Microscale Particles Research Articles

Soil fluidisation induced by fine particles migration: Insights from the Shenzhen 2015 landfill landslide

Naturally completely decomposed granite (CDG) soil typically exhibits strain-hardening behavior under undrained shear conditions. Nevertheless, flow-type landslides are not uncommon in CDG landfills. This paper endeavors to address the observed contradiction by conducting a case study of the 2015 Shenzhen landslides. Based on field investigations, we propose a hypothesis for the initiation and evolution of flow-type landslides in CDG landfill slopes, termed ‘clay particle argillization, mud-water migration, and static liquefaction’. This hypothesis was verified by element-scale internal erosion tests and triaxial tests, and further elucidated by microscale particle analysis. It was observed that the internal erosion-induced removal of plastic fine particles and retention of low-plasticity fine particles from CDG soil promotes the sliding and reorganization of coarse granules under shear stress, thereby increasing the soil's susceptibility to fluidization under undrained conditions. The proposed hypothesis and experimental findings provide new insights into the instability and subsequent extensive runout of CDG landfills and analogous broadly graded landslides.

High stability enhanced ultrasonic microfluidic structure with flexible tip coupled bubbles

Ultrasonic microfluidic technology is a technique that couples high-frequency ultrasonic excitation to microfluidic chips. To improve the issues of poor disturbance effects with flexible tip structures and the susceptibility of bubbles to thermal deformation, we propose an enhanced ultrasonic microchannel structure that couples flexible tips with bubbles aiming to improve the disturbance effects and the stability duration. Firstly, we used finite element analysis to simulate the flow field distribution characteristics of the flexible tip, the bubble, and the coupling structure and obtained the steady-state distribution characteristics of the velocity field. Next, we fabricated ultrasonic microfluidic chips based on these three structures, employing 2.8 μm polystyrene microspheres as tracers to analyze the disturbance characteristics of the flow field. Additionally, we analyzed the bubble size and growth rate within the adhering bubbles and coupling structures. Finally, we verified the applicability of the coupling structure for biological samples using human red blood cells (RBCs). Experimental results indicated that, compared to the flexible tip and adhering bubble structures, the flow field disturbance range of the coupling structure increased by 439.53% and 133.48%, respectively; the bubble growth rate reduced from 14.4% to 3.3%. The enhanced ultrasonic microfluidic structure proposed in this study shows great potential for widespread applications in micro-scale flow field disturbance and particle manipulation.

Artificial kinetochore beads establish a biorientation-like state in the spindle

Faithful chromosome segregation requires biorientation, where the pair of kinetochores on the chromosome establish bipolar microtubule attachment. The integrity of the kinetochore, a macromolecular complex built on centromeric DNA, is required for biorientation, but components sufficient for biorientation remain unknown. Here, we show that tethering the outer kinetochore heterodimer NDC80-NUF2 to the surface of apolar microbeads establishes their biorientation-like state in mouse cells. NDC80-NUF2 microbeads align at the spindle equator and self-correct alignment errors. The alignment is associated with stable bipolar microtubule attachment and is independent of the outer kinetochore proteins SPC24-SPC25, KNL1, the Mis12 complex, inner kinetochore proteins, and Aurora. Larger microbeads align more rapidly, suggesting a size-dependent biorientation mechanism. This study demonstrates a biohybrid kinetochore design for synthetic biorientation of microscale particles in cells.

Effect of Fe Element and Ultrasonic Vibration on the Microstructure and Mechanical Properties of the Cu-TiB2 Composites

