Individual Particle Analysis Research Articles

MicroAnalysis of Soot Participates Using STEM

Abstract Overview Scanning transmission electron microscopy (STEM) coupled with energy dispersive x-ray analysis (EDX) and electron energy-loss spectroscopy (EELS) has been used to characterize the elemental composition and oxidation conditions of various soot samples. The STEM employed in this investigation was the Vacuum Generators HB603-MIT, with a microanalyical resolution approaching 1 nm, that allowed the analysis of individual soot particles and aggregates. The aim of this research is quantification of the EDX spectra which is possible after background and absorption corrections. This information can then be used for comparative studies of different fuels and combustion processes. EELS has been employed to determine the amount of graphitic carbon in a soot particulate, and the detection of trace elements of low atomic number. It has been shown in soot that for Carbon the energy-loss of the p shell electrons increases with the amount of oxidation at high temperatures. Analysis and characterization of gas turbine soot, collected from an engine exhaust duct of a 737-300 aircraft showed an abundance of different elements.

Cluster Analysis of Automated Fine-Particle Analysis Using Scanning Electron Microscopy

Because of analytical advances, submicron particles as small as 0.2 μm can be characterized for chemical composition, size, and shape using scanning electron microscopy (SEM). Once these characteristics are determined, cluster analysis can be used to group the individual particles into categories based on size, shape, and chemical composition.Submicron particle analysis is important when characterizing the ash to provide information to help solve ash-related problems in coal combustion and gasification systems. Since a combustion system has an excess of oxygen available, the resulting ash is typically easier to characterize than ash from a gasification system. In a gasification system, the lack of oxygen results in additional categories high in Cl and P.Adequate dispersion of submicron particles for proper analysis of individual particles is required because of the analysis volume of the SEM beam. Therefore, an aliquot of an aqueous solution with a set sample-to-solvent ratio is drawn while being sonicated. A few drops of solution are placed on a vitreous carbon substrate, allowing for particle dispersion on the surface of a smooth substrate. Next, the particles are analyzed by the fine-particle technique (FPT).

Nuclear microprobe analysis of atmospheric aerosol samples: Comparison with bulk measurements and analyses of individual particles

Selected aerosol filter samples, which have been analyzed by bulk analysis techniques, were examined with the Oxford scanning proton microprobe using micro-PIXE and micro-RBS. From a comparison of the micro-PIXE data for large collections of particles with the bulk analysis results, it was estimated that micro-PIXE of aerosols provides data which is accurate to within 10–20%. Loss in the course of the microprobe bombardment was examined for the elements detected by PIXE, but was generally insignificant. Examples of analyses on complex particle agglomerates are presented. For individual calcareous aerosol particles from Israel, the contributing chemical compounds were identified and quantitatively determined. Several of these particles consisted of a single compound (e.g., calcium carbonate, calcium sulphate), but mixed particles with equal molar amounts of two compounds (e.g., of calcium carbonate and calcium phosphate) were also observed. It is also indicated what further improvements in nuclear microprobe analysis are especially desirable for examinations on submicrometer sized aerosol particles.

Individual particle analysis of Western Mediterranean sediment cores, Rhône suspended matter and Sahara aerosols — investigation of inputs to the sediments

Individual particle analysis using electron probe X-ray microanalysis was performed on sediment cores from the Gulf of Lions (Western Mediterranean Sea), on atmospheric aerosols sampled in Corsica and originating from Northern Africa, and on Rhône suspended matter. Cluster analysis was done to yield major particle types and kriging spatial analysis was applied to obtain the distributions of the particle types in the sediment surface layers. For three sediment cores, the depth profiles of particle groups were examined. The predominant particle types composing the sediment material in the Gulf of Lions were found to be Si-rich particles (quartz and biogenic silicate), aluminosilicate minerals (illite, kaolinite, chlorite) and Ca-rich particles (aragonite, calcite, high-Mg calcite). During the diagenesis, dissolution and crystallization processes occurred, yielding the substitution of quartz and Si-rich particles by calcium carbonates in deeper sediment layers. Only a small amount of Fe-S-rich (pyrite) particles was found in the analyzed sediments. An evident impact of Rhône derived and offshore eroded material was noticed in the sedimentation area investigated. Yet, the input of Northern Africa aerosols to the sediment vicinity was not so evidently noticeable from these results.

