Agglomeration Mechanism Research Articles

A stochastic particle model for aggregate morphology and particle size distributions under coagulation process

A new simple and efficient particle model is proposed in the present study based on the ballistic cluster–cluster agglomeration (BCCA) mechanism. The proposed Random Orientation-Tangent Point (ROTP-BCCA) model is implemented into the Monte Carlo method to investigate the aggregate coagulation process under the free molecular regime. The proposed ROTP-BCCA model is firstly used to predict the fractal characteristics of aggregates composed of monodispersed primary particles and validated by the previously reported results and is compared with the method of Lindberg et al. (L-BCCA model). Then the effects of primary particle polydispersity on the fractal characteristics, the first three order moments and the particle size distributions (PSD) of the aggregates are also investigated. The results show that the obtained fractal characteristics, the first three order moments and the particle size distributions of the aggregates for monodispersed and polydispersed primary particles from the present ROTP-BCCA model agree well with the results of L-BCCA model. Furthermore, the computational efficiency of the present proposed ROTP-BCCA model is proved to be much higher than the L-BCCA model.

Research on the Mechanism of Population Agglomeration's Role in High-Quality Economic Development in Anhui Province

In the early stages of economic development, population agglomeration significantly promotes economic growth. However, with the disappearance of the demographic dividend, negative externalities begin to strengthen. Currently, the economic development in Anhui Province faces challenges, necessitating a shift in focus from pursuing speed to pursuing quality, particularly concerning sustainable development. This paper analyzes the role of population agglomeration in high-quality economic development from the perspective of the five development concepts, constructing a mechanism to understand this relationship. Targeted recommendations for formulating appropriate population control policies and deepening the upgrading of industrial structures are proposed to promote high-quality economic development.

Discovering the common latent structure of commercial districts focusing on the spatial co-occurrence relationship between stores

Store agglomeration in a commercial district is considered to follow synergistic and complementary relationships between stores. The micro-interactions, that is, co-occurrence relationships, between stores are thought to create commercial districts’ universality and characteristics. This study aims to empirically identify latent attributes that can explain the mechanism of store agglomeration from the co-occurrence relationships between stores in commercial districts, and to identify universal characteristics in store agglomeration. We represented store agglomeration as a store co-occurrence network with stores as nodes and co-occurrence relationships between stores as links in 10 major commercial districts in Japan. We estimated latent attributes of stores that generated the store co-occurrence network and empirically clarified the quantitative and qualitative nature of store agglomeration. The co-occurrence networks of stores with estimated latent attributes were compared across those of districts, and the co-occurrence patterns common to latent attributes were clarified. The estimated latent attributes were empirically shown to have more explanatory power for the store agglomeration than the conventional business category classification, suggesting their usefulness as a new classification axis for stores. In addition, by comparing 10 districts, common co-occurrence relationships were extracted, and the universal spatial structure of store agglomeration was empirically clarified.

Industrial Agglomeration, Land Consolidation, and Agricultural Energy Inefficiency in China: An Analysis Using By-Production Technology and Simultaneous Equations Model

Improving agricultural energy inefficiency is essential for achieving sustainable agricultural development and promoting major agricultural countries to achieve carbon peak and carbon neutrality goals. This paper analyzes agricultural energy inefficiency in China, using panel data from 30 provinces between 2000 and 2021. The by-production technology model is employed to measure and decompose inefficiency, and the simultaneous equations model and moderating effect model are utilized to study the impact mechanism of industrial agglomeration, land consolidation, and agricultural energy inefficiency. The findings reveal several key points: First, the average inefficiency of agricultural energy in China increased from 0.370 to 0.514, with economic inefficiency rising at a faster rate than environmental inefficiency. Second, agricultural industrial agglomeration serves to inhibit both agricultural energy economic inefficiency and environmental inefficiency, which, in turn, hampers the development of industrial agglomeration. This relationship shows heterogeneity across the eastern, central, and western regions, as well as between major and non-major grain production areas. Third, land consolidation—both nationally and specifically in the central, major grain-producing, and non-major grain-producing areas—effectively mitigates the deterioration of agricultural energy inefficiency caused by industrial agglomeration. In the eastern region, land consolidation can enhance the inhibitory effect of industrial agglomeration on energy inefficiency. This paper highlights the interconnections between industrial agglomeration, land consolidation, and agricultural energy inefficiency, providing valuable policy references for the development of sustainable agriculture and the proactive and steady advancement of carbon peak and carbon neutrality goals.

