Growth Of Nuclei Research Articles

Study on the Continuous Whole Process Preparation of Peptizable Pseudoboehmite by High Gravity Strengthening Reaction of CO2 and Heat Transfer.

The preparation of highly peptizable pseudoboehmite faces challenges such as slow reaction rate, prolonged aging times leading to poor peptization performance, and difficulty in achieving continuous production. In this study, a novel approach was proposed involving a high gravity reactor to enhance carbonation reaction control for pseudoboehmite nucleation, a high gravity steam heating process, and a continuous aging process in pipelines. By coupling these three processes, the continuous whole process production of highly peptizable pseudoboehmite under high gravity conditions was achieved. First, the effect of high gravity reactor enhancement on the reaction and the resulting solid phase was investigated. Second, the impact of aging temperature and time on the solid phase formed at different reaction end points was studied using high gravity and steam heating of the liquid phase. Furthermore, the influence of synthesis conditions on the peptization performance of pseudoboehmite was extensively examined. Finally, the nucleation and growth mechanisms of pseudoboehmite under high gravity conditions were analyzed. It was found that increasing high gravity factor, CO2 gas flow rate, and CO2 content accelerated carbonation reaction rate, promoting pseudoboehmite crystal nucleation. Increasing aging temperature and time facilitated the growth of pseudoboehmite nuclei and improved peptization performance. The high gravity device altered the gas-liquid phase contact state of traditional kettle-type equipment, reducing the reaction time and heating time from minutes to seconds, thus achieving the continuous whole process production of pseudoboehmite with a peptization index of 100% from sodium aluminate solution by kiln flue gas.

Revolutionizing soil and waste treatment: MoS2 nanosheets turbocharge geopolymerization for eco-friendly remediation and self-cementation of arsenic-contaminated soils and municipal solid waste incineration fly ashes

In the face of escalating arsenic pollution and the mounting challenge of municipal solid waste incineration (MSWI) fly ashes, cutting-edge technology has emerged as a game-changer. By harnessing the power of MoS2 nanosheets, a revolutionary approach to double-self-cementation has been unlocked, addressing the limitations of previous methods. Through heterogeneous adsorption, MoS2 nanosheets bolstered the stability of the matrix, leading to a remarkable surge in compressive strengths and a substantial reduction in leaching toxicities of heavy metals. The compressive strengths of the cemented cubes increased as the dosage of nanosheets increased from 0.3 % to 2.4 %, with compressive strengths ranging from 24.34 to 34.21 MPa. The leaching toxicities of Zn, Cu, Cr, Cd, Pb, and As from the solidified matrix correspondingly decreased to 0.32, 0.21, 0.04, 0.01, 0.05, and 0.53 mg/L, respectively. The role played by nanosheets in inhibiting the release and transport of chloride species further underscored their pivotal contribution. Moreover, the study delved into the intricate mechanisms underlying the impact caused by nanoscale materials cementation and geopolymerization systems, shedding light on their dual function as solidification intensifiers and chemical stabilizers. The nanosheet-enhanced double-self process can be appropriately fitted by the JMAK model. The linear nuclei growth of gels controlled the solidification and geopolymerization of the precursor materials and the stabilization of HM contaminants. This groundbreaking research not only elucidates the transformative potential of MoS2 nanosheets but also paves the way for a paradigm shift in the treatment of contaminated soils and waste materials.

Room-Temperature Single-Phase Synthesis of Semiconducting Metal-Covalent Organic Frameworks With Microenvironment-Tuned Photocatalytic Efficiency.

In order to improve the solubility of metallated monomers and product crystallinity, metal-covalent organic frameworks (MCOFs) are commonly prepared via high-temperature sol-vothermal synthesis. However, it hampers the direct extraction of crystallization evolution information. Exploring facile room-temperature strategies for both synthesizing MCOFs and exploiting the crystallinity mechanism is extremely desired. Herein, by a novel single-phase synthetic strategy, three MCOFs with different microstructure is rapidly prepared based on the Schiff base reaction between planarity-tunable C3v monomers and metallated monomers at room temperature. Based on detailed time-dependent experiments and theoretical calculations, it is found that there is a planarity-tuned and competitive growth relationship between disordered structures and crystal nucleus for the first time. The high planarity of monomers boosts the formation of crystal nucleus and rapid growth, suppressing the forming of amorphous structures. In addition, the microenvironment effect on selective photocatalytic coupling of benzylamine (BA) is investigated. The strong donor-acceptor (D-A) MCOF exhibits efficient photocatalytic activity with a high conversion rate of 99% and high selectivity of 99% in 5h under the 520nm light irradiation. This work opens a new pathway to scalable and efficient synthesis of highly crystalline MCOFs.

