Mechanical Analysis Research Articles

Interfacial Stress and Crack Propagation Experimental Study in Mini-LED Chip Debonding

The ultra-miniaturization trend of chips presents new challenges for non-destructive peeling-off techniques. This study models the mini-LED chip-UV film adhesive system as a micro laminated structure and conducts the interfacial stresses and crack propagation analysis of the structure using theoretical, finite element and experimental methods. The innovations of this paper are the illustration of the negligible effect of size effect on 125 μm x 75 μm x 60 μm chips, and the determination of the technology parameter tuning method to promote chip peeling-off. Firstly, applying the first-order shear deformation theory, and considering the UV-curable acrylic adhesive layer and the UV film as elastic materials, Lamé coefficients are introduced to explore the free vibration of the micro laminated structure. The analyses indicate that the scale effect has an extremely small impact, within 0.5%, on natural frequencies of the 100-micron scale laminated structure with a small length-to-thickness ratio. Thereafter, a three parameter elastic foundation (3-PEF) model of the chip-UV film adhesive structure is established and the interfacial stresses distributions are parametrically analyzed. Additionally, an experimental platform for needle-ejecting chip peeling-off is designed and constructed. Finite element simulation, experimental observations, and image recognition of crack generation and propagation during the peeling process were performed. Results show that cracks are generated at both free ends of the adhesive layer and progressively extended inwards. This is consistent with the 3-PEF analytical solution, in which the stress concentration also occurs at free ends of the adhesive layer. The agreement between theoretical, simulation and experimental results regarding interfacial stresses provides a solid foundation for further analysis of chip peeling-off mechanism.

Design and Analysis of a Large Tolerance Docking Mechanism

On-Orbit Servicing is increasingly crucial with the growing number of spacecraft. The foundation for On-orbit servicing is space docking mechanisms. As On-Orbit Servicing tasks become more complex, the demands for docking capture mechanisms increase in both function and performance. Therefore, it is crucial to design a docking mechanism with a large tolerance. Among various docking capture mechanisms, the multi-claw capture mechanism has the advantages of low impact and reliable capture. This paper analyzes the Common Berthing Mechanism and a docking mechanism with an underactuated two-degree-of-freedom claw-type capture mechanism as its core is proposed. Subsequently, this paper provided a detailed design of the mechanism based on the principle of underactuated capture. Furthermore, this article conducts numerical analyses of key mechanisms such as the capture mechanism and guide mechanism in the design process, verifying the functionality of the mechanisms. After completing the analysis of capturing dynamics, the tolerance ability of the mechanism was also verified, various key parameters were determined, and the parameters of components such as the torsion spring were also determined. Finally, the prototype of the proposed docking mechanism is developed, and the experiment is completed to validate its functional principle and tolerance capability.

Analysis of fracture mechanism and fracture energy prediction of lightweight aggregate concrete

The fracture energy of lightweight aggregate concrete (LWAC) is comparatively lower than that of normal weight concrete (NWC), primarily due to the propensity for fracture exhibited by lightweight aggregates and their characteristics that modify the damage softening mechanism at the crack tip. Few studies have been done on how to precisely predict the LWAC fracture energy. In this work, 111 sets of three-point bending test data were gathered, and the impact of aggregate types and size, concrete density, water-cement (w/c) ratio, and compressive strength on the total average fracture energy (GF) and the initial fracture energy (Gf) was thoroughly evaluated. Five fracture energy prediction methods’ applicability were compared, and a fracture energy prediction expression appropriate for LWAC was presented. Finally, the three-point bending test was used to confirm the prediction. The results show that the fracture energy of LWAC is significantly influenced by changes in aggregate and mortar characteristics. The compressive strength has substantial correlations with the fracture energy of LWAC. After adjusting the aggregate and mortar coefficients, the prediction formula can correctly predict Gf and GF.

