Formation Mechanism Of Structures Research Articles

Colloidal Quasi-2D Methylammonium Lead Bromide Perovskite Nanostructures with Tunable Shape and High Chemical Stability.

Control over the lateral dimensions of colloidal nanostructures is a complex task which requires a deep understanding of the formation mechanism and reactivity in the corresponding systems. As a result, it provides a well-founded insight to the physical and chemical properties of these materials. In this work, the preparation of quasi-2D methylammonium lead bromide nanostripes and discuss the influence of some specific parameters on the morphology and stability of this material is demonstrated. The variation in the amount of the main ligand dodecylamine gives a large range of structures beginning with 3D brick-like particles at low concentrations, nanostripes at elevated and ultimately nanosheets at large concentrations. The amount of the co-ligand trioctylphosphine can alter the width of the nanostripe shape to a certain degree. The thickness can be adjusted by the amount of the second precursor methylammonium bromide. Additionally, insights are given for the suggested formation mechanism of these anisotropic structures as well as for stability against moisture at ambient conditions in comparison with differently synthesized nanosheet samples.

Formation trajectory of core-rim structures in BiFeO3-BaTiO3 ceramics

Microstructural characterizations and manipulations of BiFeO3-BaTiO3 (BF-BT) ceramics are attracting extensive attention, since they provide a fertile field for functionality explorations. However, for the widely existed core-rim structures with chemical inhomogeneity, the formation mechanism has not been fully understood yet. Here, we carefully tracked the formation trajectory of the core-rim structures in pseudo-cubic 0.64BiFeO3-0.36BaTiO3 ceramics prepared by solid-state reaction methods. In contrast to the popular belief, the core-rim structures characterized by BF-rich@BT-rich@average-composition triple microstructures universally appear in the ceramics with different cooling rates, suggesting that they do not form during the cooling process. Microscopic characterizations of the calcined powders demonstrate the inhomogeneous compositions and surface segregations. Subsequently, the surface BT-rich phases exhibit liquid-like behaviors promoting the diffusion of elements in the sintering process, which were blocked up during the further grain growth and left as the outer cores and nanoparticles at the triple junctions. Our results reveal the formation mechanism of the core-rim structures, and are expected to provide a necessary basis for the microstructure regulation of BiFeO3-BaTiO3 ceramics.

Quality characteristics and fibrous structure formation mechanism of walnut protein and wheat gluten meat analogues during high-moisture extrusion cooking process

Blending two or more materials to create better high-moisture meat analogues has been actively studied in the food science and technology field. Walnut protein is a high-quality plant-based protein resource, yet its full potential remains underexploited. Thus, this study focused on exploring the quality characteristics and fibrous structure formation mechanism of walnut protein (WP) and wheat gluten (WG) meat analogues during high-moisture extrusion cooking process. Results showed that the optimized WP and WG-blended high-moisture meat analogues exhibited a more pronounced anisotropic and oriented fibrous structure. The blending of WP and WG can protect the molecular chains from the thermal transition, and promote the aggregation of protein molecules mainly by enhancing the interaction between hydrophobic interactions and hydrogen bonds, increasing the apparent viscosity and forming protein subunits with larger molecular weights (>100 kDa) to stabilize the newly formed conformation. Additionally, the content of α-helix was the highest among the secondary structures. This study provides a theoretical basis for the application of WG and WP to produce HMMAs with rich fibrous structures.

Study on bulge structure formation mechanisms of laser remelting in air atmosphere

As a key feature of a part or assembly, surface structure can effectively improve the surface properties of the workpiece. Laser remelting is a promising method for surface structure formation, but sensitive to ambient gases. Therefore, this paper presents a numerical model that incorporates the contribution of air atmosphere on surface bulge structure formation. For this, the model couples a concentration field to reflect the oxygen mass transfer in the melt pool and introduces a semi-empirical function to describe the contribution of oxygen to the surface tension. Based on the model, it discusses the surface structure formation mechanisms, the heat-mass transfer characteristics, the melt flow patterns, and the surface force transient evolutions. The results reveal that the action of air atmosphere on melt flow manifests itself through two mechanisms, namely, the enhancement of inward thermocapillary forces and the introduction of outward solutocapillary forces. Furthermore, combined with the laser remelting experiments on 304 stainless steels, the established model is validated concerning the surface bulge structure size, the melt pool depth, and the oxygen distribution.