Influence mechanism of magnetron sputtering process parameters on diamond surface preprocessing interface for chip heat sink

The interface between diamond and aluminum is poor in wettability and solid solubility. The interface bonding can be improved effectively by plating metal elements on diamond surface combined with heat treatment. In this paper, the influence of adjustable process parameters on the quality of Mo layer modified by magnetron sputtering was studied based on orthogonal experiments, and Mo-coated diamond/aluminum composite materials were prepared by Spark Plasma Sintering (SPS). The results indicate that the deposition of Mo layer on the diamond surface proceeds through three stages: adsorption, surface diffusion, and stable nucleus growth, forming an initial thin film, followed by layer-by-layer stacking through repeated growth of these stages. Sputtering time and sputtering pressure are the main factors affecting the quality of the coating. Mo layers prepared under conditions of 30 min and 0.5 Pa exhibit uniform and dense surface and moderate thickness. After heat treatment, recrystallization forms equiaxed grains, and Mo2C is formed in reaction with diamond, effectively enhancing the interface bonding strength between diamond and aluminum. The thermal conductivity of the diamond/aluminum composite material reached 342 W/(mK).

Pyrolysis kinetic analysis of molten bioplastics based on the combination of real-time characterization and Guassian deconvolution: Case study of poly(lactic acid) materials.

Pyrolysis remains a promising method for the utilization of biogradable plastics. However, the kinetics and mechanisms of molten polymer pyrolysis are not well understood, and the effect of additives (mainly inorganic nucleating agents) on the reaction pathway has not been widely explored. In this work, we conducted a method using the thermogravimetric analysis-Fourier transform infrared spectrometry (TG-FTIR) combined with a model-fitting method, instead of a traditional method subjectively selecting a reaction model. The FTIR curves provided information for sub-reaction determination, and the detailed parameters were determined using Gaussian deconvolution. The calculation results revealed that the whole process of poly(latic acid) (PLA) pyrolysis is the random nucleation and nuclei growth model. The introduction of inorganic nucleating agents provided nuclei for PLA decomposition, decreasing the initial activation energy (E) from approximately 136 kJ·mol-1 to 88 and 79 kJ·mol-1 at a conversion rate of 0.01. However, the nucleating agent could hinder the generation of nuclei from PLA ontology, which led to the increase of E value after the nucleating agents were occupied.

Study on the effect of particles in oilfield produced water on the deposition process of CaCO3

In crude oil production, scale deposition significantly reduces production output and elevates operational costs, posing a severe threat to production safety. While chemical methods have been extensively explored for the scaling and inhibition of inorganic salts, the inorganic scaling triggered by solid particle scaling in complex oilfield water has largely been overlooked. This study involves the introduction of particles into a supersaturated CaCO3 solution, utilizing static scale inhibition and conductivity techniques to examine their influence on the scaling process and crystallization rate. It is evident that solid particles expedite the deposition process of CaCO3. Moreover, the deposition rate of CaCO3 is influenced by factors such as the solid particle content, particle size, and stirring speed. It is noteworthy that the presence of solid particles solely impacts the formation rate of CaCO3 crystals, without altering the total deposition. Specifically, under conditions of 70°C, 250/min stirring speed, and 0.08% SiO2 addition, the deposition rate of CaCO3 is enhanced by 13.5%. The nucleus growth rate constant increases from 11.10 × 10-3min-1 to 14.52 × 10-3min-1 and the crystal growth rate constant increases from 3.02 × 10-3min-1 to 3.36 × 10-3min-1 at most. Observations made through scanning electron microscopy (SEM) and polarized light microscopy reveal that scaling occurs predominantly on the added solid particles in later stages, indicating that solid particles in supersaturated solutions serve as crystal nuclei, inducing the growth of CaCO3 crystals and thus accelerating scaling. This research provides valuable insights for the study of scaling in complex water environments.

