Evaporation Of Elements Research Articles

Atomic Absorption Determination of the Dissolved and Suspended Forms of Elements in Natural Water with Dynamic Sorption Preconcentration in Atomizers

* Institute of Fundamental Problems of Biology, Russian Academy of Sciences, Pushchino, Moscow oblast, Russia ** Department of Chemistry, Moscow State University, Vorob’evy gory, Moscow, 119899 Russia In natural water (river, sea, atmospheric, etc.) elements occur in dissolved and suspended forms. The data on the concentrations and ratio of these forms are important for geochemical and environmental studies. For the determination of ultralow concentrations of Ag, Bi, Cd, Pb, and Tl in dissolved (El diss ) and suspended (El susp ) forms and the total concentration (El diss + El susp ), we proposed a sorption–atomic-absorption method with the dynamic preconcentration of metals on the DETATA sorbent directly in a crucible electrothermal atomizer. A filtrate, unfiltered water sample, or solution obtained after the decomposition of a suspension (< 5– 50 mL) was pumped through a crucible microcolumn with holes of small diameter in the bottom and a graphite filter. The crucible microcolumn is a part (evaporation zone) of a two/three-chamber graphite electrothermal crucible–cell/crucible–cylinder–cell atomizer. The design of the atomizers provided independent programmed heating of the evaporation zone and the atomization zone for optimizing the processes and decreasing nonselective interferences and matrix effects. The cycle of the determination of elements in a solid matrix (concentrate, concentrate + suspension) commonly included drying, pyrolysis, and atomization ( 1800– 2600°e ) with the evaporation of elements to the isothermally heated zone. For the efficient suppression of interferences, we used the principles of element vapor filtration through graphite filters (between the evaporation and atomization zones) and fractional evaporation with the subsequent independent atomic-absorption analysis of the condensate.

Trace element evaporation during coal gasification based on a thermodynamic equilibrium calculation approach

Thermodynamic equilibrium calculations using the HSC-Chemistry program were performed to determine the distribution and mode of occurrence of potentially toxic and corrosive trace elements in gases from coal gasification processes. The influence of temperature, pressure and gas atmospheres on equilibrium composition was evaluated. In these reducing conditions, the behaviour of the trace elements is complex, but some form of organization can be attempted. Elements were classified into three groups. Group A includes those elements that, according to thermodynamic data at equilibrium, could probably be condensed in coal gasification. Mn is classified in this group. Group B contains those elements that could be totally or partially in gas phase in gas cleaning conditions, and can be divided into two subgroups, depending on whether the cleaning conditions are hot or cold. Co, Be, Sb, As, Cd, Pb, Zn, Ni, V, Cr are elements in this group. Group C contains those elements that could be totally in gas phase in all the possible conditions, including flue gas emissions. Se, Hg and B are the elements that make up this group.

IN-AIR MICRO-PIXE ANALYSIS OF TISSUE SAMPLES

Micro-PIXE is capable of providing spatial distributions of elements in the micro-meter scale and its application to biology is useful to elucidate the cellular metabolism. Since, in this method, a sample target is usually irradiated with proton or α-particle beams in vacuum, beam heating results in evaporation of volatile elements and shrinking of the sample. In order to avoid these side effects, we previously developed a technique of in-air micro-PIXE analysis for samples of cultured cells. In addition to these, analysis of exposed tissue samples from living subjects is highly desirable in biological and medical research. Here, we describe a technique of in-air micro-PIXE analysis of such tissue samples. The target samples of exposed tissue slices from a Donryu rat, in which a tumor had been transplanted, were analyzed with proton micro-beams of 2.6 MeV. We report that the shape of cells and the distribution of volatile elements in the tissue sample remain uncharged when using a target preparation based on a freeze-drying method.

In-situ Work Function Measurement of Molecular Beam Epitaxy Film Surface Using RHEED-Beam Excited Secondary Electron Peaks

The relative work function of growing surface of molecular epitaxy films was measured in situ using the energy shifts observed in secondary electrons excited by reflection high energy electron diffraction beam. In the case of a superconducting perovskite YBa2Cu3Ox the measured work function showed different behaviors between the coevaporation and the sequential evaporation of the metal elements reflecting differences in the electronic structures of the growing surfaces.

