Abstract:Objective Existing studies on acoustic particle agglomeration have predominantly focused on several research areas.Kinetic models for single particles were developed,and the particle entrainment velocity by acoustic waves was measured.The acoustic wake theory has been systematically elaborated,and particle interaction simulations under the acoustic wake effect were con-ducted.Studies have also simulated the microkinetics of particle agglomeration under the coupled influence of acoustic wake and mutual scattering effects.Significant attention has been given to the discrete element method(DEM)for acoustic agglomeration characterization that incorporates particle contact processes and related numerical simulations.Although these studies have pro-vided insights into the microkinetic behaviors of acoustic particle agglomeration,the particulate acoustic agglomeration process cannot be fully characterized.This limitation primarily arises from the accuracy constraints of the current modelling approaches.To address the deficiency in existing microkinetic models for acoustic agglomeration regarding the coupled effects of acoustic wake and mutual scattering,an improved microkinetic model for particulate acoustic agglomeration under multiple coupling mechanisms was constructed,greatly enhancing the accuracy in predicting the microkinetic behaviors of particles. Methods The DEM was used to investigate the interaction between two particles of identical size in a standing wave acoustic field.The gas-phase velocity was modified under the coupled effects of acoustic wake and mutual scattering to ensure that the flow field at the particle surface satisfied the no-slip velocity boundary condition.Previous models superimposed the acoustic wave fluctuation velocity with the perturbation velocity induced by acoustic wake and mutual scattering to reproduce the multi-mechanism coupling effects.A comparative analysis was conducted between the experimental and the numerical simulation results obtained from both previous models and the improved particle acoustic agglomeration model under multiple coupling mechanisms.This validation confirmed the accuracy of the proposed model.Based on these findings,the influence of the par-ticles' initial positions on their acoustic agglomeration kinetic behaviors was further explored. Results and Discussion The improved microkinetic model for particulate acoustic agglomeration under multiple coupling mecha-nisms enabled the prediction of particle collision time.It also fully reproduced the entire process of particle interactions observed in experiments within the acoustic field,involving particle approach,collision,acoustic agglomeration,and the subse-quent movement of the formed particle aggregates.In contrast,previous models exhibited unreliable predictions regarding the post-collision kinetic behaviors of particles.For particles initially located between two adjacent nodes in a standing-wave acous-tic field,the acoustic agglomeration time of particles varied symmetrically with their initial positions due to the symmetry of the acoustic wave fluctuation equation.The closer the particles' initial positions were to the antinodes,the stronger the attractive effect of the acoustic wake,and consequently,the shorter the acoustic agglomeration time.Particles with larger diameters had a broader range of initial positions from which acoustic agglomeration could occur and required shorter acoustic agglomeration time,indicating that larger particles were more prone to acoustic agglomeration.When the particles' initial positions were close to the nodes,the weak acoustic wake effect could not overcome the repulsive force caused by mutual scattering,thereby prevent-ing particle collision and acoustic agglomeration. Conclusions In comparison with previous models,the improved DEM-based microkinetic model for particulate acoustic agglom-eration under multiple coupling mechanisms demonstrates superior accuracy in predicting kinetic behavior of particle acoustic agglomeration.This enhanced model plays a significant role in elucidating the microkinetic behaviors and underlying mecha-nisms of acoustic agglomeration processes.

Abstract:Objective Graphene,renowned for its excellent mechanical,thermal,and electrical properties,enables extensive applications across various fields.However,its industrial-scale production remains constrained by significant challenges such as severe envi-ronmental pollution,substantial production costs,and limited scalability.To address these issues,the study develops a green,efficient,and scalable method for graphene nanosheet(GN)fabrication,while also providing an effective surfactant removal strategy to enhance their applicability. Methods GNs were synthesized through a combined ball milling pretreatment and surfactant-assisted aqueous-phase ball mill-ing process.Key parameters,such as surfactant dosage,initial graphite concentration,ball milling time,and ball-to-material ratio,were optimized through univariate analysis with the mass concentration of GNs as the evaluation metric.In addition,the morphological and structural characterization of the resulting GNs were conducted,and the surfactant removal efficiency through calcination was systematically investigated. Results and Discussion Experimental studies showed that the optimal processing parameters were determined as follows:3％surfactant mass fraction,120 mg/mL initial graphite mass concentration,4 h ball milling time,and 12∶1 ball-to-material ratio.Under these conditions,the resulting GNs were produced at a maximum solution concentration of 2.42 mg/mL.Microscopic characterization results,including scanning electron microscopy(SEM),transmission electron microscopy(TEM),and atomic force microscopy(AFM),showed that about 70％of the GNs had lateral sizes between 400 nm and 800 nm and consisted of 5 to 12 layers.Raman spectroscopic analysis confirmed their high structural integrity,as evidenced by the low defect-related ID/IGratio(the ratio of peak intensity D to peak intensity G)of 0.318.In addition,calcination at 400 ℃ for 30 min under a nitro-gen atmosphere effectively removed most of the surfactants,while moderately improving the conductivity of the resulting GNs.A higher calcination temperature of 950 ℃ achieved complete surfactant removal,significantly enhancing conductivity of up to 1.3×104S/m. Conclusion This study demonstrates a green,efficient,and scalable aqueous-phase exfoliation method for producing high-quality and low-defect GNs.The combined ball milling approach offers a novel idea for graphene production and holds promise for large-scale graphene preparation.Additionally,the developed calcination-based surfactant removal method further enhances conductivity,enabling flexible application-specific optimization.This work provides a promising pathway toward sustainable,large-scale graphene manufacturing.

Abstract:Significance Flexible wearable sensors have gained rapid popularity due to the advancement of flexible electronics.Among vari-ous sensing mechanisms,piezoelectric sensors exhibit high sensitivity and energy conversion efficiency for dynamic signals,along with self-powering capability,making them ideal for long-term physiological monitoring.Polyvinylidene fluoride(PVDF),a piezoelectric polymer,offers excellent flexibility,biocompatibility,light weight,and stability,rendering it highly suitable for conformal wearable devices.However,its relatively low piezoelectric coefficient(d33)limits the sensitivity and signal-to-noise ratio of PVDF-based sensors.Therefore,enhancing the d33 of PVDF through material modification is crucial for expanding its applications in high-performance flexible sensing. Progress This review systematically outlines the main strategies developed in recent years to enhance the piezoelectric perfor-mance of poly(vinylidene fluoride)(PVDF),aiming to synergistically improve its piezoelectric output through molecular design,composite structuring,and advanced processing.The research primarily follows two pathways:one is chemical copoly-merization,where the introduction of co monomers such as TrFE or HFP reduces the energy barrier for β phase formation,lead-ing to d33 values above 50 pC/N and,further through ternary/quaternary copolymer designs that introduce relaxor ferroelectric behavior,reaching d33 values up to thousands of pC/N;the other is physical blending/compositing,in which piezoelectric ceram-ics or conductive nanomaterials are incorporated into the PVDF matrix,leveraging interfacial polarization and stress transfer to promote β phase nucleation and enhance overall polarization,thereby achieving tunable d33 values ranging from tens to hundreds of pC/N.Supported by optimized fabrication techniques such as electrospinning,high voltage poling,ice template self assembly and 3D printing,the microstructure and dipole alignment can be further controlled to fully exploit the piezoelectric potential of the material systems.In summary,a systematic strategy spanning molecular design,multiphase compositing,and microstructure control has been established,significantly advancing the piezoelectric properties of PVDF based materials.This progress drives the development of flexible,multifunctional,and integrable materials,laying an important foundation for next generation flex-ible sensors,biomedical monitoring,and smart wearable devices. Conclusions and Prospects Currently,the piezoelectric coefficient d33 of PVDF powder is primarily improved through chemical copolymerization and physical blending.In chemical copolymerization,vinylidene fluoride is mainly copolymerized with mono-mers such as trifluoroethylene and hexafluoropropylene,where steric hindrance is utilized to promote dipole orientation,thereby increasing d33.In physical blending,nanoparticles or ceramic powders with high d33,such as BaTiO3,PZT,and ZnO,are intro-duced into the PVDF matrix to enhance the d33 of PVDF powder.Additionally,processes such as 3D printing,electrospinning,and high-voltage poling can further improve the d33 of PVDF powder.With the increase in d33,PVDF-based multimodal flexible wearable sensors exhibit considerable potential in motion monitoring,health management,and related fields.

