Crystallization Time Research Articles

Multifunctional Laser-Induced Graphene-Based Microfluidic Chip for High-Performance Oocyte Cryopreservation with Low Concentration of Cryoprotectants.

Oocyte cryopreservation is essential in the field of assisted reproduction, but due to the large size and poor environmental tolerance of oocytes, cell freezing technology needs further improvement. Here, a Y-shaped microfluidic chip based on 3D graphene is ingeniously devised by combining laser-induced graphene (LIG) technology and fiber etching technology. The prepared LIG/PDMS microfluidic chip can effectively suppress ice crystal size and delay ice crystal freezing time by adjusting surface hydrophobicity. In addition, LIG endows the microfluidic chip with an outstanding photothermal effect, which allows to sharply increase its surface temperature from 25 to 71.8°C with 10s of low-power 808nm laser irradiation (0.4Wcm-2). Notably, the LIG/PDMS microfluidic chip not only replaces the traditional cryopreservation carriers, but also effectively reduces the dosage of cryoprotectants (CPAs) needed in mouse oocyte cryopreservation. Even when the concentration of CPAs is cut in half (final concentration of 7.5% ethylene glycol (EG) and 7.5% dimethyl sulfoxide (DMSO)), the survival rate of oocytes is still as high as 92.4%, significantly higher than the control group's 85.8%. Therefore, this work provides a novel design strategy to construct multifunctional microfluidic chips for high-performance oocytes cryopreservation.

Vesicularity, Density, and Crystal Size Distribution of Pumice-Scoria at South-Southeast Flank of Merapi Volcano: A Window Into Explosive Volcanic Eruption

Abstract Merapi, one of the most active volcanoes in Java Island of Sunda Arc, is a constant threat to the ten million people who live within its 10-km radius of the summit. In 2010, it experienced an explosive eruptive event, sending pumice-laden pyroclastic density currents (PDC) that extended as far as 15 km down its southeastern flank. We report field observations of PDC deposits on the south-southeast flank of the volcano and calculate the vesicularity, density and crystal size distribution of pumice–scoria fragments. The density of the pumice–scoria is measured by archimedes’ principle by weighting the sample in water. The vesicularity is determined from petrography using the point counting method. Crystal Size distribution (CSD) is determined by images from thin sections using plagioclase crystals to calculate the magma residence time. Based on their physical appearance, the pumice–scoria fragments from this area are grouped into: (1) white pumice, (2) grey pumice, and (3) dark scoria. The density of white pumice is overlapping with the grey pumice group (1.5-2 g/ml); while the dark scoria is the densest among others (>2 g/ml). The vesicularity of pumice–scoria ranges from 7-30%. CSD analysis is done in two most vesicular samples from each group. The CSD result gives both shallow and steep slopes which reflect the crystal size and population density. The slope suggests that magma residence times are (a) 11.49–249.68 years for grey pumice, (b) 5.03–194.54 years for white pumice, and (c) 3.83–273.36 years for dark scoria. This research suggests that the three types of pumice–scoria from the study area generally have similar crystallization path and time. Our CSD data shows that these pumice-scoria samples tend to have steeper slopes than lava samples, indicating a more uneven crystal-growth condition.

Competition between bead boundary fusion and crystallization kinetics in material extrusion-based additive manufacturing

Assembling polymer beads into well-defined 3D geometries through a layer by layer deposition process, such as material extrusion additive manufacturing, remains challenging due to the complex interplay between the several kinetics involved (flow, inter-beads diffusion/fusion, cooling, solidification, etc). Here, we explore the influence of physical parameters like bead cross section geometry, partial bead fusion (also called bead coalescence or bead welding) and crystallization kinetics on the 3D printing of isotactic polypropylene as a model semi-crystalline polymer. New methods for the characterization of printed stacks cross sections, interlayer cohesion and viscoelastic coalescence are introduced. Our results demonstrate how printing conditions, through input parameters like layer height and nozzle temperature, can greatly affect interlayer cohesion in relation to polymer interdiffusion at the interface. We show that the relevant timescale for fusion is mainly driven by the polymer’s rheology, and that fusion is many-fold faster under Hertzian compression, i.e. due to the effect of contact pressure. Quantitative description of the influence of the extrusion nozzle and build platform temperatures on the crystallization time of printed beads highlights how the processability window is defined by the competition between fusion and crystallization. Our approach therefore provides a framework for the optimization of process parameters based on the physical processes involved during the production run of semi-crystalline polymers.

