Particle Size Distribution Measurements Research Articles

Size and Shape Selective Classification of Nanoparticles

As nanoparticle syntheses on a large scale usually yield products with broad size and shape distributions, the properties of nanoparticle-based products need to be tuned after synthesis by narrowing the size and shape distributions or via the removal of undesired fractions. The development of property-selective classification processes requires a universal framework for the quantitative evaluation of multi-dimensional particle fractionation processes. This framework must be applicable to any property and any particle classification process. We extended the well-known one-dimensional methodology commonly used for describing particle size distributions and fractionation processes to the multi-dimensional case to account for the higher complexity of the property distribution and separation functions. In particular, multi-dimensional lognormal distributions are introduced and applied to diameter and length distributions of gold nanorods. The fractionation of nanorods via centrifugation and by orthogonal centrifugal and electric forces is modeled. Moreover, we demonstrate that analytical ultracentrifugation with a multi-wavelength detector (MWL-AUC) is a fast and very accurate method for the measurement of two-dimensional particle size distributions in suspension. The MWL-AUC method is widely applicable to any class of nanoparticles with size-, shape- or composition-dependent optical properties. In addition, we obtained distributions of the lateral diameter and the number of layers of molybdenum disulfide nanosheets via stepwise centrifugation and spectroscopic evaluation of the size fractions.

Bioaerosol Exposure during Sorting of Municipal Solid, Commercial and Industrial Waste: Concentration Levels, Size Distribution, and Biodiversity of Airborne Fungal

A study was carried out in a waste sorting plant (WSP) located in France, treating dry recyclable household waste (DRHW) as well as dry recyclable commercial and industrial waste (DRCIW). Stationary and personal inhalable samples were collected in the WSP in order to investigate bioaerosols (sampling on a filter; 2 L/min and 10 L/min) and airborne dust (CIP; 10 L/min). The aim of the study was to assess the extent to which the measurement of concentration, species composition, and particle size distribution contributes to a better assessment of the biological risks associated with exposure. The results confirmed that waste and waste sorting activities are sources of airborne fungi. Indeed, ambient concentrations ranged from 7.3 × 103 to 8.5 × 105 colony-forming units (CFU)/m3 for culturable fungi and up to 4 mg/m3 for dust. Personal exposure to inhalable dust was found up to 3 mg/m3 for dust and ranged from 8.6 × 103 to 1.5 × 106 CFU/m3 for fungi. Airborne fungal communities were found to be dominated by the Penicillium genera in both bioaerosols and settled dust samples, followed by the Aspergillus, Cladosporium, Wallemia, Mucor, and Rhizopus genera. Fungi were carried by particles of aerodynamic diameters, mainly between around 2.0 and 10.0 µm. The findings dealing with size distribution and biodiversity of bioaerosols suggest that employees are exposed to complex bioaerosols during their work and help to make a finer diagnosis of the risks involved, which is often difficult in the absence of any occupational exposure limit (OEL) value for bioaerosols in general.

The effects of ultrasound modified kerosene on the flotation of flake graphite

ABSTRACT In the mineral processing engineering, ultrasound is usually used to modify reagents to improve the flotation. The study analyses the effects of the modified kerosene on the flotation of flake graphite. The outcomes demonstrate that the modified kerosene can substantially improve flake graphite’s floatation efficiency. In comparison to unmodified kerosene, the dosage of modified kerosene can be reduced while the recovery of graphite remains the same. Furthermore, the effect of modified kerosene was evaluated using various detection techniques including particle size distribution measurement, contact angle tests, turbidity tests, and cryo-scanning electron microscopy (Cryo-SEM) . The findings indicate that ultrasound modification significantly reduces the size of kerosene to 1–2 μm droplets and improves their dispersion in the aqueous solution. The enhanced dispersion and reduced droplets size of modified kerosene led to a better interaction between kerosene and the surface of flake graphite minerals. As a result, the consumption of kerosene was reduced, but the graphite flotation efficiency was improved.