Tunable Social Hierarchies in Self-Organizing Model with Chemotactic Agents

In the Bonabeau model, chemotaxis, which is observed in social insects, such as ants, was introduced into the movement rules of agents to control the collision frequency between agents, and its effect on the mechanism of hierarchical structure formation was investigated. Like an ant, this chemotactic agent makes stochastic decisions regarding its direction of movement depending on the intensity of its released chemicals. Because of this mechanism, the agent depends on its past location history. It can perform different motions from a random walk (RW) and asymmetric attractive or repulsive interactions with other agents via the diffusion of chemotactic substances. When there is an attractive interaction between these agents, they are more likely to aggregate, which increases the effective density; thus, the disparity in the agent winning ratio is more likely to form than in a conventional model with a RW. However, in the case of repulsive interactions, the agents became more distant from each other, the effective density decreased, and a disparity in the winning ratio was less likely to form. This indicates that the disparity in the winning ratio is tunable owing to the interactions between the introduced chemotactic agents.

Chimie Douce Derived Novel P2‐Type Layered Oxide for Potassium‐Ion Batteries

AbstractThe emergence of K‐ion batteries (KIBs) heralds a promising frontier in energy storage technology, offering the potential for high specific energy density, long cycle life, and robust power capabilities, all while utilizing the abundant resources of potassium. In response to the challenges posed by synthetic intricacies related to K‐based cathodes, the effort is directed toward employing soft chemistry (chimie douce) method to unveil a hitherto‐unknown P2‐type K1/3Co1/3Mn2/3O2 (KCM) layered oxide cathode for KIBs. Comprehensive analysis using diffraction, microscopy, and spectroscopy tools reveals the ion exchange reaction proceeds through overlay ordered structure formation mechanism. The as‐prepared KCM material serves as a ≈2.9 V positive K+ insertion host. Further, it showcases an exceptional structural reversibility, robust cycling performance with ≈100% coulombic efficiency even after 100 cycles, and maintaining electrochemical stability even at elevated temperature (c.a. 40° and 50 °C). The KCM cathode exhibits in‐plane Co–Mn ordering and solid‐solution redox mechanism during (de)potassiation. Combining first‐principles calculations with experimental tools, this research demonstrates the efficacy of ambient ion‐exchange route in stabilizing promising cathode materials for KIBs. This innovative synthetic approach not only streamlines synthetic complexities, but also holds significant implications for the advancement of KIB technology for stationary energy storage.

Ultrafast dynamics and mechanism of structure formation in titanium nitride upon femtosecond laser irradiation for plasmonic enhanced photothermal effect

Femtosecond laser has great potential in controlling the surface structure of titanium nitride (TiN) to promote plasmonic photothermal effect. Studying the mechanism of femtosecond laser irradiation on the surface and inside of the TiN benefits the photothermal microdevices. Ultrafast dynamics of electrons and lattices of TiN films with different thicknesses were first studied through pump-probe technique, which found that the electron density is easier to reach the maximum on the surface than the electrons in deep-layers. High-frequency ripple was formed by tiny nucleation resulted from weak eruption of surface material on the thin TiN film, and low-frequency ripple was emerged through large nucleation of material clusters simultaneously on the thick TiN film. The blue shift and intensity changes of Raman peak on 200 nm TiN film indicate the heterogeneous structure changed from TiN to TiN0.26 after laser processing, and the vacancy occupies causes the lattice vibration weakened. The 200 nm TiN film after processing shows enhanced local surface plasma resonance absorption effect, which induced the reflectivity is reduced by 30 %, and the light and thermal conversion efficiency increased by 80 %. These results proved the promising utilization of TiN in biological and medical applications, energy collection and thermal auxiliary magnetic records.

Disulfide-Driven Charge and Hydrophobicity Rearrangement of Remodeled Membrane Proteins toward Amyloid-Type Aggregation.