Abstract:Objective China still lags behind other military powers in the application of high-pressure,high-energy propellants in rocket motors.This is primarily due to the insufficient depth and systematization in fundamental theoretical research,an incomplete understanding of the high-pressure combustion mechanisms of high-energy propellants,and limited methods for controlling their combustion characteristics under high-pressure conditions.In this paper,the combustion mechanisms of high-energy nitrate ester plasticized polyether(NEPE)propellants are investigated using advanced technical approaches,including high-pressure closed vessel tests,high-speed imaging,spectral testing,and energy calculations.It aims to reveal the regulatory mechanisms of burning rate regulators on the combustion performance of high-energy propellants and to provide technical support for their application in high-pressure solid rocket motors. Methods A high-pressure chamber with four transparent windows was used,combined with high-speed color photography with high spatiotemporal resolution,to investigate the influence of copper-containing burning rate regulator(CuLl)on the high-pressure combustion performance,flame structure,temperature distribution,and condensed-phase particle distribution of the propellants.MATLAB software was used for flame image processing,and a reconstructed model of the propellant temperature field was obtained. Results and Discussion The high-energy NEPE propellant used polyethylene glycol(PEG)as the binder,ammonium perchlo-rate(AP)and nitramine explosive(RDX)as oxidants,aluminum powder as fuel,and nitroglycerin(NG)and 1,2,4-butane-triol trinitrate(BTTN)as plasticizers.The propellant was produced using a vertical mixer and subsequently solidified.Com-pared to hydroxyl-terminated polybutadiene(HTPB)propellants,NEPE formulations exhibited higher burning rates and pres-sure exponents,primarily due to the slow decomposition of oxidants at low pressure.If the decomposition rate of oxidants under low-pressure conditions could be increased,thereby enhancing the burning rate at low pressure,the overall pressure exponent could be reduced.When doping with 1％CuL1,the decomposition peak of AP dropped from 444.7 ℃ to 339.1 ℃,a decrease of 105.6 ℃.CuL1 also catalyzed the decomposition of RDX,reducing its peak from 240.8 ℃ to 218.6 ℃,a decrease of 22.2 ℃.Consequently,the decomposition rate of oxidants increased,enhancing flame brightness near the burning surface.Without a burning rate regulator,the catalytic process relied on increasing pressure to enhance thermal feedback from the flame to the burning surface,thereby accelerating oxidant decomposition.Within the range of 1～5 MPa,the gas-phase temperature near the burning surface was consistently higher for CuL1-doped propellants,indicating more intense heat released due to enhanced oxidant decomposition.As pressure increased from 0 MPa to 15 MPa,the flame height of CuLl-containing propellant decreased slightly with a slope of 0.692 0.In contrast,the propellant without a burning rate regulator had a higher pressure exponent,and the flame height was more significantly affected by pressure,with a slope of 0.992 7.Aluminum powder under-went ignition,melting,and combustion stages.CuL1 accelerated oxidant decomposition near the burning surface,shortening the ignition-to-melting process.This led to the orderly formation of condensed-phase particles before large droplets could form,improving particle size uniformity and combustion stability.Without CuL1,the propellant aluminum powder ignited upon heat-ing near the burning surface,resulting in significant agglomeration and a broad distribution of particle sizes.During the combus-tion process of CuL1-doped propellants,aluminum powder was ejected from the burning surface.Due to the high oxidant con-centration near the burning surface,the melting process was shortened,facilitating the rapid formation of condensed-phase par-ticles after ignition,resulting in relatively uniform particle sizes.This improved the particle size distribution in the combustion chamber,reducing heat accumulation caused by aluminum powder agglomeration and thereby enhancing propellant combustion stability.When CuL1 was doped,aluminum powder agglomeration was effectively controlled,thermal accumulation was sup-pressed,and the temperature distribution near the burning surface and in the gas-phase region was relatively more uniform.The maximum temperature reached 2 718 K.The energy barrier for the decomposition of NH3 into NH2*+H*decreased from 1.84 eV to-0.89 eV,and the energy barrier for its further decomposition into NH*+H*decreased from 2.64 eV to 1.52 eV. Conclusion The continuous development of highly efficient burning rate regulators is conducive to regulating the high-pressure combustion performance of high-energy propellants.Conducting research on propellant combustion at microscopic and molecu-lar scales can reveal more inherent mechanisms controlling propellant combustion and redox reactions.

Abstract:Significance Magnesium phosphate cement(MPC)is an advanced cementitious material renowned for its ceramic-like proper-ties,making it a promising candidate for structural repair and reinforcement applications.Its rapid hardening characteristics and early-age strength development allow for efficient construction in time-sensitive projects,while its exceptional dimensional sta-bility ensures long-term structural integrity.Despite these advantages,practical challenges such as excessively short setting times and inherent brittleness have hindered its widespread adoption.To overcome these limitations,researchers have focused on modifying MPC through the strategic incorporation of mineral admixtures and high-performance fibers.These modifications aim to optimize the material's fresh-state workability,enhance its mechanical performance such as flexural and compressive strength,and improve its fracture toughness,ultimately transforming MPC into a more versatile and durable construction mate-rial suitable for diverse engineering scenarios. Progress The modification of MPC has been extensively studied through the integration of various mineral admixtures and fiber reinforcements.Mineral admixtures such as fly ash(FA),metakaolin(MK),and industrial waste slag play pivotal roles in refining the material's microstructure and enhancing its performance.For instance,FA acts as a micro-aggregate that fills the voids between MPC particles,thereby improving paste fluidity,reducing hydration heat,and mitigating the risk of thermal cracking.Its pozzolanic reactivity further contributes to long-term strength development.MK,a highly reactive aluminosilicate,accelerates the formation of stable hydration products,balancing early strength development with controllable setting times.Industrial waste slag,on the other hand,reduces production costs and promotes sustainable construction practices. Conclusions and Prospects The incorporation of mineral admixtures and fibers has profoundly influenced MPC performance,though their effects differ in scope.Mineral admixtures primarily enhance fresh-state properties,such as extending setting time,while refining the microstructure to boost mechanical strength and durability.Fibers,conversely,contribute mainly to toughen-ing mechanisms,elevating energy absorption capacity compared to plain MPC,even though they have limited influence on com-pressive strength.