A petrographic, chemical, and isotopic study of calcium‐aluminum‐rich inclusions and aluminum‐rich chondrules from the Axtell (CV3) chondrite

Abstract— Petrographic, compositional, and isotopic characteristics were studied for three calcium‐aluminum‐rich inclusions (CAIs) and four plagioclase‐bearing chondrules (three of them Al‐rich) from the Axtell (CV3) chondrite. All seven objects have analogues in Allende (CV3) and other primitive chondrites, yet Axtell, like most other chondrites, contains a distinctive suite of CAIs and chondrules. In common with Allende CAIs, CAIs in Axtell exhibit initial 26Al/27Al ratios ((26Al/27Al)0) ranging from ∼5 × 10−5 to &lt;1.1 × 10−5, and plagioclase‐bearing chondrules have (26Al/27Al)0 ratios of ∼3 × 10−6 and lower. One type‐A CAI has the characteristics of a FUN inclusion. The Al‐Mg data imply that the plagioclase‐bearing chondrules began to form &gt;2 Ma after the first CAIs. As in other CV3 chondrites, some objects in Axtell show evidence of isotopic disturbance. Axtell has experienced only mild thermal metamorphism (&lt;600 °C), probably not enough to disturb the Al‐Mg systematics. Its CAIs and chondrules have suffered extensive metasomatism, probably prior to final accretion. These data indicate that CAIs and chondrules in Axtell (and other meteorites) had an extended history of several million years before their incorporation into the Axtell parent body. These long time periods appear to require a mechanism in the early solar system to prevent CAIs and chondrules from falling into the Sun via gas drag for several million years before final accretion.We also examined the compositional relationships among the four plagioclase‐bearing chondrules (two with large anorthite laths and two barred‐olivine chondrules) and between the chondrules and CAIs. Three processes were examined: (1) igneous differentiation, (2) assimilation of a CAI by average nebular material, and (3) evaporation of volatile elements from average nebular material. We find no evidence that igneous differentiation played a role in producing the chondrule compositions, although the barred olivine compositions can be related by addition or subtraction of olivine. Methods (2) and (3) could have produced the composition of one chondrule, AXCH‐1471, but neither process explains the other compositions. Our study indicates that plagioclase‐bearing objects originated through a variety of processes.

The Inherent Capacitance of Moisturising Creams: A Source of False Positive Results?

The capacitance is a frequently used measurement of skin hydration in vivo, therefore any potential for false capacitance results is of importance. This in vitro study is to investigate the capacities of moisturising creams to cause false positive results. Adding different volumes of demineralised water and saline on dry clean plastic-backed tissue paper and measuring the capacitance values, the standard relation curve of capacitance value and volume of water was established. Four moisturising creams, petrolatum, a protective cream and a gel were then applied to the same kind of tissue paper in constant volumes, and were measured for weights and capacitance values over a 1-hour period allowing the gradual evaporation of water and volatile elements. A positive linear relationship was found between volume of water and capacitance value. All the creams had inherent capacitance that correlated with their water content. The inherent capacitance of creams decreased over time and ultimately reached comparable low values. The decrease in capacitance correlated significantly with weight reduction, except for petrolatum, which showed negligible inherent capacitance and weight reduction. The rates of decrease in capacitance value versus cream weight were significantly different for different creams. The results assured that capacitance value correlates to water content, and the inherent capacitance of creams may contribute to false positive skin capacitance in vivo if measured before water and other volatile elements of creams evaporate from the skin surface. In addition, the inherent capacitance and its durability may be relevant characteristics for further comparative studies of moisturisers and their clinical efficacy.

Investigation of evaporation and atomization processes in a variable-pressure electrothermal atomizer by laser spectroscopy using gallium as an example

A new approach to studying the evaporation and atomization of elements in graphite furnaces has been developed that combines a highly sensitive technique of laser-induced fluorescence and variable-pressure atomization. This approach allows one to work with low concentrations of analytes corresponding to real analytical conditions, to separate concurrent processes of evaporation and atomization, and to determine their parameters. The approach has been used for studying the evaporation and atomization of gallium in isothermal graphite furnaces.

