Origin of the tribofilm from MoS_(2) nanoparticle oil additives: Dependence of oil film thickness on particle aggregation in rolling point contact

The lubrication effectiveness of MoS_(2) nanoparticles as an oil additive remains unclear,restricting its application in industry to reduce friction.The goal of this work was to explore the lubrication mechanism of MoS_(2) nanoparticles as an oil additive.In this study,the oil film thickness behaviors of MoS_(2) nanoparticles in poly-alpha olefin(PAO4)base oil,PAO4 with 3 wt%dispersant(polyisobutyleneamine succinimide,PIBS),and 0W20 engine oil were investigated using an elastohydrodynamic lubrication(EHL)testing machine.Following the EHL tests,the flow patterns around the contact area and the tribofilm covering rate on contact area were studied using optical microscopy to understand the lubrication mechanism.The results indicate that both the dispersant and nanoparticle aggregation significantly affected the oil film thickness.The expected oil film thickness increase in the case of 0.1 wt%MoS_(2) in PAO4 base oil was obtained,with an increase from 30 to 60 nm over 15 min at a velocity of 50 mm/s.Flow pattern analysis revealed the formation of particle aggregation on the rolling path when lubricated with 0.1 wt%MoS_(2),which is associated with a tribofilm coverage rate of 41.5%on the contact area.However,an oil film thickness increase and particle aggregation were not observed during the tests with 0.1 wt%MoS_(2) blended with 3 wt%PIBS as the dispersant in PAO4 base oil,and for 0.75 wt%MoS_(2) in 0W20 engine oil.The results suggest that nanoparticles responsible for tribofilm formation originated from aggregates,but not the well-dispersed nanoparticles in point contact.This understanding should aid the advancement of novel lubricant additive design.

Properties of coarse particles in suspended particulate matter of the North Yellow Sea during summer

Fine particles in seawater commonly form large porous aggregates. Aggregate density and settling velocity determine the behavior of this suspended particulate matter(SPM) within the water column.However, few studies of aggregate particles over a continental shelf have been undertaken. In our case study, properties of aggregate particles, including size and composition, over the continental shelf of the North Yellow Sea were investigated. During a scienti?c cruise in July 2016, in situ ef fective particle size distributions of SPM at 10 stations were measured, while temperature and turbidity measurements and samples of water were obtained from surface, middle, and bottom layers. Dispersed and inorganic particle size distributions were determined in the laboratory. The in situ SPM was divided into(1) small particles(<32 μm),(2) medium particles(32–256 μm) and(3) large particles(>256 μm). Large particles and medium particles dominated the total volume concentrations(VCs) of in situ SPM. After dispersion, the VCs of medium particles decreased to low values(<0.1 μL/L). The VCs of large particles in the surface and middle layers also decreased markedly, although they had higher peak values(0.1–1 μL/L). This suggests that almost all in situ medium particles and some large particles were aggregated, while other large particles were single particles. Correlation analysis showed that primary particles <32 μm in?uenced the formation of these aggregates. Microscopic examination revealed that these aggregates consisted of both organic and inorganic ?ne particles, while large particles were mucus-bound organic aggregates or individual plankton.The vertical distribution of coarser particles was clearly related to water strati?cation. Generally, medium aggregate particles were dominant in SPM of the bottom layer. A thermocline blocked resuspension of?ne material into upper layers, yielding low VCs of medium-sized aggregate particles in the surface layer.Abundant large biogenic particles were present in both surface and middle layers.

Soil Aggregation and Its Relationship with Organic Carbon of Purple Soils in the Sichuan Basin,China