As a common pathological hallmark, protein aggregation into amyloids is a highly complicated phenomenon, attracting extensive research interest for elucidating its structural details and formation mechanisms. Membrane deposition and disulfide-driven protein misfolding play critical roles in amyloid-type aggregation, yet the underlying molecular process remains unclear. Here, we employed sum frequency generation (SFG) vibrational spectroscopy to comprehensively investigate the remodeling process of lysozyme, as the model protein, into amyloid-type aggregates at the cell membrane interface. It was discovered that disulfide reduction concurrently induced the transition of membrane-bound lysozyme from predominantly α-helical to antiparallel β-sheet structures, under a mode switch of membrane interaction from electrostatic to hydrophobic, and subsequent oligomeric aggregation. These findings shed light on the systematic understanding of dynamic molecular mechanisms underlying membrane-interactive amyloid oligomer formation.

EMP3 inhibits the formation of heterotypic cell-in-cell structures in hepatocellular carcinoma

Heterotypic cell-in-cell (heCIC) structures represent a unique intercellular interaction where tumor cells internalize immune cells to enhance the killing efficiency of immune cells. However, the mechanism of heCIC structure formation remains to be fully elucidated. In this study, we explored the role of epithelial membrane protein 3 (EMP3), a PMP-22/EMP/MP20 protein family member highly expressed in the patients with hepatocellular carcinoma and poor prognosis, in the formation of the heCIC structure formed by natural killer cells and hepatocellular carcinoma cells. The analysis of monoclonal hepatocellular carcinoma cell lines revealed that EMP3 presented low expression in the cells with high capability to form heCIC structure and high expression in those with low capability. Knocking down the expression of EMP3 by gene editing promoted the formation of heCIC structures, while overexpression of EMP3 significantly inhibited this process. Additionally, the expression of factors involved in the heCIC structure formation suggested that EMP3 inhibited the formation of heCIC structures by modulating the adhesion ability and cytoskeleton of tumor cells. The findings lay a foundation for enhancing the heCIC-mediated tumor immunotherapy by targeting EMP3.

Lattice Distortion Induced Ta‐doped BaTiO3 for Efficient Photocatalytic Water Splitting for Hydrogen Production

AbstractBaTiO3, as a perovskite type material with excellent chemical stability and suitable conduction, has been widely studied in the field of photocatalysis. However, it can only absorb ultraviolet light because of its wide band gap. Herein, the lifetime of photogenerated electrons of BaTiO3 doped with Ta5+ can be enhanced. To study the band structure and photocatalytic performance of Ta‐doped BaTiO3, sol‐gel assisted solid‐phase method was employed to prepare BaTiO3 doped with varying Ta5+ doping amounts, and the structure characteristic and formation mechanism of the Ta‐doped BaTiO3 were analyzed. The results showed that the heat treatment temperature reached 1052.7 °C, sufficient thermodynamic conditions were obtained for Ta5+ to dope into the BaTiO3 lattice, and lattice distortion occurred in BaTiO3. Meanwhile, the particle size after doping decreased with the increase of Ta5+ doping amount. The 1.25 mol %Ta5+‐doped BaTiO3 had the lowest band gap (3.077 eV), and the photocatalytic water splitting had the best hydrogen evolution activity, which was 2.4 times that of BaTiO3. Furthermore, the conductance potential of 1.25 mol %Ta5+‐doped BaTiO3 was more negative than that of BaTiO3, which improved the thermodynamic advantage of the photocatalytic water splitting, and it had higher and more stable photoresponse and photogenerated carrier migration rate.

Hydrodynamic mechanism for dynamical structure formation of a system of rotating particles

Based on the hydrodynamic mechanism, which takes into account the interaction of all particles, a numerical simulation of the formation of a dynamical structure in a viscous fluid was carried out. This structure is a result of the collective dynamics of rotating particles in the fluid. It is supposed that the particles have a magnetic moment and are driven into rotation by an external variable uniform magnetic field. The results of numerical modeling of collective dynamics are presented for three initial structures that can be formed by interacting dipole particles in the absence of an external magnetic field. Such equilibrium structures are a straight chain, a closed chain, and a periodic structure in the form of a flat system of particle chains. The rotation of particles sets the surrounding fluid in motion, whose flow creates hydrodynamic forces and moments that move the particles. The collective dynamics of a system of rotating particles leads to the formation of a new dynamical structure from the original one, and this new structure has its own characteristic features for each case considered. A qualitative comparison of the results of the dynamics for a particles’ system set in motion due to the action of an external moment or an external force is carried out. The proposed hydrodynamic mechanism for the formation of a dynamical structure as a result of the collective dynamics of a rotating particles’ system can be used to control structure formation in a liquid-particle system.