Customization of indium-based MOFs for enhanced adsorptive and photocatalytic of organic pollutants: Morphology involvement on performance and mechanism

Metal-organic frameworks (MOFs) as photocatalysts are promising candidates for environmental wastewater treatment owing to their tunable crystal structure, well-ordered donor–acceptor interface, and exceptional porosity. However, precise control over size and morphologies of MOFs to enhance adsorptive and photocatalytic performance is still a considerable challenge. Herein, the MIL-68(In)–NH2 (MN) MOFs with special acicular structure are customized by a facile method, in which the growth of crystal nuclei is inhibited and regulated by pyridine. The formation mechanism of MN with different morphologies and size is introduced, and their photocatalytic activities are systematically explored by degrading model pollutants tetracycline (TC) and dyes under visible light irradiation. Benefiting from its high specific surface area and the exposed large lattice spacing facet, the wool-ball morphology MN (MN-W) with surface acicular nanostructure presents an optimum photocatalytic performance compared to other MN morphologies. The MN-W also exhibits excellent adsorption capacity, remarkable cyclic stability, and good practical organic wastewater treatment capability. The possible photodegradation mechanism and pathways are elucidated, demonstrating that h+ is the primary reactive species, followed by •OH and •O2– radicals, responsible for the degradation of TC. This work is anticipated to tailoring design and modulate MOF photocatalysts for boosting the photocatalytic performance towards organic effluents remediation.

Influence of Glycerol on the Surface Morphology and Crystallinity of Polyvinyl Alcohol Films.

The structure and physicochemical properties of polyvinyl alcohol (PVA) and PVA/glycerol films have been investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetry/differential thermal analysis (TG/DTA), and advanced scanning probe microscopy (SPM). In the pure PVA films, SPM allowed us to observe ribbon-shaped domains with a different frictional and elastic contrast, which apparently originated from a correlated growth or assembly of PVA crystalline nuclei located within individual PVA clusters. The incorporation of 22% w/w glycerol led to modification in shape of those domains from ribbon-like in pure PVA to rounded in PVA/glycerol 22% w/w films; changes in the relative intensities of the XRD peaks and a decrease in the amorphous halo in the XRD pattern were also detected, while the DTA peak corresponding to the melting point remained at almost the same temperature. For higher glycerol content, FT-IR revealed additional glycerol-characteristic peaks presumably related to the formation of glycerol aggregates, and XRD, FT-IR, and DTA all indicated a reduction in crystallinity. For more than 36% w/w glycerol, the plasticization of the films complicated the acquisition of SPM images without tip-induced surface modification. Our study contributes to the understanding of crystallinity in PVA and how it is altered by a plasticizer such as glycerol.

Fabrication of an In‐situ Synthesized Porous Silica‐Ruthenium‐Nickel Composite Catalyst for Hydrolysis of Ammonia Borane

AbstractThis work investigated in‐situ synthesis of porous silica‐nickel‐ruthenium composite catalysts for hydrolysis of ammonia borane. The precursors were prepared with an anionic surfactant, sodium dodecyl sulfate (SDS), to form porous structure in the precursor particles, and the precursors was treated in aqueous solution including sodium borohydride and ammonia borane for in‐situ process to parallelly activate and use the catalysts for hydrolysis of ammonia borane. The result of TEM and nitrogen sorption measurements suggested that the primary particle size of the in‐situ synthesized catalysts decrease with increasing the amount of SDS and sodium chloride as the additive for controlling the primary particle size probably because of the effect of sodium ions to inhibit nuclei growth of the primary particles. From the EDS analyses, the composition of active nickel and ruthenium contents increased with increasing the amount of SDS and sodium chloride except for the highest amount of SDS probably because of adsorption of the metal cations with the excess amount of the surfactant anion to decrease the amount of the metal cations including the catalyst. The in‐situ synthesized catalyst including small size primary particles and high nickel and ruthenium content tended to exhibit high activity for hydrolysis of ammonia borane.