Preparation of enstatite-spinel based glass-ceramics from ferronickel slag and iron ore tailings by microwave-assisted one-step crystallization

A novel method to prepare high-quality enstatite-spinel based glass-ceramics by co-utilization of ferronickel slag (FNS) and iron ore tailings (IOT) via microwave-assisted one-step crystallization was proposed with an emphasis on the effect of IOT content on the preparation process. The thermodynamic analysis demonstrated that incorporating appropriate amounts of IOT into FNS can effectively transform olivine in FNS into enstatite. The experimental exploration revealed that the crystallization activation energy of the parent glass decreased from 564.6 kJ/mol to 351.93 kJ/mol when the IOT content increased from 30 wt% to 45 wt%. Meanwhile, the Avrami index of the parent glass increased from 3.88 to 4.81, indicating less depolymerization. In the subsequent crystallization process, with increasing content of IOT, the main phase was enstatite, accompanied by small amounts of spinel which acted as nucleation sites promoting the enstatite formation. Due to the decreased depolymerization degree that resulted in fewer nucleation sites, the average grain size of enstatite increased from 123 nm to 196 nm. By controlling crystallization of the melted mixture of 65 wt% FNS and 35 wt% IOT at 863 °C for 20 min, the resulting enstatite-spinel based glass-ceramics had excellent comprehensive properties, namely density of 3.13 g/cm3, bending strength of 153.53 MPa, Vickers microhardness of 9.22 GPa, acid resistance of 99.89%, and alkali resistance of 99.72%. With a much shorter crystallization time (1/6 of conventional one), the product obtained by microwave-assisted one-step crystallization had properties comparable to those derived from similar wastes.

Dehydration of Alcohols to Olefins Catalyzed by ZrAPSO-34 Molecular Sieve

The lower olefins (Ethylene, propylene, and butylene) are considered the key to the polymeric and petrochemical industries. Dehydration of alcohols to produce light olefins (Methanol-to-olefins reaction) over SAPO-34 molecular sieve has attractedintoigh attention. Modified SAPO-34 zeolite catalyst with Zr metal was successfully prepared under microwave irradiation using morpholine as a structure direct agent. The microwave energy power used was 800 w and the crystallization time was 200 min. The catalyst sample was characterized by XRD, SEM, EDX, BET, FTIR, and TGA analysis. XRD analysis exhibited a typical chabazite structure with high crystallinity. The analysis showed macrocrystalline particles with moderate distribution of silica in the framework structure and a low surface area of 77 m2/g. The vibration peaks of the prepared catalyst showed agreement with the SAPO-34 CHA structure. Catalyst performance towards methanol-to-olefins conversion was performed in a trickle bed reactor with temperatures of 350, 400, 450, and 500 oC at a weight hourly space velocity of 7.7 h-1. The results also reveal at a temperature of 400 oC , that the best olefins selectivity was obtained, reaching 70%, with a longer lifetime of 500 min. methanol conversion was almost 100% at all reaction temperatures. In addition, the effect of methanol concentration was investigated and the results showed that increasing of water content plays a role in increasing catalyst lifetime and preventing coke depositions in pores.

