High Nucleation Rate Research Articles

Optimal operation guidelines for direct recovery of high-purity precursor from spent lithium-ion batteries: hybrid operation model of population balance equation and data-driven classifier

The direct resynthesis of precursor from spent lithium-ion batteries (LIBs) via co-precipitation is a crucial step in closed-loop cathode recycling systems. However, design and operation strategies for producing high-purity precursors have not been comprehensively explored or optimized. Herein, we propose the optimization of co-precipitation during the recovery of spent LIBs to achieve impurity-free precursor resynthesis. By incorporating the thermodynamic equilibrium model of the leaching solution of spent LIBs into a population balance equation (PBE) model, we identified the operating ranges that prevented the formation of impurities. Bayesian optimization was employed within the screened operating ranges to determine the optimal operating conditions for minimizing both operation time and maximum particle size. This optimization was performed for both unseeded batch and semi-batch systems. The results demonstrate that the selection of an optimal semi-batch operation can reduce the operation time by 23.33% and increase the particle size by 54.75%, owing to the high nucleation and particle growth rate during the initial time step. By employing an optimization approach based on the PBE model, this study provides detailed operational guidelines for batch and semi-batch co-precipitation, enabling the production of high-purity precursor materials from spent LIBs, while minimizing both operating time and maximum particle size.

Seed-Assisted Hydrothermal Synthesis of Monodispersed Au@C Core–Shell Nanostructures for Enhancing Thermal Diffusivity of Water-Based Nanofluids

Au@C core–shell nanostructures (Au@C-NS) were synthesized through a low-temperature seed-assisted hydrothermal approach using glucose as carbon source. The material characterization and chemical analysis confirm that the synthesis method allows to obtain uniform core–shell nanostructures constituted by a crystalline metal core and an amorphous carbon shell. Depending on the synthesis conditions, their average size ranges from 146 nm to 342 nm with relative standard deviation as low as 7 %. It is proposed that the characteristic monodispersity results due to a high nucleation rate of the carbon phase at the liquid–solid interface. The obtained monodisperse Au@C-NS were used to prepare water-based nanofluids with superior heat transport properties. The thermal lens analysis shows that the thermal diffusivity of Au@C nanofluids is 9.5 % and 31.3 % higher than their Au nanofluids counterparts and pure water, respectively, at particle concentration of 285 × 1011 ml−1. Phonon-related interactions at the metal cores and carbon shells interfaces are proposed as the heat transport mechanism behind the thermal diffusivity enhancement of the Au@C water-based nanofluids.

Rapid Nucleation and Growth of Indoor Atmospheric Nanocluster Aerosol during the Use of Scented Volatile Chemical Products in Residential Buildings.

Scented volatile chemical products (sVCPs) are frequently used indoors. We conducted field measurements in a residential building to investigate new particle formation (NPF) from sVCP emissions. State-of-the-art instrumentation was used for real-time monitoring of indoor atmospheric nanocluster aerosol (NCA; 1-3 nm particles) size distributions and terpene mixing ratios. We integrated our NCA measurements with a comprehensive material balance model to analyze sVCP-nucleated indoor NCA dynamics. Our results reveal that sVCPs significantly increase indoor terpene mixing ratios (10-1,000 ppb), exceeding those in outdoor forested environments. The emitted terpenes react with indoor atmospheric O3 and initiate indoor NPF, resulting in nucleation rates as high as ∼105 cm-3 s-1 and condensational growth rates up to 300 nm h-1; these are orders of magnitude higher than those reported during outdoor NPF events. Notably, high particle nucleation rates significantly increase indoor atmospheric NCA concentrations (105-108 cm-3), and high growth rates drive their survival and growth to sizes that efficiently reach the deepest regions of the human respiratory system. We found sVCP-nucleated NCA to cause respiratory exposures and dose rates comparable to or exceeding those from primary aerosol sources such as gas stoves and diesel engines, highlighting their significant impact on indoor atmospheric environments.

