Excessive Agglomeration Research Articles

Evaluation of calcium looping CO2 capture and thermochemical energy storage performances of different stabilizers promoted CaO-based composites derived from solid wastes

Calcium looping is considered as an important high-temperature cyclic CO2 capture and concentrated solar energy storage technology. However, the dramatic inactivation of CaO over multiple carbonation-calcination cycles has seriously restricted their practical applications. In this study, a series of metal oxide (i.e. TiO2, MgO, Al2O3 and ZrO2)-stabilized CaO-based materials with high cyclic stability derived from carbide slag were synthesized via a facile and cost-effective approach for simultaneously enhanced CO2 capture and thermochemical energy storage (TCES). The results suggest that CCS-H-TiO2 exhibits high initial CO2 uptake of 0.41 gCO2/gsorbent, superior cyclic stability with an average attenuation of 1.71 %/cycle and remarkably stable energy storage density. CCS-H-Al2O3 shows the best stability with lowest attenuation rate of 9.6 %. Except for CCS-H-MgO, the stabilizers reacted with active calcium to form new phases and used as physical “barrier” and high-TT skeleton to offset the sintering stress, retain the microporous structures, hinder the excessive agglomeration and alleviate sintering.

How Does the Spatial Structure of Innovation Agglomeration Affect Energy Efficiency? From the Role of Industrial Structure Upgrading

This paper employs the instrumental variable method and the intermediary model to explore the influence of monocentric and polycentric spatial structures of innovation agglomeration on energy efficiency. This paper uses data from 2010 to 2021 in China, and also panel data regression models were used. The findings indicate that the monocentric spatial structure of provincial system innovation agglomeration is primarily concentrated in northeastern and western regions of China, whereas the polycentric spatial structure is mainly distributed in eastern coastal areas. A monocentric spatial structure inhibits the enhancement of energy efficiency, but there is an environmental paradox of excessive resource agglomeration. In contrast, a polycentric spatial structure and its strengthening tendency facilitate the improvement of energy efficiency. A monocentric spatial structure has an inhibitory impact on the improvement of energy efficiency in the three sectors of agriculture, industry, and construction, while a polycentric spatial structure aids it. A monocentric spatial structure further hinders the improvement of energy efficiency by impeding the upgrading of the industrial structure, while the upgrading of the industrial structure driven by the polycentric spatial structure plays a role in enhancing energy efficiency. The policy recommendations of this paper are intended to help coordinate the pace of innovation development between cities, adjust the spatial structure of innovation agglomeration between regions, and promote the upgrading of the comprehensive industrial structure, thereby improving overall energy efficiency.

Investigating spatiotemporal patterns and determinants of land resource misallocation in prefecture‐level China

AbstractThe misallocation of land resources is an important factor restricting the high‐quality development of China's economy. Based on the perspective of supply and demand matching, this study proposed a measurement method for the spatial misallocation of land resources and constructed two models for the testing and decomposition of factors affecting land resource spatial misallocation. We used this measurement method and these two models to explore the spatiotemporal characteristics and determinants of the spatial misallocation of land resources in China from 2000 to 2018 with the aim of providing policy recommendations for the correction of land resource misallocation in China and other developing countries. The results showed that the spatial misallocation of land resources in China showed an upward trend with evident spatial differentiation and the proportion of cities with high and severe misallocation increased. Industrial isomorphism and market misallocation are the main driving factors of land misallocation. Government misallocation and factor market abnormal development aggravate land resource misallocation. Extensive economic development and excessive factor agglomeration have a small effect on land resource spatial misallocation. Therefore, strengthening the land supply‐side reform, and implementing differentiated land allocation policies are effective pathways to control land resource misallocation in China.

Nanoflower-like NiCo2O4 Composite Graphene Oxide as a Bifunctional Catalyst for Zinc-Air Battery Cathode.