Revealing the Mechanism of Ultrasound-Assisted Spherical Agglomeration for Achieving Millimeter-Sized Agglomerates of 3-Nitro-1,2,4-triazol-5-one with High Sphericity and Tunable Sizes

Revealing the Mechanism of Ultrasound-Assisted Spherical Agglomeration for Achieving Millimeter-Sized Agglomerates of 3-Nitro-1,2,4-triazol-5-one with High Sphericity and Tunable Sizes

Application of precursor with ultra-small particle size and uniform particle distribution for ultra-high nickel single-crystal cathode materials by coprecipitation method

Ultra-high nickel single-crystal cathode materials have become the most promising for lithium-ion batteries. However, the preparation of ultra-high nickel single-crystal precursors by a continuous coprecipitation method has the disadvantages of large particle size, wide distribution, poor morphology. The extent of the inhomogeneous reactions can be more severe in single-crystal cathodes with larger particle size. Herein, the coprecipitation method with a solid concentrator was adopted, and citrate sodium was used as a complexing agent to improve the physical properties of precursors and electrochemical performance of single-crystal cathode materials. By analyzing the morphology and agglomeration mechanism of the precursor nucleuses under different pH values, it was found that hexagonal nanosheets grew along the 101 direction, and the primary particles showed thicker at pH of 11.4. The hexagonal nanosheets grew along the 001 direction, and the primary particles showed finer at pH of 12.2. The morphology and particle size uniformity of the secondary particles formed by agglomeration at these two pH values showed poor. However, hexagonal nanosheets grew synergistically along the 001 and 101 directions at pH of 11.8, so the primary particles with uniform particle size gradually agglomerated, and then the secondary particles with ultra-small particle size and uniform distribution obtained. Compared to materials prepared by the traditional continuous coprecipitation method, the precursor displays a smaller particle size(D50 = 1.8 µm), higher sphericity, uniformity and denser internal structure. In order to evaluate the performance of Ni0.94Co0.04Mn0.02(OH)2 with ultra-small particle size, the sintering conditions of LiNi0.94Co0.04Mn0.02O2 need to be explored. It was found that the LiNi0.94Co0.04Mn0.02O2 cathode material prepared at 790 °C exhibited higher discharge capacity, cycle and rate performance, compared to materials prepared at 760 °C and 820 °C. We further utilized TEM, EPMA, and XPS to test the internal structure and valence state of LiNi0.94Co0.04Mn0.02O2 cathode material. The results show that the LiNi0.94Co0.04Mn0.02O2 calcined at 790 °C has a good single crystal structure. The LiNi0.94Co0.04Mn0.02O2 cathode materials inherited the structure and particle size of Ni0.94Co0.04Mn0.02(OH)2 precursors, and displayed discharge capacity of 194.7 mAh/g and capacity retention rate of 89.8 % after 100 cycles at 1 C. The microstructure and phase transition of the as-prepared cathode material are well-maintained after long-term cycling, without obvious inter-crystalline micro-crack. The results indicate that its electrochemical performance is better than that of cathode materials with precursors prepared by a continuous coprecipitation method. This work provides new insights for the preparation of small-particle-size precursor and single-crystal cathode materials.

The mechanism of urban agglomeration causing the enhancement of regional extreme heat and drought events

Urban agglomerations formed by rapid urbanization have been found to be important ways through which human activities influence regional weather and climate. However, the role of urban agglomerations in the formation of extreme heat and drought events remains unclear. We perform numerical simulations using RegCM 5.0 on an August 2022 extreme heat event in the Yangtze River Basin in China. The results show that urban agglomerations lead to significantly increased temperature in both urban (0.6 °C increase) and non-urban (0.2 °C increase) areas. The land feedback formed by urban agglomerations significantly increases the surface sensible heat, turbulence activity, urban upward movement, and urban heat island effect. As a result, the sinking airflow is enhanced, the surface wind is increased, and a dome-shaped wind field anomaly is formed around the urban agglomerations. This widens the geographic scope of the heat event and heightens its intensity.