Reduction mechanism and energy transfer between Eu3+ and Eu2+ in Eu-doped materials synthesized in air atmosphere

Abstract This article critically examines the reduction mechanisms and energy transfer processes between trivalent europium ions (Eu3+) and divalent europium ions (Eu2+) in materials synthesized in an air atmosphere. It also encompasses various materials and conditions, including a critical analysis of the reduction mechanism and energy transfer between Eu3+ and Eu2+ in Eu-doped materials. Specific investigations include exploring the reduction process in BaMgSiO4:Eu, focusing on factors influencing the reaction. The article also covers low-temperature self-reduction, addressing conditions and mechanisms such as the charge compensation model and laser-induced reduction. Additionally, it explores the influence of charge compensation on luminescent properties, emphasizing enhancements in red emission. Investigations into the role of oxygen vacancies in the reduction of Eu3+ and their implications on material properties are presented. This article further digs into abnormal reduction processes and the formation of defect centers in Eu3+-doped pollucite, proposing a substitution defect model for the self-reduction of europium ions in silicate Ba(Eu)MgSiO4 phosphors. Unusual reduction phenomena, such as reduction via boiling water in Yb2Si2O7:Eu3+ phosphors, and reductions in various glass systems, including porous glass, ZnO–B2O3–P2O5 glasses, aluminoborosilicate glasses, europium-doped Li2B4O7 glass, and aluminosilicate oxyfluoride glass (AOG), are also thoroughly examined.

Analysis of deformation mechanism of rainfall-induced landslide in the Three Gorges Reservoir Area: Piansongshu landslide

The Three Gorges Reservoir Area (TGRA) is characterized by unique geological features that increase its susceptibility to landslides. These slopes are especially prone to destabilization when influenced by external triggers like rainfall. This research focuses on the Piansongshu landslide within the TGRA, aiming at unraveling the complex internal deformation mechanisms of landslides triggered by rainfall and providing critical insights for their prevention and mitigation. The study begins with on-site geological surveys to meticulously examine the macroscopic signs and mechanisms of deformation. It then utilizes the GeoStudio numerical simulation software to assess the landslide's stability, focusing on the changes in internal seepage fields and stability under various rainfall scenarios. Results indicate that continuous rainfall leads to the formation of a temporary saturation zone on the slope, which gradually deepens. In regions with more pronounced deformation, the infiltration line at the leading edge of accumulation notably protrudes towards the surface. Notably, the stability coefficient of the secondary shear surface of the landslide fluctuates more significantly than that of the primary sliding surface. Higher rainfall intensity and longer duration are positively correlated with a more pronounced decrease in stability coefficients. The impact on stability also varies across different rainfall patterns. As rainfall infiltrates over time, the slope's safety factor gradually decreases. This reduction continues even post-rainfall, indicating a delayed restoration period before stability returns to a safe level. These results yield valuable data for forecasting and mitigating landslides.

Study on the mechanism of energy evolution and bearing degradation in pre-cracked sandstone under non uniform cyclic loading

The engineering rock mass is affected by the original cracks, which increases the uncertainty of instability and failure mechanisms. Under the action of excavation unloading or other disturbance loads, its bearing properties are more complex and the deformation characteristics is more special, which has always been a difficult issue in the analysis of rock mechanics. In order to explore the propagation and failure mechanism of spatial micro cracks in fractured rock masses, acoustic emission (AE) experiment of sandstone was carried out under pre-static loading and low-frequency stepwise cyclic loading–unloading. The research results indicate that the peak strain and crack initiation stress of rocks with different pre-cracked positions have the highest differences of 12.62% and 18.65%, respectively. The difference between peak stress and crack initiation strain is within 4%. The pre-cracked position mainly affects the peak strain and crack initiation stress of pre-cracked rocks, and its effect on peak stress and crack initiation strain is limited. The crack initiation angle of prefabricated cracks is mainly distributed within the range of 45° − 90°, and it decreases with the increase of quantities of prefabricated cracks. The crack initiation angle of rocks with prefabricated three cracks is 30% lower than that of single crack. The research results have deepened the analysis of energy evolution and deformation damage of fractured rock masses.

