A method to correct defocused element distribution maps in electron probe microanalysis

Element distribution maps obtained on electron microprobes via the beam scan method with wavelength-dispersive spectrometers reveal a defocusing effect if they are taken at sufficiently small magnification. This effect, which occurs where the Bragg condition of the spectrometer is not adequately met, can be avoided or corrected by various methods. A method is presented here to correct defocused element distribution maps with the help of corresponding maps obtained on homogeneous standards.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Quantitative chemical phase imaging by means of energy filtering transmission electron microscopy

Electron spectroscopic imaging (ESI) in the transmission electron microscope (TEM) is a powerful method to produce 2-dimensional elemental distribution maps. These maps show in a clear way the chemical situation of a small specimen region. In this work we used a Gatan Imaging Filter (GIF) attached to a 200 kV TEM to investigate a Ba-Nd-titanate ceramic. The three phases occuring in this material could be visualized using inner-shell ionization edges (Ba M₄₅, Nd M₄₅ and Ti L₂₃). We applied different image correlation techniques to the ESI elemental maps for direct visualization of the chemical phases. First we simply overlaid the elemental maps assigning each element one colour to form an RGB image. Secondly we used the technique of scatter diagrams to classify the different phases. Finally we quantified the elemental maps by dividing them and multiplying them by the appropriate inner-shell ionization cross-sections which gave atomic ratio images. By using these methods we could clearly identify and quantify the various phases in the Ba-Nd-titanate specimen.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Particulate matter analysis at elementary schools in Curitiba,Brazil

The particulate matter indoors and outdoors of the classrooms at two schools in Curitiba, Brazil, was characterised in order to assess the indoor air quality. Information concerning the bulk composition was provided by energy-dispersive x-ray fluorescence (EDXRF). From the calculated indoor/outdoor ratios and the enrichment factors it was observed that S-, Cl- and Zn-rich particles are of concern in the indoor environment. In the present research, the chemical compositions of individual particles were quantitatively elucidated, including low-Z components like C, N and O, as well as higher-Z elements, using automated electron probe microanalysis low Z EPMA. Samples were further analysed for chemical and morphological aspects, determining the particle size distribution and classifying them according to elemental composition associations. Five classes were identified based on major elemental concentrations: aluminosilicate, soot, organic, calcium carbonate and iron-rich particles. The majority of the respirable particulate matter found inside of the classroom was composed of soot, biogenic and aluminosilicate particles. In view of the chemical composition and size distribution of the aerosol particles, local deposition efficiencies in the human respiratory system were calculated revealing the deposition of soot at alveolar level. The results showed that on average 42% of coarse particles are deposited at the extrathoracic level, whereas 24% are deposited at the pulmonary region. The fine fraction showed a deposition rate of approximately 18% for both deposition levels.     

EELS nanoanalysis for investigating both chemical composition and bonding of interlayers in composites

The paper is concerned with the application of analytical transmission electron microscopy (TEM) to characterize both chemical composition and bond state of the elements detected in interlayers in C- and SiC-fibre reinforced composites. The chemical bond state of nanometre-sized regions is characterized by means of electron energy loss spectroscopy (EELS), where respective information is gained by analysing energy loss near edge structures (ELNES). In this context results of Si-L₂₃ ELNES investigations are presented concerning the chemical bonding of silicon with carbon, nitrogen and oxygen. The specific bond state of silicon is revealed by recording series of EEL spectra at high energy resolution across the fibre/ matrix interlayers of interest. Moreover, the element distribution is imaged by energy-filtered TEM.Dedicated to Professor Dr. rer.nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Low-energy-loss EFTEM imaging of thick particles and aggregates

Electron spectroscopy imaging is a powerful tool for the elucidation of colloidal particle morphology and microchemistry, but it normally requires the use of very thin samples, typically less than 50 nm, to avoid the effects of multiple scattering. This work shows that many aspects of the internal morphology of thick particles and aggregates and the chemical component distribution are revealed using low-energy-loss electron imaging in the transmission electron microscope, benefiting from multiple scattering as well as small but significant differences in the low-energy-loss spectra of aggregate constituents. Low-loss images reveal morphological details of thick aggregates made out of colloidal polymers (natural rubber and styrene-acrylic latex) and inorganic particles (silica, montmorillonite, and aluminum phosphate) at a spatial resolution close to that achieved in the bright-field images and much better than in the elemental maps, showing the advantages of the simultaneous use of low-loss images and standard thin-cut elemental maps.     

