW as a temperature range free of any thermal events. We also characterized other core powder characteristics, such as the residual solvent content, morphology, particle size distribution, powder flowability, and thermal conductivity, as key properties for successful laser sintering. The microspheres were close to spheres, and the size of the microspheres was below 100 µm. The residual solvent content decreased with the increase of the annealing temperature. The thermal conductivities were 0.073 and 0.064 W/mK for PLA and PLLA microspheres, respectively, and this depended on the spherical shape of the microspheres. The wide angle X-ray diffraction (WAXD) studies proved that an increase in the conditioning temperature caused a slight increase in the crystallinity degree for PLLA microspheres and a clear increase in crystallization for the PLA microspheres.

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39

Kim, Kyung Hwan, Katrin Amann-Winkel, Nicolas Giovambattista, Alexander Späh, Fivos Perakis, Harshad Pathak, Marjorie Ladd Parada et al. "Experimental observation of the liquid-liquid transition in bulk supercooled water under pressure". Science 370, n. 6519 (19 novembre 2020): 978–82. http://dx.doi.org/10.1126/science.abb9385.

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We prepared bulk samples of supercooled liquid water under pressure by isochoric heating of high-density amorphous ice to temperatures of 205 ± 10 kelvin, using an infrared femtosecond laser. Because the sample density is preserved during the ultrafast heating, we could estimate an initial internal pressure of 2.5 to 3.5 kilobar in the high-density liquid phase. After heating, the sample expanded rapidly, and we captured the resulting decompression process with femtosecond x-ray laser pulses at different pump-probe delay times. A discontinuous structural change occurred in which low-density liquid domains appeared and grew on time scales between 20 nanoseconds to 3 microseconds, whereas crystallization occurs on time scales of 3 to 50 microseconds. The dynamics of the two processes being separated by more than one order of magnitude provides support for a liquid-liquid transition in bulk supercooled water.

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40

Pramatarova, Lilyana, Emilia Pecheva, Paul Montgomery, Doriana Dimova-Malinovska, Todor Petrov, Attila L. Toth e Magdalena Dimitrova. "Bioactivity of Polycrystalline Silicon Layers". Journal of Nanoscience and Nanotechnology 8, n. 2 (1 febbraio 2008): 924–30. http://dx.doi.org/10.1166/jnn.2008.d163.

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After oxygen, silicon is the second most abundant element in the environment and is present as an impurity in most materials. The widespread occurrence of siliceous biominerals as structural elements in lower plants and animals suggests that Si plays a role in the production and maintenance of connective tissue in higher organisms. It has been shown that the presence of Si is necessary in bones, cartilage and in the formation of connective tissue, as well as in some important metabolic processes. In this work, polycrystalline silicon layers are tested in terms of bioactivity, i.e., their ability to induce hydroxyapatite formation from simulated body fluid. Hydroxyapatite is a biologically compatible material with chemical similarity to the inorganic part of bones and teeth. Polycrystalline silicon layers are obtained by aluminum induced crystallization of Al and amorphous Si thin films deposited sequentially on glass substrates by radio-frequency magnetron sputtering and subsequently annealed in different atmospheres. The hydroxyapatite formation is induced by applying a method of laser-liquid-solid interaction. The method consists of irradiating the samples with laser light while immersed in a solution that is supersaturated with respect to Ca and P. As a result, heterogeneous porous sponge-like carbonate-containing hydroxyapatite is grown on the polysilicon surfaces. Crystals that are spherical in shape, containing Ca, P and O, Na, Cl, Mg, Al, Si and S, as well as well-faceted NaCl crystals are embedded in the hydroxyapatite layer. Enhancement of the hydroxyapatite growth and increased crystallinity is observed due to the applied laser-liquid-solid interaction.

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Briard, Mélody, Clément Brandel, Sandrine Morin-Grognet, Gérard Coquerel e Valérie Dupray. "Potassium Sulfate: A New Candidate to Explore Non-Photochemical Laser-Induced Nucleation Mechanisms". Crystals 11, n. 12 (16 dicembre 2021): 1571. http://dx.doi.org/10.3390/cryst11121571.