Establishing patterns in the structure formation of polymer nanocomposites based on polyamide 6 during their crystallization processes

This paper reports experimental and computational studies on patterns in the structure formation of polymer nanocomposites when different types of fillers are used. The study was conducted for nanocomposites based on polyamide 6 filled with carbon nanotubes or silicon dioxide nanoparticles. In the course of research, the mass fraction of the filler varied from 0.2 % to 4.0 %, and the cooling rate of the melt composite varied from 0.5 K/min up to 20 K/min. Data on experimental and theoretical studies into the mechanisms of structure formation of composites according to the method, which includes two stages, are given. According to the first stage, crystallization exotherms of nanocomposites were experimentally obtained when they are cooled from the melt at a given constant rate. The dependence of various characteristics of the crystallization process on the mass fraction of the filler and the cooling rate of the composite was established. At the second stage, based on the analysis of the obtained crystallization exotherms, theoretical studies were performed to determine the mechanisms of structure formation of nanocomposites at different stages of crystallization. For the initial stage, according to the nucleation equation, the presence of two mechanisms of structure formation – planar and volumetric – has been shown. Within the framework of the Kolmogorov-Avrami equation, the mechanisms of structure formation at the next stage of crystallization were established, which corresponds to the formation of ordered structures in the material within the volume of the polymer composite as a whole. The research was carried out assuming the existence of a mechanism of crystallization of the polymer matrix itself, which is realized on fluctuations in the density of the polymer, and a mechanism of crystallization, the centers of which are filler particles. The use of the proposed nanocomposites is promising for the manufacture of parts of energy equipment, electronic equipment, elements of chemical, processing, defense industry installations, etc.

Experimental and numerical investigations on formation mechanisms of hollow structures in overflow water‐assisted injection‐molded parts of short‐glass‐fiber‐reinforced polypropylene

AbstractIn water‐assisted injection molding processes, it is crucial to understand the mechanisms governing the formation of hollow structures and identify the key factors influencing their morphology and dimensional accuracy. This work combined experimental analysis and numerical simulation to investigate the influence of different mold cavities and main processing parameters on hollow structures in overflow water‐assisted injection molded parts of short‐glass‐fiber‐reinforced polypropylene, that is, hollow shape and hollow ratio. The results show that the hollow shape and hollow ratio depended not only on the cross‐sectional location but also on the cross‐sectional shape of the mold cavity. For the circular parts, the hollow shape resembled the cross‐sectional shape of the mold cavity, with a relatively small and uniform hollow ratio across cross‐sectional locations. For the noncircular parts, the hollow shape varied considerably with increasing distance from the water inlet. Moreover, the results also show that except for the influence of water‐injection delay time on the uniformity of the hollow ratio, higher melt temperature (250°C), shorter water‐injection delay time (0 s), and higher water pressure (10 MPa) contributed to the hollow shape being closer to the cross‐sectional shape of mold cavities and made hollow ratios relatively larger and more uniform.

Superhydrophobic films with high average transmittance in infrared and visible range prepared by iCVD technology

Superhydrophobic high-transmittance antireflection coatings (ARCs) have significant potential for applications in optical devices such as microscope lenses, as well as in daily life for windows and glasses. However, current technologies encounter challenges in achieving superhydrophobicity on surfaces of ARCs. Here, we successfully combine the initiated chemical vapor deposition (iCVD) process technology with surface structuring to obtain a wide-spectrum transmission-enhanced coatings exhibiting self-cleaning and superhydrophobic properties. Compared with the bared substrate, the average transmittance of the worm-like/nanocones structure increases from 93.0 % to 95.1 %. Furthermore, an impressive water contact angle of 177.1° and a sliding angle of less than 1.0° are achieved. Moreover, the transmittance and hydrophobic properties can be easily adjusted by manipulating morphology of the film. The formation mechanism and fabrication processes of nanocones and worm-like structures are comprehensively investigated for flexible adjustment of the film properties. This provides a practical solution for the application of ARCs in various scenarios.