Cu-(Fe-Ti)-TiB2 composites were prepared by in situ reaction and vacuum casting with and without ultrasonic vibration. The evolution of the microstructure and mechanical properties of the composite with the variation in Fe element was analyzed. The import of Fe elements could purify the matrix after in situ reaction and the formation of a nanoprecipitated phase, thus improving the strength of Cu-Fe-Ti-TiB2 composites. Meanwhile, compared with the traditional casting process, the Cu-Fe-Ti-TiB2 composites with ultrasonic vibration treatment exhibit uniform TiB2 particle distribution and better properties. The tensile strength and uniform elongation of the composite with a Fe content of 0.7 wt.% reached 511 MPa and 6.02%, increasing by 14.3% and 318% compared to the unalloyed composite, respectively. The tensile strength and uniform elongation of Cu-0.7Fe-Ti-TiB2 composite with ultrasonic vibration treatment increased to 533 MPa and 7.16%, respectively. The TiB2 microscale particles and Fe2Ti nanoscale precipitates with uniform distribution effectively impeded dislocation movement and recrystallization, which improved the tensile strength and stability at elevated temperatures.

Solution Synthesis and Diffusion-Mediated Formation Pathway of NbTe4 Particles.

NbTe4 is an important material because of its fundamental low-temperature electronic behavior and its potential interest for thermoelectric, catalytic, and phase-change applications, especially as nano- and microscale particles. As a tellurium-rich group V transition metal telluride, bulk NbTe4 is typically synthesized through high-temperature solid-state or metal flux reactions and NbTe4 films can be made by sputtering and annealing, but NbTe4 is generally not amenable to the lower-temperature solution-based syntheses that yield small particles. Here, we demonstrate a solvothermal route to NbTe4 particles that is based on mainstream colloidal nanoparticle synthesis. We find that the reaction proceeds in situ through a multistep pathway that begins by first forming elemental tellurium needles. NbTe4 then deposits on the surface of the tellurium needles through a diffusion-based process. Time-point studies throughout the reaction reveal that crystallographic relationships between Te and NbTe4 define how the diffusion-based reaction proceeds and help to rationalize the morphology of the resulting NbTe4 particles. As synthesized, NbTe4 particles exhibit a surface consisting of predominantly Nb-Te and reduced NbOx species, but after storage, surface oxidation transforms these species to primarily Nb2O5 and TeO2, while the NbTe4 remains unchanged. These synthetic capabilities and reaction pathway insights for NbTe4, made using a solvothermal method, will help to advance future studies on the properties and applications of this and related tellurides.

Evolution of cardiac tissue and flow mechanics in developing Japanese Medaka.

The effects of pressure drop across cardiac valve cushion regions and endocardial wall strain in the early developmental stages of a teleost species heart are poorly understood. In the presented work, we utilize microscale particle image velocimetry (μPIV) flow measurements of developing medaka hearts from 3 to 14 dpf (n = 5 at each dpf) to quantify the pressure field and endocardial wall strain. Peak pressure drop at the atrioventricular canal (ΔPAVC) and outflow tract (ΔPOFT) show a steady increase with fish age progression. Pressure drops when non-dimensionalized with blood viscosity and heart rate at each dpf are comparable with measurements in zebrafish hearts. Retrograde flows captured at these regions display a negative pressure drop. A novel metric, Endocardial Work (EW), is introduced by analyzing the ΔPAVC-strain curves, which is a non-invasive measure of work required for ventricle filling. EW is a metric that can differentiate between the linear heart stage (< 100 Pa-%), cardiac looped chamber stage (< 300 Pa-%), and the fully formed chamber stage (> 300 Pa-%).

Understanding magnetic interactions in SrFe12O19/CoFe2O4 nanocomposites: role of particle structure on exchange spring magnet behaviour

This study explores the impact of particle structure on the magnetic properties of SrFe12O19/CoFe2O4 nanocomposites. The investigation focuses on variations in particle sizes of SrFe12O19 (SHF) and CoFe2O4 (COF) with a mass ratio of 80:20, considering micro-scale poly-crystallite particles (Pp) and nano-scale mono-crystallite particles (Mp). Four sample structures (COM1, COM2, COM3, COM4) were prepared, each with different combinations of poly-crystallite and mono-crystallite particles. Morphological analysis through scanning electron microscopy and energy-dispersive x-ray spectroscopy revealed consistent grain shape and size post-sintering. Magnetic properties analysis using Permagraph indicated that grain fineness and uniformity influence the resulting magnetic properties, with composite samples featuring nano-sized hard or soft phases showing improved M r , M s , and (BH) max values compared to individual phases. The nanocomposite sample COM4, characterized by fine and uniform particle size, exhibited the highest remanence magnetization, M r (34.55 emu g−1), saturation magnetization, M s (66.44 emu g−1), and the maximum energy product, (BH) max (1.17 MGOe).