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In this paper, we report a study on the nucleation behavior of potassium sulfate (K2SO4) from aqueous solutions under the influence of unfocused nanosecond laser pulses. The objective is to contribute to the general understanding of the Non-Photochemical Laser-Induced Nucleation (NPLIN) mechanism. First, the influence of several parameters such as supersaturation as well as laser parameters (pulse energy, number of pulses, and laser polarization) on induction time, probability of nucleation and mean number of crystals in comparison with spontaneous nucleation was investigated. Then, we examined the influence of gas composition (i.e., degassing and gas bubbling (CO2 and N2)) of the supersaturated solutions on the NPLIN kinetics, showing no correlation between gas content (or nature) on the crystallization behavior. Our study questions the role of impurities within the solution regarding the mechanism of laser-induced nucleation.

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Choudhary, Madhuresh K., Rishabh Jain e Jeffrey D. Rimer. "In situ imaging of two-dimensional surface growth reveals the prevalence and role of defects in zeolite crystallization". Proceedings of the National Academy of Sciences 117, n. 46 (30 ottobre 2020): 28632–39. http://dx.doi.org/10.1073/pnas.2011806117.

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Zeolite crystallization predominantly occurs by nonclassical pathways involving the attachment of complex (alumino)silicate precursors to crystal surfaces, yet recurrent images of fully crystalline materials with layered surfaces are evidence of classical growth by molecule attachment. Here we use in situ atomic force microscopy to monitor three distinct mechanisms of two-dimensional (2D) growth of zeolite A where we show that layer nucleation from surface defects is the most common pathway. Direct observation of defects was made possible by the identification of conditions promoting layered growth, which correlates to the use of sodium as an inorganic structure-directing agent, whereas its replacement with an organic results in a nonclassical mode of growth that obscures 2D layers and markedly slows the rate of crystallization. In situ measurements of layered growth reveal that undissolved silica nanoparticles in the synthesis medium can incorporate into advancing steps on crystal surfaces to generate defects (i.e., amorphous silica occlusions) that largely go undetected in literature. Nanoparticle occlusion in natural and synthetic crystals is a topic of wide-ranging interest owing to its relevance in fields spanning from biomineralization to the rational design of functional nanocomposites. In this study, we provide unprecedented insight into zeolite surface growth by molecule addition through time-resolved microscopy that directly captures the occlusion of silica nanoparticles and highlights the prevalent role of defects in zeolite crystallization.

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Carmeli, Enrico, Bao Wang, Paolo Moretti, Davide Tranchida e Dario Cavallo. "Estimating the Nucleation Ability of Various Surfaces Towards Isotactic Polypropylene via Light Intensity Induction Time Measurements". Entropy 21, n. 11 (31 ottobre 2019): 1068. http://dx.doi.org/10.3390/e21111068.

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Crystallization of isotactic polypropylene (iPP) at the interface with crystalline films of two commercially employed nucleating agents (sodium benzoate (NaBz) and sodium 2,2’-methylene bis-(4,6-di-tert-butylphenyl)phosphate (NA-11)) and with a glass fiber (GF) was investigated using a polarized optical microscope. The analysis of the light intensity evolution during the crystallization process enabled the successful estimation of the time at which the crystal growth began, i.e., the induction time (ti), at various crystallization temperatures. Meaningful differences in the ti values were observed between the investigated systems. Moreover, the ti data have been analyzed according to different nucleation models proposed in the literature, which consider either the time to form the first crystalline layer in contact with the substrate or the time required to grow a cluster of critical size. It has been found that the two models are applicable in different temperature ranges depending on the efficiency of the given substrate. Therefore, in order to obtain the value of the surface free energy difference function, Δσ, which is directly related to the nucleation energy barrier and useful for the definition of a universal nucleating efficiency scale, a model that considers both the above-mentioned times was fitted to the overall data. The values of Δσ for the nucleation of iPP on the surface of the different substrates are thus obtained and discussed in the framework of the literature results.

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44

Beaufort, D., G. Berger, J. C. Lacharpagne e A. Meunier. "An experimental alteration of montmorillonite to a di + trioctahedral smectite assemblage at 100 and 200°C". Clay Minerals 36, n. 2 (giugno 2001): 211–25. http://dx.doi.org/10.1180/000985501750177942.

