Surface Of Dust Particles Research Articles

A potentially new type of nonchondritic interplanetary dust particle with hematite, organic carbon, amorphous Na,Ca‐aluminosilicate, and FeO‐spheres

Abstract– We used a combination of different analytical techniques to study particle W7190‐D12 using microinfrared spectroscopy, micro‐Raman spectroscopy, and field emission scanning electron microscopy (FESEM) energy dispersive X‐ray spectroscopy (EDS). The particle consists mainly of hematite (α‐Fe2O3) with considerable variations in structural disorder. It further contains amorphous (Na,K)‐bearing Ca,Al‐silicate and organic carbon. Iron‐bearing spherules (<150 nm in diameter) cover the surface of this particle. At local sites of structural disorder at the hematite surface, the hematite spheres were reduced to FeO in the presence of organic carbons forming FeO‐spheres. However, metallic Fe spheres cannot be excluded based on the available data. To the best of our knowledge, this particle is the first detection of such spherules at the surface of a stratospheric dust particle. Although there is no definitive evidence for an extraterrestrial origin of particle W7190‐D12, we suggest that it could be an IDP that had moved away from the asteroid‐forming region of the early solar system into the outer solar system of the accreting Kuiper Belt objects. After it was released from a Jupiter family comet, this particle became part of the zodiacal cloud. Atmospheric entry flash‐heating caused (1) the formation of microenvironments of reduced iron oxide when indigenous carbon materials reacted with hematite covering its surface resulting in the formation of FeO‐spheres and (2) Na‐loss from Na,Al‐plagioclase. The particle of this study, and other similar particles on this collector, may represent a potentially new type of nonchondritic IDPs associated with Jupiter family comets, although an origin in the asteroid belt cannot be ignored.

Chemical Modification of Dust Particles during Different Dust Storm Episodes

Two dust episodes (D1: February 13 and D2: March 28–29, 2004) of long-range transport from desert and loess sources, and one dust episode (D3: March 30) mainly from local area, were investigated in spring 2004 in Beijing, China. Dust samples were collected in different dust episodes and scanning electron microscopy with X-ray energy dispersive detector (SEM/EDS) was applied to study the morphology, elemental composition, and chemical modification on the surfaces of dust particles with radius from 0.1 to 6.4 μm. The morphological features of the particles reveal that the three dust plumes carried both dust particles (90–98% by number) and anthropogenic pollutants (e.g., fly ash and soot, 2–10%). Particle compositions show that the amount of S-containing dust particles was higher in D1 and D2 than in D3. Sulfates were introduced into the dust particles through heterogeneous uptake of SO2 during their transport. In all three dust episodes, fine dust particles (radius < 1 μm) showed a higher degree of chemical modification by SO2 compared to the coarse particles (radius ≥ 1 μm). Furthermore, long-range transport dust particles were more deeply modified by SO2 than particles from local areas. The composition of the dust particles indicates that alkaline mineral components determined the level of chemical modification of individual particles. Heterogeneous uptake of SO2 on a large number of dust particles would increase mass of the internally mixed sulfates on their surfaces. The results suggest that the optical properties of dust particles during dust storm episodes are gradually altered based on how far they are transported.

Cover Chem. Eng. Technol. 4/2011

AbstractNucleation of skga needles on the surface of dust particles in methanol. Courtesy of Anke Schuster

Influence of dust-particle concentration on gas-discharge plasma

A self-consistent kinetic model of a low-pressure dc glow discharge with dust particles based on Boltzmann equation for the electron energy distribution function is presented. The ions and electrons production in ionizing processes as well as their recombination on the dust-particle surface and on the discharge tube wall were taken into account. The influence of dust-particle concentration N(d) on gas discharge and dust particles parameters was investigated. It is shown that the increase of N(d) leads to the increase of an averaged electric field and ion density, and to the decrease of a dust-particle charge and electron density in the dusty cloud. The results were obtained in a wide region of different discharge and dusty plasma parameters: dust particles density 10(2)-10(8) cm(-3), discharge current density 10(-1)-10(1) mA/cm(2), and dust particles radius 1, 2, and 5 microm. The scaling laws for dust-particle surface potential and electric filed dependencies on dust-particle density, particle radius and discharge currents were revealed. It is shown that the absorption of electrons and ions on the dust particles surface does not lead to the electron energy distribution function depletion due to a self-consistent adjustment of dust particles and discharge parameters.