DEDALO: Device for Enhanced Dust Analyses with Light Obscuration sensors

Instruments based on light obscuration sensors are widely used for measuring the size distribution of insoluble sub-visible particles in liquid suspensions, being fast and suitable for in situ and real-time measurements. Such instruments are typically calibrated by means of reference polystyrene spherical particles with a specific refractive index, which unavoidably leads to systematic errors when determining the size of particles of different materials. In this paper, we propose a reliable and consistent method to overcome this limitation by setting the refractive index value according to the sample, thus achieving an improved particle size distribution (PSD) measurement. An ad hoc, ready-to-use, open source code with a graphical interface able to drive an in-line instrument and obtain a real-time correction to the PSD has been developed. The method has been extensively validated with several oil emulsions characterized by different refractive index values and the results have been compared with an independent optical method. As an example of application, we have adopted this approach for the analysis of dust suspended in meltwater of an ice core from a glacier in the Aosta Valley (Italy). We believe that our approach will strongly improve the accuracy in characterizing liquid suspensions and reduce discrepancies between data obtained with different methods. The code has been made publicly available at: https://instrumentaloptics.fisica.unimi.it/dedalo/ and on the GitHub page of the corresponding author (https://github.com/LucaTeruzzi/DEDALO).

Particle size distribution (PSD) estimation using unmanned aerial vehicle (UAV) photogrammetry for rockfill shear strength characterization

AbstractThe strength of rockfills and waste materials is significantly influenced by their particle size distribution (PSD). For large waste rockfills, PSD is fundamental to determine the shear behavior. Traditionally, PSD for rockfill, used in materials like coarse-grained aggregates, has been obtained through physical sieving. However, the particle sizes in hard rockfills can vary significantly from small particles (< 20 cm diameter) to large blocks or boulders over 100 cm, with the maximum size limited by the in situ ground conditions and blasting performance. Essentially, the sieving process is impractical, considering the scale of the mine waste dumps and the time required. Therefore, in this study, a workflow using digital detection to estimate the PSD is presented, aiming to quantify the waste dump shear strength using Barton–Kjaernsli empirical criterion. PSD from UAV is validated using manual field measurements of individual boulders. The error for coarse characteristic size prediction ranges within ± 4 mm, and the increase in the data collection frequency, area covered, and resolution of fragmentation measurement for rockfills and waste dumps using UAV allows to improve the statistical reliability of the PSD and fragmentation measurement.

Modeling titanium dioxide (TiO2) nanoclusters using a 2D sectional method with molecular dynamics (MD) determined coagulation rates

Accurate prediction of the particle size distribution (PSD) evolution of growing nanometer scale particles is important in designing gas-phase synthesis reactors for the production of nanomaterials. Towards improved predictions of growth, we model the evolution of the PSD of 1-4 nm TiO2 particles from the decomposition of titanium tetraisoproxide (TTIP) using a two-dimensional (2D) sectional method, uniquely with coagulation rates derived from molecular dynamics (MD) trajectory calculations which account for detailed particle–particle interactions. The PSDs predicted by the 2D sectional method are compared to recent experimental measurements of PSDs in the 1-3 nm range in a flow tube reactor. The nucleation of particles is modeled based on prior mobility measurements of ions attributed to TTIP and their decomposition, with the specific nucleation rate here fitted as a fraction of base nucleation rate (k) derived from these prior measurements. In the 2D sectional model, we examine the influence of the initial (nucleated) particle charge distribution on the PSD, with different coagulation rate coefficients for neutral-charged and charged-charged particle collisions. With the MD-derived coagulation rate coefficients, we find that using nucleation rate coefficients between 0.005k and 0.03k leads to strong agreement between modeled PSD and measured PSD for a wide variety of experimental residence times, initial TTIP concentrations and temperatures. Increasing the charge fraction from 0% (uncharged) to 80% (bipolar) does not result in a significant change in the PSD, because the particles rapidly self-neutralize through coagulation based on the simulation results. The results with MD-derived coagulation rate coefficients are compared to those of the sectional method with classical kinetic theory of gases (KTG) rates with a constant enhancement factor to account for potential interactions. Through comparison, we find that the predictions from the classical KTG model consistently exhibit weaker coagulation rates than the MD-derived model during the PSD evolution.

