Presence Of Ultrafine Particles Research Articles

A Study on the Effect of Particle Size on Li-Ion Battery Recycling via Flotation and Perspectives on Selective Flocculation

The recycling of active materials from Li-ion batteries (LIBs) via froth flotation has gained interest recently. To date, recycled graphite has not been pure enough for direct reuse in LIB manufacturing. The present work studied the effect of particle sizes on the grade of recycled graphite. Furthermore, selective flocculation is proposed as a novel approach to control particle sizes and thus improve graphite grade by preventing the entrainment of cathode components. Zeta potential and particle size measurements were performed to find an optimal pH for electrically selective flocculation and to study the interaction of flocculants, respectively. Batch flotation experiments were performed to investigate the effect of particle size on the purity of the recovered graphite. Results suggested that, in the absence of ultrafine fine particles, battery-grade graphite of 99.4% purity could be recovered. In the presence of ultrafine particles, a grade of 98.2% was observed. Flocculating the ultrafine feed increased the grade to 98.4%, although a drop in recovery was observed. By applying a dispersant in addition to a flocculant, the recovery could be increased while maintaining a 98.4% grade. Branched flocculants provided improved selectivity over linear flocculants. The results suggest that particle size needs to be controlled for battery-grade graphite to be recovered.

Impact of post-heat-treatment on the surface-roughness, residual stresses, and micromorphology characteristics of plasma-sprayed pure hydroxyapatite and 7%-Aloxite reinforced hydroxyapatite coatings deposited on titanium alloy-based biomedical implants

The biocompatible hydroxylapatite (Ca10(PO4)6(OH)2) (HA) coating is usually depositing on the titanium substrate to enhance the healing process of implant and to isolate it from the harsh body environment. However, poor mechanical properties of HA restrict its usage for orthopedic applications like hip and knee joints which have to bear the load. The biocompatibility is provided by HA and mechanical strength by the addition of reinforce with HA. Thermal post treatments have been mostly utilized to enhance the morphological and physicomechanical characteristics of as-deposition coatings. In the present research, the emphasis has been laid to analyze the outcome of thermal-processing on phases of hydroxyapatite in coatings developed by plasma spraying process. The surface-morphology of as-sprayed and thermally-processed, HA coated samples was studied using Scanning electron microscope (S.E.M.), Elemental-mapping, X-ray diffraction analysis (X.R.D.), and Fourier-transform infrared (F.T.-I.R.) spectroscopy techniques. The outcomes achieved from the X.R.D. analysis of the hydroxylapatite-coated samples after thermal-treatment reveal the formation of crystalline structure at 750 °C with some traces of CaO. Moreover, when the heat treatment was further done at 950 °C, the unwanted CaO was totally eliminated and coating with crystalline structure was obtained. No substrate element is visible in the X-ray mapping of coatings. The presence of ultrafine particles was observed on both substrates after the heat treatment of coatings at specified temperatures for 2hr in air. These ultrafine particles have the capability to bond with the bone and also helps for bone in-growth on their surfaces.

Chalcopyrite and Molybdenite Flotation in Seawater: The Use of Inorganic Dispersants to Reduce the Depressing Effects of Micas

The objective of this work was to study the effect of muscovite and biotite on the flotation of chalcopyrite and molybdenite in seawater, and the use of sodium hexametaphosphate and sodium silicate to improve copper and molybdenum recoveries. The impact of the inorganic dispersants on the settling properties of the resulting flotation tailings was also studied. It was found that muscovite and biotite depress the flotation of chalcopyrite and molybdenite in seawater, with this depressing effect being stronger at pH 11 than at pH 9. Sodium hexametaphosphate and sodium silicate increased the recoveries of copper and molybdenum in seawater. These dispersants render the mineral particles more negatively charged and remove the hydroxy-complexes of magnesium and calcium from the mineral particles causing dispersion of the slimes. The settling rates of the flotation tailings slightly decrease when sodium hexametaphosphate and sodium silicate were added in the flotation stage. The presence of ultrafine particles dispersed by the action of the inorganic dispersants negatively impacted the flocculation and sedimentation processes leading to high flocculant consumption, low settling rates and high turbidity of the supernatant.