Where on Earth has our water come from?

The presence of water in the Earth has long been an enigma. However, computer modelling techniques have shown that the adsorption of water onto the fractal surfaces of interplanetary dust particles, which are present in the planetary accretion disk, is sufficiently strong to provide a viable origin of terrestrial water.

Dusty plasmas: synthesis, structure and dynamics of a dust cloud in a plasma

Plasmas are energetic media that can give birth to dust particles due to the presence of reactive gases or plasma-surface interactions. Industrial plasmas are often concerned by these dust particles that can be either unwanted or useful for the process. For fusion plasmas, production of dust particles from wall erosion is a serious issue for performance and safety reasons. In this article, some aspects of dusty plasmas with potential implications for plasma experimenters will be discussed. Convenient ways for detecting the presence or the growth of dust particles will be presented. The spatial distribution of the dust cloud during the plasma phase determines the subsequent dust particle deposition. It will be shown that some reactor regions can attract or repeal these dust particles. Finally, the dust particle dynamics after the plasma extinction will be investigated. A special attention will be paid on the residual electric charge that can stay attached on the dust particle surface and on its implications for dust particle control or deposition.

Compound chondrule formation in the shock-wave heating model: Three-dimensional hydrodynamics simulation of the disruption of a partially-molten dust particle

We carried out three-dimensional hydrodynamics simulations of the disruption of a partially-molten dust particle exposed to high-speed gas flow to examine the compound chondrule formation due to mutual collisions between the fragments (fragment-collision model; [Miura, H., Yasuda, S., Nakamoto, T., 2008a. Icarus194, 811–821]). In the shock-wave heating model, which is one of the most plausible models for chondrule formation, the gas friction heats and melts the surface of the cm-sized dust particle (parent particle) and then the strong gas ram pressure causes the disruption of the molten surface layer. The hydrodynamics simulation shows details of the disruptive motion of the molten surface, production of many fragments and their trajectories parting from the parent particle, and mutual collisions among them. In our simulation, we identified 32 isolated fragments extracted from the parent particle. The size distribution of the fragments was similar to that obtained from the aerodynamic experiment in which a liquid layer was attached to a solid core and it was exposed to a gas flow. We detected 12 collisions between the fragments, which may result in the compound chondrule formation. We also analyzed the paths of all the fragments in detail and found the importance of the shadow effect in which a fragment extracted later blocks the gas flow toward a fragment extracted earlier. We examined the collision velocity and impact parameter of each collision and found that 11 collisions should result in coalescence. It means that the ratio of coalescent bodies to single bodies formed in this disruption of a parent particle is R coa = 11 / ( 32 - 11 ) = 0.52 . We concluded that compound chondrule formation can occur just after the disruption of a cm-sized molten dust particle in shock-wave heating.

Dusty Plasma Structures in Magnetic DC Discharges

AbstractResults are described of experiments in studying the effect of magnetic field on dusty plasma structures in dc discharges. The levitation of dust particles in vertically oriented dc discharges is possible either in the vicinity of the flat surface of cathode (or of special additional electrode) or in an electrostatic trap which forms at the striation head during the stratification of positive column. The most interesting one of the observed effects is that of rotation of dust structures in the case of imposition of axial magnetic field. The rotation occurs about the discharge axis of symmetry with a velocity which is a nonmonotonic function of magnetic force. An increase in the field may cause the variation of direction of rotation for the opposite. An interpretation is given of the mechanism of rotation and of the inversion of its velocity. The rotation of dust structures is caused by the tangential component of ion drag force. It is demonstrated that the inversion is, in the final analysis, associated with the competition between two mechanisms of plasma recombination, namely, those on the discharge tube wall and on the surface of dust particles. When the magnetic field increases, the latter mechanism becomes predominating as a result of magnetization of plasma, and the inversion of rotation occurs (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Cumulative processes on a dust particle in plasma

Processes of asymmetric ionization and cumulation of electric field and electron and ion flows can develop near the surface of charged dust particles in plasma. In the region of cumulation asymmetry on heating, the particle surface and ion momentum transfer arises; as a result, the dust particle moves in the plasma with high velocity.