Human emissions of size-resolved fluorescent bioaerosols in control situations

Human bioaerosols contribute significantly to indoor air quality. This study used a Wideband Integrated Bioaerosol Sensor (WIBS-4A) instrument for real-time measurement of particle size distribution and count to differentiate fluorescent bioaerosols from non-fluorescent aerosols. Through an experiment involving 12 subjects (six men and six women) wearing standard cotton clothing in a 2 m × 2 m × 2 m environmental chamber, we established a quantitative method to obtain the bioaerosol emission rate of a single subject, aiming to explore the effects of masks and sex on bioaerosol emissions from different individuals. The mean emission rates of fluorescent bioaerosols in the particle size ranges of 0.5–2.5 μm and 2.5–10 μm were 3.192±2.11×104 counts/(person·h) and 13.98±9.34×104 counts/(person·h), respectively. A comparison between those wearing and not wearing masks revealed no significant differences in the emissions of fluorescent bioaerosols. This suggests respiratory sources may not significantly impact the emissions of fluorescent bioaerosols from individuals under seated breathing conditions. Significant disparities in the fluorescent bioaerosol emission rates of different biological sexes were observed through independent sample analysis. Males exhibited 41 % and 15 % higher emission rates than females for particle size ranges of 0.5–2.5 μm and 2.5–10 μm, respectively, possibly because of different metabolic rates. A significant correlation between metabolic rates and fluorescent bioaerosols (sig = 0.044 < 0.05) was observed in all the subjects. These findings underscore the individual variations that affect bioaerosol emission rates. The data provided by this study will facilitate further analysis of the on-site measured data and source analysis.

Light Scattering Method for Aerosol Sizing Based on Machine Learning.

Optical scattering has been widely used for aerosol sizing due to its noninvasive and real-time measurement. However, it is crucial to retrieve the particle size distribution (PSD) of aerosols without prior knowledge of the refractive index. Now, it has been a great challenge to measure the refractive index in situ. In this study, a novel PSD sensing method utilizing the light scattering angular spectrum (LSAS) and machine learning techniques is proposed to address this challenge. The complex nonlinear relationship between LSAS and PSD can be constructed while accounting for the refractive index of aerosols. A miniaturized prototype sensor is designed and tested on different sizes of aerosol samples. The experiment results showed that the maximum Kullback-Leibler divergence (DKL) of PSD is 0.07, which indicates that the sensing method can provide the ability for highly accurate aerosol PSD measurement without requiring prior knowledge of the refractive index. The compacted prototype sensor shows great potential for aerosol analysis in conventional field measurements outside the laboratory.

Evaluation of methods for characterizing the fine particulate matter emissions from aircraft and other diffusion flame combustion aerosol sources

The U. S. Environmental Protection Agency in collaboration with the U. S. Air Force Arnold Engineering Development Complex conducted the VAriable Response In Aircraft nvPM Testing (VARIAnT) 3 and 4 test campaigns to compare nonvolatile particulate matter (nvPM) emissions measurements from a variety of diffusion flame combustion aerosol sources (DFCASs), including a Cummins diesel engine, a diesel powered generator, two gas turbine start carts, a J85-GE-5 turbojet engine burning multiple fuels, and a Mini-CAST soot generator. The VARIAnT research program was devised to understand reported variability in the ARP6320A sampling system nvPM measurements. The VARIAnT research program has conducted four test campaigns to date with the VARIAnT 3 and 4 campaigns devoted to: (1) assessing the response of three different black carbon mass analyzers to particles of different size, morphology, and chemical composition; (2) characterizing the particles generated by 6 different combustion sources according to morphology, effective density, and chemical composition; and (3) assessing any significant difference between black carbon as determined by the 3 mass analyzers and the total PM determined via other techniques. Results from VARIAnT 3 and 4 campaigns revealed agreement of about 20% between the Micro-Soot Sensor, the Cavity Attenuated Phase Shift (CAPS PMSSA) monitor and the thermal-optical reference method for elemental carbon (EC) mass, independent of the calibration source used. For the LII-300, the measured mass concentrations in VARIAnT 3 fall within 18% and in VARIAnT 4 fall within 27% of the reference EC mass concentration when calibrated on a combustor rig in VARIAnT 3 and on an LGT-60 start cart in VARIAnT 4, respectively. It was also found that the three mass instrument types (MSS, CAPS PMSSA, and LII-300) can exhibit different BC to reference EC ratios depending on the emission source that appear to correlate to particle geometric mean mobility diameter, morphology, or some other parameter associated with particle geometric mean diameter (GMD) with the LII-300 showing a slightly stronger apparent trend with GMD. Systematic differences in LII-300 measured mass concentrations have been reduced by calibrating with a turbine combustion as a particle source (combustor or turbine engine). With respect to the particle size measurements, the sizing instruments (TSI SMPS, TSI EEPS, and Cambustion DMS 500) were found to be in general agreement in terms of size distributions and concentrations with some exceptions. Gravimetric measurements of the total aerosol mass produced by the various DFCAs differed from the reference EC, BC and integrated particle size distribution measured aerosol masses. The measurements of particle size distributions and single particle analysis performed using the miniSPLAT indicated the presence of larger particles (≳150 nm) having more compact morphologies, higher effective density, and a composition dominated by OC and containing ash. This increased large particle fraction is also associated with higher values of single scattering albedo measured by the CAPS PMSSA instrument and higher OC measurements. These measurements indicate gas turbine engine emissions can be a more heterogeneous mix of particle types beyond the original E−31 assumption that engine exit exhaust particles are mainly composed of black carbon.