A modified drag model for the fluidization of nano-modulated Group C particles

Geldart Group C powders are inherently cohesive due to the strong interparticle forces, leading to severe agglomeration and poor fluidization capability. In this study, fluidization of nano-modulated Group C particles was investigated numerically. These particles, also known as Group C+ particles, were obtained through the nanoparticle modulation technique, with which a small fraction of nanoparticles were vigorously mixed with Group C particles so that they are adhered to the surface of the much larger Group C particles. After modification, the cohesiveness of Group C+ particle was significantly weakened, and therefore these particles could exhibit much better fluidization quality. However, the still existing cohesion resulted in the formation of small agglomerates within the system. To understand the internal agglomeration mechanisms of Group C+ particles and their impact on fluidization behaviors, a new drag model was proposed based on experimental results and the postulation of particle agglomeration. The numerical results of the cases employing the new drag model agreed well with the experimental data in terms of total and dense phase expansion. These findings revealed the drag mechanism associated with modified Group C particles, contributing to the understanding of ultrafine particle fluidization.

Mixed superoleophilic/superoleophobic hard granular media for coalescence of oil-in-water-emulsion

To enhance the coalescence separation efficiency of oil/water emulsions, the coalescence mechanism of oil droplets between two media of opposite wettability was investigated. A coalescent-bed comprising a mix of superhydrophobic and superoleophilic quartz sand, along with superhydrophilic and underwater superoleophobic quartz sand, was constructed in a coalescer. Single-factor and response surface experiments were used to study the effects of oleophilic/oleophobic sand mixing ratio, apparent velocity, initial oil concentration, bed thickness, sand particle size on coalescence-separation performance, and to determine the optimal experimental conditions. Employing the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, the agglomeration mechanism of oil droplets within the mixed particle bed was analyzed based on interfacial energy dynamics. Results indicate that the mixing ratio of the two sands significantly influences coalescence separation performance. An optimal oleophilic/oleophobic sand mixing ratio of 1:1 yielded a mass factor of 0.69 kPa−1, showcasing superior coalescence separation efficiency and an optimal balance of separation efficiency and pressure drop. Under the optimal conditions of apparent velocity of 2.7 m/h, initial oil concentration of 471.9 mg/L, bed thickness of 12.6 cm and mixed sand particle size of 0.5 mm, the oil/water separation efficiency reached 98.08 % ± 0.87 %, with effluent oil droplet size being 2.5 to 3 times larger than at the inlet. Analysis of the oil droplet coalescence mechanism revealed a synergistic effect between the two quartz sands, enhancing oil removal performance. The strong affinity of oil to the superhydrophobic and superoleophilic sand surface increases oil droplet wetting and coalescence efficiency, while the water attraction on the superhydrophilic and underwater superoleophobic sand surface forms a stable water film, improving the flux of the continuous water phase and reducing pressure drop across the bed. This study demonstrates that combining quartz sands of opposite wettability not only overcomes the limitations of single-wettability surfaces in coalescing oil removal but also achieves high efficiency and low energy consumption in oil removal.

RAP chunks produced in cold milling operation of asphalt pavement: Evaluation, mechanism, and engineering investigation in China

Cold milling is a widely used method for rehabilitating asphalt pavement, generating reclaimed asphalt pavement (RAP) chunks. Within this process, aggregates within the asphalt pavement will be crushed, forming RAP agglomerates and aggregate breakdown. However, the mechanism of these phenomena has remained unclear, and a unified evaluation method has yet to be established. In this study, RAP agglomeration and aggregate fragmentation were characterized, five distinct methods were systematically assessed, and the mechanism of RAP agglomeration and breakdown was analyzed by discrete element method (DEM) simulation based on setting different particle contact parameters, then followed by a mechanical analysis, and demonstrated in engineering. The results revealed that both agglomeration and aggregate breakdown occur within RAP particles of various sizes, with the five methods showing similar trends in quantifying these effects. Through DEM simulations and mechanical analyses, the aggregate breakdown predominantly occurs at the cutter's motion trajectory of the cutter and during crack propagation, while agglomeration was mainly related to the sliding surface's area. The milling speed and depth positively impact RAP agglomeration, while negatively affecting aggregate breakdown, and milling drum speed exerts minimal influence on these phenomena. RAP agglomeration varies considerably in different engineering projects, and cold milling parameters should be determined based on the material composition of the asphalt pavement and design requirements to control agglomeration and breakdown rates of RAP.