A multiscale bifurcation analysis using micromechanical-based constitutive tensor for granular material

The current study presents a multiscale approach that investigates material instability and localization phenomena in plastic granular materials and the discrete-continuum duality. A bifurcation and stability analysis in continuum mechanics usually requires the material’s tangent (stiffness) operator, the computation of which in a micromechanical approach such as Discrete Element Modeling (DEM) requires specific treatment. To bridge the discrete and continuum worlds, a new computational approach incorporating strain probing is proposed to reconstruct the elastoplastic constitutive tensor and its spectral characteristics from DEM simulations. The probing technique permits the computation of the tangent operator that inherits microstructural information from the discrete world to analyze bifurcation in elastoplasticity at the macro level. An incrementally linear constitutive tensor is computed, distinct for each of the ensemble of probing directions belonging to a particular tensorial zone or sector of incremental stress or strain space, thus making it directionally non-linear. Following such an approach, material instability can be evaluated from the spectral characteristics of the tangent constitutive tensor deduced from DEM probing calculations belonging to an identified tensorial zone. A meso-scale analysis is finally offered to detect shear band localization through the well-known Rice’s criterion as a continuum-based concept extended to a micromechanical discrete modeling framework. These new numerical results show that the multiscale proposed approach, which allows access to microstructural information, is consistent with a continuum one such as when predicting the localization angle during shear banding in a granular specimen in DEM.

Synergistic effects of fluorine plasma on improving carbon aerogel anodes performance in lithium-ion batteries

In this study, CF4 plasma was used to increase the lithium-ion storage performance of carbon aerogels. We confirmed the impacts of the fluorine plasma on the chemical and structural properties of F-doped carbon aerogels. Analyses of various battery performances revealed significant enhancements in the specific discharge capacities, rate performances, and cycling stabilities. These enhancements were attributed to a synergistic effect of F-doping and increased specific surface areas caused by the fluorine plasma. The increased capacities arose from plasma-induced increases in the specific surface areas, facilitating greater lithium-ion adsorption. Faster rate performances were achieved through increased conductivities due to the formation of semi-ionic C–F bonds and optimized pore structures that increased electrolyte permeability. The superior cycling stability was attributed to the stable LiF-based SEI layer generated by semi-ionic C-F bonds. These findings were confirmed by analyses of the lithium-ion storage mechanism and the postcycling SEI layers. These results showed that the F-doped carbon aerogel anodes prepared with the plasma treatments had higher discharge capacities, faster rate performances, and higher stabilities due to the synergistic effect of F-doping and etching.

Serum untargeted metabolomics analysis of the preventive mechanism of TAETEA Prebiotea on non-alcoholic fatty liver in rats

Pu-erh tea belongs to the six tea categories of black tea, according to the processing technology and quality characteristics, is divided into two types of raw tea and ripe tea. Raw tea is made from fresh leaves of tea as raw materials, through the process of greening, kneading, sun drying, steam molding and other processes made of tightly pressed tea. Ripe tea is made from Yunnan large-leafed sun green tea, using a specific process, post-fermentation (rapid post-fermentation or slow post-fermentation) processing of loose tea and tightly pressed tea. TAETEA Prebiotea is Puerh Ripe Tea, TAETEA Prebiotea has the effect of increasing insulin level and improving hyperglycemia in mice, and it also has the effect of regulating blood lipids, which can reduce the level of serum total cholesterol (TC) and triglycerides (TG), increase the level of high-density lipoprotein cholesterol (HDL-C), and improve the metabolism of lipids. Therefore, further experiments were conducted by us, and TAETEA Prebiotea was formulated into a suitable dose for the intervention of non alcoholic fatty liver disease (NAFLD) model rats, and at the end of the experiments, the samples of each group of experiments were analyzed and detected by the method of UHPLC-Q-Exactive LC-MS liquid-mass spectrometry methodology, and the relevant metabolites as well as metabolic pathways were analyzed by the method of Non targeted metabolomics analysis. As a result, 71 differential metabolites could be screened, of which 35 differential metabolites were up-regulated after intervention and 36 differential metabolites were down-regulated after intervention. Based on the KEGG pathway enrichment and Pathway Impact bubble diagram analysis, glycine, serine, threonine metabolism, arginine and proline metabolism, protein digestion and absorption, and central carbon metabolism in cancer may be the main metabolic pathways in which TAETEA Prebiotea exerted preventive effects on NAFLD rats, C00148 (Proline), C00300 (Creatine) and C00719 (Betaine) are the differential metabolites that play important regulatory roles.