Development of a Powder Analysis Procedure Based on Imaging Techniques for Examining Aggregation and Segregation Phenomena.

In this manuscript, a method that utilizes classical image techniques to assess particle aggregation and segregation, with the primary goal of validating particle size distribution determined by conventional methods, is presented. This approach can represent a supplementary tool in quality control systems for powder production processes in industries such as manufacturing and pharmaceuticals. The methodology involves the acquisition of high-resolution images, followed by their fractal and textural analysis. Fractal analysis plays a crucial role by quantitatively measuring the complexity and self-similarity of particle structures. This approach allows for the numerical evaluation of aggregation and segregation phenomena, providing valuable insights into the underlying mechanisms at play. Textural analysis contributes to the characterization of patterns and spatial correlations observed in particle images. The examination of textural features offers an additional understanding of particle arrangement and organization. Consequently, it aids in validating the accuracy of particle size distribution measurements. To this end, by incorporating fractal and structural analysis, a methodology that enhances the reliability and accuracy of particle size distribution validation is obtained. It enables the identification of irregularities, anomalies, and subtle variations in particle arrangements that might not be detected by traditional measurement techniques alone.

Jet aircraft lubrication oil droplets as contrail ice-forming particles

Abstract. The radiative characteristics and lifetimes of contrails are dependent on the number concentration of ice-forming particles in the engine exhaust plume. Aircraft gas turbine engines produce a variety of particles, yet it is understood that non-volatile black carbon aggregates are the dominant source of ice-forming particles with typical, fossil-derived jet fuel. However, with cleaner combustion technologies and the adoption of alternative fuels (e.g. hydrogen or synthetic aviation fuel), non-volatile black carbon particle emissions are expected to decrease or even be eliminated. Under these conditions, contrail properties will depend upon the concentration and characteristics of particles other than black carbon. Ultrafine (&lt; 100 nm) jet lubrication oil droplets constitute a significant fraction of the total organic particulate matter released by aircraft; however, their ability to form contrail ice crystals has hitherto been unexplored. In this work, we experimentally investigate the activation and freezing behaviour of lubrication oil droplets using an expansion chamber, assessing their potential as ice-forming particles. We generate lubrication oil droplets with a geometric mean mobility diameter of (100.9 ± 0.6) nm and show that these activate to form water droplets, which subsequently freeze when the temperature is below ∼ 235 K. We find that nucleation on lubrication oil droplets should be considered in future computational studies – particularly under soot-poor conditions – and that these studies would benefit from particle size distribution measurements at cruise altitude. Overall, taking steps to reduce lubrication oil number emissions would help reduce the climate impact of contrail cirrus.

The Influence of TiO2-Lignin Hybrid Fillers in Low-Density Polyethylene Composites on Photocatalytic Performance and UV-Barrier Properties.

