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Lead (Pb) is one of the most paradoxical elements, both having diverse practical uses, as well as being extremely toxic to humans, and especially to children. The use of Pb records a steady growth with annual production currently exceeding 10 million metric tons. In spite of the environmental awareness of modern society, humans are still exposed to Pb through its emission by smelting and mining activities, and also by Pb-bearing mine wastes and soils. Here, we review the chemical and mineralogical forms of Pb generated from smelting and mining processes and subsequently altered in tailings, slag piles, and soils. In smelter plumes, Pb is emitted to the atmosphere either in the form of smaller nano-size particulate matter (PM) often associated with S, or larger micrometer Pb-bearing PM matter accompanied by oxide-silicate matrices. Pb-bearing phases in mine tailings and impacted soils depict a greater mineralogical and chemical complexity than those emitted from smelters and the larger particle size of this PM also leads to a lower Pb bioavailability. High resolution observations in aquatic system, soils and rock coatings impacted by smelting and mining activities show the presence of Pb-bearing phosphates, sulfides, sulfates, carbonates, and oxide nanoparticles. Larger micrometer size particles of Pb-bearing minerals form often through the aggregation of Pb-bearing nanoparticles, a process commonly referred to as crystallization through particle attachment. Mobilization of Pb within soil columns is strongly affected by the transport of colloids, especially those composed of organic matter and Fe-hydroxides because Pb is taken up efficiently by these two soil components. The extraordinary variability and complexities of all of these processes suggest that future reduction of Pb contamination in the environment and its impact on human health mainly depends on eliminating or greatly reducing Pb-release from smelting operations and tailings impoundments.

Aluminium-wood particle composites were formed by casting method. Different weight fractions of wood particle as reinforcement to the Aluminium alloys were used to produce the composites. The physical and mechanical properties such as density, impact strength, tensile strength, hardness and microstructure were investigated. The results showed that the density decreases with the percentage increase in reinforcement. Also, a significant enhancement in the ultimate tensile strength (UTS) of the composite compared to that of pure aluminium was achieved. The maximum UTS of the Aluminium -wood composite is 97.69 MPa and occurred at 20%wt wood particulate addition reinforcement while that of the unreinforced Aluminium is 40.189 MPa. The impact energy varies from 47.00 J to 89.00 J with a maximum value at 10%wt wood particulate addition while the hardness varies from 52.33BHN to 62BHN with a maximum value at 10%wt. All the mechanical behaviours investigated in the study generally showed that the Aluminium -wood composite exhibited better mechanical properties than the pure Aluminium. The microstructure examination revealed that the wood particles were uniformly distributed in the metal matrix composite.

Gadolinium (III)-based T1 contrast agent have been widely used in clinical MRI. In this study, salicylic acid-gadolinium chelate was prepared via directly coordination reaction of gadolinium ion and salicylic acid. Then, three polyethylene glycols with different molecular weight were modified on the surface of salicylic acid-gadolinium by simple chemical coupling to construct three core-shell structural Gd based composites. The SEM and TEM characterization results show that the composite is a spherical particle with a diameter of about 100–200 nm. The longitudinal relaxation rate r1 of the Gal-PEG-2000 is 11.097 (mmol/L)–1/s, and the ratio of r2/r1 is as low as 2.53. The composite shows good liver and intestines MRI performances after being used in in vivo imaging, showing a good prospect of biological application.

As the demand for lithium-ion batteries increases, a better understanding of the complex phenomena involved in their operation becomes crucial. In this work, we propose a coupled thermo-chemo-mechanical model for electrode particles of Li-ion batteries. To this end, we start with a general finite strain continuum framework for the coupled thermo-chemo-mechanical problem and then narrow it down to cathode active particles of Li-ion batteries, particularly to lithium manganese oxide particles. Electrochemical kinetics at the surface of the particle and also heat generation due to current exchange are taken into account. Next, the numerical treatment of the problem using the finite element method is presented. Specific line elements are needed to evaluate the flux of ions at the surface of the particle. Finally, the performance of the proposed model is evaluated using a few representative boundary value problems., Deutsche Forschungsgemeinschaft, Projekt DEAL

Given the recent EURO 6 regulations, which include limits on particle number density (and hence size) for soot emissions from land vehicles, soot models must be capable of accurately predicting soot particle sizes. Previous modeling work has demonstrated the importance of the relative strengths of nucleation and condensation in predicting soot primary particle size. Due to this importance, a fundamental reversible model for nucleation and condensation, called the reversible PAH clustering (RPC) model, was developed in previous work through the use of statistical mechanics and the results from several recent works. In the present work, the RPC model is enhanced to include multiple nucleation (or dimerization) events from 6 different PAH size groups, resulting in 21 unique dimer pairs. In addition, a soot PAH tracking model is developed to track the amount of each PAH size group within soot particles. The addition of this model resulted in reduced computation times and the ability to investigate PAH-PAH reactions within soot particles. The results of the enhanced RPC model demonstrate that smaller PAHs are most important for the nucleation process, while small and large PAHs are important for the condensation process. These results are shown to be due to the relatively lower reversibility of condensation versus the nucleation process. These findings are discussed in light of recent experimental results in the literature and are shown to be well supported. Keywords: reversibility, PAH nucleation, PAH condensation, laminar diffusion flame, soot model