A Study on the Spatial Structures and Mechanisms of Intangible Cultural Heritage and Traditional Villages in the Dongting Lake Basin

This study focuses on 1209 national and provincial intangible cultural heritage items and 1234 traditional Chinese villages within the Dongting Lake Basin. Using kernel density analysis, centroid models, coupling models, and quantitative spatial–structural models, the present research analyzes the spatial–structural characteristics and formation mechanisms of intangible cultural heritage and traditional villages to provide scientific support for their preservation, inheritance, and effective utilization. The results revealed the following: (1) Intangible cultural heritage and traditional villages in the Dongting Lake Basin exhibit a very concentrated spatial distribution, with similar spatial–structural characteristics. (2) High spatial coupling of intangible cultural heritage and traditional villages is observable in the sub-basins of Dongting Lake, such as the Yuanjiang, Zishui, and Lishui basins, whereas the Xiangjiang Basin and Dongting Lake area present relatively lower levels of spatial coupling. In terms of the categories of intangible cultural heritage, four of them—cultural heritage, folk literature, traditional music, traditional dance, and traditional drama—have the smallest deviation distance and index values from traditional villages. The coupling degree was higher than 0.70, and there were some differences in the coupling degree between the other six categories of intangible cultural heritage and traditional villages. (3) The spatial–structural characteristics of intangible cultural heritage and traditional villages in the Dongting Lake Basin emerged from the combined effects of multiple factors, including internal connections between the two, as well as external factors such as the natural environment, socio-economic conditions, and cultural policies, all of which play crucial roles in the formation processes of these characteristics.

ВЛИЯНИЕ ПЛАСТИФИКАТОРА НА ПРОЦЕССЫ ПЕРЕКРИСТАЛЛИЗАЦИИ ПРИ ТВЕРДЕНИИ ДВЕНАДЦАТИКАЛЬЦИЕВОГО СЕМИАЛЮМИНАТА КАЛЬЦИЯ

The mechanism of structure formation during hydration of duodecalcium semialuminate in the presence of plasticizer is considered. The purpose of the study was to determine the influence of polycarboxylate-based plasticizer on the formation and morphology of the hydrate phases formed. The object of the study was the mineral duodecalcium semialuminate 12CaO-7Al2O3 of stable α-form, having cubic syngony and plasticizer on polycarboxylate basis. The structure of cement stone was studied using X-ray phase and electron microscopic analysis. The mechanism of structure formation during hydration of duodecalcium semialuminate 12CaO∙7Al2O3 in the presence of plasticizer is presented, which consists in the formation of finely dispersed poorly crystallized hexagonal crystals of calcium hydroaluminate. The presence of superplasticizer in the composition of hydrated calcium aluminate slows down the nucleation and growth of crystalline hydrates due to the film formed on the surface of the interface between liquid and solid phases, creating a structural and mechanical barrier, which leads to slower saturation of the liquid phase, but promotes the formation of a greater number of crystallization centers and simultaneous growth of small crystals of both hexagonal and cubic habitus.

СТРУКТУРА ПОР ЯЧЕИСТОГО БЕТОНА С ОТХОДАМИ СТЕКЛОБОЯ ЭЛЕКТРОННО-ЛУЧЕВЫХ ТРУБОК

To date, the issue of handling toxic unsorted waste of cathode ray tubes (CRT) glass cullet remains relevant. The present paper proposes to replace part of the fine aggregate of cellular concrete intended for sound, heat or radiation protection with CRT glass waste heat-treated in the presence of a sodium hydroxide solution. The purpose of the research is to study the structure formation of the cellular concrete pores in case of replacement of part of the aggregate. The microscopy of the samples fracture was studied both visually and using software that made it possible to estimate the pore size when convert-ing the image to the relief mode. The study showed that the aggregate replacement results not only in quantitative changes in pore size, but also in qualitative changes related to the mechanism of the pore structure formation. Thus, when adding unsorted waste heat-treated in an alkaline environment, with a particle diameter of no more than 630 μm, there was a decrease in pore size and a decrease in size distribution compared with the reference sample. The changes are caused by structure formation, which can be divided into two stages - the formation of conglomerates and their swelling. With a decrease in the diameter of the part of the waste of a maximum size of 90 μm, a decrease in the pore size was recorded compared to the reference value, but due to the concrete skeleton formation before the end of gas development, destruction of the pore walls was observed.