Weather-related changes in the dehydration of respiratory droplets on surfaces bolster bacterial endurance

HypothesisThe study shows for the first time a fivefold difference in the survivability of the bacterium Pseudomonas Aeruginosa (PA) in a realistic respiratory fluid droplet on fomites undergoing drying at different environmental conditions. For instance, in 2023, the annual average outdoor relative humidity (RH) and temperature in London (UK) is 71 % and 11 °C, whereas in New Delhi (India), it is 45 % and 26 °C, showing that disease spread from fomites could have a demographic dependence. Respiratory fluid droplet ejections containing pathogens on inanimate surfaces are crucial in disease spread, especially in nosocomial settings. However, the interplay between evaporation dynamics, internal fluid flow and precipitation and their collective influence on the distribution and survivability of pathogens at different environmental conditions are less known. ExperimentsShadowgraphy imaging is employed to study evaporation, and optical microscopy imaging is used for precipitation dynamics. Micro-particle image velocimetry (MicroPIV) measurements reveal the internal flow dynamics. Confocal imaging of fluorescently labelled PA elucidates the bacterial distribution within the deposits. FindingsThe study finds that the evaporation rate is drastically impeded during drying at elevated solutal concentrations, particularly at high RH and low temperature conditions. MicroPIV shows reduced internal flow under high RH and low temperature (low evaporation rate) conditions. Evaporation rate influences crystal growth, with delayed efflorescence and extending crystallization times. PA forms denser peripheral arrangements under high evaporation rates and shows a fivefold increase in survivability under low evaporation rates. These findings highlight the critical impact of environmental conditions on pathogen persistence and disease spread from inanimate surfaces.

Dehydration of goethite during vacuum step-heating and implications for he retentivity characterization

Uncertainty exists over what environmental conditions and mineralogical/chemical properties are required to ensure retention of helium such that (UTh)/He dates record the time of goethite crystallization. We undertook vacuum step heating experiments to determine He diffusion parameters for extrapolation to Earth surface conditions on 10 goethite specimens in which we had created a uniform distribution of 3He. Arrhenius plots of apparent diffusion coefficients on all samples follow the same pattern. At temperatures <200 °C the data define arrays consistent with progressive degassing of increasingly large crystallites. However, above 200 °C the computed diffusivities increase dramatically until about 80% of the helium is extracted, after which they suddenly decline. The sudden increase in diffusivity at 200 °C coincides with the onset of dehydration of the goethite structure, a process which continues throughout the remainder of the step heat. There is a strong correlation between evolved water and 3He amounts. These observations likely reflect previously reported processes of formation, growth, and coalescence of pores as the phase transition to hematite proceeds. While significantly higher dehydration temperatures of ∼270 °C are observed using techniques such as thermogravimetric analysis in air, the long step durations, and vacuum conditions of our experiments destabilize goethite. Orders of magnitude differences in the computed diffusivities among our samples may reflect crystallite-size-distribution control on dehydration kinetics, and the qualitative size distributions we infer from the step heats are consistent with SEM observations of crystallite lengths. Vacuum step-heating experiments in which goethite is decomposing cannot be used to determine He diffusion behavior in nature, but the inferred crystallite size distribution provides some useful indirect evidence. A strong relationship exists between metrics of the crystallite size distribution from step heating results and the degree of He retention in nature inferred from the 4He/3He method. This observation provides evidence supporting the validity of the 4He/3He technique for estimating retention, and further suggests that the dominant control on He retention in nature is the crystallite size distribution. Experiments under hydrothermal conditions in which goethite remains stable may be an alternative approach to address the question of He diffusion behavior in nature.