Assessment of damage sequence in additive manufactured composite laminates under quasi-static out-of-plane loading

The understanding of the impact behaviour of additive manufactured continuous fibre reinforced polymers must start from the analysis of the damage mechanisms. In this investigation, the impact damage in a 3D-printed continuous carbon fibre reinforced polymer is studied by means of quasi-static indentation tests. The coupons are manufactured with Fused Filament Fabrication (FFF) using a thermoplastic resin. Three indentation displacement levels were tested, analysing different phases of the impact using X-ray Computed Tomography. The effects of fibre orientation were considered, establishing a comparison between one laminate with conventional orientations (0, 90, ±45) and one with disperse orientations. Results show a progressive damage generation influenced by the inherent defects of the manufacturing process, characterized by delamination growth and stiffness reduction. Fibre and matrix breakage only appear at the final stages when the laminate peak load is reached. The considered dispersed laminate shows less delaminated interfaces compared to the conventional one.

Photocatalytic defluorination of ciprofloxacin by nitrogen-defected g-C3N4 under simulated sunlight: Mechanistic insight and pathway analysis

The photocatalytic degradation of ciprofloxacin (CIP) has been widely reported to be induced by ring cleavage and defluorination. However, the role of photo-generated reactive radicals, especially electrons, in defluorination remains controversial. This study investigates the effects of reactive radicals such as hydroxyl radicals (·OH) and electrons on CIP degradation and defluorination in photocatalytic processes by nitrogen-defected g-C3N4. Almost complete CIP degradation and 46.5 % defluorination were obtained under the best conditions tested. Scavenging tests, degradation intermediate product identification, and theoretical calculations were performed to explore the reaction routes driven by ·OH and electrons in depth. Scavenging tests revealed that ·OH and electrons were predominantly responsible for direct CIP defluorination, whereas electrons played an indirect role as critical intermediates for the formation of ·OH. Time-dependent intermediate evolution analysis demonstrated that CIP degradation mainly occurred by piperazine ring cleavage and defluorination. Density functional theory (DFT) calculations based on the Hirschfeld charge, Fukui index and electrostatic potential confirmed that zwitterionic CIP+- is more reactive than CIP+ and that the piperazine ring in CIP is susceptible to nucleophilic and radical attacks by ·O2– and ·OH. Finally, electron-assisted ·OH substitution and C-F bond cleavage were proposed as the main mechanisms for CIP defluorination. This study provides a thorough understanding of CIP defluorination mechanisms by nitrogen-defected g-C3N4-based photocatalysis.

Multiscale residual stress and mechanical behavior analysis in machining of Ti-6Al-4V alloy with advanced microscopic characterization

Machining of polycrystalline metal materials results in metallurgical modifications in the machined surface, and it can introduce multiscale residual stresses (macroscale and microscale residual stress), which may be detrimental to the mechanical properties thereby interfering with the service performance of machined parts. However, most of the current studies only focus on the macroscale residual stress, the microscale residual stresses have always been neglected since the limitations of the commonly used techniques for residual stress measurement in machined surfaces. In this study, the recently developed Focused Ion Beam-digital image correlation (FIB-DIC) ring core method was employed to evaluate the time-resolved strain relaxation and multiscale residual stress of the machined surface under different cutting conditions. The quantitative evaluation of residual stress and microstructural effects on hardness of the machined surface was conducted by combining with FIB incremental milling and nanoindentation technique. It has been observed that although the global tensile strain relaxation was captured in the ring-core region, local microscale compressive strain relaxation also occurred. The hardness of the machined surface was determined by the combined effects of microstructure and residual stress induced by machining. Specifically, the grain refinement and compressive residual stress contributed to hardening, while tensile residual stress resulted in softening of the machined surface. Furthermore, it was also observed the hardening/softening effects were enhanced with increasing intensity of tension and compression.