Filter-based offline analysis of atmospheric aerosol hygroscopicity coupled to composition analysis provides information complementary to that obtained from online analysis. However, its application itself and comparison to online analysis have remained limited to date. In this study, daily submicrometer aerosol particles (PM0.95, 50 % cutoff diameter: 0.95 μm) were collected onto quartz fiber filters in Okinawa Island, a receptor of East Asian outflow, in the autumn of 2015. The chemical composition of water-soluble matter (WSM) in PM0.95 and PM0.95 itself, and their respective hygroscopicities were characterized through the offline use of an aerosol mass spectrometer and a hygroscopicity tandem differential mobility analyzer. Thereafter, results were compared with those obtained from online analyses. Sulfate dominated the WSM mass (60 %), followed by water-soluble organic matter (WSOM, 20 %) and ammonium (13 %). WSOM accounted for most (93 %) of the mass of extracted organic matter (EOM) and the atomic O to C ratios (O : C) of WSOM and EOM were high (mean ± standard deviation were, respectively, 0.84 ± 0.08 and 0.79 ± 0.08), both of which indicate highly aged characteristics of the observed aerosol. The hygroscopic growth curves showed clear hysteresis for most samples. At 85 % RH, the calculated hygroscopicity parameter κ of the WSM (κWSM), WSOM, EOM, and PM0.95 (κPM0.95) were, respectively, 0.50 ± 0.03, 0.22 ± 0.12, 0.20 ± 0.11, and 0.47 ± 0.03. An analysis using the thermodynamic E-AIM model shows, on average, that inorganic salts and WSOM respectively contributed 88 % and 12 % of the κWSM (or κPM0.95). High similarities were found between offline and online analysis for chemical compositions that are related to particle hygroscopicity (the mass fractions and O : C of organics, and the degree of neutralization), and also for aerosol hygroscopicity. As possible factors governing the variation of κWSM, the influences of WSOM abundance and the neutralization of inorganic salts were assessed. At high RH (70–90 %), the hygroscopicity of WSM and PM0.95 was affected considerably by the presence of organic components; at low RH (20–50 %), the degree of neutralization could be important. This study not only characterized aerosol hygroscopicity at the receptor site of East Asian outflow, but also shows that the offline hygroscopicity analysis is an appropriate method, at least for aerosols of the studied type. The results encourage further applications to other environments and to more in-depth hygroscopicity analysis, in particular for organic fractions.

The phenomenon of adsorption of solid particles at fluid interfaces to stabilize emulsions or foams have been known for more than a century. Today, particle-stabilized emulsions, often referred to as Pickering emulsions, are receiving growing attention as they are encountered in oil recovery and have long been used in personal care products and food industry. In the past 10 years the focus of the Pickering emulsion has also increasingly shifted to biomedical applications with thanks to novel syntheses of a wide range of biocompatible particle stabilizers. Here, a brief overview of the development of biocompatible particles is given for Pickering emulsion stabilization, including alginate, poly(lactic-co-glycolic acid) (PLGA), and protein-based particles. The materials capable of being prepared by templating from emulsion stabilized with biocompatible particles include colloidal capsules and hierarchically porous materials. It is hoped that the understanding gained from the recent intense activity in the field will enable more researchers to modify existing materials and design new formulations, which would be beneficial for exploring more biological applications.

Acknowledgements: This work has been supported by EPSRC, via an industrial CASE award (for YC) with AWE (EP/R511870/1). © British Crown Copyright 2020/AWE., Tensile stress–strain testing and creep testing have been carried out on a polyurethane rubber, at three temperatures, with and without either particulate or short fibre alumina reinforcement. A previous paper reported concerning composites with particulate reinforcement and the present work is focused on the effect of the fibres. The samples were made via a blending and extrusion process that produced a certain degree of fibre alignment (along the direction of loading). Prior milling procedures were used to produce fibres with two different ranges of aspect ratio (with averages about 10 and 16). When expressed as true stress–strain relationships, all materials exhibit approximately linear responses. The dependence of stiffness on the volume fraction and aspect ratio of the reinforcement was found to conform well to the Eshelby model predictions. Moreover, the creep behaviour of all of the materials can be captured well by a Miller–Norton formulation, using the average matrix stress predicted by the Eshelby model. A striking conclusion is that it is both predicted and observed that short fibres are much more effective in reducing the creep rate than is the case with particles.

ispartof: ULTRASONICS SONOCHEMISTRY vol:93 status: published

Plug, a type of male mould in thermoforming, is mostly produced by conventional processes such as machining. However, in this study, plugs that are used in thermoforming were produced using Fused Deposition Modelling (FDM). Plugs were produced using Polylactic Acid (PLA) and Aluminium (Al) particle reinforced PLA filaments by a 3d printer. Plugs that are produced by FDM, were polished using 800, 1000, 1200, 1600 and 2000 grit sandpapers to reduce friction. Also, thermal effects such as temperature distribution on the region where the plug touches the plastic sheet, were investigated. It has been found that FDM can be a significant alternative for male mould production in thermoforming. Additionally, PLA filaments have great potential for tool production in thermoforming.

The super-structured nanodimensional apatitic particles have been limited explored for therapeutic applications. Furthermore, ion substituted super-structured nanodimensional apatitic particles have been rarely attempted, which motivated the present investigation. In the present work, F − and Cl − substituted hydroxyapatite (HAP) prepared via a facile and economical one-pot hydrothermal route were characterized for their structural, morphological and bioactive properties. The F − and Cl − anions (1 wt%) were individually substituted in hierarchically assembled nanostructured apatitic (HANA) particles and produced fluorine substituted Hydroxyapatite (FHAP) and chlorine substituted Hydroxyapatite (ClHAP) HANA particles, respectively. Besides comprehensive characterization, particles were systematically tested for their in-vitro ionic dissolution and drug-carrying abilities. Both FHAP and ClHAP nanoparticles exhibited monolithic apatitic structure, novel spherical morphology having substituted elements, mesoporous large surface area, and pore-volume with high thermal stability. Furthermore, both particles exhibited superior in-vitro bioactivity ability. Besides it, both FHAP and ClHAP nanoparticles exhibited superior drug loading and sustained drug release characteristics. Thus, this study presented the potentials of novel particle shapes with superior bioactivity and drug-carrying abilities, making them suitable for multipurpose therapeutic applications, including tissue regeneration and drug-carrying agents.