In situ RBS analysis of CuInSe2

CuInSe2 thin films were prepared by sequential evaporation of the constituent elements onto Mo-coated glass substrates and the layers were subsequently selenized in a closed graphite box at 400°C. The films were characterised by X-ray diffraction (XRD) and in situ, real-time Rutherford backscattering spectrometry (RBS) analysis to monitor the progress of the reaction as the elemental layers interdiffused. For the Cu/In/Se structure, XRD performed after various anneals revealed that the Cu–In layer mixed with the Se layer to form a number of binary phases. For Cu/Se/In it was found that the Cu and Se had intermixed at room temperature. In both the structures investigated the Cu–Se and In–Se binary phases formed below 200°C and upon annealing above this temperature interdiffused to form chalcopyrite CuInSe2.

Compositional and genetic relationship between chondrules, chondrule rims, metal, and matrix in the Renazzo chondrite

Individual chondrules, coarse and fine-grained metal, chondrule rims, and matrix samples were separated from the Renazzo chondrite (CR2) and studied by instrumental neutron activation analysis. Both Renazzo chondrule and matrix fractions have CI Cr/Mg concentration ratios, unlike chondrules from other classes of chondrites, which have fractionated Cr/Mg ratios. This and other arguments suggest that Renazzo chondrules and matrix formed in the same nebular region. In Renazzo, fine-grained metal—the dominant metal component, is mostly located inside chondrules or in chondrule rims. Matrix contains few coarse metal grains. Both types of metal, fine and coarse, exhibit similar chemical signatures, comparatively high in Cr and low in Ni, suggesting a genetic relationship. Although metal is mostly contained in chondrules, chondrules and matrix of Renazzo have similar common siderophile/lithophile abundance ratios. This may imply that Renazzo chondrules and metal were formed by reduction of oxidized precursors compositionally similar to CI chondrites. The CI-like concentrations of Sc, Mg, Se, and Zn in Renazzo matrix are consistent with this inference. The differences in siderophile element pattern between chondrules, chondrule metal, and matrix indicate evaporation and recondensation of volatile elements during chondrule formation. Recondensation of evaporated elements was incomplete and the degree of recondensation correlates with element volatility. The higher-than-CI K/Mg, Na/Mg, and Ga/Fe ratios of Renazzo matrix may reflect recondensation of K, Na, and Ga into the matrix. The CI Se/Sc and Zn/Sc concentration ratios of the matrix, however, reflect very limited degrees of recondensation of Se and Zn into matrix. The presence of abundant phyllosilicates and organic material in Renazzo matrix requires a low background temperature (<200 K) during formation of the Renazzo meteorite. Partial recondensation of volatile elements in a cold nebular environment implies instantaneous agglomeration of the Renazzo chondrite following chondrule formation.

Distribution of siderophile elements in CR chondrites: evidence for evaporation and recondensation during chondrule formation

New data on the chemical composition of bulk samples, and of metallic and nonmagnetic fractions of six CR chondrites (Renazzo, Y793495, PCA91082, EET92042, Acfer 209 and El Djouf 001) are reported. It is shown that volatile siderophile element abundance patterns of metallic and nonmagnetic fractions of CR chondrites are complementary and volatility-dependent. In the metallic fraction CI-normalized abundances of Au, As, Sb and Ga decrease with increasing volatility, whereas in the nonmagnetic fraction abundances increase in the same sequence as in the metallic fraction. We argue that the siderophile element patterns of the metallic and nonmagnetic fractions reflect those of the chondrule and matrix fractions of CR chondrites, respectively, based on: (1) CR metal is mostly located inside chondrules and those metal grains outside chondrules probably were also derived from chondrules; (2) element partitioning within chondrules has been reset during chondrule formation; and (3) resetting of element distribution within chondrules occurred at sufficiently reducing conditions to allow partitioning of Au, As, Sb and Ga into CR metal.The complementary siderophile element patterns of CR chondrules and matrix are difficult to explain by gradual gas loss during condensation. The CI proportions of highly volatile elements in the bulk CR chondrites further argue against the possibility of loss of solids during condensation. Thus, the fractionation of volatile elements in CR chondrites is unlikely to be the result of gas-solid fractionation during condensation.The fractionation of volatile siderophile elements between CR chondrules and matrix requires evaporation of volatile elements during chondrule formation. The matrix pattern indicates recondensation of evaporated volatile elements. It appears, based on the composition of CR matrix, that the depletion and fractionation of moderately volatile elements in the bulk CR chondrites is due to formation of CR chondrites before complete recondensation of volatile elements which were evaporated during chondrule formation. This implies that agglomeration of CR chondrites proceeded simultaneously with chondrule formation.