Developing efficient bifunctional catalysts for nonprecious metal-based oxygen reduction (ORR) and oxygen evolution (OER) is crucial to enhance the practical application of zinc-air batteries. The study harnessed electrostatic forces to anchor the nanoflower-like NiCo2O4 onto graphene oxide, mitigating the poor inherent conductivity in NiCo2O4 as a transition metal oxide and preventing excessive agglomeration of the nanoflower-like structures during catalysis. Consequently, the resulting composite, NiCo2O4-GO/C, exhibited notably superior ORR and OER catalytic performance compared to pure nanoflower-like NiCo2O4. Notably, it excelled in OER catalytic activity of the OER relative to the precious metal RuO2. As a bifunctional catalyst for ORR and OER, NiCo2O4-GO/C displayed a potential difference of 0.88 V between the ORR half-wave potential and the OER potential at 10 mA·cm-2, significantly lower than the 1.08 V observed for pure flower-like NiCo2O4 and comparable to the 0.88 V exhibited by precious metal catalysts Pt/C + RuO2. The NiCo2O4-GO/C-based zinc-air battery demonstrated a discharge capacity of 817.3 mA h·g-1, surpassing that of precious metal-based zinc-air batteries. Moreover, charge-discharge cycling tests indicated the superior stability of the NiCo2O4-GO/C-based zinc-air battery compared to its precious metal-based counterparts.

Synthesis of boronized Ti6Al4V/FHA composites by microwave sintering for dental applications

Boronized Ti6Al4V/FHA composites were prepared by microwave sintering of mixed powders of Ti6Al4V, TiB2, and synthesized fluorine-substituted hydroxyapatite (FHA) with variable compositions at 1050 °C for 30 min. The unique “lens effect” of microwave facilitated the in-situ transformation of nanoscale TiB2 into TiB, serving as the reinforcing phase within the composites. Increasing the theoretical fluorine substitution percentage of FHA from 0% to 50% caused less thermal decomposition of hydroxyapatite during sintering, promoting densification and thereby mechanical properties of the composites. However, elevating the substitution percentage to 100% led to excessive grain growth and FHA agglomeration, deteriorating the composite mechanical performance. The boronized Ti6Al4V/FHA composite produced using FHA with the theoretical fluorine substitution of 50% exhibited the highest compressive strength (397.7 MPa), proper compressive modulus (10.65 GPa) and maximum microhardness (385.3 HV). Furthermore, it showed excellent hydrophilicity and good cell adhesion, confirming its superior bioactivity for dental applications.

Effect of oxygen vacancy of lignite-char-supported Co catalysts doped with In on efficient dry reforming of methane

In this study, a series of catalysts rich in oxygen vacancies were prepared through the introduction of indium (In) for application in the dry reforming of methane. Among these catalysts, one doped with 2 wt% In, named as Co-2In/C, showcases a higher surface area (417 m2/g) and smaller particle size (4.21 nm). The stability assessment for Co-2In/C catalysts conducted under conditions of 800 °C, 0.5 MPa and a flow rate of 30,000 mL·h−1·g-1cat over 100 h resulted in CH4 and CO2 conversions of 73 % and 83 %, respectively, and a ratio of H2/CO is 0.65 without evident deactivation. The generation of more oxygen vacancies balances the redox capability of the catalyst and prevents excessive metal agglomeration. Moreover, an increase in oxygen vacancy concentration accelerates carbon elimination and extends the catalyst life.

Synergistic Charge Storage Enhancement in Supercapacitors via Ti3C2Tx MXene and CoMoO4 Nanoparticles.

MXene has emerged as a highly promising two-dimensional (2D) layered material with inherent advantages as an electrode material, such as a high electrical conductivity and spacious layer distances conducive to efficient ion transport. Despite these merits, the practical implementation faces challenges due to MXene's low theoretical capacitance and issues related to restacking. In order to overcome these limitations, we undertook a strategic approach by integrating Ti3C2Tx MXene with cobalt molybdate (CoMoO4) nanoparticles. The CoMoO4 nanoparticles bring to the table rich redox activity, high theoretical capacitance, and exceptional catalytic properties. Employing a facile hydrothermal method, we synthesized CoMoO4/Ti3C2Tx heterostructures, leveraging urea as a size-controlling agent for the CoMoO4 precursors. This innovative heterostructure design utilizes Ti3C2Tx MXene as a spacer, effectively mitigating excessive agglomeration, while CoMoO4 contributes its enhanced redox reaction capabilities. The resulting CoMoO4/Ti3C2Tx MXene hybrid material exhibited 698 F g-1 at a scan rate of 5 mV s-1, surpassing that of the individual pristine Ti3C2Tx MXene (1.7 F g-1) and CoMoO4 materials (501 F g-1). This integration presents a promising avenue for optimizing MXene-based electrode materials, addressing challenges and unlocking their full potential in various applications.