High-resolution analytical TEM of nanostructured materials

This paper briefly reviews the potential applicability of analytical transmission electron microscopy (TEM) to elucidate both structural and chemical peculiarities of materials at high lateral resolution. Examples of analytical TEM investigations performed by energy-dispersive X-ray spectroscopy (EDXS), electron energy loss spectroscopy (EELS), and energy-filtered TEM (EFTEM) are presented for different materials systems including metals, ceramics, and compound semiconductors. In particular, results are given of imaging the element distribution in the interface region between gamma matrix and gamma' precipitate in the nickel-based superalloy SC16 by energy-filtered TEM. For core-shell structured BaTiO(3) particles the chemical composition and even the chemical bonding were revealed by EELS at a resolution of about 1 nm. A sub-nanometer resolution is demonstrated by energy-selective images of the Ga distribution in the surrounding of (In,Ga)As quantum dots. Moreover, the element distribution in (Al,Ga)As/AlAs multilayers with linear concentration gradients in a range of about 10 nm was investigated by EDXS line-profile analyses and EFTEM.     

EPMA Major and Trace Element Analysis in Garnet and its Petrological Application

 A comparison between major and trace element concentrations in garnet performed by electron microprobe (EPMA) technique is reported. Quantitative spot analyses and X-ray maps of major elements (Fe, Mg, Mn, Ca) and the trace element yttrium in garnets from metamorphic rocks are presented. The selected garnet samples come from meta-pelitic and meta-basic specimens belonging to the tectonic unit of the Monte Rosa Nappe (Western Alps). In the metapelites, the quantitative Y distribution maps display a prominent increase at the core, the Y abundance varying by over two orders of magnitude, from about 80 ppm (rim) to over 2100 ppm (core). The Y profiles show well defined patterns with sharp features that do not correlate with major element distributions. A roughly comparable pattern can be supposed only with Mn. The Y distribution suggests that the diffusion of Y through the garnet is very slow compared to the major elements, thus the Y results are suitable for geothermometric estimates. In the metabasites, the Y spatial distribution is characterised by an increasing content from the core to the rim, displaying a zoning pattern opposite to the metapelite garnet. Quantitative EPMA analyses range from 1100 ppm at the rim to values lower than the detection limit at the core. Therefore, the Y content in the garnet can be related to several chemical and physical variables such as the bulk rock composition and the phase assemblage. In particular, in the xenotime-bearing metapelitic system the Y distribution seems to be correlated with metamorphic peak temperature.     

Surface Characterisation of Water-Atomised Al–Zn–Mg–Cu Alloy Powders by SIMS and AES

 The present paper focuses on the characterisation of surface composition and alloying element in-depth distribution of water-atomised Al–Zn–Mg–Cu alloy powders by secondary ion mass-spectrometry and Auger electron spectroscopy. A pronounced segregation of Mg and some impurities (Fe, Ca, S) concurrently with some Zn depletion are observed on the powder surface. The oxide film formed on the powder surface mainly consists of Al and Mg oxides. The film is non-uniform in thickness: rather coarse surface oxide islands coexist with surface areas covered by a thin (<1.8 nm) oxide layer. The extent of surface oxidation is strongly affected by solidification conditions: The average thickness of the surface oxides increases with increasing particle size or with decreasing cooling rate. All alloying elements are homogeneously distributed in the bulk of individual particles. No significant differences in chemical composition between different particles of a given powder are observed. Received November 26, 1999. Revision September 25, 2001.     

Skim and cream natural rubber particles: colloidal properties, coalescence and film formation

Cream and skim fractions of freshly tapped natural rubber latex have been studied using atomic force microscopy and scanning electric potential microscopy to elucidate the topology and charge properties in film formation. Elemental distribution maps of the particles have also been obtained using electron energy-loss imaging in a low-energy transmission electron microscope. The two rubber fractions are obtained by centrifugation. The cream fraction is stable while rapid coagulation occurs in the skim fraction. After removal of the coagulum, no further coagulation occurs and the remaining skim rubber particles are stable. The rubber particles from the cream rubber particles contain higher amount of adsorbed protein-phospholipid materials compared to those in the "self-cleaned" skim fraction. This difference in membrane property has a significant impact on the spreading of the cis-1,4-polyisoprene cores, their coalescence and film formation behavior. Coalescence of cream particles appears to be hindered by the membrane materials, forming a rough film that retains the topology of individual particles. Skim particles coalesce more readily, forming relatively smooth films.     