Abstract:Objective In practical engineering,expansion agents are commonly employed to mitigate cracking in oil well cement.However,the high-temperature and high-pressure conditions characteristic of oil well environments often make most expansion agents unsuitable.Magnesium oxide(MgO),when used as an expansion agent,forms magnesium hydroxide(Mg(OH)2)upon hydra-tion,exhibiting exceptional stability under high temperatures.This stability ensures effective and sustained expansion,making it ideal for mitigating cement cracking in oil wells.This study investigates the effects of MgO with varying activities on the expan-sion performance of oil well cement,offering guidance for the application of MgO with different activity levels in industrial settings. Methods In the experiments,the water-cement ratio was fixed at 0.44,and the curing temperature was maintained at 60 ℃.The fluidity and free liquid content of oil well cement containing MgO of different activities were measured.Mortar specimens with dimensions of 50.8 mm×50.8 mm×50.8 mm and 40 mm×40 mm×160 mm were prepared by mixing MgO of varying activi-ties into the cement and curing them in a water bath at 60 ℃ for 1,3,and 7 days.The compressive strength and expansion rate of the specimens were then evaluated.Furthermore,the effects of MgO with varying activities on the hydration exothermic rate and heat release of the oil well cement were investigated.X-ray diffraction(XRD)and scanning electron microscopy(SEM)were employed to elucidate the mechanism by which MgO influenced the cement expansion. Results and Discussion For MgO at a reaction time of 31s,the fluidity and free liquid content of the specimens reached their minimum values,showing reductions of 15％and 32％,respectively,compared to the control group(without MgO).However,as the MgO reactivity decreased,the fluidity and free liquid content of the mortar gradually increased.After incorporating MgO,the 1-day compressive strength of the cement specimens increased with decreasing MgO activity,reaching a maximum of 9.31 MPa at a reaction time of 345 s before declining.For the 3-day and 7-day compressive strengths,both exhibited an initial increase followed by a decrease as MgO activity decreased.The 3-day compressive strength peaked at 26.16 MPa at a reaction time of 426 s,representing a 25.6％increase over the control group.The 7-day compressive strength reached 29.46 MPa at a reaction time of 345 s,which was 18.7％higher than that of the control group.The expansion rate of the oil well cement increased gradually as the MgO activity decreased,under constant MgO dosage and curing temperature.The expansion rate peaked at 0.552％at 426 s,after which it stabilized or even slightly declined.This phenomenon occurred because MgO with a reaction time of 31 s reacted too rapidly at a curing temperature below 60 ℃,causing expansion to occur before internal stresses developed in the cement.As a result,the expansion was absorbed by the mortar,consuming nearly all the MgO,leaving almost no expansion effect during mid-stage hydration of the specimens.When the MgO activity decreased,the formation of Mg(OH)2 slowed,delaying the expansion reaction.Thus,with decreasing MgO activity,the expansion effect improved during the transi-tion stage.However,when the reaction time exceeded 426 s,the reaction rate became excessively slow,leaving a portion of MgO unreacted at 7 d,which led to a slight reduction in the expansion rate. Conclusion The fluidity of oil well cement increased as the activity of MgO decreased.The free liquid content rose with the reduction in MgO activity.The compressive strength increased with decreasing MgO activity,peaking at 426 s and 345 s,respectively,and then decreased.The expansion rate of oil well cement exhibited a trend of initial growth followed by a decrease as MgO activity decreased,reaching its maximum when the reaction time extended to 426 s,after which it stabilized and even slightly declined.The incorporation of MgO effectively enhances the compactness of oil well cement,reducing pores and cracks and improving both cement strength and expansion rate.

Abstract:Objective To enhance the regeneration efficiency of diesel particulate filters(DPFs),it is necessary to increase the lattice oxy-gen mobility and active oxygen content,thus improving the soot oxidation capacity of the catalyst at medium and low tempera-tures.Therefore,it is critical to develop an efficient and cost-effective catalyst that can facilitate soot oxidation under these conditions. Methods In this study,pure metal oxides,CePrOx,and CePrMnOx catalysts were synthesized using the cetyltrimethylammonium bromide(CTAB)assisted co-precipitation method.The physical and chemical properties of these catalysts were characterized by various analytical techniques.Their structure and morphology,defect degree,reduction ability,oxidation ability,and mech-anism were systematically studied. Results and Discussion Based on the characterization and experimental results,the catalytic oxidation activity test curves of soot showed that co-doping with Pr and Mn increased lattice oxygen mobility and reactive oxygen content in the catalysts.Specifi-cally,the CePrMnOx catalyst exhibited superior low-temperature oxidation ability for soot,and its t10 and t50values were 85℃and 67℃ lower than those of CeO2,respectively.X-ray diffraction(XRD)results confirmed that Pr and Mn elements were suc-cessfully doped into CeO2 lattice,leading to lattice distortion.This distortion,which altered the lattice symmetry and oxygen ion migration pathways,was likely the key factor in improving lattice oxygen mobility.Nitrogen adsorption-desorption experiments showed that the CePrMnOx catalyst hada larger specific surface area and pore volume,suggesting more active sites for reactants to interact with,thus improving the catalytic efficiency.SEM results revealed the presence of nanorods in the CePrMnOx cata-lyst,which improved the contact efficiency of active sites and further enhanced the catalytic performance.Raman and temperature-programmed reduction(TPR)results showed that the CePrMnOx catalyst hada higher oxygen vacancy concentration and stronger reduction ability.X-ray photoelectron spectroscopy(XPS)results suggested that this was due to the higher content of Ce3+,Mn3+,and surface reactive oxygen species in the CePrMnOx catalyst.In situ diffuse reflectance infrared Fourier trans-form spectroscopy(DRIFT)results showed that carbonates were the main intermediate reaction products for both CePrOxand CePrMnOx catalysts.The bidentate carbonates on the surface of the CePrOx catalyst did not fully participate in the reaction,thus covering the active sites and limiting the improvement of catalytic activity.In contrast,the CePrMnOx catalyst,with its higher active oxygen content and oxygen vacancy concentration,promoted carbonate conversion more effectively,thus improving the catalytic efficiency. Conclusion 1)The CTAB-assisted co-precipitation method not only maintains the cubic fluorite structure of CeO2 but also suc-cessfully introduces Pr and Mn elements into the CeO2lattice.This co-doped catalyst exhibits a larger specific surface area and has more active sites for reactant interaction,thus improving catalytic activity.Moreover,this method enhances the redox capac-ity of the catalyst,which is particularly important for catalytic oxidation reactions.It promotes the activation and transfer of oxy-gen,thereby improving the catalytic efficiency.2)Mn doping has a significant impact on catalyst performance.The introduction of Mn enhances the oxygen migration ability of the catalyst and increases the content of chemisorbed oxygen on the surface.Effi-cient oxygen migration is vital for soot oxidation.Additionally,higher surface chemisorbed oxygen content means more oxygen molecules can be adsorbed on the catalyst surface,providing more reactive oxygen species for oxidation reactions.These charac-teristics collectively improve the catalyst performance in soot oxidation reactions,making it more efficient at low temperatures.3)During soot oxidation,bidentate carbonates are the main reactive species.However,bidentate carbonates on the surface of the CePrOx catalyst may cover active sites,reducing catalytic activity.This occurs because the adsorption of bidentate carbon-ates may hinder reactant contact with the active site.In contrast,the CePrMnOx catalyst,due to its optimized surface properties and enhanced oxygen migration capacity,can convert bidentate carbonates more efficiently.This reduces active site coverage and improves catalyticactivity.These findings indicate that the CePrMnOxcatalyst performs better in soot oxidation,which is sig-nificant for improving catalytic efficiency and reducing environmental pollution.