97/02094 Development of a stack plume opacity index for subbituminous coal-fired utility boilers

Powder River Basin subbituminous coals were burned using conventional and low-NO{sub x} combustion conditions in a drop-tube furnace equipped with a multicyclone ash collection device. Fine ash fractions (< 2 {micro}m in diameter) collected during the tests were analyzed using computer-controlled scanning electron microscopy (CCSEM). Advances in particulate sample preparation methods enabled the CCSEM analysis of individual ash particles with submicron diameters as small as 0.1 {micro}m. The fine ash samples produced from the conventional combustion of coal consisted of discrete spherical particles, whereas particle agglomerates were characteristic of the low-NO{sub x} ash samples. Particle-size distributions of the low-NO{sub x} fine ash fractions were coarser because of the agglomeration. Theoretical light-scattering calculations indicate that for a given coal, the ash produced in low-NO{sub x} conditions causes less opacity as compared to conventional combustion conditions. The following phases were abundant in the ashes: Ca aluminosilicate, Ca aluminate, aluminosilicate, silica, (Ca, Mg)O, CaSO{sub 4}, Na{sub 2} SO{sub 4}, and (Na, K)Cl. Primary mechanisms that produced the fine ash include the thermal metamorphism of small (0.1 to 5 {micro}m) mineral grains and the vaporization and subsequent condensation of organically bound Na, Mg, and Ca, Empirical equations for estimating the concentration of fine ashmore » produced from burning subbituminous coals were formulated into an opacity index based on CCSEM coal mineral and fine ash analyses and on drop-tube furnace testing results. The effects of ash electrical resistivity on electrostatic precipitator collection efficiency are also considered in the index.« less

Quantification and characterisation of suspended particulate matter in indoor air

Quantification and characterisation of suspended particulate matter (SPM) from homes in the city of Oslo was carried out. In 29 households the dust concentrations were found to vary between 9 and 56 μg/m 3 (median value 26 μg/m 3). In 12 of the 29 households, a thorough analysis was carried out to determine the size and element distribution of the particles using transmission electron microscopy (TEM) and X-ray microanalysis (XRMA). The vast majority of the collected particles were less than 2.5 μm in diameter, i.e. they belonged to the fine fraction. In this fraction a considerable amount of soot and sulphur particles were found, usually less than 1 μm in diameter. The coarse fraction (particles > 2.5 μm in diameter) was found to consist mainly of organic material, silicates and larger soot aggregates. Both a thorough analysis of individual particles and a ‘bulk analysis’ (i.e. recording XRMA spectra from whole grid masks) were performed, and the two methods were found to show good agreement.

Microanalysis of Soot Particulates using Stem

ABSTRACTScanning transmission electron microscopy (STEM) coupled with energy dispersive x-ray analysis (EDX) and electron energy-loss spectroscopy (EELS) has been used to characterize the elemental composition and oxidation conditions of various soot samples. The STEM employed in this investigation was the Vacuum Generators HB603, with a microanalytical resolution approaching 1 rnm, that allowed the analysis of individual soot particles and aggregates. The aim of this research is quantification of the EDX spectra which is possible after background and absorption corrections. This information can then be used for comparative studies of different fuels and combustion processes. EELS has been employed to determine the amount of graphitic carbon in a soot particulate, and the detection of trace elements of low atomic number. It has been shown in soot that for Carbon the energy-loss of the p shell electrons increases with the amount of oxidation at high temperatures. Analysis and characterization of gas turbine soot, collected from an engine exhaust duct of a 737-300 aircraft showed an abundance of different elements. Some of these elements originated from the fuel and combustion processes, while other elements were components of the engine itself that combined with the soot particulates during the combustion process. The study showed that soot impurities were found in all discrete sections of aggregates, and that only one or two small soot particulates were necessary to obtain a chemical fingerprint. Other investigations include; coal soot, diesel soot at different engine operating conditions and soot produced from wood burning. The richness of the spectra obtained and the ability to quantify results represents an opportunity to accomplish source identification in a novel, powerful way.