Studying the Process of Phosphogypsum Recycling into a Calcium Sulphide-Based Luminophor.

Currently, one of the most important problems of environmental protection is the deep and complex processing of mineral raw materials. This problem is especially relevant when processing substandard ores and production waste, one of which is phosphogypsum. This study examines the process of CaSO4/CaS composite material formation during the reduction of phosphogypsum with citric acid. The composite structure formation mechanism is proposed. The resulting materials are characterized using various methods, including X-ray diffraction (XRD), transmission electron microscopy, the Scherrer method, thermogravimetric analysis (TGA), and FT-IR spectroscopy. The reduced sample emits orange radiation in the range of 500-750 nm with a quantum yield of 0.17. Experimental results showed that the sample decomposition process in the solid state consisted of two components with a predominant contribution from the long-lived component (~46 ns). The optimal conditions for producing luminescent materials by reducing phosphogypsum with citric acid were determined: a heat treatment temperature of 1073 K, a holding time of 60 min, and a reducing agent mole fraction of 37%. It was found that an increase in temperature with a simultaneous decrease in heat treatment time, as well as a decrease in temperature with a simultaneous increase in heat treatment time, led to a decrease in the luminescent properties of the synthesized material compared to optimal values. The results can be used to develop technology for recycling large-tonnage waste from the chemical industry into luminescent materials.

Mechanism Studies in Electrochemical Depolymerization Processes of Alkali and Organosolv Lignin

AbstractTo better understand the process and mechanism of lignin structural changes and relative product formation during PbO2 anode electrolysis, a Ti/Sb−SnO2/PbO2 composite electrode has been prepared and utilized for the alkaline electrolytic oxidation of both alkali lignin (AL) and bagasse organosolv lignin (OL). By combining electrochemical measurements, in‐situ FTIR, 2D‐HSQC NMR, and product distribution analysis, we not only investigate the impact of influence factors on the process of lignin depolymerization, but also reveal the depolymerization mechanism from the whole process of lignin structural changes in details. Under certain electrolysis conditions, the highest vanillin yield, 10.1 mg g−1, has been obtained through the electrolysis of alkali lignin, whereas the highest syringaldehyde yield of 4.0 mg g−1 has been achieved during the electrolysis of organic solvent lignin. In particular, AL mainly performs depolymerization through the selective cleavage C−C bonds to produce a series of G unit monomer products of vanillin, acetovanillone, and vanillic acid. By contrast, the depolymerization of OL shows significant selectivity in H units. Particularly, the production of the major H unit monomer product of 4‐vinylphenol has been confirmed by IR spectroelectrochemical studies from the oxidation and decarboxylation of p‐coumaric acid unit.

Order–disorder–order mesophase transitions in self-assembled mesoporous alumina for enhanced CO2 adsorption

The addition of a hydrophobic micelle pore expander to self-assembling mesostructured hybrid materials enables access to new combinations with differently ordered mesophases and enhanced structural properties. Here we detail our investigations into the influence of 1,3,5-trimethylbenzene (TMB) on the self-assembly behaviors of an F127 Pluronic triblock copolymer with an aluminum oxide sol additive. By varying the chemical mixing sequence, the TMB-to-F127 mass ratio and the acid-to-metal molar ratio, we observe that TMB exhibits dual roles, functioning both as a hydrophobic swelling agent and as a low dielectric co-solvent. This induces a mesophase transition from an ordered p6mm lattice to a disordered state and subsequently back to the ordered p6mm phase. We propose a structure formation mechanism based on the DLVO theory to describe the thermodynamics and kinetic mobility of the hybrid micelles during the order-disorder and ensuing disorder-order mesophase transitions. The resulting ordered mesoporous alumina structures, with considerable pore sizes (up to 12 nm), high surface areas (up to 314 m2/g) and pore volumes (up to 0.74 cm3/g), organized pore geometry and variable inorganic wall thicknesses, have shown excellent CO2 adsorption capacities and are appealing for various applications, including stable high temperature catalyst supports, separation and sensing.