Glass–Carbon–Kevlar fiber reinforced hybrid polymer composite (HPC): Part (A) mechanical and thermal characterization for high GSM laminates

The quest for light weight hybrid polymer composites (HPC) has resulted into multiple materials and structural configurations for achieving high performance in automotive and aerospace applications. Incidentally, the past reported work has (in general) involved variable GSM while investigating reinforced fiber layers. The variable GSM may lead to a random response of each layer to the applied forces and thermal degradation, due to which attributing the role of various layers to results/properties is difficult to ascertain. This research employs a uniform/consistent approach with high GSM (400) based HPC with multiple stacking sequences of glass (G), carbon (C), and Kevlar (K) to investigate thermo-mechanical properties. The research first focuses on fabrication of eleven stacking sequences of hybrid combinations, followed by identification of an optimal sequence based on mechanical (tensile strength, flexural strength, charpy impact resistance) and thermogravimetric analysis (TGA) characterization. Additionally, scanning electron microscopy (SEM) for fracture mechanisms of hybrid composites showing fiber pull out, matrix crack, and delamination. Results show that the tertiary combination having 2 Glass, 5 Carbon and 5 Kevlar layers (G2C5K5) named H9 herein provides a good balance of tensile, flexural, impact resistance and thermal properties; its deviation from the best of each category is within approximately 5, 13.5, 9.9 and 10.9 % (for tensile, flexural, impact, TGA) respectively. The range of properties evaluated in this study is deemed suitable for lightweight aircraft structures.

Three-dimensional mechanical characteristics analysis of double-shoulder tool joint under complex loads

Taking a new type of special threaded drill pipe joint as the research object, a 3D nonlinear finite element model of the double-shoulder tool joint (DSJ) including the engage and retract groove structure is established by considering the factors of structural asymmetry and contact of each engaging surface. ABAQUS/Explicit finite element method (FEM) is used to study the stress and contact pressure distribution characteristics of the critical structure of DSJ under complex loads. The accuracy of the finite element model was verified by combining with the physical test, and the connection strength and sealing performance of DSJ are evaluated. The results show that the stress concentration occurs at the key structure of DSJ under the make-up torque. The geometry size and structural discontinuity at the transition fillet of the double-shoulder structure have a significant effect on the stress and contact pressure distribution on the shoulder. Under axial tension, the stress level and stress concentration area of the whole joint and the key structure change, especially in the thread section. The sealing performance on the shoulder decreases significant, while that of the thread section increases slightly. The test results are consistent with the finite element simulation results, and this joint shows good mechanical properties, which can meet the design requirements of drilling tool manufacturers and provide data support for its optimal design and application.

Piston structure design and finite element analysis

The working characteristics of internal combustion engines rely on the explosive combustion of fuel in the combustion chamber to drive the piston movement. This working characteristic causes the main component of the combustion chamber, the piston, to bear high thermal and mechanical loads. It has very high requirements for design, manufacturing, and material selection. The working condition of the piston will affect its safety and stability. Therefore, the finite element analysis for the piston is particularly important. Thus, this article first establishes the piston model and divides it into grids in ANSYS, adds boundary conditions, and conducts analysis. The piston thermal analysis mainly includes thermal stress and deformation analysis under thermal load. The piston’s maximal thermal stress is 170.23 MPa and the deformation of thermal expansion is 0.61585 mm. The mechanical stress and deformation analysis under mechanical load are carried out. The maximal stress is 164.91 MPa and the maximal deformation caused by the mechanical stress is 0.24916 mm. Finally, the coupling analysis of thermal and mechanical stress is conducted. The maximal stress is 251.74 MPa, which is located at the outskirt margin of the piston pinhole. The maximal deformation is 0.60779 mm. The simulation analysis results indicate that the method proposed in this article provides a way to design the structure of similar automotive components such as pistons.