Hypothesis Waterborne polyurethane (WPU) is a common colloidal dispersion that can aggregate in the aqueous phase to form nanoparticles with hydrophobic polyurethane chains as the core and hydrophilic ionic groups as the shell. Considering their structure and pH-responsive functional groups, WPU nanoparticles could be ideal particulate emulsifiers for preparing pH-responsive Pickering high internal phase emulsions (HIPEs). Experiments A series of anionic WPU with different content of 2,2-bis(hydroxymethyl)propionic acid (DMPA) side chains were synthesized via a polyaddition reaction. The DMPA content, size, ζ-potential, and interfacial behaviors of WPU were then investigated. Furthermore, the effects of particle concentration, internal phase fraction (ϕ), oil type, and pH values on the Pickering HIPEs’ morphology, stability, and rheological behaviors were systematically studied. Finally, we demonstrated the emulsification–demulsification process of WPU-stabilized Pickering HIPEs and discussed its mechanism. Findings Oil-in-water (O/W) Pickering HIPEs with tailored morphology and excellent pH-responsiveness were prepared from anionic WPU nanoparticles. The WPU concentration, ϕ, and oil type had a large impact on the formation and mean droplet size of the WPU-stabilized emulsions. Rheology analysis demonstrated that the strictly limited movement of droplets endowed the WPU-stabilized HIPEs with high stability, shear sensitivity, and excellent thixotropic recovery. By simply changing the aqueous-phase pH value, the WPU-stabilized HIPEs could undergo more than ten emulsification-demulsification cycles, as the physical and interfacial properties of WPU nanoparticles were pH-dependent. The excellent performance of the WPU-stabilized pH-responsive Pickering HIPEs exhibited their potential practical applications, such as for oil transportation and recovery, emulsion polymerization, and heterogeneous catalysis.

This work presents the effects of several factors on the mechanical strength of calcium phosphate cement (CPC) based on alpha tricalcium phosphate and correlates the results with the microstructure and percentage of conversion to hydroxyapatite. Conversion rate increased by raising the setting temperature in the studied range (4–90 °C), but the strength exhibited an increasing-decreasing trend due to changes in the morphology of hydrated crystals. Plate-like crystals were formed in the range of 22–60 °C, mechanically reinforcing the material, whereas the formation and refinement of needle-like crystals at higher setting temperature decreased the strength. Moreover, cements with dissimilar particle sizes had different optimal hydrolysis temperatures that resulted in the maximum strength. The finest powder led to higher strength at lower setting temperature due to the formation of a more compact crystal network and higher conversion. Therefore, optimization of powder particle size may allow to achieve the highest possible strength at room temperature, being beneficial for the production of the strong pre-set CPC-based implants without the use of energy. Furthermore, the particle size can be also engineered to produce formulations that develop the highest strength at physiological temperature, with application as injectable bone grafts. The incorporation and crosslinking of gelatine further increased the mechanical strength of pre-set cements by bridging the hydroxyapatite crystals, the setting temperature showing a similar effect to that of gelatine-free cements. In contrast, moisture decreased the strength and reduced the brittleness by the solvating intramolecular association between hydroxyapatite crystals and between gelatine molecules. Moreover, large cement bodies were slightly weaker than small ones, but the size effect was not statistically significant.

Atmospheric organic acids (OAs) are expected to enhance methanesulfonic acid (MSA)-driven new particle formation (NPF). However, the exact role of OAs in MSA-driven NPF remains unclear. Here, we employed a two-step strategy to probe the role of OAs in MSA–methylamine (MA) NPF. Initially, we evaluated the enhancing potential of 12 commonly detected OAs in ternary MA–MSA–OA cluster formation by considering the formation free energies of the (MSA)1(MA)1(OA)1 clusters and the atmospheric concentrations of the OAs. It was found that formic acid (ForA) has the highest potential to stabilize the MA–MSA clusters. The high enhancing potential of ForA results from its acidity, structural factors such as no intramolecular H bonds, and high atmospheric abundance. The second step is to extend the MSA–MA–ForA system to larger cluster sizes. The results indicate that ForA can indeed enhance MSA–MA NPF at atmospheric conditions (the upper limited temperature is 258.15 K), indicating that ForA might have an important role in MSA-driven NPF. The enhancing effect of ForA is mainly caused by an increased formation of the (MSA)2(MA)1 cluster, which is involved in the pathway of binary MSA–MA nucleation. Hence, our results indicate that OAs might be required to facilitate MSA-driven NPF in the atmosphere.

As a state-of-the-art secondary battery, lithium-ion batteries (LIBs) have dominated the consumer electronics market since Sony unveiled the commercial secondary battery with LiCoO2 as the negative electrode material in the early 1990s. The key to the efficient operation of LIBs lies in the effective contact between the Li-ion-rich electrolyte and the active material particles in the electrode. The particle properties of the electrode materials affect the lithium ion diffusion path, diffusion resistance, contact area with the active material, the electrochemical performance and the energy density of batteries. To achieve satisfied comprehensive performance and of LIBs, it is not only necessary to focus on the modification of materials, but also to balance the properties of electrode material particles. Therefore, in this review, we analyze the influence of particle properties on the battery performance from three perspectives: particle size, particle size distribution, and particle shape. A deep understanding of the effect and mechanism of particles on electrodes and batteries will help develop and manufacture practical LIBs.