Synergistic interaction behavior of deformation mechanisms in a new metastable β-Ti alloy with high strain hardening rate

The present study successfully designed a novel metastable β titanium alloy, Ti–8.8Cr–1.9Sn, exhibiting exceptionally high strain-hardening rate (∼2.4 GPa) as well as significant total elongation (∼48.2 %). Detailed analysis of the microstructure revealed that the successive activation of primary mechanical twins and primary SIM α" within β phases, along with secondary mechanical twins and secondary SIM α" within twinning zones during deformation, which results in a highly intricate network of deformation microstructures. Meanwhile, during deformation the microstructure undergoes dynamic refinement through the continuous occurrence of mechanical twinning and phase transformations, leading to a reduction in dislocation mean free path, thereby enhancing the strain-hardening rate. Importantly, the microstructural heterogeneity is formed due to generation of numerous heterogeneous interfaces, including β/α'', β/twin, α''/twin as well as twin/twinnano, thereby inducing additional HDI hardening resulting from the formation of GNDs for accommodating strain gradients near these interfaces. Furthermore, the relative mobile dislocation density ρm/ρm0 is significantly high during deformation, due to a reduced exhaustion rate and a high nucleation rate of mobile dislocations. The values of activation volume Va and V∗ typically range from 1b3–100b3, indicating the occurrence of cross-slip and dislocation nucleation. The interaction and accumulation between GNDs and mobile dislocations further contribute to the improvement of strain hardening rate. Therefore, the synergistic interaction activities of multiple deformation mechanisms lead to enhanced strain-hardening rate along with the large plasticity.

Collective effect of Vigna sp. (mung) tubulin GTP hydrolysis rate divergence on microtubule filament assembly.

Microtubules (MTs) are dynamic cytoskeletal filaments with highly conserved sequences across evolution, polymerizing by the GTP-dependent assembly of tubulin subunits. Despite the sequence conservation, MT polymerization kinetics diverge quantitatively between vertebrate brain, the model plant Arabidopsis and the protozoan Plasmodium. Previously, tubulin purified from seedlings of the plant Vigna sp. (mung) by temperature cycling was found to have a very low critical concentration. However, the lengths of MTs were sub-micron, much shorter than brain tubulin filaments. This was explained in simulations to be the result of the collective effect of high nucleation and GTP hydrolysis rates. Here, we test the effect of GTPase rates of affinity-purified Vigna sp. tubulin on microtubule polymerization and elongation. Affinity-purified mung tubulin is active and has a critical concentration of .37 μM. The GTP-dependent polymerization kinetics are transient, consistent with previous results. Polymerization is stabilized in the presence of either GTP analog GMPPNP (non-hydrolyzable) or GMPCPP (slow-hydrolyzable). Using interference reflection microscopy (IRM) we find polymerization with the non-hydrolysable analog significantly increases filament numbers, while lengths are unaffected for both GTP analogs. However, prolonged incubation with slow-hydrolyzable GMPCPP results in long filaments, pointing to GTP hydrolysis as a key factor determining MT length. We find the average GTPase turnover number of mung tubulin is 22.8 min-1, compared to 2.04 min-1 for goat brain tubulin. Thus modulating GTPase rates affects both nucleation and elongation. This quantitative divergence in kinetics despite high sequence conservation in the GTPase domains of α- and β-tubulin could help better understand the roles of selective pressure and function in the diverse organisms.

Novel Damsissa carbon quantum dots (DCQDs) to improve the protection efficiency of permanganate phosphate conversion coats (PPC) on steel