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AbstractHydrothermal experiments were performed at 100 and 200°C and at different clay:water ratios in order to investigate the transformation of smectitic layers during the alteration of a montmorillonitic starting material. This study focused on three phenomena: (1) the amount and localization of charge within the layer of the newly-formed dioctahedral smectite; (2) the stacking of low- and high-charge layers in the dioctahedral smectitic material; and (3) the neoformation of trioctahedral smectites.In all of the runs, the formation of beidellite from montmorillonite induced morphological changes in clay particles which suggests a reaction proceeding by a dissolution-crystallization mechanism. Illite layers were detected in K-saturated montmorillonite runs after the transformation of ∼50% of the starting montmorillonite into beidellite (i.e. after 5 months of reaction with distilled water at 200°C). These illite layers were interstratified with both high-charge and low-charge dioctahedral smectites in a hypothetical three-component mixed-layer mineral.

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Kohri, Youhei, Tomoaki Takebe, Yutaka Minami, Toshitaka Kanai, Wataru Takarada e Takeshi Kikutani. "Structure and properties of low-isotacticity polypropylene elastomeric fibers prepared by sheath-core bicomponent spinning: effect of localization of high-isotacticity component near the fiber surface". Journal of Polymer Engineering 35, n. 3 (1 aprile 2015): 277–85. http://dx.doi.org/10.1515/polyeng-2014-0195.

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Abstract (sommario):

Abstract Sheath-core type bicomponent melt-spun fibers were produced by extruding the melts of low-isotacticity polypropylene (LPP) as the core component and the blend of LPP and high-isotacticity PP (IPP) as the sheath component. IPP content in the sheath was changed from 8 wt% to 40 wt% while sheath/core composition was varied from 50/50 to 10/90. Accordingly overall IPP content was kept constant at 4 wt%. Even though the overall IPP content was intact, bicomponent fibers with lower contraction ratio after spinning, higher elastic recovery and slightly higher modulus and strength were obtained by increasing the IPP content in the sheath and decreasing the sheath layer composition, i.e., localizing the IPP to the region near the surface in the fiber cross-section. Structure analysis of the as-spun fibers suggested the suppression of crystallization of LPP in the sheath by blending IPP. By contrast, enhancement of molecular orientation and crystallization of the sheath component were found to occur by localizing the IPP to the region near the fiber surface. It was speculated that this behavior was caused by the kinematic mutual interaction of the sheath and core components in the melt spinning process.

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Li, Jianfeng, Yaling Han, Weiwei Jiang, Penghe Huang, Rui Cai, Minhuan Wang e Jiming Bian. "Key role of residual lead iodide in two-step processed perovskite layer for high performance perovskite solar cells". Applied Physics Letters 122, n. 1 (2 gennaio 2023): 013901. http://dx.doi.org/10.1063/5.0131203.

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The delicate control of the crystallization behavior of the perovskite layer is critical for achieving high power conversion efficiency (PCE) and longer-term stability of perovskite solar cells (PSCs). Residual lead iodide (PbI2) was usually evitable in the two-step processed perovskite film due to incomplete reaction; however, its exact effects on the perovskite layer and resulting PSCs were not well elucidated so far. Here, the lead halide perovskite films were grown by the two-step process, where the residual PbI2 can be fine controlled by the concentration of organic salt solution. Results indicated that the properties of the perovskite layer may be varied greatly depending on the amount of residual PbI2, and a series of beneficial effects for PSCs can be achieved via suitable management of residue PbI2, i.e., prolonged carrier diffusion capacity, reduced defect density, inhibited ion migration, and interfacial charge recombination. Accordingly, an impressive PCE of 22.4% was achieved from the PSCs with optimized PbI2. Furthermore, the PSCs also displayed fairly good operational stability and retained 68% of its initial PCE after 400 h (at continuous irradiation under 1-sun illumination). This work may inspire solutions for further enhancing the performance of PSCs via fine controlled residual PbI2 in the perovskite layer.

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47

Hishida, Mitsuoki, Naohiko Kobata, Kentaro Miyano, Masaki Nobuoka, Tatsuya Okada e Takashi Noguchi. "Highly Productive Laser Annealing Manufacturing Method Using Continuous Blue WBC (Wavelength Beam Combining) Technique". Materials 17, n. 22 (5 novembre 2024): 5399. http://dx.doi.org/10.3390/ma17225399.