Ammonium Sulfate and Ultrafine Particles Affect Early Onset of Alzheimer’s Disease

Recent environmental studies have shown the impact of air quality on human health and in particular, toxicological effect of particulate matter (PM) and ultrafine particles (UFPs) on progression of neurodegenerative diseases. While in-vivo experiments reveal enhanced concentration of amyloid beta peptides in the brains of animals after the exposure to PM and UFPs, the molecular interactions between peptides and atmospheric pollutants remain obscure. In this study, molecular dynamics simulations were performed to investigate the effect of UFPs on the aggregation of amyloid beta peptides, associated with the development of Alzheimer’s Disease (AD) in human brain. In particular, the changes in the structure of eight As16-21 peptides, the segment of As1-42 peptide with the high propensity to aggregate were investigated. The aggregation kinetics of As16-21 peptides and amount of beta sheets in their secondary structures were studied in the presence of varying concentrations of NH4+ and SO4-2 ions, common secondary inorganic ions found in the environmental realm from the different sources of atmospheric pollution. Moreover, the effect of hydrophobic UFP, modelled by C60 molecule, on the structure of peptides was analysed. The aggregation kinetics was calculated by estimating the time necessary to reach Solvent Accessible Surface Area (SASA) of peptides of 60 nm2. The study demonstrated that, although, the inhibitory effect of hydrophobic UFP on the formation of beta sheets was revealed, there could be a synergistic effect of the concentration of (NH4)2SO4 salt and presence of UFP on the aggregation kinetics of peptides. Among three different salt concentrations of 0.15 M, 0.25 M and 0.35 M, the slowest aggregation of peptides in the absence of C60 molecule and the fastest aggregation in the presence of C60 were observed at 0.25 M of (NH4)2SO4.

Impact of ultrafine particles and secondary inorganic ions on early onset and progression of amyloid aggregation: Insights from molecular simulations

Alzheimer’s disease (AD) is a neurodegenerative disorder, associated with the aggregation of amyloid beta (Aβ) peptides and formation of plaques. The impact of airborne particulate matter (PM) and ultrafine particles (UFPs), on early onset and progression of AD has been recently hypothesized. Considering their small size, carbon black nanoparticles and UFPs can penetrate into human organism and affect Alzheimer’s progression. While experiments show that the exposure of PM and UFPs can lead to enhanced concentrations of Aβ peptides, the interactions between the peptides and UFPs remain obscured. Particularly, the impact of UFPs on the initial rate of aggregation of the peptides is ambiguous. Herein, we perform molecular dynamics simulations to investigate the aggregation of Aβ16-21 peptides, an aggregation-prone segment of Aβ, in the presence of UFPs, mimicked by C60, under different salt solutions suggesting the presence of the inorganic constituents of PM in the blood. In particular, the simulations were performed in the presence of Na+, Cl− and CO3−2 ions to characterize typical buffer environments and electrolytes present in human blood. Furthermore, NH4+, NO3− and SO4−2 ions, found in PM, were used in the simulations. The results revealed high propensity for the aggregation of Aβ16-21 peptides. Moreover, the peptides made clusters with C60 molecules, that would be expected to act as a nucleation site for the formation of amyloid plaques. Taken together, the results showed that UFPs affected the peptide aggregation differently, depending on the type of ions present in the simulation environment. In the presence of C60, SO4−2 and NO3− ions accelerated the aggregation of Aβ16-21 peptides, however, NH4+ ions decelerated their aggregation. In addition, UFP lowered β-sheets amounts at all environments, except NaCl solution.