From agglomeration to dispersion: How does China's noncapital functions' relief affect regional development?

AbstractAgglomeration economies can bring about positive externalities, while excessive agglomeration backfires. However, existing literature on place‐based policies mainly focuses on policies that enhance agglomeration economies. Few studies discuss dispersion policies coping with the negative externality from excessive agglomeration. Owing to the unclear effects of dispersion policies, we conduct empirical research on the noncapital function relief (NCFR) policy, which is implemented to decrease the agglomeration in Beijing, the capital of China, and promote the development of surrounding areas. Exploiting the difference‐in‐difference model, we find that the NCFR policy implementation significantly facilitates the economic growth of the surrounding areas of Beijing. Changes in the distribution of new firm entry and population are two main channels, while no significant effect on the productivity is found. Furthermore, areas that are less‐developed could benefit more from the NCFR policy. Our findings may enlighten other developing countries in urban economic management.

A Robust Fuel Cell Operating on Lunar Water Derived Fuels

The space proven fuel cell technology will likely play a crucial role in the upcoming expansion of human presence into the solar system. In particular, polymer electrolyte membrane (PEM) fuel cells excel due to their high power-density, low weight and their ability to operate on in-situ resource utilization (ISRU) based fuels. Hydrogen fuel and oxygen can be derived from lunar water, which is believed to be trapped in permanently shadowed craters on the lunar poles. However, Colaprete A. et al. found that H2S and NH3 as well as smaller quantities of other sulfur compounds and hydrocarbons are detected alongside the water ice. These compounds are well known fuel impurities which cause reversible yet also irreversible damage to the platinum catalyst and other components of the membrane electrode assembly (MEA). Commercially available fuel cells on the other hand require highly purified fuels with contamination levels in the low ppb region. Thus, these impurities pose a profound problem, even if only a fraction of them is carried onwards to the hydrogen fuel and oxygen. Subsequent intensive purification processes are costly and require large amounts of energy – a process which could render the whole approach useless.As mentioned before, H2S and other sulphur compounds adsorb strongly to the platinum metal and irreversibly degrade its catalytic activity until performance drops to unusably low levels. This effect is directly related to the amount of available catalyst, since a doubling of the platinum loading leads to a two-fold reduced degradation. We hypothesize that the resilience of a fuel cell can not only be improved by increasing the amount of platinum, yet also by using the available platinum more effectively. A lot of the platinum remains inactive within a fuel cell electrode due to different effects like excessive ionomer coverage or particle agglomeration. With the so-called platinum utilization parameter the obtained fuel cell performance is related to the total platinum weight and thus can be used to rate how effective platinum is used. In our recently published review, we found that electrospun electrodes have the highest platinum utilization out of all compared fuel cell electrode manufacturing methods. Furthermore, electrospun electrodes are reportedly less prone to other degradation mechanisms like Ostwald ripening. In this ongoing work, we aim to fabricate MEAs with fully electrospun electrodes and benchmark them against a commercial alternative. The electrodes will be operated with contaminated gases in half cell as well as full cell degradation experiments. The outcome of this research aims to support the exploration community in designing robust energy systems on the moon by investigating the effect of lunar contaminants on fuel cell systems.

Exploring the Effects of Socioeconomic Factors and Urban Forms on CO2 Emissions in Shrinking and Growing Cities

Exploring the mechanisms influencing carbon dioxide (CO2) emissions is crucial to seeking low-carbon development paths. Previous studies have analyzed the effects of socioeconomic factors and urban forms on CO2 emissions. However, little attention has been paid to the heterogeneity of their interactions in differing urban development patterns, such as growth and shrinkage. This study focused on how socioeconomic factors and urban forms work together to comprehensively affect CO2 emissions within the context of urban shrinkage and growth. A selection of 285 prefecture-level cities in China were divided into four groups of shrinking and growing cities based on a comprehensive index system. After assessing variables involving socioeconomic factors and urban forms, a panel data model was used to verify their mutual mechanisms influencing CO2 emissions. The results show that CO2 emissions in shrinking cities continue to rise due to the driving force of secondary industry and the coexistence of population loss and space expansion. For growing cities, in addition to economic development and population growth, urban forms with excessive compactness and polycentricity significantly accelerate CO2 emissions. Consequently, disorderly urban expansion should be avoided, and industrial upgrading should be promoted for shrinking cities. Meanwhile, growing cities are advised to develop modern service industries. Moreover, it is recommended that urban spatial planning follows urban functions and their development stages to avoid excessive agglomeration and polycentricity.