On the measurement of gold nanoparticle sizes by the dynamic light scattering method

The application of the dynamic light scattering (DLS) method for determining the size distribution of colloidal gold nanoparticles in a range of 1–100 nm is discussed. It is shown that rotational diffusion of nonspherical strongly scattering particles with sizes of larger than 30–40 nm results in the appearance of a false peak in a size range of about 5–10 nm. In this case, the uncritical application of the DLS method may yield particle volume or number size distributions different from those obtained by transmission electron microscopy. For weakly scattering particles with diameters of smaller that 20 nm, the DLS method demonstrates an additional peak of intensity distribution in the region of large sizes that is related to particle aggregates or byproduct particles rather than individual nanoparticles. Practical methods for solving the problem of false peaks are discussed. It is established that the width of the DLS distribution does not correspond to transmission electron microscopy data and is overestimated. The advantages and drawbacks of the methods are compared and it is noted that, at present, the DLS method is the only instrument suitable for nonperturbative and sensitive diagnostics of relatively slow aggregation processes with characteristic times on the order of 1 min. In particular, this method can be used to diagnose gold nanoparticle conjugate aggregation initiated by biospecific interactions on their surface.     

燃烧源PM2.5凝结洗涤脱除实验研究

利用蒸汽在燃烧源PM2.5表面凝结,促使PM2.5凝结长大,建立一套燃烧源PM2.5凝结洗涤的实验台;考察了颗粒粒径分布、蒸汽添加量、液气比等对两种燃烧源PM2.5凝结洗涤脱除效果的影响。采用电称低压冲击器 (ELPI)在线测试分析燃煤和燃油PM2.5凝结洗涤前后的数浓度和粒径分布特性,并用SEM和XPS对两种不同燃烧源的颗粒进行了形貌和元素组分分析。结果表明,燃煤和燃油产生的PM2.5形貌和组分具有较大的差别,燃煤PM2.5主要为硅铝矿物质,而燃油PM2.5主要为含炭物质;相同条件下,燃煤PM2.5相变脱除效果优于燃油PM2.5;随着蒸汽添加量的增加,两者的脱除效率均升高;随粒径的增大,脱除效率提高;蒸汽添加量为0.08kg/m3时,粒径为0.4μm的燃煤和燃油细颗粒的脱除效率分别81％和72％;此外,适当增加液气比有利于凝结长大含尘液滴的脱除。     

褐煤SHELL气化飞灰黏附影响因素的研究

通过激光粒度仪、X射线荧光光谱仪、扫描电子显微镜等现代化分析测试技术对褐煤样、飞灰样以及换热废锅中的积灰样进行了粒度分布、化学组成、晶体矿物组成、微观形貌、微区化学组成等特征的分析,研究影响飞灰黏附特性的因素。并通过引入富集系数,描述各个元素在煤灰、正常飞灰、废锅积灰中的迁移富集情况。结果表明,在废锅积灰中有含铁矿物的生成,同时Na、K、Fe、S、P元素在废锅积灰中发生富集,在飞灰与积灰颗粒边缘处有大量的Fe、Na元素的富集。     

Preparation of nanometer-sized In2O3 particles by a reverse microemulsion method

Nanometer-sized indium oxide (In(2)O(3)) particles have been prepared by chemical reaction of inorganic indium compounds and ammonia gas in a reverse microemulsion system consisting of water, Triton X-100 (surfactant), n-heptanol (co-surfactant), and n-octane (oil). Precursor hydroxides precipitated in the droplets of water-in-oil (W/O) microemulsion were calcined at different temperatures to form indium oxide powder. The factors affecting the particle size have been discussed; the calcination temperature is considered to be the important factor for controlling the size. In(2)O(3) calcined at 400 degrees C had a spherical form and a narrow size distribution. Calcination at 800 degrees C led to the formation of particles not only of irregular shape, but also of a wide size distribution. With the increase in calcination temperature from 400 to 800 degrees C, the average size of the particles grew from 7 to about 40 nm. The species of reactants used in the aqueous phase had a significant effect on the size of the particles. The average diameter of In(2)O(3) particles derived from reactant InCl(3) was 7 nm; that of particles derived from In(NO(3))(3) was 15 nm. The In(2)O(3) nanoparticles were characterized by transmission electron microscopy and X-ray diffraction. The phase behavior of the microemulsions is discussed.     