CdO nanoparticles (CdO NPs) were synthesized utilizing urea-assisted auto-combustion (AC) and microwave combustion (MC) methods. The structural, thermal, optical, morphological, and compositional analysis of the prepared samples were investigated after they were heat treated at 350 °C. The impact of heat treatment and the method of synthesis on their physicochemical properties were investigated. XRD was used to determine the phase, crystallite size, and lattice constant of CdO NPs. The modification of the phase and crystallite size of CdO NPs indicates the impact of the heat treatment and synthesis process. The annealing process raises the crystallite size from 28 nm to 45 nm for the auto combustion approach and from 24 nm to 40 nm for the microwave combustion method. Under heat treatment, the energy band gaps of CdO NPs from auto combustion method and microwave combustion method samples were determined to be 2.09 eV and 1.65 eV, respectively. The surface morphology of CdO NPs was documented by SEM, indicating that the particle's morphology was modified by the synthesis procedure. The nanoscale range of the particles is confirmed by TEM micrographs of annealed CdO NPs, which is closely matched with the crystallite size derived from XRD. TG-DTA was used to examine the thermal characteristics of annealed CdO NPs.

Mesoporous silica nanoparticles (MSN) are promising drug vectors due to their high drug loading capacities, degradability under biologically relevant conditions. The dissolution of MSN has been the focus of several recent studies, most of which have, however, been carried out in the absence of proteins, and do therefore not reflect the conditions prevailing during in vitro or in vivo administration of the particles. Furthermore, typically the dissolution studies are limited with respect to the range of MSN concentrations applied. Here, we report results related to the dissolution kinetics and structural particle evolution for MCM-48 MSN carried out in the presence of proteins, and where the particle concentration has been used as a parameter to cover typical concentrations used in in vitro and in vivo studies involving MSNs. Proteins adsorbing to the MSN surface form a diffusion limiting layer that leads to the intermediate formation of core-shell structured particles upon dissolution. Here, the protein concentration controls the kinetics of this process, as the amount of protein adsorbing to the MSN increase with increasing protein concentration. The results thus also imply that the MSN dissolution kinetics is faster under normally applied in vitro conditions as compared to what can be expected under full serum conditions.

Bioactive ions (Mg, Sr, Zn) doped carbonated hydroxyapatite powders (dHAp) and pure carbonated hydroxyapatite (HAp) powders were prepared by wet chemical precipitation method. The bioactive ions were incorporated into the HAp matrix by co-precipitation from solution containing the appropriate amount of chloride salt of different ions. The morphology of pure HAp was mainly needle-like in nanometre size and the particles were disordered showing quasi-amorphous structure. The ion doping changed the morphology of particles, the dHAp particles had distorted spheroid shapes. Owing to the ion addition, the crystallinity of particles decreased. Particle aggregations can also be observed in both types of samples. HAp and dHAp loaded biopolymer polyvinylpyrrolidone (PVP) composite materials have also been developed by novel electrospinning technique. It has been shown that both the HAp and dHAp particles can be successfully incorporated into the PVP fibre web matrix and simultaneously the bioceramic powders were attached to the surface of polymer fibres. The surface of fibres was not fully covered with the particles. The ceramic powder addition to the polymer solution caused the polymer fibres to become more entangled and the diameters of fibres varied over a wider range compared to the base polymer fibres without bioceramic powder addition.

Filter media made of expanded polytetrafluoroethylene filters are known to be incompatible with poly-alpha-olefin or any oil-based challenge particles, and thus, filters made of expanded polytetrafluoroethylene had limited use in pharmaceutical applications. The benefits of expanded polytetrafluoroethylene filters, e.g. intrinsic durability, more energy-efficient, chemical inertness, etc., are therefore not being fully utilized. A new expanded polytetrafluoroethylene filter media compatible with poly-alpha-olefin particles was then developed by a filter manufacturer. The goal of this study is to investigate the filtration performance and characteristics of the new expanded polytetrafluoroethylene media and to compare it with the conventional expanded polytetrafluoroethylene media. In this study, four pleated high-efficiency particulate air filters made of either the conventional or the new expanded polytetrafluoroethylene media, and either of the two variants of pleat depths (36 mm and 31 mm) were tested under two different challenge tests, one using potassium chloride (KCl) salt particles and the other using poly-alpha-olefin particles. Both challenge particles are submicron and polydisperse. The collection efficiency, pressure drop, and dust holding capacity were measured in both tests. Due to the sensitivity of KCl particle release to environmental factors, a repeatability test was also performed for the KCl test. poly-alpha-olefin test results show that the new expanded polytetrafluoroethylene filter performed remarkably better than the conventional expanded polytetrafluoroethylene filter, achieving a high amount of dust retention at the same preset final pressure drop.

A thorough understanding of chemical composition, particle pH, and pollutant emissions is essential to address the climate and human health effects of atmospheric particles. In this study, we used a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and Scanning Mobility Particle Sizer (SMPS) to characterize the composition of submicron particles. Moreover, we applied the ISORROPIA-II model to analyze the particle acidity effect on the compositional characterization of submicron particles from December 22, 2016 to January 7, 2017 in Albany, New York, USA. The results indicated that aerosols with mobility diameter from SMPS in the range 200–400 nm were the main contributors to the mass during the measurement period. The dominance of organics (47%) and sulfate (16%) was similar to previous observations in the eastern United States in Winter 2015, while the fraction of nitrate (23%) was much higher. Moreover, nitrate could easily form at colder temperatures and lower RH levels even when there were more acidic particle periods during the measurement period in Albany. The ISORROPIA-II model indicated that there were more acidic particles, which was estimated using pH values. Lower temperature conditions tended to favor nitrate formation. The nitrate concentration exceeded that of sulfate in the measurement period, even though the SO2 and NOx emissions were similar. The organics in submicron particles were strongly influenced by the local emissions in winter. However, the inorganic compounds in submicron particles could be derived from regional transport as their pollution sources originated from different directions. This may help strategize emission reductions in the future.