A stability evaluation method for deep-seated toppling in the upper Lancang river, Southwestern China

Deep-seated toppling in the upper reaches of the Lancang River, southwest China involves deformations exceeding 100 m in depth. The slope deformation is initiated by river downcutting and evolves distinctive characteristics with a depth of river incision. In this study, we propose a system for evaluating the stability of deep-seated toppled slopes in different evolutionary stages. This system contains identification criteria for each evolutionary stage and provides the corresponding stability evaluation methods. Based on the mechanical and kinematic analysis of slope blocks, the specific stage of slope movement can be identified in the field through outcrop mapping, in situ tests, surface displacement monitoring, and adit and borehole explorations. The stability evaluation methods are established based on the limiting equilibrium theory and the strain compatibility between the undisturbed zone and the toppled zone. Finally, several sample slopes in different evolution stages have been investigated to verify the applicability and accuracy of the proposed stability evaluation system. The results indicate that intense tectonic activity and rapid river incision lead to a maximum principal stress ratio exceeding 10 near the slope surface, thus triggering widespread toppling deformations along the river valley. When considering the losses of joint cohesion during the further rotation process, the safety factor of the slope drops by 7%–28%. The self-stabilization of toppling deformation can be recognized by the layer symmetry configuration after the free rotation of the deflected layers. Intensely toppled rock blocks mainly suffer sliding failures beyond the layer symmetry condition. The factor of safety of the K73 rockslide decreased from 1.17 to 0.87 by considering the development of the potential sliding surface and the toe-saturated zone.

A novel method for predicting coarse aggregate particle size distribution based on segment anything model and machine learning

Particle size distribution (PSD) is an important index property of granular materials. The conventional mechanical sieve analysis for PSD determination is labor-intensive, time-consuming, and inefficient. With the development of computer vision, image-based gradation prediction methods gradually emerge. However, previous studies mainly focused on images where individual aggregate particles are separated from each other without overlapping (i.e., not densely packed together), thus limiting their applicability. This study proposed a novel framework to predict the PSD of densely packed coarse aggregate particles, which is based on visual foundation model and machine learning with appropriate feature engineering. First, the segment anything model, which is one of the visual foundation models, was used for the instance segmentation of the densely packed aggregate particles. Then, the feature engineering was implemented with the segmentation result. The major quantitative indicators related to particle sizes were extracted from each mask, such as the area, the diameter of minimum enclosing circle, and the major axes of the equivalent ellipse of particle contours. Subsequently, the cumulative distribution curves of these indicators were plotted, followed by the data sampling operation on these curves to generate the feature vectors. The artificial neural network (ANN) model was then trained for gradation prediction with each of the feature vectors and the data points extracted from PSD curves used as the inputs and data labels, respectively. The model-training dataset consisted of 8160 different sets of digitally generated particle samples with known PSDs. Finally, verification test results of additional five different groups of digital particle samples and real coarse aggregate samples with known PSDs show that the root mean squared error (RMSE) of predicted aggregate sizes is 1.79 mm and 1.86 mm for digital and real aggregate particle samples, respectively. Therefore, the efficacy and feasibility of the proposed method was validated in terms of predicting the PSD of densely packed coarse aggregates from two-dimensional image information. As compared to the Mask RCNN combined with empirical formula of which the RMSE values were 5.12 mm and 5.84 mm for digital and real aggregate particle samples, respectively, the proposed framework demonstrates improved particle segmentation applicability and better PSD prediction accuracy.