Dissipation behaviors in submerged beam-vibrated granular systems

This study investigates intruder dynamics within granular systems, focusing on energy dissipation and phase transitions influenced by beam vibrations. Using a granular-beam experimental setup and discrete element method (DEM) simulations, we explore the dynamic responses of a simply supported beam in a granular medium under various excitation conditions. Our results reveal distinct granular phase states and their evolution pathways, driven by changes in excitation amplitude and frequency, which significantly affect energy dissipation. Key findings include the identification of vortical and disordered fluidization states that correlate with extremes in energy dissipation, underscoring the importance of characteristic lengths and times in characterizing these transitions. Additionally, amplitude-frequency characteristics and mean squared displacement (MSD) analyses link microscale particle behavior with macroscale beam dynamics, providing insights into the mechanisms of energy dissipation and dynamic heterogeneity. This research enhances our understanding of granular system mechanics, offering implications for the design and optimization of engineering applications across various fields.

Silicon Carbide-based Materials from Rice Husk

Background: Rice husk is an important agricultural waste that contains organic mass and bio-silica. Although some rice husks have been used as fuel, animal food, filler for wine fermentation, and fertilizer, the majority are discarded as agricultural waste, which does great harm to the environment. The conversion of rice husk to silicon carbide (SiC)-based materials satisfies the demand for the reutilization of solid wastes. Methods: The article reviews recent progress and patents on the SiC-based materials from rice husk. The possible development directions of the SiC-based materials from rice husks are also analyzed. Results: SiC materials with different morphologies, including microscale and nanoscale particles, nanoscale whiskers, and nanowires, can be prepared by high-temperature carbothermal reduction reaction from rice husk at the temperature of 1200-1800 °C, reaction time of 0.5-8 h, respectively. SiC-based composites, including SiC nanowires/C, Al/SiC, SiC/Si3N4, and SiC/Al2O3, can be obtained using rice husk as main source materials at 800-1800 °C. SiC-based materials exhibit great application potential in the fields of absorbents, optical devices, mechanical products, photocatalysts, semiconductors, and Li-ion batteries. Conclusion: The low cost of preparing SiC-based materials from rice husk, combining them with different compositions, and exploring new applications are important research directions in the future.

Microstructure and mechanical properties of Cu–Cr–Zr–ZrB2 composites by novel fabrication process of ultrasonic vibration treatment

Copper matrix composites with dual-scale particles were fabricated through casting with reaction. Ultrasonic vibration has been successfully introduced into the melt at about 1523 K while the microstructural development and mechanism of copper matrix composites with high-performance through a novel method of casting with ultrasonic vibration treatment are investigated. When ultrasonic vibration is applied, the distribution of micro-scale particles is greatly improved. Primary Cr phase convents to non-dendrite and large aggregates of ZrB2 particles are disrupted into small clusters because of acoustic cavitation and acoustic streaming. The ultimate tensile strength and elongation of Cu-1wt%Cr-0.3 wt%Zr-1wt%ZrB2 composite in as-cast state were 321 MPa and 14.37 %, recording a 28.4 % and 14 % increment respectively compared with the sample without treatment. After solution treatment, deformation and aging subsequently, the uniform distribution of reinforcements also decreases the average transverse grain thickness and increases the dislocation density which improve the comprehensive properties.