Characterization of bimodal bigraft ABS

In the final product of a bimodal bigraft ABS, consisting of crosslinked polybutadiene particles (diameter 100 nm) with grafted and ungrafted poly (styrene-co-acrylonitrile) (=SAN) with an acrylonitrile (=AN) content of 28 weight %, crosslinked polybutadiene particles (diameter 300 nm) with grafted and ungrafted SAN with an AN content of 12 weight % and an added SAN with an AN content of 28 weight % the following parameters can be determined: degree of grafting of the small polybutadiene particles, degree of grafting of the large polybutadiene particles, acrylonitrile content of the grafted chains of the small polybutadiene particles, acrylonitrile content of the grafted chains of the large polybutadiene particles, grafting efficiency of the large particles, average particle diameter and particle diameter distribution of the small particles, average particle diameter and particle diameter distribution of the big particles, molar mass distribution of the ungrafted chains of the large particles, chemical distribution of the ungraftd chains of the large particles, molar mass distribution of the SAN resin added, chemical distribution of the SAN resin added.Preparative differential ultracentrifugation in acetone/-butyrolacrone (volume ratio 0.550.45), FTIR spectrometry and electron microscopy of the floating and sedimentating fraction yield the degree of grafting and AN content of the graft chains of the large particles and the degree of grafting and AN content of the graft chains of the small particles.Preparative differential centrifugation, FTIR spectrometry and electron microscopy of the fractions give nearly equivalent results. Fractional demixing with the demixing solvents ethylene carbonate/tetraline of the acetone-soluble part yields the SAN with 12 weight % AN in the upper-phase and the SAN with 28 weight % AN in the lower phase.Size exclusion chromatography (SEC) and high-performance precipitation liquid chromatography (HPPLC) of the fractions yield the molecular distribution and chemical distribution of the different SAN resins. SEC, coupled with turbidimetric titration of the acetone-soluble fractions withn-hexane as precipirant, indicates SAN resin with lower AN content in addition to the SAN resin with 28 weight % AN.Dedicated to Prof. Dr. Dr. h.c. mult. Karl Heinz Büchel on the occasion of his 60th birthday     

In situ examination of uranium contaminated soil particles by micro-X-ray absorption and micro-fluorescence spectroscopies

Two complimentary spectroscopic techniques, X-ray absorption and fluorescence spectroscopy have been conducted at spatial scales of 1 to 25 μm on uranium contaminated soil sediments collected from two former nuclear materials processing facilities of the DOE: Fernald, OH and Savannah River Site, SC. A method of imbedding particles in a non-reactive Si polymer was developed such that individual particles could be examined before and after extraction with a wide range of chemicals typically used in sequential extraction techniques and others proposed forex situ chemical intervention technologies. Using both the micro-X-ray fluorescence (XRF) and micro-X-ray Absorption Near Edge Structure (XANES) techniques, both elemental and oxidation state distribution maps were generated on individual particles before and following chemical extraction. XANES can determine the relative proportion of U(VI) and U(IV) in phases comprising individual particles before and after extraction and showed that greater than 85% of the uranium existed as hexavalent U(VI). Fluorescence spectra of contaminated particles containing mainly U(VI) revealed populations of uranyl hydroxide phases and demonstrated the relative efficacy and specificity of each extraction method. Correlation of XAS and fluorescence data at micron scales provides information of U oxidation state as well as chemical form in heterogeneous samples.     