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Blue laser annealing can be used to obtain a high-mobility thin-film transistor (TFT) through a laser annealing (i.e., LTPS: low-temperature Poly-Si) process. However, the laser annealing process’s low productivity (as well as high cost) is an issue because the high output power of blue lasers still needs to be addressed. Therefore, productivity can be improved if blue laser energy is efficiently supplied during the laser annealing process using a continuous wave laser instead of a conventional pulsed excimer laser. We developed a blue laser light source (440 ± 10 nm) using the wavelength beam combining (WBC) method, which can achieve a laser power density of 73.7 kW/cm2. In this semiconductor laser, when the power was increased s by 2.9 times, the laser scanning speed was increased by 5.0 times, achieving twice the productivity of conventional lasers. After laser annealing, the size of the crystal grains varied between 2 and 15 μm, resulting in a crystallization rate of 100% by Raman scattering rsult and low resistivity of 0.04 Ωcm. This increase in production capacity is not an arithmetic increase with increased power but a geometric production progression.

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48

Zharov, M. V. "On a mathematical model of the cooling and crystallization of metal drops during centrifugal granulation". Voprosy Materialovedeniya, n. 2(114) (25 luglio 2023): 98–112. http://dx.doi.org/10.22349/1994-6716-2023-114-2-98-112.

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A mathematical model has been developed for the crystallization of aluminum alloy granules under cooling conditions in an aqueous and water-steam media. The practical significance of the mathematical model lies in predicting the average value of the dendritic parameter of the obtained granules depending on the granulation method, the characteristics of the granulation process and the size of the obtained granules. The average value of the dendritic parameter makes it possible to predict the fineness of the granule structure and, consequently, the mechanical properties of the granular material. The mathematical model makes it possible to determine the speed of a melt drop in an aqueous media and takes into account the presence of a steam jacket effect, i.e., a vapor layer that appears between a crystallizing drop and an aqueous media, which significantly reduces the intensity of heat removal and the rate of crystallization. The application of the mathematical model was tested on the obtaining of granules of high-alloyed aluminum alloys (alloys D1 and D16 of the Al–Cu–Mg system, alloys V95 and V96Ts of the Al–Zn–Mg–Cu system), made by centrifugal spraying of the melt from a perforated rotating crucible and drip method during cooling in an aqueous media. The cooling rate and the crystallization rate of the granules obtained in real experiments were determined by measuring the dendritic parameter of the material structure. The mathematical model showed a high convergence of the simulation results and of real experiments of aluminum alloy granulation.

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Panhwar, Fazil, Zhongrong Chen, S. M. Chapal Hossain, Meng Wang, Zeeshan Haider, Kashan Memon, Pengpeng Chen e Gang Zhao. "Near-infrared laser mediated modulation of ice crystallization by two-dimensional nanosheets enables high-survival recovery of biological cells from cryogenic temperatures". Nanoscale 10, n. 25 (2018): 11760–74. http://dx.doi.org/10.1039/c8nr01349g.

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50

Chan, Y. C., S. H. Fan e J. K. L. Lai. "The Effect of Cooling Rate on the Growth of Cu-Sn Intermetallics in Annealed PBGA Solder Joints". Journal of Electronic Packaging 125, n. 1 (1 marzo 2003): 153–56. http://dx.doi.org/10.1115/1.1537070.

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In this study, the diffusion behavior and microstructural evolution of Cu-Sn intermetallics at eutectic Sn-Pb solder/copper substrate interface of PBGA solder joints was studied. The PBGA solder joints were formed by different profiles, which was devised to have the same “heating factor”—the integral of the measured temperature above the liquidus (183°C) with respect to dwell time in the reflow profile, but to have different conveyor speeds. Using the theory of heat transmission, it is shown that the solder joint cooling rate during solidification increases with increasing conveyor speed. As a result, the “crystallization degree” of the solder joint microstructure decreased with the increasing of cooling rate. The thickness of IMC layer increased with extension of aging time. The growth of IMC is a diffusion-controlled process, i.e., tin diffuses into copper, and the diffusion coefficient in the “disordered region” Db is much bigger than that in the “crystallization region” Dl, so the IMC growth rate of solder joint with faster cooling rate was larger. On the other hand, although Db>Dl at all temperatures, the difference increases as temperature decrease, consequently, the difference of IMC thickness growth among different cooling rate solder joints varied according to the aging temperature.

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