Toxicological inhalation studies in rats to substantiate grouping of zinc oxide nanoforms

BackgroundSignificant variations exist in the forms of ZnO, making it impossible to test all forms in in vivo inhalation studies. Hence, grouping and read-across is a common approach under REACH to evaluate the toxicological profile of familiar substances. The objective of this paper is to investigate the potential role of dissolution, size, or coating in grouping ZnO (nano)forms for the purpose of hazard assessment. We performed a 90-day inhalation study (OECD test guideline no. (TG) 413) in rats combined with a reproduction/developmental (neuro)toxicity screening test (TG 421/424/426) with coated and uncoated ZnO nanoforms in comparison with microscale ZnO particles and soluble zinc sulfate. In addition, genotoxicity in the nasal cavity, lungs, liver, and bone marrow was examined via comet assay (TG 489) after 14-day inhalation exposure.ResultsZnO nanoparticles caused local toxicity in the respiratory tract. Systemic effects that were not related to the local irritation were not observed. There was no indication of impaired fertility, developmental toxicity, or developmental neurotoxicity. No indication for genotoxicity of any of the test substances was observed. Local effects were similar across the different ZnO test substances and were reversible after the end of the exposure.ConclusionWith exception of local toxicity, this study could not confirm the occasional findings in some of the previous studies regarding the above-mentioned toxicological endpoints. The two representative ZnO nanoforms and the microscale particles showed similar local effects. The ZnO nanoforms most likely exhibit their effects by zinc ions as no particles could be detected after the end of the exposure, and exposure to rapidly soluble zinc sulfate had similar effects. Obviously, material differences between the ZnO particles do not substantially alter their toxicokinetics and toxicodynamics. The grouping of ZnO nanoforms into a set of similar nanoforms is justified by these observations.

Micro-Scale Particle Tracking: From Conventional to Data-Driven Methods.

Micro-scale positioning techniques have become essential in numerous engineering systems. In the field of fluid mechanics, particle tracking velocimetry (PTV) stands out as a key method for tracking individual particles and reconstructing flow fields. Here, we present an overview of the micro-scale particle tracking methodologies that are predominantly employed for particle detection and flow field reconstruction. It covers various methods, including conventional and data-driven techniques. The advanced techniques, which combine developments in microscopy, photography, image processing, computer vision, and artificial intelligence, are making significant strides and will greatly benefit a wide range of scientific and engineering fields.

Adhesion characteristics of carbon nanotube gecko tapes for micrometer-sized particles

ABSTRACT A detailed understanding of the adhesive properties of a carbon nanotube (CNT)-based gecko tape with respect to microscale particles is necessary for its practical application as a supporting medium for specific solid materials. We obtained the force curves of vertically aligned CNTs (VACNTs) for individual microparticles of various diameters using atomic force microscopy and evaluated their adhesion force and adhesion length. The measured adhesive force followed the apparent contact area with increasing embedding depth and was size-dependent at scales of several tens of micrometers. The adhesive forces measured for a 20 µm-diameter bead was significantly higher than those for larger particles, which may be related to inclination of the adherent surface against the VACNT tape surface. The adhesion length depended on the type of the CNTs comprising the VACNT, rather than on the bead size. The evaluation of VACNTs with different morphologies suggested that the flexibility of the individual CNTs and the density of the CNT – CNT interconnections in the VACNTs were important factors for obtaining the true contact area to realize better adhesion of micrometer-sized particles.

DNA-Based Replication of Programmable Colloidal Assemblies.

Nature uses replication to amplify the information necessary for the intricate structures vital for life. Despite some successes with pure nucleotide structures, constructing synthetic microscale systems capable of replication remains largely out of reach. Here, a functioning strategy is shown for the replication of microscale particle assemblies using DNA-coated colloids. By positioning DNA-functionalized colloids using capillary forces and embedding them into a polymer layer, programmable sequences of patchy particles are created that act as a primer and offer precise binding of complementary particles from suspension. The strings of complementary colloids are cross-linked, released from the primer, and purified via flow cytometric sorting to achieve a purity of up to 81% of the replicated sequences. The replication of strings of up to five colloids and non-linear shapes is demonstrated with particles of different sizes and materials. Furthermore, a pathway for exponential self-replication is outlined, including preliminary data that shows the transfer of patches and binding of a second-generation of assemblies fromsuspension.