Enhanced particle precipitation from flue gas containing ultrafine particles through precharging

The collection performance of wet electrostatic precipitators (ESPs) considerably deteriorates in the presence of ultrafine particles, which confer difficulties in realizing the ultra-low emission of particulate matter (PM). In this work, the use of a wet ESP combined with a perforated precharger was proposed to investigate its electrical and collection characteristics in flue gas containing ultrafine particles and compared these characteristics with those of the common wet ESP. Results indicated that the distributions of ion density and electric field were affected by ultrafine particle loadings. With increased PM0.1 concentration from 0 mg/m3 to 100 mg/m3, the average ion density of the common wet ESP decreased by more than two orders of magnitude. Meanwhile, the particle charging and transport performance deteriorated, even for large particles (10 μm), and migration velocity sharply decreased by more than 85 %. The corona electrostatic field was significantly improved by installing the precharger. The combined wet ESP can be operated well even under problematic conditions. Additional electrons were generated by the corona discharge of the precharger, which contributed to subsequent particle capture. When the applied voltage of the precharger exceeded 15 kV, the electrostatic precipitation of 1 μm particles only slightly weakened with increased PM0.1 concentration to 40 mg/m3, and the capture of >5 μm-diameter particles was nearly unaffected by ultrafine particles.

The Effect of Electronic Cigarette User Modifications and E-liquid Adulteration on the Particle Size Profile of an Aerosolized Product

Electronic cigarettes (e-cigarettes) are an alternate nicotine delivery system that generate a condensation aerosol to be inhaled by the user. The size of the droplets formed in the aerosol can vary and contributes to drug deposition and ultimate bioavailability in the lung. The growing popularity of e-cigarette products has caused an increase in internet sources promoting the use of drugs other than nicotine (DOTNs) in e-cigarettes. The purpose of this study was to determine the effect of various e-cigarette and e-liquid modifications, such as coil resistance, battery voltage, and glycol and drug formulation, on the aerosol particle size. E-liquids containing 12 mg/mL nicotine prepared in glycol compositions of 100% propylene glycol (PG), 100% vegetable glycerin (VG), or 50:50 PG:VG were aerosolized at three voltages and three coil resistances. Methamphetamine and methadone e-liquids were prepared at 60 mg/mL in 50:50 PG:VG and all e-liquids were aerosolized onto a 10 stage Micro-Orifice Uniform Deposit Impactor. Glycol deposition correlated with drug deposition, and the majority of particles centered between 0.172–0.5 μm in diameter, representing pulmonary deposition. The 100% PG e-liquid produced the largest aerosol particles and the 100% VG and 50:50 PG:VG e-liquids produced ultra-fine particles <0.3 μm. The presence of ultrafine particles indicates that drugs can be aerosolized and reach the pulmonary alveolar regions, highlighting a potential for abuse and risk of overdose with DOTNs aerosolized in an e-cigarette system.

Study of potential transfer of aluminum to the brain via the olfactory pathway

Many employees in the aluminum industry are exposed to a range of aluminum compounds by inhalation, and the presence of ultrafine particles in the workplace has become a concern to occupational health professionals. Some metal salts and metal oxides have been shown to enter the brain through the olfactory route, bypassing the blood-brain barrier, but few studies have examined whether aluminum compounds also use this pathway. In this context, we sought to determine whether aluminum was found in rat olfactory bulbs and whether its transfer depended on physicochemical characteristics such as solubility and granulometry. Aluminum salts (chloride and fluoride) and various nanometric aluminum oxides (13nm, 20nm and 40–50nm) were administered to rats by intranasal instillation through one nostril (10μg Al/30μL for 10days). Olfactory bulbs (ipsilateral and contralateral relative to instilled nostril) were harvested and the aluminum content was determined by graphite furnace atomic absorption spectrometry after tissue mineralization. Some transfer of aluminum salts to the central nervous system via the olfactory route was observed, with the more soluble aluminum chloride being transferred at higher levels than aluminum fluoride. No cerebral translocation of any of the aluminas studied was detected.