Abstract:Objective Pyrolysis is an important way to convert biomass into char,but the complex reaction network of the pyrolysis process makes it challenging to control the properties of the resulting char.Studies have shown that temperature,among all the param-eters,is the main factor affecting pyrolysis reactions,followed by residence time.This study focuses on the correlation between char properties and pyrolysis temperature and time by conducting pyrolysis experiments on cotton fiber and peach wood at tem-peratures from 250 to 750℃ and at 350℃ for various residence times. Methods The synthesis of char was conducted in a fixed-bed reactor within a tube furnace under a nitrogen(N2)atmosphere,with a flow rate maintained at 60 mL/min.2 g of biomass was placed in a quartz tube.Before heating,N2 was introduced to establish an inert environment within the reactor.The tube furnace was heated to 250,350,450,550,650,and 750℃ at a temperature ramping rate of 10℃/min,and then held at the target temperature for 30 min.Upon completion of the heating pro-cess,the reactor was immediately removed from the furnace and quenched.In addition,to further investigate the effects of resi-dence time,the pyrolysis time was extended to 60,90,120,and 180 min at 350℃. Results and Discussion The cracking of cellulose was observed at 350℃,while the rigid structure of lignin stayed stable at this temperature.X-ray diffraction(XRD)results showed that the char generated from the pyrolysis of cotton fiber and peach wood at both 350℃ or 650℃ was primarily amorphous carbon.The char derived from peach wood had a higher degree of graphitiza-tion.The original biological structure could be preserved even after extended exposure at 350℃,whereas increasing the temperature to 650℃ led to the fracture of the structural framework.Elemental analysis and in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)results indicated that high temperatures enhanced aromatization by promoting dehydra-tion,dehydrogenation,and deoxygenation reactions.The abundance of-OH and aliphatic C-H groups reached a maximum at 300～400℃,then decreased monotonically via dehydration and dehydrogenation.This process accelerated the formation of C=O,C-H,C=C,and aromatic C-O-C bonds. Conclusions and Prospects Extending the residence time at 350℃ can accelerate the carbonization process by promoting the cracking of oxygen-containing functional groups in cellulose.However,the temperature is insufficient to drive further condensa-tion to form aromatic ring structures.Although 350℃ is not high enough to destroy the rigid structure of lignin,prolonging the exposure time at this temperature enhances the dehydrogenation reaction.Higher temperatures accelerate both carbonization and aromatization processes.This results in a continuous increase in the abundance of C=C and C-O-C bonds at the expense of the-OH,C-H,and C=O functional groups.The study provides theoretical guidance for customizing char with specific func-tional groups.

Abstract:Significance Spherical silica micropowder has garnered significant attention as an inorganic filler due to its high thermal conduc-tivity,excellent dielectric properties,good chemical stability,etc.These superior characteristics have led to its widespread application in various fields,including copper-clad laminates,epoxy resin encapsulants,coatings,cosmetics,drug delivery,catalysis.With continuous technological advancements and increasing demands from downstream industries,the quality require-ments for silica micropowder are becoming more stringent.The excellent performance of spherical silica micropowder has driven its growing market demand,making it a key focus for the future development of silica micropowder techniques. Progress Current research on spherical silica micropowder mainly focuses on its preparation methods and surface modification techniques.Preparation approaches can be broadly classified into two categories:physical and chemical methods.Physical methods,such as flame melting and plasma processing,have been employed to produce high-purity,uniformly sized particles.For instance,a study used angular silica micropowder as a raw material to produce spherical silica micropowder through flame fusion.Chemical methods,including sol-gel,microemulsion,chemical precipitation,spray drying,and vapor phase pro-cesses,have also been widely studied.For instance,a study used tetraethyl orthosilicate as the raw material and hydrochloric acid as the catalyst to synthesize spherical silica micropowder via the sol-gel method.Researchers have further innovated by exploring new silica sources and optimizing existing preparation processes,providing references for the preparation of spherical silica micropowder.For example,researchers used rice husks as the silica source and polyethylene glycol as the solvent to syn-thesize spherical silica micropowder via microwave-assisted sol-gel synthesis. In terms of surface modification,techniques such as organic modification,chemical etching,and polymer grafting are widely used.Silane coupling agents are the most commonly used modifiers.Initially,single-type silane coupling agents were generally applied,but combinations of multiple agents have been shown to enhance their properties.In a study,three different silane cou-pling agents,KH550,KH560,and phenyltrimethoxysilane,were combined to synthesize tri-functional modified spherical silica micropowder.The results indicated that these modifying agents introduced reactive groups to the spherical silica micropowder,enhancing its interfacial compatibility and adhesion with the epoxy resin matrix.Additionally,researchers have employed chemi-cal etching on the surface of micropowder to create more active sites,thereby enhancing the modification effect.For example,researchers treated spherical silica micropowder with a hot NaOH solution.The results showed that the NaOH treatment improved the surface activity and hydroxylation of the spherical silica micropowder,increasing the number of anchoring points and enhancing the dispersion of nanoparticles within the matrix. Conclusions and Prospects Numerous advancements have been made in the preparation and modification of spherical silica micropowder.Techniques such as flame melting,plasma processing,sol-gel,microemulsion,and precipitation methods can all produce spherical silica micropowder with high purity and uniform particle size.However,chemical methods often face chal-lenges related to complex processes,demanding preparation conditions,and environmental pollution,limiting their large-scale production.Physical methods,though simpler and more scalable,have more stringent requirements for temperature and equip-ment.Moreover,these methods demand high-quality natural quartz,which poses significant challenges due to the limited avail-ability of ore sources,thereby hindering sustainable production.Consequently,existing preparation technologies require further refinement for industrial-scale applications.Moreover,with the growing awareness of environmental protection,the environmen-tal impact and sustainable development strategies in the production process of spherical silica micropowder have become increas-ingly important.Future studies should prioritize the development of green and efficient preparation technologies.In terms of sur-face modification,silane coupling agents remain the most commonly used modifiers.Although the modification effects are rela-tively ideal,their high cost exerts considerable pressure on production cost control.To address this,future research should focus on developing new types of modifiers,optimizing modification processes,and conducting in-depth research on modifica-tion mechanisms.

Abstract:Objective The study primarily aims to implement effective and sustainable measures for the remediation of heavy metal pollu-tion.As heavy metal pollution in soil,especially around mining areas,become increasingly severe,it is critical to adopt com-prehensive and effective measures that significantly reduce heavy metal concentration in soil. Methods The study addressed the specific challenges of cadmium(Cd)pollution in agricultural soil surrounding the tailings goaf of a mining facility in Shibuzi Town,Anqiu City,Shandong Province,China.To mitigate Cd contamination,the study devel-oped four tailored soil amendments:sodium lignosulfonate-modified lignite humic acid,mineral-modified lignite humic acid,chitosan-modified lignite humicacid,and biochar-modified lignite humic acid.These amendments were designed to enhance soil properties and immobilize heavy metals,particularly cadmium.Using advanced analytical techniques,the impact of these modi-fied humic acids on cadmium in the contaminated soil was systematically investigated.Laboratory experiments were conducted over an extended period to monitor changes in chemical speciation,providing a comprehensive understanding of theinteractions between soil amendments and cadmium.Furthermore,the studyanalyzed thephysicochemical properties of the soil before and after adding amendments,ensuring a thorough evaluation of their effectiveness.Based on the performance metrics from these tests,two of the most effective soil amendments were selected for further study and potential large-scale field application. Results and Discussion The external morphologies of the four amendments closely matched their respective preparation meth-ods,exhibiting advantageous physicochemical properties that enhanced soil quality.Notably,these amendments significantly increased the residual cadmium content in the treated soil,while reducing the bioavailable forms.In addition to the amend-ments,agronomic methods using hyperaccumulator plants,such as L.japonicaThunb.,were employed alongside strategic appli-cations of sodium lignosulfonate-modified lignite humic acid and biochar-modified lignite humic acid.These interventions led to a substantial shiftin cadmium species within the amended soil,leading to a statistically significant reduction(p＜0.05)in cadmi-umconcentrations.These findings underscore the importance of selecting appropriate amendments tailored to specific soil condi-tions.These selected amendments demonstrated a significant reduction in cadmium bioavailability,offering a promising solution for the restoration of Cd-contaminated agricultural soil in the region. Conclusion This integrated approach achieved highly efficient removal of heavy metals,particularly cadmium(Cd),from con-taminated soil.The efficacy of this method demonstrates its potential as a robust solution for mitigating soil heavy metal pollu-tion.The research results contribute significantly to the field of soil remediation,providing technical support for developing more effective and sustainable remediation techniques.The integration of advanced humic acid-based soil amendments with hyperac-cumulator plants brings an efficient approach to mitigate soil contamination.Throughout the 60-day remediation period,regular monitoring and analysis confirmed the substantial reduction in heavy metal concentrations,validating the effectiveness of the pro-posed strategy.In conclusion,this study presents a novel and promising integrated approach for the remediation of heavy metal pollution insoil.The results provide valuable insights and practical guidance for further development of advanced soil remedia-tion techniques.Future studies should focus on refining this integrated approach to achieve even greater efficacy in mitigating heavy metal pollutionin contaminated soil and ensuring long-term environmental sustainability.