P(VDF-HFP)-based nanocomposites with elaborative PN-junction nanofillers displaying high energy storage performance

Given its wide application ranges, dielectric capacitors have garnered extensive attentions. However, due to the excessive premature agglomeration of free electrons, capacitors with nanocomposites as dielectrics fail to attain high breakdown strength (Eb), and thereby constrain their ability to achieve superior energy storage performances. To alleviate the effects of free electrons and secondary impact-ionized electrons (SIE) on Eb and leakage currents, here, a novel organic-inorganic core–shell Ni(OH)2@PDI (N@P) nanofiller with opposite double-PN-junction was well-designed and successfully synthesized by coating p-typed Ni(OH)2 nanosheets with n-typed perylene diimide (PDI). It could reduce free electron kinetic energy and mitigate SIE amounts regardless of the applied electric field direction. Furthermore, PDI, as an organic compound, can uniformly and densely coat onto surfaces of 2D Ni(OH)2, as well as enhance compatibilities between Ni(OH)2 and matrix, and thereby reducing structure defects at their interfaces. Last but not the least, Ni(OH)2 nanosheets also contribute to Eb improvement via acting as scattering centers. Experimental and simulation results concurrently affirmed positive influences of organic-inorganic N@P nanofillers on discharge energy density (Ud) and efficiency (η) of P(VDF-HFP)-based (PVH-based) nanocomposites. Remarkably, 1.3 vol% N@P/PVH achieves a high Ud of 21.7 J/cm3 and η of 81.2 % under 569.0 MV/m. More importantly, it maintains an excellent energy storage performance throughout 104 cyclic tests. This study presents a valid strategy for concurrently improving Ud and η of polymer-based nanocomposites.

The Research on Causes of Megacity Problem Based on Spatial Disequilibrium

<p>By using spatial models with lag and error and through many experiments, this paper uses distance threshold which can maximize spatial autocorrelation, instead of setting spatial weight matrix by adjacent boundaries, making measurement better suit the features of our country’s cities distribution to explore the reasons for big city disease empirically. It finds that distribution of public service distribution and spatial non-equilibrium are factors for excessive population agglomeration and therefore big city disease, and provides solutions for the factors mentioned above.</p>

Improve MOF-801 dispersibility in PVA membranes by a pre-crosslinking strategy for enhanced pervaporation performance

Interfacial defect caused by the poor dispersibility of filler particles has been a major obstacle in the application of mixed matrix membranes (MMMs). Improving the fillers dispersibility is an effective approach to improve the separation performance. In this work, for the purpose of preparing defect-free MMMs, a pre-crosslinking strategy was proposed to covalently connect the fillers to the polymer. Such covalently connection realized by the reaction between the additional carboxyl group of the MOF-801 and the hydroxyl group of Polyvinyl alcohol (PVA). The newly reacted ester group, confirmed by Fourier Transform Infrared (FTIR), was identified as a bridge between MOF-801 and PVA. This bridge provides a strong bond between the two and avoids agglomeration between the MOF particles. The uniform distribution of Zr elements observed in the Energy Dispersive Spectrometer (EDS) mapping further confirms that the MOF-801 particles are well dispersed in the MMMs. The prepared membranes exhibited a superior water flux of 3354 g m−2 h−1 for 90 wt % ethanol/water separation at 343 K and excellent stability in 92 h experiment. This study provides an inspiration for mitigating excessive particle agglomeration in MMMs.