Suspension polymerisation of vinyl chloride in presence of ultra fine filler particles

Polymer composites, filled with ultra fine particulate fillers, are alternatives to the conventional filled polymers. The reinforcement of the mechanical properties occurs to a greater extent when ultra fine particulate fillers are used in comparison with the conventional microdimensional fillers. To achieve all the benefits that the ultra fine fillers can provide, optimal dispersion as primary particles is essential. To achieve better dispersion of the inorganic particles in a polymer matrix, the ultra fine particles (UFP) are added to the polymerisation reactor so that they are dispersed in the monomer before polymerisation. Hence, the monomer is polymerised in the presence of the UFP (in situ). In this paper the effects of the UFP on the initial monomer dispersion are examined. The presence of the inorganic UFP in the polymerisation reactor influences the properties of the monomer phase and affects the drop size distribution. This in turn influences the grain sizes as well as their distribution, which influence the processability of the resin.

Preparation and characteristics of composites based on polypropylene and ultradispersed calcium carbonate

Feasibility studies directed at the parallel increase in the elastic modulus and impact toughness of polypropylene via introduction of ultradispersed CaCO3 particles with sizes of 100 (Socal U1S2) and 60 nm (Socal 312V) have been performed. The effects of the content and sizes of CaCO3 particles and the nature of a surfactant on the character of distribution of particles, the thermophysical characteristics of the polymer matrix, and the mechanical characteristics and heat resistance of the nanocomposites are analyzed. Microscopic studies reveal that nanoparticles show a tendency toward structuring. DSC studies have proved the nucleating action of ultrafine particles during the crystallization of PP. For the composites containing 15 vol % of Socal 312V CaCO3 nanoparticles, the increase in the tensile elastic modulus achieves its maximum; depending on the nature of the surfactant, the reinforcing effect increases by 70-40%. As compared to the initial PP, the presence of ultrafine particles in the composites prevents a decrease in the storage modulus of PP with increasing temperature from 0 to 50°C; as a result, the reinforcing effect increases from 30-40% at temperatures below the glass transition temperature to 40–75% at 50°C. For the nanocomposites with U1S2 in the presence of Triton X-100 or fluorinated alcohol telomer, the impact toughness increases over the entire filler content interval; when the filler concentration is 15 vol %, the impact toughness of nanocomposites is higher than that of the initial PP by factors of 3 and 4.5, respectively. It has been found that nanocomposites containing 5 vol % CaCO3 nanoparticles show the effect of thermal stabilization, which comes up to about 50°C.

Nanocrystalline Ni coatings strengthened with ultrafine particles

In this study, nanocrystalline Ni powders and thermally sprayed coatings, containing ultrafine AlN particles, were synthesized and characterized. The results indicated that the presence of AlN particles in the powders drastically decreased the dimension of agglomerates formed by cryomilling and increased the surface roughness of the agglomerates. The AlN phase was broken down into ultrafine particles of approximately 30 nm in size. These particles were dispersed in the Ni matrix and enhanced the development of a nanocrystalline structure in the Ni matrix during cryomilling. Selected-area diffraction patterns, obtained from transmission electron microscopy (TEM) and X-ray mapping with scanning electron microscopy (SEM), confirmed the presence of AlN particles in the coatings. The presence of AlN particles also led to an increase in the amount of NiO phase that was distributed in the coating, in the form of ultrafine, round particles. AlN particles increased the microhardness of the Ni coating by approximately 60 pct. Indentation-fracture results also indicated that the fine, dispersed AlN particles raised the apparent toughness of the Ni coating. The synthesized Ni coatings containing ultrafine AlN particles were characterized as equiaxed nanocrystalline grains with an average size of 24 nm, in which twins were observed. The increase in microhardness resulted from both grain refinement and the presence of ultrafine particles. The latter played the primary role in strengthening.

NONISOTHERMAL CHARACTERIZATION OF THIN-FILM OSCILLATING BEARINGS IN THE PRESENCE OF ULTRAFINE PARTICLES

The effects of viscous dissipation and thermal dispersion due to the presence of ultrafine particles in the lubricating fluid are studied on flow and heat transfer inside a non-isothermal and incompressible bearing during relief and squeezing stages. The governing equations are nondimensionlized and reduced to simpler forms based on an order-of-magnitude analysis. Analytical solution for the energy equation for a special case is obtained. Further, the influence of the thermal squeezing parameter, Eckert number, thermal dispersion coefficient, the motion characteristics of an oscillating bearing, and the perturbation parameter are determined. It is shown that the average heat transfer parameter decreases by an increase in the thermal squeezing parameter and dispersion coefficient, while it increases as both the Eckert number and amplitude motion parameter are increased.