Abstract:Significance This study aims to conduct a comprehensive review of the latest research advancements in micro-and nano-powder fillers for composite solid electrolytes(CSEs),offering valuable insights for the development of novel filler materials with supe-rior ionic conductivity,exceptional mechanical properties,and excellent chemical stability.CSEs exhibit remarkable attri-butes,including high ionic conductivity,easy processing,and a broad electrochemical window.Fillers play a crucial role in enhancing the physical and chemical properties of CSEs.This review encompasses recent research achievements in fillers,eluci-dating their mechanisms for improving the electrochemical performance of CSEs by reducing polymer chain crystallinity,facilitat-ing lithium salt dissociation,and stabilizing anionic species.Furthermore,it outlines the strengths and limitations of fillers while emphasizing the design principles for different types of fillers.The prospects for research and application of CSE fillers are promising,with future directions focusing on material innovation,optimization of filler design,utilization of advanced character-ization techniques,and expansion into new application areas.These efforts are expected to significantly advance solid-state lithium metal battery technology. Progress The polymers commonly utilized in this process,such as polyethylene oxide(PEO),polyethylene glycol diacrylate(PEGDA),and polyvinylidene fluoride(PVDF),typically demonstrate relatively high crystallinity at room temperature.The incorporation of fillers,including inert materials like Al2O3,BaTiC3,as well as fast ion conductors such as LLZTO,effectively reduces polymer crystallinity and improves the mobility of polymer chains.Early research primarily concentrated on exploring Lewis acid-base interactions between fillers and polymers,proposing that rapid ion conduction channels could be established on filler surfaces.Subsequent studies have focused on constructing these swift ion conduction channels,which are closely linked to the orientation and morphology of fillers within the polymer matrix.Recent advancements have discovered complex interactions among polymers,fillers,and lithium salts within CSEs.These interactions manifest primarily in two aspects:1)the interplay between fillers and lithium salts,which involves changes in chemical environment of lithium ions,chiefly reflected in variations of ionic conductivity and lithium ion transference numbers(tLi.);2)the interplay between fillers and polymers,involving modifi-cations in polymer's structural composition,reflected in changes of crystallinity(Xc),glass transition temperature(Tg),and spherulite formation.Despite this progress,interface stability remains the fundamental challenge for solid-state lithium batteries(SSLBs).These challenges are influenced by interactions at both CSEs/cathode and CSEs/anode surfaces,including issues such as inadequate electrolyte/electrode contact,lithium dendrite growth,and high-voltage decomposition. Conclusions and Prospects CSEs exhibit tremendous potential in advancing solid-state battery technology through the incorpo-ration of fillers to enhance their performance.This review presents a comprehensive review of various types of fillers,including inert,active,and functional fillers,as well as their characteristics and impact mechanisms on CSE performance.It illuminates the synergistic effects of fillers in enhancing electrochemical performance by reducing polymer chain crystallinity,facilitating lithium salt dissociation,and stabilizing anions.Notably,the interface interactions between fillers and the polymer matrix are pivotal for establishing rapid Li+transport pathways.By optimizing filler dispersion and improving interface compatibility,the migration rate of lithium ions can be significantly enhanced,thereby improving the conductive properties of electrolytes.Despite significant progress in optimizing filler properties through various strategies,challenges such as the impact of fillers on ion trans-port dynamics,non-uniform lithium deposition,and dendrite formation still exist.Future research should focus on the following directions:1)Material innovation.Leveraging artificial intelligence models to identify and design new fillers;2)Filler optimiza-tion.Investigating microstructural features of fillers and their effects on performance;3)Advanced characterization techniques.Utilizing cutting-edge characterization methods to explore the dynamic changes of fillers throughout the process of charging and discharging;4)High-pressure compatibility.Developing composite fillers integrated with small molecule plasticizers to improve interfacial stability.

Abstract:Objective Landslide and debris flow are significantly influenced by precipitation distribution,mountainous topography,and soil granular properties.This study aims to explore the effects of various factors,such as moisture content and soil properties,on disaster behavior.A wet granular column collapse model is constructed to analyze how different moisture levels impact collapse modes and behavior,providing a theoretical basis for disaster prevention. Methods This study investigated how moisture content affects the collapse modes and behavior of granular columns by systemati-cally varying moisture levels from dry to fully saturated conditions.The experiments employed a custom horizontal transparent channel.The glass beads with diameters of 1.0 mm and 2.0 mm and a density of about 2 500 kg/m3 were used to form the granu-lar columns.The initial aspect ratio,defined as the height-to-width ratio of the columns,varied between 1 and 3.Moisture con-tent was controlled as the mass ratio of water to particles.The centroid vector displacement method was applied to analyze the role of liquid bridges in collapse dynamics across different saturation levels.A high-speed camera captured the collapse process at 3-millisecond intervals to ensure precise measurements. Results and Discussion The collapse mode of granular columns with a particle diameter of 1 mm and an initial aspect ratio of 1 exhibited a non-monotonic transition under varying water content:initiating from continuous collapse in the dry state,progress-ing to blocked collapse at a water content of 2％,achieving static stability at 6％,reverting to blocked collapse at 8％,and ulti-mately returning to continuous collapse under over-saturated conditions with water content approaching 30％.This indicated that moisture content,along with aspect ratio and particle diameter,played a key role in determining collapse mode.The transition between collapse modes was driven by changes in liquid bridge forces.At low moisture content,liquid bridges enhanced particle cohesion,leading to blocked collapse.As moisture content increased,cohesion peaked at 6％,resulting in stability.Further increases in moisture content reduced cohesion,leading to blocked or continuous collapse.Calculation results from the centroid vector displacement method showed that moisture suppressed the vertical displacement of centroid and reduced the maximum kinetic energy during collapse compared to dry granular columns.Gravitational potential energy loss and kinetic energy changes were analyzed.For a granular column with a particle size of 1 mm and an initial aspect ratio of 1,when the water content is 2％,the gravitational potential energy loss rate is 27.2％;when the water content is 6％,the granular column remains stationary;and when the water content increases to 8％,the column exhibits"slight and slow"block collapse,with a gravitational potential energy loss rate of less than 15％.By comparing the gravitational potential energy loss rates at different water contents,the inten-sity of block collapse can be quantitatively assessed.For 2 mm particles,the energy loss rate decreased with increasing moisture content.This study found that the influence of interstitial liquids on granular column collapse followed an increasing-stable-slightly decreasing trend as moisture content increased,with the maximum influence occurring at 6％moisture content.The ratio(Sr)of the centroid displacement magnitude of wet columns to dry columns was defined,with larger Sr values indicating smaller reductions in centroid displacement due to moisture.Moisture content had a more significant impact on columns with smaller aspect ratios and particle diameters. Conclusion Moisture content is a critical factor influencing granular column collapse.For sample S1,collapse modes transi-tioned sequentially with increasing moisture:continuous→blocked→stable→blocked→continuous collapse,proving that mois-ture determines collapse patterns.Analyzing collapse modes and gravitational potential energy loss revealed that 6％moisture maximizes liquid-induced cohesion.This identifies an optimal moisture range for stability,offering key insights into wet granu-lar mechanics.A novel centroid displacement vector ratio was proposed to quantify energy conversion and liquid effects.Mois-ture not only alters the energy dissipation rates but also significantly affects the displacement ratio between wet and dry granular columns,with its influence inversely correlated to both the initial aspect ratio and particle diameter.