Novel magnetic N-doped biochar derived from sugarcane bagasse and red mud for effective adsorption of tetracycline hydrochloride

In this work, with sugarcane bagasse (SB) and red mud (RM) as raw materials, magnetic nitrogen (N)-doped biochar (MNSB) was synthesized by a facile one-pot pyrolysis method and then applied as an efficient adsorbent to remove tetracycline hydrochloride (TC-HCl) from wastewater. The results of SEM, EDS, VSM, BET, FT-IR, and XPS demonstrated that the synthesized MNSB adsorbent had a large specific surface area, excellent superparamagnetic properties, and rich mesopore pore structures. The batch adsorption experiments revealed that the TC-HCl could be removed 96.3% with the optimal adsorption conditions: MNSB dosage of 0.25g/L, initial pH of 6.58, TC-HCl initial concentration of 20mg/L, and adsorption temperature of 30oC. The analysis of adsorption kinetics and isotherms showed that the adsorption process was mainly controlled by chemisorption, and the theoretical maximum adsorption capacity of TC-HCl on MNSB was 143.9mg/g. Mechanistic analysis revealed that the excellent adsorption process of MNSB for TC-HCl was mainly contributed by pore filling, π–π interaction, hydrogen bonding, and electrostatic attraction. The recycling and settlement experiments demonstrated that MNSB had good stability and settleability. This study successfully opened new prospects that utilizing RM and SB to prepare a low-cost adsorbent to remove TC-HCl from water.

Experimental study on the retention of aerosol particles through concrete cracks under high Reynolds number flow

In the event of severe accidents in pressurized water reactor (PWR) nuclear power plants, the potential leakage of radioactive aerosols through containment cracks poses a considerable radioactive hazard to the public. Understanding aerosol transport and retention in cracks helps reduce the conservatism and uncertainty of radioactive hazard assessment. Concrete cracks are recognized as a pivotal pathway for the leakage of radioactive aerosols, and several researchers have undertaken experimental investigations concerning the aerosol transport and retention in concrete cracks. However, the majority of these studies have rather low gas flow Reynolds numbers. In this work, an experimental setup is built to study aerosol transport and retention in concrete cracks under high Reynolds number flow. The TiO2 aerosol with a mass median diameter of 1μm and two concrete crack specimens are used in experiments. The results of gas flow experiments indicate that the Reynolds number is capable of reaching 10547. Combining the flow experimental data and Suzuki’s formula, the equivalent heights of these two crack specimens are approximated as 303.67μm and 231.48μm. The experimental results indicate a notably high retention rate of aerosols, exceeding 0.8. Furthermore, under high Reynolds number flow, the retention rate varies over a relatively narrow range, with the larger the equivalent height of the crack resulting in a lower retention rate. The experimental results match well with the mechanistic analysis based on inertial deposition theory, demonstrating the rationality of the inertial deposition theory.

Radiation-induced preparation of nanoscale CoO@graphene oxide for activating peroxymonosulfate to degrade emerging organic pollutants

In this study, ionizing radiation was used to induce the in-situ formation of highly dispersed nanosized cobalt oxide on the surface of graphene oxide (R-Co-GO), which was highly effective for activating PMS to degrade sulfamethoxazole (SMX). R-Co-GO had the highest catalytic activity when 150 μL cobalt chloride hexahydrate solution was used in the precursor, and the pseudo first-order kinetic constant of SMX degradation was 0.07 min−1 with high mineralization efficiency (63.1 %) and high PMS utilization efficiency. The sulfate radicals and high-valent cobalt oxo were mainly responsible for SMX degradation. Mechanism analysis showed that cobalt active site dominated in PMS activation, which was responsible for the formation of sulfate radicals and high-valent cobalt oxo; while the carbon framework contributed to the formation of singlet oxygen. The R-Co-GO-150 had good catalytic activity and stability in five cycling experiments, in which SMX was completely degraded and the concentration of dissolved Co was below 0.1 mg/L. In addition, the R-Co-GO-150/PMS system could also degrade phenol, bisphenol A, atrazine and nitrobenzene effectively, confirming its wide applicability. This study provided a facile method to uniformly disperse the metal oxides on the surface of carbon materials, and an effective system for the removal of emerging organic pollutants from the actual wastewater.