Atomistic evidence of nucleation mechanism for the direct graphite-to-diamond transformation

The direct graphite-to-diamond transformation mechanism has been a subject of intense study and remains debated concerning the initial stages of the conversion, the intermediate phases, and their transformation pathways. Here, we successfully recover samples at the early conversion stage by tuning high-pressure/high-temperature conditions and reveal direct evidence supporting the nucleation-growth mechanism. Atomistic observations show that intermediate orthorhombic graphite phase mediates the growth of diamond nuclei. Furthermore, we observe that quenchable orthorhombic and rhombohedra graphite are stabilized in buckled graphite at lower temperatures. These intermediate phases are further converted into hexagonal and cubic diamond at higher temperatures following energetically favorable pathways in the order: graphite → orthorhombic graphite → hexagonal diamond, graphite → orthorhombic graphite → cubic diamond, graphite → rhombohedra graphite → cubic diamond. These results significantly improve our understanding of the transformation mechanism, enabling the synthesis of different high-quality forms of diamond from graphite.

Microfluidics-based condensation bioaerosol sampler for multipoint airborne virus monitoring

To facilitate rapid monitoring of airborne viruses, they must be collected with high efficiency and concentrated in a small volume of a liquid sample. In addition, the development of low-cost miniaturized samplers is essential for multipoint monitoring. Thus, in an attempt to fulfill these requirements, this study developed a microfluidic condensation bioaerosol sampler (MCBS). The developed sampler comprised two parts: a virus growth section and a virus droplet-to-liquid sample conversion section, each of which was fabricated on a chip using microfluidic technology. The condensation nucleus growth technique used in the virus growth section grew nanometer-sized airborne viruses into micro-sized droplets, making it possible to collection of viruses easier and with high efficiency. In addition, the virus droplet-to-liquid sample conversion section controlled the transport of droplets based on electrowetting technology. This enabled the collected airborne viruses to be concentrated in tens of microliters of the liquid sample. To evaluate the performance of both the sections, the virus dropletization, virus collection efficiency, and virus droplet-to-liquid sample conversion efficiency were evaluated through quantitative experiments. H1N1 and HCOV-229E viruses were used to conduct quantitative experiments on MCBS. We could obtain virus liquid samples with at 72.8- and 89.9-times higher concentration through 1:1 evaluation with a commercial sampler. Thus, the developed sampler facilitated efficient collection and concentration of airborne viruses in a compact, cost-effective manner. This is expected to facilitate rapid and accurate multipoint monitoring of viral aerosols.

On-Surface Synthesis of 2D Polymers at the Liquid-Solid Interface

Unraveling the structure and dynamics of the formation of covalent and non-covalent organic-based 2D crystalline materials is key to controlling the quality of these materials, such as the defect density and their size. Understanding these characteristics is important for controlling their properties. This contribution highlights our efforts in using scanning probe microscopy, particularly scanning tunneling microscopy (STM), to visualize the structure and dynamics of substrate-supported metal-organic frameworks (sMOFs) and substrate-supported covalent organic frameworks (sCOFs) at the liquid-solid interface.We will focus on the growth of covalent organic frameworks, primarily based on boroxine chemistry, and reveal both qualitative and quantitative details of the nucleation-elongation processes in real-time and under ambient conditions. Sequential data analysis enables the observation of the amorphous-to-crystalline transition, the time-dependent evolution of nuclei, the existence of 'non-classical' crystallization pathways, and, importantly, the experimental determination of essential crystallization parameters with excellent accuracy, including critical nucleus size, nucleation rate, and growth rate. Other aspects that will be addressed include sCOFs and chirality, as well as the formation of multilayered sCOFs. Additionally, we demonstrate that in specific cases, the electric field between the STM tip and the substrate can induce, on demand, the polymerization or depolymerization process.

Temperature-Induced Nanoarchitectonics of Monolayer Self-Assembly of Heterocoronene-Based Discotic Liquid Crystals.