A non-Maxwellian kinetic approach for charging of dust particles in discharge plasmas

Nanoparticle charging in a capacitively coupled radio frequency discharge in argon is studied using a particle in cell Monte Carlo collisions method. The plasma parameters and dust potential were calculated self-consistently for different unmovable dust profiles. A new method for definition of the dust floating potential is proposed, based on the information about electron and ion energy distribution functions, obtained during the kinetic simulations. This approach provides an accurate balance of the electron and ion currents on the dust particle surface and allows us to precisely calculate the dust floating potential. A comparison of the obtained floating potentials with the results of the traditional orbital motion limit (OML) theory shows that in the presence of the ion resonant charge exchange collisions, even when the OML approximation is valid, its results are correct only in the region of a weak electric field, where the ion drift velocity is much smaller than the thermal one. With increasing ion drift velocity, the absolute value of the calculated dust potential becomes significantly smaller than the theory predicts. This is explained by a non-Maxwellian shape of the ion energy distribution function for the case of fast ion drift.

Imaging Chemical Patches on Near-surface Atmospheric Dust Particles with NanoSIMS 50 to Identify Material Sources

The increase of traffic and the rising energy consumption mean a challenge to the air pollution control and to environmental protection. Measures of air pollution control concentrated primarily on the reduction of gaseous pollutants. However, in the field of air hygiene in Central Europe, especially the load of near-surface atmospheric dust becomes threatening to human health. A SIMS microprobe for ultra fine feature analysis is used to image the elemental composition at the surface of submicrometer urban dust particles collected at two measurement stations in the Grand Duchy of Luxembourg. The NanoSIMS 50 has been chosen because it creates one intensity image for each selected element in a high spatial resolution down to 50 nm. The atmospheric fine dust consists of a mixture of organic and inorganic compounds. The elemental composition at the surface of particles was studied using a global image segmentation technique to separate the signal from the background of the particles. The analysis of the binary intensity images was carried out using several shape and proximity measures. The patch shape complexity and distribution for industrial/urban particles were found to differ significantly from the solids collected from a forest site. We conclude that the methodology developed in the study is a reliable tool to differentiate between potential sources of airborne particulate matter.

Interaction of injected dust particles with metastable neon atoms in a radio frequency plasma

Spatial density and temperature profiles of neon metastables produced in a radio frequency (rf) discharge were investigated by means of tunable diode laser absorption spectroscopy. The experiments were performed in the PULVA1 reactor, which is designed for the study of complex (dusty) plasmas. The line averaged measured density is about 1.5×1015 m−3 in the bulk and drops almost linearly in the plasma sheath. The gas temperature is in the range of 370–390 K. The flow of metastable atoms in the plasma sheath deduced from the spatial density distribution is dominated by the flow towards the rf electrode. The sheath length is supposed as the effective diffusion length in the plasma sheath region. This approximation was used to investigate the interaction of injected particles with the plasma. The observations and estimation provide evidence for a significant interaction between metastable atoms and powder particles which is important for energy transfer from the plasma to the particles. The power per unit area absorbed by dust particles due to the collision of metastable atoms with the dust particle surface is in the range of a few tens of mW m−2.

Review of Adhesion Fundamentals for Micron-Scale Particles

The effects of various fundamental forces on the adhesion of fine dust particles are reviewed. The particle-size and distance variation of surface-energy related (e.g., van der Waals) forces are compared to similar relations for static-electric image-forces for tribo-charged particles near (or contacting) conducting surfaces. The van der Waals force (between macroscopic spheres), a patchcharge image-force and static-electric image-forces all exhibit an inverse square variation with distance; however, these forces have dramatically different ranges-of-effect. The very short-range nature of van der Waals forces (of order 10nm) is a major reason that most real contacts, involving non-smooth surfaces, exhibit adhesion forces that are substantially lower than values predicted for smooth particles. Based on studies of Lunar and Martian regolith stimulant powders, triboelectric charges on fine particles appear to scale linearly with particle size. It is shown that below some threshold size, the adhesion (to conducting surfaces) of charged dust particles possessing such a linear charge-to-size scaling relationship, may be dominated by image-charge forces, instead of surface-energy related interactions. This is counter to what might have been expected from a cursory examination of the fundamental force relations, which would suggest van der Waals adhesion forces would dominate for small particle sizes.