Carbon quantum dots (CQDs) are spherical zero dimensional nanoparticles, generally below 10 nm in size, which received increasing attention in diverse application fields owing to their important characteristics and advantages as good water solubility, potential of environmental protection and preparation from abundant and sustainable raw materials. In this work, Damsissa carbon quantum dots (DCQDs) were generated via hydrothermal reaction microwaves irradiation. The DCQDs material was characterized by FTIR, TEM, EDX, XRD, and XPS to confirm the morphological and functionality aspects as well as particle size distribution, elemental composition, crystallite structure, and elemental identification in terms of chemical state. The FTIR analysis referred to associated assignments of C-H, C=O, C=C, C-N, besides other groups. The TEM study confirmed a ranged homogenous particle distribution at 3-6 nm. The EDX and XPS results verified carbon, nitrogen and oxygen as the main elements in DCQDs. The protection efficiency performance of permanganate phosphate conversion coat (PPC) was investigated and monitored by using different concentrations of DCQDs in the coating bath utilizing the potentiodynamic polarization technique, besides electrochemical impedance spectroscopy. The results referred to 97.4% maximum protection efficiency for the coat in presence of 400 mg/L DCQDs. The impedance results showed that as the concentration of DCQDs increase, the capacity of the double layer (Cdl) decreases due to the adsorption ofDamsissa carbon dots on the steel surface. However, the potentiodynamic polarization results indicated that the presence of DCQDs in HCl solution could lead to the polarization of the cathodic and anodic curves to denote that these retard the cathodic and anodic reactions at the steel surface inhibiting the corrosion process. The coats synthesized in absence and in presence of diverse amounts of DCQDs were examined by the TEM, EDX, XPS, and XRD studies to elucidate the role of DCQDs in the improvement of the corrosion protection of the coat. The results indicated that the DCQDs molecules ofDamsissa were adsorbed at the steel surface to efficiently retard the dissolution of iron and decrease the Fe2+ ions concentration in the coating solution causing higher nucleation rate over the crystal growth and thus leading to the formation of a uniform protective film.

Mold material and dimension effects on the microstructural gradient in a glass-ceramic

Microstructural gradients can significantly affect the properties of glass-ceramics (GCs). Such spatial variations in glass-ceramic (GC) microstructure may result from a non-uniform cooling rate when the glass-forming liquid is cast into a mold. This study investigates the material and mold size influence on the cooling process, leading to a non-uniform distribution of crystalline nuclei in the parent glass. We used a high-nucleation rate, non-stoichiometric, lithium metasilicate GC as a model. Initially, the glass-forming liquid was cooled in cylindrical molds with diameters of 7 and 14 mm, made from copper and 304 stainless steel – materials with distinct thermal diffusivities. Simulated thermography, validated by thermocouple data, showed contrasting cooling profiles across the samples. Our key findings are: i) cooling rate: faster cooling in the smaller mold resulted in a lower crystal number density and a reduced crystallized volume fraction (αv) as expected; ii) mold material: surprisingly, copper molds led to quicker glass shrinkage, which facilitated the earlier formation of air gaps with reduced heat transfer and slower cooling than steel, favoring incipient crystallization during the cooling path; iii) microstructure: samples cooled in both molds exhibited higher αv in the central and upper (mold contact-free) regions due to slower cooling compared to the mold base and edges. Therefore, this study reveals how mold material and size affect microstructural gradients in GCs, paving the way for tailoring crystallization and microstructure through strategic mold design.

The role of mixing on the kinetics of nucleation and crystal growth in membrane distillation crystallisation

While mixing is considered critical in membrane distillation crystallisation, an explicit link between mixing and crystallisation mechanisms has yet to be made. This study therefore used in-line nucleation detection to determine induction time and metastable zone width, as a method to characterise the independent roles of interfacial boundary layer mixing and bulk crystalliser mixing on the kinetics of nucleation and crystal growth in membrane distillation crystallisation. Interfacial boundary layer mixing was investigated by changing Reynolds number (Re, 1300–2050), where an increase in Re also increased flux. This increased supersaturation within the boundary layer, shortened induction time, and was correlated to a higher nucleation rate. The high nucleation rates introduced smaller crystal sizes, which is an effect that can be correlated to classical nucleation theory. Mixing within the crystalliser did not modify the interfacial supersaturation at nucleation (ReN 1562–18741). However, a decrease in induction time was observed when transitioning from lower to higher mixing, which may arise from the improved distribution of the supersaturated feed within the crystalliser. The effect of crystalliser mixing was also evident on crystal growth, where larger crystals were produced at higher crystalliser stirrer speeds due to improved diffusion-controlled growth. This study therefore demonstrates that bulk and interfacial mixing can be collectively used to control crystallisation by decoupling conditions that determine nucleation and crystal growth. Morphological assessment was subsequently undertaken that evidenced how dendritic breeding and wider secondary nucleation mechanisms that dominate crystal growth at high levels of supersaturation can be mitigated through mixing. Membrane crystallisation offers a scalable geometry in which we demonstrate mixing to facilitate good control over crystal growth which is more difficult to realise in existing evaporative crystalliser design.