Abstract:Objective Food spoilage is a significant cause of food waste.To address this issue,the study designs a quartz crystal microbal-ance(QCM)sensor using a MXene-reduced graphene oxide(MXene-rGO)composite as the sensitive film.This sensor is employed to detect ammonia gas released during food spoilage,facilitating the monitoring of food spoilage levels. Methods A MXene-rGO solution was synthesized by mixing the prepared MXene solution with rGO.Scanning electron micros-copy(SEM)was employed to characterize the surface morphology of the composite material.Subsequently,a QCM experimen-tal setup was established to systematically investigate the sensor's dynamic response characteristics,linearity,sensitivity,stabil-ity,repeatability,and selectivity toward ammonia gas.Finally,experiments were conducted to validate the sensor's applicabil-ity for food spoilage detection. Results and Discussion In dynamic response tests,QCM sensors modified with MXene,rGO,and MXene-rGO were sequen-tially exposed to ammonia concentrations of 1×10-6,5×10-6,1×10-5,2×10-5,5×10-5,and 7×10-5,with air used as a reference environment.Among the three,the MXene-rGO modified QCM sensor exhibited the largest frequency shift at all concentra-tions,indicating superior sensing performance.Its frequency responses reached 18.336,59.692,78.36,107.856,252.174,and 343.992 Hz at respective ammonia concentrations.Linear fitting of the sensor output showed that the MXene-rGO modified QCM sensor exhibited the steepest linear regression slope,demonstrating excellent sensitivity.For the repeatability analysis,the MXene-rGO modified QCM sensor was tested for its response characteristics to 2×10-5 ammonia gas under room-temperature conditions.The frequency shift remained consistent across multiple repeated cycles,indicating good repeatability.Long-term stability testing conducted at ammonia concentrations of 1×105,2×10-5,and 5×10-5 over one month further confirmed its excel-lent stability.Overall,the experimental results validate the superior performance of the MXene-rGO modified QCM sensor in ammonia gas sensing applications,highlighting its potential for practical application in food spoilage monitoring systems. Conclusion This paper presents a novel ammonia gas sensor designed for monitoring food spoilage levels,employing MXene-rGO composite as the sensitive film.The sensor exhibits excellent capability in detecting ammonia gas,with a frequency shift of up to 252.174 Hz at 5×10-5 ammonia.Additionally,it demonstrates good stability and repeatability.These findings highlight its strong practical value,offering a promising sensing technology for detecting gases associated with food spoilage.

Abstract:Objective To fabricate high-performance silicon nitride(Si3N4)ceramics and enhance their application potential under high-temperature and high-thermal-load conditions,this study investigated the effects of in-situ loaded rare earth ytterbium(Yb)on the sintering behavior and final properties of Si3N4 ceramics.By introducing rare earth modification,the aim is to optimize the ceramic's microstructure and significantly enhance its thermal conductivity to meet the urgent demand for high-thermal-conductivity ceramic materials in fields such as electronic packaging and heat dissipation substrates. Methods Rare earth metal Yb was dissolved in liquid ammonia,utilizing its coordination with ammonia molecules to form an active precursor,and then coated onto the surface of Si3N4 powder via a dissolution-precipitation mechanism.After subsequent heat treatment in an inert atmosphere,YbN@Si3N4 core-shell structured powder was obtained,and this powder was subjected to hot-press sintering.The morphology and elemental distribution of the Yb-loaded Si3N4 powder were analyzed.The effects of the Yb loading content on the relative density,phase composition,microstructure,and thermal conductivity of the Si3N4 ceramics was investigated. Results and Discussion High-performance Si3N4 ceramics were successfully produced through hot-press sintering.As the mass fraction of metallic Yb increased,the density of Si3N4 ceramics showed an upward trend,while the relative density gradually decreased.The grain size of β-Si3N4 initially increased with higher Yb content but subsequently stabilized.After heat treatment at 1 850 ℃ for 5 hours,the thermal conductivity of Si3N4 ceramics was significantly improved,increasing from 36.8 W/(m·K)to 66.8 W/(m·K),representing an 82％enhancement.During this process,the loaded metallic Yb was transformed into ytter-bium nitride(YbN),which preferentially reacted with the inherent SiO2 on the surface of Si3N4 powder.This reaction increased the nitrogen-to-oxygen ratio in the sintering liquid phase and reduced the oxygen content in the Si3N4 lattice.Consequently,the thermal conductivity of the Si3N4 ceramics was improved. Conclusion In a liquid ammonia medium,rare-earth Yb,characterized by its high oxygen affinity,was in-situ loaded onto the surface of Si3N4 powder as a sintering aid.This approach not only optimized the properties of the sintering liquid phase and promoted densification and grain growth,but more critically,reduced the oxygen content in the lattice of the Si3N4 ceramics,fundamentally improving their thermal conductivity.The study provides a new strategy for fabricating high-thermal-conductivity Si3N4 ceramics.

Abstract:Significance Nanozymes,nanomaterials with intrinsic enzyme-like activities,have emerged as promising alternatives to natural enzymes due to their superior stability,tunable activity,and cost-effective synthesis.Their multifunctional nature makes them attractive for diverse applications,including biomedicine,biosensing,and environmental remediation.Among the strategies developed to enhance nanozyme performance,nitrogen regulation has shown remarkable potential.The incorporation of nitrogen in the form of vacancies,dopants,coordination structures,or nitride compounds significantly modulates the catalytic microenvi-ronment and active sites of nanozymes,thereby improving catalytic efficiency,selectivity,and stability. Progress Recent studies have revealed that nitrogen incorporation can precisely tailor the electronic structure and surface prop-erties of nanozymes,leading to enhanced activity and substrate specificity.Nitrogen vacancies introduce defect sites that can serve as catalytic centers,while nitrogen doping alters the electron density around metal or non-metal atoms,optimizing redox potential.Nitrogen coordination with metal centers offers a stable and tunable coordination environment,and metal nitrides have shown exceptional peroxidase-and oxidase-like activities due to their high conductivity and chemical stability.Moreover,the advent of single-atom nanozymes has further advanced nanozyme design,enabling atomic-level precision in active site engineer-ing.Computational tools,including density functional theory(DFT)and machine learning algorithms,are increasingly being employed to predict optimal nitrogen configurations and guide experimental efforts.These advances have driven notable applica-tions in tumor therapy,antibacterial treatment,pollutant degradation,and ultrasensitive biomolecule detection. Conclusions and Prospects Nitrogen regulation offers a versatile and powerful approach for engineering high-performance nano-zymes.By precisely tuning the chemical environment and active-site architecture,nitrogen-regulated nanozymes exhibit enhanced catalytic behaviors that often surpass those of natural enzymes.For further advancement,several key directions war-rant further exploration.First,the fundamental mechanisms of nitrogen regulation should be elucidated through advanced in situ characterization and theoretical modeling.Second,synergistic systems that combine nitrogen regulation with other strategies,such as defect engineering and hybridization,should be designed.Third,comprehensive evaluations of biosafety and long-term stability in biological and environmental systems are essential.Fourth,novel applications in immunotherapy,smart diagnostics,and sustainable catalysis should be explored.Integrating interdisciplinary approaches,particularly machine learning-guided synthesis and high-throughput screening,will be essential for accelerating the rational design of next-generation nanozymes.Continued advancements in nitrogen-regulated nanozymes are expected to drive the development of intelligent catalytic systems and expand their impact across various scientific and technological domains.