Dielectric loss is greatly important for electromagnetic wave absorption. However, the detailed mechanism for this interfacial polarization is still sorely lacking and the main contribution of dielectric loss in the supported materials has never been investigated until now. Here, we have designed a model dielectric material with a carbon-based supported structure in order to explain the main contribution of dielectric loss originated from its interfacial polarization. The experimental and theoretic results proved that the complicated nanoparticles (NPs) supported on carbon substrate (MOF-74-S1) with optimal particle distribution can form three kinds of interfacial polarizations compared with MOF-74-S2, which mainly contributes to the dielectric loss of the carbon-based composites. The optimal composition and distribution of the NPs bring enhanced dielectric loss and the best electromagnetic wave absorbing properties, with a minimum reflection loss of −33.5 dB and a broad effective absorption bandwidth of 7.6 GHz at a thickness of 2.3 mm. These findings indicate that the optimal distribution of nanoparticles is one of the promising methods to enhance the dielectric loss.

We design an interpenetrating network of silane-functionalized nanocomposites to enhance particle dispersity and interfacial bonding strength in nanocomposites. To qualitatively measure the enhanced particle dispersity in the nanocomposites, we carry out rheological characterizations and suggest a simple particle dispersity index from the viscoelastic responses. Yield stresses of the nanocomposites are obtained by fitting with the Carreau-Yasuda model. After comparing the yield stresses and elastic moduli of the nanocomposites during photo-polymerization, we confirm that interphase regions significantly affect the interfacial bonding and mechanical strengths. Prediction of elastic moduli of the nanocomposites by the Mori-Tanaka micromechanics model agrees well with the experimental data, verifying that a good interpenetrating network exists between the nanoparticles and matrix.

Injecting sulfur dioxide into the stratosphere with the intent to create an artificial reflective aerosol layer is one of the most studied options for solar radiation management. Previous modelling studies have shown that stratospheric sulfur injections have the potential to compensate for the greenhouse-gas-induced warming at the global scale. However, there is significant diversity in the modelled radiative forcing from stratospheric aerosols depending on the model and on which strategy is used to inject sulfur into the stratosphere. Until now, it has not been clear how the evolution of the aerosols and their resulting radiative forcing depends on the aerosol microphysical scheme used – that is, if aerosols are represented by a modal or sectional distribution. Here, we have studied different spatio-temporal injection strategies with different injection magnitudes using the aerosol–climate model ECHAM-HAMMOZ with two aerosol microphysical modules: the sectional module SALSA (Sectional Aerosol module for Large Scale Applications) and the modal module M7. We found significant differences in the model responses depending on the aerosol microphysical module used. In a case where SO2 was injected continuously in the equatorial stratosphere, simulations with SALSA produced an 88 %–154 % higher all-sky net radiative forcing than simulations with M7 for injection rates from 1 to 100 Tg (S) yr−1. These large differences are identified to be caused by two main factors. First, the competition between nucleation and condensation: while injected sulfur tends to produce new particles at the expense of gaseous sulfuric acid condensing on pre-existing particles in the SALSA module, most of the gaseous sulfuric acid partitions to particles via condensation at the expense of new particle formation in the M7 module. Thus, the effective radii of stratospheric aerosols were 10 %–52 % larger in M7 than in SALSA, depending on the injection rate and strategy. Second, the treatment of the modal size distribution in M7 limits the growth of the accumulation mode which results in a local minimum in the aerosol number size distribution between the accumulation and coarse modes. This local minimum is in the size range where the scattering of solar radiation is most efficient. We also found that different spatial-temporal injection strategies have a significant impact on the magnitude and zonal distribution of radiative forcing. Based on simulations with various injection rates using SALSA, the most efficient studied injection strategy produced a 33 %–42 % radiative forcing compared with the least efficient strategy, whereas simulations with M7 showed an even larger difference of 48 %–116 %. Differences in zonal mean radiative forcing were even larger than that. We also show that a consequent stratospheric heating and its impact on the quasi-biennial oscillation depend on both the injection strategy and the aerosol microphysical model. Overall, these results highlight the crucial impact of aerosol microphysics on the physical properties of stratospheric aerosol which, in turn, causes significant uncertainties in estimating the climate impacts of stratospheric sulfur injections.

In this study, the forms of occurrence of impurity elements in silicon carbide (SiC) with different particle sizes were systematically investigated using a combination of X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometry (ICP-OES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The experimental results showed that in SiC powders prepared using the Acheson process, the contents of O, free-Si, free-C, and Fe impurities are high, and those of other trace impurity elements follow the order: Ti > Al > Ni > V. Moreover, O impurities mainly cover the SiC particle surface in the form of amorphous SiO2. Fe impurities exist around SiC particles as Fe2O3, FexSiy, FexSiyTiz, and FexAlySiz phases. Impurity elements are often introduced during the smelting of SiC and/or during milling or subsequent storage.