Synthesis of Zeolite from Fly Ash and Bottom Ash and Application for Biodiesel Transesterification

Burning coal in a Coal-Fired Power Plant produces by-products like fly ash and bottom ash. Zeolite synthesized from the ash in Teluk Sirih Coal-Fired Power Plant was applied as a catalyst in the biodiesel transesterification reaction. Zeolite synthesis used the hydrothermal method with acid pretreatment. The operating conditions for fly ash zeolite are a 2.4-molar ratio SiO2/Al2O3 and a crystallization time of 6 hours. The bottom ash zeolite used a 2.0-molar ratio SiO2/Al2O3 and a crystallization time of 8 hours. The performance test of the synthesized catalyst was carried out in the transesterification reaction using waste cooking oil as a raw material with a free fatty acid content of 0.7%. The synthesized catalyst was characterized using x-ray diffraction, scanning electron microscope, and Bruneuer-emmet-teller. The biodiesel with the highest yield was analyzed based on SNI 7182: 2015. The synthesis results of the catalyst produced type A zeolite, shown by the typical X-ray diffraction pattern and supported by the morphological test results using a cube-shaped. The surface area of zeolite fly ash and bottom ash is 12.87 m2/g and 5.13 m2/g. The test showed fly ash zeolite had the highest biodiesel yield of 89.66%. Based on the characterization using SNI 7182: 2015, the color and free glycerol met the standards, while density 40 ˚C, kinematic viscosity 40 ˚C, acid number, total glycerol, methyl ester content, and water content did not meet the standards.

Imidazole-Based Ionic Liquid Engineering for Perovskite Solar Cells with High Efficiency and Excellent Stability.

Despite the remarkable progress of perovskite solar cells (PSCs), the substantial inherent defects within perovskites restrict the achievement of higher efficiency and better long-term stability. Herein, we introduced a novel multifunctional imidazole analogue, namely, 1-benzyl-3-methylimidazolium bromide (BzMIMBr), into perovskite precursors to reduce bulk defects and inhibit ion migration in inverted PSCs. The electron-rich environment of -N- in the BzMIMBr structure, which is attributed to the electron-rich adjacent benzene ring-conjugated structure, effectively passivates the uncoordinated Pb2+ cations. Moreover, the interaction between the BzMIMBr additive and perovskite can effectively hinder the deprotonation of formamidinium iodide/methylammonium iodide (FAI/MAI), extending the crystallization time and improving the quality of the perovskite precursors and films. This interaction also effectively inhibits ion migration to subsequent deposited films, leading to a noteworthy decrease in trap states. Various characterization studies show that the BzMIMBr-doped films exhibit superior film morphology and surface uniformity and reduced nonradiative carrier recombination, consequently enhancing crystallinity by reducing bulk/surface defects. The PSCs fabricated on the BzMIMBr-doped perovskite thin film exhibit a power conversion efficiency of 23.37%, surpassing that of the pristine perovskite device (20.71%). Additionally, the added BzMIMBr substantially increased the hydrophobicity of perovskite, as unencapsulated devices still retained 93% of the initial efficiency after 1800 h of exposure to air (45% relative humidity).

Magnetic field breakout in ultramassive crystallizing white dwarfs

ABSTRACT Ultramassive white dwarfs with masses $M\gtrsim 1.1\, {\rm M}_{\odot }$ probe extreme physics near the Chandrasekhar limit. Despite the rapid increase in observations, it is still unclear how many harbour carbon–oxygen (CO) versus oxygen–neon (ONe) cores. The origin of these white dwarfs and their strong magnetic fields – single stellar evolution or a stellar merger – is another open question. The steep mass–radius relation of the relativistic ultramassive white dwarfs shortens their crystallization time $t_{\rm cryst}$, such that the recently proposed crystallization dynamo mechanism may present an alternative to mergers in explaining the early appearance of magnetism in the observed population. However, the magnetic diffusion time from the convective dynamo to the white dwarf’s surface delays the magnetic field’s breakout time $t_{\rm break}\gt t_{\rm cryst}$. We compute $t_{\rm break}(M)$ for CO and ONe ultramassive white dwarfs and compare it to the local 40 pc volume-limited sample. We find that the breakout time from CO cores is too long to account for the observations. ONe crystallization dynamos remain a viable option, but their surrounding non-convective envelopes comprise only a few per cent of the total mass, such that $t_{\rm break}$ is highly sensitive to the details of stellar evolution.