Enhancing molecular self-assembly at the monolayer level offers significant potential for various applications. For monolayers made of π-conjugated discotic liquid crystal (DLC) molecule nanowires, achieving precise separation and alignment of these nanowires has been a long-standing challenge. This research explores an approach using the manipulation of subphase temperature and surface pressure within a Langmuir trough to control molecular nanowire separation. We observe notable temperature-dependent behavior: as the temperature increases from 5 to 30 °C, the monolayer collapse pressure rises steadily. In contrast, temperatures from 35 to 50 °C exhibit an initial small plateau with a nonzero slope that becomes more distinct with rising temperature. Our study of Langmuir-Blodgett (LB) films provides crucial insights into the monolayer's structure. At lower temperatures, the LB films show coalesced molecular nanowires, whereas at higher temperatures, the DLC nanowires separate and form an interconnected network. Remarkably, upon compression, this network transforms into a compact, highly uniform monolayer. To explain these temperature-dependent behaviors, we examine the area relaxation curves, which indicate a two-step molecular loss mechanism involving desorption and monolayer collapse due to the nucleation and growth of critical nuclei. This extensive study offers valuable insights into the dynamic interaction of the temperature, surface pressure, and molecular assembly, enhancing our understanding of the fundamental processes in monolayer self-assembly.

Investigating the growth behavior of titanium dioxide film prepared with direct current pulsed–magnetron sputtering technology

The direct current pulsed magnetron sputtering technology is employed to deposit TiO2 film onto the glass and Si(100) substrates. After annealing treatment, TiO2 film displays anatase (001) preferential orientation. The growth behavior of deposited and annealed TiO2 films is investigated. The results show that in the original stage, TiO2 film growth behavior is in Volmer–Weber mode, which is dominated by the diffusion effect. Considering the rivalry between TiO2 crystal nuclei, both crystallographic orientation and diffusion effects jointly dominate the film growth behavior in the rest stage. More importantly, the annealing treatment resulted in the coalescence of TiO2 crystal nuclei, as well as the growth of TiO2 crystal nuclei. Most importantly, after coalescence and growth of TiO2 nuclei, the anatase [001] crystal orientation of TiO2 grains remains the same as the normal direction of TiO2 film. Finally, after annealing treatment, TiO2 films comprise anatase (001) preferential orientation.

Growth of ferroelectric domain nuclei: Insight from a sharp-interface model

We present an analytical framework to study the impact of electromechanical properties on the growth of a ferroelectric nucleus. Ferroelectric domain evolution is typically simulated by phase-field models, which have shown that nuclei evolve from needle-like structures into complex domain patterns. However, there has been limited in-depth analysis of the interplay between electrostatics, mechanics and piezoelectricity and their effect on nucleus growth because of the complexity involved in the phase-field description. In this study, we describe the ferroelectric domain wall as a sharp interface and solve for the fields inside an elliptic ferroelectric nucleus via Eshelby’s inclusion problem. We analytically determine the driving traction profile around the nucleus to gain insight into the movement of the domain wall with and without applied electromechanical loading. We analyze how the growth is affected by the permittivity, elasticity, and piezoelectricity as well as the nucleus’ eccentricity. We further demonstrate that applied loads do not significantly affect nucleus growth, which is primarily determined by the self-equilibrated mechanical and electric field, and that the anisotropy in material properties is essential in determining the growth of a ferroelectric nucleus.

Ultrafast recrystallization and grain refinement of 2A97 Al-Cu-Li alloy by electropulsing assisted annealing at lower temperature

In the current work, a pulsed current was applied on recrystallization annealing to promote the recrystallization of cold-rolled 2A97 Al-Cu-Li alloys. Besides, the effect of stored deformation energy on electropulsing assisted recrystallization was also investigated. The results indicated that, with the assistance of electropulsing, the complete recrystallization temperature of the 55 % cold-rolled alloys was decreased from 480 °C to 440 °C, and the holding time was significantly decreased from 30 min to 15 s. Moreover, the recrystallization promotion effect of electropulsing was enhanced with the increment of stored deformation energy. As the rolled reduction increased from 23 % to 55 %, the drop in complete recrystallization temperature induced by electropulsing rose from 20 °C to 40 °C. Additionally, the average grain size decreased from 46.8 μm to 22.6 μm, leading to an enhancement in the mechanical properties of the 2A97 alloy. The microstructure observation showed that the electropulsing assisted recrystallization was a process of nucleation and nuclei growth dominated by dislocation rearrangement, and the ultrafast recrystallization at lower temperature induced by electropulsing may be attributed to the reduction of the nucleation energy barrier and the promotion of dislocation rearrangement caused by the ‘local hot spot effect’ and ‘electromigration effect’.