Fast formation of large ice pebbles after FU Orionis outbursts

During their formation, nascent planetary systems are subject to FU Orionis outbursts that heat a substantial part of the disc. This causes water ice in the affected part of the disc to sublimate as the ice line moves outwards to several to tens of astronomical units. In this paper, we investigate how the subsequent cooling of the disc impacts the particle sizes. We calculate the resulting particle sizes in a disc model with cooling times between 100 and 1000 yr, corresponding to typical FU Orionis outbursts. As the disc cools and the ice line retreats inwards, water vapour forms icy mantles on existing silicate particles. This process is called heterogeneous nucleation. The nucleation rate per surface area of silicate substrate strongly depends on the degree of super-saturation of the water vapour in the gas. Fast cooling results in high super-saturation levels, high nucleation rates, and limited condensation growth because the main ice budget is spent in the nucleation. Slow cooling, on the other hand, leads to rare ice nucleation and efficient growth of ice-nucleated particles by subsequent condensation. We demonstrate that close to the quiescent ice line, pebbles with a size of about centimetres to decimetres form by this process. The largest of these are expected to undergo cracking collisions. However, their Stokes numbers still reach values that are high enough to potentially trigger planetesimal formation by the streaming instability if the background turbulence is weak. Stellar outbursts may thus promote planetesimal formation around the water ice line in protoplanetary discs.

Microstructural evolution in doped high entropy alloys NiCoFeCr-3X (X=Pd/Al/Cu) under irradiation

Commonly studied equatomic single-phase FCC high entropy alloys based on 3d transition metals like NiCoFeCr do not provide adequate strength and radiation resistance at high doses for nuclear structural applications. In the current study, the major alloying effects like lattice distortion, ordering and clustering tendencies were investigated by adding low concentration of Pd, Al, or Cu respectively to study the doping effects on the ion irradiation response of NiCoFeCr alloy. The alloys were irradiated with 3 MeV Ni2+ ions at 500 °C to a fluence of 1 × 1017/cm2 at a beam flux of approximately 2.8 × 1012 ions/cm2/s. The microstructural evolution upon irradiation i.e., formation of dislocation networks, radiation induced segregation and precipitation, and void formation were studied in detail. Post-irradiation characterization results showed that a Pd addition leads to a high void nucleation rate but controlled void growth, which may be attributed to increased lattice distortion. In Al added HEA, our microstructural analysis indicates that radiation induced ordered L12 precipitates do not affect void swelling significantly. Cu addition led to Cu precipitation that drastically suppressed dislocation density and void swelling of the alloy. Additionally, a model was developed to qualitatively describe the trend in void swelling of typical FCC alloys under ion irradiation. This model was able to qualitatively explain the suppression and reappearance of void swelling in ion irradiated alloys that generally occurs near the region with peak implanted ion concentration.

Achieving enhanced strength retention at elevated temperatures in ultrafine-fibrous interconnected Al–Ce–Ni eutectic alloy solidified under super-gravity field

Super-gravity field was reported to strongly intensify the buoyancy-driven flow of liquid during solidification, affecting the solute convection and morphology of eutectic structure in binary alloys. In ternary eutectic alloys, certain two-phase regions with a coarse structure can usually be detected concurrently along with three-phase eutectics, leading to the formation of heterogeneous structure with limited ductility. Currently, Al–Ce–Ni ternary eutectic alloy was chosen as a modal system, which was reported for the first time to be solidified under super-gravity field with high volume fraction of three-phase eutectics. Meanwhile, the formation of ultrafine-fibrous interconnected Al11Ce3–Al3Ni eutectic clusters with more “chains” and higher spatial connectivity was detected mainly due to the relatively higher nucleation rate. The high volume fraction and refinement of interconnected Al11Ce3–Al3Ni eutectic clusters with excellent thermal stability could contribute to enhancement of ductility and tensile strength at elevated-temperature. Interestingly, the strength retention at 300 °C and 400 °C were able to reach up to ∼68.1 % and ∼33.2 %, respectively.