Separation and characterization of polyethylene wear debris from synovial fluid and tissue samples of revised knee replacements.

A study was made of in vivo-generated polyethylene wear particles as separated from synovial fluid samples and from tissue samples surrounding total knee arthroplasty. A comparison of particle size and morphology between the two particle groups was made to assess any effects of selective tissue capture, and macrophage encapsulation and digestion. In addition, a Raman spectroscopy technique was evaluated that enables positive identification of individual wear particles. The particles of the same size range found in the synovial fluid and tissue samples exhibited a comparable morphology. Notably, submicron-sized debris was present in both the synovial fluid and tissue samples surrounding knees with osteolysis. The novel micro-Raman analysis of individual particles was successful in the categorizing of wear debris as polyethylene or nonpolyethylene.

Seasonal variation of gypsum in aerosol and its effect on the acidity of wet precipitation on the Japan sea side of Japan

Variations of mineral concentrations in aerosols collected weekly for a 1 yr period (from October 1992 to September 1993) on Matsue, Shimane Prefecture, Japan, were investigated by X-ray powder diffraction (XRD) analysis. Major elemental concentrations were measured by energy dispersive X-ray analysis (EDX). Sulfate minerals in aerosol include gypsum, ferricopiapite, metavoltine and glauberite. Gypsum showed two high concentration peaks during spring and early winter, which was consistent with that of clay minerals and quartz. The ratios of gypsum to clay minerals, quartz and calcite, respectively, showed an increase of gypsum in spring. A non-agreement of concentration distribution between calcite and other soil minerals during spring implies a conversion of calcite to gypsum during transport. Individual particle analyses by EDX revealed large amounts of S-rich submicrometer particles coated on the surface of minerals. A sequence favorable to be attached by S constituents was calcite (83%) > clay minerals (68%) > fly ash (55) > quartz and feldspars (36%) The reaction between calcite and simulated acid rain solution with pHs of 3, 4 and 5 showed a formation of gypsum in 12 h, indicating that the conversion of calcite to gypsum is possible in the presence of sulfuric acid or (NH 4) 2 SO 4 aerosols during transport from the Asian continent to the Japan Islands.

Characteristics of dust-storm particles and their long-range transport from China to Japan — case studies in April 1993

Case studies on the characteristics and transport of Asian dust-storm particles are examined in this paper using particle samples collected in the spring of 1993 over China and Japan. During the dust-storm in Beijing, aerosol concentrations were one or two orders of magnitude larger than typical. The enrichment factors of pollution elements during the dust-storm were distinctly less than those before and after dust. Analyses of individual dust particles with an analytical electron microscope showed that the dust particles over China had distinct irregular shapes and contained crustal elements. After transport, the dust particles collected over Japan were modified by sea salt and/or anthropogenic pollutants.

Characterization of the Bermuda tropospheric aerosol by combined individual-particle and bulk-aerosol analysis

Marine boundary layer aerosol samples collected from Bermuda were examined by combined individual-particle analysis using an electron microprobe and bulk-sample analysis using INAA. Within the fine-fraction samples (< 2 μm) 65 particle types, including frequently occurring aggregates, are identified. Principal components analysis (PCA) indicates the presence of eight assemblages of particle types. A group of silicate and other crustal particle types are associated with bulk-sample Al, I, Mg, V, Co, Cs, Eu, Fe, Hf, Sc, and Th; this is most abundant when transport was across the ocean from North Africa. Three assemblages of S-rich particle types were generally most abundant when transport was from North America. One of these S-rich assemblages is associated with bulk-sample Zn and Se; another is associated with Cr. Also identified by PCA is a component with superfine silica, probably produced by reduction-vaporization during coal combustion. Na and Cl in bulk samples do not significantly correlate with fine-fraction Na-CI particle types, demonstrating the statistical independence of sea-salt particles in the fine fraction from sea-salt particles in the coarse fraction. A variety of individual-particle parameters are shown to be dependent upon transport direction; examples include relative concentrations of silicate types within the crustal particle assemblage, the degree of coating or agglomeration of silicates with S-bearing species, and the relative sizes of different particle types within the crustal assemblage.