The main objective of this study was to discover new packaging materials that could integrate one of the most expected properties, such as UV protection, with a self-cleaning ability defined as photocatalytic performance. Accordingly, new hybrid additives were used to transform LDPE films into materials with complex performance properties. In this study, titanium dioxide-lignin (TL) hybrid systems with a weight ratio of inorganic to organic precursors of 5-1, 1-1, and 1-5 were prepared using a mechanical method. The obtained materials and pristine components were characterized using measurement techniques and research methods, such as Fourier-transform infrared spectroscopy (FTIR), thermal stability analysis (TGA/DTG), measurement of the electrokinetic potential as a function of pH, scanning electron microscopy (SEM), and particle size distribution measurement. It was found that hydrogen bonds were formed between the organic and inorganic components, based on which the obtained systems were classified as class I hybrid materials. In the next step, inorganic-organic hybrid systems and pristine components were used as fillers for a low-density polyethylene (LDPE) composite, 5 and 10% by weight, in order to determine their impact on parameters such as tensile elongation at break. Polymer composites containing titanium dioxide in their matrix were then subjected to a test of photocatalytic properties, based on which it was found that all materials with TiO2 in their structure exhibit photocatalytic properties, whereby the best results were obtained for samples containing the TiO2-lignin hybrid system (1-1). The mechanical tests showed that the thin sheet films had a strong anisotropy due to chill-roll extrusion, ranging from 1.98 to 3.32. UV-Vis spectroscopy revealed four times higher light absorption for composites in which lignin was present than for pure LDPE, in the 250-450 nm range. On the other hand, the temperature at 5% and 30% weight loss revealed by TGA testing increased the highest performance for LDPE/TiO2 materials (by 20.4 °C and 8.7 °C, respectively).

An optical soot sizing method without prior morphology parameters

Great concern has been focused on the particle size distribution (PSD) of soot as a crucial factor of the physical and chemical properties. Optical methods are widely used to analyze the PSD of soot due to their non-invasive and real-time measurement, where the morphology parameters are essential for retrieving the PSD from optical signals. However, these parameters are difficult to obtain in field measurement. In this work, we propose a new PSD sensing method for soot without prior knowledge of the morphology parameters based on the light-scattering angular spectrum using a hybrid inverse algorithm. The light scattering angular spectrum is the intensity distribution of scattering light at different observation angles for simultaneously characterizing the PSD and the morphological parameters, which are decoupled by a hybrid inverse algorithm consisting of Tikhonov regularization and adaptive weighted particle swarm optimization (AW-PSO). A compacted and lens-free prototype sensor is designed to verify our method. The calibration experiments by spherical aerosols show that our prototype sensor provides high-precision light scattering angular spectrum measurement with maximum relative error (RE) of 14.78 %. In the tests of soot, the maximum Kullback-Leibler Divergence (DKL) of PSD is 0.28 in comparison with the reference volume equivalent PSD. The sensing method proposed in this paper provides volume equivalent PSD measurement for soot without requirement of the morphology parameters, and our prototype sensor shows great potential for soot and other non-spherical aerosol analysis in routine field measurements outside the laboratory.

Particle size distribution measurements under supercooled large drop conditions with Cloud Combination Probe in CARDC icing wind tunnel

Particle size distribution (PSD) of the icing cloud is one of the most important icing parameters for icing wind tunnels. However, accurate measurements of the PSD are challenging for supercooled large drop (SLD) conditions due to the wide droplet size spectrum and low number density of large droplets. In this study, PSD measurements with the Cloud Combination Probe (CCP) are comprehensively investigated in the CARDC icing wind tunnel. A method based on the CCP is developed for composite PSD calculation, and an icing cloud measurement test with 79 test conditions covering Appendix C and freezing drizzle conditions, is conducted for accuracy assessment of the CCP and reliability validation of the PSD calculation method. Based on the test, the effects of spurious particle images are examined first, followed by a quantitative assessment of the influences of particle size calculation and sample volume calculation on the PSD, medium volume diameter (MVD), and liquid water content (LWC). The results show that all PSD measurements are adversely impacted by spurious particle images, primarily caused by coincidence errors. For five typical particle size parameters, the effects of particle size calculation on the PSD are significant, with maximum relative deviations of about 110% for MVD and 63% for LWC. The influences of Depth-of-Field factors are not noticeable except for the manufacturer factor. Additionally, the dead time also dramatically impacts the PSD, resulting in a decrease in the MVD and LWC with maximum decreases of about 60% and 43%, respectively. Finally, the LWCs determined by composite PSDs show good agreement with the reference LWCs obtained by the SEA multi-element sensor, where the relative deviation is within ±10% for the majority of measured points. This demonstrates the CCP is suitable for wind tunnel measurements of PSDs under Appendix C and freezing drizzle conditions employing the PSD calculation method. To accurately calculate the PSD, spurious particle image removal and dead-time correction should be considered, and out-of-focus correction diameter and in-house factor are preferred.