An investigation of water uptake on clays minerals using ATR‐FTIR spectroscopy coupled with quartz crystal microbalance measurements

It is becoming increasingly clear that the heterogeneous chemistry of mineral dust aerosol is a function of relative humidity (f(RH)) as water on the surface of the mineral dust particles can enhance or inhibit its reactivity depending on the reaction. Since clay minerals make up a significant component of the mineral dust aerosol, it is important to understand water uptake on this large fraction of dust present in the Earth's atmosphere. In this study, bulk and surface properties of several types and sources of clay minerals are characterized using a variety of techniques, including surface area measurements, attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy, scanning electron microscopy coupled with energy dispersive X‐ray (SEM‐EDX) analysis, X‐Ray diffraction (XRD), Mössbauer spectroscopy, and X‐ray photoelectron spectroscopy (XPS). For these well‐characterized clays, ATR‐FTIR spectroscopy is combined with quartz crystal microbalance (QCM) mass measurements to investigate water uptake as a f(RH). Similar measurements were also done for α‐Al2O3 and synthetic NaY zeolite for comparison. Water uptake on the clay minerals, although variable and dependent on both the type and source of the clay, is greater than that found for α‐Al2O3, a metal oxide, and in many cases similar or greater than NaY zeolite, a crystalline porous material. The presence of cations with large hydration energies significantly increases the water uptake capacity for the clay minerals. The atmospheric implications of these results are discussed.

Simulation of the Formation and Morphology of Ice Mantles on Interstellar Grains

Although still poorly understood, the chemistry that occurs on the surfaces of interstellar dust particles profoundly affects the growth of molecules in theinterstellar medium.An important setof surface reactions producesicymantles of manymonolayers in cold and dense regions. Themonolayersare dominated bywater ice,but alsocontain CO, CO2, and occasionally methanol, as well as minor constituents. In this paper, the rate of production of water-ice-dominated mantles is calculated for different physical conditions of interstellar clouds and for the first time images of the morphology of interstellar ices are presented. For this purpose, the continuous-time random-walk Monte Carlo simulation technique has been used. The visual extinction, density, and gas and grain temperatures are varied. It is shown that our stochastic approach can reproduce the important observation that ice mantles only grow in the denser regions.

Ultrahigh charging of dust particles in a nonequilibrium plasma

Charging of dust particles in a plasma with the two-temperature energy distribution of electrons has been studied. It has been shown that the dust-particle potential divided by the electron temperature decreases with increasing electron temperature in the plasma with cold ions. Owing to this behavior, the potential of the dustparticle surface increases with the electron temperature more slowly than the linear function and is lower than the electron temperature (divided by the elementary charge) for T e > 5.5 eV in hydrogen and for T e > 240 eV in argon. The fraction of fast electrons at which these electrons begin to contribute to the charge of dust particles has been determined. It has been shown that the charge of micron particles can reach 106 elementary charges. The effect of the cold and thermal field emission on the charge of dust particles has been analyzed. The possibility of obtaining ultrahigh charges (to 107 elementary charges on dust particles with a radius of 50–100 μm irradiated by a 25-keV 1-mA electron beam has been demonstrated.