The impact of overqualification on the intention of urban withdrawal from the perspective of talent crowding

Talent agglomeration greatly promotes the development of cities as a special form of talent allocation. However, excessive agglomeration of talent also leads to talent crowding and overqualification, which undermines the effectiveness of employing human resources and stimulates talent urban withdrawal. Based on the data from 327 questionnaires, data analysis was performed using Mplus 8.0 and HLM 6.08, this study explores the internal mechanism between overqualification and talent's intention of urban withdrawal from the perspective of talent crowding. The following conclusions were drawn: (1) Overqualification is positively correlated with talents' intention of urban withdrawal. (2) Psychological contract breach plays a mediating effect between overqualification and the talents' intention of urban withdrawal. (3) Relational mobility is negatively correlated with talents' intention of urban withdrawal. (4) Relational mobility plays a moderating role in the relationship between overqualification and talents' intention of urban withdrawal. (5) Urban livability is negatively correlated with talents' intention of urban withdrawal. (6) Urban livability plays a moderating role in the relationship between overqualification and talents' intention of urban withdrawal. The results can further improve the human resource management theory and serve as a foundation for developing and implementing population management policies in cities.

Population agglomeration in Chinese cities: is it benefit or damage for the quality of economic development?

This paper explores the impact of population agglomeration on urban economic development quality in various cities of China. The results show that population agglomeration significantly contributes to the improvement of urban green total factor productivity by increasing population diversification, promoting knowledge spillovers, and reducing pollution emission intensity. Moreover, we find that population agglomeration in type II big cities and type I large cities significantly improves green total factor productivity, while the impact of population agglomeration in metropolises and mega-cities on green total factor productivity is not significant. On the one hand, type II big cities and type I large cities are in the period of rising economic development, the population has not yet reached saturation, and there is still a large demographic dividend space. On the other hand, excessive population agglomeration also brings about "urban diseases" such as population congestion and traffic congestion, especially in the metropolises and mega-cities. Finally, using data on producer services and its sub-sectors, we identify a more significant driving effect of high-end talent agglomeration on green total factor productivity.

Bimetallic FeNi Alloy Nanoparticles Grown on Graphene for Efficient Removal of Congo Red From Aqueous Solution

AbstractNano zero‐valent iron (nZVI) is an effective material for dye wastewater treatment, but excessive agglomeration and oxidation greatly limit its application. Herein, graphene (GR) supported FeNi bimetallic nanoparticles (FeNi@GR) are prepared by alloying and carrier supported dispersion for efficient removal of azo dyes from water. Not only can it effectively solve the problem of excessive agglomeration and oxidation of nZVI, but also the synergistic effect of bimetallic coordination formation and the excellent electron transfer ability of graphene are beneficial to enhance the reactivity of FeNi@GR. The optimal FeNi@GR is prepared by adjusting the content of GR and the removal of Congo red (CR) by FeNi@GR‐10% reached 625 mg g−1 within 150 min at pH = 7.0. Higher temperature and lower pH favor the removal of CR azo dye. The action mechanisms of FeNi@GR presumably involve the transfer of active hydrogen atoms and the transfer of electrons generated by Fe0 and Ni0. Besides, the saturation magnetization (Ms) of FeNi@GR is 68.15 emu g−1, which has excellent magnetic response performance. This work not only provides a simple and efficient method to stabilize nZVI, but also reveals that using FeNi@GR is a promising approach for the remediation of water pollution.

Agglomeration of the new energy industry and green innovation efficiency: Does the spatial mismatch of R&D resources matter?

Based on China's provincial panel data from 2011 to 2019, this paper examines the complex impact of new energy industry agglomeration on green innovation efficiency from the perspective of spatial mismatch of research and development (R&D) resources. The super slack-based measured directional distance function (super-SBM-DDF) is applied to measure the green innovation efficiency, while the least square dummy variable model (LSDV) is implemented to evaluate the mismatch of R&D resources in the new energy industry. Based on the generalized method of moment (GMM), the moderating effect model, and the dynamic threshold model are employed to investigate the threshold effect of new energy industry agglomeration on green innovation efficiency and the moderating effect of spatial mismatch of R&D resources. We come to the following findings. First, the agglomeration of China's new energy industry exhibits a “west-east-central” gradient distribution. In the meantime, there is a widespread insufficient mismatch of R&D resources in the majority of regions. Second, the agglomeration of the new energy industry can significantly boost the efficiency of green innovation. Moderate agglomeration can have a marginally enhancing effect, whereas excessive agglomeration will obscure the green innovation effect of new energy industry agglomeration. Third, the relationship between the new energy industry agglomeration and green innovation efficiency is negatively moderated by the mismatch of R&D resources, while the moderating effect is amplified by the mismatch of innovation financial resources. Fourth, there are two inflection points in the positive impact of new energy industry agglomeration on green innovation efficiency when the innovation resource mismatch is assigned as the threshold variable.