Phase-locked µPIV analysis of flow dynamics in a simulated root canal with different laser-activated irrigations.

To measure the dynamic characteristics of the flow field in a complex root canal model activated by two laser-activated irrigation (LAI) modalities at different activation energy outputs: photon-induced photoacoustic streaming (PIPS) and microshort pulse (MSP). A phase-locked micro-scale Particle Image Velocimetry (µPIV) system was employed to characterise the temporal variations of LAI-induced velocity fields in the root canal following a single laser pulse. The wall shear stress (WSS) in the lateral root canal was subsequently estimated from the phase-averaged velocity fields. Both PIPS and MSP were able to generate the 'breath mode' of the irrigant current under all tested conditions. The transient irrigation flush in the root canal peaked at speeds close to 6 m/s. However, this intense flushing effect persisted for only about 2000 µs (or 3% of a single laser-pulse activation cycle). For MSP, the maximum WSS magnitude was approximately 3.08 Pa at an activation energy of E = 20 mJ/pulse, rising to 9.01 Pa at E = 50 mJ/pulse. In comparison, PIPS elevated the WSS to 10.63 Pa at E = 20 mJ/pulse. Elevating the activation energy can boost the peak flushing velocity and the maximum WSS, thereby enhancing irrigation efficiency. Given the same activation energy, PIPS outperforms MSP. Additionally, increasing the activation frequency may be an effective strategy to improve irrigation performance further.

Atomic-Scale Characterization of Microscale Battery Particles Enabled by a High-Throughput Focused Ion Beam Milling Technique.

The cathode materials in lithium-ion batteries (LIBs) require improvements to address issues such as surface degradation, short-circuiting, and the formation of dendrites. One such method for addressing these issues is using surface coatings. Coatings can be sought to improve the durability of cathode materials, but the characterization of the uniformity and stability of the coating is important to assess the performance and lifetime of these materials. For microscale particles, there are, however, challenges associated with characterizing their surface modifications by transmission electron microscopy (TEM) techniques due to the size of these particles. Often, techniques such as focused ion beam (FIB)-assisted lift-out can be used to prepare thin cross sections to enable TEM analysis, but these techniques are very time-consuming and have a relatively low throughput. The work outlined herein demonstrates a FIB technique with direct support of microscale cathode materials on a TEM grid that increases sample throughput and reduces the processing time by 60-80% (i.e., from >5 to ∼1.5 h). The demonstrated workflow incorporates an air-liquid particle assembly followed by direct particle transfer to a TEM grid, FIB milling, and subsequent TEM analysis, which was illustrated with lithium nickel cobalt aluminum oxide particles and lithium manganese nickel oxide particles. These TEM analyses included mapping the elemental composition of cross sections of the microscale particles using energy-dispersive X-ray spectroscopy. The methods developed in this study can be extended to high-throughput characterization of additional LIB cathode materials (e.g., new compositions, coating, end-of-life studies), as well as to other microparticles and their coatings as prepared for a variety of applications.

Gold Migration and Precipitation as Collaurum in Orogenic Gold Deposits: Constrains from Microscopic Gold Particles Observed in the Alteration Zone in Shanggong Gold Ore, Henan, China

Aqueous complexation has long been considered the only viable means of transporting gold to depositional sites in hydrothermal ore-forming systems. Here, we present direct evidence supporting an alternative hypothesis, namely, the transport of gold as colloidal particles. We observed nano-scale gold particles adsorbed on halloysite and micro-scale gold particles in altered rocks by TEM and SEM in the Shanggong orogenic gold deposit. Based on this evidence, we propose a feasible model for the origin of microscopic gold particles in alteration zones. In the early stage of ore-forming fluid, gold may migrate in the form of collaurum, which is maintained by supercritical CO2 and colloidal silica. Low salinity and high pressure are conducive to the stable migration of colloidal gold. When the physicochemical conditions change, some collaurum is precipitated and adsorbed by the clay minerals produced by hydrothermal alteration, and some collaurum undergoes growth and evolves into micro-submicrometer-sized gold particles. This study highlighted the significance of collaurum in the formation of orogenic gold deposits.