Abstract Oxidized tannic acid (OTA) is a useful biomolecule with a strong tendency to form complexes with metals and proteins. In this study we open the possibility to further the application of OTA when assembled as supramolecular systems, which typically exhibit functions that correlate with shape and associated morphological features. We used machine learning (ML) to selectively engineer OTA into particles encompassing one-dimensional to three-dimensional constructs. We employed Bayesian regression to correlate colloidal suspension conditions (pH and pKa) with the size and shape of the assembled colloidal particles. Fewer than 20 experiments were found to be sufficient to build surrogate model landscapes of OTA morphology in the experimental design space, which were chemically interpretable and endowed predictive power on data. We produced multiple property landscapes from the experimental data, helping us to infer solutions that would satisfy, simultaneously, multiple design objectives. The balance between data efficiency and the depth of information delivered by ML approaches testify to their potential to engineer particles, opening new prospects in the emerging field of particle morphogenesis, impacting bioactivity, adhesion, interfacial stabilization, and other functions inherent to OTA. Impact statement Tannic acid is a versatile bio-derived material employed in coatings, surface modifiers, and emulsion and growth stabilizers, which also imparts mild anti-viral health benefits. Our recent work on the crystallization of oxidized tannic acid (OTA) colloids opens the route toward further valuable applications, but here the functional properties tend to depend strongly on particle morphology. In this study, we eschew trial-and-error morphology exploration of OTA particles in favor of a data-driven approach. We digitalized the experimental observations and input them into a Gaussian process regression algorithm to generate morphology surrogate models. These help us to visualize particle morphology in the design space of material processing conditions, and thus determine how to selectively engineer one-dimensional or three-dimensional particles with targeted functionalities. We extend this approach to visualize other experimental outcomes, including particle yield and particle surface-to-volume ratio, which are useful for the design of products based on OTA particles. Our findings demonstrate the use of data-efficient surrogate models for general materials engineering purposes and facilitate the development of next-generation OTA-based applications. Graphic abstract

The susceptibility of super paramagnetic iron oxide (SPIO) particles makes them a useful contrast agent for different purposes in MRI. These particles are typically quantified with relaxometry or by measuring the inhomogeneities they produced. These methods rely on the phase, which is unreliable for high concentrations. We present in this study a novel Deep Learning method to quantify the SPIO concentration distribution. We acquired the data with a new sequence called View Line in which the field map information is encoded in the geometry of the image. The novelty of our network is that it uses residual blocks as the bottleneck and multiple decoders to improve the gradient flow in the network. Each decoder predicts a different part of the wavelet decomposition of the concentration map. This decomposition improves the estimation of the concentration, and also it accelerates the convergence of the model. We tested our SPIO concentration reconstruction technique with simulated images and data from actual scans from phantoms. The simulations were done using images from the IXI dataset, and the phantoms consisted of plastic cylinders containing agar with SPIO particles at different concentrations. In both experiments, the model was able to quantify the distribution accurately.

Tungsten carbide (WC) reinforced metal matrix composites are ideal protective coatings against wear and are widely used for surface coating. However, WC particle dissolution, subsidence, and coating cracking are some of the known challenges limit the application of the coating fabricated by plasma cladding with traditional synchronous feeding. To address this issue, a plasma remelting and injection (PRI) method is proposed to fabricate WC reinforced metal matrix composite coatings. The optimal injection angle of the WC particles was determined by infrared image and geometric calculations, to improve the utilization rate and decrease the dissolution of the particles. The microstructure, hardness, residual stress, and WC particle distribution of the coatings fabricated by the PRI and synchronous-feeding methods were investigated, and the mechanism of WC particle dissolution was analyzed. The results indicate that the WC particles of the synchronous-feeding coating obviously sank to the coating bottom, and transcrystalline cracks appeared inside the WC particles, resulting in serious cracking of the coating. By contrast, the PRI method could effectively avoid the subsidence of WC particles and reduce the thermal damage to WC particles, which increased the coating surface hardness and reduced the residual stress and cracking tendency of the coating.

Near-infrared (NIR) fluorophores are emerging tools for biophotonics because of their reduced scattering, increased tissue penetration and low phototoxicity. However, the library of NIR fluorophores is still limited. Here, we report the NIR fluorescence of two benzene-fused oligo-BODIPYs in their hexameric (H) and octameric (O) forms. These dyes emit bright NIR fluorescence (H: maxima 943/1075 nm, O: maxima 976/1115 nm) that can be excited in the NIR (H = 921 nm, O = 956 nm) or non-resonantly over a broad range in the visible region. The emission bands of H show a bathochromic shift and peak sharpening with increasing dye concentration suggesting the presence of J-aggregates. Furthermore, the emission maxima of both H and O shift up to 20 nm in solvents of different polarity. These dyes can be used as NIR ink and imaged remotely on the macroscopic level with a stand-off distance of 20 cm. We furthermore demonstrate their versatility for biophotonics by coating microscale beads and performing microrheology via NIR video particle tracking (NIR-VPT) in biopolymer (F-actin) networks. No photodamaging of the actin filaments takes place, which is typically observed for visible fluorophores and highlights the advantages of these NIR dyes.

In this study, the temperature and volume fraction distributions of liquid silicon nanoparticles in the aerosol flow in gas-phase synthesis were retrieved using tomographic reconstruction of emission and extinction spectra in the 230–700 nm range. Measurements were done in an optically accessible microwave-plasma flow reactor fed with a SiH4/H2/Ar gas mixture. Optical emission and extinction spectra in the visible spectral range were captured along a line perpendicular to the flow direction covering the entire cross-section of the Si particle stream. Particle temperature and volume fraction distributions were determined and the preferred location of the silicon particles in a 1-mm thick zone at the circumference of the cylindric flow was revealed. The combined recording of line-resolved emission/extinction spectra is a promising method for spatially-resolved detection of nanoparticles in combustion or gas-phase synthesis.

With polystyrene nanoparticles being widely used in various applications, there is a great need for deeper knowledge on the safety, fate and biological effects of these particles on both individual living organisms and the whole ecosystems. Due to this, there is a growing interest in performing ecotoxicological studies using model plastic nanoparticles, and consequently it generates an increasing number of published papers describing the negative impact on wildlife caused by such nanoparticles. Polystyrene is the most studied nanosized plastic, therefore this review focuses on research conducted with manufactured polystyrene nanoparticles. The aim of the present article is to provide a critical methodological outline of the existing ecotoxicological studies on the effects of polystyrene nanoparticles on aquatic organisms. Going through the published articles, we noted that particle characterization especially in the test medium, can be improved. The analysis also highlights the importance of purifying the polystyrene nanoparticles before studying its toxicity. Furthermore, the size characterization of such nanoparticles is underemphasized, and in future studies, authors should consider including more techniques to achieve this goal. Finally, short-term or direct exposure scenarios do not add the most environmentally relevant knowledge in terms of the toxicity caused by polystyrene nanoparticles.