The Impact of Flocculation on In Situ and Ex Situ Particle Size Measurements by Laser Diffraction

AbstractAccurate particle size distribution (PSD) measurements of suspended particulate matter (SPM) composed of flocs and aggregates are important to improve understanding of ecological and geomorphological processes, and for environmental engineering applications. PSDs can be measured in situ (in the field) using a submersible sensor, or ex situ (in the laboratory) using samples. The methodological choice is often guided by logistical factors, and the differences in PSDs acquired by in situ and ex situ measurements is of concern. In this study, a laser‐diffraction instrument (the LISST‐200X) was used to compare in situ and ex situ PSD measurements. Samples measured ex situ were stored for three consecutive weeks and measured each week in a laboratory using different stirrer speeds. We observed that ex situ measurements display a higher D50 (median particle size) than in situ measurements of the same sample (up to 613% larger, 112% on average). Our experiments show that the difference between in situ and ex situ measurements can be explained by flocculation of the riverine sediments during the first week of storage. During the subsequent ex situ measurements, the stirring results in a significantly lower D50. Ex situ measurements are therefore unsuitable for flocculated SPM. This study provides recommendations for optimizing PSD measurements by calculating the measurement times required to obtain robust PSD measurements (exceeding 3 min per sample), which are larger for field samples with coarser particles and wider PSDs.

Hyperbranched polymer nanocomposite as a potential shale stabilizer in water-based drilling fluids for improving wellbore stability

Shale hydration has been a frequent and challenging technical problem causing wellbore instability in oil and gas drilling processes. The aim of this study is to design a novel hyperbranched polymer nanocomposite (HBPN) based on a synergistic strategy of physical plugging and chemical inhibition to improve wellbore stability. The inhibitive property of HBPN was comprehensively evaluated through the sodium montmorillonite (Na-MMT) plates immersion test, capillary suction time (CST) test, and shale hot-rolling recovery test. Results implied that HBPN presented better inhibition performance. The shale hydration rate was reduced to 0.03 in the presence of HBPN. Particularly, the shale hot-rolling recovery rate reached 80.54 % at 150 °C and presented long-term shale inhibition durability. It demonstrated excellent plugging performance in the artificial low permeability filter cakes plugging test, reaching a plugging efficiency of 42.45 % with the addition of 2.0 w/v% HBPN. The potential mechanism of action of HBPN was proposed through particle size distribution (PSD) measurement, Zeta (ζ) potential measurement, Fourier transform infrared spectroscopy (FTIR) analysis, X-ray diffraction (XRD) analysis, and scanning electron microscope (SEM) analysis. The coordination of electrostatic interaction and hydrogen bonding impelled a decrease in the ζ potential and interlayer spacing of Na-MMT. Meanwhile, HBPN could embed into formation pores and fractures to establish a tight plugging zone. This approach outlined herein might provide an avenue to strengthen wellbore stability for the drilling industry.

Impact of Metallic Impurities on the Synthesis and Properties of NMC Cathode Material Obtained by Co-Precipitation

Among the different factors that influence lithium-ion batteries (LIB) performances, the properties of the cathode active material (CAM) play a crucial role. The composition, the crystallinity and also the particle size and morphology of these materials are part of the major parameters governing the CAM behaviour. These parameters are strongly dependent of the synthesis method, especially in the case of the hydroxide precursor of the layered LiNixMnyCozO2 [1].One of the most widely spread synthesis method of such precursors is the synthesis by co-precipitation, where metal salts of Ni, Mn and Co are precipitated together in a continually-stirred tank reactor (CSTR) in carefully controlled pH- and temperature conditions[2]. Any parameter of the co-precipitation must be precisely tuned to obtain the desired material, as highlighted in the figure here after.Considering the increasing presence of wanted (coating/doping)[3] and unwanted (impurities after recycling)[4] elements in the co-precipitation process, extensive knowledge of their impact on it is of great interest. Therefore, the synthesis of NixMnyCoz(OH)2 was conducted by co-precipitation with the controlled addition of increasing amounts of elements such as Cu and Al.The effects of these additions were investigated by thoroughly characterizing the morphology of the obtained hydroxides with the help of SEM, BET, particle size distribution and porosity measurements. The composition of the synthesized hydroxides was determined by the ICP-OES technique. The possible influence on the further step of CAM synthesis, i.e. calcination, was followed by in-situ X-Ray thermodiffraction and the electrochemical performances were assessed by galvanostatic cycling the obtained CAM in lithium half-cells. This helped to evidence the varying impact of the added elements, depending on their concentration in the synthesis process.This work is supported by the German Ministry for Economy and Climate Protection (BMWK).