A novel Cu-Sn-Zr alloy with core-shell structure

In this study, a novel Cu-0.3Sn-0.2Zr (wt.%) alloy was designed to investigate the influence of Zr addition on the microstructure and properties of the Cu-0.3Sn alloys. We have discovered that the addition of Zr could not only greatly refine the grain structures of the Cu-0.3Sn alloy and contribute to forming a large number of nanoscale Zr-rich particles, but also leads to the formation of core-shell structure with a large amount of Sn atoms segregated at the surface of the microscale and nanoscale Zr-rich particles. As a result, all of the tensile strength, electrical conductivity and softening temperature of the Cu-0.3Sn-0.2Zr alloy were improved when compared with the Cu-0.3Sn alloy. After cold drawing at an accumulated strain of 6.8 combined with a two-step aging treatment, a good combination of an ultimate tensile strength of ∼724 MPa, an electrical conductivity of ∼76.8% IACS and a softening temperature of ∼425 °C were achieved in the Cu-0.3Sn-0.2Zr alloy, which was ∼147 MPa, ∼0.7 % IACS and ∼90 °C higher than that of the Cu-0.3Sn alloy after cold drawing at the same accumulated strain of 6.8, respectively. Our research elucidates that the Cu-Sn-Zr alloys represent a category of potential copper alloys with high strength, high conductivity and excellent softening resistance performance.

Dynamic Behavior of Spatially Confined Sn Clusters and Its Application in Highly Efficient Sodium Storage with High Initial Coulombic Efficiency.

Advanced battery electrodes require a cautious design of microscale particles with built-in nanoscale features to exploit the advantages of both micro- and nano-particles relative to their performance attributes. Herein, the dynamic behavior of nanosized Sn clusters and their host pores in carbon nanofiber) during sodiation and desodiation is revealed using a state-of-the-art 3D electron microscopic reconstruction technique. For the first time, the anomalous expansion of Sn clusters after desodiation is observed owing to the aggregation of clusters/single atoms. Pore connectivity is retained despite the anomalous expansion, suggesting inhibition of solid electrolyte interface formation in the sub-2-nm pores. Taking advantage of the built-in nanoconfinement feature, the CNF film with nanometer-sized interconnected pores hosting Sn clusters (≈2nm) enables high utilization (95% at a high rate of 1 A g-1) of Sn active sites while maintaining an improved initial Coulombic efficiency of 87%. The findings provide insights into electrochemical reactions in a confined space and a guiding principle in electrode design for battery applications.

Microstructure and mechanical properties of WMoCu alloy doped with different sized Mo particles

WMoCu alloys doped with Mo particles in the nanoscale or microscale range were prepared by infiltration process using the element Ni as an activating element. A comparative study was carried out on the effects of doping with nano- and micro-scale Mo particles on the microstructure and mechanical properties of WMoCu alloys. The results show that the microstructure and distribution of Mo particles is more uniform in the W60Mo25Cu15(M) alloy doped with 3 μm sized Mo particles. The addition of the activating element Ni promotes mutual diffusion between W, Mo, and Cu. A WMo transition layer is formed at the interface between W and Cu, and a core-shell structure with a thickness of about 2 μm is formed around the W particles, which has an amorphous structure at the interfaces, which increases the deformation resistance during interfacial sliding and improves the bonding strength of the WMoCu alloy. The tensile strength of the W60Mo25Cu15(M) alloy is higher than that of the W60Mo25Cu15(N) alloy and the WCu alloy both at room temperature and at elevated temperature. Especially at a high temperature of 600 °C, the tensile strength of the alloys W60Mo25Cu15(M) and W60Mo25Cu15(N) is increased by 57.44% and 32.64%, respectively, compared to the alloy W85Cu15. The fracture mechanisms of the WMoCu alloy are mainly intergranular fracture and transgranular fracture.