Abstract:Objective As one of the powder preparation methods,the spray drying method offers advantages such as simple operation and high production efficiency.This study is conducted to improve the preparation efficiency of porous silica(SiO2)microspheres and achieve their large-scale production. Methods The spherical and branched silica sols were passed through a cation exchange resin to remove alkali metal ions,ren-dering the treated silica sols acidic(pH=2～3).Based on the principles of the spray drying technique,the process parameters were set as follows:drying temperature 150 ℃,atomization pressure 0.2 MPa,and feed rate 20 mL/min.After parameter adjustment,the fan,heater,and air compressor were turned on in sequence.Once the temperature reached 150 ℃,the peristal-tic pump was switched on to deliver the silica sol into the spray dryer at the preset flow rate.The silica sol was atomized into fine droplets through the atomizer nozzle,which rapidly lost moisture upon contact with hot air in the drying chamber,forming solid SiO2 particles(porous SiO2 microspheres).The dried powder product was collected after passing through the cyclone separator.The morphology and particle size distribution of the microspheres after spray drying were observed via optical microscopy.Their morphology was further examined by scanning electron microscopy(SEM).The specific surface area,average pore size,and pore volume were measured using the Brunauer-Emmett-Teller(BET)method. Results and Discussion After spray drying spherical silica sol,the resulting porous SiO2 microspheres exhibited defects such as collapse and fracture,and the severity of these defects increased with larger particle sizes of the spherical silica sol.In contrast,short-branched silica sol yielded microspheres with excellent sphericity,with the highest specific surface area reaching up to 789.51 m2·g-1 and a pore size distribution ranging from 1 to 10 nm.Using short-branched silica sol as a reinforcing agent could improve the sphericity of porous SiO2 microspheres obtained from spray-dried long-branched silica sol.By adjusting the dosage of short-branched silica sol,the specific surface area,pore size,and pore size distribution of the microspheres could be effec-tively controlled. Conclusion For the pressure spray drying processes,the branched silica sol exhibited a higher spherization rate than the spheri-cal silica sol.Porous SiO2 microspheres produced with branched silica sol as the raw material showed a larger specific surface area and a narrower pore size distribution.Short-branched silica sol with smaller diameters produced porous SiO2 microspheres of good sphericity,large specific surface area,and narrow pore size distribution after spray drying.In contrast,long-branched silica sol with larger diameters tended to form porous SiO2 microspheres that were prone to fracture and incomplete structures.Through blending with smaller-diameter short-branched silica sol,the spherization rate could be improved,while the specific surface area and pore size of the porous SiO2 microspheres could be tuned.

Abstract:Objective The performance stability of granular material is a critical factor influencing its service.To achieve quantitative analy-sis and evaluation of the mixing uniformity of mixture components under vertical vibration conditions,and to address the limita-tions of traditional zone-division evaluation methods,including their susceptibility to gradation segregation and strong subjectiv-ity,a quantitative evaluation method for mixture uniformity is proposed based on two dimensions:the continuity and dispersity of particle distribution. Methods The segregation degree of a specific aggregate fraction in a mixture can be characterized from two dimensions.First,it relates tothe rationality of interparticle spacing,which reflects whether particles within that size range exhibit a uniform and con-tinuous spatial distribution in the mixture.Second,it concernsthe sufficiency of dispersion,which is the extent and severity of local agglomeration for that aggregate fraction.Based on these two dimensions,corresponding quantitative segregation evalua-tion indicators for each aggregatefractionweredevelopedusing spatial location information,ultimately enablinga comprehensive evaluation of the overall segregation degree of the mixture.Initially,the three-dimensional spatial distribution of particles was investigated,and the minimum particle number threshold for clusteringwas determined,typically set as twice the spatial dimen-sion(i.e.,6 for three-dimensional space).By treating the DBSCAN search radius ε as a variable parameter,a functional rela-tionship between ε and the number of clusters was established.The differences between the non-uniform state and the ideal uni-form state(where the number of clusters was always 1)were quantified using a definite integral.On this basis,the self-uniformity degree index(IS)was proposed.Large-scale numerical experiments were conducted to validate the correlation between IS and particle distribution uniformity.Three-dimensional point sets were randomly generated within a unit cube,and the IS values for each set of 100 points were calculated.The process wasrepeated 10 000 times.The results were consistent with natural distribution characteristics,confirming a linear relationship between IS and particle distribution uniformity.Subse-quently,the triangular mesh method was used to construct surface contour models for single-grade aggregates and the overall mixture,and their volumes were calculated.The surface contour volume ratio(IV)was defined as the ratio of the surface contour volume of a single-grade aggregate volume to that of the total mixture volume.When evaluating mixture uniformity,considering the significant impact of particles with larger mass fractions on the overall performance of the mixture,the uniformity degree index(IU)was calculated as a comprehensive evaluation indicator by integrating IS and IV based on the mass-weighting prin-ciple.Finally,the simulation model was validated through vertical vibration segregation tests. Results and Discussion Simulation results conducted using the EDEM softwaredemonstrated that traditional evaluation meth-ods,such as those based on fractal dimension analysis,could not fully characterize particle uniformity.Moreover,these methods relied on grid partitioning to assess the spatial distribution of aggregates,where determining an appropriate grid size is challeng-ing and the evaluation results aresensitive to both grid configuration and positioning.As aresult,such methods often failed to accurately reflect the actual distribution state of particles.To address these issues,the uniformity evaluation method proposed in this study,based on IS,IV,and IU,did not depend on grid partitioning during computation.It objectively characterized the true distribution characteristics of particles from the perspectives of continuity and dispersion,thereby offering better universality and applicability formixtures with arbitrary shapes.In a simulation of particle layer paving underhorizontal vibration mixing condi-tions,particles of the same type were stacked in cubes at equal spacing intervals.Under these conditions,the IS value consis-tently equaled 1,indicating no spatial overlap between particles.However,when the spacing between particles changed,the IV value deviated from 1 and varied accordingly.The calculated IU value reached 0.91,which was very close to 1,demonstrating that this method provided a reasonable evaluation of the gradation uniformity of uniformly distributed mixtures.Additionally,comparisons with experimental data from vertical vibration segregation tests under the same conditions showed high consistency with the simulation results.This confirmed that the particle segregation evaluation indices established in this study reliably reflectactual segregation behavior. Conclusion IS,developed based on the DBSCAN clustering algorithm,effectively evaluates the continuity of particle distribu-tion.IV quantitatively characterizes the dispersion degree of single-grade particles through the external contour volume ratio.IU,obtained through mass-weighted integration of IS and IV,accurately reflects the overall uniformity of the mixture.However,it should be noted that this method only considers the influence of volume during particle mixing,and factors such as particle den-sity differences and interparticle interaction effects are not included in the weighting of index calculations.

Abstract:Objective To reduce the erosion wear of the moving blades of flue gas turbines caused by catalyst particles in the inlet flue gas stream of refinery catalytic cracking units,enhance the operational stability and reliability of flue gas turbines,and avoid equip-ment shutdowns for maintenance,it is essential to achieve effective prevention and control of erosion wear in moving blades. Methods In this study,a single-moving blade of a flue gas turbine was taken as the research object.An experimental model of the blade was established using white light-cured acrylic resin,and black,yellow,and green resin paints were applied to visually identify the erosion areas on the blade surface.Silicon carbide(SiC)particles were used to simulate catalyst particles,and a cold-flow erosion experimental setup was established.The effects of air flow rate,catalyst particle volume concentration,and catalyst particle size in the test pipeline on the erosion areas of a single-moving blade were studied.The mass loss rate was used as an evaluation metric for the degree of erosion experienced by the blade,and the entropy evaluation method(EEM)was adopted to determine the weight values of the influence of air flow rate,air velocity,and catalyst particle size in the test pipeline on erosion degree of the single-moving blade. Results and Discussion The erosion areas of the single-moving blade were primarily concentrated on the pressure surface.The erosion area and the degree of erosion exhibited progressive changes as erosion time,air flow rate,catalyst particle volume con-centration,and particle size increased.The erosion area expanded from the blade tip to the root along the blade height direction and from the leading edge to the trailing edge along the chord direction.The leading edge wore out first,with the erosion area initially appearing black,then gray,and finally white as it spread from the upper part to the blade root along the blade height direction,indicating the most severe erosion.The wear at the blade tip occurred slightly later compared to the leading edge,with the erosion degree gradually decreasing from the leading edge to the trailing edge along the chord direction,transitioning from a mixed yellow-green color to black and then gray,reflecting relatively severe erosion.The trailing edge wore out later than the tip,with the erosion area spreading gradually from the upper part to the middle part along the blade height direction,displaying a mixed yellow-green-black color,indicating the mildest erosion.The mass loss fraction of the single-moving blade caused by SiC particles increased with elevated air flow rate,particle volume concentration,and particle size.When SiC particles had a median particle size(D50)of 275 μm and an air flow rate of 1 600 m3/h,the maximum mass loss fraction reached 4.6 mg/g.At a particle volume concentration of 80 g/m3 and D50 of 188 μm,the mass loss fraction peaked at 3.8 mg/g.When the SiC particle volume concentration was 80 g/m3 and the particle size in the test pipeline was 600 μm,the maximum mass loss fraction reached 6.4 mg/g.The weight values of air flow rate,particle volume concentration,and particle size in the test pipeline were 31.4％,25％,and 43.6％,respectively.The particle size exhibited the highest weight value,while the particle volume concentration had the lowest,indicating that particle size had the greatest influence on the mass loss fraction of the single moving blade,whereas particle volume concentration had the least influence. Conclusion The erosion areas and the degree of erosion collectively reflect the erosion characteristics caused by catalyst particle sizes on the single-moving blade.Analyzing the erosion characteristics of catalyst particles on the single-moving blade of a flue gas turbine and their influencing factors provides critical insights for enhancing turbine's operational stability and service life.