Comparison of Post-Weld Microstructures and Mechanical Properties of Electron- and Laser-Beam Welded 8090 Al&amp;ndash;Li Alloy Plates

The current paper is to compare the welding characteristics as well as the post-weld impact and bending properties of electron-beam welded (EBW) and laser-beam-welded (LBW) 5 mm thick AA 8090 Al-Li alloy plates. In comparison under the same weld depth of 5 mm, the as-welded or T6 EBW specimens exhibited higher strength and fracture toughness than the LBW counterparts by ∼7% or - 24%, respectively. The grain size and δ' precipitate size in the EBW specimens were smaller than those in the LBW ones due to mainly the lower heat input absorbed. The uniformly dispersed pores in the EBW specimens originating from volatile element evaporation were spherical in shape, <0.2 mm in size, and ∼1.3% in volume fraction, compared with the spherical or elongated pores in the LBW ones of 0.05-1 mm in size and ∼7.2% in volume fraction originating primarily from the bubbles ejected into the molten pool due to intense evaporation at the bottom part of a keyhole with the entrapment of shielding gas during rapid solidification. The joint efficiency in terms of strength was typically around 80%, which might be considered to be acceptable. But if the welded specimens were loaded under high-rate impact with a V-notch and hence multiaxial stresses, both the EBW and LBW specimens would be subject to unacceptably low joint efficiency in terms of fracture absorbed energy E t (below 20%). The E t joint efficiency decreased with increasing loading rate.

Nonstoiciometric Perovskite Type-GdRh&lt;sub&gt;3&lt;/sub&gt;B&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; Compound and It's Relation of Boron Content to Hardness and Oxidation Resistance

Polycrystalline samples of GdRh3Bx, which consists of highly reactive (Gd) and high melting (Rh, B) elements, have been successfully synthesized by arc melting method. Extreme evaporation of the constituent elements has not been observed. Compound of GdRh3Bx has perovskite type cubic structure (space group: Pm3m). Perovskite-type GdRh3Bx exists in the range of x=1.000 (20atom% B) and 0.444 (10atom% B). Lattice parameter of a in annealed GdRh3Bx depends on x, and varies lineary from a=0.41331(6)nm (x=1.000) to 0.4121(1)nm (x=0.444). The TG curve indicates that the onset-temperature of oxidation for GdRh3B1.000 is 567.3°C and for GdRh3B0.706 is 611.3°C, respectively. Weight gain by heating in air up to 1200°C for GdRh3B1.000 (20atom% B) is 6.83% and for GdRh3B0.706 (15atom% B) is 8.61%, respectively. The former value for stoichiometric compound is smaller than the latter. Both samples decompose to GdBO3 and Rh after oxidation. The micro-Vickers hardness of the annealed Gdh3Bx increases with increasing B content in the range of x=1.333-0.444, for example hardness of the annealed GdRh3B1.000 (20atom% B) is 4.2(±0.10) GPa.