Quantitative analysis of individual particles by x‐ray microfluorescence spectrometry

AbstractA fundamental parameters method using polychromatic x‐ray microbeam excitation was developed and applied to the quantitative analysis of individual particles from 50–160 μm. From the ratio of the projected area of a particle to the cross‐sectional area of the microbeam, an effective portion of the microbeam irradiating the particle can be determined and used to correct the measured x‐ray intensities. Because particles in this size range may not be infinitely thick and may contain unmeasurable elements such as C and O, calculation of the average mass thickness of the particle allows complete matrix absorption corrections to be made. For this purpose, the ratio of coherent to incoherent x‐ray tube target lines scattered from the particle was used to calculate the average atomic number of the particle, and its mass thickness was determined from incoherent scatter. A parametric equation was derived and tested. In addition, irregularly shaped particles were analyzed using a well known equation usually applied to flat samples having intermediate thickness. Both models were tested with homogeneous glass particles of known composition and size.

A note on the characterization of paint layers by transmission electron microscopy

The application of transmission electron microscopy (TEM) to the study of paint and ground layers in a sample from a fourteenth-century painting is described. The study was carried out on an ultra-thin section cut from a microsample so as to retain the original paint layer structure. The sample had a single ground layer and one, red, paint layer. Analysis of individual particles using electron diffraction identified the major and minor components in the ground and paint layers. The predominant component of the ground layer was shown to be gypsum (CaSO4·2H2O), together with some albite (NaAlSi3O8), dolomite (CaCO3·MgCO3) and calcite (CaCO3); the paint layer is composed entirely of vermilion (HgS). TEM is a powerful technique, as it allows the complete characterization of the inorganic components in each layer, commencing with a morphological study, then qualitative and quantitative microanalysis by energy dispersive X-ray spectrometry and, finally, the determination of the crystal structure by electron diffraction.

Analysis and classification of individual outdoor aerosol particles with SIMS time-of-flight mass spectrometry

Individual aerosol particles sampled in the north of the city Karlsruhe were analysed with a TOF-SIMS instrument. The results confirmed the integral analysis of many particles [1]. In order to employ a signal pattern analysis of the negative secondary ions for the classification of organic compounds an earlier classification scheme for 5 keV Ar+ bombardment was found to be generally also applicable for the TOF-SIMS conditions. Two main classes of particles were distinguished, which consist of submicron mainly organic particles of vehicle traffic provenance on one side and coarse particles of geogenic sources on the other side. Additionally, the geogenic class could be devided into a fraction consisting of lime soil and a fraction with alumo-silicate soil. A quantification of the class population was performed by counting the particles of different type.

Recent advances in the analysis of individual environmental particles. A review

Recent advances in the analysis of individual environmental particles. A review

Preparation of AlLi/SiCp composite powder by a plasma spray atomisation (PSA) technique