Towards the hydrogen pore in additively manufactured AlMgScZr alloy: Influencing factors, formation kinetics mechanism

Hydrogen pores in laser additive manufacturing (LAM) aluminum alloys have long been a major challenge for its application. In this study, the formation mechanisms of hydrogen pores and its kinetic behaviors were systematically investigated in laser directed energy deposited (L-DED) AlMgScZr alloy. The results indicated that hydrogen pores accumulated layer by layer at the melt pool boundaries, due to the high nucleation rate and insufficient time to escape of hydrogen pores at the melt pool boundaries. Dring the AlMgScZr powder at 150 °C/4 h enabled the significant decrease of moisture content from 0.0520 wt% to 0.0096 wt%, while the porosity of the L-DED sample only decreased from 0.51% to 0.36%. The increase of laser power decreased the porosity of L-DED sample. Except the L-DED parameters, the alloy composition exerted a more significant influence on hydrogen porosity. When the Mg content increased from 9 wt% to 14 wt%, the porosity exhibited an increase from 0.36 % to 0.52 %. Conversely, the incorporation and subsequent augmentation of Si content resulted in a significant reduction in porosity, reaching as low as 0.15% with an increase to 2 wt%. The solubility and diffusion coefficient of [H] in Al-Mg-Sc-Zr melt with different Mg and Si contents were calculated by density functional theory (DFT). It was observed that increasing the Si content led to a decrease in the nucleation zone for hydrogen pores and reduced porosity. A comprehensive porosity inhibition strategy that combines powder drying, process optimization, and composition regulation have been developed.

Effect of RIBS/FINS and Aspect Ratio on Flow Boiling Characteristics in Conventional Channels

Abstract In this work, experiments are conducted with conventional rectangular channels of two different aspect ratios (AR = w/d) for the horizontal boiling flow conditions at atmospheric pressure. Distilled water was used as the working substance. The heat transfer coefficients (HTC) were measured for mass fluxes and heat fluxes ranging from 85.94 kg/m2-s to 343.77 kg/m2-s and 10 kW/m2 to 100 kW/m2, respectively, and at inlet subcooled temperatures of 303 K, 313 K, and 323 K. Visualization of the boiling phenomenon was done using a high-speed camera for the two channels under similar conditions. The results show that the AR has a dominant effect on the HTC. At low heat flux values, higher HTC was noticed for the channel of higher AR (AR = 1.25) whereas, at high heat flux conditions, the HTC is higher for the channel of lower AR (AR = 0.2). With an increase in inlet subcooled temperature, the HTC decreased for both channels due to increased thermal boundary layer thickness and reduced bubble formation. Further, the channel of AR = 1.25 with ribs/fins performed better than the smooth channel due to the high bubble nucleation rate.

Predicting the size of silver nanoparticles synthesised in flow reactors: Coupling population balance models with fluid dynamic simulations

Achieving size control during nanomaterial synthesis is critical for their deployment in numerous applications due to their strong size-properties relationships. However, it remains a challenge in the field due to multi-step mechanisms in nanoparticle synthesis. In this paper, we present an experimentally-validated model able to predict the particle size and distribution of silver nanoparticles synthesised in flow reactors by coupling time-resolved fluid dynamic simulations with population balance. The model reveals fundamental correlations between reactor design and the corresponding size of the nanoparticles. It shows that increasing mixing rate, increases the overall rate of nanoparticle formation, where nanoparticle synthesis takes place homogeneously in the whole of the reaction volume. In contrast, when there is a distinguishable interface between reactant streams (i.e. low mixing rate), nucleation and growth take place in a small fraction of the reaction volume in the interface between the inlet streams. The combination of fast mixing and high average nucleation rate can lead to a burst of nuclei formation translated in small size and narrow size distribution. This work presents a new approach for the use of computational-guided design of reactors for the synthesis of nanomaterials to move the field away from current trial-and-error strategies.