Influence of the annealing schemes on the formation and stability of Ni(Pt)Si thin films: Partial, laser, total, and one-step annealings

In this study, the impact of various annealing schemes on the formation and agglomeration mechanisms of ultrathin Ni(Pt)Si films is investigated. To this end, 11 ± 1 nm-thick Ni(Pt)Si films are grown on 300 mm Si(100) wafers using various traditional rapid thermal annealing procedures as well as laser annealing. The obtained silicide films are then subjected to additional annealing between 500 and 800 °C, to evaluate their stability at high temperature. The correlation between the as-grown Ni(Pt)Si film properties and their capability to withstand agglomeration is analyzed via a complementary approach of several techniques (Rs, ellipsometry, TEM-EDX, SEM, and EBSD). Texture comparison for ultrathin films give deeper insights into the role of the NiSi-(010) and NiSi-(013) orientations in the agglomeration phenomenon. Depending on the annealing schemes used during the silicide formation, there is a strong correlation between the initial microstructure of Ni(Pt)Si films and their subsequent degradation. Indeed, cross-analysis of these different key parameters indicates that the presence of small Ni(Pt)Si grains (40 nm) obtained after laser annealing, and a high ratio of Ni(Pt)Si grains oriented along the (013) direction appears to be more efficient in delaying the agglomeration to higher temperatures.

The spatial spillover impact and transmission mechanisms of logistics agglomeration on eco-efficiency: A case study in China

This study employs spatial durbin model (SDM) and spatial mediation model to empirically investigate the relationship between logistics agglomeration (LA) and logistics eco-efficiency (LEE), as well as the transmission mechanism role of technological innovation (TI) and advanced industrial structure (AIS), using panel data on inter-provincial logistics in China from 2008 to 2020. The findings indicate a U-shaped relationship between LA and LEE. The early development of LA in China was accompanied by environmental sacrifices. Further analysis of the curves reveals that LA has spatial spillover effect on LEE. That is, insufficient concentration of LA has a siphon effect on the LEE of surrounding areas, whereas appropriate concentration of LA has a radiation effect on the LEE of surrounding areas. Spatial mediation analysis indicates that enhancing TI and developing AIS are essential channels through which LA bolsters LEE. Additionally, this study innovatively incorporates topography ruggedness and altitude as instrumental variables to account for potential endogeneity issues in the empirical model. Theoretical and practical significance is attributed to this research for China's logistics industry, particularly shedding light on the optimization of efficiency and long-term improvement of LEE through spatial reform via agglomeration zones.

Prevention of Crystal Agglomeration: Mechanisms, Factors, and Impact of Additives

Crystal agglomeration is a common phenomenon for most chemicals and pharmaceuticals. The formation of agglomerates usually lowers product purity and generates a broad particle size distribution. This review focuses on preventing agglomeration in solution crystallization, the storage of crystals, and pharmaceutical preparation processes. The agglomeration mechanisms in these stages are analyzed and the effects of operating parameters are summarized. Furthermore, effective control means related to the crystallization environment are elaborated, including solvents, ultrasound, and additives. Special attention is paid to the influence of additives in preventing the aggregation of both suspensions and dried powders. Besides additives used in solution crystallization, the roles of anti-caking agents, stabilizers of nanosuspensions, and excipients of solid dispersions are also discussed. The additive type and properties like hydrophilicity, hydrophobicity, ionic strength, viscosity, the steric hindrance effect, and intermolecular interactions between additives and crystals can greatly affect the degree of agglomeration.