Size-based analysis of incinerator fly ash using gravitational SPLITT fractionation, sedimentation field-flow fractionation, and inductively coupled plasma-atomic emission spectroscopy

Fly ash has been regarded as hazardous because of its high adsorption of toxic organic and/or inorganic pollutants. Fly ash is also known to have broad distributions of different chemical and physical properties, such as size and density. In this study, fly ash emitted from a solid waste incinerator was pre-fractionated into six sub-populations by use of gravitational SPLITT fractionation (GSF). The GSF fractions were then analyzed by sedimentation field-flow fractionation (SdFFF) and ICP–AES. SdFFF analysis showed the fly ash has a broad size distribution ranging from a few nanometers up to about 50 µm. SdFFF results were confirmed by electron microscopy. Inductively coupled plasma–atomic emission spectroscopy (ICP–AES) analysis of the GSF fractions showed the fly-ash particles contain a variety of inorganic elements including Ca, Si, Mg, Fe, and Pb. The most abundant in fly ash was Ca, followed by Si then Mg. No correlations were found between trace element concentration and particle size.     

ToF-SIMS depth profiling of oral drug delivery films for 3D visualization of active pharmaceutical particles

The size, shape, and spatial distribution of active pharmaceutical ingredient (API) are important physical characteristics of drug delivery systems that can affect the performance, stability, appearance, and even bulk properties of the end product. This study explores the feasibility of using time-of-flight secondary ion mass spectrometry (ToF-SIMS) for the 3D characterization of API particles in two commercially available oral dissolvable drug delivery films. It was found that ToF-SIMS imaging with argon gas cluster ion beam (GCIB) sputtering allowed production of 3D chemical maps that could be utilized to obtain size distributions of buprenorphine particles whose effective diameters ranged from approximately 6 μm to 41 μm, with shapes that were generally spherical with a few nonspherical structures. The particles were heterogeneously distributed both laterally and as a function of depth in the film. In addition, ToF-SIMS was able to differentiate between different oral drug delivery films based on differences in the spatial distribution of buprenorphine; in one case, the particles were distributed throughout the depth of the film, whereas the particles in the other case were localized close to the surface. Preliminary studies suggest that ToF-SIMS with argon GCIB sputtering may also allow us to provide a very rough estimate of the concentration of the APIs (factors of 2 to 4), namely buprenorphine and naloxone, at pharmacologically relevant concentrations inside organic drug delivery systems with a thickness of hundreds of micrometers.     

Investigations of precipitates in heat treated AgPd30/CuSn6 layers

The subject of the investigations are precipitation zones, which grew as a result of chemical diffusion in AgPd30/CuSn6 bimetals. These precipitation zones have been characterized by metallography, electron probe microanalysis and x-ray diffraction. The growth of precipitation zones in the plating layer and in the substrate layer in dependence on time have been determined. The use of x-ray diffraction alone for the identification of the precipitates could not supply satisfying results in every case. This problem was solved by the application of electron probe microanalysis using a correction method, which allows the estimation of the chemical composition of small particles.Dedicated to Professor Dr. rer. nat. Dr. h. c. Hubertus Nickel on the occasion of his 65th birthday     

Quantitative microbeam analysis of particles

The ability to characterize individual microscopic particles is important in many areas of science and technology. A variety of microbeam analysis methods are capable of providing information on microscopic particles. With electron probe X-ray microanalysis quantitative analysis is possible under well controlled conditions. Using computer controlled electron microscopes it is feasible to characterize a large number of individual particles. The application of this technique requires the use of multivariate data analysis procedures for the interpretation of the large amount of data obtained.     

Nanoparticle precipitation in reverse microemulsions: particle formation dynamics and tailoring of particle size distributions

In this work, a detailed experimental analysis of the nanoparticle formation dynamics and the formation mechanism in a reverse microemulsion system is given. The precipitation of barium sulfate nanoparticles inside microemulsion droplets is investigated at the molecular scale with respect to the evolution of the particle size distribution and the particle morphology by an extensive transmission electron microscope (TEM) analysis. Different mixing procedures (feeding strategies) of two reactants, barium chloride and potassium sulfate, are evaluated concerning their ability for a tailored particle design under consideration of the complete particle size distribution (modality and polydispersity). It is shown that improved knowledge about the particle formation mechanisms, the dynamics, and the influence of the colloidal microemulsion structure could be used for a tailored design of particles,for example, controlled synthesis of nanoparticles with a bimodal particle size distribution by the application of a sophisticated feeding strategy.