Anomalous Temperature-Induced Particle Size Reduction in Manganese Oxide Nanoparticles.

The intricate role of temperature in the structure-property relationship of manganese oxide nanoparticles (Mn3O4 NPs) remains an open question. In this study, we successfully synthesized Mn3O4 NPs using the hydrothermal method with two differing temperatures, namely, 90 and 150 °C. Interestingly, a smaller average particle size is found when Mn3O4 NPs are synthesized at 150 °C compared to 90 °C, corresponding to 46.54 and 63.37 nm, respectively. This was confirmed by the time variation of temperature setting of 150 °C where the size evolution was insignificant, indicating a competing effect of nucleation and growth particles. Under varying NaOH concentrations (2-6 M) at 150 °C, a reduction in the particle size is found at the highest NaOH concentration (6 M). The particle grows slightly, indicating that the growth state is dominant compared to the nucleation state at low concentrations of NaOH. This finding implies that the high nucleation rate originates from the excessive monomer supply in the high-temperature reaction. In terms of crystallinity order, the structural arrangement of Mn3O4 NPs (150 °C) is largely decreased; this is likely due to a facile redox shift to the higher oxidation state of manganese. In addition, the higher ratio of adsorbed oxygen and lattice oxygen in Mn3O4 NPs at 150 °C is indirectly due to the higher oxygen vacancy occupancies, which supported the crystallinity decrease. Our findings provide a new perspective on manganese oxide formation in hydrothermal systems.

Effect of different chain lengths of monoglyceride on the O/W interfacial properties with high-melting and low-melting crystals in low-fat aerated emulsion.

The effect of different types of monoglycerides, including monopalmitin, capryl monoglyceride (GMB), and succinylated monoglyceride (GMSA) in combination with palm kernel stearin (PKS) and beeswax (BW), on the formation, crystal network structure, and partial coalescence properties of aerated emulsions (20% w/w fat) was investigated. The stability of BW and PKS crystals with a 1% concentration of GMSA and GMB, respectively, in the oil phase was lower than the other crystals. BW-GMSA and PKS-GMB crystals exhibited a lower crystallization rate, higher contact angles and no significant peak shift in the small-angle X-ray scattering results. The BW-GMSA and PKS-GMB emulsions had a lower nucleation rate in the bulk and a higher nucleation rate at the interface, resulting in a higher fraction of crystals adsorbed at the oil/water interface. This reduced the number of interfacial proteins and led to a high degree of partial coalescence and the formation of stable aerated networks.

Impact of Variable Fault Geometries and Slip Rates on Earthquake Catalogs From Physics‐Based Simulations of a Normal Fault

AbstractPhysics‐based earthquake simulators have been developed to overcome the relatively short duration and incompleteness of historical earthquake and paleoseismic records, respectively. These simulators have the potential to be a useful addition to seismic hazard assessment as they produce millions of synthetic earthquakes over thousands to millions of years using predefined fault geometries and slip rates. Due to the sparsity of fault data and the computational expense of the modeling, it is common to simplify earthquake simulator input parameters. Fault surfaces are typically characterized by simplified mapped traces and constant dip with depth, with slip rates that are often assumed to be uniform over the fault plane. This study uses the well‐defined 3D geometry of an active normal fault in offshore Aotearoa New Zealand, the Cape Egmont Fault, to demonstrate the impact of using nonuniform slip rates and nonplanar fault geometries on the resulting synthetic earthquakes from the earthquake simulator RSQSim. Adopting variable slip rates that decrease to zero along the fault tipline (rather than uniform slip rates) reduces unrealistically high nucleation rates of seismicity along fault edges. Introduction of complex 3D fault geometries, including fault segmentation and bends on kilometer scales, and variable slip rates produces less characteristic earthquake populations, increasing the number of M6‐7 moderate‐large magnitude events. Incorporation of variable fault geometries and slip rates in physics‐based simulators may modify the seismic hazards estimated from synthetic earthquake catalogs.