Stopping-powers and straggling of 15N ions for nuclear reaction analysis at 6.385 MeV

Stopping-powers and straggling has been measured for 15N incident ions at 6.4 MeV using the well known 1H( 15N,αγ) 12C resonant nuclear reaction at 6.385 MeV. Samples have been prepared using electron beam evaporation of various elements on H terminated silicon substrates under UHV conditions with high layer quality. The H monolayer remains stable at the silicon substrate during evaporation and ion irradiation. The layer thicknesses were ranging from 500 to 2000 Å. At this thickness range the energy straggling is between 15 and 40 keV (σ) and is the main contribution to the measured width of the H profile. Surface roughness, interface quality and Doppler broadening are negligible. The measured H profiles were fitted with a Gaussian normal distribution function. In the case of target materials, as e.g. Nb, which incorporate H easily, the layers were H charged and an integrated Gauss function was used for fitting. The stopping-powers and straggling were compared with ZBL data for electronic stopping, Bohr straggling and TRIM simulations for nuclear stopping and straggling and with former experimental data obtained with same method. The data for stopping-power and straggling showed remarkable differences to former measurements.

Potassium isotope cosmochemistry: Genetic implications of volatile element depletion

We report high precision (±0.5%o) potassium isotopic determinations on bulk chondrites, achondrites, and lunar samples, on a separated chondrule, and two CAls. We find that potassium shows a remarkable isotopic homogeneity in various solar system bodies, even though there are chemical depletions of a factor of about 30, between C1 chondrites and eucrites and lunar samples. Theories that propose the evaporation of volatile elements from initially condensed (C1 chondrite) material to account for such chemical depletions, necessarily imply the existence of large isotopic mass fractionations, e.g., about +40%o for Earth, +90%o for eucrites and lunar rocks. Volatile loss of potassium (and by implication Na, Rb, Cs, and other elements of similar volatility) during chondrule formation is also ruled out. The high precision of the data place stringent limits of ≤52% on the quantity of potassium that could have been lost by partial volatilization. This is not detectable by standard chemical techniques, which can resolve 5–20% changes in the K/La and K/U ratios. The two-component models proposed by Larimer and Anders (1967) and by Wänke et al. (1984) invoke vaporization of alkalis which is not supported by the potassium isotope results. The chemical depletion of alkalis and other volatiles must have preceded the processes of chondrule, chondrite, and planetary formation, and occurred during the condensation of precursor dust, probably from a hot stage in the solar nebula.

Petrology of FeO-poor, porphyritic pyroxene chondrules in the Semarkona chondrite

The mineralogy and petrology of FeO-poor, porphyritic, pyroxene- and olivine-rich chondrules in the Semarkona (LL3.0) chondrite are described in detail. In an extension of the textural classification scheme, these chondrules are designated types IAB and IB. In type IAB chondrules, the proportion of olivine phenocrysts is between 20–80% and in type IB chondrules, olivine constitutes <20% of the phenocryst assemblage. All the chondrules studied are FeO-poor and contain olivine and low-Ca pyroxene phenocrysts in varying proportions. Olivine is present both as chadacrysts enclosed in low-Ca pyroxene and as larger phenocrysts. Ca-rich pyroxene occurs commonly as rims on low-Ca pyroxene phenocrysts. Lamellar zoning in low-Ca pyroxene, observed in backscattered electron images, is interpreted as a primary growth feature. Apparent partition coefficients between phenocrysts and mesostasis for major and minor elements are consistent with crystallization of an essentially molten chondrule at rapid cooling rates (100–1000°C/h). Within the entire type I series, there are continuous changes in textural and compositional properties that suggest common origins for all chondrules in this series. These properties include proportions of olivine and pyroxene phenocrysts, FeO contents of olivine and pyroxene phenocrysts and a complementary relationship between the proportions of refractory elements and Si-, Fe-rich precursor components in chondrule bulk compositions. Observations of the behavior of Na suggest that evaporation and recondensation of volatile elements was not an important process during formation of type I chondrules and that abundances of volatile elements were largely controlled by the abundance of a volatile-rich precursor component.