Adhesive properties and related phenomena for powdered pharmaceuticals

This report deals with adhesive properties and related phenomena of powdered materials including pharmaceuticals. The adhesive force between a powder particle and substrate as well as the tensile strength of a powder bed and tablet was measured. Various factors were found to affect powder adhesion. Physical properties such as the size, shape and surface roughness were examined. The adhesive force between a particle and substrate decreased remarkably in the presence of ultrafine particles, which is of interest since the addition of adequate amount of "glidant" causes an increase in powder fluidity. From a pharmaceutical point of view, temperature and humidity were essential to particle adhesion. For several organic substances, the adhesive force increased significantly at homologous temperatures more than ca. 0.7, suggesting the sintering mechanism to be operative. The adhsive force between polymer films and glass beads varied according to polymer and relative humidity. A close correlation of water sorbed by the polymer film with adhesive force was noted. In connection with powder fluidity, compaction properties were studied by the centrifugal and tapping methods. Apparent adhesion defined as the ratio of the adhesive force between two contacting particles to the external force acting on a particle was noted to be the primary determinant of the void fraction or the porosity of the powder bed, indicating that the probability of particle displacement essentially depended on apparent adhesion.

Dip‐Coated Ru‐V Oxide Electrodes for Electrochemical Capacitors

electrodes prepared by a dip‐coating method provide a large electrochemically active surface area. A (33%)‐(67%)/Ti electrode calcined at 450°C gave the highest value of voltammetric charge, about 50 times larger as that of a electrode. The large electrochemically active surface areas of the electrodes were characterized by a dispersion of fine particles as well as the formation of the ruthenium vanadium double oxide, , while the presence of ultrafine particles cannot be ruled out. The electric charge capacity of the electrode between 0.3 and 1.1 V (vs. RHE) at a sweep rate corresponds to 0.76 protons contributed to the adsorption on every ruthenium ion loaded on a titanium substrate.

Measurements of new particle formation and ultrafine particle growth rates at a clean continental site

Simultaneous measurements of aerosol particles and their expected gas phase precursors were made at Idaho Hill, Colorado, a remote continental site. This study used apparatus and techniques similar to those employed in an earlier study at the Mauna Loa Observatory, Hawaii [Weber et al., 1995]. New particle formation, identified by the presence of ultrafine particles (nominally 3 to 4 nm diameter), was commonly observed in downslope (westerly) air and was correlated with high sulfuric acid (H2SO4) concentrations, low relative humidity and low particle surface area concentrations. The data point to H2SO4 as a principle nucleation precursor species with typical daytime concentrations between 106 and 107 molecules cm−3. Particle production was observed at H2SO4 concentrations that are well below predicted values for binary nucleation of H2O and H2SO4, suggesting that another species participated. Particle growth rates were estimated from the data with two independent approaches and in both cases were ∼5 to 10 times higher than can be explained by condensation of H2SO4 and its associated water. This suggests that species in addition to H2S04 were also making large contributions to ultrafine particle growth. Finally, calculated steady‐state H2SO4 concentrations were found to be in good agreement with measured values if the mass accommodation coefficient for H2SO4 on aerosol surfaces was assumed equal to ∼1.