Wide and ultrawide-bandgap semiconductor surfaces: A full multiscale model

Germanium, gallium, nitrogen, and oxygen deposition on both GaN(0001) and GaN(0001̄) surfaces were investigated. A multiscale simulation framework was implemented. The DFT simulations were employed to reveal the interactions among the species and GaN surface. Energy diffusion barriers were obtained by the Nudged Elastic Band approach. A Poisson–Nernst–Planck model was implemented to calculate the concentration of each atomic species near GaN surface. The kinetic and unimolecular collision gas theories were incorporated to determine adsorption rates. These outcomes were integrated into a nanoscale kinetic Monte Carlo model. This model allowed to generate data on the surface diffusion and clustering of adsorbed atoms on GaN surfaces. As a result, an enhanced understanding of the deposition and agglomeration mechanisms was achieved. In particular, of the roles played by germanium and oxygen. Due to the relatively high diffusion energy barriers, germanium atoms act as pins around to which gallium atoms tend to cluster. The results align with both experimental observations and existing simulation literature. To the best of our knowledge, no previous DFT simulation results on germanium deposition on GaN have been reported.

Wetting and aggregation mechanisms of coal molecules via XTG and SDBS based on molecular simulation

To study the interaction process of sodium dodecyl benzene sulfonate (SDBS) and xanthan gum (XTG) molecules in a composite dust suppressant and its influence mechanisms on the wettability and agglomeration characteristics of bituminous coal dust, Material Studio software was used to establish water–XTG binary system models, water–SDBS–XTG ternary system models, and water–SDBS–XTG–coal quaternary system models. Then, molecular dynamics simulations were performed through angular distribution, relative concentration distribution, mean squared displacement (MSD), and interaction energy to study the interaction mechanism between SDBS and XTG and the change in wettability of coal dust. Results showed that the configuration in the binary system changed after stabilization, and SDBS transformed from a disordered state into a directional arrangement with the head group oriented toward the liquid phase and the tail group oriented toward the gas phase. In the ternary system, the head group of SDBS interacted with the XTG molecules, and the XTG wound into a helical structure, reducing the viscosity of the solution. With an increase in the number of SDBS molecules, the angle of the head group of SDBS and the tail chain of SDBS increased to 113.95°. The number of H bonds in the system increased from 1676 to 1697. In the quaternary system, the rate of change of the diffusion coefficient continuously increases. The absolute value of the interaction energy increased from 5920.48 kJ/mol to 9295.35 kJ/mol. The higher the concentration of SDBS, the better the adsorption effect, and the more stable the molecular configuration. The number of H bonds and the distribution area of the overlapping region between water and coal gradually increased, indicating that the larger the area where water molecules could penetrate into the coal molecules, the better the wetting effect on coal. This study reveals the intermolecular interaction process and the mechanisms of coal dust wetting and agglomeration in a composite dust suppressant. It provides theoretical support for the application of this composite dust suppressant.

City civilization, employment creation and talent agglomeration: Empirical evidence from “National Civilized City” policy in China

China's rapid urbanization has intensified urban employment pressure. The National Civilized City (NCC) policy is a significant initiative in China aimed at promoting high-quality urban development. We utilize the NCC policy as a quasi-natural experiment and employ the staggered difference-in-difference method to empirically analyze the impact of urban civilization development on full employment and human capital level. The empirical results demonstrate that NCC policy significantly promotes urban entrepreneurship and employment creation, boosts labor demand of local enterprises, and enhances the human capital level. The positive effect on employment is significant in both talent-intensive and low- and medium-skilled intensive fields. In addition, heterogeneity tests show that this positive effect is more pronounced in low-tier cities and previously polluted cities. Finally, the mechanism analysis indicates that the NCC policy can enhance employment creation through investment promotion at the city level and by expanding production scale at the firm level. The NCC policy's impact on human capital level is supported by technological advancement and innovation emphasis mechanisms from the demand side, as well as talent agglomeration mechanism from the supply side. This study provides policy recommendations for local governments to leverage the achievements of civilized cities in promoting employment.