A new magmatic crystallization age constraint for the Petrota gabbroic complex from the Jurassic Evros ophiolite, eastern Circum-Rhodope Belt, NE Greece

The Circum-Rhodope Belt is a major tectonic unit that frames both the Rhodope and the Serbo-Macedonian zones of the Alpine orogen in the northern Aegean region. In the eastern part of the Circum-Rhodope Belt, the supra-subduction zone Evros ophiolite is an important crustal component that spans 176 Ma to 169 Ma magmatic activity, which cooled down to 550 °C around 164 Ma according to published radiometric dating. This incomplete ophiolite contains in its upper crustal section gabbroic complexes, to- gether with massive and pillow lavas and dykes. In this contribution, in one of these gabbroic complexes, namely the Petrota gabbroic complex, a cross-cutting basalt dyke was dated to refine the timing of the gabbro crystallization and the temporal spread of the magmatic evolution for the whole complex. The basalt dyke yielded magmatic crystallization age at 164.5±0.93 Ma as derived from U-Pb zircon geochronology. This new crystallization age confirms the previous age for the Petrota gabbro crystallization at 169±2 Ma, but extends the span of the magmatic evolution within 7–8 Myr-lasting time interval (including the analytical errors) for the complex. The latter time interval is comparable in span to the magmatic evolution of another Evros ophi- olite gabbro occurrence at the town of Didymotycho in northeastern Greece.

Synthesis of biomass combustion fly ash derived zeolites for CO2 adsorption: Optimisation of hydrothermal synthetic pathway

Industrial biomass combustion fly ash has been investigated as a precursor for zeolites with a view to evaluate the potential for adsorption of CO2. The synthesis methodology has been optimised via Design of Experiment by employing a Taguchi L9 array. Three variables were identified as statistically significant, the crystallisation temperature, crystallisation time and the liquid to solid ratio. Analysis of the main effects revealed an optimum set of conditions which produced a sample with the highest adsorption capacity of those prepared, 1.84 mmol g−1 at 50 °C. This was a result of the conversion of the as-received fly ash into type A (LTA) and type X (FAU) zeolites after alkaline fusion with NaOH and hydrothermal treatment. The enthalpy of adsorption was estimated at -40.2kJmol−1 and was shown to be dependent on surface coverage; the isosteric enthalpy of adsorption at zero coverage was -86 kJ mol−1. The working capacity of the adsorbent was maintained at 85 % of the first adsorption uptake after a total of 40 cycles in a simulated temperature swing adsorption process (50 °C/150 °C adsorption/desorption). The equilibrium and kinetic CO2 adsorption isotherms are presented and modelled through non-linear regression to reveal the adsorption mechanisms demonstrated by the fly ash-derived zeolites. Significant heterogeneity exists within the multi-phase zeolite which presents both micro and mesoporosity. The developed adsorbent presents a feasible route to valorisation of biomass combustion fly ash with good potential for application in the separation of CO2.

Interplay between Chain Relaxation Time and Melt Crystallization Time in Microinjection Molding of Polyoxymethylene

Interplay between Chain Relaxation Time and Melt Crystallization Time in Microinjection Molding of Polyoxymethylene

Interface-Engineered Atomic Layer Deposition of 3D Li4Ti5O12 for High-Capacity Lithium-Ion 3D Thin-Film Batteries.