Theoretical and experimental investigations on material removal characteristics of small-diameter aspherical silicon carbide mould with weak magnetization-enhanced force-rheological polishing

Multi-field composite polishing with non-Newtonian fluids is a potential technology for manufacturing optical moulds. However, the correlation between the micromaterial removal mechanism and the properties of magnetic shear thickening fluid (MSTF) for weak magnetization-enhanced stress-rheological polishing (WMESRP) is still unclear. In this study, we propose a weak magnetization- enhanced stress-rheological polishing (WMESRP). Based on non-Newtonian fluid dynamics, microscopic contact mechanics, and vector discrete methods, a multi-scale material removal model (MRR) was established. Under a series of fixed-point polishing experiments, the maximum change rate between the experiment and theory was obtained as less than 5.7%. In addition, comparative experiments revealed that polishing liquids containing polyethylene glycol inhibit excessive agglomeration of particle clusters, thereby achieving a smooth surface. The proposed WMESRP method can accomplish non-destructive processing of hard and brittle ceramic materials, which can be used in various applications.

(Digital Presentation) Validation of Python-Based Automated Analysis Approach for Processing STEM/EDS Maps of Catalyst Samples in AEMFCs – a Comparative Study

Technological innovations in the field of materials science are often connected to the nanometric scale material evaluation which requires utilizing a combination of advanced characterization techniques. The extensive data acquired from these characterization techniques necessitates meticulous and efficient analysis, which can only be accomplished by automated digital image and data processing techniques. The development of such techniques will aid further advancements in the design of functional materials. In this work, we report a novel automatic analysis approach using data acquired by the Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive Spectroscopy (EDS) to determine the component distribution and microstructure descriptors for an anion exchange membrane fuel cell (AEMFC). The current research aims to validate the automated approach by comparison to a manual image processing method based on ImageJ reported in a previous study [1]. STEM and EDS data for three different Pd/CeOx-based catalyst samples with varying bulk atomic fractions of Ce/Pd were collected and analyzed. The STEM/EDS data was used to investigate how the interfacial contact area and agglomerate size distributions of Pd and Ce can be related to the microstructural-level interactions and processes and potentially affect the electrochemical performance of an anion exchange membrane fuel cell (AEMFC). The comparison highlighted the strengths and limitations of both automated and manual approaches and offered substantial justification to predict how excessive Ce agglomeration can be linked to a reduction in the electrochemical performance of the fuel cell.[1] R. K. Singh et al., “Synthesis of CeOx-Decorated Pd/C Catalysts by Controlled Surface Reactions for Hydrogen Oxidation in Anion Exchange Membrane Fuel Cells,” Adv. Funct. Mater., vol. 30, no. 38, 2020, DOI: 10.1002/adfm.202002087.

Entrepreneurial innovativeness: When too little or too much agglomeration hurts

This study sheds light on the relationship between agglomeration, entrepreneurs' internal resources and capabilities, and new ventures' innovativeness using a multilevel framework. We argue that the urban agglomeration of economic agents within a country has an inverted U-shaped relationship with new ventures' innovativeness, suggesting that both insufficient and excessive agglomeration might be detrimental to entrepreneurial innovativeness. Additionally, we perform interactions between individual level factors and urban agglomeration to examine the differential effects of entrepreneurs' internal resources and capabilities. Results confirm our hypothesising that the geographical concentration of economic agents within a country exerts an inverted U-shaped influence on new ventures' innovativeness. Furthermore, we find that entrepreneurs with higher levels of education or prior entrepreneurial experience are better equipped to benefit from agglomeration and to mitigate its negative effects; in contrast, at low levels of agglomeration, entrepreneurs with lower resources exhibit increasing marginal returns. Entrepreneurs in contact with other entrepreneurs are better positioned to deal with agglomeration externalities although their benefits and drawbacks are intensified. Our research contributes to the understanding of agglomeration externalities and entrepreneurial innovativeness, its non-linear dynamics and differential effects.