In Situ Observations of Cirrus Cloud Microphysical Properties Using the Counterflow Virtual Impactor

Abstract This study presents a new technique for making in situ measurements of cirrus cloud microphysical properties. Sampling of cirrus clouds was performed using a counterflow virtual impactor (CVI). The CVI was used to sample cloud elements larger than 4 µm in aerodynamic diameter. In conjunction with a Lyman-α hygrometer, this gave a direct measurement of the condensed water content. Sampling the cloud elements with the CVI also allowed the authors to examine the size distribution of the residual particles produced by evaporation of the cloud elements. This study discusses and evaluates the CVI technique for use in sampling cirrus clouds, especially for sampling small cloud elements. Measurements of condensed water content and cloud-element (crystal and droplet) concentrations for cirrus uncinus, floccus, and cirrostratus clouds made using the CVI during the International Cirrus Experiment experiment are presented. Examples of size distributions of the residual aerosol particles from cirrus cloud ele...

DC arc spectroscopic study of thermochemical reactions of modifiers in SiC ceramics

The aim of this work was to clarify the process of evaporation of impurity elements from silicon carbide powder of industrial purity under the action of thermochemical additives, as a step towards the development of a method for the direct determination of all impurities. Considering the influence of classical additives — (C2F4)n, AgCl, CuCl, PdCl2 on both evaporation and excitation processes, the idea was developed of a modification of the matrix itself to more easy volatile compounds, allowing the impurities to be released. A complex modifier CoF2+Ba(NO3)2 was used for that purpose. The evidence for its effective action is a complete evaporation of the elements Al, Fe, Cu, Ti, Va, Mo and B during the first 10–20 s of arcing. The mechanism of the action of a modifier was studied using a thermodynamic evaluation of thermochemical processes that take place in the electrode crater. The mechanism supposed is supported by scanning electron microscopy images of residues in the crater.

Atomic layer growth of oxide thin films with perovskite-type structure by reactive evaporation

Epitaxial growth of BaTiO3 and SrTiO3 films by the reactive evaporation method was investigated using reflection high-energy electron diffraction (RHEED). The investigations were carried out using two growth methods: coevaporation and alternate evaporation of the metal elements in an oxygen atmosphere. Atomic layer growth was achieved by the alternate supply of Ba or Sr and Ti on the growing surface. In the case of coevaporation, epitaxial growth occurred in a two-dimensional unit-cell-by-unit-cell mode. The surface of each unit cell is terminated by a (TiO2) layer. Artificial superlattices of BaTiO3/SrTiO3 were fabricated by monitoring the film thickness with the RHEED oscillations.

Some factors affecting analysis in the atom probe

Preferential evaporation and retention of elements during pulsed field evaporation of a specimen is known to affect the results of a chemical analysis in the atom probe field ion microscope. Field evaporation produced by increasing the standing voltage on the specimen alters the surface chemistry because the more easily field evaporated elements will be removed preferentially. This change in surface chemistry will result in incorrect compositions being measured for small precipitates, boundaries or surfaces. The use of pulsed field evaporation should be adopted in these cases to avoid this problem. The shape of the specimen was found to change between DC and pulsed field evaporated conditions.

Improvement of the detection limits in pure Al 2O 3 powder by thermochemical reactions in a d.c. arc plasma and non-linear blank correction

Thermochemical reactions with halides were employed in particular applications of optical emission spectrography (OES), i.e. d.c. arc excitation, to enhance weak signals and to improve the detection limits. For trace element determinations in Al 2O 3 with special graphite electrodes, the detection limits of Fe, Mn, Ni, Co and Cu, were improved by one or two orders of magnitude with sodium chloride as a thermochemical reagent. These results indicated good agreement with the results of chemical-thermodynamic trend analysis. The trace elements Fe, Mn, Ni, Co and Cu form chlorides in preference to Al. Part of the matrix element Al also reacts with chlorine to form AlCl 3. Most of this chlorine is available again at higher temperatures because AlCl 3 decomposes to AlCl at about 3300 K. In this way the alumina has an effect as an additional carrier for chlorine and improves the trace element evaporation. With this procedure for trace element determinations in alumina the blank signals of the elements Fe, Mn, Cu, Ni and Co were detectable in the Al 2O 3 calibration matrix and in the NaCl suprapur additive. These blank values were eliminated by a combination of nonlinear blank correction and a calibration using weighted nonlinear regression. From this chemometric treatment and the thermochemical reactions resulted an improvement of the limits of detection by up to two orders of magnitude.