Overview of the atmospheric research program during the International Arctic Ocean Expedition of 1991 (IAOE-91) and its scientific results

The broad aim of the Atmospheric program of the International Arctic Ocean Expedition (IAOE-91) was to test the hypothesis that marine biogenically produced dimethyl sulfide (DMS) gas can exert a significant global climatic control. The hypothesis states that DMS is transferred to the atmosphere and is oxidised to form airborne particles. Some of these grow large enough to act as cloud condensation nuclei (CCN) which help determine cloud droplet concentration. The latter has a strong influence on cloud albedo and hence on the radiation balance of the area affected. In summer, the central Arctic is a specially favourable region for studying the natural sulfur cycle in that the open waters surrounding the pack ice are the only significant sources of DMS and there are almost no anthropogenic particle sources. Concentrations of seawater and atmospheric DMS decreased at about the same rate during the period of measurements, (1 August to 6 October, latitudes 75°N to 90°N) spanning about three orders of magnitude. Methane sulfonate and nonsea salt sulfate in the submicrometer particles, which may be derived from atmospheric DMS, also decreased similarly, suggesting that the first part of the hypothesis under test was true. Influences on cloud droplet concentration and radiation balance could not be measured. Size-resolved aerosol chemistry showed a much lower proportion of methane sulfonate to be associated with supermicrometer particles than has been found elsewhere. Its molar ratio to nonsea salt sulfate suggested that the processes controlling the particulate chemistry do not exhibit a net temperature dependence. Elemental analysis of the aerosol also revealed the interesting possibility that debris from Siberian rivers transported on the moving ice represent a fairly widespread source of supermicrometer crustal material within the pack ice. Highly resolved measurements of aerosol number size distributions were made in the diameter range 3 nm to 500 nm. 3 distinct modal sizes were usually present, the “ultrafine”, “Aitken” and “accumulation” modes centred on 14, 45 and 170 nm diameter, respectively. The presence of ultrafine particles, implying recent production, was more frequent than has been found in lower latitude remote marine areas. Evidence suggests that they were mixed to the surface from higher levels. Sudden and often drastic changes in aerosol concentration and size distribution were surprisingly frequent in view of the relatively slowly changing meteorology of the central Arctic during the study period and the absence of strong pollution sources. They were most common in particles likely to have taken part in cloud formation (> 80 nm diameter). 2 factors appear to have been involved in these sudden changes. The 1st was the formation of vertical gradients in aerosol concentration due to interactions between particles and clouds or favoured regions for new particle production during periods of stability. The 2nd was sporadic localised breakdowns of the stability, bringing changed particle concentrations to the measurement level. Probable reasons for these sporadic mixing events were indicated by the structure of the Marine Boundary Layer (MBL) investigated with high resolution rawinsondes. Low level jets were present about 60% of the time, producing conditions conductive to turbulence and shear-induced waves. It is concluded that an even more detailed study of meteorological processes in the MBL in conjunction with more highly time-resolved measurements of gas-aerosol physics and chemistry appears to be essential in any future research aimed at studying the indirect, cloud mediated, effect of aerosol particles. DOI: 10.1034/j.1600-0889.1996.t01-1-00002.x

Magnetic changes accompanying the thermal decomposition of nontronite (in air) and its relevance to Martian mineralogy

Thermal treatment of nontronite in air, for long periods at 700°C or short periods at 900°C, results in destruction of the nontronite structure, a distinct reddening in color, and a spectacular increase in magnetic susceptibility and saturation magnetization (up to 4.4 Am2 /Kg). Magnetic property measurements and calculations suggest that the magnetism is due to the presence of ultrafine particles of α or γFe2O3; the precise identity has not yet been resolved. The highly magnetic thermally treated nontronite is amorphous to X rays consistent with an ultrafine grain size. Prolonged heating results in the growth of αFe2O3, as suggested by X ray, IR, and magnetic measurements. Reflectivity spectra of a sample heated for 1 hour at 900°C indicates, in addition to αFe2O3, the presence of an opaque, magnetite‐like phase. Given the composition of the starting material, and the experimental conditions, the presence of Fe3O4, is unlikely; the cause of this opacity is as yet unknown. Thermally treated nontronite has chemical, color and magnetic properties akin to those found by Viking on Mars. These results favor an origin for the fine grained Martian surface material by repeated impacts into an Fe‐rich smectite‐charged regolith (Weldon et al., 1980).