The interaction of soil aggregate dynamics with soil organic carbon is complex with varied spatio-temporal processes in macro-and micro-aggregates. This paper is to determine the aggregation of soil aggregates in purple soils （Regosols in FAO Taxonomy or Entisols in USDA Taxonomy） for four types of land use, cropland [corn （Zea mays L.）], orchard （citrus）, forestland （bamboo or cypress）, and barren land （wild grass）, and to explore their relationship with soil organic carbon in the Sichuan basin of southwestern China. Procedures and methods, including manual dry sieving procedure, Yoder＇s wet sieving procedure, pyrophosphates solution method, and Kachisky method, are used to acquire dry, wet, and chemically stable aggregates, and microaggregates. Light and heavy fractions of soil organic carbon were separated using 2.0 g·mL^-1 HgI2-KI mixed solution. The loosely, stably, and tightly combined organic carbon in heavy fraction were separated by extraction with 0.1 M NaOH and 0.1 M NaOH-0.1M Na4P2O7 mixed solution （pH 13）. The results show that the contents of dry and wet macroaggregates 〉0.25 mm in diameter were 974.1 and 900.0 g·kg^-1 highest in red brown purple soils under forestland, while 889.6 and 350.6 g·kg^-1 lowest in dark purple soil and lowest in grey brown purple soils under cropland, respectively. The chemical stability of macroaggregates was lowest in grey brown purple soil with 8.47% under cropland, and highest in red brown purple soil with 69.34% under barren land. The content of microaggregates in dark purple soils was 587g·kg^-1 higher than brown purple soils, while 655g·kg^-1 in red brown purple soils was similar to grey brown purple soils （651g·kg^-1）. Cropland conditions, only 38.4% of organic carbon was of the combined form, and 61.6% of that existed in light fraction. Forestland conditions, 90.7% of organic carbon in red brown purple soil was complexed with minerals as a form of humic substances. The contents and stability of wet aggregates 〉 0.25 mm, contents and stability of chemically stable aggregates 〉0.25 mm, contents of microaggregates 〉 0.01 mm, contents of aggregated primary particle （d〈0.01 mm） and degree of primary particles （d 〈0.01 mm） aggregation were closely related to the concentrations of total soil organic carbon, and loosely and tightly combined organic carbon in heavy fraction. Soil microaggregation could be associated with organic carbon concentration and its combined forms in heavy fraction. There was a direct relationship between microaggregation and macroaggregation of soil primary particles, because the contents of wet aggregates 〉 0.25 mm and its water stability of aggregates were highly correlated with the contents of aggregated primary particle （d 〈 0.01 mm） and the degree of primary particles （d 〈 0.01 mm） aggregation.

Application of Light Reflectance-Transmittance Measurement Method to Reconstruct Geometrical Morphology of Particle Fractal Aggregates

Particles,including soot,aerosol and ash,usually exist as fractal aggregates.The radiative properties of the particle fractal aggregates have a great influence on studying the light or heat radiative transfer in the particle medium.In the present work,the performance of the single-layer inversion model and the double-layer inversion model in reconstructing the geometric structure of particle fractal aggregates is studied based on the light reflectancetransmittance measurement method.An improved artificial fish-swarm algorithm(IAFSA)is proposed to solve the inverse problem.The result reveals that the accuracy of double-layer inversion model is more satisfactory as it can provide more uncorrelated information than the single-layer inversion model.Moreover,the developed IAFSA show higher accuracy and better robustness than the original artificial fish swarm algorithm(AFSA)for avoiding local optimization problems effectively.As a whole,the present work supplies a useful kind of measurement technology for predicting geometrical morphology of particle fractal aggregates.

3D Surface Reconstruction of Coarse Aggregate Particles from Occlusion-Free Multi-View Images

Rapidly and accurately assessing the geometric characteristics of coarse aggregate particles is crucial for ensuring pavement performance in highway engineering.This article introduces an innovative system for the three-dimensional(3D)surface reconstruction of coarse aggregate particles using occlusion-free multi-view imaging.The system captures synchronized images of particles in free fall,employing a matte sphere and a nonlinear optimization approach to estimate the camera projection matrices.A pre-trained segmentation model is utilized to eliminate the background of the images.The Shape from Silhouettes(SfS)algorithm is then applied to generate 3D voxel data,followed by the Marching Cubes algorithm to construct the 3D surface contour.Validation against standard parts and diverse coarse aggregate particles confirms the method's high accuracy,with an average measurement precision of 0.434 mm and a significant increase in scanning and reconstruction efficiency.

Aggregating particles on the O/W interface:Tuning Pickering emulsion for the enhanced drug delivery systems

The rational design of drug delivery systems has led to enhanced targeting,increased efficiency,and a reduction of side effects in chemotherapies and vaccines.As most biological reactions took place at the interface,particle-stabilized emulsion(Pickering emulsion),may offer major implications for the advanced drug loading,delivery,and controlled release.In fact,it is the aggregating particles that determined the multi-level structure,multi-valent cellular interactions,and the multi-functional physiochemical properties in drug delivery.A deeper understanding on the tunable aggregating patterns and properties,as well as the underlying mechanisms,may pave the way for the efficient drug delivery,and also aided the progressing of“Aggregology”beyond molecules to particles,emulsions,and the biomedical applications.Here,the recent development of Pickering emulsions and their applications in drug delivery were thoroughly reviewed.Strategies to control over the physiochemical properties were illustrated based on particle properties,energy input,and the choices of continuous and dispersion phases.In particular,enough emphasis was attached on the structure-effect relationship between the tunable physiochemical properties and the delivery process,such as the multi-level structure for effective loading,flexibility and permeability for enhanced delivery,and the stimuli-responsiveness for the controlled release.By channeling the unique interfacial properties and the enhanced drug delivery efficiency,this work may shed light on the rational design of Pickering emulsions for the efficient drug delivery.