Solid-state lithium batteries (SSLBs) have been identified as one kind of the most promising energy conversion and storage devices because of their safety, high energy density, and long cycling life. The development of solid-state electrolyte is vital to commercialize SSLBs. Composite polymer electrolyte (CPE), derived by compositing inorganic particles into solid polymer electrolyte has become the most practical species for SSLBs because it inherits the advantages of polymer electrolyte and simultaneously achieves enhanced ionic conductivity and mechanical properties. The characteristics of inorganic particles and their interaction with polymers strongly impact the performance of CPE, improving its ionic conductivity, mechanical properties, thermal and electrochemical stability, as well as interface compatibility with both electrodes. In this review, the effects of particle characteristics including its species, size, proportion, morphology on the ionic conductivity and mechanical properties of CPE are reviewed. Meanwhile, some novel composite strategies are also introduced including surface modification, hybridization, and alignment of particles in polymer matrices, as well as some new preparation methods of CPE. The interactions between particles and other components in CPE including polymer matrices or lithium salt are particularly focused herein to reveal the lithium conductive mechanism. Finally, a perspective on the direction of future CPE development for SSLBs is presented.

Microwave synthesis method was adopted to prepare CdO nanoparticles using polyethylene glycol (PEG), NH3 and NaOH as a co-reagent. A systematic investigation by XRD, SEM, TEM and EDS has been undertaken to evaluate the role of co-reagents on the microstructural and morphological study of the metal oxide nanostructure obtained. The pH of the solution, determined by the co-reagent used, was the main parameter addressing the morphology of CdO nanostructures obtained. By using NH3 the growth of individual CdO particle is favored at the low pH of 9, likely due to low Cd supersaturation rate at this pH. On the other hand, the presence of NaOH as co-reagent increases pH to 11, enhancing Cd supersaturation and leading mainly to formation of nanowire aggregates. The optical and photoluminescence characteristics of the different CdO nanostructures synthesized have been also evaluated.

Electrostatic precipitators (ESPs) are widely used to control air pollution. However, their applications in portable air cleaners are limited owing to ozone generation during the discharging process. In this study, we developed a compact two-stage ESP that combines corona discharging and particle collection modules. The former generates an extremely small amount of ozone using dielectric film coating, whereas the latter has a large specific surface area. A polypropylene (PP) film is coated as a dielectric material on the ground electrode of the discharging module. The corona current is reduced by the PP film, which in turn reduces the ozone generation. The efficiency of atmospheric particle collection and ozone generation were evaluated by varying the flow rates and applied voltages of the 4-channel discharging and roll-type collection modules. Additionally, the specific surface area of 707 m2/m3 of the roll-type collection module minimized the size of the device by increasing its integrity. The proposed ESP with PP coating exhibited the tendency of a conventional ESP that follows the Deutsch equation. All particles of size over 1 m were removed from the atmosphere by the proposed device at a flow rate of 194.4 L/min, which is more than three times that of human breathing. Furthermore, our experimental device removed more than 50% of the ultrafine particles of size 0.3 m without ozone generation. Therefore, the proposed device can be potentially used in portable or wearable air-cleaning devices to aid individual healthcare.

Direct absorption of sunlight with carbon nanofluids is a facile way to efficiently harvest solar-thermal energy, but poor dispersion stability of nanofluids under elevated temperatures severely limits their applications. Herein, we report a general strategy to prepare stably-dispersed medium-temperature solar-thermal nanofluids by employing crumpled particles of ethanol-wetted graphene oxide sheets as the self-dispersible photothermal converters. The crumpled particles simultaneously possess intensively-deformed surface structure, a low density and a small particle size. Such features weaken the inter-particle van der Waals attraction and gravitational sedimentation of the crumpled particles, thereby enabling their long-term stable dispersion within commercial thermal storage oils. Uniform dispersion of nanofluids was maintained after continuous heating for 2 weeks under a heating temperature up to 200 °C. The homogenously dispersed nanofluids also achieved high solar absorptance with low particle loadings, and retained the large heat capacity and suitable viscosity. These combined advantageous thermophysical properties enabled consistent high-performance medium-temperature direct absorption-based nanofluidic solar-thermal energy harvesting under large-flux solar illumination.

We investigate the microphysics of contrail formation behind commercial aircraft by means of the particle-based LCM (Lagrangian Cloud Module) box model. We extend the original LCM to cover the basic pathway of contrail formation on soot particles being activated into liquid droplets that soon after freeze into ice crystals. In our particle-based microphysical approach, simulation particles are used to represent different particle types (soot, droplets, ice crystals) and properties (mass/radius, number). The box model is applied in two frameworks. In the classical framework, we prescribe the dilution along one average trajectory in a single box model run. In the second framework, we perform a large ensemble of box model runs using 25 000 different trajectories inside an expanding exhaust jet as simulated by the LES (large-eddy simulation) model FLUDILES. In the ensemble runs, we see a strong radial dependence of the temperature and relative humidity evolution. Droplet formation on soot particles happens first near the plume edge and a few tenths of a second later in the plume centre. Averaging over the ensemble runs, the number of formed droplets and ice crystals increases more smoothly over time than for the single box model run with the average dilution. Consistent with previous studies, contrail ice crystal number varies strongly with atmospheric parameters like temperature and relative humidity near the contrail formation threshold. Close to this threshold, the apparent ice number emission index (product of freezing fraction and soot number emission index) strongly depends on the geometric-mean dry core radius and the hygroscopicity parameter of soot particles. The freezing fraction of soot particles slightly decreases with increasing soot particle number, particularly for higher soot number emissions. This weakens the increase of the apparent ice number emission index with rising soot number emission index. Comparison with box model results of a recent contrail formation study by Lewellen (2020) (using similar microphysics) shows a later onset of our contrail formation due to a weaker prescribed plume dilution. If we use the same dilution data, our evolution and Lewellen's evolution in contrail ice nucleation show an excellent agreement cross-verifying both microphysics implementations. This means that differences in contrail properties mainly result from different representations of the plume mixing and not from the microphysical modelling. Using an ensemble mean framework instead of a single trajectory does not necessarily lead to an improved scientific outcome. Contrail ice crystal numbers tend to be overestimated since the interaction between the different trajectories is not considered. The presented aerosol and microphysics scheme describing contrail formation is of intermediate complexity and thus suited to be incorporated in an LES model for 3D contrail formation studies explicitly simulating the jet expansion. Our box model results will help interpret the upcoming, more complex 3D results.