Aluminium - lithium alloys are of technological importance to the aerospace industry. The advantages of aluminium - lithium alloys over conventional high-strength aluminium alloys include significant weight savings, increased stiffness, better fatigue resistance and broader temperature capability. This alloy series however, suffer low ductility and fracture toughness when produced using the ingot metallurgy (IM) method. This shortcoming can be diminished by powder metallurgy (PM) processing techniques. Ceramic reinforcement such as carbides, oxides and nitrides are added to the metal alloys to enhance strength, modulus, wear resistance and high temperature properties.Current PM processes however, are limited to reinforcement size of >5 μm. When finer ceramic particles are added the metal matrix composites (MMC) suffer from agglomeration of the reinforcement phase leading to problems in metal-ceramic interface and poor mechanical properties. Agglomeration occurs in submicron ceramic particles as a result of Van der Waals forces and electrostatic charges. Moisture in the atmosphere also plays a part. This paper reports an alternate route in the preparation of MMC with fine ceramic particles (< μm) as the reinforcement. The MMC is prepared by a process called Plasma Spray Atomization (PSA). This was carried out by melting the metal matrix and ceramic reinforcement simultaneously in a high temperature plasma flame (∼2000° – 10,000°C). The molten droplets are fragmented into very fine composite particles when they impact on a solid rotating disk. The powder collected are characterised using standard metallographic techniques, scanning electron microscopy (SEM) and laser diffraction particle size analyser. Several parameters such as plasma gas composition, plasma are power, rotating disk speed and distance between the plasma tourch and rotating disk were investigated. The results showed that this process produced fine Al-Li/SiC composite particles in the size range 1 – 35 μm. SEM observation of polished cross sections showed the particles consist of submicron SiC particles dispersed within a single AlLi alloy particle. Quantitative analysis of individual composite particles using wavelength dispersive X-ray analysis (WDX) showed that the concentration of SiC is low in the large particles (> 20 μm) but high in particles <10 μm.

X‐ray Diffraction and Chemical Characterization of the Plastic Colloid Fraction of Chinastone

The fine particle size fraction from a South China china‐stone material used in porcelains and renowned for its plasticity was characterized to determine the chemical and crystallographic structure of the &lt;2 μm fraction. Chemical analysis suggested the presence of a chloritic material in the fine fraction, a premise which was supported by X‐ray diffraction and thermal analysis. The chinastone has a well‐defined 1.4‐nm basal spacing which did not expand when subjected to ethylene glycol. However, the (001) reflections produced an anomalous broadening and decrease in spacing to 1.28 nm when heated to 700°C. The X‐ray patterns and chemical composition are similar to those at an aluminum‐treated montmorillonite which contains condensed gibbsite interlayered between montmorillonite units. Chemical analysis of individual particles plus X‐ray and thermal analysis leads to the conclusion that the fine fraction of the chinastone is an alumina‐rich chlorite with unusually low iron and magnesium levels.

Optimization of Operating Conditions in Individual Airborne Particle Analysis by Inductively Coupled Plasma Mass Spectrometry

Operating conditions of a particle analyzer using inductively coupled plasma mass spectrometry were investigated to optimize the analysis of individual aerosol particles for zinc in the picogram to femtogram range. The signal intensities and their fluctuations from individual particles were strongly affected by the carrier gas flow rate, radio frequency power and sampling depth. The optimum operating conditions were determined and are discussed based on the vaporization and ionization processes of particles and the ion sampling process. Under the optimum operating conditions, fluctuations of the signals from monodisperse aerosols were improved to ca. 5% of relative standard deviation under favorable conditions, and the detection limit of zinc in a particle could be lowered to ca. 3fg.

A moon-based laboratory for extraterrestrial sample analysis

If organic molecules were safely delivered to the early Moon, they may still be present beneath the currently gardened lunar regolith at a depth of 10 m or more. A Moon based laboratory would be helpful to search for organic matter below the surface layers since the problem of terrestrial contamination, which has been a major concern in the past analysis of returned lunar samples, will be overcome. The moon provides also a sterile platform for collection and analysis of individual cosmic dust particles assuming special devices to slowly decelerate the particles allowing a non-destructive capture.

Identification and classification of airborne soot particles using an automated SEM/EDX

Individual particle analysis by means of an automated scanning electron microscope with an energy dispersive X-ray microanalysis system (SEM/EDX) is used for chemical classification and size determination of airborne particulate matter. Special attention is paid to the X-ray analysis of atmospheric soot particles. The preparation and use of standards, which is indispensable for obtaining good results are described and discussed in detail. The aerosol samples were collected on Nuclepore filters of two different pore sizes at a traffic island in Munich.