Upcoming energy-autonomous mm-scale Internet-of-things devices require high-energy and high-power microbatteries. On-chip 3D thin-film batteries (TFBs) are the most promising option but lack high-rate anode materials. Here, Li4Ti5O12 thin films fabricated by atomic layer deposition (ALD) are electrochemically evaluated on 3D substrates for the first time. The 3D Li4Ti5O12 reveals an excellent footprint capacity of 20.23µAhcm-2 at 1 C. The outstanding high-rate capability is demonstrated with 7.75µAhcm-2 at 5mAcm-2 (250 C) while preserving a remarkable capacity retention of 97.4% after 500 cycles. Planar films with various thicknesses exhibit electrochemical nanoscale effects and are tuned to maximize performance. The developed ALD process enables conformal high-quality spinel (111)-textured Li4Ti5O12 films on Si substrates with an area enhancement of 9. Interface engineering by employing ultrathin AlOx on the current collector facilitates a required crystallization time reduction which ensures high film and interface quality and prospective on-chip integration. This work demonstrates that 3D Li4Ti5O12 by ALD can be an attractive solution for the microelectronics-compatible fabrication of scalable high-energy and high-power Li-ion 3D TFBs.

Acceleration of Zeolite Crystallization: Current Status, Mechanisms, and Perspectives.

Zeolites are important classes of crystalline materials and possess well-defined channels and cages with molecular dimensions. They have been extensively employed as heterogeneous catalysts and gas adsorbents due to their relatively large specific surface areas, high pore volumes, compositional flexibility, definite acidity, and hydrothermal stability. The zeolite synthesis normally undergoes high-temperature hydrothermal treatments with a relatively long crystallization time, which exhibits low synthesis efficiency and high energy consumption. Various strategies, e.g., modulation of the synthesis gel compositions, employment of special silica/aluminum sources, addition of seeds, fluoride, hydroxyl (·OH) free radical initiators, and organic additives, regulation of the crystallization conditions, development of new approaches, etc., have been developed to overcome these obstacles. And, these achievements make prominent contributions to the topic of acceleration of the zeolite crystallization and promote the fundamental understanding of the zeolite formation mechanism. However, there is a lack of the comprehensive summary and analysis on them. Herein, we provide an overview of the recent achievements, highlight the significant progress in the past decades on the developments of novel and remarkable strategies to accelerate the crystallization of zeolites, and basically divide them into three main types, i.e., chemical methods, physical methods, and the derived new approaches. The principles/acceleration mechanisms, effectiveness, versatility, and degree of reality for the corresponding approaches are thoroughly discussed and summarized. Finally, the rational design of the prospective strategies for the fast synthesis of zeolites is commented on and envisioned. The information gathered here is expected to provide solid guidance for developing a more effective route to improve the zeolite crystallization and obtain the functional zeolite-based materials with more shortened durations and lowered cost and further promote their applications.

Time crystal embodies chimeralike state in periodically driven quantum spin system

Chimera states are a captivating occurrence in which a system composed of multiple interconnected elements exhibits a distinctive combination of synchronized and desynchronized behavior. The emergence of these states can be attributed to the complex interdependence between quantum entanglement and the delicate balance of interactions among system constituents. The emergence of discrete-time crystal (DTC) in typical many-body periodically driven systems occurs when there is a breaking of time translation symmetry. Coexisting coupled DTC and a ferromagnetic dynamically many-body localized (DMBL) phase at distinct regions have been investigated under the controlled spin rotational error of a disorder-free spin-1/2 chain for different types of spin-spin interactions. We contribute a novel approach for the emergence of the DTC-DMBL-chimeralike state, which is robust against external static fields in a periodically driven quantum many-body system.

Exploring the thermal properties of biodiesel after purification via solvent-aided crystallization