Abstract:Objective Titanium alloys are widely used in critical load-bearing components and engine structures in aerospace due to their excellent mechanical properties,such as high specific strength,good creep resistance,and wear resistance.With the development of aviation and military industries,the new generation of supersonic aircraft has attracted significant attention due to its increased flight speeds.The acceleration process of the aircraft imposes stringent requirements on both engine thrust and thrust-to-weight ratios,inevitably resulting in a rise in the engines' operating temperature.Therefore,developing titanium alloys with exceptional high-temperature resistance is crucial to meet the needs of high-performance aero-engines.The incorporation of hard strengthen-ing phases,such as B4C,TiC,SiC,TiB,and Ti5Si3,which possess high strength,superior high-temperature resistance,and good wear resistance,is one of the effective approaches to enhance the high-temperature mechanical properties of titanium alloys.Laser powder deposition(LPD)is a new type of metal additive manufacturing technology,characterized by its ability to directly prepare complex metal components with excellent mechanical properties and high density.In this process,metal parts are manu-factured layer by layer based on a solid three-dimensional model.The metal powder is initially melted by a high-energy density laser onto a metal substrate,forming a molten pool,which is then cooled and solidified.This process is repeated with preset mod-els and parameters until a complete three-dimensional component is formed.LPD has introduced a new technique for the prepara-tion and forming of metal parts,such as titanium matrix composites,addressing challenges in manufacturing difficult-to-produce metal parts for aerospace and other fields.However,at present,the microstructure and high-temperature strengthening mecha-nisms of titanium matrix composites prepared by LPD still remain unclear.Therefore,it is necessary to explore how the reinforc-ing phases influence the microstructure and high-temperature mechanical properties of these composites. Methods B4C-TA15 composites prepared by LPD were studied and compared with TA 15 alloys to clarify the complex relation-ship between microstructure and high-temperature mechanical properties.Firstly,B4C-TA15 composites with suitable shapes were prepared using a mixture of B4C and TA 15 powders under appropriate parameters through the LPD process.Subsequently,the morphology,grain structure,and interface bonding of the composites were assessed using microstructure characterization methods to explore their microstructural evolution.The tensile properties of the experimental samples were tested at 600 ℃ to evaluate their high-temperature performance.Finally,the strengthening mechanisms of the composites prepared by LPD were investigated by establishing correlations between microstructure and high-temperature mechanical properties. Results and Discussion According to the experimental results,a composite material with TiB and TiC reinforcing phases non-uniformly distributed within the TA 15 matrix was successfully synthesized through low-energy ball milling and the LPD process,with a B4C content of 3％.The incorporation of TiB and TiC hard reinforcing phases in the B4C-TA15 composites significantly changed the grain morphology and size of the titanium matrix,transitioning from slender,plate-like grains to near-equiaxial,square grains.The grain size of the B4C-TA15 composites was significantly reduced compared to that of the TA 15 alloys.Addi-tionally,the TiB and TiC phases were well bonded to the TA15 matrix,creating a clean and smooth bonding interface,showing a good strengthening effect.The B4C-TA15 composites demonstrated excellent high-temperature strength while maintaining good toughness and plasticity.Specifically,the tensile strength of the TA15 titanium alloy at 600 ℃ was measured at 653 MPa,whereas the B4C-TA15 composite was 803 MPa at the same temperature,marking a 22.97％increase compared to the TA 15 alloy under the same tensile conditions. Conclusion The TiB and TiC reinforcements in the B4C-TA15 composites exhibit a non-uniform distribution,resulting in a het-erogeneous structure characterized by regions with rich and poor reinforcements.In regions with poor reinforcements,the disloca-tion slip generated by the matrix is effectively impeded by the regions with rich reinforcing phases,leading to a significant"dislo-cation pinning"effect.This effect induces stress concentration,thereby enhancing the material's strength.The primary high-tem-perature strengthening mechanisms of B4C-TA15 include bearing and dislocation strengthening of in-situ formed TiB and TiC,along with fine grain strengthening facilitated by reinforcing phases.In addition,TiB and TiC reinforcements increase the service temperature of the material,inhibiting softening of the titanium matrix at high temperatures,and significantly improving the high-temperature mechanical properties of the composites.

Abstract:Objective In recent years,with the rapid development of electronic devices toward higher integration and miniaturization,the demand for efficient thermal management has increased significantly,making effective heat dissipation one of the primary research directions.Hexagonal boron nitride nanosheets(BNNSs),owing to their excellent thermal conductivity and electrical insulation properties,are ideal thermal management materials.However,current BNNS preparation techniques suffer from high costs,low yields,and considerable pollution.Therefore,developing a scalable BNNS production method for thermal manage-ment applications holds substantial practical significance. Methods A composite exfoliation method was employed.Under the synergistic effect of solid-phase(pretreatment)and liquid-phase exfoliation,high-yield BNNSs were prepared in an aqueous system with stearic acid(SA)-modified aluminum oxide(Al2O3)as a liquid-phase exfoliation additive.This process simultaneously produced the BNNSs-Al2O3-SA product(hereinafter referred to as BNNSs-Al2O3),which was then used as a composite filler and filled into epoxy resin(EP)to fabricate BNNSs-Al2O3-EP composites. Results and Discussion During the liquid-phase ball-milling exfoliation process,Al2O3 not only acted as an exfoliation additive by providing mechanical grinding but also exhibited excellent amphiphilicity due to SA modification.This enabled it to continu-ously attach onto the surfaces of newly exfoliated BNNSs,preventing repeated stacking of delaminated BN flakes and thereby sig-nificantly improving the exfoliation efficiency.Under optimized conditions(25％Al2O3-SA addition,particle size of 58.68 μm,ball-milling time of 5 h,and a ball-to-material ratio of 40:1),the prepared BNNSs achieved a yield of 17.2％,with an average lateral size of 320 nm and an average of 5 layers.Furthermore,when the filler addition reached 30％(mass fraction),the ther-mal conductivity of BNNSs-Al2O3-EP increased to 1.25 W·m-1·K-1,89％higher than Al2O3-EP,67％higher than hexagonal(h)-BN-EP,and 681％higher than pure EP. Conclusions The solid-liquid phase composite exfoliation method enables high-yield BNNSs production while avoiding post-treatment procedures and achieving effective BNNSs-Al2O3 integration.The resulting product could be directly used as a com-posite filler,synergistically enhancing the thermal conductivity of the EP matrix.This composite exfoliation method provides a novel,green,low-cost,and scalable approach for BNNSs fabrication.