Molecular insights into the impact of mineral pore size on methane hydrate formation

Natural gas hydrates are not only substantial energy sources but also have significant applications in the chemical industry and other fields. Although investigating hydrate formation in sediment minerals is crucial for their development and utilization, the underlying hydrate formation mechanism remains unclear. Here, molecular simulations were conducted in systems incorporating hydrophobic and hydrophilic pores of different sizes to investigate methane hydrate formation processes. The findings suggest that, as the hydrophobic slit size increases, there is a larger number of dissolved methane after the system reaches a metastable equilibrium state. The probability of cage formation indicates that hydrate cages readily form on hydrophobic surfaces or in the solution phase near the solution/gas interface. The larger slits are preferred for hydrate nucleation, regardless of whether the surface is hydrophobic, with most initial nuclei located near the liquid/methane interface. However, the interface perturbation can lead to the movement and growth of hydrate nuclei near the solution/methane interface into the bulk solution phase. Additionally, hydrate can nucleate and grow on the hydrophobic surface, facilitated by the adsorbed methane molecules and nonstandard cages. Pores hinder methane storage capacity in the hydrate phase due to the confinement effect and the amorphous nature of the hydrate formed. These molecular-level findings enhance our understanding of hydrate formation in sedimentary environments and porous materials, benefiting the development of natural gas hydrates and the use of porous materials for gas storage and transportation.

Thermal restoration kinetics and microstructural evolution of an Mg-RE alloy during annealing by quasi-in-situ observation

Quasi-in-situ electron backscatter diffraction method is applied to properly investigate thermal restoration kinetics and microstructural evolution of a commercial WE54 alloy after 10 % engineering pre-strain and post-annealing at 500 °C for 10, 35, and 70 min. Results show a reduction in the average grain orientation spread can effectively evaluate the restoration kinetics compared to other characteristics like average grain size or average misorientation angle. For microstructural evolution, nucleation behavior and abnormal grain growth of recrystallization nuclei as well as evolution of deformation twin have been investigated in detail. Low-angle grain boundary network due to the recovery effect provides recrystallization nuclei in the early stage of annealing, after which both continuous and discontinuous recrystallization nuclei are observed near deformation twin boundaries and original high-angle grain boundaries. Afterwards, grains with a tilting angle of 30° from the transverse direction grow abnormally, replacing the deformed grains, deformation twins, and part of some recrystallized grains. In addition, some twins can grow into the adjacent grains while de-twinning also occurs depending on twin orientations during thermal restoration.

Modeling of martensitic phase transformation accounting for inertia effects

As a diffusionless phase transformation, martensite evolves at the speed close to sound, with its kinetics and morphology dominated by the mechanical energy. However, the mechanism of martensitic phase transformation with the consideration of inertia is rarely investigated. This paper presents a multiphase-field model, where the transformation strain in martensite performs as the mechanical wave source, and in return the kinetic energy contributes to the driving force for phase transformation. As a result, the mechanical fields, i.e., the stress and the velocity, are derived according to the increment of the transformation strain. The propagation direction of the mechanical wave is corrected by considering the growth of the martensitic nucleus. With the 1D and 2D analysis, as well as the comparison against 2D static case, the mechanism of martensitic phase transformation is investigated, and the advantage of mechanical model accounting for inertia effects is illustrated.

Atomistic Insights into Nucleation of Ferroelastic Domains in PbTiO3.

Understanding the nucleation mechanism of domains is essential for domain engineering of perovskite ferroelectric materials. We proposed and examined atomistic details for nucleating ferroelastic (FS) domains by integrating topological analysis and first-principles calculations. FS domains are crystallographically treated as deformation twins. The conventional shear-shuffle nucleation mechanism under simple shear deformation is ruled out because the 1-layer elementary twinning disconnection (TD) cannot nucleate and glide in a perfect matrix. Thus, the pure-shuffle nucleation mechanism under pure shear deformation is proposed due to kinetically favored atomic shuffling. The coherency stress associated with the coherent nucleus is relaxed via forming misfit dislocations, accompanied by formation and sharpening of diffused (110)m∥(110)d domain walls (DWs). The sharp DWs enable growth of the FS nucleus through successive nucleation and gliding of TDs. These findings enrich the knowledge of domain behavior in perovskite ferroelectric materials.