A new perspective for nucleation and nanocrystallization from interfacial energy and nanoscale composition fluctuations in glasses

AbstractNucleation behaviors in glasses/supercooled liquids (SCLs) such as lithium disilicate Li2O–2SiO2, cordierite Mg2Al4Si5O18, fresnoite Ba2TiSi2O8, and K2O–Nb2O5–GeO2/TeO2 glasses were analyzed and discussed from the interfacial energy γ at SCL–nucleus interfaces and nanoscale composition fluctuations. Based on the fragility concept for SCLs and the intrinsic origin of γ, the magnitude order of γ(fragile SCL) < γ(strong SCL) was proposed to be a crucial guide for an understanding of high homogeneous nucleation rates and prominent nanocrystallization. The role of nucleating agent TiO2/ZrO2 in accelerating the nucleation rate in cordierite‐based and β‐spodumene‐type Li2O–Al2O3–SiO2‐based glasses was discussed from the new perspective of γ(homoepitaxial‐like nucleation) < γ(heteroepitaxial‐like nucleation). Ferroelectric nanocrystals such as SrxBa1–xNb2O6 in borate glasses and fluoride nanocrystals such as CaF2 are also well understood from the proposed guidelines. The present article provides a new perspective for nucleation in glasses/SCLs, contributing to the comprehensive composition design of new innovative glass‐ceramics.

Effect of Residual Stress on the Continuous Cooling Transformation of High‐Strength Low‐Alloy Hot‐Rolled Strip

The external stress will change the transformation process and microstructure of the material, and the residual stress generated during the processing of the material will also affect the transformation. Herein, the effect of residual stress is simulated by applying uniaxial elastic loads during the continuous cooling of high‐strength low‐alloy hot‐rolled strip. The transformation process and microstructure of the samples under different stress conditions are investigated. The results show that residual stress can accelerate the transformation process, and the tensile stress is greater than the compressive stress. The degree of lattice mismatch in stressed samples is larger than that in unstressed samples, leading to dislocation proliferation. It is found that there is a phenomenon of residual stress‐induced grain growth according to the statistics of grain size of different samples. Due to the higher dislocation density and smaller curvature of the parent phase interface under compressive stress, the compressive stress samples have a higher nucleation rate, resulting in smaller grain size than the tensile stress samples. In addition, the transformation texture also changes under residual stress.

Insight into the crucial reason causing the difference in secondary organic aerosol yields of monocyclic aromatic hydrocarbons with different methyl substituent numbers

The secondary organic aerosol (SOA) yield of toluene photooxidation was reported to substantially higher than that of trimethylbenzene due to the effect of the number of methyl substituents. However, the intrinsic mechanism for this disparity is not clear enough. In this study, a highly-sensitive thermal-desorption photoinduced associative ionization mass spectrometer (TD-PAI-MS) was used to real-time characterize the molecular composition and its evolution of the SOA generated from the photooxidation of toluene and 1,2,3-trimethylbenzene (1,2,3-TMB) in a smog chamber. In the new particle formation (NPF) stage, toluene generated more variety of nucleation precursors, such as benzaldehyde (MW 106) and benzoic acid (MW 122), resulting in a much higher nucleation rate and SOA number concentration. In the SOA growth/aging stage, the key SOA components of toluene were mainly dialdehydes, e.g., 2-oxopropanedial (MW 86) and 4-oxopent-2-enedial (MW 112), which played an important role in the formation of highly oxidized species (HOS) through oligomerization or cyclization reactions. In contrast, due to the presence of more methyl groups, 1,2,3-TMB was inclined to produce ketones, e.g., 2,3-butanedione (MW 86) and 3-methyl-4-oxopent-2-enal (MW 112), which would be cleaved into high-volatility low molecular compounds, e.g., acetic acid, through fragmentation. Taken together, relative to 1,2,3-TMB, the higher nucleation rate during NPF and the significant oligomerization/functionalization process during SOA growth are thought to be the major reasons resulting in the higher SOA yield of toluene. This work provides a reference for the insight into the different SOA yields of monocyclic aromatic hydrocarbons (MAHs) through further revealing the SOA formation mechanism during toluene and 1,2,3-TMB photooxidation.