Synergistic industrial agglomeration, new quality productive forces and high-quality development of the manufacturing industry

This study analysed the impact of the mechanism of the synergistic agglomeration of manufacturing and modern service industries on the high-quality development of the manufacturing industry using the entropy value method, coupling coordination degree, and E-G index. We utilised panel data of 30 provinces and cities in China from 2012 to 2022. The study found that synergistic agglomeration significantly promotes the high-quality development of the manufacturing industry, in which ‘new quality productive forces’ play a key intermediary effect, while the innovation ecosystem has direct and indirect moderating effects on the relationship between the two. Simultaneously, industrial synergistic agglomeration, development of new productivity, construction of innovation ecosystems, and high-quality development of the manufacturing industry in all provinces and cities showed a steady increase; however, there were significant differences between regions. Based on the findings of the study, policy recommendations are suggested to further promote the synergistic development of the manufacturing industry and modern service industry. At the policy level, the government should strengthen the guidance and support of industrial synergistic agglomeration and formulate differentiated policies to promote industrial synergistic agglomeration; simultaneously, it should pay attention to the cultivation of new productivity and the construction of innovation ecosystems, optimise the allocation of innovation resources, and stimulate the vitality of innovation. At the industrial level, manufacturing enterprises should actively cooperate with modern service enterprises to achieve resource sharing and technological complementation; modern service industries should improve service quality and efficiency to meet the needs of manufacturing transformation and upgrading; and close cooperation between the industry, academia, and research institutes should be established to promote technological innovation and industrial upgradation.

Aluminum particle agglomeration mechanism and microscopic combustion characteristics of NEPE propellants

Aluminum particle agglomeration mechanism and microscopic combustion characteristics of NEPE propellants

Fracture toughness of graphene/polymer nanocomposites: Well dispersion, agglomeration and toughening mechanisms

The fracture toughness of nanocomposites may be improved by addition of low content of graphene nanofillers. The improvement is directly related to density of isolated graphene nanofillers dispersed in the nanocomposites. In contrast, for higher content of graphene nanofillers, the fracture toughness improvement may be degraded due to agglomerations. Thus, the main aim of this research is to account for the influence of the agglomeration of graphene nanofillers on the fracture toughness of nanocomposites. In the first step, based on J-integral concept, some relations were presented to estimate the fracture toughness improvement due to toughening mechanisms of nanocomposites reinforced by fully isolated and aligned nanofillers. Subsequently, the influence of agglomerations on the fracture toughness of nanocomposites was considered as a semi-empirical factor. Besides, a modified factor was used to account for the random orientation of the nanofillers. To consider the role of crack pinning toughening mechanism caused by agglomerated nanofillers in the fracture toughness of nanocomposites, another relation was presented. At the end, the experimental data available in literature was applied to validate the proposed comprehensive model. It was observed that the results obtained by the model are in very good agreement with the experimental results.

Bioflocculant Producing Bacillus megaterium from Poultry Slaughterhouse Wastewater: Elucidation of Flocculation Efficacy and Mechanism

The study focused on isolating bioflocculant-producing microorganisms from poultry slaughterhouse wastewater (PSW). Microorganisms (n = 20) were isolated, and the D2 isolate, identified as Bacillus megaterium using 16S rDNA and RpoD (sigma 70), had maximum flocculation activity. Furthermore, characteristics of the bioflocculant produced by B. megaterium were determined, and the optimum storage conditions, including the flocculation mechanism, were identified. The bioflocculant was composed mainly of polysaccharides and proteins and was better stored frozen in a crude form. Furthermore, the flocculation efficacy was assessed using response surface methodology at pH 4 (min) and 9 (max), bioflocculant dosage of 1% (min) and 3% (max, v/v), indicating pH 6.5 and dosage of 2% (v/v) as optimum flocculation conditions for floc formation under ambient temperature. These results were further confirmed with microscopy assessments with zeta potential measurements confirming that the bioflocculant was ionic, albeit charge neutralization was not the primary mechanism for floc agglomeration. Hydrogen bonding was predominant, indicative of a neutralization-bridging mechanism, an assertion also based on the functional groups prevalent in the isolate-B. megaterium. The results obtained indicate that bioflocculants can be used to treat isolates that are sourced from wastewater.