Hierarchically Structured Potassium-Vanadium-Phosphate/C Composites As Possible High-Voltage Cathodic Materials for Potassium-Ion-Batteries

Potassium-ion-batteries (PIBs) share technological similarities with Lithium- and Sodium-ion batteries (LIBs/SIBs) and are based on the inter- and deintercalation of K ions between two host materials.[1] The higher atomic weight and larger ionic radius of potassium ions results in lower gravimetric and volumetric capacities compared to LIBs.[2] But they offer similar advantages as SIBs (i.e. use of aluminium as current collector on both sides, evenly distributed potassium reserves) as well as graphite could be used as anode.[2,3] Also, they are expected to offer higher cell voltages due to the low standard potential of K/K+ vs. SHE of -2.93V.[3] To unlock the full potential of PIBs, cathode materials with high average potentials above 4 V need to be developed, which would significantly improve the energy density.[4] Polyanionic compounds, especially different Vanadium-Phosphates, are prepared and investigated for this purpose. Their thermal stability and diverse structural chemistry are advantageous for high energy PIBs. [2,5] One of the often-used synthesis methods for polyanionic compounds is the solid-state reaction. [4] In my work this well-known synthesis was coupled with a spray-drying process and a subsequently sintering process for K3V2(PO4)3/C composites. This created spherical secondary particles with a size in the micrometer range and an open micro-porosity. (see attached image)Through the addition of different amounts of organic sugars as a carbon source during the synthesis or sintering step an additional carbon coating of the primary and secondary particles was achieved, as well as the morphology of the secondary particles could be influenced. The influences of the different carbon contents during synthesis and sintering were investigated by thoroughly characterizing the morphology and crystal structure of the secondary particle with the help of SEM, BET, particle size distribution, XRD and porosity measurements. First electrochemical evaluation of the synthesized material was done by galvanostatic cycling the KVP/C composites against potassium.

Permeability of sandy soils estimated from particle size distribution and field measurements

Permeability of sandy soils estimated from particle size distribution and field measurements

Measurement of number-weighted particle size distribution for CMP slurry using nanoparticle chip

Chemical mechanical polishing/planarization (CMP) slurry contains mainly abrasive grains (primary particles) with few aggregations (secondary particles). Measuring the particle size distribution (PSD) of CMP slurry is crucial for improving the productivity of the CMP process. For the quality management of CMP slurry, it is necessary to evaluate both the sizes and quantities of both the primary and secondary particles. Conventional PSD analysis methods, except for image analysis, face challenges in identifying primary and secondary particles for PSD measurements. For image analysis, the particles must be transferred from a suspension to a substrate using the conventional sampling method; however, this creates aggregates, resulting in a change in the PSD of the particles on the substrate compared to that in suspension under poly-dispersed conditions. Thus, this study proposed a novel particle sizing method using nanoparticle chip (NPC) to assist in the image analysis of the PSD. The NPC can pick up a single particle in a small volume droplet to avoid aggregation and maintain the poly-dispersed condition of the particles in suspension. The primary and secondary particles can be identified using scanning electron microscope (SEM) or atomic force microscope (AFM), and the PSD can be evaluated by measuring the area and height of the particles. Further, the quantities of both the primary and secondary particles can be counted from the substrate. This study presented a comparison of the diameter measurements using NPC and the conventional method. The results show that the NPC identified the primary and secondary particles and decreased the measurement error of the particle diameters. Consequently, the NPC proves to be superior to the conventional method for use in the PSD analysis of CMP slurry.