Fractionation of particles in deep-water sediment gravity flows is an important factor in the resulting deposit and for discriminating sedimentary environments, but remains poorly understood. Quantitative characterization of particle shape was performed for more than ten-thousand particles of experimental gravity flow experiments (both of cohesive and non-cohesive nature) made using coal and kaolin particles. Eleven particle shape parameters were calculated and their distribution and trends within the experimental basin were evaluated. Results indicate the existence of non-normal distributions and observable correlations between particle shape parameters. Shape parameters such as circularity and roundness are dominant controls on shape variation. Strong correlations exist between mean shape parameters and along-flow distance from the source for particles in non-cohesive flow experiments. Important differences were observed between shape parameter distributions of particles sampled at different areas within the experimental basin, which can be grouped based on their depositional setting (proximal or distal) using multivariate statistical analysis, especially for the non-cohesive flow experiments. A tendency for more elongated and irregularly-shaped particles at the more distal and marginal areas of the studied experimental basin was observed and validated by previous field studies in real-world deep-marine deposits. Besides, fractionation of particles is less-pronounced in cohesive flows compared with non-cohesive ones suggesting the soundness of discrimination of depositional settings based solely on particle shape characteristics is strongly dependent on parent flow characteristics. Yet, results highlight the potential of particle shape analysis in revealing spatial particle shape trends due to hydrodynamic fractionation and discriminating different depositional settings within submarine fans. This methodology may be applied to seafloor and subsurface samples to help identify the flow process and depositional environment.

Natural gas hydrates are mostly formed in low-permeability and fractured muddy sedimentary formations. Adding suitable nanoparticles to the drilling fluid system can improve its filtrate resistance and fracture plugging, and effectively weaken the invasion of drilling fluid into the reservoir. However, it is likely that nanoparticles promote hydrate formation and accumulation in wellbores and will induce accidents. Therefore, this study investigated the effect of hydrophilic silica nanoparticles with particle sizes of 30 nm, 60 nm, and 80 nm and concentrations of 0.5–4.0 wt.% on hydrate formation during upward migration of methane gas using a dynamic simulation system for hydrate formation in a wellbore. The experimental results show that under the condition of methane gas migration, hydrophilic silica nanoparticles inhibit hydrate formation. The inhibition effect increased with an increase in the particle size under a constant concentration, whereas it first increased and then decreased with increasing nanoparticle concentration under a constant particle size. The strongest inhibition effect was observed at a hydrophilic silica nanoparticle concentration of 2.0 wt.%. The influence of hydrophilic silica nanoparticles on hydrate formation may be mainly determined by their hydrophilic properties, heat and mass transfer, and gas migration in the wellbore. Our research indicates that hydrophilic silica nanoparticles can be added to hydrate drilling fluid systems if their concentration can be properly controlled.

A series of ring shear tests were conducted to investigate the ultimate particle size distribution of a carbonate sand. The tests were carried out under different stress levels, on three types of specimens: 1) uniformly graded specimens made of dry natural sand 2) remoulded specimens of the crushed sand after first shearing to large strains 3) specimens made of natural sand grains but with the same grading as in (2). The first series of tests on type (1), carried out to very large strains, led to apparently stable gradings, distinct for each stress level. Only limited additional particle breakage could be induced by remoulding the specimens after shearing (type (2)) and subjecting them to more shearing. Tests on specimens created at the apparently stable gradings (type (3)) but from the intact sand particles however led to significantly greater breakage. For the three types a stable, fractal grading was achieved. Analyses of the soil particles’ shape showed that the aspect ratio, sphericity and circularity reach a steady value at large strains, in parallel to reaching a stable grading. The mobilized angle of shearing resistance however was not significantly different in the different types of samples, suggesting the final grading dominates the behaviour.

Prediction of combustion characteristics of aluminum particle is of great significance for a variety of propulsion and power systems to achieve optimal energy release within a limited residence time. In this study, a diffusion-controlled combustion model for micro aluminum particle was developed and validated to predict the burning time and capture the evolution of particle size during combustion in environments with multiple oxidizers. Thereafter, the key factors influencing particle combustion were evaluated including particle size, ambient temperature, oxidizer concentration and characteristics of oxide cap. The burning time drops as the oxidizer concentration and the ambient temperature increase, and their influences on burning time become weakened gradually. The effect of oxidizer concentration presents more obvious than ambient temperature. As the number of oxide cap increases from 2 to 5, the burning time rises by 6.9%–27.4%. Then a non-linear empirical equation was proposed to describe the effective oxidizer, which is more accurate than the existing linear correlation, especially for H2O. Finally, a formula capable of predicting the burning time was proposed and validated, providing a convenient and accurate method for practical application.