Cooking oil undergoes rigorous purification stages before reaching the market, which likely contributes to the elevated purity achieved through solvent-aided crystallization (SAC). However, the utilization of cooking oil as biodiesel feedstock is not suitable as it is expensive, resource inefficiency and lack of sustainability. Therefore, utilization of unpurified crude palm oil (CPO) for biodiesel production is an effective replacement. This study aims to assess the efficacy of SAC using unpurified CPO as the biodiesel feedstock. Parameters investigated include crystallization temperature (6 °C–14 °C), crystallization time (20–40 min), and shaking speed (32 rpm–84 rpm). Analysis reveals that CPO exhibits a high pour point of 15.7 °C and a cloud point of 10.8 °C, indicating potential operational and storage challenges. However, crude biodiesel derived from CPO demonstrates improved characteristics, including reduced pour point, cloud point, viscosity, and density, similar to the improvements seen in purified biodiesel obtained after SAC. The findings indicate that the most suitable operating conditions to maintain low pour and cloud points are a crystallization temperature of 10 °C, crystallization time of 30 min, and shaking speed of 61 rpm. Despite these improvements, both crude and purified biodiesel surpass ASTM D6751 limits for pour and cloud points, underscoring the necessity for further optimization in biodiesel production to meet industry standards. This research highlights the potential of SAC in enhancing biodiesel quality from unrefined feedstocks, offering a cost-effective and scalable method for producing higher-quality biodiesel while addressing current limitations.

Solid-state continuous time crystal in a polariton condensate with a built-in mechanical clock.

Time crystals (TCs) are many-body systems that display spontaneous breaking of time translation symmetry. We demonstrate a TC by using driven-dissipative condensates of microcavity exciton-polaritons, spontaneously formed from an incoherent particle bath. The TC phases are controlled by the power of a continuous-wave nonresonant optical drive exciting the condensate and the interaction with cavity phonons. Those phases are, for increasing power, Larmor-like precession of the condensate pseudo-spins-a signature of continuous TC; locking of the frequency of precession to self-sustained coherent phonons-stabilized TC; and doubling of TC's period by phonons-a discrete TC with continuous excitation. These results establish microcavity polaritons as a platform for the investigation of time-broken symmetry in nonhermitian systems.

Characterization of relaxation behaviour of CF/PEKK aerospace composites using the time-temperature-crystallinity superposition principle

In this study, the Time-Temperature-Crystallinity Superposition Principle (TTCSP) was applied to determine the viscoelastic behavior of Thermo-rheological Complex Materials (TCM), specifically Carbon fibre/Poly-Ether-Ketone-Ketone (CF/PEKK) composites. The study investigated the effects of various parameters on the viscoelastic behavior of the composites, such as the degree of crystallinity after different melting temperatures, relaxation, and crystallization times. The TTCSP was utilized on the relaxation data to generate great-grand master curves for the degree of crystallinity for different laminate lay-ups. Hot press forming was employed to manufacture samples under different processing conditions, including various melting and cold crystallization temperatures. Differential Scanning Calorimetry (DSC) was employed to calculate the degree of crystallinity of CF/PEKK composites, while the Dynamic Mechanical Analyzer (DMA) was used to obtain the relaxation data. The generated great-grand master curves proved effective in predicting the relaxation behavior of the composites consolidated using single and double hold cycles at different melting temperatures and crystallization times, respectively. The great-grand master curves presented in this study can serve as valuable tool to calibrate key viscoelastic and/or thermo-viscoelastic material models for aerospace-grade CF/PEKK composites. These models are crucial for simulations aimed at predicting residual stresses and process-induced deformations during the thermoforming process.

Crystallization dynamics probed by transient resistance in phase change memory cells

Crystallization (set) time is a key bottleneck to achieve high-speed programming in phase change memory (PCM). Overcoming this limitation requires a deeper understanding of the solidification processes within nanoscale device configuration. This study explores crystallization dynamics in Ge2Sb2Te5 by measuring the transient resistance and power during the set process in confined PCM cells with nanosecond resolution. The transient resistance probes the phase, while the power can be used to evaluate temperature, thus uncovering details of the phase change dynamics. Our findings reveal a notable trend indicating that solidification from the melt results in faster crystallization compared with annealing the glassy state. Moreover, we observed notable differences in the solidification dynamics during set (crystallization) and reset (amorphization) pulses. Our nanosecond transient measurement methodology proves valuable in revealing crucial aspects of PCM crystallization dynamics, holding the potential to enable higher-speed programming.