The mineral aerosol and its impact on urban pollution aerosols over Beijing, China

A campaign of sampling total suspended particles (TSP) and fine particles ( PM 2.5 ) in Beijing from 2001 to 2004 were carried out to investigate the mineral aerosol and its impact on urban pollution aerosols, mainly sulfate, nitrate, and ammonium. In urban Beijing, mineral aerosol accounted for 32–67% of TSP, 10–70% of PM 2.5 in normal four seasons, and as high as 74% of TSP and 90% of PM 2.5 in dust storm period. The sources from outside Beijing accounted for 62% of the total mineral aerosols in TSP, and 76% in PM 2.5 in spring, 69% and 45% in TSP and PM 2.5 , respectively, in winter, ∼ 20 % of both TSP and PM 2.5 in summer and autumn; and it reached as high as 97% of TSP in dust storm days. Mineral aerosol has an important positive influence on formations of sulfate, nitrate, and ammonium, as there was a positive correlation between sulfate/nitrate/ammonium and mineral aerosol under appropriate meteorological conditions. Sulfate, and ammonium mainly existed in fine particles, PM 2.5 . Sulfate might mostly derive from the formation on the pathways of the long-range transport by the reactions of their precursors SO 2 on the surfaces of dust particles, while nitrate was mostly derived by the homogeneous reaction and the neutralization of their precursors NO 2 on surfaces of mineral aerosol. Nitrate and ammonium mostly derived from the local pollution sources.

Model Study on the Transport and Mixing of Dust Aerosols and Pollutants during an Asian Dust Storm in March 2002

The transport and mixing of dust aerosols and pollutants in East Asia during March 18 to 22, 2002 was studied using the nested air quality prediction model system (NAQPMS). Dust was primarily generated in the Gobi desert on 19 March and then swept across several areas of East Asia. The model results were verified with observations of surface weather, TSP/PM10, SO2 and lidar data. The model simulated the right timing and strength of dust events, capturing most of the variation features in dust and SO2. Numerical results showed that the dust aerosols were mainly transported in two layers and mixed with pollutants in different ways. Some of the dust kicked up in the source region was uplifted to a higher layer (200-2000 m layer) and transported downwind faster than dust of the lower level. This lower-level dust was of greater concentration. The dust arriving at the upper layer began to drop and mixed well with pollutants in the atmosphere during ”the first period”. During ”the second period”, pollutants were diluted by the dust air mass that was transported along the lower layer. The remaining pollutants mixed well with dust aerosols during this period. The mixed air mass of the higher layer (1500 m) eventually reached the Northwestern Pacific. A large amount of clouds in the upper layers potentially led to an increase in sulfate mass on the surface of dust particles.

Test of Chlorides Mixed with CaO, MgO, and Sodium Silicate for Dust Control and Soil Stabilization

It is well known that CaCl2 and MgCl2 can been used for dust control and soil stabilization in many fields. However, solutions of CaCl2 and MgCl2 are slightly acidic and their application is often forbidden in the area where acid is restricted. Furthermore, in wet seasons, CaCl2 and MgCl2 can be partly leached away by water and result in other pollution. In order to solve such problems, CaO , MgO and sodium silicate were individually mixed to the chlorides to reduce their acidity in the investigation. Based on a large number of experiments, the principal results are as follows: CaO , MgO , and sodium silicate cannot only reduce effectively the acidity of the solutions but also decrease greatly the water absorption capacity of the chlorides. The more CaO , MgO , and sodium silicate are added, the less its water absorption rate of the chlorides will be. At the same time, CaO , MgO , and sodium silicate can react with the chlorides, some ions on the surface of soil and dust particles, water and CO2 in atmosp...

Effect of ventilation rate on gradient of aerial contaminants in the confinement pig building

The principal aim of this study was to compare the aerial contaminants concentrations between the levels of ventilation rate and determine the variation pattern of aerial contaminants affected by the ventilation rate. As a result, there was not significant difference in total dust and total airborne microorganisms among three levels of ventilation rate ( P>0.05) whereas the increased ventilation rate lowered the levels of respirable dust and gaseous compounds ( P<0.05). Based on the results, it was concluded that the suspended gases in the confinement pig building generally followed the air streamline formed by the ventilation whereas the ventilation rate had little effect on the gradient of particulates, especially total dust, due to gravity generated by their size and weight. The findings that the concentrations of total airborne microorganisms were not also significantly different among the ventilation rates could be explained in terms of the fact that airborne microorganisms are easily adsorbed on the surface of dust particle.